diff --git a/desktop/index.html b/desktop/index.html
index 0fb92eb..9034e1f 100644
--- a/desktop/index.html
+++ b/desktop/index.html
@@ -26,6 +26,15 @@
           <label>Alias
             <input id="alias" type="text" placeholder="your name" />
           </label>
+          <label>Quality
+            <select id="quality">
+              <option value="auto">Auto</option>
+              <option value="good">Opus 24k</option>
+              <option value="degraded">Opus 6k</option>
+              <option value="codec2-3200">Codec2 3.2k</option>
+              <option value="catastrophic">Codec2 1.2k</option>
+            </select>
+          </label>
           <div class="form-row">
             <label class="checkbox">
               <input id="os-aec" type="checkbox" checked />
@@ -91,6 +100,15 @@
           </div>
           <div class="settings-section">
             <h3>Audio</h3>
+            <label>Quality
+              <select id="s-quality">
+                <option value="auto">Auto (adaptive)</option>
+                <option value="good">Good — Opus 24kbps</option>
+                <option value="degraded">Degraded — Opus 6kbps</option>
+                <option value="codec2-3200">Codec2 3200bps</option>
+                <option value="catastrophic">Catastrophic — Codec2 1200bps</option>
+              </select>
+            </label>
             <label class="checkbox">
               <input id="s-os-aec" type="checkbox" />
               OS Echo Cancellation (macOS VoiceProcessingIO)
diff --git a/desktop/src-tauri/src/engine.rs b/desktop/src-tauri/src/engine.rs
index 6ea2417..26c7fe9 100644
--- a/desktop/src-tauri/src/engine.rs
+++ b/desktop/src-tauri/src/engine.rs
@@ -11,9 +11,27 @@ use tracing::{error, info};
 
 use wzp_client::audio_io::{AudioCapture, AudioPlayback};
 use wzp_client::call::{CallConfig, CallEncoder};
-use wzp_proto::MediaTransport;
+use wzp_proto::{CodecId, MediaTransport, QualityProfile};
 
-const FRAME_SAMPLES: usize = 960;
+const FRAME_SAMPLES_20MS: usize = 960;
+const FRAME_SAMPLES_40MS: usize = 1920;
+
+/// Resolve a quality string from the UI to a QualityProfile.
+/// Returns None for "auto" (use default adaptive behavior).
+fn resolve_quality(quality: &str) -> Option<QualityProfile> {
+    match quality {
+        "good" | "opus" => Some(QualityProfile::GOOD),
+        "degraded" | "opus6k" => Some(QualityProfile::DEGRADED),
+        "catastrophic" | "codec2-1200" => Some(QualityProfile::CATASTROPHIC),
+        "codec2-3200" => Some(QualityProfile {
+            codec: CodecId::Codec2_3200,
+            fec_ratio: 0.5,
+            frame_duration_ms: 20,
+            frames_per_block: 5,
+        }),
+        _ => None, // "auto" or unknown
+    }
+}
 
 /// Wrapper to make non-Sync audio handles safe to store in shared state.
 /// The audio handle is only accessed from the thread that created it (drop),
@@ -60,6 +78,7 @@ impl CallEngine {
         room: String,
         alias: String,
         _os_aec: bool,
+        quality: String,
         event_cb: F,
     ) -> Result<Self, anyhow::Error>
     where
@@ -173,21 +192,32 @@ impl CallEngine {
         let send_fs = frames_sent.clone();
         let send_level = audio_level.clone();
         let send_drops = Arc::new(AtomicU64::new(0));
+        let send_quality = quality.clone();
         tokio::spawn(async move {
-            let config = CallConfig {
-                noise_suppression: false,
-                suppression_enabled: false,
-                ..CallConfig::default()
+            let profile = resolve_quality(&send_quality);
+            let config = match profile {
+                Some(p) => CallConfig {
+                    noise_suppression: false,
+                    suppression_enabled: false,
+                    ..CallConfig::from_profile(p)
+                },
+                None => CallConfig {
+                    noise_suppression: false,
+                    suppression_enabled: false,
+                    ..CallConfig::default()
+                },
             };
+            let frame_samples = (config.profile.frame_duration_ms as usize) * 48;
+            info!(codec = ?config.profile.codec, frame_samples, "send task starting");
             let mut encoder = CallEncoder::new(&config);
             encoder.set_aec_enabled(false); // OS AEC or none
-            let mut buf = vec![0i16; FRAME_SAMPLES];
+            let mut buf = vec![0i16; frame_samples];
 
             loop {
                 if !send_r.load(Ordering::Relaxed) {
                     break;
                 }
-                if capture_ring.available() < FRAME_SAMPLES {
+                if capture_ring.available() < frame_samples {
                     tokio::time::sleep(std::time::Duration::from_millis(5)).await;
                     continue;
                 }
@@ -221,15 +251,17 @@ impl CallEngine {
             }
         });
 
-        // Recv task (direct playout)
+        // Recv task (direct playout with auto codec switch)
         let recv_t = transport.clone();
         let recv_r = running.clone();
         let recv_spk = spk_muted.clone();
         let recv_fr = frames_received.clone();
         tokio::spawn(async move {
-            let mut opus_dec = wzp_codec::create_decoder(wzp_proto::QualityProfile::GOOD);
+            let initial_profile = resolve_quality(&quality).unwrap_or(QualityProfile::GOOD);
+            let mut decoder = wzp_codec::create_decoder(initial_profile);
+            let mut current_codec = initial_profile.codec;
             let mut agc = wzp_codec::AutoGainControl::new();
-            let mut pcm = vec![0i16; FRAME_SAMPLES];
+            let mut pcm = vec![0i16; FRAME_SAMPLES_40MS]; // big enough for any codec
 
             loop {
                 if !recv_r.load(Ordering::Relaxed) {
@@ -242,8 +274,24 @@ impl CallEngine {
                 .await
                 {
                     Ok(Ok(Some(pkt))) => {
-                        if !pkt.header.is_repair {
-                            if let Ok(n) = opus_dec.decode(&pkt.payload, &mut pcm) {
+                        if !pkt.header.is_repair && pkt.header.codec_id != CodecId::ComfortNoise {
+                            // Auto-switch decoder if incoming codec differs
+                            if pkt.header.codec_id != current_codec {
+                                let new_profile = match pkt.header.codec_id {
+                                    CodecId::Opus24k => QualityProfile::GOOD,
+                                    CodecId::Opus6k => QualityProfile::DEGRADED,
+                                    CodecId::Codec2_1200 => QualityProfile::CATASTROPHIC,
+                                    CodecId::Codec2_3200 => QualityProfile {
+                                        codec: CodecId::Codec2_3200,
+                                        fec_ratio: 0.5, frame_duration_ms: 20, frames_per_block: 5,
+                                    },
+                                    other => QualityProfile { codec: other, ..QualityProfile::GOOD },
+                                };
+                                info!(from = ?current_codec, to = ?pkt.header.codec_id, "recv: switching decoder");
+                                let _ = decoder.set_profile(new_profile);
+                                current_codec = pkt.header.codec_id;
+                            }
+                            if let Ok(n) = decoder.decode(&pkt.payload, &mut pcm) {
                                 agc.process_frame(&mut pcm[..n]);
                                 if !recv_spk.load(Ordering::Relaxed) {
                                     playout_ring.write(&pcm[..n]);
@@ -259,7 +307,6 @@ impl CallEngine {
                             error!("recv fatal: {e}");
                             break;
                         }
-                        // Transient error — continue
                     }
                     Err(_) => {}
                 }
diff --git a/desktop/src-tauri/src/main.rs b/desktop/src-tauri/src/main.rs
index 7a31f0d..9958a09 100644
--- a/desktop/src-tauri/src/main.rs
+++ b/desktop/src-tauri/src/main.rs
@@ -122,6 +122,7 @@ async fn connect(
     room: String,
     alias: String,
     os_aec: bool,
+    quality: String,
 ) -> Result<String, String> {
     let mut engine_lock = state.engine.lock().await;
     if engine_lock.is_some() {
@@ -129,7 +130,7 @@ async fn connect(
     }
 
     let app_clone = app.clone();
-    match CallEngine::start(relay, room, alias, os_aec, move |event_kind, message| {
+    match CallEngine::start(relay, room, alias, os_aec, quality, move |event_kind, message| {
         let _ = app_clone.emit(
             "call-event",
             CallEvent {
diff --git a/desktop/src/main.ts b/desktop/src/main.ts
index 350aa0f..913ef28 100644
--- a/desktop/src/main.ts
+++ b/desktop/src/main.ts
@@ -8,6 +8,7 @@ const callScreen = document.getElementById("call-screen")!;
 const roomInput = document.getElementById("room") as HTMLInputElement;
 const aliasInput = document.getElementById("alias") as HTMLInputElement;
 const osAecCheckbox = document.getElementById("os-aec") as HTMLInputElement;
+const qualitySelect = document.getElementById("quality") as HTMLSelectElement;
 const connectBtn = document.getElementById("connect-btn") as HTMLButtonElement;
 const connectError = document.getElementById("connect-error")!;
 const roomName = document.getElementById("room-name")!;
@@ -48,6 +49,7 @@ const sRoom = document.getElementById("s-room") as HTMLInputElement;
 const sAlias = document.getElementById("s-alias") as HTMLInputElement;
 const sOsAec = document.getElementById("s-os-aec") as HTMLInputElement;
 const sAgc = document.getElementById("s-agc") as HTMLInputElement;
+const sQuality = document.getElementById("s-quality") as HTMLSelectElement;
 const sFingerprint = document.getElementById("s-fingerprint")!;
 const sRecentRooms = document.getElementById("s-recent-rooms")!;
 const sClearRecent = document.getElementById("s-clear-recent")!;
@@ -74,6 +76,7 @@ interface Settings {
   alias: string;
   osAec: boolean;
   agc: boolean;
+  quality: string;
   recentRooms: RecentRoom[];
 }
 
@@ -81,7 +84,7 @@ function loadSettings(): Settings {
   const defaults: Settings = {
     relays: [{ name: "Default", address: "193.180.213.68:4433" }],
     selectedRelay: 0, room: "android", alias: "",
-    osAec: true, agc: true, recentRooms: [],
+    osAec: true, agc: true, quality: "auto", recentRooms: [],
   };
   try {
     const raw = localStorage.getItem("wzp-settings");
@@ -156,6 +159,7 @@ function applySettings() {
   roomInput.value = s.room;
   aliasInput.value = s.alias;
   osAecCheckbox.checked = s.osAec;
+  qualitySelect.value = s.quality || "auto";
   renderRecentRooms(s.recentRooms);
   renderRelayButton();
 }
@@ -376,7 +380,7 @@ async function doConnect() {
   userDisconnected = false;
 
   const s = loadSettings();
-  s.room = roomInput.value; s.alias = aliasInput.value; s.osAec = osAecCheckbox.checked;
+  s.room = roomInput.value; s.alias = aliasInput.value; s.osAec = osAecCheckbox.checked; s.quality = qualitySelect.value;
   const room = roomInput.value.trim();
   if (room) {
     const entry: RecentRoom = { relay: relay.address, room };
@@ -388,6 +392,7 @@ async function doConnect() {
     await invoke("connect", {
       relay: relay.address, room: roomInput.value,
       alias: aliasInput.value, osAec: osAecCheckbox.checked,
+      quality: qualitySelect.value,
     });
     showCallScreen();
   } catch (e: any) {
@@ -529,7 +534,7 @@ listen("call-event", (event: any) => {
 // ── Settings ──
 function openSettings() {
   const s = loadSettings();
-  sRoom.value = s.room; sAlias.value = s.alias; sOsAec.checked = s.osAec;
+  sRoom.value = s.room; sAlias.value = s.alias; sOsAec.checked = s.osAec; sQuality.value = s.quality || "auto";
   sFingerprint.textContent = myFingerprint || "(loading...)";
   renderSettingsRecentRooms(s.recentRooms);
   settingsPanel.classList.remove("hidden");
@@ -564,9 +569,9 @@ settingsPanel.addEventListener("click", (e) => { if (e.target === settingsPanel)
 
 settingsSave.addEventListener("click", () => {
   const s = loadSettings();
-  s.room = sRoom.value; s.alias = sAlias.value; s.osAec = sOsAec.checked;
+  s.room = sRoom.value; s.alias = sAlias.value; s.osAec = sOsAec.checked; s.quality = sQuality.value;
   saveSettingsObj(s);
-  roomInput.value = s.room; aliasInput.value = s.alias; osAecCheckbox.checked = s.osAec;
+  roomInput.value = s.room; aliasInput.value = s.alias; osAecCheckbox.checked = s.osAec; qualitySelect.value = s.quality;
   renderRecentRooms(s.recentRooms);
   closeSettings();
 });