Lightsage Raises $4M to Build Growth Stack for Software's Newest Customer: AI Agents

Lightsage Secures Seed Funding to Pioneer Agent-Led Growth

San Francisco-based startup Lightsage has raised $4M in seed funding to help software companies adapt to a fundamental shift in how their products are discovered and adopted1

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. Nexus Venture Partners led the round, with participation from prominent angel investors including former Salesforce chief technology officer Steven Tamm, Postman chief executive Abhinav Asthana, Apollo chief executive Matt Curl, and DocuSign president Robert Chatwani1

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. The startup, officially known as API-Rex Inc., is building what it calls the growth stack for software's newest customer: autonomous AI agents2

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Software Companies Must Market Their Products Directly to Autonomous AI Agents

Lightsage addresses a real transformation in software adoption. AI coding agents now pick libraries, install SDKs, and call APIs without anyone visiting a website, increasingly through model context protocol servers1

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. Human developers are letting their AI agents choose the most appropriate software on their behalf rather than scrolling through websites and reading documentation themselves2

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. Chief executive Jun Liang Lee explained the shift: "We are moving from an internet where AI tells people which software to use to one where AI increasingly uses the software itself. That changes what growth means. Visibility still matters, but the real test is whether an agent can understand your product and get a successful outcome"2

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How Lightsage Simulates Agent Interactions with Software to Optimize Discovery

The platform runs simulations across answer engines and AI coding agents, handing them real tasks and recording where they fail1

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. Lightsage helps software companies view their offerings from the perspective of autonomous AI agents by providing agents with real-world integration tasks and measuring how visible their software is compared to competitors2

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. When agents fail to complete assigned tasks, the platform identifies whether the break is discoverability, documentation, authentication, an API endpoint, or an incompatible server1

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. Teams can then fix issues and rerun tasks to measure whether agent success improves. The platform supports Claude Code, Codex, Cursor, GitHub Copilot, and OpenCode1

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Developer Tools and Early Customers Validate Agent-Led Growth Approach

Lightsage is currently focusing on developer tools, where AI agents have already become widespread2

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. Named customers include Firecrawl, Reducto, Daytona, Rime, and Tinyfish, all developer software companies1

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. These platforms use Lightsage to understand why agents sometimes choose their software and why they select competitors on other occasions2

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. As an added benefit, Lightsage provides software vendors with analytics about agentic traffic visiting their websites and insights into which agents are using their software, for which tasks, and how often2

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. Lee noted that "every software company will eventually need to optimize for that journey to unlock agent-led growth"2

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Agentic Payments Face PSD2 Regulations and Strong Customer Authentication Challenges

While agents can discover and use software, the payment dimension remains complex. In Europe, agentic payments stay subject to PSD2 regulations with no agent-specific carve-out1

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. Strong customer authentication still applies, raising open questions about who provides the payment service, who controls funds, and what counts as valid authorization once the act is delegated1

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. European payments law was written for a person approving a transaction with two factors, tied to a specific payee and amount, not for software approving one on a person's behalf1

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. The challenges are already real: Robinhood lets AI agents trade stocks and spend on a card, while Meow launched an agentic banking platform aimed at AI agents1

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Expansion Plans Target B2B Software and Cloud Infrastructure Markets

Lightsage plans to expand its commercial and engineering teams and grow capabilities across analytics, attribution, evaluation, and optimization2

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. The platform aims to target everything from APIs and software development kits to command line interfaces and agent skills2

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. Eventually, the company hopes to spread Agent-Led Growth concepts beyond developer tools to other disciplines including B2B software, cloud infrastructure, and automated payments2

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. Abhishek Sharma of Nexus Venture Partners stated: "The internet brought the economy online, with humans discovering, choosing and transacting through digital channels. But AI is now shifting that agency from humans to agents, which can discover, evaluate and act on a user's behalf. Lightsage is building the intelligence infrastructure for this new era of autonomous browsing, helping companies optimize for agent conversion"2

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. The $4M round appears modest against the ambition, especially compared to Neo's $100M raise for a control layer over agentic software1

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. Two of Lightsage's named customers have founders who also appear on its investor list1

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