Context

update_settings_file deletes unrelated settings when the settings file contains deprecated keys that need migration. For example, changing the model from the Agent Panel overwrites the entire agent block instead of just updating default_model.

The root cause is that edits_for_update used parse_json_with_comments (strict parser), which returns Err on deprecated/unknown fields. The error is swallowed by log_err(), falling back to Default::default() (empty settings). The diff then sees everything as new and replaces the entire block.

The fix switches to parse_json (the fallible/lenient parser), which returns Some(parsed_value) even when deprecated fields are present - the same pattern already used by parse_and_migrate_zed_settings.

Fixes #41344

How to Review

Single-file change in settings_store.rs, focus on edits_for_update . Compare with parse_and_migrate_zed_settings (line 702) which already uses the same parse_json approach.

Self-Review Checklist

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Video

Note : Reopens previous work from closed PR #52081 (fork was deleted)

Release Notes:

• Fixed settings being overwritten when updating a single setting via UI while the settings file contains deprecated keys.