feat: add --follow flag to console and errors commands by mvanhorn · Pull Request #867 · vercel-labs/agent-browser

mvanhorn · 2026-03-17T06:25:19Z

Summary

Add --follow (-f) flag to the console and errors commands for real-time log streaming
Polls the daemon's existing EventTracker at 500ms intervals, printing only new entries since the last poll
Supports text mode ([level] text for console, text (url:line:col) for errors) and JSON mode (one JSON object per line, NDJSON)
Runs until Ctrl+C or daemon disconnect

Evidence

Source	Evidence	Engagement
PR #826	WebSocket streaming restored in native daemon	Merged
Reddit r/ClaudeCode	Debugging browser setups is a common pain point	3 upvotes

Usage

# Stream console logs in real-time (text mode)
agent-browser console --follow

# Stream as JSON lines (one JSON object per line)
agent-browser console --follow --json

# Follow only errors
agent-browser errors --follow
# or with short flag
agent-browser errors -f

Technical notes

The implementation uses a poll-based approach rather than WebSocket streaming. The CLI sends the existing console/errors command to the daemon in a loop, tracking a last_seen index to print only new entries. The daemon's EventTracker uses an append-only model so index tracking is straightforward. This avoids modifying the daemon's streaming protocol while still delivering a good developer experience.

If demand exists for sub-500ms latency, WebSocket-based push can be added later as a follow-up.

Checklist

cargo fmt - clean
cargo clippy - clean
cargo test - 461 passed, 0 failed
Changeset included

This contribution was developed with AI assistance (Claude Code).

Add real-time log streaming to the console and errors commands via --follow (-f). Polls the daemon's EventTracker at 500ms intervals, printing only new entries since the last poll. Supports both text mode ([level] text) and JSON mode (one JSON object per line). Runs until Ctrl+C or the daemon disconnects. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vercel · 2026-03-17T06:25:23Z

@mvanhorn is attempting to deploy a commit to the Vercel Labs Team on Vercel.

A member of the Team first needs to authorize it.

cli/src/main.rs

The console log display code used "messages" and "type" to access console entries, but the daemon's EventTracker returns "entries" and "level". This meant console logs were never displayed in either follow mode or normal output. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

@ctate

…d --follow code Addresses @ctate's review: 1. Moved network_wait text output check above the generic URL handler in output.rs so "Matched: POST /api/login -> 200 (xhr)" displays correctly instead of being caught by the navigation response handler. 2. Removed --follow flag parsing and docs from this PR - that belongs in the separate console --follow PR (vercel-labs#867). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ctate

Thanks for putting this together! The follow mode is a nice addition — polling the existing EventTracker keeps things simple and avoids touching the daemon protocol.

One issue to fix before merging: -f is already the global short flag for --full (full-page screenshots). Since global flags are parsed first, agent-browser console -f would silently set full=true instead of enabling follow mode. I'd suggest dropping the -f alias and keeping only --follow, or picking a different short flag like -F.

A couple smaller things:

The last_seen index tracking in run_console_follow uses entries/level keys but run_errors_follow uses errors/text — just want to confirm these match the actual daemon response shape (the output.rs fix in this PR changes messages → entries and type → level, so it looks like the daemon response was recently updated).
If the daemon disconnects or returns an error, the loop retries silently every 500ms forever — might be worth printing a message or backing off after repeated failures.

ctate · 2026-03-17T14:20:48Z

Actually - one sec. Moving --full down in #876.

Move --full/-f from global flags (parsed in flags.rs) to command-level parsing in commands.rs, scoped to the three commands that actually use it: `screenshot`, `diff screenshot`, and `diff url`. This frees up `-f` for other commands (e.g. `--follow` on `console`/`errors`, see #867) and better reflects that full-page capture is not a global concern. Changes: - Remove `full` from Flags struct, Config struct, and global flag parsing - Remove `--full`/`-f` from clean_args global boolean flags list - Parse `--full`/`-f` inline in `screenshot` command handler - Accept `-f` shorthand in `diff screenshot` and `diff url` (previously only `--full` was accepted at command level) - Remove fallback from global `flags.full` in diff subcommands - Update tests to pass --full as a command argument rather than a global flag Fixes #876

Removes -f as a short flag for --follow on console/errors commands since -f is already the global shorthand for --full (full-page screenshots). Only --follow is supported now. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

mvanhorn · 2026-03-17T14:49:49Z

Removed -f shorthand in eca9fbf - only --follow now. Didn't realize it conflicted with --full.

* refactor: make --full/-f a command-level flag instead of global Move --full/-f from global flags (parsed in flags.rs) to command-level parsing in commands.rs, scoped to the three commands that actually use it: `screenshot`, `diff screenshot`, and `diff url`. This frees up `-f` for other commands (e.g. `--follow` on `console`/`errors`, see #867) and better reflects that full-page capture is not a global concern. Changes: - Remove `full` from Flags struct, Config struct, and global flag parsing - Remove `--full`/`-f` from clean_args global boolean flags list - Parse `--full`/`-f` inline in `screenshot` command handler - Accept `-f` shorthand in `diff screenshot` and `diff url` (previously only `--full` was accepted at command level) - Remove fallback from global `flags.full` in diff subcommands - Update tests to pass --full as a command argument rather than a global flag Fixes #876 * fix: remove stale AGENT_BROWSER_FULL env var from help and add -f shorthand tests - Remove AGENT_BROWSER_FULL from help text in output.rs since the env var is no longer read after moving --full to command-level parsing - Add test_screenshot_full_page_shorthand to verify screenshot -f works - Add test_diff_screenshot_command_full_flag_shorthand to verify diff screenshot -f works --------- Co-authored-by: ctate <366502+ctate@users.noreply.github.com>

ctate · 2026-03-17T15:43:30Z

@mvanhorn Sorry for the back and forth. --full is now scoped to screenshot, so you can do -f for follow in logs - which is common for logs

@ctate

Per @ctate's vercel-labs#876, --full is now scoped to screenshot only, so -f is free for --follow on console/errors commands. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

mvanhorn · 2026-03-17T16:04:50Z

Restored -f in bdcd7c7. Thanks for clearing that up in #876.

vercel bot reviewed Mar 17, 2026

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mvanhorn mentioned this pull request Mar 17, 2026

feat: add network wait subcommand for request-specific sync #866

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ctate reviewed Mar 17, 2026

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ctate mentioned this pull request Mar 17, 2026

refactor: make --full/-f a command-level flag instead of global #876

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ctate mentioned this pull request Mar 17, 2026

refactor: make --full/-f a command-level flag instead of global #877

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8 tasks

fix: restore -f shorthand now that --full is screenshot-scoped

bdcd7c7

Per @ctate's vercel-labs#876, --full is now scoped to screenshot only, so -f is free for --follow on console/errors commands. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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feat: add --follow flag to console and errors commands#867

feat: add --follow flag to console and errors commands#867
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