> ## Documentation Index > Fetch the complete documentation index at: https://docs.heylua.ai/llms.txt > Use this file to discover all available pages before exploring further. # Device reliability and limits > Reconnection, heartbeats, offline semantics, command and trigger limits, payload caps, and credential checks for device connections The numbers that govern a [device](/concepts/devices) connection, in one place. Client rows come from the shipped clients (`@lua-ai-global/device-client` 1.1.0, `lua-device-client` 1.3.0); the rest come from the platform. *Verified against lua-cli 3.33.0.* ## Reconnection | Client | Retry delay | Stops retrying | | --------------- | ------------------------------------------------------------------------------------ | ----------------------------------------------------- | | Node, Socket.IO | 1 s doubling to 30 s with up to 50 % jitter; 1 s after a server-initiated disconnect | After `AUTH_FAILED` or `MISSING_AUTH`; `disconnect()` | | Node, MQTT | Every 5 s | `disconnect()` | | Python | paho-mqtt: 1 s doubling to 120 s | `disconnect()` | | MicroPython | 2 s doubling to 30 s; board reset after 10 failures | Never | A `RATE_LIMITED` handshake response tells the Node Socket.IO client to wait `retryAfterMs`, clamped to 1 s–15 min, or 30 s when absent. A connection the platform closes itself, for example with `AGENT_FORBIDDEN` or `DEVICE_DISABLED`, is retried every second without limit. Every reconnection repeats the handshake, so the command list is re-sent and the tools return. ## Presence | Item | Value | | --------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Heartbeat | Every 30 s from every client; QoS 0 over MQTT | | Offline on connection close | Immediate: Socket.IO disconnect, MQTT will, or a published `offline` status | | Offline without a close | A sweep every 5 min marks devices whose last heartbeat is older than 5 min | | What offline changes | Removed from the online set, stored command list cleared, tools gone on the next turn; a `defineDevice` device keeps its tools and calls return `DEVICE_OFFLINE` | | `device_disconnected` | Fires on close only, not on the sweep | | Stored command list | Kept 24 h from connect; heartbeats don't extend it (self-describing devices only) | | Connected over 24 h | Command tools gone until reconnect, `is_online` stays; no client reconnects on a timer, so schedule `disconnect()` then `connect()` yourself | | `lua devices status` | `online`, otherwise the stored `offline`, `registered`, or `disabled` | ## Commands | Item | Value | | --------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Timeout | `timeoutMs`, 30,000 ms default, plus 2 s grace | | In flight per agent | 100; more fail with `TOO_MANY_REQUESTS` | | Retries | None unless `retry` is set; then after `TIMEOUT` or `DEVICE_ERROR` only, waiting `backoffMs × attempt` | | Not retried | `DEVICE_OFFLINE`, `TOO_MANY_REQUESTS`, a handler that throws | | Delivery | Socket.IO event with acknowledgment; MQTT QoS 1 with a persistent session | | Duplicate suppression | Clients cache command IDs for 5 min; Node and Python keep 1,000 and re-send the cached response, MicroPython prunes above 100 entries and ignores the duplicate | | Group fan-out | `device______all`, `defineDevice` devices only, one attempt per device | ## Triggers | Item | Value | | ------------------- | ------------------------------------------------------------------------------------------------------------------------------ | | Rate | 10 per second per agent; excess answered with `RATE_LIMITED` on `trigger_error`, which only the Node Socket.IO client surfaces | | Acknowledgment wait | 10 s in the Node and Python clients; none in MicroPython | | Name matching | Exact string; device `defineDevice` triggers first, then standalone triggers | | Handler time limit | 10 min, the platform's default cap for event handlers | | Handler context | `{ device: { name }, trigger: { name, triggerId } }` | | Delivery | At least once from a durable queue; a handler that throws or times out is run again, 3 attempts 60 s apart | | `trigger_result` | Never sent by the platform | | System triggers | `device_connected`, `device_disconnected` | ## Payloads and declarations | Item | Value | | ------------------------------------------------- | ---------------------------------------------------------------------------------------------------------- | | Command payload, response `data`, trigger payload | 1 MB (1,048,576 bytes) | | Response `error` string | 4 KB | | Command name | `^[a-z][a-z0-9_]{0,63}$`; others dropped | | Commands per device | 128; the rest dropped | | `inputSchema` per command | 4 KB serialized; larger drops the command | | Command description | HTML stripped, cut at 500 characters | | Device tools per agent | 128, counting each device's `is_online` tool | | Device name (`defineDevice`) | `^[a-z][a-z0-9-]*$`, compile warning otherwise; 1–200 characters, no whitespace, `/`, `+`, `#` on the wire | | Device trigger name | `^[a-z][a-z0-9_-]*$`, compile warning otherwise | | CDN upload | 100 MB per file, one file per request | ## Credentials and authentication | Item | Value | | ------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Device credential re-check while connected | Every 60 s plus up to 30 s jitter (Socket.IO); at the next publish or subscribe after 60 s (MQTT) | | Legacy API key re-check | Every 15 min plus up to 5 min jitter | | Authorization outage | Connections kept open up to 15 min past the due re-check, then closed with `CONNECT_ERROR` | | Revocation, rotation, suspension | Socket.IO connections closed at once with `AUTH_FAILED`; MQTT denied at the next publish or subscribe; the re-check is the fallback | | Failed handshakes | 5 rejected credentials per 60 s per device and credential; the next attempt gets `RATE_LIMITED` with `retryAfterMs` of 10 min, and every handshake from that pair is refused for 10 min | | MQTT connection record | 24 h, extended on every authorized publish or subscribe | | Operations | `commands`, `triggers`, `assets.upload`; enforced per message | ## See also * [How devices work](/devices/how-it-works) — the same facts as a narrative * [MQTT protocol](/devices/mqtt-protocol) — error codes and per-topic authorization * [Create a device credential](/devices/credentials) * [Node device client](/devices/node-client) and [Python device client](/devices/python-client)