fix(runner): admit recovered ACPX provider ownership

packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts

@@ -1304,6 +1304,61 @@ describe("Codex ACPX runtime adapter", () => {
     });
   });
 
+  it("admits a verified provider that starts with the first recovered turn", async () => {
+    const runtime = fakeRuntime();
+    const child = fakeChild();
+    const command = fakeCommand();
+    vi.mocked(command.spawn).mockReturnValue(child);
+    let runtimeOptions: AcpRuntimeOptions | undefined;
+    let resolvePromptStarted: (() => void) | undefined;
+    const promptStarted = new Promise<void>((resolve) => {
+      resolvePromptStarted = resolve;
+    });
+    const rawTurn = {
+      requestId: "turn-recovered",
+      promptStarted,
+      events: { async *[Symbol.asyncIterator]() {} },
+      result: new Promise<never>(() => undefined),
+      cancel: vi.fn(),
+      closeStream: vi.fn(),
+    };
+    vi.mocked(runtime.startTurn).mockImplementation(() => {
+      queueMicrotask(() => {
+        runtimeOptions?.spawnAgent?.({
+          command: "ignored",
+          args: ["--stdio"],
+          options: {},
+        });
+        resolvePromptStarted?.();
+      });
+      return rawTurn;
+    });
+    const port = await openCodexAcpxRuntime(openOptions(command), {
+      createRegistry: () => registry(),
+      createStore: () => store(),
+      awaitProviderOwnership: providerOwnershipEstablished,
+      awaitProviderExit: providerOwnershipEstablished,
+      createRuntime: (options) => {
+        runtimeOptions = options;
+        return runtime;
+      },
+    });
+
+    const turn = port.startTurn({
+      text: "Resume the task.",
+      requestId: "turn-recovered",
+    });
+    await expect(turn.promptStarted).resolves.toBeUndefined();
+    expect(command.spawn).toHaveBeenCalledTimes(1);
+    expect(() =>
+      runtimeOptions?.spawnAgent?.({
+        command: "ignored",
+        args: ["--stdio"],
+        options: {},
+      }),
+    ).toThrow("provider spawned after ownership admission was sealed");
+  });
+
   it("projects only ephemeral MCP bindings and applies fail-closed permissions", async () => {
     const runtime = fakeRuntime();
     let runtimeOptions: AcpRuntimeOptions | undefined;

packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts

@@ -17,6 +17,7 @@ import type {
   AcpxRuntimePort,
   AcpxRuntimePortIdentity,
   AcpxRuntimePortOpenOptions,
+  AcpxRuntimeTurn,
 } from "./runtime-host.js";
 import {
   assertVerifiedAcpxProviderPlatform,
@@ -1045,20 +1046,71 @@ function runtimePort(
         }
       : {}),
     startTurn(input) {
-      return runtime.startTurn({
-        handle,
-        text: input.text,
-        mode: "prompt",
-        requestId: input.requestId,
-        ...(input.signal ? { signal: input.signal } : {}),
-        ...(input.onElicitation ? { onElicitation: input.onElicitation } : {}),
-      });
+      const finishOwnershipAdmission =
+        children.beginLifetimeOwnershipAdmission();
+      let turn: AcpxRuntimeTurn;
+      try {
+        turn = runtime.startTurn({
+          handle,
+          text: input.text,
+          mode: "prompt",
+          requestId: input.requestId,
+          ...(input.signal ? { signal: input.signal } : {}),
+          ...(input.onElicitation
+            ? { onElicitation: input.onElicitation }
+            : {}),
+        });
+      } catch (error) {
+        void finishOwnershipAdmission().catch(() => undefined);
+        throw error;
+      }
+      return turnWithVerifiedLifetimeOwnership(turn, finishOwnershipAdmission);
     },
     close: closeRuntime,
   };
   return port;
 }
 
+function turnWithVerifiedLifetimeOwnership(
+  turn: AcpxRuntimeTurn,
+  finishOwnershipAdmission: () => Promise<void>,
+): AcpxRuntimeTurn {
+  // A persisted ACPX session can be loaded without starting an agent process.
+  // Keep the narrowly scoped turn admission open until either the provider has
+  // accepted the prompt or the turn has already terminalized. The synchronous
+  // stable-empty seal in SpawnedChildSet then rejects every later spawn.
+  const reachedAdmissionBoundary = Promise.race([
+    turn.promptStarted.then(
+      () => undefined,
+      () => undefined,
+    ),
+    turn.result.then(
+      () => undefined,
+      () => undefined,
+    ),
+  ]);
+  const ownershipVerified = reachedAdmissionBoundary.then(() =>
+    finishOwnershipAdmission(),
+  );
+  void ownershipVerified.catch(() => undefined);
+  return {
+    requestId: turn.requestId,
+    promptStarted: ownershipVerified.then(() => turn.promptStarted),
+    events: eventsAfterLifetimeOwnership(turn.events, ownershipVerified),
+    result: ownershipVerified.then(() => turn.result),
+    cancel: (input) => turn.cancel(input),
+    closeStream: (input) => turn.closeStream(input),
+  };
+}
+
+async function* eventsAfterLifetimeOwnership<T>(
+  events: AsyncIterable<T>,
+  ownershipVerified: Promise<void>,
+): AsyncIterable<T> {
+  await ownershipVerified;
+  yield* events;
+}
+
 async function persistedRuntimeStatus(
   sessionStore: AcpSessionStore,
   handle: AcpRuntimeHandle,
@@ -1304,19 +1356,40 @@ class SpawnedChildSet {
   }
 
   async verifyLifetimeOwnership(): Promise<void> {
-    for (;;) {
-      const ownership = this.#lifetimeOwnership.splice(0);
-      if (ownership.length === 0) {
-        // This check and seal are synchronous. Any spawn added while an
-        // earlier batch was pending is observed by the next loop iteration;
-        // no later provider can race admission after the stable-empty point.
-        this.#lifetimeOwnershipSealed = true;
-        return;
+    try {
+      for (;;) {
+        const ownership = this.#lifetimeOwnership.splice(0);
+        if (ownership.length === 0) {
+          // This check and seal are synchronous. Any spawn added while an
+          // earlier batch was pending is observed by the next loop iteration;
+          // no later provider can race admission after the stable-empty point.
+          this.#lifetimeOwnershipSealed = true;
+          return;
+        }
+        await Promise.all(ownership);
       }
-      await Promise.all(ownership);
+    } catch (error) {
+      this.#lifetimeOwnershipSealed = true;
+      throw error;
     }
   }
 
+  beginLifetimeOwnershipAdmission(): () => Promise<void> {
+    if (this.#sealed) {
+      throw new Error("ACPX provider ownership admission is closed");
+    }
+    if (!this.#lifetimeOwnershipSealed) {
+      throw new Error("ACPX provider ownership admission is already active");
+    }
+    this.#lifetimeOwnershipSealed = false;
+    let finished = false;
+    return async () => {
+      if (finished) return;
+      finished = true;
+      await this.verifyLifetimeOwnership();
+    };
+  }
+
   #track(child: ChildProcess, providerExit: ProviderExitObservation): void {
     this.#children.add(child);
     const onError = (error: unknown) => this.#errors.add(error);