Cohorts API

Base URL: /api/builder/v1. Authentication and X-Account-ID follow the existing Builder contract. Restrictive API keys require inference:execute.

Method	Path	Role	Notes
GET	/cohorts/capabilities?endpoint_id={uuid}	viewer	Effective endpoint capability; use this form in UI/client preflight.
GET	/cohorts/health	operator	Content-free aggregate registry/residency/fabric health and admissible capacity.
POST	/cohorts:plan	viewer	Read-only dry run.
POST	/cohorts:run	operator	Creates a durable root; supports Idempotency-Key.
GET	/tasks/{task_id}/cohort	viewer	Redacted summary.
GET	/tasks/{task_id}/cohort/events	viewer	Cursor JSON or SSE by Accept.
GET	/tasks/{task_id}/cohort/explanation	viewer	Redacted factors.
POST	/tasks/{task_id}/cohort:cancel	operator	Idempotent terminal cancellation.

Execution policy fields are mode, fallback, trace, max_members, latency_budget_ms and cost_budget_credits. The initial executable topology caps max_members at two even though future-compatible schemas may accept a higher server-bound value.

Cohort is opt-in and endpoint-scoped. It is currently admitted only for explicitly assigned causal/autoregressive text-generation LLM endpoints. Omitting execution continues to use Classic.

All errors use the stable Builder envelope. No endpoint returns raw intermediate representations or physical topology. Operational health contains counts and component booleans only: no node, model, container, peer or tenant identifiers.