Parsing error with structured output with model output

OSS Product Help LangChain
2

hi @Art

have you seen this Warning after resolving args_schema and ToolRuntime conflict

You’re probably seeing a serialization warning, not a real structured-output parse failure.

If your parsed values are correct, the warning usually comes from serializing the raw message object (especially with include_raw=True), where an internal parsed field is attached.

What to do

  1. If you don’t need raw output, keep include_raw=False (default).
  2. For OpenAI structured output, use method="json_schema" (and strict=True when supported by your schema).
  3. If you do need raw output, log out["parsed"] separately and sanitize out["raw"] before model_dump().
  4. Update packages (langchain, langchain-openai, openai, pydantic) to latest compatible versions.

My minimal repro

from langchain.chat_models import init_chat_model
from pydantic import BaseModel, Field

class Person(BaseModel):
    name: str = Field(description="Person name")
    age: int = Field(description="Person age")

llm = init_chat_model("openai:gpt-5-mini")
structured = llm.with_structured_output(
    Person,
    method="json_schema",
    strict=True,
    include_raw=False,
)

result = structured.invoke("John is 30 years old")
print(result.model_dump())

If you need include_raw=True

structured = llm.with_structured_output(
    Person,
    method="json_schema",
    strict=True,
    include_raw=True,
)
out = structured.invoke("John is 30 years old")

print("parsed:", out["parsed"])
print("parsing_error:", out["parsing_error"])

raw = out["raw"].model_copy(deep=True)
raw.additional_kwargs.pop("parsed", None)
safe_raw = raw.model_dump()

References used: LangChain with_structured_output reference, LangChain OpenAI structured output docs, LangChain OpenAI source