denoland/deno · error · TypeError

Invalid value for 'proxy.transport' option: ${JSONStringify(

Error message

Invalid value for 'proxy.transport' option: ${JSONStringify(proxy.transport)}

What it means

Thrown by Deno.createHttpClient when options.proxy.transport is present but not one of the supported values 'http', 'https', 'socks5', 'tcp', 'unix', or 'vsock'. The switch over transport has no matching case, so the default branch reports the offending value (JSON-stringified) as a TypeError. This is a pure config-validation error raised before any network activity.

Source

Thrown at ext/fetch/22_http_client.js:82

          const url = proxy.url;
          if (
            !StringPrototypeStartsWith(url, "socks5:") &&
            !StringPrototypeStartsWith(url, "socks5h:")
          ) {
            throw new TypeError(
              `The url passed into 'proxy.url' has an invalid scheme for this transport.`,
            );
          }
          proxy.transport = "http";
          break;
        }
        case "tcp":
        case "unix":
        case "vsock": {
          break;
        }
        default: {
          throw new TypeError(
            `Invalid value for 'proxy.transport' option: ${
              JSONStringify(proxy.transport)
            }`,
          );
        }
      }
    } else {
      proxy.transport = "http";
    }
  }
  const keyPair = loadTlsKeyPair("Deno.createHttpClient", options);
  return new HttpClient(
    op_fetch_custom_client(
      options,
      keyPair,
    ),
  );
}

View on GitHub (pinned to 89f33cbef2)

Solutions

1. Set transport to one of: 'http', 'https', 'socks5', 'tcp', 'unix', 'vsock' (exact lowercase)
2. If you only need a standard HTTP(S) proxy, omit transport entirely — it defaults to 'http'
3. Lowercase/validate the value against an allowlist before passing it to createHttpClient

Example fix

// before
const client = Deno.createHttpClient({
  proxy: { transport: 'SOCKS5', url: 'socks5://127.0.0.1:1080' },
});

// after
const client = Deno.createHttpClient({
  proxy: { transport: 'socks5', url: 'socks5://127.0.0.1:1080' },
});

const TRANSPORTS = new Set(['http', 'https', 'socks5', 'tcp', 'unix', 'vsock']);
function normalizeTransport(p) {
  if (p.transport == null) return { ...p, transport: 'http' };
  const t = String(p.transport).toLowerCase();
  if (!TRANSPORTS.has(t)) {
    throw new Error(`invalid proxy.transport '${p.transport}'; expected one of ${[...TRANSPORTS].join(', ')}`);
  }
  return { ...p, transport: t };
}

/** @param {unknown} t */
function isValidTransport(t) {
  return typeof t === 'string' &&
    ['http', 'https', 'socks5', 'tcp', 'unix', 'vsock'].includes(t);
}

When it happens

Trigger: Deno.createHttpClient({ proxy: { transport: 'SOCKS5', url: 'socks5://...' } }) — wrong casing, typos like 'sock', values like 'http2', or non-string values (e.g. 5) all land in the default branch.

Common situations: Case-mismatched values from env vars or YAML configs, outdated docs/older Deno versions where fewer transports existed, or programmatically computed transport strings with a typo.

Related errors

• The url passed into 'proxy.url' has an invalid scheme for th
• Cannot create cron job, a unique name is required: received
• Cannot create cron job, a schedule is required: received 'un
• ERR_PROXY_INVALID_CONFIG
• ERR_INVALID_ARG_TYPE

AI-assisted analysis of denoland/deno@89f33cbef2 (2026-08-16). Data as JSON: /api/errors/e64e1813b9d526f5. Report an issue: GitHub.