Teams break functionality into focused Lambda Annotation projects, deploy them independently, and often place them behind a single API Gateway. The architecture scales beautifully—but documentation doesn’t always keep up.
With LambdaOpenApi 1.1.0, we’re introducing a new capability designed specifically for this reality: the OpenAPI Schema Merge Tool.
LambdaOpenApi has always focused on producing accurate, compile-time OpenAPI specifications directly from your Lambda code. That works extremely well—right up until you have:
What you end up with is a collection of perfectly valid OpenAPI specs… and no clean way to present them as a single platform API.
This friction shows up everywhere:
LambdaOpenApi 1.1.0 adds a first-class solution to this problem.
The new OpenAPI Merge Tool allows you to combine multiple OpenAPI specifications into one unified definition, while preserving the boundaries and intent of each underlying service.
It’s designed for teams that:
Most importantly, it does this without forcing you to change how you structure or deploy your services.
This release isn’t about squeezing everything back into a monolith.
The merge tool respects the reality of modern serverless systems:
You can namespace APIs, keep schemas distinct, and still present a cohesive platform surface—something that’s historically been painful to achieve without custom scripts or fragile build steps.
LambdaOpenApi has always been opinionated about one thing: your OpenAPI spec should reflect your code, not drift from it.
The merge tool extends that philosophy one step further:
No hand-edited mega-specs. No guesswork. No duct tape.
LambdaOpenApi 1.1.0 lays the groundwork for:
Better platform-level documentation
If you’re already using LambdaOpenApi across multiple services, this release is designed to fit directly into your existing workflow.
Check out the full documentation for the OpenAPI Merge Tool to see how it fits into your architecture.
]]>LambdaOpenApi grew out of an internal tool we built to support our own production AWS Lambda applications. After using it successfully in real workloads, we refined it, generalized it, and open-sourced it so the broader .NET and Lambda community can benefit from the same streamlined OpenAPI workflow.
LambdaOpenApi is a lightweight, compile-time OpenAPI generator for AWS Lambda Annotations .NET applications. Define your API with simple C# attributes and get a complete OpenAPI 3.x document at build time — no runtime work, no manual YAML, and no drift.
Using the .NET CLI:
dotnet add package Oproto.Lambda.OpenApi
Or via the NuGet Package Manager:
Install-Package Oproto.Lambda.OpenApi
Fully compile-time generation using C# source generators — no reflection, no startup scanning, and no cold-start impact.
Works directly with AWS Lambda Annotations (HTTP attributes, request/response types, errors, and more).
Describe your entire API surface using C# attributes. Routes, inputs, outputs, and metadata stay clean and discoverable.
Produces a complete, standards-compliant OpenAPI document your tooling can rely on.
Follow the Getting Started guide on our documentation site to generate your first OpenAPI spec in minutes.
LambdaOpenApi aims to remain small, stable, and focused — but your feedback helps keep it sharp. If you discover any issues or have suggestions, feel free to open an issue on GitHub.
Thank you for trying out LambdaOpenApi — we hope it makes your Lambda development experience simpler and smoother!
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