Stop mailbox-mail occupancy from flooding the send queue

CHANGELOG.md

@@ -36,6 +36,10 @@ parallel copies under `docs/` or `scripts/notes/`. At cut time: rename
 
 ### Fixed
 
+- Occupancy injects mailbox mail once when a worker burst finishes: one
+  in-flight drive, in-flight ids until send succeeds, and wake copy that
+  does not say the reports were already collected. Overlapping flushes
+  no longer fill the send queue or replay the same reports as new turns.
 - Stalled workers get a full `stallTimeoutMs` grace after the first
   continuation nudge before salvage. Stall pings inside that window wait
   instead of counting toward escalation. Mailbox mail re-flushes from the

src/subagent/index.ts

@@ -29,7 +29,9 @@ export {
 export { driveOpenTasksAfterFleetDry } from "./fleet-dry-drive.js";
 export {
   driveMailboxMail,
+  latchMailboxMailDrive,
   MAILBOX_MAIL_WAKE_PREFIX,
+  mailboxMailWakeLine,
   occupancyShouldYieldWait,
 } from "./mailbox-mail-drive.js";
 export {

src/subagent/mailbox-mail-drive.test.ts

@@ -3,7 +3,9 @@ import { createFleetMailbox } from "./agent-fleet.js";
 import {
   buildMailboxMailPrompt,
   driveMailboxMail,
+  latchMailboxMailDrive,
   MAILBOX_MAIL_WAKE_PREFIX,
+  mailboxMailWakeLine,
   occupancyShouldYieldWait,
 } from "./mailbox-mail-drive.js";
 import { createSubAgentSessionStore } from "./session-store.js";
@@ -41,9 +43,8 @@ describe("buildMailboxMailPrompt", () => {
     expect(prompt.startsWith(MAILBOX_MAIL_WAKE_PREFIX)).toBe(true);
     expect(prompt).toContain("worker-1");
     expect(prompt).toContain("shipped");
-    expect(prompt).toContain(
-      "already collected — do not call wait_agents for these agent_ids",
-    );
+    expect(prompt).toContain(mailboxMailWakeLine());
+    expect(prompt).not.toContain("already collected");
   });
 });
 
@@ -211,6 +212,80 @@ describe("driveMailboxMail", () => {
     expect(records.get("w1")?.collected).toBe(true);
   });
 
+  test("two flushes while send is pending deliver once", async () => {
+    const records = new Map<string, FleetDryMailboxRecord>([
+      ["w1", { status: "done", report: "ok" }],
+    ]);
+    const mailbox = mapMailbox(records);
+    const sends: string[] = [];
+    let resolveSend: ((ok: boolean) => void) | undefined;
+    const driven = await driveMailboxMail({
+      parentProcessing: false,
+      mailbox,
+      lanes: [],
+      beginSystemContinuation: () => undefined,
+      send: (prompt) => {
+        sends.push(prompt);
+        return new Promise<boolean>((resolve) => {
+          resolveSend = resolve;
+        });
+      },
+    });
+    expect(driven).toBe(true);
+    expect(sends).toHaveLength(1);
+    expect(records.get("w1")?.collected).not.toBe(true);
+    expect(
+      await driveMailboxMail({
+        parentProcessing: false,
+        mailbox,
+        lanes: [],
+        beginSystemContinuation: () => {
+          throw new Error("must not begin");
+        },
+        send: () => {
+          throw new Error("must not send");
+        },
+      }),
+    ).toBe(false);
+    expect(sends).toHaveLength(1);
+    resolveSend?.(true);
+    await Promise.resolve();
+    expect(records.get("w1")?.collected).toBe(true);
+  });
+
+  test("failed send can retry once", async () => {
+    const records = new Map<string, FleetDryMailboxRecord>([
+      ["w1", { status: "done", report: "ok" }],
+    ]);
+    const mailbox = mapMailbox(records);
+    const sends: string[] = [];
+    expect(
+      await driveMailboxMail({
+        parentProcessing: false,
+        mailbox,
+        lanes: [],
+        beginSystemContinuation: () => undefined,
+        send: () => {
+          throw new Error("send failed");
+        },
+      }),
+    ).toBe(false);
+    expect(records.get("w1")?.collected).not.toBe(true);
+    expect(
+      await driveMailboxMail({
+        parentProcessing: false,
+        mailbox,
+        lanes: [],
+        beginSystemContinuation: () => undefined,
+        send: (prompt) => {
+          sends.push(prompt);
+        },
+      }),
+    ).toBe(true);
+    expect(sends).toHaveLength(1);
+    expect(records.get("w1")?.collected).toBe(true);
+  });
+
   test("awaiting_director is not mailbox mail", async () => {
     const records = new Map<string, FleetDryMailboxRecord>([
       ["ask", { status: "awaiting_director" }],
@@ -232,6 +307,91 @@ describe("driveMailboxMail", () => {
   });
 });
 
+describe("latchMailboxMailDrive", () => {
+  test("overlapping flushes send once until the in-flight collect settles", async () => {
+    const records = new Map<string, FleetDryMailboxRecord>([
+      ["done", { status: "done", report: "ok", description: "lane" }],
+    ]);
+    const sends: string[] = [];
+    let resolveSend: (() => void) | undefined;
+    const sent = new Promise<void>((resolve) => {
+      resolveSend = resolve;
+    });
+    const driver = latchMailboxMailDrive(() =>
+      driveMailboxMail({
+        parentProcessing: false,
+        mailbox: mapMailbox(records),
+        lanes: [],
+        beginSystemContinuation: () => undefined,
+        send: (prompt) => {
+          sends.push(prompt);
+          resolveSend?.();
+        },
+      }),
+    );
+    expect(driver()).toBe(true);
+    expect(driver()).toBe(false);
+    expect(driver()).toBe(false);
+    await sent;
+    expect(sends).toHaveLength(1);
+    expect(sends[0]).toContain(MAILBOX_MAIL_WAKE_PREFIX);
+  });
+
+  test("a false drive does not latch the next flush", () => {
+    let calls = 0;
+    const driver = latchMailboxMailDrive(() => {
+      calls += 1;
+      return false;
+    });
+    expect(driver()).toBe(false);
+    expect(driver()).toBe(false);
+    expect(calls).toBe(2);
+  });
+
+  test("after the in-flight drive settles, a new terminal can send", async () => {
+    const records = new Map<string, FleetDryMailboxRecord>([
+      ["first", { status: "done", report: "one" }],
+    ]);
+    const mailbox = mapMailbox(records);
+    const sends: string[] = [];
+    let sawSend: (() => void) | undefined;
+    const waitForSend = (): Promise<void> =>
+      new Promise<void>((resolve) => {
+        sawSend = resolve;
+      });
+    const driver = latchMailboxMailDrive(() =>
+      driveMailboxMail({
+        parentProcessing: false,
+        mailbox,
+        lanes: [],
+        beginSystemContinuation: () => undefined,
+        send: (prompt) => {
+          sends.push(prompt);
+          sawSend?.();
+        },
+      }),
+    );
+    const first = waitForSend();
+    expect(driver()).toBe(true);
+    await first;
+    expect(sends).toHaveLength(1);
+    records.set("second", { status: "done", report: "two" });
+    const second = waitForSend();
+    let retried = false;
+    for (let i = 0; i < 10; i++) {
+      await Promise.resolve();
+      if (driver()) {
+        retried = true;
+        break;
+      }
+    }
+    expect(retried).toBe(true);
+    await second;
+    expect(sends).toHaveLength(2);
+    expect(sends[1]).toContain("second");
+  });
+});
+
 describe("occupancyShouldYieldWait", () => {
   test("yields on uncollected terminal, fail, or ask; not on live or collected", () => {
     expect(occupancyShouldYieldWait(undefined)).toBe(false);

src/subagent/mailbox-mail-drive.ts

@@ -16,10 +16,46 @@ import {
 
 export const MAILBOX_MAIL_WAKE_PREFIX = "mailbox mail";
 
+/**
+ * First-delivery instruction. Occupancy handed these reports to the parent;
+ * do not call wait_agents. Must not say "already collected" — that makes the
+ * first wake look like a replay.
+ */
+export function mailboxMailWakeLine(): string {
+  return `${MAILBOX_MAIL_WAKE_PREFIX} — occupancy delivered these worker reports (do not call wait_agents for these agent_ids):`;
+}
+
 function isPromiseLike(value: unknown): value is Promise<unknown> {
   return typeof value === "object" && value !== null && "then" in value;
 }
 
+/**
+ * Ids occupancy has snapshotted and handed to send, but not yet taken.
+ * A second flush must not start another parent turn for the same reports.
+ * Failed send clears the set so a later flush can retry. Weak-keyed so a
+ * mailbox object can go away without a leak.
+ */
+const deliveringByMailbox = new WeakMap<FleetDryMailbox, Set<string>>();
+
+function deliveringSet(mailbox: FleetDryMailbox): Set<string> {
+  let ids = deliveringByMailbox.get(mailbox);
+  if (ids === undefined) {
+    ids = new Set();
+    deliveringByMailbox.set(mailbox, ids);
+  }
+  return ids;
+}
+
+function releaseDelivering(
+  mailbox: FleetDryMailbox | undefined,
+  ids: readonly string[],
+): void {
+  if (mailbox === undefined) return;
+  const delivering = deliveringByMailbox.get(mailbox);
+  if (delivering === undefined) return;
+  for (const id of ids) delivering.delete(id);
+}
+
 export function occupancyShouldYieldWait(
   mailbox: FleetDryMailbox | undefined,
 ): boolean {
@@ -37,10 +73,7 @@ export function occupancyShouldYieldWait(
 export function buildMailboxMailPrompt(
   reports: readonly CollectedWorkerReport[],
 ): string {
-  return [
-    `${MAILBOX_MAIL_WAKE_PREFIX} — worker reports (already collected — do not call wait_agents for these agent_ids):`,
-    JSON.stringify(reports),
-  ].join("\n");
+  return [mailboxMailWakeLine(), JSON.stringify(reports)].join("\n");
 }
 
 export function driveMailboxMail(args: {
@@ -59,20 +92,30 @@ export function driveMailboxMail(args: {
 async function driveMailboxMailAfterCollect(
   args: Parameters<typeof driveMailboxMail>[0],
 ): Promise<boolean> {
-  const reports = await collectUncollectedTerminals(
-    args.mailbox,
-    args.lanes,
-    false,
-    args.writeBlob,
-  );
+  const delivering =
+    args.mailbox !== undefined
+      ? deliveringSet(args.mailbox)
+      : new Set<string>();
+  const reports = (
+    await collectUncollectedTerminals(
+      args.mailbox,
+      args.lanes,
+      false,
+      args.writeBlob,
+    )
+  ).filter((report) => !delivering.has(report.agent_id));
   if (reports.length === 0) return false;
+  const ids = reports.map((report) => report.agent_id);
+  for (const id of ids) delivering.add(id);
   const prompt = buildMailboxMailPrompt(reports);
   const takeReports = (): void => {
-    for (const report of reports) {
-      args.mailbox?.take(report.agent_id);
+    for (const id of ids) {
+      args.mailbox?.take(id);
     }
+    releaseDelivering(args.mailbox, ids);
   };
   const fail = (): boolean => {
+    releaseDelivering(args.mailbox, ids);
     args.onSendFailure?.();
     return false;
   };
@@ -83,10 +126,10 @@ async function driveMailboxMailAfterCollect(
       void sent.then(
         (result) => {
           if (result !== false) takeReports();
-          else args.onSendFailure?.();
+          else fail();
         },
         () => {
-          args.onSendFailure?.();
+          fail();
         },
       );
       return true;
@@ -98,3 +141,25 @@ async function driveMailboxMailAfterCollect(
   }
   return true;
 }
+
+/**
+ * Store-subscribe, stall-poll, and idle-with-fleet settle all flush mailbox
+ * mail. `driveMailboxMail` does not mark the parent busy until after an
+ * awaited collect, so overlapping flushes would each call `send()` and fill
+ * the agent's depth-16 queue. Hold one drive until that promise settles.
+ */
+export function latchMailboxMailDrive(
+  drive: () => boolean | Promise<boolean>,
+): () => boolean {
+  let inFlight = false;
+  return () => {
+    if (inFlight) return false;
+    const driven = drive();
+    if (driven === false) return false;
+    inFlight = true;
+    void Promise.resolve(driven).finally(() => {
+      inFlight = false;
+    });
+    return true;
+  };
+}

src/tui/queued-delivery.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, test } from "bun:test";
+import { mailboxMailWakeLine } from "../subagent/mailbox-mail-drive.js";
 import type { PendingImageAttachment } from "./image-attachments.js";
 import {
   createDeliveryGeneration,
@@ -296,15 +297,13 @@ describe("createLeftoverSend", () => {
     });
 
     leftoverSend("ask_director wake — see @src/foo.ts");
-    leftoverSend(
-      "mailbox mail — worker reports (already collected — do not call wait_agents for these agent_ids):\n[]",
-    );
+    leftoverSend(`${mailboxMailWakeLine()}\n[]`);
     leftoverSend("please read @src/foo.ts");
     await awaitTail();
     expect(ingested).toEqual(["please read @src/foo.ts"]);
     expect(sent).toEqual([
       "ask_director wake — see @src/foo.ts",
-      "mailbox mail — worker reports (already collected — do not call wait_agents for these agent_ids):\n[]",
+      `${mailboxMailWakeLine()}\n[]`,
       "please read @src/foo.ts ingested",
     ]);
   });