diff --git a/crates/relicario-core/src/lib.rs b/crates/relicario-core/src/lib.rs
index 829ac50..8599466 100644
--- a/crates/relicario-core/src/lib.rs
+++ b/crates/relicario-core/src/lib.rs
@@ -94,6 +94,11 @@ pub mod device;
 pub use device::{fingerprint, DeviceEntry, RevokedEntry, generate_keypair, sign, verify};
 
 pub mod org;
+pub use org::{
+    generate_org_key, unwrap_org_key, wrap_org_key,
+    CollectionDef, MemberId, OrgCollections, OrgId, OrgManifest,
+    OrgManifestEntry, OrgMember, OrgMembers, OrgMeta, OrgRole,
+};
 
 pub mod tar_safe;
 pub use tar_safe::{safe_unpack_git_archive, DEFAULT_MAX_UNCOMPRESSED};
diff --git a/crates/relicario-core/src/org.rs b/crates/relicario-core/src/org.rs
index 5444b35..5b02caa 100644
--- a/crates/relicario-core/src/org.rs
+++ b/crates/relicario-core/src/org.rs
@@ -1 +1,493 @@
 //! Org vault types, crypto, and schema for multi-user self-hosted deployments.
+
+use rand::{rngs::OsRng, RngCore};
+use serde::{Deserialize, Serialize};
+use zeroize::Zeroizing;
+
+use crate::error::{RelicarioError, Result};
+use crate::ids::ItemId;
+use crate::item_types::ItemType;
+
+// ── IDs ──────────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(transparent)]
+pub struct OrgId(pub String);
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(transparent)]
+pub struct MemberId(pub String);
+
+impl OrgId {
+    pub fn new() -> Self {
+        let mut bytes = [0u8; 8];
+        OsRng.fill_bytes(&mut bytes);
+        Self(hex::encode(bytes))
+    }
+    pub fn as_str(&self) -> &str { &self.0 }
+}
+
+impl Default for OrgId {
+    fn default() -> Self { Self::new() }
+}
+
+impl MemberId {
+    pub fn new() -> Self {
+        let mut bytes = [0u8; 8];
+        OsRng.fill_bytes(&mut bytes);
+        Self(hex::encode(bytes))
+    }
+    pub fn as_str(&self) -> &str { &self.0 }
+    pub fn is_valid(&self) -> bool {
+        self.0.len() == 16 && self.0.chars().all(|c| c.is_ascii_hexdigit())
+    }
+}
+
+impl Default for MemberId {
+    fn default() -> Self { Self::new() }
+}
+
+// ── Roles ────────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum OrgRole {
+    Owner,
+    Admin,
+    Member,
+}
+
+impl OrgRole {
+    pub fn can_manage_members(&self) -> bool {
+        matches!(self, OrgRole::Owner | OrgRole::Admin)
+    }
+    pub fn can_manage_owners(&self) -> bool {
+        matches!(self, OrgRole::Owner)
+    }
+}
+
+// ── Members ──────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrgMember {
+    pub member_id: MemberId,
+    pub display_name: String,
+    pub role: OrgRole,
+    /// SSH public key string (openssh format: "ssh-ed25519 AAAA...")
+    pub ed25519_pubkey: String,
+    /// Collection slugs this member can access.
+    #[serde(default)]
+    pub collections: Vec<String>,
+    pub added_at: i64,
+    pub added_by: MemberId,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrgMembers {
+    pub schema_version: u32,
+    pub members: Vec<OrgMember>,
+}
+
+impl OrgMembers {
+    pub fn new() -> Self {
+        Self { schema_version: 1, members: Vec::new() }
+    }
+
+    pub fn find_by_id(&self, id: &MemberId) -> Option<&OrgMember> {
+        self.members.iter().find(|m| &m.member_id == id)
+    }
+
+    pub fn find_by_id_mut(&mut self, id: &MemberId) -> Option<&mut OrgMember> {
+        self.members.iter_mut().find(|m| &m.member_id == id)
+    }
+
+    pub fn validate(&self) -> Result<()> {
+        for m in &self.members {
+            if !m.member_id.is_valid() {
+                return Err(RelicarioError::Format(
+                    format!("invalid member_id: {}", m.member_id.0)
+                ));
+            }
+        }
+        Ok(())
+    }
+}
+
+impl Default for OrgMembers {
+    fn default() -> Self { Self::new() }
+}
+
+// ── Collections ───────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CollectionDef {
+    pub slug: String,
+    pub display_name: String,
+    pub created_by: MemberId,
+    pub created_at: i64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrgCollections {
+    pub schema_version: u32,
+    pub collections: Vec<CollectionDef>,
+}
+
+impl OrgCollections {
+    pub fn new() -> Self {
+        Self { schema_version: 1, collections: Vec::new() }
+    }
+
+    pub fn contains_slug(&self, slug: &str) -> bool {
+        self.collections.iter().any(|c| c.slug == slug)
+    }
+
+    pub fn validate(&self) -> Result<()> {
+        for c in &self.collections {
+            if c.slug.is_empty() || c.slug.contains('/') || c.slug.contains('.') {
+                return Err(RelicarioError::Format(
+                    format!("invalid collection slug: {:?}", c.slug)
+                ));
+            }
+        }
+        Ok(())
+    }
+}
+
+impl Default for OrgCollections {
+    fn default() -> Self { Self::new() }
+}
+
+// ── Org meta ─────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrgMeta {
+    pub schema_version: u32,
+    pub org_id: OrgId,
+    pub display_name: String,
+    pub created_at: i64,
+}
+
+impl OrgMeta {
+    pub fn new(display_name: String) -> Self {
+        Self {
+            schema_version: 1,
+            org_id: OrgId::new(),
+            display_name,
+            created_at: crate::time::now_unix(),
+        }
+    }
+}
+
+// ── Org manifest ─────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrgManifestEntry {
+    pub id: ItemId,
+    pub r#type: ItemType,
+    pub title: String,
+    #[serde(default)]
+    pub tags: Vec<String>,
+    pub modified: i64,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub trashed_at: Option<i64>,
+    /// Collection this item belongs to.
+    pub collection: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrgManifest {
+    pub schema_version: u32,
+    pub entries: Vec<OrgManifestEntry>,
+}
+
+impl OrgManifest {
+    pub fn new() -> Self {
+        Self { schema_version: 1, entries: Vec::new() }
+    }
+
+    /// Return only entries whose collection is in `member.collections`.
+    pub fn filter_for_member(&self, member: &OrgMember) -> Self {
+        let granted: std::collections::HashSet<&str> =
+            member.collections.iter().map(|s| s.as_str()).collect();
+        Self {
+            schema_version: self.schema_version,
+            entries: self.entries.iter()
+                .filter(|e| granted.contains(e.collection.as_str()))
+                .cloned()
+                .collect(),
+        }
+    }
+}
+
+impl Default for OrgManifest {
+    fn default() -> Self { Self::new() }
+}
+
+// ── Key wrap / unwrap (ECIES: X25519 + XChaCha20-Poly1305) ───────────────────
+
+/// Generate a random 256-bit org master key.
+pub fn generate_org_key() -> Zeroizing<[u8; 32]> {
+    let mut key = Zeroizing::new([0u8; 32]);
+    OsRng.fill_bytes(key.as_mut());
+    key
+}
+
+/// Derive an X25519 static secret from an ed25519 seed (standard RFC 7748 path).
+fn ed25519_seed_to_x25519_secret(seed: &[u8; 32]) -> x25519_dalek::StaticSecret {
+    use sha2::{Digest, Sha512};
+    let h = Sha512::digest(seed.as_ref());
+    let mut scalar = [0u8; 32];
+    scalar.copy_from_slice(&h[..32]);
+    // RFC 7748 clamping
+    scalar[0] &= 248;
+    scalar[31] &= 127;
+    scalar[31] |= 64;
+    x25519_dalek::StaticSecret::from(scalar)
+}
+
+/// Parse an OpenSSH ed25519 public key string and return its X25519 form.
+fn openssh_ed25519_to_x25519_pk(openssh: &str) -> Result<x25519_dalek::PublicKey> {
+    use ssh_key::PublicKey;
+    let pk = PublicKey::from_openssh(openssh.trim())
+        .map_err(|e| RelicarioError::Format(format!("bad SSH pubkey: {e}")))?;
+    let ed_bytes = pk.key_data().ed25519()
+        .ok_or_else(|| RelicarioError::Format("expected ed25519 key".into()))?
+        .0;
+    let verifying = ed25519_dalek::VerifyingKey::from_bytes(&ed_bytes)
+        .map_err(|e| RelicarioError::Format(format!("bad ed25519 pubkey: {e}")))?;
+    Ok(x25519_dalek::PublicKey::from(verifying.to_montgomery().to_bytes()))
+}
+
+/// Wrap `org_key` for a recipient identified by their OpenSSH ed25519 public key.
+///
+/// Output layout: `ephemeral_x25519_pk(32) || version(1) || nonce(24) || ciphertext+tag`
+pub fn wrap_org_key(org_key: &Zeroizing<[u8; 32]>, recipient_openssh_pubkey: &str) -> Result<Vec<u8>> {
+    use sha2::{Digest, Sha256};
+    use x25519_dalek::EphemeralSecret;
+
+    let recipient_pk = openssh_ed25519_to_x25519_pk(recipient_openssh_pubkey)?;
+
+    let ephemeral_sk = EphemeralSecret::random_from_rng(OsRng);
+    let ephemeral_pk = x25519_dalek::PublicKey::from(&ephemeral_sk);
+
+    let shared = ephemeral_sk.diffie_hellman(&recipient_pk);
+
+    // Domain-separated KDF. All intermediates carrying the DH secret are held in
+    // Zeroizing so they are wiped on drop (H6).
+    let mut kdf_input: Zeroizing<Vec<u8>> = Zeroizing::new(Vec::with_capacity(32 + 32 + 32));
+    kdf_input.extend_from_slice(shared.as_bytes());
+    kdf_input.extend_from_slice(ephemeral_pk.as_bytes());
+    kdf_input.extend_from_slice(recipient_pk.as_bytes());
+
+    // Copy the digest straight into a Zeroizing array. The GenericArray returned
+    // by Sha256::digest is not Zeroize (generic-array's impl is feature-gated and
+    // not enabled here), so we move the bytes into an owned [u8; 32] whose own
+    // Zeroize impl wipes them on drop.
+    let mut wrap_key: Zeroizing<[u8; 32]> = Zeroizing::new([0u8; 32]);
+    wrap_key.copy_from_slice(&Sha256::digest(kdf_input.as_slice()));
+
+    let encrypted = crate::crypto::encrypt(&wrap_key, org_key.as_ref())?;
+
+    let mut out = Vec::with_capacity(32 + encrypted.len());
+    out.extend_from_slice(ephemeral_pk.as_bytes());
+    out.extend_from_slice(&encrypted);
+    Ok(out)
+}
+
+/// Unwrap a key blob produced by `wrap_org_key` using the recipient's ed25519 seed.
+pub fn unwrap_org_key(wrapped: &[u8], ed25519_seed: &Zeroizing<[u8; 32]>) -> Result<Zeroizing<[u8; 32]>> {
+    use sha2::{Digest, Sha256};
+
+    // Minimum: 32 (ephemeral_pk) + 41 (version+nonce+tag for 32-byte plaintext)
+    if wrapped.len() < 32 + 41 {
+        return Err(RelicarioError::Format("wrapped key blob too short".into()));
+    }
+
+    let ephemeral_pk = x25519_dalek::PublicKey::from(
+        <[u8; 32]>::try_from(&wrapped[..32]).unwrap()
+    );
+    let encrypted = &wrapped[32..];
+
+    let recipient_sk = ed25519_seed_to_x25519_secret(ed25519_seed);
+    let recipient_pk = x25519_dalek::PublicKey::from(&recipient_sk);
+
+    let shared = recipient_sk.diffie_hellman(&ephemeral_pk);
+
+    let mut kdf_input: Zeroizing<Vec<u8>> = Zeroizing::new(Vec::with_capacity(32 + 32 + 32));
+    kdf_input.extend_from_slice(shared.as_bytes());
+    kdf_input.extend_from_slice(ephemeral_pk.as_bytes());
+    kdf_input.extend_from_slice(recipient_pk.as_bytes());
+
+    let mut wrap_key: Zeroizing<[u8; 32]> = Zeroizing::new([0u8; 32]);
+    wrap_key.copy_from_slice(&Sha256::digest(kdf_input.as_slice()));
+
+    let plaintext = Zeroizing::new(crate::crypto::decrypt(&wrap_key, encrypted)?);
+    if plaintext.len() != 32 {
+        return Err(RelicarioError::Format(
+            format!("unwrapped key has wrong length: {}", plaintext.len())
+        ));
+    }
+
+    let mut key = Zeroizing::new([0u8; 32]);
+    key.copy_from_slice(&plaintext);
+    Ok(key)
+}
+
+// ── Tests ─────────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn member_id_is_16_hex_chars() {
+        let id = MemberId::new();
+        assert_eq!(id.0.len(), 16);
+        assert!(id.0.chars().all(|c| c.is_ascii_hexdigit()));
+    }
+
+    #[test]
+    fn member_ids_are_unique() {
+        let mut seen = std::collections::HashSet::new();
+        for _ in 0..1_000 {
+            assert!(seen.insert(MemberId::new().0));
+        }
+    }
+
+    #[test]
+    fn org_id_is_16_hex_chars() {
+        let id = OrgId::new();
+        assert_eq!(id.0.len(), 16);
+    }
+
+    #[test]
+    fn org_role_can_manage_members() {
+        assert!(OrgRole::Owner.can_manage_members());
+        assert!(OrgRole::Admin.can_manage_members());
+        assert!(!OrgRole::Member.can_manage_members());
+    }
+
+    #[test]
+    fn collection_slug_validation_rejects_slash() {
+        let mut c = OrgCollections::new();
+        c.collections.push(CollectionDef {
+            slug: "bad/slug".into(),
+            display_name: "Bad".into(),
+            created_by: MemberId::new(),
+            created_at: 0,
+        });
+        assert!(c.validate().is_err());
+    }
+
+    #[test]
+    fn filter_for_member_restricts_collections() {
+        let mut manifest = OrgManifest::new();
+        manifest.entries.push(OrgManifestEntry {
+            id: ItemId::new(),
+            r#type: crate::item_types::ItemType::SecureNote,
+            title: "A".into(),
+            tags: vec![],
+            modified: 0,
+            trashed_at: None,
+            collection: "prod".into(),
+        });
+        manifest.entries.push(OrgManifestEntry {
+            id: ItemId::new(),
+            r#type: crate::item_types::ItemType::SecureNote,
+            title: "B".into(),
+            tags: vec![],
+            modified: 0,
+            trashed_at: None,
+            collection: "dev".into(),
+        });
+
+        let member = OrgMember {
+            member_id: MemberId::new(),
+            display_name: "Alice".into(),
+            role: OrgRole::Member,
+            ed25519_pubkey: String::new(),
+            collections: vec!["prod".into()],
+            added_at: 0,
+            added_by: MemberId::new(),
+        };
+
+        let filtered = manifest.filter_for_member(&member);
+        assert_eq!(filtered.entries.len(), 1);
+        assert_eq!(filtered.entries[0].collection, "prod");
+    }
+
+    #[test]
+    fn generate_org_key_is_32_bytes() {
+        let key = generate_org_key();
+        assert_eq!(key.len(), 32);
+    }
+
+    /// Pinned RFC 8032 known-answer vector for the ed25519→X25519 map. The seed
+    /// and expected X25519 public key are from ed25519-dalek's own reference
+    /// test (`tests/x25519.rs`, section 7.1 vector A). The expected value is a
+    /// HARD-CODED LITERAL — NOT recomputed by the production code path — so a
+    /// correlated cross-crate-version regression in the birational map (where
+    /// both our derivation and a naive re-derivation would drift together) is
+    /// still caught. If this test ever fails after a dep bump, the wrap/unwrap
+    /// keyspace changed and every existing `keys/<id>.enc` blob is invalidated.
+    #[test]
+    fn ed25519_to_x25519_pinned_rfc8032_vector() {
+        let seed: [u8; 32] =
+            hex::decode("9d61b19deffd5a60ba844af492ec2cc44449c5697b326919703bac031cae7f60")
+                .unwrap()
+                .try_into()
+                .unwrap();
+        // Derive the X25519 *public* key the same way wrap/unwrap derives the
+        // recipient's static secret from a seed.
+        let secret = ed25519_seed_to_x25519_secret(&seed);
+        let public = x25519_dalek::PublicKey::from(&secret);
+        assert_eq!(
+            hex::encode(public.as_bytes()),
+            "d85e07ec22b0ad881537c2f44d662d1a143cf830c57aca4305d85c7a90f6b62e",
+        );
+    }
+
+    #[test]
+    fn wrap_unwrap_round_trip() {
+        // Generate an ed25519 keypair to act as the member's device key
+        use ed25519_dalek::SigningKey;
+        let mut seed = [0u8; 32];
+        OsRng.fill_bytes(&mut seed);
+        let signing_key = SigningKey::from_bytes(&seed);
+        let pubkey_openssh = ssh_key::PrivateKey::from(
+            ssh_key::private::Ed25519Keypair::from(&signing_key),
+        )
+        .public_key()
+        .to_openssh()
+        .expect("openssh");
+
+        let org_key = generate_org_key();
+        let wrapped = wrap_org_key(&org_key, &pubkey_openssh).expect("wrap");
+        let seed_zeroizing = Zeroizing::new(seed);
+        let unwrapped = unwrap_org_key(&wrapped, &seed_zeroizing).expect("unwrap");
+
+        assert_eq!(*org_key, *unwrapped);
+    }
+
+    #[test]
+    fn unwrap_with_wrong_seed_fails() {
+        use ed25519_dalek::SigningKey;
+        let mut seed = [0u8; 32];
+        OsRng.fill_bytes(&mut seed);
+        let signing_key = SigningKey::from_bytes(&seed);
+        let pubkey_openssh = ssh_key::PrivateKey::from(
+            ssh_key::private::Ed25519Keypair::from(&signing_key),
+        )
+        .public_key()
+        .to_openssh()
+        .expect("openssh");
+
+        let org_key = generate_org_key();
+        let wrapped = wrap_org_key(&org_key, &pubkey_openssh).expect("wrap");
+
+        let wrong_seed = Zeroizing::new([0xFFu8; 32]);
+        let result = unwrap_org_key(&wrapped, &wrong_seed);
+        assert!(result.is_err());
+    }
+}