stage-batch33: v0.51.151 / Release DW — SSE reattach + title-lang + composer cap

[nesquena-hermes]

stage-batch33 — 3-PR mid-risk batch (v0.51.151 / Release DW)

3 contributor PRs, all MERGEABLE, full pytest 6713 passed / 0 failed / 161s, Opus advisor SHIP-AS-IS.

Contents

PR	Author	Summary	Files
#2925	@wirtsi	SSE reattach on session-switch return + close leaked stream connections (closes #2924)	7 files +156/-17
#2984	@ai-ag2026	Keep generated session titles in conversation language	2 files +124
#2946	@Koraji95-coder	Cap composer max-width at 1600px on ultrawide viewports (#2856 Position A)	1 file +5

Verification

• Targeted pytest (subset): 176 passed, 0 failed, 7.67s
• Sequential full pytest: 6713 passed, 11 skipped, 1 xfailed, 2 xpassed, 0 failed, 161.55s
• Opus advisor: SHIP-AS-IS, 0 MUST-FIX, 4 SHOULD-FIX (filed as follow-up issue)
• Pre-Opus gate: JS syntax, Python ast.parse, merge markers, CHANGELOG TBD, lock hygiene, Docker surface, string-assertion sweep — all clean

Extra fix in this stage

Pre-existing pytest failure on master (test_named_custom_provider_models_endpoint_network_error_uses_short_timeout) was caught by the full-suite gate. Root cause: the test recorder picked up unrelated background probes (Copilot v2 token, OpenRouter free-tier discovery) that now run during get_available_models(). Fix narrows the recorder to the broken-proxy endpoint only — the contract being pinned is unchanged. Single test-only commit.

Build skew sanity check

All three contributor branches MERGEABLE against current master at the time of staging. Stale-base dual-diff check:

• ux(composer): cap composer-box max-width at 1600px on ultrawide viewports (#2856) #2946: 1 file +5 from merge-base (5-LOC CSS), clean
• fix: keep generated titles in conversation language #2984: 2 files +124 from merge-base, clean
• fix: reattach SSE on session-switch return + close leaked stream connections #2925: 7 files +156/-17 from merge-base (squashed 9 commits — wirtsi did revert-and-reapply gymnastics that produced a noisy commit history; net diff is clean)

Follow-ups to file post-merge

Opus flagged 4 SHOULD-FIX items (none ship-blocking):

1. _detect_title_language German false-positive surface (api/streaming.py:1381-1394) — common tokens like 'session', 'die', 'der', 'das' can trigger German detection on English-with-tech-jargon prompts. Should require ≥3 hits or drop the most-ambiguous tokens.
2. Hardcoded 'Alte Session Bilder' German fallback (api/streaming.py:1872-1877) — branch-specific one-off, tech debt.
3. Title-language rule only knows German exemplars — uneven UX vs other locales.
4. _isSessionActivelyViewed gate is broader than the comment claims (static/messages.js:2155-2158) — focus-gated reconnect.
5. Implicit DOM↔INFLIGHT contract on reattach (static/messages.js:661-670) — load-bearing invariant not asserted.

Will file as single follow-up issue after release lands.

[zoilanyferrer9-stack]

• Targeted pytest (subset): 176 passed, 0 failed, 7.67s
• Sequential full pytest: 6713 passed, 11 skipped, 1 xfailed, 2 xpassed, 0 failed, 161.55s
• Opus advisor: SHIP-AS-IS, 0 MUST-FIX, 4 SHOULD-FIX (filed as follow-up issue)
• Pre-Opus gate: JS syntax, Python ast.parse, merge markers, CHANGELOG TBD, lock hygiene, Docker surface, string-assertion sweep — all clean

Extra fix in this stage

Pre-existing pytest failure on master (test_named_custom_provider_models_endpoint_network_error_uses_short_timeout) was caught by the full-suite gate. Root cause: the test recorder picked up unrelated background probes (Copilot v2 token, OpenRouter free-tier discovery) that now run during get_available_models(). Fix narrows the recorder to the broken-proxy endpoint only — the contract being pinned is unchanged. Single test-only commit.

Opus flagged 4 SHOULD-FIX items (none ship-blocking):

1. _detect_title_language German false-positive surface (api/streaming.py:1381-1394) — common tokens like 'session', 'die', 'der', 'das' can trigger German detection on English-with-tech-jargon prompts. Should require ≥3 hits or drop the most-ambiguous tokens.
2. Hardcoded 'Alte Session Bilder' German fallback (api/streaming.py:1872-1877) — branch-specific one-off, tech debt.
3. Title-language rule only knows German exemplars — uneven UX vs other locales.
4. _isSessionActivelyViewed gate is broader than the comment claims (static/messages.js:2155-2158) — focus-gated reconnect.
5. Implicit DOM↔INFLIGHT contract on reattach (static/messages.js:661-670) — load-bearing invariant not asserted.

Will file as single follow-up issue after release lands.