Senior Frontend / UX Engineer – AI-Driven Full Stack | Contractor | LATAM
General Information
Location: Remote – Latin America
Contract Type: Independent Contractor (full-time)
Industry / Project: Fintech – Digital Wallet for cross-border payments
Time Zone: ART
English Level: B2
About the Role
We are looking for a Senior Frontend / UX Engineer to join a fast-growing U.S. fintech company that is simplifying cross-border payments and international money transfers, with a strong focus on the Latino community in the United States.
You will help build its Digital Wallet, the product through which users manage and move their money.
This is a frontend-first role.
Your main job will be to build excellent user experiences: turning product requirements and UX/UI designs into intuitive, scalable, production-ready wallet features.
You will also use AI-powered development tools to extend your reach across the stack, including Backend for Frontend (BFF) services, API integrations, and supporting backend functionality, so you can deliver complete features on your own when needed.
We are looking for someone who goes beyond implementing screens.
You should understand how users interact with financial products, spot opportunities to improve the experience, and balance user experience, technical quality, and delivery speed.
Your work will directly affect how easily and confidently users send money to their families and manage their finances.
Responsibilities
Design, develop, and maintain high-quality user interfaces for a Digital Wallet.
Translate UX/UI designs and product requirements into functional, intuitive, and responsive applications.
Collaborate with product and design teams to improve user journeys, interactions, and overall usability.
Own features end to end, from initial requirements through implementation and delivery.
Use AI-powered development tools to speed up frontend and full-stack development.
Build and maintain Backend for Frontend (BFF) services that support application requirements.
Implement API integrations and supporting backend functionality when needed.
Ensure consistency, performance, accessibility, and maintainability across the application.
Take part in code reviews and help improve development practices.
Find ways to simplify development workflows through AI-assisted engineering.
Requirements Must-Have
Strong hands-on experience with React, JavaScript, and TypeScript.
Experience building fintech applications, digital wallets , or payment platforms.
Solid understanding of UX principles, usability, interaction design, and user-centered development.
A proven track record of building polished, production-ready user interfaces.
Experience turning Figma designs or equivalent UX/UI specifications into working applications.
Practical experience with AI-assisted coding tools such as Cursor, Claude Code, GitHub Copilot, or similar.
Ability to deliver complete features across frontend and backend boundaries.
Experience with REST APIs, third-party integrations, and Backend for Frontend (BFF) architectures.
Strong understanding of frontend architecture, reusable components, and state management.
Experience working in Agile product development environments.
Strong communication, problem-solving, and independent execution skills.
Comfort working hands-on with production code.
Nice-to-Have
Experience with React Native and cross-platform mobile development.
Familiarity with Node.js and modern backend frameworks.
Experience building and maintaining design systems.
Knowledge of authentication, authorization, and secure development for financial applications.
Experience with AI-driven development workflows and agentic coding tools.
Understanding of mobile-first design, accessibility, and frontend performance optimization.
What We Offer (Contractor)
Contractor agreement with payment in USD.
100% remote work in an international setting.
Access to Argentine public holidays.




Direct involvement in modernizing core platform observability for a high-growth fintech ecosystem.
Professional development, learning platforms, and referral programs.
Explore this and other opportunities at:
AI Research Engineer (Agentic Posttraining) 100% Remote Worldwide
Join Tether and Shape the Future of Digital Finance
At Tether, we're not just building products, we're pioneering a global financial revolution.
Our cutting-edge solutions empower businesses—from exchanges and wallets to payment processors and ATMs—to seamlessly integrate reserve-backed tokens across blockchains.
By harnessing the power of blockchain technology, Tether enables you to store, send, and receive digital tokens instantly, securely, and globally, all at a fraction of the cost.
Transparency is the bedrock of everything we do, ensuring trust in every transaction.
Innovate with Tether
Tether Finance: Our innovative product suite features the world's most trusted stablecoin, USDT , relied upon by hundreds of millions worldwide, alongside pioneering digital asset tokenization services.
But that's just the beginning:
Tether Power: Driving sustainable growth, our energy solutions optimize excess power for Bitcoin mining using eco-friendly practices in state-of-the-art, geo-diverse facilities.
Tether Data: Fueling breakthroughs in AI and peer-to-peer technology, we reduce infrastructure costs and enhance global communications with cutting‐edge solutions like KEET , our flagship app that redefines secure and private data sharing.
Tether Education : Democratizing access to top-tier digital learning, we empower individuals to thrive in the digital and gig economies, driving global growth and opportunity.
Tether Evolution : At the intersection of technology and human potential, we are pushing the boundaries of what is possible, crafting a future where innovation and human capabilities merge in powerful, unprecedented ways.
Why Join Us?
Our team is a global talent powerhouse, working remotely from every corner of the world.
If you're passionate about making a mark in the fintech space, this is your opportunity to collaborate with some of the brightest minds, pushing boundaries and setting new standards.
We've grown fast, stayed lean, and secured our place as a leader in the industry.
If you have excellent English communication skills and are ready to contribute to the most innovative platform on the planet, Tether is the place for you.
Are you ready to be part of the future?
About the job
As a member of the AI model team, you will drive innovation in post‐training methodologies, with a special focus on agentic behaviors and tool use.
Your work will refine pre‐trained models so that they not only deliver enhanced intelligence and domain specific capabilities, but also learn to reason, plan, and autonomously invoke external tools to solve real world, multi step tasks and applications on edge devices (i.e., smartphones).
You will work on a wide spectrum of systems, ranging from streamlined, resource efficient agents that run on limited hardware to complex multi modal architectures integrating text, images, and audio, all optimized for tool augmented decision making.
We expect you to have deep expertise in large language model architectures and substantial experience in post‐training for agentic workflows, including tool use fine tuning, function calling, and reinforcement learning from feedback on multi turn interactions.
You will adopt a hands‐on, research driven approach to developing, testing,



and implementing new post‐training algorithms that unlock goal directed behavior, self correction, and reliable tool invocation.
Your responsibilities include curating agentic training data (e.g., trajectories of tool use, reasoning chains, environment interactions), strengthening baseline performance, and identifying as well as resolving bottlenecks in post‐training for tool augmented agents to achieve SOTA model quality.
The goal is to build models that do not just know but also act, use tools, and adapt, pushing the limits of what agentic AI can achieve.
Responsibilities
Conduct end‐to‐end research and engineering initiatives to advance post‐training of agentic and tool‐use models to achieve SOTA results.
Drive broad, cross‐cutting model improvements, including factuality, instruction adherence, tool/function use, multi‐agent coordination, and reasoning calibration.
Design and enhance large‐scale post‐training systems, including data pipelines, training workflows, evaluation frameworks, and benchmark infrastructure.
Develop rigorous evaluation suites and diagnostic tools to assess model readiness for deployment.
Strengthen feedback loops from real‐world product usage, incorporating both explicit and implicit user signals into post‐training.
Collaborate with tooling, product, and training teams to improve the usefulness, reliability, and agentic capabilities of frontier models.
Closely liaise with research, engineering and cross‐functional teams to determine which integrations are production‐ready for inclusion in major model releases.
Degree in Computer Science, Machine Learning, or a related field; advanced degree (MS/PhD) preferred with a strong publication record in top‐tier AI conferences.
Experience with multimodal post‐training workflows and data pipelines, particularly for agentic systems and tool use.
Hands‐on experience applying post‐training at scale using distributed training frameworks (e.g., multi‐node GPU environments).
Demonstrated experience improving model capabilities in areas such as reasoning, tool use, and multi‐agent coordination that achieve SOTA results.
Proven track record of open‐source contributions related to agentic systems or tool use (code, datasets, or models) on platforms such as GitHub or Hugging Face.
Publications at leading AI conferences (e.g., NeurIPS, ICML, ICLR, ACL, CVPR, ECCV).
AI Research Engineer (Kernel & Inference Optimization) 100% Remote Worldwide
Join Tether and Shape the Future of Digital Finance
At Tether, we're not just building products, we're pioneering a global financial revolution.
Our cutting‐edge solutions empower businesses—from exchanges and wallets to payment processors and ATMs—to seamlessly integrate reserve‐backed tokens across blockchains.
By harnessing the power of blockchain technology, Tether enables you to store, send, and receive digital tokens instantly, securely, and globally, all at a fraction of the cost.
Transparency is the bedrock of everything we do, ensuring trust in every transaction.
Innovate with Tether
Tether Finance: Our innovative product suite features the world's most trusted stablecoin, USDT , relied upon by hundreds of millions worldwide, alongside pioneering digital asset tokenization services.
But that's just the beginning:
Tether Power: Driving sustainable growth, our energy solutions optimize excess power for Bitcoin mining using eco‐friendly practices in state‐of‐the‐art, geo‐diverse facilities.
Tether Data: Fueling breakthroughs in AI and peer‐to‐peer technology, we reduce infrastructure costs and enhance general communications with cutting‐edge solutions like KEET , our flagship app that redefines secure and private data sharing.
Tether Education : Democratizing access to top‐tier digital learning, we empower individuals to thrive in the digital and gig economies, driving global growth and opportunity.
Tether Evolution : At the intersection of
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