> ## Documentation Index
> Fetch the complete documentation index at: https://www.agentworldprotocol.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Events and errors

> World events, the error taxonomy, and recovery expectations.

## World events

Worlds emit `world.event` notifications for state changes not tied to a specific action: `entity_appeared`, `entity_removed`, `collision`, `e_stop_engaged`, `e_stop_released`, `envelope_violation`, `grant_expired`, `safe_state_entered`, `safe_state_exited`, `channel_degraded`, `world_resetting`, `world_shutdown`. Events carry `ts_mono_ns`, `status_seq`, and structured detail. Custom events use `x-<vendor>.` names. `[AWP-EVT-001]`

`world.event` notifications travel only on the control channel, where `status_seq` orders them against action statuses and resumption replays them. A `text/event+json` observation channel carries the world's own structured samples — detections, scene deltas, game state — and MUST NOT carry the events of this registry. `[AWP-EVT-003]`

`e_stop_engaged` MUST terminate every non-terminal action: `executing` actions → `failed` (reason `e_stop`); `pending_approval`, `queued`, and `accepted` actions → `cancelled` (reason `e_stop`). Action admission is suspended (`AWP_ESTOP_ACTIVE`) until `e_stop_released`. `[AWP-EVT-002]`

## Status reasons

Terminal `action.status` notifications in `rejected`, `failed`, or `cancelled` carry a `reason` from this registry (AWP-LIF-004). Vendor reasons use `x-<vendor>.` names.

| Reason               | Terminal states   | Cause                                                                                                               |
| -------------------- | ----------------- | ------------------------------------------------------------------------------------------------------------------- |
| `params_invalid`     | rejected          | Params failed `params_schema` (AWP-ACT-002)                                                                         |
| `forbidden`          | rejected          | Type or embodiment not granted (AWP-ACT-003)                                                                        |
| `envelope`           | rejected, failed  | Envelope exceeded with `on_violation: reject`, or violated during execution (AWP-ENV-002/003)                       |
| `approval_denied`    | rejected          | Approver denied (AWP-APR-002)                                                                                       |
| `approval_timeout`   | rejected          | No approval decision in time (AWP-APR-003)                                                                          |
| `deadline_exceeded`  | rejected, failed  | `deadline_ms` expired (AWP-ACT-004)                                                                                 |
| `stale_intent`       | rejected          | `valid_until_ns` passed, or the basis observation exceeded `max_basis_age_ms`, before execution began (AWP-SAF-013) |
| `cancelled_by_agent` | cancelled         | `action.cancel` (AWP-LIF-005)                                                                                       |
| `superseded`         | cancelled         | A newer `replace`/`blend` submission arrived before execution (AWP-PRE-003)                                         |
| `e_stop`             | failed, cancelled | `e_stop_engaged` (AWP-EVT-002)                                                                                      |
| `connection_lost`    | failed            | Safe-state entry terminated execution (AWP-SAF-003)                                                                 |
| `safe_state`         | cancelled         | Safe-state entry cancelled a pre-execution action (AWP-SAF-003)                                                     |
| `session_closed`     | cancelled         | `session.close` or reconnect-window expiry (AWP-SES-006)                                                            |
| `world_reset`        | cancelled         | `world.reset` or `world.restore` (AWP-PRM-006)                                                                      |
| `watchdog`           | failed            | No valid command frame within `watchdog_ms` (AWP-CMD-005)                                                           |
| `world_error`        | failed            | World-internal failure; `detail` explains                                                                           |

## Error taxonomy

Errors surface as JSON-RPC error objects with AWP codes (see [error codes](/api-reference/error-codes)):

| Range | Area     | Examples                                                                                                                                                                                                                                                  |
| ----- | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| 1xxx  | Protocol | `AWP_VERSION_UNSUPPORTED` (1001), `AWP_MALFORMED` (1002)                                                                                                                                                                                                  |
| 2xxx  | Session  | `AWP_EMBODIMENT_UNAVAILABLE` (2001), `AWP_TIME_MODEL_UNSUPPORTED` (2002), `AWP_SESSION_EXPIRED` (2003), `AWP_SESSION_EXISTS` (2004), `AWP_SESSION_UNKNOWN` (2005), `AWP_INTEGER_RANGE` (2006), `AWP_CHANNEL_UNKNOWN` (2007)                               |
| 3xxx  | Action   | `AWP_PARAMS_INVALID` (3001), `AWP_BUSY` (3002), `AWP_QUEUE_FULL` (3003), `AWP_ACTION_ID_CONFLICT` (3004), `AWP_ESTOP_ACTIVE` (3005), `AWP_TICK_NOT_AUTHORIZED` (3006), `AWP_STALE_INTENT` (3007), `AWP_ACTION_UNKNOWN` (3008), `AWP_TICK_MISMATCH` (3009) |
| 4xxx  | Safety   | `AWP_FORBIDDEN` (4001), `AWP_ENVELOPE_EXCEEDED` (4002), `AWP_APPROVAL_DENIED` (4003), `AWP_APPROVAL_TIMEOUT` (4004)                                                                                                                                       |

Every error object marks `retryable: true|false` in `data`. Agents MUST NOT retry non-retryable errors with identical parameters. `[AWP-ERR-001]`