Lightsage, an early-stage startup that’s helping software companies to sell their products to artificial intelligence agents, said today it has raised $4 million to spark a new era of “agent-led growth.”

The seed funding round was led by Nexus Venture Partners and saw participation from a host of prominent angel investors, including Postman Inc. Chief Executive Abhinav Asthana, DocuSign Inc. President Robert Chatwani, Apollo GraphQL CEO Matt Curl and former Salesforce Inc. Chief Technology Officer Steven Tamm.

The startup, officially known as API-Rex Inc., says software developers need to be aware that they’re no longer selling their products to just humans. With the rise of autonomous AI agents like Claude Code, Microsoft Corp.’s Copilot and Cursor, humans are a lot less involved in the software engineering process than they used to be.

But it’s not just that people are doing less coding themselves. Human developers want to save time wherever possible, and it means they’re no longer scrolling through websites and reading through documentation. Instead, they’re letting their AI agents choose the most appropriate software on their behalf.

What this means is that software developers cannot just rely on marketing their products to humans. They have to target those agents directly, and that requires an entirely different approach to marketing, said Lightsage co-founder and CEO Jun Liang Lee.

“We are moving from an internet where AI tells people which software to use to one where AI increasingly uses the software itself,” he explained. “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.”

Lightsage has theorized a new concept of agent-led growth, where software developers grow adoption of their tools by specifically targeting AI agents. Its platform runs simulations across multiple coding agents and answer engines to help software companies view their offerings from the perspective of autonomous agents.

As the startup explains, it can be tricky to understand how agents choose which software to use. It provides AI agents with real-world integration tasks, instructs them to go shopping, and then measures how visible its customer’s software is in comparison to rival platforms. It will then get the agent to actually use their product.

If the agent fails to complete the assigned task using their software, it will find out why – whether that’s because of confusing documentation, broken API endpoints, flawed authentication or incompatible Model Context Protocol servers. Once the problem has been identified, it will then show customers how to fix it.

As an added benefit, Lightsage provides software vendors with analytics about the agentic traffic visiting their websites and insights into which agents are using their software, for which tasks and how often. “We think every software company will eventually need to optimize for that journey to unlock agent-led growth,” Lee said.

For now, Lightsage is specifically focusing on developer software, because it says this is the area where AI agents have already become extremely widespread. Its platform has already been used to good effect by software firms like Reducto, Daytone, Firecrawl, Rime and Tinyfish, helping them to understand why agents sometimes choose their platforms, and why they go with their competitor’s platforms on other occasions.

Lightsage’s goal now is to expand its commercial and engineering teams and grow its capabilities across analytics, attribution, evaluation and optimization, targeting everything from APIs and software development kits to command line interfaces and agent skills. Eventually, it hopes to spread the agent-led growth concept to other disciplines, such as business-to-business software, cloud infrastructure and automated payments.

Abhishek Sharma of Nexus Venture Partners said he knows an opportunity when he sees one, and believes it’s obvious where the digital economy is headed. “The internet brought the economy online, with humans discovering, choosing and transacting through digital channels,” he said. “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.”

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