diff --git a/crates/rutster-media/src/opus_codec.rs b/crates/rutster-media/src/opus_codec.rs
index 6a47428..dae5708 100644
--- a/crates/rutster-media/src/opus_codec.rs
+++ b/crates/rutster-media/src/opus_codec.rs
@@ -42,6 +42,15 @@ pub struct OpusDecoder {
     // Reusable decode buffer: avoids allocating 480 i16s per frame on the
     // hot path. `Option<PcmFrame>` would also work; a flat array keeps the
     // reuse obvious.
+    //
+    // F9 (adversarial review, cleared): the buffer is exactly 480 i16 =
+    // 20 ms @ 24 kHz mono. libopus is initialized with `SAMPLE_RATE =
+    // 24_000` and `Channels::Mono`, so a 20 ms frame decodes to exactly
+    // 480 samples and fits. A 40/60 ms frame (Chrome doesn't send these
+    // by default but Opus allows them) yields `OPUS_BUFFER_TOO_SMALL`
+    // → `decode()` returns `Err` → the `Option`-shaped `decode` wrapper
+    // routes to `None` → drop+observe per §3.8 (already the documented
+    // correct behavior; this comment makes the 20-ms assumption explicit).
     pcm_buf: [i16; SAMPLES_PER_FRAME],
 }