Protox is an Elixir library for Google Protocol Buffers (protobuf) that provides encoding/decoding to/from binary wire format, code generation from .proto schemas, and compile-time schema compilation. It supports both proto2 and proto3 syntaxes. The library is used by defining a module with `use Protox` and providing either an inline schema string or a list of .proto files; this macro triggers protoc to parse the definitions and generates Elixir structs with encode/decode functions, unknown field handling, and schema introspection. The generated code is self-contained and only requires the protox runtime for encoding/decoding primitives. The architecture is a mix of compile-time code generation (via Elixir macros) and runtime encoding/decoding primitives. Key entry points include the `Protox` macro, `Protox.encode/1`, `Protox.decode/2`, and the `mix protox.generate` task for generating standalone source files. The library relies on `protoc` (the protobuf compiler) only at compile time to produce a binary descriptor; all runtime operations are pure Elixir. External dependencies are minimal: protoc must be in PATH during development, and the runtime has no non-OTP dependencies. Protox emphasizes correctness and performance: it passes Google's official conformance test suite, uses property-based testing with StreamData, mutation testing with Muex, and maintains near-100% test coverage. The encoding/decoding paths are heavily optimized with unrolled varint loops, inline binary pattern matching, and careful accumulator management to minimize allocations. The library also supports unknown fields, message merging, proto2 required fields, nested extensions, and proto3 optional fields.