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type: adr id: adr-0059 status: accepted created: 2026-06-11 updated: 2026-06-11

ADR-0059 — Frontmatter type: is the sole artifact discriminator

Context

Artifact identification previously hinged on a filename infix; the adopter audit (O-012 §1) found a naming convention with no consuming tool to be pure ceremony that fights editors, renderers, and casual file operations, and the strategic synthesis directs plain .md everywhere. The workspace model already identified artifacts by frontmatter in practice.

Decision

1. Every corpus artifact is a plain .md file whose frontmatter type: identifies it (spec | task | review | finding | status | intake | inventory | change-plan | audit | bug-report | adr | research | prd | rfc | threat-model). Tools and agents discriminate on type:, never on filename.
2. No corpus file, template, example, or fixture uses a .corpus. filename infix. The optional stricter spec surface is selected by format: sol (ADR-0058) — frontmatter, not filename.
3. The names *.corpus.ir.json and *.corpus.plan.json survive only as reserved contract names on the future-CLI page for machine-emitted artifacts no shipped tool produces today.

Alternatives considered

Alternative	Why weaker
Keep the infix as an optional convention	A residue with no remaining function once format: sol exists; two selectors invite drift
Discriminate by directory	Breaks on co-located and small-team layouts; type: travels with the file

Consequences

Positive: zero naming ceremony; renders everywhere; enterprise-friendly. Negative: tools must read frontmatter (trivial). Neutral: greppability moves from filename to type: line.

Status

Accepted. Supersedes the filename-infix partition model of the former source-artifacts reference; refines ADR-0030 and ADR-0054.

Propagation

All file-producing surfaces; conformance manifest (format: sol selector); corpus-cli parser targets.

Addendum (2026-06-11): the reserved machine-artifact contract names are spelled without the infix — <spec>.ir.json / <spec>.plan.json — consistent with §2; the future-CLI page is their only home. No IR fixtures ship; the schemas are the contract.