chenhg5/cc-connect · error

Content-Length too large: %d

Error message

Content-Length too large: %d

What it means

readMessage enforces a 10 MB cap on the declared Content-Length to prevent huge or malicious allocations (`body := make([]byte, contentLength)` would otherwise allocate whatever the peer claims). If the header value exceeds 10*1024*1024 the message is rejected with "Content-Length too large: %d".

Source

Thrown at agent/copilot/jsonrpc.go:115

			// End of headers
			break
		}
		if strings.HasPrefix(line, "Content-Length: ") {
			val := strings.TrimPrefix(line, "Content-Length: ")
			n, err := strconv.Atoi(strings.TrimSpace(val))
			if err != nil {
				return nil, fmt.Errorf("invalid Content-Length: %w", err)
			}
			contentLength = n
		}
		// Ignore other headers (Content-Type, etc.)
	}

	if contentLength < 0 {
		return nil, fmt.Errorf("missing Content-Length header")
	}
	if contentLength > 10*1024*1024 {
		return nil, fmt.Errorf("Content-Length too large: %d", contentLength)
	}

	body := make([]byte, contentLength)
	if _, err := io.ReadFull(lr.reader, body); err != nil {
		return nil, fmt.Errorf("read body: %w", err)
	}
	return body, nil
}

// rpcClient manages JSON-RPC request IDs and pending responses.
type rpcClient struct {
	writer *lspWriter
	nextID atomic.Int64

	pendingMu sync.Mutex
	pending   map[int64]chan *jsonRPCResponse
}

View on GitHub (pinned to 4000b2338a)

Solutions

1. Fix the message producer to send the true byte length of its JSON body
2. If you legitimately need larger messages, raise the 10*1024*1024 cap in jsonrpc.go and re-test
3. Log and inspect the declared length vs actual bytes to find the framing bug
4. Split oversized payloads at the protocol level rather than in one frame

Example fix

// before (test/mock emits wrong length)
body := buildHugeResult()
fmt.Fprintf(w, "Content-Length: %d\r\n\r\n", len(body)*2)
// after
fmt.Fprintf(w, "Content-Length: %d\r\n\r\n", len(body))

func plausibleContentLength(n int) bool {
    return n > 0 && n <= 10*1024*1024
}

body, err := readMessage(lr)
if err != nil {
    if strings.Contains(err.Error(), "too large") {
        slog.Error("copilot: oversized frame declared", "err", err)
        return errFatal
    }
    return err
}

When it happens

Trigger: The copilot child process (or test mock) sends a Content-Length header whose value is greater than 10485760 bytes — e.g. a corrupt/misencoded large payload, a bogus integer in a test fixture, or a malformed writer emitting an absurd length.

Common situations: TestLSPReader_TooLargeContentLength style fixtures; a writer that emits the body length before appending more content (counting wrong); a hostile/corrupted child process; unit confusion (bytes vs KiB) when constructing a big fake response.

Understand the failure class

Background: payload too large / request exceeds maximum size: why libraries cap bytes and how to fix oversize payloads — this error's family across 50 libraries.

Related errors

• hook input exceeds %d bytes
• invalid Content-Length: %w
• missing Content-Length header
• copilot: session.delete: %s
• copilot: session.delete failed: %s

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/488cc07b4fdbde0e. Report an issue: GitHub.