Unity Issue Tracker - Prefabs are corrupted due to inline-styled YAML when UnityYAMLMerge is used to merge prefabs

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In Progress in 6000.6.X

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Issue ID

Regression

Prefabs are corrupted due to inline-styled YAML when UnityYAMLMerge is used to merge prefabs

-

Jan 06, 2026

How to reproduce:

Locate the UnityYAMLMerge tool in “<Unity Editor version Path>\Editor\Data\Tools“ directory
Copy the path to the UnityYAMLMerge tool
Extract and open the “minimal_test.zip“ directory
Edit the “test_merge.bat“ in Notepad
Replace the value for “UNITY_YAML_MERGE“ with the path to the UnityYAMLMerge copied in step 2
Save the changes and run the script
Edit the “merge_result.prefab“ in Notepad
Observe the array format of "m_RemovedGameObjects"

Actual results: The array is listed in this format: [ {}, {}, {} ]
Expected results: The array is listed in this format:
- {}
- {}
- {}

Reproducible in: 2023.1.0a1, 6000.0.67f1, 6000.3.7f1, 6000.4.0b7, 6000.5.0a6

Reproduced on: Windows 11 Pro (25H2), macOS 15.7.2 (reported against)
Not reproduced on: No other environment tested

Note: Both array interpretations are correct YAML-wise, however, Unity accepts only the expected (block/list) type array