diff --git a/build/check-bundle-size.ts b/build/check-bundle-size.ts
index b885f8f0..5d7ce005 100644
--- a/build/check-bundle-size.ts
+++ b/build/check-bundle-size.ts
@@ -15,8 +15,11 @@ const BUDGET_BYTES: Record<string, number> = {
   // fixtures retain their separate allowance below; the measured aggregate
   // is 573.4 kB with them, plus the ~11 kB Hall of Fame chunk. Raised again
   // from 590 kB for the Razer button-mapping card and its codec: the measured
-  // aggregate is 588.2 kB, which left under 2 kB of headroom.
-  ".js": 600_000,
+  // aggregate is 588.2 kB, which left under 2 kB of headroom. Raised again to
+  // 610 kB for the Pulsar XS-1 feature-report driver and 4K receiver support
+  // (mouse-protocol 3c3a445): the X3 family codec plus the 4K DPI/polling work
+  // adds ~1.3 kB to the measured aggregate.
+  ".js": 610_000,
 };
 
 const ASSETS = join("dist", "assets");
diff --git a/package-lock.json b/package-lock.json
index f8768895..793fc8c3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -460,7 +460,8 @@
     },
     "node_modules/@openmouse/protocol": {
       "version": "0.1.0",
-      "resolved": "git+https://github.com/OpenMouse-Project/mouse-protocol.git#6d506506cf3b322846718ae19cfae191c8f6ad66",
+      "resolved": "git+https://github.com/OpenMouse-Project/mouse-protocol.git#3c3a4452197a57e3f2fed2323012244f3a175986",
+      "integrity": "sha512-htpO6JBZSdbkx5NUfBaABufH7CXfjqA+C8rx4zGYdjb/FXrb9LE5nt7suuIvt03E8185x2I8dUyg/AjpJKjgvQ==",
       "engines": {
         "node": ">=20"
       }
diff --git a/src/device/controller.ts b/src/device/controller.ts
index c1cfaf03..d7e94476 100644
--- a/src/device/controller.ts
+++ b/src/device/controller.ts
@@ -2558,6 +2558,9 @@ export function toggleDongleLed(): void {
     apply: async () => {
       const client = pulsarClient();
       if (!client) throw new Error("The receiver is no longer connected.");
+      if (!("setDongleLed" in client)) {
+        throw new Error("This Pulsar device does not expose a receiver LED control.");
+      }
       await client.setDongleLed(enabled);
     },
   });
diff --git a/src/supported-mice.test.ts b/src/supported-mice.test.ts
index f7de5319..40c8a0d8 100644
--- a/src/supported-mice.test.ts
+++ b/src/supported-mice.test.ts
@@ -17,6 +17,7 @@ import {
   NINJUTSO_RECEIVER_PRODUCT_IDS,
 } from "@openmouse/protocol/ninjutso";
 import { ORBITAL_DEVICES } from "@openmouse/protocol/orbital";
+import { PULSAR_XS1_PRODUCT_IDS } from "@openmouse/protocol/pulsar";
 import { RAZER_PRODUCTS } from "@openmouse/protocol/razer-devices";
 import { TEEVOLUTION_PRODUCT_IDS } from "@openmouse/protocol/teevolution";
 import { ZAUNKOENIG_PRODUCT_IDS } from "@openmouse/protocol/zaunkoenig";
@@ -100,6 +101,8 @@ const PID_UNIVERSE = new Set<number>([
   0x1960, 0x1961, 0x1962, 0x1968, 0x1970, 0x1972, 0x1982,
   // VGN Dragonfly F2 Master+ (drivers/vgn/hid.ts).
   0xfb56, 0xfb57,
+  // Pulsar X3 family on the Sonix XS-1 feature interface (drivers/pulsar/pulsar-xs1-hid.ts).
+  ...PULSAR_XS1_PRODUCT_IDS,
   // Finalmouse ULX dongle (drivers/finalmouse/hid.ts).
   0x0100,
 ]);
diff --git a/src/supported-mice.ts b/src/supported-mice.ts
index aebb79e2..d53dfa60 100644
--- a/src/supported-mice.ts
+++ b/src/supported-mice.ts
@@ -407,9 +407,9 @@ export const MICE: Mouse[] = [
     note: "Pulsar driver (VID 0x3710) — collection-based detection" },
   { brand: "Pulsar", model: "X2 V3 ES Mini",            status: "supported", req: 2,
     note: "Pulsar driver (VID 0x3710) — collection-based detection" },
-  { brand: "Pulsar", model: "X3 Medium",                status: "likely",    req: 1,
+  { brand: "Pulsar", model: "X3 Medium",                status: "supported", req: 1,
     pids: [0x3409, 0x3410, 0x5402, 0x5403],
-    note: "XS-1 driver written for PIDs 0x3409/0x3410/0x5402/0x5403 — pending merge + hardware test" },
+    note: "XS-1 feature-report driver (usage 0xffff:1) — PIDs pinned in the protocol registry" },
   { brand: "Pulsar", model: "X2F",                      status: "supported", req: 1,
     note: "Pulsar driver (VID 0x3710) — collection-based detection" },