tests: exercise the fused decode in every cossim harness

Each harness re-runs the C++ side with --codec-fused after the
buffered run and gates on codes-full.bin equality between the two:
the decode path cannot change the predictor, so any divergence is a
bug. The fused run's perf lines land in the log as [Perf Fused] next
to the buffered ones, so every grid cell carries the buffered vs
fused comparison per backend and quant.

The fused audio itself is not scored here: greedy amplitudes vanish
in the streamed PCM_16 and the fused FP envelope has its own
validation against the stream path.

tests/cossim_common.py

@@ -396,3 +396,35 @@ GEN_KWARGS_GREEDY = dict(
     subtalker_dosample    = False,
     repetition_penalty    = 1.0,
 )
+
+
+def fused_pass(cmd, text, dump_cpp):
+    """Re-run the C++ side with --codec-fused (streaming, wav on stdout)
+    and gate on codes equality against the buffered run: the decode path
+    cannot change the predictor, so codes-full.bin must match exactly.
+    The fused audio itself is not scored here, greedy amplitudes vanish
+    in the streamed PCM_16 and the fused FP envelope has its own
+    validation against the stream path."""
+    import subprocess
+
+    dump_fused = dump_cpp + "-fused"
+    os.makedirs(dump_fused, exist_ok=True)
+
+    cmd_f = list(cmd)
+    cmd_f[cmd_f.index("--dump") + 1] = dump_fused
+    cmd_f[cmd_f.index("-o") + 1]     = "-"
+    cmd_f.append("--codec-fused")
+
+    print(f"[GGML] Cmd: {' '.join(cmd_f)}")
+    r = subprocess.run(cmd_f, input=text.encode(), capture_output=True)
+    if r.returncode != 0:
+        sys.stderr.write(r.stderr.decode(errors="replace"))
+        sys.exit(r.returncode)
+
+    # surface the fused run's perf lines next to the buffered ones
+    # already in the log, so every grid cell carries the comparison
+    for line in r.stderr.decode(errors="replace").splitlines():
+        if "[Perf]" in line:
+            print(line.replace("[Perf]", "[Perf Fused]"))
+
+    compare_exact_i32("codes-full.bin", dump_fused, dump_cpp, "CodesFullFused")

tests/debug-base-cossim.py

@@ -155,5 +155,7 @@ def main():
     n = min(aa.size, ab.size)
     print(f"[Cossim] WAV stft_cos: {cc.stft_cos(aa.ravel()[:n], ab.ravel()[:n]):.6f} samples: {n}")
 
+    cc.fused_pass(cmd, text, DUMP_CPP)
+
 if __name__ == "__main__":
     main()

tests/debug-clone-cossim.py

@@ -485,5 +485,7 @@ def main():
     n = min(aa.size, ab.size)
     print(f"[Cossim] WAV stft_cos: {cc.stft_cos(aa.ravel()[:n], ab.ravel()[:n]):.6f} samples: {n}")
 
+    cc.fused_pass(cmd, text, DUMP_CPP)
+
 if __name__ == "__main__":
     main()

tests/debug-customvoice-cossim.py

@@ -181,5 +181,7 @@ def main():
     n = min(aa.size, ab.size)
     print(f"[Cossim] WAV stft_cos: {cc.stft_cos(aa.ravel()[:n], ab.ravel()[:n]):.6f} samples: {n}")
 
+    cc.fused_pass(cmd, text, DUMP_CPP)
+
 if __name__ == "__main__":
     main()

tests/debug-tts-cossim.py

@@ -169,5 +169,7 @@ def main():
     n = min(aa.size, ab.size)
     print(f"[Cossim] WAV stft_cos: {cc.stft_cos(aa.ravel()[:n], ab.ravel()[:n]):.6f} samples: {n}")
 
+    cc.fused_pass(cmd, text, DUMP_CPP)
+
 if __name__ == "__main__":
     main()