feat(browser): heap, connection and orientation traces on trackers + producers (BT1)

[krassx]

What

Second slice of the system-traces design (PR #53, §14.5 follow-ons): finishes moving the browser traces.system set onto the tracker/producer structure from ST0′ (#55) and deletes the legacy sampler.

• MemoryTracker — the single performance.memory poll timer; starts only on a subscriber, never starts where the engine has no performance.memory.
• ConnectionTracker — online/offline + navigator.connection change.
• OrientationTracker — screen.orientation change + orientationchange.
• MemoryProducer (ram_js_heap_*, polled), AdvertisedMemoryProducer (ram_system_advertised), ConnectionProducer, OrientationProducer (de-duplicated, held so the provider refresh keeps them in a rolling window).
• Removed: createBrowserSystemTracesSampler and BrowserTracesEnv (beta; systemMetricsSampler stays as an override). Wire values and names are unchanged.
• Launch (browser + webview) passes its injected window and scheduler to the trackers.

Worth a look

• A latent bug this fixes. The old sampler copied navigator with { ...navigator }. On a real browser onLine, connection and deviceMemory are accessors on the prototype, so the spread drops them and the connection trace would have reported unknown and ram_system_advertised would never appear. The producers now read the live objects; a test pins this with a prototype-getter navigator. I verified this against the DOM semantics and a prototype-getter fake, not in a real browser.
• One test changed for a reason. launch-stop-recovery.test.ts now sets captureSystemTraces: false: the new connection producer writes a baseline row even in Node, which gives stop() data to persist and breaks that file's tight 5-step deadline budget. The empty legacy sampler used to guarantee no data.
• Not in this PR: the shared PageLifecycleTracker. The events source and these trackers each still attach their own online/offline/orientationchange listeners (the launch tests isolate one with captureSystemEvents: false). That is the next slice.

Verification

• Test-first; mutator loop over the three trackers, the producers, the env helper and the launch wiring — survivors were either strengthened with tests or are equivalent (orientationToWire(type, angle) ignores angle whenever type is present, which the tracker always supplies).
• pnpm ci:local passes (lint, typecheck, cycles, per-package coverage). E2E not run locally.

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Reviewing files that changed from the base of the PR and between 09b274a and d690ab4.

📒 Files selected for processing: 2

• packages/browser/src/trackers/memory-tracker.test.ts
• packages/browser/src/trackers/memory-tracker.ts

🚧 Files skipped from review as they are similar to previous changes: 2

• packages/browser/src/trackers/memory-tracker.ts
• packages/browser/src/trackers/memory-tracker.test.ts

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📝 Summary

Summary by CodeRabbit

• New Features
  • Browser and WebView captures now include memory, connection, and screen-orientation traces based on live browser readings. Connection, orientation, and advertised-memory traces update when readings change.
  • Battery traces continue to be collected, including when a custom system metrics sampler is configured.
• Changes
  • A custom system metrics sampler replaces heap, connection, and orientation traces; battery traces remain active.
  • Browser trace setup now uses the updated producer-based configuration.

The browser package replaces its system-trace sampler with memory, connection, and orientation trackers and tracker-backed producers. Browser and webview launches use these producers by default. A supplied systemMetricsSampler replaces heap, connection, and orientation traces, while battery tracing remains producer-backed. The package exports the new browser trace environment API and removes the former sampler API. Tests cover tracker lifecycle, trace values, launch behavior, and cleanup.

Priority: ➖ Normal

Change: Feature

Merge Risk: ⚪ Minimal · up to d690a

No actionable merge-blocking issue is established for the reviewed change; it is ready for normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 14 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly identifies the main change: moving browser heap, connection, and orientation traces to trackers and producers.
Description check		The description directly explains the tracker and producer migration, removed legacy APIs, launch wiring, tests, verification status, and known scope limits.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Inline comments:
Review comments at @packages/browser/src/trackers/memory-tracker.ts:
- Line 81: Update the cleanup logic around #timer and clearInterval to retain
the timer handle when cleanup throws, and prevent activation from creating
another polling timer while that potentially live timer remains; clear the
handle only after cleanup succeeds.

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• .changeset/browser-traces-on-trackers.md
• docs/PROGRESS.md
• packages/browser/src/launch.test.ts
• packages/browser/src/launch.ts
• packages/browser/src/trace-producers.sensors.test.ts
• packages/browser/src/trace-producers.ts
• packages/browser/src/trackers/memory-tracker.test.ts
• packages/browser/src/trackers/memory-tracker.ts
• packages/webview/src/launch.test.ts
• packages/webview/src/launch.ts

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[claude]

Claude finished @krassx's task in 47s —— View job

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Review of PR #62: browser heap, connection and orientation traces on trackers and producers

I found no real issues, so there are no inline comments. I read the PR as a static review of the code at d690ab49. I did not run tests, lint or typecheck. When I last checked, the CI run for this push was still in progress. The earlier CI run (on the previous push) passed.

Earlier finding: looks fixed. CodeRabbit flagged that MemoryTracker dropped its timer handle when clearInterval threw, which could leave a live timer with no reference. d690ab49 fixes this in packages/browser/src/trackers/memory-tracker.ts:86-96. #release() clears the handle only after the clear succeeds. onActivate (line 71) retries the release and does not arm a second timer if it fails again. That removes the duplicate-heap-row scenario.

What I checked

• Tracker lifecycle: InterceptorBase calls onActivate/onDeactivate on subscriber presence only. The three trackers attach listeners and the timer in onActivate, guard every runtime call, and remove only what actually attached. A throwing navigator.connection or screen.orientation getter is reported rather than thrown out of on().
• Producer and provider contract:
  • MemoryProducer uses emit, so heap rows are polled and never held or refreshed, as the provider contract requires.
  • ConnectionProducer, OrientationProducer and AdvertisedMemoryProducer use emitIfChanged, so they are held and refreshed, as intended. This matters because refreshMs keeps these traces inside a rolling window.
  • Restarting the provider is safe. Producer start() clears its de-dup map and stop() unsubscribes.
• Latent { ...navigator } bug: The fix is correct. The producers now read the live nav.onLine, nav.connection and nav.deviceMemory on each snapshot, so prototype accessors are no longer dropped.
• systemMetricsSampler override: sensors: false builds the battery producer only, so the sampler and the sensor producers cannot both emit heap, connection or orientation rows.
• Launch wiring: The browser launch passes the injected win and scheduler. The webview launch spreads window and scheduler only when defined, which matches how win is typed there.
• Wire values: Names and mappers (connectionTypeToWire, orientationToWire) are unchanged.

Minor, no action needed

• Duplicate listeners: The connection and orientation trackers each attach their own online/offline/orientationchange listeners alongside the events source. The PR description already scopes the shared lifecycle tracker to the next slice.
• Unreleased handle: If a failed clearInterval leaves a handle behind and the engine later stops answering performance.memory, onActivate returns early at line 68 before the retry on line 71. The leftover timer then keeps polling and emits nothing, so it is harmless.
• Non-browser runtimes with navigator: If the browser tracker is used in Node ≥21, Bun or Deno, nav.onLine !== false reports online when onLine is undefined. That explains the launch-stop-recovery test change and does not affect real browsers.
• Docstring warning: CodeRabbit's docstring-coverage warning is not something I'd act on here.

Summary

1. Overall risk: Low
2. Merge recommendation: Approve once the in-progress CI run passes. E2E was not run locally, per the PR description.
3. Most important issues to fix: None.
4. Positives:
   • The tracker/producer split is clean, and every tracker guards its runtime calls.
   • The prototype-getter navigator regression test pins the latent bug.
   • Handling of a failing timer release is conservative.
   • The legacy-sampler override semantics are documented in code and in the changeset.
     · Branch: feat/browser-trackers