diff --git a/backend/generator.py b/backend/generator.py
index 905376c..38fe692 100644
--- a/backend/generator.py
+++ b/backend/generator.py
@@ -199,7 +199,7 @@ async def generate_guide(guide_id: str, topic: str, format_name: str, instructio
             if guide_id in _cancelled:
                 return
             if returncode != 0:
-                await _fail(guide_id, f"Generator-Fehler: {stderr[:1000]}")
+                await _fail(guide_id, _claude_error("Generator-Fehler", returncode, stdout, stderr))
                 return
 
             if not html_path.exists():
@@ -217,7 +217,7 @@ async def generate_guide(guide_id: str, topic: str, format_name: str, instructio
             returncode, review_out, review_err = await _run_claude(guide_id, content_prompt, AGENT_TIMEOUT, model=MODEL_GUIDE)
 
             if returncode != 0:
-                await _fail(guide_id, f"Inhalts-Review-Fehler: {review_err[:1000]}")
+                await _fail(guide_id, _claude_error("Inhalts-Review-Fehler", returncode, review_out, review_err))
                 return
 
             review_text = review_out.strip()
@@ -230,10 +230,10 @@ async def generate_guide(guide_id: str, topic: str, format_name: str, instructio
                 current_step = "Inhalts-Korrektur"
                 current_timeout = AGENT_TIMEOUT
                 fix_prompt = _build_fix_prompt(topic, format_name, html_path, feedback)
-                returncode, _, fix_err = await _run_claude(guide_id, fix_prompt, AGENT_TIMEOUT, model=MODEL_GUIDE)
+                returncode, fix_out, fix_err = await _run_claude(guide_id, fix_prompt, AGENT_TIMEOUT, model=MODEL_GUIDE)
 
                 if returncode != 0:
-                    await _fail(guide_id, f"Fix-Fehler: {fix_err[:1000]}")
+                    await _fail(guide_id, _claude_error("Fix-Fehler", returncode, fix_out, fix_err))
                     return
 
             # Step 3: PDF rendern
@@ -287,7 +287,7 @@ async def rework_guide(guide_id: str, topic: str, format_name: str, instructions
             if guide_id in _cancelled:
                 return
             if returncode != 0:
-                await _fail(guide_id, f"Rework-Fehler: {stderr[:1000]}")
+                await _fail(guide_id, _claude_error("Rework-Fehler", returncode, stdout, stderr))
                 return
 
             if not tmp_html.exists():
@@ -320,6 +320,16 @@ async def rework_guide(guide_id: str, topic: str, format_name: str, instructions
             tmp_pdf.unlink(missing_ok=True)
 
 
+def _claude_error(label: str, returncode: int, stdout: str, stderr: str) -> str:
+    stderr = (stderr or "").strip()
+    if stderr:
+        return f"{label}: {stderr[:1000]}"
+    tail = (stdout or "").strip()[-500:]
+    if tail:
+        return f"{label} (exit {returncode}, stderr leer): …{tail}"
+    return f"{label} (exit {returncode}, ohne Ausgabe)"
+
+
 async def _fail(guide_id: str, msg: str) -> None:
     now = datetime.now(timezone.utc).isoformat()
     await update_guide(guide_id, status="error", progress=None, error_msg=msg, updated_at=now)