From 3e8baf1e8803b4a068ef756d7575bbc8a73c8a2c Mon Sep 17 00:00:00 2001
From: Joey Krug <joeykrug@gmail.com>
Date: Fri, 13 Feb 2026 05:54:26 +0000
Subject: [PATCH] fix: drain queued work immediately after resetAllLanes()

resetAllLanes() now calls drainLane() for lanes with pending queue
entries after resetting generation/activeTaskIds. This prevents queued
work from stalling indefinitely when no subsequent enqueueCommandInLane()
call arrives after a SIGUSR1 restart.

Safe because the drain happens after all lanes are fully reset (generation
bumped, activeTaskIds cleared, draining=false), so concurrency invariants
are preserved.
---
 src/process/command-queue.test.ts | 27 +++++++--------------------
 src/process/command-queue.ts      | 13 +++++++++++--
 2 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/src/process/command-queue.test.ts b/src/process/command-queue.test.ts
index f55115452e9..ac617ddda23 100644
--- a/src/process/command-queue.test.ts
+++ b/src/process/command-queue.test.ts
@@ -169,7 +169,7 @@ describe("command queue", () => {
     await task;
   });
 
-  it("resetAllLanes requires a fresh enqueue to trigger draining", async () => {
+  it("resetAllLanes drains queued work immediately after reset", async () => {
     const lane = `reset-test-${Date.now()}-${Math.random().toString(16).slice(2)}`;
     setCommandLaneConcurrency(lane, 1);
 
@@ -196,31 +196,18 @@ describe("command queue", () => {
     await new Promise((r) => setTimeout(r, 5));
     expect(task2Ran).toBe(false);
 
-    // Simulate SIGUSR1: reset all lanes (as if interrupted tasks' finally blocks never ran).
+    // Simulate SIGUSR1: reset all lanes. Queued work (task2) should be
+    // drained immediately — no fresh enqueue needed.
     resetAllLanes();
 
-    // Complete the stale in-flight task; generation mismatch should make
-    // its completion path a no-op for queue bookkeeping/draining.
+    // Complete the stale in-flight task; generation mismatch makes its
+    // completion path a no-op for queue bookkeeping.
     resolve1();
     await task1;
-    await new Promise((r) => setTimeout(r, 5));
 
-    const task2BeforeTrigger = await Promise.race([
-      task2.then(() => "ran"),
-      new Promise<"timed-out">((resolve) => setTimeout(() => resolve("timed-out"), 50)),
-    ]);
-    expect(task2BeforeTrigger).toBe("timed-out");
-    expect(task2Ran).toBe(false);
-
-    // A fresh enqueue triggers drain and allows queued work to resume.
-    let task3Ran = false;
-    const task3 = enqueueCommandInLane(lane, async () => {
-      task3Ran = true;
-    });
-
-    await Promise.all([task2, task3]);
+    // task2 should have been pumped by resetAllLanes's drain pass.
+    await task2;
     expect(task2Ran).toBe(true);
-    expect(task3Ran).toBe(true);
   });
 
   it("waitForActiveTasks ignores tasks that start after the call", async () => {
diff --git a/src/process/command-queue.ts b/src/process/command-queue.ts
index 62e333eaac4..9ee4c741719 100644
--- a/src/process/command-queue.ts
+++ b/src/process/command-queue.ts
@@ -200,14 +200,23 @@ export function clearCommandLane(lane: string = CommandLane.Main) {
  * preserved — they represent pending user work that should still execute
  * after restart.
  *
- * Does not call `drainLane()` directly. New work naturally resumes when the
- * next `enqueueCommandInLane()` call triggers a fresh drain pass.
+ * After resetting, drains any lanes that still have queued entries so
+ * preserved work is pumped immediately rather than waiting for a future
+ * `enqueueCommandInLane()` call (which may never come).
  */
 export function resetAllLanes(): void {
+  const lanesToDrain: string[] = [];
   for (const state of lanes.values()) {
     state.generation += 1;
     state.activeTaskIds.clear();
     state.draining = false;
+    if (state.queue.length > 0) {
+      lanesToDrain.push(state.lane);
+    }
+  }
+  // Drain after the full reset pass so all lanes are in a clean state first.
+  for (const lane of lanesToDrain) {
+    drainLane(lane);
   }
 }