Universal kinds; data-driven per-host support; default-deny lossy installs

Context

Different agent hosts have different first-class concepts. A Claude Code "skill" (frontmatter + body + scripts) is not structurally identical to a Cursor "rule" (markdown injected into context) or a Codex AGENTS.md file. dotpack has to decide whether kind means the same thing across hosts (universal taxonomy) or is host-specific (claude-code:skill ≠ cursor:rule).

Decision

Kinds are universal: dotpack defines one taxonomy (skill, agent, command, memory, hook, mcp-server, rule). Per-host kind support is data on the adapter, not a queryable interface artifact — for the file-drop adapter (claude-code, gemini-cli, codex), it's Policy.Layouts membership: a kind present in Layouts is supported; a kind absent is unsupported and Plan returns kind X not yet supported. Per-instance lossiness (the third state in the original three-level rating) is not declared by the adapter; it is computed by the orchestrator at install time from schema aliases per ADR-0012 §8. Default install policy refuses lossy installs unless the user passes --allow-lossy.

Why

Universal kinds keep dotpack's schema and adapter contract small; otherwise every cross-host install would require explicit kind translation and the schema explodes per ecosystem.

Per-host kind support lives as data on the adapter rather than as a separately-queryable Capabilities() method because there is no production consumer of the queryable form — Plan's typed kind X not yet supported error is the only enforcement point the CLI actually traverses. A parallel Capabilities() declaration on the same data invited drift and added an interface method without a caller. Codex-no-agent is now expressed as KindAgent absent from Policy.Layouts, which the adapter docstring annotates as a deliberate decision (not an oversight): "codex CLI documents no native agent loading directory per developers.openai.com/codex."

Per-instance lossiness is computed from the schema (per ADR-0012 §8) rather than declared by the adapter so that adding a host doesn't require restating which fields the schema already names as host-specific. The schema is the single source of truth: each deliberately_excluded entry carries a canonical_concept slug and an aliases: [{host, field_name}, ...] object array; the orchestrator walks the resource's extensions, looks up canonical concepts, and flags any whose alias array doesn't name the target host.

Default-deny on lossy preserves the multi-host value prop: if --agent agents-cli claims to install your skill, by default that means a real install, not a degraded approximation. Users who want lossy behavior have an explicit flag — informed consent.

Consequences

Per-host kind support is a load-bearing per-adapter artifact (in the file-drop adapter, the Layouts map on Policy) and must be kept current as ecosystems evolve. Adapters whose Plan rejects a kind produce a clear error rather than a silent partial install. Users who want lossy behavior have an explicit --allow-lossy flag — informed consent.

A future dotpack adapter caps {name} CLI is still natural — it would render Layouts membership as a per-kind table for human inspection — but does not need to traverse a separate interface method to do so.

Rule-kind addendum (2026-05-27). rule is a named Markdown guidance fragment with YAML introduction metadata. Canonical shared sources live at .agents/rules/<name>.md; adapters materialize project/user rule files at .claude/rules/<name>.md, .gemini/rules/<name>.md, and .codex/rules/<name>.md. The agents-cli umbrella fans out rule installs to Gemini CLI and Codex, preserving one manifest record with ID agents-cli:rule:<name>. See ADR-0013.

History. The original 2026-05-24 version of this ADR posited a three-level per-(kind, adapter) capability matrix (native / lossy / unsupported) returned by an Adapter.Capabilities() method. The 2026-05-25 architecture review (cards #1 and #5) collapsed that machinery: card #1 made per-host kind support data-derived from Policy.Layouts membership; card #5 dropped the Capabilities() method, KindCapabilityMatrix, CapabilityLevel, and the Native / Lossy / Unsupported constants. The pre-2026-05-24 mechanism for declaring host-specific fields (originally proposed as adapter-side lossy_when_fields: [...] lists in this ADR) was already superseded by ADR-0012 §8's schema-side alias arrays. The rationale (single source of truth, safer failure mode, lower new-adapter onboarding cost) is in ADR-0012. The per-resource install-time check and the default-deny-without---allow-lossy policy stand.