lucabol · Aug 10, 2026 · Aug 9, 2026 · Aug 9, 2026 · Aug 9, 2026 · Aug 9, 2026
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -191,7 +191,7 @@ jobs:
         run: cargo test
 
       - name: Archive installer coexistence tests
-        run: python -m unittest scripts.test_installers.WindowsInstallerCoexistenceTests
+        run: python -m unittest scripts.test_installers.UnixInstallerCoexistenceTests
 
       - name: Integration tests — positive (freestanding)
         shell: bash
@@ -413,6 +413,14 @@ jobs:
       - name: Run unit tests (53 tests)
         run: cargo test
 
+      - name: Install Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: "3.x"
+
+      - name: Archive installer coexistence tests
+        run: python -m unittest scripts.test_installers.WindowsInstallerCoexistenceTests
+
       - name: Integration tests — positive (freestanding)
         shell: pwsh
         run: |

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
@@ -382,6 +382,34 @@ jobs:
             throw "The release contract lists no profiles for ${env:RELEASE_TARGET}."
           }
           $binRoot = Join-Path $env:RUNNER_TEMP 'oscan-release-binaries'
+          $sharedBinDir = Join-Path $binRoot 'shared'
+          New-Item -ItemType Directory -Path $sharedBinDir -Force | Out-Null
+          Remove-Item Env:OSCAN_DISTRIBUTION_PROFILE, Env:OSCAN_DEFAULT_BACKEND, `
+            Env:OSCAN_DISTRIBUTION_BACKEND, Env:OSCAN_INPROCESS_TOOLCHAIN_DIR, `
+            Env:OSCAN_INPROCESS_ASSETS_DIR, Env:RUSTFLAGS -ErrorAction SilentlyContinue
+          $env:OSCAN_VERSION = $env:RELEASE_TAG
+          if ($env:RELEASE_TARGET -eq 'windows-x86_64') {
+            $env:RUSTFLAGS = '-C target-feature=+crt-static'
+          }
+          Write-Host "::group::cargo build shared profile selectors"
+          # backend-c satisfies the package build contract without pulling in
+          # LLVM; selector code itself is backend-independent and is built once.
+          & cargo build --release --no-default-features --features backend-c `
+            --bin oscan-selector --bin oscan-default
+          if ($LASTEXITCODE -ne 0) {
+            throw "cargo build failed for the shared profile selectors."
+          }
+          $executableSuffix = [System.IO.Path]::GetExtension($env:RELEASE_BINARY_NAME)
+          foreach ($selectorName in @('oscan-selector', 'oscan-default')) {
+            $selectorOutput = Join-Path 'target/release' "$selectorName$executableSuffix"
+            if (-not (Test-Path -LiteralPath $selectorOutput -PathType Leaf)) {
+              throw "cargo produced no shared selector at $selectorOutput."
+            }
+            Copy-Item -LiteralPath $selectorOutput `
+              -Destination (Join-Path $sharedBinDir "$selectorName$executableSuffix") -Force
+          }
+          Write-Host "::endgroup::"
+
           foreach ($profile in $profiles) {
             $variant = $variants[$profile]
             $profileSpec = $contract['profiles'][$profile]
@@ -406,7 +434,7 @@ jobs:
             $env:OSCAN_DISTRIBUTION_PROFILE = $profile
             $env:OSCAN_DEFAULT_BACKEND = [string]$profileSpec['default_backend']
             $env:OSCAN_VERSION = $env:RELEASE_TAG
-            & cargo build --release --no-default-features --features $featureList
+            & cargo build --release --no-default-features --features $featureList --bin oscan
             if ($LASTEXITCODE -ne 0) {
               throw "cargo build failed for profile '$profile'."
             }
@@ -433,6 +461,14 @@ jobs:
           $variants = $contract['variants'][$target]['profiles']
           $profiles = $env:RELEASE_PROFILES.Split(',', [System.StringSplitOptions]::RemoveEmptyEntries)
           $binRoot = Join-Path $env:RUNNER_TEMP 'oscan-release-binaries'
+          $executableSuffix = [System.IO.Path]::GetExtension($env:RELEASE_BINARY_NAME)
+          $selectorBinary = Join-Path (Join-Path $binRoot 'shared') "oscan-selector$executableSuffix"
+          $defaultManagerBinary = Join-Path (Join-Path $binRoot 'shared') "oscan-default$executableSuffix"
+          foreach ($sharedBinary in @($selectorBinary, $defaultManagerBinary)) {
+            if (-not (Test-Path -LiteralPath $sharedBinary -PathType Leaf)) {
+              throw "No shared selector binary was built for $target (expected $sharedBinary)."
+            }
+          }
           $outputDir = Join-Path $env:RUNNER_TEMP 'oscan-release-artifacts'
           $uploadDir = Join-Path $env:GITHUB_WORKSPACE 'release-upload'
           New-Item -ItemType Directory -Path $uploadDir -Force | Out-Null
@@ -456,6 +492,8 @@ jobs:
               Profile = $profile
               Version = $version
               BinaryPath = $binary
+              SelectorBinaryPath = $selectorBinary
+              DefaultManagerBinaryPath = $defaultManagerBinary
               OutputDir = $outputDir
             }
             if ($components -contains 'direct_link_sidecar') {
@@ -560,7 +598,10 @@ jobs:
           }
           $adminRoot = Join-Path $msiScratch 'admin'
           New-Item -ItemType Directory -Path $adminRoot -Force | Out-Null
+          $env:LOCALAPPDATA = Join-Path $msiScratch 'local-app-data'
+          New-Item -ItemType Directory -Path $env:LOCALAPPDATA -Force | Out-Null
           $produced = @()
+          $sharedSelectorDigests = $null
 
           foreach ($profile in $profiles) {
             $variant = $contract['variants'][$target]['profiles'][$profile]
@@ -569,6 +610,15 @@ jobs:
             if (-not (Test-Path -LiteralPath $bundleDir -PathType Container)) {
               throw "The staged $target/$profile bundle is missing at $bundleDir; the MSI must be built from the bundle that was packaged and smoked."
             }
+            $bundleSelectorDigests = @(
+              (Get-FileHash -LiteralPath (Join-Path $bundleDir 'oscan-selector.exe') -Algorithm SHA256).Hash,
+              (Get-FileHash -LiteralPath (Join-Path $bundleDir 'oscan-default.exe') -Algorithm SHA256).Hash
+            )
+            if ($null -eq $sharedSelectorDigests) {
+              $sharedSelectorDigests = $bundleSelectorDigests
+            } elseif (($bundleSelectorDigests -join ',') -ne ($sharedSelectorDigests -join ',')) {
+              throw "The $profile package does not contain the exact shared selector binaries used by its sibling profiles."
+            }
             $msiName = ([string]$variant['msi_name_template']).Replace('{version}', $version)
             if ($produced -contains $msiName) {
               throw "Two Windows profiles claim the same MSI name '$msiName'."
@@ -593,10 +643,12 @@ jobs:
             }
 
             $installedRoot = Join-Path $adminRoot "PFiles64\Oscan\profiles\$profile\$version"
+            $installedSelectorDir = Join-Path $adminRoot 'PFiles64\Oscan\bin'
             & ./scripts/smoke-release.ps1 `
               -Target $target `
               -Profile $profile `
               -InstalledPackageDir $installedRoot `
+              -InstalledSelectorDir $installedSelectorDir `
               -Version $version `
               -ScratchDir (Join-Path $msiScratch "smoke-$profile")
             if ($LASTEXITCODE -ne 0) {
@@ -619,13 +671,51 @@ jobs:
           if ($missing.Count -gt 0 -or $unexpected.Count -gt 0) {
             throw "MSI set differs from the release contract. Missing: $($missing -join ', '); unexpected: $($unexpected -join ', ')."
           }
-          $selector = Join-Path $adminRoot 'PFiles64\Oscan\bin\oscan.cmd'
+          $selector = Join-Path $adminRoot 'PFiles64\Oscan\bin\oscan.exe'
           if (-not (Test-Path -LiteralPath $selector -PathType Leaf)) {
             throw "The coinstalled MSI image has no shared oscan selector."
           }
-          & $selector --version | Out-Null
+          $defaultManager = Join-Path $adminRoot 'PFiles64\Oscan\bin\oscan-default.exe'
+          if (-not (Test-Path -LiteralPath $defaultManager -PathType Leaf)) {
+            throw "The coinstalled MSI image has no oscan-default manager."
+          }
+          $selectorVersion = [System.Diagnostics.FileVersionInfo]::GetVersionInfo($selector).ProductVersion
+          if ($selectorVersion -ne $version) {
+            throw "The selector PE version is '$selectorVersion', expected '$version'."
+          }
+
+          foreach ($selection in @('c', 'full')) {
+            & $defaultManager set $selection | Out-Null
+            if ($LASTEXITCODE -ne 0) {
+              throw "Could not explicitly select the '$selection' profile."
+            }
+            $selectedVersion = & $selector --version | Out-String
+            if ($LASTEXITCODE -ne 0 -or $selectedVersion -notmatch "distribution: $selection") {
+              throw "The shared selector did not dispatch to the explicitly selected '$selection' profile."
+            }
+          }
+          $fullShim = Join-Path $adminRoot 'PFiles64\Oscan\bin\oscan-full.cmd'
+          $hiddenFullShim = "$fullShim.hidden"
+          Move-Item -LiteralPath $fullShim -Destination $hiddenFullShim
+          try {
+            & $selector --version 2>$null | Out-Null
+            if ($LASTEXITCODE -eq 0) {
+              throw "Removing the explicitly selected profile silently fell back to another MSI profile."
+            }
+          } finally {
+            Move-Item -LiteralPath $hiddenFullShim -Destination $fullShim
+          }
+          & $defaultManager auto | Out-Null
           if ($LASTEXITCODE -ne 0) {
-            throw "The coinstalled MSI selector failed."
+            throw "Could not enable automatic profile selection."
+          }
+          $automaticMode = & $defaultManager show | Out-String
+          if ($LASTEXITCODE -ne 0 -or $automaticMode -notmatch 'default profile: auto \(currently full\)') {
+            throw "The selection manager did not persist automatic mode with the expected current profile."
+          }
+          $automaticVersion = & $selector --version | Out-String
+          if ($LASTEXITCODE -ne 0 -or $automaticVersion -notmatch 'distribution: full') {
+            throw "Automatic mode did not resolve the expected full > llvm > cranelift > c priority."
           }
 
       - name: Upload packaged artifacts

diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -2,6 +2,7 @@
 name = "oscan"
 version = "0.1.0"
 edition = "2021"
+default-run = "oscan"
 
 # Backend selection at compile time. The default developer build enables
 # every backend and keeps the existing capability-based default behavior;
@@ -58,6 +59,7 @@ tempfile = "3"
 windows-sys = { version = "0.61", features = [
     "Win32_Foundation",
     "Win32_Security",
+    "Win32_Storage_FileSystem",
     "Win32_System_Threading",
 ] }
 
@@ -66,3 +68,4 @@ windows-sys = { version = "0.61", features = [
 # time (docs/design/native-link-embedding.md §5.2) using the same crate
 # `src/backend/native_assets.rs` uses at runtime.
 sha2 = "0.10"
+winresource = "0.1"
diff --git a/README.md b/README.md
@@ -62,29 +62,41 @@ Install full, or select a slim package explicitly:
 
 ```powershell
 iwr -useb https://raw.githubusercontent.com/lucabol/Oscan/master/scripts/install-latest.ps1 -OutFile install-latest.ps1
-.\install-latest.ps1 -Profile full -SetDefault
+.\install-latest.ps1 -Profile full
+oscan-default set full
 .\install-latest.ps1 -Backend llvm
 .\install-latest.ps1 -Backend cranelift
 .\install-latest.ps1 -Backend c
 ```
 
 Archive profiles coexist as `oscan-full`, `oscan-llvm`, `oscan-cranelift`, and
-`oscan-c`. The first archive install safely creates `oscan`; later installs
-preserve that selection unless `-SetDefault` is passed. Open a new terminal,
-then check:
+`oscan-c`. Plain `oscan` uses a per-user sticky selection shared by archive and
+MSI installs. Installing or upgrading a profile never changes an existing
+selection. If none exists, the first `oscan` invocation chooses the
+highest-priority installed profile and persists that exact choice.
 
 ```powershell
+oscan-default set full       # explicit and sticky
+oscan-default show
 oscan --version
+oscan-default auto           # optional full > llvm > cranelift > c fallback
 ```
 
+Removing the explicitly selected profile does not silently switch compilers:
+`oscan` fails with instructions until that profile is reinstalled or
+`oscan-default set <profile>`/`oscan-default auto` is run. MSI selection is
+always performed after installation as the target user; `-SetDefault` remains
+archive-only because MSI installation is elevated.
+
 ### Linux
 
 Download an archive and `SHA256SUMS`, verify it, extract it, and run the
 included installer. This example installs full and selects it as the default:
 
 ```bash
 tar xf oscan-vX.Y.Z-linux-x86_64-full.tar.xz
-./oscan-vX.Y.Z-linux-x86_64-full/install.sh --set-default
+./oscan-vX.Y.Z-linux-x86_64-full/install.sh
+oscan-default set full
 oscan --version
 oscan app.osc --backend cranelift
 ```
@@ -106,8 +118,8 @@ tar xf oscan-vX.Y.Z-macos-x86_64-c.tar.gz
 ```
 
 Run the included `install.sh` to create `oscan-c` without disturbing another
-profile, then run `oscan-c --version`. Pass `--set-default` only when the plain
-`oscan` command should select this profile.
+profile, then run `oscan-c --version`. Select it with `oscan-default set c`;
+`--set-default` remains a compatible installer shortcut.
 
 ### Build from source