What causes "RGBA buffer too short: expected at least {} bytes for {}x{}, got {}" in xai-org/grok-build?

Size the buffer as width * height * 4 before capture, or re-capture after the dimensions are final.

RGBA buffer too short: expected at least {} bytes for {}x{},

Error message

RGBA buffer too short: expected at least {} bytes for {}x{}, got {}

What it means

encode_rgba_to_png validates that the RGBA pixel buffer holds at least width * height * 4 bytes before PNG-encoding it. A shorter buffer would produce a truncated/corrupt image, so the function bails with the expected and actual sizes.

Source

Thrown at crates/codegen/xai-grok-shared/src/clipboard.rs:2196

        #[cfg(not(target_os = "linux"))]
        {
            let _ = path;
            anyhow::bail!("image clipboard not supported on this platform")
        }
    }

    /// Encode raw RGBA pixels into PNG bytes.
    pub(super) fn encode_rgba_to_png(
        rgba: &[u8],
        width: u32,
        height: u32,
    ) -> anyhow::Result<Vec<u8>> {
        use image::codecs::png::PngEncoder;
        use image::{ColorType, ImageEncoder};

        let expected_len = (width as usize) * (height as usize) * 4;
        if rgba.len() < expected_len {
            anyhow::bail!(
                "RGBA buffer too short: expected at least {} bytes for {}x{}, got {}",
                expected_len,
                width,
                height,
                rgba.len()
            );
        }

        let mut png_buf = Vec::with_capacity(expected_len / 4);
        let encoder = PngEncoder::new(&mut png_buf);
        encoder.write_image(rgba, width, height, ColorType::Rgba8.into())?;
        Ok(png_buf)
    }

    pub fn get_attachments() -> anyhow::Result<super::ClipboardAttachments> {
        // `ContentNotAvailable` is already Ok(None); other file_list errors must
        // not skip get_image when a raster is still present.
        let file_urls = match get_file_urls() {

View on GitHub (pinned to bc7f02eddd)

Solutions

Size the buffer as width * height * 4 before capture, or re-capture after the dimensions are final.
Verify whether the source data is RGB (3 bytes/px) and convert to RGBA before encoding.
Recompute width/height from the actual buffer length (len / 4) instead of passing stale values.

Example fix

// before
let png = encode_rgba_to_png(&rgba, new_w, new_h)?;
// after
let expected = new_w as usize * new_h as usize * 4;
assert_eq!(rgba.len(), expected, "RGBA buffer/dimension mismatch");
let png = encode_rgba_to_png(&rgba, new_w, new_h)?;

Defensive patterns

Strategy: validation

Validate before calling

fn validate_rgba_buffer(rgba: &[u8], width: u32, height: u32) -> Result<(), String> {
    let expected = width as usize * height as usize * 4;
    if rgba.len() < expected {
        return Err(format!("RGBA buffer too short: need {expected}, have {}", rgba.len()));
    }
    Ok(())
}
// call before encode_rgba_to_png
validate_rgba_buffer(&rgba, w, h)?;

Try / catch

match encode_rgba_to_png(&rgba, w, h) {
    Ok(png) => png,
    Err(e) if e.to_string().starts_with("RGBA buffer too short") => {
        // recover: recompute dims from buffer length
        let len = rgba.len() / 4;
        encode_rgba_to_png(&rgba, (len / row_len) as u32, row_len as u32)?
    }
    Err(e) => return Err(e),
}

Prevention

Compute buffer size from the same width/height values you pass to the encoder
Re-verify dimensions after any resize/scale step before encoding
Use checked multiplication (width as usize).checked_mul(height).and_then(|v| v.checked_mul(4))
Confirm pixel format is RGBA (4 bytes/px), not RGB (3 bytes/px)

When it happens

Trigger: Calling encode_rgba_to_png(rgba, width, height) where rgba.len() < width * height * 4 — e.g. passing a buffer captured from a screen region whose dimensions were recomputed after the buffer was captured.

Common situations: Screen-capture code that resizes the width/height after grabbing pixels; off-by-one or stride mismatches (buffer sized for width*height*3 RGB); DPI-scaled captures where logical vs physical pixels differ.

Related errors

AI-assisted analysis of xai-org/grok-build@bc7f02eddd (2026-08-31). Data as JSON: /api/errors/8752a30b7b73a80d. Report an issue: GitHub.