diff --git a/src/plugin/event.test.ts b/src/plugin/event.test.ts
index 49ed2c031..8b10a5950 100644
--- a/src/plugin/event.test.ts
+++ b/src/plugin/event.test.ts
@@ -335,7 +335,7 @@ describe("createEventHandler - idle deduplication", () => {
 		expect(spawnTmuxPane).toHaveBeenCalledTimes(1)
 	})
 
-	it("dedups real-idle-after-synthetic-idle within 500ms", async () => {
+	it("does NOT dedup real-idle-after-synthetic-idle within 500ms", async () => {
 		//#given
 		const dispatchCalls: EventInput[] = []
 		const eventHandler = createIdleTrackingEventHandler(dispatchCalls)
@@ -359,9 +359,11 @@ describe("createEventHandler - idle deduplication", () => {
 		}))
 
 		//#then
-		expect(dispatchCalls).toHaveLength(1)
+		expect(dispatchCalls).toHaveLength(2)
 		expect(dispatchCalls[0]?.event.type).toBe("session.idle")
 		expect((dispatchCalls[0]?.event.properties as { sessionID?: string } | undefined)?.sessionID).toBe(sessionId)
+		expect(dispatchCalls[1]?.event.type).toBe("session.idle")
+		expect((dispatchCalls[1]?.event.properties as { sessionID?: string } | undefined)?.sessionID).toBe(sessionId)
 	})
 
 	it("dedups back-to-back real session.idle events for the same sessionID within 500ms", async () => {
diff --git a/src/plugin/event.ts b/src/plugin/event.ts
index 265244f29..e8bb49a7d 100644
--- a/src/plugin/event.ts
+++ b/src/plugin/event.ts
@@ -415,6 +415,9 @@ export function createEventHandler(args: {
         const emittedAt = recentSyntheticIdles.get(sessionID);
         if (emittedAt !== undefined && now - emittedAt < DEDUP_WINDOW_MS) {
           recentSyntheticIdles.delete(sessionID);
+          // Let real idle events through even when a synthetic idle fired moments earlier.
+          // OpenCode diagnostics expect a concrete session.idle event signal.
+          recentAnyIdles.delete(sessionID);
         }
         recentRealIdles.set(sessionID, now);
         if (!shouldDispatchIdleEvent(sessionID, now)) {