FastAPI 0.140+Pydantic 2.8

Why?

Why is FastAPI 0.140 incompatible with Pydantic 2.8?

Requirement

Pydantic >=2.9.0

Selected version

Pydantic 2.8

Evaluation

2.8.2 does not satisfy >=2.9.0

Conclusion

INCOMPATIBLE

Evidence

CompatHub reports compatibility from upstream sources rather than making unsupported claims of its own.

• FastAPI PyPI releases

  Confidence: HIGH

  https://pypi.org/pypi/fastapi/0.140.13/json

  Retrieved 2 September 2026

  Requirement: >=2.9.0

Pydantic versions

Compatibility is derived from the project's declared Pydantic requirement (>=2.9.0); it does not mean every version combination has been independently tested.

• 2.6❌
• 2.7❌
• 2.8❌
• 2.9✓
• 2.10✓
• 2.11✓
• 2.12✓
• 2.13✓

Other Pydantic versions satisfying this requirement

FastAPI 0.140 — compatible Pydantic lines tracked in CompatHub

• ✓Pydantic 2.9version line
• ✓Pydantic 2.10version line
• ✓Pydantic 2.11version line
• ✓Pydantic 2.12version line
• ✓Pydantic 2.13version line

Other FastAPI versions

Only lines with relevant compatibility evidence are listed.

• FastAPI 0.141
• FastAPI 0.140
• FastAPI 0.139
• FastAPI 0.138
• FastAPI 0.137
• FastAPI 0.136
• FastAPI 0.135
• FastAPI 0.134
• FastAPI 0.133
• FastAPI 0.132
• FastAPI 0.131
• FastAPI 0.130
• FastAPI 0.129
• FastAPI 0.128
• FastAPI 0.127
• FastAPI 0.126

Lifecycle context

Lifecycle status is separate from compatibility. An EOL component can still satisfy a documented version requirement.