diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index 4956020321..04d14248b1 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -751,6 +751,9 @@ function reasoningOptionVariants(model: Provider.Model): Record<string, Record<s
   if (!budget) return {}
 
   switch (model.api.npm) {
+    case "@openrouter/ai-sdk-provider":
+      return reasoningBudgetVariants(budget, (max_tokens) => ({ reasoning: { max_tokens } }), model.limit.output)
+
     case "@ai-sdk/gateway":
       if (idIncludes(model, "anthropic")) {
         return reasoningBudgetVariants(
diff --git a/packages/opencode/test/provider/transform.test.ts b/packages/opencode/test/provider/transform.test.ts
index ff373f6e72..d1230dd6e7 100644
--- a/packages/opencode/test/provider/transform.test.ts
+++ b/packages/opencode/test/provider/transform.test.ts
@@ -3133,6 +3133,26 @@ describe("ProviderTransform.variants", () => {
       expect(Object.keys(result)).toEqual(["low", "high"])
       expect(result.low).toEqual({ reasoning: { effort: "low" } })
     })
+
+    test("budget token reasoning_options use max_tokens", () => {
+      const result = ProviderTransform.variants(
+        createMockModel({
+          id: "openrouter/anthropic/claude-sonnet-4.5",
+          providerID: "openrouter",
+          api: {
+            id: "anthropic/claude-sonnet-4.5",
+            url: "https://openrouter.ai",
+            npm: "@openrouter/ai-sdk-provider",
+          },
+          reasoning_options: [{ type: "budget_tokens", min: 1024, max: 63999 }],
+          limit: { context: 1_000_000, output: 64_000 },
+        }),
+      )
+      expect(result).toEqual({
+        high: { reasoning: { max_tokens: 16_000 } },
+        max: { reasoning: { max_tokens: 63_999 } },
+      })
+    })
   })
 
   describe("@ai-sdk/gateway", () => {