[BUG] Desktop 1.12603.1 (macOS): chat prose regular-weight font renders too thin; Chat font setting has no effect (Code tab unaffected)

Note to maintainers: This is about the consumer Claude desktop app (the macOS app for chatting on Pro/Max), not the Claude Code CLI. No public bug tracker exists for the consumer desktop app, so filing here per precedent (#59703, #48473). Please route/relabel rather than close as invalid.

What's wrong?

After updating to Claude Desktop 1.12603.1 (3df4fd) 2026-06-11, regular-weight body text in the Chat tab renders noticeably thinner/lighter than in previous builds, to the point of eye strain. Bold text renders correctly. The Code tab is completely unaffected.

Changing Settings > Appearance > Chat font (Default / Match System / Dyslexic Friendly) makes no difference. A full app restart (Cmd+Q) and zoom reset (Cmd+0) do not help. This points to a regular-weight CSS regression in the chat-bubble (prose) renderer in this build, not a font-selection or system-level issue.

At least one other user has reported the identical symptom on the same version (1.12603.1).

Steps to reproduce

1. Update to Claude Desktop 1.12603.1
2. Open any chat in the Chat tab
3. Observe regular-weight body text appears thin/blurry; bold appears normal
4. Change Settings > Appearance > Chat font — no effect
5. Switch to the Code tab — text renders normally there

Expected

Chat prose regular-weight text renders at the same weight as prior builds.

Actual

Regular-weight text is too thin/blurry; only bold is comfortably legible.

Environment

• Claude Desktop: 1.12603.1 (3df4fd) 2026-06-11
• OS: macOS
• Affected: Chat tab prose (regular weight)
• Not affected: bold text, Code tab