fix(provider): omit deprecated Gemini sampling defaults

packages/opencode/src/provider/transform.ts

@@ -516,12 +516,14 @@ export function message(msgs: ModelMessage[], model: Provider.Model, options: Re
   return msgs
 }
 
+const GEMINI_OMITS_SAMPLING = /gemini-(?:3[.-](?:5-flash-lite|(?:[6-9]|\d{2,}))|(?:[4-9]|\d{2,}))(?:[.-]|$)/
+
 export function temperature(model: Provider.Model) {
   const id = model.id.toLowerCase()
   if (id.includes("north-mini-code")) return 1.0
   if (id.includes("qwen")) return 0.55
   if (id.includes("claude")) return undefined
-  if (id.includes("gemini")) return 1.0
+  if (id.includes("gemini")) return GEMINI_OMITS_SAMPLING.test(id) ? undefined : 1.0
   if (id.includes("glm-4.6")) return 1.0
   if (id.includes("glm-4.7")) return 1.0
   if (id.includes("minimax-m2")) return 1.0
@@ -538,7 +540,8 @@ export function temperature(model: Provider.Model) {
 export function topP(model: Provider.Model) {
   const id = model.id.toLowerCase()
   if (id.includes("qwen")) return 1
-  if (["minimax-m2", "gemini", "kimi-k2.5", "kimi-k2p5", "kimi-k2-5"].some((s) => id.includes(s))) {
+  if (id.includes("gemini")) return GEMINI_OMITS_SAMPLING.test(id) ? undefined : 0.95
+  if (["minimax-m2", "kimi-k2.5", "kimi-k2p5", "kimi-k2-5"].some((s) => id.includes(s))) {
     return 0.95
   }
   return undefined
@@ -550,7 +553,7 @@ export function topK(model: Provider.Model) {
     if (["m2.", "m25", "m21"].some((s) => id.includes(s))) return 40
     return 20
   }
-  if (id.includes("gemini")) return 64
+  if (id.includes("gemini")) return GEMINI_OMITS_SAMPLING.test(id) ? undefined : 64
   return undefined
 }
 

packages/opencode/test/provider/transform.test.ts

@@ -3190,6 +3190,32 @@ describe("ProviderTransform.temperature - Cohere North", () => {
   })
 })
 
+describe("ProviderTransform sampling defaults - Gemini", () => {
+  const model = (id: string) =>
+    ({
+      id: `google/${id}`,
+      api: { id },
+    }) as any
+
+  test.each(["gemini-3.5-flash-lite", "gemini-3.6-flash", "gemini-4-pro"])(
+    "omits deprecated sampling controls for %s",
+    (id) => {
+      expect(ProviderTransform.temperature(model(id))).toBeUndefined()
+      expect(ProviderTransform.topP(model(id))).toBeUndefined()
+      expect(ProviderTransform.topK(model(id))).toBeUndefined()
+    },
+  )
+
+  test.each(["gemini-2.5-flash", "gemini-3.1-flash-lite", "gemini-3.5-flash"])(
+    "preserves sampling defaults for %s",
+    (id) => {
+      expect(ProviderTransform.temperature(model(id))).toBe(1)
+      expect(ProviderTransform.topP(model(id))).toBe(0.95)
+      expect(ProviderTransform.topK(model(id))).toBe(64)
+    },
+  )
+})
+
 describe("ProviderTransform.reasoningVariants", () => {
   const model = (reasoning_options: ModelsDev.Model["reasoning_options"]) => ({ reasoning_options }) as ModelsDev.Model
   const target = (npm: string, id = "test-model") =>