DeepSeek V4 --variant none is accepted but does not disable thinking

Description

models.dev declares both a thinking toggle and effort values for deepseek-v4-*, but reasoningVariants() in packages/opencode/src/provider/transform.ts returns as soon as it finds the effort entry, so the toggle is dropped and only low|high|max are offered. --variant none is accepted on the CLI today and silently does nothing — the model still returns reasoning.

Because that early return is non-undefined, the reasoningVariants(model, base) ?? ProviderTransform.variants(base) fallback at provider.ts:1310 never runs for these models either.

The switch differs by provider. Zen accepts reasoning_effort: "none" and ignores thinking entirely — thinking: "nonsense" also returns 200, and its validator reports literal['none','minimal','low','medium','high','xhigh','max']. api.deepseek.com is the other way round: thinking is disabled with {"thinking": {"type": "disabled"}} and reasoning_effort is documented as low|high|max only (https://api-docs.deepseek.com/guides/thinking_mode).

Related: #41955 patches this same function but sends reasoning_effort: "none", which is correct for zen; #31795 sends thinking.type=disabled, correct for api.deepseek.com, but patches variants(), which isn't reached for models that declare reasoning_options. Happy to open a PR.

OpenCode version

1.18.25

Steps to reproduce

1. opencode run --model opencode/deepseek-v4-flash --variant none --format json --thinking -- "What is 17*23? Answer with just the number."
2. A {"type":"reasoning", ...} part is still emitted, so thinking was never disabled.

Operating System

macOS 26.0