diff --git a/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts b/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts
index fbb618c57d2..8c7b8b945ee 100644
--- a/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts
+++ b/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts
@@ -1188,6 +1188,12 @@ describe("OpenCodeServerDriver", () => {
     expect(
       events.filter((event) => event.eventType === "item.delta"),
     ).toHaveLength(1);
+    // The session names the exact spawned `opencode serve`, so cleanup can prove it is gone.
+    expect(events.find((event) => event.eventType === "session.started")?.payload).toMatchObject({
+      processId: spawns[0]!.pid,
+      processGroupId: spawns[0]!.processGroupId,
+      processStartedAt: expect.stringMatching(/^\d{4}-\d{2}-\d{2}T/),
+    });
     expect(
       events.find((event) => event.eventType === "item.delta")?.payload.text,
     ).toBe("done [guide](guide.md)");
diff --git a/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.ts b/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.ts
index 76f9fd97e1d..fa1451c4caa 100644
--- a/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.ts
+++ b/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.ts
@@ -1,4 +1,5 @@
 import { isOpenRouterUrl, OPENROUTER_ATTRIBUTION_HEADERS } from "../openrouter-attribution.js";
+import { readLocalProcessStartedAt } from "../../live/linux-process-start.js";
 import { spawn, type ChildProcess } from "node:child_process";
 import { resolveCompletionContinuation } from "../completion-continuation.js";
 import { createHash, randomBytes } from "node:crypto";
@@ -231,6 +232,8 @@ interface OpenCodeRuntime {
   version: string;
   permissionMode: "allow" | "ask" | "deny";
   process: ChildProcess;
+  /** OS identity of the spawned `opencode serve`, so cleanup can prove that exact process is gone. */
+  processIdentity: { processId: number; processGroupId: number | null; processStartedAt: string | null } | null;
   bridge: OpenCodeMcpBridge;
   trace: ProviderTraceFileSink | null;
   sensitiveValues: readonly string[];
@@ -624,6 +627,7 @@ class OpenCodeHarnessSession implements HarnessSession {
     this.#emit(input.snapshot ? "session.resumed" : "session.started", {
       driverSessionId: input.providerSessionId,
       providerSessionId: input.providerSessionId,
+      ...(input.runtime.processIdentity ?? {}),
       context: {
         protocolVersion: "http+sse/v1",
         opencodeVersion: input.runtime.version,
@@ -2726,6 +2730,11 @@ async function startRuntime(input: {
       providerChild.once("spawn", resolve);
       providerChild.once("error", reject);
     });
+    const processIdentity = child.pid ? {
+      processId: child.pid,
+      processGroupId: globalThis.process.platform === "win32" || !isolateProcessGroup ? null : child.pid,
+      processStartedAt: readLocalProcessStartedAt(child.pid),
+    } : null;
     if (child.pid)
       await input.options.onSpawn?.({
         pid: child.pid,
@@ -2762,6 +2771,7 @@ async function startRuntime(input: {
       version,
       permissionMode: input.options.permissionMode ?? "allow",
       process: child,
+      processIdentity,
       bridge,
       trace: input.trace,
       sensitiveValues,
diff --git a/packages/paperclip-runner/src/live/linux-process-start.ts b/packages/paperclip-runner/src/live/linux-process-start.ts
index 66abe1322dc..ed46e1da3f6 100644
--- a/packages/paperclip-runner/src/live/linux-process-start.ts
+++ b/packages/paperclip-runner/src/live/linux-process-start.ts
@@ -38,3 +38,48 @@ export function readLinuxProcessStartedAt(pid: number, options: LinuxProcessStar
   }
   return new Date(value).toISOString();
 }
+
+/** OS start time of a local process as an ISO string, or null when it cannot be read. */
+export function readLocalProcessStartedAt(pid: number): string | null {
+  if (!Number.isInteger(pid) || pid <= 0) return null;
+  try {
+    if (process.platform === "linux") {
+      return readLinuxProcessStartedAt(pid);
+    }
+    if (
+      ["darwin", "freebsd", "openbsd", "aix", "sunos"].includes(
+        process.platform,
+      )
+    ) {
+      const raw = execFileSync("ps", ["-o", "lstart=", "-p", String(pid)], {
+        encoding: "utf8",
+        timeout: 1_500,
+        windowsHide: true,
+      }).trim();
+      const parsed = new Date(raw);
+      return Number.isNaN(parsed.getTime()) ? null : parsed.toISOString();
+    }
+    if (process.platform === "win32") {
+      const script = [
+        `$target = Get-Process -Id ${pid} -ErrorAction Stop`,
+        "$target.StartTime.ToUniversalTime().ToString('o')",
+      ].join("; ");
+      for (const command of ["powershell.exe", "pwsh.exe"]) {
+        try {
+          const raw = execFileSync(
+            command,
+            ["-NoLogo", "-NoProfile", "-NonInteractive", "-Command", script],
+            { encoding: "utf8", timeout: 1_500, windowsHide: true },
+          ).trim();
+          const parsed = new Date(raw);
+          if (!Number.isNaN(parsed.getTime())) return parsed.toISOString();
+        } catch {
+          // Try the other supported PowerShell host.
+        }
+      }
+    }
+  } catch {
+    // Process exit and restricted process metadata both produce no fingerprint.
+  }
+  return null;
+}
diff --git a/packages/paperclip-runner/src/live/runnerd-codex-transport.ts b/packages/paperclip-runner/src/live/runnerd-codex-transport.ts
index c5cdae6cb56..e5398ce79ff 100644
--- a/packages/paperclip-runner/src/live/runnerd-codex-transport.ts
+++ b/packages/paperclip-runner/src/live/runnerd-codex-transport.ts
@@ -25,7 +25,7 @@ import { waitForWarmAttachmentReadiness } from "./warm-attachment-readiness.js";
 import { resolveCodexCommand } from "../drivers/codex/codex-command.js";
 import { isCanonicalProviderEventType } from "../provider-events.js";
 import { execFileSync } from "node:child_process";
-import { readLinuxProcessStartedAt } from "./linux-process-start.js";
+import { readLocalProcessStartedAt } from "./linux-process-start.js";
 import { createHash, randomUUID } from "node:crypto";
 import {
   appendFileSync,
@@ -117,49 +117,6 @@ const RUNNER_BOOTSTRAP_TICKET_TTL_MS = 60_000;
 const RUNNERD_MAX_OUTBOX_BYTES = 16 * 1024 * 1024;
 const RUNNERD_P0_RESERVE_BYTES = 1024 * 1024;
 
-function readLocalProcessStartedAt(pid: number): string | null {
-  if (!Number.isInteger(pid) || pid <= 0) return null;
-  try {
-    if (process.platform === "linux") {
-      return readLinuxProcessStartedAt(pid);
-    }
-    if (
-      ["darwin", "freebsd", "openbsd", "aix", "sunos"].includes(
-        process.platform,
-      )
-    ) {
-      const raw = execFileSync("ps", ["-o", "lstart=", "-p", String(pid)], {
-        encoding: "utf8",
-        timeout: 1_500,
-        windowsHide: true,
-      }).trim();
-      const parsed = new Date(raw);
-      return Number.isNaN(parsed.getTime()) ? null : parsed.toISOString();
-    }
-    if (process.platform === "win32") {
-      const script = [
-        `$target = Get-Process -Id ${pid} -ErrorAction Stop`,
-        "$target.StartTime.ToUniversalTime().ToString('o')",
-      ].join("; ");
-      for (const command of ["powershell.exe", "pwsh.exe"]) {
-        try {
-          const raw = execFileSync(
-            command,
-            ["-NoLogo", "-NoProfile", "-NonInteractive", "-Command", script],
-            { encoding: "utf8", timeout: 1_500, windowsHide: true },
-          ).trim();
-          const parsed = new Date(raw);
-          if (!Number.isNaN(parsed.getTime())) return parsed.toISOString();
-        } catch {
-          // Try the other supported PowerShell host.
-        }
-      }
-    }
-  } catch {
-    // Process exit and restricted process metadata both produce no fingerprint.
-  }
-  return null;
-}
 
 const CONTROL_PLANE_STATE_MAX_BYTES = 256 * 1024 * 1024;