diff --git a/src/agents/claude_client.py b/src/agents/claude_client.py
index 661180d..3cae369 100644
--- a/src/agents/claude_client.py
+++ b/src/agents/claude_client.py
@@ -54,7 +54,12 @@ async def call_claude(prompt: str, tools: str | None = "WebSearch,WebFetch", mod
     if tools:
         cmd.extend(["--allowedTools", tools])
     else:
-        cmd.extend(["--max-turns", "1"])
+        cmd.extend(["--max-turns", "1", "--allowedTools", ""])
+        cmd.extend(["--append-system-prompt",
+            "CRITICAL: You are a JSON-only output agent. "
+            "Output EXCLUSIVELY a single valid JSON object. "
+            "No explanatory text, no markdown fences, no continuation of previous responses. "
+            "Start your response with { and end with }."])
 
     process = await asyncio.create_subprocess_exec(
         *cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE,
@@ -76,8 +81,21 @@ async def call_claude(prompt: str, tools: str | None = "WebSearch,WebFetch", mod
 
     if process.returncode != 0:
         error_msg = stderr.decode("utf-8", errors="replace").strip()
-        logger.error(f"Claude CLI Fehler (Exit {process.returncode}): {error_msg}")
-        raise RuntimeError(f"Claude CLI Fehler: {error_msg}")
+        stdout_msg = stdout.decode("utf-8", errors="replace").strip()
+
+        # Rate-Limit-Fehler kommen als JSON auf stdout, nicht auf stderr
+        error_type = "cli_error"
+        rate_limit_keywords = ["hit your limit", "rate limit", "resets", "rate_limit", "overloaded"]
+        combined_output = f"{error_msg} {stdout_msg}".lower()
+        if any(kw in combined_output for kw in rate_limit_keywords):
+            error_type = "rate_limit"
+            logger.warning(f"Claude CLI Rate-Limit (Exit {process.returncode}): {stdout_msg or error_msg}")
+        else:
+            logger.error(f"Claude CLI Fehler (Exit {process.returncode}): {error_msg}")
+            if stdout_msg:
+                logger.error(f"Claude CLI stdout bei Fehler: {stdout_msg[:500]}")
+
+        raise RuntimeError(f"Claude CLI Fehler [{error_type}]: {stdout_msg or error_msg}")
 
     raw = stdout.decode("utf-8", errors="replace").strip()
     usage = ClaudeUsage()