diff --git a/backend/internal/provider/chatgpt/client.go b/backend/internal/provider/chatgpt/client.go
index b78d2e6..a6fc18b 100644
--- a/backend/internal/provider/chatgpt/client.go
+++ b/backend/internal/provider/chatgpt/client.go
@@ -898,29 +898,41 @@ func (c *Client) startImageGeneration(ctx context.Context, session tlsclient.Htt
 	scanner := bufio.NewScanner(resp.Body)
 	scanner.Buffer(make([]byte, 0, 1024*1024), 8*1024*1024)
 	var chunks []string
-	sseStart := time.Now()
-	// Watchdog: once the conversation id is known, the stream may go silent
-	// without ever emitting the async marker, leaving scanner.Scan() blocked on
-	// a read for the whole ctx budget. Closing the body unblocks the read so the
-	// loop exits and we fall through to polling.
-	convFound := make(chan struct{})
+	refIDs := uploadedRefIDSet(refs)
+	// Watchdog: scanner.Scan() blocks on a read while the SSE is silent, which
+	// would hold the whole ctx budget. ChatGPT's inline image pipeline keeps the
+	// connection open with periodic ": ping" keepalives (~15s apart) while the
+	// image renders, then streams the asset (a role:"tool" multimodal_text turn
+	// carrying image_asset_pointer / sediment://) in the same SSE. So this is an
+	// *idle* timeout reset on every received line — a fixed grace from the
+	// conversation id would abort mid-render before the asset arrives. It only
+	// closes the body (unblocking the read) once the stream is genuinely silent.
+	activity := make(chan struct{}, 1)
 	watchdogDone := make(chan struct{})
 	defer close(watchdogDone)
 	go func() {
-		select {
-		case <-convFound:
-		case <-watchdogDone:
-			return
-		}
-		timer := time.NewTimer(sseAsyncGrace)
+		timer := time.NewTimer(sseIdleGrace)
 		defer timer.Stop()
-		select {
-		case <-timer.C:
-			resp.Body.Close()
-		case <-watchdogDone:
+		for {
+			select {
+			case <-activity:
+				if !timer.Stop() {
+					<-timer.C
+				}
+				timer.Reset(sseIdleGrace)
+			case <-timer.C:
+				resp.Body.Close()
+				return
+			case <-watchdogDone:
+				return
+			}
 		}
 	}()
 	for scanner.Scan() {
+		select {
+		case activity <- struct{}{}:
+		default:
+		}
 		line := scanner.Text()
 		if !strings.HasPrefix(line, "data:") {
 			continue
@@ -936,7 +948,6 @@ func (c *Client) startImageGeneration(ctx context.Context, session tlsclient.Htt
 		if conversationID == "" {
 			if match := conversationIDRE.FindStringSubmatch(payload); len(match) >= 2 {
 				conversationID = match[1]
-				close(convFound)
 			}
 		}
 		newFiles, newSeds := scanForIDs(payload)
@@ -945,18 +956,15 @@ func (c *Client) startImageGeneration(ctx context.Context, session tlsclient.Htt
 		if !asyncStarted && containsAsyncMarker(payload) {
 			asyncStarted = true
 		}
-		// Async pipeline: ChatGPT no longer streams the image inline — it returns
-		// a placeholder tool turn (image_gen_async / image_gen_task_id) and
-		// delivers the asset later via conversation polling. Once we have the
-		// conversation id there is nothing more to read here, so stop instead of
-		// holding the SSE open until [DONE] (a stalled stream would otherwise burn
-		// the whole generation budget and surface as "context deadline exceeded").
-		//
-		// The async marker normally arrives within ~1s of the conversation id. We
-		// still only wait a short grace for it (the watchdog above unblocks a
-		// silent stream) so a request that never engages the async pipeline is
-		// detected quickly instead of burning the whole budget.
-		if conversationID != "" && (asyncStarted || time.Since(sseStart) >= sseAsyncGrace) {
+		// Stop once the image pipeline is confirmed engaged (async/tool marker) or
+		// the generated asset id has streamed inline. The stream echoes back the
+		// user's uploaded reference images too, so exclude those ids before deciding
+		// — otherwise an edit request would stop on its own upload. The idle watchdog
+		// above bounds a silent stream; pollForImage backstops asset retrieval when
+		// nothing streamed inline.
+		haveAsset := len(dropIDs(append([]string(nil), fileIDs...), refIDs)) > 0 ||
+			len(dropIDs(append([]string(nil), sedimentIDs...), refIDs)) > 0
+		if conversationID != "" && (asyncStarted || haveAsset) {
 			break
 		}
 	}
@@ -969,15 +977,13 @@ func (c *Client) startImageGeneration(ctx context.Context, session tlsclient.Htt
 	if conversationID == "" {
 		return "", nil, nil, errors.New("chatgpt SSE closed without conversation_id")
 	}
-	// Intermittently (~10% on gpt-5-5-thinking) the stream returns a conversation
-	// id but never emits the async pipeline marker and no image is ever produced —
-	// polling such a conversation only burns the whole budget and surfaces as the
-	// non-retryable "image poll timeout". The async marker is the reliable "the
-	// image generation task actually started" signal, so when it is absent (and
-	// nothing was streamed inline) treat the attempt as a transient upstream
-	// failure. That is retryable: a fresh submission reliably engages the pipeline,
-	// so the pool retries the same account a few times and then fails over to
-	// another account (换号重试) instead of failing the request.
+	// The stream closed with a conversation id but no sign the image pipeline
+	// engaged — no async/tool marker and no asset streamed inline. Polling such a
+	// conversation only burns the whole budget and surfaces as the non-retryable
+	// "image poll timeout", so treat the attempt as a transient upstream failure.
+	// That is retryable: a fresh submission reliably engages the pipeline, so the
+	// pool retries the same account a few times and then fails over to another
+	// account (换号重试) instead of failing the request.
 	if !asyncStarted && len(fileIDs) == 0 && len(sedimentIDs) == 0 {
 		return "", nil, nil, fmt.Errorf("%w: image generation did not start (no async marker)", ErrTemporaryUpstream)
 	}
diff --git a/backend/internal/provider/chatgpt/util.go b/backend/internal/provider/chatgpt/util.go
index 5243c52..4ac2fd0 100644
--- a/backend/internal/provider/chatgpt/util.go
+++ b/backend/internal/provider/chatgpt/util.go
@@ -18,12 +18,13 @@ const (
 	defaultClientVersion     = "prod-db390ebea64862bf1899c420a4c736e0cf639747"
 	defaultClientBuildNumber = "7904904"
 	defaultPOWScript         = "https://chatgpt.com/backend-api/sentinel/sdk.js"
-	// sseAsyncGrace bounds how long startImageGeneration keeps reading the SSE
-	// waiting for the image_gen_async marker after the conversation id is known.
-	// The marker normally arrives within ~1s; when it never streams (intermittent
-	// on gpt-5-5-thinking) we must not hold the stream open for the whole ctx
-	// budget, so we break after this grace and fall through to polling.
-	sseAsyncGrace = 10 * time.Second
+	// sseIdleGrace bounds how long startImageGeneration keeps reading the image
+	// SSE with no activity at all before giving up. ChatGPT's inline image pipeline
+	// holds the stream open with periodic ": ping" keepalives (~15s apart) while
+	// the image renders, so this is an *idle* timeout reset on every received line
+	// (see the watchdog in startImageGeneration): it only fires when the stream is
+	// genuinely silent, not on the normal render wait.
+	sseIdleGrace = 45 * time.Second
 
 	// pictureV2Command is the "@创建图片" ecosystem mention the ChatGPT web app
 	// prepends to an image (picture_v2) prompt; the server identifies the image
@@ -56,7 +57,7 @@ var (
 	// async image pipeline (image is delivered later via conversation polling
 	// rather than inline in the SSE stream). Their presence means "generating —
 	// keep polling", NOT failure.
-	asyncMarkers = []string{"image_gen_async", "image_gen_task_id", "trigger_async_ux"}
+	asyncMarkers = []string{"image_gen_async", "image_gen_task_id", "trigger_async_ux", "ImageGenToolTemporal", "image_gen_title"}
 
 	// contentPolicyMarkers are stable substrings of ChatGPT's content-audit
 	// refusal message. When one appears in an assistant turn the prompt was