[CRITICAL] SerializedDictionary does not serialize changes made from script in Unity 6000.0.73f1

[briezar]

Environment

• Unity version: 6000.0.73f1

Description

SerializedDictionary does not serialize or refresh correctly when modified from script.

If the dictionary is modified via scripting such as in OnEnable, the runtime value changes but the Inspector does not update. Changes will be lost upon script recompilation.

Reproduction

Example:

using UnityEngine;
using AYellowpaper.SerializedCollections;

public class TestBehaviour : MonoBehaviour
{
    [SerializeField]
    private SerializedDictionary<int, int> _dictionary;

    private void OnEnable()
    {
        _dictionary.Clear();
        _dictionary.Add(Random.Range(0, 100), Random.Range(0, 100));

        Debug.Log(_dictionary.Count);
    }
}

Steps to reproduce

1. Add the component to a GameObject.
2. Observe the dictionary in the Inspector.
3. Enter Play Mode.

Expected result

The Inspector should reflect the modified dictionary contents.

Actual result

• Debug.Log shows the dictionary was modified successfully.
• The Inspector does not update to reflect the changes.
• The serialized value is unchanged.

Notes

This issue has a 100% reproduction rate on Unity 6000.0.73f1.