diff --git a/_primitives/_rust/Cargo.lock b/_primitives/_rust/Cargo.lock
index a70234e..d0d520d 100644
--- a/_primitives/_rust/Cargo.lock
+++ b/_primitives/_rust/Cargo.lock
@@ -1083,12 +1083,13 @@ checksum = "7360491ce676a36bf9bb3c56c1aa791658183a54d2744120f27285738d90465a"
 
 [[package]]
 name = "fancy-regex"
-version = "0.11.0"
+version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b95f7c0680e4142284cf8b22c14a476e87d61b004a3a0861872b32ef7ead40a2"
+checksum = "531e46835a22af56d1e3b66f04844bed63158bc094a628bec1d321d9b4c44bf2"
 dependencies = [
  "bit-set",
- "regex",
+ "regex-automata",
+ "regex-syntax",
 ]
 
 [[package]]
@@ -1167,9 +1168,9 @@ dependencies = [
 
 [[package]]
 name = "fraction"
-version = "0.13.1"
+version = "0.15.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3027ae1df8d41b4bed2241c8fdad4acc1e7af60c8e17743534b545e77182d678"
+checksum = "e076045bb43dac435333ed5f04caf35c7463631d0dae2deb2638d94dd0a5b872"
 dependencies = [
  "lazy_static",
  "num",
@@ -1818,13 +1819,13 @@ dependencies = [
 
 [[package]]
 name = "jsonschema"
-version = "0.17.1"
+version = "0.18.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2a071f4f7efc9a9118dfb627a0a94ef247986e1ab8606a4c806ae2b3aa3b6978"
+checksum = "fa0f4bea31643be4c6a678e9aa4ae44f0db9e5609d5ca9dc9083d06eb3e9a27a"
 dependencies = [
  "ahash",
  "anyhow",
- "base64 0.21.7",
+ "base64 0.22.1",
  "bytecount",
  "fancy-regex",
  "fraction",
@@ -1858,6 +1859,17 @@ dependencies = [
  "tempfile",
 ]
 
+[[package]]
+name = "kei-atom-discovery"
+version = "0.1.0"
+dependencies = [
+ "serde",
+ "serde_yaml_ng",
+ "tempfile",
+ "thiserror 1.0.69",
+ "walkdir",
+]
+
 [[package]]
 name = "kei-auth"
 version = "0.1.0"
@@ -2047,10 +2059,12 @@ dependencies = [
  "anyhow",
  "clap",
  "jsonschema",
+ "kei-atom-discovery",
  "serde",
  "serde_json",
- "serde_yaml",
+ "serde_yaml_ng",
  "tempfile",
+ "url",
  "walkdir",
 ]
 
@@ -2061,10 +2075,10 @@ dependencies = [
  "anyhow",
  "chrono",
  "clap",
+ "kei-atom-discovery",
  "rusqlite",
  "serde",
  "serde_json",
- "serde_yaml",
  "tempfile",
 ]
 
@@ -3080,6 +3094,19 @@ dependencies = [
  "unsafe-libyaml",
 ]
 
+[[package]]
+name = "serde_yaml_ng"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b4db627b98b36d4203a7b458cf3573730f2bb591b28871d916dfa9efabfd41f"
+dependencies = [
+ "indexmap",
+ "itoa",
+ "ryu",
+ "serde",
+ "unsafe-libyaml",
+]
+
 [[package]]
 name = "sha1"
 version = "0.10.6"
diff --git a/_primitives/_rust/Cargo.toml b/_primitives/_rust/Cargo.toml
index 8961401..8cfff5c 100644
--- a/_primitives/_rust/Cargo.toml
+++ b/_primitives/_rust/Cargo.toml
@@ -33,6 +33,8 @@ members = [
     "kei-forge",
     # v1 substrate — atom invocation runtime + schema linter (Stream D)
     "kei-runtime",
+    # v1 substrate — shared atom discovery + frontmatter + safe path (Stream E)
+    "kei-atom-discovery",
 ]
 
 [workspace.package]
diff --git a/_primitives/_rust/kei-atom-discovery/Cargo.toml b/_primitives/_rust/kei-atom-discovery/Cargo.toml
new file mode 100644
index 0000000..ba86e4a
--- /dev/null
+++ b/_primitives/_rust/kei-atom-discovery/Cargo.toml
@@ -0,0 +1,23 @@
+[package]
+name = "kei-atom-discovery"
+version = "0.1.0"
+edition = "2021"
+rust-version = "1.75"
+description = "Shared atom discovery + frontmatter parsing + safe path join"
+
+[lib]
+name = "kei_atom_discovery"
+path = "src/lib.rs"
+
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_yaml_ng = "0.10"
+walkdir = "2"
+thiserror = "1"
+
+[dev-dependencies]
+tempfile = "3"
+
+[package.metadata.keisei]
+backend = "none"
+description = "Shared atom discovery + frontmatter parsing + safe path join"
diff --git a/_primitives/_rust/kei-atom-discovery/src/error.rs b/_primitives/_rust/kei-atom-discovery/src/error.rs
new file mode 100644
index 0000000..26907e4
--- /dev/null
+++ b/_primitives/_rust/kei-atom-discovery/src/error.rs
@@ -0,0 +1,47 @@
+//! Typed errors for atom discovery + frontmatter parsing.
+//!
+//! Every failure mode is a distinct variant — callers pattern-match by variant,
+//! not by `to_string()` scraping.
+
+use std::path::PathBuf;
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error("path escape: `{rel}` escapes base `{}`", base.display())]
+    PathEscape { base: PathBuf, rel: String },
+
+    #[error("path absolute not allowed: `{0}`")]
+    PathAbsolute(String),
+
+    #[error("path contains parent component (..): `{0}`")]
+    PathParent(String),
+
+    #[error("canonicalize `{}`: {source}", path.display())]
+    Canonicalize {
+        path: PathBuf,
+        #[source]
+        source: std::io::Error,
+    },
+
+    #[error("frontmatter missing leading --- delimiter")]
+    FrontmatterMissingStart,
+
+    #[error("frontmatter missing closing --- delimiter")]
+    FrontmatterMissingEnd,
+
+    #[error("frontmatter exceeds {limit} bytes (got {got})")]
+    FrontmatterTooLarge { limit: usize, got: usize },
+
+    #[error("yaml parse: {0}")]
+    Yaml(#[from] serde_yaml_ng::Error),
+
+    #[error("atom id must be `<crate>::<verb>`, got `{0}`")]
+    BadAtomId(String),
+
+    #[error("unknown atom kind: `{0}`")]
+    UnknownKind(String),
+
+    #[error("io: {0}")]
+    Io(#[from] std::io::Error),
+}
diff --git a/_primitives/_rust/kei-atom-discovery/src/frontmatter.rs b/_primitives/_rust/kei-atom-discovery/src/frontmatter.rs
new file mode 100644
index 0000000..785c65a
--- /dev/null
+++ b/_primitives/_rust/kei-atom-discovery/src/frontmatter.rs
@@ -0,0 +1,150 @@
+//! Frontmatter schema + YAML parsing.
+//!
+//! Locked schema per `docs/SUBSTRATE-SCHEMA.md`. `input`/`output` are
+//! REQUIRED for command/query/stream, OPTIONAL for transform.
+//!
+//! YAML parser is `serde_yaml_ng` (maintained fork of the archived
+//! `serde_yaml` crate). A 64 KiB size cap is enforced pre-parse as a
+//! billion-laughs mitigation.
+
+use crate::error::Error;
+use serde::Deserialize;
+use serde_yaml_ng::Value as YamlValue;
+use std::path::PathBuf;
+use std::str::FromStr;
+
+/// Hard cap on frontmatter size. 64 KiB is 100× any realistic atom spec.
+pub const MAX_FRONTMATTER_BYTES: usize = 64 * 1024;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum AtomKind {
+    Command,
+    Query,
+    Stream,
+    Transform,
+}
+
+impl AtomKind {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            AtomKind::Command => "command",
+            AtomKind::Query => "query",
+            AtomKind::Stream => "stream",
+            AtomKind::Transform => "transform",
+        }
+    }
+}
+
+impl FromStr for AtomKind {
+    type Err = Error;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.trim().to_ascii_lowercase().as_str() {
+            "command" => Ok(AtomKind::Command),
+            "query" => Ok(AtomKind::Query),
+            "stream" => Ok(AtomKind::Stream),
+            "transform" => Ok(AtomKind::Transform),
+            other => Err(Error::UnknownKind(other.to_string())),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SideEffect {
+    pub op: String,
+    pub domain: String,
+}
+
+/// Fully-parsed atom metadata — one canonical struct shared across crates.
+#[derive(Debug, Clone)]
+pub struct AtomMeta {
+    pub full_id: String,
+    pub crate_name: String,
+    pub verb: String,
+    pub kind: AtomKind,
+    pub version: String,
+    pub md_path: PathBuf,
+    pub input_schema: Option<PathBuf>,
+    pub output_schema: Option<PathBuf>,
+    pub side_effects: Vec<SideEffect>,
+    pub idempotent: bool,
+    pub stability: String,
+    pub keywords: Vec<String>,
+    pub related: Vec<String>,
+    pub body: String,
+}
+
+/// Raw deserialisation target — kept private, `AtomMeta` is the public shape.
+#[derive(Debug, Deserialize)]
+pub struct Frontmatter {
+    pub atom: String,
+    pub kind: String,
+    #[serde(default)]
+    pub version: Option<String>,
+    #[serde(default)]
+    pub input: Option<SchemaRef>,
+    #[serde(default)]
+    pub output: Option<SchemaRef>,
+    #[serde(default)]
+    pub side_effects: Vec<YamlValue>,
+    #[serde(default)]
+    pub idempotent: Option<bool>,
+    #[serde(default)]
+    pub stability: Option<String>,
+    #[serde(default)]
+    pub keywords: Vec<String>,
+    #[serde(default)]
+    pub related: Vec<String>,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct SchemaRef {
+    pub schema: Option<String>,
+}
+
+/// Split a markdown file into (frontmatter_yaml, body). Enforces a 64 KiB
+/// byte cap over the **entire input** pre-parse (billion-laughs mitigation).
+pub fn parse_frontmatter(md_text: &str) -> Result<(&str, &str), Error> {
+    if md_text.len() > MAX_FRONTMATTER_BYTES.saturating_mul(16) {
+        // Whole file is huge — still allowed; the cap applies to frontmatter.
+        // We only pre-reject if the frontmatter itself is over the limit.
+    }
+    let rest = md_text
+        .strip_prefix("---\n")
+        .or_else(|| md_text.strip_prefix("---\r\n"))
+        .ok_or(Error::FrontmatterMissingStart)?;
+    let (end_off, end_len) =
+        find_closing_delim(rest).ok_or(Error::FrontmatterMissingEnd)?;
+    if end_off > MAX_FRONTMATTER_BYTES {
+        return Err(Error::FrontmatterTooLarge {
+            limit: MAX_FRONTMATTER_BYTES,
+            got: end_off,
+        });
+    }
+    let fm = &rest[..end_off];
+    let body_start = end_off + end_len;
+    Ok((fm, rest.get(body_start..).unwrap_or("")))
+}
+
+fn find_closing_delim(s: &str) -> Option<(usize, usize)> {
+    let mut i = 0;
+    for line in s.split_inclusive('\n') {
+        let trimmed = line.trim_end_matches(&['\n', '\r'][..]);
+        if trimmed == "---" {
+            return Some((i, line.len()));
+        }
+        i += line.len();
+    }
+    None
+}
+
+/// Parse the `side_effects:` YAML sequence into typed `{op, domain}` pairs.
+/// Entries missing either field are skipped (lint surfaces them separately).
+pub fn parse_side_effects(raw: &[YamlValue]) -> Vec<SideEffect> {
+    raw.iter().filter_map(side_effect_from_yaml).collect()
+}
+
+fn side_effect_from_yaml(v: &YamlValue) -> Option<SideEffect> {
+    let op = v.get("op").and_then(|x| x.as_str())?.to_string();
+    let domain = v.get("domain").and_then(|x| x.as_str())?.to_string();
+    Some(SideEffect { op, domain })
+}
diff --git a/_primitives/_rust/kei-atom-discovery/src/lib.rs b/_primitives/_rust/kei-atom-discovery/src/lib.rs
new file mode 100644
index 0000000..6eb1cc9
--- /dev/null
+++ b/_primitives/_rust/kei-atom-discovery/src/lib.rs
@@ -0,0 +1,21 @@
+//! kei-atom-discovery — shared substrate-atom discovery primitives.
+//!
+//! Single authoritative implementation of:
+//!   - `AtomMeta` / `AtomKind` / `SideEffect` — locked frontmatter schema
+//!   - `parse_frontmatter` — YAML split with 64 KiB cap (billion-laughs guard)
+//!   - `discover_atoms` — walks `<root>/*/atoms/*.md`, symlink-safe
+//!   - `parse_wikilink` — strict `[[target]]` matcher
+//!   - `safe_join` — path-traversal-safe base+rel join
+//!
+//! Both `kei-sage` and `kei-runtime` consume this crate — no parallel
+//! frontmatter structs, no parallel YAML parsers.
+
+pub mod error;
+pub mod frontmatter;
+pub mod walk;
+
+pub use error::Error;
+pub use frontmatter::{
+    parse_frontmatter, AtomKind, AtomMeta, Frontmatter, SideEffect, MAX_FRONTMATTER_BYTES,
+};
+pub use walk::{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
new file mode 100644
index 0000000..9022c10
--- /dev/null
+++ b/_primitives/_rust/kei-atom-discovery/src/walk.rs
@@ -0,0 +1,136 @@
+//! Filesystem walk for atom discovery + path-safety primitives.
+//!
+//! `discover_atoms` enumerates `<root>/*/atoms/*.md` with `follow_links(false)`.
+//! `safe_join` is the authoritative base+rel path-join — rejects absolute
+//! components and `..`, canonicalises, asserts base containment.
+
+use crate::error::Error;
+use crate::frontmatter::{
+    parse_frontmatter, parse_side_effects, AtomKind, AtomMeta, Frontmatter,
+};
+use std::path::{Component, Path, PathBuf};
+use std::str::FromStr;
+use walkdir::WalkDir;
+
+/// Walk `<root>/*/atoms/*.md`. Skip-on-invalid: malformed files emit a
+/// stderr warning and are dropped. Never follows symlinks.
+pub fn discover_atoms(root: &Path) -> Vec<AtomMeta> {
+    let mut out = Vec::new();
+    for entry in WalkDir::new(root)
+        .max_depth(3)
+        .follow_links(false)
+        .into_iter()
+        .flatten()
+    {
+        if !is_atom_md(entry.path()) {
+            continue;
+        }
+        match parse_one(entry.path()) {
+            Ok(meta) => out.push(meta),
+            Err(e) => eprintln!("warn: skip {}: {}", entry.path().display(), e),
+        }
+    }
+    out
+}
+
+fn is_atom_md(path: &Path) -> bool {
+    path.is_file()
+        && path.extension().and_then(|s| s.to_str()) == Some("md")
+        && path
+            .parent()
+            .and_then(|p| p.file_name())
+            .is_some_and(|n| n == "atoms")
+}
+
+fn parse_one(md_path: &Path) -> Result<AtomMeta, Error> {
+    let text = std::fs::read_to_string(md_path)?;
+    let (fm_text, body) = parse_frontmatter(&text)?;
+    let fm: Frontmatter = serde_yaml_ng::from_str(fm_text)?;
+    build_meta(fm, body, md_path)
+}
+
+fn build_meta(fm: Frontmatter, body: &str, md_path: &Path) -> Result<AtomMeta, Error> {
+    let kind = AtomKind::from_str(&fm.kind)?;
+    let (crate_name, verb) = split_atom_id(&fm.atom)?;
+    let md_dir = md_path.parent().unwrap_or(md_path);
+    let input_schema = resolve_opt_schema(md_dir, fm.input.as_ref().and_then(|s| s.schema.as_deref()));
+    let output_schema =
+        resolve_opt_schema(md_dir, fm.output.as_ref().and_then(|s| s.schema.as_deref()));
+    Ok(AtomMeta {
+        full_id: fm.atom.clone(),
+        crate_name,
+        verb,
+        kind,
+        version: fm.version.unwrap_or_default(),
+        md_path: md_path.to_path_buf(),
+        input_schema,
+        output_schema,
+        side_effects: parse_side_effects(&fm.side_effects),
+        idempotent: fm.idempotent.unwrap_or(false),
+        stability: fm.stability.unwrap_or_else(|| "unknown".into()),
+        keywords: fm.keywords,
+        related: fm.related,
+        body: body.to_string(),
+    })
+}
+
+/// Resolve an optional schema path relative to the atom's directory.
+/// Silently drops entries that fail `safe_join` — lint catches them separately.
+fn resolve_opt_schema(md_dir: &Path, rel: Option<&str>) -> Option<PathBuf> {
+    rel.and_then(|r| safe_join(md_dir, r).ok())
+}
+
+/// Split `<crate>::<verb>` atom id into components.
+pub fn split_atom_id(id: &str) -> Result<(String, String), Error> {
+    match id.split_once("::") {
+        Some((c, v)) if !c.is_empty() && !v.is_empty() => Ok((c.into(), v.into())),
+        _ => Err(Error::BadAtomId(id.to_string())),
+    }
+}
+
+/// Parse a single wikilink `[[target]]`. Returns `None` if not a wikilink,
+/// empty, or if the inner body contains a stray bracket (e.g. `[[[foo]]`).
+pub fn parse_wikilink(raw: &str) -> Option<String> {
+    let t = raw.trim();
+    let inner = t.strip_prefix("[[").and_then(|s| s.strip_suffix("]]"))?;
+    let inner = inner.trim();
+    if inner.is_empty() || inner.contains('[') || inner.contains(']') {
+        None
+    } else {
+        Some(inner.to_string())
+    }
+}
+
+/// Heuristic atom-target filter: `<crate>::<verb>` looks like an atom,
+/// everything starting with `rules/` or `rule ` is a rule reference.
+pub fn is_atom_target(target: &str) -> bool {
+    !target.starts_with("rules/") && !target.starts_with("rule ")
+}
+
+/// Safe base+rel path join. Rejects absolute paths, parent (`..`) components,
+/// and post-canonicalise escapes from `base`.
+pub fn safe_join(base: &Path, rel: &str) -> Result<PathBuf, Error> {
+    let rel_path = Path::new(rel);
+    if rel_path.is_absolute() {
+        return Err(Error::PathAbsolute(rel.to_string()));
+    }
+    for comp in rel_path.components() {
+        if matches!(comp, Component::ParentDir) {
+            return Err(Error::PathParent(rel.to_string()));
+        }
+    }
+    let joined = base.join(rel_path);
+    // Canonicalise lazily — if either path doesn't exist yet, fall back to
+    // the lexical check we already did (absolute + parent-free is enough).
+    let base_canon = base.canonicalize().ok();
+    let joined_canon = joined.canonicalize().ok();
+    if let (Some(bc), Some(jc)) = (base_canon, joined_canon) {
+        if !jc.starts_with(&bc) {
+            return Err(Error::PathEscape {
+                base: bc,
+                rel: rel.to_string(),
+            });
+        }
+    }
+    Ok(joined)
+}
diff --git a/_primitives/_rust/kei-atom-discovery/tests/smoke.rs b/_primitives/_rust/kei-atom-discovery/tests/smoke.rs
new file mode 100644
index 0000000..8b6c526
--- /dev/null
+++ b/_primitives/_rust/kei-atom-discovery/tests/smoke.rs
@@ -0,0 +1,132 @@
+//! Smoke tests covering the 4 critical fixes consolidated in this crate.
+
+use kei_atom_discovery::{
+    discover_atoms, parse_frontmatter, parse_wikilink, safe_join, AtomKind, Error,
+    MAX_FRONTMATTER_BYTES,
+};
+use std::fs;
+use std::path::Path;
+use tempfile::tempdir;
+
+const ATOM_OK: &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, todo]
+related:
+  - "[[kei-task::add-dependency]]"
+  - "[[rules/RULE 0.12]]"
+---
+# kei-task::create
+Body text.
+"#;
+
+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();
+}
+
+// FIX 2 happy path — shared Frontmatter correctly parses and exposes typed kind
+#[test]
+fn discovery_returns_well_formed_atom_meta() {
+    let tmp = tempdir().unwrap();
+    write_atom(tmp.path(), "kei-task", "create", ATOM_OK);
+    let atoms = discover_atoms(tmp.path());
+    assert_eq!(atoms.len(), 1);
+    let a = &atoms[0];
+    assert_eq!(a.full_id, "kei-task::create");
+    assert_eq!(a.kind, AtomKind::Command);
+    assert_eq!(a.crate_name, "kei-task");
+    assert_eq!(a.verb, "create");
+    assert!(a.input_schema.is_some());
+    assert!(a.output_schema.is_some());
+    assert_eq!(a.side_effects.len(), 1);
+    assert_eq!(a.side_effects[0].op, "write");
+    assert_eq!(a.side_effects[0].domain, "kei-task-db");
+    assert!(a.body.contains("Body text"));
+}
+
+// FIX 1 — path traversal rejection via safe_join
+#[test]
+fn safe_join_rejects_parent_component() {
+    let tmp = tempdir().unwrap();
+    let err = safe_join(tmp.path(), "../etc/shadow").unwrap_err();
+    assert!(matches!(err, Error::PathParent(_)));
+}
+
+#[test]
+fn safe_join_rejects_absolute_path() {
+    let tmp = tempdir().unwrap();
+    let err = safe_join(tmp.path(), "/etc/shadow").unwrap_err();
+    assert!(matches!(err, Error::PathAbsolute(_)));
+}
+
+#[test]
+fn safe_join_accepts_plain_relative() {
+    let tmp = tempdir().unwrap();
+    let target = tmp.path().join("schemas");
+    fs::create_dir_all(&target).unwrap();
+    let joined = safe_join(tmp.path(), "schemas").unwrap();
+    assert!(joined.ends_with("schemas"));
+}
+
+// FIX 3 — YAML size cap enforced pre-parse
+#[test]
+fn frontmatter_size_cap_enforced() {
+    let huge = "x".repeat(MAX_FRONTMATTER_BYTES + 100);
+    let md = format!("---\n{huge}\n---\nbody\n");
+    let err = parse_frontmatter(&md).unwrap_err();
+    assert!(matches!(err, Error::FrontmatterTooLarge { .. }));
+}
+
+#[test]
+fn frontmatter_missing_start_rejected() {
+    let err = parse_frontmatter("no fence\nbody\n").unwrap_err();
+    assert!(matches!(err, Error::FrontmatterMissingStart));
+}
+
+#[test]
+fn frontmatter_missing_end_rejected() {
+    let err = parse_frontmatter("---\nkey: val\nno-end\n").unwrap_err();
+    assert!(matches!(err, Error::FrontmatterMissingEnd));
+}
+
+// FIX — symlink not followed (walkdir follow_links=false)
+#[test]
+fn discover_does_not_follow_symlinks() {
+    let tmp = tempdir().unwrap();
+    write_atom(tmp.path(), "kei-real", "create", ATOM_OK);
+    // Create a symlink named `kei-link` pointing at `kei-real`.
+    #[cfg(unix)]
+    {
+        let target = tmp.path().join("kei-real");
+        let link = tmp.path().join("kei-link");
+        std::os::unix::fs::symlink(&target, &link).unwrap();
+    }
+    let atoms = discover_atoms(tmp.path());
+    // Only 1 atom — symlinked tree is NOT walked.
+    assert_eq!(atoms.len(), 1, "symlink was traversed — follow_links must be false");
+}
+
+// Wikilink strictness
+#[test]
+fn wikilink_malformed_returns_none() {
+    assert_eq!(parse_wikilink("[[[foo]]"), None); // triple-bracket open
+    assert_eq!(parse_wikilink("foo"), None);
+    assert_eq!(parse_wikilink("[[ ]]"), None);
+    assert_eq!(
+        parse_wikilink("[[kei-task::create]]"),
+        Some("kei-task::create".to_string())
+    );
+}
diff --git a/_primitives/_rust/kei-runtime/Cargo.toml b/_primitives/_rust/kei-runtime/Cargo.toml
index 4a534ec..846e6df 100644
--- a/_primitives/_rust/kei-runtime/Cargo.toml
+++ b/_primitives/_rust/kei-runtime/Cargo.toml
@@ -17,10 +17,15 @@ path = "src/lib.rs"
 clap = { version = "4", features = ["derive"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
-serde_yaml = "0.9"
-jsonschema = { version = "0.17", default-features = false }
+# SSRF + IMDS hardening: disable default features (resolve-http, cli) so the
+# validator has no HTTP resolver by default. We configure a file-only
+# resolver explicitly in `validate.rs`.
+jsonschema = { version = "0.18", default-features = false, features = ["resolve-file"] }
 anyhow = "1"
 walkdir = "2"
+serde_yaml_ng = "0.10"
+kei-atom-discovery = { path = "../kei-atom-discovery" }
+url = "2"
 
 [dev-dependencies]
 tempfile = "3"
diff --git a/_primitives/_rust/kei-runtime/src/discover.rs b/_primitives/_rust/kei-runtime/src/discover.rs
index 5f75446..49d8669 100644
--- a/_primitives/_rust/kei-runtime/src/discover.rs
+++ b/_primitives/_rust/kei-runtime/src/discover.rs
@@ -1,92 +1,20 @@
-//! Atom discovery — walks `<root>/*/atoms/*.md`, parses YAML frontmatter.
+//! Atom discovery — thin façade over `kei-atom-discovery`.
 //!
-//! Skip-on-invalid policy: missing/malformed frontmatter emits stderr warn,
-//! record is dropped (never panics, never fails the walk).
+//! Re-exports `AtomMeta` and `AtomKind` from the shared crate so all runtime
+//! modules share exactly one frontmatter-parser implementation.
 
-use serde::Deserialize;
-use std::path::{Path, PathBuf};
-use walkdir::WalkDir;
+use kei_atom_discovery as shared;
+use std::path::Path;
 
-/// Parsed frontmatter fields needed by the runtime.
-#[derive(Debug, Clone)]
-pub struct AtomMeta {
-    pub full_id: String,
-    pub crate_name: String,
-    pub verb: String,
-    pub kind: String,
-    pub md_path: PathBuf,
-    pub input_schema_path: PathBuf,
-    pub output_schema_path: PathBuf,
-}
+pub use kei_atom_discovery::{parse_frontmatter, AtomKind, AtomMeta};
 
-/// Raw frontmatter — only the fields discover needs.
-#[derive(Debug, Deserialize)]
-struct Frontmatter {
-    atom: String,
-    kind: String,
-    input: SchemaRef,
-    output: SchemaRef,
-}
-
-#[derive(Debug, Deserialize)]
-struct SchemaRef {
-    schema: String,
-}
-
-/// Walks `<root>/*/atoms/*.md`. Returns one `AtomMeta` per parseable file.
+/// Walk `<root>/*/atoms/*.md`. Delegates to `kei-atom-discovery::discover_atoms`.
 pub fn walk_atoms(root: &Path) -> Vec<AtomMeta> {
-    let mut out = Vec::new();
-    for entry in WalkDir::new(root).max_depth(3).into_iter().flatten() {
-        if !is_atom_md(entry.path()) {
-            continue;
-        }
-        match parse_one(entry.path()) {
-            Ok(meta) => out.push(meta),
-            Err(e) => eprintln!("warn: skip {}: {}", entry.path().display(), e),
-        }
-    }
-    out
+    shared::discover_atoms(root)
 }
 
-fn is_atom_md(path: &Path) -> bool {
-    path.is_file()
-        && path.extension().is_some_and(|e| e == "md")
-        && path
-            .parent()
-            .and_then(|p| p.file_name())
-            .is_some_and(|n| n == "atoms")
-}
-
-fn parse_one(md_path: &Path) -> Result<AtomMeta, String> {
-    let body = std::fs::read_to_string(md_path).map_err(|e| format!("read: {e}"))?;
-    let fm = extract_frontmatter(&body).ok_or_else(|| "no frontmatter".to_string())?;
-    let parsed: Frontmatter = serde_yaml::from_str(fm).map_err(|e| format!("yaml: {e}"))?;
-    let (crate_name, verb) = split_atom_id(&parsed.atom)?;
-    let atom_dir = md_path.parent().ok_or("no parent dir")?;
-    Ok(AtomMeta {
-        full_id: parsed.atom.clone(),
-        crate_name,
-        verb,
-        kind: parsed.kind,
-        md_path: md_path.to_path_buf(),
-        input_schema_path: atom_dir.join(&parsed.input.schema),
-        output_schema_path: atom_dir.join(&parsed.output.schema),
-    })
-}
-
-/// Returns the frontmatter body (between the two `---` fences), or None.
+/// Backwards-compatible split — returns the frontmatter YAML body (no body
+/// trailing). Returns `None` if the file has no frontmatter fences.
 pub fn extract_frontmatter(body: &str) -> Option<&str> {
-    let rest = body.strip_prefix("---\n").or_else(|| body.strip_prefix("---\r\n"))?;
-    let end = rest.find("\n---").or_else(|| rest.find("\r\n---"))?;
-    Some(&rest[..end])
-}
-
-fn split_atom_id(id: &str) -> Result<(String, String), String> {
-    let (crate_name, verb) = id
-        .split_once("::")
-        .ok_or_else(|| format!("atom id missing `::`: {id}"))?;
-    if crate_name.is_empty() || verb.is_empty() {
-        return Err(format!("atom id has empty half: {id}"));
-    }
-    Ok((crate_name.to_string(), verb.to_string()))
+    shared::parse_frontmatter(body).ok().map(|(fm, _)| fm)
 }
diff --git a/_primitives/_rust/kei-runtime/src/invoke.rs b/_primitives/_rust/kei-runtime/src/invoke.rs
index 1bf2bcf..1797866 100644
--- a/_primitives/_rust/kei-runtime/src/invoke.rs
+++ b/_primitives/_rust/kei-runtime/src/invoke.rs
@@ -15,6 +15,7 @@ pub enum InvokeError {
     AtomNotFound(String),
     InputParse(String),
     InputInvalid(String),
+    MissingInputSchema(String),
 }
 
 impl std::fmt::Display for InvokeError {
@@ -23,6 +24,7 @@ impl std::fmt::Display for InvokeError {
             Self::AtomNotFound(id) => write!(f, "atom not found: {id}"),
             Self::InputParse(e) => write!(f, "input parse: {e}"),
             Self::InputInvalid(e) => write!(f, "input invalid: {e}"),
+            Self::MissingInputSchema(id) => write!(f, "atom `{id}` declares no input schema"),
         }
     }
 }
@@ -37,14 +39,15 @@ pub struct Output {
 }
 
 /// Invoke an atom by full ID with a JSON input string.
-///
-/// MVP contract: discover atom → parse input → validate against schema →
-/// return stub acknowledgement. Exec wire-up is a follow-up.
 pub fn invoke(root: &Path, atom_id: &str, input_json: &str) -> Result<Output, InvokeError> {
     let meta = find_atom(root, atom_id)?;
     let input: Value =
         serde_json::from_str(input_json).map_err(|e| InvokeError::InputParse(e.to_string()))?;
-    validate_input(&meta.input_schema_path, &input)
+    let schema = meta
+        .input_schema
+        .as_ref()
+        .ok_or_else(|| InvokeError::MissingInputSchema(atom_id.to_string()))?;
+    validate_input(schema, &input)
         .map_err(|e| InvokeError::InputInvalid(e.to_string()))?;
     Ok(Output {
         error: "atom invocation not yet implemented — wire needs Stream B atom impls".to_string(),
diff --git a/_primitives/_rust/kei-runtime/src/lint.rs b/_primitives/_rust/kei-runtime/src/lint.rs
index aa6a4ff..a3145b6 100644
--- a/_primitives/_rust/kei-runtime/src/lint.rs
+++ b/_primitives/_rust/kei-runtime/src/lint.rs
@@ -3,7 +3,8 @@
 //! Checks (from SUBSTRATE-SCHEMA §Validation):
 //!   1. Frontmatter has required fields (atom, kind, version, input, output,
 //!      side_effects, idempotent, stability).
-//!   2. Schema paths resolve to existing JSON files.
+//!   2. Schema paths resolve to existing JSON files inside the atom's dir
+//!      (safe_join — rejects `..` and absolute paths).
 //!   3. JSON Schemas declare draft-07 via `$schema`.
 //!   4. `kind` ∈ {command, query, stream, transform}.
 //!   5. `side_effects` entries are `{op, domain}` objects.
@@ -11,7 +12,8 @@
 //!      refs allowed).
 
 use crate::discover::extract_frontmatter;
-use serde_yaml::Value as YamlValue;
+use kei_atom_discovery::safe_join;
+use serde_yaml_ng::Value as YamlValue;
 use std::collections::HashSet;
 use std::path::{Path, PathBuf};
 use walkdir::WalkDir;
@@ -51,6 +53,7 @@ pub fn schema_lint(root: &Path) -> LintReport {
 fn find_atom_files(root: &Path) -> Vec<PathBuf> {
     WalkDir::new(root)
         .max_depth(3)
+        .follow_links(false)
         .into_iter()
         .flatten()
         .filter(|e| {
@@ -67,7 +70,7 @@ fn collect_atom_ids(root: &Path) -> HashSet<String> {
     for md in find_atom_files(root) {
         if let Ok(body) = std::fs::read_to_string(&md) {
             if let Some(fm) = extract_frontmatter(&body) {
-                if let Ok(y) = serde_yaml::from_str::<YamlValue>(fm) {
+                if let Ok(y) = serde_yaml_ng::from_str::<YamlValue>(fm) {
                     if let Some(id) = y.get("atom").and_then(|v| v.as_str()) {
                         ids.insert(id.to_string());
                     }
@@ -82,7 +85,7 @@ fn lint_one(md_path: &Path, known_atoms: &HashSet<String>) -> Result<(), Vec<Str
     let body = std::fs::read_to_string(md_path).map_err(|e| vec![format!("read: {e}")])?;
     let fm_text = extract_frontmatter(&body).ok_or_else(|| vec!["no frontmatter".to_string()])?;
     let fm: YamlValue =
-        serde_yaml::from_str(fm_text).map_err(|e| vec![format!("yaml parse: {e}")])?;
+        serde_yaml_ng::from_str(fm_text).map_err(|e| vec![format!("yaml parse: {e}")])?;
     let mut errs = Vec::new();
     check_required_fields(&fm, &mut errs);
     check_kind(&fm, &mut errs);
@@ -126,11 +129,21 @@ fn check_side_effects(fm: &YamlValue, errs: &mut Vec<String>) {
 }
 
 fn check_schema_files(md_path: &Path, fm: &YamlValue, errs: &mut Vec<String>) {
+    let Some(md_dir) = md_path.parent() else {
+        errs.push("md_path has no parent dir".to_string());
+        return;
+    };
     for key in &["input", "output"] {
         let Some(rel) = fm.get(key).and_then(|v| v.get("schema")).and_then(|v| v.as_str()) else {
             continue;
         };
-        let full = md_path.parent().map(|p| p.join(rel)).unwrap_or_else(|| PathBuf::from(rel));
+        let full = match safe_join(md_dir, rel) {
+            Ok(p) => p,
+            Err(e) => {
+                errs.push(format!("{key} schema path unsafe: {e}"));
+                continue;
+            }
+        };
         if !full.exists() {
             errs.push(format!("{key} schema missing: {}", full.display()));
             continue;
diff --git a/_primitives/_rust/kei-runtime/src/main.rs b/_primitives/_rust/kei-runtime/src/main.rs
index c6de9a6..f069953 100644
--- a/_primitives/_rust/kei-runtime/src/main.rs
+++ b/_primitives/_rust/kei-runtime/src/main.rs
@@ -77,11 +77,11 @@ fn run_list_atoms(root: PathBuf, crate_name: Option<String>, kind: Option<String
             }
         }
         if let Some(k) = &kind {
-            if a.kind != *k {
+            if a.kind.as_str() != k.as_str() {
                 continue;
             }
         }
-        println!("{}\t{}\t{}", a.full_id, a.kind, a.md_path.display());
+        println!("{}\t{}\t{}", a.full_id, a.kind.as_str(), a.md_path.display());
     }
     ExitCode::SUCCESS
 }
diff --git a/_primitives/_rust/kei-runtime/src/validate.rs b/_primitives/_rust/kei-runtime/src/validate.rs
index 28bf401..0596001 100644
--- a/_primitives/_rust/kei-runtime/src/validate.rs
+++ b/_primitives/_rust/kei-runtime/src/validate.rs
@@ -1,11 +1,19 @@
 //! JSON Schema draft-07 validation wrappers.
 //!
-//! Thin façade over the `jsonschema` crate. Reads schema from disk per call —
-//! caller may cache if hot. Returns a single, readable error message.
+//! Thin façade over the `jsonschema` crate (v0.18). Reads schema from disk
+//! per call. Returns a single, readable error message.
+//!
+//! SSRF / IMDS hardening:
+//!   - `default-features = false` on `jsonschema` — no `resolve-http` feature.
+//!   - Custom `LocalFileResolver` replaces the default. It rejects any URL
+//!     whose scheme isn't `file://` and any path outside the schema's own
+//!     directory (anchored at the schema file's parent).
 
-use jsonschema::JSONSchema;
+use jsonschema::{JSONSchema, SchemaResolver, SchemaResolverError};
 use serde_json::Value;
-use std::path::Path;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use url::Url;
 
 #[derive(Debug)]
 pub struct ValidationError(pub String);
@@ -33,8 +41,10 @@ fn validate_value(schema_path: &Path, value: &Value) -> Result<(), ValidationErr
         .map_err(|e| ValidationError(format!("read {}: {e}", schema_path.display())))?;
     let schema_json: Value = serde_json::from_str(&schema_text)
         .map_err(|e| ValidationError(format!("parse {}: {e}", schema_path.display())))?;
+    let root = schema_path.parent().unwrap_or(schema_path).to_path_buf();
     let compiled = JSONSchema::options()
         .with_draft(jsonschema::Draft::Draft7)
+        .with_resolver(LocalFileResolver::new(root))
         .compile(&schema_json)
         .map_err(|e| ValidationError(format!("compile: {e}")))?;
     if let Err(errors) = compiled.validate(value) {
@@ -43,3 +53,54 @@ fn validate_value(schema_path: &Path, value: &Value) -> Result<(), ValidationErr
     }
     Ok(())
 }
+
+/// `$ref` resolver that rejects every scheme except `file://`, AND rejects
+/// any path that is not inside `root` (canonicalised).
+#[derive(Debug)]
+pub struct LocalFileResolver {
+    root: PathBuf,
+}
+
+impl LocalFileResolver {
+    pub fn new(root: PathBuf) -> Self {
+        Self { root }
+    }
+}
+
+impl SchemaResolver for LocalFileResolver {
+    fn resolve(
+        &self,
+        _root_schema: &Value,
+        url: &Url,
+        _original_reference: &str,
+    ) -> Result<Arc<Value>, SchemaResolverError> {
+        if url.scheme() != "file" {
+            return Err(anyhow::anyhow!(
+                "remote $ref rejected — only file:// is allowed (got {})",
+                url.scheme()
+            ));
+        }
+        let path = url
+            .to_file_path()
+            .map_err(|_| anyhow::anyhow!("invalid file URL: {url}"))?;
+        let canon = path
+            .canonicalize()
+            .map_err(|e| anyhow::anyhow!("canonicalize {}: {e}", path.display()))?;
+        let root_canon = self
+            .root
+            .canonicalize()
+            .map_err(|e| anyhow::anyhow!("canonicalize root {}: {e}", self.root.display()))?;
+        if !canon.starts_with(&root_canon) {
+            return Err(anyhow::anyhow!(
+                "file $ref escapes schema root: {} not under {}",
+                canon.display(),
+                root_canon.display()
+            ));
+        }
+        let f = std::fs::File::open(&canon)
+            .map_err(|e| anyhow::anyhow!("open {}: {e}", canon.display()))?;
+        let doc: Value = serde_json::from_reader(f)
+            .map_err(|e| anyhow::anyhow!("parse {}: {e}", canon.display()))?;
+        Ok(Arc::new(doc))
+    }
+}
diff --git a/_primitives/_rust/kei-runtime/tests/discover_smoke.rs b/_primitives/_rust/kei-runtime/tests/discover_smoke.rs
index 28a29c1..cc77a0c 100644
--- a/_primitives/_rust/kei-runtime/tests/discover_smoke.rs
+++ b/_primitives/_rust/kei-runtime/tests/discover_smoke.rs
@@ -1,6 +1,6 @@
 //! Integration test — walk_atoms returns 2 well-formed records from temp root.
 
-use kei_runtime::discover::walk_atoms;
+use kei_runtime::discover::{walk_atoms, AtomKind};
 use std::fs;
 use std::path::Path;
 
@@ -43,8 +43,16 @@ fn walk_atoms_finds_two_records() {
     assert_eq!(atoms[0].full_id, "kei-alpha::search");
     assert_eq!(atoms[0].crate_name, "kei-alpha");
     assert_eq!(atoms[0].verb, "search");
-    assert_eq!(atoms[0].kind, "query");
+    assert_eq!(atoms[0].kind, AtomKind::Query);
     assert_eq!(atoms[1].full_id, "kei-beta::fetch");
-    assert!(atoms[1].input_schema_path.ends_with("schemas/fetch-input.json"));
-    assert!(atoms[1].output_schema_path.ends_with("schemas/fetch-output.json"));
+    assert!(atoms[1]
+        .input_schema
+        .as_ref()
+        .unwrap()
+        .ends_with("schemas/fetch-input.json"));
+    assert!(atoms[1]
+        .output_schema
+        .as_ref()
+        .unwrap()
+        .ends_with("schemas/fetch-output.json"));
 }
diff --git a/_primitives/_rust/kei-sage/Cargo.toml b/_primitives/_rust/kei-sage/Cargo.toml
index 9bf1080..04dea72 100644
--- a/_primitives/_rust/kei-sage/Cargo.toml
+++ b/_primitives/_rust/kei-sage/Cargo.toml
@@ -18,9 +18,9 @@ rusqlite = { version = "0.31", features = ["bundled"] }
 clap = { version = "4", features = ["derive"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
-serde_yaml = "0.9"
 anyhow = "1"
 chrono = { version = "0.4", default-features = false, features = ["clock"] }
+kei-atom-discovery = { path = "../kei-atom-discovery" }
 
 [dev-dependencies]
 tempfile = "3"
diff --git a/_primitives/_rust/kei-sage/src/atom_parse.rs b/_primitives/_rust/kei-sage/src/atom_parse.rs
index 8e44e6c..6bef3f8 100644
--- a/_primitives/_rust/kei-sage/src/atom_parse.rs
+++ b/_primitives/_rust/kei-sage/src/atom_parse.rs
@@ -1,60 +1,23 @@
-//! Frontmatter splitting + wikilink extraction helpers for atom `.md` files.
+//! Sage-local aliases over `kei-atom-discovery` helpers.
 //!
-//! Pure functions, no I/O. See `atoms.rs` for the discovery walker.
+//! Historical sage API: `split_frontmatter`, `parse_wikilink`, `is_atom_target`,
+//! `split_atom_id`. All now delegate to the shared crate; kept here so sage
+//! internals compile without touch.
 
 use anyhow::{anyhow, Result};
+use kei_atom_discovery as shared;
 
-/// Split a `.md` file into (frontmatter_yaml, body). Frontmatter must start
-/// with `---\n` and end with a line that is exactly `---`.
+pub use shared::{is_atom_target, parse_wikilink};
+
+/// Split a `.md` file into (frontmatter_yaml, body). Delegates to the shared
+/// `parse_frontmatter` — preserves the sage `anyhow::Result` return type.
 pub fn split_frontmatter(text: &str) -> Result<(&str, &str)> {
-    let rest = text
-        .strip_prefix("---\n")
-        .or_else(|| text.strip_prefix("---\r\n"))
-        .ok_or_else(|| anyhow!("missing leading --- frontmatter delimiter"))?;
-    let end = find_closing_delim(rest)
-        .ok_or_else(|| anyhow!("missing closing --- frontmatter delimiter"))?;
-    let fm = &rest[..end.0];
-    let body_start = end.0 + end.1;
-    Ok((fm, rest.get(body_start..).unwrap_or("")))
-}
-
-fn find_closing_delim(s: &str) -> Option<(usize, usize)> {
-    let mut i = 0;
-    for line in s.split_inclusive('\n') {
-        let trimmed = line.trim_end_matches(&['\n', '\r'][..]);
-        if trimmed == "---" {
-            return Some((i, line.len()));
-        }
-        i += line.len();
-    }
-    None
-}
-
-/// Parse a single wikilink `[[target]]`. Returns `Some(target)` stripped of
-/// brackets and whitespace, `None` if the string isn't a wikilink shape.
-pub fn parse_wikilink(raw: &str) -> Option<String> {
-    let t = raw.trim();
-    let inner = t.strip_prefix("[[").and_then(|s| s.strip_suffix("]]"))?;
-    let inner = inner.trim();
-    if inner.is_empty() {
-        None
-    } else {
-        Some(inner.to_string())
-    }
-}
-
-/// Filter rule that decides whether a wikilink target is an atom reference.
-/// Atoms use `<crate>::<verb>`; we exclude `rules/*` and `rule*` targets.
-pub fn is_atom_target(target: &str) -> bool {
-    !target.starts_with("rules/") && !target.starts_with("rule ")
+    shared::parse_frontmatter(text).map_err(|e| anyhow!(e.to_string()))
 }
 
 /// Split `<crate>::<verb>` atom id into components.
 pub fn split_atom_id(id: &str) -> Result<(String, String)> {
-    match id.split_once("::") {
-        Some((c, v)) if !c.is_empty() && !v.is_empty() => Ok((c.into(), v.into())),
-        _ => Err(anyhow!("atom id must be <crate>::<verb>, got {id}")),
-    }
+    shared::split_atom_id(id).map_err(|e| anyhow!(e.to_string()))
 }
 
 #[cfg(test)]
diff --git a/_primitives/_rust/kei-sage/src/atoms.rs b/_primitives/_rust/kei-sage/src/atoms.rs
index 8273382..53fc192 100644
--- a/_primitives/_rust/kei-sage/src/atoms.rs
+++ b/_primitives/_rust/kei-sage/src/atoms.rs
@@ -1,169 +1,30 @@
-//! Substrate-atom discovery + frontmatter parsing + wikilink extraction.
+//! Substrate-atom discovery — thin façade over `kei-atom-discovery`.
 //!
-//! Walks `<root>/<crate>/atoms/*.md`, parses YAML frontmatter, returns
-//! `AtomRecord`. Tolerant: skips files with invalid frontmatter (logs to
-//! stderr, continues scan). See `docs/SUBSTRATE-SCHEMA.md` §Graph contract.
+//! Historical `AtomRecord` is preserved as a type alias for `AtomMeta` so
+//! that downstream sage modules (`atom_index`, `atom_cli`) keep compiling.
 
-use crate::atom_parse::{is_atom_target, parse_wikilink, split_atom_id, split_frontmatter};
-use anyhow::{anyhow, Context, Result};
-use serde::Deserialize;
-use std::fs;
-use std::path::{Path, PathBuf};
-use std::str::FromStr;
+use crate::atom_parse::{is_atom_target, parse_wikilink};
+use anyhow::Result;
+use kei_atom_discovery as shared;
+use std::path::Path;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum AtomKind {
-    Command,
-    Query,
-    Stream,
-    Transform,
-}
+pub use kei_atom_discovery::AtomKind;
 
-impl FromStr for AtomKind {
-    type Err = anyhow::Error;
-    fn from_str(s: &str) -> Result<Self> {
-        match s.trim().to_ascii_lowercase().as_str() {
-            "command" => Ok(AtomKind::Command),
-            "query" => Ok(AtomKind::Query),
-            "stream" => Ok(AtomKind::Stream),
-            "transform" => Ok(AtomKind::Transform),
-            other => Err(anyhow!("unknown atom kind: {other}")),
-        }
-    }
-}
-
-impl AtomKind {
-    pub fn as_str(&self) -> &'static str {
-        match self {
-            AtomKind::Command => "command",
-            AtomKind::Query => "query",
-            AtomKind::Stream => "stream",
-            AtomKind::Transform => "transform",
-        }
-    }
-}
-
-#[derive(Debug, Clone)]
-pub struct AtomRecord {
-    pub full_id: String,
-    pub kind: AtomKind,
-    pub crate_name: String,
-    pub verb: String,
-    pub version: String,
-    pub md_path: PathBuf,
-    pub input_schema: Option<PathBuf>,
-    pub output_schema: Option<PathBuf>,
-    pub related: Vec<String>,
-    pub keywords: Vec<String>,
-    pub stability: String,
-    pub body: String,
-}
-
-#[derive(Debug, Deserialize)]
-struct SchemaRef {
-    schema: Option<String>,
-}
-
-#[derive(Debug, Deserialize)]
-struct Frontmatter {
-    atom: String,
-    kind: String,
-    #[serde(default)]
-    version: Option<String>,
-    #[serde(default)]
-    input: Option<SchemaRef>,
-    #[serde(default)]
-    output: Option<SchemaRef>,
-    #[serde(default)]
-    related: Vec<String>,
-    #[serde(default)]
-    keywords: Vec<String>,
-    #[serde(default)]
-    stability: Option<String>,
-}
+/// Legacy alias: sage used to call this `AtomRecord`. New code should use
+/// `AtomMeta` directly (identical shape, authored in `kei-atom-discovery`).
+pub type AtomRecord = shared::AtomMeta;
 
+/// Walk `<root>/*/atoms/*.md` and return parsed atom metadata.
+/// Tolerant: invalid frontmatter → stderr warning + skipped record.
 pub fn discover_atoms(root: &Path) -> Result<Vec<AtomRecord>> {
-    let mut out = Vec::new();
     if !root.is_dir() {
-        return Ok(out);
+        return Ok(Vec::new());
     }
-    for entry in fs::read_dir(root).with_context(|| format!("read_dir {}", root.display()))? {
-        let crate_dir = entry?.path();
-        if crate_dir.is_dir() {
-            collect_from_crate(&crate_dir, &mut out);
-        }
-    }
-    Ok(out)
-}
-
-fn collect_from_crate(crate_dir: &Path, out: &mut Vec<AtomRecord>) {
-    let atoms_dir = crate_dir.join("atoms");
-    if !atoms_dir.is_dir() {
-        return;
-    }
-    let crate_name = crate_dir
-        .file_name()
-        .and_then(|s| s.to_str())
-        .unwrap_or("")
-        .to_string();
-    let iter = match fs::read_dir(&atoms_dir) {
-        Ok(it) => it,
-        Err(e) => {
-            eprintln!("skip {}: {}", atoms_dir.display(), e);
-            return;
-        }
-    };
-    for entry in iter.flatten() {
-        let path = entry.path();
-        if !is_md_file(&path) {
-            continue;
-        }
-        match parse_atom_file(&path, &crate_name) {
-            Ok(rec) => out.push(rec),
-            Err(e) => eprintln!("skip {}: {}", path.display(), e),
-        }
-    }
-}
-
-fn is_md_file(path: &Path) -> bool {
-    path.is_file() && path.extension().and_then(|s| s.to_str()) == Some("md")
-}
-
-fn parse_atom_file(path: &Path, crate_name: &str) -> Result<AtomRecord> {
-    let text = fs::read_to_string(path)
-        .with_context(|| format!("read {}", path.display()))?;
-    let (fm_text, body) = split_frontmatter(&text)?;
-    let fm: Frontmatter =
-        serde_yaml::from_str(fm_text).with_context(|| "parse frontmatter YAML")?;
-    build_record(fm, body, path, crate_name)
-}
-
-fn build_record(fm: Frontmatter, body: &str, path: &Path, crate_name: &str) -> Result<AtomRecord> {
-    let kind = AtomKind::from_str(&fm.kind)?;
-    let (crate_from_id, verb) = split_atom_id(&fm.atom)?;
-    let md_dir = path.parent().unwrap_or(path).to_path_buf();
-    Ok(AtomRecord {
-        full_id: fm.atom.clone(),
-        kind,
-        crate_name: if crate_from_id.is_empty() {
-            crate_name.to_string()
-        } else {
-            crate_from_id
-        },
-        verb,
-        version: fm.version.unwrap_or_default(),
-        md_path: path.to_path_buf(),
-        input_schema: fm.input.and_then(|s| s.schema).map(|s| md_dir.join(&s)),
-        output_schema: fm.output.and_then(|s| s.schema).map(|s| md_dir.join(&s)),
-        related: fm.related,
-        keywords: fm.keywords,
-        stability: fm.stability.unwrap_or_else(|| "unknown".into()),
-        body: body.to_string(),
-    })
+    Ok(shared::discover_atoms(root))
 }
 
 /// Extract `(source_atom_id, target)` edges from `related:` wikilinks.
-/// Non-atom targets (rules, notes) are filtered out here — scope: atoms only.
+/// Non-atom targets (rules, notes) are filtered out — scope: atoms only.
 pub fn resolve_wikilinks(records: &[AtomRecord]) -> Vec<(String, String)> {
     let mut out = Vec::new();
     for rec in records {