dsh-model-router

A DeepSeek Harness (DSH) plugin that turns model selection into intelligent routing: declare a virtual model id in config, bind it to a routing algorithm over a list of real provider/model candidates, and use the virtual id anywhere — agent options, model picker. Every call is transparently dispatched to a real model chosen by the algorithm, with automatic failover.

What it does

• Virtual model ids. A route such as routed-chat behaves like any real model in the picker, but is a facade over a candidate pool you define.
• Transparent failover. When a candidate fails, the next one is tried — same request, no user-visible error — and the plugin records which real model served each call, so a failover is always visible in the provenance instead of silent.
• Two routing algorithms (pluggable extension point):
  • priority — always try the first candidate; skip it only on failure. Failed candidates get exponential backoff, giving a struggling model time to recover before it is tried again.
  • round-robin — distribute calls across the pool.
• Your own algorithm. RoutingAlgorithm is a factory contract (select, onFailure, optional onDispatch/onSuccess) — implement one and register it.

Why it exists

Model pools are the reality: a cheap fast model, a strong one, a spare. Hardcoding one id means a provider outage becomes your outage. Routing at the plugin layer means the rest of the harness never learns about failure — and never has to.

Install

npm pack
dsh plugin --profile <your-profile> add file:/path/to/dsh-model-router-<version>.tgz

Or straight from GitHub:

dsh plugin --profile <your-profile> add github:andrepontesmelo/dsh-model-router

Quick start

Add a route to your profile's cordis.patch.yml:

{
  "routes": [
    {
      "id": "routed-chat",
      "algorithm": "priority",              // "priority" | "round-robin"
      "candidates": [
        { "provider": "deepseek-official", "model": "deepseek-v4-flash" },
        { "provider": "pi-ai", "model": "..." }
      ]
    }
  ]
}

Pick routed-chat in the model picker (or set it as an agent's model) and route. On failover, the response provenance shows the real model that answered and any candidates sleeping in their backoff window.

Writing your own algorithm

An algorithm is a factory (ctx, routes) => algorithm:

{
  select(route, callCtx)      // -> candidate | undefined (pure — no state advance)
  onFailure(route, candidate) // record the failure so select skips it
  onDispatch?(route, candidate) // first dispatch of a request
  onSuccess?(route, candidate)  // optional
}

The shim probes select for boolean checks, so it must stay pure; state advances happen in the on* callbacks. The test suite in test/ pins these seam mechanics.

Roadmap

• Session stickiness — pin a session to the candidate that first served it (not yet implemented).
• Per-model reasoning-level customization (not yet implemented).

Requirements

• Node ≥ 22.
• A DSH profile to install into; candidates point at providers already configured there.

Test

npm test        # unit suite
npm run smoke   # end-to-end smoke against a live profile

License

MIT — see LICENSE.