ADR 001: Defer LangGraph Runtime

Status: Accepted (defer LangGraph) Date: 2026-05-12

Update (2026-06-01): The RIG hard-cut (#696) retired the in-process /v1/tasks/* path on the agent service. Agentic workloads now route through the RIG runtime control plane (per-OSA sandboxed runtimes — see #401 / #662 and docs/architecture/RIG_HARD_CUT_RUNTIME_PORT_PLAN.md). The original "LangGraph deferred" decision below still stands — LangGraph remains explicitly not part of the running service.

Decision

Humanwork will not ship a LangGraph runtime or /graph/invoke rollback path in the current agent deployment. The active runtime is the Hermes-backed FastAPI service exposed through /chat, /chat/stream, and /v1/chat.

Rationale

• The team is standardizing on Hermes Agent rather than maintaining a second agent orchestration framework.
• The LangGraph path was not the deployed Railway runtime and created confusion about what was actually supported.
• Removing the rollback keeps dependency, test, and deployment scope focused on the code path we intend to operate.

Consequences

• agent/graph.py, agent/legacy_graph.py, and /graph/invoke are removed.
• LangGraph and LangChain dependencies are removed from the agent runtime.
• Future agent orchestration work should be implemented through Hermes Agent or a new ADR that explicitly reopens this decision.