Inspect — AgBOM

AI agents add and remove capabilities at runtime: a model swap mid-session, a hot-loaded MCP server, a new A2A peer, a knowledge source registered after sessionStart. Without inspectability, every Guardian policy that depends on what the agent is (rather than only what it does) becomes unverifiable.

The Agent Bill of Materials (AgBOM) is a queryable, dynamic inventory of the components an Observed Agent uses: Models, MCP servers, A2A peers, Tools, Knowledge sources, Memory stores, and Agent capabilities.

AgBOM extends industry standards

ACS doesn't introduce a new BOM format. The canonical AgBOM is a structured component graph; CycloneDX, SPDX, and SWID outputs are deterministic derivations of the same graph.

AgBOM emission is the subject of the ACS-Inspect conformance profile. When Guardian policy depends on component inventory (e.g. banning a model or tool at the boundary), the deployment MUST implement ACS-Inspect.

Wire methods

The agbom/* namespace is reserved by Specification §3. Two methods are defined in v0.1.0:

Method	Direction	Trigger
agbom/snapshot	Observed → Guardian	Once after sessionStart, before any content-bearing hook; and after any handshake renegotiation. Carries the full AgBOM.
agbom/changed	Observed → Guardian	Whenever a component is added, removed, or version-changed mid-session. Carries either a full snapshot or a diff (added[], removed[], changed[]).

Both methods follow the standard ACS request envelope and are written into the SessionContext audit chain — AgBOM mutation is part of the security-relevant history of the session. Decisions are normally allow; Guardians MAY return deny to refuse a session whose component graph contains a banned component, or to block a hot-swap.

agbom/changed is part of the ACS-Inspect-Dynamic profile extension. Deployments that claim only ACS-Inspect emit a single snapshot and do not track mid-session mutations.

Canonical schema

Every component graph is expressed in the canonical AgBOM document (agbom/document.json). Components are typed; the type set in v0.1.0 is:

Type	Required fields	Optional fields
model	id, name, version, provider, endpoint (URI), context_window	args (model-config snapshot)
mcp_server	id, name, version, endpoint (URI), tools[]	—
a2a_peer	id, endpoint (URI), protocol_version	agent_card_ref (URI to peer's Agent Card if known)
tool	id, name, version, provider, capability (abstract: filesystem.delete, network.egress, process.execute, …)	—
knowledge_source	id, name, source_type (vector_db/search_index/knowledge_base/web_search/other)	endpoint (URI), schema_ref (URI)
memory_store	id, name, scope (session/user/tenant/global), store_type	path (URI), window_size
agent_capability	id, name, description	tools[], mcp_servers[], a2a_peers[]
skill	id, name, description, definition (ref, digest)	declared_capabilities[], tools[], mcp_servers[], a2a_peers[], models[], composed_skills[]

The full per-component schema is agbom/component.json.

Every component SHOULD carry registration_provenance (who declared it — framework / configuration / runtime discovery) so AgBOM mutations are traceable in the same lineage system as data flow. Deployments claiming ACS-Provenance MUST populate registration_provenance on every component.

Output format mappings

The canonical document is the source of truth; serialized output is a deterministic derivation. The mapping rules live in inspect/format-mapping.json.

Standard	ACS extension	Status
CycloneDX 1.6	Extending CycloneDX	Working draft
SPDX 3.0	Extending SPDX	Working draft
SWID	Extending SWID	Working draft

A Guardian MAY request a specific serialization in the handshake's AgBOM negotiation (agbom_serializations_supported in ServerHello); the canonical form is always the source of truth and the serializations are derivations.

ACS-Inspect conformance bar

A deployment claiming ACS-Inspect MUST:

1. Emit agbom/snapshot once per session, before content-bearing hooks fire.
2. Have the Guardian accept agbom/snapshot, write it into the SessionContext audit chain, and serialize the canonical AgBOM into at least one of {CycloneDX 1.6, SPDX 3.0, SWID} on request.

A deployment claiming ACS-Inspect-Dynamic additionally MUST:

1. Emit agbom/changed on every mutation to the component graph.
2. Write those mutations into the audit chain.

Without -Dynamic, a deployment that hot-swaps components silently is not Inspect-conformant for that session — the Guardian's view of the agent diverges from runtime reality.

Triggers for AgBOM updates

• Model added, removed, or version-changed.
• MCP server discovered, removed, or version-changed.
• A2A peer registered or deregistered.
• Tool registered, removed, or capability-changed.
• Knowledge source connected or disconnected.
• Memory store attached or detached.
• Agent capability declared or revoked.