diff --git a/src/engine/audio/Audio_Resampler.cpp b/src/engine/audio/Audio_Resampler.cpp
index 41299c09..c9769f18 100644
--- a/src/engine/audio/Audio_Resampler.cpp
+++ b/src/engine/audio/Audio_Resampler.cpp
@@ -66,10 +66,13 @@ size_t SpeexResampler::processBuffer(const void* src, size_t sourceLength, size_
 
     if (mDestRate == mSourceRate)
     {
+        // Pass-through, but never write past the caller's buffer: clamp to its
+        // capacity instead of trusting sourceLength (which is caller/file driven).
         assert(destCapacity >= sourceLength);
-        memcpy(dest, src, sourceLength);
-        sourceProcessed = sourceLength;
-        return sourceLength;
+        size_t copied = std::min(sourceLength, destCapacity);
+        memcpy(dest, src, copied);
+        sourceProcessed = copied;
+        return copied;
     }
 
     if (!mContext)
diff --git a/src/engine/audio/Audio_WavFile.cpp b/src/engine/audio/Audio_WavFile.cpp
index 8a917088..1609dc59 100644
--- a/src/engine/audio/Audio_WavFile.cpp
+++ b/src/engine/audio/Audio_WavFile.cpp
@@ -150,6 +150,14 @@ bool WavFileReader::open(const std::filesystem::path& p)
         if (mBits != 16)
             THROW_READERROR;
 
+        // The read path is mono-only: it divides byte counts by AUDIO_CHANNELS
+        // and starts the resampler with AUDIO_CHANNELS. Reject anything else -
+        // a multi-channel file would make read() copy more source bytes than the
+        // caller's (mono-sized) output buffer can hold. Also reject a zero rate,
+        // which would divide by zero in readRaw() / poison the resampler ratio.
+        if (mChannels != AUDIO_CHANNELS || mSamplerate == 0)
+            THROW_READERROR;
+
         // Look for the chunk 'data'
         mInput->seekg(fmtStart + std::streampos(fmtSize));
 
diff --git a/src/engine/media/MT_SingleAudioStream.cpp b/src/engine/media/MT_SingleAudioStream.cpp
index e01c5c2d..8dac1ee6 100644
--- a/src/engine/media/MT_SingleAudioStream.cpp
+++ b/src/engine/media/MT_SingleAudioStream.cpp
@@ -37,11 +37,14 @@ void SingleAudioStream::copyPcmTo(Audio::DataWindow& output, int needed)
         // Number of bytes to fill on this step
         auto requested = needed - output.filled();
 
+        // requested is in bytes: 16-bit samples at AUDIO_SAMPLERATE/AUDIO_CHANNELS
+        constexpr int bytesPerMs = AUDIO_SAMPLERATE / 1000 * sizeof(int16_t) * AUDIO_CHANNELS;
+
         auto options = AudioReceiver::DecodeOptions{
             .mRealtimeProcessing = true,
             .mResampleToMainRate = true,
             .mSkipDecode = false,
-            .mElapsed  = std::chrono::milliseconds(requested / (AUDIO_SAMPLERATE / 1000))
+            .mElapsed  = std::chrono::milliseconds(requested / bytesPerMs)
         };
 
         // Try to get the data from receiver / decoder