diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.test.ts b/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
index 295926b266446a9e63ad924ce5fe8a222c6d4bd5..7917b8360946f0536d44d7725610e139bd54163d 100644
--- a/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
@@ -73,6 +73,8 @@ class FakeClaudeQuery implements AsyncIterable<SDKMessage> {
   public readonly setMaxThinkingTokensCalls: Array<number | null> = [];
   public closeCalls = 0;
   public closeError: unknown | undefined;
+  /** Set by tests that exercise Claude's graceful interrupt. */
+  public interrupt?: () => Promise<unknown>;
 
   emit(message: SDKMessage): void {
     if (this.done) {
@@ -3255,6 +3257,83 @@ describe("ClaudeAdapterLive", () => {
     );
   });
 
+  it.effect("interruptTurn lets Claude abort the turn before closing the session", () => {
+    const harness = makeHarness();
+    return Effect.gen(function* () {
+      const adapter = yield* ClaudeAdapter;
+      const session = yield* adapter.startSession({
+        threadId: THREAD_ID,
+        provider: ProviderDriverKind.make("claudeAgent"),
+        runtimeMode: "full-access",
+      });
+      yield* adapter.sendTurn({
+        threadId: session.threadId,
+        input: "hello",
+        attachments: [],
+      });
+
+      const turnCompletedFiber = yield* adapter.streamEvents.pipe(
+        Stream.filter((event) => event.type === "turn.completed"),
+        Stream.take(1),
+        Stream.runCollect,
+        Effect.forkChild,
+      );
+      let closeCallsAtInterrupt: number | undefined;
+      harness.query.interrupt = async () => {
+        closeCallsAtInterrupt = harness.query.closeCalls;
+        harness.query.emit({
+          type: "result",
+          subtype: "error_during_execution",
+          is_error: false,
+          errors: ["Error: Request was aborted."],
+          session_id: "sdk-session",
+          uuid: "result-interrupted",
+        } as unknown as SDKMessage);
+      };
+
+      yield* adapter.interruptTurn(session.threadId);
+
+      assert.equal(closeCallsAtInterrupt, 0);
+      assert.equal(harness.query.closeCalls, 1);
+      const [turnCompleted] = Array.from(yield* Fiber.join(turnCompletedFiber));
+      assert.equal(turnCompleted?.type, "turn.completed");
+      if (turnCompleted?.type === "turn.completed") {
+        assert.equal(turnCompleted.payload.state, "interrupted");
+      }
+    }).pipe(
+      Effect.provideService(Random.Random, makeDeterministicRandomService()),
+      Effect.provide(harness.layer),
+    );
+  });
+
+  it.effect("interruptTurn closes the session when Claude never aborts the turn", () => {
+    const harness = makeHarness();
+    return Effect.gen(function* () {
+      const adapter = yield* ClaudeAdapter;
+      const session = yield* adapter.startSession({
+        threadId: THREAD_ID,
+        provider: ProviderDriverKind.make("claudeAgent"),
+        runtimeMode: "full-access",
+      });
+      yield* adapter.sendTurn({
+        threadId: session.threadId,
+        input: "hello",
+        attachments: [],
+      });
+      harness.query.interrupt = () => new Promise(() => {});
+
+      const interruptFiber = yield* adapter.interruptTurn(session.threadId).pipe(Effect.forkChild);
+      yield* TestClock.adjust("3 seconds");
+      yield* Fiber.join(interruptFiber);
+
+      assert.equal(harness.query.closeCalls, 1);
+      assert.equal(yield* adapter.hasSession(session.threadId), false);
+    }).pipe(
+      Effect.provideService(Random.Random, makeDeterministicRandomService()),
+      Effect.provide(harness.layer),
+    );
+  });
+
   it.effect("keeps the session available when process close fails", () => {
     const harness = makeHarness();
     return Effect.gen(function* () {
diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.ts b/apps/server/src/provider/Layers/ClaudeAdapter.ts
index 6e30f52417802e7c57ef581b5ee27c968db0da04..d50b3cbb9248da46ecf45d0af3ba12f6e8ac58c3 100644
--- a/apps/server/src/provider/Layers/ClaudeAdapter.ts
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.ts
@@ -385,6 +385,8 @@ interface ClaudeTaskAgentState {
  * lifetime; oldest entries evict first.
  */
 const PENDING_TASK_MODEL_CAP = 64;
+/** How long Stop waits for Claude to abort a turn before killing the process. */
+const CLAUDE_INTERRUPT_GRACE = "3 seconds";
 
 /**
  * Buffers a subagent snapshot's authoritative model under its
@@ -453,10 +455,14 @@ interface ClaudeSessionContext {
   lastThreadStartedId: string | undefined;
   /** Limits already announced for the running turn, keyed `window:resetsAt`. */
   announcedUsageLimits: { turnId: string; keys: Set<string> } | undefined;
+  /** Resolved by completeTurn while Stop waits for Claude to abort the turn. */
+  interruptedTurnSettled: Deferred.Deferred<void> | undefined;
   stopped: boolean;
 }
 
 interface ClaudeQueryRuntime extends AsyncIterable<SDKMessage> {
+  /** SDK Query.interrupt — present on real queries; optional for test doubles. */
+  readonly interrupt?: () => Promise<unknown>;
   readonly setModel: (model?: string) => Promise<void>;
   readonly setPermissionMode: (mode: PermissionMode) => Promise<void>;
   readonly setMaxThinkingTokens: (maxThinkingTokens: number | null) => Promise<void>;
@@ -2836,6 +2842,9 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
 
     const updatedAt = yield* nowIso;
     context.turnState = undefined;
+    if (context.interruptedTurnSettled) {
+      yield* Deferred.succeed(context.interruptedTurnSettled, undefined);
+    }
     context.session = {
       ...context.session,
       status: "ready",
@@ -5045,6 +5054,7 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
         lastAssistantUuid: resumeState?.resumeSessionAt,
         lastThreadStartedId: undefined,
         announcedUsageLimits: undefined,
+        interruptedTurnSettled: undefined,
         stopped: false,
       };
       yield* Ref.set(contextRef, context);
@@ -5276,6 +5286,7 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
   const interruptTurn: ClaudeAdapterShape["interruptTurn"] = Effect.fn("interruptTurn")(
     function* (threadId, _turnId) {
       const context = yield* requireSession(threadId);
+      yield* settleInterruptedTurn(context);
       // interrupt() can acknowledge while resumed background tasks keep the
       // CLI alive. Stop is a hard session boundary for Claude, so close the
       // query and let the SDK escalate to SIGKILL when graceful exit fails.
@@ -5283,6 +5294,25 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
     },
   );
 
+  // Lets Claude abort the running turn through its own path before Stop kills
+  // the process, so the prompt reaches the transcript. Killing a first turn
+  // before Claude writes it leaves a resume cursor for a session Claude never
+  // saved, and every later message fails with "No conversation found".
+  const settleInterruptedTurn = Effect.fn("settleInterruptedTurn")(function* (
+    context: ClaudeSessionContext,
+  ) {
+    const interrupt = context.query.interrupt?.bind(context.query);
+    if (context.stopped || !context.turnState || !interrupt) return;
+    const settled = yield* Deferred.make<void>();
+    context.interruptedTurnSettled = settled;
+    yield* Effect.tryPromise(interrupt).pipe(
+      Effect.ignore,
+      Effect.andThen(Deferred.await(settled)),
+      Effect.timeoutOption(CLAUDE_INTERRUPT_GRACE),
+    );
+    context.interruptedTurnSettled = undefined;
+  });
+
   const readThread: ClaudeAdapterShape["readThread"] = Effect.fn("readThread")(
     function* (threadId) {
       const context = yield* requireSession(threadId);