Summary

Fixes a silent-failure path in resolveModelForDelegateTask where a user-configured categories.*.model that is not reachable on the user's connected providers was returned verbatim, bypassing the user's own fallback_models array. The team-mode category member (e.g. hyperplan's artistry) then spawned targeting an unreachable model.

The bug

src/tools/delegate-task/model-selection.ts, lines 57-64 (pre-patch):

const userModel = normalizeModel(input.userModel)
if (userModel) {
  const parsed = parseUserFallbackModel(userModel)
  if (parsed?.variant) {
    return { model: parsed.baseModel, variant: parsed.variant }
  }
  return { model: userModel }
}

The moment input.userModel was set, the function returned it immediately — never checking reachability against input.availableModels, never iterating input.userFallbackModels. For a user with:

"categories": {
  "artistry": {
    "model": "opencode/gemini-3.1-pro",
    "fallback_models": [
      { "model": "amazon-bedrock/us.anthropic.claude-opus-4-7", "variant": "max" },
      { "model": "openai/gpt-5.5" }
    ]
  }
}

… and a provider set that includes openai + amazon-bedrock but not opencode-hosted gemini, the team member was launched against opencode/gemini-3.1-pro and the user's carefully-authored fallbacks were silently ignored. Runtime-fallback can't intercept this either because the provider rejects the model up-front.

The fix

When the provider-models cache is warm (availableModels.size > 0) AND the user provided fallback_models, we now:

1. Verify the user's primary model is reachable via fuzzyMatchModel. If yes → return it (fast path, identical to old behavior).
2. If not reachable, iterate userFallbackModels and promote the first reachable entry, with matchedFallback: true.
3. If neither reachable, return userResult as-is — preserving the legacy "trust the user" behavior.

Cold-cache first-run behavior is untouched (size > 0 guard). The existing pre-cache test at model-selection.test.ts:42-55 still passes unchanged — deliberate: on first run we have no authoritative availability data and must honor user intent.

Tests

Three new regression cases in model-selection.test.ts:

• #when user primary model is unreachable and user fallback_models are provided → #then promotes the first reachable user fallback
• #then keeps the user primary when it IS reachable (fast path preserved)
• #then returns the user primary as-is when no user fallback is reachable either (trust-user legacy behavior)

Verification

bun test src/tools/delegate-task/model-selection.test.ts
→ 25 pass, 0 fail

bun test src/tools/delegate-task/
→ 393 pass, 0 fail

bun run typecheck
→ clean

User impact

Users who observed hyperplan (or any team-mode category spawn) silently running with fewer members than requested — because one member's primary model wasn't reachable — will now see that member resolve via their configured fallbacks. No config change required on the user side; existing fallback_models entries now work as documented.

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Summary by cubic

Fixes model selection so user fallback_models are used when the category’s primary model isn’t available on connected providers. This prevents team members from spawning with unreachable models and restores graceful fallback.

• Bug Fixes
  • In resolveModelForDelegateTask, when availability data exists and userFallbackModels are set, verify the primary; if unreachable, promote the first reachable fallback and set matchedFallback: true.
  • Preserve cold-cache behavior: return the user primary as-is when availability is unknown.
  • Add tests for: unreachable primary → reachable fallback, reachable primary retained, and both unreachable → primary kept.

^{Written for commit 711b753. Summary will update on new commits.}