A statusline gauge for Claude Code that gives you a glanceable read on context load: how full the window is, and how long the conversation arc has grown. Zero dependencies, Node 18+.

That's the full multi-line view from context-check --demo. In your statusline (--line mode) you see just the top row — Opus 4.8 ▓▓▓▓▓▓▓░░░ 62% drift risk — colored green / amber / red as the bar slides through zones.

The base case is the statusline. You wire context-check --line into your Claude Code settings once. From then on a single colored row sits at the bottom of your prompt and updates every turn. You don't run anything — you just glance down. The whole value is the moment you notice the bar slide into amber (drift risk) or red (dilution / compaction wall), which is your cue to restate a hard constraint or run /compact.

When you want the reasoning, not just the signal, run context-check directly. The multi-line gauge adds the per-zone advice line, the auto-compact note, and the hypothesis disclaimer.

Both modes drive one decision: keep going, restate a constraint, or compact now.

Claude Code already ships two adjacent features. /context prints the current token breakdown on demand, and auto-compact kicks in at auto_compact_threshold_percent (default 80%) to truncate before the window overruns.

What Claude doesn't ship: a passive, always-on visual gauge with zones and drift measurement. /context is poll-the-data, auto-compact is the last-second safety net — neither tells you mid-conversation that you're sliding from sharp into drift risk. That's the gap context-check fills.

npm install -g github:wallacedrew/context-check
context-check install

Two lines. The first puts context-check on your PATH (requires Node 18+). The second writes the statusline block into ~/.claude/settings.json (saving a .bak of whatever was there). Reload Claude Code and the gauge appears.

Using nodenv (or another shim-based version manager)? Run nodenv rehash after the npm install so the shim picks up the new binary — otherwise context-check install will be "command not found".

Add --with-dir to install, and the row gets prefixed with the current project folder:

context-check install --with-dir

You'll see my-project | Opus 4.8 ▓▓▓▓░░░░░░ 42% sharp instead of just the model + gauge. Re-run context-check install (without the flag) to switch back; no --force needed either way.

Pin a specific version with #v1.1.0 (or any tag/branch/SHA) on the install URL:

npm install -g github:wallacedrew/context-check#v1.1.0

If context-check install finds a different statusLine already configured (something that isn't ours), it refuses and points you at --force. If you'd rather configure by hand, drop this block into ~/.claude/settings.json yourself:

{
  "statusLine": {
    "type": "command",
    "command": "context-check --line"
  }
}

context-check uninstall
npm uninstall -g context-check

The first command removes the statusLine block from ~/.claude/settings.json (saving the original to .bak first). It recognizes both variants of our command (with or without --with-dir) and removes either without --force. The second removes the binary. Run the subcommand before the npm uninstall — once the binary's gone, the subcommand goes with it.

# See sample output without piping anything
context-check --demo

# Or pipe a session JSON object (this is what Claude Code does for you)
echo '{"model":{"display_name":"Opus 4.8"},"context_window":{"used_percentage":62}}' \
  | context-check

The bar's color tells you which of six zones you're in:

A row showing ⚠ means you've crossed Claude Code's auto-compact threshold (80% by default); auto-compact will kick in soon.

• Never crashes in statusline mode. All failure paths degrade to a single readable line and exit 0.
• Never hangs. stdin read times out at 200ms.
• Respects NO_COLOR. Set the env var to disable ANSI escape codes.

Does it phone home? No. Pure stdin processing — read JSON, render to stdout, exit. No network calls anywhere in the source. The tarball is src/*.js (~10 files, ~10 kB total) plus README and LICENSE; the whole tool is readable in a few minutes.

Does /resume work? Yes. Turn depth is counted by tailing transcript_path from the session JSON, so resuming an old session just hands the gauge a longer transcript to count from.

Does it work on Bedrock (or any provider without used_percentage)? Partially. When context_window.used_percentage isn't populated the gauge falls through to current_usage.*_input_tokens. If neither is available the row shows --% blind. This is expected behavior, not a crash — the data simply isn't populated yet.

Something else? File an issue at https://github.com/wallacedrew/context-check/issues.

Source layout, data contract, edge cases, roadmap, and how to run the tests / cut a release live in DEVELOPMENT.md.