fix(opencode): let config opt out of Anthropic thinking blockBinding (#46820)

Co-authored-by: Aiden Cline <aidenpcline@gmail.com>

packages/opencode/src/provider/transform.ts

@@ -706,17 +706,29 @@ function anthropicBindsThinking(apiId: string) {
 const ANTHROPIC_BLOCK_BINDING = { prefixMismatchBehavior: "drop_block" }
 
 function anthropicBlockBinding(model: Provider.Model, options: { [x: string]: any }) {
+  const sdk = sdkKey(model.api.npm)
+  const key = sdk === "bedrock" ? "reasoningConfig" : sdk === "anthropic" ? "thinking" : undefined
+  // Consume the OpenCode-only opt-out even on models outside the default scope.
+  if (key && options[key]?.blockBinding === false) {
+    const result = { ...options, [key]: { ...options[key] } }
+    delete result[key].blockBinding
+    if (Object.keys(result[key]).length === 0) delete result[key]
+    return result
+  }
+
   if (!anthropicBindsThinking(model.api.id)) return options
   switch (model.api.npm) {
     case "@ai-sdk/anthropic":
     case "@ai-sdk/google-vertex/anthropic": {
       const thinking = options.thinking ?? { type: "adaptive" }
       if (thinking.type !== "adaptive" && thinking.type !== "enabled") return options
+      if (thinking.blockBinding !== undefined) return options
       return { ...options, thinking: { ...thinking, blockBinding: ANTHROPIC_BLOCK_BINDING } }
     }
     case "@ai-sdk/amazon-bedrock": {
       const reasoningConfig = options.reasoningConfig ?? { type: "adaptive" }
       if (reasoningConfig.type !== "adaptive" && reasoningConfig.type !== "enabled") return options
+      if (reasoningConfig.blockBinding !== undefined) return options
       return { ...options, reasoningConfig: { ...reasoningConfig, blockBinding: ANTHROPIC_BLOCK_BINDING } }
     }
   }

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

@@ -938,6 +938,21 @@ describe("ProviderTransform.providerOptions", () => {
           ).toEqual({ [sdk.key]: { [sdk.option]: { type: "enabled", budgetTokens: 4000 } } })
         })
 
+        test.each(["claude-fable-5-1", "claude-opus-5"])("honors explicit binding controls for %s", (id) => {
+          const model = claude(sdk.npm, id)
+          const options = Object.freeze({
+            [sdk.option]: Object.freeze({ type: "adaptive", blockBinding: false }),
+          })
+          expect(ProviderTransform.providerOptions(model, options)).toEqual({
+            [sdk.key]: { [sdk.option]: { type: "adaptive" } },
+          })
+          expect(ProviderTransform.providerOptions(model, { [sdk.option]: { blockBinding: false } })).toEqual({
+            [sdk.key]: {},
+          })
+          const custom = { [sdk.option]: { type: "adaptive", blockBinding: { prefixMismatchBehavior: "error" } } }
+          expect(ProviderTransform.providerOptions(model, custom)).toEqual({ [sdk.key]: custom })
+        })
+
         test.each([
           ["claude-opus-5", "default"],
           ["claude-opus-5", "high"],