Reviewer requested identification of potential challenges and non-optimal descriptions in the proposed architecture doc.

Description fixes

• Hono: removed "edge-ready" claim — Socket.io requires a persistent Node.js http.Server; serverless/edge deployment is ruled out
• JWT: "stateless" applies only to access tokens; refresh tokens are Redis-stored for revocation
• AI routing: expanded from vague "Per-SDK calls" to explicit SDK list
• Package manager: resolved "npm or Bun" ambiguity → npm
• Drizzle pooling: Drizzle has no built-in pool; corrected to postgres.js driver / PgBouncer
• AI streaming: resolved "SSE or WebSocket" — SSE to requester, server relays chunks over Socket.io to room
• Model identifiers: pinned to versioned names (claude-sonnet-4-5) instead of informal aliases

Schema fixes

• users.avatar: NOT NULL → nullable; color gains a CHECK constraint
• versions.action: unvalidated free text → CHECK with defined enum values
• versions.message_id: ON DELETE CASCADE → ON DELETE SET NULL + snapshot TEXT column to preserve audit content on message deletion

Batch flush hardening

• Added token budget check before provider API call (prevents cryptic context-window errors at runtime)
• Wrapped AI call + DB write in a transaction (queued messages preserved on failure)

New section: Potential Challenges & Points to Notice (12 items)

• Hono + Socket.io wiring (must share raw http.Server)
• SSE → Socket.io fan-out relay design (per-token vs. buffered)
• Context window limits during flush (token counting required)
• Presence TTL (30 s) too close to heartbeat (20 s) → false disconnects; recommendation: 3× ratio
• Multi-instance presence race condition on reconnect
• Audit trail integrity when messages are hard-deleted
• last_activity requires trigger or careful application-level UPDATE
• OAuth/social login schema (provider, provider_id) must be planned from Phase 1
• WebSocket events unrate-limited (REST is; Socket.io is not)
• Shared types between src/ and server/ need npm workspaces from the start
• No unit/integration tests until Phase 6 E2E — testing added to earlier phases
• Free-text model column fragile against provider renames

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