Developer Platform

Extensible container services

Add custom code in an isolated container, then expose it through declared endpoints the BuildWithHQ runtime can safely invoke.

Visual builders are fast until a developer needs something the platform did not predict. BuildWithHQ's container model is the escape hatch: write the custom service you need, then expose its useful behavior through a small, declared endpoint contract.

The container does not replace the platform

Custom code reaches platform-managed application records through the BuildWithHQ gateway. The gateway validates the caller and endpoint permission, sends the approved payload to the container service, validates the response contract, and records the invocation outcome.

Endpoint manifest

Each exposed service endpoint can declare:

• a stable endpoint key;
• HTTP method and private route;
• input and output JSON schemas;
• required permission key;
• sync or asynchronous execution mode;
• timeout and payload limits; and
• whether outbound network access is sealed or restricted to an allowlist.

{
  "endpointKey": "company.enrich",
  "method": "POST",
  "route": "/v1/company/enrich",
  "executionMode": "sync",
  "requiredPermission": "records.write",
  "inputSchema": {},
  "outputSchema": {}
}

Invocation path

POST /v1/apps/{saasAppId}/services/{serviceKey}/endpoints/{endpointKey}:invoke

1. A page, workflow, REST action, or MCP tool requests the endpoint by stable key.
2. The platform resolves the installed endpoint and verifies license/health state.
3. Authorization and disclosure checks run before dispatch.
4. The gateway invokes the private container route.
5. The response is validated, safe output is returned, and the invocation result is recorded.

Why this matters

Developers get normal code and normal libraries when they need them, while the application retains one permission model and one orchestration layer. You do not have to choose between the speed of a visual builder and the freedom of custom architecture.

For the builder-side package and deployment model, see Appliances and endpoints and Container and Postgres.

Public service contracts use the BuildWithHQ gateway. Private container addresses remain internal, while the gateway applies authorization, schemas, rate limits, and auditing.