diff --git a/graphify/llm.py b/graphify/llm.py
index 560bbcb88..0d76f5a4a 100644
--- a/graphify/llm.py
+++ b/graphify/llm.py
@@ -1274,9 +1274,10 @@ def _call_claude_cli(user_message: str, max_tokens: int = 8192, *, deep_mode: bo
         **_no_window_kwargs(),
     )
     if proc.returncode != 0:
-        raise RuntimeError(
-            f"claude -p exited {proc.returncode}: {proc.stderr.strip()[:500]}"
-        )
+        # The CLI writes usage-limit and auth errors to stdout, not stderr.
+        # Fall back to the stdout tail when stderr is empty.
+        detail = proc.stderr.strip()[:500] or proc.stdout.strip()[-500:]
+        raise RuntimeError(f"claude -p exited {proc.returncode}: {detail}")
 
     envelope = _claude_cli_envelope(proc.stdout)
 
@@ -2076,7 +2077,9 @@ def _rec(inp, out) -> None:
             **_no_window_kwargs(),
         )
         if proc.returncode != 0:
-            raise RuntimeError(f"claude -p exited {proc.returncode}: {proc.stderr.strip()[:500]}")
+            # See _call_claude_cli: the CLI writes these errors to stdout.
+            _detail = proc.stderr.strip()[:500] or proc.stdout.strip()[-500:]
+            raise RuntimeError(f"claude -p exited {proc.returncode}: {_detail}")
         envelope = _claude_cli_envelope(proc.stdout)
         cli_usage = envelope.get("usage") or {}
         if cli_usage:
diff --git a/tests/test_llm_errors.py b/tests/test_llm_errors.py
new file mode 100644
index 000000000..2162158a2
--- /dev/null
+++ b/tests/test_llm_errors.py
@@ -0,0 +1,41 @@
+"""claude-cli error surfacing when the CLI reports failures on stdout."""
+
+from __future__ import annotations
+
+from types import SimpleNamespace
+
+import pytest
+
+from graphify import llm as llmmod
+
+
+def _proc(returncode=1, stdout="", stderr=""):
+    return SimpleNamespace(returncode=returncode, stdout=stdout, stderr=stderr)
+
+
+def test_claude_cli_error_prefers_stderr(monkeypatch):
+    import shutil as _shutil
+    import subprocess as _subprocess
+
+    monkeypatch.setattr(_shutil, "which", lambda _: "/usr/bin/claude")
+    monkeypatch.setattr(
+        _subprocess, "run", lambda *a, **k: _proc(stderr="real stderr", stdout="noise")
+    )
+    with pytest.raises(RuntimeError, match="real stderr"):
+        llmmod._call_claude_cli("hi")
+
+
+def test_claude_cli_error_falls_back_to_stdout(monkeypatch):
+    import shutil as _shutil
+    import subprocess as _subprocess
+
+    monkeypatch.setattr(_shutil, "which", lambda _: "/usr/bin/claude")
+    monkeypatch.setattr(
+        _subprocess,
+        "run",
+        lambda *a, **k: _proc(
+            stdout='{"type":"result","result":"Claude AI usage limit reached|1752200000"}'
+        ),
+    )
+    with pytest.raises(RuntimeError, match="usage limit reached"):
+        llmmod._call_claude_cli("hi")