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Prevent title and subtitle duplication in published post bodies #537
Description
Problem
When a Markdown source contains title and subtitle front matter and repeats those values at the start of the Markdown body, the resulting Substack draft can show the title/subtitle both in Substack's header fields and in the article body.
Initial evidence
- Front matter is correctly removed by
parseFrontmatter(). preparePost()removes only a leading Markdown heading that exactly matches the resolved title.- It does not remove a matching leading subtitle paragraph/heading.
- Checked-in
examples/basic.mdcurrently repeats the front-matter title as a body H1. - Documentation does not state the canonical no-duplication source shape.
- Agent integration packages provide MCP launch metadata but no authoring guardrail for this ambiguity.
Reproduction
---
title: "Example title"
subtitle: "Example subtitle"
---
# Example title
Example subtitle
Actual body.Expected prepared body: Actual body.
Actual prepared body: subtitle remains in the generated ProseMirror body. Title removal is limited to an exact leading heading match and is not documented.
Acceptance criteria
- Normalize an exact leading title plus exact leading subtitle out of the prepared body without removing legitimate non-matching content.
- Cover title-only, title+subtitle, formatting, mismatch, and no-front-matter cases with regression tests.
- Document one canonical source format for users and agents.
- Correct misleading checked-in examples.
- Preserve title fallback from a leading heading when front matter has no title.
Activity
edithatogo commentedon Aug 10, 2026
Resolved by T18-01. Exact leading title/subtitle metadata repetitions are normalized at the shared preparation boundary; mismatches and fallback behavior are preserved. Local verification: 14 focused tests, 933 total tests, typecheck and contract checks passed.
Fix title and subtitle body duplication (#542)
Close T18-01 patch coverage gap (#543)
edithatogo commentedon Aug 10, 2026
T18-01 closeout receipt:
59e5dfc3ca76b53250fba450b247f70dc6af0003cdbb8e9a75c70495c687d0790aa694fb2da29127masteris at remote merge SHAcdbb8e9a75c70495c687d0790aa694fb2da29127