nanobot/pr-description.md

fix(feishu): smart message format selection (fixes #1548)

Problem

Currently, the Feishu channel sends all messages as interactive cards (msg_type: "interactive"). This is overkill for short, simple replies like "OK" or "收到" — they look heavy and unnatural compared to normal chat messages.

Solution

Implement smart message format selection that picks the most appropriate Feishu message type based on content analysis:

Content Type	Format	msg_type
Short plain text (≤ 200 chars, no markdown)	Text	text
Medium text with links (≤ 2000 chars, no complex formatting)	Rich Text Post	post
Long text, code blocks, tables, headings, bold/italic, lists	Interactive Card	interactive

How it works

1. _detect_msg_format(content) — Analyzes the message content and returns the optimal format:

   • Checks for complex markdown (code blocks, tables, headings) → interactive
   • Checks for simple markdown (bold, italic, lists) → interactive
   • Checks for links → post (Feishu post format supports <a> tags natively)
   • Short plain text → text
   • Medium plain text → post

2. _markdown_to_post(content) — Converts markdown links [text](url) to Feishu post format with proper a tags. Each line becomes a paragraph in the post body.

3. Modified send() method — Uses _detect_msg_format() to choose the right format, then dispatches to the appropriate sending logic.

Design decisions

• Post format for links only: Feishu's post format ([[{"tag":"text",...}]]) doesn't support bold/italic rendering, so we only use it for messages containing links (where the a tag adds real value). Messages with bold/italic/lists still use cards which render markdown properly.
• Conservative thresholds: 200 chars for text, 2000 chars for post — these keep the UX natural without being too aggressive.
• Backward compatible: The card rendering path is completely unchanged. Only the routing logic is new.

Testing

Format detection tested against 13 cases covering all content types:

• ✅ Plain text → text
• ✅ Links → post
• ✅ Bold/italic/code/tables/headings/lists → interactive
• ✅ Long content → interactive
• ✅ Post format generates valid Feishu post JSON with proper a tags

Changes

• nanobot/channels/feishu.py: Added _detect_msg_format(), _markdown_to_post(), and updated send() method