v1.99.0

pydantic/pydantic-aiv1.99.0May 20, 2026by DouweM

AI Summary

This release focuses on security by fixing an IPv6 transition form bypass and adds support for the new Gemini 3.5 Flash model.

Key Highlights

Fixed SSRF bypass via IPv6 transition forms (Security).
Added support for `gemini-3.5-flash` model.
Fixed OpenAI strict schemas with regex lookarounds.

New Features

Add `gemini-3.5-flash` model
Avoid OpenAI strict schemas with regex lookarounds

Full Release Notes

<!-- Release notes generated using configuration in .github/release.yml at main -->

## What's Changed
### 🛡️ Security
* Normalize IPv6 transition forms in URL validation by @DouweM in https://github.com/pydantic/pydantic-ai/pull/5528
	* Security advisory: SSRF cloud-metadata blocklist bypass via IPv6-encoded address forms https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-cqp8-fcvh-x7r3
	* You are affected **only** if your application explicitly opts a `FileUrl` into `force_download='allow-local'` on a URL that is, or could be, influenced by untrusted input.
	* You are **not** affected if you use any of the bundled integrations to ingest user input: `Agent.to_web` / `clai web`; `VercelAIAdapter`; `AGUIAdapter` / `Agent.to_ag_ui`
### 🚀 Features
* Add `gemini-3.5-flash` model by @dsfaccini in https://github.com/pydantic/pydantic-ai/pull/5527
### 🐛 Bug Fixes
* Avoid OpenAI strict schemas with regex lookarounds by @dsfaccini in https://github.com/pydantic/pydantic-ai/pull/5519


**Full Changelog**: https://github.com/pydantic/pydantic-ai/compare/v1.98.0...v1.99.0