local explorer: add telemetry

[emily-shen]

I would recommend reviewing the first commit separately to the rest - there I’ve extracted telemetry/metrics helpers from wrangler into workers-utils. edit: un-moved this to workers-utils.

We then pass these options into miniflare via a new ‘telemetry’ option. We can’t just directly get the telemetry settings in miniflare, because users can set telemetry config in their wrangler config.
Telemetry settings are then passed to the explorer worker via a JSON binding.

We collect telemetry in the API, rather than in the UI, because we want to detect API-only usage as well.

This is done by adding a middleware component that sends an event after all API requests. The telemetry event schema can be seen in the changes description.

Telemetry is only collected when accessed via wrangler dev, not via the vite plugin or standalone miniflare.

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows: will add tests in a followup. have tested manually and events are showing up in amplitude
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: general explorer docs being added separately. telemetry docs updated here.

A picture of a cute animal (not mandatory, but encouraged)

[changeset-bot]

🦋 Changeset detected

Latest commit: 3b31d42

The changes in this PR will be included in the next version bump.

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[github-actions]

Changeset Review

Reviewed Changeset: local-explorer-telemetry.md

✅ All changesets look good

Validation Summary

Check	Status	Notes
Version Type	✅	Correctly marked as minor - telemetry/analytics changes should be minor per guidelines
Changelog Quality	✅	Meaningful description with clear explanation of what's collected, how to disable it, and event schema
Markdown Headers	✅	No h1/h2/h3 headers found; uses bold text for emphasis which is correct
Analytics	✅	Minor bump is appropriate for telemetry collection changes
Dependabot	N/A	Not a dependency update changeset
Experimental Features	✅	Explicitly notes that Local Explorer and local REST API are experimental

Notes

• Good inclusion of the event schema for transparency
• Clear instructions on how to disable telemetry (wrangler telemetry disable)
• Appropriately scoped to only when dev session is started via Wrangler

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

This PR adds anonymous telemetry to the Local Explorer, sending usage events to Sparrow for successful API requests. The implementation is clean — route name mapping, fire-and-forget event dispatch, and piggybacking off wrangler's existing metrics.json config.

I posted one actionable issue:

1. WRANGLER_SEND_METRICS env var not respected — getLocalExplorerTelemetryConfig() in packages/miniflare/src/shared/telemetry-config.ts only reads permission from metrics.json, but wrangler's own telemetry system checks WRANGLER_SEND_METRICS env var with highest priority. Users who rely on this env var (common in CI) to disable telemetry would still have local explorer telemetry active. I posted a suggestion with a fix.

github run

[pkg-pr-new]

create-cloudflare

npm i https://pkg.pr.new/create-cloudflare@13392

@cloudflare/kv-asset-handler

npm i https://pkg.pr.new/@cloudflare/kv-asset-handler@13392

miniflare

npm i https://pkg.pr.new/miniflare@13392

@cloudflare/pages-shared

npm i https://pkg.pr.new/@cloudflare/pages-shared@13392

@cloudflare/unenv-preset

npm i https://pkg.pr.new/@cloudflare/unenv-preset@13392

@cloudflare/vite-plugin

npm i https://pkg.pr.new/@cloudflare/vite-plugin@13392

@cloudflare/vitest-pool-workers

npm i https://pkg.pr.new/@cloudflare/vitest-pool-workers@13392

@cloudflare/workers-editor-shared

npm i https://pkg.pr.new/@cloudflare/workers-editor-shared@13392

wrangler

npm i https://pkg.pr.new/wrangler@13392

commit: 3b31d42

[workers-devprod]

Codeowners approval required for this PR:

• ✅ @cloudflare/wrangler

Show detailed file reviewers

[petebacondarwin]

Looking good - a few things that are maybe not quite blocking but I thought I would be defensive and not officially approve yet.

[petebacondarwin]

Sweet and simple. Need to update that changeset though

[workers-devprod]

Codeowners reviews satisfied