Obsidian Parallel Reader

An Obsidian plugin that splits any long note into a left/right parallel-reading layout: the original content stays on the left; LLM-generated section summaries appear on the right. Scrolling the source highlights the matching summary card; clicking a summary jumps the source editor.

Inspired by the reading workflow demo in this Bilibili video.

Features

• Self-adaptive segmentation — the LLM decides natural topic boundaries, no need to match markdown headings. Short adjacent sections merge; long ones split.
• Anchor-based line resolution — summaries carry a verbatim quote from the source; the plugin finds the line number by indexOf (with graceful fallbacks).
• Scroll-sync highlighting — scrolling the source editor updates the active card in the summary pane.
• Right-click → copy — Markdown / plain text / anchor quote / jump to source, as a native Obsidian context menu.
• Markdown rendering — summaries render through Obsidian's official MarkdownRenderer, so tables, bold, code, wikilinks all work.
• Persistent cache — generated summaries are cached by SHA-1 of source content. Reopening a note shows the cached view instantly; edits invalidate the cache (shows a stale banner).
• Three backends — Claude Code CLI, Codex CLI, or Anthropic API. CLI backends reuse your existing subscription and don't need a separate API key.

Installation

Manual install (until this lands in Community Plugins)

1. Clone this repo into .obsidian/plugins/parallel-reader/ in your vault, or symlink it there:

   ln -s /path/to/obsidian-parallel-reader /path/to/YourVault/.obsidian/plugins/parallel-reader
   

2. In Obsidian: Settings → Community plugins → Installed plugins → enable Parallel Reader.

Pick a backend

Backend	Auth	Cost	Notes
Claude Code CLI	OAuth in macOS Keychain	Included in Claude subscription	⚠️ Keychain ACL may block Obsidian subprocess reads — may not work from GUI
Codex CLI	File-based token (~/.codex/auth.json)	Included in ChatGPT Plus	✅ Works from Obsidian GUI; recommended
Anthropic API (direct)	API key in plugin settings	Separate billing	Fallback when CLI auth fails

Configure the CLI path

Obsidian launched from Finder does not inherit your shell PATH. Create a stable symlink in ~/bin/ and point the plugin setting at it:

mkdir -p ~/bin
# Claude Code (Mach-O binary, no Node needed)
ln -sf "$(readlink -f "$(which claude)")" ~/bin/claude
# Codex (Node script — use the wrapper pattern below instead)
cat > ~/bin/codex <<'EOF'
#!/bin/bash
NODE="/path/to/your/node"
CODEX_JS="/path/to/@openai/codex/bin/codex.js"
exec "$NODE" "$CODEX_JS" "$@"
EOF
chmod +x ~/bin/codex

Then in the plugin settings, paste /Users/you/bin/codex (or ~/bin/claude) into CLI 路径, and click Test to verify.

Commands

Command	What it does
为当前笔记生成对照笔记（缓存优先）	Show cached summary if present, otherwise call LLM
强制重新生成（绕过缓存）	Re-run the LLM even if cache matches
打开对照笔记面板	Open right-pane view (loads cache if present)
清除当前笔记的缓存	Drop the cache entry for the active note
清除所有缓存	Wipe all cached summaries

Interaction

Action	Effect
Left-click a card body	Scroll source editor to that section
Right-click a card	Context menu: Copy Markdown / Copy plain text / Copy anchor / Jump
Drag to select text	Normal text selection (does not trigger jump)
Scroll source editor	Active card gets highlighted on the right

Design notes

The LLM is asked to return JSON with this shape:

{
  "cards": [
    {
      "title": "3-10 character short heading",
      "anchor": "40-80 characters, verbatim from source, used for line resolution",
      "gist": "20-40 character one-line summary serving as a lead-in",
      "bullets": ["3-6 supporting details, 20-50 chars each"]
    }
  ]
}

• The anchor is the key mechanism that keeps scroll-sync working without relying on markdown headings. It's copied verbatim so content.indexOf(anchor) finds the origin line; graceful fallbacks (prefix trimming, whitespace normalization) handle minor LLM drift.
• The gist + bullets dual structure was chosen after several iterations — pure prose felt wall-of-text, pure bullets felt fragmented. A one-line lead-in before bullets gives both overview and scannable detail.
• Output is rendered via MarkdownRenderer.render() so any tables / bold / code / wikilinks in the LLM response render natively.

Known limitations

• Document size cap: 20,000 characters. Longer notes are truncated.
• Claude Code CLI auth: Obsidian subprocess reads of the macOS Keychain Claude Code-credentials service may fail due to code-signing ACL. Codex backend doesn't have this issue.
• No streaming: generation is a single batch call; expect ~5-15s wait depending on document length and backend.
• Preview mode: scroll-sync uses Obsidian's setEphemeralState which works in reading mode too, but accuracy depends on how CodeMirror resolves line positions.

License

MIT