Compaction: count only completed auto-compactions (#24056)

* Compaction: count only completed auto-compactions

* Compaction: count only non-retry completions

* Changelog: note completed-only compaction counting

* Agents/Compaction: guard optional compaction increment

src/agents/pi-embedded-subscribe.handlers.compaction.ts

@@ -5,7 +5,6 @@ import type { EmbeddedPiSubscribeContext } from "./pi-embedded-subscribe.handler
 
 export function handleAutoCompactionStart(ctx: EmbeddedPiSubscribeContext) {
   ctx.state.compactionInFlight = true;
-  ctx.incrementCompactionCount();
   ctx.ensureCompactionPromise();
   ctx.log.debug(`embedded run compaction start: runId=${ctx.params.runId}`);
   emitAgentEvent({
@@ -40,6 +39,9 @@ export function handleAutoCompactionEnd(
 ) {
   ctx.state.compactionInFlight = false;
   const willRetry = Boolean(evt.willRetry);
+  if (!willRetry) {
+    ctx.incrementCompactionCount?.();
+  }
   if (willRetry) {
     ctx.noteCompactionRetry();
     ctx.resetForCompactionRetry();

src/agents/pi-embedded-subscribe.subscribe-embedded-pi-session.waits-multiple-compaction-retries-before-resolving.test.ts

@@ -30,6 +30,21 @@ describe("subscribeEmbeddedPiSession", () => {
     expect(resolved).toBe(true);
   });
 
+  it("does not count compaction until end event", async () => {
+    const { emit, subscription } = createSubscribedSessionHarness({
+      runId: "run-compaction-count",
+    });
+
+    emit({ type: "auto_compaction_start" });
+    expect(subscription.getCompactionCount()).toBe(0);
+
+    emit({ type: "auto_compaction_end", willRetry: true });
+    expect(subscription.getCompactionCount()).toBe(0);
+
+    emit({ type: "auto_compaction_end", willRetry: false });
+    expect(subscription.getCompactionCount()).toBe(1);
+  });
+
   it("emits compaction events on the agent event bus", async () => {
     const { emit } = createSubscribedSessionHarness({
       runId: "run-compaction",