[bitifirefly]

Changes

• Reuse the product chat input and message components for Dify and LangChain.
• Isolate drafts, attachments, navigation and late streaming callbacks.
• Share server-side moderation, quota reservation, admission and submission identity.
• Keep each backend's existing sole history writer; add an additive governance migration.

Validation

• Full Jest, root/API/shared types, changed-file quality checks, architecture guards and production builds completed in the pinned development toolchain.
• Isolated PostgreSQL fresh/upgrade, strict RLS, quota races and legacy-run compatibility; actual LangChain two-turn/tool/history regression.
• Stage production-mode acceptance follows develop integration.

Deployment

Apply the additive governance migration before updating API and Web together. Existing browser tabs must refresh. No production deployment or release is included.