Mermaid Fence Helper

Adds mermaid immediately AFTER an opening backtick fence, producing ```mermaid. Closing fences remain unchanged.

Install on Windows

1. Extract the ZIP.
2. In your Obsidian vault folder, open .obsidian, then plugins (create plugins if needed).
3. Copy the entire mermaid-fence-helper folder there. The files must be directly at .obsidian/plugins/mermaid-fence-helper/main.js and manifest.json, with no extra nested folder.
4. Restart Obsidian. Open Settings → Community plugins, enable community plugins if needed, then enable Mermaid Fence Helper.

No build step, Node installation, or paid service is needed.

Use

Automatic mode is off by default for new installations. You can enable it in Settings → Mermaid Fence Helper. When enabled, pasting or editing a complete unlabeled code block starting with flowchart TD, graph LR, or another recognized Mermaid diagram declaration labels its opening fence automatically. Updating preserves your existing setting; turn it off in settings if it was previously enabled.

For existing notes: open the note in editing mode, press Ctrl+P, and choose Mermaid Fence Helper: Add mermaid to diagram blocks in this note.

If you want every unlabeled backtick block in the current note converted, use Mermaid Fence Helper: Add mermaid to ALL unlabeled blocks in this note. This also converts non-diagram blocks, so use it only in notes where that is intended. You can assign either command a shortcut under Settings → Hotkeys.

Behavior and limits

• Only edits the current editor; does not scan or rewrite your whole vault.
• Preserves closing fences, content, line endings, and existing language labels.
• Handles multiple blocks, longer backtick fences, and blockquote/callout fences. Tilde blocks are tracked but not converted.
• Waits for a complete pair of fences. A lone opening fence is left unchanged.
• Automatic detection uses the first nonblank, non-comment line. Mermaid blocks with YAML configuration before their diagram declaration need the ALL command.
• Fences in list items with more than three leading spaces are not supported.
• Disable automatic mode in the plugin settings before undoing an automatic conversion; otherwise later edits can label it again.

Validated with automated parser and mocked Obsidian editor tests. Not tested inside a running Obsidian installation.

API reference: https://docs.obsidian.md/Plugins/Editor/Editor