diff --git a/crates/core/src/upgrade/mod.rs b/crates/core/src/upgrade/mod.rs
index c5f3b87..c4fdd34 100644
--- a/crates/core/src/upgrade/mod.rs
+++ b/crates/core/src/upgrade/mod.rs
@@ -56,6 +56,9 @@ pub enum Origin {
     Checkout { repo: PathBuf },
     /// `cargo install`.
     Cargo,
+    /// A Nix package, run from the store: Nix updates it with the rest of
+    /// the system or profile.
+    Nix,
     /// None of these.
     Unknown,
 }
@@ -73,6 +76,10 @@ impl Origin {
     /// where the system's own directories are read from.
     pub fn detect_at(exe: &Path, home: &Path, cargo_home: Option<&Path>, root: &Path) -> Self {
         let bin_dir = exe.parent().unwrap_or(Path::new("/"));
+        // Read-only and owned by Nix, whichever profile or wrapper started it.
+        if exe.starts_with("/nix/store") {
+            return Self::Nix;
+        }
         if bin_dir == home.join(".local/bin") {
             return Self::Installer { bin_dir: bin_dir.to_path_buf() };
         }
@@ -154,6 +161,11 @@ impl Origin {
                 )],
                 note: "This Lightforge was installed with cargo.".to_owned(),
             },
+            Self::Nix => say(
+                &[],
+                "Lightforge comes from Nix, which updates it: once the package or flake \
+                 input has the new version, rebuild your system or profile.",
+            ),
             Self::Unknown => say(
                 &[INSTALLER_COMMAND],
                 "Lightforge cannot tell how it was installed here. The installer puts it \
@@ -326,6 +338,10 @@ mod tests {
         );
         assert_eq!(detect("/home/u/.cargo/bin/lightforge-gui", &empty), Origin::Cargo);
         assert_eq!(detect("/opt/lightforge/lightforge-gui", &empty), Origin::Unknown);
+        assert_eq!(
+            detect("/nix/store/00000000000000000000000000000000-lightforge/bin/lightforge-gui", &empty),
+            Origin::Nix
+        );
         let _ = std::fs::remove_dir_all(&empty);
     }
 
diff --git a/crates/launcher-gui/src/tests.rs b/crates/launcher-gui/src/tests.rs
index 79c7465..e089466 100644
--- a/crates/launcher-gui/src/tests.rs
+++ b/crates/launcher-gui/src/tests.rs
@@ -1190,6 +1190,7 @@ fn the_update_card_draws_for_every_route_and_stage() {
         Origin::Deb,
         Origin::Copr { atomic: true },
         Origin::Checkout { repo: "/home/u/lightforge".into() },
+        Origin::Nix,
         Origin::Unknown,
     ];
     let stages = [