stash: changes up to the first deploy test of the agressive run

.gitignore

@@ -2,6 +2,7 @@
 data/
 outputs/
 artifacts/
+.airfrans_resume/
 
 # Python
 .venv/

configs/aggressive_smoke.toml

@@ -0,0 +1,46 @@
+[run]
+name = "aggressive_smoke"
+seed = 20260723
+artifact_dir = "artifacts/current_run/training_runs"
+
+[data]
+root = "data/processed/full"
+train_cases = 45
+val_cases = 3
+test_cases = 2
+points_per_case = 999999999
+batch_size = 4096
+
+[model]
+type = "film_fourier_mlp"
+hidden_width = 4096
+depth = 12
+activation = "gelu"
+coordinate_features = ["x", "y", "sdf"]
+fourier_scales = [1.0, 2.0, 4.0, 8.0, 16.0, 32.0]
+condition_width = 1024
+condition_depth = 3
+condition_dim = 512
+
+[optim]
+lr = 0.0001
+weight_decay = 0.0001
+steps = 5000
+log_interval = 500
+
+[device]
+type = "cuda"
+allow_cpu_fallback = false
+benchmark_kernels = true
+
+[loss]
+type = "normalized_mse"
+
+[precision]
+dtype = "bf16"
+
+[checkpoint]
+interval_seconds = 1800
+
+[stability]
+max_grad_norm = 1.0

configs/aggressive_smoke_local.toml

@@ -0,0 +1,46 @@
+[run]
+name = "aggressive_smoke_local"
+seed = 20260723
+artifact_dir = "artifacts/runs"
+
+[data]
+root = "artifacts/processed_preflight_one"
+train_cases = 1
+val_cases = 0
+test_cases = 0
+points_per_case = 8192
+batch_size = 512
+
+[model]
+type = "film_fourier_mlp"
+hidden_width = 256
+depth = 4
+activation = "gelu"
+coordinate_features = ["x", "y", "sdf"]
+fourier_scales = [1.0, 2.0, 4.0, 8.0]
+condition_width = 128
+condition_depth = 2
+condition_dim = 128
+
+[optim]
+lr = 0.0003
+weight_decay = 0.0001
+steps = 20
+log_interval = 10
+
+[device]
+type = "cuda"
+allow_cpu_fallback = false
+benchmark_kernels = true
+
+[loss]
+type = "normalized_mse"
+
+[precision]
+dtype = "bf16"
+
+[checkpoint]
+interval_seconds = 0
+
+[stability]
+max_grad_norm = 1.0

configs/remote_smoke.toml

@@ -1,19 +1,19 @@
 [run]
-name = "airfrans-smoke"
-timeout_minutes = 45
+name = "airfrans-aggressive-smoke"
+timeout_minutes = 360
 local_artifact_dir = "artifacts/remote_runs"
 max_attempts = 2
 
 [provider]
 kind = "vastai"
-disk_gb = 64
-max_price_per_hour = 0.60
+disk_gb = 128
+max_price_per_hour = 0.80
 image = "vastai/base:0.0.2"
 
 [provider.gpu]
 name = "RTX 4090"
 count = 1
-min_vram_gb = 16
+min_vram_gb = 20
 
 [selection]
 min_reliability = 0.95
@@ -45,12 +45,12 @@ uv run --no-dev python -c "import torch; assert torch.cuda.is_available(); print
 
 [data]
 validation_command = """
-uv run --no-dev python -c "from pathlib import Path; files=sorted(Path('data/processed/minimal').glob('*.npz')); assert len(files) >= 6; print(f'processed_minimal_cases={len(files)}')"
+uv run --no-dev python -c "from pathlib import Path; files=sorted(Path('data/processed/full').glob('*.npz')); assert len(files) >= 50; print(f'processed_full_cases={len(files)}')"
 """
 
 [job]
 command = """
-uv run --no-dev remote-run smoke-train configs/remote_mlp_tiny.toml --artifact-dir artifacts/current_run --run-id "$AIRFRANS_REMOTE_RUN_ID"
+uv run --no-dev remote-run smoke-train configs/aggressive_smoke.toml --artifact-dir artifacts/current_run --run-id "$AIRFRANS_REMOTE_RUN_ID"
 """
 artifact_dir = "artifacts/current_run"
 heartbeat_file = "artifacts/current_run/heartbeat.json"
@@ -59,9 +59,17 @@ metrics_file = "artifacts/current_run/metrics.jsonl"
 [artifacts]
 mode = "rsync"
 required = [
-  "final_metrics.json",
+  "config.toml",
   "metrics.jsonl",
-  "checkpoint.pt",
+  "latest_metrics.json",
+  "heartbeat.json",
+  "checkpoint_latest.pt",
+  "checkpoint_best.pt",
+  "checkpoint_final.pt",
+  "final_metrics.json",
+  "split_manifest.json",
+  "data_manifest.json",
+  "normalization.json",
   "run_manifest.json",
   "environment_manifest.json",
   "artifact_manifest.json",

pyproject.toml

@@ -27,4 +27,5 @@ dev = [
     "nbclient>=0.10.2",
     "nbformat>=5.10.4",
     "skypilot[vast]>=0.12.3.post1",
+    "pytest>=9.1.1",
 ]

src/airfrans_frontier/cli.py

@@ -17,8 +17,16 @@ def build_parser() -> argparse.ArgumentParser:
     inspect_raw.add_argument("--sample-limit", type=int, default=5)
     inspect_raw.set_defaults(command="inspect-raw")
 
+    process_raw = subparsers.add_parser("process-raw", help="convert raw OpenFOAM cases into training tensors")
+    process_raw.add_argument("--raw-dir", default=str(DEFAULT_RAW_DATA_DIR))
+    process_raw.add_argument("--output-dir", default="data/processed/full")
+    process_raw.add_argument("--limit", type=int)
+    process_raw.add_argument("--force", action="store_true")
+    process_raw.set_defaults(command="process-raw")
+
     train = subparsers.add_parser("train", help="train a configured baseline model")
     train.add_argument("config", help="path to a training config TOML file")
+    train.add_argument("--resume", help="path to checkpoint_latest.pt to resume from")
     train.set_defaults(command="train")
 
     return parser
@@ -44,6 +52,28 @@ def main(argv: list[str] | None = None) -> int:
         print(format_raw_inspection(report, sample_limit=args.sample_limit))
         return 0 if report.matches_manifest else 1
 
+    if args.command == "process-raw":
+        if args.limit is not None and args.limit <= 0:
+            print("error: --limit must be positive", file=sys.stderr)
+            return 1
+        from airfrans_frontier.raw.process import process_raw_dataset
+
+        try:
+            result = process_raw_dataset(
+                resolve_path(args.raw_dir),
+                resolve_path(args.output_dir),
+                limit=args.limit,
+                force=args.force,
+            )
+        except (FileNotFoundError, NotADirectoryError, ValueError) as exc:
+            print(f"error: {exc}", file=sys.stderr)
+            return 1
+        print(f"output_dir: {result.output_dir}")
+        print(f"case_count: {result.case_count}")
+        print(f"total_points: {result.total_points}")
+        print(f"manifest: {result.manifest_path}")
+        return 0
+
     if args.command == "train":
         from airfrans_frontier.runtime import remove_pythonpath_entries
 
@@ -51,7 +81,7 @@ def main(argv: list[str] | None = None) -> int:
         from airfrans_frontier.training.loop import train_from_config_path
 
         try:
-            result = train_from_config_path(resolve_path(args.config))
+            result = train_from_config_path(resolve_path(args.config), resume_path=resolve_path(args.resume) if args.resume else None)
         except (FileNotFoundError, NotADirectoryError, ValueError, RuntimeError) as exc:
             print(f"error: {exc}", file=sys.stderr)
             return 1

src/airfrans_frontier/models/__init__.py

@@ -1,5 +1,6 @@
 """Baseline model definitions."""
 
+from airfrans_frontier.models.film import FourierFiLMMLP
 from airfrans_frontier.models.mlp import PointwiseMLP
 
-__all__ = ["PointwiseMLP"]
+__all__ = ["FourierFiLMMLP", "PointwiseMLP"]

src/airfrans_frontier/models/film.py

@@ -0,0 +1,144 @@
+from __future__ import annotations
+
+import math
+from collections.abc import Sequence
+
+import torch
+from torch import nn
+
+
+class FourierFiLMMLP(nn.Module):
+    """Coordinate trunk modulated by per-simulation condition features.
+
+    `feature_names` identifies coordinate columns. Every non-coordinate column is
+    treated as a condition feature; repeated per-point condition rows are
+    collapsed inside `forward` so FiLM parameters are generated once per unique
+    simulation condition in a batch.
+    """
+
+    def __init__(
+        self,
+        *,
+        feature_names: Sequence[str],
+        output_dim: int,
+        coordinate_features: Sequence[str] = ("x", "y", "sdf"),
+        fourier_scales: Sequence[float] = (1.0, 2.0, 4.0, 8.0, 16.0),
+        trunk_width: int = 1024,
+        trunk_depth: int = 8,
+        condition_width: int = 512,
+        condition_depth: int = 3,
+        condition_dim: int = 512,
+        activation: str = "gelu",
+    ) -> None:
+        super().__init__()
+        if output_dim <= 0:
+            raise ValueError("output_dim must be positive")
+        if trunk_width <= 0:
+            raise ValueError("trunk_width must be positive")
+        if trunk_depth <= 0:
+            raise ValueError("trunk_depth must be positive")
+        if condition_width <= 0:
+            raise ValueError("condition_width must be positive")
+        if condition_depth <= 0:
+            raise ValueError("condition_depth must be positive")
+        if condition_dim <= 0:
+            raise ValueError("condition_dim must be positive")
+
+        names = tuple(feature_names)
+        if len(set(names)) != len(names):
+            raise ValueError("feature_names must be unique")
+        coordinate_names = tuple(coordinate_features)
+        missing = [name for name in coordinate_names if name not in names]
+        if missing:
+            raise ValueError(f"Missing coordinate features for FourierFiLMMLP: {missing}")
+        condition_names = tuple(name for name in names if name not in set(coordinate_names))
+        if not condition_names:
+            raise ValueError("FourierFiLMMLP requires at least one condition feature")
+
+        self.feature_names = names
+        self.coordinate_names = coordinate_names
+        self.condition_names = condition_names
+        self.register_buffer("coordinate_indices", torch.tensor([names.index(name) for name in coordinate_names], dtype=torch.long), persistent=False)
+        self.register_buffer("condition_indices", torch.tensor([names.index(name) for name in condition_names], dtype=torch.long), persistent=False)
+        self.register_buffer("fourier_scales", torch.tensor(tuple(float(scale) for scale in fourier_scales), dtype=torch.float32), persistent=False)
+
+        coordinate_dim = len(coordinate_names)
+        fourier_dim = coordinate_dim * (1 + 2 * len(tuple(fourier_scales)))
+        self.input = nn.Linear(fourier_dim, trunk_width)
+        self.condition_encoder = _mlp(
+            input_dim=len(condition_names),
+            hidden_width=condition_width,
+            output_dim=condition_dim,
+            depth=condition_depth,
+            activation=activation,
+        )
+        self.blocks = nn.ModuleList(
+            _FiLMResidualBlock(width=trunk_width, condition_dim=condition_dim, activation=activation)
+            for _ in range(trunk_depth)
+        )
+        self.output_norm = nn.LayerNorm(trunk_width)
+        self.output = nn.Linear(trunk_width, output_dim)
+        self.activation = _activation(activation)
+
+    def forward(self, features: torch.Tensor) -> torch.Tensor:
+        coordinates = features.index_select(dim=1, index=self.coordinate_indices)
+        conditions = features.index_select(dim=1, index=self.condition_indices)
+        coordinate_embedding = _fourier_features(coordinates, self.fourier_scales)
+        hidden = self.input(coordinate_embedding)
+
+        unique_conditions, inverse = torch.unique(conditions, dim=0, return_inverse=True)
+        condition_embedding = self.condition_encoder(unique_conditions)
+        for block in self.blocks:
+            hidden = block(hidden, condition_embedding, inverse)
+        hidden = self.output_norm(hidden)
+        hidden = self.activation(hidden)
+        return self.output(hidden)
+
+
+class _FiLMResidualBlock(nn.Module):
+    def __init__(self, *, width: int, condition_dim: int, activation: str) -> None:
+        super().__init__()
+        self.norm = nn.LayerNorm(width)
+        self.linear = nn.Linear(width, width)
+        self.film = nn.Linear(condition_dim, 2 * width)
+        self.activation = _activation(activation)
+
+    def forward(self, hidden: torch.Tensor, condition_embedding: torch.Tensor, inverse: torch.Tensor) -> torch.Tensor:
+        gamma_beta = self.film(condition_embedding).index_select(dim=0, index=inverse)
+        gamma, beta = gamma_beta.chunk(2, dim=1)
+        update = self.linear(self.activation(self.norm(hidden)))
+        update = update * (1.0 + gamma) + beta
+        return hidden + update
+
+
+def _fourier_features(coordinates: torch.Tensor, scales: torch.Tensor) -> torch.Tensor:
+    if scales.numel() == 0:
+        return coordinates
+    phases = coordinates.unsqueeze(-1) * scales.to(device=coordinates.device, dtype=coordinates.dtype) * math.pi
+    encoded = torch.cat((coordinates, torch.sin(phases).flatten(1), torch.cos(phases).flatten(1)), dim=1)
+    return encoded
+
+
+def _mlp(*, input_dim: int, hidden_width: int, output_dim: int, depth: int, activation: str) -> nn.Sequential:
+    layers: list[nn.Module] = []
+    current_dim = input_dim
+    for _ in range(depth - 1):
+        layers.append(nn.Linear(current_dim, hidden_width))
+        layers.append(_activation(activation))
+        current_dim = hidden_width
+    layers.append(nn.Linear(current_dim, output_dim))
+    layers.append(_activation(activation))
+    return nn.Sequential(*layers)
+
+
+def _activation(name: str) -> nn.Module:
+    normalized = name.lower()
+    if normalized == "gelu":
+        return nn.GELU()
+    if normalized == "relu":
+        return nn.ReLU()
+    if normalized == "silu":
+        return nn.SiLU()
+    if normalized == "tanh":
+        return nn.Tanh()
+    raise ValueError(f"Unsupported activation: {name}")

src/airfrans_frontier/raw/process.py

@@ -0,0 +1,414 @@
+from __future__ import annotations
+
+import gzip
+import json
+import math
+import re
+import time
+from collections.abc import Iterator
+from dataclasses import dataclass, asdict
+from pathlib import Path
+from typing import TextIO
+
+import numpy as np
+from numpy.typing import NDArray
+
+from airfrans_frontier.paths import DEFAULT_RAW_DATA_DIR
+
+FloatArray = NDArray[np.float32]
+INT_RE = re.compile(r"-?\d+")
+FLOAT_RE = re.compile(r"[-+]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][-+]?\d+)?")
+SIM_RE = re.compile(
+    r"^airFoil2D_(?P<turbulence>[^_]+)_"
+    r"(?P<u_inf>-?\d+(?:\.\d+)?)_"
+    r"(?P<alpha>-?\d+(?:\.\d+)?)_"
+    r"(?P<params>.+)$"
+)
+FEATURE_NAMES = np.array(
+    [
+        "x",
+        "y",
+        "sdf",
+        "u_inf",
+        "log_re",
+        "aoa_deg",
+        "aoa_sin",
+        "aoa_cos",
+        "naca_param_0",
+        "naca_param_1",
+        "naca_param_2",
+        "naca_param_3",
+        "naca_param_0_mask",
+        "naca_param_1_mask",
+        "naca_param_2_mask",
+        "naca_param_3_mask",
+    ],
+    dtype="U32",
+)
+TARGET_NAMES = np.array(["velocity_x", "velocity_y", "pressure", "turbulent_viscosity"], dtype="U32")
+
+
+@dataclass(frozen=True)
+class ProcessingResult:
+    output_dir: Path
+    case_count: int
+    total_points: int
+    manifest_path: Path
+
+
+@dataclass(frozen=True)
+class CaseMetadata:
+    case_id: str
+    turbulence: str
+    u_inf: float
+    alpha_deg: float
+    naca_params: tuple[float, ...]
+    nu: float
+    reynolds: float
+    timestep: str
+
+
+def process_raw_dataset(
+    raw_dir: str | Path = DEFAULT_RAW_DATA_DIR,
+    output_dir: str | Path = "data/processed/full",
+    *,
+    limit: int | None = None,
+    force: bool = False,
+) -> ProcessingResult:
+    raw_root = Path(raw_dir).expanduser()
+    if not raw_root.is_dir():
+        raise NotADirectoryError(f"Raw AirfRANS directory not found: {raw_root}")
+    out_root = Path(output_dir).expanduser()
+    out_root.mkdir(parents=True, exist_ok=True)
+
+    case_dirs = sorted(path for path in raw_root.iterdir() if path.is_dir() and path.name.startswith("airFoil2D_"))
+    if limit is not None:
+        case_dirs = case_dirs[:limit]
+    if not case_dirs:
+        raise ValueError(f"No raw AirfRANS case directories found under: {raw_root}")
+
+    records: list[dict[str, object]] = []
+    started = time.perf_counter()
+    total_points = 0
+    for case_dir in case_dirs:
+        target_path = out_root / f"{case_dir.name}.npz"
+        if target_path.exists() and not force:
+            with np.load(target_path, allow_pickle=False) as npz:
+                points = int(npz["features"].shape[0])
+            records.append({"case_id": case_dir.name, "path": str(target_path), "points": points, "skipped_existing": True})
+            total_points += points
+            continue
+        metadata, features, targets = process_raw_case(case_dir)
+        _atomic_save_npz(
+            target_path,
+            features=features,
+            targets=targets,
+            feature_names=FEATURE_NAMES,
+            target_names=TARGET_NAMES,
+            metadata=json.dumps(_metadata_json(metadata), sort_keys=True),
+        )
+        points = int(features.shape[0])
+        total_points += points
+        records.append({"case_id": case_dir.name, "path": str(target_path), "points": points, "metadata": _metadata_json(metadata)})
+
+    manifest = {
+        "raw_dir": str(raw_root),
+        "output_dir": str(out_root),
+        "case_count": len(records),
+        "total_points": total_points,
+        "feature_names": FEATURE_NAMES.tolist(),
+        "target_names": TARGET_NAMES.tolist(),
+        "elapsed_seconds": time.perf_counter() - started,
+        "cases": records,
+    }
+    manifest_path = out_root / "manifest.json"
+    manifest_path.write_text(json.dumps(manifest, indent=2, sort_keys=True) + "\n")
+    return ProcessingResult(output_dir=out_root, case_count=len(records), total_points=total_points, manifest_path=manifest_path)
+
+
+def process_raw_case(case_dir: str | Path) -> tuple[CaseMetadata, FloatArray, FloatArray]:
+    root = Path(case_dir).expanduser()
+    if not root.is_dir():
+        raise NotADirectoryError(f"Raw case directory not found: {root}")
+    timestep = _latest_timestep(root)
+    metadata = _case_metadata(root, timestep=timestep)
+
+    points = _parse_vector_list(root / "constant" / "polyMesh" / "points.gz", columns=3).astype(np.float64, copy=False)
+    owner = _parse_label_list(root / "constant" / "polyMesh" / "owner.gz")
+    neighbour = _parse_label_list(root / "constant" / "polyMesh" / "neighbour.gz")
+    U = _parse_vector_list(root / timestep / "U.gz", columns=3)
+    p = _parse_scalar_list(root / timestep / "p.gz")
+    nut = _parse_scalar_list(_field_path(root / timestep, "turbulenceProperties:nut.gz", "nut.gz"))
+    n_cells = int(U.shape[0])
+    if p.shape[0] != n_cells or nut.shape[0] != n_cells:
+        raise ValueError(f"Field row count mismatch in {root}")
+
+    centers, airfoil_centers = _cell_centers_and_airfoil(points, owner, neighbour, root / "constant" / "polyMesh")
+    if centers.shape[0] != n_cells:
+        raise ValueError(f"Mesh cell count mismatch in {root}: centers={centers.shape[0]} field={n_cells}")
+    sdf = _distance_to_airfoil(centers, airfoil_centers)
+    condition = _condition_features(metadata, n_cells)
+    features = np.concatenate((centers.astype(np.float32), sdf[:, None], condition), axis=1)
+    targets = np.stack((U[:, 0], U[:, 1], p, nut), axis=1).astype(np.float32, copy=False)
+    _validate_finite(root, features, targets)
+    return metadata, features.astype(np.float32, copy=False), targets
+
+
+def _metadata_json(metadata: CaseMetadata) -> dict[str, object]:
+    payload = asdict(metadata)
+    payload["naca_params"] = list(metadata.naca_params)
+    return payload
+
+
+def _latest_timestep(root: Path) -> str:
+    candidates: list[tuple[float, str]] = []
+    for path in root.iterdir():
+        if not path.is_dir():
+            continue
+        try:
+            value = float(path.name)
+        except ValueError:
+            continue
+        if (path / "U.gz").is_file() and (path / "p.gz").is_file():
+            candidates.append((value, path.name))
+    if not candidates:
+        raise ValueError(f"No numeric timestep with U.gz/p.gz found in {root}")
+    return max(candidates)[1]
+
+
+def _case_metadata(root: Path, *, timestep: str) -> CaseMetadata:
+    match = SIM_RE.match(root.name)
+    if match is None:
+        raise ValueError(f"Unexpected AirfRANS case name: {root.name}")
+    params = tuple(float(value) for value in match.group("params").split("_"))
+    u_inf = float(match.group("u_inf"))
+    alpha = float(match.group("alpha"))
+    nu = _transport_nu(root / "constant" / "transportProperties")
+    return CaseMetadata(
+        case_id=root.name,
+        turbulence=match.group("turbulence"),
+        u_inf=u_inf,
+        alpha_deg=alpha,
+        naca_params=params,
+        nu=nu,
+        reynolds=u_inf / nu,
+        timestep=timestep,
+    )
+
+
+def _transport_nu(path: Path) -> float:
+    text = _read_text(path, max_bytes=20_000)
+    match = re.search(r"^\s*nu\s+([^;]+);", text, flags=re.MULTILINE)
+    if match is None:
+        raise ValueError(f"Could not parse nu from {path}")
+    values = FLOAT_RE.findall(match.group(1))
+    if not values:
+        raise ValueError(f"Could not parse numeric nu from {path}")
+    return float(values[-1])
+
+
+def _condition_features(metadata: CaseMetadata, n_cells: int) -> FloatArray:
+    params = np.zeros(4, dtype=np.float32)
+    mask = np.zeros(4, dtype=np.float32)
+    for index, value in enumerate(metadata.naca_params[:4]):
+        params[index] = float(value)
+        mask[index] = 1.0
+    alpha_rad = math.radians(metadata.alpha_deg)
+    row = np.array(
+        [
+            metadata.u_inf,
+            math.log(metadata.reynolds),
+            metadata.alpha_deg,
+            math.sin(alpha_rad),
+            math.cos(alpha_rad),
+            *params.tolist(),
+            *mask.tolist(),
+        ],
+        dtype=np.float32,
+    )
+    return np.repeat(row[None, :], n_cells, axis=0)
+
+
+def _cell_centers_and_airfoil(
+    points: NDArray[np.float64],
+    owner: NDArray[np.int64],
+    neighbour: NDArray[np.int64],
+    poly_mesh: Path,
+) -> tuple[FloatArray, FloatArray]:
+    n_cells = int(max(int(owner.max(initial=0)), int(neighbour.max(initial=0))) + 1)
+    sums = np.zeros((n_cells, 2), dtype=np.float64)
+    counts = np.zeros(n_cells, dtype=np.int32)
+    boundary = _parse_boundary(poly_mesh / "boundary")
+    if "aerofoil" not in boundary:
+        raise ValueError(f"Missing aerofoil boundary patch in {poly_mesh / 'boundary'}")
+    aerofoil_start = int(boundary["aerofoil"]["startFace"])
+    aerofoil_stop = aerofoil_start + int(boundary["aerofoil"]["nFaces"])
+    airfoil_faces: list[NDArray[np.float64]] = []
+
+    for face_index, vertices in enumerate(_iter_faces(poly_mesh / "faces.gz")):
+        face_center = points[vertices, :2].mean(axis=0)
+        owner_cell = int(owner[face_index])
+        sums[owner_cell] += face_center
+        counts[owner_cell] += 1
+        if face_index < len(neighbour):
+            neighbour_cell = int(neighbour[face_index])
+            sums[neighbour_cell] += face_center
+            counts[neighbour_cell] += 1
+        if aerofoil_start <= face_index < aerofoil_stop:
+            airfoil_faces.append(face_center)
+    if np.any(counts == 0):
+        raise ValueError(f"Mesh contains {int(np.sum(counts == 0))} cells without faces in {poly_mesh}")
+    if not airfoil_faces:
+        raise ValueError(f"No aerofoil face centers parsed from {poly_mesh}")
+    centers = (sums / counts[:, None]).astype(np.float32)
+    return centers, np.asarray(airfoil_faces, dtype=np.float32)
+
+
+def _distance_to_airfoil(centers: FloatArray, airfoil_centers: FloatArray, *, chunk_size: int = 8192) -> FloatArray:
+    result = np.empty(centers.shape[0], dtype=np.float32)
+    airfoil = airfoil_centers.astype(np.float32, copy=False)
+    for start in range(0, centers.shape[0], chunk_size):
+        stop = min(start + chunk_size, centers.shape[0])
+        diff = centers[start:stop, None, :] - airfoil[None, :, :]
+        dist2 = np.sum(diff * diff, axis=2)
+        result[start:stop] = np.sqrt(np.min(dist2, axis=1)).astype(np.float32)
+    return result
+
+
+def _parse_boundary(path: Path) -> dict[str, dict[str, int | str]]:
+    text = _read_text(path, max_bytes=500_000)
+    patches: dict[str, dict[str, int | str]] = {}
+    for name, body in re.findall(r"\n\s*([A-Za-z][A-Za-z0-9_]*)\s*\n\s*\{(.*?)\n\s*\}", text, flags=re.DOTALL):
+        n_faces = _assignment(body, "nFaces")
+        start_face = _assignment(body, "startFace")
+        patch_type = _assignment(body, "type") or ""
+        if n_faces is not None and start_face is not None:
+            patches[name] = {"type": patch_type, "nFaces": int(n_faces), "startFace": int(start_face)}
+    return patches
+
+
+def _assignment(text: str, key: str) -> str | None:
+    match = re.search(rf"^\s*{re.escape(key)}\s+([^;]+);", text, flags=re.MULTILINE)
+    return match.group(1).strip() if match else None
+
+
+def _parse_vector_list(path: Path, *, columns: int) -> NDArray[np.float32]:
+    rows: list[list[float]] = []
+    expected = None
+    in_values = False
+    with _open_text(path) as stream:
+        for line in stream:
+            stripped = line.strip()
+            if not in_values:
+                if expected is None and stripped.isdigit():
+                    expected = int(stripped)
+                    continue
+                if expected is not None and stripped == "(":
+                    in_values = True
+                    continue
+                continue
+            if stripped == ")":
+                break
+            values = [float(item) for item in FLOAT_RE.findall(stripped)]
+            if len(values) >= columns:
+                rows.append(values[:columns])
+    array = np.asarray(rows, dtype=np.float32)
+    if expected is not None and array.shape[0] != expected:
+        raise ValueError(f"{path}: parsed {array.shape[0]} rows, expected {expected}")
+    return array
+
+
+def _parse_scalar_list(path: Path) -> FloatArray:
+    return _parse_vector_list(path, columns=1).reshape(-1)
+
+
+def _parse_label_list(path: Path) -> NDArray[np.int64]:
+    values: list[int] = []
+    expected = None
+    in_values = False
+    with _open_text(path) as stream:
+        for line in stream:
+            stripped = line.strip()
+            if not in_values:
+                if expected is None and stripped.isdigit():
+                    expected = int(stripped)
+                    continue
+                if expected is not None and stripped == "(":
+                    in_values = True
+                    continue
+                continue
+            if stripped == ")":
+                break
+            if stripped:
+                values.append(int(stripped))
+    array = np.asarray(values, dtype=np.int64)
+    if expected is not None and array.shape[0] != expected:
+        raise ValueError(f"{path}: parsed {array.shape[0]} labels, expected {expected}")
+    return array
+
+
+def _iter_faces(path: Path) -> Iterator[NDArray[np.int64]]:
+    expected = None
+    in_values = False
+    count = 0
+    with _open_text(path) as stream:
+        for line in stream:
+            stripped = line.strip()
+            if not in_values:
+                if expected is None and stripped.isdigit():
+                    expected = int(stripped)
+                    continue
+                if expected is not None and stripped == "(":
+                    in_values = True
+                    continue
+                continue
+            if stripped == ")":
+                break
+            values = [int(item) for item in INT_RE.findall(stripped)]
+            if values:
+                count += 1
+                yield np.asarray(values[1:], dtype=np.int64)
+    if expected is not None and count != expected:
+        raise ValueError(f"{path}: parsed {count} faces, expected {expected}")
+
+
+def _field_path(root: Path, preferred: str, fallback: str) -> Path:
+    preferred_path = root / preferred
+    if preferred_path.is_file():
+        return preferred_path
+    fallback_path = root / fallback
+    if fallback_path.is_file():
+        return fallback_path
+    raise FileNotFoundError(f"Missing field {preferred} or {fallback} under {root}")
+
+
+def _open_text(path: Path) -> TextIO:
+    if path.suffix == ".gz":
+        return gzip.open(path, "rt", errors="replace")
+    return path.open("rt", errors="replace")
+
+
+def _read_text(path: Path, *, max_bytes: int) -> str:
+    if path.suffix == ".gz":
+        with gzip.open(path, "rb") as stream:
+            data = stream.read(max_bytes)
+    else:
+        data = path.read_bytes()[:max_bytes]
+    return data.decode("utf-8", errors="replace")
+
+
+def _validate_finite(root: Path, features: FloatArray, targets: FloatArray) -> None:
+    if features.shape[1] != len(FEATURE_NAMES):
+        raise ValueError(f"Feature width mismatch in {root}: {features.shape[1]} != {len(FEATURE_NAMES)}")
+    if targets.shape[1] != len(TARGET_NAMES):
+        raise ValueError(f"Target width mismatch in {root}: {targets.shape[1]} != {len(TARGET_NAMES)}")
+    if not np.isfinite(features).all():
+        raise ValueError(f"Non-finite features in {root}")
+    if not np.isfinite(targets).all():
+        raise ValueError(f"Non-finite targets in {root}")
+
+
+def _atomic_save_npz(path: Path, **arrays: object) -> None:
+    tmp = path.with_name(path.name + ".tmp.npz")
+    np.savez_compressed(tmp, **arrays)
+    tmp.replace(path)

src/airfrans_frontier/remote/artifacts.py

@@ -5,26 +5,71 @@ import json
 from pathlib import Path
 from typing import Any, Iterable
 
+import torch
 
-DEFAULT_REQUIRED = ("final_metrics.json", "metrics.jsonl", "checkpoint.pt", "run_manifest.json")
+BASE_REQUIRED = (
+    "config.toml",
+    "metrics.jsonl",
+    "latest_metrics.json",
+    "heartbeat.json",
+    "checkpoint_latest.pt",
+    "checkpoint_best.pt",
+)
+SUCCESS_REQUIRED = ("final_metrics.json", "checkpoint_final.pt")
+FAILURE_REQUIRED = ("failure_report.json",)
+DEFAULT_REQUIRED = BASE_REQUIRED
 
 
-def verify_artifacts(artifact_dir: str | Path, required: Iterable[str] = DEFAULT_REQUIRED) -> dict[str, Any]:
+def verify_artifacts(
+    artifact_dir: str | Path,
+    required: Iterable[str] = DEFAULT_REQUIRED,
+    *,
+    require_terminal: bool = True,
+) -> dict[str, Any]:
     root = Path(artifact_dir)
     if not root.exists():
         raise FileNotFoundError(f"Artifact directory not found: {root}")
     if not root.is_dir():
         raise ValueError(f"Artifact path is not a directory: {root}")
 
-    missing = [name for name in required if not (root / name).is_file()]
+    required_names = tuple(required)
+    missing = [name for name in required_names if not (root / name).is_file()]
     if missing:
         raise ValueError(f"Artifact directory missing required files: {', '.join(missing)}")
 
-    _validate_json(root / "final_metrics.json")
-    _validate_json(root / "run_manifest.json")
-    _validate_jsonl(root / "metrics.jsonl")
+    has_final = (root / "final_metrics.json").is_file()
+    has_failure = (root / "failure_report.json").is_file()
+    if require_terminal and not has_final and not has_failure:
+        raise ValueError("Artifact directory has no terminal artifact: final_metrics.json or failure_report.json")
+    if has_final:
+        missing_success = [name for name in SUCCESS_REQUIRED if not (root / name).is_file()]
+        if missing_success:
+            raise ValueError(f"Successful artifact directory missing files: {', '.join(missing_success)}")
+    if has_failure:
+        missing_failure = [name for name in FAILURE_REQUIRED if not (root / name).is_file()]
+        if missing_failure:
+            raise ValueError(f"Failed artifact directory missing files: {', '.join(missing_failure)}")
 
-    files = sorted(path for path in root.rglob("*") if path.is_file())
+    for json_name in (
+        "latest_metrics.json",
+        "heartbeat.json",
+        "final_metrics.json",
+        "failure_report.json",
+        "run_manifest.json",
+        "split_manifest.json",
+        "data_manifest.json",
+        "normalization.json",
+    ):
+        path = root / json_name
+        if path.is_file():
+            _validate_json(path)
+    _validate_jsonl(root / "metrics.jsonl")
+    for checkpoint_name in ("checkpoint_latest.pt", "checkpoint_best.pt", "checkpoint_final.pt"):
+        path = root / checkpoint_name
+        if path.is_file():
+            _validate_checkpoint_metadata(path)
+
+    files = sorted(path for path in root.rglob("*") if path.is_file() and path.name not in {"artifact_manifest.json", "checksums.txt"})
     manifest = {
         "artifact_dir": str(root),
         "file_count": len(files),
@@ -69,3 +114,16 @@ def _validate_jsonl(path: Path) -> None:
                 json.loads(stripped)
             except json.JSONDecodeError as exc:
                 raise ValueError(f"Invalid JSONL artifact {path}:{line_number}: {exc}") from exc
+
+
+def _validate_checkpoint_metadata(path: Path) -> None:
+    try:
+        checkpoint = torch.load(path, map_location="cpu", weights_only=False)
+    except Exception as exc:
+        raise ValueError(f"Invalid checkpoint artifact {path}: {exc}") from exc
+    if not isinstance(checkpoint, dict):
+        raise ValueError(f"Checkpoint artifact is not a mapping: {path}")
+    required = ("schema_version", "step", "model_state_dict", "optimizer_state_dict", "normalization")
+    missing = [name for name in required if name not in checkpoint]
+    if missing:
+        raise ValueError(f"Checkpoint artifact {path} missing keys: {', '.join(missing)}")

src/airfrans_frontier/remote/cli.py

@@ -46,6 +46,7 @@ def build_parser() -> argparse.ArgumentParser:
     smoke.add_argument("training_config")
     smoke.add_argument("--artifact-dir", required=True)
     smoke.add_argument("--run-id", required=True)
+    smoke.add_argument("--resume", help="path to checkpoint_latest.pt to resume from")
     smoke.set_defaults(command="smoke-train")
 
     run = subparsers.add_parser("run", help="select a Vast offer and execute a SkyPilot run")
@@ -82,7 +83,12 @@ def main(argv: list[str] | None = None) -> int:
             print(json.dumps({"status": "ok", "file_count": manifest["file_count"]}, sort_keys=True))
             return 0
         if args.command == "smoke-train":
-            output = run_smoke_training(args.training_config, artifact_dir=args.artifact_dir, run_id=args.run_id)
+            output = run_smoke_training(
+                args.training_config,
+                artifact_dir=args.artifact_dir,
+                run_id=args.run_id,
+                resume_path=args.resume or os.environ.get("AIRFRANS_RESUME_CHECKPOINT"),
+            )
             print(f"artifact_dir: {output}")
             return 0
         if args.command == "run":
@@ -147,15 +153,18 @@ def _run(config_path: str | Path, *, dry_run: bool, skip_down: bool) -> int:
     selection = select_offer(config)
     selection_path = local_run_dir / "selection_manifest.json"
     selection_path.write_text(json.dumps(selection.to_manifest(), indent=2, sort_keys=True) + "\n")
-
-    state("RENDERING_SKYPILOT_CONFIG", selected_offer_id=selection.selected_offer_id)
-    sky_yaml = render_skypilot_yaml(config, selection, run_id=run_id)
-    sky_yaml_path = local_run_dir / "sky.yaml"
-    sky_yaml_path.write_text(sky_yaml)
     (local_run_dir / "config.toml").write_text(config.raw_text)
     write_skyignore(config)
 
     if dry_run:
+        sky_yaml_path = _write_attempt_sky_yaml(
+            config=config,
+            selection=selection,
+            run_id=run_id,
+            local_run_dir=local_run_dir,
+            resume_checkpoint=None,
+            attempt=1,
+        )
         state("DRY_RUN", selected_offer_id=selection.selected_offer_id, sky_yaml=str(sky_yaml_path))
         print(f"run_id: {run_id}")
         print(f"selection: {selection_path}")
@@ -163,28 +172,122 @@ def _run(config_path: str | Path, *, dry_run: bool, skip_down: bool) -> int:
         return 0
 
     env = _subprocess_env()
-    try:
-        state("PROVISIONING", selected_offer_id=selection.selected_offer_id)
-        _run_checked(["sky", "launch", "-c", run_id, str(sky_yaml_path), "-y"], env=env, timeout=config.run.timeout_minutes * 60)
-
-        state("COLLECTING", selected_offer_id=selection.selected_offer_id)
-        _collect_with_rsync(cluster=run_id, remote_dir=config.job.artifact_dir, local_dir=local_run_dir, env=env)
-
-        state("VERIFYING_ARTIFACTS", selected_offer_id=selection.selected_offer_id)
-        verify_artifacts(local_run_dir, required=config.artifacts.required)
-    except Exception as exc:
-        state("FAILED", selected_offer_id=selection.selected_offer_id, error=str(exc))
+    last_error: str | None = None
+    for attempt in range(1, config.run.max_attempts + 1):
+        resume_checkpoint = _stage_resume_checkpoint(local_run_dir, run_id)
+        sky_yaml_path = _write_attempt_sky_yaml(
+            config=config,
+            selection=selection,
+            run_id=run_id,
+            local_run_dir=local_run_dir,
+            resume_checkpoint=resume_checkpoint,
+            attempt=attempt,
+        )
+        state(
+            "PROVISIONING",
+            selected_offer_id=selection.selected_offer_id,
+            attempt=attempt,
+            resume_checkpoint=str(resume_checkpoint) if resume_checkpoint is not None else None,
+        )
+        return_code = _run_sky_with_periodic_collection(
+            cluster=run_id,
+            sky_yaml_path=sky_yaml_path,
+            config=config,
+            local_run_dir=local_run_dir,
+            env=env,
+        )
+        state("COLLECTING", selected_offer_id=selection.selected_offer_id, attempt=attempt, return_code=return_code)
+        _collect_best_effort(cluster=run_id, remote_dir=config.job.artifact_dir, local_dir=local_run_dir, env=env)
+        status = _classify_artifacts(local_run_dir)
+        if status == "success":
+            state("VERIFYING_ARTIFACTS", selected_offer_id=selection.selected_offer_id, attempt=attempt)
+            verify_artifacts(local_run_dir, required=config.artifacts.required)
+            if config.cleanup.on_success == "sky_down" and not skip_down:
+                state("CLEANING_UP", selected_offer_id=selection.selected_offer_id, attempt=attempt)
+                _run_checked(["sky", "down", run_id, "-y"], env=env, timeout=300)
+            state("SUCCEEDED", selected_offer_id=selection.selected_offer_id, attempt=attempt)
+            print(f"run_id: {run_id}")
+            print(f"artifacts: {local_run_dir}")
+            return 0
+        if status == "failure_report":
+            last_error = "training wrote failure_report.json"
+            state("FAILED_TRAINING", selected_offer_id=selection.selected_offer_id, attempt=attempt, error=last_error)
+            if config.cleanup.on_failure == "sky_down" and not skip_down:
+                _run_best_effort(["sky", "down", run_id, "-y"], env=env)
+            raise RuntimeError(last_error)
+        last_error = f"SkyPilot job ended without terminal artifacts, return_code={return_code}"
+        state("RETRYING", selected_offer_id=selection.selected_offer_id, attempt=attempt, error=last_error)
         if config.cleanup.on_failure == "sky_down" and not skip_down:
             _run_best_effort(["sky", "down", run_id, "-y"], env=env)
-        raise
-    else:
-        if config.cleanup.on_success == "sky_down" and not skip_down:
-            state("CLEANING_UP", selected_offer_id=selection.selected_offer_id)
-            _run_checked(["sky", "down", run_id, "-y"], env=env, timeout=300)
-        state("SUCCEEDED", selected_offer_id=selection.selected_offer_id)
-        print(f"run_id: {run_id}")
-        print(f"artifacts: {local_run_dir}")
-        return 0
+
+    state("FAILED", selected_offer_id=selection.selected_offer_id, error=last_error or "max attempts exhausted")
+    raise RuntimeError(last_error or "max attempts exhausted")
+
+
+def _write_attempt_sky_yaml(
+    *,
+    config: RemoteRunConfig,
+    selection: SelectionResult,
+    run_id: str,
+    local_run_dir: Path,
+    resume_checkpoint: Path | None,
+    attempt: int,
+) -> Path:
+    sky_yaml = render_skypilot_yaml(
+        config,
+        selection,
+        run_id=run_id,
+        resume_checkpoint=resume_checkpoint,
+    )
+    sky_yaml_path = local_run_dir / f"sky_attempt_{attempt}.yaml"
+    sky_yaml_path.write_text(sky_yaml)
+    if attempt == 1:
+        (local_run_dir / "sky.yaml").write_text(sky_yaml)
+    return sky_yaml_path
+
+
+def _stage_resume_checkpoint(local_run_dir: Path, run_id: str) -> Path | None:
+    latest = local_run_dir / "checkpoint_latest.pt"
+    if not latest.is_file():
+        return None
+    resume_dir = Path(".airfrans_resume") / run_id
+    resume_dir.mkdir(parents=True, exist_ok=True)
+    destination = resume_dir / "checkpoint_latest.pt"
+    shutil.copy2(latest, destination)
+    return destination
+
+
+def _run_sky_with_periodic_collection(
+    *,
+    cluster: str,
+    sky_yaml_path: Path,
+    config: RemoteRunConfig,
+    local_run_dir: Path,
+    env: dict[str, str],
+) -> int:
+    process = subprocess.Popen(["sky", "launch", "-c", cluster, str(sky_yaml_path), "-y"], env=env)
+    deadline = time.monotonic() + config.run.timeout_minutes * 60
+    next_collect = time.monotonic() + config.run.artifact_sync_interval_seconds
+    while True:
+        return_code = process.poll()
+        if return_code is not None:
+            return int(return_code)
+        now = time.monotonic()
+        if now >= deadline:
+            process.terminate()
+            try:
+                process.wait(timeout=30)
+            except subprocess.TimeoutExpired:
+                process.kill()
+            return int(process.returncode or 124)
+        if config.run.artifact_sync_interval_seconds == 0 or now >= next_collect:
+            _collect_best_effort(cluster=cluster, remote_dir=config.job.artifact_dir, local_dir=local_run_dir, env=env)
+            if _classify_artifacts(local_run_dir) in {"success", "failure_report"}:
+                return_code = process.poll()
+                if return_code is not None:
+                    return int(return_code)
+            next_collect = now + max(1, config.run.artifact_sync_interval_seconds)
+        time.sleep(min(5.0, max(0.1, next_collect - now)))
 
 
 def _collect_with_rsync(*, cluster: str, remote_dir: Path, local_dir: Path, env: dict[str, str]) -> None:
@@ -193,6 +296,23 @@ def _collect_with_rsync(*, cluster: str, remote_dir: Path, local_dir: Path, env:
     _run_checked(["rsync", "-Pavz", source, f"{local_dir}/"], env=env, timeout=600)
 
 
+def _collect_best_effort(*, cluster: str, remote_dir: Path, local_dir: Path, env: dict[str, str]) -> None:
+    try:
+        _collect_with_rsync(cluster=cluster, remote_dir=remote_dir, local_dir=local_dir, env=env)
+    except Exception:
+        pass
+
+
+def _classify_artifacts(local_run_dir: Path) -> str:
+    if (local_run_dir / "final_metrics.json").is_file() and (local_run_dir / "checkpoint_final.pt").is_file():
+        return "success"
+    if (local_run_dir / "failure_report.json").is_file():
+        return "failure_report"
+    if (local_run_dir / "checkpoint_latest.pt").is_file():
+        return "restartable"
+    return "incomplete"
+
+
 def _run_checked(argv: list[str], *, env: dict[str, str], timeout: int) -> None:
     subprocess.run(argv, check=True, env=env, timeout=timeout)
 

src/airfrans_frontier/remote/config.py

@@ -12,6 +12,7 @@ class RunConfig:
     timeout_minutes: int
     local_artifact_dir: Path
     max_attempts: int
+    artifact_sync_interval_seconds: int
 
 
 @dataclass(frozen=True)
@@ -190,6 +191,7 @@ def load_remote_run_config(path: str | Path) -> RemoteRunConfig:
             timeout_minutes=_integer(run_raw, "timeout_minutes", minimum=1, default=60),
             local_artifact_dir=_path(run_raw, "local_artifact_dir", default="artifacts/remote_runs"),
             max_attempts=_integer(run_raw, "max_attempts", minimum=1, default=2),
+            artifact_sync_interval_seconds=_integer(run_raw, "artifact_sync_interval_seconds", minimum=0, default=1800),
         ),
         provider=provider,
         selection=selection,

src/airfrans_frontier/remote/skypilot.py

@@ -6,7 +6,13 @@ from airfrans_frontier.remote.config import RemoteRunConfig
 from airfrans_frontier.remote.vast import SelectionResult
 
 
-def render_skypilot_yaml(config: RemoteRunConfig, selection: SelectionResult, *, run_id: str) -> str:
+def render_skypilot_yaml(
+    config: RemoteRunConfig,
+    selection: SelectionResult,
+    *,
+    run_id: str,
+    resume_checkpoint: str | Path | None = None,
+) -> str:
     setup = _compose_setup(config)
     run = _compose_run(config, run_id=run_id)
     accelerator = _accelerator(config)
@@ -25,13 +31,17 @@ def render_skypilot_yaml(config: RemoteRunConfig, selection: SelectionResult, *,
         if not image.startswith("docker:"):
             image = f"docker:{image}"
         lines.append(f"  image_id: {image}")
+    env_lines = [
+        "envs:",
+        f"  AIRFRANS_REMOTE_RUN_ID: {run_id}",
+    ]
+    if resume_checkpoint is not None:
+        env_lines.append(f"  AIRFRANS_RESUME_CHECKPOINT: {_yaml_scalar(str(resume_checkpoint))}")
     lines.extend(
         [
             "",
             f"workdir: {_yaml_scalar(str(config.workspace.workdir))}",
-            "",
-            "envs:",
-            f"  AIRFRANS_REMOTE_RUN_ID: {run_id}",
+            *env_lines,
             "",
             "setup: |",
             *_indent_block(setup),

src/airfrans_frontier/remote/smoke.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+import os
 import platform
 import shutil
 import subprocess
@@ -13,7 +14,13 @@ from airfrans_frontier.remote.artifacts import verify_artifacts
 from airfrans_frontier.runtime import remove_pythonpath_entries
 
 
-def run_smoke_training(config_path: str | Path, *, artifact_dir: str | Path, run_id: str) -> Path:
+def run_smoke_training(
+    config_path: str | Path,
+    *,
+    artifact_dir: str | Path,
+    run_id: str,
+    resume_path: str | Path | None = None,
+) -> Path:
     remove_pythonpath_entries()
     from airfrans_frontier.training.loop import train_from_config_path
 
@@ -40,13 +47,32 @@ def run_smoke_training(config_path: str | Path, *, artifact_dir: str | Path, run
             "timestamp": time.time(),
         },
     )
-    result = train_from_config_path(config_path)
+    previous_observability_dir = os.environ.get("AIRFRANS_OBSERVABILITY_DIR")
+    previous_run_id = os.environ.get("AIRFRANS_REMOTE_RUN_ID")
+    os.environ["AIRFRANS_OBSERVABILITY_DIR"] = str(output_dir)
+    os.environ["AIRFRANS_REMOTE_RUN_ID"] = run_id
+    try:
+        result = train_from_config_path(config_path, resume_path=resume_path or os.environ.get("AIRFRANS_RESUME_CHECKPOINT"))
+    finally:
+        if previous_observability_dir is None:
+            os.environ.pop("AIRFRANS_OBSERVABILITY_DIR", None)
+        else:
+            os.environ["AIRFRANS_OBSERVABILITY_DIR"] = previous_observability_dir
+        if previous_run_id is None:
+            os.environ.pop("AIRFRANS_REMOTE_RUN_ID", None)
+        else:
+            os.environ["AIRFRANS_REMOTE_RUN_ID"] = previous_run_id
     finished = time.time()
 
     training_dir = result.run_dir
     required_from_training = [
         "final_metrics.json",
         "metrics.jsonl",
+        "latest_metrics.json",
+        "heartbeat.json",
+        "checkpoint_latest.pt",
+        "checkpoint_best.pt",
+        "checkpoint_final.pt",
         "checkpoint.pt",
         "config.toml",
         "normalization.json",
@@ -67,16 +93,23 @@ def run_smoke_training(config_path: str | Path, *, artifact_dir: str | Path, run
         "training_run_dir": str(training_dir),
         "artifact_dir": str(output_dir),
         "final_metrics_path": str(output_dir / "final_metrics.json"),
-        "checkpoint_path": str(output_dir / "checkpoint.pt"),
+        "checkpoint_path": str(output_dir / "checkpoint_latest.pt"),
+        "resume_path": str(resume_path) if resume_path is not None else None,
     }
     _write_json(output_dir / "run_manifest.json", run_manifest)
+    latest_metrics = _read_json(output_dir / "latest_metrics.json")
     _write_json(
         heartbeat_path,
         {
             "run_id": run_id,
             "phase": "completed",
+            "epoch": latest_metrics.get("epoch"),
+            "step": latest_metrics.get("step"),
+            "latest_checkpoint": "checkpoint_final.pt",
+            "latest_metrics": latest_metrics,
             "started_at": started,
             "finished_at": finished,
+            "updated_at": time.time(),
             "timestamp": time.time(),
         },
     )
@@ -123,5 +156,12 @@ def environment_manifest() -> dict[str, Any]:
     return manifest
 
 
+def _read_json(path: Path) -> dict[str, Any]:
+    if not path.is_file():
+        return {}
+    data = json.loads(path.read_text())
+    return data if isinstance(data, dict) else {}
+
+
 def _write_json(path: Path, data: Any) -> None:
     path.write_text(json.dumps(data, indent=2, sort_keys=True) + "\n")

src/airfrans_frontier/training/artifacts.py

@@ -1,6 +1,9 @@
 from __future__ import annotations
 
+import hashlib
 import json
+import os
+import time
 from datetime import datetime, timezone
 from pathlib import Path
 from typing import Any, Mapping
@@ -9,8 +12,9 @@ import torch
 
 
 class ArtifactWriter:
-    def __init__(self, run_dir: Path) -> None:
+    def __init__(self, run_dir: Path, *, mirror_dir: Path | None = None) -> None:
         self.run_dir = run_dir
+        self.mirror_dir = mirror_dir
 
     @classmethod
     def create(cls, base_dir: str | Path, run_name: str) -> ArtifactWriter:
@@ -24,10 +28,20 @@ class ArtifactWriter:
             candidate = base_path / f"{timestamp}_{safe_name}_{suffix}"
             suffix += 1
         candidate.mkdir(parents=True)
-        return cls(candidate)
+        mirror_dir = _observability_dir()
+        return cls(candidate, mirror_dir=mirror_dir)
+
+    @classmethod
+    def resume_or_create(cls, base_dir: str | Path, run_name: str, resume_path: str | Path | None) -> ArtifactWriter:
+        mirror_dir = _observability_dir()
+        if resume_path is not None:
+            candidate = Path(resume_path).expanduser().parent
+            if (candidate / "metrics.jsonl").is_file():
+                return cls(candidate, mirror_dir=mirror_dir)
+        return cls.create(base_dir, run_name)
 
     def write_config(self, config_text: str) -> None:
-        (self.run_dir / "config.toml").write_text(config_text)
+        self._write_text_file("config.toml", config_text)
 
     def write_split_manifest(self, split_manifest: Mapping[str, Any]) -> None:
         self.write_json("split_manifest.json", dict(split_manifest))
@@ -36,17 +50,124 @@ class ArtifactWriter:
         self.write_json("normalization.json", dict(normalization))
 
     def append_metrics(self, metrics: Mapping[str, Any]) -> None:
-        with (self.run_dir / "metrics.jsonl").open("a") as file:
-            file.write(json.dumps(dict(metrics), sort_keys=True) + "\n")
+        payload = dict(metrics)
+        line = json.dumps(payload, sort_keys=True) + "\n"
+        self._append_text("metrics.jsonl", line)
+        self._write_json_file("latest_metrics.json", payload)
+        self._write_json_file("heartbeat.json", _heartbeat_payload(payload, self.run_dir))
 
     def write_final_metrics(self, metrics: Mapping[str, Any]) -> None:
         self.write_json("final_metrics.json", dict(metrics))
 
     def write_json(self, name: str, data: Mapping[str, Any]) -> None:
-        (self.run_dir / name).write_text(json.dumps(dict(data), indent=2, sort_keys=True) + "\n")
+        self._write_json_file(name, dict(data))
 
-    def save_checkpoint(self, payload: Mapping[str, Any]) -> None:
-        torch.save(_to_cpu(payload), self.run_dir / "checkpoint.pt")
+    def write_failure_report(self, report: Mapping[str, Any]) -> None:
+        self.write_json("failure_report.json", dict(report))
+
+    def write_artifact_manifest(self) -> None:
+        manifest_text, checksums_text = _artifact_manifest_text(self.run_dir)
+        self._write_text_file("artifact_manifest.json", manifest_text)
+        self._write_text_file("checksums.txt", checksums_text)
+
+    def save_checkpoint(self, payload: Mapping[str, Any], *, name: str) -> None:
+        cpu_payload = _to_cpu(payload)
+        self._save_checkpoint_file(name, cpu_payload)
+
+    def _save_checkpoint_file(self, name: str, payload: Mapping[str, Any]) -> None:
+        _atomic_torch_save(payload, self.run_dir / name)
+        if self.mirror_dir is not None:
+            self.mirror_dir.mkdir(parents=True, exist_ok=True)
+            _atomic_torch_save(payload, self.mirror_dir / name)
+
+    def _append_text(self, name: str, text: str) -> None:
+        _append_text(self.run_dir / name, text)
+        if self.mirror_dir is not None:
+            self.mirror_dir.mkdir(parents=True, exist_ok=True)
+            _append_text(self.mirror_dir / name, text)
+
+    def _write_json_file(self, name: str, data: Mapping[str, Any]) -> None:
+        text = json.dumps(dict(data), indent=2, sort_keys=True) + "\n"
+        _write_text(self.run_dir / name, text)
+        if self.mirror_dir is not None:
+            self.mirror_dir.mkdir(parents=True, exist_ok=True)
+            _write_text(self.mirror_dir / name, text)
+
+    def _write_text_file(self, name: str, text: str) -> None:
+        _write_text(self.run_dir / name, text)
+        if self.mirror_dir is not None:
+            self.mirror_dir.mkdir(parents=True, exist_ok=True)
+            _write_text(self.mirror_dir / name, text)
+
+
+def _heartbeat_payload(metrics: Mapping[str, Any], run_dir: Path) -> dict[str, Any]:
+    return {
+        "run_id": os.environ.get("AIRFRANS_REMOTE_RUN_ID"),
+        "phase": metrics.get("phase", "training"),
+        "epoch": metrics.get("epoch"),
+        "step": metrics.get("step"),
+        "updated_at": time.time(),
+        "run_dir": str(run_dir),
+        "latest_checkpoint": metrics.get("latest_checkpoint"),
+        "latest_metrics": dict(metrics),
+    }
+
+
+def _observability_dir() -> Path | None:
+    raw = os.environ.get("AIRFRANS_OBSERVABILITY_DIR")
+    if not raw:
+        return None
+    return Path(raw).expanduser()
+
+
+def _append_text(path: Path, text: str) -> None:
+    with path.open("a") as file:
+        file.write(text)
+        file.flush()
+        os.fsync(file.fileno())
+
+
+def _write_text(path: Path, text: str) -> None:
+    with path.open("w") as file:
+        file.write(text)
+        file.flush()
+        os.fsync(file.fileno())
+
+
+def _atomic_torch_save(payload: Mapping[str, Any], path: Path) -> None:
+    tmp_path = path.with_name(f"{path.name}.tmp")
+    torch.save(payload, tmp_path)
+    tmp_path.replace(path)
+
+
+def _artifact_manifest_text(root: Path) -> tuple[str, str]:
+    files = sorted(
+        path
+        for path in root.rglob("*")
+        if path.is_file() and path.name not in {"artifact_manifest.json", "checksums.txt"}
+    )
+    manifest = {
+        "artifact_dir": str(root),
+        "file_count": len(files),
+        "files": [
+            {
+                "path": str(path.relative_to(root)),
+                "bytes": path.stat().st_size,
+                "sha256": _sha256_file(path),
+            }
+            for path in files
+        ],
+    }
+    checksums = "".join(f"{item['sha256']}  {item['path']}\n" for item in manifest["files"])
+    return json.dumps(manifest, indent=2, sort_keys=True) + "\n", checksums
+
+
+def _sha256_file(path: Path) -> str:
+    digest = hashlib.sha256()
+    with path.open("rb") as file:
+        for chunk in iter(lambda: file.read(1024 * 1024), b""):
+            digest.update(chunk)
+    return digest.hexdigest()
 
 
 def _safe_name(value: str) -> str:

src/airfrans_frontier/training/config.py

@@ -29,6 +29,11 @@ class ModelConfig:
     hidden_width: int
     depth: int
     activation: str
+    coordinate_features: tuple[str, ...]
+    fourier_scales: tuple[float, ...]
+    condition_width: int
+    condition_depth: int
+    condition_dim: int
 
 
 @dataclass(frozen=True)
@@ -39,6 +44,21 @@ class OptimConfig:
     log_interval: int | None = None
 
 
+@dataclass(frozen=True)
+class CheckpointConfig:
+    interval_seconds: int
+
+
+@dataclass(frozen=True)
+class StabilityConfig:
+    max_grad_norm: float | None
+
+
+@dataclass(frozen=True)
+class PrecisionConfig:
+    dtype: str
+
+
 @dataclass(frozen=True)
 class DeviceConfig:
     type: str
@@ -61,6 +81,9 @@ class TrainingConfig:
     optim: OptimConfig
     device: DeviceConfig
     loss: LossConfig
+    checkpoint: CheckpointConfig
+    stability: StabilityConfig
+    precision: PrecisionConfig
 
 
 _REQUIRED_SECTIONS = ("run", "data", "model", "optim", "device", "loss")
@@ -89,6 +112,21 @@ def load_training_config(path: str | Path) -> TrainingConfig:
     optim_raw = raw["optim"]
     device_raw = raw["device"]
     loss_raw = raw["loss"]
+    checkpoint_raw = raw.get("checkpoint", {})
+    if checkpoint_raw is None:
+        checkpoint_raw = {}
+    if not isinstance(checkpoint_raw, dict):
+        raise ValueError("Training config [checkpoint] section must be a table")
+    stability_raw = raw.get("stability", {})
+    if stability_raw is None:
+        stability_raw = {}
+    if not isinstance(stability_raw, dict):
+        raise ValueError("Training config [stability] section must be a table")
+    precision_raw = raw.get("precision", {})
+    if precision_raw is None:
+        precision_raw = {}
+    if not isinstance(precision_raw, dict):
+        raise ValueError("Training config [precision] section must be a table")
 
     run = RunConfig(
         name=_string(run_raw, "name"),
@@ -104,10 +142,15 @@ def load_training_config(path: str | Path) -> TrainingConfig:
         batch_size=_integer(data_raw, "batch_size", minimum=1),
     )
     model = ModelConfig(
-        type=_choice(_string(model_raw, "type"), {"mlp"}, "model.type"),
+        type=_choice(_string(model_raw, "type"), {"mlp", "film_fourier_mlp"}, "model.type"),
         hidden_width=_integer(model_raw, "hidden_width", minimum=1),
         depth=_integer(model_raw, "depth", minimum=1),
         activation=_choice(_string(model_raw, "activation").lower(), {"gelu", "relu", "silu", "tanh"}, "model.activation"),
+        coordinate_features=_string_tuple(model_raw, "coordinate_features", default=("x", "y", "sdf")),
+        fourier_scales=_number_tuple(model_raw, "fourier_scales", default=(1.0, 2.0, 4.0, 8.0, 16.0)),
+        condition_width=_integer(model_raw, "condition_width", minimum=1, default=_integer(model_raw, "hidden_width", minimum=1)),
+        condition_depth=_integer(model_raw, "condition_depth", minimum=1, default=2),
+        condition_dim=_integer(model_raw, "condition_dim", minimum=1, default=_integer(model_raw, "hidden_width", minimum=1)),
     )
     optim = OptimConfig(
         lr=_number(optim_raw, "lr", minimum=0.0, exclusive_minimum=True),
@@ -121,6 +164,15 @@ def load_training_config(path: str | Path) -> TrainingConfig:
         benchmark_kernels=_boolean(device_raw, "benchmark_kernels"),
     )
     loss = LossConfig(type=_choice(_string(loss_raw, "type"), {"normalized_mse"}, "loss.type"))
+    checkpoint = CheckpointConfig(
+        interval_seconds=_integer(checkpoint_raw, "interval_seconds", minimum=0, default=1800),
+    )
+    stability = StabilityConfig(
+        max_grad_norm=_optional_number(stability_raw, "max_grad_norm", minimum=0.0, exclusive_minimum=True),
+    )
+    precision = PrecisionConfig(
+        dtype=_choice(_string(precision_raw, "dtype", default="float32").lower(), {"float32", "bf16"}, "precision.dtype"),
+    )
 
     requested_cases = data.train_cases + data.val_cases + data.test_cases
     if requested_cases <= 0:
@@ -135,6 +187,9 @@ def load_training_config(path: str | Path) -> TrainingConfig:
         optim=optim,
         device=device,
         loss=loss,
+        checkpoint=checkpoint,
+        stability=stability,
+        precision=precision,
     )
 
 
@@ -146,15 +201,23 @@ def _path(section: dict[str, Any], key: str) -> Path:
     return Path.cwd() / path
 
 
-def _string(section: dict[str, Any], key: str) -> str:
-    value = _required(section, key)
+def _string(section: dict[str, Any], key: str, *, default: str | None = None) -> str:
+    if key not in section:
+        if default is not None:
+            return default
+        raise ValueError(f"Training config missing key: {key}")
+    value = section[key]
     if not isinstance(value, str) or not value:
         raise ValueError(f"Expected non-empty string for {key}")
     return value
 
 
-def _integer(section: dict[str, Any], key: str, *, minimum: int | None = None) -> int:
-    value = _required(section, key)
+def _integer(section: dict[str, Any], key: str, *, minimum: int | None = None, default: int | None = None) -> int:
+    if key not in section:
+        if default is not None:
+            return default
+        raise ValueError(f"Training config missing key: {key}")
+    value = section[key]
     if isinstance(value, bool) or not isinstance(value, int):
         raise ValueError(f"Expected integer for {key}")
     if minimum is not None and value < minimum:
@@ -187,6 +250,48 @@ def _number(
     return result
 
 
+def _optional_number(
+    section: dict[str, Any],
+    key: str,
+    *,
+    minimum: float | None = None,
+    exclusive_minimum: bool = False,
+) -> float | None:
+    if key not in section:
+        return None
+    return _number(section, key, minimum=minimum, exclusive_minimum=exclusive_minimum)
+
+
+def _number_tuple(section: dict[str, Any], key: str, *, default: tuple[float, ...]) -> tuple[float, ...]:
+    if key not in section:
+        return default
+    value = section[key]
+    if not isinstance(value, list) or not value:
+        raise ValueError(f"Expected non-empty number array for {key}")
+    result: list[float] = []
+    for item in value:
+        if isinstance(item, bool) or not isinstance(item, (int, float)):
+            raise ValueError(f"Expected number array for {key}")
+        result.append(float(item))
+    return tuple(result)
+
+
+def _string_tuple(section: dict[str, Any], key: str, *, default: tuple[str, ...]) -> tuple[str, ...]:
+    if key not in section:
+        return default
+    value = section[key]
+    if not isinstance(value, list) or not value:
+        raise ValueError(f"Expected non-empty string array for {key}")
+    result: list[str] = []
+    for item in value:
+        if not isinstance(item, str) or not item:
+            raise ValueError(f"Expected non-empty string array for {key}")
+        result.append(item)
+    if len(set(result)) != len(result):
+        raise ValueError(f"Expected unique strings for {key}")
+    return tuple(result)
+
+
 def _boolean(section: dict[str, Any], key: str) -> bool:
     value = _required(section, key)
     if not isinstance(value, bool):

src/airfrans_frontier/training/loop.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import hashlib
+import os
 import random
 import time
 from dataclasses import asdict, dataclass
@@ -10,7 +12,7 @@ import numpy as np
 import torch
 from torch.nn import functional as F
 
-from airfrans_frontier.models import PointwiseMLP
+from airfrans_frontier.models import FourierFiLMMLP, PointwiseMLP
 from airfrans_frontier.training.artifacts import ArtifactWriter
 from airfrans_frontier.training.config import TrainingConfig, load_training_config
 from airfrans_frontier.training.data import DatasetBundle, build_dataset_bundle, load_processed_dataset
@@ -22,6 +24,12 @@ from airfrans_frontier.training.normalize import (
     normalize_targets,
 )
 
+CHECKPOINT_SCHEMA_VERSION = 1
+LATEST_CHECKPOINT = "checkpoint_latest.pt"
+BEST_CHECKPOINT = "checkpoint_best.pt"
+FINAL_CHECKPOINT = "checkpoint_final.pt"
+LEGACY_CHECKPOINT = "checkpoint.pt"
+
 
 @dataclass(frozen=True)
 class TrainingResult:
@@ -29,14 +37,17 @@ class TrainingResult:
     final_metrics: dict[str, Any]
 
 
-def train_from_config_path(path: str | Path) -> TrainingResult:
+def train_from_config_path(path: str | Path, resume_path: str | Path | None = None) -> TrainingResult:
     config = load_training_config(path)
-    return train(config)
+    return train(config, resume_path=resume_path or os.environ.get("AIRFRANS_RESUME_CHECKPOINT"))
 
 
-def train(config: TrainingConfig) -> TrainingResult:
+def train(config: TrainingConfig, *, resume_path: str | Path | None = None) -> TrainingResult:
     _seed_all(config.run.seed)
     device = select_device(config)
+    resume = Path(resume_path).expanduser() if resume_path else None
+    writer = ArtifactWriter.resume_or_create(config.run.artifact_dir, config.run.name, resume)
+    writer.write_config(config.config_text)
 
     samples = load_processed_dataset(config.data.root)
     bundle = build_dataset_bundle(
@@ -53,6 +64,27 @@ def train(config: TrainingConfig) -> TrainingResult:
         feature_names=bundle.feature_names,
         target_names=bundle.target_names,
     )
+    writer.write_split_manifest(bundle.split.to_dict())
+    writer.write_json(
+        "data_manifest.json",
+        {
+            "root": str(config.data.root),
+            "case_count": len(samples),
+            "total_points": sum(sample.num_points for sample in samples),
+            "feature_names": list(bundle.feature_names),
+            "target_names": list(bundle.target_names),
+            "cases": [
+                {
+                    "case_id": sample.case_id,
+                    "points": sample.num_points,
+                    "path": str(sample.source_path),
+                }
+                for sample in samples
+            ],
+        },
+    )
+    writer.write_normalization(stats.to_dict())
+
     train_features = normalize_features(bundle.train.features, stats)
     train_targets = normalize_targets(bundle.train.targets, stats)
     val_features = normalize_features(bundle.val.features, stats) if bundle.val is not None else None
@@ -60,24 +92,54 @@ def train(config: TrainingConfig) -> TrainingResult:
     test_features = normalize_features(bundle.test.features, stats) if bundle.test is not None else None
     test_targets = normalize_targets(bundle.test.targets, stats) if bundle.test is not None else None
 
-    model = PointwiseMLP(
-        input_dim=train_features.shape[1],
-        output_dim=train_targets.shape[1],
-        hidden_width=config.model.hidden_width,
-        depth=config.model.depth,
-        activation=config.model.activation,
-    ).to(device)
+    model = _build_model(config, bundle, output_dim=train_targets.shape[1]).to(device)
     optimizer = torch.optim.AdamW(
         model.parameters(),
         lr=config.optim.lr,
         weight_decay=config.optim.weight_decay,
     )
-    writer = ArtifactWriter.create(config.run.artifact_dir, config.run.name)
-    writer.write_config(config.config_text)
-    writer.write_split_manifest(bundle.split.to_dict())
-    writer.write_normalization(stats.to_dict())
 
+    rng = np.random.default_rng(config.run.seed + 404)
     started = time.perf_counter()
+    start_step = 0
+    best_val_loss: float | None = None
+    initial_train_loss: float | None = None
+
+    if resume is not None:
+        try:
+            checkpoint = _load_checkpoint(resume, device)
+            _validate_resume_checkpoint(checkpoint, config, bundle, stats)
+            model.load_state_dict(checkpoint["model_state_dict"])
+            optimizer.load_state_dict(checkpoint["optimizer_state_dict"])
+            start_step = int(checkpoint["step"])
+            best_val_loss = _optional_float(checkpoint.get("best_val_loss"))
+            initial_train_loss = _optional_float(checkpoint.get("initial_train_loss"))
+            _restore_rng_state(checkpoint, rng)
+        except Exception as exc:
+            _write_failure(
+                writer,
+                phase="resume",
+                step=0,
+                error_type=type(exc).__name__,
+                error_message=str(exc),
+                latest_checkpoint=str(resume),
+            )
+            raise
+        writer.append_metrics(
+            _log_metrics(
+                event="resume",
+                step=start_step,
+                train_loss=None,
+                val_loss=best_val_loss,
+                elapsed_seconds=0.0,
+                lr=_learning_rate(optimizer),
+                grad_norm=None,
+                points_per_sec=None,
+                device=device,
+                latest_checkpoint=LATEST_CHECKPOINT,
+            )
+        )
+
     initial_train = evaluate_arrays(
         model,
         train_features,
@@ -98,64 +160,188 @@ def train(config: TrainingConfig) -> TrainingResult:
         if val_features is not None and val_targets is not None
         else None
     )
+    if initial_train_loss is None:
+        initial_train_loss = initial_train["loss"]
+    if best_val_loss is None and initial_val is not None:
+        best_val_loss = initial_val["loss"]
+
     writer.append_metrics(
         _log_metrics(
-            step=0,
+            event="initial_eval" if start_step == 0 else "resume_eval",
+            step=start_step,
             train_loss=initial_train["loss"],
             val_loss=initial_val["loss"] if initial_val is not None else None,
             elapsed_seconds=0.0,
+            lr=_learning_rate(optimizer),
+            grad_norm=None,
+            points_per_sec=None,
+            device=device,
+            latest_checkpoint=LATEST_CHECKPOINT,
         )
     )
+    _save_training_checkpoint(
+        writer,
+        LATEST_CHECKPOINT,
+        config=config,
+        bundle=bundle,
+        stats=stats,
+        model=model,
+        optimizer=optimizer,
+        rng=rng,
+        step=start_step,
+        best_val_loss=best_val_loss,
+        initial_train_loss=initial_train_loss,
+    )
+    _save_training_checkpoint(
+        writer,
+        BEST_CHECKPOINT,
+        config=config,
+        bundle=bundle,
+        stats=stats,
+        model=model,
+        optimizer=optimizer,
+        rng=rng,
+        step=start_step,
+        best_val_loss=best_val_loss,
+        initial_train_loss=initial_train_loss,
+    )
 
     log_interval = config.optim.log_interval or max(1, config.optim.steps // 10)
-    rng = np.random.default_rng(config.run.seed + 404)
+    last_checkpoint_at = time.monotonic()
+    last_log_at = time.perf_counter()
+    last_log_step = start_step
+    last_grad_norm: float | None = None
     model.train()
-    for step in range(1, config.optim.steps + 1):
-        batch_features, batch_targets = _sample_batch(
-            train_features,
-            train_targets,
-            batch_size=config.data.batch_size,
-            rng=rng,
-        )
-        features_tensor = _to_device(batch_features, device)
-        targets_tensor = _to_device(batch_targets, device)
-
-        optimizer.zero_grad(set_to_none=True)
-        predictions = model(features_tensor)
-        loss = F.mse_loss(predictions, targets_tensor)
-        loss.backward()
-        optimizer.step()
-
-        if step % log_interval == 0 or step == config.optim.steps:
-            train_eval = evaluate_arrays(
-                model,
+    try:
+        for step in range(start_step + 1, config.optim.steps + 1):
+            batch_features, batch_targets = _sample_batch(
                 train_features,
                 train_targets,
                 batch_size=config.data.batch_size,
-                device=device,
-                target_names=bundle.target_names,
+                rng=rng,
             )
-            val_eval = (
-                evaluate_arrays(
+            features_tensor = _to_device(batch_features, device)
+            targets_tensor = _to_device(batch_targets, device)
+
+            optimizer.zero_grad(set_to_none=True)
+            with _autocast_context(config, device):
+                predictions = model(features_tensor)
+                loss = F.mse_loss(predictions, targets_tensor)
+            if not torch.isfinite(loss):
+                _write_failure(
+                    writer,
+                    phase="training",
+                    step=step,
+                    error_type="NonFiniteLoss",
+                    error_message="loss is NaN or Inf",
+                    latest_loss=float(loss.detach().cpu().item()),
+                    latest_grad_norm=last_grad_norm,
+                    latest_checkpoint=LATEST_CHECKPOINT,
+                )
+                raise RuntimeError("nonfinite loss")
+            loss.backward()
+            try:
+                grad_norm_tensor = torch.nn.utils.clip_grad_norm_(
+                    model.parameters(),
+                    config.stability.max_grad_norm if config.stability.max_grad_norm is not None else float("inf"),
+                    error_if_nonfinite=True,
+                )
+            except RuntimeError as exc:
+                _write_failure(
+                    writer,
+                    phase="training",
+                    step=step,
+                    error_type="NonFiniteGradient",
+                    error_message=str(exc),
+                    latest_loss=float(loss.detach().cpu().item()),
+                    latest_grad_norm=last_grad_norm,
+                    latest_checkpoint=LATEST_CHECKPOINT,
+                )
+                raise RuntimeError("nonfinite gradients") from exc
+            last_grad_norm = float(grad_norm_tensor.detach().cpu().item())
+            optimizer.step()
+
+            now = time.monotonic()
+            should_checkpoint = (
+                config.checkpoint.interval_seconds == 0
+                or now - last_checkpoint_at >= config.checkpoint.interval_seconds
+                or step == config.optim.steps
+            )
+            if should_checkpoint:
+                _save_training_checkpoint(
+                    writer,
+                    LATEST_CHECKPOINT,
+                    config=config,
+                    bundle=bundle,
+                    stats=stats,
+                    model=model,
+                    optimizer=optimizer,
+                    rng=rng,
+                    step=step,
+                    best_val_loss=best_val_loss,
+                    initial_train_loss=initial_train_loss,
+                )
+                last_checkpoint_at = now
+
+            if step % log_interval == 0 or step == config.optim.steps:
+                train_eval = evaluate_arrays(
                     model,
-                    val_features,
-                    val_targets,
+                    train_features,
+                    train_targets,
                     batch_size=config.data.batch_size,
                     device=device,
                     target_names=bundle.target_names,
                 )
-                if val_features is not None and val_targets is not None
-                else None
-            )
-            writer.append_metrics(
-                _log_metrics(
-                    step=step,
-                    train_loss=train_eval["loss"],
-                    val_loss=val_eval["loss"] if val_eval is not None else None,
-                    elapsed_seconds=time.perf_counter() - started,
+                val_eval = (
+                    evaluate_arrays(
+                        model,
+                        val_features,
+                        val_targets,
+                        batch_size=config.data.batch_size,
+                        device=device,
+                        target_names=bundle.target_names,
+                    )
+                    if val_features is not None and val_targets is not None
+                    else None
                 )
-            )
-            model.train()
+                current_metric = val_eval["loss"] if val_eval is not None else train_eval["loss"]
+                if best_val_loss is None or current_metric < best_val_loss:
+                    best_val_loss = current_metric
+                    _save_training_checkpoint(
+                        writer,
+                        BEST_CHECKPOINT,
+                        config=config,
+                        bundle=bundle,
+                        stats=stats,
+                        model=model,
+                        optimizer=optimizer,
+                        rng=rng,
+                        step=step,
+                        best_val_loss=best_val_loss,
+                        initial_train_loss=initial_train_loss,
+                    )
+                elapsed = time.perf_counter() - started
+                interval_elapsed = max(time.perf_counter() - last_log_at, 1e-9)
+                points_per_sec = (step - last_log_step) * config.data.batch_size / interval_elapsed
+                writer.append_metrics(
+                    _log_metrics(
+                        event="train_eval",
+                        step=step,
+                        train_loss=train_eval["loss"],
+                        val_loss=val_eval["loss"] if val_eval is not None else None,
+                        elapsed_seconds=elapsed,
+                        lr=_learning_rate(optimizer),
+                        grad_norm=last_grad_norm,
+                        points_per_sec=points_per_sec,
+                        device=device,
+                        latest_checkpoint=LATEST_CHECKPOINT if should_checkpoint else None,
+                    )
+                )
+                last_log_at = time.perf_counter()
+                last_log_step = step
+                model.train()
+    except Exception:
+        raise
 
     final_train = evaluate_arrays(
         model,
@@ -192,40 +378,105 @@ def train(config: TrainingConfig) -> TrainingResult:
 
     elapsed = time.perf_counter() - started
     final_metrics: dict[str, Any] = {
-        "initial_train_loss": initial_train["loss"],
+        "initial_train_loss": initial_train_loss,
         "train_loss": final_train["loss"],
         "train_mse_per_channel": final_train["per_channel_mse"],
         "val_loss": final_val["loss"] if final_val is not None else None,
         "val_mse_per_channel": final_val["per_channel_mse"] if final_val is not None else None,
         "test_loss": final_test["loss"] if final_test is not None else None,
         "test_mse_per_channel": final_test["per_channel_mse"] if final_test is not None else None,
+        "best_val_loss": best_val_loss,
         "parameter_count": count_parameters(model),
+        "model_type": config.model.type,
+        "precision": config.precision.dtype,
         "train_cases": len(bundle.split.train_ids),
         "val_cases": len(bundle.split.val_ids),
         "test_cases": len(bundle.split.test_ids),
         "points_per_case": config.data.points_per_case,
         "steps": config.optim.steps,
         "elapsed_seconds": elapsed,
+        "checkpoint_interval_seconds": config.checkpoint.interval_seconds,
+        "resumed_from": str(resume) if resume is not None else None,
         **device_metrics(device),
     }
     writer.write_final_metrics(final_metrics)
-    writer.save_checkpoint(
-        {
-            "step": config.optim.steps,
-            "model_type": config.model.type,
-            "input_dim": train_features.shape[1],
-            "output_dim": train_targets.shape[1],
-            "model_config": asdict(config.model),
-            "model_state_dict": model.state_dict(),
-            "optimizer_state_dict": optimizer.state_dict(),
-            "normalization": stats.to_dict(),
-            "target_names": bundle.target_names,
-            "feature_names": bundle.feature_names,
-            "final_metrics": final_metrics,
-        }
+    _save_training_checkpoint(
+        writer,
+        FINAL_CHECKPOINT,
+        config=config,
+        bundle=bundle,
+        stats=stats,
+        model=model,
+        optimizer=optimizer,
+        rng=rng,
+        step=config.optim.steps,
+        best_val_loss=best_val_loss,
+        initial_train_loss=initial_train_loss,
+        final_metrics=final_metrics,
     )
+    _save_training_checkpoint(
+        writer,
+        LEGACY_CHECKPOINT,
+        config=config,
+        bundle=bundle,
+        stats=stats,
+        model=model,
+        optimizer=optimizer,
+        rng=rng,
+        step=config.optim.steps,
+        best_val_loss=best_val_loss,
+        initial_train_loss=initial_train_loss,
+        final_metrics=final_metrics,
+    )
+    writer.append_metrics(
+        _log_metrics(
+            event="completed",
+            phase="completed",
+            step=config.optim.steps,
+            train_loss=final_train["loss"],
+            val_loss=final_val["loss"] if final_val is not None else None,
+            elapsed_seconds=elapsed,
+            lr=_learning_rate(optimizer),
+            grad_norm=last_grad_norm,
+            points_per_sec=None,
+            device=device,
+            latest_checkpoint=FINAL_CHECKPOINT,
+        )
+    )
+    writer.write_artifact_manifest()
     return TrainingResult(run_dir=writer.run_dir, final_metrics=final_metrics)
 
+def _autocast_context(config: TrainingConfig, device: torch.device):
+    if config.precision.dtype == "float32" or device.type != "cuda":
+        return torch.autocast(device_type=device.type, enabled=False)
+    return torch.autocast(device_type=device.type, dtype=torch.bfloat16)
+
+
+
+def _build_model(config: TrainingConfig, bundle: DatasetBundle, *, output_dim: int) -> torch.nn.Module:
+    if config.model.type == "mlp":
+        return PointwiseMLP(
+            input_dim=bundle.train.features.shape[1],
+            output_dim=output_dim,
+            hidden_width=config.model.hidden_width,
+            depth=config.model.depth,
+            activation=config.model.activation,
+        )
+    if config.model.type == "film_fourier_mlp":
+        return FourierFiLMMLP(
+            feature_names=bundle.feature_names,
+            output_dim=output_dim,
+            coordinate_features=config.model.coordinate_features,
+            fourier_scales=config.model.fourier_scales,
+            trunk_width=config.model.hidden_width,
+            trunk_depth=config.model.depth,
+            condition_width=config.model.condition_width,
+            condition_depth=config.model.condition_depth,
+            condition_dim=config.model.condition_dim,
+            activation=config.model.activation,
+        )
+    raise ValueError(f"Unsupported model type: {config.model.type}")
+
 
 def select_device(config: TrainingConfig) -> torch.device:
     requested = config.device.type
@@ -303,14 +554,210 @@ def _seed_all(seed: int) -> None:
 
 def _log_metrics(
     *,
+    event: str,
     step: int,
-    train_loss: float,
+    train_loss: float | None,
     val_loss: float | None,
     elapsed_seconds: float,
+    lr: float,
+    grad_norm: float | None,
+    points_per_sec: float | None,
+    device: torch.device,
+    latest_checkpoint: str | None,
+    phase: str = "training",
 ) -> dict[str, Any]:
     return {
+        "event": event,
+        "phase": phase,
+        "epoch": 0,
         "step": step,
         "train_loss": train_loss,
         "val_loss": val_loss,
+        "lr": lr,
+        "grad_norm": grad_norm,
         "elapsed_seconds": elapsed_seconds,
+        "points_per_sec": points_per_sec,
+        "latest_checkpoint": latest_checkpoint,
+        **_memory_metrics(device),
     }
+
+
+def _memory_metrics(device: torch.device) -> dict[str, int | None]:
+    if device.type != "cuda":
+        return {
+            "gpu_memory_allocated_mb": None,
+            "gpu_memory_reserved_mb": None,
+            "gpu_memory_peak_allocated_mb": None,
+        }
+    index = device.index if device.index is not None else torch.cuda.current_device()
+    return {
+        "gpu_memory_allocated_mb": int(torch.cuda.memory_allocated(index) // (1024 * 1024)),
+        "gpu_memory_reserved_mb": int(torch.cuda.memory_reserved(index) // (1024 * 1024)),
+        "gpu_memory_peak_allocated_mb": int(torch.cuda.max_memory_allocated(index) // (1024 * 1024)),
+    }
+
+
+def _learning_rate(optimizer: torch.optim.Optimizer) -> float:
+    return float(optimizer.param_groups[0]["lr"])
+
+
+def _save_training_checkpoint(
+    writer: ArtifactWriter,
+    name: str,
+    *,
+    config: TrainingConfig,
+    bundle: DatasetBundle,
+    stats: NormalizationStats,
+    model: torch.nn.Module,
+    optimizer: torch.optim.Optimizer,
+    rng: np.random.Generator,
+    step: int,
+    best_val_loss: float | None,
+    initial_train_loss: float | None,
+    final_metrics: dict[str, Any] | None = None,
+) -> None:
+    writer.save_checkpoint(
+        _checkpoint_payload(
+            config=config,
+            bundle=bundle,
+            stats=stats,
+            model=model,
+            optimizer=optimizer,
+            rng=rng,
+            step=step,
+            best_val_loss=best_val_loss,
+            initial_train_loss=initial_train_loss,
+            final_metrics=final_metrics,
+        ),
+        name=name,
+    )
+
+
+def _checkpoint_payload(
+    *,
+    config: TrainingConfig,
+    bundle: DatasetBundle,
+    stats: NormalizationStats,
+    model: torch.nn.Module,
+    optimizer: torch.optim.Optimizer,
+    rng: np.random.Generator,
+    step: int,
+    best_val_loss: float | None,
+    initial_train_loss: float | None,
+    final_metrics: dict[str, Any] | None,
+) -> dict[str, Any]:
+    return {
+        "schema_version": CHECKPOINT_SCHEMA_VERSION,
+        "run_id": os.environ.get("AIRFRANS_REMOTE_RUN_ID", config.run.name),
+        "epoch": 0,
+        "step": step,
+        "best_val_loss": best_val_loss,
+        "initial_train_loss": initial_train_loss,
+        "model_type": config.model.type,
+        "input_dim": bundle.train.features.shape[1],
+        "output_dim": bundle.train.targets.shape[1],
+        "model_config": asdict(config.model),
+        "model_state_dict": model.state_dict(),
+        "optimizer_state_dict": optimizer.state_dict(),
+        "config": config.config_text,
+        "config_hash": _config_hash(config),
+        "normalization": stats.to_dict(),
+        "target_names": bundle.target_names,
+        "feature_names": bundle.feature_names,
+        "rng_state": random.getstate(),
+        "numpy_rng_state": np.random.get_state(),
+        "torch_rng_state": torch.get_rng_state(),
+        "cuda_rng_state": torch.cuda.get_rng_state_all() if torch.cuda.is_available() else None,
+        "batch_rng_state": rng.bit_generator.state,
+        "final_metrics": final_metrics,
+    }
+
+
+def _load_checkpoint(path: Path, device: torch.device) -> dict[str, Any]:
+    if not path.is_file():
+        raise FileNotFoundError(f"Resume checkpoint not found: {path}")
+    payload = torch.load(path, map_location=device, weights_only=False)
+    if not isinstance(payload, dict):
+        raise ValueError(f"Resume checkpoint is not a mapping: {path}")
+    return payload
+
+
+def _validate_resume_checkpoint(
+    checkpoint: dict[str, Any],
+    config: TrainingConfig,
+    bundle: DatasetBundle,
+    stats: NormalizationStats,
+) -> None:
+    if checkpoint.get("schema_version") != CHECKPOINT_SCHEMA_VERSION:
+        raise ValueError("unsupported checkpoint schema_version")
+    if checkpoint.get("model_type") != config.model.type:
+        raise ValueError("checkpoint model type does not match config")
+    if checkpoint.get("model_config") != asdict(config.model):
+        raise ValueError("checkpoint model config does not match config")
+    if checkpoint.get("config_hash") != _config_hash(config):
+        raise ValueError("checkpoint config hash does not match config")
+    if tuple(checkpoint.get("feature_names", ())) != bundle.feature_names:
+        raise ValueError("checkpoint feature names do not match dataset")
+    if tuple(checkpoint.get("target_names", ())) != bundle.target_names:
+        raise ValueError("checkpoint target names do not match dataset")
+    if "normalization" not in checkpoint:
+        raise ValueError("checkpoint missing normalization")
+    if "optimizer_state_dict" not in checkpoint:
+        raise ValueError("checkpoint missing optimizer state")
+    if checkpoint.get("normalization") != stats.to_dict():
+        raise ValueError("checkpoint normalization does not match dataset")
+
+
+def _restore_rng_state(checkpoint: dict[str, Any], rng: np.random.Generator) -> None:
+    if "rng_state" in checkpoint:
+        random.setstate(checkpoint["rng_state"])
+    if "numpy_rng_state" in checkpoint:
+        np.random.set_state(checkpoint["numpy_rng_state"])
+    if "torch_rng_state" in checkpoint:
+        torch_state = checkpoint["torch_rng_state"]
+        if isinstance(torch_state, torch.Tensor):
+            torch_state = torch_state.cpu()
+        torch.set_rng_state(torch_state)
+    cuda_rng_state = checkpoint.get("cuda_rng_state")
+    if cuda_rng_state is not None and torch.cuda.is_available():
+        torch.cuda.set_rng_state_all([state.cpu() if isinstance(state, torch.Tensor) else state for state in cuda_rng_state])
+    if "batch_rng_state" in checkpoint:
+        rng.bit_generator.state = checkpoint["batch_rng_state"]
+
+
+def _config_hash(config: TrainingConfig) -> str:
+    return hashlib.sha256(config.config_text.encode()).hexdigest()
+
+
+def _optional_float(value: Any) -> float | None:
+    if value is None:
+        return None
+    return float(value)
+
+
+def _write_failure(
+    writer: ArtifactWriter,
+    *,
+    phase: str,
+    step: int,
+    error_type: str,
+    error_message: str,
+    latest_loss: float | None = None,
+    latest_grad_norm: float | None = None,
+    latest_checkpoint: str | None = None,
+) -> None:
+    writer.write_failure_report(
+        {
+            "run_id": os.environ.get("AIRFRANS_REMOTE_RUN_ID"),
+            "phase": phase,
+            "epoch": 0,
+            "step": step,
+            "error_type": error_type,
+            "error_message": error_message,
+            "latest_loss": latest_loss,
+            "latest_grad_norm": latest_grad_norm,
+            "latest_checkpoint": latest_checkpoint,
+            "timestamp": time.time(),
+        }
+    )
+    writer.write_artifact_manifest()

tests/test_remote_run.py

@@ -2,10 +2,14 @@ from __future__ import annotations
 
 import json
 import tempfile
+import shutil
 import unittest
 from pathlib import Path
 
+import torch
+
 from airfrans_frontier.remote.artifacts import verify_artifacts
+from airfrans_frontier.remote.cli import _classify_artifacts, _stage_resume_checkpoint
 from airfrans_frontier.remote.config import load_remote_run_config
 from airfrans_frontier.remote.skypilot import render_skypilot_yaml
 from airfrans_frontier.remote.vast import VastOffer, choose_offer
@@ -18,7 +22,7 @@ class RemoteRunConfigTests(unittest.TestCase):
         self.assertEqual(config.provider.kind, "vastai")
         self.assertEqual(config.provider.gpu.name, "RTX 4090")
         self.assertEqual(config.job.artifact_dir.as_posix(), "artifacts/current_run")
-        self.assertIn("checkpoint.pt", config.artifacts.required)
+        self.assertIn("checkpoint_latest.pt", config.artifacts.required)
 
 
 class VastSelectionTests(unittest.TestCase):
@@ -50,23 +54,78 @@ class VastSelectionTests(unittest.TestCase):
         self.assertIn("selected_offer_id: 123", yaml)
         self.assertNotIn("sky launch", yaml)
         self.assertIn("remote-run smoke-train", yaml)
+        self.assertIn("configs/aggressive_smoke.toml", yaml)
+
+    def test_rendered_yaml_can_pass_resume_checkpoint(self) -> None:
+        config = load_remote_run_config("configs/remote_smoke.toml")
+        result = choose_offer([offer(123, price=0.30, host=22), offer(124, price=0.40, host=23)], config, query={})
+
+        yaml = render_skypilot_yaml(
+            config,
+            result,
+            run_id="airfrans-test",
+            resume_checkpoint=".airfrans_resume/airfrans-test/checkpoint_latest.pt",
+        )
+
+        self.assertIn("AIRFRANS_RESUME_CHECKPOINT: .airfrans_resume/airfrans-test/checkpoint_latest.pt", yaml)
 
 
 class ArtifactVerificationTests(unittest.TestCase):
     def test_verify_artifacts_requires_contract_files_and_writes_manifest(self) -> None:
         with tempfile.TemporaryDirectory() as tmp:
             root = Path(tmp)
-            (root / "final_metrics.json").write_text(json.dumps({"loss": 1.0}) + "\n")
-            (root / "metrics.jsonl").write_text(json.dumps({"step": 0}) + "\n")
-            (root / "checkpoint.pt").write_bytes(b"weights")
-            (root / "run_manifest.json").write_text(json.dumps({"exit_code": 0}) + "\n")
+            _write_contract_artifacts(root, success=True)
 
             manifest = verify_artifacts(root)
 
-            self.assertEqual(manifest["file_count"], 4)
+            self.assertGreaterEqual(manifest["file_count"], 8)
             self.assertTrue((root / "artifact_manifest.json").is_file())
             self.assertTrue((root / "checksums.txt").is_file())
 
+    def test_verify_artifacts_accepts_failure_report_terminal_state(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            _write_contract_artifacts(root, success=False)
+            (root / "failure_report.json").write_text(json.dumps({"error_type": "NonFiniteLoss"}) + "\n")
+
+            manifest = verify_artifacts(root)
+
+            self.assertGreaterEqual(manifest["file_count"], 7)
+
+    def test_classifies_and_stages_restart_checkpoint(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            self.assertEqual(_classify_artifacts(root), "incomplete")
+            _write_contract_artifacts(root, success=False)
+            self.assertEqual(_classify_artifacts(root), "restartable")
+
+            staged = _stage_resume_checkpoint(root, "test-run")
+
+            self.assertIsNotNone(staged)
+            assert staged is not None
+            self.assertTrue(staged.is_file())
+            self.assertEqual(staged.as_posix(), ".airfrans_resume/test-run/checkpoint_latest.pt")
+            shutil.rmtree(".airfrans_resume")
+
+
+def _write_contract_artifacts(root: Path, *, success: bool) -> None:
+    (root / "config.toml").write_text("[run]\nname = 'test'\n")
+    (root / "metrics.jsonl").write_text(json.dumps({"step": 0}) + "\n")
+    (root / "latest_metrics.json").write_text(json.dumps({"step": 0}) + "\n")
+    (root / "heartbeat.json").write_text(json.dumps({"phase": "training"}) + "\n")
+    checkpoint = {
+        "schema_version": 1,
+        "step": 0,
+        "model_state_dict": {},
+        "optimizer_state_dict": {},
+        "normalization": {},
+    }
+    torch.save(checkpoint, root / "checkpoint_latest.pt")
+    torch.save(checkpoint, root / "checkpoint_best.pt")
+    if success:
+        torch.save(checkpoint, root / "checkpoint_final.pt")
+        (root / "final_metrics.json").write_text(json.dumps({"loss": 1.0}) + "\n")
+
 
 def offer(
     offer_id: int,

tests/test_training_loop.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+import os
 import subprocess
 import sys
 import tempfile
@@ -14,9 +15,10 @@ remove_pythonpath_entries()
 
 import numpy as np
 import torch
+from unittest.mock import Mock
 
 from airfrans_frontier.training.config import load_training_config
-from airfrans_frontier.training.loop import select_device
+from airfrans_frontier.training.loop import train, select_device
 
 
 FEATURE_NAMES = np.array(["re_norm", "aoa_norm", "x", "y", "sdf"])
@@ -58,6 +60,10 @@ def write_training_config(
     artifact_dir: Path,
     device_type: str,
     allow_cpu_fallback: bool = False,
+    steps: int = 1000,
+    log_interval: int = 250,
+    checkpoint_interval_seconds: int = 1800,
+    hidden_width: int = 128,
 ) -> None:
     path.write_text(
         f"""
@@ -76,15 +82,15 @@ batch_size = 64
 
 [model]
 type = "mlp"
-hidden_width = 128
+hidden_width = {hidden_width}
 depth = 4
 activation = "gelu"
 
 [optim]
 lr = 0.01
 weight_decay = 0.0
-steps = 1000
-log_interval = 250
+steps = {steps}
+log_interval = {log_interval}
 
 [device]
 type = "{device_type}"
@@ -93,6 +99,9 @@ benchmark_kernels = true
 
 [loss]
 type = "normalized_mse"
+
+[checkpoint]
+interval_seconds = {checkpoint_interval_seconds}
 """.strip()
         + "\n"
     )
@@ -130,11 +139,17 @@ class TrainingLoopTests(unittest.TestCase):
                 device_type=device_type,
             )
 
+            live_dir = tmp_path / "live"
+            env = os.environ | {
+                "AIRFRANS_OBSERVABILITY_DIR": str(live_dir),
+                "AIRFRANS_REMOTE_RUN_ID": "test-run",
+            }
             result = subprocess.run(
                 [sys.executable, "-m", "airfrans_frontier.cli", "train", str(config_path)],
                 text=True,
                 capture_output=True,
                 check=False,
+                env=env,
             )
             self.assertEqual(result.returncode, 0, msg=f"stdout={result.stdout}\nstderr={result.stderr}")
             run_dir_line = next(line for line in result.stdout.splitlines() if line.startswith("run_dir: "))
@@ -145,11 +160,274 @@ class TrainingLoopTests(unittest.TestCase):
             self.assertLess(final_metrics["train_loss"], final_metrics["initial_train_loss"] * 0.1)
             self.assertLess(final_metrics["train_loss"], 1e-2)
             self.assertTrue((run_dir / "checkpoint.pt").exists())
+            self.assertTrue((run_dir / "checkpoint_latest.pt").exists())
+            self.assertTrue((run_dir / "checkpoint_best.pt").exists())
+            self.assertTrue((run_dir / "checkpoint_final.pt").exists())
+            checkpoint = torch.load(run_dir / "checkpoint_latest.pt", map_location="cpu", weights_only=False)
+            for key in (
+                "schema_version",
+                "step",
+                "model_state_dict",
+                "optimizer_state_dict",
+                "config_hash",
+                "normalization",
+                "feature_names",
+                "target_names",
+                "rng_state",
+                "torch_rng_state",
+                "batch_rng_state",
+            ):
+                self.assertIn(key, checkpoint)
+            self.assertEqual(list(run_dir.glob("*.tmp")), [])
+            self.assertTrue((run_dir / "artifact_manifest.json").is_file())
+            self.assertTrue((run_dir / "checksums.txt").is_file())
             self.assertTrue((run_dir / "metrics.jsonl").exists())
+            heartbeat = json.loads((live_dir / "heartbeat.json").read_text())
+            self.assertEqual(heartbeat["run_id"], "test-run")
+            self.assertEqual(heartbeat["phase"], "completed")
+            self.assertTrue(np.isfinite(heartbeat["latest_metrics"]["train_loss"]))
+            self.assertTrue((live_dir / "latest_metrics.json").is_file())
             self.assertEqual(final_metrics["device"].startswith("cuda"), torch.cuda.is_available())
             if torch.cuda.is_available():
                 self.assertIn("T550", final_metrics["gpu_name"])
 
+    def test_resume_uses_existing_run_dir_and_appends_metrics(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            data_root = tmp_path / "data"
+            artifact_dir = tmp_path / "artifacts"
+            config_path = tmp_path / "config.toml"
+            write_toy_simulator_dataset(data_root, cases=4, points=64)
+            write_training_config(
+                config_path,
+                data_root=data_root,
+                artifact_dir=artifact_dir,
+                device_type="cpu",
+                steps=4,
+                log_interval=1,
+                checkpoint_interval_seconds=0,
+                hidden_width=32,
+            )
+
+            first = subprocess.run(
+                [sys.executable, "-m", "airfrans_frontier.cli", "train", str(config_path)],
+                text=True,
+                capture_output=True,
+                check=False,
+            )
+            self.assertEqual(first.returncode, 0, msg=f"stdout={first.stdout}\nstderr={first.stderr}")
+            run_dir_line = next(line for line in first.stdout.splitlines() if line.startswith("run_dir: "))
+            run_dir = Path(run_dir_line.removeprefix("run_dir: "))
+
+            second = subprocess.run(
+                [
+                    sys.executable,
+                    "-m",
+                    "airfrans_frontier.cli",
+                    "train",
+                    str(config_path),
+                    "--resume",
+                    str(run_dir / "checkpoint_latest.pt"),
+                ],
+                text=True,
+                capture_output=True,
+                check=False,
+            )
+            self.assertEqual(second.returncode, 0, msg=f"stdout={second.stdout}\nstderr={second.stderr}")
+            resumed_dir_line = next(line for line in second.stdout.splitlines() if line.startswith("run_dir: "))
+            self.assertEqual(Path(resumed_dir_line.removeprefix("run_dir: ")), run_dir)
+
+            metrics = [json.loads(line) for line in (run_dir / "metrics.jsonl").read_text().splitlines()]
+            self.assertTrue(any(metric["event"] == "resume" and metric["step"] == 4 for metric in metrics))
+            final_metrics = json.loads((run_dir / "final_metrics.json").read_text())
+            self.assertEqual(final_metrics["resumed_from"], str(run_dir / "checkpoint_latest.pt"))
+
+    def test_nonfinite_loss_writes_failure_report_without_final_checkpoint(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            data_root = tmp_path / "data"
+            artifact_dir = tmp_path / "artifacts"
+            config_path = tmp_path / "config.toml"
+            write_toy_simulator_dataset(data_root, cases=4, points=64)
+            write_training_config(
+                config_path,
+                data_root=data_root,
+                artifact_dir=artifact_dir,
+                device_type="cpu",
+                steps=4,
+                log_interval=1,
+                checkpoint_interval_seconds=0,
+                hidden_width=32,
+            )
+            config = load_training_config(config_path)
+            bad_loss = torch.tensor(float("nan"), requires_grad=True)
+            with patch("airfrans_frontier.training.loop.F.mse_loss", Mock(return_value=bad_loss)):
+                with self.assertRaisesRegex(RuntimeError, "nonfinite loss"):
+                    train(config)
+
+            run_dirs = sorted(path for path in artifact_dir.iterdir() if path.is_dir())
+            self.assertEqual(len(run_dirs), 1)
+            run_dir = run_dirs[0]
+            report = json.loads((run_dir / "failure_report.json").read_text())
+            self.assertEqual(report["error_type"], "NonFiniteLoss")
+            self.assertEqual(report["step"], 1)
+            checkpoint = torch.load(run_dir / "checkpoint_latest.pt", map_location="cpu", weights_only=False)
+            self.assertEqual(checkpoint["step"], 0)
+            self.assertFalse((run_dir / "checkpoint_final.pt").exists())
+            self.assertTrue((run_dir / "artifact_manifest.json").is_file())
+            self.assertTrue((run_dir / "checksums.txt").is_file())
+
+    def test_nonfinite_gradient_writes_failure_report(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            data_root = tmp_path / "data"
+            artifact_dir = tmp_path / "artifacts"
+            config_path = tmp_path / "config.toml"
+            write_toy_simulator_dataset(data_root, cases=4, points=64)
+            write_training_config(
+                config_path,
+                data_root=data_root,
+                artifact_dir=artifact_dir,
+                device_type="cpu",
+                steps=4,
+                log_interval=1,
+                checkpoint_interval_seconds=0,
+                hidden_width=32,
+            )
+            config = load_training_config(config_path)
+            with patch("airfrans_frontier.training.loop.torch.nn.utils.clip_grad_norm_", Mock(side_effect=RuntimeError("nonfinite"))):
+                with self.assertRaisesRegex(RuntimeError, "nonfinite gradients"):
+                    train(config)
+
+            run_dir = next(path for path in artifact_dir.iterdir() if path.is_dir())
+            report = json.loads((run_dir / "failure_report.json").read_text())
+            self.assertEqual(report["error_type"], "NonFiniteGradient")
+            self.assertEqual(report["step"], 1)
+            self.assertFalse((run_dir / "checkpoint_final.pt").exists())
+            self.assertTrue((run_dir / "artifact_manifest.json").is_file())
+            self.assertTrue((run_dir / "checksums.txt").is_file())
+
+    def test_film_fourier_training_smoke_learns_conditioned_point_field(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            tmp_path = Path(tmp)
+            data_root = tmp_path / "data"
+            artifact_dir = tmp_path / "artifacts"
+            config_path = tmp_path / "config.toml"
+            data_root.mkdir()
+            feature_names = np.array(
+                [
+                    "x",
+                    "y",
+                    "sdf",
+                    "u_inf",
+                    "log_re",
+                    "aoa_deg",
+                    "aoa_sin",
+                    "aoa_cos",
+                    "naca_param_0",
+                    "naca_param_1",
+                    "naca_param_2",
+                    "naca_param_3",
+                    "naca_param_0_mask",
+                    "naca_param_1_mask",
+                    "naca_param_2_mask",
+                    "naca_param_3_mask",
+                ]
+            )
+            rng = np.random.default_rng(42)
+            for case_index in range(4):
+                x = rng.uniform(-1.0, 1.0, size=96).astype(np.float32)
+                y = rng.uniform(-1.0, 1.0, size=96).astype(np.float32)
+                sdf = np.sqrt(x * x + y * y).astype(np.float32)
+                aoa = np.float32(-5.0 + 5.0 * case_index)
+                u_inf = np.float32(30.0 + case_index)
+                condition = np.tile(
+                    np.array(
+                        [
+                            u_inf,
+                            np.log(u_inf / np.float32(1.5e-5)),
+                            aoa,
+                            np.sin(np.deg2rad(aoa)),
+                            np.cos(np.deg2rad(aoa)),
+                            2.0 + case_index,
+                            4.0,
+                            12.0,
+                            0.0,
+                            1.0,
+                            1.0,
+                            1.0,
+                            0.0,
+                        ],
+                        dtype=np.float32,
+                    ),
+                    (x.shape[0], 1),
+                )
+                features = np.concatenate((np.stack((x, y, sdf), axis=1), condition), axis=1).astype(np.float32)
+                targets = np.stack(
+                    (
+                        0.1 * x + 0.01 * aoa,
+                        -0.2 * y + 0.001 * u_inf,
+                        x * y,
+                        0.05 * sdf + 0.001 * case_index,
+                    ),
+                    axis=1,
+                ).astype(np.float32)
+                np.savez(
+                    data_root / f"case_{case_index:02d}.npz",
+                    features=features,
+                    targets=targets,
+                    feature_names=feature_names,
+                    target_names=TARGET_NAMES,
+                )
+            config_path.write_text(
+                f"""
+[run]
+name = "film_contract"
+seed = 0
+artifact_dir = "{artifact_dir}"
+
+[data]
+root = "{data_root}"
+train_cases = 2
+val_cases = 1
+test_cases = 1
+points_per_case = 96
+batch_size = 64
+
+[model]
+type = "film_fourier_mlp"
+hidden_width = 64
+depth = 2
+activation = "gelu"
+coordinate_features = ["x", "y", "sdf"]
+fourier_scales = [1.0, 2.0]
+condition_width = 32
+condition_depth = 2
+condition_dim = 32
+
+[optim]
+lr = 0.003
+weight_decay = 0.0
+steps = 60
+log_interval = 20
+
+[device]
+type = "cpu"
+allow_cpu_fallback = false
+benchmark_kernels = false
+
+[loss]
+type = "normalized_mse"
+""".strip()
+                + "\n"
+            )
+            result = train(load_training_config(config_path))
+
+            self.assertTrue(np.isfinite(result.final_metrics["train_loss"]))
+            self.assertEqual(result.final_metrics["model_type"], "film_fourier_mlp")
+            self.assertEqual(result.final_metrics["precision"], "float32")
+            self.assertTrue((result.run_dir / "checkpoint_final.pt").is_file())
+
 
 if __name__ == "__main__":
     unittest.main()

uv.lock

@@ -189,6 +189,7 @@ dev = [
     { name = "nbformat" },
     { name = "numpy", version = "2.4.6", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version < '3.12'" },
     { name = "numpy", version = "2.5.1", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version >= '3.12'" },
+    { name = "pytest" },
     { name = "skypilot", extra = ["vast"] },
 ]
 
@@ -205,6 +206,7 @@ dev = [
     { name = "nbclient", specifier = ">=0.10.2" },
     { name = "nbformat", specifier = ">=5.10.4" },
     { name = "numpy", specifier = ">=2.4.0" },
+    { name = "pytest", specifier = ">=9.1.1" },
     { name = "skypilot", extras = ["vast"], specifier = ">=0.12.3.post1" },
 ]
 
@@ -1396,6 +1398,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/ea/02/aafbf0c3e1468c7c0f607065363b49c381de7e4bb43ae6674684a3fafe92/ijson-3.5.1-pp311-pypy311_pp73-win_amd64.whl", hash = "sha256:4b75b6bf4b0dbb0df24947db6722cd5723ce8d6e6b13fddbfc98db312ba82237", size = 54922, upload-time = "2026-07-06T17:37:41.879Z" },
 ]
 
+[[package]]
+name = "iniconfig"
+version = "2.3.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/72/34/14ca021ce8e5dfedc35312d08ba8bf51fdd999c576889fc2c24cb97f4f10/iniconfig-2.3.0.tar.gz", hash = "sha256:c76315c77db068650d49c5b56314774a7804df16fee4402c1f19d6d15d8c4730", size = 20503, upload-time = "2025-10-18T21:55:43.219Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/cb/b1/3846dd7f199d53cb17f49cba7e651e9ce294d8497c8c150530ed11865bb8/iniconfig-2.3.0-py3-none-any.whl", hash = "sha256:f631c04d2c48c52b84d0d0549c99ff3859c98df65b3101406327ecc7d53fbf12", size = 7484, upload-time = "2025-10-18T21:55:41.639Z" },
+]
+
 [[package]]
 name = "invoke"
 version = "3.0.3"
@@ -2752,6 +2763,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/ec/73/6fd0bb9ce84138c3857f12e9de63bc901852975a092d545f18087a204aa2/platformdirs-4.10.1-py3-none-any.whl", hash = "sha256:0e4eff26be2d75293977f7cddc153fd9b8eaa7fb0c7b64ffe4076cb443117443", size = 22906, upload-time = "2026-07-18T03:53:42.576Z" },
 ]
 
+[[package]]
+name = "pluggy"
+version = "1.6.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/f9/e2/3e91f31a7d2b083fe6ef3fa267035b518369d9511ffab804f839851d2779/pluggy-1.6.0.tar.gz", hash = "sha256:7dcc130b76258d33b90f61b658791dede3486c3e6bfb003ee5c9bfb396dd22f3", size = 69412, upload-time = "2025-05-15T12:30:07.975Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/54/20/4d324d65cc6d9205fabedc306948156824eb9f0ee1633355a8f7ec5c66bf/pluggy-1.6.0-py3-none-any.whl", hash = "sha256:e920276dd6813095e9377c0bc5566d94c932c33b27a3e3945d8389c374dd4746", size = 20538, upload-time = "2025-05-15T12:30:06.134Z" },
+]
+
 [[package]]
 name = "prettytable"
 version = "3.18.0"
@@ -3219,6 +3239,22 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/10/bd/c038d7cc38edc1aa5bf91ab8068b63d4308c66c4c8bb3cbba7dfbc049f9c/pyparsing-3.3.2-py3-none-any.whl", hash = "sha256:850ba148bd908d7e2411587e247a1e4f0327839c40e2e5e6d05a007ecc69911d", size = 122781, upload-time = "2026-01-21T03:57:55.912Z" },
 ]
 
+[[package]]
+name = "pytest"
+version = "9.1.1"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "colorama", marker = "sys_platform == 'win32'" },
+    { name = "iniconfig" },
+    { name = "packaging" },
+    { name = "pluggy" },
+    { name = "pygments" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/e4/47/b9efed96c114afcfa3c9d3fe98a76a1d14c74a9e266d397cf6eb64be5e01/pytest-9.1.1.tar.gz", hash = "sha256:1088fbde8f2b49d95a549a195707afa7a76a3ce9bcadc26b6d71f0ffda5fe313", size = 1636369, upload-time = "2026-06-19T10:58:32.857Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/24/25/1de2678b631f5a49215c6c96fff41ba892b0a34df68d6d80292b1b48aa7f/pytest-9.1.1-py3-none-any.whl", hash = "sha256:37a86b45efb9a47a61a36449063e8e18d0cab3161329fc099eb21783169c4f0c", size = 386536, upload-time = "2026-06-19T10:58:31.347Z" },
+]
+
 [[package]]
 name = "python-barcode"
 version = "0.16.1"