> ## Documentation Index > Fetch the complete documentation index at: https://docs.judt.ai/llms.txt > Use this file to discover all available pages before exploring further. # Create a preview link > Returns a short-lived URL that opens the sandbox's dev server in a browser. The request starts the dev server if it isn't running, and waits for it to serve the sandbox's current files, including a rebuild that a recent change started. If the dev server can't build or start the App, the request returns `422 preview_failed`, and `detail` has the dev server's output from that build. After a change breaks a rebuild, the dev server keeps serving the previous build, but the request still returns `422` until the App builds again. To check the App after a change, call this endpoint, then read its logs with `GET /api/apps/{id}/logs`. ## OpenAPI ````yaml /api-reference/openapi.json post /api/apps/{id}/preview openapi: 3.1.0 info: title: Judt API version: 1.0.0 description: >- The Judt API creates and runs Apps. Each App has a sandbox, where you and agents edit and run its source, and a production deployment that serves it. ## Authentication Send an API token or an OAuth access token in the `Authorization` header. - **API token:** send it as a bearer token. A token belongs to one organization, and you create and revoke tokens in the dashboard. A token scoped to one App can reach only that App. An organization-wide token can also create a short-lived token for one App with `POST /api/tokens`, to give to an agent or an MCP client. - **OAuth access token:** an agent gets one when a person approves its access to one organization, so the person never handles a token. Reads need the `apps:read` scope, and changes need `apps:write`. To register and sign in, follow https://judt.ai/auth.md. Send the token as a bearer token, or with a DPoP proof if it's bound to a DPoP key. One access token can work on both this API and the MCP server at https://api.judt.ai/mcp. ## Sandboxes Creating an App reserves its address, but it doesn't start a sandbox or publish anything. There's no endpoint to start a sandbox. A request that needs the sandbox starts it first, so the first request after the sandbox goes idle takes longer. Files, Git, commands, commits, restores, previews, and deployments all need the sandbox. The sandbox stops on its own when it's idle. If `sandbox_status` is `failed`, the most recent start failed, and the API retries it while the sandbox is needed. ## Pagination A list returns one page at a time, in the form `{"results": [...], "has_more": true, "next_cursor": "CURSOR"}`. To get the next page, list again with `cursor` set to `next_cursor`, and the same `sort` and filters. Results that arrive while you page don't shift your pages. On the last page, `has_more` is `false`, and `next_cursor` still finds results added later. ## Retries A request that creates, changes, or deletes something returns `200` after the work is done, with the resource as it is afterward. To retry a request safely, send an `Idempotency-Key` header. For 30 days, a retry with the same key and input returns the first request's result instead of repeating the work. If you don't send a key, the API generates one and returns it in the `Idempotency-Key` response header. Setting and deleting a Secret take no key, because repeating them changes nothing. A visitor token or a preview link is created fresh each time, because nothing is stored to repeat. The API records file writes and deletes, commands, commits, and restores before it runs them. The response status tells you what to do next: - `503` or `504`: the action is recorded but not finished. To get its result, retry with the same key. A new key would run the action again. - `4xx` or `502`: the result is final. A retry with the same key returns the same response. A `504 request_timeout` response says how far the work got and which event to check. The work continues, and a retry with the same key picks it up. ## Troubleshooting To see what happened to an App's sandbox, deployments, and deletion, list its events with `GET /api/apps/{id}/events`. To see what the App's code did, including requests, output, exceptions, and failed builds, list its logs with `GET /api/apps/{id}/logs`. ## Time limits Requests have the following time limits: - Stopping the sandbox: 120 seconds. - File writes, commits, and restores: 120 seconds. - Commands: the command's `timeout_seconds`, up to 120 seconds, plus 60 seconds to stop it and save its result. - Publishing, unpublishing, deleting an App, and changing production settings: 540 seconds, including any sandbox start. If a file write, commit, restore, or command has to start the sandbox, it gets up to 120 more seconds. ## Errors An error returns a JSON body in the form `{"error": {"code": "CODE", "message": "MESSAGE", "detail": "DETAIL", "request_id": "REQUEST_ID"}}`. The `code` value is stable, so check it rather than `message`. The `detail` value is optional. When a parameter or a body field isn't valid, the request returns `400 invalid_request`, `message` names the field, and `detail` lists every problem if there's more than one. When the server rejects a credential, it returns a JSON error body and sets the `WWW-Authenticate` header. A `401` response includes the `resource_metadata` URL in `WWW-Authenticate` (RFC 9728): | Status | Error code / header | Cause | Action | |---|---|---|---| | `401` | `unauthenticated` | The request has no credential, or the API token or OAuth access token is invalid, expired, or revoked. | Send a valid API token or OAuth access token. | | `401` | `invalid_token` | `WWW-Authenticate` error when an API token or OAuth access token is expired, revoked, or issued for a different `resource` audience. | Refresh the access token, or request a token for the target server. | | `401` | `invalid_dpop_proof` | The `DPoP` proof header is missing, expired, replayed, or signed for a different HTTP method or URL. | Create a new DPoP proof for the request method and URL. | | `403` | `insufficient_scope` | The OAuth token does not have the required scope (`apps:read` or `apps:write`). | Request authorization with the scope named in `WWW-Authenticate`. | | `403` | `app_scoped_token` | An App-scoped API token called `POST /api/apps` or `POST /api/tokens`. | Use an organization-wide API token. | | `403` | `api_token_required` | An OAuth access token called `POST /api/tokens`. | Use an organization-wide API token. | | `403` | `sign_in_required` | A Personal Agent Session Token was used before the user signed in or after the user signed out. | Tell the user to sign in to the Session. | | `403` | `forbidden` | Your organization role (`member`) does not allow this action. | Ask an organization `owner` or `admin` to do the action. | servers: - url: https://api.judt.ai security: [] tags: - name: Account description: >- See who a credential acts for: the person, the organization, and what the credential can reach. - name: Apps description: Create, update, and delete Apps, and control who can reach them. - name: Tokens description: >- Create short-lived API tokens that reach one App, to give to an agent or an MCP client. - name: Secrets description: >- Store values, such as API keys, that an App reads at runtime. Responses never include Secret values. - name: Files description: Read and write the source files in an App's sandbox. - name: Sandbox description: >- Run commands, use Git, commit and restore source, and preview the App's sandbox. - name: Deployments description: Publish an App's source to production, and take it offline. - name: Monitoring description: See what happened to an App, and what its code did. - name: Templates description: The starting points for new Apps. - name: Agents description: >- Work with the in-product coding agent: sessions, turns, events, and the models it runs on. The agent itself works only through this API. - name: Feedback description: Tell the Judt team about bugs, friction, and anything else. paths: /api/apps/{id}/preview: post: tags: - Sandbox summary: Create a preview link description: >- Returns a short-lived URL that opens the sandbox's dev server in a browser. The request starts the dev server if it isn't running, and waits for it to serve the sandbox's current files, including a rebuild that a recent change started. If the dev server can't build or start the App, the request returns `422 preview_failed`, and `detail` has the dev server's output from that build. After a change breaks a rebuild, the dev server keeps serving the previous build, but the request still returns `422` until the App builds again. To check the App after a change, call this endpoint, then read its logs with `GET /api/apps/{id}/logs`. operationId: create_preview parameters: - name: id in: path required: true description: A unique ID that starts with `app_`. schema: type: string pattern: ^app_[0-9A-Za-z]{24}$ example: app_Zj7XhMgplmTJcp5Dk4vcYuk0 - name: Idempotency-Key in: header required: false description: >- A key for this request, up to 200 printable characters. The request stores nothing, so a retry makes a new one whatever the key; the API returns the key in the `Idempotency-Key` response header. schema: type: string minLength: 1 maxLength: 200 responses: '200': description: The preview link. headers: Idempotency-Key: schema: type: string description: >- The key this request ran under: the one you sent, or one the API generated. To pick up the work after a timeout, retry with this key. content: application/json: schema: $ref: '#/components/schemas/PreviewResult' '400': $ref: '#/components/responses/Error' '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' '404': $ref: '#/components/responses/Error' '410': $ref: '#/components/responses/Error' '422': description: >- - `preview_failed`: the dev server can't build or start the App. `detail` has its output from that build. Change the source, then retry. content: application/json: schema: $ref: '#/components/schemas/Error' '429': $ref: '#/components/responses/Error' '502': description: >- The sandbox returned a response that the API can't use, such as `sandbox_incompatible` or `helper_output_too_large`. Retrying doesn't change the result. content: application/json: schema: $ref: '#/components/schemas/Error' '503': $ref: '#/components/responses/Error' '504': $ref: '#/components/responses/Error' security: - ApiToken: [] - OAuth: - apps:write - DPoP: - apps:write components: schemas: PreviewResult: $schema: https://json-schema.org/draft/2020-12/schema type: object properties: url: type: string format: uri description: A URL that opens the sandbox's dev server. expires_at: type: string format: date-time description: When the URL stops working. example: '2026-10-03T14:01:30.000Z' required: - url - expires_at additionalProperties: false Error: type: object required: - error properties: error: type: object required: - code - message - request_id properties: code: type: string description: A stable code for the error, such as `not_found`. message: type: string description: A readable explanation of the error. detail: type: string description: >- More information, if any: the sandbox's error, a provider message, or, for a `504`, how far the work got and the ID of its latest event. request_id: type: string description: The request's ID. Include it when you contact support. responses: Error: description: An error, with its code and the request ID. content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: ApiToken: type: http scheme: bearer description: >- An API token for one organization. You create and revoke tokens in the dashboard. A token scoped to one App can reach only that App, so give that kind of token to an agent. An organization-wide token can create a short-lived one with `POST /api/tokens`. OAuth: type: oauth2 description: >- An OAuth access token for one person and organization, sent as a bearer token. https://judt.ai/auth.md describes the ways an agent can get one. Request the resource https://api.judt.ai, and also https://api.judt.ai/mcp to use the same token on the MCP server. The person's role still applies. flows: authorizationCode: authorizationUrl: https://judt.ai/api/auth/oauth2/authorize tokenUrl: https://judt.ai/api/auth/oauth2/token refreshUrl: https://judt.ai/api/auth/oauth2/token scopes: apps:read: >- See the organization's Apps, with their files, deployments, and logs. apps:write: >- Change the organization's Apps: edit files, run commands, deploy, and manage Secrets. DPoP: type: http scheme: DPoP description: >- An OAuth access token bound to a DPoP key (RFC 9449), sent with a DPoP proof. A token request with a DPoP proof gets one, and a Personal Agent Protocol Session Token is one: a Personal Agent starts at https://judt.ai/.well-known/poppy.json. Scopes are the same as for OAuth. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.