[saddlepaddle]

Why

The measurement #7388 existed to take is done. Vercel Observability, grouped by function_region:

	p50 TTFB
iad1	293.5ms
pdx1	41.8ms

But the sampler was never what produced that. It collected zero spans across twenty minutes of live production traffic — while errors flowed normally, host-service traced fine, quota sat clear, and the config was live and correct on ba4bbec87.

Why revert instead of keeping a trickle

"Keep a small sample" isn't available. The sampler doesn't collect a small number of spans, it collects none — so leaving it in place gives config that looks like it samples and doesn't. The next person to read this file would believe it.

Reverting restores the honest state: tracing is off, and off is a thing you can reason about.

What the note preserves

The comment now records that a narrow sampler was tried and produced nothing, so the next attempt starts from "this app cannot currently be traced, cause unknown" rather than from picking a sample rate. That's the actual finding, and it's worth chasing on its own merits — an untraceable API makes the next production mystery much harder than this one was.

Ruled out so far: quota, org-level span ingestion, DSN rate limits, a stale deploy, and name matching (Sentry's docs confirm name is unparametrized at sampling time, but all three route substrings match that form anyway). Suspect but unconfirmed: @sentry/nextjs 10.68 server instrumentation under Next.js 16.3 + Turbopack.

https://claude.ai/code/session_01Ho5jMfrUs1e65svM8M2Hc6

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Summary by cubic

Reverts the region-move tracing sampler now that the measurement is done, restoring the previous state where tracing is off. The sampler collected zero spans across 20 minutes of production traffic, so leaving it would have implied sampling works when it doesn't. The comment now records the failed attempt and notes that the app currently cannot be traced for unknown reasons.

^{Written for commit f6ca02d. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes
  • Disabled span tracing for API routes, including desktop version checks, Gmail push notifications, and tRPC requests.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 0a78b3c5-954b-48a7-bcb8-bcb7c88141ab

📥 Commits

Reviewing files that changed from the base of the PR and between ba4bbec and f6ca02d.

📒 Files selected for processing (1)

• apps/api/sentry.server.config.ts

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📝 Walkthrough

Walkthrough

The API Sentry configuration removes the tracesSampler callback. Without tracesSampleRate or tracesSampler, span tracing is disabled for all API routes.

Changes

API tracing configuration

Layer / File(s)	Summary
Disable route-specific sampling apps/api/sentry.server.config.ts	Removes sampling rates for desktop/version, gmail/push, and trpc. Sentry no longer samples API spans.

Estimated code review effort: 2 (Simple) | ~5 minutes

Merge Risk: ⚪ Minimal · up to f6ca0

API span tracing is intentionally disabled after the measurement period. No unresolved merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description clearly explains the change, measurement results, and unresolved tracing issue. However, it omits the required “How I tested it” section and checklist, and it uses “Why” instead of the…	Add a “How I tested it” section with validation steps and results. Add the required checklist and mark each applicable item. Rename “Why” to “What & why” or include the full template heading.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the API tracing sampler revert and follows conventional commit format.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
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.

Full details: Description check

Explanation

The description clearly explains the change, measurement results, and unresolved tracing issue. However, it omits the required “How I tested it” section and checklist, and it uses “Why” instead of the template’s “What & why” heading.

• Fix all pre-merge checks with AI

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/revert-region-tracing

Warning

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🔧 Biome (2.5.10)

apps/api/sentry.server.config.ts

Biome could not lint this file: nested root configuration. Check the repository's Biome configuration and plugins.

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