Default `k3` fallback family misses `opencode-go/kimi-k3`

[sleegme]

What happened?

The shipped fallback chain for claude-fable-5 uses k3:max, but it does not expand to OpenCode Go's Kimi K3 model (opencode-go/kimi-k3).

On senpi 2026.8.9-2, /fallback showed the Fable chain expanding only to Claude Opus entries even though the live model registry/current model included (opencode-go) kimi-k3:max.

This looks deterministic from the current implementation:

• retry-fallback/settings.ts ships "claude-fable-5": ["k3:max", ...]
• retry-fallback/expansion.ts::matchesFamily() only matches an exact family id or a dash-suffixed variant (k3 / k3-*)
• kimi-k3 therefore does not match the bare family k3

This matters because OpenCode Go users with Kimi K3 do not get the intended Fable → K3 fallback route.

Steps to reproduce

1. Use a model registry containing opencode-go/kimi-k3.
2. Run /fallback and inspect the shipped Fable fallback chain.
3. Observe that opencode-go/kimi-k3:max is absent from the expanded chain.

Expected behavior

Kimi K3 models exposed as kimi-k3 should be eligible for the shipped k3 fallback family, or the shipped selector should use an alias/family rule that resolves them without weakening the conservative family matcher.

Version

2026.8.9-2

[sleegme]

AI disclosure: I used ChatGPT to help draft and structure this report after inspecting the observed /fallback output and the current fallback-family matching code.