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 tool names drawn from its own vocabulary, as a
   comma-separated string or a YAML list (`agent-definition.md:37`); Copilot CLI expects a list
   drawn from a different alias vocabulary (`execute`/`read`/`edit`/`search`/`agent`/`web`). The
   incompatibility is the vocabulary, not the punctuation: a value correct for one harness names
   tools the other does not have.
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. *(Still unconfirmed as of the 2026-08-14 amendment
   below, which admits `disallowedTools` as an explicitly accepted risk rather than by resolving
   this question.)*

## 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.

*(Narrowed by the 2026-08-14 amendment below: `disallowedTools` is admitted as a fifth allowed
field. `tools:` and every other Claude-only knob remain excluded on the reasoning given here.)*

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.

## Amendment (2026-08-14): the write fence comes back as a denylist

The decision above generalised from `tools:` to "no tool restriction at all". That over-reached.
The unportability argument is specific to the **allowlist**: Claude Code reads `tools:` as a
delimited string of its own tool names, Copilot CLI reads it as a list drawn from its
alias vocabulary (`execute`/`read`/`edit`/`search`/`agent`/`web`), so one value is wrong on one
harness. That reasoning stands, and `tools:` stays out of every plugin-scope agent.

A **denylist** has no such conflict. The evidence for that splits three ways, and this amendment
states which part is which rather than asserting the whole as settled.

**Confirmed — Claude Code honours it for plugin subagents.**
`plugins/kyberforge/docs/research/docs/claude-code-plugins/agent-definition.md:39` documents
`disallowedTools` as a "Denylist applied before `tools`… Takes precedence over `tools`", and — the
part that matters here — it is **not** in that document's plugin-subagent ignore list. Line 99
names exactly three fields plugin agents silently ignore: `hooks`, `mcpServers`, `permissionMode`.
`disallowedTools` is absent from that list. Claude Code is also the harness where the fence is
actually wanted, so the field earns its place on this evidence alone.

**Inferred — the field is very likely inert on Copilot CLI, but by analogy, not by documentation.**
`plugins/kyberforge/docs/research/docs/github-copilot-plugins/troubleshooting.md:50` and `:53`
record Copilot *silently ignoring* two agent frontmatter fields it does not process (`mcp-servers`
and `metadata` outside the cloud runtime) rather than erroring on them. That is a documented
tolerance for *known-but-unprocessed* keys, which is adjacent to, not identical to, tolerance for
an *unknown* key. No stronger evidence exists: a sweep of the vendored Copilot corpus
(`agent-definition.md`, `api-reference.md`, `troubleshooting.md`, `configuration.md`) documents
unknown-key handling nowhere.

**Unverified — Copilot's loader behaviour on an unrecognised key.** Context item 2 above says this
is unconfirmed by research and that remains true; nothing found since changes it. An earlier
revision of this amendment claimed "an unrecognised frontmatter key is inert" as settled fact and
attributed it to apm's verbatim-copy behaviour. That attribution was a non-sequitur — verbatim copy
describes what *apm* does at compile time and says nothing about what *Copilot* does at load time —
and the claim contradicted this ADR's own Context section.

**So this is an accepted risk, stated as one.** Blast radius if the inference is wrong and Copilot
errors on the key: the three affected plugin-scope agents fail to load under Copilot CLI. It is
loud, not silent; it is confined to three agents in three plugins; no other primitive and no Claude
Code path is affected; and the remedy is a one-line frontmatter deletion. What the denylist shape
*does* rule out categorically — independent of loader behaviour — is the failure mode that motivated
dropping `tools:` in the first place: a denied name the other harness does not recognise denies
nothing, so a mis-shaped value can never grant or misroute a capability. The risk is a load failure,
never a silent over-grant. That asymmetry is why the same verbatim copy that makes `tools:`
unshippable makes `disallowedTools` worth shipping.

So the read-only orchestrator agents regain their write fence: `gitea-orchestrate`,
`apm-orchestrate` and `lint-runner` each carry `disallowedTools: Edit, Write, NotebookEdit` plus
explicit prose in the body stating the agent does not edit files. `git-orchestrate` is deliberately
excluded — it legitimately declared `edit` before the conversion and still needs to write.

**Residual — the fence is partial, and the prose is doing more of the work than the field is.**
`disallowedTools: Edit, Write, NotebookEdit` denies exactly those three tools. It does not deny
`Bash`, and at plugin scope these agents carry no `tools:` and therefore inherit it, so
`bash -c 'echo … > f'` remains unfenced by frontmatter. Only the body prose covers that path. This
is not a regression introduced here — the pre-conversion `tools:` allowlists also granted `Bash`,
so the shell route was open then too — but the ADR should not credit the mechanism with more than
it delivers. Closing it would need a `disallowedTools` entry for `Bash`, which these agents cannot
take because they legitimately shell out.

Net position: the allowlist stays dropped for the reason originally given, and the denylist is
admitted as the portable-by-construction half of what was lost. It restores a real, Claude-Code-
confirmed write fence against the tool-call path, not a complete write sandbox. The consequence
below is narrowed accordingly.

Enforcement follows the decision: `agent-audit`'s plugin-scope validator reads its allowlist as
data from the `apm-agent-allowlist` section of
`plugins/kyberforge/.apm/skills/agent-audit/references/field-inventory.md`, and that line now reads
`name description model source_keys disallowedTools`. `disallowedTools` also stays in that file's
`claude-code-only-fields` list, which is not a contradiction — that list governs whether a field
may cross the CC/Copilot boundary in a real project/user-scope *pair*, a different question from
whether a field is safe under verbatim copy in a single vendor-neutral file.

## Consequences

- Every plugin-scope APM agent loses per-agent tool *allowlisting* 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.
  Tool **denial** is not part of that loss — see the 2026-08-14 amendment above.
- **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 for plugin-scope agents, while continuing to serve its original
  two-blocklist role for project/user-scope validation. That file's `apm-agent-allowlist` section
  is the authoritative list and is read as data by `validate.sh`; as amended on 2026-08-14 it holds
  `name`/`description`/`model`/`source_keys`/`disallowedTools` — `source_keys` for provenance
  tracking, validated separately by `validate-provenance.sh` against `sources.md` rather than being
  a provider-specific field, and `disallowedTools` per the amendment above.