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The capsule

A todo’s identity lives in an HTML comment at the end of the line. Obsidian’s Reading view does not render it, and in Live Preview MarkTodo hides it unless you turn on Show todo ID capsule in editor.

- [/] Demo old floor @high due @ 2026-07-01 <!-- mt id=a2c3Xk9P -->
  • The id is 8 characters and is stamped lazily — only when a todo is first acted on or adopted. Plain checkboxes you never touch stay plain.
  • Unknown keys inside the capsule are preserved verbatim, so a newer version of MarkTodo can add things without an older one destroying them.

Tags and [[links]] stay inline too, exactly where you put them. Round-trips are byte-stable by construction: every write aborts rather than drop a todo.