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# Preview trace-to-eval capture for a run

GET https://api.runtype.com/v1/eval/executions/{executionId}/capture-preview

Dry-run of POST /eval/suites/\{id}/cases/from-execution: reconstructs the agent execution exactly as capture would (same reader, same message math) and returns its recorded actions with the fork index each one maps to, plus whether the case would be fully replayable. Reads only — nothing is written. Restricted to agent executions the caller owns.

Reference: https://docs.runtype.com/api-reference/runtype-api/evals/preview-trace-to-eval-capture-for-a-run

## Authentication

- `Authorization` header (bearer token, required) — API key or Clerk session token

## Servers

- `https://api.runtype.com` (Production, default)
- `https://api.runtype-staging.com` (Staging)

## Request

### Path parameters

- `executionId` (string, required)

## Response

### 200

Capture preview

- `actions` (list of CaptureExecutionPreviewAction, required) — The recorded tool-call actions in invocation order — the fork-picker rows.
- `defaultForkMessageIndex` (integer, required) — The fork the server uses when `forkMessageIndex` is omitted: just before the last recorded action, or the end of the seed for a run with no tool calls.
- `executionId` (string, required)
- `messageCount` (integer, required) — Length of the full reconstructed history (seed messages + one call/result pair per action).
- `replayable` (boolean, required) — True when every recorded tool output would be captured in full (nothing truncated).

## Errors

### 400 Bad Request Error

Invalid request

- `error` (string, required)
- `code` (string, optional) — Stable error code. `insufficient_scope` marks an API key that lacks a scope this request needs.
- `details` (list of ErrorDetailsItems, optional)
- `requiredScopes` (list of string, optional) — On `insufficient_scope`: every API key scope this request needs.

### 401 Unauthorized Error

Unauthorized

- `error` (string, required)
- `code` (string, optional) — Stable error code. `insufficient_scope` marks an API key that lacks a scope this request needs.
- `details` (list of ErrorDetailsItems, optional)
- `requiredScopes` (list of string, optional) — On `insufficient_scope`: every API key scope this request needs.

### 403 Forbidden Error

Forbidden

- `error` (string, required)
- `code` (string, optional) — Stable error code. `insufficient_scope` marks an API key that lacks a scope this request needs.
- `details` (list of ErrorDetailsItems, optional)
- `requiredScopes` (list of string, optional) — On `insufficient_scope`: every API key scope this request needs.

### 404 Not Found Error

Not found

- `error` (string, required)
- `code` (string, optional) — Stable error code. `insufficient_scope` marks an API key that lacks a scope this request needs.
- `details` (list of ErrorDetailsItems, optional)
- `requiredScopes` (list of string, optional) — On `insufficient_scope`: every API key scope this request needs.

### 500 Internal Server Error

Internal server error

- `error` (string, required)
- `code` (string, optional) — Stable error code. `insufficient_scope` marks an API key that lacks a scope this request needs.
- `details` (list of ErrorDetailsItems, optional)
- `requiredScopes` (list of string, optional) — On `insufficient_scope`: every API key scope this request needs.

## Types

### CaptureExecutionPreviewAction

- `forkMessageIndex` (integer, required) — Pass this as `forkMessageIndex` on the capture request to make THIS action the graded next step (the history is frozen just before it).
- `toolName` (string, required)
- `input` (any, optional) — Recorded call input (pattern-scrubbed).
- `isError` (boolean, optional) — True when the recorded call failed (its output is the error payload).
- `truncated` (boolean, optional) — True when the recorded output was capped at capture; makes the case partially replayable.

### ErrorDetailsItems

- `message` (string, required)
- `code` (string, optional) — Stable Runtype validation code (e.g. MISSING_REQUIRED_FIELD, INVALID_ENUM).
- `path` (string, optional) — Dotted JSON path to the offending field.
- `suggestion` (string, optional) — Actionable hint (allowed values, accepted range, …).

## Examples

**Response**

```json
{
  "actions": [
    {
      "forkMessageIndex": 1,
      "toolName": "string",
      "input": null,
      "isError": true,
      "truncated": true
    }
  ],
  "defaultForkMessageIndex": 1,
  "executionId": "string",
  "messageCount": 1,
  "replayable": true
}
```

**SDK Code**

```python
import requests

url = "https://api.runtype.com/v1/eval/executions/executionId/capture-preview"

headers = {"Authorization": "Bearer <token>"}

response = requests.get(url, headers=headers)

print(response.json())
```

```javascript
const url = 'https://api.runtype.com/v1/eval/executions/executionId/capture-preview';
const options = {method: 'GET', headers: {Authorization: 'Bearer <token>'}};

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"
	"net/http"
	"io"
)

func main() {

	url := "https://api.runtype.com/v1/eval/executions/executionId/capture-preview"

	req, _ := http.NewRequest("GET", url, nil)

	req.Header.Add("Authorization", "Bearer <token>")

	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.runtype.com/v1/eval/executions/executionId/capture-preview")

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

request = Net::HTTP::Get.new(url)
request["Authorization"] = 'Bearer <token>'

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.get("https://api.runtype.com/v1/eval/executions/executionId/capture-preview")
  .header("Authorization", "Bearer <token>")
  .asString();
```

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

$client = new \GuzzleHttp\Client();

$response = $client->request('GET', 'https://api.runtype.com/v1/eval/executions/executionId/capture-preview', [
  'headers' => [
    'Authorization' => 'Bearer <token>',
  ],
]);

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

```csharp
using RestSharp;

var client = new RestClient("https://api.runtype.com/v1/eval/executions/executionId/capture-preview");
var request = new RestRequest(Method.GET);
request.AddHeader("Authorization", "Bearer <token>");
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = ["Authorization": "Bearer <token>"]

let request = NSMutableURLRequest(url: NSURL(string: "https://api.runtype.com/v1/eval/executions/executionId/capture-preview")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "GET"
request.allHTTPHeaderFields = headers

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()
```