Who contributed to FastAPI & Pydantic on May 17, 2026?

2 developers shipped this update, including connorcarpenter15 and cyphercodes.

What were the notable FastAPI & Pydantic updates?

Only deepcopy non-updated fields in `model_copy()` and Fallback to `create_model()` overload definition when `__base__` is set to a type variable.

FastAPI & Pydantic

FastAPI and the Pydantic + SQLModel async-Python stack

Pick a date

Topics: Python Full archive →

The Wire · Showcase

PYDANTIC FIXES DEEPCOPY CRASH IN MODEL_COPY

By RepoJournal · Filed 06:03 UTC on May 17, 2026 · About FastAPI & Pydantic

2 people shipped this

connorcarpenter15 @connorcarpenter15 1 cited

cyphercodes @cyphercodes 1 cited

Pydantic's `model_copy(deep=True)` no longer tries to deepcopy fields you're about to replace, fixing crashes when those fields hold undeepcopyable objects like GPU tensors or C extensions.

The fix [1] is surgical and high-impact. Before, `model_copy(deep=True, update={...})` would deepcopy every field including ones you're immediately replacing, which breaks when those fields contain native C extensions, file handles, or GPU tensors. Now it only deepcopies fields that survive the update, and it properly maintains shared references between fields by using a single `memo` dict across all deepcopy calls. This preserves the behavior for `__pydantic_extra__` and `__pydantic_private__` as well. In parallel, the Pydantic team fixed a mypy plugin regression [2] where `create_model(..., __base__=cls)` inside a classmethod would lose the `Self` type. The mypy plugin now falls back to the normal overload definition when `__base__` is a type variable, keeping proper generic inference. Expect these in the next release.

Action items

→ Watch for next Pydantic release with model_copy fix if you use deep=True with GPU tensors or C extension fields pydantic/pydantic [monitor]
→ If using dynamic models with create_model in classmethods, test with upcoming Pydantic release for proper type narrowing pydantic/pydantic [plan]

References

[1] Only deepcopy non-updated fields in `model_copy()` ↗ pydantic/pydantic
[2] Fallback to `create_model()` overload definition when `__base__` is set to a type variable ↗ pydantic/pydantic

Quick answers

What shipped in FastAPI & Pydantic on May 17, 2026?: Pydantic's `model_copy(deep=True)` no longer tries to deepcopy fields you're about to replace, fixing crashes when those fields hold undeepcopyable objects like GPU tensors or C extensions. In total, 6 commits and 6 pull requests landed.
Who contributed to FastAPI & Pydantic on May 17, 2026?: 2 developers shipped this update, including connorcarpenter15 and cyphercodes.
What were the notable FastAPI & Pydantic updates?: Only deepcopy non-updated fields in `model_copy()` and Fallback to `create_model()` overload definition when `__base__` is set to a type variable.

FASTAPI 0.140.0 CUTS MEMORY OVERHEAD IN DEPENDENCIES

FastAPI shipped a memory optimization that simplifies how dependencies are processed, backed by months of community analysis and benchmarking.

python 9 shipped 1-min read

FastAPI & Pydantic 1 day ago

FASTAPI AND SQLMODEL STANDARDIZE ON UV, PYDANTIC DOCS BLOCKED ON SETTINGS DRIFT

Tiangolo shipped Library Skills documentation across FastAPI and SQLModel while pivoting both projects toward uv as the default package manager, but Pydantic's docs build is failing due to version mismatch in pydantic-settings.

python 10 shipped 1-min read

FastAPI & Pydantic 2 days ago

SQLMODEL FIXES TERMYNAL SCROLL JAR ACROSS DOCS

Interactive code examples in SQLModel documentation no longer hijack your scroll position when you click the restart or fast-forward controls.

python 2 shipped 1-min read

FastAPI & Pydantic 3 days ago

FASTAPI AND PYDANTIC SHIFT TO UV FOR DOCS AND DEPENDENCIES

FastAPI's documentation is standardizing on uv project templates, signaling a broader ecosystem shift toward Python's fastest-growing package manager.

python 7 shipped 1-min read

Elsewhere on the wire

AI Agents about 9 hours ago

CLAUDE OPUS 5 LANDS ACROSS THE STACK

The newest Anthropic model is now live in langchain, Cline, and llama-index, with native support for extended reasoning and 1M context windows.

ai-agents 28 shipped 1-min read

Local LLMs about 9 hours ago

OLLAMA LANDS LAGUNA SUPPORT AND CRUSHES MEMORY LEAKS WHILE SGLANG HITS V0.5.16 WITH CONFIDENCE-DRIVEN SPECULATIVE DECODING

Ollama shipped three critical performance and reliability fixes for Metal residency and concurrent access patterns, while SGL-Lang released 0.5.16 with a new speculative algorithm hitting 383.7 tok/s on DeepSeek-V4.