Cover same-tick stall pings and document the grace window

Queued empty continuations with no clock advance must nudge then wait,
not salvage. Architecture now describes stallNudgeAt instead of a
consecutive-ping streak.

Author: TheGreatAxios

docs/ARCHITECTURE.md

@@ -140,7 +140,7 @@ The ChatDirector counts consecutive assistant turns that contain tool calls and
 
 #### Sub-agent stall management
 
-`SubAgentDirector` tracks `lastActivityAt`, updated on every real `inference.done` and `tool.done`. Directors are pure `decide(event, ...)` functions with no timer of their own and the reactor has no proactive "idle" event, so a genuinely silent worker (e.g. parked on a long-running background command with nothing else to do) produces no event for the director to react to. `runSubAgent` (`src/subagent/index.ts`) arms an external interval, at `subAgentStallTimeoutMs`, that pings the same content-less continuation channel the compaction governor uses to re-enter an idle reactor (`requestContinuation`). The director only acts on a ping if the elapsed time since `lastActivityAt` has crossed the timeout — a ping delivered while a tool call is still executing simply queues until that cycle finishes, so "no pending harness-tracked work" falls out of when the check can run at all rather than needing separate bookkeeping. The first stall past the timeout gets one continuation nudge (asking the worker to check on the background work or report status); a second **consecutive** stall (no activity since that nudge) escalates to the existing salvage path, returning a `stalled` `forcedStopReport` with the same structured shape (summary/findings/blockers) as `turn-budget` and `cancelled`. Any real activity between pings resets the streak, so a worker that is genuinely working through a slow single turn is never penalized. After the worker has already replied with a terminal report (complete envelope or salvage), further empty continuations — idle-compact meter sync or stall pings — return `wait` instead of falling through to `DefaultDirector.infer`; only a non-empty parent message (`resume_agent` / `send_input`) re-opens the brief.
+`SubAgentDirector` tracks `lastActivityAt`, updated on every real `inference.done` and `tool.done`. Directors are pure `decide(event, ...)` functions with no timer of their own and the reactor has no proactive "idle" event, so a genuinely silent worker (e.g. parked on a long-running background command with nothing else to do) produces no event for the director to react to. `runSubAgent` (`src/subagent/index.ts`) arms an external interval, at `subAgentStallTimeoutMs`, that pings the same content-less continuation channel the compaction governor uses to re-enter an idle reactor (`requestContinuation`). The director only acts on a ping if the elapsed time since `lastActivityAt` has crossed the timeout — a ping delivered while a tool call is still executing simply queues until that cycle finishes, so "no pending harness-tracked work" falls out of when the check can run at all rather than needing separate bookkeeping. The first stall past the timeout records `stallNudgeAt` and issues one continuation nudge (asking the worker to check on the background work or report status). Later empty pings inside `subAgentStallTimeoutMs` of that instant wait without stopping or treating the ping as activity; salvage fires only once a ping arrives after that grace with still no `tool.done` / turn-boundary reset. That grace is what keeps two queued interval ticks from salvaging hundreds of milliseconds after the nudge. Any real activity clears `stallNudgeAt`, so a worker that is genuinely working through a slow single turn is never penalized. After the worker has already replied with a terminal report (complete envelope or salvage), further empty continuations — idle-compact meter sync or stall pings — return `wait` instead of falling through to `DefaultDirector.infer`; only a non-empty parent message (`resume_agent` / `send_input`) re-opens the brief.
 
 **Intervention log**: every stop and nudge is appended as one JSONL record to `interventions.jsonl` in the firing worker's trace dir (`src/subagent/intervention-log.ts`), carrying the trigger's measured value beside the threshold it crossed, the provider/model/family it fired on, and the run state at that moment (turns used vs budget, tool calls, read/edit counts). A refused parent re-dispatch is recorded on the parent side, where no worker run exists to record it. The parent also appends one `outcome` record per completed dispatch — the salvage kind `classifyBriefSalvage` assigned, or a clean-complete marker, plus the dispatch count — so the log carries dispatch outcomes as well as interventions, and a stop record can later be read alongside what the dispatch it touched actually produced. Writes are fire-and-forget and swallow their own errors — a diagnostic must not be able to fail a run. `scripts/intervention-forensics.ts` aggregates these across local sessions: per-intervention counts by model family, the measured-value distribution against the threshold, two context columns (stops that fired on runs which had already edited files; stops that fired before half the turn budget was spent — neither is a measured false-positive rate, since either is equally consistent with a correct stop or a wrong one), and outcome counts by kind. This exists because every threshold in this tree was set by judgment and four of those judgments were later reverted — a threshold change is expected to cite this data (CL-6938).
 

src/subagent/nudge-director.test.ts

@@ -1015,6 +1015,35 @@ describe("SubAgentDirector post-complete terminalization (CL-7068)", () => {
 });
 
 describe("SubAgentDirector stall nudge grace", () => {
+  test("two queued empty pings in the same tick nudge then wait, not stop", async () => {
+    let now = 3_000_000;
+    const director = new SubAgentDirector(
+      "system",
+      [],
+      undefined,
+      1_000,
+      () => now,
+    );
+    const caps = capabilities();
+
+    await director.decide(inferenceDoneText("working"), state, caps);
+
+    now += 1_000;
+    const first = actions(
+      await director.decide(messageReceived(""), state, caps),
+    );
+    expect(first).toContainEqual({
+      type: "checkpoint",
+      message: "subagent-stall-nudge",
+    });
+    expect(first.some((action) => action.type === "reply")).toBe(false);
+
+    const second = actions(
+      await director.decide(messageReceived(""), state, caps),
+    );
+    expect(second).toEqual([{ type: "wait" }]);
+  });
+
   test("queued pings inside grace wait; stop only after grace with no activity", async () => {
     let now = 1_000_000;
     const director = new SubAgentDirector(