diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index ded416e66d95..c1c115f6c0b9 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -355,6 +355,7 @@ export namespace ProviderTransform {
     switch (model.api.npm) {
       case "@openrouter/ai-sdk-provider":
         if (!model.id.includes("gpt") && !model.id.includes("gemini-3")) return {}
+
         return Object.fromEntries(OPENAI_EFFORTS.map((effort) => [effort, { reasoning: { effort } }]))
 
       // TODO: YOU CANNOT SET max_tokens if this is set!!!
@@ -395,6 +396,36 @@ export namespace ProviderTransform {
       case "@ai-sdk/deepinfra":
       // https://v5.ai-sdk.dev/providers/ai-sdk-providers/deepinfra
       case "@ai-sdk/openai-compatible":
+        // When using openai-compatible SDK with Claude/Anthropic models,
+        // we must use snake_case (budget_tokens) as the SDK doesn't convert parameter names
+        // and the OpenAI-compatible API spec uses snake_case
+        if (
+          model.providerID === "anthropic" ||
+          model.api.id.includes("anthropic") ||
+          model.api.id.includes("claude") ||
+          model.id.includes("anthropic") ||
+          model.id.includes("claude")
+        ) {
+          return {
+            high: {
+              thinking: {
+                type: "enabled",
+                budget_tokens: 16000,
+              },
+            },
+            max: {
+              thinking: {
+                type: "enabled",
+                budget_tokens: 31999,
+              },
+            },
+          }
+        }
+        // Following logic for the `@ai-sdk/openai` case
+        if (id.includes("codex")) {
+          if (id.includes("5.2")) return Object.fromEntries([...WIDELY_SUPPORTED_EFFORTS, "xhigh"].map((effort) => [effort, { reasoning: { effort } }]))
+          return Object.fromEntries(WIDELY_SUPPORTED_EFFORTS.map((effort) => [effort, { reasoning: { effort } }]))
+        } 
         return Object.fromEntries(WIDELY_SUPPORTED_EFFORTS.map((effort) => [effort, { reasoningEffort: effort }]))
 
       case "@ai-sdk/azure":