Daeseon Yoo

The goal

One always-visible strip (top-right) with a tiny color gauge per provider — Claude · Codex · Antigravity — and a click-to-open popup with 5-hour + weekly bars, reset countdowns, and the plan label. The hard part was never the UI; it was: can we read each provider's real remaining limit locally, without spending a token?

What's actually readable, per provider (verified on the machine)

Codex — real, zero-network. Every Codex turn writes a rate_limits object into ~/.codex/sessions/**/rollout-*.jsonl (primary = 5h, secondary = weekly, each with used_percent + resets_at). Read the newest file's last such line → done. No token, no HTTP.
Claude — the twist. The on-disk rateLimits in transcripts is always null; stats-cache.json is consumption history, not remaining quota. So we first built a ccusage-style estimate: sum tokens from the last 7 days of transcripts, bucket into a rolling 5-hour window, and gauge against the user's own busiest 5h (no fabricated Anthropic cap). Honest — but it didn't match the real numbers.
Antigravity — deferred. No clean local file; quota lives behind a local language-server RPC (needs the IDE running, which it wasn't) or an undocumented Google internal endpoint. Left as a "later, best-effort" slot rather than shipping something fragile.

The estimate ≠ reality, so we went looking for the real endpoint

The gauge showed one thing; claude.ai → Settings → Usage showed 5% session / 9% weekly, Max (20x). The relative "vs your own peak" estimate is honest but it isn't the real quota. That screen exists, so something serves the real data.

It does: GET https://api.anthropic.com/api/oauth/usage, authed with the OAuth access token Claude Code stores in the macOS Keychain (security find-generic-password -s "Claude Code-credentials" → JSON with accessToken, subscriptionType: "max", rateLimitTier: "default_claude_max_20x"). The Keychain item also gives the plan label with zero network.

Before writing a parser against a guessed shape, we made one live call and read the actual response:

{ "five_hour":  { "utilization": 8.0,  "resets_at": "2026-06-07T23:00:00Z" },
  "seven_day":  { "utilization": 10.0, "resets_at": "2026-06-14T11:59:59Z" },
  "seven_day_sonnet": { "utilization": 0.0, "resets_at": "..." } }

Near 1:1 with the Settings UI. utilization is 0–100, resets_at is ISO. Bearer alone works.

What shipped

Rust usage.rs: read_codex_usage() (local file), read_claude_real() (Keychain → api/oauth/usage, fail-soft) with read_claude_usage_estimate() as the fallback if the endpoint errors / token expires / shape changes. The gauge tag flips green "실측" vs amber "추정" so you always know which you're looking at.
The call is a usage query — zero tokens, no inference. It reuses the user's own credential (the macOS Keychain consent prompt is the user granting access — BYO). We never log the token.
Perf: the heavy transcript scan only runs as a fallback now; the whole snapshot is cached (60s) and computed off-thread (spawn_blocking), with a 40 MB scan cap, so the popup is instant.

The lesson (Pattern)

Twice in this thread the cheap-but-wrong move was to assume — first "Claude limits aren't readable" (false: they are, via the OAuth endpoint), then the JSON shape. The fix both times was the same: make one real call and read the actual bytes before writing the code. Verify the endpoint, then implement.