fix(runner): address phase 2 tutorial QA

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/paperclip-runner/README.md

@@ -23,6 +23,14 @@ pnpm --filter @paperclipai/paperclip-runner verify
 The verification command requires a stable Rust toolchain with `cargo` on
 `PATH`, in addition to Node.js 20+ and pnpm 9+.
 
+Minimal Debian/Ubuntu hosts without root access can extract the required
+Playwright browser libraries into a user-owned cache and run the same acceptance
+sequence with:
+
+```sh
+pnpm --filter @paperclipai/paperclip-runner verify:rootless
+```
+
 The tracer's final line is stable:
 
 ```json
@@ -64,8 +72,9 @@ pnpm --filter @paperclipai/paperclip-runner browser:dev --host 127.0.0.1 --port
 | `trace:phase2` | Run one native local session through the Rust runner and fake harness. |
 | `record:phase2` | Capture a validated happy-path live trace as a replay fixture. |
 | `browser:dev` | Start the standalone live/replay browser devtool. |
-| `test:browser` | Exercise static replay and live scenarios, then capture screenshots. |
+| `test:browser` | Exercise static replay and live scenarios, then capture temporary screenshots under ignored test output. |
 | `verify` | Run the complete Phase 0, Phase 1, and Phase 2 acceptance sequence. |
+| `verify:rootless` | Extract Debian/Ubuntu browser libraries without root, then run `verify`. |
 
 ## Navigate
 

packages/paperclip-runner/devtools/browser/static-replay.spec.ts

@@ -1,10 +1,6 @@
 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 Phase 1 fixture", async ({ page }) => {
+test("validates and renders the shared Phase 1 fixture", async ({ page }, testInfo) => {
   await page.goto("/");
   await page.getByRole("button", { name: "Static replay" }).click();
   await expect(page.getByRole("heading", { name: "Live local runner" })).toBeVisible();
@@ -15,7 +11,7 @@ test("validates and renders the shared Phase 1 fixture", async ({ page }) => {
     "The scripted run completed successfully.",
   );
   await page.screenshot({
-    path: resolve(packageRoot, "knowledge/evidence/phase-01-static-replay.png"),
+    path: testInfo.outputPath("phase-01-static-replay.png"),
     fullPage: true,
   });
 });
@@ -32,7 +28,7 @@ test("shows duplicate and unsupported-version replay states", async ({ page }) =
   await expect(page.getByText(/protocolVersion 2 is unsupported/)).toBeVisible();
 });
 
-test("streams a live run and proves replay parity", async ({ page }) => {
+test("streams a live run and proves replay parity", async ({ page }, testInfo) => {
   await page.goto("/");
   await page.getByRole("button", { name: "Start local run" }).click();
   await expect(page.getByTestId("live-status")).toHaveText("Terminal");
@@ -41,12 +37,12 @@ test("streams a live run and proves replay parity", async ({ page }) => {
   await expect(page.getByTestId("process-facts")).toContainText("done");
   await expect(page.getByTestId("parity-result")).toContainText("Match");
   await page.screenshot({
-    path: resolve(packageRoot, "knowledge/evidence/phase-02-live-complete.png"),
+    path: testInfo.outputPath("phase-02-live-complete.png"),
     fullPage: true,
   });
 });
 
-test("resolves live permission and input requests", async ({ page }) => {
+test("resolves live permission and input requests", async ({ page }, testInfo) => {
   await page.goto("/");
   await page.getByLabel("Scenario").selectOption("permission-input");
   await page.getByRole("button", { name: "Start local run" }).click();
@@ -58,7 +54,7 @@ test("resolves live permission and input requests", async ({ page }) => {
     }).first(),
   ).toContainText("permission: Allow the fake driver to write its local fixture?");
   await page.screenshot({
-    path: resolve(packageRoot, "knowledge/evidence/phase-02-live-permission.png"),
+    path: testInfo.outputPath("phase-02-live-permission.png"),
     fullPage: true,
   });
   await page.getByRole("button", { name: "Allow" }).click();
@@ -68,13 +64,14 @@ test("resolves live permission and input requests", async ({ page }) => {
       hasText: "runtime_request.resolved",
     }).first(),
   ).toContainText("Resolved permission: Allow the fake driver to write its local fixture?");
+  await page.waitForTimeout(10_500);
   await page.getByLabel("Response").fill("phase-02-browser-trace");
   await page.getByRole("button", { name: "Send input" }).click();
   await expect(page.getByTestId("live-status")).toHaveText("Terminal");
   await expect(page.getByTestId("parity-result")).toContainText("Match");
 });
 
-test("interrupts a live turn without duplicating terminal state", async ({ page }) => {
+test("interrupts a live turn without duplicating terminal state", async ({ page }, testInfo) => {
   await page.goto("/");
   await page.getByLabel("Scenario").selectOption("interrupted");
   await page.getByRole("button", { name: "Start local run" }).click();
@@ -87,7 +84,7 @@ test("interrupts a live turn without duplicating terminal state", async ({ page
   await expect(page.getByTestId("terminal-badge")).toHaveAttribute("data-tone", "neutral");
   await expect(page.getByTestId("timeline").getByText("run.terminal")).toHaveCount(1);
   await page.screenshot({
-    path: resolve(packageRoot, "knowledge/evidence/phase-02-live-interrupted.png"),
+    path: testInfo.outputPath("phase-02-live-interrupted.png"),
     fullPage: true,
   });
 });

packages/paperclip-runner/docs/tutorials/end-to-end.md

@@ -39,6 +39,13 @@ The one-command form after installation is:
 pnpm --filter @paperclipai/paperclip-runner verify
 ```
 
+On a minimal Debian or Ubuntu host without root access, use the rootless browser
+dependency path:
+
+```sh
+pnpm --filter @paperclipai/paperclip-runner verify:rootless
+```
+
 ## Cumulative guarantees
 
 - the fixture is validated before any mock-core mutation;

packages/paperclip-runner/docs/tutorials/phase-01-static-replay.md

@@ -98,8 +98,9 @@ pnpm --filter @paperclipai/paperclip-runner check:browser-tokens
 pnpm --filter @paperclipai/paperclip-runner test:browser
 ```
 
-Expected: two Playwright tests pass and the happy-path screenshot is written to
-`packages/paperclip-runner/knowledge/evidence/phase-01-static-replay.png`.
+Expected: the Playwright tests pass and temporary screenshots are written under
+the ignored `packages/paperclip-runner/test-results/` directory. The regression
+suite does not rewrite committed evidence images.
 
 ## What this proves
 

packages/paperclip-runner/docs/tutorials/phase-02-local-runner.md

@@ -34,6 +34,16 @@ On a minimal Linux host, install the browser libraries too:
 pnpm --filter @paperclipai/paperclip-runner exec playwright install-deps chromium
 ```
 
+`playwright install-deps` requires root. On a Debian or Ubuntu host where root
+is unavailable, use the package's rootless verification command instead. It
+downloads the required browser-library packages into a user-owned cache,
+extracts them without installing system packages, and scopes `LD_LIBRARY_PATH`
+to the verification process:
+
+```sh
+pnpm --filter @paperclipai/paperclip-runner verify:rootless
+```
+
 ## 1. Run the package verification path
 
 ```sh
@@ -52,7 +62,7 @@ pnpm --filter @paperclipai/paperclip-runner trace:phase2 -- --scenario happy-pat
 
 Expected summary facts:
 
-- `eventCount` is `18`;
+- `eventCount` is `19`;
 - `terminalCount` is `1`;
 - `semanticResult` is `done`;
 - harness and runner exit codes are `0`.
@@ -100,6 +110,8 @@ Open `http://127.0.0.1:4179`, then follow these steps:
 4. Confirm `Live and replay reducer output` says `Match`.
 5. Select `Permission and input`, start the run, and choose **Allow**.
 6. Enter a trace name and choose **Send input**. Confirm the run completes.
+   Each interactive request remains open for five minutes. If it expires, the
+   page reports that the run finished and asks you to start a new run.
 7. Select `Interruption`, start the run, and choose **Interrupt turn** when the
    button becomes active.
 8. Confirm the terminal badge says `cancelled`, the semantic result says
@@ -108,6 +120,10 @@ Open `http://127.0.0.1:4179`, then follow these steps:
 
 Stop Vite with `Ctrl+C`.
 
+The browser regression suite writes its temporary screenshots under the
+ignored `packages/paperclip-runner/test-results/` directory. It never rewrites
+the committed evidence images linked below.
+
 ## 5. Inspect the evidence
 
 - [Complete live run](../../knowledge/evidence/phase-02-live-complete.png)

packages/paperclip-runner/knowledge/evidence/2026-08-07-phase-02-verification.md

@@ -4,7 +4,7 @@ title: Phase 2 verification
 description: Exact tools, commands, results, and screenshots for the local runner and fake harness.
 tags: [native-runner, phase-2, verification, rust, supervisor, fake-driver, browser]
 status: stable
-generated: { by: openai/gpt-5, at: 2026-08-07T21:10:00Z }
+generated: { by: openai/gpt-5, at: 2026-08-07T22:13:00Z }
 phase: "2"
 ---
 
@@ -16,7 +16,7 @@ phase: "2"
 - Vitest: `4.1.10`
 - Vite: `6.4.1`
 - Playwright: `1.61.1`
-- Rust/Cargo: `1.97.1` in the run scratch directory
+- Rust/Cargo: `1.97.1` in the user-local toolchain
 
 # Commands and observed results
 
@@ -27,8 +27,8 @@ cargo fmt --manifest-path packages/paperclip-runner/runner/Cargo.toml --all -- -
 cargo test --manifest-path packages/paperclip-runner/runner/Cargo.toml --locked --workspace
 ```
 
-Result: exit 0. Rust formatting passed. Fifteen library tests and one supervisor
-integration test passed. The cleanup test proved that the harness and spawned
+Result: exit 0. Rust formatting passed. Eighteen library tests and two supervisor
+integration tests passed. The cleanup test proved that the harness and spawned
 worker process group both stop.
 
 ## 2. TypeScript and live-run conformance
@@ -39,11 +39,11 @@ pnpm --filter @paperclipai/paperclip-runner typecheck:typescript
 pnpm --filter @paperclipai/paperclip-runner typecheck:browser
 ```
 
-Result: exit 0. Seven Vitest files and 38 tests passed. The Phase 2 cases cover
+Result: exit 0. Eight Vitest files and 46 tests passed. The Phase 2 cases cover
 driver lifecycle, command and file items, bounded logs, duplicate commands,
 permission/input, interruption, error exit versus semantic result, duplicate
-terminal suppression, controller-disconnect cleanup, credentials, and
-live/replay parity.
+terminal suppression, controller-disconnect cleanup, credentials, live/replay
+parity, and the operator-safe rejection of a command sent after completion.
 
 ## 3. CLI scenario matrix
 
@@ -59,11 +59,11 @@ Observed facts:
 
 | Scenario | Events | Terminal | Semantic result | Harness exit | Runner exit |
 |---|---:|---:|---|---:|---:|
-| happy path | 18 | 1 | `done` | 0 | 0 |
-| permission/input | 19 | 1 | `done` | 0 | 0 |
-| interrupted | 15 | 1 | `yielded` | 130 | 0 |
-| error | 14 | 1 | `yielded` | 7 | 0 |
-| duplicate terminal | 14 | 1 | `done` | 0 | 0 |
+| happy path | 19 | 1 | `done` | 0 | 0 |
+| permission/input | 20 | 1 | `done` | 0 | 0 |
+| interrupted | 16 | 1 | `yielded` | 130 | 0 |
+| error | 15 | 1 | `yielded` | 7 | 0 |
+| duplicate terminal | 15 | 1 | `done` | 0 | 0 |
 
 The duplicate turn command returned one duplicate receipt and did not create a
 second `turn.started` event.
@@ -76,14 +76,30 @@ pnpm --filter @paperclipai/paperclip-runner check:browser-tokens
 pnpm --filter @paperclipai/paperclip-runner test:browser
 ```
 
-Result: exit 0. Vite transformed 219 modules. The token check passed. Five
-Playwright tests passed in 3.5 seconds. They cover Phase 1 static replay,
+Result: exit 0. Vite transformed 219 modules. The token check passed. Six
+Playwright tests passed in 14.3 seconds. They cover Phase 1 static replay,
 duplicate/version states, live completion and replay parity, permission/input,
-and interruption with one terminal event.
+and interruption with one terminal event. The permission/input test deliberately
+waited 10.5 seconds before submitting input and still completed with replay
+parity.
 
-The minimal host lacked Chromium libraries. The test used Ubuntu packages
-extracted under `$PAPERCLIP_RUN_SCRATCH_DIR/playwright-libs` through
-`LD_LIBRARY_PATH`; no system library was installed.
+The documented development server was also started directly:
+
+```sh
+pnpm --filter @paperclipai/paperclip-runner browser:dev --host 127.0.0.1 --port 4179
+curl -fsS http://127.0.0.1:4179/
+curl -fsS http://127.0.0.1:4179/src/main.tsx
+```
+
+Result: both requests returned successfully, the Vite process stayed alive, and
+dependency optimization emitted none of the Ajv downlevel-transform errors.
+
+The minimal host lacked Chromium libraries. The rootless helper downloaded
+and extracted the matching Ubuntu packages under
+`$PAPERCLIP_RUN_SCRATCH_DIR/arm64`, then scoped `LD_LIBRARY_PATH` to
+the verification process. No system package was installed and no root access
+was used. Playwright screenshots were written under ignored `test-results/`
+paths, leaving the committed evidence images unchanged.
 
 ## 5. Boundary and knowledge checks
 
@@ -98,13 +114,13 @@ v0.2 bundle passed validation.
 ## 6. Complete package acceptance sequence
 
 ```sh
-pnpm --filter @paperclipai/paperclip-runner verify
+pnpm --filter @paperclipai/paperclip-runner verify:rootless
 ```
 
-Result: exit 0 with the run-scratch Rust and browser-library paths active. The
-command built Rust, TypeScript, and browser outputs; ran all typechecks, tests,
-goldens, parity, token, boundary, browser, docs, and OKF checks; ran the Phase 0
-tracer and Phase 1 replay; and finished with the Phase 2 happy-path summary.
+Result: exit 0 with the rootless browser-library path active. The command built
+Rust, TypeScript, and browser outputs; ran all typechecks, tests, goldens,
+parity, token, boundary, browser, docs, and OKF checks; ran the Phase 0 tracer
+and Phase 1 replay; and finished with the Phase 2 happy-path summary.
 
 # Browser artifacts
 
@@ -112,25 +128,25 @@ tracer and Phase 1 replay; and finished with the Phase 2 happy-path summary.
 
 [Phase 2 completed run screenshot](phase-02-live-complete.png)
 
-- PNG: 1440 × 1786, RGB
-- SHA-256: `6c49da63df4de4e2d7e5958bd66cdefa492819474526c345328dcd2b575b887a`
-- Shows 18 validated events, process exit 0, semantic result `done`, one terminal
+- PNG: 1440 × 1851, RGB
+- SHA-256: `01524691337ad58d1b9f4592685a7d3b67d225e1c8aede6afdc576d1a5b5dc15`
+- Shows 19 validated events, process exit 0, semantic result `done`, one terminal
   event, and live/replay `Match`.
 
 ## Permission request
 
 [Phase 2 permission screenshot](phase-02-live-permission.png)
 
-- PNG: 1440 × 1131, RGB
-- SHA-256: `192c0b244694d22cfe880e814dade1714ae48ab18a2047aaa2c7714419a0328b`
+- PNG: 1440 × 1196, RGB
+- SHA-256: `1b33f2345299badef63f8f9ea300aa3d9d46148e5f29aca0b8419c5526f7881d`
 - Shows the live pending permission request before resolution.
 
 ## Interrupted run
 
 [Phase 2 interrupted run screenshot](phase-02-live-interrupted.png)
 
-- PNG: 1440 × 1591, RGB
-- SHA-256: `11003e92e776afe670a4a2c958770b4f844ff373115ff93c3aee1e54238b2bd4`
+- PNG: 1440 × 1656, RGB
+- SHA-256: `35a6d90e9647bb3ac477c39240652ad9c427c93cec10f2eeada609001d6a45dc`
 - Shows exit 130, semantic result `yielded`, cancelled terminal state, one
   terminal event, and live/replay `Match`.
 

packages/paperclip-runner/package.json

@@ -46,7 +46,8 @@
     "record:phase2": "pnpm run trace:phase2 -- --quiet --output knowledge/evidence/phase-02-happy-path.json",
     "browser:dev": "pnpm run build:typescript && pnpm run build:phase2-binaries && 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 && pnpm run trace:phase2 -- --quiet"
+    "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 && pnpm run trace:phase2 -- --quiet",
+    "verify:rootless": "bash scripts/verify-rootless-linux.sh"
   },
   "devDependencies": {
     "@playwright/test": "^1.61.1",

packages/paperclip-runner/runner/crates/runner-core/src/phase2.rs

@@ -18,6 +18,8 @@ const RUNNER_STREAM_SCHEMA: &str = "paperclip.runner.stream.v1";
 const RUNNER_COMMAND_SCHEMA: &str = "paperclip.prp.command.v1";
 const HARNESS_COMMAND_SCHEMA: &str = "paperclip.fake_harness.command.v1";
 const HARNESS_MESSAGE_SCHEMA: &str = "paperclip.fake_harness.message.v1";
+const HARNESS_COMMAND_TIMEOUT: Duration = Duration::from_secs(10);
+const INTERACTIVE_REQUEST_TIMEOUT: Duration = Duration::from_secs(5 * 60);
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct Phase2Error(String);
@@ -1327,9 +1329,14 @@ fn receive_harness_command(
     command_type: &str,
     request_id: Option<&str>,
 ) -> Result<HarnessCommand, Phase2Error> {
+    let timeout = if command_type == "request.resolve" {
+        INTERACTIVE_REQUEST_TIMEOUT
+    } else {
+        HARNESS_COMMAND_TIMEOUT
+    };
     loop {
         let command = receiver
-            .recv_timeout(Duration::from_secs(10))
+            .recv_timeout(timeout)
             .map_err(|_| Phase2Error::invalid(format!("timed out waiting for {command_type}")))?;
         if command.schema != HARNESS_COMMAND_SCHEMA {
             continue;

packages/paperclip-runner/scripts/verify-rootless-linux.sh

@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+if [[ "$(uname -s)" != "Linux" ]]; then
+  printf 'verify:rootless supports Debian and Ubuntu Linux hosts only.\n' >&2
+  exit 1
+fi
+
+for required_command in apt-cache apt-get dpkg dpkg-deb; do
+  if ! command -v "$required_command" >/dev/null 2>&1; then
+    printf 'verify:rootless requires %s (Debian/Ubuntu package tooling).\n' "$required_command" >&2
+    exit 1
+  fi
+done
+
+rootless_cache_base="${PAPERCLIP_RUNNER_BROWSER_DEPS_DIR:-${PAPERCLIP_RUN_SCRATCH_DIR:-${XDG_CACHE_HOME:-${HOME:?HOME is not set}/.cache}/paperclip-runner/playwright-libs}}"
+debian_architecture="$(dpkg --print-architecture)"
+rootless_deps_dir="$rootless_cache_base/$debian_architecture"
+rootless_marker="$rootless_deps_dir/.complete-v2"
+
+select_available_package() {
+  local candidate
+  for candidate in "$@"; do
+    if apt-cache show "$candidate" >/dev/null 2>&1; then
+      printf '%s\n' "$candidate"
+      return 0
+    fi
+  done
+  printf 'No supported package candidate found for: %s\n' "$*" >&2
+  return 1
+}
+
+if [[ ! -f "$rootless_marker" ]]; then
+  browser_packages=(
+    "$(select_available_package libatk1.0-0t64 libatk1.0-0)"
+    "$(select_available_package libatspi2.0-0t64 libatspi2.0-0)"
+    "$(select_available_package libxcomposite1)"
+    "$(select_available_package libxdamage1)"
+    "$(select_available_package libxfixes3)"
+    "$(select_available_package libxi6)"
+    "$(select_available_package libxrandr2)"
+    "$(select_available_package libxrender1)"
+    "$(select_available_package libgbm1)"
+    "$(select_available_package libasound2t64 libasound2)"
+  )
+  download_dir="$(mktemp -d "${TMPDIR:-/tmp}/paperclip-runner-browser-deps.XXXXXX")"
+  trap 'rm -rf "$download_dir"' EXIT
+  mkdir -p "$rootless_deps_dir"
+
+  (
+    cd "$download_dir"
+    apt-get download "${browser_packages[@]}"
+  )
+
+  shopt -s nullglob
+  downloaded_packages=("$download_dir"/*.deb)
+  if [[ ${#downloaded_packages[@]} -ne ${#browser_packages[@]} ]]; then
+    printf 'Expected %s browser-library packages, downloaded %s.\n' \
+      "${#browser_packages[@]}" "${#downloaded_packages[@]}" >&2
+    exit 1
+  fi
+  for package_archive in "${downloaded_packages[@]}"; do
+    # Host applications can inject unrelated runtime libraries (for example an
+    # embedded database's liblzma). System package tooling must use system libs.
+    env -u LD_LIBRARY_PATH dpkg-deb --extract "$package_archive" "$rootless_deps_dir"
+  done
+  touch "$rootless_marker"
+fi
+
+case "$debian_architecture" in
+  amd64) library_triplet="x86_64-linux-gnu" ;;
+  arm64) library_triplet="aarch64-linux-gnu" ;;
+  *)
+    printf 'verify:rootless does not yet map Debian architecture %s.\n' "$debian_architecture" >&2
+    exit 1
+    ;;
+esac
+
+rootless_library_path="$rootless_deps_dir/usr/lib/$library_triplet:$rootless_deps_dir/lib/$library_triplet:$rootless_deps_dir/usr/lib"
+printf 'Running Phase 2 verification with rootless browser libraries from %s.\n' "$rootless_deps_dir"
+LD_LIBRARY_PATH="$rootless_library_path${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}" pnpm run verify

packages/paperclip-runner/src/mock-core/phase2-local-runner.test.ts

@@ -143,6 +143,21 @@ describe.sequential("Phase 2 local runner and fake harness", () => {
       .toHaveLength(1);
   });
 
+  it("rejects commands after completion with an operator-safe restart message", async () => {
+    const handle = await startPhase2Scenario({
+      scenario: "happy-path",
+      delayMs: 1,
+    });
+
+    await handle.completion;
+
+    await expect(
+      handle.resolveRequest("request_after_completion", { text: "too late" }),
+    ).rejects.toThrow(
+      "This request expired because the local run already finished. Start a new run.",
+    );
+  });
+
   it("produces the same snapshot for validated live events and replay", async () => {
     const trace = await runPhase2Scenario({ scenario: "happy-path", delayMs: 1 });
     let live = createPhase2LiveSnapshot(trace);

packages/paperclip-runner/src/mock-core/phase2-local-runner.ts

@@ -336,6 +336,15 @@ class LocalRunnerController implements Phase2RunHandle {
     command: PrpCommand,
     recordCommand: boolean,
   ): Promise<Phase2CommandReceipt> {
+    if (
+      this.#settled ||
+      this.#process.stdin.destroyed ||
+      !this.#process.stdin.writable
+    ) {
+      return Promise.reject(
+        new Error("This request expired because the local run already finished. Start a new run."),
+      );
+    }
     if (recordCommand) {
       this.#commands.push(structuredClone(command));
     }

packages/paperclip-runner/vite.config.ts

@@ -17,6 +17,13 @@ export default defineConfig({
   preview: {
     host: "127.0.0.1",
   },
+  // Vite's dev dependency optimizer has its own esbuild target. Keep it in
+  // sync with the standalone browser build so Ajv is never downlevelled.
+  optimizeDeps: {
+    esbuildOptions: {
+      target: "esnext",
+    },
+  },
   build: {
     outDir: resolve(packageRoot, "dist-browser"),
     emptyOutDir: true,