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fix(lib): apply strict JSON schema transform to tuple prefixItems #3588

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fix(lib): apply strict JSON schema transform to tuple prefixItems #3588

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9 changes: 9 additions & 0 deletions src/openai/lib/_pydantic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,15 @@ def _ensure_strict_json_schema(
if is_dict(items):
json_schema["items"] = _ensure_strict_json_schema(items, path=(*path, "items"), root=root)

# tuples / positional arrays
# { 'type': 'array', 'prefixItems': [{...}, {...}] }
prefix_items = json_schema.get("prefixItems")
if is_list(prefix_items):
json_schema["prefixItems"] = [
_ensure_strict_json_schema(item, path=(*path, "prefixItems", str(i)), root=root)

@chatgpt-codex-connector chatgpt-codex-connector Bot Aug 9, 2026

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P2 Badge Prevent infinite expansion of recursive tuple refs

When a recursive Pydantic model contains a tuple element such as tuple[Annotated[Node, Field(description="child")]], this traversal reaches the $ref with its description, expands the referenced Node, and then walks into the same prefixItems entry again. This repeats until to_strict_json_schema() raises RecursionError; self- and mutually recursive tuple schemas therefore need explicit cycle handling rather than unconditional descent.

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for i, item in enumerate(prefix_items)
]

# unions
any_of = json_schema.get("anyOf")
if is_list(any_of):
Expand Down
75 changes: 75 additions & 0 deletions tests/lib/test_pydantic.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,10 @@
from __future__ import annotations

from enum import Enum
from typing import Tuple
from typing_extensions import Annotated

import pytest
from pydantic import Field, BaseModel
from inline_snapshot import snapshot

Expand Down Expand Up @@ -169,6 +172,78 @@ def test_most_types() -> None:
)


class Location(BaseModel):
lat: float
long: float


class Route(BaseModel):
endpoints: Tuple[
Annotated[Location, Field(description="The starting point.")],
Annotated[Location, Field(description="The ending point.")],
]


@pytest.mark.skipif(PYDANTIC_V1, reason="`prefixItems` is only emitted by pydantic v2")
def test_tuple_prefix_items_ref_expansion() -> None:
# tuple elements are emitted under `prefixItems`; the strict transform must
# recurse into them the same way it does for `items`, otherwise a `$ref` that
# carries sibling keys (e.g. a field description) is left un-expanded and the
# API rejects the resulting schema.
assert to_strict_json_schema(Route) == snapshot(
{
"$defs": {
"Location": {
"properties": {
"lat": {"title": "Lat", "type": "number"},
"long": {"title": "Long", "type": "number"},
},
"required": ["lat", "long"],
"title": "Location",
"type": "object",
"additionalProperties": False,
}
},
"properties": {
"endpoints": {
"maxItems": 2,
"minItems": 2,
"prefixItems": [
{
"description": "The starting point.",
"properties": {
"lat": {"title": "Lat", "type": "number"},
"long": {"title": "Long", "type": "number"},
},
"required": ["lat", "long"],
"title": "Location",
"type": "object",
"additionalProperties": False,
},
{
"description": "The ending point.",
"properties": {
"lat": {"title": "Lat", "type": "number"},
"long": {"title": "Long", "type": "number"},
},
"required": ["lat", "long"],
"title": "Location",
"type": "object",
"additionalProperties": False,
},
],
"title": "Endpoints",
"type": "array",
}
},
"required": ["endpoints"],
"title": "Route",
"type": "object",
"additionalProperties": False,
}
)


class Color(Enum):
RED = "red"
BLUE = "blue"
Expand Down