ARCHIVED TRAINING / narwhals-dev/narwhals

narwhals-dev__narwhals-2864

This is a preserved training example. Membership in the current training wave has not been verified.

Problem statement

bug: `ArrowSeries.scatter` raises out of bound error
pyarrow backed series raises an out of bound error in scatter if `indices`:

- is not 0
- are not full length of the series

Repro:

```py
import narwhals as nw
import pyarrow as pa

tbl = pa.table({"a": [1, 2, 3], "b": [142, 124, 132]})
frame = nw.from_native(tbl, eager_only=True)
ser = frame["a"]

try:
    result = ser.scatter(1, 999)
except Exception as exc:
    print(exc)


try:
    result = ser.scatter([0, 2], [999, 888])
except Exception as exc:
    print(exc)
```

> Index 1 out of bounds
> Index 2 out of bounds

Training membership

opd_e4b_cispo_v5 opd_e4b_pure_v6a opd_e4b_pure_v6b opd_e4b_pure_v7 opd_e4b_pure_v7b opd_e4b_self_audit_v4

Task issues extracted from preserved verified_rft_messages training examples. This is not a verified current RL wave manifest.

Task and snapshot provenance

Snapshot captured 2026-11-12T17:06:59.476467+00:00 · Autoresearch-Arena/gemma-4-developer-agent

{
  "datasets": [
    "opd_e4b_cispo_v5",
    "opd_e4b_pure_v6a",
    "opd_e4b_pure_v6b",
    "opd_e4b_pure_v7",
    "opd_e4b_pure_v7b",
    "opd_e4b_self_audit_v4"
  ],
  "examples": 21,
  "instance_id": "narwhals-dev__narwhals-2864",
  "problem_statement": "bug: `ArrowSeries.scatter` raises out of bound error\npyarrow backed series raises an out of bound error in scatter if `indices`:\n\n- is not 0\n- are not full length of the series\n\nRepro:\n\n```py\nimport narwhals as nw\nimport pyarrow as pa\n\ntbl = pa.table({\"a\": [1, 2, 3], \"b\": [142, 124, 132]})\nframe = nw.from_native(tbl, eager_only=True)\nser = frame[\"a\"]\n\ntry:\n    result = ser.scatter(1, 999)\nexcept Exception as exc:\n    print(exc)\n\n\ntry:\n    result = ser.scatter([0, 2], [999, 888])\nexcept Exception as exc:\n    print(exc)\n```\n\n> Index 1 out of bounds\n> Index 2 out of bounds",
  "repo": "narwhals-dev/narwhals",
  "source": "v2/experiments/train_data/opd_e4b_cispo_v5/verified_rft_messages.jsonl",
  "source_sha256": "a43610ad0dfb6ace95375cfae09000f41afc0338cc925af870a4ade7a9b20c4c"
}

{
  "captured_at": "2026-11-12T17:06:59.476467+00:00",
  "membership": "archived training",
  "membership_evidence": "Task issues extracted from preserved verified_rft_messages training examples. This is not a verified current RL wave manifest.",
  "name": "Preserved post-training task archive",
  "source": "Autoresearch-Arena/gemma-4-developer-agent",
  "source_revision": "016496de222aaafca0d4ee4c18efc63ba616f76e",
  "sources": [
    {
      "path": "v2/experiments/train_data/opd_e4b_cispo_v5/verified_rft_messages.jsonl",
      "sha256": "a43610ad0dfb6ace95375cfae09000f41afc0338cc925af870a4ade7a9b20c4c"
    },
    {
      "path": "v2/experiments/train_data/opd_e4b_hybrid_v3/verified_rft_messages.jsonl",
      "sha256": "bd326303eb127e8e5e08f03daf97bb88d79d19709d59f3f93f348bc56686a8df"
    },
    {
      "path": "v2/experiments/train_data/opd_e4b_onpolicy_v3/verified_rft_messages.jsonl",
      "sha256": "960c680e797e823a0d3a22f4b1d5ef60a72971373d703b877340b0c9126aaf68"
    },
    {
      "path": "v2/experiments/train_data/opd_e4b_pure_v6a/verified_rft_messages.jsonl",
      "sha256": "f045b7ca5b3883a1e2eaee81e1c02a4a1b53dd7b7b36e98bacb2ba5823a15148"
    },
    {
      "path": "v2/experiments/train_data/opd_e4b_pure_v6b/verified_rft_messages.jsonl",
      "sha256": "0f62460a9706eea5e1605255896f191ab00cb5706c5f1f2e1c293e9a718218dc"
    },
    {
      "path": "v2/experiments/train_data/opd_e4b_pure_v7/verified_rft_messages.jsonl",
      "sha256": "e37f7bd675322f3f81500b73559d60d5f602ca0537bf19f5cb06332c728c7b72"
    },
    {
      "path": "v2/experiments/train_data/opd_e4b_pure_v7b/verified_rft_messages.jsonl",
      "sha256": "b864bdc8695183433eef6e31cb8d33fad44ba3aded2170c1ade4ad5b2944ce23"
    },
    {
      "path": "v2/experiments/train_data/opd_e4b_self_audit_v4/verified_rft_messages.jsonl",
      "sha256": "0026023745afb8f3dc1c176dc7f7171157b4ad5a66656b524af218e8e19ceee6"
    },
    {
      "path": "v2/experiments/train_data/rft_e4b_aligned_v2/verified_rft_messages.jsonl",
      "sha256": "92a4515fee9d152b0d4c510ee3ce4caaaffe2003ba7584469f8027f174aab18c"
    },
    {
      "path": "v2/experiments/train_data/rft_v1/verified_rft_messages.jsonl",
      "sha256": "a42453ccd7ac7680b0a03865e8e7080bc8bf74c8d9d193b440c441ed46f8512b"
    },
    {
      "path": "v2/experiments/train_data/rft_v2/verified_rft_messages.jsonl",
      "sha256": "18f4b3bd7e651f83c6acab479c9475e3fa50dc652a384f309e97146983ac85ba"
    }
  ]
}