diff --git a/src/drivers/razer/devices.test.ts b/src/drivers/razer/devices.test.ts
index c27d7f0..ef50045 100644
--- a/src/drivers/razer/devices.test.ts
+++ b/src/drivers/razer/devices.test.ts
@@ -247,6 +247,20 @@ test("the asymmetric lift-off write probe is only armed where it was confirmed",
   for (const id of armed) assert.equal(RAZER_PRODUCTS.get(id)?.verified, true);
 });
 
+test("button mapping is only offered on connections where class 0x02 answered", () => {
+  // Gated per product id and per connection, not per model. An all-zero reply
+  // decodes as "Disabled" on every control, so a transport that does not
+  // implement class 0x02 does not fail loudly — it produces a full, plausible
+  // set of controls that all read Disabled and silently do nothing. Hence an
+  // allowlist, and hence a hardware run per entry even for two connections of
+  // the same mouse.
+  const offered = RAZER_PRODUCT_IDS.filter((id) => RAZER_PRODUCTS.get(id)?.buttonMapping === true);
+  assert.deepEqual(offered.sort(), [0x00c0, 0x00c1]);
+  for (const id of offered) {
+    assert.equal(RAZER_PRODUCTS.get(id)?.verified, true, `0x${id.toString(16)} offers button mapping without being verified`);
+  }
+});
+
 test("no product is claimed by both this registry and a dedicated Razer driver", () => {
   // `driverFor` returns the first match in DEVICE_DRIVERS, so an overlap would
   // silently kill whichever driver is registered later.
diff --git a/src/razer/devices.ts b/src/razer/devices.ts
index 5e23eec..1beea44 100644
--- a/src/razer/devices.ts
+++ b/src/razer/devices.ts
@@ -77,8 +77,18 @@ export interface RazerProduct {
    * only ever been exercised on the Viper V3 Pro. Other Razer mice may well use
    * a different class or a different control-index scheme, so nothing is
    * offered to them until it has been checked on hardware. Gates both
-   * `RazerButtonControl` and `RazerToggleControl` — same command, same
-   * per-model risk, no reason to split them.
+   * `RazerButtonControl` and `RazerToggleControl` — same command, same risk,
+   * no reason to split them.
+   *
+   * Set per product id, which means per *connection*: the cable and the
+   * receiver are separate entries for one mouse and were verified separately.
+   * That is not pedantry about provenance — the failure mode is silent.
+   * `razerDecodeButtonMapping` reads `type=0x00, len=0x00, value=0x00` as
+   * "Disabled", so a transport that does not implement the class answers
+   * all-zero and yields a full, ordinary-looking set of controls that every
+   * read reports as Disabled and every write appears to accept.
+   * `readButtonMappings`'s null-collapse cannot catch it, because the dict
+   * comes back populated.
    */
   buttonMapping?: boolean;
   /** Also accept a vendor-defined collection as the control interface. */
@@ -371,6 +381,10 @@ const VIPER_V3_PRO = {
   hasBattery: true,
   liftOff: true,
   asymmetricLiftOff: true,
+  // Class 0x02 is confirmed on both of this model's connections, so it belongs
+  // on the shared preset rather than on one product id. It sat on `0x00c1`
+  // alone while only the receiver had been exercised.
+  buttonMapping: true,
   verified: true,
 } as const;
 
@@ -386,12 +400,7 @@ const PRODUCT_DEFINITIONS: ReadonlyArray<[number, Omit<RazerProduct, "transactio
   [0x00a5, { model: "Viper V2 Pro", wireless: false, highRatePolling: false, ...VIPER_V2_PRO }],
   [0x00a6, { model: "Viper V2 Pro", wireless: true, highRatePolling: true, ...VIPER_V2_PRO }],
   [0x00c0, { model: "Viper V3 Pro", wireless: false, pollingRates: RATES_1K, highRatePolling: false, ...VIPER_V3_PRO }],
-  // `buttonMapping` is set here rather than on the shared `VIPER_V3_PRO`
-  // preset because class 0x02 has only ever been exercised over the receiver.
-  // The cable (0x00c0) is the same mouse and very likely answers the same way,
-  // but that has not been checked, and a shared protocol family is not
-  // evidence for a specific product id and connection path.
-  [0x00c1, { model: "Viper V3 Pro", wireless: true, pollingRates: RATES_8K, highRatePolling: true, ...VIPER_V3_PRO, buttonMapping: true }],
+  [0x00c1, { model: "Viper V3 Pro", wireless: true, pollingRates: RATES_8K, highRatePolling: true, ...VIPER_V3_PRO }],
   [0x006e, { model: "DeathAdder Essential", ...DEATHADDER_ESSENTIAL }],
   [0x0071, { model: "DeathAdder Essential White Edition", ...DEATHADDER_ESSENTIAL }],
   [0x0098, { model: "DeathAdder Essential (2021)", ...DEATHADDER_ESSENTIAL }],