diff --git a/LAWS/CHAT.md b/LAWS/CHAT.md
index 90f52f25..917e9174 100644
--- a/LAWS/CHAT.md
+++ b/LAWS/CHAT.md
@@ -5,7 +5,6 @@
 - The composer MUST queue every accepted message into the selected chat's queue, including before that chat's session is ready.
 - The composer MUST queue accepted messages into the selected chat's queue in their acceptance order.
 - The selected chat's queue MUST retain the message and persona intent most recently accepted from the composer or a user edit.
-- A chat's queue MUST dispatch each message to that chat's session with the model and provider shown when the composer queued it.
 - A chat's queue MUST NOT dispatch a message to that chat's session before every message ahead of it in the queue.
 - A message MUST NOT be dispatched from the queue until its session is ready.
 - A session MUST be ready for dispatch from its queue only when it can begin processing that queue's first message.
diff --git a/src/features/chat/hooks/__tests__/useChatSessionController.test.ts b/src/features/chat/hooks/__tests__/useChatSessionController.test.ts
index 09985619..d12c33d7 100644
--- a/src/features/chat/hooks/__tests__/useChatSessionController.test.ts
+++ b/src/features/chat/hooks/__tests__/useChatSessionController.test.ts
@@ -1188,6 +1188,48 @@ describe("useChatSessionController", () => {
     });
   });
 
+  it("discards in-flight Agent Builder preparation when its queue record is removed", async () => {
+    const pendingDraft = deferred<{ path: string; slug: string }>();
+    mockPreSeedDraftAgent.mockReturnValueOnce(pendingDraft.promise);
+    useChatStore.getState().enqueueTransportReadyMessage("session-1", {
+      persona: { kind: "inherit" },
+      text: "make a reviewer",
+      sendOptions: {
+        chips: [{ label: "agent-builder", type: "skill" }],
+      },
+    });
+    const queuedRecord =
+      useChatStore.getState().queuedMessageBySession["session-1"]?.[0];
+
+    renderHook(() => useChatSessionController({ sessionId: "session-1" }));
+
+    await waitFor(() => {
+      expect(mockPreSeedDraftAgent).toHaveBeenCalledWith("session-1");
+    });
+    act(() => {
+      useChatStore
+        .getState()
+        .dismissQueuedMessage("session-1", queuedRecord?.recordId);
+    });
+    await act(async () => {
+      pendingDraft.resolve({
+        path: "/Users/x/.agents/agents/removed-queue-record.md",
+        slug: "removed-queue-record",
+      });
+      await pendingDraft.promise;
+    });
+
+    await waitFor(() => {
+      expect(mockDeletePersonaSource).toHaveBeenCalledWith(
+        "/Users/x/.agents/agents/removed-queue-record.md",
+      );
+    });
+    const session = useChatSessionStore.getState().getSession("session-1");
+    expect(session?.intent).toBeUndefined();
+    expect(session?.targetAgentPath).toBeUndefined();
+    expect(mockUseChatSendMessage).not.toHaveBeenCalled();
+  });
+
   it("marks queued Agent Builder preparation as failed without dropping its send", async () => {
     mockPreSeedDraftAgent.mockRejectedValueOnce(
       new Error("draft creation failed"),
diff --git a/src/features/chat/hooks/useBackgroundQueuedMessageDrain.test.tsx b/src/features/chat/hooks/useBackgroundQueuedMessageDrain.test.tsx
index d8922248..b569c4b0 100644
--- a/src/features/chat/hooks/useBackgroundQueuedMessageDrain.test.tsx
+++ b/src/features/chat/hooks/useBackgroundQueuedMessageDrain.test.tsx
@@ -86,6 +86,22 @@ function releasedRecord(): QueuedMessageRecord & { kind: "transport-ready" } {
   };
 }
 
+function agentBuilderRecord(): QueuedMessageRecord & {
+  kind: "transport-ready";
+} {
+  return {
+    kind: "transport-ready",
+    recordId: "agent-builder-record",
+    payload: {
+      text: "make a reviewer",
+      persona: { kind: "inherit" },
+      sendOptions: {
+        chips: [{ label: "agent-builder", type: "skill" }],
+      },
+    },
+  };
+}
+
 function ordinaryRecord(): QueuedMessageRecord & { kind: "transport-ready" } {
   return {
     kind: "transport-ready",
@@ -1210,6 +1226,53 @@ describe("useBackgroundQueuedMessageDrain", () => {
     ).toEqual([BACKEND_SESSION_ID]);
   });
 
+  it("keeps an unmounted Agent Builder head parked after promotion until its draft target is prepared", async () => {
+    const builder = agentBuilderRecord();
+    seedDraftSession();
+    useChatStore.setState({
+      queuedMessageBySession: { [DRAFT_SESSION_ID]: [builder] },
+    });
+
+    render(<DrainHarness />);
+    act(() => promoteDraft());
+
+    expect(
+      mocks.sendQueuedPromptToExistingSessionInBackground,
+    ).not.toHaveBeenCalled();
+    expect(
+      useChatStore.getState().queuedMessageBySession[BACKEND_SESSION_ID]?.[0],
+    ).toBe(builder);
+
+    const releaseOwner = registerForegroundQueueOwner(BACKEND_SESSION_ID);
+    act(() => {
+      useChatSessionStore.getState().patchSession(BACKEND_SESSION_ID, {
+        intent: "build-agent",
+        agentBuilderOpen: true,
+        targetAgentPath: "/Users/x/.agents/agents/reviewer.md",
+        targetAgentSlug: "reviewer",
+      });
+    });
+    expect(
+      mocks.sendQueuedPromptToExistingSessionInBackground,
+    ).not.toHaveBeenCalled();
+
+    act(() => releaseOwner());
+
+    await waitFor(() =>
+      expect(
+        mocks.sendQueuedPromptToExistingSessionInBackground,
+      ).toHaveBeenCalledOnce(),
+    );
+    expect(
+      mocks.sendQueuedPromptToExistingSessionInBackground,
+    ).toHaveBeenCalledWith(
+      BACKEND_SESSION_ID,
+      builder,
+      expect.any(Function),
+      expect.any(Function),
+    );
+  });
+
   it("keeps a queued head parked without toasting when creation failed", async () => {
     const ordinary = ordinaryRecord();
     seedDraftSession("failed");
diff --git a/src/features/chat/hooks/useBackgroundQueuedMessageDrain.ts b/src/features/chat/hooks/useBackgroundQueuedMessageDrain.ts
index 9107ca96..783e0a6f 100644
--- a/src/features/chat/hooks/useBackgroundQueuedMessageDrain.ts
+++ b/src/features/chat/hooks/useBackgroundQueuedMessageDrain.ts
@@ -5,6 +5,7 @@ import { i18n } from "@/shared/i18n";
 import {
   assertQueuedSessionReady,
   isQueuedSessionReady,
+  QueuedSessionNotReadyError,
 } from "@/features/chat/lib/queuedMessageReadiness";
 import { PreCommitSendRejectedError } from "@/features/chat/lib/preCommitSendRejection";
 import {
@@ -17,6 +18,7 @@ import {
   subscribeForegroundQueueOwnership,
 } from "@/features/chat/lib/foregroundQueueOwnership";
 import { isBerdctlCrossSessionQueuedMessage } from "@/features/chat/lib/queuedMessageOrigin";
+import { isAgentBuilderQueuePreparationReady } from "@/features/chat/lib/agentBuilderQueueReadiness";
 import { useChatSessionStore } from "@/features/chat/stores/chatSessionStore";
 import {
   type QueuedMessageRecord,
@@ -138,7 +140,13 @@ function isBackgroundDrainableHead(
   record: QueuedMessageRecord & { kind: "transport-ready" },
   sessionId: string,
 ): boolean {
-  if (isBerdctlCrossSessionQueuedMessage(record)) {
+  if (
+    isBerdctlCrossSessionQueuedMessage(record) ||
+    !isAgentBuilderQueuePreparationReady(
+      record,
+      useChatSessionStore.getState().getSession(sessionId),
+    )
+  ) {
     return false;
   }
   if (record.releasedFromDeferred) {
@@ -246,6 +254,14 @@ function drainQueuedMessage(sessionId: string, ownerId: string): void {
         queuedMessage,
       );
       assertQueuedSessionReady(state.getSessionRuntime(sessionId));
+      if (
+        !isAgentBuilderQueuePreparationReady(
+          queuedMessage,
+          useChatSessionStore.getState().getSession(sessionId),
+        )
+      ) {
+        throw new QueuedSessionNotReadyError();
+      }
     },
     () => {
       useChatStore
diff --git a/src/features/chat/hooks/useChatSessionController.ts b/src/features/chat/hooks/useChatSessionController.ts
index 6ba6d0e8..3cbe97a4 100644
--- a/src/features/chat/hooks/useChatSessionController.ts
+++ b/src/features/chat/hooks/useChatSessionController.ts
@@ -2227,18 +2227,53 @@ export function useChatSessionController({
     isQueuePreparationReady,
   );
   const pendingBuilderActivationRef = useRef<
-    Record<string, Promise<ChatSession | null>>
+    Record<
+      string,
+      {
+        promise: Promise<ChatSession | null>;
+        queueRecordId?: string;
+      }
+    >
   >({});
 
+  const isQueuedAgentBuilderRecordAuthoritative = useCallback(
+    (recordId: string) => {
+      const record =
+        useChatStore.getState().queuedMessageBySession[stateSessionId]?.[0];
+      return Boolean(
+        record?.recordId === recordId &&
+          record.kind === "transport-ready" &&
+          isAgentBuilderSkillSendOptions(record.payload.sendOptions),
+      );
+    },
+    [stateSessionId],
+  );
+
   const ensureCurrentSessionIsAgentBuilder = useCallback(
-    async (options?: { requireSelectedSkill?: boolean }) => {
+    async (options?: {
+      requireSelectedSkill?: boolean;
+      queueRecordId?: string;
+    }) => {
       if (!sessionId) {
         return null;
       }
 
       const pendingActivation = pendingBuilderActivationRef.current[sessionId];
       if (pendingActivation) {
-        return pendingActivation;
+        if (
+          !options?.queueRecordId ||
+          pendingActivation.queueRecordId === options.queueRecordId
+        ) {
+          return pendingActivation.promise;
+        }
+        await pendingActivation.promise;
+      }
+
+      if (
+        options?.queueRecordId &&
+        !isQueuedAgentBuilderRecordAuthoritative(options.queueRecordId)
+      ) {
+        return null;
       }
 
       const activation = (async () => {
@@ -2259,6 +2294,16 @@ export function useChatSessionController({
         }
 
         const target = await preSeedDraftAgent(sessionId);
+        if (
+          options?.queueRecordId &&
+          !isQueuedAgentBuilderRecordAuthoritative(options.queueRecordId)
+        ) {
+          await deletePersonaSource(target.path).catch((error) => {
+            console.error("Failed to delete superseded agent draft:", error);
+          });
+          return null;
+        }
+
         const liveChatSessions = useChatSessionStore.getState();
         const liveSession = liveChatSessions.getSession(sessionId);
         const liveSkills =
@@ -2308,29 +2353,44 @@ export function useChatSessionController({
         return { ...currentSession, ...patch };
       })();
 
-      pendingBuilderActivationRef.current[sessionId] = activation;
+      const pendingEntry = {
+        promise: activation,
+        queueRecordId: options?.queueRecordId,
+      };
+      pendingBuilderActivationRef.current[sessionId] = pendingEntry;
       try {
         return await activation;
       } finally {
-        if (pendingBuilderActivationRef.current[sessionId] === activation) {
+        if (pendingBuilderActivationRef.current[sessionId] === pendingEntry) {
           delete pendingBuilderActivationRef.current[sessionId];
         }
       }
     },
-    [sessionId, stateSessionId],
+    [isQueuedAgentBuilderRecordAuthoritative, sessionId, stateSessionId],
   );
 
   useEffect(() => {
     if (!queuedAgentBuilderSendNeedsPreparation || !sessionId) {
       return;
     }
-    void ensureCurrentSessionIsAgentBuilder().catch((error) => {
-      console.error("Failed to prepare queued agent builder:", error);
-      markAgentBuilderSessionPreparationFailed(sessionId);
-    });
+    const queueRecordId = queuedHead?.recordId;
+    if (!queueRecordId) {
+      return;
+    }
+    void ensureCurrentSessionIsAgentBuilder({ queueRecordId }).catch(
+      (error) => {
+        if (!isQueuedAgentBuilderRecordAuthoritative(queueRecordId)) {
+          return;
+        }
+        console.error("Failed to prepare queued agent builder:", error);
+        markAgentBuilderSessionPreparationFailed(sessionId);
+      },
+    );
   }, [
     ensureCurrentSessionIsAgentBuilder,
+    isQueuedAgentBuilderRecordAuthoritative,
     queuedAgentBuilderSendNeedsPreparation,
+    queuedHead?.recordId,
     sessionId,
   ]);
 
diff --git a/src/features/chat/lib/__tests__/queuedSessionSend.test.ts b/src/features/chat/lib/__tests__/queuedSessionSend.test.ts
index bf4eb7e0..5e3a1e67 100644
--- a/src/features/chat/lib/__tests__/queuedSessionSend.test.ts
+++ b/src/features/chat/lib/__tests__/queuedSessionSend.test.ts
@@ -46,6 +46,20 @@ function seedSession(creationState?: "pending" | "failed"): void {
   });
 }
 
+function agentBuilderRecord(): QueuedMessageRecord & {
+  kind: "transport-ready";
+} {
+  return {
+    kind: "transport-ready",
+    recordId: "builder-record",
+    payload: {
+      text: "make a reviewer",
+      persona: { kind: "inherit" },
+      sendOptions: { chips: [{ label: "agent-builder", type: "skill" }] },
+    },
+  };
+}
+
 function queuedRecord(): QueuedMessageRecord & { kind: "transport-ready" } {
   return {
     kind: "transport-ready",
@@ -194,6 +208,28 @@ describe("sendQueuedPromptToExistingSessionInBackground", () => {
     mocks.loadSessionMessages.mockResolvedValue(true);
   });
 
+  it("rejects an Agent Builder send until the session owns a prepared draft target", async () => {
+    seedSession();
+    useChatSessionStore.setState((state) => ({
+      sessions: state.sessions.map((session) => ({
+        ...session,
+        intent: "build-agent" as const,
+        agentBuilderOpen: true,
+      })),
+    }));
+    const beforeUserMessageCommitted = vi.fn();
+
+    const error = await sendQueuedPromptToExistingSessionInBackground(
+      SESSION_ID,
+      agentBuilderRecord(),
+      beforeUserMessageCommitted,
+    ).catch((caught: unknown) => caught);
+
+    expect(error).toBeInstanceOf(PreCommitSendRejectedError);
+    expect(mocks.loadSessionMessages).not.toHaveBeenCalled();
+    expect(beforeUserMessageCommitted).not.toHaveBeenCalled();
+  });
+
   it("rejects a send to a creating session without committing anything", async () => {
     seedSession("pending");
     const beforeUserMessageCommitted = vi.fn();
diff --git a/src/features/chat/lib/agentBuilderQueueReadiness.ts b/src/features/chat/lib/agentBuilderQueueReadiness.ts
new file mode 100644
index 00000000..c13eb18f
--- /dev/null
+++ b/src/features/chat/lib/agentBuilderQueueReadiness.ts
@@ -0,0 +1,32 @@
+import { isAgentBuilderSkillSendOptions } from "@/features/chat/lib/agentBuilderSkill";
+import type { ChatSession } from "@/features/chat/stores/chatSessionStore";
+import type { QueuedMessageRecord } from "@/features/chat/stores/chatStore";
+
+/**
+ * Agent Builder queue records are dispatchable only after a foreground owner
+ * has created and adopted the final-session-owned draft target. The background
+ * drain must not bypass that preparation when no chat is mounted.
+ */
+export function getAgentBuilderQueuePreparedTargetPath(
+  record: QueuedMessageRecord & { kind: "transport-ready" },
+  session: ChatSession | null | undefined,
+): string | null | undefined {
+  if (!isAgentBuilderSkillSendOptions(record.payload.sendOptions)) {
+    return undefined;
+  }
+  if (
+    session?.intent !== "build-agent" ||
+    session.agentBuilderOpen === false ||
+    !session.targetAgentPath
+  ) {
+    return null;
+  }
+  return session.targetAgentPath;
+}
+
+export function isAgentBuilderQueuePreparationReady(
+  record: QueuedMessageRecord & { kind: "transport-ready" },
+  session: ChatSession | null | undefined,
+): boolean {
+  return getAgentBuilderQueuePreparedTargetPath(record, session) !== null;
+}
diff --git a/src/features/chat/lib/queuedSessionSend.ts b/src/features/chat/lib/queuedSessionSend.ts
index 992e12cc..cd8ba53a 100644
--- a/src/features/chat/lib/queuedSessionSend.ts
+++ b/src/features/chat/lib/queuedSessionSend.ts
@@ -13,11 +13,14 @@ import {
 
 import { loadWorkspaceInstructionFiles } from "@/features/chat/api/workspaceContext";
 import { sendPromptInBackground } from "@/features/chat/lib/backgroundSend";
+import { composeBuilderSendOptions } from "@/features/chat/hooks/useBuilderSendInterceptor";
+import { getAgentBuilderQueuePreparedTargetPath } from "@/features/chat/lib/agentBuilderQueueReadiness";
 import { isFirstCommittedUserMessage } from "@/features/chat/lib/chatFirstMessage";
 import {
   trackChatMessageSent,
   trackChatSessionStarted,
 } from "@/features/chat/lib/chatTelemetry";
+import { QueuedSessionNotReadyError } from "@/features/chat/lib/queuedMessageReadiness";
 import { loadSessionMessages } from "@/features/chat/lib/sessionActivation";
 import {
   SessionDispatchContentionError,
@@ -259,6 +262,22 @@ export async function sendQueuedPromptToExistingSessionInBackground(
   beforeUserMessageCommitted?: () => void,
   onPromptDispatched?: () => void,
 ): Promise<void> {
+  let preparedBuilderTargetPath: string | undefined;
+  const assertAgentBuilderPreparationReady = () => {
+    const targetPath = getAgentBuilderQueuePreparedTargetPath(
+      queuedMessage,
+      useChatSessionStore.getState().getSession(sessionId),
+    );
+    if (
+      targetPath === null ||
+      (preparedBuilderTargetPath !== undefined &&
+        targetPath !== preparedBuilderTargetPath)
+    ) {
+      throw new QueuedSessionNotReadyError();
+    }
+    return targetPath;
+  };
+  assertAgentBuilderPreparationReady();
   const acquisition = await acquireExistingSessionForBackgroundSend(sessionId);
   if (acquisition.status === "contended") {
     throw new SessionDispatchContentionError(acquisition.waiter);
@@ -275,7 +294,6 @@ export async function sendQueuedPromptToExistingSessionInBackground(
   const targetLease = acquisition;
   try {
     const { payload } = queuedMessage;
-    const sendOptions = payload.sendOptions ?? {};
     const payloadPersonaIntent = payload.persona;
     const payloadPersona =
       payloadPersonaIntent.kind === "persona"
@@ -338,6 +356,14 @@ export async function sendQueuedPromptToExistingSessionInBackground(
           formatAvailableSkillsCatalogPrompt(skills),
         )
       : undefined;
+    const sessionBeforeSend = useChatSessionStore
+      .getState()
+      .getSession(sessionId);
+    preparedBuilderTargetPath = assertAgentBuilderPreparationReady();
+    const sendOptions = composeBuilderSendOptions(
+      sessionBeforeSend,
+      payload.sendOptions ?? {},
+    );
     const personaSystemPrompt =
       sendOptions.capturedPersonaSystemPrompt ??
       formatPersonaSystemPrompt(persona);
@@ -408,7 +434,10 @@ export async function sendQueuedPromptToExistingSessionInBackground(
         executionSystemPrompt,
       },
       payload.attachments,
-      beforeUserMessageCommitted,
+      () => {
+        assertAgentBuilderPreparationReady();
+        beforeUserMessageCommitted?.();
+      },
       fireSendTelemetry,
       () => assertSessionExecutionTarget(sessionId, preparedExecutionTarget),
       onPromptDispatched,