millibar

Usage pressure on a very small bar.

Controls a BUSY Bar — an open-source desk device with a 72×16 LED pixel display, a rotary encoder, three buttons, a five-position mode switch, and an RGB status light — from TypeScript.

The headline app is a modular monitor: press the dial to switch between monitor modules — Claude Code usage limits, token history, the Grok weekly credit pool, CPU load, and whatever you add next — rotate it to cycle the screens inside a module, and press START to refresh, with the status light fading cyan while it fetches.

What it looks like

Rendered loops with showcase data, not captures: tools/readme-shots.ts drives each module's real render() on fixture data along a scripted timeline (the startup sweep, a refresh, the dial turning), rasterizes every frame with the firmware's own fonts — the rasterizer reproduces a real /api/screen capture pixel-for-pixel (its validate mode) — and draws the 72×16 frames as an LED panel in a looping APNG. Anything that doesn't animate shows the settled frame.

Claude gauge — one limit window at a time: label, countdown to the window's reset, percentage, and the severity-coloured bar. The notch is the pace tick, marking how much of the window has elapsed — fill past it means tokens are going faster than time.

Claude dashboard — every window at once: one slim bar per window under the detail row for the selected one, whose bar runs at full brightness behind the marker at the left edge while the other rows dim.

Claude history — the last 30 days of token spend, one stacked per-model bar per day…

…and its ALL screen, the all-time calendar heatmap, one cell per day:

Grok weekly — the SuperGrok shared credit pool on the same gauge layout, counting down to the weekly reset.

CPU load — load averages normalised by core count: sustained pressure, not instantaneous CPU%.

Setup

From npm:

bun add -g millibar         # or: npm install -g millibar
mbar                        # run the monitor

Or try it without installing anything:

bunx millibar               # one-off run of the monitor (npx millibar works too)
bunx millibar probe         # any subcommand; flags pass through as usual

Whichever package manager installs it, the CLI itself runs on Bun — 1.3+ must be on your PATH (npm install -g doesn't change that).

From a clone, for development:

bun install
bun run tools/smoke.ts        # connectivity smoke test
bun link                # installs the global `mbar` command (~/.bun/bin)

The smoke test should print your device's model, firmware, battery, and timer state. If it hangs or errors, see Troubleshooting.

Scripts

Command	What it does
bun run tools/smoke.ts	Smoke test — prints device status and busy-timer state.
mbar (or bun run src/mbar.ts)	The monitor. Switchable modules on the display: Claude Code limits, token history (last 30/7 days, stacked by model), the Grok weekly credit pool, and CPU load. Dial press switches modules, rotation cycles screens, START refreshes, BACK twice quits. --modules gauge,cpu picks which modules run (and their order).
bun run src/input.ts	Prints button, switch, and encoder events live.
bun run src/led.ts pulse "#00CCFF" 1400 2	Pulses the status light — colour, duration ms, cycles.
bun run src/led.ts fade "#F00,#0F0,#00F" 3000 hsv	Crossfades through colour stops — stops, duration ms, rgb|hsv.
bun run tools/plasma.ts [seconds]	Generates, uploads, and plays a looping plasma animation.
bun run tools/flame.ts [start-level]	Flame. Fire rises from the bottom; the dial sets its intensity (16 levels). Changes glide one level at a time, phase-matched, so they're smooth and immediate. --preview [out.png] renders a local contact sheet instead.
bun run tools/sweep.ts [targets...]	Test bench for the monitor's percentage-change animation: eased bar sweep, white-hot leading edge, rolling counter, severity-colour lerp. Scripted (10 47 85), interactive (no args), or --demo; reports the frame rate the device actually sustains.
bun run tools/history-intro.ts [preview|play]	Test bench for the history module's appearance intros (bars rising with white tips, heatmap sweeping in). preview writes looping APNGs and an HTML page; play demos all three on the device and verifies the frames on the wire.
bun run tools/chime.ts [freqs-hz...]	Synthesizes a chime, uploads it, and plays it on the speaker.
bun run tools/click.ts [--once]	Clicks the speaker whenever the rotary dial moves.
bun run tools/screenshot.ts [out.png] [front|back] [scale]	Captures a display to PNG.
bun run tools/readme-shots.ts generate|check|validate	Regenerates the README's screen loops — the modules' real render() on showcase data, filmed over a scripted timeline and rasterized with the firmware's fonts (fetched from a pinned firmware revision; --fw <checkout> to use a local one), no device needed. Deterministic: check exits 1 if docs/img no longer matches what the code renders. validate diffs the rasterizer against a real capture.
mbar probe|routes|show|init|set|rm|order	Connection config. Manages the persistent route list (USB / LAN / cloud, with credentials) and probes which route answers. --route <names> forces a run onto specific routes. See Connecting.
mbar api <cmd>	Storage CLI. Browse and manage the device's 7 GB /ext partition and per-app assets: ls/df/cat/get/put/mv/mkdir/rm, plus apps/push/wipe for asset directories. mbar api help for the full list.

Connecting to the device

Every script resolves the device through the same ordered route list — by default the fixed USB-Ethernet address, then the LAN hostname:

usb   10.0.4.20              (USB-Ethernet, fixed)
lan   busy.bar               (mDNS hostname on the LAN)
cloud https://api.busy.app   (remote proxy — add it yourself, needs a token)

Routes are probed in parallel (GET /api/version) and the first one, in order, that answers like a BUSY device wins. If the winning route dies mid-run — USB unplugged — the next request re-probes and fails over to the next route without a restart.

The list persists in ~/.config/mbar/config.json, managed with mbar's connection subcommands (the file is written 0600 because it can hold credentials; without it the usb + lan defaults above apply):

mbar probe        # every route's status, and which one wins
mbar routes       # just the route names, one per line
mbar set cloud https://api.busy.app --token <token>
mbar set lan 192.168.1.50 --first   # add/update, move to front
mbar show|init|rm <name>|order <name...>
mbar --help       # full usage, including the monitor and env vars

To force a run onto specific routes without editing the config, name them: mbar --route cloud runs the monitor over the proxy, mbar probe --route cloud,lan probes those two in that order. The flag is MBAR_ROUTE in env form, which every script in the repo honours. Forced routes are still probed — a dead forced route is a loud error, not a silent fallback — while MBAR_ADDR stays the unprobed escape hatch and wins over both.

Credentials, both optional, per route:

• --token — a cloud API token from https://cloud.busy.app/api-tokens, sent as Authorization: Bearer …. Required for the api.busy.app proxy route, and it must be created with the BUSY Bar access scope — an Account-scope token gets the same HTTP 403 as an invalid one, and the scope can't be inspected after creation (see DEVICE.md, Authentication).
• --password — the device's HTTP Access Password (web UI: Settings → HTTP Access), sent as an X-API-Token header (x-api-token query parameter on WebSockets). Only needed if you enabled that setting.

Caveat: there is no button input over the cloud proxy — it rejects every WebSocket upgrade at its edge (verified: any path 403s the moment the Upgrade headers appear, valid token or not), so the monitor reports input unavailable and runs without the dial. Drawing, audio, and storage go through plain HTTP and work the same over any route.

Configuration

All via environment variables; every one has a working default.

Variable	Default	Applies to
MBAR_ADDR	unset	bypasses the route config: talk to exactly this IP/hostname/URL, unprobed (wins over MBAR_ROUTE)
MBAR_ROUTE	unset	force selection to these config routes — comma-separated names, tried in that order, still probed. Same as mbar --route
MBAR_TOKEN	unset	cloud token for routes that don't carry their own
MBAR_PASSWORD	unset	HTTP Access Password for routes that don't carry their own
MBAR_CONFIG	~/.config/mbar/config.json	where the route config lives
MBAR_POLL_INTERVAL_MS	600000 (10 min)	monitor — how often the usage API is polled
MBAR_REFRESH_COOLDOWN_MS	5000	monitor — floor between button-triggered fetches
MBAR_PRIORITY	50	monitor — draw priority, 1–100
MBAR_SWITCH_BUTTON	OK	monitor — which button event the dial press reports as (OK|BACK|START)
MBAR_MODULES	unset (all)	monitor — which modules run and their cycle order, comma-separated (gauge,dash,history,grok,cpu); the first named is the startup module. Unset includes grok only when a grok login exists. Same as mbar --modules (the flag wins)
MBAR_ANIMATIONS	on	monitor — off stills everything that moves: value changes snap instead of sweeping, and the history screens appear without their intros. Same as mbar --no-animations (the flag wins)
CLAUDE_CONFIG_DIR	~/.claude	usage — where credentials are read from off-macOS

Modules

Each is usable on its own, not just by the monitor.

• src/usage.ts — reads Claude Code's own usage limits (5-hour, 7-day, per-model) from an undocumented endpoint, using the OAuth token Claude Code already stores. See USAGE-API.md.
• src/stats.ts — reads Claude Code's local stats cache, the per-day token history behind its own usage graphs (there is no server endpoint for history). Drawn by the monitor's history module as stacked per-model bars over the last 30 or 7 days, plus an all-time calendar heatmap. See USAGE-GRAPH.md.
• src/grok-usage.ts — reads the SuperGrok shared weekly credit pool (the data behind the Grok CLI's /usage panel) with the OIDC token grok login already stores. See GROK-USAGE-API.md.
• src/connection.ts — the route resolver behind every device request: loads the persistent config, probes routes in priority order, injects credentials (deviceFetch(), wsUrl(), connectedBar()), and re-probes on network failure so callers fail over without noticing.
• src/input.ts — listenInput() streams button, switch, and encoder events off the device's protobuf WebSocket. Decodes only the input field, so it needs no protobuf runtime.
• src/led.ts — pulseLed() and fadeLed() animate the status light smoothly, despite the firmware only exposing a fixed 3-blink notification preset.
• src/anim.ts — encodeAnim() writes the device's native bicycle0 animation container (RLE-compressed BGR frames, named sections), reverse-engineered from the open-source firmware.
• src/png.ts — encodePng(), the minimal PNG writer behind screenshots and local previews.
• src/snd.ts — pcm16() converts float samples to the device's .snd audio format (raw s16le mono 44.1 kHz).
• src/display.ts — the draw transport plus DisplaySession, which serialises draws, stamps timeouts, and scrubs elements whose ids disappear between draws (the firmware otherwise leaves them on screen). Also the shared render kit: severity colours, font metrics, the compact countdown, progressBar().
• src/sweep.ts — PctSweep, the time-based value animation the modules share: eased sweeps, colour lerps, the bar's cooling leading edge. Frames are computed from the wall clock, so slow draws drop frames instead of stretching the animation.
• src/module.ts — the MonitorModule contract and per-module scheduler.
• src/host.ts — runHost() runs modules against one device: input routing, module switching, the heartbeat repaint, status-light ownership, shutdown.
• src/modules/ — the modules themselves: claude-gauge.ts (one limit window at a time, on the provider-agnostic layout in limit-gauge.ts), claude-dash.ts (every window at once; the shared poll/stale/cache machinery lives in limit-poller.ts), claude-history.ts, grok-gauge.ts (the Grok weekly pool on the same gauge layout), cpu.ts (1/5/15-minute load averages normalised by core count — sustained pressure, not instantaneous CPU%).
• src/mbar.ts — the entry point that registers modules with the host.

Monitor behaviour

The Claude gauge shows one limit window at a time: a label, a dark-grey countdown to the window's reset, a percentage, and a progress bar recoloured by severity (green below 50%, amber below 80%, red above). Its sibling the Claude dashboard puts every window on one screen — one slim bar per window, under the same detail row for the selected window, whose bar runs at full brightness behind a two-pixel marker at the left edge while the other rows dim to 45%. The two modules share one deduplicated fetch, so the pair costs the rate-limited usage API no more than a single module would. The countdown (4:59, 6D4H, 59M) ticks once a minute and drops precision — or hides — when a long model label leaves it no room.

A faint tick on each usage bar marks how much of that window has elapsed, so the bar reads as a race: fill ahead of the tick means tokens are going faster than time. Under pace the tick sits in the empty track, just lighter than it; over pace it sits submerged in the fill as a darker notch of the fill colour.

Value changes animate rather than snap: the bar sweeps to its new fill with ease-out, the percentage rolls through the intermediate values, the severity colour crossfades when a sweep crosses a band boundary, and a white-hot pixel rides the fill's leading edge, cooling into the bar once it lands. The same sweep plays when the encoder switches windows and when a module's data goes stale (a fade to grey in place). CPU load jitter under 3% jumps silently so the head doesn't flash every poll. The effect can be tuned and timed standalone with bun run tools/sweep.ts, which also reports the frame rate the device actually sustains.

• Press the dial (its press arrives as the OK button event — override with MBAR_SWITCH_BUTTON if your press reports differently) to switch to the next module: Claude gauge → Claude dashboard → Claude history → Grok weekly → CPU load → back. (The Grok gauge — the SuperGrok weekly credit pool on the same layout — joins the cycle only when a grok login exists; without one it sits out rather than erroring.) Each module keeps polling while hidden, so switching always lands on fresh data, and each remembers which screen it was on.
• Rotate the encoder to cycle the active module's screens — 5H → 7D → per-model windows (e.g. FABLE) on both limit modules (on the dashboard the marker walks the bars), 30D/7D bars → ALL heatmap on Claude history, 1M/5M/15M load windows on CPU. The Grok gauge has a single GROK screen (the weekly pool is its whole scope), so rotation does nothing there. The limit window list is rebuilt each poll, since the API adds and drops model windows; the selection follows its label rather than its index so a refresh never jumps you elsewhere.
• Press START to refresh the active module immediately. Three cyan dots replace the countdown while fetching and the status light fades. During cooldown a press still repaints (without refetching), so a blank screen is always recoverable — every button press ends in a repaint.
• Press BACK twice within 5 s to quit from the device: the first press paints an AGAIN = QUIT prompt over a draining time bar, the second plays the firmware's own turn-off animation and exits cleanly. Any other input dismisses the prompt.
• A failed update blinks the status light red, once (preempting the cyan fetch fade), and the shown values dim to stale grey until a fetch succeeds. A rate-limit back-off (429) skips the blink — it's routine, and would otherwise recur every backed-off cycle — but still dims.
• The last successful usage read is cached in ~/.cache/mbar/usage.json (grok-usage.json for the Grok module), so a restart while the API is unreachable or rate-limited starts from the previous values — grey with a ? on the label, like any stale data — until a live fetch replaces them. Grok tokens expire after ~6 hours; the gauge dims to stale over an expired one and recovers on its own the next time any grok CLI use refreshes the stored token.
• Moving the mode switch off OFF silences the monitor — no repaints, no status-light frames, no button or encoder handling — because the system screens own the display there. Back on OFF, it repaints once the device's power-down animation has finished (~1.2 s). The switch position can't be read at startup, so a monitor launched with the switch already away draws until the first flip it sees.
• Draws carry a 90-second timeout, refreshed by a once-a-minute heartbeat repaint (which also keeps countdowns ticking), so the display self-clears within ~90 s if the process dies. Ctrl-C clears it explicitly.

Buttons keep their normal device functions too — depending on device state, OK and START can start a BUSY session, and BACK blanks the canvas. That's the device's own behaviour, not the monitor's.

Writing a monitor module

A module is one file in src/modules/ implementing MonitorModule (see src/module.ts): a poll() that updates its data and returns its own cadence and refresh cooldown, a render() that returns the element list for its current state, and optionally onEncoder() for its screens. Register it in src/mbar.ts and the host does the rest — id namespacing, element scrubbing on switch, timeouts, input routing, and status-light arbitration. The Grok module is the worked example: a sibling fetch client next to src/usage.ts (src/grok-usage.ts) plus a thin binding (src/modules/grok-gauge.ts) of the shared gauge layout (src/modules/limit-gauge.ts) to a UsageSource; nothing else changed.

Troubleshooting

Device unreachable. mbar probe reports every configured route's status and which one scripts will use. To poke by hand: curl http://10.0.4.20/api/status (USB-Ethernet, fixed address) or http://busy.bar/ (LAN).

Display went black. Most likely BACK was pressed, which dismisses the drawing layer and drops to a stub app that renders nothing — the display is not off. Any draw reclaims it. See DEVICE.md.

Not drawn due to low priority. Another app holds the display at an equal or higher priority. Clear it (curl -X DELETE "http://10.0.4.20/api/display/draw?application_name=NAME") or draw higher. Note that two draw-based scripts running at once will fight over the screen.

no Claude Code OAuth credentials found. Run claude auth to sign in.

No Grok module in the cycle. The default roster includes it only when ~/.grok/auth.json exists — run grok login (naming it explicitly with --modules grok instead makes the missing login a hard error).

Usage numbers dimmed with a ? label. The last fetch failed and stale values are being shown. Repeated manual refreshes can trigger a 429; the monitor honours Retry-After and recovers on its own.

Documentation

• DEVICE.md — everything learned about the hardware and its HTTP API: drawing, priorities, the animation format, input events, the status light, and the spec's inaccuracies. Read this before touching device code.
• USAGE-API.md — the undocumented Claude Code usage endpoint.
• GROK-USAGE-API.md — the undocumented Grok weekly credit-pool endpoint behind the Grok gauge.
• USAGE-GRAPH.md — where the "last N days" usage graphs come from (local stats, not a server endpoint) and how the history module renders them.
• CLAUDE.md — working practices for this repo.

Requirements

Bun 1.3+, a BUSY Bar reachable over USB-Ethernet, the LAN, or the cloud proxy, and Claude Code signed in (for the monitor). The Grok gauge additionally wants a grok login; without one it simply sits out of the module cycle. Credential reading is implemented for the macOS Keychain with a file fallback elsewhere.