# Implementation Plan: Gradio Agent Chat (LangGraph)

**Branch**: `033-gradio-agent-chat` | **Date**: 2026-06-08 | **Spec**: `spec.md`

## Summary

Gradio agent backend + Svelte frontend via `@gradio/client submit()`. LangGraph `create_react_agent()` + `interrupt()`/`Command(resume=...)` + `PostgresSaver` + `RunnableWithMessageHistory`. Structured JSON metadata streaming. No REST confirmations, no custom WebSocket.

## Technical Context

**Language**: Python 3.9+/TypeScript Svelte 5 runes
**Key Dependencies**: gradio>=5.0, langgraph>=0.2, langchain-core>=0.3, langchain-openai>=0.3, langgraph-checkpoint-postgres, pdfplumber, openpyxl (back); @gradio/client (front)
**Storage**: PostgreSQL 16 (persistence + checkpoints via langgraph-checkpoint-postgres)
**Testing**: pytest (back), vitest L1 model + L2 UX (front)
**Frontend**: SvelteKit SPA, model-first (AgentChatModel.svelte.ts C4), runes-only
**Performance**: First token <1.5s, streaming 60fps, file upload ≤10MB

## Constitution Check — Passed

All 8 principles satisfied: semantic contracts, decision memory, external orchestrator, module discipline, RBAC, Svelte 5 runes, test-driven C3+, attention-optimized.

## Project Structure

### New/Changed Files
```
backend/src/agent/         — app.py, langgraph_setup.py, tools.py, middleware.py, document_parser.py
backend/src/api/routes/    — agent_conversations.py, auth.py
backend/src/models/        — agent.py
backend/src/schemas/       — agent.py
frontend/src/lib/models/   — AgentChatModel.svelte.ts (rewritten)
frontend/src/lib/components/assistant/ — ConversationList, ToolCallCard, ConfirmationCard, ConnectionIndicator
frontend/src/routes/agent/ — +page.svelte
frontend/src/types/        — agent.ts
docker/                    — Dockerfile.agent, docker-compose.yml updated, nginx.conf updated
```

## Deprecated
`backend/src/api/routes/assistant/_tool_registry.py` → `@DEPRECATED` Tombstone (FR-022).
#endregion (plan summary)