Root cause found + on-device embed capture + KV=100 restored

Root cause: embeds must come from SAME NPU model instance.
Python fp32 embeds cause divergence on NPU fp16 after ~20 steps.

Solution: Java pipeline captures embeds on-device during generation.
Captured embeds work perfectly with C++ pipeline (validated "bon").

- Added capture mode: touch /data/local/tmp/kazeia/capture_mode
- Embeds saved to captured_embeds.bin (same format as pipeline input)
- KV_LEN restored to 100 (KV=64 lost role tokens → quality loss)
- C++ uses pre-computed embeds as-is (no double codec_sum)

Production path: Java pipeline RTF 1.8 for new texts (good quality)
Replay path: C++ pipeline RTF 1.26 with captured embeds

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

kazeia-android/app/src/main/java/com/kazeia/tts/Qwen3TtsEngine.kt

@@ -1067,10 +1067,13 @@ class Qwen3TtsEngine(
 
         nlog("PTE pipeline: prefill=${prefill.size}, trailing=${trailingEmbeds.size}")
 
+        // Capture mode: save all talker inputs for reuse with C++ pipeline
+        val capturedEmbeds = mutableListOf<FloatArray>()
+
         // ===== PREFILL =====
         val tPrefill = System.currentTimeMillis()
         for (step in prefill.indices) {
-            // Unmask position
+            capturedEmbeds.add(prefill[step].clone())  // capture prefill input
             val maskIdx = TALKER_PTE_KV_LEN - 1 - minOf(pos, TALKER_PTE_KV_LEN - 1)
             if (maskIdx >= 0) maskData[maskIdx] = 0f
 
@@ -1139,6 +1142,8 @@ class Qwen3TtsEngine(
                 else -> sumEmb(codecSum, padE)
             }
 
+            capturedEmbeds.add(nextEmbed.clone())  // capture decode input
+
             // 3. Talker step
             val maskIdx = TALKER_PTE_KV_LEN - 1 - minOf(pos, TALKER_PTE_KV_LEN - 1)
             if (maskIdx >= 0) maskData[maskIdx] = 0f
@@ -1192,6 +1197,26 @@ class Qwen3TtsEngine(
 
         val n = allCodes.size
         nlog("Generated $n tokens | Talker(PTE): ${totalTalkerMs}ms (${totalTalkerMs/maxOf(n,1)}ms/step) | CP(PTE): ${totalCpMs}ms (${totalCpMs/maxOf(n,1)}ms/step)")
+
+        // Save captured embeds for C++ pipeline reuse
+        if (capturedEmbeds.isNotEmpty()) {
+            try {
+                val capPath = "/data/local/tmp/kazeia/captured_embeds.bin"
+                val nPrefill = prefill.size
+                val fos = java.io.FileOutputStream(capPath)
+                val hdr = java.nio.ByteBuffer.allocate(8).order(java.nio.ByteOrder.LITTLE_ENDIAN)
+                hdr.putInt(nPrefill); hdr.putInt(capturedEmbeds.size)
+                fos.write(hdr.array())
+                for (emb in capturedEmbeds) {
+                    val buf = java.nio.ByteBuffer.allocate(TALKER_DIM * 4).order(java.nio.ByteOrder.LITTLE_ENDIAN)
+                    for (v in emb) buf.putFloat(v)
+                    fos.write(buf.array())
+                }
+                fos.close()
+                nlog("Captured ${capturedEmbeds.size} embeds → $capPath")
+            } catch (e: Exception) { nlog("Capture save failed: ${e.message}") }
+        }
+
         return allCodes.toTypedArray()
     }
 
@@ -2299,8 +2324,10 @@ class Qwen3TtsEngine(
         nlog("Loaded $nTotal embeds ($nPrefill prefill + ${nTotal - nPrefill} decode)")
 
         val allCodes: Array<IntArray>
+        // Check if capture mode requested (force Java path to capture embeds)
+        val captureMode = File("/data/local/tmp/kazeia/capture_mode").exists()
         // Native C++ pipeline using SAME Java Module instances (no quality loss)
-        if (talkerPteModule != null && cpPteModule != null) {
+        if (!captureMode && talkerPteModule != null && cpPteModule != null) {
             // C++ loop on Java's Module instances — same QNN compilation, no JNI overhead
             val prefillFlat = FloatArray(nPrefill * TALKER_DIM)
             for (i in 0 until nPrefill) System.arraycopy(embeds[i], 0, prefillFlat, i * TALKER_DIM, TALKER_DIM)
@@ -2449,9 +2476,13 @@ class Qwen3TtsEngine(
             return Pair(hidden, logits)
         }
 
+        // Capture embeds for C++ reuse
+        val capturedEmbeds = mutableListOf<FloatArray>()
+
         // ===== PREFILL =====
         val tPrefill = System.currentTimeMillis()
         for (step in prefillEmbeds.indices) {
+            capturedEmbeds.add(prefillEmbeds[step].clone())
             val (h, logits) = talkerStep(prefillEmbeds[step])
             pastHidden = h
             if (step == prefillEmbeds.size - 1) {
@@ -2480,12 +2511,12 @@ class Qwen3TtsEngine(
             if (trailingIdx < trailingEmbeds.size) {
                 nextEmbed = trailingEmbeds[trailingIdx]; trailingIdx++
             } else {
-                // Build from codec embeddings + trailing text (pad)
                 val codecSum = FloatArray(TALKER_DIM)
                 addEmb(codecSum, codecEmb(codes[0]))
                 for (cb in 1 until NUM_CODEBOOKS) addEmb(codecSum, cpEmb(cb - 1, codes[cb]))
                 nextEmbed = sumEmb(codecSum, padE)
             }
+            capturedEmbeds.add(nextEmbed.clone())
 
             val tTalker0 = System.currentTimeMillis()
             val (h, logits) = talkerStep(nextEmbed)
@@ -2506,7 +2537,26 @@ class Qwen3TtsEngine(
 
         val n = allCodes.size
         nlog("Generated $n tokens | Talker(PTE): ${totalTalkerMs}ms (${totalTalkerMs/maxOf(n,1)}ms/step) | CP(PTE): ${totalCpMs}ms (${totalCpMs/maxOf(n,1)}ms/step)")
-        nlog("CB0 Java: [${generatedCb0.joinToString(",")}]")
+
+        // Save captured embeds
+        if (capturedEmbeds.isNotEmpty()) {
+            try {
+                val capPath = "/data/local/tmp/kazeia/captured_embeds.bin"
+                val nPrefill = prefillEmbeds.size
+                val fos = java.io.FileOutputStream(capPath)
+                val hdr = java.nio.ByteBuffer.allocate(8).order(java.nio.ByteOrder.LITTLE_ENDIAN)
+                hdr.putInt(nPrefill); hdr.putInt(capturedEmbeds.size)
+                fos.write(hdr.array())
+                for (emb in capturedEmbeds) {
+                    val buf = java.nio.ByteBuffer.allocate(TALKER_DIM * 4).order(java.nio.ByteOrder.LITTLE_ENDIAN)
+                    for (v in emb) buf.putFloat(v)
+                    fos.write(buf.array())
+                }
+                fos.close()
+                nlog("Captured ${capturedEmbeds.size} embeds → $capPath (${nPrefill} prefill + ${capturedEmbeds.size - nPrefill} decode)")
+            } catch (e: Exception) { nlog("Capture save failed: ${e.message}") }
+        }
+
         return allCodes.toTypedArray()
     }