ccusage 0.1.1

Claude Code usage monitor — fetches rate limits from Anthropic's API

ccusage

Claude Code usage monitor. Fetches your real rate limit data from Anthropic's API and displays it in the Claude Code statusline.

Example output

ccusage command:

Plan: max_5x
  Session (5h)         39%  resets 1h26m
  Week (all)           15%  resets 143h26m
  Week (Sonnet)        39%  resets 65h26m
  Extra usage          $0.00 / $1000.00

Claude Code statusline (self-caching — refreshes from API when stale, no daemon needed):

~/projects/myapp [Opus 4.6] 5h:39% 7d:15% son:39% | $1.37 | max_5x | reset:1h26m

Install

uv tool install ccusage

Then run:

# Check usage once
ccusage

# Run the daemon (keeps usage-limits.json updated)
ccusage daemon

Configure the statusline in ~/.claude/settings.json:

{
  "statusLine": {
    "type": "command",
    "command": "ccusage statusline"
  }
}

Commands

Command	Description
ccusage	Show current usage (colored terminal output)
ccusage json	Print raw JSON
ccusage daemon [-i SECS]	Run in foreground, refresh every 5 min (customizable)
ccusage statusline	Claude Code statusline (self-caching, no daemon needed)
ccusage install	Print setup instructions

How Claude Code rate limiting works

Discovered by inspecting Claude Code's bundled cli.js (v2.1.32).

Data sources

Claude Code gets rate limit data from two places:

1. /api/oauth/usage endpoint — Called by the /status slash command. Returns utilization percentages and reset times for each rate limit bucket. Requires the anthropic-beta: oauth-2025-04-20 header.

2. Response headers on every API call — Every message response includes headers like:

   • anthropic-ratelimit-unified-{claim}-utilization (0-100 float)
   • anthropic-ratelimit-unified-{claim}-reset (unix timestamp)
   • anthropic-ratelimit-unified-status (allowed / allowed_warning / rejected)
   • anthropic-ratelimit-unified-fallback (available when fallback models are available)
   • anthropic-ratelimit-unified-overage-status / overage-reset
   • anthropic-ratelimit-unified-representative-claim

Rate limit types

Type	Key in API response	Description
five_hour	five_hour	Rolling 5-hour session window
seven_day	seven_day	Rolling 7-day all-models window
seven_day_sonnet	seven_day_sonnet	Rolling 7-day Sonnet-specific window
seven_day_opus	seven_day_opus	Rolling 7-day Opus-specific window
overage	extra_usage	Extra/overage usage (if enabled)

API response format

GET https://api.anthropic.com/api/oauth/usage
Authorization: Bearer <oauth_access_token>
anthropic-beta: oauth-2025-04-20

{
    "five_hour": {
        "utilization": 35.0,
        "resets_at": "2026-02-06T22:00:00+00:00"
    },
    "seven_day": {
        "utilization": 14.0,
        "resets_at": "2026-02-12T20:00:00+00:00"
    },
    "seven_day_sonnet": {
        "utilization": 39.0,
        "resets_at": "2026-02-09T14:00:00+00:00"
    },
    "seven_day_opus": null,
    "seven_day_oauth_apps": null,
    "seven_day_cowork": null,
    "iguana_necktie": null,
    "extra_usage": {
        "is_enabled": true,
        "monthly_limit": 100000,
        "used_credits": 0.0,
        "utilization": null
    }
}

Authentication

The OAuth token lives at ~/.claude/.credentials.json:

{
    "claudeAiOauth": {
        "accessToken": "sk-ant-oat01-...",
        "refreshToken": "sk-ant-ort01-...",
        "expiresAt": 1770412938485,
        "subscriptionType": "team",
        "rateLimitTier": "default_claude_max_5x"
    }
}

The access token expires roughly hourly. Claude Code refreshes it automatically — as long as you have an active Claude Code session, the token stays valid for ccusage to read.

Warning thresholds (from cli.js)

Claude Code shows inline warnings based on these thresholds:

five_hour:  90% utilization when 72% of window has passed
seven_day:  75% at 60%, 50% at 35%, 25% at 15%

Other endpoints found in cli.js

• /api/oauth/profile — User profile
• /api/oauth/account/settings — Account settings
• /api/claude_code/policy_limits — Org policy limits (needs organizationUuid)
• /api/organization/claude_code_first_token_date — Org onboarding date

Local files Claude Code uses

File	Written by	Contains
~/.claude/.credentials.json	Claude Code	OAuth tokens, plan tier
~/.claude/stats-cache.json	Claude Code	Local usage stats (message counts, token counts per model)
~/.claude/usage-limits.json	ccusage daemon	Cached API usage data (this tool)
~/.claude/statsig/	Claude Code	Feature flags, experiment assignments