diff --git a/open-sse/executors/github.js b/open-sse/executors/github.js
index 22feae3..9e2f654 100644
--- a/open-sse/executors/github.js
+++ b/open-sse/executors/github.js
@@ -114,6 +114,12 @@ export class GithubExecutor extends BaseExecutor {
     return !/gpt-5\.4/i.test(model);
   }
 
+  // GitHub Copilot /chat/completions doesn't support thinking/reasoning_effort.
+  // OpenClaw sends thinking: { type: "enabled" } for Claude models which causes 400.
+  supportsThinking() {
+    return false;
+  }
+
   transformRequest(model, body, stream, credentials) {
     const transformed = { ...body };
     if (this.requiresMaxCompletionTokens(model) && transformed.max_tokens !== undefined) {
@@ -124,6 +130,11 @@ export class GithubExecutor extends BaseExecutor {
     if (!this.supportsTemperature(model) && transformed.temperature !== undefined) {
       delete transformed.temperature;
     }
+    // Strip thinking/reasoning_effort — unsupported on /chat/completions
+    if (!this.supportsThinking(model)) {
+      delete transformed.thinking;
+      delete transformed.reasoning_effort;
+    }
     return transformed;
   }