Software Engineer at fractional-ai | San Francisco

Join a pioneering team of former Google engineers who have developed ground-breaking defensive technologies, such as Safe Browsing and reCAPTCHA. We are on a mission to confront an urgent challenge: combating the rising tide of adversarial AI attacks that threaten organizations globally.Operating in stealth mode, we are targeting a lucrative $5B+ market that is primed for innovation. Conventional detection methodologies are proving inadequate against the speed and sophistication of AI-driven assaults. Current adversaries are leveraging AI to engineer tailored, high-evasion attacks, leaving traditional systems vulnerable.Your Role:You will design a network of AI agents that are rapid, cost-effective, and precise, collaborating to identify and neutralize emerging threats. Your work will dive deep into real-time threat data, continuously evolving your agents in a fast-paced environment. These agents will function under an orchestration layer that fosters quick adaptation and learning.The Excitement of the ChallengeRapidly Evolving Models: The landscape changes daily; solutions that worked yesterday may be outdated today.Intelligent Adversaries: We are engaged in a real-time arms race against cunning, AI-enhanced attackers crafting sophisticated payloads.No Existing Playbook: We are forging new detection paradigms as swiftly as threats evolve. This high-stakes work places you in the heart of the action from day one.If you thrive on solving challenging problems with rapid feedback, this is your opportunity.Why We Are Positioned to SucceedExpansive Market: The market is vast at $5B and expanding quickly, while established players struggle to adapt.Proven Track Record: Our team has previously developed the foundational technology for Safe Browsing (serving over 5B users) and reCAPTCHA (protecting more than 5M websites) during our time at Google.Experienced Team: This is our third endeavor in creating a category-defining security enterprise, and we know how to scale our technology and our organization effectively.Deeply Integrated AI and Security: We embed AI from the outset rather than layering it on top.Top Talent: We hire only the highest achievers; many on our team were in the top 1% of engineers at Google. If you excelled in your previous role, you will fit right in.Agility: We prioritize speed and efficiency in everything we do.

Join Our Innovative Team at Simple AIAt Simple AI, we are transforming enterprise communications through cutting-edge voice AI agents. Our highly realistic agents empower leading companies such as DoorDash, xAI, and Omaha Steaks to efficiently manage a variety of phone operations, including customer support, order processing, and lead qualification.As we experience exponential growth and a surge in customer demand, we are seeking a few founding software engineers to help us navigate this exciting journey and develop systems for the future. Our passionate team operates from our vibrant San Francisco office five days a week, driven by a shared vision of leveraging AI to make a significant impact in the world.We are proud to be backed by esteemed investors and operators, including Y Combinator, Massive Tech Ventures, and industry leaders such as Michael Seibel (Twitch), Jared Friedman (Scribd), and more.

About the RoleJoin our innovative team at saris-ai, a pioneering applied AI startup based in San Francisco and Montreal. We are on a mission to redefine the banking industry by addressing a $100 billion annual challenge that is rapidly evolving. Our cutting-edge multi-turn AI agentic systems are at the forefront of this transformation.Our objective is to develop automated solutions that require sophisticated long-context reasoning, seamless tool integration across legacy systems, and stringent compliance mechanisms, particularly in scenarios where conventional answers are elusive.With successful real-world deployments and a rapidly expanding client base, we are seeking passionate and technically adept builders eager to make a significant impact from the start.We are in search of an AI Sales Engineer who will play a pivotal role in enhancing productivity and efficiency within financial institutions through innovative AI solutions. In this role, you will lead discovery calls with various departments to identify workflow challenges and design impactful AI-driven solutions. You will serve as the technical authority during sales cycles, assisting clients in recognizing problems, framing solutions, and articulating ROI.This position combines elements of customer engagement and workflow analysis.Your Key Responsibilities Include:Conduct discovery and technical scoping calls with potential clients to uncover operational inefficiencies in financial institutions.Develop workflow maps and reports to identify bottlenecks and pinpoint opportunities for agentic AI automation.Collaborate with the Sales team to co-manage the pre-sales process from initial discovery to proposal delivery.Engage with executive stakeholders, presenting clear and compelling insights on how Agentic AI can deliver measurable ROI and transform operations at scale.Work closely with cross-functional teams including sales, customer success, and product to ensure customer satisfaction and success.

Join Saris AI as an AI Systems Engineer, where you will play a pivotal role in designing and implementing innovative solutions that leverage artificial intelligence technologies. You will collaborate closely with cross-functional teams to develop AI systems that enhance our products and services, driving impactful results for our clients.

Role OverviewLocation: San Francisco, CA Work Model: In-officeAbout Effective AIAt Effective AI, we are pioneering the future of work, focusing on sophisticated AI solutions for complex knowledge tasks rather than simple, repetitive functions. Our goal is to develop advanced AI Teammates that excel in intricate workflows and collaborate seamlessly with human professionals. Our initial challenge is to revolutionize the trillion-dollar U.S. Property & Casualty insurance sector, an area rich in data and complexity, ideal for our innovative approach.We have successfully secured $10 million in seed funding from prominent investors including Lightspeed Ventures and Valor Equity Partners.Our passionate team operates out of San Francisco, where we value in-person collaboration to address these pressing challenges.Your ResponsibilitiesAs a Founding Software Engineer, you will be an integral member of our founding team, significantly influencing the design and development of our core product from inception. You will confront critical challenges in agentic AI, crafting Teammates capable of managing essential insurance functions such as underwriting and claims processing.Specifically, you will:Facilitate long-term task completion by creating the foundational architecture for AI agents to plan and execute multi-step processes reliably over prolonged interactions.Develop advanced reasoning functionalities, enabling agents to make informed decisions based on ambiguous or incomplete information, akin to human experts.Create intelligent, tool-utilizing agents capable of selecting and employing a variety of external tools—APIs, databases, web searches, and Excel-based pricing algorithms—to gather information and take decisive actions.Design adaptive and learning systems, equipping our AI Teammates to learn from feedback and adjust to evolving conditions such as regulatory changes or market dynamics.Your ProfileWe seek an innovative and driven builder excited to tackle substantial challenges.You possess a solid foundation in computer science and remarkable problem-solving capabilities, evidenced by impactful projects or previous experience.Your genuine enthusiasm for AI fuels your passion for tackling complex issues.

Saris AI develops advanced AI automation for the banking sector, with teams in San Francisco, Montreal, and Toronto. The company addresses large-scale automation challenges, focusing on long-context reasoning, integrating with legacy systems, and meeting strict compliance needs. Saris AI’s AI agents are already active in production, supporting real customer workflows as the business expands. Role overview The San Francisco engineering team is seeking an Engineering Manager. This leader will guide engineers through shifting priorities and frequent ambiguity. The position involves building and leading teams, managing projects from concept to launch, and ensuring the delivery of reliable software that powers AI-driven products. What you will do Build and lead engineering teams focused on automation and AI Oversee software projects from initial idea through production launch Adapt to changing requirements and priorities as the company grows Address the technical challenges unique to deploying software in AI systems Requirements Proven experience building and leading engineering teams History of delivering software projects from start to finish Comfort working in environments where priorities and requirements shift quickly Understanding of the complexities involved in AI-driven software deployment Location This role is based in San Francisco.

About the RoleWe are on the lookout for a skilled Forward Deployed AI Engineer to join our dynamic team at Stack AI. This position is crucial for implementing enterprise-level AI solutions with an emphasis on Retrieval-Augmented Generation (RAG) pipelines and large language model (LLM) workflows. Your contributions will significantly enhance our offerings to Fortune 500 companies and enterprises across diverse sectors.Role Overview:In this role, you will seamlessly integrate large language models into enterprise systems, collaborating with strategic accounts to tailor solutions that meet their technical needs. Utilizing the Stack AI platform, you’ll engage with clients to co-create innovative solutions that address their evolving challenges.Key Responsibilities:Enhance and maintain solutions for strategic accounts using the Stack AI platform.Analyze and document requirements and relationships within target enterprise offices.Identify opportunities and provide insights to shape our go-to-market strategy.Directly contribute to the Stack AI codebase, transforming customer feedback into enhancements for the Python backend and React/Next.js TypeScript frontend.Project future opportunities and secure high-value contracts.Draft proposals, present to stakeholders, and lead engaging product demonstrations.Promote Stack AI at enterprise conferences and events.

About David AIDavid AI is pioneering the audio data research landscape, applying a rigorous R&D approach to dataset development akin to the methodologies used in AI labs for model creation. Our goal is to integrate AI seamlessly into real-world applications, with audio serving as the perfect entry point due to its inherent versatility and human connection. As the audio AI field progresses, the demand for high-quality training data becomes critical, and that's where David AI excels.Founded in 2024 by a team of experienced engineers and operators from Scale AI, David AI has quickly gained traction, serving prominent clients among FAANG companies and AI research labs. Recently, we secured a $50M Series B funding round from esteemed investors including Meritech, NVIDIA, Jack Altman (Alt Capital), Amplify Partners, and First Round Capital.Our team embodies intelligence, humility, ambition, and a close-knit ethos. We are on the lookout for exceptional talent in research, engineering, product, and operations to join us in advancing the frontiers of audio AI.About Our Engineering TeamAt David AI, our engineering team is responsible for constructing the pipelines, platforms, and models that convert raw audio into valuable data for top AI labs and enterprises. We pride ourselves on our collaborative environment, comprising product engineers, infrastructure specialists, and machine learning experts dedicated to leading the charge in audio data research.We operate at a fast pace, taking ownership of our projects from conception through to production. Our team develops real-time processing pipelines capable of managing terabytes of audio data daily while deploying innovative generative audio models.About This RoleAs a Product Engineer at David AI, you will design and implement state-of-the-art tools that enable our users to leverage audio data effectively for training their AI models. You will collaborate closely with researchers to continuously refine our data collection methodologies.Your ResponsibilitiesDeliver full-stack features that will be utilized by thousands of users on a daily basis.Develop scalable systems that create essential data processing pipelines, extracting actionable insights from terabytes of audio data each day.Construct, deploy, and assess LLM and DSP-based solutions to enhance our clients' comprehension of intricate features within our datasets.Rapidly iterate on research hypotheses by collaborating with researchers and the operations team to deploy enhancements efficiently.

About Simple AIAt Simple AI, we are pioneering cutting-edge voice AI solutions tailored for enterprises. Our lifelike voice agents empower renowned companies such as DoorDash, xAI, and Omaha Steaks in managing diverse phone operations ranging from customer support to order intake and lead qualification. As we experience rapid revenue growth, we seek a couple of founding software engineers to help us meet current customer demands while developing innovative systems for the future. Our team is passionate about harnessing AI to transform the world, and we operate from our San Francisco office five days a week.Simple AI is proudly supported by top-tier investors and industry leaders, including Y Combinator, Massive Tech Ventures, and prominent figures like Michael Seibel (co-founder of Twitch), Jared Friedman (Scribd), Alexandr Wang (Scale AI), Matt Van Horn (June Oven and Lyft), Suhail Doshi (Mixpanel), JJ Fliegelman (WayUp), and Scott Wu (Cognition).Meet the FoundersThe founders, Catheryn Li and Zach Kamran, previously led software teams at Y Combinator, where they launched numerous products for YC founders, including the co-founder matching site. Cat brings experience from Instagram and Facebook and holds degrees in mathematics and computer science from MIT. Zach studied computer science and statistics at the University of Chicago and led software initiatives at PEAK6.What We ProvideCompetitive salary with significant equity opportunitiesEmployee-friendly equity termsOffice located in San FranciscoComprehensive health, dental, and vision insuranceComplimentary lunch and dinner at the officeFree Uber rides home after 8:30 PMRegular team events and offsite activitiesYour Qualifications4+ years of relevant software engineering experience.Exceptional problem-solving skills and a passion for tackling technical challenges.A customer-centric mindset coupled with strong communication skills and a keen interest in product design and prioritization.Self-motivated with the ability to work independently.A genuine enthusiasm for continual learning and keeping abreast of the latest advancements in AI.

Join Our Team as a Machine Learning EngineerSaris-AI is a pioneering applied AI startup, based in San Francisco and Montreal, focused on revolutionizing the banking sector. Our mission is to address a colossal $100 billion/year challenge that is rapidly expanding, innovating the limits of what can be achieved with advanced multi-turn AI systems.We aim to automate complex workflows that necessitate long-context reasoning, orchestration of tools across legacy systems, and rigorous compliance processes—solving problems that currently lack definitive solutions.Our team has successfully deployed AI agents that manage real customer workflows effectively in production. As we expand our customer base and accelerate our growth, we are in search of highly skilled technical builders who aspire to make a significant impact in the early stages of our journey.As a foundational Machine Learning Engineer, you will own our entire ML stack and bring custom agents to life.

Responsibilities:Develop Our Product. Take ownership of software features that enhance our AI platform, empowering private market investors to analyze deals swiftly and accurately. This role requires you to actively engage in coding and delivering essential platform components from the ground up.Ensure Quality and Excellence. Establish and maintain coding standards, architectural guidelines, and review procedures; mentor fellow engineers. Co-cultivate a culture centered on practical, reliable, and test-driven development that swiftly meets business requirements.Scale for Growth. Assist in monitoring and scaling the architecture of our platform and its infrastructure.Collaborate Across Functions. Engage closely with product, security, and go-to-market teams to translate our strategic roadmap into actionable features and deliverables.

About Vooma Vooma is building automation-focused enterprise software, moving beyond traditional systems of record. The team develops LLM-powered agents and orchestrators that handle complex business tasks alongside people, aiming to boost autonomy and efficiency in daily operations. The company’s current mission centers on creating an AI orchestration platform tailored for the US trucking industry, which moves over $800 billion in goods each year. Although trucking is essential to the economy, much of logistics still relies on manual work, making it a strong fit for AI-driven solutions. Vooma’s products help shippers, freight brokers, and trucking companies win more business and manage freight operations more smoothly. AI agents automate critical workflows across voice, email, and SMS, supporting the full load lifecycle. Vooma is backed by Index Ventures, Craft Ventures, Y-Combinator, and leaders from the logistics sector. Role Overview: AI Engineer The founding team is looking for an AI Engineer to help train and refine advanced models for real-world use. This role focuses on applied AI, where new capabilities are transformed into reliable, high-performing systems that make a measurable difference. Success in this position comes from a strong grasp of model behavior and a talent for building systems that improve through structured data feedback loops. The right person enjoys rapid deployment, learning from real-world usage, and iterating toward highly effective solutions. Location This role is based in Vooma’s San Francisco office.

Overview: Join strala-ai as we redefine the insurance industry using cutting-edge technology.In just under a year, strala-ai has achieved impressive multi seven-figure ARR and is experiencing rapid growth at 50% month-over-month. We are backed by top-tier investors, including Peter Thiel’s Founders Fund, and led by partners with strong ties to OpenAI, Cognition, and Scale AI. Our talented team hails from prestigious institutions such as Harvard, Berkeley, and Oxford, and includes professionals from leading firms like Optiver, AMD, and Palantir, many with backgrounds in ICPC and NeurIPS.Key Responsibilities:Lead the deployment of multi-modal, agentic AI systems in production, ensuring significant business outcomes. You will manage client deployments from start to finish, being the key liaison for senior client stakeholders.Develop and nurture client relationships by understanding their challenges and aligning on priorities, establishing yourself as the trusted advisor for AI adoption.Create, build, and enhance AI agents that optimize claims outcomes through prompt engineering, model integration, and rapid prototyping using AI-assisted coding tools.Engage with applied AI daily, scoping and developing new features to support our customers in scaling and improving claims results.Integrate our solutions into client environments, collaborating directly with their technical teams on APIs and systems.Coordinate with our core platform team to facilitate smooth delivery, providing actionable insights for product enhancement.Document and share best practices in internal playbooks to scale our Forward Deployed Engineering efforts effectively.Ideal Candidate:Exhibit a founder's mindset, taking ownership of challenges, acting swiftly, and finding solutions, whether that means engaging in client calls or executing quick integrations.Possess over 2 years of experience in a role that merges technical expertise with client-facing responsibilities (e.g., agent engineering, forward deployed engineering, growth engineer, or founding engineer/founder).Demonstrate a strong technical foundation with proficiency in Python, APIs, cloud platforms, and modern AI/ML tools.Familiarity with LLMs, prompt engineering, and agentic AI concepts, as well as comfortability with AI-assisted development workflows for rapid solution delivery.Excel in articulating complex concepts to non-technical stakeholders.

Join the Revolution at Retell AIRetell AI is pioneering the future of call centers through innovative voice AI, driven by first principles thinking.In just 18 months since our inception, we have empowered thousands of businesses with our AI voice agents, transforming how sales, support, and logistics calls are managed—previously requiring extensive human teams. Supported by prestigious investors such as Y Combinator and Alt Capital, we've rapidly scaled from $5M ARR to an impressive $36M ARR with a compact yet dynamic team of 20.Our ambition for 2026 is to create a revolutionary customer experience platform, where entire contact centers are powered by AI. Moving beyond basic automation, we aim to develop intelligent AI “workers” that serve as frontline agents, QA analysts, and managers, continuously enhancing customer interactions without the need for constant human oversight.As we expand, we are seeking passionate engineers who are eager to solve challenging technical problems, act swiftly, and make a significant impact in one of the fastest-growing voice AI startups. Let’s shape the future together.

About CollateCollate is an innovative AI-driven document generation platform tailored for the life sciences sector. Our mission is to streamline paperwork through advanced AI technology, enabling our clients to deliver life-saving innovations to patients significantly faster. Serving as a comprehensive solution, Collate enhances every phase of drug, diagnostic, and medical device development—from initial concept to market readiness.Under the leadership of our CEO Surbhi Sarna, a distinguished former General Partner at Y Combinator, and our CTO Nate Smith, a former Visiting Partner at Y Combinator, our team comprises AI researchers, engineers, and designers with experience from top-tier companies like Google, Nvidia, Meta, and Netflix. Impressively, 40% of our team are former founders themselves.We are a compact, elite team backed by over $30 million in seed funding from renowned investors including Redpoint, First Round Capital, Conviction, and Y Combinator, along with industry leaders in healthcare and AI. This is a unique opportunity to become part of a groundbreaking company poised to make a significant impact, guided by experienced founders with the resources to scale effectively.About the RoleWe are seeking a passionate AI Engineer to assist in developing and operationalizing the models and systems that drive Collate's innovative products. Your role will bridge the realms of machine learning, software engineering, and product development—transforming pioneering research into dependable, user-centric functionalities.This position offers a remarkable chance to influence the application of advanced AI in the life sciences sector, where performance, safety, and trust are as crucial as innovation. As one of the initial AI-focused engineers at Collate, you will help establish standards for evaluating and deploying models that have a direct impact on drug and medical device development.

Join us at Comulate, where we are revolutionizing the insurance back office through advanced AI technology. Our platform is designed to transform costly and tedious accounting processes, marking the beginning of our mission to unlock the vast sums spent on manual operations within the insurance sector.In early 2025, we proudly announced our Series B funding, led by BOND & Workday, which comes as a testament to our remarkable growth and ambitious expansion plans.

Join David AI as a Staff Product EngineerAt David AI, we are pioneering the field of audio data research, applying a rigorous R&D methodology to create robust datasets that empower AI models. Our vision is to integrate AI seamlessly into daily life, with audio serving as the key medium. As the demand for high-quality training data grows, we position ourselves as the solution.Founded in 2024 by a team of seasoned engineers from Scale AI, we quickly garnered the trust of leading FAANG companies and AI labs. Our recent $50M Series B funding round was led by prestigious investors including Meritech and NVIDIA, underscoring our potential in the audio AI landscape.We pride ourselves on our dynamic, collaborative, and ambitious team, and we are on the lookout for exceptional talent in research, engineering, product, and operations to help us redefine audio AI.About Our Engineering TeamOur engineering team is at the forefront of innovation, building the infrastructure, platforms, and models that convert raw audio into valuable data for top-tier AI labs and enterprises. We are a close-knit group of product engineers, infrastructure experts, and machine learning specialists who are dedicated to establishing the first-ever audio data research organization.We operate with agility, taking ownership of our projects from inception to deployment, delivering production-ready solutions on a daily basis. Our engineers design real-time pipelines that manage vast amounts of speech data while deploying advanced generative audio models.Your RoleAs a Staff Product Engineer, you will spearhead our Product Engineering team, developing state-of-the-art products that enable our clients to harness audio data effectively for model training. You will collaborate with researchers to continually refine our data collection methodologies.Your ResponsibilitiesLead the development of full-stack features, rapidly iterating to deliver daily innovations to our users.Construct scalable systems that process terabytes of audio data and extract actionable insights.Deploy and assess LLM- and DSP-based solutions to enhance customer understanding of their data.Facilitate research iterations and deployment interfaces for data collection in collaboration with researchers and operations.

Join Our Innovative Team at Retell AIRetell AI is at the forefront of revolutionizing the call center industry through advanced voice AI technology. In just 18 months since our inception, we have empowered thousands of businesses to optimize their sales, support, and logistics calls, which previously relied on large teams of human agents. Supported by prominent investors including Y Combinator and Alt Capital, we've achieved remarkable growth, scaling from $5 million to $36 million in annual recurring revenue (ARR) while expanding our talented team to 20 members.Our ambitious vision for 2026 is to develop a state-of-the-art customer experience platform, transforming entire contact centers with AI. Unlike traditional automation that requires ongoing human oversight, we are building intelligent AI "workers" capable of functioning as frontline agents, quality assurance analysts, and managers, constantly enhancing customer interactions.If you are a passionate innovator eager to solve complex technical challenges and make a tangible impact at one of the fastest-growing voice AI startups, we invite you to join us in shaping the future.Ranked among the top 50 AI applications by a16z: a16z List4th on Brex's Fast-Growing Software Vendors of 2025: Brex BenchmarkFeatured as a leading startup on: Leanaileaderboard

fractional-ai is looking for a Senior or Staff Software Engineer to join the San Francisco office. This position centers on building advanced AI solutions with a team that values both technical depth and collaboration. Role overview This role focuses on designing and developing AI-driven systems. The work involves solving technical challenges and contributing to projects that push the boundaries of what AI can achieve. Collaboration with other engineers and stakeholders is a key part of daily responsibilities. Who will thrive Experienced engineers with a strong background in software development Those who enjoy working on complex technical problems Individuals who value teamwork and open communication Location This position is based in the San Francisco office.