diff --git a/docs/PRD-mtu-discovery.md b/docs/PRD-mtu-discovery.md
new file mode 100644
index 0000000..1808544
--- /dev/null
+++ b/docs/PRD-mtu-discovery.md
@@ -0,0 +1,59 @@
+# PRD: QUIC Path MTU Discovery
+
+## Problem
+
+WarzonePhone uses conservative 1200-byte QUIC datagrams. Some network paths support larger MTUs (1400+), wasting bandwidth. Some broken paths (VPNs, tunnels, double-NAT, cellular) have MTU < 1200, causing silent packet drops — this may explain why Opus 64k fails on some paths while 24k works (larger encoded frames + FEC repair packets).
+
+## Solution
+
+Enable Quinn's built-in Path MTU Discovery (PMTUD) and handle edge cases:
+1. PMTUD probes larger packet sizes and discovers the actual path MTU
+2. Graceful fallback when datagrams exceed discovered MTU
+3. Expose MTU in metrics for debugging
+
+## Implementation
+
+### Phase 1: Enable PMTUD in Quinn
+
+`crates/wzp-transport/src/config.rs` — update `transport_config()`:
+
+```rust
+// Enable PMTUD (Quinn default is enabled, but we should ensure it)
+config.mtu_discovery_config(Some(quinn::MtuDiscoveryConfig::default()));
+
+// Set minimum MTU for safety (some paths can't handle 1200)
+// Quinn default min is 1200, which is the QUIC spec minimum
+```
+
+Quinn's `MtuDiscoveryConfig` has:
+- `interval`: how often to probe (default: 600s)
+- `upper_bound`: max MTU to probe (default: 1452 for IPv4)
+- `minimum_change`: min MTU increase to be worth probing (default: 20)
+
+### Phase 2: Handle MTU-related Failures
+
+In federation forwarding (`send_raw_datagram`), if the datagram exceeds the connection's current MTU, Quinn returns an error. Handle gracefully:
+- Log warning with packet size vs MTU
+- Drop the packet (don't crash)
+- Track in metrics: `wzp_relay_mtu_exceeded_total`
+
+### Phase 3: Codec-Aware MTU
+
+When the path MTU is small, the relay or client should:
+- Prefer lower-bitrate codecs (smaller packets)
+- Reduce FEC ratio (fewer repair packets)
+- This feeds into the adaptive quality system
+
+### Phase 4: Expose MTU in Stats
+
+- Add `path_mtu` to relay metrics (per peer)
+- Add `path_mtu` to client stats (visible in UI)
+- Log MTU on connection establishment
+
+## Non-Goals (v1)
+
+- Datagram fragmentation (QUIC datagrams are atomic — either fit or don't)
+- Manual MTU override per relay config
+- MTU-based codec selection (future, needs adaptive quality)
+
+## Effort: 1 day
diff --git a/scripts/build-and-notify.sh b/scripts/build-and-notify.sh
index 2d501d5..699b1a7 100755
--- a/scripts/build-and-notify.sh
+++ b/scripts/build-and-notify.sh
@@ -68,7 +68,8 @@ find "$BASE_DIR/data/source" "$BASE_DIR/data/cache" \
 # Clean jniLibs
 rm -rf "$BASE_DIR/data/source/android/app/src/main/jniLibs/arm64-v8a"
 
-notify "WZP build started..."
+GIT_HASH=$(cd $BASE_DIR/data/source && git rev-parse --short HEAD 2>/dev/null || echo unknown)
+notify "WZP Android build started [$GIT_HASH]..."
 
 echo ">>> Building in Docker..."
 docker run --rm --user 1000:1000 \
@@ -112,7 +113,7 @@ APK=$(find "$BASE_DIR/data/source/android" -name "app-debug*.apk" -path "*/outpu
 if [ -n "$APK" ]; then
     URL=$(curl -s -F "file=@$APK" -H "Authorization: $rusty_auth_token" "$rusty_address")
     echo "UPLOAD_URL=$URL"
-    notify "WZP build done! APK: $URL"
+    notify "WZP Android [$GIT_HASH] done! APK: $URL"
     echo ">>> Done! APK at: $URL"
 else
     notify "WZP build FAILED - no APK"
diff --git a/scripts/build-linux-docker.sh b/scripts/build-linux-docker.sh
index a04239a..07d73ad 100755
--- a/scripts/build-linux-docker.sh
+++ b/scripts/build-linux-docker.sh
@@ -114,7 +114,8 @@ docker run --rm \
 URL=$(curl -s -F "file=@/tmp/wzp-linux-x86_64.tar.gz" -H "Authorization: $rusty_auth_token" "$rusty_address")
 if [ -n "$URL" ]; then
     echo "UPLOAD_URL=$URL"
-    notify "WZP Linux x86_64 binaries ready! $URL"
+    GIT_HASH=$(cd /build/source && git rev-parse --short HEAD 2>/dev/null || echo unknown)
+notify "WZP Linux x86_64 [$GIT_HASH] ready! $URL"
     echo ">>> Done! Binaries at: $URL"
 else
     notify "WZP Linux build FAILED - upload error"