diff --git a/Cargo.lock b/Cargo.lock
index 8fa8498..7747153 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -171,6 +171,7 @@ dependencies = [
  "atrium-oauth",
  "base64",
  "lgtm-core",
+ "moka",
  "rand 0.8.6",
  "reqwest",
  "serde",
diff --git a/crates/server/src/routes/mod.rs b/crates/server/src/routes/mod.rs
index 981062b..0d07c51 100644
--- a/crates/server/src/routes/mod.rs
+++ b/crates/server/src/routes/mod.rs
@@ -2,6 +2,7 @@ pub mod buyer_auth;
 pub mod claims;
 pub mod entitlements;
 pub mod link;
+pub mod pds;
 pub mod public;
 pub mod webhooks;
 pub mod xrpc;
diff --git a/crates/server/src/routes/pds.rs b/crates/server/src/routes/pds.rs
new file mode 100644
index 0000000..c44581a
--- /dev/null
+++ b/crates/server/src/routes/pds.rs
@@ -0,0 +1,75 @@
+//! `GET /api/pds-capabilities?actor=<handle|did>` — reports whether an actor's PDS is
+//! spaces-compatible (SPEC §8 / spikes/spaces-alpha). Consumed by the shop + `ssh lgtm.shop`.
+
+use std::sync::Arc;
+
+use axum::extract::Query;
+use axum::response::IntoResponse;
+use axum::routing::get;
+use axum::{Extension, Json, Router};
+use serde_json::json;
+
+use atproto::{Actor, Resolver};
+
+use crate::routes::xrpc::invalid_request;
+use crate::state::AppState;
+
+/// Build the capability JSON. Pure over its inputs so the shape + degradation are unit-tested
+/// without a network. `did`/`handle`/`pds` are null when unknown; `reason` is set only when
+/// `spaces_compatible` is false.
+fn capability_json(
+    actor: &str,
+    did: Option<&str>,
+    handle: Option<&str>,
+    pds: Option<&str>,
+    spaces_compatible: bool,
+    reason: Option<&str>,
+    checked_at: &str,
+) -> serde_json::Value {
+    json!({
+        "actor": actor,
+        "did": did,
+        "handle": handle,
+        "pds": pds,
+        "spacesCompatible": spaces_compatible,
+        "reason": reason,
+        "checkedAt": checked_at,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn compatible_shape() {
+        let v = capability_json(
+            "natemoo.re",
+            Some("did:plc:abc"),
+            Some("natemoo.re"),
+            Some("https://pds.example"),
+            true,
+            None,
+            "2026-08-21T00:00:00Z",
+        );
+        assert_eq!(v["spacesCompatible"], true);
+        assert_eq!(v["did"], "did:plc:abc");
+        assert!(v["reason"].is_null());
+    }
+
+    #[test]
+    fn unresolved_degrades_gracefully() {
+        let v = capability_json(
+            "ghost.invalid",
+            None,
+            None,
+            None,
+            false,
+            Some("unresolved handle"),
+            "2026-08-21T00:00:00Z",
+        );
+        assert_eq!(v["spacesCompatible"], false);
+        assert!(v["did"].is_null());
+        assert_eq!(v["reason"], "unresolved handle");
+    }
+}