chore: import upstream snapshot with attribution

scripts/chat.py

@@ -0,0 +1,65 @@
+"""
+Chat / inference CLI for any stage checkpoint (base, SFT, DPO, PPO, GRPO).
+
+Model dimensions are read from the checkpoint, so you only pass the path. Use the chat
+template for instruction-tuned models, or --raw for base-model continuation.
+
+One-shot:
+    PYTHONPATH=. python scripts/chat.py --ckpt /ephemeral/ckpts/sft.pt --prompt "What is 13 + 29?"
+    PYTHONPATH=. python scripts/chat.py --ckpt /ephemeral/ckpts/grpo.pt --prompt "..." --greedy
+    PYTHONPATH=. python scripts/chat.py --ckpt /ephemeral/ckpts/base_pretrained.pt --raw --prompt "Once upon a time"
+Interactive REPL (no --prompt):
+    PYTHONPATH=. python scripts/chat.py --ckpt /ephemeral/ckpts/sft.pt
+"""
+
+from __future__ import annotations
+
+import argparse
+
+import torch
+
+from src.post_training.inference import generate_reply, load_model_from_ckpt
+
+
+def main():
+    p = argparse.ArgumentParser()
+    p.add_argument("--ckpt", required=True)
+    p.add_argument("--prompt", default=None, help="one-shot prompt; omit for interactive REPL")
+    p.add_argument("--system", default=None, help="optional system message (chat mode)")
+    p.add_argument("--raw", action="store_true", help="base-model continuation (no chat template)")
+    p.add_argument("--max_new_tokens", type=int, default=256)
+    p.add_argument("--temperature", type=float, default=0.8)
+    p.add_argument("--top_p", type=float, default=0.95)
+    p.add_argument("--top_k", type=int, default=None)
+    p.add_argument("--greedy", action="store_true", help="deterministic argmax decoding")
+    p.add_argument("--device", default="cuda" if torch.cuda.is_available() else "cpu")
+    args = p.parse_args()
+
+    model = load_model_from_ckpt(args.ckpt, args.device)
+    n = sum(p.numel() for p in model.parameters())
+    print(f"loaded {args.ckpt} ({n/1e6:.0f}M params) on {args.device} | "
+          f"mode={'raw' if args.raw else 'chat'} {'greedy' if args.greedy else f'T={args.temperature} top_p={args.top_p}'}")
+
+    def reply(text):
+        return generate_reply(model, text, device=args.device, system=args.system, raw=args.raw,
+                              max_new_tokens=args.max_new_tokens, temperature=args.temperature,
+                              top_p=args.top_p if args.top_p < 1 else None, top_k=args.top_k, greedy=args.greedy)
+
+    if args.prompt is not None:
+        print(reply(args.prompt))
+        return
+
+    print("Interactive chat (Ctrl-D / 'exit' to quit).")
+    while True:
+        try:
+            text = input("\nyou> ").strip()
+        except EOFError:
+            break
+        if text in ("exit", "quit"):
+            break
+        if text:
+            print("bot>", reply(text))
+
+
+if __name__ == "__main__":
+    main()