Add the Copilot Agent Plugins 1.0 marketplace bundle (R2)

vscode_copilot models only VS Code's repo-local hooks
(.github/hooks/agentseam.json, "no bundle format"). GitHub Copilot's
marketplace intake is a different artifact entirely: Agent Plugins
1.0, plugin.json at bundle root plus com.github.copilot/hooks/hooks.json.
Both known consumers emit Copilot marketplace plugins, so this bundle
format cannot stay a consumer concern without breaking standalone.

New distinct `copilot` PACKAGING row (unit=plugin), sourced from
microsoft/vscode-docs' own agent-plugins.md: skills and mcp.json are
the standard's portable component types, found by location exactly
like every other plugin format here (skills/{name}/SKILL.md is now
shared by five formats, not four); everything else Copilot can hold
lives under the client-specific com.github.copilot/ namespace.
plugin.json requires a fixed $schema field to be recognized as this
format at all -- packaging.plan()'s manifest renderer gained
`manifest_fixed` to render it, since omitting it silently falls back
to an unrelated legacy format. Slash commands degrade honestly to a
PART_LIMITS refusal: the folder is documented, the file format inside
it is not.

The honesty gate: whether Copilot actually executes these hooks once
installed. Two primary vendor sources establish that it does -- VS
Code's own docs state plugin hooks "fire in addition to any other
hooks configured for the same event," and separately that Copilot CLI
and the Copilot app read the same com.github.copilot namespace;
Copilot CLI's own hooks-reference.md independently lists
"hooks contributed by installed plugins" in its combined, executed
hook-loading order. Recorded as docs-basis, not live-verified, with an
open, unconfirmed bug report (github/copilot-cli#2540) noted rather
than omitted.

No separate adapter is registered for "copilot": vscode_copilot's
adapter already claims this exact wire dialect (verified: VS Code and
Copilot CLI share one hook engine, two event-name spellings), so a
second adapter with an identical claims() would make every VS
Code/Copilot CLI payload ambiguous to adapters.detect() and break
dispatch for both. The matrix row (tier=TIER_UNADAPTED, events={})
reflects that honestly: no capability claimed under this identity that
dispatch cannot actually deliver, with the real, cited evidence in
notes/verified rather than silently omitted. instructions.py and
permissions_data.py both updated for the new matrix membership:
instruction files point at the same repo files vscode_copilot already
uses (same product, same repo), and the permissions capability stays
unrecorded (a distribution-only identity has no live settings surface
of its own to duplicate vscode_copilot's).

packaging_data.py split: PART_LIMITS/ALSO_READS/UNRECORDED moved to
packaging_limits.py (re-exported) to keep both files under the
300-line budget.

Marketplace INDEX aggregation stays out of scope per the spec --
this is the bundle FORMAT only.

Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>

Author: jothimani-rajendran

README.md

@@ -88,10 +88,10 @@ updated   AGENTS.md
 created   CLAUDE.md
 created   .junie/guidelines.md
 ...
-covered by AGENTS.md: aider, codex_cli, cursor, gemini_cli, kimi_code, vscode_copilot, windsurf, zed
+covered by AGENTS.md: codex_cli, copilot, cursor, gemini_cli, kimi_code, vscode_copilot, windsurf, zed
 ```
 
-15 agents reached with 9 files written, because 7 of them read `AGENTS.md` natively and a
+16 agents reached with 9 files written, because 8 of them read `AGENTS.md` natively and a
 second copy would only drift. Content is written as a marker-delimited block, so anything a
 human wrote in those files is preserved untouched — and `instructions --list` shows what
 a repo is already telling its agents.

src/agentseam/instructions.py

@@ -41,6 +41,14 @@
         "shared": True,
         "imports": None,
     },
+    # Not a second product: a repo running an installed Agent Plugins 1.0 "copilot" bundle
+    # (packaging_data.PACKAGING) is running actual GitHub Copilot, which reads the same
+    # repo-level instructions file regardless of which surface installed the plugin.
+    "copilot": {
+        "files": [".github/copilot-instructions.md", ".github/agents/agentseam.agent.md"],
+        "shared": True,
+        "imports": None,
+    },
     "gemini_cli": {"files": ["GEMINI.md", ".gemini/GEMINI.md"], "shared": True, "imports": None},
     "windsurf": {"files": [".windsurf/rules/agentseam.md", ".windsurfrules"], "shared": True, "imports": None},
     # Aider discovers nothing by convention: it reads the files listed under `read:` in

src/agentseam/matrix_evidence.py

@@ -70,6 +70,32 @@
             "stop",
         ),
     },
+    "copilot": {
+        # Not the vscode_copilot row's product -- this is the honesty gate for hooks shipped
+        # inside an Agent Plugins 1.0 MARKETPLACE bundle specifically (packaging_data.py's
+        # "copilot" row). No adapter is registered under this name (see matrix_gaps.py's
+        # "copilot" row for why), so this evidence documents what was found, not a dispatch
+        # path reachable from here.
+        "basis": BASIS_DOCS,
+        "version": "VS Code 1.110+ (Agent Plugins 1.0); Copilot CLI per docs, no build pinned",
+        "date": "2026-08-29",
+        "method": (
+            "vendor docs read from a clone: microsoft/vscode-docs "
+            "docs/agent-customization/agent-plugins.md states plainly, for VS Code's own "
+            "engine, 'When a plugin is enabled, its hooks fire in addition to any other hooks "
+            "configured for the same event,' and separately that VS Code 'reads custom agents, "
+            "slash commands, rules, and hooks from the com.github.copilot namespace, which "
+            "GitHub Copilot CLI and the GitHub Copilot app also read.' github/docs "
+            "content/copilot/reference/hooks-reference.md corroborates for the CLI side: its "
+            "documented hook-loading order combines policy, user, and project hooks with "
+            "'hooks contributed by installed plugins.' Neither document was read against a "
+            "running build, and an open, unconfirmed bug report (github/copilot-cli#2540, "
+            "v1.0.18) says a plugin's hooks.json hooks did not fire for one reporter -- filed "
+            "against the Legacy Copilot format's root hooks.json, not the Agent Plugins 1.0 "
+            "com.github.copilot/hooks/hooks.json path this row is about, and not confirmed by "
+            "a maintainer, but recorded rather than omitted."
+        ),
+    },
     "cursor": {
         "basis": BASIS_LIVE_PARTIAL,
         "version": "3.17.8",

src/agentseam/matrix_gaps.py

@@ -21,6 +21,20 @@
 from .matrix_terms import TIER_NONE, TIER_UNADAPTED
 
 GAPS = {
+    "copilot": {
+        # Not "no surface" (TIER_NONE would say that, and it would be false -- see
+        # EVIDENCE/NOTES) and not "nobody built the adapter yet" in the usual TIER_UNADAPTED
+        # sense either: an adapter under this name would collide with vscode_copilot's, which
+        # already dispatches this exact wire dialect. This row exists so
+        # packaging_data.PACKAGING's "copilot" identity (the Agent Plugins 1.0 marketplace
+        # bundle) has a matrix row at all, per test_packaging's completeness invariant.
+        "display": "GitHub Copilot (Agent Plugins 1.0 marketplace bundle)",
+        "tier": TIER_UNADAPTED,
+        "config": None,
+        "verified": EVIDENCE["copilot"],
+        "events": {},
+        "notes": NOTES["copilot"],
+    },
     "replit": {
         "display": "Replit Agent",
         "tier": TIER_UNADAPTED,

src/agentseam/matrix_notes.py

@@ -9,6 +9,22 @@
 from __future__ import annotations
 
 NOTES = {
+    "copilot": "TIER_UNADAPTED and events={} are deliberate, not a placeholder for an adapter "
+    "that has not been written yet: a real adapter under this name would claim every payload "
+    "vscode_copilot already claims (the wire dialect is documented as identical), and "
+    "adapters.detect() treats a payload two adapters both claim as unidentified -- registering "
+    "one here would silently stop dispatch working for every existing VS Code/Copilot CLI "
+    "user. A hook that ships inside a copilot-format bundle is dispatched through the "
+    "vscode_copilot adapter at runtime; 'copilot' exists only as packaging_data.PACKAGING's "
+    "identity for the Agent Plugins 1.0 marketplace bundle FORMAT, a genuinely different "
+    "artifact from vscode_copilot's repo-local .github/hooks/agentseam.json (own manifest, "
+    "own namespaced paths, published to a marketplace rather than committed to a repo). "
+    "The honest capability answer is NOT 'none': see EVIDENCE['copilot'] for what was found "
+    "-- VS Code documents plugin hooks as firing alongside workspace hooks, and documents "
+    "Copilot CLI and the Copilot app as reading the same com.github.copilot namespace; "
+    "Copilot CLI's own hooks-reference.md separately lists installed-plugin hooks as one of "
+    "its combined, executed sources. Recorded here as docs-basis evidence, not a live "
+    "capability claim, because nothing here was run against a live build.",
     "junie": "Strongest gate here: PreToolUse returns allow/ask/block and carries "
     "updatedInput, so block, ask and rewrite are all native. Its event names and field "
     "names are Claude Code's by design; project_path is what separates the two payloads. "

src/agentseam/packaging.py

@@ -210,13 +210,20 @@ def _manifest(agent, bundle, kinds):
 
     Only the parts the bundle actually has are declared. Pointing at `./skills` in a bundle
     with no skills advertises a directory that is not there.
+
+    `manifest_fixed` is a third thing again: fields a format requires on every manifest
+    regardless of what the bundle holds -- Agent Plugins 1.0's `$schema` is the only one
+    today, and it is load-bearing rather than decorative: without it the host falls back to
+    reading the file as an unrelated legacy format, silently mislabeling the whole bundle.
     """
     row = PACKAGING[agent]
     if not row["manifest"]:
         return None
     body = {"name": bundle.name, "version": bundle.version}
     if bundle.description:
         body["description"] = bundle.description
+    for key, value in (row.get("manifest_fixed") or {}).items():
+        body[key] = value
     for kind, (key, value) in sorted((row.get("declares") or {}).items()):
         if kind in kinds:
             body[key] = value

src/agentseam/packaging_data.py

@@ -224,69 +224,55 @@
             "date": "2026-08-26",
         },
     },
-}
-
-#: Why a specific agent cannot hold a specific part. Without these the generic message
-#: ("this format has no place for it") would understate Gemini, which supports MCP servers
-#: perfectly well -- just in the manifest rather than in a file of its own.
-PART_LIMITS = {
-    ("codex_cli", MCP): "MCP servers are declared inside .codex-plugin/plugin.json under "
-    "`mcp_servers`, not in a file of their own",
-    ("codex_cli", COMMAND): "the manifest reads command paths from a `commands` field, but the "
-    "command FILE format was not established here -- a guessed format ships a plugin whose "
-    "commands silently do not load",
-    ("codex_cli", SUBAGENT): "no subagent field exists in the plugin manifest",
-    ("codex_cli", EXECUTABLE): "RawPluginManifest's field list is exhaustive (name, version, "
-    "description, keywords, skills, mcp_servers, apps, hooks, interface) and none names a "
-    "bundled executable or scripts path; whether an undeclared file elsewhere in the plugin "
-    "directory survives installation to be referenced by a hook command was not established here",
-    ("cursor", MCP): "no MCP declaration was established for this plugin format",
-    ("cursor", COMMAND): "no command format was established for this plugin format",
-    ("cursor", SUBAGENT): "no subagent format was established for this plugin format",
-    ("cursor", EXECUTABLE): "no scripts/executable location was established for this closed-source "
-    "plugin format; the documented layout (.cursor-plugin/, skills/, rules/, mcp.json) names "
-    "no place for one",
-    ("gemini_cli", MCP): "MCP servers are declared inside gemini-extension.json, not in a file "
-    "of their own; a rendered .mcp.json would simply be ignored",
-    ("vscode_copilot", MCP): "MCP servers are configured by the editor rather than shipped alongside these parts",
-}
-
-#: Folders an agent reads that belong to *another* agent. This is the interop surface:
-#: a repository that ships .claude/skills is already shipping skills to VS Code.
-ALSO_READS = {
-    "vscode_copilot": {
-        SKILL: (SHARED_SKILL_DIR, ".claude/skills", "~/.agents/skills", "~/.copilot/skills", "~/.claude/skills"),
-        SUBAGENT: (".claude/agents", "~/.copilot/agents", "~/.claude/agents"),
-        HOOKS: (".claude/settings.json", ".claude/settings.local.json", "~/.claude/settings.json"),
+    "copilot": {
+        # The Agent Plugins 1.0 MARKETPLACE bundle -- a distinct artifact from vscode_copilot's
+        # repo-local .github/hooks/agentseam.json, per the spec: skills and MCP are the
+        # standard's own portable component types, found by location; everything else Copilot
+        # can hold is client-specific and lives under the com.github.copilot/ namespace inside
+        # the bundle. No "declares": both portable and namespaced parts are discovered by
+        # location, never resolved from the manifest.
+        "unit": "plugin",
+        "manifest": "plugin.json",
+        "manifest_format": "json",
+        # Required and fixed, not bundle-varying: without it a rendered plugin.json is
+        # auto-detected as the unrelated Legacy "Copilot" format instead (VS Code's own
+        # fallback rule -- see the row's "verified" -- silently mislabeling the whole bundle).
+        "manifest_fixed": {"$schema": "https://agent-plugins.org/schemas/1.0.0/plugin.schema.json"},
+        "project_root": "{bundle}",
+        "plugin_root": ("${PLUGIN_ROOT}",),
+        "parts": {
+            SKILL: "skills/{name}/SKILL.md",
+            SUBAGENT: "com.github.copilot/agents/{name}.agent.md",
+            COMMAND: None,
+            HOOKS: "com.github.copilot/hooks/hooks.json",
+            MCP: "mcp.json",
+            EXECUTABLE: "scripts/{name}",
+        },
+        "notes": (
+            "skills/ and mcp.json are the standard's own portable component types -- "
+            "byte-identical skills/{name}/SKILL.md to every other plugin format here -- found "
+            "by location like the manifest fields say. Everything else Copilot can hold "
+            "(agents, hooks, and slash commands) is client-specific and lives under "
+            "com.github.copilot/, which other clients ignore so the bundle stays portable. "
+            "scripts/ sits at the bundle root, outside the namespace, exactly as the vendor's "
+            "own example places a hook's script -- referenced via ${PLUGIN_ROOT}, the token "
+            "this format defines (NOT ${CLAUDE_PLUGIN_ROOT}, which is the Legacy Copilot "
+            "format's spelling, alongside ${PLUGIN_ROOT}, per the same vendor table). "
+            "See MATRIX['copilot'] for whether these hooks actually run once installed -- "
+            "the honesty gate this row exists to pass."
+        ),
+        "verified": {
+            "method": "vendor source read from a clone: microsoft/vscode-docs "
+            "docs/agent-customization/agent-plugins.md -- the directory example, the plugin "
+            "manifest field table ($schema required), the plugin-format auto-detection rule "
+            "(no $schema falls back to the unrelated Legacy Copilot format), and the "
+            "plugin-root token table (Agent Plugins 1.0: ${PLUGIN_ROOT} only)",
+            "date": "2026-08-29",
+        },
     },
 }
 
-#: Every agent the matrix knows that has no packaging format recorded here, and why.
-#:
-#: Exhaustive on purpose, and enforced by a test: recorded plus unrecorded must equal the
-#: matrix exactly. A missing agent reads as "nothing to package here" when the truth is
-#: "nobody looked", and that is the one thing this module must never say by accident.
-#:
-#: Several of these are *not* blanks. Where a vendor's own hook documentation proves that
-#: skills or subagents exist -- a SubagentStop event, a define_subagent tool, a loader that
-#: mentions skills -- that is recorded, because "we could not find the layout" and "there is
-#: no such thing" are different answers and only one of them is true.
-UNRECORDED = {
-    "aider": "no packaging format established here",
-    "antigravity": "subagents provably exist -- define_subagent and invoke_subagent are tools it "
-    "offers, and its file reader takes an IsSkillFile argument -- but the on-disk layout was "
-    "not established here",
-    "devin": "skills provably exist -- its hook loader is documented as following the same "
-    "discovery rules as skills and rules -- but their layout was not read here",
-    "grok": "subagents provably exist (SubagentStart and SubagentStop hook events), and it has an "
-    "extensions system, but neither layout was established here",
-    "junie": "extensions provably exist and ship hooks at hooks/hooks.json in the Claude "
-    "plugin layout, with ${JUNIE_EXTENSION_ROOT} aliasing ${CLAUDE_PLUGIN_ROOT} -- but the "
-    "rest of the extension layout, and how skills and commands sit in it, was not read here",
-    "kimi_code": "subagents provably exist (a SubagentStop hook event, and a documented agents "
-    "and sub-agents feature) but their layout was not read here",
-    "replit": "no packaging format established here",
-    "tabnine": "no packaging format established here; vendor documentation is unreachable from this environment",
-    "windsurf": "vendor documentation unreachable from the environment this was written in",
-    "zed": "no packaging format established here",
-}
+#: PART_LIMITS, ALSO_READS, and UNRECORDED moved to packaging_limits.py to keep this module
+#: under the line budget; re-exported here so `from .packaging_data import ...` still works
+#: everywhere it already did.
+from .packaging_limits import ALSO_READS, PART_LIMITS, UNRECORDED  # noqa: E402,F401