HarnessRouter - Bring the world's best AI agents into your app, with one API

@omri_ben_shoham1 Thank you for your question, this touches some of the deepest core of our product. "One API" does mean you're trusting our uptime, so let me be straight about where the line actually is.

Honest answer to the direct question: no, we don't silently fail a call over to you hitting the provider directly. If our control plane is down, calls through it are down. Pretending otherwise would be the wrong answer. So the real question is how much we've done to make "HarnessRouter is down" rare and non-catastrophic, and where you keep an escape hatch.

What's in our hands:

- Provider/model failover within an agent loop turn. A request walks a chain of connections, if the primary provider errors or rate-limits, it falls back to the next authorized provider/model automatically, and the substitution is recorded in run metadata so it's auditable, not silent. So "the agent behind the call is having a bad day" is largely handled.
- Stateless, horizontally-scaled control plane. The routing layer holds no per-turn state that can't be rebuilt, so it scales out and a bad node doesn't take the fleet.
- Turns survive infrastructure failure. Every turn's events are written to durable storage as they happen, and an in-flight turn is recoverable/resumable if the node running it dies, you get the finished work, not a black hole. (This one we just hardened specifically because it's the scary failure mode.)

What's still shared risk, honestly: a total outage of our edge is a hard dependency, same as any API you build on (your DB, your auth provider, Stripe). We're not magic there.

The escape hatch that should matter to you: we're not a lock-in. In our next minor release, we will support BYOK, and the models are the same frontier models you'd call directly, so if you ever needed to, routing around us is a config change, not a rewrite. That asymmetry is deliberate: the pitch only works if leaving is cheap.

Happy to go deeper on the failover chain or the durability model. You can DM me or contact us at contact@harnessrouter.ai

@shivsak thank you so much for your support, Shiv! I will DM you on LinkedIn!

@shivsak  I spent months building agent harnesses myself before I talked with @renchu_song , so I really understand the pain of building the whole harness layer: sandboxes, permissions, orchestration, cost controls, and more.

That’s why your feeling resonates so much. We’re happy to finally ship the harness layer as a service, so fewer developers have to suffer through building all of it from scratch.

@jacob_hernandez4 thank you so much for your support! We'd love to hear more about your use case on orchestration and sandbox management for agents.

@jacob_hernandez4 Thanks Jacob! You’re speaking my mind. Orchestration and sandbox management were exactly the headaches, and a big reason I’m so excited we finally built this.

@johnny_chang Hi Johnny, you read our minds! Yes, persistent data is our next major release. Our ultimate goal is for builders to be able to monetize your product on our platform, so we will expose a managed database layer each generated app can read/write to, no separate DB to stand up, no extra billing account to wire in, it just comes with the app.

Once that's in place, the natural next step is letting you charge your own end users through the same platform (usage or one-time), so the whole loop (build, persist, monetize) happens in one place.

Not shipped yet, but it's the thing we're building toward right now. Would love to hear what shape of persistence you'd actually want (structured DB vs. simple key-value vs. file storage) feeds directly into how we design it.

@himanshi_kum563 Thanks Rohit, that's exactly the framing we're going for. "Another chat UI" wasn't interesting to us, what agents like Codex and Claude Code can actually do (real files, real code, real tasks) is the valuable part, and that shouldn't be locked inside the two AI monopolists' chat window. Wiring that into whatever product you're already building is the whole point. Appreciate you getting it 🙏

@himanshi_kum563 Sharp! If building an app is like building the car, we’re shipping the engine layer developers can plug into any vehicle.

@noctis06 Great question, this is exactly the part that decides whether you can trust it in production, so let me be precise.

State is on us, not you. HarnessRouter maintains the in-flight state for a run, you don't write resume logic. Every run streams its events (reasoning, tool calls, tool results, file writes) to durable storage as they happen, and the run's workspace is checkpointed, so the run has a durable identity you can reconnect to rather than a fragile in-memory session you'd have to babysit.

One correction on the premise: in our model, agents run autonomously inside an isolated per-run sandbox, they don't pause mid-task to ask the app for tool permission. Tool calls (shell, file edits, web, etc.) execute inside that sandbox without round-tripping to your app for approval, so there's no "app must handle the permission handshake" step. The human-in-the-loop gating is the immediately next feature we will launch in next minor release.

Recovery, concretely:
- Connection drop / client disconnect: the run does not get cancelled when your connection drops. It keeps executing server-side; you reconnect and catch up, either by re-subscribing to the live event stream or by reading the run's stored events. Nothing is lost, no resume code on your side.
- Long runs / timeout: each run has a configurable wall-clock cap (with a hard ceiling), so a runaway can't hang forever, and the state up to that point is durable and readable.
- Follow-ups: a next turn resumes the same conversation + workspace by run/session id, independent of which machine handled the previous turn.

So the short version: you build against a durable run you poll or stream, not a live socket you have to keep alive. A dropped browser tab, a redeploy on your side, or a flaky network doesn't lose the work.

Happy to go deeper on the event/replay model if you're designing around it, feel free to DM me or contact us at contact@harnessrouter.ai

@artinbogdanov Thank you for your support Artin!