abi/screenshot-to-code · error · ValueError

Update requests require history or fileState.content

Error message

Update requests require history or fileState.content

What it means

Raised in build_prompt_construction_plan (backend/prompts/plan.py) for generation_type == "update" when neither update source exists: the history list is empty AND file_state is None or its `content` is blank/whitespace. An update generation needs prior context — either chat history or a snapshot of the current file — to know what to update; with neither, no construction strategy can be selected and the plan fails fast.

Solutions

1. Include the conversation history (at least one prior user message) in the update request.
2. Or include fileState with non-blank `content` — the current code snapshot to update from.
3. If there is genuinely nothing to update from, send generation_type "create" instead.
4. On the frontend, guard the update flow: require either an existing chat history or a loaded file before enabling update mode.

Example fix

# before
build_prompt_construction_plan(stack, input_mode, "update", history=[], file_state=None)

# after — provide a snapshot
build_prompt_construction_plan(
    stack, input_mode, "update", history=[],
    file_state={"content": current_code, "path": "index.html"},
)

def can_build_update(history: list, file_state: dict | None) -> bool:
    if len(history) > 0:
        return True
    return bool(file_state and file_state.get("content", "").strip())

from typing import Any

def has_update_source(history: list[dict], file_state: dict[str, Any] | None) -> bool:
    """True when an update generation has history or a usable file snapshot."""
    return len(history) > 0 or bool(
        isinstance(file_state, dict) and file_state.get("content", "").strip()
    )

try:
    plan = build_prompt_construction_plan(stack, input_mode, generation_type, history, file_state)
except ValueError as e:
    if "require history or fileState.content" in str(e):
        return error_response("Update needs chat history or the current file content", 400)
    raise

When it happens

Trigger: Calling the prompt pipeline with generation_type="update", history=[] and file_state=None; or file_state={"content": " "} (whitespace only, stripped to empty); or file_state={"path": "..."} with no content key. Typical producer: a WebSocket update request whose history array the client didn't populate.

Common situations: Frontend sends an update chat message before any prior generation exists in the session; session/history lost after a page reload or backend restart; clients constructing update requests manually without the file snapshot; frontend sends fileState without content (only path).

Related errors

• Update history must include at least one user message
• Unsupported input mode
• Video mode requires a video to be provided
• Active session is pinned to set , not
• At least one model is required

AI-assisted analysis of abi/screenshot-to-code@d026163f58 (2026-08-14). Data as JSON: /api/errors/b237478386795026. Report an issue: GitHub.

Appendix: source

Thrown at backend/prompts/plan.py:22

    PromptHistoryMessage,
    Stack,
)


def derive_prompt_construction_plan(
    stack: Stack,
    input_mode: InputMode,
    generation_type: str,
    history: list[PromptHistoryMessage],
    file_state: dict[str, str] | None,
) -> PromptConstructionPlan:
    if generation_type == "update":
        if len(history) > 0:
            strategy = "update_from_history"
        elif file_state and file_state.get("content", "").strip():
            strategy = "update_from_file_snapshot"
        else:
            raise ValueError("Update requests require history or fileState.content")
        return {
            "generation_type": "update",
            "input_mode": input_mode,
            "stack": stack,
            "construction_strategy": strategy,
        }

    return {
        "generation_type": "create",
        "input_mode": input_mode,
        "stack": stack,
        "construction_strategy": "create_from_input",
    }

View on GitHub (pinned to d026163f58)