diff --git a/library/src/network.rs b/library/src/network.rs
index 2248bd3..1504bc8 100644
--- a/library/src/network.rs
+++ b/library/src/network.rs
@@ -247,12 +247,22 @@ pub struct PatchCheckRequest {
     /// The unique ID of this device. This is a random UUID generated by Shorebird and _not_ the
     /// device's UUID or any other identifier that has meaning outside of Shorebird.
     pub client_id: String,
-    // We specifically do not send a patch number as part of this request because we always want to
-    // know what the latest available patch is.
+    /// The number of the patch currently running on the device, if any.
+    ///
+    /// Supersedes the legacy `patch_number` field. `patch_number` is
+    /// retained server-side for compatibility with older clients that still
+    /// rely on its short-circuit response path; newer updaters populate
+    /// this field instead.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub current_patch_number: Option<usize>,
 }
 
 impl PatchCheckRequest {
-    pub fn new(config: &UpdateConfig, client_id: &str) -> PatchCheckRequest {
+    pub fn new(
+        config: &UpdateConfig,
+        client_id: &str,
+        current_patch_number: Option<usize>,
+    ) -> PatchCheckRequest {
         PatchCheckRequest {
             app_id: config.app_id.clone(),
             channel: config.channel.clone(),
@@ -260,6 +270,7 @@ impl PatchCheckRequest {
             platform: current_platform().to_string(),
             arch: current_arch().to_string(),
             client_id: client_id.to_string(),
+            current_patch_number,
         }
     }
 }
@@ -404,6 +415,7 @@ mod tests {
                 platform: "".to_string(),
                 arch: "".to_string(),
                 client_id: "".to_string(),
+                current_patch_number: None,
             },
         );
         assert!(result.is_err());
diff --git a/library/src/updater.rs b/library/src/updater.rs
index bcde590..e7c5aa8 100644
--- a/library/src/updater.rs
+++ b/library/src/updater.rs
@@ -273,7 +273,12 @@ pub fn should_auto_update() -> anyhow::Result<bool> {
 /// Returns true if an update is available for download. Will return false if the update is already
 /// downloaded and ready to install.
 pub fn check_for_downloadable_update(channel: Option<&str>) -> anyhow::Result<bool> {
-    let client_id = with_state(|state| Ok(state.client_id()))?;
+    let (client_id, current_patch_number) = with_state(|state| {
+        Ok((
+            state.client_id().to_string(),
+            state.currently_booting_patch().map(|p| p.number),
+        ))
+    })?;
 
     let (request, url, request_fn) = with_config(|config| {
         let mut config = config.clone();
@@ -283,7 +288,7 @@ pub fn check_for_downloadable_update(channel: Option<&str>) -> anyhow::Result<bo
         }
 
         Ok((
-            PatchCheckRequest::new(&config, &client_id),
+            PatchCheckRequest::new(&config, &client_id, current_patch_number),
             patches_check_url(&config.base_url),
             config.network_hooks.patch_check_request_fn,
         ))
@@ -400,7 +405,11 @@ fn update_internal(_: &UpdaterLockState, channel: Option<&str>) -> anyhow::Resul
             shorebird_error!("Failed to clear events: {:?}", err);
         }
         // Update our outer state with the new state.
-        Ok(PatchCheckRequest::new(&config, &state.client_id()))
+        Ok(PatchCheckRequest::new(
+            &config,
+            &state.client_id(),
+            state.currently_booting_patch().map(|p| p.number),
+        ))
     })?;
 
     // Check for update.