> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://onepin.ai/docs/reference/api-reference/workflows/runs/start/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://onepin.ai/_mcp/server.

# Start Run

POST https://api.onepin.ai/api/v1/workflows/{workflow_id}/runs
Content-Type: application/json

Start a new execution of a workflow (202 Accepted).

Enqueues the workflow for asynchronous execution and returns the newly
created run in `pending` or `running` status. The run progresses through
its nodes in the background; poll `GET /runs/{run_id}/status` for
lightweight progress updates, or `GET /runs/{run_id}` once to load the
immutable definition snapshot.

The optional request body supplies run-scoped inputs: `script_text`
(and optionally `source_language`) replaces the source\_script text for
THIS run's snapshot only — the stored workflow definition is not
modified, so concurrent runs with different scripts cannot race.
Requires exactly one source\_script node (422 otherwise).

Use `POST /runs/preview` or `POST /estimate` to compute the credit cost
before committing to an actual run — those endpoints are read-only and
incur no charges.

Returns 409 if the workspace is at its concurrent-run limit or another
run for this workflow is already active.

Requires at least `editor` role in the workspace; viewers cannot run workflows.

Reference: https://onepin.ai/docs/reference/api-reference/workflows/runs/start

## Authentication

- `Authorization` header (bearer token, required) — Clerk JWT token
- `Authorization` header (bearer token, required) — Onepin live API key (`op_live_...`). Test and public keys are reserved in Phase 1.

## Servers

- `https://api.onepin.ai` (prod, default)
- `https://dev-api.onepin.ai` (dev)

## Request

### Path parameters

- `workflow_id` (string, required)

### Headers

- `X-Workspace-Id` (string, optional, nullable)

### Body (application/json)

This endpoint expects a WorkflowRunStartIn.

- `script_text` (string, optional, nullable) — Run this workflow with this script text instead of the text saved in the workflow's source_script node. Applied to the run's definition snapshot only.
- `source_language` (string, optional, nullable) — BCP-47 language of script_text (e.g. en-us). Optional; when omitted the saved source_language (or automatic detection) applies.

## Response

### 202

Successful Response

- `data` (WorkflowRunOut, required)
- `meta` (Meta, required)

## Errors

### 422 Unprocessable Entity Error

Validation Error

- `detail` (list of ValidationError, optional)

## Types

### WorkflowRunOut

- `id` (string, required)
- `workflow_id` (string, required)
- `status` (string, required)
- `run_number` (integer, required)
- `token_cost` (integer, required)
- `created_at` (datetime, required)
- `updated_at` (datetime, required)
- `total_nodes` (integer, optional, default: 0)
- `total_steps` (integer, optional, default: 0)
- `finished_steps` (integer, optional, default: 0)
- `finished_nodes` (integer, optional, default: 0) — Graph nodes that have reached a terminal state, judged by each node's highest-iteration step, so a retried node counts once. Pair with total_nodes for 'N of M completed'. A node interrupted by an automatic pause does NOT count while parked (its step is cancelled with a hard recovery checkpoint and is reopened in place on resume), so that kind of pause neither inflates the count nor drops it on resume. A partial-recovery resume schedules a NEW iteration for the node, so the count can drop by one until that iteration finishes. finished_steps counts rows and never excludes the parked row.
- `held_nodes` (list of HeldNodeOut, optional, nullable) — Nodes the run is parked in front of, each with the locales it will process. Meaningful while status == 'paused'; cleared to null on resume and RETAINED on a run cancelled while paused. Null (never []) also means never computed: a run paused before this field shipped, or one parked straight from 'pending'. [] means it WAS computed and nothing is held. Excludes nodes skipped by an upstream discard and a node interrupted mid-execution by an automatic pause (that one is visible as its own cancelled step).
- `usage_summary` (map from string to any, optional)
- `started_at` (datetime, optional, nullable)
- `completed_at` (datetime, optional, nullable)
- `pause_requested_at` (datetime, optional, nullable)
- `paused_at` (datetime, optional, nullable)
- `paused_ms` (integer, optional, default: 0)
- `pause_reason` (enum, optional, nullable) — Why the run is paused or draining toward an automatic pause. Manual pauses use user; null when no pause is active.
  - Allowed values: `user`, `provider_outage`, `provider_rate_limited`, `provider_billing`, `node_timeout`
- `pause_error` (string, optional, nullable) — Aggregate customer-facing explanation for an automatic pause. Null for manual pauses and separate from terminal error.
- `error` (string, optional, nullable)
- `has_export` (boolean, optional, default: false)
- `triggered_by` (TriggeredByOut, optional, nullable) — Actor that triggered a workflow run. ``user_name`` is guaranteed non-empty: derived from ``donut.utils.user.user_display_name`` which falls back to ``email`` when both first/last names are empty (``email`` is NOT NULL on User).
- `credits` (integer, optional, default: 0) — Credits debited from the user's spendable balance for this run; excludes invoiced overage.

### Meta

- `request_id` (string, required)
- `timestamp` (datetime, required)

### ValidationError

- `loc` (list of ValidationErrorLocItems, required)
- `msg` (string, required)
- `type` (string, required)
- `input` (any, optional)
- `ctx` (ValidationErrorCtx, optional)

### HeldNodeOut

One node the run is parked in front of — it has no step row yet.

- `node_id` (string, required)
- `locales` (list of string, optional) — Locales of the lines this node will process once the run resumes. Empty means render no language line.

### TriggeredByOut

Actor that triggered a workflow run. ``user_name`` is guaranteed non-empty: derived from ``donut.utils.user.user_display_name`` which falls back to ``email`` when both first/last names are empty (``email`` is NOT NULL on User).

- `user_id` (string, required)
- `user_name` (string, required)

### ValidationErrorLocItems

### ValidationErrorCtx

## Examples

**Request**

```json
{}
```

**Response**

```json
{
  "data": {
    "id": "string",
    "workflow_id": "string",
    "status": "string",
    "run_number": 1,
    "token_cost": 1,
    "created_at": "2024-01-15T09:30:00Z",
    "updated_at": "2024-01-15T09:30:00Z",
    "total_nodes": 0,
    "total_steps": 0,
    "finished_steps": 0,
    "finished_nodes": 0,
    "held_nodes": [
      {
        "node_id": "string",
        "locales": [
          "string"
        ]
      }
    ],
    "usage_summary": {},
    "started_at": "2024-01-15T09:30:00Z",
    "completed_at": "2024-01-15T09:30:00Z",
    "pause_requested_at": "2024-01-15T09:30:00Z",
    "paused_at": "2024-01-15T09:30:00Z",
    "paused_ms": 0,
    "pause_reason": "user",
    "pause_error": "string",
    "error": "string",
    "has_export": false,
    "triggered_by": {
      "user_id": "string",
      "user_name": "string"
    },
    "credits": 0
  },
  "meta": {
    "request_id": "string",
    "timestamp": "2024-01-15T09:30:00Z"
  }
}
```

**SDK Code**

```python
import requests

url = "https://api.onepin.ai/api/v1/workflows/workflow_id/runs"

payload = {}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.json())
```

```javascript
const url = 'https://api.onepin.ai/api/v1/workflows/workflow_id/runs';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{}'
};

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

```go
package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.onepin.ai/api/v1/workflows/workflow_id/runs"

	payload := strings.NewReader("{}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby
require 'uri'
require 'net/http'

url = URI("https://api.onepin.ai/api/v1/workflows/workflow_id/runs")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{}"

response = http.request(request)
puts response.read_body
```

```java
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api.onepin.ai/api/v1/workflows/workflow_id/runs")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{}")
  .asString();
```

```php
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api.onepin.ai/api/v1/workflows/workflow_id/runs', [
  'body' => '{}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

echo $response->getBody();
```

```csharp
using RestSharp;

var client = new RestClient("https://api.onepin.ai/api/v1/workflows/workflow_id/runs");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = [] as [String : Any]

let postData = JSONSerialization.data(withJSONObject: parameters, options: [])

let request = NSMutableURLRequest(url: NSURL(string: "https://api.onepin.ai/api/v1/workflows/workflow_id/runs")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```

> Onepin is a voice workflow platform that orchestrates, validates, and ships production-ready audio across 33 TTS models.