Exercise 3 — Solution

Task: A new rules file, say a hypothetical "video_lesson_rules.md", is
written and saved into the rules/ folder, but the chapter-writer
forgets one specific step. Based on this chapter's own comparison
table, what will actually happen the next time a new session starts,
and why?

The most likely forgotten step is adding a corresponding
@rules/video_lesson_rules.md line to CLAUDE.md's own include list.

What happens the next time a new session starts: nothing about
video_lesson_rules.md is automatically loaded at all. The file genuinely
exists on disk, correctly written, sitting in the rules/ folder exactly
where every other rules file lives - but CLAUDE.md only pulls in the
specific files it explicitly references via an @rules/ line. A rules
file that exists but was never added to that list is invisible to a
new session by default, exactly the same as if it had never been
written - the session will have no idea any video-lesson conventions
exist unless someone happens to read the file manually, or references
it directly in that session's own conversation.

This is precisely why the chapter's own comparison table lists "A new
rules file must be added to the @rules/ list to be included" under
"What's still needed" for the automatic-inclusion system - it's the
one manual step this whole design didn't eliminate, just narrowed down
to a single one-time action per new rules file, rather than something
that has to be repeated every single session the way the old R1
recovery prompt did.

Notes:
- This scenario is a genuine, easy-to-make mistake in practice - it's
  entirely possible to write a real, correct rules file and forget the
  one-line wiring step that actually makes it take effect automatically.
- Chapter 10's own capstone works through this exact "wiring a new
  rules file into CLAUDE.md" step in full, specifically to make this
  easy-to-miss step concrete and memorable rather than just described
  in the abstract.