diff --git a/.github/workflows/build-gpui-windows.yml b/.github/workflows/build-gpui-windows.yml
index 20baf16..0551682 100644
--- a/.github/workflows/build-gpui-windows.yml
+++ b/.github/workflows/build-gpui-windows.yml
@@ -10,6 +10,14 @@ on:
     branches: [main, gpui]
   pull_request:
 
+# A newer push to the same branch or PR makes an unfinished build of the older
+# one pointless, so cancel it instead of letting them pile up. Never on main:
+# those builds are the ones that fill the shared cache, and a cancelled run
+# saves nothing.
+concurrency:
+  group: build-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
+
 jobs:
   build:
     runs-on: windows-latest
@@ -23,9 +31,15 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@stable
 
+      # The installer is its own cargo workspace with its own target folder,
+      # so it needs its own cache entry. `shared-key` lets release.yml reuse
+      # what this builds.
       - uses: Swatinem/rust-cache@v2
         with:
-          workspaces: gpui
+          workspaces: |
+            gpui
+            gpui/installer
+          shared-key: windows
 
       # gpui/build.rs bundles the protocol drivers with esbuild, so the root
       # node_modules must exist first.
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 329fdd9..fc4b4db 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -56,13 +56,19 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@stable
 
+      # Same cache the build workflow fills on main, installer included.
       - uses: Swatinem/rust-cache@v2
         with:
-          workspaces: gpui
+          workspaces: |
+            gpui
+            gpui/installer
+          shared-key: windows
 
       - name: Install JS dependencies
         run: npm ci
 
+      # A tag can point at any commit, so don't publish without the tests.
+      # Cheap now: the shared cache already holds the test build.
       - name: Test
         run: cargo test
         working-directory: gpui
diff --git a/gpui/installer/Cargo.toml b/gpui/installer/Cargo.toml
index f78873e..57d1ac1 100644
--- a/gpui/installer/Cargo.toml
+++ b/gpui/installer/Cargo.toml
@@ -32,7 +32,9 @@ mslnk = "0.1"
 [build-dependencies]
 winres = "0.1"
 
+# No LTO here: the installer is a small dialog, and fat LTO over the whole GPUI
+# dependency tree was the slowest step of every build for a few percent of size.
 [profile.release]
-lto = true
-codegen-units = 1
+lto = false
+codegen-units = 16
 strip = true