fix(mac chat): strip gemma-4 reasoning-channel bleed (\nthought) from displayed answer

Cut the decoded text at the first channel marker (<|channel / <channel / \nthought
/ \nthink) so the chat shows only the natural-language answer. Applied to both
the full fused-engine chat (harness _gen_turn) and the lightweight AR chat.

Co-authored-by: FluffyAIcode <FluffyAIcode@users.noreply.github.com>

Author: cursoragent

scripts/chat_mlx_kakeya.py

@@ -192,8 +192,14 @@ def _iter():
                 stop_reason = "loop"
                 break
         dt = max(time.time() - t0, 1e-9)
+        _txt = tok.decode(toks, skip_special_tokens=True)
+        # gemma-4 sometimes bleeds its reasoning channel after the answer; cut it.
+        for _cut in ("<|channel", "<channel", "\nthought", "\nthink"):
+            _i = _txt.find(_cut)
+            if _i > 0:
+                _txt = _txt[:_i]
         return {
-            "text": tok.decode(toks, skip_special_tokens=True),
+            "text": _txt.strip(),
             "n_tokens": len(toks),
             "stop_reason": stop_reason,
             "decode_tps": round(len(toks) / dt, 2),

scripts/research/k3_integrated_niah_eval_mac.py

@@ -808,6 +808,13 @@ def _gen_turn(pid: List[int]) -> Dict[str, Any]:
                     txt = tokenizer.decode(res["tokens"])
                 for marker in ("<turn|>", "<end_of_turn>", "<eos>"):
                     txt = txt.replace(marker, "")
+                # gemma-4 sometimes bleeds its reasoning channel after the answer
+                # (e.g. a trailing "\nthought ...") — cut at the first channel
+                # marker so the chat shows only the natural-language answer.
+                for cut in ("<|channel", "<channel", "\nthought", "\nthink"):
+                    idx = txt.find(cut)
+                    if idx > 0:
+                        txt = txt[:idx]
                 res["text"] = txt.strip()
                 res["resident_kv_bytes"] = int(
                     sum(int(getattr(c, "nbytes", 0)) for c in (adapter._cache or [])))