diff --git a/crates/music-dht/src/catalog.rs b/crates/music-dht/src/catalog.rs
new file mode 100644
index 0000000..76401d2
--- /dev/null
+++ b/crates/music-dht/src/catalog.rs
@@ -0,0 +1,148 @@
+//! Shared wire shapes for Furumi catalog streams.
+//!
+//! The DHT itself only indexes compact search records. Applications can expose
+//! richer, peer-to-peer catalog slices over this protocol when another peer
+//! needs a browseable library view.
+
+use serde::{Deserialize, Serialize};
+
+/// ALPN of the Furumi catalog stream protocol.
+pub const CATALOG_ALPN: &[u8] = b"furumi-fd/catalog/1";
+
+/// Request sent by a catalog client.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogRequest {
+    /// Artist name for full artist-card and image requests.
+    #[serde(default)]
+    pub artist: String,
+    /// Requested resource kind.
+    #[serde(default)]
+    pub want: Option<String>,
+    /// Release title for release-cover requests.
+    #[serde(default)]
+    pub release: Option<String>,
+    /// Opaque pagination cursor for browse slices.
+    #[serde(default)]
+    pub cursor: Option<String>,
+    /// Desired number of entries for browse slices.
+    #[serde(default)]
+    pub limit: Option<usize>,
+}
+
+/// Response returned by a catalog peer.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogResponse {
+    /// Whether the request succeeded.
+    pub ok: bool,
+    /// Human-readable error message when `ok` is false.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub error: Option<String>,
+    /// Full artist card for `catalog` requests.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub artist: Option<CatalogArtist>,
+    /// Compact artist previews for `artists` slice requests.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub artists: Vec<CatalogArtistPreview>,
+    /// Optional release card for future direct release requests.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub release: Option<CatalogRelease>,
+    /// Next pagination cursor for browse slices.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub next_cursor: Option<String>,
+}
+
+/// Compact artist entry used by paginated library browsing.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogArtistPreview {
+    /// Normalized artist key.
+    pub artist_key: String,
+    /// Display artist name.
+    pub name: String,
+    /// Optional image path or peer-local image handle.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub image_path: Option<String>,
+    /// Number of releases where the artist is a primary release artist.
+    pub release_count: i64,
+    /// Number of tracks where the artist appears.
+    pub track_count: i64,
+}
+
+/// Full artist card returned by the catalog protocol.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogArtist {
+    /// Display artist name.
+    pub name: String,
+    /// Releases owned by this artist.
+    #[serde(default)]
+    pub releases: Vec<CatalogRelease>,
+    /// Release appearances where this artist is not the primary artist.
+    #[serde(default)]
+    pub appears_on: Vec<CatalogAppearance>,
+}
+
+/// Release appearance used by full artist cards.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogAppearance {
+    /// Release title.
+    pub release_title: String,
+    /// Release type.
+    #[serde(default)]
+    pub release_type: String,
+    /// Release year.
+    pub year: Option<i32>,
+    /// Track where the artist appears.
+    pub track: CatalogTrack,
+}
+
+/// Release card returned by the catalog protocol.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogRelease {
+    /// Release title.
+    pub title: String,
+    /// Release type.
+    #[serde(default)]
+    pub release_type: String,
+    /// Release year.
+    pub year: Option<i32>,
+    /// Tracks on this release.
+    #[serde(default)]
+    pub tracks: Vec<CatalogTrack>,
+}
+
+/// Track entry returned inside catalog cards.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogTrack {
+    /// Track title.
+    pub title: String,
+    /// Main artists.
+    #[serde(default)]
+    pub artists: Vec<String>,
+    /// Featured artists.
+    #[serde(default)]
+    pub featured_artists: Vec<String>,
+    /// Track number.
+    pub track_number: Option<i32>,
+    /// Disc number.
+    pub disc_number: Option<i32>,
+    /// Track duration in seconds.
+    pub duration_seconds: Option<f64>,
+    /// Stable audio content id when known.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub content_id: Option<String>,
+    /// Peer-local item id used by legacy fetch paths.
+    pub item_id: String,
+}
+
+/// Header returned by catalog image requests before the image bytes.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CatalogImageHeader {
+    /// Whether the image request succeeded.
+    pub ok: bool,
+    /// Human-readable error message when `ok` is false.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub error: Option<String>,
+    /// MIME type of the returned image.
+    pub mime_type: String,
+    /// Size of the following image payload in bytes.
+    pub size: u64,
+}
diff --git a/crates/music-dht/src/lib.rs b/crates/music-dht/src/lib.rs
index 1d2dd40..0dd5f75 100644
--- a/crates/music-dht/src/lib.rs
+++ b/crates/music-dht/src/lib.rs
@@ -77,6 +77,7 @@
 #![warn(missing_docs)]
 #![forbid(unsafe_code)]
 
+pub mod catalog;
 mod config;
 mod database;
 pub mod device_sync;