# Anthropic OAuth Usage API — Confirmed Details

Verified live on 10.0.0.28 by Claude Opus, 2026-06-27.

## Endpoint

```
GET https://api.anthropic.com/api/oauth/usage
Authorization: Bearer <token from ~/.claude/.credentials.json → .claudeAiOauth.accessToken>
anthropic-beta: oauth-2025-04-20
```

## Response Fields

| Field | Meaning | Notes |
|-------|---------|-------|
| `five_hour.utilization` | Rolling 5-hour session usage (0–100) | Account-wide, not per-session |
| `five_hour.resets_at` | UTC ISO-8601 reset timestamp | |
| `seven_day.utilization` | Weekly cap usage (0–100) | ALL models combined |
| `seven_day.resets_at` | UTC ISO-8601 reset timestamp | |
| `seven_day_opus` | Opus-specific weekly | null on this plan |
| `limits[]` | Array with severity (normal/warning) | For threshold alerts |

## Token Expiry

`~/.claude/.credentials.json` has `expiresAt`. If expired, the curl 401s. Token auto-refreshes on next interactive `claude` run, but a headless-only loop can go stale. Not blocking for normal use — interactive runs keep it fresh.

## Context % Formula (from print-mode JSON)

```
context_pct = (input_tokens + cache_creation_input_tokens + cache_read_input_tokens)
            / modelUsage[model].contextWindow * 100
```

All fields come from the same `--output-format json` envelope — zero extra HTTP calls.