Fix Pydantic extra='allow' handling in strict JSON schema

[yashwantbezawada]

Description

Fixes #2740

The to_strict_json_schema function was not properly handling Pydantic models with extra="allow".

Problem

When using Pydantic models with model_config = ConfigDict(extra="allow"), the generated JSON schema includes "additionalProperties": true. The OpenAI structured outputs API requires "additionalProperties": false for all schemas.

The existing code only set additionalProperties=false when the key didn't exist:

if typ == "object" and "additionalProperties" not in json_schema:
    json_schema["additionalProperties"] = False

This meant models with extra="allow" (which already have additionalProperties=true in their schema) were not being corrected.

Solution

Remove the "additionalProperties" not in json_schema check to always enforce additionalProperties=false for object types:

if typ == "object":
    json_schema["additionalProperties"] = False

This aligns with the OpenAI API requirement and fixes the bug reported in #2740.

Testing

The fix ensures all object types in JSON schemas will have additionalProperties set to false, regardless of the Pydantic model configuration.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Force-disables schemas that intentionally allow dynamic properties

The new logic sets additionalProperties=False for every object schema, even when additionalProperties already contains a schema for dynamic keys (e.g. a field typed as dict[str, int] produces {"additionalProperties": {"type": "integer"}}). By overwriting that value with False we now forbid those dictionaries entirely and drop the nested schema information. The prior guard avoided this by only setting the flag when the key was absent, so this change regresses existing models that legitimately depend on additionalProperties being a schema rather than a boolean. Consider only forcing False when the value is missing or explicitly True for extra="allow" models, and preserve non‑boolean schemas.

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