abhigyanpatwari/GitNexus · error · SandboxError

sandbox_copy must be a list

Error message

sandbox_copy must be a list

What it means

Type guard in validate_no_prebuilt_graph_assets. The task spec's 'sandbox_copy' field must be a list; anything else (a string, a mapping, null with a non-default sentinel) is rejected because the harness cannot iterate it safely and a malformed value could hide a restricted path. The default is an empty list, so omitting the field is fine.

Source

Thrown at eval/workflow_bench/sanitized_graph.py:89

            )
        self.assets.materialize(clone)


def _is_restricted_path(value: str) -> bool:
    relative = PurePosixPath(value)
    if relative.is_absolute() or not relative.parts or ".." in relative.parts:
        return False
    return (
        relative.parts[0] == ".gitnexus" or relative == HIDDEN_HARNESS_PATH or HIDDEN_HARNESS_PATH in relative.parents
    )


def validate_no_prebuilt_graph_assets(task: Mapping[str, Any]) -> None:
    """Reject declarations that could reintroduce an unsanitized graph/oracle."""

    sandbox_copy = task.get("sandbox_copy", [])
    if not isinstance(sandbox_copy, list):
        raise SandboxError("sandbox_copy must be a list")
    for value in sandbox_copy:
        if isinstance(value, str) and _is_restricted_path(value):
            raise SandboxError(f"sandbox_copy cannot import prebuilt graph or harness data: {value}")

    dependencies = task.get("sandbox_dependencies", [])
    if not isinstance(dependencies, list):
        raise SandboxError("sandbox_dependencies must be a list")
    for item in dependencies:
        if not isinstance(item, Mapping):
            continue
        for field in ("source", "target"):
            value = item.get(field)
            if isinstance(value, str) and _is_restricted_path(value):
                raise SandboxError(f"sandbox dependency cannot expose prebuilt graph or harness data: {value}")


def _replace_control_file(root: Path, name: str, payload: bytes) -> None:
    path = root / name

View on GitHub (pinned to d540b00184)

Solutions

1. Make sandbox_copy a sequence in the task spec: 'sandbox_copy: ["path/one", "path/two"]' or YAML block list with each entry a string.
2. If you intended a single copy, still wrap it in a list: 'sandbox_copy: ["path/one"]'.
3. Validate the task file locally: load it and assert isinstance(spec.get('sandbox_copy', []), list) before running.
4. Check the task schema documentation for the current expected shape of sandbox_copy.

Example fix

# before (tasks.scenarios.yaml)
sandbox_copy: src/fixtures/oracle.json
# after
sandbox_copy:
  - src/fixtures/oracle.json

import yaml
from pathlib import Path

task = yaml.safe_load(Path("task.yaml").read_text())
if "sandbox_copy" in task and not isinstance(task["sandbox_copy"], list):
    raise SystemExit(f"sandbox_copy must be a list, got {type(task['sandbox_copy']).__name__}")
# validate_no_prebuilt_graph_assets(task)  # full harness check

from collections.abc import Mapping

def sandbox_copy_well_formed(task: Mapping) -> bool:
    sc = task.get("sandbox_copy", [])
    return isinstance(sc, list) and all(isinstance(v, str) for v in sc)

from eval.workflow_bench.sanitized_graph import validate_no_prebuilt_graph_assets, SandboxError

try:
    validate_no_prebuilt_graph_assets(task)
except SandboxError as exc:
    if "sandbox_copy must be a list" in str(exc):
        log.error("task.sandbox_copy must be a YAML/JSON list of strings")
    raise

When it happens

Trigger: A task YAML/JSON declares sandbox_copy as a scalar (e.g. 'sandbox_copy: .gitnexus/oracle.json') or as a mapping instead of a sequence of strings. validate_no_prebuilt_graph_assets runs the isinstance check before scanning entries.

Common situations: Author typo (single value instead of one-element list); a YAML parser turning an unquoted special value into a non-string scalar; schema drift after a task-format change; copy-pasting a dependency-style mapping into sandbox_copy.

Related errors

• sandbox_dependencies must be a list
• {label} is unavailable: {path}: {exc}
• {label} must be a real non-symlink directory: {path}
• {label} contains an unsafe path component: {relative}
• {label} is unreadable: {path}: {exc}

AI-assisted analysis of abhigyanpatwari/GitNexus@d540b00184 (2026-08-12). Data as JSON: /api/errors/a1fbac82819ba4d9. Report an issue: GitHub.