server returned partial content without a resumable request

Error message

server returned partial content without a resumable request

What it means

During a resumable HTTP download, a server responded 206 (partial content) even though the request was not resumable (no resume state was available, and a previous restart without resume already happened). mise cannot trust partial data it never asked for, so it clears the partial and bails.

Solutions

Bypass or fix the proxy/cache in front of the server — it's returning partial content for non-Range requests.
Retry from a different mirror or direct download source.
Clear the partial download cache and retry in case stale state contributed.

Defensive patterns

Strategy: fallback

Validate before calling

curl -fsSI -H 'Range: bytes=0-0' "$url" | grep -i '^content-range:' || echo "server mishandles Range requests"

Prevention

Probe servers/proxies for correct Range behavior before relying on resumable downloads
Bypass caching layers that always answer 206
Use mirrors known to support conditional GET correctly

When it happens

Trigger: The downloader retries a failed download without a Range header (after clearing resume state), the server still returns 206 Partial Content, and this is the second time it happens (restarted_without_resume already true).

Common situations: Broken/misbehaving proxy or CDN that always returns 206 regardless of Range headers; buggy caching layer mangling requests; server-side middleware that rewrites Range requests.

Related errors

AI-assisted analysis of jdx/mise@533346cc37 (2026-09-17). Data as JSON: /api/errors/4b1be733b03966ff. Report an issue: GitHub.

Appendix: source

Thrown at src/http.rs:1140

                    debug!("range request at offset {offset} was unsatisfied for {total} bytes");
                }
                partial.clear()?;
                if offset > 0 && !restarted_without_resume {
                    restarted_without_resume = true;
                    continue;
                }
                resp.error_for_status_ref()?;
            }

            let (write_offset, total_size, validator, resumable, effective_filename) =
                if resp.status() == StatusCode::PARTIAL_CONTENT {
                    let Some((state, _)) = resume else {
                        partial.clear()?;
                        if !restarted_without_resume {
                            restarted_without_resume = true;
                            continue;
                        }
                        bail!("server returned partial content without a resumable request");
                    };
                    let content_range = resp
                        .headers()
                        .get(CONTENT_RANGE)
                        .and_then(|value| value.to_str().ok())
                        .and_then(parse_content_range);
                    let Some(ParsedContentRange::Bytes { start, end, total }) = content_range
                    else {
                        partial.clear()?;
                        if restarted_without_resume {
                            bail!("server returned an invalid Content-Range response");
                        }
                        restarted_without_resume = true;
                        continue;
                    };
                    let validator = response_validator(resp.headers());
                    let response_length_matches = resp
                        .content_length()

View on GitHub (pinned to 533346cc37)