FAQ

Is PRECC safe to use?

Yes. PRECC uses the official Claude Code PreToolUse hook mechanism – the same extension point that Anthropic designed for exactly this purpose. The hook:

• Runs entirely offline (no network calls in the hot path)
• Completes in under 5 milliseconds
• Is fail-open: if anything goes wrong, the original command runs unmodified
• Only modifies commands, never executes them itself
• Stores data locally in SQLite databases

Does PRECC work with other AI coding tools?

PRECC is designed specifically for Claude Code. It relies on the PreToolUse hook protocol that Claude Code provides. It does not work with Cursor, Copilot, Windsurf, or other AI coding tools.

What data does telemetry send?

Telemetry is opt-in only. When enabled, it sends:

• PRECC version, OS, and architecture
• Aggregate counts (commands intercepted, skills activated)
• Average hook latency

It does not send command text, file paths, project names, or any personally identifiable information. You can preview the exact payload with precc telemetry preview before opting in. See Telemetry for full details.

How do I uninstall PRECC?

PRECC is fully reversible — remove it in three steps:

1. Remove the hook registration:

   # Delete the hook entry from Claude Code's settings
   # (precc init added it; removing it disables PRECC)
   

2. Remove the binary:

   rm ~/.local/bin/precc ~/.local/bin/precc-hook ~/.local/bin/precc-learner
   

3. Remove data (optional):

   rm -rf ~/.local/share/precc/
   rm -rf ~/.config/precc/
   

My license expired. What happens?

PRECC reverts to the Community tier. All core functionality continues to work:

• Built-in skills remain active
• Hook pipeline runs normally
• precc savings shows the summary view
• precc ingest and session mining work

Pro features become unavailable until you renew:

• precc savings --all (detailed breakdown)
• precc compress
• precc gif
• precc gha
• precc geofence
• Email reports

The hook does not seem to be running. How do I debug?

Run precc doctor first — it automates every check below. To diagnose by hand:

1. Check that the hook is registered:

   precc init
   

2. Test the hook manually:

   echo '{"tool_input":{"command":"cargo build"}}' | precc-hook
   

3. Check that the binary is on your PATH:

   which precc-hook
   

4. Check Claude Code’s hook configuration in ~/.claude/settings.json.

Does PRECC slow down Claude Code?

No. The hook completes in under 5 milliseconds (p99). This is imperceptible compared to the time Claude spends reasoning and generating responses.

Can I use PRECC in CI/CD?

PRECC is designed for interactive Claude Code sessions. In CI/CD, there is no Claude Code instance to hook into. However, precc gha can analyze failed GitHub Actions runs from any environment.

How do mined skills differ from built-in skills?

Built-in skills ship with PRECC and cover common wrong-directory patterns. Mined skills are learned from your specific session logs – they capture patterns unique to your workflow. Both are stored in SQLite and evaluated identically by the hook pipeline.

Can I share skills with my team?

Yes. Export any skill to TOML with precc skills export NAME and share the file. Team members can place it in their skills/ directory or import it into their heuristics database.

Why do I see zero tokens saved?

If precc savings reports 0 tokens despite an active Claude Code session burning input/output tokens, the hook is not firing. Three causes account for almost every reported instance:

1. You are on v0.3.42 or v0.3.43. These releases shipped a data-path regression where the hook wrote metrics to a directory that the CLI then read from a different directory — both ran, but the savings number stayed at 0. Fixed in v0.3.44 (data paths routed through db::data_dir()). Upgrade with:

   precc update
   

2. Your settings.json is missing the hook entry. Run precc doctor (available in v0.3.53+). It checks each precondition of the hot path — settings file, hook entry, binary on $PATH, heuristics DB, recent invocations — and reports the first one that fails:

   precc doctor
   

   If doctor is not available because you are on an older release, run precc init to (re)register the hook.

3. Your session has not yet hit a skill trigger. PRECC only intercepts Bash commands matching one of the active skills. If your session has been pure file editing or pure web fetching against domains not covered by webfetch-opencli, you have not yet given the hook anything to compress or rewrite. This is normal. Run precc skills list to see what triggers exist.

If after upgrading and running precc doctor you still see zero savings, file an issue at https://github.com/peri-a-i/precc-cc/issues with the output of precc doctor.

My MCP server (e.g. lean-ctx) is pegging CPU. How do I kill it safely without taking Claude Code down with it?

PRECC does not ship or supervise MCP servers — but this is a recurring trap because some MCP binaries (notably lean-ctx) are also invoked as per-Bash-tool-call wrappers by the Claude Code harness, not just as long-running servers. A naive pkill <name> then matches many short-lived wrappers in addition to the server.

Identify the runaway PID, do not kill by name:

pgrep -f "^lean-ctx$" \
  | xargs -I{} ps -o pid,%cpu,etime,args -p {} \
  | sort -k2 -nr | head -3

The top row is the long-running server (large etime, high %cpu). Send SIGTERM to only that PID:

kill -TERM <pid>

Avoid these forms, all of which can also kill Claude Code or break in-flight tool calls:

• pkill lean-ctx — matches transient lean-ctx -c <cmd> wrappers spawned per Bash tool call.
• pkill -9 -f lean-ctx — same broad match, plus ungraceful exit leaves the MCP stdio half-open.
• pkill -g <pgid> / kill -- -<pgid> — kills the whole process group, which includes claude itself when the MCP server shares a session with it.

If after a clean SIGTERM the server does not exit within a few seconds, escalate with kill -KILL <pid> on the same single PID (still not by name). Claude Code will lose those MCP tools until you restart it; it should not exit on its own.

This advice is independent of PRECC — but PRECC users frequently run lean-ctx, so it is worth documenting here.

What is OpenCLI and do I need it?

OpenCLI is a third-party Node.js tool that turns ~148 websites into structured-output CLI commands (opencli hackernews top, opencli reddit search <q>, opencli arxiv search <q>, …). PRECC ships two built-in skills that work with it:

• webfetch-opencli-hint — fires on curl/wget/http/fetch against any of 11 OpenCLI-supported domains and suggest_fix-es the equivalent opencli <site> … command. Suggestion only; never modifies the command.
• webfetch-opencli-hackernews — auto-rewrites curl|wget news.ycombinator.com to opencli hackernews top with an inline command -v opencli fallback to the original command if OpenCLI isn’t installed.

You don’t need OpenCLI for PRECC to work. The hint skill costs nothing; the auto-rewrite skill is safe to ship default-on because of the fallback.

If you want OpenCLI’s WebFetch token savings, install it with:

precc init --opencli

That runs npm install -g @jackwener/opencli (Node.js 20+ required). For cookie-reuse on logged-in pages, also install OpenCLI’s Chrome extension separately — see the project README. The extension requests broad permissions (debugger, <all_urls>, cookies); review them before installing.

precc doctor reports OpenCLI’s presence on $PATH as an informational line:

i opencli: installed (webfetch-opencli skills will auto-rewrite)

or

i opencli: not installed (run `precc init --opencli` if you want WebFetch token savings)

Never marks doctor as failing — the integration is fully opt-in.