louislam/dockge · error · Error

Command must be a number.

Error message

Command must be a number.

What it means

The terminalResize socket handler validates every argument type before touching the terminal. The `rows` parameter arrived as something other than a number (string, null, undefined, object...), so the handler throws immediately instead of writing a bad value to the terminal. The copy-pasted message says 'Command' but this branch is really about the rows dimension.

Source

Thrown at backend/agent-socket-handlers/terminal-socket-handler.ts:178

                callbackResult({
                    ok: true,
                }, callback);
            } catch (e) {
                callbackError(e, callback);
            }
        });

        // Resize Terminal
        agentSocket.on("terminalResize", async (terminalName: unknown, rows: unknown, cols: unknown) => {
            log.info("terminalResize", `Terminal: ${terminalName}`);
            try {
                checkLogin(socket);
                if (typeof terminalName !== "string") {
                    throw new Error("Terminal name must be a string.");
                }

                if (typeof rows !== "number") {
                    throw new Error("Command must be a number.");
                }
                if (typeof cols !== "number") {
                    throw new Error("Command must be a number.");
                }

                let terminal = Terminal.getTerminal(terminalName);

                // log.info("terminal", terminal);
                if (terminal instanceof Terminal) {
                    //log.debug("terminalInput", "Terminal found, writing to terminal.");
                    terminal.rows = rows;
                    terminal.cols = cols;
                } else {
                    throw new Error(`${terminalName} Terminal not found.`);
                }
            } catch (e) {
                log.debug("terminalResize",
                        // Added to prevent the lint error when adding the type

View on GitHub (pinned to f809ae192b)

Solutions

1. Pass rows as a JavaScript number: socket.emit('terminalResize', terminalName, Number(rows), cols)
2. On the client, coerce/validate before emitting: if (typeof rows !== 'number') throw new TypeError('rows must be a number')
3. Check the emitting code actually passes rows and cols positionally in the right order

Example fix

// before
socket.emit("terminalResize", terminalName, terminal.rows.toString(), terminal.cols);
// after
socket.emit("terminalResize", terminalName, parseInt(rowsInput, 10), parseInt(colsInput, 10));

function isValidResize(p) { return typeof p.terminalName === "string" && typeof p.rows === "number" && Number.isFinite(p.rows) && typeof p.cols === "number" && Number.isFinite(p.cols); }
if (!isValidResize(payload)) throw new TypeError("terminalResize requires (string, number, number)");
socket.emit("terminalResize", payload.terminalName, payload.rows, payload.cols);

function isNumber(v: unknown): v is number { return typeof v === "number" && Number.isFinite(v); }

try { socket.emit("terminalResize", name, rows, cols); } catch (e) { if (e instanceof TypeError) { /* coerce and retry: Number(rows) */ } else { throw e; } }

When it happens

Trigger: Emitting socket event `terminalResize` with a non-number second argument, e.g. socket.emit('terminalResize', 'stack1', '80', 24) passing rows as a string, or omitting it so rows === undefined.

Common situations: Frontend code passing xterm dimensions from DOM strings or form inputs without Number() conversion; stale clients predating the rows/cols signature; agents forwarding JSON where numbers were serialized as strings.

Understand the failure class

Background: Invalid argument type errors: "must be of type string", "expected X, got Y", and ERR_INVALID_ARG_TYPE explained — this error's family across 15 libraries.

Related errors

• Command must be a string.
• Stack name must be a string.
• Service name must be a string.
• Shell must be a string.
• Stack name and service name must be strings

AI-assisted analysis of louislam/dockge@f809ae192b (2026-08-31). Data as JSON: /api/errors/42b1eb1edebe368e. Report an issue: GitHub.