Kong/insomnia · error · Error

failed to parse cookie, the cookie string seems invalid

Error message

failed to parse cookie, the cookie string seems invalid

What it means

Cookie constructor guard: the argument was a string, but tough-cookie's Cookie.parse returned null, meaning the string is not a syntactically valid Set-Cookie/Cookie serialisation (bad name=value syntax, illegal characters, or malformed attributes).

Solutions

1. Pass a valid cookie string like 'name=value; Path=/'
2. Pass a CookieOptions object instead of a raw string
3. Sanitize input before constructing cookies in scripts

When it happens

Trigger: Thrown at packages/insomnia-scripting-environment/src/objects/cookies.ts:42 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of Kong/insomnia@d9bb2b0142 (2026-08-26). Data as JSON: /api/errors/e3eeb27d398ef9f4. Report an issue: GitHub.

Appendix: source

Thrown at packages/insomnia-scripting-environment/src/objects/cookies.ts:42

  httpOnly?: boolean;
  hostOnly?: boolean;
  session?: boolean;
  extensions?: { key: string; value: string }[];
}

export class Cookie extends Property {
  override readonly _kind: string = 'Cookie';
  protected cookie: ToughCookie;
  private extensions?: { key: string; value: string }[];
  private insoExtensions: InsomniaCookieExtensions = {};

  constructor(cookieDef: CookieOptions | string) {
    super();

    if (typeof cookieDef === 'string') {
      const cookieDefParsed = Cookie.parse(cookieDef);
      if (!cookieDefParsed) {
        throw new Error('failed to parse cookie, the cookie string seems invalid');
      }
      cookieDef = cookieDefParsed;
    }

    const def = { ...cookieDef };
    this.extensions = def.extensions ? [...def.extensions] : [];
    def.extensions = [];

    const cookie = ToughCookie.fromJSON(def);
    if (!cookie) {
      throw new Error('failed to parse cookie, the cookie string seems invalid');
    }

    this.id = cookieDef.id || '';
    this.cookie = cookie;
    this.insoExtensions = {
      creation: cookieDef.creation,
      creationIndex: cookieDef.creationIndex,

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