diff --git a/packages/opencode/src/provider/provider.ts b/packages/opencode/src/provider/provider.ts
index 0d6c4a707ac..ae493eaa0d9 100644
--- a/packages/opencode/src/provider/provider.ts
+++ b/packages/opencode/src/provider/provider.ts
@@ -73,7 +73,7 @@ export namespace Provider {
         options: {
           headers: {
             "anthropic-beta":
-              "claude-code-20250219,interleaved-thinking-2025-05-14,fine-grained-tool-streaming-2025-05-14",
+              "claude-code-20250219,interleaved-thinking-2025-05-14,fine-grained-tool-streaming-2025-05-14,adaptive-thinking-2026-01-28,context-1m-2025-08-07",
           },
         },
       }
diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index b4f1aaca4d5..bca9fe17a83 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -447,8 +447,33 @@ export namespace ProviderTransform {
 
       case "@ai-sdk/anthropic":
       // https://v5.ai-sdk.dev/providers/ai-sdk-providers/anthropic
-      case "@ai-sdk/google-vertex/anthropic":
+      case "@ai-sdk/google-vertex/anthropic": {
         // https://v5.ai-sdk.dev/providers/ai-sdk-providers/google-vertex#anthropic-provider
+        const modelId = model.id || ""
+        const isOpus46 =
+          modelId.includes("claude-opus-4.6") ||
+          modelId.includes("claude-opus-4-6") ||
+          modelId.includes("claude-opus-4.6")
+
+        if (isOpus46) {
+          // Opus 4.6 uses adaptive thinking with effort levels
+          return {
+            high: {
+              thinking: {
+                type: "enabled",
+                effort: "high",
+              },
+            },
+            max: {
+              thinking: {
+                type: "enabled",
+                effort: "max",
+              },
+            },
+          }
+        }
+
+        // Older models use manual thinking with budgetTokens
         return {
           high: {
             thinking: {
@@ -463,6 +488,7 @@ export namespace ProviderTransform {
             },
           },
         }
+      }
 
       case "@ai-sdk/amazon-bedrock":
         // https://v5.ai-sdk.dev/providers/ai-sdk-providers/amazon-bedrock