[brennanb2025]

Summary

Hardens the crash-breadcrumb pipeline against repeated renderer error storms and closes two edge cases in the #8279 guards.

Problem

The crash-breadcrumb ring holds only 30 events and is snapshotted into crash reports. renderer_error and renderer_unhandled_rejection previously used the uncoalesced path, so a repeating error could evict the useful pre-crash trail and create one durable trace record per occurrence. The local trace sink serializes these records and flushes them to disk.

Fix

• Route renderer errors and unhandled rejections with a stable message through recordCoalescedCrashBreadcrumb using a 30-second window.
• Key coalescing by the full sanitized message plus sanitized stack/source/type evidence, so unrelated failures with the same generic message cannot suppress each other.
• Suppress duplicate durable trace spans with the same decision; the next recorded span carries suppressedSinceLast.
• Keep state bounded: sanitization caps each identity field and the store caps the map at 128 keys.
• Leave message-less failures uncoalesced because they do not have a safe identity; use errorMessage when an Error object provides one.
• Handle SSH path-probe rejection separately from xterm callback failures, preventing a throwing/stale callback from being invoked twice or recreating an unhandled rejection.
• Suppress only Chromium's exact benign ResizeObserver messages; application errors that merely mention a ResizeObserver loop remain visible.

Performance evidence

• A deterministic 1,000-event duplicate storm creates one durable trace span instead of 1,000.
• Suppressed duplicates use the store's O(1) lookup/return path.
• Coalescing state remains capped at 128 keys; no timers, polling, subprocesses, provider scans, or growing buffers are added.

Terminal reliability contract

• Invariant (xterm-addon.boundary-containment): rejected remote file probes and throwing/stale xterm callbacks remain pane-scoped, invoke the consumer at most once, and do not escape as unhandled rejections.
• Failure source: [Bug]: Renderer crashes to white screen on macOS — unhandled rejections accumulate causing memory leak and ResizeObserver loop (v1.4.128–1.4.135) #8260 and the post-merge review of fix: stop renderer heap leak from unhandled terminal teardown rejections (#8260) #8279's SSH teardown guard.
• Oracle: renderer-unit tests force a rejected path-existence probe and a throwing xterm callback, then assert an empty-link result or exactly one callback invocation. Source-aware breadcrumb tests also prove same-message failures at different sites retain distinct identities.
• Gate: existing experimental, partial xterm-addon.boundary-containment gate; its focused command passes with the terminal file-link suite added to the run.
• Provider/platform coverage: the containment code is platform-neutral renderer TypeScript. The SSH/remote rejection shape has direct deterministic coverage; local, daemon, WSL, and mobile/relay PTY ownership and I/O paths are unaffected. No live SSH soak or separate Windows/Linux desktop run is claimed here.
• Performance budget: one bounded candidate pass and the existing path probes remain; no retry, polling, liveness scan, session listing, startup await, or subprocess work is introduced.
• Diagnostics: repeated renderer failures retain a bounded suppressed count and source-aware identity in both the in-memory breadcrumb and resumed durable trace.
• Residual gaps: this does not prove the broader rejection-free SSH/xterm heap growth is fixed; that investigation remains in feat(terminal): trim scrollback of hidden SSH terminals after cold-park delay #8655.

Screenshots

No visual change.

Testing

• 199 focused crash-reporting, observability, renderer-diagnostics, and terminal-link tests pass after rebasing onto current main.
• Full node/CLI/web TypeScript check passes.
• Full lint, switch-exhaustiveness, reliability-gate, max-lines-ratchet, bundled-skill, and localization checks pass.
• Hosted PR verification passed at the prior head on the repository's required Node 24; the pushed review fix triggers a fresh run.

AI Review Report

• Audited error identity, coalescing bounds, trace serialization, SSH teardown, callback settlement, ResizeObserver classification, cleanup, and source-aware diagnostic preservation.
• Verified macOS/Linux/Windows-neutral behavior; the SSH rejection path has direct regression coverage and no Git/provider behavior changes.
• Fixed false coalescing for long, message-less, and same-message/different-source failures, duplicate callback settlement, and over-broad benign-error suppression.

Security Audit

• Renderer data is sanitized and secret/path-redacted before it enters a coalescing key or durable trace.
• No new IPC capability, network request, filesystem path, credential handling, or persisted unbounded state is introduced.
• Source-aware keys remain bounded by per-field sanitization and the existing 128-key store cap.

Notes

This is a follow-up to #8279 / #8260. It protects diagnostic context and removes trace-write amplification, but does not claim to solve the rejection-free SSH/xterm heap growth reported later. That residual terminal-memory investigation is tracked separately in #8655.

[coderabbitai]

📝 Walkthrough

Walkthrough

Renderer error and unhandled rejection breadcrumbs now use bounded coalescing keys and a fixed interval, with suppression metadata included in resumed durable tracing. Non-error breadcrumbs retain direct recording. Terminal link handling separates probe rejections from callback failures to avoid duplicate callbacks. ResizeObserver suppression now targets only recognized benign messages, while other related application errors are recorded. Tests cover these behaviors.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly matches the main change: coalescing repeated renderer error breadcrumbs in crash reporting.
Description check	✅ Passed	The description covers Summary, Screenshots, Testing, AI Review Report, Security Audit, and Notes, with enough detail for the PR.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

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