Available twins

GET /twins returns the twins your organization can provision right now, with the scenarios each one publishes. The pages below describe what they model.

Resend

Email delivery, domains, keys, contacts and broadcasts. The conformance suite drives the twin through the official Resend Python SDK 2.41.0. Slug: resend

Area	Modelled
Emails	Single sends and batches of up to 100, retrieve and list with newest-first cursor pagination, schedule, reschedule, cancel, `html`, `text`, templates, CC, BCC, reply-to, tags, idempotent replay and rejection of reuse with a changed payload
Delivery	Queued, scheduled, sent, delivered, delayed, bounced, complained, opened, clicked and suppressed, moved by advancing
Domains	Create, retrieve, list, update, delete, simulated SPF and DKIM records, region and tracking settings, refusal of sends from an unverified custom domain, and asynchronous verification that completes on advance
API keys	Create, list, rename, revoke, full-access and sending-only permissions, bearer authentication, the required `User-Agent` header, and missing, invalid, restricted, revoked and rate-limited credentials
Contacts and segments	Contacts by id or email, names, subscription state, properties, topics, segment membership, segment CRUD, and the deprecated audiences API
Broadcasts	Draft CRUD, audience or segment targeting, immediate or scheduled sends, cancellation, and materialization into emails on advance

Scenarios: hard-bounce, spam-complaint, delayed-delivery, suppressed-contact, unverified-domain, rate-limited-key. Not modelled: webhooks, webhook events and webhook deliveries. Any route outside the table answers 501 in Resend’s error envelope.

Linear

Issue tracking through Linear’s GraphQL API. The conformance suite drives the twin through @linear/sdk 95.0.0, the only SDK Linear publishes. Slug: linear

Area	Modelled
Workspace	One organization, one team (`ENG`), three people including the one your key acts as, Linear’s six default workflow states, and labels with the duplicate-name refusal
Issues	Create, update, delete, archive and unarchive; read by id or identifier; title, description, priority, state, assignee, labels, due date and estimate with Linear’s own validators; server-computed `identifier`, `number`, `url`, `branchName`, `priorityLabel`, `sortOrder` and `boardOrder`; state-derived `startedAt`, `completedAt`, `canceledAt` and `autoArchivedAt`; `includeArchived`
Comments	Create, update, delete and read, `issueId` as an id or an identifier, `editedAt` on an edit, and the `url` Linear builds
Provider behavior	Linear’s error envelope, including which failures answer `200` with a `data: null` body; Relay connections read as `nodes` or `edges { cursor node }`, forwards and backwards
Authentication	A raw `lin_api_` key in `Authorization`, one `401` for missing, unknown and revoked keys, and the `400` Linear answers a key sent with a `Bearer` prefix

Every record the baseline creates carries the same identifier in every container, so a seed plan can name the team, its people, its states and its labels before any container exists. Records created afterwards get identifiers of the sandbox’s own. Advancing moves each open issue one step along its workflow: Backlog to Todo, Todo to In Progress, In Progress to Done, and a Done or Canceled issue to auto-archived. Scenarios: busy-team, completed-work, revoked-api-key. Not modelled: projects, milestones, initiatives, cycles, roadmaps, documents, attachments, reactions and templates; the organization query and workspace or team settings; webhooks, integrations, OAuth applications and agent sessions; issue relations, sub-issues and history; API-key management; and filter, orderBy or sort arguments. A refused argument is refused rather than ignored, so a caller never reads an issue as created the way it asked when it was not.

Two rules every twin keeps

A route or field a twin does not model is refused in the provider’s own error shape rather than filled in with something plausible, and CI proves the rest against the provider’s SDK. Read a refusal as the edge of the twin. See not modelled. Need a provider that is not here? Tell us at hi@twinbay.ai.

Getting Started

Concepts

Interfaces

Available twins

Resend

Linear

Two rules every twin keeps

​Resend

​Linear

​Two rules every twin keeps

Resend

Linear

Two rules every twin keeps