agent-tail

name	agent-tail
description	Capture browser console logs and dev server output to files with agent-tail. Use when debugging runtime errors, checking console output, tailing or diagnosing logs, or setting up Vite/Next.js log capture.

agent-tail

Pipes browser console output and dev server stdout/stderr to plain log files on disk so you can grep, tail, and read them directly.

Reading logs

agent-tail tail -n 200
agent-tail tail browser -n 50
agent-tail tail -f
grep -ri "error\|warn" tmp/logs/latest/
tail -50 tmp/logs/latest/browser.log
tail -f tmp/logs/latest/*.log

Use plain tail if direct file paths are easier. Use agent-tail tail if you want the CLI to resolve the latest session for you and forward flags like -f and -n 200 directly to tail.

Log files

Logs live in tmp/logs/latest/ (a symlink to the newest session directory, stable across restarts):

File	Source
browser.log	Browser console.*, unhandled errors/rejections (Vite or Next.js plugin)
<name>.log	stdout/stderr of a named service (CLI)
combined.log	All services interleaved, prefixed with [name] (CLI)

Log format

[HH:MM:SS.mmm] [LEVEL  ] message (source-url)
    stack trace indented with 4 spaces

Levels are uppercased and padded to 7 characters (LOG , WARN , ERROR ).

CLI

agent-tail run 'fe: npm run dev' 'api: uv run server'   # run multiple services
agent-tail wrap api -- uv run fastapi-server              # add to existing session
agent-tail init                                           # create session only
tail -f tmp/logs/latest/*.log                             # tail directly by path
agent-tail tail -f                                        # tail all logs in latest session
agent-tail tail browser -n 50                             # tail one log in latest session

Flags (work with all commands):

--log-dir <dir>       Log directory (default: tmp/logs)
--max-sessions <n>    Max sessions to keep (default: 10)
--no-combined         Don't write combined.log
--exclude <pattern>   Exclude lines matching pattern (repeatable, /regex/ or substring)
--mute <name>         Mute service from terminal + combined.log (still logs to <name>.log)

See references/cli-reference.md for full details.

Setup

npm install -D agent-tail

• CLI (any stack): Add agent-tail run 'name: command' to your dev script
• Vite: See references/setup-vite.md
• Next.js: See references/setup-nextjs.md (config wrapper + layout script + API route)

Agent instructions

Add to your project's CLAUDE.md, .cursorrules, or equivalent:

## Dev Logs

All dev server output is captured to `tmp/logs/`. The latest session
is symlinked at `tmp/logs/latest/`.

When debugging, check logs before guessing about runtime behavior:

    grep -ri "error\|warn" tmp/logs/latest/
    tail -50 tmp/logs/latest/browser.log
    agent-tail tail browser -n 50

.gitignore

Add tmp/ to .gitignore. agent-tail warns on startup if the log directory isn't gitignored.