> ## Documentation Index > Fetch the complete documentation index at: https://docs.continuouslabs.ai/llms.txt > Use this file to discover all available pages before exploring further. # Errors > Every error is an application/problem+json body with a stable code and a human-readable detail. Control-plane request failures use `application/problem+json`. The generated error schema owns the exact shape. For example: ```json theme={null} { "code": "simulation_stopped", "detail": "The Simulation is stopped.", "validation": null } ``` The nullable `validation` field carries safe specification diagnostics when a build request is rejected. Use the stable `code` in programs. Show `detail` to people. The endpoint examples show the detail for each stated failure. IDs, quota counts, and other request values can change. ## Resource errors A successful HTTP read can return a Simulator or World whose build has failed. Its `error` field describes that resource outcome, separately from an HTTP request failure. Use the generated resource schema for the supported codes and fields. Simulator diagnostics can include a bounded `reason`, a plain-text `agent_message`, and structured `validation` issues. A `specification_validation_failed` result needs corrected input before another build. A canceled Simulator uses status `canceled` and error code `build_canceled`. ## Codes | Status | `code` | When | | ------ | ---------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------- | | `400` | `bad_request` | The `cursor` or `status` filter is invalid, a JSON body is malformed, or a data-plane body could not be read. | | `400` | `simulator_unknown` | A `simulator_id`, `parent_id`, `simulators[]` entry, or list filter does not resolve in this workspace or the catalog. | | `401` | `auth_invalid` | The API key is missing or invalid. | | `403` | `auth_forbidden` | The resource belongs to another workspace, the request deletes a catalog Simulator, or the request cancels a build that another workspace owns. | | `400` | `invalid_read_only_header` | Data plane only: `Continuous-Read-Only` must contain one `true` or `false` value. | | `403` | `simulation_read_only` | Data plane only: the operation can write, or the Simulator artifact cannot prove read-only support. | | `404` | `simulation_not_found`, `simulator_not_found`, `world_not_found` | The ID in the path is unknown. On the data plane, `simulation_not_found` also answers any path under `_sim`. | | `404` | `not_found` | The route is unknown. | | `404` | `clock_advance_not_found` | The requested clock operation does not exist for this resource. | | `405` | `method_not_allowed` | The route exists but not for this method. | | `408` | `request_timeout` | Reading the request body timed out. Any operation with a body can answer it. | | `409` | `simulator_not_ready` | Create a Simulation, build a World, or start an incremental build from a Simulator that is not `ready`. | | `409` | `simulation_stopped` | List steps, fork, or send a data-plane request to a stopped Simulation. | | `409` | `simulation_world_owned` | Stop, start, advance, or delete a World member directly. | | `409` | `simulation_platform_owned` | Change a Simulation that the platform has in use. | | `409` | `simulator_in_use` | Delete a Simulator that has dependent Worlds, Simulations, or child Simulators. | | `409` | `world_conflict` | Start or stop a World in a state that does not admit it. | | `409` | `clock_conflict` | A clock operation or conflicting lifecycle operation is already active, or an idempotency key is reused with a different target. | | `413` | `payload_too_large` | The request exceeds a [transport limit](/api-reference/quotas#size-limits). | | `415` | `unsupported_media_type` | A JSON operation received a non-JSON body, or `POST /v1/simulators` received a body that is not `multipart/form-data`. | | `422` | `validation` | The request violates the schema: for example `at_step` is not a recorded step, the multipart part set is invalid, or `ttl_seconds` is out of range. | | `429` | `simulation_quota_exceeded` | The workspace is at its active Simulation limit. | | `429` | `build_rate_exceeded` | The workspace has used its Simulator builds for the current UTC day. | | `429` | `simulation_capacity` | Continuous has no free Simulation capacity. Retry after a short delay. | | `500` | `internal` | The server failed unexpectedly. | | `500` | `simulation_template_missing` | The Simulation runtime template is unavailable. | | `503` | `simulation_provider_unavailable` | The Simulation runtime provider is unavailable. Retry after a short delay. | | `503` | `internal_unavailable` | A dependency of the API is unavailable. Retry the request. | | `503` | `auth_provider_unavailable` | The authentication provider is unavailable. Retry the request. | | `503` | `simulation_unreachable` | Data plane only: the runtime is waking, cannot be reached, or returned an unusable error. | | `504` | `simulation_timeout` | The Simulation runtime did not start in time. Retry the request. | The endpoint pages show examples for `internal_unavailable` and `auth_provider_unavailable`; either can appear on any operation. `Retry-After` gives a delay in seconds. It accompanies `build_rate_exceeded` until the UTC day ends, build storage failures and operation timeouts on `POST /v1/simulators`, and retryable data-plane `simulation_unreachable` responses. Other `internal_unavailable` and authentication failures can omit it. Simulator and World requests above their concurrent build limits return `202` with status `pending`. They start when a slot is free in their separate queues. See [Quotas and limits](/api-reference/quotas) for the `429` and `413` limits.