Flue vs Building from Scratch

Flue is declarative-first: you describe the agent (createAgent({ model, instructions, tools })) and the framework owns the loop. Tools register with valibot schemas — a smaller, faster-typed alternative to Zod — and state is stored as a Durable Stream: a replayable event log persisted in Cloudflare Durable Objects, so an agent can crash and pick back up.

What makes it distinct from other TypeScript agent frameworks is the cross-runtime deployment story. The same agent config deploys to Cloudflare Durable Objects (its home turf), plain Node, GitHub Actions, or GitLab CI — useful when the same logic runs both in production and inside a CI pipeline. It's built on the Pi harness, the same runtime powering OpenClaw, so agents in that ecosystem share tooling and observability.

A declarative agent is just a config object plus a dispatcher. Read the config, register the tools in a dict, run the loop. Valibot schemas are Zod-shaped and interchangeable — pick either.

Durable Streams are a checkpointed event log. Naive version: append { step, state, timestamp } to Postgres or a file after each iteration; on restart, replay in order. Cloudflare Durable Objects give you the same replayability with per-agent locking and no external DB, which is real value if you're already on Cloudflare Workers.

Cross-runtime deployment is a build script that targets wrangler vs node vs a GitHub Action YAML. The declarative agent + event-log state + multi-target build fits in about 80 lines of TypeScript if you're not paying for Durable Object locking.

Flue is the pick when the deploy target is Cloudflare Workers + Durable Objects, and you want an agent framework that treats that as the primary runtime rather than a bolt-on. Durable Objects give per-agent persistence and locking for free — that's a real primitive to build on, and Flue exposes it directly.

It's also the right call when the same agent needs to run in both production and CI — e.g., a research agent that runs on user demand in a Worker and also nightly in a GitHub Action. The cross-runtime config saves you from maintaining two builds. Teams building on the Pi/OpenClaw stack get tooling reuse across their agent workloads.

If your agent runs in one place, doesn't need replayable state, and doesn't touch Cloudflare, Flue's runtime story doesn't pay off. You're paying for conventions and a valibot dependency without using the Durable Object piece.

A 60-line fetch-based agent with a JSON file for state handles the majority of production workloads without another framework in the tree. Reach for Flue when Durable Objects, Pi tooling, or cross-runtime deploy is the actual constraint — not before.