`allOf` + `unevaluatedProperties` does not work

[dukhaSlayer]

Describe the bug

I'm trying to build a mixin schema with:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://example.com/test.schema.json",
  "title": "Test",
  "type": "object",
  "allOf": [
    { "$ref": "#/$defs/FieldsA" },
    { "$ref": "#/$defs/FieldsB" }
  ],
  "unevaluatedProperties": false,
  "$defs": {
    "FieldsA": {
      "type": "object",
      "additionalProperties": true,
      "properties": {
        "name": { "type": "string" },
        "age": { "type": "integer" }
      },
      "required": ["name"]
    },
    "FieldsB": {
      "type": "object",
      "additionalProperties": true,
      "properties": {
        "email": { "type": "string", "format": "email" },
        "phone": { "type": "string" }
      },
      "required": ["email"]
    }
  }
}

And data being

# yaml-language-server: $schema=./test.schema.yaml

name: John Doe
age: 30
email: john@example.com
phone: "+1234567890"
#foo: bar  # <- uncomment to test: should be rejected by unevaluatedProperties

Testing on both release and nightly (1.22 or 1.22.2026022708)

Other packages validate it perfectly. E.g.:

uv run check-jsonschema --schemafile data/test/test.schema.yaml data/test/test.yaml
ok -- validation done

Expected Behavior

Document pass validation with (name+email) or e.g. (name + email + phone). And don't pass on foo field.

Current Behavior

Every field in my document shows an error "Property {} is not allowed"

Steps to Reproduce

Create 2 files, open data file.

Environment

• Windows
• Mac
• Linux
• other (please specify)

[shin19991207]

Hi @dukhaSlayer

1. Re the "Property {} is not allowed" errors on every field — I tried reproducing the issue in VS Code using the JSON schema you shared, but I’m not seeing those errors. Could you let me know which IDE you’re using?

2. Regarding the expectation that the foo field should be rejected — I don’t think this is a bug. I tested your schema using https://www.jsonschemavalidator.net/ with the following input, and it reports no errors:

   {
     "name": "John Doe",
     "age": 30,
     "email": "john@example.com",
     "phone": "+1234567890",
     "foo": "bar"
   }

   I checked the specs and I believe the given schema does allow any extra property:

   • allOf means both FieldsA and FieldsB are applied
   • In each branch, additionalProperties: true accepts properties not listed in properties, and those properties are considered "validated/evaluated" by additionalProperties (see https://json-schema.org/draft/2020-12/json-schema-core#section-10.3.2.3)
   • unevaluatedProperties only runs on properties that were not already evaluated by properties, patternProperties, additionalProperties, etc.... (see https://json-schema.org/draft/2020-12/json-schema-core#section-11.3)

   So by the time unevaluatedProperties: false runs, foo is already evaluated by additionalProperties: true in the allOf branches, so it is not rejected.