Cold-start default model is stale: substring priority list picks gemini-3-pro-preview over every newer model #39125

What happened

I run opencode headless in fresh sandboxes every day (eval harness, 180 tasks/day) with a single gateway provider configured and no model set. Every single run picks google/gemini-3-pro-preview. That model is a generation behind and it never changes, so I dug into why. Verified on 1.18.7 (current npm latest).

The cause

packages/opencode/src/provider/provider.ts (dev branch):

const priority = ["gpt-5", "claude-sonnet-4", "big-pickle", "gemini-3-pro"]
export function sort<T extends { id: string }>(models: T[]) {
  return sortBy(
    models,
    [(model) => priority.findIndex((filter) => model.id.includes(filter)), "desc"],
    [(model) => (model.id.includes("latest") ? 0 : 1), "asc"],
    [(model) => model.id, "desc"],
  )
}

defaultModel falls through cfg.model -> recents in state/model.json -> sort(provider.models)[0]. With no config and no state, the priority list decides, and it has gone stale in a few compounding ways:

1. Substring pins don't survive model generations. "gemini-3-pro" doesn't match google/gemini-3.1-pro-preview (that id contains gemini-3.1-pro), so the successor can never win. Meanwhile gpt-5.5 and claude-sonnet-4.6 do match their pins, but at lower priority indexes, so they lose to the older gemini pin.
2. findIndex + "desc" means the last array entry is the highest priority. Easy to misread as first-wins. Either way the top preference is whatever was appended last, back when gemini-3-pro was current.
3. The final tie-break is reverse-alphabetical id, which is the only reason -preview beats -image (p > i). Nothing checks capabilities at this point. If the catalog gained a -vision or -realtime sibling it would sort above -preview and become the default.
4. Only status: deprecated/alpha get filtered before the sort, so a superseded-but-active preview model stays eligible forever.

Repro

Clean machine (no state/model.json), opencode.json with just a gateway provider and no model:

{
  "provider": {
    "vercel": { "options": { "apiKey": "{env:AI_GATEWAY_API_KEY}" } }
  }
}

opencode run "hello" picks google/gemini-3-pro-preview. Emulating sort() over that provider's catalog (499 models in the 1.18.7 build) ranks:

1. google/gemini-3-pro-preview
2. google/gemini-3-pro-image
3. anthropic/claude-sonnet-4

Why nobody notices

The recents fallback shadows this for anyone who has ever picked a model interactively. Ephemeral environments hit the cold-start path every time - CI, sandboxes, containers, eval harnesses - and they're all quietly running on gemini-3-pro-preview today.

Suggested fix

Any of these kills the staleness class rather than today's instance:

• Use release_date in the ranking. It's already on every model and getSmallModel already sorts by it - defaultModel could prefer the newest model within a preferred family/capability set.
• Match on the catalog's family metadata (e.g. gemini-pro) instead of raw id substrings, so successor generations inherit the preference.
• At minimum, filter for toolcall + text output ahead of the id tie-break so an image variant can't become the default by alphabetical accident.

Happy to PR whichever direction you prefer.

Environment: opencode 1.18.7 (npm opencode-ai, also confirmed in 1.17.0), single gateway provider via opencode.json, no model configured, clean state.