## 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.
Adam Perry @ OpenAI
f97d5c3275