diff --git a/packages/provider-bridge-acp/src/bridge/bridge.test.ts b/packages/provider-bridge-acp/src/bridge/bridge.test.ts
index 0ea207288..77ac9439b 100644
--- a/packages/provider-bridge-acp/src/bridge/bridge.test.ts
+++ b/packages/provider-bridge-acp/src/bridge/bridge.test.ts
@@ -2346,6 +2346,25 @@ describe("acp bridge", () => {
     expect(threadEventsOfType("turn/completed")).toHaveLength(1);
   });
 
+  it("retries a busy prompt after the agent reports that the session is idle", async () => {
+    const promptLog = join(workspaceDir, "busy-prompt-log.jsonl");
+    const { providerThreadId } = await startThread({
+      envVars: {
+        FAKE_ACP_BUSY_RESPONSES: "1",
+        FAKE_ACP_PROMPT_LOG: promptLog,
+      },
+    });
+    const turnId = sendTurnRequest("turn/start", providerThreadId, {
+      input: [{ type: "text", text: "after-busy", mentions: [] }],
+    });
+    await waitForResponse(turnId);
+
+    const completed = await waitForTurnCompleted();
+    expect(completed).toMatchObject({ status: "completed" });
+    expect(loggedPrompts(promptLog)).toEqual(["after-busy", "after-busy"]);
+    expect(threadEventsOfType("provider/error")).toEqual([]);
+  });
+
   it("runs the builtin /compact command as compaction, not as a prompt", async () => {
     const promptLog = join(workspaceDir, "compact-prompt-log.jsonl");
     const { providerThreadId } = await startThread({
diff --git a/packages/provider-bridge-acp/src/bridge/fake-acp-agent.mjs b/packages/provider-bridge-acp/src/bridge/fake-acp-agent.mjs
index 270fce317..4afab391a 100755
--- a/packages/provider-bridge-acp/src/bridge/fake-acp-agent.mjs
+++ b/packages/provider-bridge-acp/src/bridge/fake-acp-agent.mjs
@@ -121,6 +121,9 @@ const fakeModels = [
 ];
 
 let activePromptId = null;
+let remainingBusyResponses = Number(
+  process.env.FAKE_ACP_BUSY_RESPONSES ?? "0",
+);
 let nextAgentRequestId = 1000;
 let selectedModel = "fake/default";
 let selectedEffort = "none";
@@ -432,6 +435,29 @@ async function handlePrompt(message) {
     return;
   }
 
+  if (remainingBusyResponses > 0) {
+    remainingBusyResponses -= 1;
+    activePromptId = null;
+    send({
+      jsonrpc: "2.0",
+      id: message.id,
+      error: {
+        code: -32003,
+        message: "Agent is busy",
+        data: { reason: "session_busy", hint: "wait" },
+      },
+    });
+    setTimeout(
+      () =>
+        notifyUpdate({
+          sessionUpdate: "session_info_update",
+          title: "ready",
+        }),
+      10,
+    );
+    return;
+  }
+
   if (text === "/compact") {
     // OpenCode treats this exact prompt as a provider-local control.
     const compactMessage = process.env.FAKE_ACP_COMPACT_AGENT_MESSAGE;