* fix(providers): gate premium opencode-zen/opencode-go models behind an API key (#8681)
Root cause: the free/noauth opencode provider (and opencode-zen/opencode-go)
expose the full upstream model list including PREMIUM models (gpt-5, claude-*,
gemini-*, kimi-k2.6, etc.). With a keyless connection, the executor sends no
Authorization header and upstream returns 401 'Missing API key' for any
premium model — which is the exact string the client shows.
Fix: add a request-time gate in OpencodeExecutor.execute() that detects
keyless connections + premium models and returns a clear 402 error with
message 'This model requires an opencode API key — add one in Settings →
Providers.' instead of proxying the raw upstream 401.
Free models (known free catalog + suffix) continue to work keyless
(deepseek-v4-flash-free, big-pickle, etc.). Users with a valid opencode API
key keep premium access. opencode-go has no free tier — all models require
a key.
* fix(providers): use a free opencode model in the #7993 proxy-routing test
The #8681 keyless-premium gate short-circuits 'grok-code' (a premium
model) with 402 before any fetch happens, so the proxy-egress assertion
never saw a request. Swap to 'deepseek-v4-flash-free' (already applied
to the sibling opencode-proxy-rotation-4954.test.ts in this same PR)
so the test again exercises the proxy-routing path it targets.
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Co-authored-by: diegosouzapw <diegosouzapw@users.noreply.github.com>
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