🐛 Fix PEP 695 sequence aliases in form models - #16111
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July 30, 2026 10:52
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Summary
PEP 695 type aliases that resolve to sequence types are classified as scalar annotations when extracting form data. FastAPI consequently calls
FormData.get()instead ofFormData.getlist(), so only the final repeated value reaches Pydantic.This change unwraps
TypeAliasTypebefore sequence detection and extends the existing form-model tests to cover both plain and aliased list fields.Related discussion: #16100