diff --git a/src/services/claude.ts b/src/services/claude.ts
index 5f23270..1d05cc7 100644
--- a/src/services/claude.ts
+++ b/src/services/claude.ts
@@ -42,10 +42,12 @@ function runClaude(args: string[], cwd: string): Promise<string> {
   });
 }
 
+const SYSTEM_PROMPT = "Always respond in Russian. Be concise.";
+
 export class ClaudeService {
   async createSession(prompt: string, cwd: string): Promise<ClaudeResult> {
     const raw = await runClaude(
-      ["-p", prompt, "--output-format", "json", "--dangerously-skip-permissions"],
+      ["-p", prompt, "--output-format", "json", "--dangerously-skip-permissions", "--system-prompt", SYSTEM_PROMPT],
       cwd,
     );