LangGraph JS SDK : errors are parsed as JSON

[arthberman]

Checked other resources

• This is a bug, not a usage question. For questions, please use GitHub Discussions.
• I added a clear and detailed title that summarizes the issue.
• I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example).
• I included a self-contained, minimal example that demonstrates the issue INCLUDING all the relevant imports. The code run AS IS to reproduce the issue.

Example Code

app.get("/test", async (c) => {
  const client = new Client({
    apiUrl: "http://localhost:2024",
  });
  const thread = await client.threads.get("non-existent-thread");
  return c.json({
    thread,
  });
});

Error Message and Stack Trace (if applicable)

[wrangler:inf] GET /test 500 Internal Server Error (39ms)
✘ [ERROR] SyntaxError: Unexpected token 'I', "Invalid th"... is not valid JSON

      at async Array.<anonymous>

Description

• when the API return an error (forbidden, not found, ...), the SDK systematically parse it as JSON
• error is not throw as it should be
• we can't see the complete error

System Info

python -m langchain_core.sys_info

System Information

OS: Darwin
OS Version: Darwin Kernel Version 24.2.0: Fri Dec 6 19:00:33 PST 2024; root:xnu-11215.61.5~2/RELEASE_ARM64_T8122
Python Version: 3.12.5 (main, Aug 14 2024, 04:32:18) [Clang 18.1.8 ]

Package Information

langchain_core: 0.3.34
langchain: 0.3.18
langchain_community: 0.3.17
langsmith: 0.3.8
langchain_anthropic: 0.3.7
langchain_aws: 0.2.12
langchain_openai: 0.3.5
langchain_text_splitters: 0.3.6
langgraph_api: 0.0.23
langgraph_cli: 0.1.71
langgraph_license: Installed. No version info available.
langgraph_sdk: 0.1.51
langgraph_storage: Installed. No version info available.

Optional packages not installed

langserve

Other Dependencies

aiohttp<4.0.0,>=3.8.3: Installed. No version info available.
anthropic<1,>=0.45.0: Installed. No version info available.
async-timeout<5.0.0,>=4.0.0;: Installed. No version info available.
boto3: 1.36.18
click: 8.1.8
cryptography: 43.0.3
dataclasses-json<0.7,>=0.5.7: Installed. No version info available.
httpx: 0.28.1
httpx-sse<1.0.0,>=0.4.0: Installed. No version info available.
jsonpatch<2.0,>=1.33: Installed. No version info available.
jsonschema-rs: 0.25.1
langchain-anthropic;: Installed. No version info available.
langchain-aws;: Installed. No version info available.
langchain-cohere;: Installed. No version info available.
langchain-community;: Installed. No version info available.
langchain-core<1.0.0,>=0.3.34: Installed. No version info available.
langchain-deepseek;: Installed. No version info available.
langchain-fireworks;: Installed. No version info available.
langchain-google-genai;: Installed. No version info available.
langchain-google-vertexai;: Installed. No version info available.
langchain-groq;: Installed. No version info available.
langchain-huggingface;: Installed. No version info available.
langchain-mistralai;: Installed. No version info available.
langchain-ollama;: Installed. No version info available.
langchain-openai;: Installed. No version info available.
langchain-text-splitters<1.0.0,>=0.3.6: Installed. No version info available.
langchain-together;: Installed. No version info available.
langchain<1.0.0,>=0.3.18: Installed. No version info available.
langgraph: 0.2.71
langgraph-checkpoint: 2.0.12
langsmith-pyo3: Installed. No version info available.
langsmith<0.4,>=0.1.125: Installed. No version info available.
langsmith<0.4,>=0.1.17: Installed. No version info available.
numpy: 2.2.2
numpy<2,>=1.26.4;: Installed. No version info available.
numpy<3,>=1.26.2;: Installed. No version info available.
openai<2.0.0,>=1.58.1: Installed. No version info available.
orjson: 3.10.15
packaging<25,>=23.2: Installed. No version info available.
pydantic: 2.10.6
pydantic-settings<3.0.0,>=2.4.0: Installed. No version info available.
pydantic<3.0.0,>=2.5.2;: Installed. No version info available.
pydantic<3.0.0,>=2.7.4: Installed. No version info available.
pydantic<3.0.0,>=2.7.4;: Installed. No version info available.
pyjwt: 2.10.1
pytest: Installed. No version info available.
python-dotenv: 1.0.1
PyYAML>=5.3: Installed. No version info available.
requests: 2.32.3
requests-toolbelt: 1.0.0
requests<3,>=2: Installed. No version info available.
rich: Installed. No version info available.
SQLAlchemy<3,>=1.4: Installed. No version info available.
sse-starlette: 2.1.3
starlette: 0.45.3
structlog: 24.4.0
tenacity: 9.0.0
tenacity!=8.4.0,<10,>=8.1.0: Installed. No version info available.
tenacity!=8.4.0,<10.0.0,>=8.1.0: Installed. No version info available.
tiktoken<1,>=0.7: Installed. No version info available.
typing-extensions>=4.7: Installed. No version info available.
uvicorn: 0.34.0
watchfiles: 1.0.4
zstandard: 0.23.0

[dqbd]

Hello! Thank you for reporting, taking a look