## What happens `chunking.py` tracks fenced code blocks — a `##` inside a fence is prose, and adr-927aa43d9635 says so explicitly. `markdown_sections.py` does not track them at all: `_HEADING_RE` is matched line by line with no fence state. The two therefore disagree about what the sections of a document *are*. Reproduced on a body whose rule quotes a markdown template: headings the reader sees : ['Rule 7', 'Purpose', 'Owns', 'Rule 8'] headings the chunker sees: ['Rule 7'] ## Why it is blocking Three failures, worst last. `docir get --section "Rule 7"` returns a fragment that stops at the fake heading — ending with an **unclosed** fence. The reader gets invalid markdown and no indication that anything was cut. An unknown-heading error lists the phantom headings as real ones, so the flag that exists to save a full-body read sends the caller to a heading that is not a section. And `docir update --replace-section "Rule 7" --body "..."` writes the replacement at the true start but ends it at the fake boundary, leaving the remainder of the quoted template stranded at top level with a stray closing fence. The body is corrupted, the command reports success, and nothing in `docir check` detects it. ## Where it bites today `arch-322e5f992ad2` (Architecture Rules) quotes a `CONTRACT.md` template in rule 7 and a decision-record template in rule 14. Both are inside fences, and both currently read as sections — so that document cannot be edited section-wise without losing text. ## What it needs Fence tracking in `markdown_sections.py`, shared with `chunking.py` rather than written twice — the two disagreeing is the defect, so a second copy of the rule would only postpone it. `_locate_section`, `_section_end` and `section_headings` all need it, since a caller can reach the same divergence through any of them. The regression guard has to inject the bug: a body with a fenced `##`, asserting that the reader and the chunker return the *same* heading list, and that a replace round-trips without moving text outside the section. ## Resolution Fixed by `markdown_headings.scan_headings`, one fence-aware scanner both `markdown_sections` and `chunking` now read; the private regex pair is gone from each. `arch-322e5f992ad2` reports 24 real sections where it used to report 25 with 10 phantoms, and `--section "7. Contract documentation"` now returns the whole rule, fences balanced, at 1,051 characters. `tests/modules/documents/test_markdown_headings.py` guards it two ways, and both were verified by injecting the defect. Removing fence tracking from the scanner fails 6 tests; giving the reader its own naive scanner again fails 5, including the sweep over every document in this repo. The agreement guard's first version asserted `chunked <= read`, which the second injection passed — a naive reader returns *more* headings, which is the direction the original bug went. It now asserts set equality against the shared scanner. Worth remembering: the subset assertion looked like a check and was not one.