Project 6 — LangGraph agent

Requirements

Convert the assistant into an explicit state graph, add durable progress, clarification/approval pauses, and safe resume.

Architecture

Router node → read/search or draft nodes → review → validated continuation → response. State and transitions are inspectable.

Technologies

TypeScript LangGraph, compatible schemas, supported durable checkpointer, safe business services, stream event projection.

Database design

Run ownership/version, checkpoint reference, immutable draft, pending review event, and authenticated decision record.

API design

Start/status/resume routes; require ownership and current pending event on resume.

AI design

Model nodes handle intent and language; deterministic nodes handle permissions, validation, review routing, and budget enforcement.

Security

Server-controlled identity, restricted graph tools, exact draft approval, safe state streams, and idempotent effects.

Evaluation

Worker restart, concurrent thread requests, replay, duplicate resume, rejected approval, and versioned pending runs.

Observability

Node timings, state transitions, checkpoint errors, pause age, resumed outcomes, and linked traces.

Deployment

Durable store, deployment draining/migration plan, serialized per-thread writes, rollback compatible with pending state.

Interview questions

• “Why LangGraph?” Answer: explicit state, branching, and recovery.
• “What repeats after interrupt?” Answer: the interrupted node can restart, so isolate side effects and use idempotency.

Acceptance: A restarted worker resumes an authorized task without duplicate external effects.