The reading corpus's exclusion floor closes its frontmatter block earlier than the canonical reader: blockCloser (internal/core/reading/project.go) closes on any column-0 line opening with three dashes, so a column-0 `----` or `--- x` ends the floor's block while frontmatter.IsDelimiter, frontmatter.Fields and a YAML reader read on to the real `---`. The keys between the two closes are frontmatter to the canonical reader and invisible to excludedKeyInFirstBlock and unresolvableFrontmatterShape, so an excluded key there reaches the corpus under a manifest asserting its refusal. Probe: a block opened by `---`, holding `foo: 1`, then `----`, then `secret: x`, then `---` — floor close is line 2, canonical close line 4, Fields reports secret, and excludedKeyInFirstBlock does not refuse it. The allowlist reason in delimiter_canonical_test.go (the floor 'refuses more, never less') is false for this shape.

The reading corpus's exclusion floor closes its frontmatter block earlier than the canonical reader: blockCloser (internal/core/reading/project.go) closes on any column-0 line opening with three dashes, so a column-0 ---- or --- x ends the floor's block while frontmatter.IsDelimiter, frontmatter.Fields and a YAML reader read on to the real ---. The keys between the two closes are frontmatter to the canonical reader and invisible to excludedKeyInFirstBlock and unresolvableFrontmatterShape, so an excluded key there reaches the corpus under a manifest asserting its refusal. Probe: a block opened by ---, holding foo: 1, then ----, then secret: x, then --- — floor close is line 2, canonical close line 4, Fields reports secret, and excludedKeyInFirstBlock does not refuse it. The allowlist reason in delimiter_canonical_test.go (the floor 'refuses more, never less') is false for this shape.

Grounds

• pursued: an excluded key between a ---- (or --- x, BOM-led or CRLF) and the canonical close is refused, and every committed markdown file reads identically through the floor; a document Fields reads a key from that the floor admits would show it wrong