Overview

We are looking for a Senior Frontend Engineer – SDK Lead with strong expertise in React 19, TypeScript, ShadCN, Tailwind CSS, and TanStack Query to architect and lead the development of a high-quality, TypeScript-strict React SDK.

The ideal candidate should have hands-on experience building React component libraries or SDKs consumed by multiple teams, with deep knowledge of streaming protocols, real-time state management, public API design, release management, and modern frontend architecture.

Experience with AI/LLM chat interfaces, streaming completions, tool calls, and multi-provider AI abstractions will be highly valued.

Key Responsibilities

• Architect and develop a TypeScript-strict, ESM-only React SDK supporting multiple streaming protocols, including:
• OpenAI SSE
• AG-UI custom events
• Solve complex real-time frontend challenges involving:
• Streamed tool-call correlation
• Reasoning-token extraction across different providers
• AbortController lifecycle and cancellation
• Real-time state synchronization
• Local-first storage and eviction strategies
• Design scalable and extensible SDK APIs for consumption by multiple product and engineering teams.
• Establish robust state-management patterns using React, useReducer, Context, and TanStack React Query.
• Develop reusable components and interfaces using React 19, ShadCN, Tailwind CSS, and TypeScript.
• Own the complete SDK release lifecycle, including:
• Semantic versioning (SemVer)
• Changesets
• CHANGELOG management
• Breaking-change coordination
• Peer-dependency compatibility
• Lead technical integration calls with consumer/product teams.
• Triage integration issues and work closely with consuming teams to resolve technical challenges.
• Define and negotiate API contracts and extensibility patterns such as:
• Transport factories
• Request/response mappers
• Feature-flag presets
• Establish comprehensive automated test coverage for a complex public API surface.
• Create migration guides and technical documentation for major and breaking releases.
• Contribute to frontend architecture, coding standards, performance optimization, and engineering best practices.
• Mentor engineers and provide technical leadership on SDK architecture and implementation.

Required Skills & Experience

• 7+ years of frontend/software development experience, with at least 5+ years of experience shipping React component libraries or SDKs consumed by multiple teams.
• Strong hands-on expertise with:
• React 19
• TypeScript 5.7+
• ShadCN
• Tailwind CSS
• TanStack React Query
• Deep TypeScript knowledge, including:
• Generics
• Discriminated unions
• Strict mode
• Type narrowing
• Declaration emit
• Advanced type-safe API design
• Strong experience with React SDK/component-library architecture and public API design.
• Strong understanding of SSE and real-time streaming protocols.
• Experience handling:
• Streaming responses
• Event parsing
• Tool-call streaming
• Stream cancellation
• AbortController patterns
• Concurrent/partial state updates
• Strong knowledge of real-time state management using useReducer, Context, and React Query.
• Experience with ESM-only packages and modern JavaScript/TypeScript package architecture.
• Hands-on experience with monorepo tooling, preferably Turborepo.
• Strong understanding of SemVer, Changesets, changelog management, and release workflows.
• Ability to manage breaking changes and peer-dependency compatibility.
• Strong communication skills with the ability to lead technical discussions with product and engineering teams.
• Experience writing technical documentation, migration guides, and API specifications.

Preferred Skills

• Experience building AI/LLM-powered chat interfaces.
• Experience with:
• Streaming LLM completions
• Tool/function calling
• Tool-call rendering
• Reasoning-token handling
• Multi-model routing
• Multi-provider AI abstractions
• Strong understanding of React 19 Server Component boundaries and "use client" directives.
• Experience with Storybook 10.x.
• Experience with Biome for linting and formatting.
• Experience with tsdown for package/library bundling.
• Experience with Portkey AI Gateway or similar multi-provider AI gateway/abstraction platforms.
• Experience designing extensible transport and provider abstraction layers.

Tech Stack

• TypeScript 5.7
• React 19
• ShadCN
• Tailwind CSS
• TanStack React Query
• tsdown
• Turborepo
• Biome
• Storybook 10
• SSE
• OpenAI Streaming
• AG-UI
• Changesets
• Private npm Registry

Ideal Candidate Profile

The ideal candidate is an architect-level frontend engineer who can do more than build React UI components. They should be comfortable owning a public SDK/API from architecture through release, solving difficult streaming and state-management problems, working with AI/LLM integrations, and collaborating directly with multiple consuming engineering teams.

Strong emphasis will be placed on TypeScript depth, React SDK architecture, streaming protocols, real-time systems, API design, release management, and technical leadership.