fix: prevent circular $ref in zodTextFormat for branded types

[fuleinist]

Summary

Fixes circular $ref generation in zodTextFormat when using Zod branded types (e.g., z.string().brand()).

Problem

When using a branded type like z.string().brand("SlideId">()) and reusing it multiple times in a schema, zodTextFormat was generating a circular $ref that references itself:

{
  "definitions": {
    "test_properties_a": {
      "$ref": "#/definitions/test_properties_a"
    }
  }
}

This circular reference is invalid and cannot be resolved.

Root Cause

The issue was in parseDef function in the vendored zod-to-json-schema package. When parsing a branded type:

1. The branded type def was added to refs.seen with the current path
2. parseBrandedDef then parsed the underlying type, which also got added to refs.seen with the SAME path
3. When the branded type was encountered again, a $ref was created pointing to that path
4. When resolving the definition, the underlying type was found in refs.seen at that same path, causing a circular reference

Solution

Modified parseDef to treat branded types as transparent wrappers. When a branded type is encountered, it now directly parses the underlying type without adding the branded def to refs.seen. This prevents the circular reference issue.

Changes

• Modified src/_vendor/zod-to-json-schema/parseDef.ts to handle ZodBranded types specially by parsing the underlying type directly

Testing

Verified with the reproduction case from the issue - no more circular references in the generated schema.

Fixes #1739

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve branded schema metadata when unwrapping

Returning immediately for ZodBranded bypasses the addMeta(def, refs, jsonSchema) block below, so metadata defined on the branded wrapper (not the inner type) is silently dropped. This changes output for schemas like z.string().brand(...).describe("..."), where description/markdownDescription used to be emitted from the branded def but now disappear, which can materially change generated JSON schema guidance in zodTextFormat/zodResponseFormat.

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