Location: San Francisco (Hybrid: 3 days in SoMA) | Open to London (5 days/month in SF)
Type: Full-Time
Team: Research Tribe
Focus: Agent Systems Engineer
Who we are
We're a team of founders, engineers, researchers, creatives, and operators building what we believe will be one of the defining companies of the AI era.
The hardest part of building products isn’t writing code - it’s predicting human behavior.
Until now, it’s been guesswork. Blok changes that. We simulate real user behavior before anything ships.
Who we are not
We are not your average SF startup. We’re a diverse team of 15 people - hailing from 10 countries and speaking 10 languages with a range of non-traditional backgrounds.We are not remote: We value the energy of solving hard problems on a whiteboard in our SF HQ.We are not “researching to learn”: Research and product move in tight, high-velocity loops. If it doesn’t become code to solve a customer problem, it doesn't exist.How we work
We operate under Blok OS - a playbook for how we build, collaborate, and make decisions in a high-velocity environment:
Anchor Days: We’re in the SF HQ (SoMA) 3 days/week (Mon, Tues, Thurs) to solve hard problems together.Core Collaboration Hours: We’re online 9-11am PT daily so the whole team (SF ↔ UK) can collaborate in real time.Deep Work: Outside of that, we protect uninterrupted time to build.What you’ll own & build
As a Member of Technical Staff within the Research Tribe, you’ll be one of the early engineers shaping the core systems that power Blok.
You won’t just build agents - you’ll design the infrastructure that governs how they operate: how they coordinate, how they’re evaluated, and how their behavior improves over time.
This is a deeply technical role bridging distributed systems, machine intelligence, and product - turning stochastic models into reliable, production-grade systems.
Multi-Agent Systems Architecture: Design and implement agentic systems, rather than prompt chains, at scale. You’ll define agent topologies, robust orchestration layers, structured state management, persistent and scoped memory, tool-use registries and execution, and build structured, inspectable systems. You’re building a long-running harness-based agentic platform, not wiring together LLM API calls.Behavioral & Persona Modelling: Simulate user archetypes with goal-directed behavior. You’ll design data-grounded personas, enable “computer-use” on real interfaces, and develop agents with critique and reflection loops. You’re producing measurable, actionable behavior.Evaluation & Prompt Engineering: Design prompt schemas and reasoning templates as integrated systems. You’ll build frameworks that measure behavioral fidelity and failure modes, and implement automated and HITL feedback. If it can’t be measured, it doesn’t ship.Signal & Insight Systems: Build systems that transform raw agent outputs into high-signal insights. You’ll cluster observations across runs, implement severity scoring, and map behavioral signals to product decisions. Turn noisy outputs into decisions.Production Reliability: Build the infrastructure to operate agents in production. You’ll implement tracing, attribution, and cost monitoring, detect failure modes and design fallbacks, circuit breakers, and evaluation pipelines. The bar is production reliability.Why Blok
The People: Join a global team of founders, engineers, researchers, and adventurers obsessed with human behavior - we’re curious, willing to be wrong, and privileged to be solving hard problems at the frontier.The Problem: Deep science with real impact. We leverage behavioral modeling, cognitive science, and cutting-edge AI to solve real product challenges for real customers.The Velocity: Ship fast and learn faster. Work directly with customers and see the impact of your work in hours, not weeks or months.The Backing: Backed by Rackhouse, Weekend Fund, Protagonist, MaC, and scouts at a16z, Greylock, and CRV. Plus operators from Discord, Airbnb, Meta, and Google.The Member Of Staff Philosophy: You don’t care about titles - you value extreme ownership.Who you are
Systems, Not Prompts: You prioritize state machines, orchestration layers, and tool-use contracts over prompt hacking. You build for reliability, inspectability, and improvability - you’re uncomfortable with “it just works sometimes.” If it can’t be measured, it doesn’t ship.Production Experience: You have 5+ years building complex software and 2+ years shipping agentic LLM systems. You’ve built harnesses where agents manage tool selection, error recovery, and multi-step execution autonomously in production environments that run, break, and evolve.Orchestration Systems: You’re experienced with multi-agent orchestration, sandboxed execution, and complex backends. You optimize for coordination, scoped memory & context, and how agents degrade gracefully under pressure.Python Mastery: You’re an expert in async programming and structured data modelling (Pydantic), building maintainable, scalable systems designed for extensibility.Fast, Iterative Builder: You thrive when research and product move together. You’re comfortable shipping quickly, learning from real users, and refining systems in tight loops.High Ownership, Low Ego: You take responsibility for what you build. You’re willing to be wrong, change your mind, and prioritize being effective over being “theoretically right.”Comfortable at the Frontier: You’re excited by ambiguous problems. You’re not waiting for best practices - you’re defining them.Product Intuition: You prioritize signal over noise because outputs matter. You care that what you build helps someone make a decision.All Backgrounds Welcome: Some of us are dropouts, some have PhDs. Some are tech veterans, some are first-timers. What matters - how you think, build, and work together in teams..Comp & benefits
Salary: $180-250k + meaningful equity upsideHealth: 100% paid medical, dental & visionPTO: 28 days (inc 5 company reset days on stats) that we all takeEnvironment: Beautiful office in SoMa, fully stocked and optimized for deep workWFH: 2 days/week (Wed & Fri) to catch up on laundry, save time commuting, and let your cat walk across the keyboardAdventures: 2 annual offsites (we’re back from Las Vegas and planning something fun in Sept), plus we host regular team dinners and events in the cityJoin us
If this sounds like you, send us something that tells us who you are - not just your resume. We’re hiring to build the future!
