abhigyanpatwari/GitNexus · error · ValueError

task {task_id} sandbox_copy must be a string list

Error message

task {task_id} sandbox_copy must be a string list

What it means

Raised by select_tasks when `sandbox_copy` is missing, not a list, or any element is not a nonblank string (runner_tasks.py:53-54). sandbox_copy lists host paths to copy into the sandbox, so each must be a nonempty path string.

Source

Thrown at eval/workflow_bench/runner_tasks.py:54

        task = dict(raw_task)
        for field in required_strings:
            if not isinstance(task.get(field), str) or not task[field].strip():
                raise ValueError(f"task {index} requires a nonblank string {field}")
        for field in optional_strings:
            if field in task and not isinstance(task[field], str):
                raise ValueError(f"task {task['id']} field {field} must be a string")
        task_id = task["id"]
        if not re.fullmatch(r"[A-Za-z0-9][A-Za-z0-9._-]{0,127}", task_id):
            raise ValueError(f"task id must be a simple artifact-safe slug: {task_id!r}")
        if task_id in seen:
            raise ValueError(f"duplicate task id: {task_id}")
        seen.add(task_id)
        expensive = task.get("expensive", False)
        if not isinstance(expensive, bool):
            raise ValueError(f"task {task_id} expensive metadata must be boolean")
        copies = task.get("sandbox_copy", [])
        if not isinstance(copies, list) or not all(isinstance(path, str) and path for path in copies):
            raise ValueError(f"task {task_id} sandbox_copy must be a string list")
        dependencies = task.get("sandbox_dependencies", [])
        if not isinstance(dependencies, list):
            raise ValueError(f"task {task_id} sandbox_dependencies must be a list")
        for dependency in dependencies:
            if (
                not isinstance(dependency, Mapping)
                or set(dependency) != {"source", "target"}
                or not all(isinstance(dependency[field], str) and dependency[field] for field in ("source", "target"))
            ):
                raise ValueError(
                    f"task {task_id} sandbox_dependencies entries require nonblank source and target strings"
                )
        validate_oracle_declaration(task)
        if expensive and not include_expensive:
            skipped.append(task_id)
        else:
            selected.append(task)
    if not selected:

View on GitHub (pinned to d540b00184)

Solutions

1. Make sandbox_copy a YAML list of nonempty path strings.
2. Remove entries that are blank or null.
3. If no copies are needed, omit the key (defaults to []).

Example fix

# before
- id: t1
  sandbox_copy: /etc/config
# after
- id: t1
  sandbox_copy:
    - /etc/config

for i, t in enumerate(doc.get("tasks", [])):
    c = t.get("sandbox_copy", [])
    if not isinstance(c, list) or not all(isinstance(p, str) and p for p in c):
        raise SystemExit(f"task {i} sandbox_copy must be a nonempty string list")

def sandbox_copy_is_valid(task: dict) -> bool:
    c = task.get("sandbox_copy", [])
    return isinstance(c, list) and all(isinstance(p, str) and p for p in c)

When it happens

Trigger: `sandbox_copy: /a/path` (a scalar instead of a list), a list containing None/numbers/empty strings, or a YAML block that folds into a string.

Common situations: Writing a single path without list brackets; leaving a placeholder empty string; an entry that resolves to null.

Related errors

• task {task_id} sandbox_dependencies must be a list
• task {index} requires a nonblank string {field}
• task {task['id']} field {field} must be a string
• task {task_id} expensive metadata must be boolean
• task {task_id} sandbox_dependencies entries require nonblank

AI-assisted analysis of abhigyanpatwari/GitNexus@d540b00184 (2026-08-12). Data as JSON: /api/errors/43b2b5afd4e1164c. Report an issue: GitHub.