Post a message to a task
POST /tasks/{id}/messages
Requires: tasks.chat
Payload shapes are not yet fully described. The endpoint, authentication and permissions are accurate; unconstrained JSON marks the shapes still awaiting extraction.
Authorizations
Section titled “Authorizations ”Parameters
Section titled “ Parameters ”Path Parameters
Section titled “Path Parameters ”Resource ULID.
Header Parameters
Section titled “Header Parameters ”Org scope: me or an org slug. Absent means the caller’s active/personal org. It selects the workspace used for permission checks and for most resource filters; operation-specific access rules still apply.
Request Body required
Section titled “Request Body required ”object
Responses
Section titled “ Responses ”Stored, with no unrouted condition. This does NOT assert that an agent received it — a human-to-human message and a /retry-gh both answer 200 with nobody addressed.
Accepted and stored, with a delivery issue or an invalid Backstage To: warning — the body carries unrouted.reason. Clients gate their working indicator on routed, which is false here.
BAD_JSON — the body is not valid JSON, or INVALID_REQUEST — the decoded body does not match the route’s request schema.
object
object
Stable, machine-readable error code
Human-readable explanation
Present on 403 — the permission the caller lacked
Present on 402 — gated feature
Present on 402 — the plan’s cap
Present on 402 — the current plan
UNAUTHORIZED — missing or invalid token, or an org-scoped API key (only user-scoped keys are accepted).
object
object
Stable, machine-readable error code
Human-readable explanation
Present on 403 — the permission the caller lacked
Present on 402 — gated feature
Present on 402 — the plan’s cap
Present on 402 — the current plan
PLAN_LIMIT — the workspace’s plan does not include API access. Every API-key call can return this; session-token calls never do.
object
object
Stable, machine-readable error code
Human-readable explanation
Present on 403 — the permission the caller lacked
Present on 402 — gated feature
Present on 402 — the plan’s cap
Present on 402 — the current plan
FORBIDDEN (lacking the required permission) or SCOPE_REQUIRED (no workspace, or a membership change in progress).
object
object
Stable, machine-readable error code
Human-readable explanation
Present on 403 — the permission the caller lacked
Present on 402 — gated feature
Present on 402 — the plan’s cap
Present on 402 — the current plan
TASK_NOT_FOUND.
SCOPE_REQUIRED — the x-uai-org scope names a workspace that does not exist, or one the caller is not a member of. The two are deliberately indistinguishable: a 403 would confirm the workspace exists.
object
object
Stable, machine-readable error code
Human-readable explanation
Present on 403 — the permission the caller lacked
Present on 402 — gated feature
Present on 402 — the plan’s cap
Present on 402 — the current plan
Nothing was stored, so the whole send may be retried. UPLOAD_NOT_BINDABLE — an upload id is not attachable to this task; MESSAGE_NOT_ROUTED — the router persisted nothing.
object
object
Stable, machine-readable error code
Human-readable explanation
Present on 403 — the permission the caller lacked
Present on 402 — gated feature
Present on 402 — the plan’s cap
Present on 402 — the current plan
SCOPE_REQUIRED — membership reconciliation required, or membership verification unavailable.
object
object
Stable, machine-readable error code
Human-readable explanation
Present on 403 — the permission the caller lacked
Present on 402 — gated feature
Present on 402 — the plan’s cap
Present on 402 — the current plan