What causes "Cloud agent harness execution failed (HTTP {status})." in Hmbown/CodeWhale?

Retry the job — transient toolbox failures and mid-run reaps are the most common cause.

Cloud agent harness execution failed

Error message

Cloud agent harness execution failed (HTTP {status}).

What it means

Thrown by `run_harness` when the sandbox toolbox `POST process/execute` call returns a non-2xx HTTP status. The harness command was dispatched to the sandbox but the toolbox itself rejected or failed the execution request — this is a transport/API-level failure, distinct from the harness command merely exiting non-zero (error 783).

Solutions

Retry the job — transient toolbox failures and mid-run reaps are the most common cause.
Check the sandbox state in the provider dashboard; if it is destroyed/stopped, the job must be re-dispatched on a fresh sandbox.
For 4xx statuses, confirm the installed provider matches the expected `process/execute` contract ({command, cwd, timeout}); a provider version change may require upgrading the tool.
If long commands routinely fail, lower per-command timeout_secs or split the work so requests fit the provider's request limits.

Defensive patterns

Strategy: retry

Try / catch

match result {
    Err(e) if e.to_string().contains("harness execution failed") => {
        // sandbox may have been reaped; re-dispatch on a fresh sandbox
        retry_on_fresh_sandbox(job)
    }
    other => other,
}

Prevention

Keep the sandbox active during long turns (the code already raises the request budget — do not shrink it back to the 120s cap).
Split very long commands into smaller harness steps.
Retry on a fresh sandbox; treat the failed sandbox as lost.
Watch for provider 4xx changes that indicate an API contract drift.

When it happens

Trigger: Dispatching a harness command when the toolbox returns non-success: sandbox was reaped/terminated mid-run (404/5xx), the request exceeded the harness budget timeout, toolbox is unhealthy, or the request payload was rejected (4xx).

Common situations: Long-running agent turns whose sandbox idle-timed out at the provider; Daytona capacity/instance failure mid-job; network interruption during a multi-minute harness request; provider API contract change causing 422.

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

AI-assisted analysis of Hmbown/CodeWhale@73e0f67d83 (2026-09-22). Data as JSON: /api/errors/f768a1d21d81d05c. Report an issue: GitHub.

Appendix: source

Thrown at crates/tui/src/cloud_dispatch.rs:1665

            "command": shell_quote_join(&command.argv),
            "cwd": command.cwd,
            "timeout": command.timeout_secs,
        });
        // This call carries the declared turn budget (an hour for the agent
        // entry), so it asks for that budget plus slack per request — never the
        // 120s control-plane cap that used to bound it.
        let response = Self::send_json_on(
            &Self::blocking_client()?,
            Self::harness_client_budget_secs(command),
            reqwest::Method::POST,
            &url,
            &api_key,
            body,
        )?;
        let status = response.status();
        let text = response.text().unwrap_or_default();
        if !status.is_success() {
            bail!("Cloud agent harness execution failed (HTTP {status}).");
        }
        let parsed: serde_json::Value = serde_json::from_str(&text)
            .context("the sandbox returned an unreadable harness result")?;
        let exit_code = parsed
            .get("exitCode")
            .and_then(serde_json::Value::as_i64)
            .unwrap_or(0);
        let result = parsed
            .get("result")
            .and_then(serde_json::Value::as_str)
            .unwrap_or("");
        if exit_code != 0 {
            bail!(
                "Cloud agent harness exited with code {exit_code}: {}",
                sanitize_error(result)
            );
        }
        Ok(result.chars().take(MAX_HARNESS_OUTPUT_CHARS).collect())

View on GitHub (pinned to 73e0f67d83)