fix: preserve interaction replies across chat recovery

tests/chat/responseInputs.test.ts

@@ -1,8 +1,35 @@
 import { expect, it, mock } from "bun:test";
-import { ResponseInputTracker, type ResponseInput } from "../../src/chat/response-inputs.js";
+import { ResponseInputTracker, WaitingResponseInputQueue, type ResponseInput } from "../../src/chat/response-inputs.js";
 
 const input = (id: number): ResponseInput => ({ id: `msg_${String(id).padStart(32, "0")}`, text: `Input ${id}`, delivery: "steer", status: "pending" });
 
+it("serializes waiting input admission, deduplicates retries and enforces capacity without resuming", async () => {
+  const pending: ResponseInput[] = [];
+  const enqueue = mock(async (_session: string, item: ResponseInput, options?: { resume?: boolean }) => {
+    expect(options?.resume).toBe(false);
+    pending.push(item);
+  });
+  const queue = new WaitingResponseInputQueue({ listPendingUserInputs: async () => pending,
+    agentMessageState: async () => "missing", enqueueUserInput: enqueue });
+  await Promise.all([queue.submit("s", input(1)), queue.submit("s", input(1))]);
+  expect(enqueue).toHaveBeenCalledTimes(1);
+  await expect(queue.submit("s", { ...input(1), text: "different" })).rejects.toMatchObject({ status: 409 });
+  const results = await Promise.allSettled(Array.from({ length: 20 }, (_, i) => queue.submit("s", input(i + 2))));
+  expect(results.filter((result) => result.status === "fulfilled")).toHaveLength(19);
+  expect(pending).toHaveLength(20);
+  expect(enqueue).toHaveBeenCalledTimes(20);
+});
+
+it("does not reinject a consumed waiting input or infer absence after a native read failure", async () => {
+  const enqueue = mock(async () => {});
+  const runtime = { listPendingUserInputs: async () => [], agentMessageState: async () => "delivered" as const, enqueueUserInput: enqueue };
+  await expect(new WaitingResponseInputQueue(runtime).submit("s", input(1))).resolves.toMatchObject({ status: "delivered" });
+  expect(enqueue).not.toHaveBeenCalled();
+  const unavailable = { ...runtime, agentMessageState: async () => { throw new Error("native unavailable"); } };
+  await expect(new WaitingResponseInputQueue(unavailable).submit("s", input(2))).rejects.toThrow("native unavailable");
+  expect(enqueue).not.toHaveBeenCalled();
+});
+
 it("waits for admission at completion, deduplicates concurrent retries and closes only after native consumption", async () => {
   let release = () => {};
   const gate = new Promise<void>((resolve) => { release = resolve; });