LLM Engineer Jobs at Startups

SpaceX is building Super Intelligence to help humanity understand the universe, developing the full Super Intelligence stack from supercomputers to large language models and applications. This role focuses on the most critical post-training and reinforcement learning challenges, including reward modeling, preference optimization (RLHF/DPO), and RL for improving reasoning, truthfulness, and real-world capabilities. You will work on cutting-edge AI problems with the ultimate goal of making life multiplanetary and expanding consciousness to the stars.

$180k - $600k

SpaceXSI is building Super Intelligence to help humanity understand the universe, developing the full Super Intelligence stack from supercomputers to large language models and applications. This role is at the intersection of engineering and data operations, focusing on ensuring engineering teams receive high-quality data for training and evaluation. You will partner with model teams, design projects to capture meaningful signals, and drive data yield and evaluation lift, influencing data strategy through hands-on technical work.

$144k - $220k

Harvey is transforming legal and professional services by combining advanced agentic AI, an enterprise platform, and deep domain expertise. This role offers a unique opportunity to contribute to a rapidly scaling company at a pivotal moment, defining a new category in real-time. The team operates with intensity, ownership, and a commitment to excellence, driven by values of decisiveness, simplicity, and continuous improvement. If you are motivated to do your best work alongside driven individuals, Harvey is the place to build the future of professional services.

$230k - $340k

Snorkel AI

Snorkel AI is seeking Senior and Staff Product Engineers with strong backend experience to help shape and deliver product capabilities that simplify complex workflows for users. This role involves owning backend features from concept to production, collaborating closely with Product, Design, and Engineering teams. You will be instrumental in building and evolving APIs, services, data models, and workflow capabilities that support the product, focusing on areas like data cataloging, agent benchmarking, and workflow automation. The ideal candidate possesses sound technical judgment and a commitment to product quality, usability, and impact.

$208k - $315k

Figure is an AI robotics company developing autonomous general-purpose humanoid robots with the goal of shipping human-level intelligence. The Helix team is seeking an experienced AI Training Performance Engineer to elevate model training. This role focuses on enhancing distributed training frameworks for large-scale model training, optimizing GPU kernels, evaluating different accelerator types, and co-designing models for maximum hardware utilization.

$200k - $400k

You'll join the Grok Voice Model team as a software engineer. You'll design, build, and run the software systems behind Grok Voice, which delivers natural, low-latency, multilingual spoken interactions across devices and in real time. The team owns the full engineering stack behind the model, from large-scale data processing to distributed training to production deployment.

$150k - $450k

Together AI

As a Forward Deployed Engineer (FDE) focused on Post-Training, you will be a hands-on technical partner to strategic customers who are using fine-tuning and reinforcement learning to build differentiated models on open-source foundations. You will work alongside Solutions Architects as the deep-domain specialist in post-training, guiding customers through data strategy, algorithm selection, experiment design, and evaluation, and sizing the compute required. Your role is crucial in ensuring the successful delivery of post-training Proofs of Concept (POCs), driving adoption of the fine-tuning and RL platform, and translating customer goals into measurable improvements in model quality. This position directly impacts customer success, company growth, and the enhancement of our core platform.

$270k - $300k

Together AI

As a Forward Deployed Engineer (FDE) focused on Inference & Post-Training, you will be a hands-on technical partner to strategic customers looking to leverage high-quality models and perform inference at scale. You will act as a deep-domain specialist in inference optimization, fine-tuning pipelines, and production deployment, partnering with Solutions Architects. FDEs add significant value by ensuring complex Proofs of Concept (POCs) are met, facilitating platform adoption, and guiding tailored optimization efforts, directly impacting customer success and company growth.

$270k - $300k

Supabase

Supabase is seeking a Software Engineer to join their Turso core database team. This role focuses on advancing the future of agentic databases, specifically by contributing to the Turso Open Source database and its Cloud offering. You will work on enhancing Postgres compatibility, ensuring system reliability, maintaining cloud operations, and improving scalability to support a massive increase in database usage. The ideal candidate thrives in a fast-paced, asynchronous environment and is passionate about building scalable database technologies for a world with millions of daily agent-created databases.

Salary not listed

voize

voize is building AI companions to seamlessly take over digital workflows for frontline workers, amplifying their impact rather than replacing them. With significant Series A funding and a growing user base, the company is seeking a Senior Fullstack Engineer to co-own its in-house ML App. This platform is crucial for annotation, data exploration, ML training orchestration, model evaluation, and managing sensitive data flows, aiming to make external vendor solutions unnecessary.

Salary not listed

Supabase

Supabase is seeking a Python SDK Engineer to join their SDK team. This role focuses on enhancing how developers interact with Supabase through Python, ensuring the SDK is a library that Python developers genuinely enjoy using. You will work on building and evolving the Python SDK across various Supabase services, including database, auth, storage, realtime, and functions, with both synchronous and asynchronous APIs. The position involves proactive development, identifying and building missing features, and contributing to the open-source community. A key aspect of this role is owning the typing experience for the SDK, ensuring it's fully typed and checker-friendly, and maintaining compatibility across diverse Python environments and frameworks. You will also be responsible for tracking platform changes and reflecting them in the SDK, designing public APIs, and making the SDK legible to AI coding agents.

Salary not listed

Cursor

SpaceXAI is building Super Intelligence to help humanity understand the universe, from supercomputers to large language models and user-facing applications. As a Software Engineer on the Model Lifecycle and Signals team, you will be responsible for integrating frontier models into user-facing products at a massive scale. This role involves deciding which models to use, monitoring their performance, and providing feedback to shape future model development. You will work at the intersection of infrastructure, data, and product, bringing models from preview to production, analyzing real-world data, and collaborating with research, inference, product, and data science teams to improve both products and models. Your contributions will have a compounding impact across all products and shipped models.

Salary not listed

Cosine is developing autonomous software-engineering systems for organizations that prioritize reliability, security, and control. Our Lumen Enterprise models are designed to understand and modify real codebases, utilizing tools, running tests, and producing maintainable software. We are seeking a Machine Learning Engineer to enhance and train these models across the entire training stack, including pre-training, supervised fine-tuning, and reinforcement learning. This role offers exposure to all facets of the model training lifecycle, from performance profiling to implementing new RL algorithms, and requires a hands-on approach with a focus on software quality.

Salary not listed

Tenstorrent is a leader in AI technology, focusing on performance, ease of use, and cost efficiency. We are building a high-performance RISC-V CPU and a comprehensive AI platform. Join our AI IP software team to help customers integrate AI workloads into products built on Tenstorrent technology. This role involves working directly with customers to integrate models, answer technical questions, and solve integration challenges across models, compilers, and runtime workflows. It's a hands-on software role with opportunities to learn and contribute to cutting-edge AI technology.

Salary not listed

Handshake AI works with frontier labs on their most consequential data, evaluation, and post-training challenges, building systems that turn expert human knowledge into data and evaluations to improve frontier models. Handshake Labs is developing external AI products, research platforms, and customer-facing AI systems, evolving custom-built work into reusable products and platforms. This role is for a Member of Technical Staff, Post-Training, a broad, high-ownership position for researchers who build, requiring the ability to reason deeply about model improvement and translate that reasoning into reliable systems. You will partner with researchers, domain experts, and customers to transform ambiguous post-training questions into experiments, evaluation frameworks, data pipelines, and products, with significant influence over technical direction and culture.

Salary not listed

We are seeking an ML Systems Engineer to contribute to the training of our Lumen LLMs, which are based on open-source software engineering models. This role is interdisciplinary, involving the development and deployment of reinforcement learning training environments, working with large-scale synthetic data pipelines, and building an ML platform for training large models in distributed settings. The goal is to train models that not only provide correct answers but also write readable, maintainable code aligned with architectural patterns. This position is ideal for someone passionate about the evolving landscape of coding agents, where data, RL environments, and opinionated reward functions are shaping future SWE model standards.

Salary not listed

Handshake AI works directly with frontier labs on their most consequential data, evaluation, and post-training challenges, building systems that turn expert human knowledge into data and evaluations that improve frontier models. Handshake Labs is building external AI products, research platforms, and customer-facing AI systems, evolving custom-built work into reusable products and platforms. This role focuses on building the data systems essential for frontier model training, improving how we generate, process, and prepare complex and sensitive data, whether through synthetic data generation or anonymization while preserving structure. You will partner with researchers, domain experts, legal/compliance stakeholders, and customers to translate ambiguous data questions into experiments, pipelines, and durable products, with significant influence over technical direction, standards, and culture.

Salary not listed

Code Metal

Code Metal is seeking a Lead Backend Engineer to join their Modeling & Simulation team. This role will lead the backend and data engineering team responsible for building the Python services, APIs, and data systems that power a next-generation wargaming and decision-support platform. The ideal candidate will balance people leadership with hands-on technical ownership, providing Principal-level backend engineering judgment, guiding architecture, and tackling complex technical challenges while growing a team of engineers. This platform is crucial for enabling government users to make critical multi-billion-dollar force-design decisions.

$253k - $294k

Monte Carlo is seeking a Senior Fullstack Engineer to join their team and build the core of their agent trust platform. This role involves developing backend services, distributed systems, and agentic workflows that enable enterprises to monitor and trust AI in production. You will take ownership of problems from initial concept through prototyping, architecture, development, testing, and deployment, ensuring reliability, observability, and scalability as the platform grows. The position is primarily backend-focused but includes shipping React surfaces when necessary, and involves building and maintaining data pipelines for analytics, ML, and customer-facing features. You will collaborate with product, ML, and infrastructure teams to deliver customer value.

$180k - $230k

Haven Safety AI is building an enterprise learning intelligence layer for safety, designed to help high-risk organizations learn faster from incidents and prevent future occurrences. The platform integrates with existing EHS systems to enhance incident investigation, assessment, and learning processes. It leverages current incident evidence, company knowledge, historical cases, and an industry knowledge graph, with specialized AI agents analyzing various data points to produce traceable assessments. This role is a build-and-operate position focused on the AI and LLM engineering layer, connecting the evidence base and knowledge graph to the product experiences used by investigators and safety leaders. The work is technically demanding and operationally critical, serving enterprise customers in regulated, safety-critical industries where precision, traceability, evaluation, and human oversight are paramount.

Salary not listed

This role sits at the intersection of technical expertise and customer engagement, focused on helping customers and internal teams bring up and optimize AI models on Tenstorrent platforms. As a Software Engineer on the AI Models / System Bring-Up team, you will be responsible for porting, validating, and optimizing AI models on Tenstorrent platforms. Working across models, runtime software, and hardware, you will help connect new models, models not yet running on Tenstorrent hardware, and research-stage workloads to stable, high-performance systems.

Salary not listed

Together AI

As a Forward Deployed Engineer (FDE) focused on Inference & Post-Training, you will be a hands-on technical partner to strategic customers looking to leverage high-quality models and perform inference at scale. You will act as a deep-domain specialist in inference optimization, fine-tuning pipelines, and production deployment, partnering with Solutions Architects. FDEs add significant value by ensuring complex Proofs of Concept (POCs) are met, facilitating platform adoption, and guiding tailored optimization efforts, directly impacting customer success and platform hardening.

Salary not listed

EnCharge AI is seeking a highly skilled and experienced AI Compiler Engineer to spearhead the development and optimization of graph compilers tailored for cutting-edge AI and ML workloads. This role involves collaborating with hardware architects and AI researchers to enhance performance, optimize computation graphs, and enable efficient model deployment on EnCharge's Inference Accelerators. The ideal candidate will architect, design, and implement optimizations for AI model execution on graph compilers to improve performance, reduce latency, and maximize hardware utilization.

$190k - $255k

Handshake is seeking a Senior Software Engineer to join the Backend Platform team, with a primary focus on supporting Handshake AI (HAI) and internal AI initiatives. This role involves building and maintaining backend services, shared platform capabilities, and developer tooling. The work will center on core backend platform concerns such as service architecture, APIs, data systems, performance, reliability, and developer experience, with an increasing use of LLMs and agents. The ideal candidate will possess strong backend fundamentals combined with practical knowledge of LLM-powered and agentic systems.

$208k - $260k