About Lightsage
Lightsage helps software companies see how AI coding agents and answer engines discover, choose and use their products, then diagnoses why agents fail. It raised a $4 million seed round in September 2026, led by Nexus Venture Partners.
What is Lightsage?
What is Lightsage?
Lightsage is an early-stage startup, officially API-Rex Inc., that helps software companies sell their products to AI agents. It is built on a concept it calls agent-led growth: as tools like Claude Code, Copilot and Cursor increasingly pick and use software on a developer's behalf, vendors need to market to agents, not just humans.
The platform runs simulations across multiple coding agents and answer engines so software companies can see their offerings from an agent's perspective. Lightsage gives agents real-world integration tasks, has them shop for tools, and measures how visible a customer's software is compared with rivals. It then has the agent actually use the product. If the agent fails, Lightsage finds out why, whether because of confusing documentation, broken API endpoints, flawed authentication or incompatible MCP servers, and shows how to fix it.
Lightsage also provides analytics on agentic traffic, showing which agents use a vendor's software, for which tasks and how often. It currently focuses on developer software and has worked with firms including Reducto, Firecrawl, Rime and Tinyfish.
Co-founder and CEO Jun Liang Lee leads the company, which plans to extend into APIs, SDKs, CLIs and agent skills.
Pros
- Measures product visibility across multiple coding agents and answer engines
- Tests whether agents can actually complete tasks with your product
- Pinpoints failure causes such as documentation, API, auth or MCP issues
- Adds analytics on agentic traffic and usage patterns
Cons
- Currently focused on developer software only
- Agent-led growth is a new, still-forming category
- Pricing is not published
How to Use Lightsage
- 1Add your product
Set up your software, docs and APIs in Lightsage.
- 2Run agent simulations
Let Lightsage task coding agents and answer engines with real integration jobs that could use your tool.
- 3Review visibility and failures
See how often agents pick you versus rivals and why they fail when using your product.
- 4Fix and track
Apply recommended fixes and monitor agentic traffic analytics over time.