BoundaryML/baml · error

No download URL for asset

Error message

No download URL for asset

What it means

After finding the matching asset, get_playground_dist reads asset["browser_download_url"].as_str(). If the asset object lacks that field (or it isn't a string), this error is returned. A GitHub release asset should always carry browser_download_url, so this indicates a malformed or unexpected asset object.

Source

Thrown at engine/playground-server/src/server.rs:168

    }

    tracing::info!("Parsing JSON response...");
    let release: serde_json::Value = resp
        .json()
        .await
        .map_err(|e| anyhow::anyhow!("Failed to parse JSON response: {e}"))?;

    // Find the main asset
    let assets = release["assets"]
        .as_array()
        .ok_or_else(|| anyhow::anyhow!("No assets in release metadata"))?;
    let asset = assets
        .iter()
        .find(|a| a["name"].as_str() == Some(&web_panel_asset_name))
        .ok_or_else(|| anyhow::anyhow!("No asset named '{}' in release", web_panel_asset_name))?;
    let download_url = asset["browser_download_url"]
        .as_str()
        .ok_or_else(|| anyhow::anyhow!("No download URL for asset"))?;

    // Find the checksum asset
    let checksum_asset = assets
        .iter()
        .find(|a| a["name"].as_str() == Some(&checksum_asset_name))
        .ok_or_else(|| {
            anyhow::anyhow!(
                "No checksum asset named '{}' in release",
                checksum_asset_name
            )
        })?;
    let checksum_url = checksum_asset["browser_download_url"]
        .as_str()
        .ok_or_else(|| anyhow::anyhow!("No download URL for checksum asset"))?;

    tracing::info!(
        "Found assets - main: {}, checksum: {}",
        download_url,

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Inspect the asset JSON and confirm browser_download_url is present; fix the mocked/intermediary payload if it is synthetic.
2. Use the html_url/upload URL to reconstruct the download URL as a fallback if the field is genuinely absent.
3. Update parsing code if the GitHub API schema changed.

// preflight: confirm asset objects carry browser_download_url
let v: serde_json::Value = reqwest::get(&api_url).await?.json().await?;
let ok = v["assets"].as_array().map_or(false, |a| {
    a.iter().all(|x| x["browser_download_url"].is_string())
});
if !ok { eprintln!("Release payload missing browser_download_url fields"); }

fn download_url<'a>(asset: &'a serde_json::Value) -> Option<&'a str> {
    asset["browser_download_url"].as_str()
}

match get_playground_dist().await {
    Err(e) if e.to_string().contains("No download URL for asset") => {
        eprintln!("Malformed asset payload — inspect the GitHub API response");
    }
    other => other?,
}

When it happens

Trigger: The matched asset JSON has no string browser_download_url field — e.g. hand-crafted/mock release metadata, or an unexpected API payload shape.

Common situations: Testing against mocked GitHub API responses missing fields; a GitHub API payload change; proxy-injected JSON that drops fields.

Understand the failure class

Background: "invalid response format", "malformed payload", "missing data field": when an API returns 200 but the response shape is wrong — this error's family across 23 libraries.

Related errors

• No assets in release metadata
• No download URL for checksum asset
• Failed to parse JSON response: {e}
• `{BAML_JSON_JSON}` is declared by the stdlib
• Failed to deserialize value: {e}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/6fcc991d5a5ea25f. Report an issue: GitHub.