zeroclaw-labs/zeroclaw · error · anyhow::Error

Unsupported scroll direction '{direction}'. Use up/down/left

Error message

Unsupported scroll direction '{direction}'. Use up/down/left/right

What it means

The rust_native backend implements scroll by translating direction into window.scrollBy deltas: up=(0,-amount), down=(0,amount), left=(-amount,0), right=(amount,0), with amount defaulting to 600 pixels. The match has no fallback mapping, so any direction string outside the four exact lowercase names bails before touching the page.

Source

Thrown at crates/zeroclaw-tools/src/browser.rs:1750

                    let client = self.active_client()?;
                    let element = find_element(client, &selector).await?;
                    hover_element(client, &element).await?;

                    Ok(json!({
                        "backend": "rust_native",
                        "action": "hover",
                        "selector": selector,
                    }))
                }
                BrowserAction::Scroll { direction, pixels } => {
                    let client = self.active_client()?;
                    let amount = i64::from(pixels.unwrap_or(600));
                    let (dx, dy) = match direction.as_str() {
                        "up" => (0, -amount),
                        "down" => (0, amount),
                        "left" => (-amount, 0),
                        "right" => (amount, 0),
                        _ => anyhow::bail!(
                            "Unsupported scroll direction '{direction}'. Use up/down/left/right"
                        ),
                    };

                    let position = client
                        .execute(
                            "window.scrollBy(arguments[0], arguments[1]); return { x: window.scrollX, y: window.scrollY };",
                            vec![json!(dx), json!(dy)],
                        )
                        .await
                        .context("Failed to execute scroll script")?;

                    Ok(json!({
                        "backend": "rust_native",
                        "action": "scroll",
                        "position": position,
                    }))
                }

View on GitHub (pinned to 88bb9c8533)

Solutions

Use exactly one of up/down/left/right, lowercase
Normalize and trim the direction string before calling
For 'scroll to top', use press with key="Home" instead of an unsupported direction value

Example fix

// before
{"action": "scroll", "direction": "Bottom"}
// after
{"action": "scroll", "direction": "down", "pixels": 4000}

Defensive patterns

Strategy: validation

Validate before calling

const SCROLL_DIRECTIONS: &[&str] = &["up", "down", "left", "right"];
let direction = direction.trim().to_lowercase();
if !SCROLL_DIRECTIONS.contains(&direction.as_str()) {
    return Err(format!("invalid scroll direction: {direction}"));
}

Try / catch

match tool.execute(args).await {
    Ok(res) => { /* ... */ }
    Err(e) if e.to_string().contains("Unsupported scroll direction") => {
        // fix the direction value; retrying unchanged always fails
    }
    Err(e) => return Err(e),
}

Prevention

Normalize direction strings (trim + lowercase) before dispatch
Constrain direction in the tool schema with an enum of the four values
Map UI concepts like 'scroll to top' to press+Home, not invented directions

When it happens

Trigger: Sending {"action": "scroll", "direction": "UP"}, "top", "bottom", or "vertical" — the comparison is exact and case-sensitive.

Common situations: LLMs inventing 'top'/'bottom' to scroll to page ends; callers forwarding user input without normalizing case; assuming Playwright-style direction names (pageDown, pageUp).

Related errors

AI-assisted analysis of zeroclaw-labs/zeroclaw@88bb9c8533 (2026-08-23). Data as JSON: /api/errors/bf18693937b1381b. Report an issue: GitHub.