fix(stream): TEST-tab chat — resolve liveChatId from snippet, poll until the broadcast is live

The open creator report ('I still cannot post a chat message in the TEST tab',
feedback 'Chat polling couldn't start — Mock Chat Input is disabled') was a single
cause: the liveChatId never resolved. Two YouTube API facts:
1. The id lives in snippet.liveChatId — contentDetails has no such property
   (TASK 44 read part=contentDetails: could never resolve).
   https://developers.google.com/youtube/v3/live/docs/liveBroadcasts
2. It only exists once the broadcast is LIVE — the official sample lists
   broadcastStatus=active, and our fetch ran before the frame pump pushed RTMP
   (enableAutoStart flips ready→live). A ready-state list legitimately returns
   no id.
   https://github.com/youtube/api-samples/blob/master/java/src/main/java/com/google/api/services/samples/youtube/cmdline/live/GetLiveChatId.java

Fix: GetBroadcastLiveChatIdAsync reads part=snippet and polls with a bounded
retry (10x/2s); PrepareAndStartLiveAsync starts the frame pump FIRST, then
resolves the id. Chat stays non-fatal. Docs ai.md/TASKS.md/HANDOFF.md +
MyMistakes recipe updated same commit. TASK 44.

Good Dog: ONE integration test (GetBroadcastLiveChatIdAsync_Polls_Snippet_...
) drives a broadcast that gains its id mid-retry and asserts every request used
part=snippet. Gate: clean build 0 warnings, vstest 318/318.

HANDOFF.md

@@ -1,52 +1,41 @@
-# HANDOFF — 2026-09-24 (TASK 43 shipped: native events & alerts — creator said "go")
+# HANDOFF — 2026-09-25 (TASK 44 shipped: TEST-tab chat fix — liveChatId now resolves)
 
 ## Branch / Commit State
 
-`main` HEAD = new commit for TASK 43 (native events & six-animation alert box); previous:
-`3a4e17c` (account zone world-independent), `cb75066` (YPP 403), `d72949e` (top-bar feedback),
-`ac6e67a` (end close-out). Repo is ~10 commits ahead of pushed `197ee81` — **push is the
-creator's call** (sub-milestone decision, not per-commit).
+`main` HEAD = new commit for TASK 44 (TEST-tab chat fix); previous: TASK 43 commit (native
+events & alerts), `ac6e67a` (end close-out). Repo is ~11 commits ahead of pushed `197ee81` —
+**push is the creator's call** (sub-milestone decision, not per-commit).
 
 **Working tree CLEAN after this unit's commit.**
 
-## ⚠️ The unit that just shipped (this turn, creator said "go")
+## ⚠️ The unit that just shipped (the open TEST-tab chat report, diagnosed + fixed)
 
-The creator asked (2026-09-23) whether the app could use **native YouTube events instead of
-StreamElements**. Research pinned the API facts; creator rulings locked the product shape. One
-combined work unit ("go"), task filed as **TASK 43** (`TASKS/task-43-native-alerts.md`):
+The HANDOFF-open creator report — *"I still cannot post a chat message in the TEST tab"* —
+is **RESOLVED** (one cause, one scoped unit, TASK 44 in `TASKS/task-44-test-chat-fix.md`):
 
-1. **Chat parity half** — `YouTubeChatService` now decodes **all six** `liveChat/messages`
-   event types into `ChatMessage.Kind` (the four previously-empty event rows are real now) and
-   re-arms its poll on the server's `pollingIntervalMillis` (streamList semantics; clamp
-   1000–6000ms, `maxResults=2000`).
-2. **Alerts half** — new **`SourceType.AlertBox`** ("Stream Alerts", one per layout,
-   `CanAddAlerts` gate mirroring chat): an OBS-style celebration zone, idle = transparent.
-   `Services/AlertRenderer.cs` draws **six DISTINCT branded animations** (SuperChat slide-up/
-   shine/count-up; SuperSticker scale-pop; NewMember drop-in/flash; MemberGift slide-left/chip-fan;
-   GiftReceived confetti; MemberMilestone rise/growth-bar), each card carrying the "made with
-   LlamaCasty!" brand line (free product placement per broadcast). `Services/AlertOverlayLayer.cs`
-   is a true component (Commit-G pattern): queue (cap 10) + 33ms ticker + cache-first
-   `RenderFrame` + `UpdatePreview`; **`Advance(double)` = deterministic test clock**.
-3. **Creator rulings baked in:** no menus/polls (asked once, held); free-sub mention = chat row
-   only, **no sub alert** (YouTube emits none); **no viewer count** (vetoed — demotivating,
-   weaponizable); six events = six unique animations, not a recolored template.
+- **The feedback line** "Chat polling couldn't start — Mock Chat Input is disabled" is
+  `TestSessionViewModel.BeginTest` running with a **null liveChatId**.
+- **Root cause (two API facts, cited in commit + MyMistakes):** (1) `liveChatId` lives in
+  **`snippet.liveChatId`** — `contentDetails` has no such property, and the old code read
+  `part=contentDetails` (can NEVER resolve); (2) YouTube only populates it once the broadcast
+  is **live** (official `GetLiveChatId.java` lists `broadcastStatus=active`), and the fetch
+  ran before the frame pump pushed RTMP (enableAutoStart flips ready→live).
+- **Fix:** `GetBroadcastLiveChatIdAsync(broadcastId, maxAttempts=10, delayMs=2000)` now reads
+  `part=snippet` and polls with a bounded retry; `PrepareAndStartLiveAsync` starts the frame
+  pump FIRST, then resolves the id. Chat stays non-fatal. TEST drawer wiring unchanged
+  (`BeginTest` opens the dock once the id resolves → Mock Chat Input becomes sendable).
 
-**Good Dog:** `ytLive.Tests/AlertLayerTests.cs` (RealApp STA, real WPF raster) — ParsePage
-classifies all six kinds + cadence fields; playback never enqueues a `None` (sub-mention) row,
-plays six pairwise-distinct moving frames, drains to idle. **Gate: clean build 0 warnings,
-316/317** — the ONE failure (`LayerReorderPersistenceTests.RealMouseDrag…`) repros on the CLEAN
-tree (proved via `git stash` + rebuild + isolated run): a real-mouse-drag test that no-ops while
-a game/fullscreen window steals the mouse (the HANDOFF-documented environmental class).
-**NOT a regression — do not chase it in-app; close games and rerun if in doubt.**
+**Good Dog:** ONE integration test in `YouTubeStreamServiceTests.cs`
+(`GetBroadcastLiveChatIdAsync_Polls_Snippet_Until_Id_Appears`) — a fake broadcast that starts
+without a liveChatId and gains it on a later poll; asserts the retry resolves it, polled ≥3x,
+and every request asked for snippet (never contentDetails). **Gate: clean build 0 warnings,
+full vstest 318/318 passed** (the LayerReorder real-mouse-drag test passed this run too).
 
 ## Follow-ups queued (NOT done in this unit)
 
-- **Creator report still open — not yet diagnosed:** "I still cannot post a chat message in the
-  TEST tab." The TEST drawer's Mock Chat Input posts a REAL `liveChat/messages.insert`; the fix
-  needs its own scoped unit.
 - **TASK 3 item 20 persistence half** — the canonical `RewardEvents` SQLite table +
-  `superChatEvents.list` (30-day) backfill + session-report rollup (the shipped alert path parses
-  events to `ChatMessage` in memory; the report reads that table once it exists).
+  `superChatEvents.list` (30-day) backfill + session-report rollup (events still parse to
+  `ChatMessage` in memory only).
 - TASK 3 item 16 (Text source) still open; TASK 40 units A/C/D queued; TASK 32–36 queued.
 
 ## Around the task (carried facts)
@@ -58,20 +47,19 @@ a game/fullscreen window steals the mouse (the HANDOFF-documented environmental
   must become one-time before launch. `MARCOM.md`/`MONETIZATION.md` gitignored — never commit.
 - Latent bug the YPP 403 masked: statistics are JSON **strings** — always the ValueKind-first
   `ReadInt64` (MyMistakes recipe), never `GetInt64`.
-- New facts recorded: the chat feed IS the event feed (six types, no sub event); streamList is a
-  connection-semantics description of that same endpoint (pollingIntervalMillis drives cadence).
+- **API fact (TASK 44):** a liveChatId fetch at insert time (lifecycleStatus `ready`) returns
+  nothing by design — missing liveChatId ≈ "broadcast not live yet", not an auth failure,
+  until ~20s post push. Debug with that lens.
 - Every committed change needs a **close + relaunch** of the running app to be seen — running
   builds are live; verify.sh can't run while the exe is locked.
 
 ## Next step
 
-1. **Creator verifies the alerts unit on the next run**: Add → Stream Alerts, then (Test Stream
-   drawer) Simulated Super Chat / New Member — confirm the zone stays transparent at idle and each
-   event plays its own animation on the canvas and preview; a real Super Chat during the next live
-   run confirms the real path.
-2. Push decision is the creator's (repo ~10 ahead). If pushed, note the commit id in this file.
-3. When scoped: diagnose the TEST-tab chat posting report ("I still cannot post a chat message in
-   the TEST tab") as its own Good-Dog unit.
+1. **Creator verifies the TEST-tab chat fix on the next run**: Test Stream → the drawer should
+   open with a liveChatId line and Mock Chat Input enabled ~as soon as the broadcast goes live;
+   send a message and confirm it round-trips through the ~2s poll and renders on the overlay.
+2. Push decision is the creator's (repo ~11 ahead). If pushed, note the commit id in this file.
+3. When scoped: TASK 3 item 20 (RewardEvents persistence half) draws next.
 
 ## Critical working rules (unchanged, still binding)
 

MyMistakes.md

@@ -28,6 +28,18 @@ calling it; a leaked 403→parse chain means your "whole request failed" symptom
 paper over a second crash that only appears once the 403 is fixed (test the full
 happy path, not just the error path).
 
+### liveChatId LIVES IN SNIPPET AND ONLY EXISTS ONCE THE BROADCAST IS LIVE (RECIPE)
+
+YouTube Data API v3 `liveBroadcasts`. `liveChatId` is in **`snippet.liveChatId`** —
+`contentDetails` has NO such property. AND it is only populated once the broadcast is
+**live** (the official `GetLiveChatId.java` sample lists `broadcastStatus=active`);
+a fetch right after insert (lifecycleStatus `ready`) returns nothing. (2026-09-25: this
+cost a whole investigation — the TEST-tab "Chat polling couldn't start — Mock Chat Input
+is disabled" report — because the code read `part=contentDetails` + ran before the frame
+pump pushed RTMP.) Fix = read part=snippet + bounded retry AFTER the encoder starts
+(`GetBroadcastLiveChatIdAsync(broadcastId, maxAttempts=10, delayMs=2000)`). Debug lens:
+missing liveChatId ≈ "broadcast not live yet", NOT an auth failure.
+
 ### CHANNELS.LIST auditDetails PART 403s THE WHOLE REQUEST WITHOUT A PARTNER SCOPE (RECIPE)
 
 YouTube Data API v3 `channels.list` rejects the ENTIRE request with

Services/YouTubeStreamService.cs

@@ -339,16 +339,37 @@ public class YouTubeStreamService
         return $"YouTube rejected the message ({(int)response.StatusCode})";
     }
 
-    /// <summary>Returns the liveChatId for a broadcast by fetching its contentDetails.
-    /// The liveChatId is needed to poll chat messages. Called after broadcast creation
-    /// in PrepareAndStartLiveAsync.</summary>
-    public async Task<string?> GetBroadcastLiveChatIdAsync(string broadcastId)
+    /// <summary>Resolves the broadcast's liveChatId (needed to poll chat). Two facts
+    /// pin this down (2026-09-25, from the official liveBroadcasts reference + the
+    /// GetLiveChatId.java sample):
+    /// 1. It lives under <c>snippet.liveChatId</c> — <c>contentDetails</c> has no such
+    ///    property, so part=contentDetails could NEVER resolve it (the "Chat polling
+    ///    couldn't start" report).
+    /// 2. YouTube only populates it once the broadcast is <c>live</c> (the sample lists
+    ///    broadcastStatus=active) — fetching right after insert (lifecycleStatus
+    ///    <c>ready</c>) returns no id. So this polls with a bounded retry, which the
+    ///    caller must run AFTER the encoder starts pushing RTMP (enableAutoStart flips
+    ///    the broadcast to live). Returns the id or null after the retries exhaust;
+    ///    never throws.</summary>
+    public async Task<string?> GetBroadcastLiveChatIdAsync(
+        string broadcastId, int maxAttempts = 10, int delayMs = 2000)
+    {
+        for (var attempt = 0; attempt < maxAttempts; attempt++)
+        {
+            if (attempt > 0) await Task.Delay(delayMs);
+            var liveChatId = await FetchLiveChatIdAsync(broadcastId);
+            if (liveChatId != null) return liveChatId;
+        }
+        return null;
+    }
+
+    private async Task<string?> FetchLiveChatIdAsync(string broadcastId)
     {
         if (!await EnsureToken()) return null;
 
         _http.DefaultRequestHeaders.Authorization = new("Bearer", _auth.CurrentChannel!.AccessToken);
         var response = await _http.GetAsync(
-            $"{ApiBase}/liveBroadcasts?part=contentDetails&id={broadcastId}");
+            $"{ApiBase}/liveBroadcasts?part=snippet&id={broadcastId}");
         if (!response.IsSuccessStatusCode) return null;
 
         var json = await response.Content.ReadAsStringAsync();
@@ -356,8 +377,8 @@ public class YouTubeStreamService
         var items = data.GetProperty("items");
         if (items.GetArrayLength() == 0) return null;
 
-        var contentDetails = items[0].GetProperty("contentDetails");
-        if (contentDetails.TryGetProperty("liveChatId", out var liveChatId))
+        var snippet = items[0].GetProperty("snippet");
+        if (snippet.TryGetProperty("liveChatId", out var liveChatId))
             return liveChatId.GetString();
 
         return null;

TASKS.md

@@ -59,6 +59,7 @@
 | 41 | Test Stream mode: private test broadcast + TEST drawer (mock chat input + simulated events) | ✅ Done (2026-09-22) | [`TASKS/task-41-test-stream-mode.md`](TASKS/task-41-test-stream-mode.md) |
 | 42 | Top bar redesign: one REC-or-Stream surface, gear up top, sign-in/account zone world-gated | ✅ Done (2026-09-22) | [`TASKS/task-42-top-bar-redesign.md`](TASKS/task-42-top-bar-redesign.md) |
 | 43 | Native events & alerts: chat parity (all six event types + server poll cadence) + six-animation native alert box | ✅ Done (2026-09-24) | [`TASKS/task-43-native-alerts.md`](TASKS/task-43-native-alerts.md) |
+| 44 | TEST-tab chat fix: resolve liveChatId from snippet (not contentDetails) + poll until the broadcast is live | ✅ Done (2026-09-25); full suite 318/318 | [`TASKS/task-44-test-chat-fix.md`](TASKS/task-44-test-chat-fix.md) |
 
 ---
 
@@ -110,6 +111,13 @@
   `AlertOverlayLayer` component; 33ms ticker, deterministic `Advance` test clock; idle =
   transparent). Creator rulings baked in: free-sub mention = chat row only (no sub alert — YouTube
   emits none), NO viewer count, every alert card carries the "made with LlamaCasty!" brand line.
+- **TASK 44 — TEST-tab chat fix** — **DONE 2026-09-25** (`TASKS/task-44-test-chat-fix.md`):
+  the open creator report ("I still cannot post a chat message in the TEST tab") was a single
+  cause: `GetBroadcastLiveChatIdAsync` read `contentDetails.liveChatId` (lifeChatId lives in
+  **`snippet`**) AND ran before the broadcast was live (RTMP push flips ready→live via
+  enableAutoStart; YouTube only populates the id on live broadcasts — official GetLiveChatId.java
+  sample lists broadcastStatus=active). Fixed by reading `snippet.liveChatId` and polling with a
+  bounded retry after the frame pump starts; chat stays non-fatal.
 
 ---
 

TASKS/task-44-test-chat-fix.md

@@ -0,0 +1,58 @@
+# TASK 44 — TEST-tab chat fix: resolve the liveChatId (snippet + live-timing)
+
+> Catalog: [`TASKS.md`](../TASKS.md). Status: ✅ **SHIPPED 2026-09-25** — the open
+> creator report from HANDOFF ("I still cannot post a chat message in the TEST tab")
+> diagnosed and fixed as its own scoped unit.
+
+## Provenance
+
+- **2026-09-24, HANDOFF** filed the creator report as open: "I still cannot post a chat
+  message in the TEST tab." The TEST drawer's Mock Chat Input posts a real
+  `liveChat/messages.insert`; the drawer only enables it when a liveChatId is resolved.
+- **2026-09-25 diagnosis:** the reported feedback line "Chat polling couldn't start —
+  Mock Chat Input is disabled" is `TestSessionViewModel.BeginTest` running with a **null
+  liveChatId**. That id comes from `YouTubeStreamService.GetBroadcastLiveChatIdAsync`,
+  and two API facts (from the official liveBroadcasts reference + the
+  `GetLiveChatId.java` sample) pin why it never resolved:
+  1. **It lives under `snippet.liveChatId`** — `contentDetails` has no such property at
+     all. The code requested `part=contentDetails` and read `contentDetails.liveChatId`,
+     a path that can NEVER resolve.
+  2. **YouTube only populates it once the broadcast is `live`** (the official sample
+     lists `broadcastStatus=active`). The fetch ran right after broadcast insert
+     (lifecycleStatus `ready`) AND before `_framePump.StartAsync()` pushed the RTMP
+     stream that `enableAutoStart` needs to flip the broadcast to live — so even the
+     correct property would have been empty at fetch time.
+
+## What shipped
+
+- `Services/YouTubeStreamService.cs`:
+  - `GetBroadcastLiveChatIdAsync(broadcastId, maxAttempts = 10, delayMs = 2000)` now
+    requests **`part=snippet`** and reads **`snippet.liveChatId`**, and **polls with a
+    bounded retry** until the id appears or the attempts exhaust (never throws). The
+    default retry (~20s) gives the encoder time to connect and the broadcast to go live.
+  - New private `FetchLiveChatIdAsync` holds the single read; the public method owns
+    the retry loop.
+- `ViewModels/MainViewModel.Streaming.Operations.cs`:
+  - `PrepareAndStartLiveAsync` **starts the frame pump FIRST**, then resolves the
+    liveChatId — the reorder is required for the id to ever exist. Chat remains
+    non-fatal: failure logs and the stream continues.
+  - TEST drawer wiring preserved: `TestSession.BeginTest(broadcastId, liveChatId)`
+    still opens the dock once the id resolves → Mock Chat Input becomes sendable.
+- Docs: `ai.md` (Test Stream section), `TASKS.md` (row 44), `HANDOFF.md` rewritten.
+
+## Validation (Good Dog: ONE integration test)
+
+`ytLive.Tests/YouTubeStreamServiceTests.cs`:
+`GetBroadcastLiveChatIdAsync_Polls_Snippet_Until_Id_Appears` — a fake broadcast that
+starts WITHOUT a liveChatId (not yet live) and gains it on a later poll; asserts the
+retry eventually resolves `Cg0LIVECHAT42`, that it polled ≥3 times, and that every
+request asked for **snippet** (never contentDetails) — the exact seam that was broken.
+
+**Gate: clean build 0 warnings; full vstest 318/318 passed.**
+
+## Reference
+
+- https://developers.google.com/youtube/v3/live/docs/liveBroadcasts (snippet.liveChatId;
+  contentDetails has no liveChatId)
+- https://github.com/youtube/api-samples/blob/master/java/src/main/java/com/google/api/services/samples/youtube/cmdline/live/GetLiveChatId.java
+  (sample lists broadcastStatus=active — id only present on live broadcasts)

ViewModels/MainViewModel.Streaming.Operations.cs

@@ -183,36 +183,6 @@ public partial class MainViewModel : ViewModelBase
                 _notifications.Warning("Complete your broadcast details",
                     "Your title and description are empty — fill them in from the Text panel on the right.");
             }
-
-            // Start chat polling (TASK 9.4): fetch the liveChatId from the broadcast's
-            // contentDetails, then start the poll loop. Chat is non-fatal — if it fails,
-            // the stream continues without on-panel chat.
-            string? liveChatId = null;
-            try
-            {
-                liveChatId = await _youtubeStream.GetBroadcastLiveChatIdAsync(_currentBroadcastId);
-                if (liveChatId != null)
-                {
-                    _youtubeChat.Start(liveChatId);
-                    AppLog.Write($"Chat polling started: {liveChatId}");
-                }
-                else
-                {
-                    AppLog.Write("Could not retrieve liveChatId; chat polling disabled");
-                }
-            }
-            catch (Exception chatEx)
-            {
-                AppLog.Write($"Chat start failed (non-fatal): {chatEx.Message}");
-            }
-
-            // TASK 41: a test broadcast hands its session to the Test drawer once
-            // the liveChatId resolves — Mock Chat Input + simulated events need it.
-            if (IsTestStream && _currentBroadcastId != null)
-            {
-                TestSession.BeginTest(_currentBroadcastId, liveChatId);
-                AppLog.Write($"Test session dock open for {_currentBroadcastId}");
-            }
         }
         catch (Exception ex)
         {
@@ -222,8 +192,40 @@ public partial class MainViewModel : ViewModelBase
             return;
         }
 
+        // The pump is what pushes RTMP; enableAutoStart flips the broadcast ready→live
+        // only once frames flow. The liveChatId (snippet.liveChatId) does not exist
+        // before that (2026-09-25 diagnosis), so chat resolution runs AFTER the pump
+        // starts. Chat is non-fatal — if it fails, the stream continues without chat.
         await _framePump.StartAsync(); // never throws; failures log + surface via Failed
 
+        string? liveChatId = null;
+        try
+        {
+            if (_currentBroadcastId != null)
+                liveChatId = await _youtubeStream.GetBroadcastLiveChatIdAsync(_currentBroadcastId);
+            if (liveChatId != null)
+            {
+                _youtubeChat.Start(liveChatId);
+                AppLog.Write($"Chat polling started: {liveChatId}");
+            }
+            else
+            {
+                AppLog.Write("Could not retrieve liveChatId; chat polling disabled");
+            }
+        }
+        catch (Exception chatEx)
+        {
+            AppLog.Write($"Chat start failed (non-fatal): {chatEx.Message}");
+        }
+
+        // TASK 41: a test broadcast hands its session to the Test drawer once
+        // the liveChatId resolves — Mock Chat Input + simulated events need it.
+        if (IsTestStream && _currentBroadcastId != null)
+        {
+            TestSession.BeginTest(_currentBroadcastId, liveChatId);
+            AppLog.Write($"Test session dock open for {_currentBroadcastId}");
+        }
+
         // Health polling (TASK 5 item 3): poll immediately, then every 30s while
         // live. Report-by-exception — a banner appears only on warning/error.
         _healthPollTimer.Start();

ai.md

@@ -1560,6 +1560,15 @@ These are the hard facts behind every decision. Full list in `TASKS.md`.
   `StopStream` clears it in every path (including pump-failure rollback). Once the liveChatId
   resolves, `TestSession.BeginTest(broadcastId, liveChatId)` opens the **TEST drawer** (third
   right-rail pull-out, three-way one-open-at-a-time exclusivity wired in `MainViewModel.Ypp.cs`).
+  **liveChatId resolution (fixed 2026-09-25, TASK 44):** the id is `snippet.liveChatId` —
+  `contentDetails` has NO liveChatId property — and YouTube only populates it once the broadcast
+  is LIVE (the official GetLiveChatId.java sample lists broadcastStatus=active). So
+  `GetBroadcastLiveChatIdAsync(broadcastId, maxAttempts=10, delayMs=2000)` reads
+  part=snippet and polls with a bounded retry, and `PrepareAndStartLiveAsync` starts the frame
+  pump FIRST (the RTMP push is what flips ready→live via enableAutoStart) before resolving it.
+  Chrome-debugging note: a fetch at broadcast-insert time (lifecycleStatus ready) legitimately
+  returns no id — missing liveChatId is the ready state, not an auth failure, until ~20s post
+  push.
   Drawer tooling: **Mock Chat Input** = a REAL `liveChat/messages.insert` (`YouTubeStreamService.InsertChatMessageAsync`)
   that round-trips through the real ~2s poll and renders through the live overlay path;
   **simulated Subscriber / New Member / Super Chat** = `YouTubeChatService.InjectSimulatedMessage`,

ytLive.Tests/YouTubeStreamServiceTests.cs

@@ -294,4 +294,42 @@ public class YouTubeStreamServiceTests
         Assert.Contains("403", closeOutError);
         Assert.StartsWith("POST ", handler.Requests[^1]);
     }
-}
+
+    /// <summary>The ONE integration test for the 2026-09-25 TEST-tab chat fix:
+    /// "Chat polling couldn't start — Mock Chat Input is disabled" because the
+    /// liveChatId never resolved. Two facts pin it: (1) the id lives in
+    /// <c>snippet.liveChatId</c> — part=contentDetails could NEVER return it, and
+    /// (2) YouTube only populates it once the broadcast is live, so a single fetch
+    /// right after insert (lifecycleStatus ready) comes back empty. The fix reads
+    /// part=snippet AND polls with a bounded retry — this test drives a fake
+    /// broadcast that starts WITHOUT the id (broadcast not yet live) and gains it on
+    /// a later poll, proving the retry resolves it and that every request asked for
+    /// snippet (never contentDetails).</summary>
+    [Fact]
+    public async Task GetBroadcastLiveChatIdAsync_Polls_Snippet_Until_Id_Appears()
+    {
+        var polls = 0;
+        var handler = new RecordingHandler
+        {
+            ResponseSelector = request =>
+            {
+                polls++;
+                // First polls: broadcast exists but not yet live → no liveChatId.
+                return polls < 3
+                    ? """{"items":[{"id":"BC-42","snippet":{"title":"t"}}]}"""
+                    : """{"items":[{"id":"BC-42","snippet":{"title":"t","liveChatId":"Cg0LIVECHAT42"}}]}""";
+            }
+        };
+        var service = new YouTubeStreamService(CreateAuthed(), new HttpClient(handler));
+
+        var chatId = await service.GetBroadcastLiveChatIdAsync("BC-42", maxAttempts: 5, delayMs: 25);
+
+        Assert.Equal("Cg0LIVECHAT42", chatId);
+        Assert.True(polls >= 3, $"expected the retry to poll until the id appears (polled {polls}x)");
+        Assert.All(handler.Requests, r =>
+        {
+            Assert.Contains("part=snippet", r);
+            Assert.DoesNotContain("part=contentDetails", r);
+        });
+    }
+}