feat(worker): surface the handoff round budget in the merge-helper handoff brief

A handler session only learned the chain was capped when handoff_list_handler threw at the end of its work, stranding open tasks. The round count already lived in HandoffRoundTracker the whole time -- it just never reached the brief. InteractiveLaunchSpecService now reads HandoffRoundTracker.GetState (read-only, doesn't advance the round) and renders round N of MaxHandoffs plus the remaining count into the handoff brief, replacing the old one-line finalNote. The rejection error also names the next action (start a new handler run) instead of just failing.
2026-09-02 14:26:56 +02:00
parent 20685827fb
commit 81a5fc5d33
7 changed files with 110 additions and 18 deletions
@@ -198,6 +198,63 @@ public sealed class HandoffMcpToolsTests : IDisposable
            secondSut.HandoffListHandler(handlerTask.Id, survivors, "wait", CancellationToken.None));
    }

+    [Theory]
+    [InlineData(1, 3)]
+    [InlineData(2, 2)]
+    [InlineData(4, 0)]
+    public void HandoffRoundTracker_GetState_ReportsCountAfterNRegistrations(int registrations, int expectedRemaining)
+    {
+        var tracker = new HandoffRoundTracker();
+        var taskId = Guid.NewGuid().ToString();
+
+        for (var i = 0; i < registrations; i++)
+            tracker.Register(taskId, "wait");
+
+        var (count, sealedState) = tracker.GetState(taskId);
+        Assert.Equal(registrations, count);
+        Assert.Equal(expectedRemaining, HandoffRoundTracker.MaxHandoffs - count);
+        Assert.False(sealedState);
+    }
+
+    [Fact]
+    public void HandoffRoundTracker_GetState_UnregisteredTask_ReturnsZero()
+    {
+        var tracker = new HandoffRoundTracker();
+        var (count, sealedState) = tracker.GetState(Guid.NewGuid().ToString());
+        Assert.Equal(0, count);
+        Assert.False(sealedState);
+    }
+
+    [Fact]
+    public void HandoffRoundTracker_Register_DoesNotMutateStateVisibleFromGetState_BeyondItsOwnCall()
+    {
+        var tracker = new HandoffRoundTracker();
+        var taskId = Guid.NewGuid().ToString();
+
+        tracker.Register(taskId, "wait");
+        var (beforeCount, _) = tracker.GetState(taskId);
+        Assert.Equal(1, beforeCount);
+
+        // GetState itself must be read-only -- calling it repeatedly must not advance the round.
+        tracker.GetState(taskId);
+        tracker.GetState(taskId);
+        var (afterCount, _) = tracker.GetState(taskId);
+        Assert.Equal(beforeCount, afterCount);
+    }
+
+    [Fact]
+    public void HandoffRoundTracker_RejectedHandoff_ErrorNamesTheNextAction()
+    {
+        var tracker = new HandoffRoundTracker();
+        var taskId = Guid.NewGuid().ToString();
+        tracker.Register(taskId, "merge_final");
+
+        var result = tracker.Register(taskId, "wait");
+
+        Assert.True(result.Rejected);
+        Assert.Contains("new handler run", result.Error, StringComparison.OrdinalIgnoreCase);
+    }
+
    [Fact]
    public async Task HandoffListHandler_TwoHandlerTasks_DoNotShareACounter()
    {