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Adam Perry @ OpenAI
f97d5c3275
## Why Fat LTO makes release builds substantially slower without providing enough measured runtime benefit to justify the release CI long pole. The build-profile investigation found that keeping Cargo's default release `opt-level=3` and switching from fat LTO to ThinLTO (`3/thin/1`) reduced a clean `codex-cli` release build from 2073.893 seconds to 1243.172 seconds, a 40.06% improvement. The resulting binary increased from 196.7 MiB to 211.8 MiB (+7.63%). Measured runtime changes were small: the worst image workload median was +0.86% and app-server startup was +0.31% relative to fat LTO. ThinLTO retains cross-crate optimization while avoiding most of the fat-LTO build cost. This deliberately avoids global size optimization: final-executable testing showed a substantial regression on the image request path, which is expected to become more important as image usage grows. ## What changed - Set the workspace release profile to `lto = "thin"`, retaining Cargo's default release `opt-level=3`. - Remove release and CI workflow-specific LTO overrides so release-profile builds consistently use the workspace setting. - Remove the now-unused Windows release workflow input and related diagnostic output. ## Validation - Confirmed the release profile parses with `cargo metadata --no-deps --format-version 1`. - CI validates release builds across the supported target matrix.
f97d5c3275
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2026-06-04 20:07:53 +00:00
History
Workflow Strategy
The workflows in this directory are split so that pull requests get fast, review-friendly signal while main still gets the full cross-platform verification pass.
Pull Requests
bazel.ymlis the main pre-merge verification path for Rust code. It runs Bazeltestand Bazelclippyon the supported Bazel targets, including the generated Rust test binaries needed to lint inline#[cfg(test)]code.rust-ci.ymlkeeps the Cargo-native PR checks intentionally small:cargo fmt --checkcargo shearargument-comment-linton Linux, macOS, and Windowstools/argument-comment-lintpackage tests when the lint or its workflow wiring changes
Post-Merge On main
bazel.ymlalso runs on pushes tomain. This re-verifies the merged Bazel path and helps keep the BuildBuddy caches warm.rust-ci-full.ymlis the full Cargo-native verification workflow. It keeps the heavier checks off the PR path while still validating them after merge:- the full Cargo
clippymatrix - the full Cargo
nextestmatrix via per-platform archive-backed shards - Windows ARM64 nextest archives cross-compiled on Windows x64, then replayed on native Windows ARM64 shards
- release-profile Cargo builds
- cross-platform
argument-comment-lint - Linux remote-env tests
- the full Cargo
Rule Of Thumb
- If a build/test/clippy check can be expressed in Bazel, prefer putting the PR-time version in
bazel.yml. - Keep
rust-ci.ymlfast enough that it usually does not dominate PR latency. - Reserve
rust-ci-full.ymlfor heavyweight Cargo-native coverage that Bazel does not replace yet.