classification / train-kev.py
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# /// script
# requires-python = ">=3.11"
# dependencies = []
#
# [tool.hf-jobs]
# flavor = "a100-large"
# timeout = "1h"
# secrets = ["HF_TOKEN"]
# ///
"""
Fine-tune a Kev decision model on your own labelled questions, on one HF Jobs GPU.
Kev (https://github.com/jaredpalmer/kev) answers yes/no, multiple-choice and rating questions
about a text, with a probability for each answer. This script is a thin launcher around Kev's
own commands. It pins one Kev commit and one set of released weights, installs Kev, and then runs:
1. `kev.train`: a LoRA + pointer-head delta from the released Kev-4B, on your training records.
2. `kev.benchmark`: the fine-tuned model and the released model, on your development records.
3. `kev.calibrate`: a calibration report for the fine-tuned model (report only, nothing changes).
All training and evaluation code is Kev's. Kev's own recipes run on Modal (the `kev-finetune`
skill) or on a GPU you have; this script is for people whose data and credit are on the Hub.
Input: a folder with `train.jsonl` and `development.jsonl` in Kev's record format (see the README).
Output: an empty or new folder on a mounted bucket. Each result is copied there as soon as it is
written: the checkpoint, both benchmark reports, the calibration report and `run.json`.
Example, with input and output in a bucket:
hf jobs uv run --flavor a100-large --timeout 1h --secrets HF_TOKEN \\
-v hf://buckets/<you>/kev-data:/mnt/kev \\
https://huggingface.co/datasets/uv-scripts/classification/raw/main/train-kev.py \\
/mnt/kev/newsgroups /mnt/kev/runs/newsgroups-v1
Tested on 2026-10-30 (a100-large, 31 min, about $1.29): 20 Newsgroups, 846 training and 426 test
posts after Kev's length limit. Accuracy 72.3% fine-tuned vs 62.4% for the released Kev-4B. One seed.
"""
import argparse
import json
import os
import subprocess
import sys
import time
from pathlib import Path
KEV_REPO = "https://github.com/jaredpalmer/kev"
KEV_TAG = "kev-1.0"
KEV_COMMIT = "6b719c3c3f367295f6ef336f4f751cf5ff970abc" # the kev-1.0 tag on 2026-11-03
# jaredpalmer/kev-4b: the commit `@v1.0` resolved to on 2026-10-30 and 2026-11-03 (same weights as
# the v1.0 tag). Pinned by commit, because a tag can move.
INIT_MODEL = "jaredpalmer/kev-4b@6cfce5c2fa4b4bd64026336ab649c5ca78857d52"
BASE_MODEL = "Qwen/Qwen3.5-4B-Base"
BASE_REVISION = "1001bb4d826a52d1f399e183466143f4da7b741b" # main on 2026-11-03 (last change 2026-04-23)
QUESTION_TYPES = ("noul", "choice", "score")
MAX_OPTIONS = 255 # kev/api.py
WORK_DIR = Path("/tmp/kev")
SCRATCH = Path("/tmp/out")
def run(command, cwd=WORK_DIR):
print(f"\n$ {' '.join(command)}", flush=True)
started = time.time()
subprocess.run(command, cwd=cwd, check=True)
print(f"[{time.time() - started:.0f}s]", flush=True)
def check_gpu():
try:
listing = subprocess.run(["nvidia-smi", "-L"], capture_output=True, text=True)
except FileNotFoundError:
listing = None
if listing is None or listing.returncode != 0 or "GPU" not in listing.stdout:
sys.exit("No GPU found. Run this on a GPU flavor, for example --flavor a100-large.")
print(listing.stdout.strip(), flush=True)
def question_problem(question):
"""Why a labelled question is not in Kev's format, or None. Rules from kev/api.py and Kev's README:
noul labels are true/false; choice criteria is an object of options and the label is one of them;
score criteria is a list of levels and the label is a level's position from 0."""
if not isinstance(question, dict) or question.get("type") not in QUESTION_TYPES:
return f"needs a type: one of {', '.join(QUESTION_TYPES)}"
if "label" not in question:
return "needs a label"
kind, label, criteria = question["type"], question["label"], question.get("criteria")
if kind == "noul" and not isinstance(label, bool):
return "is a noul question, so its label must be true or false"
if kind == "choice":
if not isinstance(criteria, dict) or not 1 <= len(criteria) <= MAX_OPTIONS:
return f"is a choice question, so its criteria must be an object with 1 to {MAX_OPTIONS} options"
if label not in criteria:
return f"has label {label!r}, which is not one of its criteria"
if kind == "score":
if not isinstance(criteria, list) or not 1 <= len(criteria) <= MAX_OPTIONS:
return f"is a score question, so its criteria must be a list of 1 to {MAX_OPTIONS} levels"
if isinstance(label, bool) or not isinstance(label, int) or not 0 <= label < len(criteria):
return f"is a score question, so its label must be a level position from 0 to {len(criteria) - 1}"
return None
def check_records(path):
"""Fail before any GPU time is spent if a record is not in Kev's labelled format."""
if not path.is_file():
sys.exit(f"{path} not found. The input folder needs train.jsonl and development.jsonl.")
count = 0
with path.open() as f:
for line_number, line in enumerate(f, start=1):
if not line.strip():
continue
where = f"{path.name} line {line_number}"
try:
record = json.loads(line)
except json.JSONDecodeError as error:
sys.exit(f"{where}: not valid JSON ({error}).")
if not isinstance(record, dict) or record.get("state") is None:
sys.exit(f'{where}: a record needs a "state" (text, or any JSON object or list).')
questions = record.get("questions")
if not isinstance(questions, dict) or not questions:
sys.exit(f'{where}: a record needs a non-empty "questions" object.')
for name, question in questions.items():
problem = question_problem(question)
if problem:
sys.exit(f'{where}: question "{name}" {problem}.')
count += 1
if count == 0:
sys.exit(f"{path} has no records.")
print(f"{path.name}: {count} records", flush=True)
return count
def mount_of(path, mounts_file=Path("/proc/self/mounts")):
"""(mount point, filesystem type, device) of the mount that holds `path`."""
best = ("", "", "")
for line in mounts_file.read_text().splitlines():
device, mount_point, fstype = line.split()[:3]
holds_path = path == Path(mount_point) or Path(mount_point) in path.parents
if holds_path and len(mount_point) > len(best[0]):
best = (mount_point, fstype, device)
return best
def prepare_output(output_dir):
"""Fail before any GPU time is spent if the results would be lost or mixed with an old run."""
if os.environ.get("JOB_ID"):
# on Jobs, only a mounted bucket outlives the container (it shows as device "hf-mount")
mount_point, fstype, device = mount_of(output_dir)
if device != "hf-mount":
sys.exit(f"{output_dir} is not on a mounted bucket (it is on {mount_point}, {fstype or 'unknown'}). "
"Mount one with -v hf://buckets/<you>/<bucket>:/mnt/kev and write under /mnt/kev.")
if output_dir.exists() and any(output_dir.iterdir()):
sys.exit(f"{output_dir} is not empty. Use a new folder for each run.")
output_dir.mkdir(parents=True, exist_ok=True)
(output_dir / "run.json").write_text(json.dumps({"status": "started"})) # also checks that the folder is writable
def install_kev():
run(["git", "clone", "-q", "--depth", "1", "--branch", KEV_TAG, KEV_REPO, str(WORK_DIR)], cwd="/tmp")
head = subprocess.run(["git", "rev-parse", "HEAD"], cwd=WORK_DIR, check=True, capture_output=True, text=True)
if head.stdout.strip() != KEV_COMMIT:
sys.exit(f"{KEV_TAG} now points to {head.stdout.strip()}, not {KEV_COMMIT}. Check the Kev release notes.")
run(["uv", "sync", "--no-dev", "-q"])
cuda = subprocess.run(["uv", "run", "python", "-c", "import torch; print(torch.cuda.is_available())"],
cwd=WORK_DIR, capture_output=True, text=True)
if cuda.stdout.strip() != "True":
sys.exit(f"PyTorch in Kev's environment cannot use the GPU.\n{cuda.stderr[-2000:]}")
def save(name, output_dir):
"""Copy one finished result to the output folder, so a later failure cannot lose it."""
destination = output_dir / name
destination.mkdir(parents=True, exist_ok=True)
subprocess.run(["cp", "-r", f"{SCRATCH / name}/.", str(destination)], check=True)
print(f"saved {destination}", flush=True)
def train(args):
command = [
"uv", "run", "python", "-m", "kev.train",
"--data", str(args.input_dir / "train.jsonl"),
"--base", BASE_MODEL,
"--base_revision", BASE_REVISION,
"--init_from", args.init_from,
"--epochs", str(args.epochs),
"--lr", str(args.lr),
"--batch", "1", "--accum", "8", "--dtype", "bf16", "--checkpointing", "1",
"--device", "cuda",
"--out", str(SCRATCH / "checkpoint"),
]
if args.max_steps:
command += ["--max_steps", str(args.max_steps)]
run(command)
def benchmark(model, data, name):
run(["uv", "run", "python", "-m", "kev.benchmark", "--run", str(model), "--data", str(data), "--out", str(SCRATCH / name)])
def calibrate():
"""Kev's calibration report. It needs enough development records for its folds, so a failure
here is reported and the run goes on: the checkpoint and benchmarks are already saved."""
try:
run(["uv", "run", "python", "-m", "kev.calibrate", "--rows", str(SCRATCH / "finetuned-development" / "rows.json")])
report = json.loads((SCRATCH / "finetuned-development" / "calibration.json").read_text())
except (subprocess.CalledProcessError, OSError, json.JSONDecodeError) as error:
print(f"kev.calibrate failed ({error}); see the messages above. The other results are saved.", flush=True)
return None
return report.get("workload_temperature")
def headline(name):
clean = json.loads((SCRATCH / name / "report.json").read_text())["clean"]
return {"n": clean["n"], "acc": round(clean["acc"], 4), "ece": round(clean["ece"], 4)}
def main():
parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
parser.add_argument("input_dir", type=Path, help="Folder with train.jsonl and development.jsonl in Kev's format")
parser.add_argument("output_dir", type=Path, help="New or empty folder for the results, on a mounted bucket")
parser.add_argument("--init-from", default=INIT_MODEL, help="Released Kev model to start from (repo@revision)")
parser.add_argument("--epochs", type=int, default=2)
parser.add_argument("--lr", type=float, default=2e-5)
parser.add_argument("--max-steps", type=int, default=0, help="Stop after this many optimizer steps, for a smoke test")
args = parser.parse_args()
# Kev's commands run from its own checkout, so relative paths must not reach them
args.input_dir = args.input_dir.resolve()
args.output_dir = args.output_dir.resolve()
check_gpu()
check_records(args.input_dir / "train.jsonl")
check_records(args.input_dir / "development.jsonl")
prepare_output(args.output_dir)
started = time.time()
install_kev()
development = args.input_dir / "development.jsonl"
train(args)
save("checkpoint", args.output_dir)
benchmark(SCRATCH / "checkpoint", development, "finetuned-development")
save("finetuned-development", args.output_dir)
benchmark(args.init_from, development, "baseline-development")
save("baseline-development", args.output_dir)
temperature = calibrate()
if temperature is not None:
# copy only the new file: the saved reports stay as they are
calibration = SCRATCH / "finetuned-development" / "calibration.json"
subprocess.run(["cp", str(calibration), str(args.output_dir / "finetuned-development")], check=True)
print(f"saved {args.output_dir / 'finetuned-development' / 'calibration.json'}", flush=True)
summary = {
"status": "completed",
"kev_commit": KEV_COMMIT,
"init_from": args.init_from,
"base_revision": BASE_REVISION,
"finetuned": headline("finetuned-development"),
"released": headline("baseline-development"),
"workload_temperature": temperature,
"seconds": round(time.time() - started),
}
(args.output_dir / "run.json").write_text(json.dumps(summary, indent=2))
print(json.dumps(summary), flush=True)
if __name__ == "__main__":
main()