abi/screenshot-to-code · error · ValueError

Prompt item {index} is missing a prompt string.

Error message

Prompt item {index} is missing a prompt string.

What it means

ValueError("Prompt item {index} is missing a prompt string.") raised by load_prompts() when an array element is a dict but its "prompt" key is absent, not a string, or a blank/whitespace-only string. The check is isinstance(prompt, str) and prompt.strip(), so empty prompts are rejected too. Aborts the eval run at load time.

Source

Thrown at backend/run_image_generation_evals.py:83

    prompts: list[PromptItem] = []
    for index, item in enumerate(cast(list[Any], raw), start=1):
        if isinstance(item, str):
            prompts.append(
                {
                    "id": f"{index:03d}",
                    "category": "Prompt",
                    "prompt": item,
                }
            )
            continue

        if not isinstance(item, dict):
            raise ValueError(f"Prompt item {index} must be a string or object.")

        item_dict = cast(dict[str, Any], item)
        prompt = item_dict.get("prompt")
        if not isinstance(prompt, str) or not prompt.strip():
            raise ValueError(f"Prompt item {index} is missing a prompt string.")

        prompt_id = item_dict.get("id")
        category = item_dict.get("category")
        prompts.append(
            {
                "id": prompt_id if isinstance(prompt_id, str) else f"{index:03d}",
                "category": category if isinstance(category, str) else "Prompt",
                "prompt": prompt,
            }
        )

    return prompts


def build_replicate_input(
    model: ReplicateEvalModel, prompt: str
) -> dict[str, str | int | float | bool]:
    if model == "flux_2_klein":

View on GitHub (pinned to d026163f58)

Solutions

1. At the reported index, ensure the object has "prompt": "<non-empty text>" spelled exactly lowercase
2. If the key was typo'd ("text"/"Prompt"), rename it to "prompt"
3. Drop or fill empty-prompt rows before exporting the file

Example fix

// before
[{"id": "p1", "text": "a cat"}]

// after
[{"id": "p1", "prompt": "a cat"}]

def validate_prompt_objects(items: list) -> list[int]:
    bad = []
    for i, item in enumerate(items, start=1):
        if isinstance(item, dict):
            p = item.get("prompt")
            if not isinstance(p, str) or not p.strip():
                bad.append(i)
    return bad

from typing import Any, TypeGuard

def has_valid_prompt(item: dict[str, Any]) -> TypeGuard[dict[str, Any]]:
    p = item.get("prompt")
    return isinstance(p, str) and bool(p.strip())

try:
    load_prompts(prompt_file)
except ValueError as e:
    if "missing a prompt string" in str(e):
        idx = int(str(e).split()[2])
        fill_or_drop_prompt(prompt_file, idx)

When it happens

Trigger: Array elements like {"id": "p1", "category": "Landscape"} (no prompt key), {"prompt": 123}, or {"prompt": " "}.

Common situations: Prompt objects built from spreadsheets/CSV where the prompt column is empty for some rows; typo'd key such as "text" or "Prompt" instead of "prompt" (keys are case-sensitive).

Related errors

• Prompt file must contain a JSON array.
• Prompt item {index} must be a string or object.
• Invalid brief entry in {set_name}: id={brief_id!r}
• No stack was provided
• No model was provided

AI-assisted analysis of abi/screenshot-to-code@d026163f58 (2026-08-14). Data as JSON: /api/errors/ee0690c3d9bd41fb. Report an issue: GitHub.