Coasty Sessions API

openapi: 3.2.0
info:
  title: Coasty Public Sessions API
  version: 1.0.0
  summary: Computer Use Agents, scheduled automation, and managed VMs.
  description: '# Coasty Public API


    Coasty is a Computer Use Agent (CUA) platform: predict actions from screenshots,

    provision managed VMs, and run scheduled automation against them. ## Authentication


    All endpoints (except `/v1/triggers/webhook/{webhook_id}` and health checks) require an API key. Pass it as either:


    - `X-API-Key: sk-coasty-live-...` (or `sk-coasty-test-...` for sandbox)

    - `Authorization: Bearer sk-coasty-live-...`


    The external webhook endpoint does not use an API key, but it is authenticated:

    send the HMAC-SHA256 `Coasty-Signature` credential documented on that operation. Test-mode keys (`sk-coasty-test-*`) preserve the same core schemas for documented

    sandbox-supported operations and never debit Coasty credits. With a test Coasty key,

    explicit BYOK is provider-direct only for the direct CUA flow: `POST /v1/predict`,

    `POST /v1/ground`, `POST /v1/sessions`, and `POST /v1/sessions/{id}/predict`. Predict, ground, and session create require an explicit per-request X-LLM-Api-Key plus

    X-LLM-Provider under test auth. A body provider without that header returns 422

    LLM_KEY_NOT_CONFIGURED: Stored provider keys are unavailable for test API keys. Send

    X-LLM-Api-Key explicitly for direct BYOK. Test auth never reads or uses a stored live provider

    key. Session create fixes that explicit key for

    inherited predicts but makes no inference call. Predict, ground, and session predict can bill

    the supplied provider account. Managed-mode Task runs, Workflow runs, and schedules remain

    deterministic sandbox. BYOK intent on those async endpoints returns 422

    LLM_PROVIDER_UNSUPPORTED before execution: BYOK is unavailable for synthetic test runs,

    workflows, and schedules. Use managed mode or a live Coasty API key. They never decrypt or

    require a stored provider key and do not call or bill Anthropic/OpenAI. Live-only stored BYOK-key access or mutation is unavailable to test keys. Keep real provider

    secrets out of sandbox and CI requests, and use a live Coasty key for real async execution. ## Pricing & budgeting


    Published base rates and defaults (read effective deployed CUA/task pricing at

    `GET /v1/models` → `pricing`, and machine runtime pricing at `GET /v1/machines/pricing`):


    | Endpoint | Credits |

    |---|---|

    | `POST /v1/predict` | Managed: 5 base; BYOK: 0 |

    | `POST /v1/sessions` | Managed: 10 fixed; BYOK: 0 |

    | `POST /v1/sessions/{id}/predict` | Managed: 4 base; BYOK: 0 |

    | `POST /v1/ground` | Managed: 3 base; BYOK: 0 |

    | `POST /v1/parse` | 0 (free) |


    Predict and session-predict can add provider-visible trajectory-image, HD current/trajectory

    image, v1-engine, and combined system_prompt + trimmed-instructions (>500 chars) surcharges. Ground can add only the current-image HD surcharge; session creation has no surcharge. Managed-model published defaults: scheduled CUA execution bills the consumer subscription-credit balance

    at 10 credits/minute with a 20-credit start minimum for non-Unlimited accounts. Unlimited

    bypasses that runtime credit meter/start gate but retains token and concurrency safeguards. Managed schedule create/run-now use a $0.20 API-wallet eligibility gate. BYOK schedules

    bypass that gate and the runtime credit meter and debit zero Coasty platform credits. Live-key schedule execution is provider-billed. Managed-mode test execution is deterministic sandbox; test-auth BYOK intent returns 422 LLM_PROVIDER_UNSUPPORTED. Read `GET /v1/models` →

    `pricing.schedules` for effective values, plan applicability, and webhook policy. Your subscription tier (`free | starter | professional | enterprise`) is

    reported on the key, but the developer API is PREPAID: what bounds you is your

    credit balance, not your plan. Custom prompts in particular are NOT tier-gated. `system_prompt` and `instructions` are available on every tier including free,

    against a budget of 32,000 characters SHARED between the two fields (the sum is

    measured, and exceeding it returns 400 INPUT_TOO_LARGE).'
  contact:
    name: Coasty Developer Support
    url: https://coasty.ai/support
    email: founders@coasty.ai
  license:
    name: MIT
    identifier: MIT
  termsOfService: https://coasty.ai/terms
servers:
- url: https://coasty.ai
  description: Production
- url: https://coasty.ai
  description: Sandbox — use sk-coasty-test-* keys against the same host. No Coasty billing. Explicit-header BYOK can call the provider only for predict, ground, and inherited session predict; session create fixes the header key without inference, and test auth never reads a stored live key. Managed-mode Tasks, Workflows, and schedules remain deterministic sandbox. BYOK intent on those async endpoints returns 422 LLM_PROVIDER_UNSUPPORTED before execution and makes no provider call.
security:
- apiKey: []
- bearerAuth: []
tags:


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# Full source: https://raw.githubusercontent.com/api-evangelist/coasty/refs/heads/main/openapi/coasty-sessions-api-openapi.yml