xai-org/grok-build · error

Task panicked: {}

Error message

Task panicked: {}

What it means

During multipart upload, each part is uploaded in a spawned task; if the task's JoinHandle returns Err (the task panicked or was cancelled rather than returning a result), the code wraps it as "Task panicked: {e}" and records it as a part upload error. It indicates an internal panic in a part-upload task, not an HTTP failure from the server.

Source

Thrown at crates/codegen/xai-file-utils/src/storage_client.rs:1730

        &self,
        tasks: Vec<(u32, tokio::task::JoinHandle<Result<UploadedPartInfo>>)>,
    ) -> Result<Vec<UploadedPartInfo>> {
        let mut uploaded_parts = Vec::with_capacity(tasks.len());
        let mut upload_errors = Vec::new();

        for (part_num, task) in tasks {
            match task.await {
                Ok(Ok(part_info)) => {
                    tracing::debug!("Part {} uploaded successfully", part_num);
                    uploaded_parts.push(part_info);
                }
                Ok(Err(e)) => {
                    tracing::error!("Part {} upload failed: {}", part_num, e);
                    upload_errors.push((part_num, e));
                }
                Err(e) => {
                    tracing::error!("Part {} task panicked: {}", part_num, e);
                    upload_errors.push((part_num, anyhow::anyhow!("Task panicked: {}", e)));
                }
            }
        }

        if !upload_errors.is_empty() {
            let error_msgs: Vec<String> = upload_errors
                .iter()
                .map(|(part, e)| format!("part {}: {}", part, e))
                .collect();
            anyhow::bail!("Multipart upload failed: {}", error_msgs.join("; "));
        }

        Ok(uploaded_parts)
    }

    /// Initialize a multipart upload session with signed URLs for direct upload.
    /// Includes retry logic for transient failures.
    async fn multipart_init(&self, file_size: u64) -> Result<MultipartInitResponse> {

View on GitHub (pinned to bc7f02eddd)

Solutions

1. Inspect the wrapped JoinError/panic message to find the panicking code path.
2. Ensure the runtime is not shut down while multipart uploads are in flight.
3. Reduce part size or validate part counts to avoid edge cases triggering the panic.
4. Upgrade/patch the library if the panic is an internal bug; enable panic backtraces (RUST_BACKTRACE=1) to locate it.

Example fix

// before
RUST_BACKTRACE=0 ./my-uploader

// after
RUST_BACKTRACE=full ./my-uploader

// Catch panics in your own per-part logic before spawning, and keep runtime alive
let result = std::panic::catch_unwind(|| prepare_part(part));
if result.is_err() {
    anyhow::bail!("part {} preparation panicked; fix inputs before multipart upload", part_num);
}

match client.upload_multipart(reader, part_size).await {
    Ok(resp) => use(resp),
    Err(e) if e.to_string().contains("Task panicked") => {
        tracing::error!("multipart worker panicked: {e:#}; retrying smaller parts");
        // fallback: re-run with smaller part_size or sequential uploads
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: A part-upload task panicking (e.g. unwrap on None, index out of bounds, or an abort inside the task future); runtime shutdown or JoinError::Cancel aborting the task mid-upload.

Common situations: Bug in the part-upload path triggered by unusual part sizes or content; tokio runtime dropping tasks during shutdown; OOM or other panics inside reqwest handling for very large parts; panic in a custom resolver/callback invoked in the task.

Related errors

• bridge spawn
• PTY write channel closed
• Failed to parse part {} response: {}
• agent runtime worker join: {e}
• blocking pre-allocate task panicked: {e}

AI-assisted analysis of xai-org/grok-build@bc7f02eddd (2026-08-31). Data as JSON: /api/errors/ace94d3979f452af. Report an issue: GitHub.