[Feature]: Independently configurable font size for AI responses

[GammelSami]

Problem or use case

The existing Interface font size setting already enlarges AI assistant responses together with the rest of the interface. What is missing is a separate setting for the AI assistant's response text. This is the one text surface I want to make larger; the rest of the interface is already at a comfortable size.

Long AI responses would be easier to read if I could enlarge them independently, while keeping the sidebar, controls, prompt input, terminal, and code at their preferred sizes.

Proposed solution

Add an AI response font size setting under Appearance / Typography. It should control the prose and rendered Markdown in assistant messages independently of the existing interface, prompt, terminal, and code font-size settings.

Smallest useful scope

• A font-size control with a live preview and reset to default.
• Apply the preference to existing and newly generated assistant responses.
• Scale Markdown paragraphs, lists, and headings consistently, with suitable line spacing.
• Persist the preference across restarts.
• Preserve the separate code font-size preference for fenced code blocks.

Alternatives considered

Whole-app zoom or increasing the interface font size also enlarges other elements. I only want larger AI responses, so these do not provide the independent control I need.

Related reports

I searched existing issues and discussions for font, font size, text size, and typography. #6424 and #7438 concern tool-call details; this request specifically concerns the assistant's answer text.

Source verification

Checked the current web/desktop implementation at commit 061543e9e5b54ec0048725c37d52fef2962df173:

• SettingsPanels.tsx: Interface font size is described as affecting everything outside code blocks and the terminal. Typography exposes Interface, Prompt, Code, and Terminal sizes.
• appearanceFonts.ts: the Interface preference sets the root element font size.
• MessagesTimeline.tsx: assistant answers use ChatMarkdown, whose base text uses text-sm and therefore scales with the root size.
• packages/contracts/src/settings.ts: there is no separate assistant-response font-size preference.

This request is specifically for independent sizing, not for basic resizing of AI responses. Verification was by source inspection, not by running the UI.