holocron/docs/adr/0016-apm-agent-primitive-drops-provider-specific-fields.md

Plugin-scope agent-author omits tools: and all Claude-only fields from .apm/agents/*.agent.md

This ADR is a narrower, downstream consequence discovered while designing issue #89's implementation under ADR-0015's broader direction (Microsoft APM replaces hand-authored plugin/marketplace authoring). It does not restate ADR-0015's rationale — see that ADR for the parent decision.

Context

APM's agent primitive (.apm/agents/<name>.agent.md) has no per-target integrator in apm compile — confirmed via APM's own Python source (integration/targets.py and related files, cited in plugins/kyberforge/docs/research/docs/microsoft-apm/agent-primitive-schema.md). Compilation does a naive verbatim copy of the whole frontmatter and body to both the Claude Code and Copilot CLI targets. This is unlike:

• The skill primitive, which is also a straight copy (confirmed in the same research doc) but has no field semantics to conflict — SKILL.md's content is target-agnostic already.
• The prompt, instructions, and hooks primitives, which each get real per-target reconstruction through a dedicated integrator (field allowlisting, key renaming, dropped-field warnings).

Because the agent primitive ships the same frontmatter unchanged to both harnesses, two concrete incompatibilities surface:

1. tools: — Claude Code expects a space-separated tool-name string; Copilot CLI expects a list drawn from its own alias vocabulary (execute/read/edit/search/agent/web). A value correct for one harness is wrong for the other.
2. Claude-only knobs with no Copilot equivalent — isolation, maxTurns, effort, memory, permissionMode. Writing any of these means Copilot's copy carries frontmatter keys it doesn't recognize at all. Whether Copilot's agent loader ignores unknown keys or errors on them is unconfirmed by research.

Decision

At plugin scope only (destination package has an apm.yml at its root — an APM producer package compiled via apm compile), .apm/agents/<name>.agent.md carries only name, description, model, and the prose body. No tools: field, no Claude-only fields, at all.

Absent tools: means inherit-all-tools on both harnesses — the one value that is never wrong on either target, unlike a present, harness-specific value that is guaranteed wrong on at least one of them.

agent-audit, at plugin scope, is intended to flag — as a SUGGESTION, not a FAIL, since this is an upstream schema limitation rather than an authoring mistake — any agent whose description or body implies a need for tool restriction or a Claude-only behavior the frontmatter can no longer express. This would give visibility into the gap without pretending the schema can do something it can't. Not yet implemented: check_apm_agent_file() in validate.sh currently validates only the field allowlist, name, description, and body-emptiness/length — it has no heuristic for this case. Tracked as follow-up work.

Scope boundary

This decision applies to plugin-scope agent-author only. Project scope (.claude/agents/

• .github/agents/) and user scope (~/.claude/agents/ + ~/.copilot/agents/) are not APM packages — neither goes through apm compile — so both keep today's dual-file Claude+Copilot pair model exactly as ADR-0005 and ADR-0008 already describe. Those two ADRs remain fully authoritative for project and user scope; only their plugin-scope clauses are affected by this ADR (see the update notes appended to each).

Considered options

Pick one harness's vocabulary and accept breakage on the other (rejected). E.g. always write Claude's space-separated tools: string. Rejected because it ships a value that is silently wrong (or possibly a hard error) on Copilot, and which harness "wins" would be an arbitrary, undocumented asymmetry.

Same as above, but agent-audit flags the cross-harness breakage as a tracked finding (rejected). Rejected for the same core reason — it still ships a wrong value to a real harness. Tracking the breakage doesn't prevent it, and the chosen decision already gets equivalent visibility (a SUGGESTION finding) without ever shipping the wrong value in the first place.

Consequences

• Every plugin-scope APM agent loses per-agent tool restriction and any Claude-only capability (isolation, maxTurns, effort, memory, permissionMode) until APM ships a real per-target integrator for the agent primitive. This is a known, accepted regression, not an oversight.
• ADR-0005 is partially superseded — its plugin-scope clause ("directory containing plugin.json is plugin scope → both files land in <root>/agents/") no longer applies. Plugin scope is now "directory containing apm.yml → single vendor-neutral file lands in <root>/.apm/agents/." Project and user scope, and the rest of ADR-0005, are unaffected.
• ADR-0008 is partially superseded — its counterpart-derivation/pair-validation mechanism no longer applies at plugin scope; agent-audit takes the single file directly there. Project and user scope, where a real pair still exists, are unaffected.
• ADR-0009 is not superseded. The mechanism it established — agent-audit reading field lists from references/field-inventory.md rather than hardcoding them, with a source_keys provenance chain — survives and is reused. Only the content shape changes for plugin scope: field-inventory.md shifts from two side-by-side CC-only/Copilot-only blocklists to one vendor-neutral allowlist (name/description/model) for plugin-scope agents, while continuing to serve its original two-blocklist role for project/user-scope validation.