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# Fix: Occasional 502 Internal Server Error Returning Raw HTML via Python SDK #1923 #6

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# Fix: Occasional 502 Internal Server Error Returning Raw HTML via Python SDK #1923 #6

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99957f3
fix: sanitize 502 HTML responses from error messages
Hellnight2005 Feb 4, 2026
1e7ede5
fix: handle UnicodeDecodeError when parsing API responses
Hellnight2005 Feb 4, 2026
8cfe813
fix: guard response.text access to prevent unhandled UnicodeDecodeError
Hellnight2005 Feb 4, 2026
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39 changes: 32 additions & 7 deletions src/lingodotdev/engine.py
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Original file line number Diff line number Diff line change
Expand Up @@ -217,9 +217,18 @@ async def _localize_chunk(
if not response.is_success:
response_preview = self._truncate_response(response.text)
if 500 <= response.status_code < 600:
error_details = ""
try:
error_json = response.json()
if isinstance(error_json, dict) and "error" in error_json:
error_details = f" {error_json['error']}"
except Exception:
pass

raise RuntimeError(
raise RuntimeError(
f"Server error ({response.status_code}): {response.reason_phrase}. "
f"This may be due to temporary service issues. Response: {response_preview}"
f"Server error ({response.status_code}): {response.reason_phrase}.{error_details} "
"This may be due to temporary service issues."
)
elif response.status_code == 400:
raise ValueError(
Expand Down Expand Up @@ -463,9 +472,18 @@ async def recognize_locale(self, text: str) -> str:
if not response.is_success:
response_preview = self._truncate_response(response.text)
if 500 <= response.status_code < 600:
error_details = ""
try:
error_json = response.json()
if isinstance(error_json, dict) and "error" in error_json:
error_details = f" {error_json['error']}"
except Exception:
pass

raise RuntimeError(
f"Server error ({response.status_code}): {response.reason_phrase}. "
f"This may be due to temporary service issues. Response: {response_preview}"
raise RuntimeError(
f"Server error ({response.status_code}): {response.reason_phrase}.{error_details} "
"This may be due to temporary service issues."
)
raise RuntimeError(
f"Error recognizing locale ({response.status_code}): {response.reason_phrase}. "
Expand Down Expand Up @@ -498,10 +516,17 @@ async def whoami(self) -> Optional[Dict[str, str]]:
return {"email": payload["email"], "id": payload["id"]}

if 500 <= response.status_code < 600:
response_preview = self._truncate_response(response.text)
error_details = ""
try:
error_json = response.json()
if isinstance(error_json, dict) and "error" in error_json:
error_details = f" {error_json['error']}"
except Exception:
pass

raise RuntimeError(
f"Server error ({response.status_code}): {response.reason_phrase}. "
f"This may be due to temporary service issues. Response: {response_preview}"
f"Server error ({response.status_code}): {response.reason_phrase}.{error_details} "
"This may be due to temporary service issues."
)

return None
Expand Down
63 changes: 63 additions & 0 deletions tests/test_502_handling.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,63 @@
import pytest
import json
from unittest.mock import Mock, patch
from lingodotdev import LingoDotDevEngine


@pytest.mark.asyncio
async def test_502_html_handling():
"""Test that 502 errors with HTML bodies are sanitized"""
config = {"api_key": "test_key", "api_url": "https://api.test.com"}

html_body = "<html><body>" + ("<h1>502 Bad Gateway</h1>" * 50) + "</body></html>"
assert len(html_body) > 200 # Ensure it triggers truncation

with patch("lingodotdev.engine.httpx.AsyncClient.post") as mock_post:
mock_response = Mock()
mock_response.is_success = False
mock_response.status_code = 502
mock_response.reason_phrase = "Bad Gateway"
mock_response.text = html_body
mock_response.json.side_effect = ValueError(
"Not JSON"
) # simulating non-JSON response
mock_post.return_value = mock_response

async with LingoDotDevEngine(config) as engine:
with pytest.raises(RuntimeError) as exc_info:
await engine.localize_text("hello", {"target_locale": "es"})

error_msg = str(exc_info.value)

# Assertions
assert "Server error (502): Bad Gateway." in error_msg
assert "This may be due to temporary service issues." in error_msg
assert "Response:" not in error_msg
assert "<html>" not in error_msg
assert "<body>" not in error_msg


@pytest.mark.asyncio
async def test_500_json_handling():
"""Test that 500 errors with JSON bodies are preserved"""
config = {"api_key": "test_key", "api_url": "https://api.test.com"}
error_json = {"error": "Specific internal error message"}

with patch("lingodotdev.engine.httpx.AsyncClient.post") as mock_post:
mock_response = Mock()
mock_response.is_success = False
mock_response.status_code = 500
mock_response.reason_phrase = "Internal Server Error"
mock_response.text = json.dumps(error_json) # Needed for response_preview
mock_response.json.return_value = error_json
mock_post.return_value = mock_response

async with LingoDotDevEngine(config) as engine:
with pytest.raises(RuntimeError) as exc_info:
await engine.localize_text("hello", {"target_locale": "es"})

error_msg = str(exc_info.value)

# Assertions
assert "Server error (500): Internal Server Error." in error_msg
assert "Specific internal error message" in error_msg