Switch development log item format as JSON #89168

huozhi · 2026-01-28T13:34:05Z

Change the dev next.js log file to a more structural format, each logging item is a JSON so that we can easily parse or let agents search through the file.

Before:

[00:00:12.345] Browser LOG     Test message
[00:00:13.456] Server  ERROR   Server error

After:

{"timestamp":"00:00:12.345","source":"Browser","level":"LOG","message":"Test message"}
{"timestamp":"00:00:13.456","source":"Server","level":"ERROR","message":"Server error"}

cursor · 2026-01-28T13:34:06Z

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
_{Learn more about Cursor Agents}

nextjs-bot · 2026-01-28T13:50:49Z

Tests Passed

nextjs-bot · 2026-01-28T13:50:58Z

Allow CI Workflow Run

approve CI run for commit: d6705ea

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

- Convert log entries from text format to JSON format - Each log entry is now a JSON object with timestamp, source, level, and message - Improves searching ability for agents parsing logs - Update all related tests to expect JSON format Co-authored-by: jiachi <jiachi@vercel.com>

Fix lint failure caused by auto-generated next-env.d.ts files in CI

nextjs-bot · 2026-01-29T11:45:46Z

Stats from current PR

✅ No significant changes detected

📊 All Metrics

📖 Metrics Glossary

Dev Server Metrics:

Listen = TCP port starts accepting connections
First Request = HTTP server returns successful response
Cold = Fresh build (no cache)
Warm = With cached build artifacts

Build Metrics:

Fresh = Clean build (no .next directory)
Cached = With existing .next directory

Change Thresholds:

Time: Changes < 50ms AND < 10%, OR < 2% are insignificant
Size: Changes < 1KB AND < 1% are insignificant
All other changes are flagged to catch regressions

⚡ Dev Server

Metric	Canary	PR	Change	Trend
Cold (Listen)	455ms	455ms	✓	▁▁▁▁▁
Cold (Ready in log)	440ms	439ms	✓	▇█▆▂▆
Cold (First Request)	1.146s	1.198s	✓	█▇█▃▇
Warm (Listen)	457ms	456ms	✓	▁▁▁▁▁
Warm (Ready in log)	444ms	442ms	✓	▂▁▁▅▁
Warm (First Request)	346ms	343ms	✓	█▄▁█▁

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	506ms	506ms	✓	▁▁▁▁▁
Cold (Ready in log)	487ms	484ms	✓	▁▁▃▃▃
Cold (First Request)	1.991s	2.001s	✓	▁▁▂▂▂
Warm (Listen)	507ms	507ms	✓	▁▁▁▁▁
Warm (Ready in log)	482ms	483ms	✓	▁▁▃▃▃
Warm (First Request)	2.064s	2.063s	✓	▁▁▂▂▂

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	4.388s	4.307s	✓	▁▁▁▇▁
Cached Build	4.314s	4.334s	✓	▁▁▁█▁

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	15.824s	15.804s	✓	▁▁▁▁▁
Cached Build	15.838s	15.815s	✓	▁▁▁▁▁
node_modules Size	462 MB	462 MB	✓	█████

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **432 kB** → **432 kB** ✓

81 files with content-based hashes (individual files not comparable between builds)

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	760 B	767 B	✓
Total	760 B	767 B	⚠️ +7 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	451 B	449 B	✓
Total	451 B	449 B	✅ -2 B

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.47 kB	N/A	-
6280-HASH.js gzip	52.7 kB	N/A	-
6335.HASH.js gzip	169 B	N/A	-
912-HASH.js gzip	4.53 kB	N/A	-
e8aec2e4-HASH.js gzip	62.3 kB	N/A	-
framework-HASH.js gzip	59.7 kB	59.7 kB	✓
main-app-HASH.js gzip	256 B	254 B	✓
main-HASH.js gzip	39 kB	39 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
262-HASH.js gzip	N/A	4.52 kB	-
2889.HASH.js gzip	N/A	169 B	-
5602-HASH.js gzip	N/A	5.48 kB	-
6948ada0-HASH.js gzip	N/A	62.3 kB	-
9544-HASH.js gzip	N/A	53.2 kB	-
Total	226 kB	226 kB	⚠️ +477 B

Polyfills

	Canary	PR	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Total	39.4 kB	39.4 kB	✓

Pages

	Canary	PR	Change
_app-HASH.js gzip	194 B	194 B	✓
_error-HASH.js gzip	183 B	180 B	🟢 3 B (-2%)
css-HASH.js gzip	331 B	330 B	✓
dynamic-HASH.js gzip	1.81 kB	1.81 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	351 B	352 B	✓
hooks-HASH.js gzip	384 B	383 B	✓
image-HASH.js gzip	580 B	581 B	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	2.49 kB	2.49 kB	✓
routerDirect..HASH.js gzip	320 B	319 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	315 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.97 kB	✅ -1 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	126 kB	126 kB	✓
page.js gzip	246 kB	247 kB	✓
Total	373 kB	373 kB	⚠️ +269 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	617 B	615 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	33.1 kB	33 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.7 kB	34.6 kB	✅ -88 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	732 B	735 B	✓
Total	732 B	735 B	⚠️ +3 B

Build Cache

	Canary	PR	Change
0.pack gzip	3.71 MB	3.73 MB	🔴 +16.2 kB (+0%)
index.pack gzip	101 kB	101 kB	✓
index.pack.old gzip	102 kB	101 kB	🟢 1.05 kB (-1%)
Total	3.91 MB	3.93 MB	⚠️ +15.9 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	308 kB	308 kB	✓
app-page-exp..prod.js gzip	164 kB	164 kB	✓
app-page-tur...dev.js gzip	308 kB	308 kB	✓
app-page-tur..prod.js gzip	164 kB	164 kB	✓
app-page-tur...dev.js gzip	305 kB	305 kB	✓
app-page-tur..prod.js gzip	162 kB	162 kB	✓
app-page.run...dev.js gzip	305 kB	305 kB	✓
app-page.run..prod.js gzip	162 kB	162 kB	✓
app-route-ex...dev.js gzip	70.2 kB	70.2 kB	✓
app-route-ex..prod.js gzip	48.8 kB	48.8 kB	✓
app-route-tu...dev.js gzip	70.2 kB	70.2 kB	✓
app-route-tu..prod.js gzip	48.8 kB	48.8 kB	✓
app-route-tu...dev.js gzip	69.8 kB	69.8 kB	✓
app-route-tu..prod.js gzip	48.6 kB	48.6 kB	✓
app-route.ru...dev.js gzip	69.8 kB	69.8 kB	✓
app-route.ru..prod.js gzip	48.6 kB	48.6 kB	✓
dist_client_...dev.js gzip	324 B	324 B	✓
dist_client_...dev.js gzip	326 B	326 B	✓
dist_client_...dev.js gzip	318 B	318 B	✓
dist_client_...dev.js gzip	317 B	317 B	✓
pages-api-tu...dev.js gzip	43.1 kB	43.1 kB	✓
pages-api-tu..prod.js gzip	32.8 kB	32.8 kB	✓
pages-api.ru...dev.js gzip	43.1 kB	43.1 kB	✓
pages-api.ru..prod.js gzip	32.8 kB	32.8 kB	✓
pages-turbo....dev.js gzip	52.4 kB	52.4 kB	✓
pages-turbo...prod.js gzip	39.3 kB	39.3 kB	✓
pages.runtim...dev.js gzip	52.3 kB	52.3 kB	✓
pages.runtim..prod.js gzip	39.3 kB	39.3 kB	✓
server.runti..prod.js gzip	62.5 kB	62.5 kB	✓
Total	2.75 MB	2.75 MB	⚠️ +4 B

📝 Changed Files (4 files)

Files with changes:

pages-api-tu..ntime.dev.js
pages-api.runtime.dev.js
pages-turbo...ntime.dev.js
pages.runtime.dev.js

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nextjs-bot added created-by: Next.js team PRs by the Next.js team. tests type: next labels Jan 28, 2026

huozhi changed the title ~~Development log JSON~~ Switch development log item format as JSON Jan 28, 2026

huozhi added the CI approved Approve running CI for fork label Jan 28, 2026

cursoragent and others added 2 commits January 29, 2026 11:22

Add next-env.d.ts to prettier ignore

2b57423

Fix lint failure caused by auto-generated next-env.d.ts files in CI

cursor bot force-pushed the cursor/development-log-json-d724 branch from d6705ea to 2b57423 Compare January 29, 2026 11:22

huozhi marked this pull request as ready for review January 29, 2026 12:18

huozhi requested review from gaojude and timneutkens January 29, 2026 12:18

gaojude approved these changes Jan 29, 2026

View reviewed changes

huozhi merged commit 9b90d1b into canary Jan 29, 2026
160 checks passed

huozhi deleted the cursor/development-log-json-d724 branch January 29, 2026 13:14

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Switch development log item format as JSON #89168

Switch development log item format as JSON #89168

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