feat: add support for building with Bazel

.bazelrc

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+common --repo_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
+common --repo_env=BAZEL_NO_APPLE_CPP_TOOLCHAIN=1
+
+common --disk_cache=~/.cache/bazel-disk-cache
+common --repo_contents_cache=~/.cache/bazel-repo-contents-cache
+common --repository_cache=~/.cache/bazel-repo-cache
+
+common --experimental_platform_in_output_dir
+
+common --enable_platform_specific_config
+# TODO(zbarsky): We need to untangle these libc constraints to get linux remote builds working.
+common:linux --host_platform=//:local
+common --@rules_cc//cc/toolchains/args/archiver_flags:use_libtool_on_macos=False
+common --@toolchains_llvm_bootstrapped//config:experimental_stub_libgcc_s
+
+# We need to use the sh toolchain on windows so we don't send host bash paths to the linux executor.
+common:windows --@rules_rust//rust/settings:experimental_use_sh_toolchain_for_bootstrap_process_wrapper
+
+# TODO(zbarsky): rules_rust doesn't implement this flag properly with remote exec...
+# common --@rules_rust//rust/settings:pipelined_compilation
+
+common --incompatible_strict_action_env
+# Not ideal, but We need to allow dotslash to be found
+common --test_env=PATH=/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
+
+common --test_output=errors
+common --bes_results_url=https://app.buildbuddy.io/invocation/
+common --bes_backend=grpcs://remote.buildbuddy.io
+common --remote_cache=grpcs://remote.buildbuddy.io
+common --remote_download_toplevel
+common --nobuild_runfile_links
+common --remote_timeout=3600
+common --noexperimental_throttle_remote_action_building
+common --experimental_remote_execution_keepalive
+common --grpc_keepalive_time=30s
+
+# This limits both in-flight executions and concurrent downloads. Even with high number
+# of jobs execution will still be limited by CPU cores, so this just pays a bit of
+# memory in exchange for higher download concurrency.
+common --jobs=30
+
+common:remote --extra_execution_platforms=//:rbe
+common:remote --remote_executor=grpcs://remote.buildbuddy.io
+common:remote --jobs=800
+

.github/workflows/Dockerfile.bazel

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+FROM ubuntu:24.04
+
+# TODO(mbolin): Published to docker.io/mbolin491/codex-bazel:latest for
+# initial debugging, but we should publish to a more proper location.
+#
+# docker buildx create --use
+# docker buildx build --platform linux/amd64 -f .github/workflows/Dockerfile.bazel -t mbolin491/codex-bazel:latest --push .
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    curl git python3 ca-certificates && \
+    rm -rf /var/lib/apt/lists/*
+
+# Install dotslash.
+RUN curl -LSfs "https://github.com/facebook/dotslash/releases/download/v0.5.8/dotslash-ubuntu-22.04.$(uname -m).tar.gz" | tar fxz - -C /usr/local/bin
+
+# Ubuntu 24.04 ships with user 'ubuntu' already created with UID 1000.
+USER ubuntu
+
+WORKDIR /workspace

.github/workflows/bazel.yml

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+name: Bazel (experimental)
+
+# Note this workflow was originally derived from:
+# https://github.com/cerisier/toolchains_llvm_bootstrapped/blob/main/.github/workflows/ci.yaml
+
+on:
+  pull_request: {}
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+concurrency:
+  # Cancel previous actions from the same PR or branch except 'main' branch.
+  # See https://docs.github.com/en/actions/using-jobs/using-concurrency and https://docs.github.com/en/actions/learn-github-actions/contexts for more info.
+  group: concurrency-group::${{ github.workflow }}::${{ github.event.pull_request.number > 0 && format('pr-{0}', github.event.pull_request.number) || github.ref_name }}${{ github.ref_name == 'main' && format('::{0}', github.run_id) || ''}}
+  cancel-in-progress: ${{ github.ref_name != 'main' }}
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # macOS
+          - os: macos-15-xlarge
+            target: aarch64-apple-darwin
+          - os: macos-15-xlarge
+            target: x86_64-apple-darwin
+
+          # Linux
+          - os: ubuntu-24.04-arm
+            target: aarch64-unknown-linux-gnu
+          - os: ubuntu-24.04
+            target: x86_64-unknown-linux-gnu
+          - os: ubuntu-24.04-arm
+            target: aarch64-unknown-linux-musl
+          - os: ubuntu-24.04
+            target: x86_64-unknown-linux-musl
+          # TODO: Enable Windows once we fix the toolchain issues there.
+          #- os: windows-latest
+          #  target: x86_64-pc-windows-gnullvm
+    runs-on: ${{ matrix.os }}
+
+    # Configure a human readable name for each job
+    name: Local Bazel build on ${{ matrix.os }} for ${{ matrix.target }}
+
+    steps:
+      - uses: actions/checkout@v6
+
+      # Some integration tests rely on DotSlash being installed.
+      # See https://github.com/openai/codex/pull/7617.
+      - name: Install DotSlash
+        uses: facebook/install-dotslash@v2
+
+      - name: Make DotSlash available in PATH (Unix)
+        if: runner.os != 'Windows'
+        run: cp "$(which dotslash)" /usr/local/bin
+
+      - name: Make DotSlash available in PATH (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: Copy-Item (Get-Command dotslash).Source -Destination "$env:LOCALAPPDATA\Microsoft\WindowsApps\dotslash.exe"
+
+      # Install Bazel via Bazelisk
+      - name: Set up Bazel
+        uses: bazelbuild/setup-bazelisk@v3
+
+      # TODO(mbolin): Bring this back once we have caching working. Currently,
+      # we never seem to get a cache hit but we still end up paying the cost of
+      # uploading at the end of the build, which takes over a minute!
+      #
+      # Cache build and external artifacts so that the next ci build is incremental.
+      # Because github action caches cannot be updated after a build, we need to
+      # store the contents of each build in a unique cache key, then fall back to loading
+      # it on the next ci run. We use hashFiles(...) in the key and restore-keys- with
+      # the prefix to load the most recent cache for the branch on a cache miss. You
+      # should customize the contents of hashFiles to capture any bazel input sources,
+      # although this doesn't need to be perfect. If none of the input sources change
+      # then a cache hit will load an existing cache and bazel won't have to do any work.
+      # In the case of a cache miss, you want the fallback cache to contain most of the
+      # previously built artifacts to minimize build time. The more precise you are with
+      # hashFiles sources the less work bazel will have to do.
+      # - name: Mount bazel caches
+      #   uses: actions/cache@v4
+      #   with:
+      #     path: |
+      #       ~/.cache/bazel-repo-cache
+      #       ~/.cache/bazel-repo-contents-cache
+      #     key: bazel-cache-${{ matrix.os }}-${{ hashFiles('**/BUILD.bazel', '**/*.bzl', 'MODULE.bazel') }}
+      #     restore-keys: |
+      #       bazel-cache-${{ matrix.os }}
+
+      - name: Configure Bazel startup args (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          # Use a very short path to reduce argv/path length issues.
+          "BAZEL_STARTUP_ARGS=--output_user_root=C:\" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
+
+      - name: bazel test //...
+        env:
+          BUILDBUDDY_API_KEY: ${{ secrets.BUILDBUDDY_API_KEY }}
+        shell: bash
+        run: |
+          bazel $BAZEL_STARTUP_ARGS --bazelrc=.github/workflows/ci.bazelrc test //... \
+            --build_metadata=REPO_URL=https://github.com/openai/codex.git \
+            --build_metadata=COMMIT_SHA=$(git rev-parse HEAD) \
+            --build_metadata=ROLE=CI \
+            --build_metadata=VISIBILITY=PUBLIC \
+            "--remote_header=x-buildbuddy-api-key=$BUILDBUDDY_API_KEY"

.github/workflows/ci.bazelrc

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+common --remote_download_minimal
+common --nobuild_runfile_links
+common --keep_going
+
+# Prefer to run the build actions entirely remotely so we can dial up the concurrency.
+# Currently remote builds only work on Mac hosts, until we untangle the libc constraints mess on linux.
+common:macos --config=remote
+common:macos --strategy=remote
+
+# We have platform-specific tests, so execute the tests locally using the strongest sandboxing available on each platform.
+common:macos --strategy=TestRunner=darwin-sandbox,local
+# Note: linux-sandbox is stronger, but not available in GHA.
+common:linux --strategy=TestRunner=processwrapper-sandbox,local
+common:windows --strategy=TestRunner=local
+

BUILD.bazel

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+# We mark the local platform as glibc-compatible so that rust can grab a toolchain for us.
+# TODO(zbarsky): Upstream a better libc constraint into rules_rust.
+# We only enable this on linux though for sanity, and because it breaks remote execution.
+platform(
+    name = "local",
+    constraint_values = [
+        "@toolchains_llvm_bootstrapped//constraints/libc:gnu.2.28",
+    ],
+    parents = [
+        "@platforms//host",
+    ],
+)
+
+platform(
+    name = "rbe",
+    constraint_values = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+        "@bazel_tools//tools/cpp:clang",
+        "@toolchains_llvm_bootstrapped//constraints/libc:gnu.2.28",
+    ],
+    exec_properties = {
+        # Ubuntu-based image that includes git, python3, dotslash, and other
+        # tools that various integration tests need.
+        # Verify at https://hub.docker.com/layers/mbolin491/codex-bazel/latest/images/sha256:8c9ff94187ea7c08a31e9a81f5fe8046ea3972a6768983c955c4079fa30567fb
+        "container-image": "docker://docker.io/mbolin491/codex-bazel@sha256:8c9ff94187ea7c08a31e9a81f5fe8046ea3972a6768983c955c4079fa30567fb",
+        "OSFamily": "Linux",
+    },
+)

MODULE.bazel

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+bazel_dep(name = "platforms", version = "1.0.0")
+bazel_dep(name = "toolchains_llvm_bootstrapped", version = "0.3.1")
+archive_override(
+    module_name = "toolchains_llvm_bootstrapped",
+    integrity = "sha256-9ks21bgEqbQWmwUIvqeLA64+Jk6o4ZVjC8KxjVa2Vw8=",
+    strip_prefix = "toolchains_llvm_bootstrapped-e3775e66a7b6d287c705ca0cd24497ef4a77c503",
+    urls = ["https://github.com/cerisier/toolchains_llvm_bootstrapped/archive/e3775e66a7b6d287c705ca0cd24497ef4a77c503/master.tar.gz"],
+    patch_strip = 1,
+    patches = [
+        "//patches:llvm_toolchain_archive_params.patch",
+    ],
+)
+
+osx = use_extension("@toolchains_llvm_bootstrapped//toolchain/extension:osx.bzl", "osx")
+osx.framework(name = "ApplicationServices")
+osx.framework(name = "AppKit")
+osx.framework(name = "ColorSync")
+osx.framework(name = "CoreFoundation")
+osx.framework(name = "CoreGraphics")
+osx.framework(name = "CoreServices")
+osx.framework(name = "CoreText")
+osx.framework(name = "CFNetwork")
+osx.framework(name = "Foundation")
+osx.framework(name = "ImageIO")
+osx.framework(name = "Kernel")
+osx.framework(name = "OSLog")
+osx.framework(name = "Security")
+osx.framework(name = "SystemConfiguration")
+
+register_toolchains(
+    "@toolchains_llvm_bootstrapped//toolchain:all",
+)
+
+bazel_dep(name = "rules_cc", version = "0.2.16")
+bazel_dep(name = "rules_platform", version = "0.1.0")
+bazel_dep(name = "rules_rust", version = "0.68.1")
+single_version_override(
+    module_name = "rules_rust",
+    patch_strip = 1,
+    patches = [
+        "//patches:rules_rust.patch",
+        "//patches:rules_rust_windows_gnu.patch",
+        "//patches:rules_rust_musl.patch",
+    ],
+)
+
+RUST_TRIPLES = [
+    "aarch64-unknown-linux-musl",
+    "aarch64-apple-darwin",
+    "aarch64-pc-windows-gnullvm",
+    "x86_64-unknown-linux-musl",
+    "x86_64-apple-darwin",
+    "x86_64-pc-windows-gnullvm",
+]
+
+rust = use_extension("@rules_rust//rust:extensions.bzl", "rust")
+rust.toolchain(
+    edition = "2024",
+    extra_target_triples = RUST_TRIPLES,
+    versions = ["1.90.0"],
+)
+use_repo(rust, "rust_toolchains")
+
+register_toolchains("@rust_toolchains//:all")
+
+bazel_dep(name = "rules_rs", version = "0.0.23")
+
+crate = use_extension("@rules_rs//rs:extensions.bzl", "crate")
+crate.from_cargo(
+    cargo_lock = "//codex-rs:Cargo.lock",
+    cargo_toml = "//codex-rs:Cargo.toml",
+    platform_triples = RUST_TRIPLES,
+)
+
+bazel_dep(name = "openssl", version = "3.5.4.bcr.0")
+
+crate.annotation(
+    build_script_data = [
+        "@openssl//:gen_dir",
+    ],
+    build_script_env = {
+        "OPENSSL_DIR": "$(execpath @openssl//:gen_dir)",
+        "OPENSSL_NO_VENDOR": "1",
+        "OPENSSL_STATIC": "1",
+    },
+    crate = "openssl-sys",
+    data = ["@openssl//:gen_dir"],
+)
+
+inject_repo(crate, "openssl")
+
+# Fix readme inclusions
+crate.annotation(
+    crate = "windows-link",
+    patch_args = ["-p1"],
+    patches = [
+        "//patches:windows-link.patch"
+    ],
+)
+
+WINDOWS_IMPORT_LIB = """
+load("@rules_cc//cc:defs.bzl", "cc_import")
+
+cc_import(
+    name = "windows_import_lib",
+    static_library = glob(["lib/*.a"])[0],
+)
+"""
+
+crate.annotation(
+    additive_build_file_content = WINDOWS_IMPORT_LIB,
+    crate = "windows_x86_64_gnullvm",
+    gen_build_script = "off",
+    deps = [":windows_import_lib"],
+)
+crate.annotation(
+    additive_build_file_content = WINDOWS_IMPORT_LIB,
+    crate = "windows_aarch64_gnullvm",
+    gen_build_script = "off",
+    deps = [":windows_import_lib"],
+)
+use_repo(crate, "crates")