diff --git a/src/drivers/endgame/egg-ot-hid.test.ts b/src/drivers/endgame/egg-ot-hid.test.ts
index b2f9a7b..0d664b5 100644
--- a/src/drivers/endgame/egg-ot-hid.test.ts
+++ b/src/drivers/endgame/egg-ot-hid.test.ts
@@ -306,6 +306,6 @@ test("a mouse that never sends the response packet reports the raw tx/rx trace",
   const client = new EggOtHidClient(fake.device);
   await assert.rejects(
     () => client.readStatus(),
-    /did not answer OT profile block 0\. Trace: tx 33 [0-9a-f ]+ \| rx 00 14 [0-9a-f ]+ \| rx 00 00 [0-9a-f ]+ x\d+/,
+    /did not answer OT profile block 0\. Trace: tx 33 [0-9a-f ]+ \| rx 00 14 [0-9a-f ]+ \| rx 00 00 [0-9a-f ]+ x\d+.*\. Collections: usage 0xff00:0x1 · feature 0x0/,
   );
 });
diff --git a/src/drivers/endgame/egg-ot-hid.ts b/src/drivers/endgame/egg-ot-hid.ts
index 5c10bbd..bad4bfb 100644
--- a/src/drivers/endgame/egg-ot-hid.ts
+++ b/src/drivers/endgame/egg-ot-hid.ts
@@ -381,9 +381,9 @@ export class EggOtHidClient {
       reply = await this.exchange(otEncodeQueryPacket(block, profileIndex), true);
     } catch (error) {
       const message = error instanceof Error ? error.message : String(error);
-      throw new Error(`OT profile block ${block} failed: ${message} Trace: ${this.describeTrace()}`);
+      throw new Error(`OT profile block ${block} failed: ${message} ${this.describeFailureContext()}`);
     }
-    if (!reply) throw new Error(`The mouse did not answer OT profile block ${block}. Trace: ${this.describeTrace()}`);
+    if (!reply) throw new Error(`The mouse did not answer OT profile block ${block}. ${this.describeFailureContext()}`);
     return reply.subarray(OT_PAYLOAD_INDEX);
   }
 
@@ -392,6 +392,11 @@ export class EggOtHidClient {
     return this.trace.length > 0 ? this.trace.join(" | ") : "no packets";
   }
 
+  /** Trace plus the granted HID collections, so a refused write shows which interface the browser handed us. */
+  private describeFailureContext(): string {
+    return `Trace: ${this.describeTrace()}. Collections: ${this.describeCollections()}`;
+  }
+
   private record(direction: "tx" | "rx" | "err", detail: Uint8Array | string): void {
     const text = typeof detail === "string"
       ? detail