From 1b51f95c6c9283fe9af2fb5529152f3548ed5e56 Mon Sep 17 00:00:00 2001
From: Dotta <bippadotta@protonmail.com>
Date: Fri, 7 Aug 2026 19:13:00 +0000
Subject: [PATCH] feat(runner): add phase 1 static replay contract

Co-Authored-By: Paperclip <noreply@paperclip.ing>
---
 packages/paperclip-runner/.gitignore          |   3 +
 .../devtools/browser/index.html               |  13 +
 .../devtools/browser/playwright.config.ts     |  20 +
 .../devtools/browser/src/App.tsx              | 229 +++++
 .../browser/src/components/ui/badge.tsx       |  19 +
 .../browser/src/components/ui/button.tsx      |  15 +
 .../browser/src/components/ui/card.tsx        |  26 +
 .../browser/src/components/ui/textarea.tsx    |  15 +
 .../devtools/browser/src/main.tsx             |  16 +
 .../devtools/browser/src/styles.css           | 430 ++++++++
 .../devtools/browser/static-replay.spec.ts    |  30 +
 packages/paperclip-runner/package.json        |  31 +-
 .../fixtures/phase-01/duplicate-event.json    |  30 +
 .../fixtures/phase-01/failed-run.json         | 106 ++
 .../golden/duplicate-event.snapshot.json      | 130 +++
 .../golden/duplicate-event.summary.json       |  11 +
 .../phase-01/golden/failed-run.snapshot.json  | 143 +++
 .../phase-01/golden/failed-run.summary.json   |   9 +
 .../phase-01/golden/happy-path.snapshot.json  | 166 ++++
 .../phase-01/golden/happy-path.summary.json   |   9 +
 .../golden/interrupted-run.snapshot.json      | 137 +++
 .../golden/interrupted-run.summary.json       |   9 +
 .../phase-01/golden/source-gap.snapshot.json  | 125 +++
 .../phase-01/golden/source-gap.summary.json   |  18 +
 .../unknown-optional-fields.snapshot.json     | 111 +++
 .../unknown-optional-fields.summary.json      |   9 +
 .../fixtures/phase-01/happy-path.json         | 230 +++++
 .../fixtures/phase-01/interrupted-run.json    |  90 ++
 .../fixtures/phase-01/source-gap.json         |  19 +
 .../phase-01/unknown-optional-fields.json     |  19 +
 .../unsupported-required-version.json         |  13 +
 .../protocol/schemas/capabilities.schema.json |  44 +
 .../protocol/schemas/command.schema.json      |  43 +
 .../protocol/schemas/event.schema.json        |  72 ++
 .../protocol/schemas/fixture.schema.json      |  42 +
 .../protocol/schemas/identity.schema.json     |  36 +
 .../protocol/schemas/request.schema.json      |  53 +
 .../protocol/schemas/result.schema.json       | 121 +++
 .../protocol/schemas/terminal.schema.json     |  25 +
 .../runner/crates/runner-core/src/lib.rs      |   2 +
 .../runner/crates/runner-core/src/phase1.rs   | 308 ++++++
 .../scripts/check-browser-tokens.mjs          |  67 ++
 .../scripts/generate-phase1-goldens.mjs       |  59 ++
 .../generate-protocol-schema-module.mjs       |  43 +
 .../paperclip-runner/src/cli/phase1-replay.ts |  17 +
 packages/paperclip-runner/src/index.ts        |   4 +
 .../src/protocol/generated/schema-bundle.ts   | 924 ++++++++++++++++++
 .../src/protocol/phase1-contract.test.ts      | 142 +++
 .../src/protocol/phase1-contract.ts           | 271 +++++
 .../src/protocol/phase1-loader.ts             |  32 +
 .../src/reducer/session-reducer.test.ts       |  73 ++
 .../src/reducer/session-reducer.ts            | 354 +++++++
 .../src/tracer/phase1-replay.test.ts          |  23 +
 .../src/tracer/phase1-replay.ts               |  21 +
 .../paperclip-runner/tsconfig.browser.json    |  12 +
 packages/paperclip-runner/vite.config.ts      |  20 +
 56 files changed, 5034 insertions(+), 5 deletions(-)
 create mode 100644 packages/paperclip-runner/.gitignore
 create mode 100644 packages/paperclip-runner/devtools/browser/index.html
 create mode 100644 packages/paperclip-runner/devtools/browser/playwright.config.ts
 create mode 100644 packages/paperclip-runner/devtools/browser/src/App.tsx
 create mode 100644 packages/paperclip-runner/devtools/browser/src/components/ui/badge.tsx
 create mode 100644 packages/paperclip-runner/devtools/browser/src/components/ui/button.tsx
 create mode 100644 packages/paperclip-runner/devtools/browser/src/components/ui/card.tsx
 create mode 100644 packages/paperclip-runner/devtools/browser/src/components/ui/textarea.tsx
 create mode 100644 packages/paperclip-runner/devtools/browser/src/main.tsx
 create mode 100644 packages/paperclip-runner/devtools/browser/src/styles.css
 create mode 100644 packages/paperclip-runner/devtools/browser/static-replay.spec.ts
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/duplicate-event.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/failed-run.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.snapshot.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.summary.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.snapshot.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.summary.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.snapshot.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.summary.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.snapshot.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.summary.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.snapshot.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.summary.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.snapshot.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.summary.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/happy-path.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/interrupted-run.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/source-gap.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/unknown-optional-fields.json
 create mode 100644 packages/paperclip-runner/protocol/fixtures/phase-01/unsupported-required-version.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/capabilities.schema.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/command.schema.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/event.schema.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/fixture.schema.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/identity.schema.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/request.schema.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/result.schema.json
 create mode 100644 packages/paperclip-runner/protocol/schemas/terminal.schema.json
 create mode 100644 packages/paperclip-runner/runner/crates/runner-core/src/phase1.rs
 create mode 100644 packages/paperclip-runner/scripts/check-browser-tokens.mjs
 create mode 100644 packages/paperclip-runner/scripts/generate-phase1-goldens.mjs
 create mode 100644 packages/paperclip-runner/scripts/generate-protocol-schema-module.mjs
 create mode 100644 packages/paperclip-runner/src/cli/phase1-replay.ts
 create mode 100644 packages/paperclip-runner/src/protocol/generated/schema-bundle.ts
 create mode 100644 packages/paperclip-runner/src/protocol/phase1-contract.test.ts
 create mode 100644 packages/paperclip-runner/src/protocol/phase1-contract.ts
 create mode 100644 packages/paperclip-runner/src/protocol/phase1-loader.ts
 create mode 100644 packages/paperclip-runner/src/reducer/session-reducer.test.ts
 create mode 100644 packages/paperclip-runner/src/reducer/session-reducer.ts
 create mode 100644 packages/paperclip-runner/src/tracer/phase1-replay.test.ts
 create mode 100644 packages/paperclip-runner/src/tracer/phase1-replay.ts
 create mode 100644 packages/paperclip-runner/tsconfig.browser.json
 create mode 100644 packages/paperclip-runner/vite.config.ts

diff --git a/packages/paperclip-runner/.gitignore b/packages/paperclip-runner/.gitignore
new file mode 100644
index 00000000000..cb98e73ffe5
--- /dev/null
+++ b/packages/paperclip-runner/.gitignore
@@ -0,0 +1,3 @@
+/dist-browser/
+/playwright-report/
+/test-results/
diff --git a/packages/paperclip-runner/devtools/browser/index.html b/packages/paperclip-runner/devtools/browser/index.html
new file mode 100644
index 00000000000..301dbcf965f
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/index.html
@@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <meta name="color-scheme" content="light dark" />
+    <title>Paperclip Runner · PRP Static Replay</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>
diff --git a/packages/paperclip-runner/devtools/browser/playwright.config.ts b/packages/paperclip-runner/devtools/browser/playwright.config.ts
new file mode 100644
index 00000000000..0eb2bc3a5c6
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/playwright.config.ts
@@ -0,0 +1,20 @@
+import { defineConfig } from "@playwright/test";
+
+export default defineConfig({
+  testDir: ".",
+  testMatch: "static-replay.spec.ts",
+  fullyParallel: false,
+  workers: 1,
+  reporter: "line",
+  use: {
+    baseURL: "http://127.0.0.1:4179",
+    viewport: { width: 1440, height: 1000 },
+  },
+  webServer: {
+    command:
+      "pnpm exec vite preview --config vite.config.ts --host 127.0.0.1 --port 4179",
+    url: "http://127.0.0.1:4179",
+    reuseExistingServer: false,
+    timeout: 30_000,
+  },
+});
diff --git a/packages/paperclip-runner/devtools/browser/src/App.tsx b/packages/paperclip-runner/devtools/browser/src/App.tsx
new file mode 100644
index 00000000000..9d202fc5260
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/src/App.tsx
@@ -0,0 +1,229 @@
+import { useMemo, useState } from "react";
+
+import { replayPhase1FixtureText } from "../../../src/tracer/phase1-replay";
+import type { SessionSnapshot } from "../../../src/reducer/session-reducer";
+import { Badge } from "./components/ui/badge";
+import { Button } from "./components/ui/button";
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+  CardTitle,
+} from "./components/ui/card";
+import { Textarea } from "./components/ui/textarea";
+
+const fixtureFiles = import.meta.glob(
+  "../../../protocol/fixtures/phase-01/*.json",
+  { eager: true, query: "?raw", import: "default" },
+) as Record<string, string>;
+
+const fixtureOrder = [
+  "happy-path",
+  "failed-run",
+  "interrupted-run",
+  "duplicate-event",
+  "source-gap",
+  "unknown-optional-fields",
+  "unsupported-required-version",
+];
+
+interface BrowserFixture {
+  key: string;
+  label: string;
+  source: string;
+}
+
+const browserFixtures = Object.entries(fixtureFiles)
+  .map(([path, source]): BrowserFixture => {
+    const key = path.split("/").at(-1)?.replace(/\.json$/, "") ?? path;
+    const parsed = JSON.parse(source) as { name?: string };
+    return { key, label: parsed.name ?? key, source };
+  })
+  .sort((left, right) => fixtureOrder.indexOf(left.key) - fixtureOrder.indexOf(right.key));
+
+function terminalTone(snapshot: SessionSnapshot) {
+  if (snapshot.integrity === "gap_detected") {
+    return "warning" as const;
+  }
+  if (snapshot.terminal?.runTerminalState === "succeeded") {
+    return "success" as const;
+  }
+  if (snapshot.terminal?.runTerminalState === "failed") {
+    return "danger" as const;
+  }
+  return "neutral" as const;
+}
+
+function SnapshotSummary({ snapshot }: { snapshot: SessionSnapshot }) {
+  return (
+    <>
+      <div className="snapshot-heading">
+        <div>
+          <p className="eyebrow">Final session snapshot</p>
+          <h2>{snapshot.fixtureName}</h2>
+        </div>
+        <Badge tone={terminalTone(snapshot)} data-testid="terminal-badge">
+          {snapshot.integrity === "gap_detected"
+            ? "Gap detected"
+            : (snapshot.terminal?.runTerminalState ?? snapshot.runPhase)}
+        </Badge>
+      </div>
+
+      <dl className="snapshot-grid">
+        <div>
+          <dt>Run</dt>
+          <dd>{snapshot.identity.runId}</dd>
+        </div>
+        <div>
+          <dt>Session</dt>
+          <dd>{snapshot.identity.normalizedSessionId}</dd>
+        </div>
+        <div>
+          <dt>Turn</dt>
+          <dd>{snapshot.terminal?.turnTerminalState ?? snapshot.turnState}</dd>
+        </div>
+        <div>
+          <dt>Events</dt>
+          <dd>{snapshot.timeline.length}</dd>
+        </div>
+      </dl>
+
+      {snapshot.proposedResult ? (
+        <div className="result-summary" data-testid="result-summary">
+          <span>Reported {snapshot.proposedResult.reportedWorkDisposition}</span>
+          <p>{snapshot.proposedResult.summary}</p>
+        </div>
+      ) : null}
+
+      {snapshot.gaps.length > 0 ? (
+        <div className="diagnostic" role="status">
+          Missing source sequence {snapshot.gaps.flatMap((gap) => gap.missing).join(", ")}.
+          Replay remains inspectable but is not complete.
+        </div>
+      ) : null}
+
+      <div className="timeline-heading">
+        <h3>Ordered timeline</h3>
+        <span>{snapshot.duplicateEventIds.length} duplicate events ignored</span>
+      </div>
+      <ol className="timeline" data-testid="timeline">
+        {snapshot.timeline.map((event) => (
+          <li key={event.sourceEventId}>
+            <span className="sequence" aria-hidden="true">
+              {event.sourceSeq}
+            </span>
+            <div>
+              <div className="timeline-title">
+                <code>{event.eventType}</code>
+                <time dateTime={event.emittedAt}>{event.emittedAt.slice(11, 23)}</time>
+              </div>
+              <p>{event.summary}</p>
+            </div>
+          </li>
+        ))}
+      </ol>
+
+      <details className="snapshot-json">
+        <summary>Inspect snapshot JSON</summary>
+        <pre>{JSON.stringify(snapshot, null, 2)}</pre>
+      </details>
+    </>
+  );
+}
+
+export function App() {
+  const defaultFixture = browserFixtures[0];
+  if (defaultFixture === undefined) {
+    throw new Error("No Phase 1 fixtures were bundled");
+  }
+  const [selectedFixture, setSelectedFixture] = useState(defaultFixture.key);
+  const [source, setSource] = useState(defaultFixture.source);
+  const [replay, setReplay] = useState(() => replayPhase1FixtureText(defaultFixture.source));
+  const selected = useMemo(
+    () => browserFixtures.find((fixture) => fixture.key === selectedFixture),
+    [selectedFixture],
+  );
+
+  function chooseFixture(key: string) {
+    const fixture = browserFixtures.find((candidate) => candidate.key === key);
+    if (fixture === undefined) {
+      return;
+    }
+    setSelectedFixture(key);
+    setSource(fixture.source);
+    setReplay(replayPhase1FixtureText(fixture.source));
+  }
+
+  return (
+    <main className="app-shell">
+      <header className="page-header">
+        <div>
+          <p className="eyebrow">Paperclip Runner Protocol · Phase 1</p>
+          <h1>Static session replay</h1>
+          <p>
+            Validate an editable PRP fixture and reduce its ordered events with the same
+            contract used by the CLI.
+          </p>
+        </div>
+        <Badge tone="neutral">Standalone · no Paperclip core</Badge>
+      </header>
+
+      <div className="workspace-grid">
+        <Card aria-labelledby="fixture-editor-title">
+          <CardHeader>
+            <CardTitle id="fixture-editor-title">Fixture input</CardTitle>
+            <CardDescription>
+              Choose a conformance case or edit the JSON, then validate and replay it.
+            </CardDescription>
+          </CardHeader>
+          <CardContent className="editor-content">
+            <label htmlFor="fixture-select">Fixture</label>
+            <select
+              id="fixture-select"
+              value={selectedFixture}
+              onChange={(event) => chooseFixture(event.target.value)}
+            >
+              {browserFixtures.map((fixture) => (
+                <option key={fixture.key} value={fixture.key}>
+                  {fixture.label}
+                </option>
+              ))}
+            </select>
+            <label htmlFor="fixture-source">PRP JSON</label>
+            <Textarea
+              id="fixture-source"
+              spellCheck={false}
+              value={source}
+              onChange={(event) => setSource(event.target.value)}
+            />
+            <div className="editor-actions">
+              <span>{selected?.label ?? "Edited fixture"}</span>
+              <Button type="button" onClick={() => setReplay(replayPhase1FixtureText(source))}>
+                Validate &amp; replay
+              </Button>
+            </div>
+          </CardContent>
+        </Card>
+
+        <section className="replay-panel" aria-live="polite">
+          {replay.ok ? (
+            <SnapshotSummary snapshot={replay.snapshot} />
+          ) : (
+            <div className="validation-errors" role="alert">
+              <Badge tone="danger">Validation failed</Badge>
+              <h2>Fixture cannot be replayed</h2>
+              <ul>
+                {replay.issues.map((issue, index) => (
+                  <li key={`${issue.path}-${index}`}>
+                    <code>{issue.path}</code> — {issue.message}
+                  </li>
+                ))}
+              </ul>
+            </div>
+          )}
+        </section>
+      </div>
+    </main>
+  );
+}
diff --git a/packages/paperclip-runner/devtools/browser/src/components/ui/badge.tsx b/packages/paperclip-runner/devtools/browser/src/components/ui/badge.tsx
new file mode 100644
index 00000000000..261ceb4dd0a
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/src/components/ui/badge.tsx
@@ -0,0 +1,19 @@
+import * as React from "react";
+
+/** Source-adapted shadcn Badge with semantic state supplied through data-tone. */
+export function Badge({
+  className = "",
+  tone = "neutral",
+  ...props
+}: React.ComponentProps<"span"> & {
+  tone?: "neutral" | "success" | "warning" | "danger";
+}) {
+  return (
+    <span
+      data-slot="badge"
+      data-tone={tone}
+      className={`ui-badge ${className}`.trim()}
+      {...props}
+    />
+  );
+}
diff --git a/packages/paperclip-runner/devtools/browser/src/components/ui/button.tsx b/packages/paperclip-runner/devtools/browser/src/components/ui/button.tsx
new file mode 100644
index 00000000000..8184dbab840
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/src/components/ui/button.tsx
@@ -0,0 +1,15 @@
+import * as React from "react";
+
+/** Source-adapted shadcn Button for the standalone, non-Tailwind devtool. */
+export function Button({
+  className = "",
+  ...props
+}: React.ComponentProps<"button">) {
+  return (
+    <button
+      data-slot="button"
+      className={`ui-button ${className}`.trim()}
+      {...props}
+    />
+  );
+}
diff --git a/packages/paperclip-runner/devtools/browser/src/components/ui/card.tsx b/packages/paperclip-runner/devtools/browser/src/components/ui/card.tsx
new file mode 100644
index 00000000000..ba52d1ce93f
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/src/components/ui/card.tsx
@@ -0,0 +1,26 @@
+import * as React from "react";
+
+function slotClass(slot: string, className: string | undefined) {
+  return `${slot} ${className ?? ""}`.trim();
+}
+
+/** Source-adapted shadcn Card family for the standalone devtool. */
+export function Card({ className, ...props }: React.ComponentProps<"section">) {
+  return <section data-slot="card" className={slotClass("ui-card", className)} {...props} />;
+}
+
+export function CardHeader({ className, ...props }: React.ComponentProps<"div">) {
+  return <div data-slot="card-header" className={slotClass("ui-card-header", className)} {...props} />;
+}
+
+export function CardTitle({ className, ...props }: React.ComponentProps<"h2">) {
+  return <h2 data-slot="card-title" className={slotClass("ui-card-title", className)} {...props} />;
+}
+
+export function CardDescription({ className, ...props }: React.ComponentProps<"p">) {
+  return <p data-slot="card-description" className={slotClass("ui-card-description", className)} {...props} />;
+}
+
+export function CardContent({ className, ...props }: React.ComponentProps<"div">) {
+  return <div data-slot="card-content" className={slotClass("ui-card-content", className)} {...props} />;
+}
diff --git a/packages/paperclip-runner/devtools/browser/src/components/ui/textarea.tsx b/packages/paperclip-runner/devtools/browser/src/components/ui/textarea.tsx
new file mode 100644
index 00000000000..c5bd29f44d2
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/src/components/ui/textarea.tsx
@@ -0,0 +1,15 @@
+import * as React from "react";
+
+/** Source-adapted shadcn Textarea for editable fixture JSON. */
+export function Textarea({
+  className = "",
+  ...props
+}: React.ComponentProps<"textarea">) {
+  return (
+    <textarea
+      data-slot="textarea"
+      className={`ui-textarea ${className}`.trim()}
+      {...props}
+    />
+  );
+}
diff --git a/packages/paperclip-runner/devtools/browser/src/main.tsx b/packages/paperclip-runner/devtools/browser/src/main.tsx
new file mode 100644
index 00000000000..8bcbe49a016
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/src/main.tsx
@@ -0,0 +1,16 @@
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+
+import { App } from "./App";
+import "./styles.css";
+
+const root = document.getElementById("root");
+if (root === null) {
+  throw new Error("Browser replay root element is missing");
+}
+
+createRoot(root).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+);
diff --git a/packages/paperclip-runner/devtools/browser/src/styles.css b/packages/paperclip-runner/devtools/browser/src/styles.css
new file mode 100644
index 00000000000..770f35334a7
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/src/styles.css
@@ -0,0 +1,430 @@
+:root {
+  color-scheme: light;
+  --background: #f7f7f5;
+  --foreground: #191917;
+  --card: #ffffff;
+  --card-foreground: #191917;
+  --muted: #efefeb;
+  --muted-foreground: #66665f;
+  --border: #deded7;
+  --primary: #242420;
+  --primary-foreground: #ffffff;
+  --success: #17633a;
+  --success-surface: #e9f5ed;
+  --warning: #8a5a10;
+  --warning-surface: #fff4dc;
+  --danger: #a02f2f;
+  --danger-surface: #fceaea;
+  --ring: #66665f;
+  --font-sans: Inter, ui-sans-serif, system-ui, sans-serif;
+  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
+  --font-size-xs: 0.75rem;
+  --font-size-sm: 0.875rem;
+  --font-size-md: 1rem;
+  --font-size-lg: 1.25rem;
+  --font-size-xl: 1.75rem;
+  --line-tight: 1.2;
+  --line-normal: 1.5;
+  --weight-medium: 500;
+  --weight-semibold: 600;
+  --space-1: 0.25rem;
+  --space-2: 0.5rem;
+  --space-3: 0.75rem;
+  --space-4: 1rem;
+  --space-5: 1.25rem;
+  --space-6: 1.5rem;
+  --space-8: 2rem;
+  --space-10: 2.5rem;
+  --radius-sm: 0.375rem;
+  --radius-md: 0.625rem;
+  --shadow-sm: 0 0.0625rem 0.125rem rgb(0 0 0 / 0.05);
+  --editor-height: 32rem;
+  --page-width: 90rem;
+  --control-height: 2.5rem;
+  --timeline-column: 2rem;
+  --motion-fast: 120ms;
+}
+
+* {
+  box-sizing: border-box;
+}
+
+body {
+  margin: 0;
+  min-width: 20rem;
+  background: var(--background);
+  color: var(--foreground);
+  font-family: var(--font-sans);
+  font-size: var(--font-size-sm);
+  line-height: var(--line-normal);
+}
+
+button,
+select,
+textarea {
+  font: inherit;
+}
+
+h1,
+h2,
+h3,
+p {
+  margin: 0;
+}
+
+.app-shell {
+  width: min(100%, var(--page-width));
+  margin-inline: auto;
+  padding: var(--space-8);
+}
+
+.page-header,
+.snapshot-heading,
+.timeline-heading,
+.editor-actions,
+.timeline-title {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: var(--space-4);
+}
+
+.page-header {
+  align-items: flex-start;
+  margin-bottom: var(--space-8);
+}
+
+.page-header > div {
+  display: grid;
+  gap: var(--space-2);
+}
+
+.page-header h1 {
+  font-size: var(--font-size-xl);
+  line-height: var(--line-tight);
+  letter-spacing: -0.02em;
+}
+
+.page-header p:not(.eyebrow),
+.ui-card-description,
+.timeline-heading span,
+.editor-actions span,
+dt {
+  color: var(--muted-foreground);
+}
+
+.eyebrow {
+  color: var(--muted-foreground);
+  font-size: var(--font-size-xs);
+  font-weight: var(--weight-semibold);
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+}
+
+.workspace-grid {
+  display: grid;
+  grid-template-columns: minmax(22rem, 0.8fr) minmax(28rem, 1.2fr);
+  gap: var(--space-8);
+  align-items: start;
+}
+
+.ui-card {
+  display: grid;
+  gap: var(--space-5);
+  padding: var(--space-6);
+  background: var(--card);
+  color: var(--card-foreground);
+  border: 0.0625rem solid var(--border);
+  border-radius: var(--radius-md);
+  box-shadow: var(--shadow-sm);
+}
+
+.ui-card-header,
+.ui-card-content,
+.editor-content {
+  display: grid;
+  gap: var(--space-3);
+}
+
+.ui-card-title,
+.snapshot-heading h2 {
+  font-size: var(--font-size-lg);
+  line-height: var(--line-tight);
+  font-weight: var(--weight-semibold);
+}
+
+.ui-card-description {
+  font-size: var(--font-size-sm);
+}
+
+.ui-button {
+  min-height: var(--control-height);
+  padding: var(--space-2) var(--space-4);
+  border: 0;
+  border-radius: var(--radius-sm);
+  background: var(--primary);
+  color: var(--primary-foreground);
+  font-weight: var(--weight-medium);
+  cursor: pointer;
+  transition: opacity var(--motion-fast) ease;
+}
+
+.ui-button:hover {
+  opacity: 0.88;
+}
+
+.ui-button:focus-visible,
+select:focus-visible,
+.ui-textarea:focus-visible {
+  outline: 0.125rem solid var(--ring);
+  outline-offset: 0.125rem;
+}
+
+.ui-badge {
+  display: inline-flex;
+  align-items: center;
+  width: fit-content;
+  min-height: 1.625rem;
+  padding-inline: var(--space-2);
+  border-radius: 999rem;
+  background: var(--muted);
+  color: var(--muted-foreground);
+  font-size: var(--font-size-xs);
+  font-weight: var(--weight-semibold);
+  text-transform: capitalize;
+  white-space: nowrap;
+}
+
+.ui-badge[data-tone="success"] {
+  background: var(--success-surface);
+  color: var(--success);
+}
+
+.ui-badge[data-tone="warning"] {
+  background: var(--warning-surface);
+  color: var(--warning);
+}
+
+.ui-badge[data-tone="danger"] {
+  background: var(--danger-surface);
+  color: var(--danger);
+}
+
+label,
+dt {
+  font-size: var(--font-size-xs);
+  font-weight: var(--weight-semibold);
+}
+
+select,
+.ui-textarea {
+  width: 100%;
+  border: 0.0625rem solid var(--border);
+  border-radius: var(--radius-sm);
+  background: var(--card);
+  color: var(--card-foreground);
+}
+
+select {
+  min-height: var(--control-height);
+  padding: var(--space-2) var(--space-3);
+}
+
+.ui-textarea {
+  min-height: var(--editor-height);
+  resize: vertical;
+  padding: var(--space-3);
+  font-family: var(--font-mono);
+  font-size: var(--font-size-xs);
+  line-height: var(--line-normal);
+  tab-size: 2;
+}
+
+.replay-panel {
+  display: grid;
+  gap: var(--space-6);
+}
+
+.snapshot-heading {
+  align-items: flex-start;
+}
+
+.snapshot-heading > div {
+  display: grid;
+  gap: var(--space-2);
+}
+
+.snapshot-grid {
+  display: grid;
+  grid-template-columns: repeat(4, minmax(0, 1fr));
+  gap: var(--space-4);
+  margin: 0;
+  padding-block: var(--space-5);
+  border-block: 0.0625rem solid var(--border);
+}
+
+.snapshot-grid div {
+  min-width: 0;
+}
+
+dd {
+  margin: var(--space-1) 0 0;
+  overflow: hidden;
+  font-family: var(--font-mono);
+  font-size: var(--font-size-xs);
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.result-summary {
+  display: grid;
+  gap: var(--space-1);
+}
+
+.result-summary span {
+  color: var(--muted-foreground);
+  font-size: var(--font-size-xs);
+  font-weight: var(--weight-semibold);
+  text-transform: uppercase;
+}
+
+.result-summary p {
+  font-size: var(--font-size-md);
+}
+
+.diagnostic,
+.validation-errors {
+  padding: var(--space-4);
+  border-radius: var(--radius-sm);
+  background: var(--warning-surface);
+  color: var(--warning);
+}
+
+.validation-errors {
+  display: grid;
+  gap: var(--space-4);
+  background: var(--danger-surface);
+  color: var(--danger);
+}
+
+.validation-errors ul {
+  margin: 0;
+  padding-left: var(--space-5);
+}
+
+.timeline-heading {
+  margin-top: var(--space-2);
+}
+
+.timeline-heading h3 {
+  font-size: var(--font-size-md);
+}
+
+.timeline-heading span {
+  font-size: var(--font-size-xs);
+}
+
+.timeline {
+  display: grid;
+  gap: 0;
+  margin: 0;
+  padding: 0;
+  list-style: none;
+}
+
+.timeline li {
+  display: grid;
+  grid-template-columns: var(--timeline-column) minmax(0, 1fr);
+  gap: var(--space-3);
+  padding-block: var(--space-3);
+}
+
+.timeline li + li {
+  border-top: 0.0625rem solid var(--border);
+}
+
+.sequence {
+  display: inline-grid;
+  place-items: center;
+  align-self: start;
+  width: var(--timeline-column);
+  height: var(--timeline-column);
+  border-radius: 999rem;
+  background: var(--muted);
+  color: var(--muted-foreground);
+  font-family: var(--font-mono);
+  font-size: var(--font-size-xs);
+}
+
+.timeline-title code,
+.snapshot-json pre,
+.validation-errors code {
+  font-family: var(--font-mono);
+}
+
+.timeline-title code {
+  font-size: var(--font-size-xs);
+  font-weight: var(--weight-semibold);
+}
+
+.timeline-title time,
+.timeline li p {
+  color: var(--muted-foreground);
+  font-size: var(--font-size-xs);
+}
+
+.timeline li p {
+  margin-top: var(--space-1);
+}
+
+.snapshot-json {
+  border-top: 0.0625rem solid var(--border);
+  padding-top: var(--space-4);
+}
+
+.snapshot-json summary {
+  cursor: pointer;
+  font-weight: var(--weight-medium);
+}
+
+.snapshot-json pre {
+  max-height: var(--editor-height);
+  overflow: auto;
+  padding: var(--space-4);
+  border-radius: var(--radius-sm);
+  background: var(--muted);
+  font-size: var(--font-size-xs);
+}
+
+@media (max-width: 60rem) {
+  .workspace-grid {
+    grid-template-columns: 1fr;
+  }
+
+  .ui-textarea {
+    min-height: 20rem;
+  }
+}
+
+@media (max-width: 36rem) {
+  .app-shell {
+    padding: var(--space-5);
+  }
+
+  .page-header,
+  .snapshot-heading,
+  .timeline-heading {
+    align-items: flex-start;
+    flex-direction: column;
+  }
+
+  .snapshot-grid {
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  :root {
+    --motion-fast: 0ms;
+  }
+}
diff --git a/packages/paperclip-runner/devtools/browser/static-replay.spec.ts b/packages/paperclip-runner/devtools/browser/static-replay.spec.ts
new file mode 100644
index 00000000000..e21b73c675a
--- /dev/null
+++ b/packages/paperclip-runner/devtools/browser/static-replay.spec.ts
@@ -0,0 +1,30 @@
+import { expect, test } from "@playwright/test";
+import { resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const packageRoot = fileURLToPath(new URL("../..", import.meta.url));
+
+test("validates and renders the shared happy-path fixture", async ({ page }) => {
+  await page.goto("/");
+  await expect(page.getByRole("heading", { name: "Static session replay" })).toBeVisible();
+  await expect(page.getByTestId("terminal-badge")).toHaveText("succeeded");
+  await expect(page.getByTestId("timeline").getByRole("listitem")).toHaveCount(9);
+  await expect(page.getByTestId("result-summary")).toContainText(
+    "The scripted run completed successfully.",
+  );
+  await page.screenshot({
+    path: resolve(packageRoot, "knowledge/evidence/phase-01-static-replay.png"),
+    fullPage: true,
+  });
+});
+
+test("shows duplicate and unsupported-version fixture states", async ({ page }) => {
+  await page.goto("/");
+  await page.getByLabel("Fixture", { exact: true }).selectOption("duplicate-event");
+  await expect(page.getByText("1 duplicate events ignored")).toBeVisible();
+  await page
+    .getByLabel("Fixture", { exact: true })
+    .selectOption("unsupported-required-version");
+  await expect(page.getByRole("heading", { name: "Fixture cannot be replayed" })).toBeVisible();
+  await expect(page.getByText(/protocolVersion 2 is unsupported/)).toBeVisible();
+});
diff --git a/packages/paperclip-runner/package.json b/packages/paperclip-runner/package.json
index a7015406a00..996853a2b7e 100644
--- a/packages/paperclip-runner/package.json
+++ b/packages/paperclip-runner/package.json
@@ -16,26 +16,47 @@
     "README.md"
   ],
   "scripts": {
-    "build": "pnpm run build:typescript && pnpm run build:rust",
-    "build:typescript": "tsc -p tsconfig.json",
+    "build": "pnpm run build:typescript && pnpm run build:rust && pnpm run build:browser",
+    "build:typescript": "pnpm run generate:protocol-types && tsc -p tsconfig.json",
     "build:rust": "cargo build --manifest-path runner/Cargo.toml --locked --workspace",
-    "typecheck": "pnpm run typecheck:typescript && pnpm run typecheck:rust",
-    "typecheck:typescript": "tsc -p tsconfig.json --noEmit",
+    "build:browser": "vite build --config vite.config.ts",
+    "typecheck": "pnpm run typecheck:typescript && pnpm run typecheck:rust && pnpm run typecheck:browser",
+    "typecheck:typescript": "pnpm run check:protocol-types && tsc -p tsconfig.json --noEmit",
     "typecheck:rust": "cargo check --manifest-path runner/Cargo.toml --locked --workspace",
+    "typecheck:browser": "tsc -p tsconfig.browser.json --noEmit",
     "test": "pnpm run test:typescript && pnpm run test:rust && node --test scripts/check-forbidden-imports.test.mjs",
     "test:typescript": "vitest run",
     "test:rust": "cargo test --manifest-path runner/Cargo.toml --locked --workspace",
+    "test:browser": "pnpm run build:browser && playwright test --config devtools/browser/playwright.config.ts",
+    "generate:protocol-types": "node scripts/generate-protocol-schema-module.mjs",
+    "check:protocol-types": "node scripts/generate-protocol-schema-module.mjs --check",
+    "generate:phase1-goldens": "pnpm run build:typescript && node scripts/generate-phase1-goldens.mjs",
+    "check:phase1-goldens": "node scripts/generate-phase1-goldens.mjs --check",
+    "check:browser-tokens": "node scripts/check-browser-tokens.mjs",
     "check:forbidden-imports": "node scripts/check-forbidden-imports.mjs",
     "check:phase0-parity": "vitest run src/tracer/phase0-runner.test.ts && cargo test --manifest-path runner/Cargo.toml --locked -p paperclip-runner-core runs_the_mock_core_path_with_stable_output && node -e \"process.stdout.write('Rust and TypeScript Phase 0 tracer output matches the shared golden fixture.\\n')\"",
+    "check:phase1-parity": "vitest run src/reducer/session-reducer.test.ts && cargo test --manifest-path runner/Cargo.toml --locked -p paperclip-runner-core phase1_fixture_parity && node -e \"process.stdout.write('Rust and TypeScript Phase 1 reducer summaries match the shared golden fixtures.\\n')\"",
     "docs:validate": "node scripts/validate-doc-links.mjs && node scripts/validate-okf.mjs",
     "trace:phase0": "pnpm run trace:phase0:rust",
     "trace:phase0:rust": "pnpm run build:rust && cargo run --quiet --manifest-path runner/Cargo.toml --locked -p paperclip-runner-core --bin phase0-tracer",
     "trace:phase0:typescript": "pnpm run build:typescript && node dist/tracer/phase0.js",
-    "verify": "pnpm run build && pnpm run test && pnpm run check:forbidden-imports && pnpm run docs:validate && pnpm run check:phase0-parity && pnpm run trace:phase0"
+    "replay:phase1": "pnpm run build:typescript && node dist/cli/phase1-replay.js",
+    "browser:dev": "vite --config vite.config.ts",
+    "browser:preview": "vite preview --config vite.config.ts",
+    "verify": "pnpm run build && pnpm run typecheck && pnpm run check:phase1-goldens && pnpm run test && pnpm run check:browser-tokens && pnpm run test:browser && pnpm run check:forbidden-imports && pnpm run docs:validate && pnpm run check:phase0-parity && pnpm run check:phase1-parity && pnpm run trace:phase0 && pnpm run replay:phase1"
   },
   "devDependencies": {
+    "@playwright/test": "^1.61.1",
     "@types/node": "^22.20.1",
+    "@types/react": "^19.2.17",
+    "@types/react-dom": "^19.2.3",
+    "@vitejs/plugin-react": "^4.7.0",
+    "ajv": "^8.20.0",
+    "json-schema-to-ts": "^3.1.1",
+    "react": "^19.2.7",
+    "react-dom": "^19.2.7",
     "typescript": "^5.7.3",
+    "vite": "^6.1.0",
     "vitest": "^4.1.10"
   }
 }
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/duplicate-event.json b/packages/paperclip-runner/protocol/fixtures/phase-01/duplicate-event.json
new file mode 100644
index 00000000000..39db5c8b1eb
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/duplicate-event.json
@@ -0,0 +1,30 @@
+{
+  "schema": "paperclip.prp.fixture.v1", "fixtureVersion": 1, "protocolVersion": 1,
+  "name": "Duplicate event", "description": "At-least-once delivery repeats one source event without repeating its effect.",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1", "companyId": "company_phase1", "issueId": "issue_phase1_duplicate",
+    "runId": "run_phase1_duplicate", "environmentLeaseId": "lease_phase1_duplicate", "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_duplicate", "driverSessionId": "driver_phase1_duplicate"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1", "sessionReusePolicy": "new_per_run", "driver": { "kind": "fake", "version": "1.0.0" },
+    "steer": false, "interrupt": true, "resume": true, "runtimeRequests": false, "structuredResult": true, "typedEvents": true
+  },
+  "commands": [
+    { "schema": "paperclip.prp.command.v1", "commandId": "command_duplicate_prepare", "controllerSeq": 1, "type": "run.prepare", "issuedAt": "2026-08-07T12:30:00.000Z", "payload": {} }
+  ],
+  "events": [
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_duplicate_01", "sourceSeq": 1, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_duplicate", "normalizedSessionId": "session_phase1_duplicate", "eventType": "session.started", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:30:00.010Z", "payload": {} },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_duplicate_02", "sourceSeq": 2, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_duplicate", "normalizedSessionId": "session_phase1_duplicate", "turnId": "turn_phase1_duplicate", "eventType": "turn.started", "schemaVersion": 1, "priority": 1, "emittedAt": "2026-08-07T12:30:00.020Z", "payload": {} },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_duplicate_03", "sourceSeq": 3, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_duplicate", "normalizedSessionId": "session_phase1_duplicate", "turnId": "turn_phase1_duplicate", "itemId": "item_phase1_duplicate", "eventType": "item.completed", "schemaVersion": 1, "priority": 1, "emittedAt": "2026-08-07T12:30:00.030Z", "payload": { "kind": "assistant_message", "text": "Exactly one projection." } },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_duplicate_03", "sourceSeq": 3, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_duplicate", "normalizedSessionId": "session_phase1_duplicate", "turnId": "turn_phase1_duplicate", "itemId": "item_phase1_duplicate", "eventType": "item.completed", "schemaVersion": 1, "priority": 1, "emittedAt": "2026-08-07T12:30:00.030Z", "payload": { "kind": "assistant_message", "text": "Exactly one projection." } },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_duplicate_04", "sourceSeq": 4, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_duplicate", "normalizedSessionId": "session_phase1_duplicate", "eventType": "run.result.proposed", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:30:00.040Z",
+      "payload": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "done", "summary": "Duplicate delivery was idempotent.", "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": true, "criteria": [], "remainingWork": [] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [] }
+    },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_duplicate_05", "sourceSeq": 5, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_duplicate", "normalizedSessionId": "session_phase1_duplicate", "turnId": "turn_phase1_duplicate", "eventType": "turn.completed", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:30:00.050Z", "payload": {} },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_duplicate_06", "sourceSeq": 6, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_duplicate", "normalizedSessionId": "session_phase1_duplicate", "eventType": "run.terminal", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:30:00.060Z", "payload": { "schema": "paperclip.prp.terminal.v1", "turnTerminalState": "completed", "runTerminalState": "succeeded", "reportedWorkDisposition": "done" } }
+  ],
+  "requests": [],
+  "result": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "done", "summary": "Duplicate delivery was idempotent.", "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": true, "criteria": [], "remainingWork": [] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [] }
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/failed-run.json b/packages/paperclip-runner/protocol/fixtures/phase-01/failed-run.json
new file mode 100644
index 00000000000..2b2aa167bd1
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/failed-run.json
@@ -0,0 +1,106 @@
+{
+  "schema": "paperclip.prp.fixture.v1",
+  "fixtureVersion": 1,
+  "protocolVersion": 1,
+  "name": "Failed run",
+  "description": "The driver reports an item and turn failure before the run terminalizes.",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_failed",
+    "runId": "run_phase1_failed",
+    "environmentLeaseId": "lease_phase1_failed",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_failed",
+    "driverSessionId": "driver_phase1_failed"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "new_per_run",
+    "driver": { "kind": "fake", "version": "1.0.0" },
+    "steer": true,
+    "interrupt": true,
+    "resume": true,
+    "runtimeRequests": true,
+    "structuredResult": true,
+    "typedEvents": true
+  },
+  "commands": [
+    {
+      "schema": "paperclip.prp.command.v1",
+      "commandId": "command_failed_prepare",
+      "controllerSeq": 1,
+      "type": "run.prepare",
+      "issuedAt": "2026-08-07T12:10:00.000Z",
+      "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.command.v1",
+      "commandId": "command_failed_turn",
+      "controllerSeq": 2,
+      "type": "turn.start",
+      "issuedAt": "2026-08-07T12:10:00.010Z",
+      "payload": { "text": "Run failing scenario" }
+    }
+  ],
+  "events": [
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_failed_01", "sourceSeq": 1,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_failed",
+      "normalizedSessionId": "session_phase1_failed", "eventType": "session.started", "schemaVersion": 1,
+      "priority": 0, "emittedAt": "2026-08-07T12:10:00.020Z", "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_failed_02", "sourceSeq": 2,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_failed",
+      "normalizedSessionId": "session_phase1_failed", "turnId": "turn_phase1_failed",
+      "eventType": "turn.started", "schemaVersion": 1, "priority": 1,
+      "emittedAt": "2026-08-07T12:10:00.030Z", "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_failed_03", "sourceSeq": 3,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_failed",
+      "normalizedSessionId": "session_phase1_failed", "turnId": "turn_phase1_failed", "itemId": "item_failed_command",
+      "eventType": "item.failed", "schemaVersion": 1, "priority": 0,
+      "emittedAt": "2026-08-07T12:10:00.040Z", "payload": { "kind": "command", "message": "Command exited with code 1" }
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_failed_04", "sourceSeq": 4,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_failed",
+      "normalizedSessionId": "session_phase1_failed", "turnId": "turn_phase1_failed",
+      "eventType": "run.result.proposed", "schemaVersion": 1, "priority": 0,
+      "emittedAt": "2026-08-07T12:10:00.050Z",
+      "payload": {
+        "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "yielded",
+        "summary": "The scripted command failed and needs a retry.",
+        "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": false, "criteria": [], "remainingWork": [{ "description": "Retry the failed command", "blocksCompletion": true }] },
+        "evidence": [], "verification": [{ "commandOrCheck": "fake command", "status": "failed" }],
+        "attentionRequests": [], "artifacts": [],
+        "continuation": { "kind": "retry", "summary": "Retry after correcting the command", "idempotencyKey": "retry_phase1_failed" }
+      }
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_failed_05", "sourceSeq": 5,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_failed",
+      "normalizedSessionId": "session_phase1_failed", "turnId": "turn_phase1_failed",
+      "eventType": "turn.failed", "schemaVersion": 1, "priority": 0,
+      "emittedAt": "2026-08-07T12:10:00.060Z", "payload": { "message": "Fake driver failure" }
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_failed_06", "sourceSeq": 6,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_failed",
+      "normalizedSessionId": "session_phase1_failed", "eventType": "run.terminal", "schemaVersion": 1,
+      "priority": 0, "emittedAt": "2026-08-07T12:10:00.070Z",
+      "payload": { "schema": "paperclip.prp.terminal.v1", "turnTerminalState": "failed", "runTerminalState": "failed", "reportedWorkDisposition": "yielded" }
+    }
+  ],
+  "requests": [],
+  "result": {
+    "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "yielded",
+    "summary": "The scripted command failed and needs a retry.",
+    "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": false, "criteria": [], "remainingWork": [{ "description": "Retry the failed command", "blocksCompletion": true }] },
+    "evidence": [], "verification": [{ "commandOrCheck": "fake command", "status": "failed" }],
+    "attentionRequests": [], "artifacts": [],
+    "continuation": { "kind": "retry", "summary": "Retry after correcting the command", "idempotencyKey": "retry_phase1_failed" }
+  }
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.snapshot.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.snapshot.json
new file mode 100644
index 00000000000..b16a5fbbf24
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.snapshot.json
@@ -0,0 +1,130 @@
+{
+  "schema": "paperclip.prp.session-snapshot.v1",
+  "fixtureName": "Duplicate event",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_duplicate",
+    "runId": "run_phase1_duplicate",
+    "environmentLeaseId": "lease_phase1_duplicate",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_duplicate",
+    "driverSessionId": "driver_phase1_duplicate"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "new_per_run",
+    "driver": {
+      "kind": "fake",
+      "version": "1.0.0"
+    },
+    "steer": false,
+    "interrupt": true,
+    "resume": true,
+    "runtimeRequests": false,
+    "structuredResult": true,
+    "typedEvents": true
+  },
+  "runPhase": "terminal",
+  "sessionState": "running",
+  "turnState": "completed",
+  "activeTurnId": null,
+  "items": [
+    {
+      "itemId": "item_phase1_duplicate",
+      "kind": "assistant_message",
+      "status": "completed",
+      "text": "Exactly one projection."
+    }
+  ],
+  "requests": [],
+  "proposedResult": {
+    "schema": "paperclip.run_result.v1",
+    "reportedWorkDisposition": "done",
+    "summary": "Duplicate delivery was idempotent.",
+    "completionClaim": {
+      "contractRevision": "phase1-contract-v1",
+      "objectiveSatisfied": true,
+      "criteria": [],
+      "remainingWork": []
+    },
+    "evidence": [],
+    "verification": [],
+    "attentionRequests": [],
+    "artifacts": []
+  },
+  "terminal": {
+    "schema": "paperclip.prp.terminal.v1",
+    "turnTerminalState": "completed",
+    "runTerminalState": "succeeded",
+    "reportedWorkDisposition": "done"
+  },
+  "timeline": [
+    {
+      "position": 1,
+      "sourceEventId": "event_duplicate_01",
+      "sourceSeq": 1,
+      "eventType": "session.started",
+      "emittedAt": "2026-08-07T12:30:00.010Z",
+      "summary": "session started"
+    },
+    {
+      "position": 2,
+      "sourceEventId": "event_duplicate_02",
+      "sourceSeq": 2,
+      "eventType": "turn.started",
+      "emittedAt": "2026-08-07T12:30:00.020Z",
+      "summary": "turn started"
+    },
+    {
+      "position": 3,
+      "sourceEventId": "event_duplicate_03",
+      "sourceSeq": 3,
+      "eventType": "item.completed",
+      "emittedAt": "2026-08-07T12:30:00.030Z",
+      "itemId": "item_phase1_duplicate",
+      "summary": "Completed assistant_message"
+    },
+    {
+      "position": 4,
+      "sourceEventId": "event_duplicate_04",
+      "sourceSeq": 4,
+      "eventType": "run.result.proposed",
+      "emittedAt": "2026-08-07T12:30:00.040Z",
+      "summary": "Duplicate delivery was idempotent."
+    },
+    {
+      "position": 5,
+      "sourceEventId": "event_duplicate_05",
+      "sourceSeq": 5,
+      "eventType": "turn.completed",
+      "emittedAt": "2026-08-07T12:30:00.050Z",
+      "summary": "turn completed"
+    },
+    {
+      "position": 6,
+      "sourceEventId": "event_duplicate_06",
+      "sourceSeq": 6,
+      "eventType": "run.terminal",
+      "emittedAt": "2026-08-07T12:30:00.060Z",
+      "summary": "Run succeeded"
+    }
+  ],
+  "sourceCursors": {
+    "runner:runner_phase1": 6
+  },
+  "processedEventIds": [
+    "event_duplicate_01",
+    "event_duplicate_02",
+    "event_duplicate_03",
+    "event_duplicate_04",
+    "event_duplicate_05",
+    "event_duplicate_06"
+  ],
+  "duplicateEventIds": [
+    "event_duplicate_03"
+  ],
+  "outOfOrderEventIds": [],
+  "gaps": [],
+  "integrity": "complete"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.summary.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.summary.json
new file mode 100644
index 00000000000..28616e9e3a0
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/duplicate-event.summary.json
@@ -0,0 +1,11 @@
+{
+  "runId": "run_phase1_duplicate",
+  "integrity": "complete",
+  "timelineCount": 6,
+  "duplicateEventIds": [
+    "event_duplicate_03"
+  ],
+  "gaps": [],
+  "turnTerminalState": "completed",
+  "runTerminalState": "succeeded"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.snapshot.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.snapshot.json
new file mode 100644
index 00000000000..4151a85207b
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.snapshot.json
@@ -0,0 +1,143 @@
+{
+  "schema": "paperclip.prp.session-snapshot.v1",
+  "fixtureName": "Failed run",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_failed",
+    "runId": "run_phase1_failed",
+    "environmentLeaseId": "lease_phase1_failed",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_failed",
+    "driverSessionId": "driver_phase1_failed"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "new_per_run",
+    "driver": {
+      "kind": "fake",
+      "version": "1.0.0"
+    },
+    "steer": true,
+    "interrupt": true,
+    "resume": true,
+    "runtimeRequests": true,
+    "structuredResult": true,
+    "typedEvents": true
+  },
+  "runPhase": "terminal",
+  "sessionState": "running",
+  "turnState": "failed",
+  "activeTurnId": null,
+  "items": [
+    {
+      "itemId": "item_failed_command",
+      "kind": "command",
+      "status": "failed",
+      "text": ""
+    }
+  ],
+  "requests": [],
+  "proposedResult": {
+    "schema": "paperclip.run_result.v1",
+    "reportedWorkDisposition": "yielded",
+    "summary": "The scripted command failed and needs a retry.",
+    "completionClaim": {
+      "contractRevision": "phase1-contract-v1",
+      "objectiveSatisfied": false,
+      "criteria": [],
+      "remainingWork": [
+        {
+          "description": "Retry the failed command",
+          "blocksCompletion": true
+        }
+      ]
+    },
+    "evidence": [],
+    "verification": [
+      {
+        "commandOrCheck": "fake command",
+        "status": "failed"
+      }
+    ],
+    "attentionRequests": [],
+    "artifacts": [],
+    "continuation": {
+      "kind": "retry",
+      "summary": "Retry after correcting the command",
+      "idempotencyKey": "retry_phase1_failed"
+    }
+  },
+  "terminal": {
+    "schema": "paperclip.prp.terminal.v1",
+    "turnTerminalState": "failed",
+    "runTerminalState": "failed",
+    "reportedWorkDisposition": "yielded"
+  },
+  "timeline": [
+    {
+      "position": 1,
+      "sourceEventId": "event_failed_01",
+      "sourceSeq": 1,
+      "eventType": "session.started",
+      "emittedAt": "2026-08-07T12:10:00.020Z",
+      "summary": "session started"
+    },
+    {
+      "position": 2,
+      "sourceEventId": "event_failed_02",
+      "sourceSeq": 2,
+      "eventType": "turn.started",
+      "emittedAt": "2026-08-07T12:10:00.030Z",
+      "summary": "turn started"
+    },
+    {
+      "position": 3,
+      "sourceEventId": "event_failed_03",
+      "sourceSeq": 3,
+      "eventType": "item.failed",
+      "emittedAt": "2026-08-07T12:10:00.040Z",
+      "itemId": "item_failed_command",
+      "summary": "Command exited with code 1"
+    },
+    {
+      "position": 4,
+      "sourceEventId": "event_failed_04",
+      "sourceSeq": 4,
+      "eventType": "run.result.proposed",
+      "emittedAt": "2026-08-07T12:10:00.050Z",
+      "summary": "The scripted command failed and needs a retry."
+    },
+    {
+      "position": 5,
+      "sourceEventId": "event_failed_05",
+      "sourceSeq": 5,
+      "eventType": "turn.failed",
+      "emittedAt": "2026-08-07T12:10:00.060Z",
+      "summary": "turn failed"
+    },
+    {
+      "position": 6,
+      "sourceEventId": "event_failed_06",
+      "sourceSeq": 6,
+      "eventType": "run.terminal",
+      "emittedAt": "2026-08-07T12:10:00.070Z",
+      "summary": "Run failed"
+    }
+  ],
+  "sourceCursors": {
+    "runner:runner_phase1": 6
+  },
+  "processedEventIds": [
+    "event_failed_01",
+    "event_failed_02",
+    "event_failed_03",
+    "event_failed_04",
+    "event_failed_05",
+    "event_failed_06"
+  ],
+  "duplicateEventIds": [],
+  "outOfOrderEventIds": [],
+  "gaps": [],
+  "integrity": "complete"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.summary.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.summary.json
new file mode 100644
index 00000000000..05013879af3
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/failed-run.summary.json
@@ -0,0 +1,9 @@
+{
+  "runId": "run_phase1_failed",
+  "integrity": "complete",
+  "timelineCount": 6,
+  "duplicateEventIds": [],
+  "gaps": [],
+  "turnTerminalState": "failed",
+  "runTerminalState": "failed"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.snapshot.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.snapshot.json
new file mode 100644
index 00000000000..f19c4146659
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.snapshot.json
@@ -0,0 +1,166 @@
+{
+  "schema": "paperclip.prp.session-snapshot.v1",
+  "fixtureName": "Happy path",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_happy",
+    "runId": "run_phase1_happy",
+    "environmentLeaseId": "lease_phase1_happy",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_happy",
+    "driverSessionId": "driver_phase1_happy",
+    "providerSessionId": "provider_phase1_happy"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "new_per_run",
+    "driver": {
+      "kind": "fake",
+      "version": "1.0.0"
+    },
+    "steer": true,
+    "interrupt": true,
+    "resume": true,
+    "runtimeRequests": true,
+    "structuredResult": true,
+    "typedEvents": true,
+    "unsupported": []
+  },
+  "runPhase": "terminal",
+  "sessionState": "running",
+  "turnState": "completed",
+  "activeTurnId": null,
+  "items": [
+    {
+      "itemId": "item_phase1_message",
+      "kind": "assistant_message",
+      "status": "completed",
+      "text": "Validated fixture. Replay complete."
+    }
+  ],
+  "requests": [],
+  "proposedResult": {
+    "schema": "paperclip.run_result.v1",
+    "reportedWorkDisposition": "done",
+    "summary": "The scripted run completed successfully.",
+    "completionClaim": {
+      "contractRevision": "phase1-contract-v1",
+      "objectiveSatisfied": true,
+      "criteria": [],
+      "remainingWork": []
+    },
+    "evidence": [],
+    "verification": [
+      {
+        "commandOrCheck": "fixture replay",
+        "status": "passed"
+      }
+    ],
+    "attentionRequests": [],
+    "artifacts": []
+  },
+  "terminal": {
+    "schema": "paperclip.prp.terminal.v1",
+    "turnTerminalState": "completed",
+    "runTerminalState": "succeeded",
+    "reportedWorkDisposition": "done",
+    "workAssessmentId": "assessment_phase1_happy",
+    "statusDecisionId": "decision_phase1_happy"
+  },
+  "timeline": [
+    {
+      "position": 1,
+      "sourceEventId": "event_happy_01",
+      "sourceSeq": 1,
+      "eventType": "runtime.phase.changed",
+      "emittedAt": "2026-08-07T12:00:00.030Z",
+      "summary": "Phase changed to workspace_preparing"
+    },
+    {
+      "position": 2,
+      "sourceEventId": "event_happy_02",
+      "sourceSeq": 2,
+      "eventType": "session.started",
+      "emittedAt": "2026-08-07T12:00:00.040Z",
+      "summary": "session started"
+    },
+    {
+      "position": 3,
+      "sourceEventId": "event_happy_03",
+      "sourceSeq": 3,
+      "eventType": "turn.started",
+      "emittedAt": "2026-08-07T12:00:00.050Z",
+      "summary": "turn started"
+    },
+    {
+      "position": 4,
+      "sourceEventId": "event_happy_04",
+      "sourceSeq": 4,
+      "eventType": "item.started",
+      "emittedAt": "2026-08-07T12:00:00.060Z",
+      "itemId": "item_phase1_message",
+      "summary": "Started assistant_message"
+    },
+    {
+      "position": 5,
+      "sourceEventId": "event_happy_05",
+      "sourceSeq": 5,
+      "eventType": "item.delta",
+      "emittedAt": "2026-08-07T12:00:00.070Z",
+      "itemId": "item_phase1_message",
+      "summary": "Validated fixture. "
+    },
+    {
+      "position": 6,
+      "sourceEventId": "event_happy_06",
+      "sourceSeq": 6,
+      "eventType": "item.completed",
+      "emittedAt": "2026-08-07T12:00:00.080Z",
+      "itemId": "item_phase1_message",
+      "summary": "Completed assistant_message"
+    },
+    {
+      "position": 7,
+      "sourceEventId": "event_happy_07",
+      "sourceSeq": 7,
+      "eventType": "run.result.proposed",
+      "emittedAt": "2026-08-07T12:00:00.090Z",
+      "summary": "The scripted run completed successfully."
+    },
+    {
+      "position": 8,
+      "sourceEventId": "event_happy_08",
+      "sourceSeq": 8,
+      "eventType": "turn.completed",
+      "emittedAt": "2026-08-07T12:00:00.100Z",
+      "summary": "turn completed"
+    },
+    {
+      "position": 9,
+      "sourceEventId": "event_happy_09",
+      "sourceSeq": 9,
+      "eventType": "run.terminal",
+      "emittedAt": "2026-08-07T12:00:00.110Z",
+      "summary": "Run succeeded"
+    }
+  ],
+  "sourceCursors": {
+    "runner:runner_phase1": 9
+  },
+  "processedEventIds": [
+    "event_happy_01",
+    "event_happy_02",
+    "event_happy_03",
+    "event_happy_04",
+    "event_happy_05",
+    "event_happy_06",
+    "event_happy_07",
+    "event_happy_08",
+    "event_happy_09"
+  ],
+  "duplicateEventIds": [],
+  "outOfOrderEventIds": [],
+  "gaps": [],
+  "integrity": "complete"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.summary.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.summary.json
new file mode 100644
index 00000000000..913d0d7d075
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/happy-path.summary.json
@@ -0,0 +1,9 @@
+{
+  "runId": "run_phase1_happy",
+  "integrity": "complete",
+  "timelineCount": 9,
+  "duplicateEventIds": [],
+  "gaps": [],
+  "turnTerminalState": "completed",
+  "runTerminalState": "succeeded"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.snapshot.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.snapshot.json
new file mode 100644
index 00000000000..c2f9f55ecf2
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.snapshot.json
@@ -0,0 +1,137 @@
+{
+  "schema": "paperclip.prp.session-snapshot.v1",
+  "fixtureName": "Interrupted run",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_interrupted",
+    "runId": "run_phase1_interrupted",
+    "environmentLeaseId": "lease_phase1_interrupted",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_interrupted",
+    "driverSessionId": "driver_phase1_interrupted"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "reuse_per_issue",
+    "driver": {
+      "kind": "fake",
+      "version": "1.0.0"
+    },
+    "steer": true,
+    "interrupt": true,
+    "resume": true,
+    "runtimeRequests": true,
+    "structuredResult": true,
+    "typedEvents": true
+  },
+  "runPhase": "terminal",
+  "sessionState": "running",
+  "turnState": "interrupted",
+  "activeTurnId": null,
+  "items": [],
+  "requests": [
+    {
+      "requestId": "request_interrupted_permission",
+      "requestKind": "runtime",
+      "status": "pending",
+      "prompt": "Allow the fake command?"
+    }
+  ],
+  "proposedResult": {
+    "schema": "paperclip.run_result.v1",
+    "reportedWorkDisposition": "yielded",
+    "summary": "The turn was interrupted.",
+    "completionClaim": {
+      "contractRevision": "phase1-contract-v1",
+      "objectiveSatisfied": false,
+      "criteria": [],
+      "remainingWork": [
+        {
+          "description": "Resume the interrupted turn",
+          "blocksCompletion": true
+        }
+      ]
+    },
+    "evidence": [],
+    "verification": [],
+    "attentionRequests": [],
+    "artifacts": [],
+    "continuation": {
+      "kind": "same_agent",
+      "summary": "Resume in the same normalized session",
+      "idempotencyKey": "resume_phase1_interrupted"
+    }
+  },
+  "terminal": {
+    "schema": "paperclip.prp.terminal.v1",
+    "turnTerminalState": "interrupted",
+    "runTerminalState": "cancelled",
+    "reportedWorkDisposition": "yielded"
+  },
+  "timeline": [
+    {
+      "position": 1,
+      "sourceEventId": "event_interrupted_01",
+      "sourceSeq": 1,
+      "eventType": "session.started",
+      "emittedAt": "2026-08-07T12:20:00.020Z",
+      "summary": "session started"
+    },
+    {
+      "position": 2,
+      "sourceEventId": "event_interrupted_02",
+      "sourceSeq": 2,
+      "eventType": "turn.started",
+      "emittedAt": "2026-08-07T12:20:00.030Z",
+      "summary": "turn started"
+    },
+    {
+      "position": 3,
+      "sourceEventId": "event_interrupted_03",
+      "sourceSeq": 3,
+      "eventType": "runtime_request.created",
+      "emittedAt": "2026-08-07T12:20:00.040Z",
+      "summary": "runtime_request created"
+    },
+    {
+      "position": 4,
+      "sourceEventId": "event_interrupted_04",
+      "sourceSeq": 4,
+      "eventType": "turn.interrupted",
+      "emittedAt": "2026-08-07T12:20:00.060Z",
+      "summary": "turn interrupted"
+    },
+    {
+      "position": 5,
+      "sourceEventId": "event_interrupted_05",
+      "sourceSeq": 5,
+      "eventType": "run.result.proposed",
+      "emittedAt": "2026-08-07T12:20:00.070Z",
+      "summary": "The turn was interrupted."
+    },
+    {
+      "position": 6,
+      "sourceEventId": "event_interrupted_06",
+      "sourceSeq": 6,
+      "eventType": "run.terminal",
+      "emittedAt": "2026-08-07T12:20:00.080Z",
+      "summary": "Run cancelled"
+    }
+  ],
+  "sourceCursors": {
+    "runner:runner_phase1": 6
+  },
+  "processedEventIds": [
+    "event_interrupted_01",
+    "event_interrupted_02",
+    "event_interrupted_03",
+    "event_interrupted_04",
+    "event_interrupted_05",
+    "event_interrupted_06"
+  ],
+  "duplicateEventIds": [],
+  "outOfOrderEventIds": [],
+  "gaps": [],
+  "integrity": "complete"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.summary.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.summary.json
new file mode 100644
index 00000000000..f0bd9da2f01
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/interrupted-run.summary.json
@@ -0,0 +1,9 @@
+{
+  "runId": "run_phase1_interrupted",
+  "integrity": "complete",
+  "timelineCount": 6,
+  "duplicateEventIds": [],
+  "gaps": [],
+  "turnTerminalState": "interrupted",
+  "runTerminalState": "cancelled"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.snapshot.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.snapshot.json
new file mode 100644
index 00000000000..fe8e12a8dd2
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.snapshot.json
@@ -0,0 +1,125 @@
+{
+  "schema": "paperclip.prp.session-snapshot.v1",
+  "fixtureName": "Source sequence gap",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_gap",
+    "runId": "run_phase1_gap",
+    "environmentLeaseId": "lease_phase1_gap",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_gap",
+    "driverSessionId": "driver_phase1_gap"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "new_per_run",
+    "driver": {
+      "kind": "fake",
+      "version": "1.0.0"
+    },
+    "steer": false,
+    "interrupt": false,
+    "resume": true,
+    "runtimeRequests": false,
+    "structuredResult": true,
+    "typedEvents": true
+  },
+  "runPhase": "terminal",
+  "sessionState": "running",
+  "turnState": "completed",
+  "activeTurnId": null,
+  "items": [],
+  "requests": [],
+  "proposedResult": {
+    "schema": "paperclip.run_result.v1",
+    "reportedWorkDisposition": "needs_review",
+    "summary": "The source gap requires reconciliation.",
+    "completionClaim": {
+      "contractRevision": "phase1-contract-v1",
+      "objectiveSatisfied": false,
+      "criteria": [],
+      "remainingWork": [
+        {
+          "description": "Replay missing source event",
+          "blocksCompletion": true
+        }
+      ]
+    },
+    "evidence": [],
+    "verification": [],
+    "attentionRequests": [],
+    "artifacts": []
+  },
+  "terminal": {
+    "schema": "paperclip.prp.terminal.v1",
+    "turnTerminalState": "completed",
+    "runTerminalState": "succeeded",
+    "reportedWorkDisposition": "needs_review"
+  },
+  "timeline": [
+    {
+      "position": 1,
+      "sourceEventId": "event_gap_01",
+      "sourceSeq": 1,
+      "eventType": "session.started",
+      "emittedAt": "2026-08-07T12:40:00.010Z",
+      "summary": "session started"
+    },
+    {
+      "position": 2,
+      "sourceEventId": "event_gap_02",
+      "sourceSeq": 2,
+      "eventType": "turn.started",
+      "emittedAt": "2026-08-07T12:40:00.020Z",
+      "summary": "turn started"
+    },
+    {
+      "position": 3,
+      "sourceEventId": "event_gap_04",
+      "sourceSeq": 4,
+      "eventType": "run.result.proposed",
+      "emittedAt": "2026-08-07T12:40:00.040Z",
+      "summary": "The source gap requires reconciliation."
+    },
+    {
+      "position": 4,
+      "sourceEventId": "event_gap_05",
+      "sourceSeq": 5,
+      "eventType": "turn.completed",
+      "emittedAt": "2026-08-07T12:40:00.050Z",
+      "summary": "turn completed"
+    },
+    {
+      "position": 5,
+      "sourceEventId": "event_gap_06",
+      "sourceSeq": 6,
+      "eventType": "run.terminal",
+      "emittedAt": "2026-08-07T12:40:00.060Z",
+      "summary": "Run succeeded"
+    }
+  ],
+  "sourceCursors": {
+    "runner:runner_phase1": 6
+  },
+  "processedEventIds": [
+    "event_gap_01",
+    "event_gap_02",
+    "event_gap_04",
+    "event_gap_05",
+    "event_gap_06"
+  ],
+  "duplicateEventIds": [],
+  "outOfOrderEventIds": [],
+  "gaps": [
+    {
+      "sourceKey": "runner:runner_phase1",
+      "expected": 3,
+      "received": 4,
+      "missing": [
+        3
+      ]
+    }
+  ],
+  "integrity": "gap_detected"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.summary.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.summary.json
new file mode 100644
index 00000000000..ec1ff0a6484
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/source-gap.summary.json
@@ -0,0 +1,18 @@
+{
+  "runId": "run_phase1_gap",
+  "integrity": "gap_detected",
+  "timelineCount": 5,
+  "duplicateEventIds": [],
+  "gaps": [
+    {
+      "sourceKey": "runner:runner_phase1",
+      "expected": 3,
+      "received": 4,
+      "missing": [
+        3
+      ]
+    }
+  ],
+  "turnTerminalState": "completed",
+  "runTerminalState": "succeeded"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.snapshot.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.snapshot.json
new file mode 100644
index 00000000000..1627a30b120
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.snapshot.json
@@ -0,0 +1,111 @@
+{
+  "schema": "paperclip.prp.session-snapshot.v1",
+  "fixtureName": "Unknown optional fields",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_future",
+    "runId": "run_phase1_future",
+    "environmentLeaseId": "lease_phase1_future",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_future",
+    "driverSessionId": "driver_phase1_future",
+    "futureIdentityLabel": "preserved"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "new_per_run",
+    "driver": {
+      "kind": "fake",
+      "version": "1.1.0",
+      "futureDriverField": true
+    },
+    "steer": true,
+    "interrupt": true,
+    "resume": true,
+    "runtimeRequests": true,
+    "structuredResult": true,
+    "typedEvents": true,
+    "futureCapability": {
+      "mode": "optional"
+    }
+  },
+  "runPhase": "terminal",
+  "sessionState": "running",
+  "turnState": "completed",
+  "activeTurnId": null,
+  "items": [],
+  "requests": [],
+  "proposedResult": {
+    "schema": "paperclip.run_result.v1",
+    "reportedWorkDisposition": "done",
+    "summary": "Unknown optional fields did not change the v1 projection.",
+    "completionClaim": {
+      "contractRevision": "phase1-contract-v1",
+      "objectiveSatisfied": true,
+      "criteria": [],
+      "remainingWork": []
+    },
+    "evidence": [],
+    "verification": [],
+    "attentionRequests": [],
+    "artifacts": [],
+    "futureResultAnnotation": {
+      "safe": true
+    }
+  },
+  "terminal": {
+    "schema": "paperclip.prp.terminal.v1",
+    "turnTerminalState": "completed",
+    "runTerminalState": "succeeded",
+    "reportedWorkDisposition": "done",
+    "futureTerminalReason": "optional"
+  },
+  "timeline": [
+    {
+      "position": 1,
+      "sourceEventId": "event_future_01",
+      "sourceSeq": 1,
+      "eventType": "session.started",
+      "emittedAt": "2026-08-07T12:50:00.010Z",
+      "summary": "session started"
+    },
+    {
+      "position": 2,
+      "sourceEventId": "event_future_02",
+      "sourceSeq": 2,
+      "eventType": "run.result.proposed",
+      "emittedAt": "2026-08-07T12:50:00.020Z",
+      "summary": "Unknown optional fields did not change the v1 projection."
+    },
+    {
+      "position": 3,
+      "sourceEventId": "event_future_03",
+      "sourceSeq": 3,
+      "eventType": "turn.completed",
+      "emittedAt": "2026-08-07T12:50:00.030Z",
+      "summary": "turn completed"
+    },
+    {
+      "position": 4,
+      "sourceEventId": "event_future_04",
+      "sourceSeq": 4,
+      "eventType": "run.terminal",
+      "emittedAt": "2026-08-07T12:50:00.040Z",
+      "summary": "Run succeeded"
+    }
+  ],
+  "sourceCursors": {
+    "runner:runner_phase1": 4
+  },
+  "processedEventIds": [
+    "event_future_01",
+    "event_future_02",
+    "event_future_03",
+    "event_future_04"
+  ],
+  "duplicateEventIds": [],
+  "outOfOrderEventIds": [],
+  "gaps": [],
+  "integrity": "complete"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.summary.json b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.summary.json
new file mode 100644
index 00000000000..c8d98d53165
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/golden/unknown-optional-fields.summary.json
@@ -0,0 +1,9 @@
+{
+  "runId": "run_phase1_future",
+  "integrity": "complete",
+  "timelineCount": 4,
+  "duplicateEventIds": [],
+  "gaps": [],
+  "turnTerminalState": "completed",
+  "runTerminalState": "succeeded"
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/happy-path.json b/packages/paperclip-runner/protocol/fixtures/phase-01/happy-path.json
new file mode 100644
index 00000000000..934f1dc54f2
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/happy-path.json
@@ -0,0 +1,230 @@
+{
+  "schema": "paperclip.prp.fixture.v1",
+  "fixtureVersion": 1,
+  "protocolVersion": 1,
+  "name": "Happy path",
+  "description": "A typed assistant message completes and the run proposes a successful result.",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1",
+    "companyId": "company_phase1",
+    "issueId": "issue_phase1_happy",
+    "runId": "run_phase1_happy",
+    "environmentLeaseId": "lease_phase1_happy",
+    "runnerInstanceId": "runner_phase1",
+    "normalizedSessionId": "session_phase1_happy",
+    "driverSessionId": "driver_phase1_happy",
+    "providerSessionId": "provider_phase1_happy"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1",
+    "sessionReusePolicy": "new_per_run",
+    "driver": { "kind": "fake", "version": "1.0.0" },
+    "steer": true,
+    "interrupt": true,
+    "resume": true,
+    "runtimeRequests": true,
+    "structuredResult": true,
+    "typedEvents": true,
+    "unsupported": []
+  },
+  "commands": [
+    {
+      "schema": "paperclip.prp.command.v1",
+      "commandId": "command_happy_prepare",
+      "controllerSeq": 1,
+      "type": "run.prepare",
+      "issuedAt": "2026-08-07T12:00:00.000Z",
+      "payload": { "workspace": "fixture" }
+    },
+    {
+      "schema": "paperclip.prp.command.v1",
+      "commandId": "command_happy_session",
+      "controllerSeq": 2,
+      "type": "session.open",
+      "issuedAt": "2026-08-07T12:00:00.010Z",
+      "payload": { "reuse": "new_per_run" }
+    },
+    {
+      "schema": "paperclip.prp.command.v1",
+      "commandId": "command_happy_turn",
+      "controllerSeq": 3,
+      "type": "turn.start",
+      "issuedAt": "2026-08-07T12:00:00.020Z",
+      "payload": { "text": "Inspect the fixture" }
+    }
+  ],
+  "events": [
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_01",
+      "sourceSeq": 1,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "eventType": "runtime.phase.changed",
+      "schemaVersion": 1,
+      "priority": 1,
+      "emittedAt": "2026-08-07T12:00:00.030Z",
+      "payload": { "phase": "workspace_preparing" }
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_02",
+      "sourceSeq": 2,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "eventType": "session.started",
+      "schemaVersion": 1,
+      "priority": 0,
+      "emittedAt": "2026-08-07T12:00:00.040Z",
+      "payload": { "driverSessionId": "driver_phase1_happy" }
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_03",
+      "sourceSeq": 3,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "turnId": "turn_phase1_happy",
+      "eventType": "turn.started",
+      "schemaVersion": 1,
+      "priority": 1,
+      "emittedAt": "2026-08-07T12:00:00.050Z",
+      "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_04",
+      "sourceSeq": 4,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "turnId": "turn_phase1_happy",
+      "itemId": "item_phase1_message",
+      "eventType": "item.started",
+      "schemaVersion": 1,
+      "priority": 1,
+      "emittedAt": "2026-08-07T12:00:00.060Z",
+      "payload": { "kind": "assistant_message", "text": "" }
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_05",
+      "sourceSeq": 5,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "turnId": "turn_phase1_happy",
+      "itemId": "item_phase1_message",
+      "eventType": "item.delta",
+      "schemaVersion": 1,
+      "priority": 2,
+      "emittedAt": "2026-08-07T12:00:00.070Z",
+      "payload": { "text": "Validated fixture. " }
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_06",
+      "sourceSeq": 6,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "turnId": "turn_phase1_happy",
+      "itemId": "item_phase1_message",
+      "eventType": "item.completed",
+      "schemaVersion": 1,
+      "priority": 1,
+      "emittedAt": "2026-08-07T12:00:00.080Z",
+      "payload": { "kind": "assistant_message", "text": "Validated fixture. Replay complete." }
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_07",
+      "sourceSeq": 7,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "turnId": "turn_phase1_happy",
+      "eventType": "run.result.proposed",
+      "schemaVersion": 1,
+      "priority": 0,
+      "emittedAt": "2026-08-07T12:00:00.090Z",
+      "payload": {
+        "schema": "paperclip.run_result.v1",
+        "reportedWorkDisposition": "done",
+        "summary": "The scripted run completed successfully.",
+        "completionClaim": {
+          "contractRevision": "phase1-contract-v1",
+          "objectiveSatisfied": true,
+          "criteria": [],
+          "remainingWork": []
+        },
+        "evidence": [],
+        "verification": [{ "commandOrCheck": "fixture replay", "status": "passed" }],
+        "attentionRequests": [],
+        "artifacts": []
+      }
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_08",
+      "sourceSeq": 8,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "turnId": "turn_phase1_happy",
+      "eventType": "turn.completed",
+      "schemaVersion": 1,
+      "priority": 0,
+      "emittedAt": "2026-08-07T12:00:00.100Z",
+      "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.event.v1",
+      "sourceEventId": "event_happy_09",
+      "sourceSeq": 9,
+      "sourceInstanceId": "runner_phase1",
+      "sourceKind": "runner",
+      "runId": "run_phase1_happy",
+      "normalizedSessionId": "session_phase1_happy",
+      "eventType": "run.terminal",
+      "schemaVersion": 1,
+      "priority": 0,
+      "emittedAt": "2026-08-07T12:00:00.110Z",
+      "payload": {
+        "schema": "paperclip.prp.terminal.v1",
+        "turnTerminalState": "completed",
+        "runTerminalState": "succeeded",
+        "reportedWorkDisposition": "done",
+        "workAssessmentId": "assessment_phase1_happy",
+        "statusDecisionId": "decision_phase1_happy"
+      }
+    }
+  ],
+  "requests": [],
+  "result": {
+    "schema": "paperclip.run_result.v1",
+    "reportedWorkDisposition": "done",
+    "summary": "The scripted run completed successfully.",
+    "completionClaim": {
+      "contractRevision": "phase1-contract-v1",
+      "objectiveSatisfied": true,
+      "criteria": [],
+      "remainingWork": []
+    },
+    "evidence": [],
+    "verification": [{ "commandOrCheck": "fixture replay", "status": "passed" }],
+    "attentionRequests": [],
+    "artifacts": []
+  }
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/interrupted-run.json b/packages/paperclip-runner/protocol/fixtures/phase-01/interrupted-run.json
new file mode 100644
index 00000000000..ea82a42085a
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/interrupted-run.json
@@ -0,0 +1,90 @@
+{
+  "schema": "paperclip.prp.fixture.v1",
+  "fixtureVersion": 1,
+  "protocolVersion": 1,
+  "name": "Interrupted run",
+  "description": "A pending runtime permission request is followed by an explicit turn interruption.",
+  "identity": {
+    "schema": "paperclip.prp.identity.v1", "companyId": "company_phase1", "issueId": "issue_phase1_interrupted",
+    "runId": "run_phase1_interrupted", "environmentLeaseId": "lease_phase1_interrupted",
+    "runnerInstanceId": "runner_phase1", "normalizedSessionId": "session_phase1_interrupted",
+    "driverSessionId": "driver_phase1_interrupted"
+  },
+  "capabilities": {
+    "schema": "paperclip.prp.capabilities.v1", "sessionReusePolicy": "reuse_per_issue",
+    "driver": { "kind": "fake", "version": "1.0.0" }, "steer": true, "interrupt": true,
+    "resume": true, "runtimeRequests": true, "structuredResult": true, "typedEvents": true
+  },
+  "commands": [
+    {
+      "schema": "paperclip.prp.command.v1", "commandId": "command_interrupted_prepare", "controllerSeq": 1,
+      "type": "run.prepare", "issuedAt": "2026-08-07T12:20:00.000Z", "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.command.v1", "commandId": "command_interrupted_turn", "controllerSeq": 2,
+      "type": "turn.start", "issuedAt": "2026-08-07T12:20:00.010Z", "payload": { "text": "Wait for interruption" }
+    },
+    {
+      "schema": "paperclip.prp.command.v1", "commandId": "command_interrupted_interrupt", "controllerSeq": 3,
+      "type": "turn.interrupt", "issuedAt": "2026-08-07T12:20:00.050Z", "payload": { "reason": "operator" }
+    }
+  ],
+  "events": [
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_interrupted_01", "sourceSeq": 1,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_interrupted",
+      "normalizedSessionId": "session_phase1_interrupted", "eventType": "session.started", "schemaVersion": 1,
+      "priority": 0, "emittedAt": "2026-08-07T12:20:00.020Z", "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_interrupted_02", "sourceSeq": 2,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_interrupted",
+      "normalizedSessionId": "session_phase1_interrupted", "turnId": "turn_phase1_interrupted",
+      "eventType": "turn.started", "schemaVersion": 1, "priority": 1,
+      "emittedAt": "2026-08-07T12:20:00.030Z", "payload": {}
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_interrupted_03", "sourceSeq": 3,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_interrupted",
+      "normalizedSessionId": "session_phase1_interrupted", "turnId": "turn_phase1_interrupted",
+      "eventType": "runtime_request.created", "schemaVersion": 1, "priority": 0,
+      "emittedAt": "2026-08-07T12:20:00.040Z",
+      "payload": { "request": { "schema": "paperclip.runtime_request.v1", "requestKind": "runtime", "requestId": "request_interrupted_permission", "type": "permission", "status": "pending", "prompt": "Allow the fake command?" } }
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_interrupted_04", "sourceSeq": 4,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_interrupted",
+      "normalizedSessionId": "session_phase1_interrupted", "turnId": "turn_phase1_interrupted",
+      "eventType": "turn.interrupted", "schemaVersion": 1, "priority": 0,
+      "emittedAt": "2026-08-07T12:20:00.060Z", "payload": { "reason": "operator" }
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_interrupted_05", "sourceSeq": 5,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_interrupted",
+      "normalizedSessionId": "session_phase1_interrupted", "eventType": "run.result.proposed", "schemaVersion": 1,
+      "priority": 0, "emittedAt": "2026-08-07T12:20:00.070Z",
+      "payload": {
+        "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "yielded", "summary": "The turn was interrupted.",
+        "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": false, "criteria": [], "remainingWork": [{ "description": "Resume the interrupted turn", "blocksCompletion": true }] },
+        "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [],
+        "continuation": { "kind": "same_agent", "summary": "Resume in the same normalized session", "idempotencyKey": "resume_phase1_interrupted" }
+      }
+    },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_interrupted_06", "sourceSeq": 6,
+      "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_interrupted",
+      "normalizedSessionId": "session_phase1_interrupted", "eventType": "run.terminal", "schemaVersion": 1,
+      "priority": 0, "emittedAt": "2026-08-07T12:20:00.080Z",
+      "payload": { "schema": "paperclip.prp.terminal.v1", "turnTerminalState": "interrupted", "runTerminalState": "cancelled", "reportedWorkDisposition": "yielded" }
+    }
+  ],
+  "requests": [
+    { "schema": "paperclip.runtime_request.v1", "requestKind": "runtime", "requestId": "request_interrupted_permission", "type": "permission", "status": "pending", "prompt": "Allow the fake command?" }
+  ],
+  "result": {
+    "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "yielded", "summary": "The turn was interrupted.",
+    "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": false, "criteria": [], "remainingWork": [{ "description": "Resume the interrupted turn", "blocksCompletion": true }] },
+    "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [],
+    "continuation": { "kind": "same_agent", "summary": "Resume in the same normalized session", "idempotencyKey": "resume_phase1_interrupted" }
+  }
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/source-gap.json b/packages/paperclip-runner/protocol/fixtures/phase-01/source-gap.json
new file mode 100644
index 00000000000..8f20a862e7b
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/source-gap.json
@@ -0,0 +1,19 @@
+{
+  "schema": "paperclip.prp.fixture.v1", "fixtureVersion": 1, "protocolVersion": 1,
+  "name": "Source sequence gap", "description": "The runner stream skips source sequence 3 and replay records the missing cursor.",
+  "identity": { "schema": "paperclip.prp.identity.v1", "companyId": "company_phase1", "issueId": "issue_phase1_gap", "runId": "run_phase1_gap", "environmentLeaseId": "lease_phase1_gap", "runnerInstanceId": "runner_phase1", "normalizedSessionId": "session_phase1_gap", "driverSessionId": "driver_phase1_gap" },
+  "capabilities": { "schema": "paperclip.prp.capabilities.v1", "sessionReusePolicy": "new_per_run", "driver": { "kind": "fake", "version": "1.0.0" }, "steer": false, "interrupt": false, "resume": true, "runtimeRequests": false, "structuredResult": true, "typedEvents": true },
+  "commands": [{ "schema": "paperclip.prp.command.v1", "commandId": "command_gap_prepare", "controllerSeq": 1, "type": "run.prepare", "issuedAt": "2026-08-07T12:40:00.000Z", "payload": {} }],
+  "events": [
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_gap_01", "sourceSeq": 1, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_gap", "normalizedSessionId": "session_phase1_gap", "eventType": "session.started", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:40:00.010Z", "payload": {} },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_gap_02", "sourceSeq": 2, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_gap", "normalizedSessionId": "session_phase1_gap", "turnId": "turn_phase1_gap", "eventType": "turn.started", "schemaVersion": 1, "priority": 1, "emittedAt": "2026-08-07T12:40:00.020Z", "payload": {} },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_gap_04", "sourceSeq": 4, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_gap", "normalizedSessionId": "session_phase1_gap", "eventType": "run.result.proposed", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:40:00.040Z",
+      "payload": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "needs_review", "summary": "The source gap requires reconciliation.", "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": false, "criteria": [], "remainingWork": [{ "description": "Replay missing source event", "blocksCompletion": true }] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [] }
+    },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_gap_05", "sourceSeq": 5, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_gap", "normalizedSessionId": "session_phase1_gap", "turnId": "turn_phase1_gap", "eventType": "turn.completed", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:40:00.050Z", "payload": {} },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_gap_06", "sourceSeq": 6, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_gap", "normalizedSessionId": "session_phase1_gap", "eventType": "run.terminal", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:40:00.060Z", "payload": { "schema": "paperclip.prp.terminal.v1", "turnTerminalState": "completed", "runTerminalState": "succeeded", "reportedWorkDisposition": "needs_review" } }
+  ],
+  "requests": [],
+  "result": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "needs_review", "summary": "The source gap requires reconciliation.", "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": false, "criteria": [], "remainingWork": [{ "description": "Replay missing source event", "blocksCompletion": true }] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [] }
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/unknown-optional-fields.json b/packages/paperclip-runner/protocol/fixtures/phase-01/unknown-optional-fields.json
new file mode 100644
index 00000000000..911627b4138
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/unknown-optional-fields.json
@@ -0,0 +1,19 @@
+{
+  "schema": "paperclip.prp.fixture.v1", "fixtureVersion": 1, "protocolVersion": 1,
+  "name": "Unknown optional fields", "description": "A future producer adds optional fields that a PRP v1 consumer preserves and ignores safely.",
+  "futureFixtureHint": { "producerVersion": "1.1-preview" },
+  "identity": { "schema": "paperclip.prp.identity.v1", "companyId": "company_phase1", "issueId": "issue_phase1_future", "runId": "run_phase1_future", "environmentLeaseId": "lease_phase1_future", "runnerInstanceId": "runner_phase1", "normalizedSessionId": "session_phase1_future", "driverSessionId": "driver_phase1_future", "futureIdentityLabel": "preserved" },
+  "capabilities": { "schema": "paperclip.prp.capabilities.v1", "sessionReusePolicy": "new_per_run", "driver": { "kind": "fake", "version": "1.1.0", "futureDriverField": true }, "steer": true, "interrupt": true, "resume": true, "runtimeRequests": true, "structuredResult": true, "typedEvents": true, "futureCapability": { "mode": "optional" } },
+  "commands": [{ "schema": "paperclip.prp.command.v1", "commandId": "command_future_prepare", "controllerSeq": 1, "type": "run.prepare", "issuedAt": "2026-08-07T12:50:00.000Z", "payload": {}, "futureDeadlineMode": "soft" }],
+  "events": [
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_future_01", "sourceSeq": 1, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_future", "normalizedSessionId": "session_phase1_future", "eventType": "session.started", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:50:00.010Z", "payload": { "futureSessionDetail": "ignored" }, "futureEnvelopeField": 42 },
+    {
+      "schema": "paperclip.prp.event.v1", "sourceEventId": "event_future_02", "sourceSeq": 2, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_future", "normalizedSessionId": "session_phase1_future", "eventType": "run.result.proposed", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:50:00.020Z",
+      "payload": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "done", "summary": "Unknown optional fields did not change the v1 projection.", "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": true, "criteria": [], "remainingWork": [] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [], "futureResultAnnotation": { "safe": true } }
+    },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_future_03", "sourceSeq": 3, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_future", "normalizedSessionId": "session_phase1_future", "turnId": "turn_phase1_future", "eventType": "turn.completed", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:50:00.030Z", "payload": {} },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_future_04", "sourceSeq": 4, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_future", "normalizedSessionId": "session_phase1_future", "eventType": "run.terminal", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T12:50:00.040Z", "payload": { "schema": "paperclip.prp.terminal.v1", "turnTerminalState": "completed", "runTerminalState": "succeeded", "reportedWorkDisposition": "done", "futureTerminalReason": "optional" } }
+  ],
+  "requests": [],
+  "result": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "done", "summary": "Unknown optional fields did not change the v1 projection.", "completionClaim": { "contractRevision": "phase1-contract-v1", "objectiveSatisfied": true, "criteria": [], "remainingWork": [] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [], "futureResultAnnotation": { "safe": true } }
+}
diff --git a/packages/paperclip-runner/protocol/fixtures/phase-01/unsupported-required-version.json b/packages/paperclip-runner/protocol/fixtures/phase-01/unsupported-required-version.json
new file mode 100644
index 00000000000..3c6d4402771
--- /dev/null
+++ b/packages/paperclip-runner/protocol/fixtures/phase-01/unsupported-required-version.json
@@ -0,0 +1,13 @@
+{
+  "schema": "paperclip.prp.fixture.v1", "fixtureVersion": 1, "protocolVersion": 2,
+  "name": "Unsupported required version", "description": "A fixture that requires PRP v2 must fail closed in a PRP v1 consumer.",
+  "identity": { "schema": "paperclip.prp.identity.v1", "companyId": "company_phase1", "issueId": "issue_phase1_v2", "runId": "run_phase1_v2", "environmentLeaseId": "lease_phase1_v2", "runnerInstanceId": "runner_phase1", "normalizedSessionId": "session_phase1_v2", "driverSessionId": "driver_phase1_v2" },
+  "capabilities": { "schema": "paperclip.prp.capabilities.v1", "sessionReusePolicy": "new_per_run", "driver": { "kind": "future", "version": "2.0.0" }, "steer": true, "interrupt": true, "resume": true, "runtimeRequests": true, "structuredResult": true, "typedEvents": true },
+  "commands": [{ "schema": "paperclip.prp.command.v1", "commandId": "command_v2_prepare", "controllerSeq": 1, "type": "run.prepare", "issuedAt": "2026-08-07T13:00:00.000Z", "payload": {} }],
+  "events": [
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_v2_01", "sourceSeq": 1, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_v2", "normalizedSessionId": "session_phase1_v2", "eventType": "run.result.proposed", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T13:00:00.010Z", "payload": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "done", "summary": "This result requires PRP v2.", "completionClaim": { "contractRevision": "phase1-contract-v2", "objectiveSatisfied": true, "criteria": [], "remainingWork": [] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [] } },
+    { "schema": "paperclip.prp.event.v1", "sourceEventId": "event_v2_02", "sourceSeq": 2, "sourceInstanceId": "runner_phase1", "sourceKind": "runner", "runId": "run_phase1_v2", "normalizedSessionId": "session_phase1_v2", "eventType": "run.terminal", "schemaVersion": 1, "priority": 0, "emittedAt": "2026-08-07T13:00:00.020Z", "payload": { "schema": "paperclip.prp.terminal.v1", "turnTerminalState": "completed", "runTerminalState": "succeeded", "reportedWorkDisposition": "done" } }
+  ],
+  "requests": [],
+  "result": { "schema": "paperclip.run_result.v1", "reportedWorkDisposition": "done", "summary": "This result requires PRP v2.", "completionClaim": { "contractRevision": "phase1-contract-v2", "objectiveSatisfied": true, "criteria": [], "remainingWork": [] }, "evidence": [], "verification": [], "attentionRequests": [], "artifacts": [] }
+}
diff --git a/packages/paperclip-runner/protocol/schemas/capabilities.schema.json b/packages/paperclip-runner/protocol/schemas/capabilities.schema.json
new file mode 100644
index 00000000000..bdf38a2cb33
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/capabilities.schema.json
@@ -0,0 +1,44 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/capabilities.schema.json",
+  "title": "PRP negotiated capabilities",
+  "type": "object",
+  "required": [
+    "schema",
+    "sessionReusePolicy",
+    "driver",
+    "steer",
+    "interrupt",
+    "resume",
+    "runtimeRequests",
+    "structuredResult",
+    "typedEvents"
+  ],
+  "properties": {
+    "schema": { "const": "paperclip.prp.capabilities.v1" },
+    "sessionReusePolicy": {
+      "enum": ["new_per_run", "reuse_per_issue", "reuse_per_workspace"]
+    },
+    "driver": {
+      "type": "object",
+      "required": ["kind", "version"],
+      "properties": {
+        "kind": { "type": "string", "minLength": 1, "maxLength": 80 },
+        "version": { "type": "string", "minLength": 1, "maxLength": 80 }
+      },
+      "additionalProperties": true
+    },
+    "steer": { "type": "boolean" },
+    "interrupt": { "type": "boolean" },
+    "resume": { "type": "boolean" },
+    "runtimeRequests": { "type": "boolean" },
+    "structuredResult": { "type": "boolean" },
+    "typedEvents": { "type": "boolean" },
+    "unsupported": {
+      "type": "array",
+      "items": { "type": "string", "minLength": 1 },
+      "uniqueItems": true
+    }
+  },
+  "additionalProperties": true
+}
diff --git a/packages/paperclip-runner/protocol/schemas/command.schema.json b/packages/paperclip-runner/protocol/schemas/command.schema.json
new file mode 100644
index 00000000000..60c662fecb4
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/command.schema.json
@@ -0,0 +1,43 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/command.schema.json",
+  "title": "PRP runner command",
+  "type": "object",
+  "required": ["schema", "commandId", "controllerSeq", "type", "issuedAt", "payload"],
+  "properties": {
+    "schema": { "const": "paperclip.prp.command.v1" },
+    "commandId": { "type": "string", "minLength": 1, "maxLength": 160 },
+    "controllerSeq": { "type": "integer", "minimum": 1 },
+    "type": {
+      "enum": [
+        "run.prepare",
+        "session.open",
+        "turn.start",
+        "turn.steer",
+        "turn.interrupt",
+        "turn.stop",
+        "request.resolve",
+        "interaction.receipt",
+        "session.snapshot",
+        "session.close",
+        "run.cancel",
+        "runner.drain",
+        "runner.shutdown"
+      ]
+    },
+    "issuedAt": { "type": "string", "format": "date-time" },
+    "deadlineAt": { "type": "string", "format": "date-time" },
+    "precondition": {
+      "type": "object",
+      "properties": {
+        "runnerState": { "type": "array", "items": { "type": "string" } },
+        "runState": { "type": "array", "items": { "type": "string" } },
+        "sessionState": { "type": "array", "items": { "type": "string" } },
+        "activeTurnId": { "type": ["string", "null"] }
+      },
+      "additionalProperties": true
+    },
+    "payload": { "type": "object", "additionalProperties": true }
+  },
+  "additionalProperties": true
+}
diff --git a/packages/paperclip-runner/protocol/schemas/event.schema.json b/packages/paperclip-runner/protocol/schemas/event.schema.json
new file mode 100644
index 00000000000..3fe654d1f6c
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/event.schema.json
@@ -0,0 +1,72 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/event.schema.json",
+  "title": "PRP native event",
+  "type": "object",
+  "required": [
+    "schema",
+    "sourceEventId",
+    "sourceSeq",
+    "sourceInstanceId",
+    "sourceKind",
+    "runId",
+    "eventType",
+    "schemaVersion",
+    "priority",
+    "emittedAt",
+    "payload"
+  ],
+  "properties": {
+    "schema": { "const": "paperclip.prp.event.v1" },
+    "sourceEventId": { "type": "string", "minLength": 1, "maxLength": 160 },
+    "sourceSeq": { "type": "integer", "minimum": 1 },
+    "sourceInstanceId": { "type": "string", "minLength": 1, "maxLength": 160 },
+    "sourceKind": { "enum": ["runner", "control_plane"] },
+    "runId": { "type": "string", "minLength": 1, "maxLength": 160 },
+    "normalizedSessionId": { "type": "string", "minLength": 1, "maxLength": 160 },
+    "turnId": { "type": "string", "minLength": 1, "maxLength": 160 },
+    "itemId": { "type": "string", "minLength": 1, "maxLength": 160 },
+    "eventType": {
+      "enum": [
+        "runner.connected", "runner.reconnected", "runner.disconnected", "runner.draining", "runner.diagnostic",
+        "runtime.phase.changed", "sandbox.metric", "workspace.ready",
+        "harness.starting", "harness.ready", "harness.exited", "harness.diagnostic",
+        "session.starting", "session.started", "session.resuming", "session.resumed", "session.reconciled", "session.closed", "session.failed",
+        "turn.submitted", "turn.accepted", "turn.started", "turn.completed", "turn.failed", "turn.interrupted", "turn.cancelled",
+        "item.started", "item.delta", "item.completed", "item.failed",
+        "mcp_app.discovered", "mcp_app.resource.resolved", "mcp_app.initializing", "mcp_app.ready", "mcp_app.tool_input", "mcp_app.tool_result", "mcp_app.action.requested", "mcp_app.action.resolved", "mcp_app.host_context.changed", "mcp_app.failed", "mcp_app.teardown",
+        "runtime_request.created", "runtime_request.resolved", "runtime_request.expired", "runtime_request.cancelled",
+        "interaction.request.proposed", "interaction.request.materialized", "interaction.request.rejected", "interaction.response.progressed", "interaction.response.resolved", "interaction.response.delivered",
+        "run.result.proposed", "run.result.accepted", "run.result.rejected",
+        "attention.request.proposed", "attention.request.routed", "attention.request.resolved", "attention.request.expired", "attention.request.superseded",
+        "work.assessment.recorded", "issue.status.decision.recorded", "issue.status.decision.applied", "issue.status.decision.rejected", "issue.status.decision.superseded",
+        "run.terminal"
+      ]
+    },
+    "schemaVersion": { "const": 1 },
+    "priority": { "enum": [0, 1, 2] },
+    "emittedAt": { "type": "string", "format": "date-time" },
+    "observedAt": { "type": "string", "format": "date-time" },
+    "payload": { "type": "object", "additionalProperties": true },
+    "debug": { "type": "object", "additionalProperties": true }
+  },
+  "allOf": [
+    {
+      "if": { "properties": { "eventType": { "const": "run.terminal" } } },
+      "then": {
+        "properties": {
+          "payload": { "$ref": "https://paperclip.dev/schemas/prp/v1/terminal.schema.json" }
+        }
+      }
+    },
+    {
+      "if": { "properties": { "eventType": { "const": "run.result.proposed" } } },
+      "then": {
+        "properties": {
+          "payload": { "$ref": "https://paperclip.dev/schemas/prp/v1/result.schema.json" }
+        }
+      }
+    }
+  ],
+  "additionalProperties": true
+}
diff --git a/packages/paperclip-runner/protocol/schemas/fixture.schema.json b/packages/paperclip-runner/protocol/schemas/fixture.schema.json
new file mode 100644
index 00000000000..18d33ade541
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/fixture.schema.json
@@ -0,0 +1,42 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/fixture.schema.json",
+  "title": "PRP scripted replay fixture",
+  "type": "object",
+  "required": [
+    "schema",
+    "fixtureVersion",
+    "protocolVersion",
+    "name",
+    "description",
+    "identity",
+    "capabilities",
+    "commands",
+    "events",
+    "result"
+  ],
+  "properties": {
+    "schema": { "const": "paperclip.prp.fixture.v1" },
+    "fixtureVersion": { "const": 1 },
+    "protocolVersion": { "const": 1 },
+    "name": { "type": "string", "minLength": 1, "maxLength": 120 },
+    "description": { "type": "string", "minLength": 1, "maxLength": 1000 },
+    "identity": { "$ref": "https://paperclip.dev/schemas/prp/v1/identity.schema.json" },
+    "capabilities": { "$ref": "https://paperclip.dev/schemas/prp/v1/capabilities.schema.json" },
+    "commands": {
+      "type": "array",
+      "items": { "$ref": "https://paperclip.dev/schemas/prp/v1/command.schema.json" }
+    },
+    "events": {
+      "type": "array",
+      "minItems": 1,
+      "items": { "$ref": "https://paperclip.dev/schemas/prp/v1/event.schema.json" }
+    },
+    "requests": {
+      "type": "array",
+      "items": { "$ref": "https://paperclip.dev/schemas/prp/v1/request.schema.json" }
+    },
+    "result": { "$ref": "https://paperclip.dev/schemas/prp/v1/result.schema.json" }
+  },
+  "additionalProperties": true
+}
diff --git a/packages/paperclip-runner/protocol/schemas/identity.schema.json b/packages/paperclip-runner/protocol/schemas/identity.schema.json
new file mode 100644
index 00000000000..8279ef857c7
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/identity.schema.json
@@ -0,0 +1,36 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/identity.schema.json",
+  "title": "PRP identity graph",
+  "type": "object",
+  "required": [
+    "schema",
+    "companyId",
+    "issueId",
+    "runId",
+    "environmentLeaseId",
+    "runnerInstanceId",
+    "normalizedSessionId",
+    "driverSessionId"
+  ],
+  "properties": {
+    "schema": { "const": "paperclip.prp.identity.v1" },
+    "companyId": { "$ref": "#/$defs/stableId" },
+    "issueId": { "$ref": "#/$defs/stableId" },
+    "runId": { "$ref": "#/$defs/stableId" },
+    "environmentLeaseId": { "$ref": "#/$defs/stableId" },
+    "runnerInstanceId": { "$ref": "#/$defs/stableId" },
+    "normalizedSessionId": { "$ref": "#/$defs/stableId" },
+    "driverSessionId": { "$ref": "#/$defs/stableId" },
+    "providerSessionId": { "$ref": "#/$defs/stableId" }
+  },
+  "additionalProperties": true,
+  "$defs": {
+    "stableId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160,
+      "pattern": "^[A-Za-z0-9][A-Za-z0-9._:-]*$"
+    }
+  }
+}
diff --git a/packages/paperclip-runner/protocol/schemas/request.schema.json b/packages/paperclip-runner/protocol/schemas/request.schema.json
new file mode 100644
index 00000000000..2175bba9333
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/request.schema.json
@@ -0,0 +1,53 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/request.schema.json",
+  "title": "PRP request",
+  "oneOf": [
+    {
+      "type": "object",
+      "required": ["schema", "requestKind", "requestId", "type", "status", "prompt"],
+      "properties": {
+        "schema": { "const": "paperclip.runtime_request.v1" },
+        "requestKind": { "const": "runtime" },
+        "requestId": { "type": "string", "minLength": 1, "maxLength": 160 },
+        "type": { "enum": ["permission", "input"] },
+        "status": { "enum": ["pending", "resolved", "expired", "cancelled"] },
+        "prompt": { "type": "string", "minLength": 1, "maxLength": 4000 },
+        "choices": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "required": ["key", "label"],
+            "properties": {
+              "key": { "type": "string", "minLength": 1 },
+              "label": { "type": "string", "minLength": 1 }
+            },
+            "additionalProperties": true
+          }
+        }
+      },
+      "additionalProperties": true
+    },
+    {
+      "type": "object",
+      "required": ["schema", "requestKind", "requestId", "kind", "blocking", "payload"],
+      "properties": {
+        "schema": { "const": "paperclip.interaction_request.v1" },
+        "requestKind": { "const": "issue_thread" },
+        "requestId": { "type": "string", "minLength": 1, "maxLength": 160 },
+        "kind": {
+          "enum": [
+            "request_confirmation",
+            "request_checkbox_confirmation",
+            "request_item_verdicts",
+            "ask_user_questions",
+            "suggest_tasks"
+          ]
+        },
+        "blocking": { "type": "boolean" },
+        "payload": { "type": "object", "additionalProperties": true }
+      },
+      "additionalProperties": true
+    }
+  ]
+}
diff --git a/packages/paperclip-runner/protocol/schemas/result.schema.json b/packages/paperclip-runner/protocol/schemas/result.schema.json
new file mode 100644
index 00000000000..09faaa92363
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/result.schema.json
@@ -0,0 +1,121 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/result.schema.json",
+  "title": "PRP structured run result",
+  "type": "object",
+  "required": [
+    "schema",
+    "reportedWorkDisposition",
+    "summary",
+    "completionClaim",
+    "evidence",
+    "verification",
+    "attentionRequests",
+    "artifacts"
+  ],
+  "properties": {
+    "schema": { "const": "paperclip.run_result.v1" },
+    "reportedWorkDisposition": {
+      "enum": ["done", "blocked", "needs_review", "yielded"]
+    },
+    "summary": { "type": "string", "minLength": 1, "maxLength": 12000 },
+    "completionClaim": {
+      "type": "object",
+      "required": ["contractRevision", "objectiveSatisfied", "criteria", "remainingWork"],
+      "properties": {
+        "contractRevision": { "type": "string", "minLength": 1 },
+        "objectiveSatisfied": { "type": "boolean" },
+        "criteria": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "required": ["criterionId", "status", "evidenceRefs"],
+            "properties": {
+              "criterionId": { "type": "string", "minLength": 1 },
+              "status": { "enum": ["satisfied", "not_satisfied", "unknown"] },
+              "evidenceRefs": { "type": "array", "items": { "type": "string" } },
+              "explanation": { "type": "string" }
+            },
+            "additionalProperties": true
+          }
+        },
+        "remainingWork": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "required": ["description", "blocksCompletion"],
+            "properties": {
+              "description": { "type": "string", "minLength": 1 },
+              "blocksCompletion": { "type": "boolean" }
+            },
+            "additionalProperties": true
+          }
+        }
+      },
+      "additionalProperties": true
+    },
+    "evidence": { "type": "array", "items": { "type": "object" } },
+    "verification": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "required": ["commandOrCheck", "status"],
+        "properties": {
+          "commandOrCheck": { "type": "string", "minLength": 1 },
+          "status": { "enum": ["passed", "failed", "not_run"] },
+          "detail": { "type": "string" },
+          "artifactRef": { "type": "string" }
+        },
+        "additionalProperties": true
+      }
+    },
+    "blocker": {
+      "type": "object",
+      "required": ["reasonCode", "owner", "unblockAction", "scope"],
+      "properties": {
+        "reasonCode": { "type": "string", "minLength": 1 },
+        "owner": { "type": "object", "additionalProperties": true },
+        "unblockAction": { "type": "string", "minLength": 1 },
+        "scope": { "enum": ["current_track", "task_wide"] }
+      },
+      "additionalProperties": true
+    },
+    "attentionRequests": { "type": "array", "items": { "type": "object" } },
+    "artifacts": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "required": ["kind", "ref"],
+        "properties": {
+          "kind": { "type": "string", "minLength": 1 },
+          "ref": { "type": "string", "minLength": 1 },
+          "title": { "type": "string" }
+        },
+        "additionalProperties": true
+      }
+    },
+    "continuation": {
+      "type": "object",
+      "required": ["kind", "summary", "idempotencyKey"],
+      "properties": {
+        "kind": {
+          "enum": ["same_agent", "retry", "delegated_issue", "response_wake", "monitor"]
+        },
+        "summary": { "type": "string", "minLength": 1 },
+        "idempotencyKey": { "type": "string", "minLength": 1 }
+      },
+      "additionalProperties": true
+    }
+  },
+  "allOf": [
+    {
+      "if": { "properties": { "reportedWorkDisposition": { "const": "blocked" } } },
+      "then": { "required": ["blocker"] }
+    },
+    {
+      "if": { "properties": { "reportedWorkDisposition": { "const": "yielded" } } },
+      "then": { "required": ["continuation"] }
+    }
+  ],
+  "additionalProperties": true
+}
diff --git a/packages/paperclip-runner/protocol/schemas/terminal.schema.json b/packages/paperclip-runner/protocol/schemas/terminal.schema.json
new file mode 100644
index 00000000000..69397e9c76d
--- /dev/null
+++ b/packages/paperclip-runner/protocol/schemas/terminal.schema.json
@@ -0,0 +1,25 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/terminal.schema.json",
+  "title": "PRP run terminal state",
+  "type": "object",
+  "required": [
+    "schema",
+    "turnTerminalState",
+    "runTerminalState",
+    "reportedWorkDisposition"
+  ],
+  "properties": {
+    "schema": { "const": "paperclip.prp.terminal.v1" },
+    "turnTerminalState": {
+      "enum": ["completed", "failed", "interrupted", "cancelled"]
+    },
+    "runTerminalState": { "enum": ["succeeded", "failed", "cancelled"] },
+    "reportedWorkDisposition": {
+      "enum": ["done", "blocked", "needs_review", "yielded"]
+    },
+    "workAssessmentId": { "type": "string", "minLength": 1 },
+    "statusDecisionId": { "type": "string", "minLength": 1 }
+  },
+  "additionalProperties": true
+}
diff --git a/packages/paperclip-runner/runner/crates/runner-core/src/lib.rs b/packages/paperclip-runner/runner/crates/runner-core/src/lib.rs
index b0730569ac7..0b85caa636d 100644
--- a/packages/paperclip-runner/runner/crates/runner-core/src/lib.rs
+++ b/packages/paperclip-runner/runner/crates/runner-core/src/lib.rs
@@ -1,5 +1,7 @@
 #![forbid(unsafe_code)]
 
+pub mod phase1;
+
 use std::error::Error;
 use std::fmt::{self, Display, Formatter};
 
diff --git a/packages/paperclip-runner/runner/crates/runner-core/src/phase1.rs b/packages/paperclip-runner/runner/crates/runner-core/src/phase1.rs
new file mode 100644
index 00000000000..e8533475289
--- /dev/null
+++ b/packages/paperclip-runner/runner/crates/runner-core/src/phase1.rs
@@ -0,0 +1,308 @@
+use std::collections::HashMap;
+use std::error::Error;
+use std::fmt::{self, Display, Formatter};
+
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+pub const PRP_PROTOCOL_VERSION: u64 = 1;
+const PRP_FIXTURE_VERSION: u64 = 1;
+const PRP_FIXTURE_SCHEMA: &str = "paperclip.prp.fixture.v1";
+const PRP_EVENT_SCHEMA: &str = "paperclip.prp.event.v1";
+
+#[derive(Clone, Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct Phase1Fixture {
+    schema: String,
+    fixture_version: u64,
+    protocol_version: u64,
+    identity: Phase1Identity,
+    events: Vec<Phase1Event>,
+    result: Value,
+}
+
+#[derive(Clone, Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct Phase1Identity {
+    run_id: String,
+}
+
+#[derive(Clone, Debug, Deserialize, PartialEq)]
+#[serde(rename_all = "camelCase")]
+struct Phase1Event {
+    schema: String,
+    source_event_id: String,
+    source_seq: u64,
+    source_instance_id: String,
+    source_kind: String,
+    run_id: String,
+    schema_version: u64,
+    event_type: String,
+    payload: Value,
+}
+
+#[derive(Clone, Debug, Deserialize, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Phase1SequenceGap {
+    source_key: String,
+    expected: u64,
+    received: u64,
+    missing: Vec<u64>,
+}
+
+#[derive(Clone, Debug, Deserialize, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Phase1ParitySummary {
+    run_id: String,
+    integrity: String,
+    timeline_count: usize,
+    duplicate_event_ids: Vec<String>,
+    gaps: Vec<Phase1SequenceGap>,
+    turn_terminal_state: Option<String>,
+    run_terminal_state: Option<String>,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Phase1Error(String);
+
+impl Phase1Error {
+    fn invalid(message: impl Into<String>) -> Self {
+        Self(message.into())
+    }
+}
+
+impl Display for Phase1Error {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> fmt::Result {
+        formatter.write_str(&self.0)
+    }
+}
+
+impl Error for Phase1Error {}
+
+pub fn reduce_phase1_fixture(input: &str) -> Result<Phase1ParitySummary, Phase1Error> {
+    let fixture: Phase1Fixture = serde_json::from_str(input)
+        .map_err(|error| Phase1Error::invalid(format!("fixture must be valid JSON: {error}")))?;
+    if fixture.protocol_version != PRP_PROTOCOL_VERSION {
+        return Err(Phase1Error::invalid(format!(
+            "unsupported required protocolVersion {}; expected {PRP_PROTOCOL_VERSION}",
+            fixture.protocol_version
+        )));
+    }
+    if fixture.fixture_version != PRP_FIXTURE_VERSION {
+        return Err(Phase1Error::invalid(format!(
+            "unsupported required fixtureVersion {}; expected {PRP_FIXTURE_VERSION}",
+            fixture.fixture_version
+        )));
+    }
+    if fixture.schema != PRP_FIXTURE_SCHEMA {
+        return Err(Phase1Error::invalid(format!(
+            "unsupported required fixture schema {}; expected {PRP_FIXTURE_SCHEMA}",
+            fixture.schema
+        )));
+    }
+
+    let mut delivery_counts = HashMap::<&str, usize>::new();
+    for event in &fixture.events {
+        *delivery_counts
+            .entry(event.source_event_id.as_str())
+            .or_default() += 1;
+    }
+    let mut duplicate_event_ids = delivery_counts
+        .into_iter()
+        .filter_map(|(event_id, count)| (count > 1).then(|| event_id.to_owned()))
+        .collect::<Vec<_>>();
+    duplicate_event_ids.sort();
+
+    let mut seen = HashMap::<&str, &Phase1Event>::new();
+    let mut cursors = HashMap::<String, u64>::new();
+    let mut gaps = Vec::<Phase1SequenceGap>::new();
+    let mut timeline_count = 0_usize;
+    let mut turn_terminal_state = None;
+    let mut run_terminal_state = None;
+    let mut proposed_result_count = 0_usize;
+    let mut terminal_count = 0_usize;
+
+    for event in &fixture.events {
+        if event.schema != PRP_EVENT_SCHEMA {
+            return Err(Phase1Error::invalid(format!(
+                "unsupported required event schema {}; expected {PRP_EVENT_SCHEMA}",
+                event.schema
+            )));
+        }
+        if event.schema_version != 1 {
+            return Err(Phase1Error::invalid(format!(
+                "unsupported required event schemaVersion {}; expected 1",
+                event.schema_version
+            )));
+        }
+        if event.run_id != fixture.identity.run_id {
+            return Err(Phase1Error::invalid(
+                "event runId must match identity.runId",
+            ));
+        }
+        if let Some(previous) = seen.get(event.source_event_id.as_str()) {
+            if *previous != event {
+                return Err(Phase1Error::invalid(
+                    "duplicate sourceEventId deliveries must be byte-equivalent",
+                ));
+            }
+            continue;
+        }
+        seen.insert(event.source_event_id.as_str(), event);
+
+        let key = format!("{}:{}", event.source_kind, event.source_instance_id);
+        let cursor = *cursors.get(&key).unwrap_or(&0);
+        let expected = cursor + 1;
+        if event.source_seq <= cursor {
+            continue;
+        }
+        if event.source_seq > expected {
+            gaps.push(Phase1SequenceGap {
+                source_key: key.clone(),
+                expected,
+                received: event.source_seq,
+                missing: (expected..event.source_seq).collect(),
+            });
+        }
+        cursors.insert(key, event.source_seq);
+        timeline_count += 1;
+
+        match event.event_type.as_str() {
+            "run.result.proposed" => {
+                proposed_result_count += 1;
+                if event.payload != fixture.result {
+                    return Err(Phase1Error::invalid(
+                        "fixture result must match the run.result.proposed event payload",
+                    ));
+                }
+            }
+            "run.terminal" => {
+                terminal_count += 1;
+                turn_terminal_state = event
+                    .payload
+                    .get("turnTerminalState")
+                    .and_then(Value::as_str)
+                    .map(str::to_owned);
+                run_terminal_state = event
+                    .payload
+                    .get("runTerminalState")
+                    .and_then(Value::as_str)
+                    .map(str::to_owned);
+            }
+            _ => {}
+        }
+    }
+
+    if proposed_result_count != 1 {
+        return Err(Phase1Error::invalid(
+            "scripted fixtures must contain exactly one unique run.result.proposed event",
+        ));
+    }
+    if terminal_count != 1 {
+        return Err(Phase1Error::invalid(
+            "scripted fixtures must contain exactly one unique run.terminal event",
+        ));
+    }
+
+    Ok(Phase1ParitySummary {
+        run_id: fixture.identity.run_id,
+        integrity: if gaps.is_empty() {
+            "complete".to_owned()
+        } else {
+            "gap_detected".to_owned()
+        },
+        timeline_count,
+        duplicate_event_ids,
+        gaps,
+        turn_terminal_state,
+        run_terminal_state,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{reduce_phase1_fixture, Phase1ParitySummary};
+    use serde_json::Value;
+
+    fn assert_fixture_parity(fixture: &str, expected: &str) {
+        let actual = reduce_phase1_fixture(fixture).expect("fixture should reduce");
+        let expected: Phase1ParitySummary =
+            serde_json::from_str(expected).expect("golden summary should parse");
+        assert_eq!(actual, expected);
+    }
+
+    macro_rules! parity_case {
+        ($name:ident, $fixture:literal, $golden:literal) => {
+            #[test]
+            fn $name() {
+                assert_fixture_parity(
+                    include_str!(concat!(
+                        "../../../../protocol/fixtures/phase-01/",
+                        $fixture,
+                        ".json"
+                    )),
+                    include_str!(concat!(
+                        "../../../../protocol/fixtures/phase-01/golden/",
+                        $golden,
+                        ".summary.json"
+                    )),
+                );
+            }
+        };
+    }
+
+    parity_case!(phase1_fixture_parity_happy_path, "happy-path", "happy-path");
+    parity_case!(phase1_fixture_parity_failed_run, "failed-run", "failed-run");
+    parity_case!(
+        phase1_fixture_parity_interrupted_run,
+        "interrupted-run",
+        "interrupted-run"
+    );
+    parity_case!(
+        phase1_fixture_parity_duplicate_event,
+        "duplicate-event",
+        "duplicate-event"
+    );
+    parity_case!(phase1_fixture_parity_source_gap, "source-gap", "source-gap");
+    parity_case!(
+        phase1_fixture_parity_unknown_optional_fields,
+        "unknown-optional-fields",
+        "unknown-optional-fields"
+    );
+
+    #[test]
+    fn phase1_fixture_parity_rejects_unsupported_required_version() {
+        let error = reduce_phase1_fixture(include_str!(
+            "../../../../protocol/fixtures/phase-01/unsupported-required-version.json"
+        ))
+        .expect_err("PRP v2 fixture must fail closed");
+        assert!(error
+            .to_string()
+            .contains("unsupported required protocolVersion 2"));
+    }
+
+    #[test]
+    fn phase1_fixture_parity_rejects_unsupported_fixture_version() {
+        let fixture = include_str!("../../../../protocol/fixtures/phase-01/happy-path.json")
+            .replace("\"fixtureVersion\": 1", "\"fixtureVersion\": 2");
+        let error =
+            reduce_phase1_fixture(&fixture).expect_err("fixture version 2 must fail closed");
+        assert!(error
+            .to_string()
+            .contains("unsupported required fixtureVersion 2"));
+    }
+
+    #[test]
+    fn phase1_fixture_parity_rejects_a_mismatched_declared_result() {
+        let mut fixture: Value = serde_json::from_str(include_str!(
+            "../../../../protocol/fixtures/phase-01/happy-path.json"
+        ))
+        .expect("fixture should parse");
+        fixture["result"]["summary"] = Value::String("Contradictory result".to_owned());
+        let error = reduce_phase1_fixture(&fixture.to_string())
+            .expect_err("mismatched result must fail closed");
+        assert!(error
+            .to_string()
+            .contains("fixture result must match the run.result.proposed event payload"));
+    }
+}
diff --git a/packages/paperclip-runner/scripts/check-browser-tokens.mjs b/packages/paperclip-runner/scripts/check-browser-tokens.mjs
new file mode 100644
index 00000000000..5e39abedf50
--- /dev/null
+++ b/packages/paperclip-runner/scripts/check-browser-tokens.mjs
@@ -0,0 +1,67 @@
+import { readFile, readdir } from "node:fs/promises";
+import { dirname, extname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const packageRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..");
+const sourceRoot = resolve(packageRoot, "devtools/browser/src");
+
+async function sourceFiles(directory) {
+  const entries = await readdir(directory, { withFileTypes: true });
+  const nested = await Promise.all(
+    entries.map((entry) => {
+      const path = resolve(directory, entry.name);
+      return entry.isDirectory() ? sourceFiles(path) : [path];
+    }),
+  );
+  return nested.flat();
+}
+
+const componentRules = [
+  ["hex color", /#[0-9a-f]{3,8}\b/i],
+  ["raw pixel value", /\b\d+(?:\.\d+)?px\b/],
+  ["inline style", /\bstyle\s*=\s*\{/],
+  ["raw font size", /\bfont(?:-size|Size)\s*[:=]/],
+  ["arbitrary Tailwind value", /\b[a-z-]+-\[[^\]]+\]/],
+];
+const violations = [];
+
+for (const path of await sourceFiles(sourceRoot)) {
+  if (![".ts", ".tsx"].includes(extname(path))) {
+    continue;
+  }
+  const source = await readFile(path, "utf8");
+  for (const [label, pattern] of componentRules) {
+    if (pattern.test(source)) {
+      violations.push(`${path.slice(packageRoot.length + 1)}: ${label}`);
+    }
+  }
+}
+
+const styles = await readFile(resolve(sourceRoot, "styles.css"), "utf8");
+for (const token of [
+  "--background",
+  "--foreground",
+  "--card",
+  "--primary",
+  "--muted",
+  "--border",
+  "--ring",
+  "--font-sans",
+  "--font-mono",
+  "--space-1",
+  "--radius-sm",
+  "--motion-fast",
+]) {
+  if (!styles.includes(`${token}:`)) {
+    violations.push(`devtools/browser/src/styles.css: missing ${token}`);
+  }
+}
+
+if (violations.length > 0) {
+  process.stderr.write(`Standalone browser token check failed:\n- ${violations.join("\n- ")}\n`);
+  process.exitCode = 1;
+} else {
+  process.stdout.write(
+    "Standalone browser token check passed; component visual values stay in styles.css.\n",
+  );
+}
diff --git a/packages/paperclip-runner/scripts/generate-phase1-goldens.mjs b/packages/paperclip-runner/scripts/generate-phase1-goldens.mjs
new file mode 100644
index 00000000000..756d3f7abf9
--- /dev/null
+++ b/packages/paperclip-runner/scripts/generate-phase1-goldens.mjs
@@ -0,0 +1,59 @@
+import { mkdir, readFile, writeFile } from "node:fs/promises";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+import {
+  parsePrpFixtureText,
+  phase1ParitySummary,
+  reducePrpFixture,
+} from "../dist/index.js";
+
+const packageRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..");
+const fixtureDirectory = resolve(packageRoot, "protocol/fixtures/phase-01");
+const goldenDirectory = resolve(fixtureDirectory, "golden");
+const fixtureNames = [
+  "happy-path",
+  "failed-run",
+  "interrupted-run",
+  "duplicate-event",
+  "source-gap",
+  "unknown-optional-fields",
+];
+const check = process.argv.includes("--check");
+const stale = [];
+
+await mkdir(goldenDirectory, { recursive: true });
+for (const fixtureName of fixtureNames) {
+  const source = await readFile(resolve(fixtureDirectory, `${fixtureName}.json`), "utf8");
+  const validation = parsePrpFixtureText(source);
+  if (!validation.ok) {
+    throw new Error(
+      `${fixtureName}.json failed validation: ${validation.issues.map((issue) => issue.message).join("; ")}`,
+    );
+  }
+  const snapshot = reducePrpFixture(validation.fixture);
+  const outputs = [
+    ["snapshot", snapshot],
+    ["summary", phase1ParitySummary(snapshot)],
+  ];
+  for (const [kind, value] of outputs) {
+    const path = resolve(goldenDirectory, `${fixtureName}.${kind}.json`);
+    const generated = `${JSON.stringify(value, null, 2)}\n`;
+    if (check) {
+      if ((await readFile(path, "utf8").catch(() => "")) !== generated) {
+        stale.push(`${fixtureName}.${kind}.json`);
+      }
+    } else {
+      await writeFile(path, generated);
+    }
+  }
+}
+
+if (stale.length > 0) {
+  process.stderr.write(`Phase 1 golden files are stale:\n- ${stale.join("\n- ")}\n`);
+  process.exitCode = 1;
+} else if (check) {
+  process.stdout.write("Phase 1 golden snapshots and parity summaries are current.\n");
+} else {
+  process.stdout.write("Generated Phase 1 golden snapshots and parity summaries.\n");
+}
diff --git a/packages/paperclip-runner/scripts/generate-protocol-schema-module.mjs b/packages/paperclip-runner/scripts/generate-protocol-schema-module.mjs
new file mode 100644
index 00000000000..b1c2420977e
--- /dev/null
+++ b/packages/paperclip-runner/scripts/generate-protocol-schema-module.mjs
@@ -0,0 +1,43 @@
+import { readFile, writeFile } from "node:fs/promises";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const packageRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..");
+const schemaDirectory = resolve(packageRoot, "protocol/schemas");
+const outputPath = resolve(packageRoot, "src/protocol/generated/schema-bundle.ts");
+const schemaNames = [
+  "identity",
+  "capabilities",
+  "command",
+  "terminal",
+  "request",
+  "result",
+  "event",
+  "fixture",
+];
+
+const schemas = await Promise.all(
+  schemaNames.map(async (name) => ({
+    name,
+    value: JSON.parse(await readFile(resolve(schemaDirectory, `${name}.schema.json`), "utf8")),
+  })),
+);
+
+const declarations = schemas
+  .map(({ name, value }) => `export const ${name}Schema = ${JSON.stringify(value, null, 2)} as const;`)
+  .join("\n\n");
+const bundle = schemaNames.map((name) => `  ${name}: ${name}Schema,`).join("\n");
+const generated = `// Generated by scripts/generate-protocol-schema-module.mjs. Do not edit.\n\n${declarations}\n\nexport const prpSchemaBundle = {\n${bundle}\n} as const;\n`;
+
+if (process.argv.includes("--check")) {
+  const current = await readFile(outputPath, "utf8").catch(() => "");
+  if (current !== generated) {
+    process.stderr.write("Generated PRP schema module is stale. Run pnpm generate:protocol-types.\n");
+    process.exitCode = 1;
+  } else {
+    process.stdout.write("Generated PRP schema module matches the JSON Schema sources.\n");
+  }
+} else {
+  await writeFile(outputPath, generated);
+  process.stdout.write("Generated src/protocol/generated/schema-bundle.ts.\n");
+}
diff --git a/packages/paperclip-runner/src/cli/phase1-replay.ts b/packages/paperclip-runner/src/cli/phase1-replay.ts
new file mode 100644
index 00000000000..be36dd3ad1c
--- /dev/null
+++ b/packages/paperclip-runner/src/cli/phase1-replay.ts
@@ -0,0 +1,17 @@
+import { readFile } from "node:fs/promises";
+import { resolve } from "node:path";
+import { pathToFileURL } from "node:url";
+
+import { formatPhase1Replay, replayPhase1FixtureText } from "../tracer/phase1-replay.js";
+
+const defaultFixtureUrl = new URL(
+  "../../protocol/fixtures/phase-01/happy-path.json",
+  import.meta.url,
+);
+const input = process.argv[2];
+const fixtureUrl = input === undefined ? defaultFixtureUrl : pathToFileURL(resolve(input));
+const result = replayPhase1FixtureText(await readFile(fixtureUrl, "utf8"));
+process.stdout.write(`${formatPhase1Replay(result)}\n`);
+if (!result.ok) {
+  process.exitCode = 1;
+}
diff --git a/packages/paperclip-runner/src/index.ts b/packages/paperclip-runner/src/index.ts
index a12b6e66352..3412abcef45 100644
--- a/packages/paperclip-runner/src/index.ts
+++ b/packages/paperclip-runner/src/index.ts
@@ -4,4 +4,8 @@ export * from "./contracts/native-session-backend.js";
 export * from "./contracts/types.js";
 export * from "./mock-core/mock-control-plane-adapter.js";
 export * from "./protocol/phase0-fixture.js";
+export * from "./protocol/phase1-contract.js";
+export * from "./protocol/phase1-loader.js";
+export * from "./reducer/session-reducer.js";
 export * from "./tracer/phase0-runner.js";
+export * from "./tracer/phase1-replay.js";
diff --git a/packages/paperclip-runner/src/protocol/generated/schema-bundle.ts b/packages/paperclip-runner/src/protocol/generated/schema-bundle.ts
new file mode 100644
index 00000000000..46c62d0e076
--- /dev/null
+++ b/packages/paperclip-runner/src/protocol/generated/schema-bundle.ts
@@ -0,0 +1,924 @@
+// Generated by scripts/generate-protocol-schema-module.mjs. Do not edit.
+
+export const identitySchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/identity.schema.json",
+  "title": "PRP identity graph",
+  "type": "object",
+  "required": [
+    "schema",
+    "companyId",
+    "issueId",
+    "runId",
+    "environmentLeaseId",
+    "runnerInstanceId",
+    "normalizedSessionId",
+    "driverSessionId"
+  ],
+  "properties": {
+    "schema": {
+      "const": "paperclip.prp.identity.v1"
+    },
+    "companyId": {
+      "$ref": "#/$defs/stableId"
+    },
+    "issueId": {
+      "$ref": "#/$defs/stableId"
+    },
+    "runId": {
+      "$ref": "#/$defs/stableId"
+    },
+    "environmentLeaseId": {
+      "$ref": "#/$defs/stableId"
+    },
+    "runnerInstanceId": {
+      "$ref": "#/$defs/stableId"
+    },
+    "normalizedSessionId": {
+      "$ref": "#/$defs/stableId"
+    },
+    "driverSessionId": {
+      "$ref": "#/$defs/stableId"
+    },
+    "providerSessionId": {
+      "$ref": "#/$defs/stableId"
+    }
+  },
+  "additionalProperties": true,
+  "$defs": {
+    "stableId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160,
+      "pattern": "^[A-Za-z0-9][A-Za-z0-9._:-]*$"
+    }
+  }
+} as const;
+
+export const capabilitiesSchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/capabilities.schema.json",
+  "title": "PRP negotiated capabilities",
+  "type": "object",
+  "required": [
+    "schema",
+    "sessionReusePolicy",
+    "driver",
+    "steer",
+    "interrupt",
+    "resume",
+    "runtimeRequests",
+    "structuredResult",
+    "typedEvents"
+  ],
+  "properties": {
+    "schema": {
+      "const": "paperclip.prp.capabilities.v1"
+    },
+    "sessionReusePolicy": {
+      "enum": [
+        "new_per_run",
+        "reuse_per_issue",
+        "reuse_per_workspace"
+      ]
+    },
+    "driver": {
+      "type": "object",
+      "required": [
+        "kind",
+        "version"
+      ],
+      "properties": {
+        "kind": {
+          "type": "string",
+          "minLength": 1,
+          "maxLength": 80
+        },
+        "version": {
+          "type": "string",
+          "minLength": 1,
+          "maxLength": 80
+        }
+      },
+      "additionalProperties": true
+    },
+    "steer": {
+      "type": "boolean"
+    },
+    "interrupt": {
+      "type": "boolean"
+    },
+    "resume": {
+      "type": "boolean"
+    },
+    "runtimeRequests": {
+      "type": "boolean"
+    },
+    "structuredResult": {
+      "type": "boolean"
+    },
+    "typedEvents": {
+      "type": "boolean"
+    },
+    "unsupported": {
+      "type": "array",
+      "items": {
+        "type": "string",
+        "minLength": 1
+      },
+      "uniqueItems": true
+    }
+  },
+  "additionalProperties": true
+} as const;
+
+export const commandSchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/command.schema.json",
+  "title": "PRP runner command",
+  "type": "object",
+  "required": [
+    "schema",
+    "commandId",
+    "controllerSeq",
+    "type",
+    "issuedAt",
+    "payload"
+  ],
+  "properties": {
+    "schema": {
+      "const": "paperclip.prp.command.v1"
+    },
+    "commandId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160
+    },
+    "controllerSeq": {
+      "type": "integer",
+      "minimum": 1
+    },
+    "type": {
+      "enum": [
+        "run.prepare",
+        "session.open",
+        "turn.start",
+        "turn.steer",
+        "turn.interrupt",
+        "turn.stop",
+        "request.resolve",
+        "interaction.receipt",
+        "session.snapshot",
+        "session.close",
+        "run.cancel",
+        "runner.drain",
+        "runner.shutdown"
+      ]
+    },
+    "issuedAt": {
+      "type": "string",
+      "format": "date-time"
+    },
+    "deadlineAt": {
+      "type": "string",
+      "format": "date-time"
+    },
+    "precondition": {
+      "type": "object",
+      "properties": {
+        "runnerState": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        },
+        "runState": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        },
+        "sessionState": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        },
+        "activeTurnId": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "additionalProperties": true
+    },
+    "payload": {
+      "type": "object",
+      "additionalProperties": true
+    }
+  },
+  "additionalProperties": true
+} as const;
+
+export const terminalSchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/terminal.schema.json",
+  "title": "PRP run terminal state",
+  "type": "object",
+  "required": [
+    "schema",
+    "turnTerminalState",
+    "runTerminalState",
+    "reportedWorkDisposition"
+  ],
+  "properties": {
+    "schema": {
+      "const": "paperclip.prp.terminal.v1"
+    },
+    "turnTerminalState": {
+      "enum": [
+        "completed",
+        "failed",
+        "interrupted",
+        "cancelled"
+      ]
+    },
+    "runTerminalState": {
+      "enum": [
+        "succeeded",
+        "failed",
+        "cancelled"
+      ]
+    },
+    "reportedWorkDisposition": {
+      "enum": [
+        "done",
+        "blocked",
+        "needs_review",
+        "yielded"
+      ]
+    },
+    "workAssessmentId": {
+      "type": "string",
+      "minLength": 1
+    },
+    "statusDecisionId": {
+      "type": "string",
+      "minLength": 1
+    }
+  },
+  "additionalProperties": true
+} as const;
+
+export const requestSchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/request.schema.json",
+  "title": "PRP request",
+  "oneOf": [
+    {
+      "type": "object",
+      "required": [
+        "schema",
+        "requestKind",
+        "requestId",
+        "type",
+        "status",
+        "prompt"
+      ],
+      "properties": {
+        "schema": {
+          "const": "paperclip.runtime_request.v1"
+        },
+        "requestKind": {
+          "const": "runtime"
+        },
+        "requestId": {
+          "type": "string",
+          "minLength": 1,
+          "maxLength": 160
+        },
+        "type": {
+          "enum": [
+            "permission",
+            "input"
+          ]
+        },
+        "status": {
+          "enum": [
+            "pending",
+            "resolved",
+            "expired",
+            "cancelled"
+          ]
+        },
+        "prompt": {
+          "type": "string",
+          "minLength": 1,
+          "maxLength": 4000
+        },
+        "choices": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "required": [
+              "key",
+              "label"
+            ],
+            "properties": {
+              "key": {
+                "type": "string",
+                "minLength": 1
+              },
+              "label": {
+                "type": "string",
+                "minLength": 1
+              }
+            },
+            "additionalProperties": true
+          }
+        }
+      },
+      "additionalProperties": true
+    },
+    {
+      "type": "object",
+      "required": [
+        "schema",
+        "requestKind",
+        "requestId",
+        "kind",
+        "blocking",
+        "payload"
+      ],
+      "properties": {
+        "schema": {
+          "const": "paperclip.interaction_request.v1"
+        },
+        "requestKind": {
+          "const": "issue_thread"
+        },
+        "requestId": {
+          "type": "string",
+          "minLength": 1,
+          "maxLength": 160
+        },
+        "kind": {
+          "enum": [
+            "request_confirmation",
+            "request_checkbox_confirmation",
+            "request_item_verdicts",
+            "ask_user_questions",
+            "suggest_tasks"
+          ]
+        },
+        "blocking": {
+          "type": "boolean"
+        },
+        "payload": {
+          "type": "object",
+          "additionalProperties": true
+        }
+      },
+      "additionalProperties": true
+    }
+  ]
+} as const;
+
+export const resultSchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/result.schema.json",
+  "title": "PRP structured run result",
+  "type": "object",
+  "required": [
+    "schema",
+    "reportedWorkDisposition",
+    "summary",
+    "completionClaim",
+    "evidence",
+    "verification",
+    "attentionRequests",
+    "artifacts"
+  ],
+  "properties": {
+    "schema": {
+      "const": "paperclip.run_result.v1"
+    },
+    "reportedWorkDisposition": {
+      "enum": [
+        "done",
+        "blocked",
+        "needs_review",
+        "yielded"
+      ]
+    },
+    "summary": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 12000
+    },
+    "completionClaim": {
+      "type": "object",
+      "required": [
+        "contractRevision",
+        "objectiveSatisfied",
+        "criteria",
+        "remainingWork"
+      ],
+      "properties": {
+        "contractRevision": {
+          "type": "string",
+          "minLength": 1
+        },
+        "objectiveSatisfied": {
+          "type": "boolean"
+        },
+        "criteria": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "required": [
+              "criterionId",
+              "status",
+              "evidenceRefs"
+            ],
+            "properties": {
+              "criterionId": {
+                "type": "string",
+                "minLength": 1
+              },
+              "status": {
+                "enum": [
+                  "satisfied",
+                  "not_satisfied",
+                  "unknown"
+                ]
+              },
+              "evidenceRefs": {
+                "type": "array",
+                "items": {
+                  "type": "string"
+                }
+              },
+              "explanation": {
+                "type": "string"
+              }
+            },
+            "additionalProperties": true
+          }
+        },
+        "remainingWork": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "required": [
+              "description",
+              "blocksCompletion"
+            ],
+            "properties": {
+              "description": {
+                "type": "string",
+                "minLength": 1
+              },
+              "blocksCompletion": {
+                "type": "boolean"
+              }
+            },
+            "additionalProperties": true
+          }
+        }
+      },
+      "additionalProperties": true
+    },
+    "evidence": {
+      "type": "array",
+      "items": {
+        "type": "object"
+      }
+    },
+    "verification": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "required": [
+          "commandOrCheck",
+          "status"
+        ],
+        "properties": {
+          "commandOrCheck": {
+            "type": "string",
+            "minLength": 1
+          },
+          "status": {
+            "enum": [
+              "passed",
+              "failed",
+              "not_run"
+            ]
+          },
+          "detail": {
+            "type": "string"
+          },
+          "artifactRef": {
+            "type": "string"
+          }
+        },
+        "additionalProperties": true
+      }
+    },
+    "blocker": {
+      "type": "object",
+      "required": [
+        "reasonCode",
+        "owner",
+        "unblockAction",
+        "scope"
+      ],
+      "properties": {
+        "reasonCode": {
+          "type": "string",
+          "minLength": 1
+        },
+        "owner": {
+          "type": "object",
+          "additionalProperties": true
+        },
+        "unblockAction": {
+          "type": "string",
+          "minLength": 1
+        },
+        "scope": {
+          "enum": [
+            "current_track",
+            "task_wide"
+          ]
+        }
+      },
+      "additionalProperties": true
+    },
+    "attentionRequests": {
+      "type": "array",
+      "items": {
+        "type": "object"
+      }
+    },
+    "artifacts": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "required": [
+          "kind",
+          "ref"
+        ],
+        "properties": {
+          "kind": {
+            "type": "string",
+            "minLength": 1
+          },
+          "ref": {
+            "type": "string",
+            "minLength": 1
+          },
+          "title": {
+            "type": "string"
+          }
+        },
+        "additionalProperties": true
+      }
+    },
+    "continuation": {
+      "type": "object",
+      "required": [
+        "kind",
+        "summary",
+        "idempotencyKey"
+      ],
+      "properties": {
+        "kind": {
+          "enum": [
+            "same_agent",
+            "retry",
+            "delegated_issue",
+            "response_wake",
+            "monitor"
+          ]
+        },
+        "summary": {
+          "type": "string",
+          "minLength": 1
+        },
+        "idempotencyKey": {
+          "type": "string",
+          "minLength": 1
+        }
+      },
+      "additionalProperties": true
+    }
+  },
+  "allOf": [
+    {
+      "if": {
+        "properties": {
+          "reportedWorkDisposition": {
+            "const": "blocked"
+          }
+        }
+      },
+      "then": {
+        "required": [
+          "blocker"
+        ]
+      }
+    },
+    {
+      "if": {
+        "properties": {
+          "reportedWorkDisposition": {
+            "const": "yielded"
+          }
+        }
+      },
+      "then": {
+        "required": [
+          "continuation"
+        ]
+      }
+    }
+  ],
+  "additionalProperties": true
+} as const;
+
+export const eventSchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/event.schema.json",
+  "title": "PRP native event",
+  "type": "object",
+  "required": [
+    "schema",
+    "sourceEventId",
+    "sourceSeq",
+    "sourceInstanceId",
+    "sourceKind",
+    "runId",
+    "eventType",
+    "schemaVersion",
+    "priority",
+    "emittedAt",
+    "payload"
+  ],
+  "properties": {
+    "schema": {
+      "const": "paperclip.prp.event.v1"
+    },
+    "sourceEventId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160
+    },
+    "sourceSeq": {
+      "type": "integer",
+      "minimum": 1
+    },
+    "sourceInstanceId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160
+    },
+    "sourceKind": {
+      "enum": [
+        "runner",
+        "control_plane"
+      ]
+    },
+    "runId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160
+    },
+    "normalizedSessionId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160
+    },
+    "turnId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160
+    },
+    "itemId": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 160
+    },
+    "eventType": {
+      "enum": [
+        "runner.connected",
+        "runner.reconnected",
+        "runner.disconnected",
+        "runner.draining",
+        "runner.diagnostic",
+        "runtime.phase.changed",
+        "sandbox.metric",
+        "workspace.ready",
+        "harness.starting",
+        "harness.ready",
+        "harness.exited",
+        "harness.diagnostic",
+        "session.starting",
+        "session.started",
+        "session.resuming",
+        "session.resumed",
+        "session.reconciled",
+        "session.closed",
+        "session.failed",
+        "turn.submitted",
+        "turn.accepted",
+        "turn.started",
+        "turn.completed",
+        "turn.failed",
+        "turn.interrupted",
+        "turn.cancelled",
+        "item.started",
+        "item.delta",
+        "item.completed",
+        "item.failed",
+        "mcp_app.discovered",
+        "mcp_app.resource.resolved",
+        "mcp_app.initializing",
+        "mcp_app.ready",
+        "mcp_app.tool_input",
+        "mcp_app.tool_result",
+        "mcp_app.action.requested",
+        "mcp_app.action.resolved",
+        "mcp_app.host_context.changed",
+        "mcp_app.failed",
+        "mcp_app.teardown",
+        "runtime_request.created",
+        "runtime_request.resolved",
+        "runtime_request.expired",
+        "runtime_request.cancelled",
+        "interaction.request.proposed",
+        "interaction.request.materialized",
+        "interaction.request.rejected",
+        "interaction.response.progressed",
+        "interaction.response.resolved",
+        "interaction.response.delivered",
+        "run.result.proposed",
+        "run.result.accepted",
+        "run.result.rejected",
+        "attention.request.proposed",
+        "attention.request.routed",
+        "attention.request.resolved",
+        "attention.request.expired",
+        "attention.request.superseded",
+        "work.assessment.recorded",
+        "issue.status.decision.recorded",
+        "issue.status.decision.applied",
+        "issue.status.decision.rejected",
+        "issue.status.decision.superseded",
+        "run.terminal"
+      ]
+    },
+    "schemaVersion": {
+      "const": 1
+    },
+    "priority": {
+      "enum": [
+        0,
+        1,
+        2
+      ]
+    },
+    "emittedAt": {
+      "type": "string",
+      "format": "date-time"
+    },
+    "observedAt": {
+      "type": "string",
+      "format": "date-time"
+    },
+    "payload": {
+      "type": "object",
+      "additionalProperties": true
+    },
+    "debug": {
+      "type": "object",
+      "additionalProperties": true
+    }
+  },
+  "allOf": [
+    {
+      "if": {
+        "properties": {
+          "eventType": {
+            "const": "run.terminal"
+          }
+        }
+      },
+      "then": {
+        "properties": {
+          "payload": {
+            "$ref": "https://paperclip.dev/schemas/prp/v1/terminal.schema.json"
+          }
+        }
+      }
+    },
+    {
+      "if": {
+        "properties": {
+          "eventType": {
+            "const": "run.result.proposed"
+          }
+        }
+      },
+      "then": {
+        "properties": {
+          "payload": {
+            "$ref": "https://paperclip.dev/schemas/prp/v1/result.schema.json"
+          }
+        }
+      }
+    }
+  ],
+  "additionalProperties": true
+} as const;
+
+export const fixtureSchema = {
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://paperclip.dev/schemas/prp/v1/fixture.schema.json",
+  "title": "PRP scripted replay fixture",
+  "type": "object",
+  "required": [
+    "schema",
+    "fixtureVersion",
+    "protocolVersion",
+    "name",
+    "description",
+    "identity",
+    "capabilities",
+    "commands",
+    "events",
+    "result"
+  ],
+  "properties": {
+    "schema": {
+      "const": "paperclip.prp.fixture.v1"
+    },
+    "fixtureVersion": {
+      "const": 1
+    },
+    "protocolVersion": {
+      "const": 1
+    },
+    "name": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 120
+    },
+    "description": {
+      "type": "string",
+      "minLength": 1,
+      "maxLength": 1000
+    },
+    "identity": {
+      "$ref": "https://paperclip.dev/schemas/prp/v1/identity.schema.json"
+    },
+    "capabilities": {
+      "$ref": "https://paperclip.dev/schemas/prp/v1/capabilities.schema.json"
+    },
+    "commands": {
+      "type": "array",
+      "items": {
+        "$ref": "https://paperclip.dev/schemas/prp/v1/command.schema.json"
+      }
+    },
+    "events": {
+      "type": "array",
+      "minItems": 1,
+      "items": {
+        "$ref": "https://paperclip.dev/schemas/prp/v1/event.schema.json"
+      }
+    },
+    "requests": {
+      "type": "array",
+      "items": {
+        "$ref": "https://paperclip.dev/schemas/prp/v1/request.schema.json"
+      }
+    },
+    "result": {
+      "$ref": "https://paperclip.dev/schemas/prp/v1/result.schema.json"
+    }
+  },
+  "additionalProperties": true
+} as const;
+
+export const prpSchemaBundle = {
+  identity: identitySchema,
+  capabilities: capabilitiesSchema,
+  command: commandSchema,
+  terminal: terminalSchema,
+  request: requestSchema,
+  result: resultSchema,
+  event: eventSchema,
+  fixture: fixtureSchema,
+} as const;
diff --git a/packages/paperclip-runner/src/protocol/phase1-contract.test.ts b/packages/paperclip-runner/src/protocol/phase1-contract.test.ts
new file mode 100644
index 00000000000..7597fde999e
--- /dev/null
+++ b/packages/paperclip-runner/src/protocol/phase1-contract.test.ts
@@ -0,0 +1,142 @@
+import { readFile } from "node:fs/promises";
+
+import { describe, expect, it } from "vitest";
+
+import {
+  negotiateProtocolVersion,
+  parsePrpFixtureText,
+  PRP_PROTOCOL_VERSION,
+} from "./phase1-contract.js";
+
+const fixtureDirectory = new URL("../../protocol/fixtures/phase-01/", import.meta.url);
+const validFixtures = [
+  "happy-path.json",
+  "failed-run.json",
+  "interrupted-run.json",
+  "duplicate-event.json",
+  "source-gap.json",
+  "unknown-optional-fields.json",
+];
+
+async function readFixture(name = "happy-path.json"): Promise<Record<string, unknown>> {
+  return JSON.parse(
+    await readFile(new URL(name, fixtureDirectory), "utf8"),
+  ) as Record<string, unknown>;
+}
+
+describe("PRP v1 JSON Schema contract", () => {
+  for (const fixtureName of validFixtures) {
+    it(`validates ${fixtureName}`, async () => {
+      const result = parsePrpFixtureText(
+        await readFile(new URL(fixtureName, fixtureDirectory), "utf8"),
+      );
+      expect(result.ok).toBe(true);
+    });
+  }
+
+  it("preserves unknown optional fields for forward compatibility", async () => {
+    const result = parsePrpFixtureText(
+      await readFile(new URL("unknown-optional-fields.json", fixtureDirectory), "utf8"),
+    );
+    expect(result.ok).toBe(true);
+    if (result.ok) {
+      expect(result.fixture.futureFixtureHint).toEqual({
+        producerVersion: "1.1-preview",
+      });
+      expect(result.fixture.events[0]?.futureEnvelopeField).toBe(42);
+    }
+  });
+
+  it("fails closed on an unsupported required protocol version", async () => {
+    const result = parsePrpFixtureText(
+      await readFile(new URL("unsupported-required-version.json", fixtureDirectory), "utf8"),
+    );
+    expect(result).toMatchObject({
+      ok: false,
+      issues: [
+        {
+          code: "unsupported_required_version",
+          path: "/protocolVersion",
+        },
+      ],
+    });
+  });
+
+  it("fails closed on unsupported nested required schema versions", async () => {
+    const fixture = await readFixture();
+    const events = fixture.events as Array<Record<string, unknown>>;
+    events[0]!.schemaVersion = 2;
+    expect(parsePrpFixtureText(JSON.stringify(fixture))).toMatchObject({
+      ok: false,
+      issues: [
+        {
+          code: "unsupported_required_version",
+          path: "/events/0/schemaVersion",
+        },
+      ],
+    });
+  });
+
+  it("requires the declared result to match the replayed result event", async () => {
+    const fixture = await readFixture();
+    const result = fixture.result as Record<string, unknown>;
+    result.summary = "A contradictory expected result.";
+    expect(parsePrpFixtureText(JSON.stringify(fixture))).toMatchObject({
+      ok: false,
+      issues: [
+        {
+          code: "binding_mismatch",
+          path: "/result",
+        },
+      ],
+    });
+  });
+
+  it("rejects a duplicate event id carrying different content", async () => {
+    const fixture = await readFixture("duplicate-event.json");
+    const events = fixture.events as Array<Record<string, unknown>>;
+    const payload = events[3]!.payload as Record<string, unknown>;
+    payload.text = "A mutated duplicate.";
+    expect(parsePrpFixtureText(JSON.stringify(fixture))).toMatchObject({
+      ok: false,
+      issues: [
+        {
+          code: "binding_mismatch",
+          path: "/events/3/sourceEventId",
+        },
+      ],
+    });
+  });
+
+  it("requires exactly one unique terminal event", async () => {
+    const fixture = await readFixture();
+    const events = fixture.events as Array<Record<string, unknown>>;
+    fixture.events = events.filter((event) => event.eventType !== "run.terminal");
+    expect(parsePrpFixtureText(JSON.stringify(fixture))).toMatchObject({
+      ok: false,
+      issues: [
+        {
+          code: "binding_mismatch",
+          path: "/events",
+        },
+      ],
+    });
+  });
+
+  it("reports invalid JSON without throwing", () => {
+    expect(parsePrpFixtureText("{")).toMatchObject({
+      ok: false,
+      issues: [{ code: "invalid_json", path: "/" }],
+    });
+  });
+
+  it("selects only an overlapping supported protocol version", () => {
+    expect(
+      negotiateProtocolVersion(
+        { min: 1, max: PRP_PROTOCOL_VERSION },
+        { min: 1, max: 2 },
+      ),
+    ).toBe(1);
+    expect(negotiateProtocolVersion({ min: 2, max: 3 }, { min: 1, max: 1 })).toBeNull();
+  });
+});
diff --git a/packages/paperclip-runner/src/protocol/phase1-contract.ts b/packages/paperclip-runner/src/protocol/phase1-contract.ts
new file mode 100644
index 00000000000..ad2431f7c45
--- /dev/null
+++ b/packages/paperclip-runner/src/protocol/phase1-contract.ts
@@ -0,0 +1,271 @@
+import {
+  Ajv2020,
+  type ErrorObject,
+  type ValidateFunction,
+} from "ajv/dist/2020.js";
+import type { FromSchema } from "json-schema-to-ts";
+
+import {
+  capabilitiesSchema,
+  commandSchema,
+  eventSchema,
+  fixtureSchema,
+  identitySchema,
+  prpSchemaBundle,
+  requestSchema,
+  resultSchema,
+  terminalSchema,
+} from "./generated/schema-bundle.js";
+
+export const PRP_PROTOCOL_NAME = "paperclip.runner";
+export const PRP_PROTOCOL_VERSION = 1;
+export const PRP_FIXTURE_SCHEMA = "paperclip.prp.fixture.v1";
+
+type EventReferences = [typeof terminalSchema, typeof resultSchema];
+export type PrpIdentity = FromSchema<typeof identitySchema>;
+export type PrpCapabilities = FromSchema<typeof capabilitiesSchema>;
+export type PrpCommand = FromSchema<typeof commandSchema>;
+export type PrpTerminalState = FromSchema<typeof terminalSchema>;
+export type PrpRequest = FromSchema<typeof requestSchema>;
+export type PrpStructuredRunResult = FromSchema<typeof resultSchema>;
+export type PrpEvent = FromSchema<
+  typeof eventSchema,
+  { references: EventReferences }
+>;
+/** Runtime-validated composition of the JSON-Schema-derived contract types. */
+export interface PrpFixture {
+  schema: typeof PRP_FIXTURE_SCHEMA;
+  fixtureVersion: 1;
+  protocolVersion: typeof PRP_PROTOCOL_VERSION;
+  name: string;
+  description: string;
+  identity: PrpIdentity;
+  capabilities: PrpCapabilities;
+  commands: PrpCommand[];
+  events: PrpEvent[];
+  requests?: PrpRequest[];
+  result: PrpStructuredRunResult;
+  [key: string]: unknown;
+}
+
+export type ProtocolValidationIssueCode =
+  | "invalid_json"
+  | "schema_validation"
+  | "unsupported_required_version"
+  | "binding_mismatch";
+
+export interface ProtocolValidationIssue {
+  code: ProtocolValidationIssueCode;
+  path: string;
+  message: string;
+}
+
+export type ProtocolValidationResult =
+  | { ok: true; fixture: PrpFixture; issues: [] }
+  | { ok: false; fixture: null; issues: ProtocolValidationIssue[] };
+
+export interface ProtocolVersionRange {
+  min: number;
+  max: number;
+}
+
+const ajv = new Ajv2020({ allErrors: true, strict: true, strictRequired: false });
+ajv.addFormat("date-time", {
+  type: "string",
+  validate(value: string) {
+    return /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d{3})?Z$/.test(value);
+  },
+});
+for (const schema of Object.values(prpSchemaBundle)) {
+  ajv.addSchema(schema);
+}
+
+const registeredFixtureValidator = ajv.getSchema(fixtureSchema.$id);
+if (registeredFixtureValidator === undefined) {
+  throw new Error("PRP fixture validator was not registered");
+}
+const fixtureValidator = registeredFixtureValidator as ValidateFunction<PrpFixture>;
+
+function asRecord(value: unknown): Record<string, unknown> | null {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+    ? (value as Record<string, unknown>)
+    : null;
+}
+
+function canonicalJson(value: unknown): string {
+  if (Array.isArray(value)) {
+    return `[${value.map(canonicalJson).join(",")}]`;
+  }
+  const object = asRecord(value);
+  if (object !== null) {
+    return `{${Object.keys(object)
+      .sort()
+      .map((key) => `${JSON.stringify(key)}:${canonicalJson(object[key])}`)
+      .join(",")}}`;
+  }
+  return JSON.stringify(value) ?? "undefined";
+}
+
+function versionIssues(value: unknown): ProtocolValidationIssue[] {
+  const fixture = asRecord(value);
+  if (fixture === null) {
+    return [];
+  }
+
+  const issues: ProtocolValidationIssue[] = [];
+  for (const [field, supported] of [
+    ["fixtureVersion", 1],
+    ["protocolVersion", PRP_PROTOCOL_VERSION],
+  ] as const) {
+    const actual = fixture[field];
+    if (typeof actual === "number" && actual !== supported) {
+      issues.push({
+        code: "unsupported_required_version",
+        path: `/${field}`,
+        message: `${field} ${actual} is unsupported; this implementation requires ${supported}`,
+      });
+    }
+  }
+
+  if (Array.isArray(fixture.events)) {
+    fixture.events.forEach((entry, index) => {
+      const event = asRecord(entry);
+      const actual = event?.schemaVersion;
+      if (typeof actual === "number" && actual !== 1) {
+        issues.push({
+          code: "unsupported_required_version",
+          path: `/events/${index}/schemaVersion`,
+          message: `event schemaVersion ${actual} is unsupported; this implementation requires 1`,
+        });
+      }
+    });
+  }
+  return issues;
+}
+
+function ajvIssue(error: ErrorObject): ProtocolValidationIssue {
+  return {
+    code: "schema_validation",
+    path: error.instancePath || "/",
+    message: error.message ?? "does not match the PRP schema",
+  };
+}
+
+function bindingIssues(fixture: PrpFixture): ProtocolValidationIssue[] {
+  const issues: ProtocolValidationIssue[] = [];
+  const uniqueEvents = new Map<string, PrpEvent>();
+  fixture.events.forEach((event, index) => {
+    if (event.runId !== fixture.identity.runId) {
+      issues.push({
+        code: "binding_mismatch",
+        path: `/events/${index}/runId`,
+        message: "event runId must match identity.runId",
+      });
+    }
+    if (
+      event.normalizedSessionId !== undefined &&
+      event.normalizedSessionId !== fixture.identity.normalizedSessionId
+    ) {
+      issues.push({
+        code: "binding_mismatch",
+        path: `/events/${index}/normalizedSessionId`,
+        message: "event normalizedSessionId must match identity.normalizedSessionId",
+      });
+    }
+    const existing = uniqueEvents.get(event.sourceEventId);
+    if (existing === undefined) {
+      uniqueEvents.set(event.sourceEventId, event);
+    } else if (canonicalJson(existing) !== canonicalJson(event)) {
+      issues.push({
+        code: "binding_mismatch",
+        path: `/events/${index}/sourceEventId`,
+        message: "duplicate sourceEventId deliveries must be byte-equivalent",
+      });
+    }
+  });
+
+  fixture.commands.forEach((command, index) => {
+    if (command.controllerSeq !== index + 1) {
+      issues.push({
+        code: "binding_mismatch",
+        path: `/commands/${index}/controllerSeq`,
+        message: `controllerSeq must be ${index + 1} in a scripted fixture`,
+      });
+    }
+  });
+
+  const distinctEvents = [...uniqueEvents.values()];
+  const proposedResults = distinctEvents.filter(
+    (event) => event.eventType === "run.result.proposed",
+  );
+  if (proposedResults.length !== 1) {
+    issues.push({
+      code: "binding_mismatch",
+      path: "/events",
+      message: "scripted fixtures must contain exactly one unique run.result.proposed event",
+    });
+  } else if (canonicalJson(proposedResults[0]?.payload) !== canonicalJson(fixture.result)) {
+    issues.push({
+      code: "binding_mismatch",
+      path: "/result",
+      message: "fixture result must match the run.result.proposed event payload",
+    });
+  }
+
+  const terminalEvents = distinctEvents.filter(
+    (event) => event.eventType === "run.terminal",
+  );
+  if (terminalEvents.length !== 1) {
+    issues.push({
+      code: "binding_mismatch",
+      path: "/events",
+      message: "scripted fixtures must contain exactly one unique run.terminal event",
+    });
+  }
+  return issues;
+}
+
+export function validatePrpFixture(value: unknown): ProtocolValidationResult {
+  const unsupported = versionIssues(value);
+  if (unsupported.length > 0) {
+    return { ok: false, fixture: null, issues: unsupported };
+  }
+  if (!fixtureValidator(value)) {
+    return {
+      ok: false,
+      fixture: null,
+      issues: (fixtureValidator.errors ?? []).map(ajvIssue),
+    };
+  }
+
+  const bindings = bindingIssues(value);
+  return bindings.length === 0
+    ? { ok: true, fixture: value, issues: [] }
+    : { ok: false, fixture: null, issues: bindings };
+}
+
+export function parsePrpFixtureText(text: string): ProtocolValidationResult {
+  try {
+    return validatePrpFixture(JSON.parse(text) as unknown);
+  } catch (error) {
+    return {
+      ok: false,
+      fixture: null,
+      issues: [
+        {
+          code: "invalid_json",
+          path: "/",
+          message: error instanceof Error ? error.message : "fixture is not valid JSON",
+        },
+      ],
+    };
+  }
+}
+
+export function negotiateProtocolVersion(
+  runner: ProtocolVersionRange,
+  controller: ProtocolVersionRange,
+): number | null {
+  const selected = Math.min(runner.max, controller.max);
+  return selected >= Math.max(runner.min, controller.min) ? selected : null;
+}
diff --git a/packages/paperclip-runner/src/protocol/phase1-loader.ts b/packages/paperclip-runner/src/protocol/phase1-loader.ts
new file mode 100644
index 00000000000..f5bfac54fdd
--- /dev/null
+++ b/packages/paperclip-runner/src/protocol/phase1-loader.ts
@@ -0,0 +1,32 @@
+import { readFile } from "node:fs/promises";
+
+import {
+  parsePrpFixtureText,
+  type ProtocolValidationIssue,
+  type PrpFixture,
+} from "./phase1-contract.js";
+
+export const phase1HappyFixtureUrl = new URL(
+  "../../protocol/fixtures/phase-01/happy-path.json",
+  import.meta.url,
+);
+
+export class PrpFixtureValidationError extends Error {
+  readonly issues: ProtocolValidationIssue[];
+
+  constructor(issues: ProtocolValidationIssue[]) {
+    super(issues.map((issue) => `${issue.path}: ${issue.message}`).join("; "));
+    this.name = "PrpFixtureValidationError";
+    this.issues = issues;
+  }
+}
+
+export async function loadPrpFixture(
+  url: URL = phase1HappyFixtureUrl,
+): Promise<PrpFixture> {
+  const result = parsePrpFixtureText(await readFile(url, "utf8"));
+  if (!result.ok) {
+    throw new PrpFixtureValidationError(result.issues);
+  }
+  return result.fixture;
+}
diff --git a/packages/paperclip-runner/src/reducer/session-reducer.test.ts b/packages/paperclip-runner/src/reducer/session-reducer.test.ts
new file mode 100644
index 00000000000..8d3c0c7624f
--- /dev/null
+++ b/packages/paperclip-runner/src/reducer/session-reducer.test.ts
@@ -0,0 +1,73 @@
+import { readFile } from "node:fs/promises";
+
+import { describe, expect, it } from "vitest";
+
+import { parsePrpFixtureText, type PrpFixture } from "../protocol/phase1-contract.js";
+import {
+  reducePrpFixture,
+  reduceSessionEvents,
+  type SessionSnapshot,
+} from "./session-reducer.js";
+
+const fixtureDirectory = new URL("../../protocol/fixtures/phase-01/", import.meta.url);
+const fixtureNames = [
+  "happy-path",
+  "failed-run",
+  "interrupted-run",
+  "duplicate-event",
+  "source-gap",
+  "unknown-optional-fields",
+];
+
+async function loadFixture(name: string): Promise<PrpFixture> {
+  const result = parsePrpFixtureText(
+    await readFile(new URL(`${name}.json`, fixtureDirectory), "utf8"),
+  );
+  if (!result.ok) {
+    throw new Error(result.issues.map((issue) => issue.message).join("; "));
+  }
+  return result.fixture;
+}
+
+async function loadGolden(name: string): Promise<SessionSnapshot> {
+  return JSON.parse(
+    await readFile(new URL(`golden/${name}.snapshot.json`, fixtureDirectory), "utf8"),
+  ) as SessionSnapshot;
+}
+
+describe("deterministic PRP session reducer", () => {
+  for (const fixtureName of fixtureNames) {
+    it(`matches the ${fixtureName} golden snapshot`, async () => {
+      expect(reducePrpFixture(await loadFixture(fixtureName))).toEqual(
+        await loadGolden(fixtureName),
+      );
+    });
+  }
+
+  it("is deterministic and idempotent when the same batch is replayed", async () => {
+    const fixture = await loadFixture("happy-path");
+    const first = reducePrpFixture(fixture);
+    expect(reducePrpFixture(fixture)).toEqual(first);
+    expect(reduceSessionEvents(first, fixture.events)).toEqual(first);
+  });
+
+  it("deduplicates at-least-once delivery before projection effects", async () => {
+    const snapshot = reducePrpFixture(await loadFixture("duplicate-event"));
+    expect(snapshot.duplicateEventIds).toEqual(["event_duplicate_03"]);
+    expect(snapshot.items).toHaveLength(1);
+    expect(snapshot.timeline).toHaveLength(6);
+  });
+
+  it("records a source cursor gap without inventing the missing event", async () => {
+    const snapshot = reducePrpFixture(await loadFixture("source-gap"));
+    expect(snapshot.integrity).toBe("gap_detected");
+    expect(snapshot.gaps).toEqual([
+      {
+        sourceKey: "runner:runner_phase1",
+        expected: 3,
+        received: 4,
+        missing: [3],
+      },
+    ]);
+  });
+});
diff --git a/packages/paperclip-runner/src/reducer/session-reducer.ts b/packages/paperclip-runner/src/reducer/session-reducer.ts
new file mode 100644
index 00000000000..16b54225309
--- /dev/null
+++ b/packages/paperclip-runner/src/reducer/session-reducer.ts
@@ -0,0 +1,354 @@
+import type {
+  PrpCapabilities,
+  PrpEvent,
+  PrpFixture,
+  PrpIdentity,
+  PrpStructuredRunResult,
+  PrpTerminalState,
+} from "../protocol/phase1-contract.js";
+
+export interface SessionTimelineEntry {
+  position: number;
+  sourceEventId: string;
+  sourceSeq: number;
+  eventType: PrpEvent["eventType"];
+  emittedAt: string;
+  itemId?: string;
+  summary: string;
+}
+
+export interface SessionItemSnapshot {
+  itemId: string;
+  kind: string;
+  status: "running" | "completed" | "failed";
+  text: string;
+}
+
+export interface SessionRequestSnapshot {
+  requestId: string;
+  requestKind: string;
+  status: string;
+  prompt: string;
+}
+
+export interface SequenceGap {
+  sourceKey: string;
+  expected: number;
+  received: number;
+  missing: number[];
+}
+
+export interface SessionSnapshot {
+  schema: "paperclip.prp.session-snapshot.v1";
+  fixtureName: string;
+  identity: PrpIdentity;
+  capabilities: PrpCapabilities;
+  runPhase: string;
+  sessionState: "not_started" | "running" | "closed" | "failed";
+  turnState:
+    | "not_started"
+    | "running"
+    | "completed"
+    | "failed"
+    | "interrupted"
+    | "cancelled";
+  activeTurnId: string | null;
+  items: SessionItemSnapshot[];
+  requests: SessionRequestSnapshot[];
+  proposedResult: PrpStructuredRunResult | null;
+  terminal: PrpTerminalState | null;
+  timeline: SessionTimelineEntry[];
+  sourceCursors: Record<string, number>;
+  processedEventIds: string[];
+  duplicateEventIds: string[];
+  outOfOrderEventIds: string[];
+  gaps: SequenceGap[];
+  integrity: "complete" | "gap_detected";
+}
+
+function record(value: unknown): Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+    ? (value as Record<string, unknown>)
+    : {};
+}
+
+function stringValue(value: unknown, fallback = ""): string {
+  return typeof value === "string" ? value : fallback;
+}
+
+function sourceKey(event: PrpEvent): string {
+  return `${event.sourceKind}:${event.sourceInstanceId}`;
+}
+
+function timelineSummary(event: PrpEvent): string {
+  const payload = record(event.payload);
+  if (event.eventType === "runtime.phase.changed") {
+    return `Phase changed to ${stringValue(payload.phase, "unknown")}`;
+  }
+  if (event.eventType === "item.started") {
+    return `Started ${stringValue(payload.kind, "item")}`;
+  }
+  if (event.eventType === "item.delta") {
+    return stringValue(payload.text, "Item updated");
+  }
+  if (event.eventType === "item.completed") {
+    return `Completed ${stringValue(payload.kind, "item")}`;
+  }
+  if (event.eventType === "item.failed") {
+    return stringValue(payload.message, "Item failed");
+  }
+  if (event.eventType === "run.result.proposed") {
+    return stringValue(payload.summary, "Structured result proposed");
+  }
+  if (event.eventType === "run.terminal") {
+    return `Run ${stringValue(payload.runTerminalState, "terminal")}`;
+  }
+  return event.eventType.replaceAll(".", " ");
+}
+
+function upsertItem(
+  items: SessionItemSnapshot[],
+  event: PrpEvent,
+  status: SessionItemSnapshot["status"],
+): void {
+  if (event.itemId === undefined) {
+    return;
+  }
+  const payload = record(event.payload);
+  const existing = items.find((item) => item.itemId === event.itemId);
+  const text = stringValue(payload.text);
+  if (existing === undefined) {
+    items.push({
+      itemId: event.itemId,
+      kind: stringValue(payload.kind, "diagnostic"),
+      status,
+      text,
+    });
+    return;
+  }
+  existing.kind = stringValue(payload.kind, existing.kind);
+  existing.status = status;
+  if (event.eventType === "item.delta") {
+    existing.text += text;
+  } else if (text.length > 0) {
+    existing.text = text;
+  }
+}
+
+function applyProjection(snapshot: SessionSnapshot, event: PrpEvent): void {
+  const payload = record(event.payload);
+  switch (event.eventType) {
+    case "runtime.phase.changed":
+      snapshot.runPhase = stringValue(payload.phase, snapshot.runPhase);
+      break;
+    case "session.started":
+    case "session.resumed":
+      snapshot.sessionState = "running";
+      break;
+    case "session.closed":
+      snapshot.sessionState = "closed";
+      break;
+    case "session.failed":
+      snapshot.sessionState = "failed";
+      break;
+    case "turn.started":
+      snapshot.turnState = "running";
+      snapshot.activeTurnId = event.turnId ?? null;
+      break;
+    case "turn.completed":
+      snapshot.turnState = "completed";
+      snapshot.activeTurnId = null;
+      break;
+    case "turn.failed":
+      snapshot.turnState = "failed";
+      snapshot.activeTurnId = null;
+      break;
+    case "turn.interrupted":
+      snapshot.turnState = "interrupted";
+      snapshot.activeTurnId = null;
+      break;
+    case "turn.cancelled":
+      snapshot.turnState = "cancelled";
+      snapshot.activeTurnId = null;
+      break;
+    case "item.started":
+    case "item.delta":
+      upsertItem(snapshot.items, event, "running");
+      break;
+    case "item.completed":
+      upsertItem(snapshot.items, event, "completed");
+      break;
+    case "item.failed":
+      upsertItem(snapshot.items, event, "failed");
+      break;
+    case "runtime_request.created": {
+      const request = record(payload.request ?? payload);
+      const requestId = stringValue(request.requestId);
+      if (
+        requestId.length > 0 &&
+        !snapshot.requests.some((candidate) => candidate.requestId === requestId)
+      ) {
+        snapshot.requests.push({
+          requestId,
+          requestKind: stringValue(request.requestKind, "runtime"),
+          status: stringValue(request.status, "pending"),
+          prompt: stringValue(request.prompt),
+        });
+      }
+      break;
+    }
+    case "runtime_request.resolved":
+    case "runtime_request.expired":
+    case "runtime_request.cancelled": {
+      const requestId = stringValue(payload.requestId);
+      const request = snapshot.requests.find((candidate) => candidate.requestId === requestId);
+      if (request !== undefined) {
+        request.status = event.eventType.split(".").at(-1) ?? request.status;
+      }
+      break;
+    }
+    case "run.result.proposed":
+      snapshot.proposedResult = structuredClone(
+        event.payload as PrpStructuredRunResult,
+      );
+      break;
+    case "run.terminal":
+      snapshot.terminal = structuredClone(event.payload as PrpTerminalState);
+      snapshot.runPhase = "terminal";
+      break;
+  }
+}
+
+function addGap(snapshot: SessionSnapshot, event: PrpEvent, expected: number): void {
+  const key = sourceKey(event);
+  if (
+    snapshot.gaps.some(
+      (gap) => gap.sourceKey === key && gap.expected === expected && gap.received === event.sourceSeq,
+    )
+  ) {
+    return;
+  }
+  snapshot.gaps.push({
+    sourceKey: key,
+    expected,
+    received: event.sourceSeq,
+    missing: Array.from(
+      { length: event.sourceSeq - expected },
+      (_, index) => expected + index,
+    ),
+  });
+}
+
+export function createSessionSnapshot(fixture: PrpFixture): SessionSnapshot {
+  return {
+    schema: "paperclip.prp.session-snapshot.v1",
+    fixtureName: fixture.name,
+    identity: structuredClone(fixture.identity),
+    capabilities: structuredClone(fixture.capabilities),
+    runPhase: "queued",
+    sessionState: "not_started",
+    turnState: "not_started",
+    activeTurnId: null,
+    items: [],
+    requests: [],
+    proposedResult: null,
+    terminal: null,
+    timeline: [],
+    sourceCursors: {},
+    processedEventIds: [],
+    duplicateEventIds: [],
+    outOfOrderEventIds: [],
+    gaps: [],
+    integrity: "complete",
+  };
+}
+
+export function applyPrpEvent(
+  current: SessionSnapshot,
+  event: PrpEvent,
+): SessionSnapshot {
+  if (current.processedEventIds.includes(event.sourceEventId)) {
+    return current;
+  }
+
+  const snapshot = structuredClone(current);
+  const key = sourceKey(event);
+  const cursor = snapshot.sourceCursors[key] ?? 0;
+  const expected = cursor + 1;
+  if (event.sourceSeq <= cursor) {
+    if (!snapshot.outOfOrderEventIds.includes(event.sourceEventId)) {
+      snapshot.outOfOrderEventIds.push(event.sourceEventId);
+    }
+    snapshot.integrity = "gap_detected";
+    return snapshot;
+  }
+  if (event.sourceSeq > expected) {
+    addGap(snapshot, event, expected);
+  }
+
+  snapshot.sourceCursors[key] = event.sourceSeq;
+  snapshot.processedEventIds.push(event.sourceEventId);
+  snapshot.timeline.push({
+    position: snapshot.timeline.length + 1,
+    sourceEventId: event.sourceEventId,
+    sourceSeq: event.sourceSeq,
+    eventType: event.eventType,
+    emittedAt: event.emittedAt,
+    ...(event.itemId === undefined ? {} : { itemId: event.itemId }),
+    summary: timelineSummary(event),
+  });
+  applyProjection(snapshot, event);
+  snapshot.integrity =
+    snapshot.gaps.length > 0 || snapshot.outOfOrderEventIds.length > 0
+      ? "gap_detected"
+      : "complete";
+  return snapshot;
+}
+
+export function reduceSessionEvents(
+  current: SessionSnapshot,
+  events: readonly PrpEvent[],
+): SessionSnapshot {
+  const counts = new Map<string, number>();
+  for (const event of events) {
+    counts.set(event.sourceEventId, (counts.get(event.sourceEventId) ?? 0) + 1);
+  }
+
+  let snapshot = structuredClone(current);
+  for (const [eventId, count] of counts) {
+    if (count > 1 && !snapshot.duplicateEventIds.includes(eventId)) {
+      snapshot.duplicateEventIds.push(eventId);
+    }
+  }
+  snapshot.duplicateEventIds.sort();
+  for (const event of events) {
+    snapshot = applyPrpEvent(snapshot, event);
+  }
+  return snapshot;
+}
+
+export function reducePrpFixture(fixture: PrpFixture): SessionSnapshot {
+  return reduceSessionEvents(createSessionSnapshot(fixture), fixture.events);
+}
+
+export interface Phase1ParitySummary {
+  runId: string;
+  integrity: SessionSnapshot["integrity"];
+  timelineCount: number;
+  duplicateEventIds: string[];
+  gaps: SequenceGap[];
+  turnTerminalState: string | null;
+  runTerminalState: string | null;
+}
+
+export function phase1ParitySummary(snapshot: SessionSnapshot): Phase1ParitySummary {
+  return {
+    runId: snapshot.identity.runId,
+    integrity: snapshot.integrity,
+    timelineCount: snapshot.timeline.length,
+    duplicateEventIds: [...snapshot.duplicateEventIds],
+    gaps: structuredClone(snapshot.gaps),
+    turnTerminalState: snapshot.terminal?.turnTerminalState ?? null,
+    runTerminalState: snapshot.terminal?.runTerminalState ?? null,
+  };
+}
diff --git a/packages/paperclip-runner/src/tracer/phase1-replay.test.ts b/packages/paperclip-runner/src/tracer/phase1-replay.test.ts
new file mode 100644
index 00000000000..0d2c94c0c98
--- /dev/null
+++ b/packages/paperclip-runner/src/tracer/phase1-replay.test.ts
@@ -0,0 +1,23 @@
+import { readFile } from "node:fs/promises";
+
+import { describe, expect, it } from "vitest";
+
+import { formatPhase1Replay, replayPhase1FixtureText } from "./phase1-replay.js";
+
+describe("Phase 1 replay tracer", () => {
+  it("formats the validated reducer snapshot for CLI consumers", async () => {
+    const source = await readFile(
+      new URL("../../protocol/fixtures/phase-01/happy-path.json", import.meta.url),
+      "utf8",
+    );
+    const result = replayPhase1FixtureText(source);
+    expect(result.ok).toBe(true);
+    expect(JSON.parse(formatPhase1Replay(result))).toMatchObject({
+      ok: true,
+      snapshot: {
+        integrity: "complete",
+        terminal: { runTerminalState: "succeeded" },
+      },
+    });
+  });
+});
diff --git a/packages/paperclip-runner/src/tracer/phase1-replay.ts b/packages/paperclip-runner/src/tracer/phase1-replay.ts
new file mode 100644
index 00000000000..d2eafdd4fbf
--- /dev/null
+++ b/packages/paperclip-runner/src/tracer/phase1-replay.ts
@@ -0,0 +1,21 @@
+import {
+  parsePrpFixtureText,
+  type ProtocolValidationIssue,
+} from "../protocol/phase1-contract.js";
+import { reducePrpFixture, type SessionSnapshot } from "../reducer/session-reducer.js";
+
+export type Phase1ReplayResult =
+  | { ok: true; snapshot: SessionSnapshot; issues: [] }
+  | { ok: false; snapshot: null; issues: ProtocolValidationIssue[] };
+
+export function replayPhase1FixtureText(text: string): Phase1ReplayResult {
+  const validation = parsePrpFixtureText(text);
+  if (!validation.ok) {
+    return { ok: false, snapshot: null, issues: validation.issues };
+  }
+  return { ok: true, snapshot: reducePrpFixture(validation.fixture), issues: [] };
+}
+
+export function formatPhase1Replay(result: Phase1ReplayResult): string {
+  return JSON.stringify(result, null, 2);
+}
diff --git a/packages/paperclip-runner/tsconfig.browser.json b/packages/paperclip-runner/tsconfig.browser.json
new file mode 100644
index 00000000000..81f66f96486
--- /dev/null
+++ b/packages/paperclip-runner/tsconfig.browser.json
@@ -0,0 +1,12 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "jsx": "react-jsx",
+    "lib": ["ES2023", "DOM", "DOM.Iterable"],
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "rootDir": ".",
+    "types": ["vite/client"]
+  },
+  "include": ["devtools/browser/src/**/*.ts", "devtools/browser/src/**/*.tsx"]
+}
diff --git a/packages/paperclip-runner/vite.config.ts b/packages/paperclip-runner/vite.config.ts
new file mode 100644
index 00000000000..49a825967e7
--- /dev/null
+++ b/packages/paperclip-runner/vite.config.ts
@@ -0,0 +1,20 @@
+import { resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+import react from "@vitejs/plugin-react";
+import { defineConfig } from "vite";
+
+const packageRoot = fileURLToPath(new URL(".", import.meta.url));
+
+export default defineConfig({
+  root: resolve(packageRoot, "devtools/browser"),
+  plugins: [react()],
+  build: {
+    outDir: resolve(packageRoot, "dist-browser"),
+    emptyOutDir: true,
+    // The standalone devtool targets current evergreen browsers. Keeping the
+    // emitted syntax modern also avoids asking Vite to downlevel Ajv's runtime
+    // validator, which recent esbuild releases intentionally do not support.
+    target: "esnext",
+  },
+});