Senior Software Engineer, Frontend / Full Stack (Identity Platform)

Phantom seeks a Senior Software Engineer for its Identity Platform to own authentication, signing, and key management flows across web and mobile. Fully remote, 180+ team, backed by a16z.

Phantom connects tens of millions of people to open markets — perpetuals, prediction markets, tokenized assets, stablecoins — with self-custody at its core. The Identity Platform is the trust root of Phantom: authentication, unlocking, onboarding/key generation, and the signing pipeline that every transaction flows through. Responsibilities: - Own and evolve the signing path for every transaction in Phantom - Build and harden authentication, unlocking, biometrics, and account access flows across web and mobile - Ship passkeys (WebAuthn) and MFA improvements with a strong security/usability balance - Own onboarding and key lifecycle flows: key generation/derivation, seed phrase flows, seedless registration, hardware wallet pairing - Own sensitive key export/import experiences and related safety rails - Write and maintain high-signal, non-flaky tests (unit/integration/e2e) for critical paths; ensure safe rollouts via monitoring and staged releases

- 7+ years of experience - Strong TypeScript skills; comfortable shipping code across browser, Node.js, and mobile JS runtimes - Proven ability to build high-signal, low-flake test suites for critical systems - Familiarity with auth concepts and common mechanisms (sessions/tokens, MFA/OTP, WebAuthn/passkeys) - Strong engineering fundamentals: system design, debugging, and production reliability - Nice-to-have: deeper experience with OAuth2/OIDC, WebAuthn internals, cryptography, or key management systems; Web3/wallet or signing-flow experience; security- or money-adjacent experience (identity, payments, custody); Rust experience (or strong interest in learning it)