Flank API

Flank is the visual workflow editor for the brain-owned workflow engine. It does not expose an API of its own and it does not own workflow data — it is a client of brain’s HTTP workflow API. This page documents the brain endpoints flank consumes and how flank’s editor surface maps onto them.

For the canonical definitions of Workflow, Subworkflow, Node, Engine, Execution, and Contract, see the T-Bone glossary.

How flank consumes brain

Flank’s TanStack Start server functions call brain over HTTP for every workflow operation. The client lives in apps/flank/app/lib/brain-http-client.ts. The editor itself (ReactFlow canvas) never talks to brain directly — it goes through these server functions, which attach the caller’s Clerk session and forward to brain.

Brain authorizes workflow operations behind the ADMIN role. The human surfaces (flank, fennec) authenticate with a Clerk session against brain’s /workflow/* controllers; sirloin authenticates service-to-service against brain’s API-key “Beef” surface (@Controller('api/*')). Flank only uses the Clerk-session surface.

Operations flank uses

These are the brain workflow-engine operations flank’s server functions invoke. The authoritative request/response shapes live in brain; this is the editor’s view of them.

Operation	Purpose
List / get workflows	Populate the editor’s workflow list and load a graph for editing.
Save workflow (create / update draft)	Persist graph + input schema edits back to brain as a draft.
Get workflow contract	Read the input_schema / pricing / output_schema brain serves, to render and validate node configuration.
Publish workflow	Promote a draft to a numbered, immutable version that external executors may use.
Execute / sandbox a workflow	Run a draft as a test (sandbox) execution without a published version, or trigger a normal execution.
List / get executions	Read executions and their per-node traces (status, timing, inputs, outputs, errors) for the editor’s execution views.

Subworkflows are handled through the same workflow operations (a workflow pins a subworkflow version); nodes are edited as part of a workflow’s graph, not as standalone entities.

Editor surface

Flank’s own HTTP surface is the TanStack Start app on port 3100: the editor routes and the server functions behind them. It is consumed only by the browser-based editor, not by other services.

• apps/flank/app/routes/ — editor and execution routes (e.g. workflows.$id.tsx, executions.$id.tsx)
• apps/flank/app/components/flow/ — the ReactFlow editor (FlowEditor, NodePalette, NodeConfigPanel, nodes)
• apps/flank/app/lib/brain-http-client.ts — the brain HTTP client used by server functions
• apps/flank/app/lib/ — graph serialization and other client utilities

Legacy, being retired. Flank previously exposed a gRPC FlankExecutionService (running executions in its own in-process engine) and consumed a gRPC FlankStorageService implemented by sirloin (workflow/adapter/secret/execution CRUD), with an agentic FlankMCP tooling layer in sirloin. Those paths are superseded by brain’s HTTP API. Where any of that wiring still exists it is transitional and should not be built on. TODO(@law): remove the retired gRPC storage/execution/MCP wiring once no flow depends on it.

Source paths

• apps/flank/app/lib/brain-http-client.ts — brain HTTP client
• apps/flank/app/routes/ — editor + execution routes
• apps/flank/app/components/flow/ — ReactFlow editor
• apps/flank/app/lib/ — graph serializer and client utilities