Fix live broadcast privacy promotion (#13)

## Summary

- align privacy-only `liveBroadcasts.update` requests with `part=status`
- preserve made-for-kids status and exact privacy readback verification
- add regression coverage and update the latest release notes

## Root Cause

The helper requested `part=status` but also sent `snippet` and
`contentDetails` in the resource body. YouTube rejected those extra
resource parts with HTTP 400 `unexpectedPart` after the broadcast had
already reached healthy `live` state. The supervisor therefore entered
cooldown without promoting the existing event from unlisted to public.

## Impact

Healthy managed broadcasts can now be promoted to the configured final
privacy without creating, completing, or replacing the event. The
mutation remains serialized and is still verified through a fresh remote
readback before stable state is recorded.

## Validation

- focused regression observed failing before the implementation and
passing afterward
- `pytest -q`: 198 passed
- `ruff check .`: passed
- production scripts compile with `python3 -m py_compile`
- `git diff --check`: passed
- Gemini 3.1 Pro high-effort code review: no findings

## Rollback

Restore the prior API helper artifact and restart the encoder service. A
successful visibility change is intentionally not reverted because
public visibility is the configured target; no broadcast identity
changes are introduced by this patch.

## Public-Safety Checklist

- [x] No OAuth client files, refresh tokens, stream keys, camera
credentials, broadcast IDs, or generated runtime state were committed.
- [x] Documentation was updated for the user-facing behavior change.
- [x] Local tests and independent review passed.

Author: sumitake

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable project changes are recorded here. The README shows only the most recent entry.
 
+## 2026-07-11 - Live Visibility Publication Fix
+
+- Corrected privacy-only `liveBroadcasts.update` requests so `part=status` sends only the matching `id` and `status` resource fields, eliminating HTTP 400 `unexpectedPart` failures after the healthy-live gate.
+- Preserved made-for-kids status and post-update privacy verification while removing unrelated scheduled-start and monitor-stream fields from publication requests.
+- Added regression coverage for the exact part/body contract used to promote an existing live broadcast without creating or replacing it.
+
 ## 2026-07-11 - Optional Video Telemetry
 
 - Added an opt-in `videos.list` command and one-shot collector for aggregate live-stream timing, viewer, view, like, and comment metrics.

README.md

@@ -517,10 +517,10 @@ Each eligible collection performs one [`videos.list`](https://developers.google.
 
 Only the most recent changelog entry is shown here. See `CHANGELOG.md` for full history.
 
-### 2026-07-11 - Optional Video Telemetry
+### 2026-07-11 - Live Visibility Publication Fix
 
-- Added disabled-by-default, quota-bounded aggregate video telemetry through one read-only `videos.list` call per eligible collection, with private local snapshots, write-ahead throttling, retention, and independent system or user timers.
-- Telemetry remains isolated from FFmpeg supervision, broadcast recovery, lifecycle transitions, privacy changes, and retry state.
+- Corrected the privacy-only YouTube update payload so a healthy live broadcast can be promoted from unlisted to the configured final visibility without an HTTP 400 `unexpectedPart` failure.
+- Publication still preserves the existing broadcast and verifies the remote privacy readback before declaring the stream stable.
 
 ## Repository Layout
 

bin/youtube-autoencoder-api

@@ -921,22 +921,9 @@ def set_broadcast_privacy(broadcast_id: str, privacy: str) -> dict[str, Any]:
     current = broadcast_by_id(broadcast_id)
     if current is None:
         raise ReconciliationError(f"liveBroadcast not found: {broadcast_id}")
-    snippet = current.get("snippet") or {}
-    content_details = current.get("contentDetails") or {}
-    monitor = content_details.get("monitorStream") or {}
     status = current.get("status") or {}
-    scheduled_start = snippet.get("scheduledStartTime")
-    if not scheduled_start:
-        raise ReconciliationError("broadcast has no scheduledStartTime required for privacy update")
     body = {
         "id": broadcast_id,
-        "snippet": {"scheduledStartTime": scheduled_start},
-        "contentDetails": {
-            "monitorStream": {
-                "enableMonitorStream": bool(monitor.get("enableMonitorStream", True)),
-                "broadcastStreamDelayMs": int(monitor.get("broadcastStreamDelayMs") or 0),
-            }
-        },
         "status": {
             "privacyStatus": privacy,
             "selfDeclaredMadeForKids": bool(status.get("selfDeclaredMadeForKids", False)),

tests/test_api.py

@@ -741,9 +741,11 @@ def test_list_managed_broadcasts_requires_exact_marker(load_script, monkeypatch)
     assert [item["id"] for item in api.list_managed_broadcasts("encoder-1")] == ["broadcast-1"]
 
 
-def test_set_broadcast_privacy_preserves_required_fields_and_verifies_readback(load_script, monkeypatch):
+def test_set_broadcast_privacy_sends_only_status_part_and_verifies_readback(load_script, monkeypatch):
     api = load_script("youtube-autoencoder-api", "yta_api_privacy")
     current = managed_broadcast(api, "broadcast-1", "live")
+    current["snippet"].pop("scheduledStartTime")
+    current["contentDetails"].pop("monitorStream")
     public = {
         **current,
         "status": {**current["status"], "privacyStatus": "public"},
@@ -768,8 +770,6 @@ def fake_api(method, path, params, body=None):
             "params": {"part": "status"},
             "body": {
                 "id": "broadcast-1",
-                "snippet": {"scheduledStartTime": "2026-07-10T21:00:00Z"},
-                "contentDetails": {"monitorStream": {"enableMonitorStream": True, "broadcastStreamDelayMs": 0}},
                 "status": {"privacyStatus": "public", "selfDeclaredMadeForKids": False},
             },
         }