Problem: NoInspectionAvailable with logfire.instrument_pydantic + SQLModel (old logfire bug, fixed) —— Trove problem library

What you will run into

A simple FastAPI + SQLModel app, after adding logfire.instrument_pydantic, fails in TestClient tests with sqlalchemy.exc.NoInspectionAvailable: No inspection system is available for object of type ...; removing that line makes it work.

You'd think logfire is broken — it's actually a known conflict between old logfire versions and SQLModel, long since fixed.

Why this happens

logfire's Pydantic instrumentation inspects model objects and collides with SQLModel's SQLAlchemy inspection path (a known SQLModel issue, fastapi/sqlmodel#71);

triggered by logfire 2.11.0 and earlier, fixed 2024-12-30 in 2.11.1 (official issue #728, closed).

"Instrumentation" means hooking into a third-party library: logfire's Pydantic instrumentation intercepts model creation/validation to inject observability logic.

The root conflict is two inspection paths colliding: a SQLModel model is simultaneously a Pydantic model and a SQLAlchemy model;

logfire inspects it via the Pydantic path, while SQLModel underneath goes through SQLAlchemy's inspection system — the two mechanisms inspect the same object incompatibly, and old logfire versions blow up with NoInspectionAvailable.

This is a dependency-version-combination problem (a specific logfire × SQLModel version cross), not a coding mistake — "removing instrument_pydantic makes it work" is exactly the proof that your business code is fine.

The deterministic path for this class of problem is fixed: first check "is this a known issue" (issue search;

official fixed version) -> upgrade to the fixed version -> re-verify with a minimal case (that's how this marketplace verified it: minimal case per the issue description, HTTP 200 with no error on 4.41.0).

For version-combination problems, upgrade beats modifying code.

Step by step

1. Upgrade logfire — Required

pip install -U logfire

Domestically add -i https://pypi.tuna.tsinghua.edu.cn/simple.

2. If it still appears: check the instrumentation call order — Required

instrument_pydantic and instrument_fastapi(app) must be called correctly (with 4.41.0, FastAPI instrumentation must be called with the app passed after creation, and the logfire[fastapi] extra must be installed first).

How to confirm it works

Minimal case runs normally (measured output shape):

FastAPI + SQLModel + TestClient + instrument_pydantic + instrument_fastapi
→ HTTP 200, no NoInspectionAvailable (measured with logfire 4.41.0)

Other environments

Symptom

A simple FastAPI + SQLModel app, after adding logfire.instrument_pydantic, reports sqlalchemy.exc.NoInspectionAvailable: No inspection system is available for object of type ... when tested with TestClient; removing that line makes it normal.

Cause

logfire's Pydantic instrumentation inspects model objects and conflicts with SQLModel's SQLAlchemy inspection path (known SQLModel issue, fastapi/sqlmodel#71); triggered by logfire 2.11.0 and earlier, fixed in 2.11.1 on 2024-12-30 (official issue #728, closed).

Solution

1. Upgrade logfire to >=2.11.1 (recorded version 4.41.0 already includes the fix): pip install -U logfire (add -i https://pypi.tuna.tsinghua.edu.cn/simple in China).
2. If it still appears: check the call order of instrument_pydantic and instrument_fastapi(app) (in 4.41.0 the FastAPI instrumentation must be called after app creation with the app argument, and the logfire[fastapi] extra must be installed first).