# /// script
# requires-python = ">=3.11,<3.13"
# dependencies = [
#   "torch>=2.8,<2.10",
#   "numpy>=2.0",
#   "huggingface-hub>=0.34",
#   "safetensors>=0.5",
#   "datasets>=2.19",
#   "tokenizers>=0.20",
#   "bitsandbytes",
#   "torchao",
#   "pyarrow",
# ]
# ///

"""
Smilyai-G1 : Fast Sparse General-Assistant Transformer — FSDP2 EDITION (8xH200)
~20B total params | ~2B active per token

v7 — DATA-MIX + OBSERVABILITY (on top of v6 host-RAM fixes):

 23. TOKEN-WEIGHTED SOURCE SCHEDULER. v6 picked a source per *document*; a
     stack-v3 document is a whole repository (~60K tokens) vs ~1K for a web
     page, so 20% of docs became ~70% of tokens. Session 3's train-loss drop
     (3.1 -> 1.7) was this, not model progress. Now a deficit scheduler picks
     the source furthest behind its TOKEN quota -> exact mix regardless of
     document length. Zero throughput cost.
 24. Repo cap 262K -> 64K chars so one repo can't monopolise ~15 consecutive
     micro-batches.
 25. stack-v3 arrow batch_size 64 -> 4 rows (each row is a whole repo; this
     was several hundred GB of host RAM across 32 readers).
 26. EOS: session 3 ran with eos_id=0 (no known EOS name found). Now scans the
     tokenizer's added tokens for anything that looks like end-of-text, logs
     what it picked, and honours G1_EOS_TOKEN=<token string> as an override.
 27. PER-SOURCE LOSS. The `folder` tag was the *last appended* document's
     source, not the batch's. Batches are now tagged by MAJORITY source of
     their tokens, and the log prints loss + batch share per source every
     log_every steps (rank-0 local window).
 28. Session-3 note: train loss is NOT comparable across sessions when the
     mix changes. Use [val] (fineweb-edu only) as the progress signal.

Invariant: *** EVERY collective must be executed by EVERY rank, in the same order. ***

RUN:
    export HF_TOKEN=...
    export G1_SESSION_ID=4
    export MAX_TRAINING_HOURS=138
    export G1_WORK_DIR=/some/real/local/disk     # NOT tmpfs (check: df -hT /tmp)
    export MALLOC_ARENA_MAX=2
    # optional: export G1_EOS_TOKEN='<|endoftext|>'
    torchrun --nproc_per_node=8 train_g1_fsdp.py
"""

import os

os.environ.setdefault("PYTORCH_CUDA_ALLOC_CONF", "expandable_segments:True")
os.environ.setdefault("TORCHINDUCTOR_COMPILE_THREADS", "1")
os.environ.setdefault("HF_HUB_DISABLE_PROGRESS_BARS", "1")
os.environ.setdefault("HF_DATASETS_DISABLE_PROGRESS_BARS", "1")
os.environ.setdefault("ARROW_DEFAULT_MEMORY_POOL", "system")
os.environ.setdefault("OMP_NUM_THREADS", "4")
try:
    import ctypes
    _libc = ctypes.CDLL("libc.so.6")
    _libc.mallopt(-8, 2)            # M_ARENA_MAX
    _libc.mallopt(-1, 128 * 1024)   # M_TRIM_THRESHOLD
except Exception:
    pass

import gc, json, time, math, random, logging, threading, queue, shutil, collections, datetime as _dt
from dataclasses import dataclass, asdict
from typing import Optional, Tuple, List, Iterator

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.distributed as dist
import torch.multiprocessing as mp
from torch.utils.data import Dataset, DataLoader

try:
    from torch.distributed.fsdp import fully_shard, MixedPrecisionPolicy
except ImportError:
    from torch.distributed._composable.fsdp import fully_shard, MixedPrecisionPolicy

from torch.distributed.tensor import DTensor, distribute_tensor
from torch.distributed.checkpoint.state_dict import (
    get_model_state_dict, set_model_state_dict,
    get_optimizer_state_dict, set_optimizer_state_dict,
    StateDictOptions,
)

import triton
import triton.language as tl

from huggingface_hub import HfApi, hf_hub_download, upload_file, login as hf_login

try:
    import bitsandbytes as bnb
    HAS_BNB = True
except ImportError:
    HAS_BNB = False

try:
    from safetensors.torch import save_file as st_save
    HAS_ST = True
except ImportError:
    HAS_ST = False

try:
    from flash_attn import flash_attn_func
    HAS_FLASH = True
except ImportError:
    HAS_FLASH = False

try:
    from torchao.float8 import convert_to_float8_training, Float8LinearConfig
    HAS_FP8 = True
except ImportError:
    HAS_FP8 = False
    convert_to_float8_training = None
    Float8LinearConfig = None

os.environ["TOKENIZERS_PARALLELISM"] = "false"
torch.set_float32_matmul_precision('high')
torch.backends.cuda.matmul.allow_tf32 = True
torch.backends.cudnn.allow_tf32 = True
torch.backends.cuda.enable_flash_sdp(True)
torch.backends.cuda.enable_mem_efficient_sdp(True)

try:
    import torch._dynamo
    torch._dynamo.config.cache_size_limit = 64
    torch._dynamo.config.suppress_errors = True
    torch._dynamo.config.capture_scalar_outputs = True
except Exception:
    pass

logging.basicConfig(level=logging.INFO, format='%(asctime)s | %(message)s', datefmt='%H:%M:%S')
for _noisy in ("httpx", "httpcore", "urllib3", "filelock",
               "huggingface_hub", "huggingface_hub.hf_api",
               "huggingface_hub.file_download", "datasets", "fsspec"):
    logging.getLogger(_noisy).setLevel(logging.WARNING)

log = logging.getLogger("smilyai-g1-fsdp")
_MODULE_IS_MASTER = os.environ.get("RANK", "0") == "0"
if _MODULE_IS_MASTER:
    log.info(f"[env] flash_attn={HAS_FLASH} | bnb={HAS_BNB}")

# ─────────────────────────────────────────────────────────────────────────────
#  HF SETUP / WORK DIR / HOST-MEMORY TOOLS
# ─────────────────────────────────────────────────────────────────────────────
HF_TOKEN    = os.environ.get("HF_TOKEN", "")
SESSION_ID  = int(os.environ.get("G1_SESSION_ID", "4"))
REPO_PREFIX = "hugging-science/Smilyai-G1-20B-v2-session-"
HF_MODEL_REPO = f"{REPO_PREFIX}{SESSION_ID:03d}"

if not HF_TOKEN:
    if _MODULE_IS_MASTER:
        log.warning("[hf] HF_TOKEN not set — uploads/downloads will fail. export HF_TOKEN=...")
else:
    try:
        hf_login(token=HF_TOKEN)
        if _MODULE_IS_MASTER:
            log.info("[hf] logged in")
    except Exception as e:
        if _MODULE_IS_MASTER:
            log.warning(f"[hf] login failed: {e}")

hf_api = HfApi()

def _is_ram_backed(path: str) -> bool:
    try:
        best = ("", "")
        with open("/proc/mounts") as f:
            for line in f:
                parts = line.split()
                if len(parts) >= 3 and path.startswith(parts[1]) and len(parts[1]) > len(best[0]):
                    best = (parts[1], parts[2])
        return best[1] in ("tmpfs", "ramfs")
    except Exception:
        return False

_WORK = os.environ.get("G1_WORK_DIR", "/tmp")
if _is_ram_backed(_WORK):
    _fb = os.path.join(os.getcwd(), "g1_work")
    if _MODULE_IS_MASTER:
        log.warning(f"[disk] {_WORK} is RAM-backed — a 127GB checkpoint there IS host RAM. "
                    f"Falling back to {_fb}. Set G1_WORK_DIR to a real local disk.")
    _WORK = _fb
LOCAL_CACHE   = os.path.join(_WORK, "g1_cache")
TEMP_CKPT_DIR = os.path.join(_WORK, "g1_ckpts")
os.makedirs(LOCAL_CACHE, exist_ok=True)
os.makedirs(TEMP_CKPT_DIR, exist_ok=True)

def host_mem_str() -> str:
    out = []
    try:
        with open("/proc/self/status") as f:
            for line in f:
                if line.startswith("VmRSS:"):
                    out.append(f"rss={int(line.split()[1])/1024**2:.1f}GB"); break
        with open("/proc/meminfo") as f:
            for line in f:
                if line.startswith("MemAvailable:"):
                    out.append(f"avail={int(line.split()[1])/1024**2:.0f}GB"); break
        for cur, mx in (("/sys/fs/cgroup/memory.current", "/sys/fs/cgroup/memory.max"),
                        ("/sys/fs/cgroup/memory/memory.usage_in_bytes",
                         "/sys/fs/cgroup/memory/memory.limit_in_bytes")):
            try:
                c = int(open(cur).read()); m = open(mx).read().strip()
                if m != "max" and int(m) < (1 << 60):
                    out.append(f"cgroup={c/1024**3:.0f}/{int(m)/1024**3:.0f}GB"); break
            except Exception:
                continue
    except Exception:
        pass
    return "host " + " ".join(out) if out else "host=?"

def start_mem_watchdog(rank: int):
    def _loop():
        last = 0.0
        while True:
            time.sleep(15)
            try:
                avail, total = None, 0.0
                with open("/proc/meminfo") as f:
                    for line in f:
                        if line.startswith("MemTotal:"):     total = int(line.split()[1]) / 1024**2
                        if line.startswith("MemAvailable:"): avail = int(line.split()[1]) / 1024**2
                if avail is not None and avail < max(0.05 * total, 8.0) and time.time() - last > 60:
                    log.error(f"[mem-watchdog] rank={rank} HOST RAM CRITICAL — {host_mem_str()}")
                    last = time.time()
            except Exception:
                pass
    threading.Thread(target=_loop, daemon=True).start()

MAX_HOURS  = float(os.environ.get("MAX_TRAINING_HOURS", "138.0"))
START_TIME = time.time()
def elapsed_h():   return (time.time() - START_TIME) / 3600
def remaining_h(): return MAX_HOURS - elapsed_h()
def should_stop_local():
    if elapsed_h() >= MAX_HOURS:
        log.info("[time] budget done"); return True
    return False
def vram_gb():       return torch.cuda.memory_allocated() / 1024**3
def vram_total_gb(): return torch.cuda.get_device_properties(torch.cuda.current_device()).total_memory / 1024**3
def vram_str():      return f"{vram_gb():.1f}/{vram_total_gb():.0f}GB"

def ensure_repo():
    try:
        hf_api.repo_info(repo_id=HF_MODEL_REPO, repo_type="model", token=HF_TOKEN)
    except Exception:
        hf_api.create_repo(repo_id=HF_MODEL_REPO, repo_type="model", private=False, token=HF_TOKEN)
        log.info(f"[hf] created {HF_MODEL_REPO}")
    log.info(f"[hf] USING REPO: {HF_MODEL_REPO}")

def upload_to_hf(local: str, remote: str) -> bool:
    try:
        upload_file(path_or_fileobj=local, path_in_repo=remote,
                    repo_id=HF_MODEL_REPO, repo_type="model", token=HF_TOKEN)
        log.info(f"[hf] up {remote}")
        return True
    except Exception as e:
        log.error(f"[hf] upload failed: {e}")
        return False

METRICS_FILE = os.path.join(TEMP_CKPT_DIR, f"metrics_session_{SESSION_ID:03d}.jsonl")
def log_metrics(**kw):
    m = {'timestamp': time.time(), 'elapsed_hours': elapsed_h(), 'session_id': SESSION_ID, **kw}
    with open(METRICS_FILE, 'a') as f:
        f.write(json.dumps(m) + '\n')
    return m
def upload_metrics():
    if os.path.exists(METRICS_FILE):
        upload_to_hf(METRICS_FILE, f"metrics_session_{SESSION_ID:03d}.jsonl")

# ─────────────────────────────────────────────────────────────────────────────
#  MOTIVATION / PROGRESS BOARD
# ─────────────────────────────────────────────────────────────────────────────
import datetime
try:
    import matplotlib; matplotlib.use("Agg"); import matplotlib.pyplot as plt
    HAS_MPL = True
except ImportError:
    HAS_MPL = False

SAMPLES_FILE = os.path.join(TEMP_CKPT_DIR, "samples.md")
SUMMARY_FILE = os.path.join(TEMP_CKPT_DIR, "summary.jsonl")
PROGRESS_MD  = os.path.join(TEMP_CKPT_DIR, "PROGRESS.md")
_step_clock  = []
_tok         = None

def _real_steps_per_hour():
    if len(_step_clock) < 2: return None
    (s0, t0), (s1, t1) = _step_clock[0], _step_clock[-1]
    if t1 - t0 < 30 or s1 <= s0: return None
    return (s1 - s0) / (t1 - t0) * 3600

def sessions_left(step, total):
    sph = _real_steps_per_hour()
    if sph is None: return None
    usable_h = max(MAX_HOURS - 0.75, 8.0)
    return max(math.ceil((total - step) / max(sph * usable_h, 1)), 0)

def session_banner():
    try:
        files = hf_api.list_repo_files(repo_id=HF_MODEL_REPO, repo_type="model", token=HF_TOKEN)
        pts = [f for f in files if f.endswith(".pt")]
        latest = max([int(f.split("step")[-1].split(".")[0]) for f in pts]) if pts else 0
    except Exception:
        pts, latest = [], 0
    log.info("🌱" * 25)
    log.info(f"WELCOME BACK — feed #{len(pts)+1}. Smilyai survived {len(pts)} sessions.")
    log.info(f"Latest checkpoint on the Hub: step {latest:,}")
    log.info("🌱" * 25)

def _bootstrap_from_hub(local, remote):
    try:
        src = hf_hub_download(HF_MODEL_REPO, remote, cache_dir=TEMP_CKPT_DIR, token=HF_TOKEN)
        shutil.copy(src, local)
        log.info(f"[motiv] restored {remote}")
    except Exception:
        pass

def _get_tokenizer():
    global _tok
    if _tok is None:
        try:
            _tok = get_tokenizer(Config())
        except Exception as e:
            log.warning(f"[tokenizer] failed: {e}")
            _tok = None
    return _tok

DOMAIN_TOKEN = ""

@torch.no_grad()
def make_sample(model, prompt="def fibonacci(n):", max_new=48, temp=0.8, top_p=0.95):
    try:
        tok = _get_tokenizer()
        if tok is None: return None
        token_ids = tok.encode(DOMAIN_TOKEN + prompt, add_special_tokens=False).ids[-128:]
        if not token_ids: return None
        device = next(model.parameters()).device
        ids = torch.tensor([token_ids], device=device)
    except Exception as e:
        log.warning(f"[sample] tokenizer error: {e}"); return None

    gen = torch.Generator(device=device); gen.manual_seed(1234)
    was_training = model.training
    model.eval()
    try:
        for _ in range(max_new):
            with torch.amp.autocast('cuda', dtype=model.cfg.dtype):
                logits, _ = model(ids[:, -model.cfg.max_len:], None)
            p = F.softmax(logits[:, -1].float() / temp, dim=-1)
            sp, si = torch.sort(p, descending=True)
            keep = (torch.cumsum(sp, -1) - sp) < top_p
            sp = sp * keep
            sp = sp / sp.sum(-1, keepdim=True).clamp_min(1e-9)
            nxt = si.gather(-1, torch.multinomial(sp, 1, generator=gen))
            ids = torch.cat([ids, nxt], dim=1)
    finally:
        if was_training: model.train()
    try:
        return tok.decode(ids[0].tolist())
    except Exception as e:
        log.warning(f"[sample] decode error: {e}")
        return None

def record_sample(model, step, is_master: bool):
    txt = make_sample(model)
    if not is_master:
        return
    with open(SAMPLES_FILE, "a") as f:
        f.write(f"\n## step {step:,} — {datetime.datetime.now():%d %b %H:%M}\n> {txt or '(skipped)'}\n")
    upload_to_hf(SAMPLES_FILE, "samples.md")
    if txt: log.info(f"[motiv] sample » {txt[:120]!r}")

def make_loss_chart():
    if not (HAS_MPL and os.path.exists(METRICS_FILE)): return
    tr, va = [], []
    for line in open(METRICS_FILE):
        try: m = json.loads(line)
        except Exception: continue
        if "loss" in m and "step" in m: tr.append((m["step"], m["loss"]))
        elif "val_loss" in m and "step" in m: va.append((m["step"], m["val_loss"]))
    if not tr: return
    fig, ax = plt.subplots(figsize=(10, 5))
    ax.plot(*zip(*tr), lw=1, label="train")
    if va: ax.plot(*zip(*va), "o-", color="tab:red", label="val")
    ax.set_xlabel("step"); ax.set_ylabel("loss"); ax.grid(alpha=.3); ax.legend()
    ax.set_title("Smilyai-G1 20B learning curve 🌱")
    p = os.path.join(TEMP_CKPT_DIR, "loss_curve.png")
    fig.savefig(p, dpi=110, bbox_inches="tight"); plt.close(fig)
    upload_to_hf(p, "loss_curve.png"); os.remove(p)

def update_progress_md(cfg, step, epoch, tr_loss, val_loss):
    rec = {"t": f"{datetime.datetime.now():%d %b %H:%M}", "step": step, "epoch": epoch,
           "loss": round(tr_loss, 4) if tr_loss is not None else None,
           "val": round(val_loss, 4) if (val_loss is not None and val_loss == val_loss) else None}
    with open(SUMMARY_FILE, "a") as f: f.write(json.dumps(rec) + "\n")
    sl = sessions_left(step, cfg.total_steps); sl = f"~{sl}" if sl is not None else "?"
    lines = ["# Smilyai-G1 20B · live progress 🌱", "",
             f"**{100*step/cfg.total_steps:.1f}% trained** · estimated clicks left: **{sl}** 🖱️", "",
             "> Note: train loss is only comparable within a session — the data mix changed between "
             "sessions 2, 3 and 4. Use **val loss** (fineweb-edu only) as the progress signal.", "",
             "| when | step | train loss | val loss |", "|---|---|---|---|"]
    for line in open(SUMMARY_FILE):
        try: r = json.loads(line)
        except Exception: continue
        lines.append(f"| {r['t']} | {r['step']:,} | {r['loss'] if r['loss'] is not None else '—'} "
                     f"| {r['val'] if r['val'] is not None else '—'} |")
    with open(PROGRESS_MD, "w") as f: f.write("\n".join(lines) + "\n")
    upload_to_hf(PROGRESS_MD, "PROGRESS.md")

# ─────────────────────────────────────────────────────────────────────────────
#  CONFIG
# ─────────────────────────────────────────────────────────────────────────────
@dataclass
class Config:
    vocab_size: int = 131_072

    d_model:    int   = 2048
    n_layers:   int   = 32
    n_heads:    int   = 16
    n_kv_heads: int   = 4
    max_len:    int   = 2048
    rope_theta: float = 500_000.0

    n_experts:          int   = 56
    top_k:              int   = 2
    expert_hidden_mult: float = 0.875
    shared_hidden_mult: float = 2.0
    n_shared_experts:   int   = 1
    aux_loss_coef:      float = 0.01
    bias_update_rate:  float = 0.001
    bias_update_every: int   = 10
    bias_cap:          float = 2.0
    bias_decay:        float = 0.0005
    usage_ema_decay:   float = 0.99
    moe_block_m:        int   = 64

    tie_embeddings:   bool  = True

    muon_lr:     float = 0.02
    muon_min_lr: float = 0.002
    muon_mom:    float = 0.95
    adamw_lr:    float = 1.5e-4
    adamw_min_lr:float = 1.5e-5
    beta1:       float = 0.9
    beta2:       float = 0.95
    wd:          float = 0.1
    grad_clip:   float = 1.0
    warmup:      int   = 3000
    total_steps: int   = 300_000

    micro_batch: int = 2
    grad_accum:  int = 16

    log_every:   int = 10
    eval_every:  int = 500
    ckpt_every:  int = 1000

    enable_dpo_bursts: bool = False
    dpo_start_step:    int  = 250_000
    dpo_every:         int  = 500
    dpo_beta:          float= 0.1

    # (repo_id, split, text_field, TOKEN weight, hf_config_name_or_None)
    # v7: weights are honoured by TOKEN count (deficit scheduler), not by document count.
    dataset_sources: tuple = (
        ("HuggingFaceFW/fineweb-edu",                  "train", "text",     200_000_000_000, None),
        ("HuggingFaceCode/stack-v3-train",             "train", "content",  100_000_000_000, None),
        ("opencsg/chinese-fineweb-edu",                "train", "text",      60_000_000_000, None),
        ("hotchpotch/fineweb-2-edu-japanese",          "train", "text",      40_000_000_000, None),
        ("KORMo-Team/korean-web-collection",           "train", "text",      30_000_000_000, None),
        ("HuggingFaceFW/fineweb",                      "train", "text",      70_000_000_000, "sample-350BT"),
    )
    tokenizer_repo: str = "Smilyai-labs/Smilyai-U1-B-Tokenizer"

    tokenizer_workers: int = 4
    prefetch_shards: int = 20
    shuffle_buffer: int = 500

    use_compile: bool = False
    use_fp8: bool = False

    @property
    def dtype(self): return torch.bfloat16
    @property
    def head_dim(self): return self.d_model // self.n_heads
    def tokens_per_step(self, bs, world_size=1): return bs * self.grad_accum * self.max_len * world_size

    def arch_fingerprint(self) -> dict:
        return {
            "vocab_size": self.vocab_size, "d_model": self.d_model,
            "n_layers": self.n_layers, "n_heads": self.n_heads,
            "n_kv_heads": self.n_kv_heads, "n_experts": self.n_experts,
            "top_k": self.top_k, "expert_hidden_mult": self.expert_hidden_mult,
            "shared_hidden_mult": self.shared_hidden_mult,
            "tie_embeddings": self.tie_embeddings,
        }

# ─────────────────────────────────────────────────────────────────────────────
#  DISTRIBUTED HELPERS
# ─────────────────────────────────────────────────────────────────────────────
def dist_ready() -> bool:
    return dist.is_available() and dist.is_initialized()

def distributed_mean(value: float, device: torch.device) -> float:
    t = torch.tensor(float(value), dtype=torch.float64, device=device)
    if dist_ready():
        dist.all_reduce(t, op=dist.ReduceOp.SUM)
        t /= dist.get_world_size()
    return t.item()

def broadcast_flag(value: bool, device: torch.device) -> bool:
    flag = torch.tensor(int(bool(value)), dtype=torch.int32, device=device)
    if dist_ready():
        dist.broadcast(flag, src=0)
    return bool(flag.item())

def all_ok(ok: bool, device: torch.device) -> bool:
    t = torch.tensor(int(bool(ok)), dtype=torch.int32, device=device)
    if dist_ready():
        dist.all_reduce(t, op=dist.ReduceOp.MIN)
    return bool(t.item())

def distributed_should_stop(device: torch.device, is_master: bool, step: int, total_steps: int) -> bool:
    stop = (should_stop_local() or step >= total_steps) if is_master else False
    return broadcast_flag(stop, device)

# ─────────────────────────────────────────────────────────────────────────────
#  TRITON KERNELS
# ─────────────────────────────────────────────────────────────────────────────
@triton.jit
def smilyai_rmsnorm_fwd(X, W, Y, RSTD, stride_row, N, eps, BLOCK_N: tl.constexpr):
    row = tl.program_id(0)
    X += row * stride_row; Y += row * stride_row
    cols = tl.arange(0, BLOCK_N); mask = cols < N
    x = tl.load(X + cols, mask=mask, other=0.0).to(tl.float32)
    var = tl.sum(x * x, axis=0) / N
    rstd = 1.0 / tl.sqrt(var + eps)
    tl.store(RSTD + row, rstd)
    w = tl.load(W + cols, mask=mask, other=0.0).to(tl.float32)
    tl.store(Y + cols, (x * rstd * w).to(Y.dtype.element_ty), mask=mask)

@triton.jit
def smilyai_rmsnorm_bwd(X, W, DY, DX, DW_PARTIAL, RSTD, stride_row, N, BLOCK_N: tl.constexpr):
    row = tl.program_id(0)
    X += row * stride_row; DY += row * stride_row; DX += row * stride_row
    cols = tl.arange(0, BLOCK_N); mask = cols < N
    x  = tl.load(X  + cols, mask=mask, other=0.0).to(tl.float32)
    dy = tl.load(DY + cols, mask=mask, other=0.0).to(tl.float32)
    w  = tl.load(W  + cols, mask=mask, other=0.0).to(tl.float32)
    rstd = tl.load(RSTD + row)
    wdy  = w * dy
    s    = tl.sum(x * wdy, axis=0)
    dx   = rstd * wdy - (rstd * rstd * rstd / N) * x * s
    tl.store(DX + cols, dx.to(DX.dtype.element_ty), mask=mask)
    tl.store(DW_PARTIAL + row * N + cols, dy * x * rstd, mask=mask)

@triton.jit
def smilyai_swiglu_fwd(GATE, UP, OUT, N, BLOCK: tl.constexpr):
    pid  = tl.program_id(0)
    offs = pid * BLOCK + tl.arange(0, BLOCK); mask = offs < N
    g = tl.load(GATE + offs, mask=mask, other=0.0).to(tl.float32)
    u = tl.load(UP   + offs, mask=mask, other=0.0).to(tl.float32)
    tl.store(OUT + offs, (g * tl.sigmoid(g) * u).to(OUT.dtype.element_ty), mask=mask)

@triton.jit
def smilyai_swiglu_bwd(GATE, UP, DOUT, DGATE, DUP, N, BLOCK: tl.constexpr):
    pid  = tl.program_id(0)
    offs = pid * BLOCK + tl.arange(0, BLOCK); mask = offs < N
    g    = tl.load(GATE + offs, mask=mask, other=0.0).to(tl.float32)
    u    = tl.load(UP   + offs, mask=mask, other=0.0).to(tl.float32)
    dout = tl.load(DOUT + offs, mask=mask, other=0.0).to(tl.float32)
    s    = tl.sigmoid(g); silu = g * s; dsilu = s * (1.0 + g * (1.0 - s))
    tl.store(DGATE + offs, (dout * u * dsilu).to(DGATE.dtype.element_ty), mask=mask)
    tl.store(DUP   + offs, (dout * silu    ).to(DUP.dtype.element_ty),   mask=mask)

class _TritonRMSNormFn(torch.autograd.Function):
    @staticmethod
    @torch.compiler.disable
    def forward(ctx, x, w, eps):
        orig = x.shape; x2 = x.reshape(-1, orig[-1]).contiguous()
        M, N = x2.shape; y = torch.empty_like(x2)
        rstd = torch.empty(M, device=x.device, dtype=torch.float32)
        BN = triton.next_power_of_2(N)
        w = w.contiguous()
        smilyai_rmsnorm_fwd[(M,)](x2, w, y, rstd, x2.stride(0), N, eps, BLOCK_N=BN)
        ctx.save_for_backward(x2, w, rstd); ctx.BN = BN; ctx.orig = orig
        return y.view(orig)

    @staticmethod
    @torch.compiler.disable
    def backward(ctx, dy):
        x2, w, rstd = ctx.saved_tensors; M, N = x2.shape
        dy2 = dy.reshape(M, N).contiguous()
        dx  = torch.empty_like(x2)
        dwp = torch.empty(M, N, device=x2.device, dtype=torch.float32)
        smilyai_rmsnorm_bwd[(M,)](x2, w, dy2, dx, dwp, rstd, x2.stride(0), N, BLOCK_N=ctx.BN)
        return dx.view(ctx.orig), dwp.sum(0).to(w.dtype), None

class RMSNorm(nn.Module):
    def __init__(self, dim: int, eps: float = 1e-6):
        super().__init__(); self.eps = eps; self.w = nn.Parameter(torch.ones(dim))
    def forward(self, x):
        if x.is_cuda: return _TritonRMSNormFn.apply(x, self.w, self.eps)
        x32 = x.float()
        return (x32 * torch.rsqrt(x32.pow(2).mean(-1, keepdim=True) + self.eps) * self.w).to(x.dtype)

class _FusedSwiGLUFn(torch.autograd.Function):
    @staticmethod
    @torch.compiler.disable
    def forward(ctx, gate, up):
        shape = gate.shape; g = gate.reshape(-1).contiguous(); u = up.reshape(-1).contiguous()
        N = g.numel(); out = torch.empty_like(g); BLOCK = 1024
        smilyai_swiglu_fwd[(triton.cdiv(N, BLOCK),)](g, u, out, N, BLOCK=BLOCK)
        ctx.save_for_backward(g, u); ctx.shape = shape; ctx.BLOCK = BLOCK
        return out.view(shape)

    @staticmethod
    @torch.compiler.disable
    def backward(ctx, dout):
        g, u = ctx.saved_tensors; N = g.numel()
        dout_flat = dout.reshape(-1).contiguous()
        dgate = torch.empty_like(g); dup = torch.empty_like(u)
        smilyai_swiglu_bwd[(triton.cdiv(N, ctx.BLOCK),)](g, u, dout_flat, dgate, dup, N, BLOCK=ctx.BLOCK)
        return dgate.view(ctx.shape), dup.view(ctx.shape)

def fused_swiglu(gate, up):
    return _FusedSwiGLUFn.apply(gate, up) if gate.is_cuda else F.silu(gate) * up

def precompute_rope(head_dim, max_len, theta, device):
    inv_freq = 1.0 / (theta ** (torch.arange(0, head_dim, 2, device=device, dtype=torch.float32) / head_dim))
    pos = torch.arange(max_len, device=device, dtype=torch.float32)
    freqs = torch.outer(pos, inv_freq)
    return freqs.cos(), freqs.sin()

def apply_rope(x, cos, sin):
    dt = x.dtype
    L = x.shape[1]; h = x.shape[-1] // 2
    c = cos[:L].unsqueeze(0).unsqueeze(2); s = sin[:L].unsqueeze(0).unsqueeze(2)
    x32 = x.float()
    x1, x2 = x32[..., :h], x32[..., h:]
    return torch.cat([x1 * c - x2 * s, x2 * c + x1 * s], dim=-1).to(dt)

class GQAAttention(nn.Module):
    def __init__(self, cfg: Config, layer_idx: int):
        super().__init__()
        self.n_heads    = cfg.n_heads
        self.n_kv_heads = cfg.n_kv_heads
        self.hd         = cfg.head_dim
        d = cfg.d_model
        self.wq = nn.Linear(d, self.n_heads    * self.hd, bias=False)
        self.wk = nn.Linear(d, self.n_kv_heads * self.hd, bias=False)
        self.wv = nn.Linear(d, self.n_kv_heads * self.hd, bias=False)
        self.wo = nn.Linear(self.n_heads * self.hd, d, bias=False)
        self.q_norm = RMSNorm(self.hd)
        self.k_norm = RMSNorm(self.hd)
        std = 0.02
        for m in [self.wq, self.wk, self.wv]: nn.init.normal_(m.weight, std=std)
        nn.init.normal_(self.wo.weight, std=std / math.sqrt(2 * cfg.n_layers))

    def _attend(self, q, k, v):
        if HAS_FLASH and q.is_cuda and q.dtype in (torch.bfloat16, torch.float16):
            return flash_attn_func(q, k, v, causal=True)
        B, L, Hq, D = q.shape; Hkv = k.shape[2]
        qt = q.transpose(1,2); kt = k.transpose(1,2); vt = v.transpose(1,2)
        if Hq != Hkv:
            rep = Hq // Hkv
            kt = kt.repeat_interleave(rep, 1); vt = vt.repeat_interleave(rep, 1)
        out = F.scaled_dot_product_attention(qt, kt, vt, is_causal=True)
        return out.transpose(1, 2)

    def forward(self, x, cos, sin):
        B, L, _ = x.shape
        q = self.wq(x).view(B, L, self.n_heads,    self.hd)
        k = self.wk(x).view(B, L, self.n_kv_heads, self.hd)
        v = self.wv(x).view(B, L, self.n_kv_heads, self.hd)
        q, k = self.q_norm(q), self.k_norm(k)
        q, k = apply_rope(q, cos, sin), apply_rope(k, cos, sin)
        out = self._attend(q, k, v)
        return self.wo(out.reshape(B, L, -1))

# ─────────────────────────────────────────────────────────────────────────────
#  FUSED GROUPED-GEMM MOE DISPATCH
# ─────────────────────────────────────────────────────────────────────────────
_moe_autotune_configs = [
    triton.Config({"BLOCK_N": 64,  "BLOCK_K": 32}, num_warps=4, num_stages=3),
    triton.Config({"BLOCK_N": 128, "BLOCK_K": 32}, num_warps=8, num_stages=3),
    triton.Config({"BLOCK_N": 128, "BLOCK_K": 64}, num_warps=8, num_stages=4),
    triton.Config({"BLOCK_N": 64,  "BLOCK_K": 64}, num_warps=4, num_stages=4),
]

@triton.autotune(configs=_moe_autotune_configs, key=["K", "N"])
@triton.jit
def _moe_gemm_kernel(
    A_ptr, B_ptr, C_ptr, block_expert_ptr,
    M_padded, K, N,
    stride_am, stride_ak,
    stride_be, stride_bk, stride_bn,
    stride_cm, stride_cn,
    BLOCK_M: tl.constexpr, BLOCK_N: tl.constexpr, BLOCK_K: tl.constexpr,
):
    pid_m = tl.program_id(0)
    pid_n = tl.program_id(1)
    e     = tl.load(block_expert_ptr + pid_m).to(tl.int64)
    offs_m = pid_m * BLOCK_M + tl.arange(0, BLOCK_M)
    offs_n = pid_n * BLOCK_N + tl.arange(0, BLOCK_N)
    offs_k = tl.arange(0, BLOCK_K)
    m_mask = offs_m < M_padded
    n_mask = offs_n < N
    a_ptrs = A_ptr + offs_m[:, None] * stride_am + offs_k[None, :] * stride_ak
    b_ptrs = B_ptr + e * stride_be + offs_k[:, None] * stride_bk + offs_n[None, :] * stride_bn
    acc = tl.zeros((BLOCK_M, BLOCK_N), dtype=tl.float32)
    for k0 in range(0, K, BLOCK_K):
        k_mask = (k0 + offs_k) < K
        a = tl.load(a_ptrs, mask=m_mask[:, None] & k_mask[None, :], other=0.0)
        b = tl.load(b_ptrs, mask=k_mask[:, None] & n_mask[None, :], other=0.0)
        acc    = tl.dot(a, b, acc)
        a_ptrs += BLOCK_K * stride_ak
        b_ptrs += BLOCK_K * stride_bk
    tl.store(
        C_ptr + offs_m[:, None] * stride_cm + offs_n[None, :] * stride_cn,
        acc.to(tl.bfloat16), mask=m_mask[:, None] & n_mask[None, :],
    )

def _grouped_linear_raw(A, W, block_expert, M_padded, transpose, BM):
    E, OUT, IN = W.shape
    if not transpose:
        K, N = IN, OUT; stride_bk = W.stride(2); stride_bn = W.stride(1)
    else:
        K, N = OUT, IN; stride_bk = W.stride(1); stride_bn = W.stride(2)
    C    = torch.empty((M_padded, N), device=A.device, dtype=torch.bfloat16)
    grid = lambda META: (triton.cdiv(M_padded, BM), triton.cdiv(N, META["BLOCK_N"]))
    _moe_gemm_kernel[grid](
        A, W, C, block_expert, M_padded, K, N,
        A.stride(0), A.stride(1),
        W.stride(0), stride_bk, stride_bn,
        C.stride(0), C.stride(1),
        BLOCK_M=BM,
    )
    return C

@triton.autotune(configs=_moe_autotune_configs, key=["K", "N"], reset_to_zero=["DW_ptr"])
@triton.jit
def _moe_dw_kernel(
    A_ptr, DC_ptr, DW_ptr, block_expert_ptr,
    M_padded, K, N,
    stride_am, stride_ak,
    stride_dcm, stride_dcn,
    stride_dwe, stride_dwn, stride_dwk,
    BLOCK_M: tl.constexpr, BLOCK_N: tl.constexpr, BLOCK_K: tl.constexpr,
):
    pid_m = tl.program_id(0)
    pid_n = tl.program_id(1)
    pid_k = tl.program_id(2)
    e     = tl.load(block_expert_ptr + pid_m).to(tl.int64)
    offs_m = pid_m * BLOCK_M + tl.arange(0, BLOCK_M)
    offs_n = pid_n * BLOCK_N + tl.arange(0, BLOCK_N)
    offs_k = pid_k * BLOCK_K + tl.arange(0, BLOCK_K)
    m_mask = offs_m < M_padded
    n_mask = offs_n < N
    k_mask = offs_k < K
    a  = tl.load(A_ptr  + offs_m[:, None] * stride_am  + offs_k[None, :] * stride_ak,
                 mask=m_mask[:, None] & k_mask[None, :], other=0.0)
    dc = tl.load(DC_ptr + offs_m[:, None] * stride_dcm + offs_n[None, :] * stride_dcn,
                 mask=m_mask[:, None] & n_mask[None, :], other=0.0)
    tl.atomic_add(
        DW_ptr + e * stride_dwe + offs_n[:, None] * stride_dwn + offs_k[None, :] * stride_dwk,
        tl.dot(tl.trans(dc), a),
        mask=n_mask[:, None] & k_mask[None, :],
    )

def _grouped_dw_raw(A, dC, block_expert, E, OUT, IN, M_padded, BM):
    DW   = torch.zeros((E, OUT, IN), device=A.device, dtype=torch.float32)
    grid = lambda META: (
        triton.cdiv(M_padded, BM),
        triton.cdiv(OUT, META["BLOCK_N"]),
        triton.cdiv(IN,  META["BLOCK_K"]),
    )
    _moe_dw_kernel[grid](
        A, dC, DW, block_expert, M_padded, IN, OUT,
        A.stride(0), A.stride(1),
        dC.stride(0), dC.stride(1),
        DW.stride(0), DW.stride(1), DW.stride(2),
        BLOCK_M=BM,
    )
    return DW

class GroupedLinearFn(torch.autograd.Function):
    @staticmethod
    def forward(ctx, A, W, block_expert, padded_offsets, M_padded, BM):
        A = A.contiguous().to(torch.bfloat16)
        W = W.contiguous()
        C = _grouped_linear_raw(A, W, block_expert, M_padded, False, BM)
        ctx.save_for_backward(A, W, block_expert, padded_offsets)
        ctx.M_padded = M_padded
        ctx.BM       = BM
        return C

    @staticmethod
    def backward(ctx, dC):
        A, W, block_expert, _ = ctx.saved_tensors
        dC = dC.contiguous().to(torch.bfloat16)
        dA = _grouped_linear_raw(dC, W, block_expert, ctx.M_padded, True, ctx.BM) \
             if ctx.needs_input_grad[0] else None
        dW = _grouped_dw_raw(A, dC, block_expert, W.shape[0], W.shape[1], W.shape[2],
                             ctx.M_padded, ctx.BM).to(W.dtype) \
             if ctx.needs_input_grad[1] else None
        return dA, dW, None, None, None, None

def moe_align_block_size(expert_ids, num_experts, block_size, device):
    counts        = torch.bincount(expert_ids, minlength=num_experts)
    padded_counts = ((counts + block_size - 1) // block_size) * block_size
    padded_offsets      = torch.zeros(num_experts + 1, dtype=torch.long, device=device)
    padded_offsets[1:]  = torch.cumsum(padded_counts, dim=0)
    orig_offsets        = torch.zeros(num_experts + 1, dtype=torch.long, device=device)
    orig_offsets[1:]    = torch.cumsum(counts, dim=0)
    total_padded          = int(padded_offsets[-1].item())
    sort_idx              = torch.argsort(expert_ids, stable=True)
    num_blocks_per_expert = padded_counts // block_size
    block_expert          = torch.repeat_interleave(
        torch.arange(num_experts, device=device), num_blocks_per_expert
    )
    n_rows               = expert_ids.numel()
    arange_total         = torch.arange(n_rows, device=device)
    sorted_expert_of_row = expert_ids[sort_idx]
    row_within_expert    = arange_total - orig_offsets[sorted_expert_of_row]
    dest                 = padded_offsets[sorted_expert_of_row] + row_within_expert
    perm       = torch.full((total_padded,), -1, dtype=torch.long, device=device)
    perm[dest] = sort_idx
    return perm, block_expert, total_padded, padded_offsets

class MoEFFN(nn.Module):
    def __init__(self, cfg: Config, layer_idx: int):
        super().__init__()
        d = cfg.d_model
        h = int(d * cfg.expert_hidden_mult)
        E = cfg.n_experts
        self.E = E; self.d = d; self.h = h
        self.top_k          = cfg.top_k
        self.aux_loss_coef  = cfg.aux_loss_coef
        self.block_m        = cfg.moe_block_m

        self.gate_w = nn.Parameter(torch.empty(E, h, d))
        self.up_w   = nn.Parameter(torch.empty(E, h, d))
        self.down_w = nn.Parameter(torch.empty(E, d, h))
        nn.init.normal_(self.gate_w, std=0.02)
        nn.init.normal_(self.up_w,   std=0.02)
        nn.init.normal_(self.down_w, std=0.02 / math.sqrt(2 * cfg.n_layers))

        self.router = nn.Linear(d, E, bias=False)
        nn.init.normal_(self.router.weight, std=0.02)

        sh = int(d * cfg.shared_hidden_mult)
        self.shared_gate = nn.Linear(d, sh, bias=False)
        self.shared_up   = nn.Linear(d, sh, bias=False)
        self.shared_down = nn.Linear(sh, d, bias=False)
        nn.init.normal_(self.shared_gate.weight, std=0.02)
        nn.init.normal_(self.shared_up.weight,   std=0.02)
        nn.init.normal_(self.shared_down.weight, std=0.02 / math.sqrt(2 * cfg.n_layers))

        self.bias_update_rate  = cfg.bias_update_rate
        self.bias_cap          = cfg.bias_cap
        self.bias_decay        = cfg.bias_decay
        self.usage_ema_decay   = cfg.usage_ema_decay
        self.register_buffer('expert_bias',      torch.zeros(E, dtype=torch.float32))
        self.register_buffer('expert_usage_ema', torch.zeros(E, dtype=torch.float32))
        self._bias_capped_warned = False
        self.last_aux_loss = torch.tensor(0.0, dtype=torch.float32)

    @torch.no_grad()
    def accumulate_usage(self, topk_i):
        counts = F.one_hot(topk_i, self.E).float().sum(dim=(0, 1))
        self.expert_usage_ema.mul_(self.usage_ema_decay).add_(counts, alpha=1 - self.usage_ema_decay)

    @torch.no_grad()
    def update_bias(self):
        if dist_ready():
            dist.all_reduce(self.expert_usage_ema, op=dist.ReduceOp.AVG)
        usage = self.expert_usage_ema
        avg   = usage.mean().clamp_min(1e-6)
        error = ((avg - usage) / avg).clamp(-1.0, 1.0)
        self.expert_bias.add_(self.bias_update_rate * error)
        self.expert_bias.mul_(1.0 - self.bias_decay)
        self.expert_bias.clamp_(-self.bias_cap, self.bias_cap)
        if not self._bias_capped_warned and bool((self.expert_bias.abs() >= self.bias_cap * 0.99).any()):
            log.warning(f"[moe] expert_bias hit cap ({self.bias_cap}) on some expert")
            self._bias_capped_warned = True

    def dead_expert_count(self, threshold: float = 1e-6) -> int:
        return int((self.expert_usage_ema < threshold).sum().item())

    def capped_expert_count(self) -> int:
        return int((self.expert_bias.abs() >= self.bias_cap * 0.99).sum().item())

    def forward(self, x):
        B, L, D = x.shape; T = B * L
        x_flat = x.reshape(T, D)
        E, top_k, BM = self.E, self.top_k, self.block_m
        device = x.device

        shared_out = self.shared_down(
            fused_swiglu(self.shared_gate(x_flat), self.shared_up(x_flat)))

        logits = self.router(x_flat).float()
        probs  = F.softmax(logits, dim=-1)

        biased    = logits + self.expert_bias.detach().float()
        _, topk_i = torch.topk(biased, top_k, dim=-1)
        topk_p    = probs.gather(-1, topk_i)
        topk_p    = topk_p / topk_p.sum(-1, keepdim=True).clamp_min(1e-9)

        with torch.no_grad():
            f_i = F.one_hot(topk_i, E).float().sum(1).mean(0)
        p_i = probs.mean(0)
        self.last_aux_loss = (E * (f_i * p_i).sum()) * self.aux_loss_coef

        if self.training:
            self.accumulate_usage(topk_i)

        expert_ids_flat = topk_i.reshape(-1)
        gate_flat       = topk_p.reshape(-1).to(x.dtype)
        token_idx_flat  = torch.arange(T, device=device).unsqueeze(1).expand(T, top_k).reshape(-1)

        perm, block_expert, total_padded, padded_offsets = moe_align_block_size(
            expert_ids_flat, E, BM, device)

        valid      = perm >= 0
        gather_idx = perm.clamp_min(0)
        src_token  = token_idx_flat[gather_idx]
        A_padded   = x_flat[src_token] * valid.unsqueeze(1).to(x_flat.dtype)

        gate = GroupedLinearFn.apply(A_padded, self.gate_w, block_expert, padded_offsets, total_padded, BM)
        up   = GroupedLinearFn.apply(A_padded, self.up_w,   block_expert, padded_offsets, total_padded, BM)
        down = GroupedLinearFn.apply(fused_swiglu(gate, up), self.down_w, block_expert, padded_offsets, total_padded, BM)

        gate_vals = (gate_flat[gather_idx] * valid.to(gate_flat.dtype)).unsqueeze(1)
        routed_out = torch.zeros(T, D, dtype=down.dtype, device=device)
        routed_out.index_add_(0, src_token, (down * gate_vals.to(down.dtype)))

        return (routed_out.to(x.dtype) + shared_out).view(B, L, D)

class Block(nn.Module):
    def __init__(self, cfg: Config, layer_idx: int):
        super().__init__()
        self.norm1 = RMSNorm(cfg.d_model)
        self.norm2 = RMSNorm(cfg.d_model)
        self.attn  = GQAAttention(cfg, layer_idx)
        self.ffn   = MoEFFN(cfg, layer_idx)

    def forward(self, x, cos, sin):
        x = x + self.attn(self.norm1(x), cos, sin)
        x = x + self.ffn (self.norm2(x))
        return x

class SmilyaiG1(nn.Module):
    def __init__(self, cfg: Config):
        super().__init__()
        self.cfg   = cfg
        self.embed = nn.Embedding(cfg.vocab_size, cfg.d_model)
        nn.init.normal_(self.embed.weight, std=0.02)
        self.blocks      = nn.ModuleList([Block(cfg, i) for i in range(cfg.n_layers)])
        self.final_norm  = RMSNorm(cfg.d_model)
        if not cfg.tie_embeddings:
            self.lm_head = nn.Linear(cfg.d_model, cfg.vocab_size, bias=False)
            nn.init.normal_(self.lm_head.weight, std=0.02 / math.sqrt(cfg.n_layers))
        else:
            self.lm_head = None
        self.register_buffer("rope_cos", torch.zeros(cfg.max_len, cfg.head_dim // 2, dtype=torch.float32), persistent=False)
        self.register_buffer("rope_sin", torch.zeros(cfg.max_len, cfg.head_dim // 2, dtype=torch.float32), persistent=False)
        self._rope_ready = False
        self._step = 0
        self._last_lm_loss  = None
        self._last_aux_loss = None
        self._log_summary()

    def _raw_blocks(self):
        return [getattr(b, "_orig_mod", b) for b in self.blocks]

    def init_rope(self, device):
        c, s = precompute_rope(self.cfg.head_dim, self.cfg.max_len, self.cfg.rope_theta, device)
        self.rope_cos = c.float()
        self.rope_sin = s.float()
        self._rope_ready = True

    def force_fp32_balancing_buffers(self):
        for b in self._raw_blocks():
            b.ffn.expert_bias      = b.ffn.expert_bias.float()
            b.ffn.expert_usage_ema = b.ffn.expert_usage_ema.float()

    def _log_summary(self):
        cfg = self.cfg
        total   = sum(p.numel() for p in self.parameters())
        attn_p  = sum(p.numel() for n, p in self.named_parameters() if 'attn'   in n)
        shared_p= sum(p.numel() for n, p in self.named_parameters() if 'shared' in n)
        h_e     = int(cfg.d_model * cfg.expert_hidden_mult)
        routed_total  = cfg.n_layers * cfg.n_experts * (2*cfg.d_model*h_e + h_e*cfg.d_model)
        routed_active = routed_total * (cfg.top_k / cfg.n_experts)
        active_est    = attn_p + shared_p + routed_active + cfg.d_model * cfg.vocab_size
        log.info("=" * 70)
        log.info("Smilyai-G1  20B — plain GQA + Sparse MoE (FSDP2)")
        log.info(f"  d={cfg.d_model} L={cfg.n_layers} heads={cfg.n_heads} kv={cfg.n_kv_heads}")
        log.info(f"  MoE: {cfg.n_experts} experts, top_k={cfg.top_k}, shared_mult={cfg.shared_hidden_mult}")
        log.info(f"  Total params: {total/1e9:.2f}B")
        log.info(f"  Active/token (estimate): {active_est/1e9:.2f}B  (target ~2B)")
        log.info(f"  vocab={cfg.vocab_size} | Flash: {HAS_FLASH}")
        log.info(f"  Muon LR: {cfg.muon_lr} (aspect-ratio scaling)")
        log.info(f"  Compile: {cfg.use_compile}")
        log.info("=" * 70)

    def count_params(self): return sum(p.numel() for p in self.parameters())
    def collect_aux_loss(self): return sum(b.ffn.last_aux_loss for b in self._raw_blocks())
    def set_step(self, s: int): self._step = s

    def update_expert_bias(self):
        for b in self._raw_blocks():
            b.ffn.update_bias()

    def dead_expert_report(self):
        raw    = self._raw_blocks()
        dead   = [b.ffn.dead_expert_count()   for b in raw]
        capped = [b.ffn.capped_expert_count() for b in raw]
        return dead, sum(dead), capped, sum(capped)

    def forward(self, tokens, targets=None):
        B, L  = tokens.shape; device = tokens.device
        if not self._rope_ready:
            self.init_rope(device)
        cos, sin = self.rope_cos[:L], self.rope_sin[:L]

        x = self.embed(tokens)
        for block in self.blocks:
            x = block(x, cos, sin)

        x     = self.final_norm(x)
        logits= F.linear(x, self.embed.weight) if self.lm_head is None else self.lm_head(x)

        if targets is None:
            return logits, None

        lm_loss  = F.cross_entropy(
            logits[:, :-1].reshape(-1, self.cfg.vocab_size).float(),
            targets[:, 1:].reshape(-1), ignore_index=-1)
        aux_loss   = self.collect_aux_loss()
        total_loss = lm_loss + aux_loss
        self._last_lm_loss  = lm_loss.detach()
        self._last_aux_loss = aux_loss.detach() if torch.is_tensor(aux_loss) \
                              else torch.tensor(float(aux_loss), device=device)
        return logits, total_loss

# ─────────────────────────────────────────────────────────────────────────────
#  FP8 / FSDP / COMPILE
# ─────────────────────────────────────────────────────────────────────────────
_FP8_SKIP = ("router", "lm_head", "embed")

def fp8_capable_gpu() -> bool:
    return torch.cuda.is_available() and \
           torch.cuda.get_device_capability(torch.cuda.current_device())[0] >= 9

def apply_fp8(model: SmilyaiG1, cfg: Config, is_master: bool) -> SmilyaiG1:
    if not cfg.use_fp8:
        if is_master: log.info("[fp8] disabled")
        return model
    if not HAS_FP8:
        if is_master: log.warning("[fp8] torchao not installed — staying bf16")
        return model
    if not fp8_capable_gpu():
        if is_master: log.warning("[fp8] pre-Hopper GPU — staying bf16")
        return model
    convert_to_float8_training(
        model,
        config=Float8LinearConfig.from_recipe_name("rowwise"),
        module_filter_fn=lambda m, fqn: (
            isinstance(m, nn.Linear) and not any(s in fqn for s in _FP8_SKIP)
        ),
    )
    if is_master:
        log.info("[fp8] converted dense nn.Linear layers to float8 (rowwise); MoE stays bf16")
    return model

def apply_fsdp(model: SmilyaiG1, cfg: Config) -> SmilyaiG1:
    if not dist_ready():
        log.warning("[fsdp] no process group — running unsharded (single GPU)")
        return model
    mp_policy = MixedPrecisionPolicy(param_dtype=torch.bfloat16, reduce_dtype=torch.float32)
    for block in model.blocks:
        fully_shard(block, mp_policy=mp_policy)
    fully_shard(model, mp_policy=mp_policy)
    if torch.cuda.is_available():
        torch.cuda.empty_cache()
    return model

def apply_compile(model: SmilyaiG1, cfg: Config, is_master: bool) -> SmilyaiG1:
    if not cfg.use_compile:
        if is_master: log.info("[compile] disabled")
        return model
    compiled = 0
    for i, block in enumerate(model.blocks):
        try:
            model.blocks[i] = torch.compile(block, dynamic=True, mode="default", fullgraph=False)
            compiled += 1
        except Exception as e:
            if is_master:
                log.warning(f"[compile] block {i} failed, staying eager: {e}")
        if torch.cuda.is_available():
            torch.cuda.empty_cache()
    if is_master:
        if compiled > 0:
            log.info(f"[compile] compiled {compiled}/{len(model.blocks)} blocks")
        else:
            log.warning("[compile] ALL blocks fell back to eager")
    return model

# ─────────────────────────────────────────────────────────────────────────────
#  MUON — DTensor-aware
# ─────────────────────────────────────────────────────────────────────────────
def newton_schulz_5(G: torch.Tensor, steps: int = 5) -> torch.Tensor:
    a, b, c = 3.4445, -4.7750, 2.0315
    squeeze  = (G.ndim == 2)
    X = (G.unsqueeze(0) if squeeze else G).bfloat16()
    transposed = X.size(-2) < X.size(-1)
    if transposed: X = X.transpose(-2,-1)
    X = X / (X.norm(dim=(-2,-1), keepdim=True) + 1e-7)
    for _ in range(steps):
        A = X @ X.transpose(-2,-1)
        X = a*X + (b*A + c*A@A) @ X
    if transposed: X = X.transpose(-2,-1)
    return X.squeeze(0) if squeeze else X

@torch.no_grad()
def stochastic_round_to(dtype: torch.dtype, x_fp32: torch.Tensor) -> torch.Tensor:
    if dtype != torch.bfloat16:
        return x_fp32.to(dtype)
    bits = x_fp32.contiguous().view(torch.int32)
    noise = torch.randint(0, 1 << 16, bits.shape, device=bits.device, dtype=torch.int32)
    rounded = (bits + noise) & -65536
    return rounded.view(torch.float32).to(torch.bfloat16)

class Muon(torch.optim.Optimizer):
    def __init__(self, params, lr=0.02, momentum=0.95, wd=0.0):
        super().__init__(list(params), dict(lr=lr, momentum=momentum, wd=wd))

    @torch.no_grad()
    def step(self, closure=None):
        for g in self.param_groups:
            lr, mom, wd = g['lr'], g['momentum'], g['wd']
            for p in g['params']:
                if p.grad is None:
                    continue
                grad = p.grad
                is_dtensor = isinstance(p, DTensor)
                st = self.state[p]
                if 'buf' not in st:
                    st['buf'] = torch.zeros_like(grad, dtype=torch.float32)
                buf = st['buf']
                buf.mul_(mom).add_(grad.to(torch.float32))
                gnest = grad.to(torch.float32).add(buf, alpha=mom)
                full = gnest.full_tensor() if is_dtensor else gnest
                if full.ndim in (2, 3):
                    u = newton_schulz_5(full)
                    rows, cols = full.shape[-2], full.shape[-1]
                    scale  = max(1.0, rows / cols) ** 0.5
                    update = u.to(torch.float32) * (lr * 0.2 * scale)
                else:
                    update = full * lr
                del full
                if is_dtensor:
                    upd_local = distribute_tensor(update, p.device_mesh, p.placements).to_local()
                    p_local = p.to_local()
                else:
                    upd_local = update
                    p_local   = p.data
                if wd > 0:
                    p_local.mul_(1.0 - lr * wd)
                p_local.sub_(stochastic_round_to(p_local.dtype, upd_local.contiguous()))

def build_optimizers(model: SmilyaiG1, cfg: Config, is_master: bool):
    muon_p, adamw_p = [], []
    for name, p in model.named_parameters():
        if not p.requires_grad: continue
        if p.ndim in (2, 3) and 'embed' not in name and 'lm_head' not in name:
            muon_p.append(p)
        else:
            adamw_p.append(p)
    muon_opt = Muon(muon_p, lr=cfg.muon_lr, momentum=cfg.muon_mom, wd=cfg.wd)
    groups = [{'params': adamw_p, 'lr': cfg.adamw_lr}]
    if dist_ready():
        adamw_opt = torch.optim.AdamW(groups, betas=(cfg.beta1, cfg.beta2), weight_decay=cfg.wd, foreach=True)
        if is_master: log.info("[optim] Muon (FIXED scale) + foreach AdamW (DTensor-safe)")
    elif HAS_BNB:
        adamw_opt = bnb.optim.AdamW8bit(groups, betas=(cfg.beta1, cfg.beta2), weight_decay=cfg.wd)
        if is_master: log.info("[optim] Muon (FIXED) + 8-bit AdamW (single GPU)")
    else:
        adamw_opt = torch.optim.AdamW(groups, betas=(cfg.beta1, cfg.beta2), weight_decay=cfg.wd, fused=True)
        if is_master: log.info("[optim] Muon (FIXED) + fused AdamW (single GPU)")
    if is_master:
        log.info(f"[optim] Muon={sum(p.numel() for p in muon_p)/1e6:.1f}M | "
                 f"AdamW={sum(p.numel() for p in adamw_p)/1e6:.1f}M")
    return muon_opt, adamw_opt

def cosine_lr(step, warmup, total, peak, minimum):
    if step < warmup:  return peak * (step + 1) / warmup
    if step >= total:  return minimum
    t = (step - warmup) / (total - warmup)
    return minimum + 0.5 * (peak - minimum) * (1 + math.cos(math.pi * t))

# ─────────────────────────────────────────────────────────────────────────────
#  LIVE MULTI-SOURCE STREAMING
# ─────────────────────────────────────────────────────────────────────────────
try:
    from datasets import load_dataset
    import datasets as _hfds
    HAS_DATASETS = True
    try: _hfds.disable_progress_bars()
    except Exception: pass
    try:
        import pyarrow as _pa
        _pa.set_cpu_count(2); _pa.set_io_thread_count(4)
    except Exception:
        pass
except ImportError:
    HAS_DATASETS = False

_g1_tokenizer = None

def get_tokenizer(cfg: Config):
    global _g1_tokenizer
    if _g1_tokenizer is not None:
        return _g1_tokenizer
    from tokenizers import Tokenizer
    tok_path = hf_hub_download(repo_id=cfg.tokenizer_repo, filename="tokenizer.json",
                               cache_dir=LOCAL_CACHE, token=HF_TOKEN)
    _g1_tokenizer = Tokenizer.from_file(tok_path)
    got_vocab = _g1_tokenizer.get_vocab_size()
    if got_vocab != cfg.vocab_size:
        log.warning(f"[tokenizer] loaded vocab_size={got_vocab} != cfg.vocab_size="
                    f"{cfg.vocab_size} — fix Config.vocab_size to match the real tokenizer.")
    return _g1_tokenizer

_EOS_CACHE: Optional[int] = None

def _resolve_eos(tok) -> int:
    """v7: env override > known names > scan added tokens for anything EOS-like > id 0 (logged loudly)."""
    global _EOS_CACHE
    if _EOS_CACHE is not None:
        return _EOS_CACHE
    override = os.environ.get("G1_EOS_TOKEN", "").strip()
    if override:
        tid = tok.token_to_id(override)
        if tid is not None:
            log.info(f"[tokenizer] EOS from G1_EOS_TOKEN: {override!r} -> id {tid}")
            _EOS_CACHE = tid; return tid
        log.warning(f"[tokenizer] G1_EOS_TOKEN={override!r} not in vocab — falling back to auto-detect")
    for cand in ("<|endoftext|>", "<|end_of_text|>", "</s>", "<eos>", "<|eos|>", "<|eot_id|>",
                 "<|im_end|>", "[EOS]", "<end_of_text>", "<|end|>"):
        tid = tok.token_to_id(cand)
        if tid is not None:
            log.info(f"[tokenizer] EOS auto-detected: {cand!r} -> id {tid}")
            _EOS_CACHE = tid; return tid
    try:
        added = tok.get_added_tokens_decoder()
        names = {tid: t.content for tid, t in added.items()}
        for tid, name in names.items():
            low = name.lower()
            if ("eos" in low or "end" in low) and "pad" not in low and "unk" not in low:
                log.info(f"[tokenizer] EOS heuristically picked from added tokens: {name!r} -> id {tid}")
                _EOS_CACHE = tid; return tid
        log.error(f"[tokenizer] NO EOS TOKEN FOUND. Added tokens are: {names}. "
                  f"Set G1_EOS_TOKEN to the right one. Using id 0 as a document separator for now.")
    except Exception as e:
        log.error(f"[tokenizer] could not inspect added tokens ({e}); using id 0 as separator")
    _EOS_CACHE = 0
    return 0

_STACK_KEEP_LANGS = {
    "Python", "JavaScript", "TypeScript", "Java", "C", "C++", "C#",
    "Go", "Rust", "Ruby", "PHP", "Swift", "Kotlin", "Scala", "Shell",
    "SQL", "HTML", "CSS", "Markdown", "R", "Julia", "Lua", "Haskell",
    "Elixir", "Erlang", "Dart", "Zig", "CUDA", "Fortran",
}
_MIN_CODE_CHARS = 64
_MAX_CODE_CHARS = 65536
_MAX_DOC_CHARS  = 1_000_000   # any source: hard cap before tokenizing
_MAX_REPO_CHARS = 65_536      # v7: stack-v3 cap per repo (~16K tokens ≈ 2 micro-batches)

def _extract_stack_v3_text(row: dict) -> Optional[str]:
    files = row.get("files")
    if not files:
        return None
    parts, total = [], 0
    for f in files:
        content = f.get("content", "")
        if not content:
            continue
        lang = f.get("language", "")
        if lang and lang not in _STACK_KEEP_LANGS:
            continue
        if len(content) < _MIN_CODE_CHARS or len(content) > _MAX_CODE_CHARS:
            continue
        parts.append(f"# {f.get('file_path', '')}\n{content}")
        total += len(content)
        if total >= _MAX_REPO_CHARS:
            break
    return "\n\n".join(parts) if parts else None

def _extract_text(row: dict, text_field: str, repo_id: str) -> Optional[str]:
    if "stack-v3" in repo_id:
        text = row.get("text") if ("text" in row and "files" not in row) else _extract_stack_v3_text(row)
    else:
        text = row.get(text_field)
    if not text or not isinstance(text, str):
        return None
    return text[:_MAX_DOC_CHARS] if len(text) > _MAX_DOC_CHARS else text

def _open_source_stream(repo_id: str, split: str, shard_index: int, num_shards: int,
                        shuffle_buffer: int = 0, shuffle_seed: int = 0,
                        config_name: Optional[str] = None, text_field: str = "text"):
    is_stack = "stack-v3" in repo_id
    need_col = "files" if is_stack else text_field
    args = (repo_id, config_name) if config_name else (repo_id,)
    kw = dict(split=split, streaming=True)
    try:
        # parquet: only the needed column; tiny arrow batches for stack-v3 (each row = a whole repo)
        ds = load_dataset(*args, columns=[need_col], batch_size=(4 if is_stack else 64), **kw)
    except Exception:
        ds = load_dataset(*args, **kw)

    if num_shards > 1:
        ds = ds.shard(num_shards=num_shards, index=shard_index)

    if is_stack:
        cols = ds.column_names
        ds = ds.map(lambda r: {"text": _extract_stack_v3_text(r) or ""}, remove_columns=cols)
        ds = ds.filter(lambda r: len(r["text"]) > 0)

    if shuffle_buffer > 0:
        ds = ds.shuffle(buffer_size=shuffle_buffer, seed=shuffle_seed)
    return ds

def _short_src(repo_id: str) -> str:
    return repo_id.split("/")[-1][:18]

class LiveStreamingDataset:
    def __init__(self, cfg: Config, batch_size: int, rank: int, world_size: int):
        if not HAS_DATASETS:
            raise RuntimeError("the `datasets` package is required for live streaming")
        self.cfg          = cfg
        self.batch_size   = batch_size
        self.rank         = rank
        self.world_size   = world_size
        self.max_len      = cfg.max_len
        self.n_workers    = max(1, cfg.tokenizer_workers)
        self.total_shards = world_size * self.n_workers
        self.tok          = get_tokenizer(cfg)
        self.eos_id       = _resolve_eos(self.tok)

        qsize = max(cfg.prefetch_shards, self.n_workers * 2)
        self._q: queue.Queue = queue.Queue(maxsize=qsize)
        self._stop = threading.Event()
        self._workers = [threading.Thread(target=self._fetch_loop, args=(w,), daemon=True)
                         for w in range(self.n_workers)]
        for t in self._workers:
            t.start()
        log.info(f"[stream] rank={rank}/{world_size}: {self.n_workers} tokenizer threads "
                 f"({self.total_shards} global shards) | {len(cfg.dataset_sources)} sources | "
                 f"shuffle_buffer={cfg.shuffle_buffer} eos_id={self.eos_id} session={SESSION_ID}")

    def _fetch_loop(self, worker_id: int):
        shard_index  = self.rank * self.n_workers + worker_id
        shuffle_seed = 1234 + shard_index + SESSION_ID * 97
        try:
            streams, failed = [], []
            for repo_id, split, text_field, w, config_name in self.cfg.dataset_sources:
                try:
                    streams.append([
                        _open_source_stream(repo_id, split, shard_index, self.total_shards,
                                            shuffle_buffer=self.cfg.shuffle_buffer,
                                            shuffle_seed=shuffle_seed,
                                            config_name=config_name, text_field=text_field),
                        text_field, repo_id, split, float(w), config_name])
                except Exception as e:
                    log.error(f"[stream] rank={self.rank}.w{worker_id} FAILED TO OPEN {repo_id}: {str(e)[:300]}")
                    failed.append(repo_id)
            if failed:
                log.error(f"[stream] rank={self.rank}.w{worker_id} MISSING SOURCES (0% contribution): {failed}")
            if not streams:
                log.error(f"[stream] rank={self.rank}.w{worker_id} NO SOURCES OPENED — worker is dead")
                return

            rng   = np.random.default_rng(shuffle_seed)
            iters = [iter(s[0]) for s in streams]
            probs = np.array([s[4] for s in streams], dtype=np.float64); probs /= probs.sum()
            consumed = np.zeros(len(iters), dtype=np.float64)     # tokens consumed per source
            if worker_id == 0 and self.rank == 0:
                log.info("[stream] target TOKEN mix (deficit-scheduled):")
                for s, p in zip(streams, probs):
                    log.info(f"  {s[2]:55s} {p*100:5.1f}%")

            buf: List[int] = []
            segs: List[List[int]] = []      # [source_idx, n_tokens] in buffer order
            pos = 0
            need = self.max_len * self.batch_size

            while not self._stop.is_set():
                # v7: deficit scheduler — the source furthest BEHIND its token quota goes next.
                deficit = (consumed + 1.0) / probs
                idx = int(np.argmin(deficit * rng.uniform(0.9, 1.1, size=len(iters))))
                _, text_field, repo_id, split, _w, config_name = streams[idx]
                try:
                    row = next(iters[idx])
                except StopIteration:
                    streams[idx][0] = _open_source_stream(
                        repo_id, split, shard_index, self.total_shards,
                        shuffle_buffer=self.cfg.shuffle_buffer, shuffle_seed=shuffle_seed + 1,
                        config_name=config_name, text_field=text_field)
                    iters[idx] = iter(streams[idx][0]); continue
                except Exception as e:
                    log.warning(f"[stream] rank={self.rank}.w{worker_id} read error on {repo_id}: {str(e)[:300]}")
                    consumed[idx] += need    # don't hammer a broken source
                    time.sleep(1.0); continue

                text = _extract_text(row, text_field, repo_id)
                del row
                if not text:
                    continue
                try:
                    ids = self.tok.encode(text, add_special_tokens=False).ids
                except Exception:
                    continue
                del text
                ids.append(self.eos_id)
                n = len(ids)
                buf.extend(ids)
                del ids
                segs.append([idx, n])
                consumed[idx] += n

                while len(buf) - pos >= need:
                    if self._stop.is_set():
                        return
                    # v7: tag the batch with the MAJORITY source of its tokens
                    counts: dict = {}
                    remaining = need
                    while remaining > 0 and segs:
                        s = segs[0]
                        take = min(s[1], remaining)
                        counts[s[0]] = counts.get(s[0], 0) + take
                        s[1] -= take; remaining -= take
                        if s[1] == 0:
                            segs.pop(0)
                    maj = max(counts, key=counts.get) if counts else idx
                    arr = np.array(buf[pos:pos + need], dtype=np.int64).reshape(self.batch_size, self.max_len)
                    pos += need
                    self._q.put((torch.from_numpy(arr), streams[maj][2]))
                if pos:                       # one O(n) compaction per document
                    del buf[:pos]; pos = 0
        except Exception as e:
            log.error(f"[stream] rank={self.rank}.w{worker_id} fetch loop crashed: {str(e)[:300]}")

    def __iter__(self) -> Iterator[Tuple[torch.Tensor, str]]:
        return self

    def __next__(self) -> Tuple[torch.Tensor, str]:
        while not self._stop.is_set():
            try:
                return self._q.get(timeout=60)
            except queue.Empty:
                log.warning(f"[stream] rank={self.rank} queue empty — waiting for data … ({host_mem_str()})")
        raise StopIteration

    def close(self):
        self._stop.set()
        try:
            while True: self._q.get_nowait()
        except queue.Empty:
            pass
        for t in self._workers:
            t.join(timeout=5)

def build_val_loader(cfg: Config) -> Optional[DataLoader]:
    if not HAS_DATASETS:
        return None
    tok = get_tokenizer(cfg)
    repo_id, split, text_field, _, config_name = max(cfg.dataset_sources, key=lambda s: s[3])
    try:
        ds = _open_source_stream(repo_id, split, 0, 1, shuffle_buffer=0,
                                 config_name=config_name, text_field=text_field)
    except Exception as e:
        log.warning(f"[val] could not open {repo_id}: {str(e)[:300]}")
        return None

    eos_id = _resolve_eos(tok)
    buf: List[int] = []
    rows = []
    n_val_seqs = 128
    try:
        for row in ds:
            text = _extract_text(row, text_field, repo_id)
            if not text:
                continue
            ids = tok.encode(text, add_special_tokens=False).ids
            ids.append(eos_id)
            buf.extend(ids)
            while len(buf) >= cfg.max_len:
                rows.append(np.array(buf[:cfg.max_len], dtype=np.int64))
                buf = buf[cfg.max_len:]
                if len(rows) >= n_val_seqs:
                    break
            if len(rows) >= n_val_seqs:
                break
    except Exception as e:
        log.warning(f"[val] stream error: {str(e)[:300]}")
    del ds

    if not rows:
        log.warning(f"[val] got no validation rows from {repo_id}")
        return None
    data = np.stack(rows, axis=0)

    class _ValDS(Dataset):
        def __len__(self):         return len(data)
        def __getitem__(self, i):  return torch.from_numpy(data[i])

    return DataLoader(_ValDS(), batch_size=min(cfg.micro_batch, 4),
                      shuffle=False, num_workers=0, pin_memory=True, drop_last=True)

# ─────────────────────────────────────────────────────────────────────────────
#  CHECKPOINTING — async on rank 0, heap-friendly
# ─────────────────────────────────────────────────────────────────────────────
_ckpt_thread: Optional[threading.Thread] = None

def _async_save_and_upload(payload: list, step, epoch, cfg_dict, loss):
    name  = f"g1_s{SESSION_ID:03d}_step{step:07d}"
    local = os.path.join(TEMP_CKPT_DIR, f"{name}.pt")
    try:
        t0 = time.time()
        model_sd, muon_sd, adamw_sd = payload.pop()
        torch.save({'model': model_sd, 'muon': muon_sd, 'adamw': adamw_sd,
                    'step': step, 'epoch': epoch, 'loss': loss, 'config': cfg_dict}, local)
        del model_sd, muon_sd, adamw_sd
        gc.collect()
        log.info(f"[ckpt-async] saved in {time.time()-t0:.1f}s, heap freed ({host_mem_str()}), uploading…")
        upload_to_hf(local, f"{name}.pt")
        log.info(f"[ckpt-async] step={step} uploaded ({time.time()-t0:.1f}s total)")
    except Exception as e:
        log.error(f"[ckpt-async] failed: {e}")
    finally:
        try: os.remove(local)
        except OSError: pass

def save_ckpt(model, muon, adamw, step, epoch, cfg, loss, is_master: bool):
    global _ckpt_thread
    if is_master and _ckpt_thread is not None and _ckpt_thread.is_alive():
        log.warning("[ckpt] previous checkpoint still in flight — waiting before gathering another")
        _ckpt_thread.join()
    opts = StateDictOptions(full_state_dict=True, cpu_offload=True)
    model_sd = get_model_state_dict(model, options=opts)
    try:    muon_sd = get_optimizer_state_dict(model, muon, options=opts)
    except Exception as e:
        log.warning(f"[ckpt] could not gather muon state: {e}"); muon_sd = {}
    try:    adamw_sd = get_optimizer_state_dict(model, adamw, options=opts)
    except Exception as e:
        log.warning(f"[ckpt] could not gather adamw state: {e}"); adamw_sd = {}
    if not is_master:
        del model_sd, muon_sd, adamw_sd
        return
    payload = [(model_sd, muon_sd, adamw_sd)]
    del model_sd, muon_sd, adamw_sd
    _ckpt_thread = threading.Thread(target=_async_save_and_upload,
                                    args=(payload, step, epoch, asdict(cfg), loss), daemon=True)
    _ckpt_thread.start()
    log.info(f"[ckpt] step={step} gathered ({host_mem_str()}), saving+uploading in background")

def _find_latest_ckpt():
    for sid in range(SESSION_ID, 0, -1):
        repo = f"{REPO_PREFIX}{sid:03d}"
        try:
            files = hf_api.list_repo_files(repo_id=repo, repo_type="model", token=HF_TOKEN)
        except Exception:
            continue
        ckpts = sorted([f for f in files if f.endswith(".pt") and "step" in f],
                       key=lambda x: int(x.split("step")[-1].split(".")[0]))
        if ckpts:
            return repo, ckpts[-1]
    return None, None

def load_ckpt(model, muon, adamw, cfg, device, is_master: bool):
    ckpt = None
    dl_dir = os.path.join(TEMP_CKPT_DIR, "resume_dl")
    meta = torch.zeros(3, dtype=torch.float64, device=device)
    loss_t = torch.zeros(1, dtype=torch.float64, device=device)
    mismatch_flag = torch.zeros(1, dtype=torch.int32, device=device)

    if is_master:
        repo, ckpt_name = _find_latest_ckpt()
        if repo is None:
            log.warning("[ckpt] no checkpoint in this or any earlier session repo — fresh start")
        else:
            try:
                shutil.rmtree(dl_dir, ignore_errors=True)
                path = hf_hub_download(repo, ckpt_name, local_dir=dl_dir, token=HF_TOKEN)
                ckpt = torch.load(path, map_location="cpu", weights_only=False, mmap=True)
                log.info(f"[ckpt] mapped {ckpt_name} ({host_mem_str()})")
                saved_cfg = ckpt.get('config', {})
                mismatches = [f"{k}: ckpt={saved_cfg[k]} vs live={v}"
                              for k, v in cfg.arch_fingerprint().items()
                              if k in saved_cfg and saved_cfg[k] != v]
                if mismatches:
                    log.error("[ckpt] ARCHITECTURE MISMATCH — refusing to resume: " + "; ".join(mismatches))
                    mismatch_flag[0] = 1; ckpt = None
                else:
                    meta[0] = 1.0; meta[1] = float(ckpt['step']); meta[2] = float(ckpt['epoch'])
                    loss_t[0] = float(ckpt['loss'])
                    if repo != HF_MODEL_REPO:
                        log.info(f"[ckpt] resuming from an EARLIER session's repo: {repo}/{ckpt_name}")
            except Exception as e:
                log.error(f"[ckpt] FOUND {repo}/{ckpt_name} BUT COULD NOT LOAD IT: {e} — fresh start")
                ckpt = None

    if dist_ready():
        dist.broadcast(meta, src=0); dist.broadcast(loss_t, src=0); dist.broadcast(mismatch_flag, src=0)
    if mismatch_flag.item() > 0:
        raise RuntimeError("Checkpoint architecture mismatch — see rank 0 log.")
    if meta[0].item() < 0.5:
        return 0, 0, float('inf')

    opts = StateDictOptions(full_state_dict=True, broadcast_from_rank0=True)
    set_model_state_dict(model, model_state_dict=(ckpt['model'] if is_master else {}), options=opts)
    try:
        set_optimizer_state_dict(model, muon, optim_state_dict=(ckpt['muon'] if is_master else {}), options=opts)
    except Exception as e:
        log.warning(f"[ckpt] muon state not restored: {e}")
    try:
        set_optimizer_state_dict(model, adamw, optim_state_dict=(ckpt['adamw'] if is_master else {}), options=opts)
    except Exception as e:
        log.warning(f"[ckpt] adamw state not restored: {e}")

    step, epoch, loss = int(meta[1].item()), int(meta[2].item()), float(loss_t[0].item())
    del ckpt
    gc.collect()
    if is_master:
        shutil.rmtree(dl_dir, ignore_errors=True)
        log.info(f"[ckpt] resumed step={step} loss={loss:.4f} ✅ | {host_mem_str()}")
    return step, epoch, loss

def save_final(model, cfg, step, epoch, loss, is_master: bool):
    opts = StateDictOptions(full_state_dict=True, cpu_offload=True)
    model_sd = get_model_state_dict(model, options=opts)
    if not is_master:
        return
    name  = f"g1_final_s{SESSION_ID:03d}_step{step:07d}"
    mname = f"{name}.safetensors" if HAS_ST else f"{name}.pt"
    mpath = os.path.join(TEMP_CKPT_DIR, mname)
    cpath = os.path.join(TEMP_CKPT_DIR, f"{name}_config.json")
    if HAS_ST:
        st_save({k: v.contiguous() for k, v in model_sd.items()}, mpath)
    else:
        torch.save(model_sd, mpath)
    del model_sd; gc.collect()
    with open(cpath, 'w') as f:
        json.dump({**asdict(cfg), 'step': step, 'epoch': epoch,
                   'loss': loss, 'arch': 'Smilyai-G1-20B'}, f, indent=2)
    upload_to_hf(mpath, mname); upload_to_hf(cpath, os.path.basename(cpath))
    for p in (mpath, cpath):
        try: os.remove(p)
        except OSError: pass

@torch.no_grad()
def validate(model, val_loader, device, cfg, n=100):
    if val_loader is None:
        return float('nan')
    was_training = model.training
    model.eval(); losses = []
    for i, batch in enumerate(val_loader):
        if i >= n: break
        batch = batch.to(device, non_blocking=True)
        with torch.amp.autocast('cuda', dtype=cfg.dtype):
            _, loss = model(batch, batch)
        lm = getattr(model, '_last_lm_loss', None)
        lm = lm if lm is not None else loss
        if lm is not None and torch.isfinite(lm):
            losses.append(lm.item())
    if was_training: model.train()
    local = float(np.mean(losses)) if losses else float('nan')
    if math.isnan(local):
        return local
    return distributed_mean(local, device)

# ─────────────────────────────────────────────────────────────────────────────
#  TRAIN
# ─────────────────────────────────────────────────────────────────────────────
def train():
    if not torch.cuda.is_available():
        raise RuntimeError("this script requires CUDA GPUs")

    local_rank = int(os.environ.get("LOCAL_RANK", "0"))
    rank       = int(os.environ.get("RANK", "0"))
    world_size = int(os.environ.get("WORLD_SIZE", "1"))
    torch.cuda.set_device(local_rank)
    device = torch.device("cuda", local_rank)
    if world_size > 1 and not dist_ready():
        dist.init_process_group(backend="nccl", init_method="env://", device_id=device,
                                timeout=_dt.timedelta(minutes=20))
    is_master = (rank == 0)
    if not is_master:
        log.setLevel(logging.WARNING)

    torch.manual_seed(42 + rank); np.random.seed(42 + rank); random.seed(42 + rank)

    log.info(f"[env] rank={rank}/{world_size} device={device} | "
             f"GPU={torch.cuda.get_device_name(local_rank)} | VRAM={vram_total_gb():.0f}GB")
    log.info(f"[env] {host_mem_str()} | work_dir={_WORK}")
    start_mem_watchdog(rank)

    if is_master:
        ensure_repo()
        session_banner()
        _bootstrap_from_hub(METRICS_FILE, os.path.basename(METRICS_FILE))
        _bootstrap_from_hub(SAMPLES_FILE, "samples.md")
        _bootstrap_from_hub(SUMMARY_FILE, "summary.jsonl")
    if dist_ready():
        dist.barrier()

    cfg = Config()

    if local_rank == 0:
        try: get_tokenizer(cfg)
        except Exception as e: log.warning(f"[tokenizer] pre-load failed, will retry lazily: {e}")
    if dist_ready():
        dist.barrier()
    if local_rank != 0:
        try: get_tokenizer(cfg)
        except Exception as e: log.warning(f"[tokenizer] pre-load failed, will retry lazily: {e}")

    _prev_dtype = torch.get_default_dtype()
    torch.set_default_dtype(cfg.dtype)
    try:
        model = SmilyaiG1(cfg)
    finally:
        torch.set_default_dtype(_prev_dtype)
    model = model.to(cfg.dtype).to(device)
    gc.collect()
    model.init_rope(device)
    model.force_fp32_balancing_buffers()
    log.info(f"[env] model on GPU | {vram_str()} | {host_mem_str()}")

    model = apply_fp8(model, cfg, is_master)
    model = apply_fsdp(model, cfg)
    model = apply_compile(model, cfg, is_master)

    muon, adamw = build_optimizers(model, cfg, is_master)

    start_step, start_epoch, best_loss = load_ckpt(model, muon, adamw, cfg, device, is_master)
    if dist_ready():
        dist.barrier()

    last_val = float('nan')
    bs = cfg.micro_batch

    stream = LiveStreamingDataset(cfg, batch_size=bs, rank=rank, world_size=world_size)
    val_loader = build_val_loader(cfg)

    if is_master:
        log.info("=" * 70)
        log.info(f"Smilyai-G1 | {model.count_params()/1e9:.2f}B total params | "
                 f"Session {SESSION_ID} | FSDP2 world={world_size}")
        log.info(f"  micro_batch={bs}/GPU  grad_accum={cfg.grad_accum}  "
                 f"eff_batch={bs*cfg.grad_accum*world_size}  max_len={cfg.max_len}")
        log.info(f"  {cfg.tokens_per_step(bs, world_size)/1e6:.1f}M tok/step | "
                 f"{MAX_HOURS}h budget | streaming=True | compile={cfg.use_compile}")
        log.info(f"  Muon LR={cfg.muon_lr} | resumed at step={start_step} | {host_mem_str()}")
        log.info("  NOTE: train loss is only comparable within a session — the mix changed. Watch [val].")
        log.info("=" * 70)

    step, epoch = start_step, start_epoch
    losses, aux_losses = [], []
    src_window: collections.deque = collections.deque(maxlen=200)   # (source, lm_loss) per micro-batch, rank 0
    model.train(); model.zero_grad(set_to_none=True)
    t0 = time.time(); last_ckpt = time.time()

    try:
        record_sample(model, step, is_master)
    except Exception as e:
        log.warning(f"[sample] {e}")

    accum_n = 0
    while not distributed_should_stop(device, is_master, step, cfg.total_steps):
        try:
            batch, folder = next(stream)
        except StopIteration:
            log.warning(f"[stream] rank={rank} exhausted — sleeping 60s")
            time.sleep(60); continue
        except Exception as e:
            log.error(f"[data] rank={rank} {e}"); time.sleep(5); continue

        batch = batch.to(device, non_blocking=True)

        try:
            with torch.amp.autocast('cuda', dtype=cfg.dtype):
                _, loss = model(batch, batch)
                loss_s  = loss / cfg.grad_accum
            loss_s.backward()
            micro_ok = bool(torch.isfinite(loss))
            if micro_ok:
                lm_only  = getattr(model, '_last_lm_loss', loss)
                aux_only = getattr(model, '_last_aux_loss', None)
                lm_f = float(lm_only)
                losses.append(lm_f)
                aux_losses.append(float(aux_only) if aux_only is not None else 0.0)
                src_window.append((folder, lm_f))
            del loss, loss_s
        except torch.OutOfMemoryError:
            log.error(f"[oom] rank={rank} step={step} CUDA OOM | {vram_str()} | {host_mem_str()}")
            log.error(torch.cuda.memory_summary(abbreviated=True))
            raise

        if not all_ok(micro_ok, device):
            if is_master: log.error(f"[skip] step={step} non-finite loss on >=1 rank")
            model.zero_grad(set_to_none=True); accum_n = 0
            continue

        accum_n += 1
        if accum_n < cfg.grad_accum:
            continue

        mlr = cosine_lr(step, cfg.warmup, cfg.total_steps, cfg.muon_lr, cfg.muon_min_lr)
        alr = cosine_lr(step, cfg.warmup, cfg.total_steps, cfg.adamw_lr, cfg.adamw_min_lr)
        for g in muon.param_groups:  g['lr'] = mlr
        for g in adamw.param_groups: g['lr'] = alr

        norm = torch.nn.utils.clip_grad_norm_(model.parameters(), cfg.grad_clip)
        if isinstance(norm, DTensor):
            norm = norm.full_tensor()
        if not torch.isfinite(norm):
            if is_master: log.error("[nan] grad-norm non-finite — skipping step")
            model.zero_grad(set_to_none=True); accum_n = 0; continue

        muon.step(); adamw.step(); model.zero_grad(set_to_none=True)

        step += 1
        model.set_step(step)
        accum_n = 0
        if len(losses) > 500: losses = losses[-500:]
        if len(aux_losses) > 500: aux_losses = aux_losses[-500:]

        if step % cfg.bias_update_every == 0:
            model.update_expert_bias()

        if step % cfg.log_every == 0 and losses:
            avg     = distributed_mean(float(np.mean(losses[-50:])), device)
            avg_aux = distributed_mean(float(np.mean(aux_losses[-50:])), device) if aux_losses else 0.0
            _step_clock.append((step, time.time()))
            if len(_step_clock) > 300: _step_clock.pop(0)
            sph = _real_steps_per_hour()
            tps = (sph * cfg.tokens_per_step(bs, world_size) / 3600) if sph else \
                  (max(step - start_step, 1) * cfg.tokens_per_step(bs, world_size) / max(time.time() - t0, 1))
            if is_master:
                # per-source breakdown of the last 200 micro-batches on rank 0
                by_src: dict = collections.defaultdict(list)
                for s, l in src_window: by_src[s].append(l)
                n_tot = max(len(src_window), 1)
                per_src = " ".join(f"{_short_src(s)}:{np.mean(v):.2f}({100*len(v)/n_tot:.0f}%)"
                                   for s, v in sorted(by_src.items(), key=lambda kv: -len(kv[1])))
                log_metrics(step=step, loss=avg, aux=avg_aux, tok_s=tps, folder=folder,
                            per_source={s: [float(np.mean(v)), len(v) / n_tot] for s, v in by_src.items()})
                sl = sessions_left(step, cfg.total_steps)
                suffix = f" | ~{sl} more sessions" if sl is not None else ""
                log.info(f"step {step:06d} | ep {epoch+1} | lm {avg:.4f} | aux {avg_aux:.4f} | "
                         f"ppl {math.exp(min(avg,20)):.1f} | {tps/1e3:.1f}K tok/s | "
                         f"{vram_str()} | {remaining_h():.1f}h left{suffix}")
                log.info(f"  [mix] {per_src}")
                if step % (cfg.log_every * 10) == 0:
                    log.info(f"  [{host_mem_str()}]")

        if step % cfg.eval_every == 0:
            vl = validate(model, val_loader, device, cfg)
            if is_master and vl == vl:
                marker = " *NEW BEST*" if vl < best_loss else ""
                if vl < best_loss: best_loss = vl
                last_val = vl
                log_metrics(step=step, val_loss=vl)
                log.info(f"  [val] loss={vl:.4f} ppl={math.exp(min(vl,20)):.1f}{marker}")
                dead, total_dead, capped, total_capped = model.dead_expert_report()
                total_experts = cfg.n_experts * cfg.n_layers
                if total_dead > 0:
                    log.info(f"  [experts] dead={total_dead}/{total_experts}")
                else:
                    log.info(f"  [experts] all {total_experts} experts alive ✅")
                if total_capped > 0:
                    log.info(f"  [experts] bias-capped={total_capped}/{total_experts}")
            try:
                record_sample(model, step, is_master)
            except Exception as e:
                log.warning(f"[sample] {e}")
            if dist_ready():
                dist.barrier()

        local_due = (step % cfg.ckpt_every == 0) or ((time.time() - last_ckpt) > 1800)
        if broadcast_flag(local_due if is_master else False, device):
            save_ckpt(model, muon, adamw, step, epoch, cfg, losses[-1] if losses else 0.0, is_master)
            if is_master:
                update_progress_md(cfg, step, epoch,
                                   float(np.mean(losses[-50:])) if losses else None, last_val)
                make_loss_chart(); upload_metrics()
            last_ckpt = time.time()

    log.info(f"[rank {rank}] DONE training loop")
    stream.close()

    if is_master and _ckpt_thread is not None and _ckpt_thread.is_alive():
        log.info("[ckpt] waiting for final in-flight checkpoint upload to finish…")
        _ckpt_thread.join()

    vm = validate(model, val_loader, device, cfg, n=300)
    if vm != vm:
        vm = losses[-1] if losses else 0.0
    save_final(model, cfg, step, epoch, vm, is_master)
    if is_master:
        try:
            update_progress_md(cfg, step, epoch, float(np.mean(losses[-50:])) if losses else None, vm)
            make_loss_chart(); upload_metrics()
        except Exception as e:
            log.warning(f"[motiv] final refresh failed: {e}")
        log.info(f"Steps={step:,} | Epochs={epoch+1} | Time={elapsed_h():.2f}h | Final val={vm:.4f}")

    if dist_ready():
        dist.barrier()
        dist.destroy_process_group()


def _spawn_worker(local_rank: int, world_size: int):
    os.environ["LOCAL_RANK"] = str(local_rank)
    os.environ["RANK"]       = str(local_rank)
    os.environ["WORLD_SIZE"] = str(world_size)
    train()


def launch():
    if "RANK" in os.environ and "WORLD_SIZE" in os.environ:
        train()
        return
    world_size = torch.cuda.device_count()
    if world_size < 1:
        raise RuntimeError("No CUDA GPUs are visible")
    expected_world = int(os.environ.get("EXPECTED_WORLD_SIZE", str(world_size)))
    if world_size != expected_world:
        raise RuntimeError(f"Expected {expected_world} visible GPUs, found {world_size}; "
                           "refusing to run with the wrong allocation")
    os.environ.setdefault("MASTER_ADDR", "127.0.0.1")
    os.environ.setdefault("MASTER_PORT", "29500")
    os.environ.setdefault("TORCH_NCCL_ASYNC_ERROR_HANDLING", "1")
    mp.spawn(_spawn_worker, args=(world_size,), nprocs=world_size, join=True)


if __name__ == "__main__":
    launch()