Cancel current turn

POST

/v1/sessions/{session_id}/cancel

const url = 'https://app.everruns.com/api/v1/sessions/example/cancel';
const options = {method: 'POST'};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}

curl --request POST \
  --url https://app.everruns.com/api/v1/sessions/example/cancel

Cancels the currently running turn in the session. If no turn is running, this is a no-op and returns success (idempotent). When a turn is active:

Cancel the underlying workflow execution
Emit a turn.cancelled event
Insert an agent message indicating the turn was cancelled
Set the session status back to idle

Parameters

Path Parameters

session_id

required

string

Session ID (prefixed, e.g., session_…)

Responses

200

Turn cancelled, or no-op (status: no_op) if no turn was running

application/json

Response from cancel turn endpoint

object

message

required

Human-readable message

string

status

required

Whether the cancellation was performed or was a no-op

string

Allowed values: cancelled no_op

Example

{
  "message": "Turn cancelled successfully",
  "status": "cancelled"
}

400

Invalid session ID

404

Session not found

application/json

Standard error response.

Wire shape is RFC 9457 Problem Details: every error response includes title and status, and may include detail, code, allowed_actions, retry_after_seconds, instance, and type. The content type is rewritten to application/problem+json by [problem_json_content_type].

object

allowed_actions

Recovery actions the caller can take next.

Array<object>

Agent-actionable link describing a follow-up the caller can take. Used in two contexts:

Error recovery — ErrorResponse.allowed_actions carries rels like retry, retry-later, unarchive, get-existing so the agent knows the right next call after a 4xx/429.
Entity hypermedia — WithUrls<T>.allowed_actions carries state-aware rels like cancel, events, self, update on the entity itself so the agent can follow links instead of reconstructing routes from prose.

The shape is intentionally identical across both contexts; the closed rel vocabulary documented in specs/api-conventions.md distinguishes them.

object

hint

Short, agent-readable hint (e.g. “Shorten ‘name’ to <= 200 chars.”, “Cancel the active turn for this session.”).

string | null

href

Absolute (preferred) or relative URL the caller may invoke directly. Always present on entity hypermedia actions (WithUrls<T>.allowed_actions); optional on error-recovery actions (ErrorResponse.allowed_actions) where the matching operation_id is enough and the URI is implicit from the failed call.

string | null

method

HTTP method to use against href. Required for entity hypermedia actions; usually omitted on error-recovery actions where the same operation is retried with its original method.

string | null

operation_id

OpenAPI operationId the caller should invoke. Lets an MCP client resolve the call without parsing href.

string | null

rel

required

Link relation describing the action. Closed vocabulary documented in specs/api-conventions.md — examples: self, cancel, pause, resume, events, retry, retry-later, unarchive, get-existing, delete, update.

string

schema_ref

OpenAPI $ref to the request-body schema, when the action takes one (e.g. #/components/schemas/UpdateSessionRequest). Lets a tool-calling agent fetch the input shape without scanning the whole spec.

string | null

code

Stable, machine-readable error code (snake_case).

string | null

detail

Human-readable explanation specific to this occurrence.

string | null

instance

Request URI for this occurrence.

string | null

retry_after_seconds

Seconds the caller should wait before retrying (429 / transient 503).

integer | null format: int32

status

required

HTTP status code; mirrors the response status line.

integer format: int32

title

required

Short, human-readable summary of the problem (e.g. “Not Found”).

string

type

RFC 9457 problem type URI. Optional; identifies the problem class.

string | null

Example

{
  "code": "session_not_found",
  "detail": "Session session_01933b5a000070008000000000000001 not found in org org_00000000000000000000000000000001.",
  "status": 404,
  "title": "Not Found",
  "type": "https://docs.everruns.com/errors/session_not_found"
}

500

Internal server error