diff --git a/_capabilities/policy/no-git-ops/capability.toml b/_capabilities/policy/no-git-ops/capability.toml
index 4089790..bb2421a 100644
--- a/_capabilities/policy/no-git-ops/capability.toml
+++ b/_capabilities/policy/no-git-ops/capability.toml
@@ -24,3 +24,16 @@ rust-module = "gates::policy_no_git_ops"
 event = "PreToolUse:Bash"
 severity = "block"
 bypass-env = "ORCHESTRATOR_META"
+
+[taxonomy]
+kingdom = "capability"
+mechanism = "gate"
+domain = "policy"
+layer = "agent-substrate"
+stability = "stable"
+language = "rust"
+
+[lineage]
+parents = []
+creator = "ag-orchestrator-human"
+created = "2026-04-23"
diff --git a/_capabilities/quality/cargo-check-green/capability.toml b/_capabilities/quality/cargo-check-green/capability.toml
index 419c84e..e78e767 100644
--- a/_capabilities/quality/cargo-check-green/capability.toml
+++ b/_capabilities/quality/cargo-check-green/capability.toml
@@ -19,3 +19,16 @@ path = "text.md"
 rust-module = "verifies::quality_cargo_check_green"
 run-mode = "both"
 when = "on-return"
+
+[taxonomy]
+kingdom = "capability"
+mechanism = "verify"
+domain = "quality"
+layer = "agent-substrate"
+stability = "stable"
+language = "rust"
+
+[lineage]
+parents = []
+creator = "ag-orchestrator-human"
+created = "2026-04-23"
diff --git a/_capabilities/tools/bash-allowlist/capability.toml b/_capabilities/tools/bash-allowlist/capability.toml
index fecb498..8d43416 100644
--- a/_capabilities/tools/bash-allowlist/capability.toml
+++ b/_capabilities/tools/bash-allowlist/capability.toml
@@ -27,3 +27,16 @@ path = "text.md"
 rust-module = "gates::tools_bash_allowlist"
 event = "PreToolUse:Bash"
 severity = "block"
+
+[taxonomy]
+kingdom = "capability"
+mechanism = "gate"
+domain = "tools"
+layer = "agent-substrate"
+stability = "stable"
+language = "rust"
+
+[lineage]
+parents = []
+creator = "ag-orchestrator-human"
+created = "2026-04-23"
diff --git a/_primitives/_rust/kei-atom-discovery/src/frontmatter.rs b/_primitives/_rust/kei-atom-discovery/src/frontmatter.rs
index 785c65a..5a5ff89 100644
--- a/_primitives/_rust/kei-atom-discovery/src/frontmatter.rs
+++ b/_primitives/_rust/kei-atom-discovery/src/frontmatter.rs
@@ -54,6 +54,41 @@ pub struct SideEffect {
     pub domain: String,
 }
 
+/// Optional taxonomy facets per `docs/TAXONOMY.md`. All fields optional.
+/// Format-agnostic: deserialises from YAML atom frontmatter OR TOML
+/// capability / manifest / role files.
+#[derive(Debug, Clone, Default, PartialEq, Eq, Deserialize)]
+pub struct TaxonomyFacets {
+    #[serde(default)]
+    pub kingdom: Option<String>,
+    #[serde(default)]
+    pub mechanism: Option<String>,
+    #[serde(default)]
+    pub domain: Option<String>,
+    #[serde(default)]
+    pub layer: Option<String>,
+    #[serde(default)]
+    pub stage: Option<String>,
+    #[serde(default)]
+    pub stability: Option<String>,
+    #[serde(default)]
+    pub language: Option<String>,
+}
+
+/// Optional lineage metadata — wikilink parents + creator DNA + created date.
+/// All fields optional. `parents` defaults to an empty vec.
+#[derive(Debug, Clone, Default, PartialEq, Eq, Deserialize)]
+pub struct Lineage {
+    #[serde(default)]
+    pub parents: Vec<String>,
+    #[serde(default)]
+    pub creator: Option<String>,
+    #[serde(default)]
+    pub created: Option<String>,
+    #[serde(default)]
+    pub fork_from: Option<String>,
+}
+
 /// Fully-parsed atom metadata — one canonical struct shared across crates.
 #[derive(Debug, Clone)]
 pub struct AtomMeta {
@@ -71,6 +106,8 @@ pub struct AtomMeta {
     pub keywords: Vec<String>,
     pub related: Vec<String>,
     pub body: String,
+    pub taxonomy: Option<TaxonomyFacets>,
+    pub lineage: Option<Lineage>,
 }
 
 /// Raw deserialisation target — kept private, `AtomMeta` is the public shape.
@@ -94,6 +131,10 @@ pub struct Frontmatter {
     pub keywords: Vec<String>,
     #[serde(default)]
     pub related: Vec<String>,
+    #[serde(default)]
+    pub taxonomy: Option<TaxonomyFacets>,
+    #[serde(default)]
+    pub lineage: Option<Lineage>,
 }
 
 #[derive(Debug, Deserialize)]
diff --git a/_primitives/_rust/kei-atom-discovery/src/lib.rs b/_primitives/_rust/kei-atom-discovery/src/lib.rs
index 4a9a6f0..1d838da 100644
--- a/_primitives/_rust/kei-atom-discovery/src/lib.rs
+++ b/_primitives/_rust/kei-atom-discovery/src/lib.rs
@@ -16,7 +16,8 @@ pub mod walk;
 
 pub use error::Error;
 pub use frontmatter::{
-    parse_frontmatter, AtomKind, AtomMeta, Frontmatter, SideEffect, MAX_FRONTMATTER_BYTES,
+    parse_frontmatter, AtomKind, AtomMeta, Frontmatter, Lineage, SideEffect, TaxonomyFacets,
+    MAX_FRONTMATTER_BYTES,
 };
 pub use walk::{
     classify_wikilink, discover_atoms, is_atom_target, parse_wikilink, safe_join, split_atom_id,
diff --git a/_primitives/_rust/kei-atom-discovery/src/walk.rs b/_primitives/_rust/kei-atom-discovery/src/walk.rs
index 340b8d8..303e058 100644
--- a/_primitives/_rust/kei-atom-discovery/src/walk.rs
+++ b/_primitives/_rust/kei-atom-discovery/src/walk.rs
@@ -71,6 +71,8 @@ fn build_meta(fm: Frontmatter, body: &str, md_path: &Path) -> Result<AtomMeta, E
         keywords: fm.keywords,
         related: fm.related,
         body: body.to_string(),
+        taxonomy: fm.taxonomy,
+        lineage: fm.lineage,
     })
 }
 
diff --git a/_primitives/_rust/kei-atom-discovery/tests/taxonomy_smoke.rs b/_primitives/_rust/kei-atom-discovery/tests/taxonomy_smoke.rs
new file mode 100644
index 0000000..93e7c25
--- /dev/null
+++ b/_primitives/_rust/kei-atom-discovery/tests/taxonomy_smoke.rs
@@ -0,0 +1,154 @@
+//! Taxonomy + Lineage facet parsing smoke tests.
+//!
+//! Covers (a) full 7-facet taxonomy + lineage with multiple parents,
+//! (b) partial taxonomy (only kingdom + mechanism) — remaining fields None,
+//! (c) backward-compat: atom without any [taxonomy]/[lineage] still parses,
+//! (d) lineage.parents array parses correctly (multi-parent diamond lineage).
+
+use kei_atom_discovery::{discover_atoms, Lineage, TaxonomyFacets};
+use std::fs;
+use std::path::Path;
+use tempfile::tempdir;
+
+const ATOM_FULL: &str = r#"---
+atom: kei-task::create
+kind: command
+version: "0.1.0"
+input:
+  schema: schemas/create-input.json
+output:
+  schema: schemas/create-output.json
+side_effects:
+  - { op: write, domain: kei-task-db }
+idempotent: false
+stability: stable
+keywords: [task]
+related: []
+taxonomy:
+  kingdom: atom
+  mechanism: transform
+  domain: task
+  layer: atom-substrate
+  stage: runtime
+  stability: stable
+  language: rust
+lineage:
+  parents:
+    - "[[kei-task::add-dependency]]"
+    - "[[rules/RULE 0.12]]"
+  creator: ag-orchestrator-human
+  created: "2026-04-23"
+  fork_from: dna-abc123
+---
+# body
+"#;
+
+const ATOM_PARTIAL: &str = r#"---
+atom: kei-task::update
+kind: command
+version: "0.1.0"
+input:
+  schema: schemas/create-input.json
+output:
+  schema: schemas/create-output.json
+side_effects: []
+taxonomy:
+  kingdom: atom
+  mechanism: transform
+lineage:
+  parents: []
+---
+# body
+"#;
+
+const ATOM_NO_FACETS: &str = r#"---
+atom: kei-task::delete
+kind: command
+version: "0.1.0"
+input:
+  schema: schemas/create-input.json
+output:
+  schema: schemas/create-output.json
+side_effects: []
+---
+# body
+"#;
+
+fn write_atom(root: &Path, crate_name: &str, verb: &str, body: &str) {
+    let atoms_dir = root.join(crate_name).join("atoms");
+    fs::create_dir_all(atoms_dir.join("schemas")).unwrap();
+    fs::write(atoms_dir.join(format!("{verb}.md")), body).unwrap();
+    fs::write(atoms_dir.join("schemas").join("create-input.json"), "{}").unwrap();
+    fs::write(atoms_dir.join("schemas").join("create-output.json"), "{}").unwrap();
+}
+
+fn find<'a>(
+    atoms: &'a [kei_atom_discovery::AtomMeta],
+    full_id: &str,
+) -> &'a kei_atom_discovery::AtomMeta {
+    atoms
+        .iter()
+        .find(|a| a.full_id == full_id)
+        .expect("atom present")
+}
+
+#[test]
+fn full_taxonomy_and_lineage_parse() {
+    let tmp = tempdir().unwrap();
+    write_atom(tmp.path(), "kei-task", "create", ATOM_FULL);
+    let atoms = discover_atoms(tmp.path());
+    let a = find(&atoms, "kei-task::create");
+    let tax: &TaxonomyFacets = a.taxonomy.as_ref().expect("taxonomy present");
+    assert_eq!(tax.kingdom.as_deref(), Some("atom"));
+    assert_eq!(tax.mechanism.as_deref(), Some("transform"));
+    assert_eq!(tax.domain.as_deref(), Some("task"));
+    assert_eq!(tax.layer.as_deref(), Some("atom-substrate"));
+    assert_eq!(tax.stage.as_deref(), Some("runtime"));
+    assert_eq!(tax.stability.as_deref(), Some("stable"));
+    assert_eq!(tax.language.as_deref(), Some("rust"));
+    let lin: &Lineage = a.lineage.as_ref().expect("lineage present");
+    assert_eq!(lin.creator.as_deref(), Some("ag-orchestrator-human"));
+    assert_eq!(lin.created.as_deref(), Some("2026-04-23"));
+    assert_eq!(lin.fork_from.as_deref(), Some("dna-abc123"));
+}
+
+#[test]
+fn partial_taxonomy_leaves_rest_none() {
+    let tmp = tempdir().unwrap();
+    write_atom(tmp.path(), "kei-task", "update", ATOM_PARTIAL);
+    let atoms = discover_atoms(tmp.path());
+    let a = find(&atoms, "kei-task::update");
+    let tax = a.taxonomy.as_ref().expect("taxonomy present");
+    assert_eq!(tax.kingdom.as_deref(), Some("atom"));
+    assert_eq!(tax.mechanism.as_deref(), Some("transform"));
+    assert!(tax.domain.is_none());
+    assert!(tax.layer.is_none());
+    assert!(tax.stage.is_none());
+    assert!(tax.stability.is_none());
+    assert!(tax.language.is_none());
+    let lin = a.lineage.as_ref().expect("lineage present");
+    assert!(lin.parents.is_empty());
+    assert!(lin.creator.is_none());
+}
+
+#[test]
+fn no_facets_section_still_parses_backward_compat() {
+    let tmp = tempdir().unwrap();
+    write_atom(tmp.path(), "kei-task", "delete", ATOM_NO_FACETS);
+    let atoms = discover_atoms(tmp.path());
+    let a = find(&atoms, "kei-task::delete");
+    assert!(a.taxonomy.is_none(), "no [taxonomy] → None");
+    assert!(a.lineage.is_none(), "no [lineage] → None");
+}
+
+#[test]
+fn lineage_parents_array_preserved() {
+    let tmp = tempdir().unwrap();
+    write_atom(tmp.path(), "kei-task", "create", ATOM_FULL);
+    let atoms = discover_atoms(tmp.path());
+    let a = find(&atoms, "kei-task::create");
+    let lin = a.lineage.as_ref().expect("lineage present");
+    assert_eq!(lin.parents.len(), 2);
+    assert_eq!(lin.parents[0], "[[kei-task::add-dependency]]");
+    assert_eq!(lin.parents[1], "[[rules/RULE 0.12]]");
+}
diff --git a/docs/TAXONOMY.md b/docs/TAXONOMY.md
new file mode 100644
index 0000000..3e35bb4
--- /dev/null
+++ b/docs/TAXONOMY.md
@@ -0,0 +1,209 @@
+# TAXONOMY — Canonical Facet Vocabulary
+
+> Graph, not tree. Every primitive is a node; facets are orthogonal labels.
+> Multi-faceted nodes are allowed (and expected). No facet is mandatory —
+> the entire `[taxonomy]` and `[lineage]` sections are OPTIONAL on every
+> manifest shape (`capability.toml`, `_manifests/**/*.toml`, `_roles/*.toml`,
+> atom markdown frontmatter).
+
+---
+
+## Why facets, not a tree
+
+A classical rooted tree (e.g. "capability → gate → policy → no-git-ops")
+forces an arbitrary primary axis. Real primitives live in several axes at
+once: `no-git-ops` is a *capability* (kingdom), a *gate* (mechanism), a
+*policy* (domain), targets the *agent-substrate* (layer), is *stable*, and
+ships as a *rust* module. A tree makes five of those six second-class.
+
+Facets let a catalog query along any axis independently:
+
+- "all `gate` mechanisms" — security review surface
+- "all `verify` mechanisms" — quality/CI surface
+- "all `policy`-domain primitives" — rule-coverage surface
+- "all `experimental` stability" — risk review
+- "all `rust` language" — build-graph
+
+No primitive needs to choose a primary axis. Multiple facets coexist.
+
+---
+
+## Facets
+
+### `kingdom` — What kind of thing is this?
+
+```
+kingdom = capability | atom | skill | block | runtime | schema | role | manifest
+```
+
+- `capability` — agent-substrate capability (gate / verify / transform)
+- `atom` — substrate atom (command / query / stream / transform)
+- `skill` — user-invocable skill (`/skill-name`)
+- `block` — composable prompt-block
+- `runtime` — runtime module consuming atoms/capabilities
+- `schema` — JSON schema referenced by atom I/O
+- `role` — agent-role manifest (`_roles/*.toml`)
+- `manifest` — assembled agent manifest (`_manifests/**/*.toml`)
+
+### `mechanism` — How does it act?
+
+```
+mechanism = gate | verify | transform | store | compose | fetch | analyze | router | cache
+```
+
+- `gate` — PreToolUse-style deny decision (e.g. `no-git-ops`, `bash-allowlist`)
+- `verify` — post-condition check (e.g. `cargo-check-green`)
+- `transform` — pure value-in/value-out (no side-effects)
+- `store` — persisted state (SQLite, filesystem, ledger)
+- `compose` — assembles other primitives (manifests, pipes)
+- `fetch` — retrieves external data (provider, api)
+- `analyze` — inspects input, emits report
+- `router` — dispatches based on classification
+- `cache` — memoizes pure invocations
+
+### `domain` — What subject-matter area?
+
+```
+domain = policy | quality | scope | safety | output | tools | research | content | social | task | sage
+```
+
+- `policy` — RULE 0.x enforcement / compliance gates
+- `quality` — cargo-check, tests-green, constructor-pattern
+- `scope` — write-whitelist, file-denylist, path-guards
+- `safety` — secret scanning, citation verification
+- `output` — response shape, formatter, report-gen
+- `tools` — tool allowlists, bash patterns, deny-tools
+- `research` — research agents, search-core, fetch primitives
+- `content` — content-store, content-normalizer
+- `social` — social-store, social-normalizer
+- `task` — task primitives (kei-task)
+- `sage` — higher-level reasoning / kei-sage primitives
+
+### `layer` — Which substrate does it live in?
+
+```
+layer = atom-substrate | agent-substrate | cross | tooling
+```
+
+- `atom-substrate` — substrate for callable atoms (kei-runtime, kei-pipe)
+- `agent-substrate` — substrate for agent manifests (capabilities, roles)
+- `cross` — spans both (shared discovery, schemas)
+- `tooling` — pure developer tooling (kei-forge, validators)
+
+### `stage` — When is it active?
+
+```
+stage = runtime | design-time | ephemeral
+```
+
+- `runtime` — executes during agent turns
+- `design-time` — consumed at assembly / scaffold time
+- `ephemeral` — one-shot (migration, provision, smoke)
+
+### `stability` — Maturity
+
+```
+stability = experimental | beta | stable | deprecated
+```
+
+Standard semver-style ladder. `deprecated` primitives must name a successor
+in `[lineage]` or their `text.md`.
+
+### `language` — Implementation medium
+
+```
+language = rust | shell | md | toml | json | jsonschema
+```
+
+- `rust` — primary implementation in a Rust crate
+- `shell` — bash / posix script
+- `md` — markdown (atoms, capability text, documentation)
+- `toml` — config-only (capability manifest, role manifest)
+- `json` / `jsonschema` — data / schema definitions
+
+Multiple languages can apply (e.g. atom markdown with a JSON schema attached
+and a Rust runtime) — but the `language` facet names the PRIMARY medium of
+the node being described.
+
+---
+
+## `[lineage]` — Graph edges, not tree edges
+
+```
+parents = ["[[ancestor-one]]", "[[ancestor-two]]"]   # wikilinks to predecessors
+creator = "ag-orchestrator-human"                    # DNA id or human slug
+created = "2026-04-23"                               # ISO-8601 date
+fork_from = "dna-abc123..."                          # parent DNA if forked
+```
+
+- `parents` — wikilinks (`[[slug]]`) to primitives this one extends or
+  composes. Multiple parents allowed (diamond lineage). A primitive with
+  no `parents` is a root of its sub-graph.
+- `creator` — identity responsible for the primitive's existence. For
+  human-authored nodes: `ag-orchestrator-human` or a slug. For agent-
+  authored: the agent's DNA id.
+- `created` — ISO-8601 date (YYYY-MM-DD). When the manifest was first
+  authored, not when it was last edited.
+- `fork_from` — if this primitive was forked from another (DNA id), record
+  the source here so the graph shows the edge.
+
+---
+
+## Example — fully-faceted capability manifest
+
+```toml
+[capability]
+name = "policy::no-git-ops"
+category = "policy"
+version = "1.0"
+description = "..."
+rationale = "..."
+
+[restricts]
+tool-patterns = ['^git( |$)', '^gh repo']
+
+[parameterized]
+accepts = []
+
+[text]
+path = "text.md"
+
+[gate]
+rust-module = "gates::policy_no_git_ops"
+event = "PreToolUse:Bash"
+severity = "block"
+
+# Optional — all fields optional individually too.
+[taxonomy]
+kingdom = "capability"
+mechanism = "gate"
+domain = "policy"
+layer = "agent-substrate"
+stability = "stable"
+language = "rust"
+
+[lineage]
+parents = []
+creator = "ag-orchestrator-human"
+created = "2026-04-23"
+```
+
+---
+
+## Non-breaking contract
+
+- Every field in `[taxonomy]` and `[lineage]` is OPTIONAL.
+- The entire `[taxonomy]` and `[lineage]` sections are OPTIONAL.
+- Manifests without either section parse exactly as before (backward-compat
+  guaranteed by `taxonomy_smoke.rs` tests in `kei-atom-discovery`).
+- New primitives SHOULD include at least `kingdom` + `mechanism` + `domain`.
+- The facet vocabularies are additive — new values can be appended without
+  breaking existing consumers. Unknown values pass through as strings.
+
+---
+
+## Rule lock
+
+2026-04-23. Vocabularies live in this file; any new allowed value lands here
+first. Runtime consumers (kei-atom-discovery, kei-sage, kei-runtime) MUST
+treat unknown values as strings (never crash on new vocabulary).