fix(next): bundle the instrumentation factory and stop capturing evlog's own output

[HugoRCD]

🔗 Linked issue

No issue. Reported by a user deploying defineNodeInstrumentation to Vercel.

📚 Description

Two bugs in evlog/next/instrumentation, both hit with defineNodeInstrumentation({ ..., captureOutput: true }).

Every route returns 500 once deployed. The gate loaded evlog/next/instrumentation/create through a computed import(/* webpackIgnore: true */ ...). Turbopack keeps it as a bare runtime import and the output file trace does not include evlog, so register() throws Cannot find package 'evlog' on Vercel or a copied standalone build, and Next.js fails every request. With webpack the trace includes evlog, but the factory loads unbundled from node_modules, where NEXT_RUNTIME is not inlined, so its NEXT_RUNTIME === 'nodejs' check sees undefined and captureOutput never applies.

The gate now runs if (process.env.NEXT_RUNTIME === 'nodejs') await import('./instrumentation-create'). Both bundlers inline NEXT_RUNTIME: the Node.js build bundles the factory and the logger into instrumentation.js, and the Edge build drops the branch. No change to exports.

Drains receive every event twice. In JSON mode, outputWideEvent writes through console.log / console.error, and the patched process.stdout.write / process.stderr.write captured that line again as log.info / log.error. Pretty output already bypassed the patch through a global slot holding the native write. That slot is replaced by a __evlogOwnOutput flag set around every write evlog makes itself, and both patches pass flagged writes through.

Verification

Next.js 16.4.0, output: 'standalone', with the standalone output copied to a directory that has no parent node_modules, as on Vercel. Routes: POST /api/webhook (withEvlog), GET /api/hello (plain console.log), GET /api/edge (Edge runtime).

Build	webhook	hello	edge	Route console.log captured
2.30.1, Turbopack	500	500	500	n/a, register() throws
2.30.1, webpack	202	200	200	no
this branch, Turbopack	202	200	200	yes
this branch, webpack	202	200	200	yes

On this branch, evlog is absent from the deployed node_modules and no Edge output file contains the logger, on either bundler. Server output after the fix (Turbopack), with the wide event printed once and the route's console.log captured:

{"method":"POST","path":"/api/webhook","requestId":"76317051-fca4-4e22-83bd-cea2377798be","outcome":"ignored","status":202,"durationMs":1,"duration":"1ms","timestamp":"2026-10-10T17:47:25.756Z","level":"info","service":"verify","environment":"production"}
{"timestamp":"2026-10-10T17:47:25.774Z","level":"info","service":"verify","environment":"production","source":"stdout","message":"plain line from a route"}

Tests:

• test/next/instrumentation-bundle.test.ts bundles a root instrumentation.ts from dist with esbuild (NEXT_RUNTIME defined, next external), runs register() in a temp directory with no node_modules, and checks the Edge bundle leaves the logger out. The Node.js case failed on main with ERR_MODULE_NOT_FOUND.
• Two captureOutput tests in test/next/instrumentation.test.ts assert the drain receives one event for JSON output and nothing extra for pretty and tagged output. On main the drain received 4 events.

pnpm run lint, pnpm run typecheck (including evlog-telemetry), pnpm run test, pnpm test:coverage and pnpm api:snapshot (no diff) pass locally.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

Summary by CodeRabbit

• Bug Fixes
  • Evlog’s own console output is no longer captured again as structured log events, preventing duplicate logging.
  • Next.js instrumentation now bundles correctly for Node.js deployments without node_modules and works with both Turbopack and webpack.
  • Captured output is displayed once as structured terminal output when silent is disabled; with silent enabled, original output remains available alongside drain delivery.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated
evi	Ready	Preview	Oct 10, 2026 6:00pm UTC
evlog-docs	Ready	Preview, v0	Oct 10, 2026 6:00pm UTC
evlog-render-lab	Ready	Preview	Oct 10, 2026 6:00pm UTC
evlog-telemetry	Ready	Preview	Oct 10, 2026 6:00pm UTC
just-use-evlog	Ready	Preview	Oct 10, 2026 6:00pm UTC

[github-actions]

Thank you for following the naming conventions! 🙏

[coderabbitai]

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• Review profile: CHILL
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📥 Commits

Reviewing files that changed from the base of the PR and between 49af75e and a5b0112.

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📒 Files selected for processing (8)

• .changeset/capture-output-own-events.md
• .changeset/next-instrumentation-bundling.md
• apps/docs/content/4.integrate/frameworks/02.nextjs.md
• packages/evlog/src/logger.ts
• packages/evlog/src/next/instrumentation-create.ts
• packages/evlog/src/next/instrumentation-gate.ts
• packages/evlog/test/next/instrumentation-bundle.test.ts
• packages/evlog/test/next/instrumentation.test.ts

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[pkg-pr-new]

@evlog/cli

npm i https://pkg.pr.new/@evlog/cli@816

evlog

npm i https://pkg.pr.new/evlog@816

@evlog/nuxthub

npm i https://pkg.pr.new/@evlog/nuxthub@816

@evlog/signals

npm i https://pkg.pr.new/@evlog/signals@816

@evlog/telemetry

npm i https://pkg.pr.new/@evlog/telemetry@816

commit: a5b0112