Start a run

POST/v1/sessions/{session_id}/runs

Start one run inside an existing session. The session serializes its runs. idempotency_key is scoped to the session and prevents a retry from starting a second run; a request without a key always creates a new run. By default the endpoint returns 202 Accepted with the admitted run; set Accept: text/event-stream or add ?stream=true to stream immediately, or reconnect later through the run’s events endpoint.

Generated from the Platform API specification on 2026-09-04.

Path parameters

Parameter	Type	Description
session_id	string	The session, as returned by Create a session.

Query parameters

Parameter	Type	Description
stream	boolean	Stream the run’s events instead of returning the admitted run.

Headers

Header	Required	Description
Authorization	yes	Bearer plus a short-lived OAuth access token issued for the Tanomis API audience. Backends obtain tokens with an organization automation client; the CLI’s human login is not an application credential.
X-Organization-ID	yes	The organization_id from the workspace projection you selected in GET /v1/me/workspaces.
X-Workspace-Tenant-ID	yes	The nested tenant_id from the same projection. A header cannot widen what the token grants. Some single-workspace or self-hosted environments take X-Tenant-ID instead, as supplied by their administrator.

Request body

Field	Type	Required	Description
input	object	required	Passed to the agent as JSON. The shape is defined by your agent’s entrypoint.
idempotency_key	string	optional	Scoped to the session; a retry with the same key returns the original run. At most 255 bytes.
attachments	array	optional	Files prepared and uploaded in this session, as { "file_id": ... } objects.
work	object	optional	Settlement-mode agents only. Send either subject (open new work) or work_id (continue work opened by an earlier session).
work.subject	string	optional	Opens new work, for example invoice:INV-1842.
work.work_id	string	optional	Continues work opened by an earlier session.
work.contract_ref	string	optional	Sent together with contract_version when opening work. Cannot be added or changed later.
work.contract_version	string	optional	Sent together with contract_ref.

Responses

Status	Meaning
200	With streaming requested: the run’s server-sent event stream.
202	The run was admitted. Poll it or open the event stream.
404	No such session in the selected tenant.
409	The idempotency key matched a run with a different body, or the session cannot admit a run.

Request

cURL

Terminal

curl -X POST "https://api.tanomis.com/v1/sessions/ses_7d4f9c/runs" \
  -H "Authorization: Bearer $TANOMIS_TOKEN" \
  -H "X-Organization-ID: $TANOMIS_ORG" \
  -H "X-Workspace-Tenant-ID: $TANOMIS_WORKSPACE" \
  -H "Content-Type: application/json" \
  -d '{
    "input": {
      "prompt": "Draft a concise reply for the customer."
    },
    "idempotency_key": "support-case-1842-reply-1"
  }'

Python

import httpx

response = httpx.post(
    f"https://api.tanomis.com/v1/sessions/{session_id}/runs",
    headers={
        "Authorization": f"Bearer {token}",
        "X-Organization-ID": organization_id,
        "X-Workspace-Tenant-ID": tenant_id,
    },
    json={
        "input": {
            "prompt": "Draft a concise reply for the customer.",
        },
        "idempotency_key": "support-case-1842-reply-1",
    },
)
response.raise_for_status()
result = response.json()

TypeScript

const response = await fetch(`https://api.tanomis.com/v1/sessions/${sessionId}/runs`, {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${token}`,
    "X-Organization-ID": organizationId,
    "X-Workspace-Tenant-ID": tenantId,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "input": {
      "prompt": "Draft a concise reply for the customer."
    },
    "idempotency_key": "support-case-1842-reply-1"
  }),
});
if (!response.ok) throw new Error(`${response.status} ${await response.text()}`);
const result = await response.json();

Response

202 Accepted

{
  "id": "run_a12bc3",
  "session_id": "ses_7d4f9c",
  "status": "running",
  "started_at": "2026-09-02T11:43:02Z"
}

Attach files

Reference files that were prepared and uploaded in this session (see Prepare a file) when starting the run.

Request

{
  "input": {
    "prompt": "Summarize the attached case."
  },
  "attachments": [
    {
      "file_id": "file_b172c9"
    }
  ],
  "idempotency_key": "case-summary-run-v1"
}

Settlement-mode agents

For a settlement-mode agent, the first run in a new session must declare the work it serves. Use work.subject to open new work, or work.work_id to continue work opened by an earlier session; send either, never both. When opening work, contract_ref and contract_version may establish a contract and must be sent together. Later requests may omit the contract or restate that exact pair, but cannot add or change it. The admitted run includes settlement_work_id; store it if another session may need to continue the same work. Standard-mode agents do not require a work object. Durable work and settlement are tenant capabilities: for a version in settlement mode, an unavailable settlement boundary fails session activation rather than silently running without it.

Request

{
  "input": {
    "prompt": "Reconcile invoice INV-1842."
  },
  "work": {
    "subject": "invoice:INV-1842",
    "contract_ref": "billing/reconciliation",
    "contract_version": "2026-09"
  },
  "idempotency_key": "invoice-1842-attempt-1"
}

Response

{
  "id": "run_a12bc3",
  "session_id": "ses_7d4f9c",
  "status": "running",
  "started_at": "2026-09-02T11:43:02Z",
  "settlement_work_id": "work_f61ca9"
}