Senior Full Stack Software Engineer at Retell AI | San Francisco

Baseten creates AI inference solutions for clients such as Cursor, Notion, OpenEvidence, Abridge, Clay, Gamma, and Writer. The team blends AI research, infrastructure, and developer tools to help organizations deploy advanced models. Backed by $300M in Series E funding from BOND, IVP, Spark Capital, Greylock, and Conviction, Baseten is expanding quickly and shaping the landscape for engineers building AI products. Role overview The Software Engineer - Voice AI role centers on building and deploying open-source voice models for real-world use. Voice is becoming a key interface across the web, and this position addresses the technical challenges of bringing production-ready Voice AI to market. The work supports applications in productivity, customer service, clinical dialogue, creator tools, education, and more, helping to change how people interact with technology across sectors. This engineer leads Baseten’s Voice AI efforts, guiding the proprietary inference stack that powers Voice AI models. The role balances shaping the product roadmap with hands-on engineering. Collaboration is a core part of the job, working closely with Forward Deployed Engineers, Model Performance Engineers, and other technical teams to advance Voice AI capabilities. Sample projects and initiatives The world's fastest Whisper, with streaming and diarization Canopy Labs selects Baseten for Orpheus TTS inference Partnering with the Core Product team to build an orchestration framework for a multi-model voice agent Working with the Training Platform team to support ongoing training of voice models Designing a developer-friendly API and SDK to encourage self-service adoption of Baseten Voice AI products Location San Francisco

About Aqua VoiceAqua Voice is pioneering the voice input landscape for the AI era. By training our own models and creating deep OS integrations, we ensure that voice technology is executed flawlessly across the entire stack.The evolution of work is upon us; individual contributor roles are transforming as we now manage AI agents, a task that naturally aligns with voice interactions.We are not focused on traditional conversational agents; instead, we champion a voice-in-text-out (VITO) approach, believing that voice functionality should operate above traditional applications, and that innovative startups can lead in this domain.With an unwavering commitment to this vision, our progress has been promising, and we invite you to be a part of our journey.The RoleAs a growing team, you will have the opportunity to engage with all facets of our system.Recent projects include:Development of a real-time transcription server capable of managing thousands of concurrent audio streams.Training and deploying custom speech recognition models.Creating native integrations for macOS and Windows utilizing advanced system APIs.Technology StackFrontend: TypeScript, React, Next.js, ElectronBackend: Python, real-time server (Bun/Node.js), WebSocketsNative: Swift (macOS), C# (Windows)Machine Learning: Custom speech recognition models, inference pipelinesInfrastructure: Terraform, StripePrior experience with all these technologies is not required.Qualifications- Showcase your previous work and projects.- Adaptable in switching between programming languages and domains.- Capable of taking ownership of projects from concept to production.- Proficient in writing clean and maintainable code.- Experience with production systems is essential.- A positive attitude and a collaborative spirit are a must!

About Retell AIAt Retell AI, we are pioneering the future of call centers through innovative voice AI technology. Our cutting-edge solutions are transforming how companies engage with customers.In just 18 months since our inception, we've empowered thousands of businesses with our AI voice agents that efficiently manage sales, support, and logistics calls, significantly reducing the need for large teams of human agents. Supported by industry-leading investors including Y Combinator and Alt Capital, we've grown our annual recurring revenue from $5M to an impressive $36M while expanding our team from 5 to 20 talented individuals since 2025.Our ambitious vision for 2026 is to develop a state-of-the-art customer experience platform where entire contact centers are driven by AI. Unlike basic automation requiring constant human oversight, we’re engineering intelligent AI “workers” capable of serving as frontline agents, quality assurance analysts, and managerial roles, all while optimizing customer interactions continuously.We are rapidly expanding and seeking driven builders who thrive on solving complex technical challenges, act decisively, and wish to make a tangible impact in one of the fastest-growing voice AI startups.Join us in shaping the future!Recognized as a top 50 AI application in the a16z list: https://tinyurl.com/5853dt2xRanked #4 in Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025Featured among the top startups on: https://leanaileaderboard.com/

Baseten seeks a Software Engineer to focus on Voice AI within the Inference Runtime team. This San Francisco-based role centers on building and refining AI models that power voice interaction features in Baseten products. Role overview This position involves hands-on work with AI models for voice-driven applications. The engineer will help shape how users interact with voice technology by developing and optimizing the underlying systems. What you will do Develop and optimize AI models for applications that use voice as a primary interface Work on inference runtime systems to support responsive and intelligent voice experiences Contribute directly to Baseten's products, influencing the future of voice technology for users Location This position is based in San Francisco.

About Aqua VoiceAqua Voice is pioneering the voice input technology for the AI era. Our unique approach involves training proprietary models and establishing deep integrations with operating systems, ensuring optimal voice interaction capabilities.The landscape of work is evolving; the traditional role of an individual contributor is being replaced by the management of AI agents, making voice interaction a natural fit for this new paradigm.Rather than developing mere conversational agents, we envision a more intuitive method of computer interaction—voice input leading to text output (VITO). We assert that voice technology should operate at a foundational level, allowing a small, agile company like ours to innovate and excel.We are passionately committed to this mission, and our initial results have been promising. Join us in shaping the future!The OpportunityWe are looking for an iOS Engineer to help us build Aqua Voice from the ground up. This greenfield project offers you the chance to shape the mobile experience entirely.Your Contributions Will Include:Developing a native iOS application with system-level voice input features (including keyboard extensions, Shortcuts, and Siri integration).Implementing real-time audio capture and streaming to our transcription backend.Creating deep iOS integrations to enhance user experience.This role requires a focus on native performance and comprehensive system integration—this is not just a web view wrapper.Technology StackSwift (SwiftUI + UIKit where applicable)Audio Technologies: AVFoundation, Audio Unit, real-time streamingNetworking: WebSockets, streaming protocolsSystem Integrations: Keyboard extensions, Shortcuts, accessibility APIs

About UsAt Sierra, we are pioneering a transformative platform that empowers businesses to enhance customer interactions through advanced AI technology. While our primary operations are in-person at our San Francisco headquarters, we are expanding our presence globally with offices in Atlanta, New York, London, France, Singapore, and Japan.Our culture is built on core values: Trust, Customer Obsession, Craftsmanship, Intensity, and Family. These principles guide our actions and define our collaborative spirit.Founded by industry leaders Bret Taylor and Clay Bavor, Sierra benefits from their extensive expertise in tech innovation and leadership from renowned companies such as Salesforce, Facebook, and Google.Your RoleJoin our dynamic engineering team of approximately 40 highly skilled professionals, including notable engineers like Mihai, Belinda, Arya, and Wei. You will work within small, autonomous teams focused on solving complex customer challenges. Your key responsibilities will include:Transcription: Develop robust systems for accurate speech recognition and transcription across multiple languages, ensuring low latency and high performance.Synthesis: Create advanced speech generation technologies that align with diverse brand voices and styles.Runtime Optimization: Enhance the efficiency and responsiveness of voice applications to deliver seamless user experiences.

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 Aircall as a Senior Software Engineer specializing in AI Voice Agents, where you'll play a pivotal role in designing and implementing innovative voice solutions. Your expertise in software development and artificial intelligence will help us enhance customer interactions through cutting-edge technology.

Join Deepgram, a pioneering leader in voice AI technology, as a Software Engineer specializing in Voice Agents for the restaurant industry. You will play a vital role in developing innovative AI applications that enhance customer experiences and streamline restaurant operations. Your expertise in software development and passion for AI will contribute to transforming how restaurants interact with their customers.

About Nooks.ai:Nooks is revolutionizing the sales landscape with our AI Sales Assistant Platform (ASAP), designed to eliminate mundane tasks and empower sales representatives to prioritize meaningful customer interactions. Our technology has enabled thousands of sales professionals to exceed their quotas, saved clients countless hours, and generated hundreds of millions of dollars in sales pipeline. Nooks is trusted by sales teams from leading companies such as Hubspot, Rippling, and Toast, as well as many others.As a high-performing team, we have successfully secured over $70M in funding from prestigious venture capital firms, including Kleiner Perkins, which marked its first investment in sales technology in over a decade by choosing Nooks. Over the last two years, we've achieved remarkable growth, quadrupling our annual recurring revenue (ARR) and then tripling it again, with plans to do so once more this year.To learn more about us, visit Nooks.ai. In this role, you will take ownership of our backend infrastructure for real-time audio and video calling (including Twilio, Salesfloor, A/V quality, recordings, and transcriptions), ensuring our dialer can scale reliably to handle 10x the current volume.Your Key Responsibilities:Architect and enhance our real-time voice infrastructure (WebRTC/SIP/Twilio).Guarantee that call quality and latency consistently meet SLA targets on a global scale.Develop services for advanced functionalities such as call transfers, monitoring, and recordings.Create observability and debugging tools to optimize call flows.Collaborate with Product and Support teams to implement new A/V features and ensure rapid issue resolution.Ideal Candidate Profile:6 to 10+ years of experience in backend or infrastructure engineering, particularly with real-time audio/video or telephony systems.Proven hands-on experience with technologies such as WebRTC, SIP, Twilio, or similar platforms.Strong understanding of distributed systems and low-latency infrastructure.Experience in debugging and optimizing Quality of Service (QoS) metrics including latency, jitter, and packet loss.At Nooks, our compensation package for eligible roles includes a base salary, equity options, and comprehensive benefits. The base salary is just one part of the total compensation, which may also encompass equity, health, dental, vision, life and disability insurance, hybrid work arrangements, and unlimited paid time off. Please note that benefits are subject to change and may vary based on the employment jurisdiction.

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 Nooks.ai:Nooks is revolutionizing the sales landscape with our AI Sales Assistant Platform (ASAP) that streamlines operations, allowing sales representatives to concentrate on building meaningful customer relationships and boosting their sales pipeline. Our innovative platform has empowered thousands of sales professionals to achieve their quotas, saving clients countless hours and generating hundreds of millions in revenue. Trusted by sales teams at leading companies like Hubspot, Rippling, and Toast, Nooks is at the forefront of sales technology.Backed by over $70M in funding from premier venture capitalists, including Kleiner Perkins, Nooks is experiencing exceptional growth, having increased our Annual Recurring Revenue (ARR) by 4x and then 3x in recent years. We aim to achieve another 3x growth this year, continuing our trajectory of success.For more information, visit Nooks.ai.As a Senior Software Engineer specializing in voice AI, you will take ownership of our backend infrastructure for real-time audio/video communication, ensuring it scales efficiently to handle increased usage.Responsibilities:Design and enhance real-time voice infrastructure utilizing WebRTC, SIP, and Twilio.Monitor and optimize call quality and latency to comply with global SLA targets.Develop advanced features including call transfers, monitoring, and recordings.Create observability and debugging tools to streamline call flow management.Collaborate with Product and Support teams to facilitate new A/V feature rollouts and expedite issue resolution.Qualifications:6–10+ years of experience in backend or infrastructure engineering, specifically in real-time audio/video or telephony systems.Proven expertise with WebRTC, SIP, Twilio, or similar technology stacks.Solid understanding of distributed systems and low-latency infrastructure.Experience in debugging and optimizing Quality of Service (QoS) metrics such as latency, jitter, and packet loss.Compensation at Nooks for qualified roles includes a competitive base salary, equity options, and a comprehensive benefits package. Our offerings include health, dental, vision, life, and disability insurance coverage, a flexible hybrid work environment, and unlimited paid time off. Benefits may vary based on location and are subject to change.

Join our team at Anthropic as a Senior / Staff+ Software Engineer specializing in Voice Platform development. In this role, you will be instrumental in advancing our voice technology initiatives, working closely with cross-functional teams to create innovative solutions that enhance user experiences.

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

Join Us at Retell AIRetell AI is revolutionizing the call center industry by leveraging innovative voice AI technology based on first principles.In just 18 months since our inception, we have attracted thousands of companies that rely on Retell's AI voice agents to efficiently manage sales, support, and logistics calls, previously handled by large teams of human agents. Supported by renowned investors such as Y Combinator and Alt Capital, we have rapidly grown from $5M to $36M in Annual Recurring Revenue (ARR) with a dedicated team of 20.Looking ahead to 2026, our ambition is to establish a state-of-the-art customer experience platform entirely powered by AI. We aim to create intelligent AI “workers” capable of serving as frontline agents, quality assurance analysts, and managers, continuously optimizing customer interactions without the need for constant human oversight.We are on an exciting growth trajectory and are seeking driven individuals who are eager to solve complex technical challenges, accelerate progress, and make a significant impact at one of the fastest-growing voice AI startups.Let’s innovate the future together!Ranked as a top 50 AI app by a16z: https://tinyurl.com/5853dt2x#4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025One of the top startups on: https://leanaileaderboard.com/

Join Our TeamAqua Voice is pioneering the voice interaction layer for the AI-driven era. We develop our own models and create deep OS integrations, as mastering voice technology necessitates control over the entire stack.The landscape of work is evolving rapidly. It's no longer just about individual contributions; now, you manage AI agents, and voice interaction is ideally suited for this new paradigm.We are not in the business of crafting conversational agents. Our vision is that the most intuitive way to engage with your computer is through voice commands with text responses (VITO). We believe that voice technology should operate at a layer above applications, and as a small company, we have the potential to push boundaries in this area.With relentless dedication, we are making great strides, and we invite you to be part of this journey.Your RoleWe are seeking a talented designer who is also proficient in coding.You will take the reins on design for our desktop applications, web platforms, and marketing collateral. You will implement your designs using React, TypeScript, and CSS.This is primarily a design-focused position. We prioritize your aesthetic sense over the speed of engineering.

About Aqua VoiceAqua Voice is revolutionizing voice input for the AI era. We develop proprietary models and create deep operating system integrations, as mastering voice technology necessitates comprehensive control over the entire stack.The workplace landscape is evolving. Individual contributor roles are being replaced by the need to manage AI agents, and this transition is ideally suited for voice interaction.Unlike conventional conversational agents, we advocate for a voice-first approach where voice input leads to text output (VITO). We assert that voice interaction should transcend application layers, and our nimble organization is committed to pushing boundaries in this domain.Our relentless pursuit of excellence in this space has yielded promising results, and we invite you to be part of our journey.The RoleAs a Staff Engineer, you will take ownership of technical systems across the entire stack. Being a small, post-product-market-fit team, we are experiencing growth with real users facing real challenges.We favor modern technologies—opting for Bun over Node, Fly over AWS when applicable, and PyTorch over outdated ML frameworks.Your ResponsibilitiesGPU Inference: We independently run our Automatic Speech Recognition models.Real-time Transcription: Implementing WebSocket state machines, multi-provider failover, and achieving sub-100ms latency targets while tracking over 30 metrics per session.Native Applications: Utilizing Swift for macOS, C# for Windows, and Electron IPC for system-level programming.Backend Development: Employing Django for billing and analytics, Celery for background tasks, and PostgreSQL for database management.You will be involved in all aspects of our infrastructure and product development.Technology Stack- Languages: TypeScript, Python, Swift, C#- Runtime Environments: Bun, Node.js, Django, FastAPI- Machine Learning: PyTorch- Infrastructure: Fly.io, Terraform, AWS (RDS), Redis- Protocols: gRPC, WebSocket, RESTQualifications- Proven experience in building and managing systems at scale.- Strong architectural opinions that are adaptable.- Comfortable being the foremost technical expert in the room.- Capable of transforming ambiguous problems into functional systems.- Ability to write production-ready code.

About Sage CareSage Care is a dynamic and rapidly expanding healthcare startup, founded by a team of visionary leaders from major tech companies like Apple, Uber, and Carbon Health, and supported by esteemed venture capital firms including General Catalyst and Chelsea Clinton. Our mission is to revolutionize healthcare by streamlining care navigation, making it accessible and efficient for everyone.Our innovative platform empowers patients to easily locate the right healthcare providers and enables clinicians to prioritize those who require assistance the most. By leveraging cutting-edge AI technologies, we ensure that patients have quicker access to care, leading to improved health outcomes and significant economic advantages at scale.Having established successful partnerships with healthcare systems across the U.S., we are now extending our reach internationally, particularly in the MENA region, where we are collaborating with local health systems to implement our AI-driven care navigation solutions.About the RoleWe are seeking a highly skilled Staff AI Engineer to spearhead the design and advancement of our AI voice agents. This pivotal role will involve creating and managing AI systems that perform effectively in real-world environments.You will be responsible for the comprehensive behavior of our agents, overseeing their orchestration, tool utilization, latency, evaluation, and the management of failures.Your work will involve tackling complex, non-deterministic systems, crafting an architecture that ensures consistency, observability, and scalability in production settings.What You’ll DoDesign and oversee the architecture of AI agents, encompassing orchestration, tool usage, and control flow.Create systems that guarantee reliable agent operation across diverse real-world interactions.Develop and refine evaluation frameworks to assess agent quality and behavior.Identify and troubleshoot complex issues in production, including edge cases, failures, and regressions.Enhance performance across the system stack, focusing on latency, cost, and reliability.Establish patterns and best practices for building and operating AI agents.Mentor fellow engineers and elevate the standards of AI systems design and execution.What We’re Looking ForRequired QualificationsMinimum of 7 years of experience in software engineering.Proven experience in developing and managing AI agents or conversational systems in production settings.Deep understanding of:Agent orchestration and control mechanisms.Real-world systems and their operational challenges.

ABOUT RETELL AIRetell AI is at the forefront of revolutionizing call centers with innovative voice AI technology, utilizing first principles to redefine customer interactions.In just 18 months since our inception, thousands of companies have adopted Retell's AI voice agents to manage sales, support, and logistics calls that previously required extensive human teams. Supported by prestigious investors such as Y Combinator and Alt Capital, we have rapidly scaled to $36M ARR with a lean team of 20, up from $5M at the start of 2025.Our vision for 2026 is to create a modern customer experience (CX) platform where entire contact centers are powered by AI, moving beyond basic automation that relies on constant human intervention to intelligent AI “workers” that operate as frontline agents, quality assurance analysts, and managers, continuously executing, monitoring, and enhancing customer interactions.As we grow, we seek passionate builders eager to tackle challenging technical problems, accelerate progress, and make a genuine impact within one of the fastest-growing voice AI startups.Join us in shaping the future.Ranked among the top 50 AI applications in a16z's list: https://tinyurl.com/5853dt2x#4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025Also recognized as a top-ranking startup on: https://leanaileaderboard.com/ABOUT THE ROLEAs a Senior Software Engineer - Support Automations at Retell, you will take charge of the technical support for our advanced, agentic voice AI platform. This hands-on leadership role involves personally troubleshooting complex customer issues, developing AI agents and automations, and guiding a growing team of support engineers.You will work at the intersection of engineering, customer relations, and product development, ensuring exceptional reliability, swift resolutions, and scalable support as Retell expands.This position is perfect for someone who thrives on solving intricate technical challenges in high-pressure environments, engages directly with customers, and enjoys building systems and teams from the ground up.