BoundaryML/baml · error

baml.fetch_as: HTTP request failed: HTTP {} Body: {} at {:?}

Error message

baml.fetch_as: HTTP request failed: HTTP {}
Body: {} at {:?}

What it means

baml.fetch_as performs an HTTP GET of the given URL and requires a success (2xx) status. When the response status is not successful, it throws this error embedding the HTTP status code and the response body (or a placeholder if the body could not be read).

Source

Thrown at engine/baml-compiler/src/thir/interpret.rs:2774

            };

            let target_type = &type_args[0];

            // Make HTTP request
            let response = reqwest::get(&url).await.with_context(|| {
                format!(
                    "baml.fetch_as: failed to fetch URL '{}' at {:?}",
                    url, meta.0
                )
            })?;

            let status = response.status();
            if !status.is_success() {
                let body = response
                    .text()
                    .await
                    .unwrap_or_else(|_| "<failed to read body>".to_string());
                bail!(
                    "baml.fetch_as: HTTP request failed: HTTP {}\nBody: {} at {:?}",
                    status,
                    body,
                    meta.0
                );
            }

            let body = response.text().await.with_context(|| {
                format!(
                    "baml.fetch_as: failed to read response body at {:?}",
                    meta.0
                )
            })?;

            // Parse the JSON body into the target type
            let parsed_value = parse_json_to_baml_value(&body, target_type, meta)?;
            Ok(parsed_value)
        }

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Read the HTTP status and body included in the error message to identify the server-side cause
2. Fix the URL (path, host, port) if it is wrong
3. Add/refresh authentication (query param, header, token) if the status is 401/403
4. Handle 429 by backing off and retrying; investigate server logs for 5xx

Example fix

// before
let v = baml.fetch_as::<MyType>("http://host:9000/wrong-path")
// after
let v = baml.fetch_as::<MyType>("http://host:9000/correct-path")

// Pre-check the endpoint returns 2xx before relying on fetch_as:
// curl -s -o /dev/null -w "%{http_code}" "$URL"  # expect 2xx

match evaluate_builtin_function(...).await {
    Err(e) if e.contains("baml.fetch_as: HTTP request failed") => {
        // log status/body from message; retry on 429/5xx, fail fast on 4xx
    }
    other => other?,
}

When it happens

Trigger: Calling baml.fetch_as::<T>(url) against a URL that returns 404, 500, 401, 403, 429, or any other non-2xx status.

Common situations: Wrong endpoint path or port; server-side bug producing a 500; expired auth so the remote returns 401/403; rate limiting (429); calling a URL that no longer exists.

Understand the failure class

Background: "API error: {status}" and "HTTP 401/403/404/429/5xx" errors: non-2xx HTTP responses explained — this error's family across 27 libraries.

Related errors

• Failed to fetch media: {e:?}
• baml.fetch_as: HTTP request failed: HTTP {status} Body: {bod
• Failed to fetch media bytes: {e:?}
• Failed to fetch media: {} {}, {}
• Failed to fetch: {url}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/045097dbe740a231. Report an issue: GitHub.