- Celly is a pure C# implementation of Google's Common Expression Language (CEL) that passes 100% of the official conformance suite.
- CEL allows safe, terminating expression evaluation for policies, validation, and rules without arbitrary code execution.
- Celly is built entirely in managed C# without WebAssembly or native bindings, ensuring cross-platform compatibility.
- The engine is optimized for repeated evaluation, outperforming cel-go on comprehension-heavy expressions due to rope-style list accumulation.
- Celly ships with protovalidate support for .NET, making it the first implementation to pass buf's full conformance suite.
- It provides a simple API: compile once, evaluate many times, with immutable and thread-safe programs.
- Performance benchmarks show Celly is ~1.2x faster than other managed options and faster than cel-go on specific workloads.