The bottom composer now edits and reruns the current generation node while canvas-visible actions own downstream node creation. NewApiWG media normalization, video frame extraction, and node quick-add keep generated media flows explicit and connected rather than hidden behind the prompt box.
Constraint: Composer must not call providers directly or create hidden downstream branches when a node is selected
Constraint: NewApiWG video families use inconsistent media schemas, so common media aliases are normalized in the provider adapter
Rejected: Let the bottom composer create next-step nodes from selected outputs | hides graph mutation and conflicts with the PRD source-of-truth rules
Rejected: Put NewApiWG model-family payload rules in the composer | provider-specific schemas would leak into UI state
Confidence: high
Scope-risk: moderate
Directive: Keep provider payload normalization in provider/executor layers; do not move it into GenerationComposer
Tested: npm run test:run -- src/components/__tests__/GenerationComposer.test.tsx
Tested: npm run test:run -- src/components/__tests__/WorkflowCanvas.test.tsx
Tested: npm run test:run -- src/components/__tests__/GenerateVideoNode.test.tsx
Tested: npm run test:run -- src/app/api/generate/providers/__tests__/newapiwg.test.ts src/app/api/generate/__tests__/route.test.ts
Tested: npm run test:run -- src/store/execution/__tests__/videoProcessingExecutors.test.ts
Tested: npm run build
Not-tested: npm run lint fails because next lint is incompatible with the current Next 16 script configuration