AGENTS.md

1# gRPC C++ Agents Collaboration Guide
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3This document outlines conventions and best practices for AI-assisted development in the gRPC C++ codebase.
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5## Preferred Tools & Libraries
6*   Prefer gRPC types before absl.
7*   Prefer std types when available, use absl types when not
8*   Prefer `std::optional` over `absl::optional`
9*   gRPC uses C++17, so we can't use C++20 onwards types.
10*   The Python implementation cannot depend on the protobuf library, so any shared libraries must expose a C-style API that does not rely on C++ protobuf types.
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12## Code Style & Conventions
13*   `#include <grpc/support/port_platform.h>` is not required unless its macros are needed for compilation.
14*   Only include headers that are actively used.
15*   Abseil headers are sorted before gRPC headers.
16*   For public api headers (in `include/grpc`) we use `<grpc/...>`.
17    *   Example: `#include <grpc/grpc.h>`
18*   Prefer explicit types over `std::pair` or `std::tuple` for return types.
19*   Use `LOG(ERROR)` from `absl/log/log.h` for logging errors, never use `std::cerr` or `gpr_log`.
20*   The `fuzztest.h` header is located at `fuzztest/fuzztest.h`.
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22## About gRPC
23*   gRPC uses its own macros for Bazel libraries, tests, etc. Each directory should have a `grpc_package` declaration. For libraries use `grpc_cc_library`, for tests `grpc_cc_test`.
24*   Dependencies on non-gRPC libraries (like gtest or absl) are listed in the `external_deps` attribute.
25*   The `:grpc` BUILD target is not allowed to depend on the C++ protobuf library, either directly or transitively.
26*   Build files for implementation code are typically located in `src/core/BUILD` and `BUILD`. Do not add new `BUILD` files under the `src/` tree without explicit instruction.
27*   Tests are located in `test/core` and `test/cpp` (corresponding to the `src` directories). These test directories contain their own `BUILD` files.
28*   Fuzz tests use `fuzztest_main` instead of `gtest_main`.
29*   When depending on a `grpc_proto_library`, the name of the `cc_library` target is the same as the `name` of the `grpc_proto_library` rule itself, not `[name]_cc_proto` as one might expect from standard Bazel `cc_proto_library` rules. The build system error messages can be misleading in this case.
30*   The 'gtest' external_dep also includes 'gmock'.
31*   All `upb` related build rules (`grpc_upb_proto_library`, `grpc_upb_proto_reflection_library`) for protos defined anywhere in the repository must be defined in the root `BUILD` file. They should not be placed in the `BUILD` file of the subdirectory where the proto is located.
32*   Core end-to-end tests are defined in `test/core/end2end/BUILD` using the `grpc_core_end2end_test_suite` macro. This macro generates multiple `grpc_cc_test` targets by combining a configuration file (like `end2end_http2_config.cc`) with individual test implementation files located in `test/core/end2end/tests/`. The final test target name is created by appending `_test` to the `name` attribute of the macro. For example, `grpc_core_end2end_test_suite(name = "end2end_http2", ...)` generates the test target `//test/core/end2end:end2end_http2_test`.
33*   Unused named parameters is a compilation failure.
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