Y Combinator Winter 2026 (W26) Companies

/dev/fast is an AI-native code review platform that enables developers to review pull requests 10x larger in half the time by focusing on architecture rather than implementation details. It uses AI agents to reduce mean time-in-review by 2x while optimizing token costs, and includes a git server built on object storage for reliability.

1 investor

10x Science provides an AI platform that automates protein characterization for drug developers, reducing months of manual analysis to speed the evaluation of therapeutic candidates in early-stage development.

2 investors

21st.dev provides a library of thousands of components and templates from the community for developers to use in building applications.

2 investors

Aemon builds autonomous AI research systems that solve hard technical optimization problems by self-accelerating experimentation within customer codebases. The system learns from the frontier of research, runs experiments, and delivers validated technical breakthroughs for enterprise customers.

2 investors

Agentic Fabriq provides an identity and access governance platform for AI agents, enabling secure authentication, permissions management, and audit logging across agent deployments. The platform allows agents to act on behalf of users while maintaining security and compliance across enterprise tools and data.

1 investor

Alt-X operates an AI-powered infrastructure platform that connects buyers and sellers of private company stakes, starting with venture secondaries and expanding to other private assets. The platform automates diligence, valuation, and transaction execution to reduce the time, cost, and opacity inherent in private market transactions.

1 investor

An open-source design editor that allows developers and AI coding agents to collaborate on creating, modifying, and deploying UI components in real time, with changes directly converted to production code.

1 investor

Approxima provides AI agents that handle routine software development tasks including scoping work, writing code, validating fixes in isolated environments, and deploying to production, freeing developers to focus on novel work.

1 investor

The ARC Prize Foundation is a non-profit organization creating human-calibrated benchmarks to measure progress toward Artificial General Intelligence (AGI). It focuses on identifying capability gaps between human and artificial intelligence on tasks that are simple for humans but difficult for current AI systems.

1 investor

ashr provides testing and evaluation infrastructure for AI agents, allowing developers to run tests, catch failures, and debug agent behavior before production deployment. The platform offers real-time tracing, prompt versioning, and automated failure detection for teams building autonomous agents.

1 investor

Asimov collects real-world human activity data at scale from diverse environments to create annotated datasets for training robotics AI models. The company operates both as a data collection platform where individuals earn money for recording their activities and as a service for businesses whose workers perform physical tasks, offering zero-cost labor in exchange for recording data.

1 investor

Aurorin builds a modern CAD platform designed to accelerate engineering iteration by reducing software latency and integrating AI-native workflows. The company targets engineers and product teams who need faster design feedback cycles across industries including aerospace, robotics, and medical devices.

1 investor

AutoSitu provides software tools for urban planning and regulatory compliance in housing and infrastructure development. The company helps navigate zoning codes and public-sector review processes to accelerate project delivery.

2 investors

Autumn AI identifies early-stage startup founders and companies through signals like incorporation filings, GitHub activity, social media follows, and hiring pages before they appear in public directories. The platform helps companies like Brex discover and prioritize emerging founders.

1 investor

Avoice provides administrative and workflow management software for architecture and engineering practices, handling specification writing, submittal tracking, RFI coordination, and drawing markup. The platform serves architects and engineers, enabling them to focus on design rather than administrative tasks.

1 investor

AxionOrbital Space develops AI models that convert synthetic aperture radar data into optical-like imagery, enabling continuous Earth observation regardless of cloud cover or time of day. The technology serves defense, commodities trading, and disaster response applications.

1 investor

Axis builds an AI system that helps commodities traders monitor markets and deploy trading models for metals, agricultural products, and energy, covering derivatives, inventory, geopolitical factors, and other market signals relevant to their trading decisions.

1 investor

Balance provides real-time, audit-ready accounting and bookkeeping powered by AI, combining automated financial processing with dedicated human accountants. The platform serves growing businesses that need affordable, integrated financial operations without manual accounting overhead.

1 investor

BaseFrame identifies repetitive work tasks across a company's existing tools and provides specifications for AI automation. It helps small businesses discover and automate routine tasks without requiring new software or data migration.

1 investor

Beacon Health builds AI agents that automate healthcare workflows in electronic health record (EHR) systems for physicians and healthcare organizations. The platform records clinical workflows and converts them into deployable agents that can execute multi-step tasks across multiple EHR systems to support value-based care, quality improvement, and clinical operations.

1 investor

BeeSafe AI operates a fraud prevention platform that identifies mule accounts and fraudulent infrastructure by engaging directly with scammers in real-time. The platform serves financial services institutions and government agencies to prevent scams and application fraud.

3 investors

Beyond Reach Labs develops deployable solar arrays for space infrastructure that deliver high power per launch. The company addresses energy challenges for orbital data centers, lunar operations, and next-generation space platforms by overcoming the structural limitations of traditional solar array designs.

1 investor

Bidflow is an AI tool that automatically counts electrical devices, lighting fixtures, and lighting controls from construction drawings. It serves electrical contractors and lighting distributors who need to prepare bids and quotes quickly.

1 investor

Booko uses AI to predict which service appointment slots won't fill and automatically applies targeted discounts to recover revenue from unsold time. The platform integrates with existing booking systems (MindBody, Mariana Tek, etc.) to analyze demand patterns and incentivize customers to book previously empty slots across fitness studios, salons, med spas, consulting, and similar service businesses.

1 investor