n8n-io/n8n · error · Error

Invalid integer for ${flag}

Error message

Invalid integer for ${flag}

What it means

The parseIntArg helper (line 265) calls nextArg to get the raw value, then parseInt(raw, 10). If the result is NaN, the value was not a valid base-10 integer and the error identifies which flag received the bad value. This catches non-numeric input before it silently becomes NaN in downstream iteration/concurrency/maxAttempts arithmetic.

Source

Thrown at packages/@n8n/instance-ai/evaluations/cli/build-mcp-manifest.ts:268

		return JSON.parse(content);
	} catch (error) {
		const msg = error instanceof Error ? error.message : String(error);
		throw new Error(`Failed to parse ${label} at ${path}: ${msg}`);
	}
}

function nextArg(argv: string[], i: number, flag: string): string {
	const value = argv[i + 1];
	if (value === undefined || value.startsWith('--')) {
		throw new Error(`Missing value for ${flag}`);
	}
	return value;
}

function parseIntArg(argv: string[], i: number, flag: string): number {
	const raw = nextArg(argv, i, flag);
	const parsed = parseInt(raw, 10);
	if (Number.isNaN(parsed)) throw new Error(`Invalid integer for ${flag}`);
	return parsed;
}

// ---------------------------------------------------------------------------
// Build outcome + test-case prompt source
//
// The `claude -p` invocation, MCP config staging, prompt flattening, and
// workflow-id extraction live in ./mcp-builder (shared with the fused
// --build-via-mcp eval path). This file owns only the manifest/stats concerns.
// ---------------------------------------------------------------------------

interface BuildOutcome {
	slug: string;
	iteration: number;
	workflowId: string | null;
	cost: number;
	turns: number;
	durationMs: number;

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Provide a valid whole number for the flag (e.g. --iterations 3)
2. Verify no accidental spaces or quotes around the value
3. Check that the value is numeric, not a word or empty string

Example fix

# before
pnpm eval:build-mcp-manifest --iterations three

# after
pnpm eval:build-mcp-manifest --iterations 3

// Validate integer values in wrapper scripts before passing to the CLI:
function parseIntOrThrow(raw: string, flag: string): number {
  const n = Number.parseInt(raw, 10);
  if (Number.isNaN(n)) throw new Error(`Invalid integer for ${flag}: ${raw}`);
  return n;
}

function isIntegerString(v: string): boolean {
  return /^-?\d+$/.test(v.trim());
}

When it happens

Trigger: Running `pnpm eval:build-mcp-manifest --iterations abc`, `--concurrency x`, or any integer flag with a non-numeric token. Note: parseInt('1.5') returns 1 (not NaN), so floats with integer prefixes are accepted; only fully non-numeric values trigger this.

Common situations: Typo in a numeric argument (e.g. spelling out 'three' instead of 3). Copy-paste error. A variable expansion that produced an empty string or non-numeric value.

Related errors

• --max-attempts must be >= 1
• Missing value for ${flag}
• --source langtracer requires --suite <slug>
• Workflow directory not found: ${workflowDir}
• --build-cwd directory does not exist: ${args.buildCwd}

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/1de2acaec2db7169. Report an issue: GitHub.