diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..ba6e1d4
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,3 @@
+# MIME fixtures and golden renders contain intentional CRLF and mixed line endings.
+# Preserve their bytes on Windows too; checkout conversion breaks exact comparisons.
+src-tauri/fixtures/** -text
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index eb2ade0..9b12a94 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -167,8 +167,7 @@ jobs:
             libxdo-dev \
             libssl-dev \
             build-essential \
-            flatpak \
-            flatpak-builder
+            flatpak
 
       - uses: actions/setup-node@v6
         with:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 3f99d19..3079aa3 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -240,7 +240,7 @@ jobs:
 
       - run: |
           sudo apt-get update
-          sudo apt-get install -y flatpak flatpak-builder
+          sudo apt-get install -y flatpak
 
       - name: Build the flatpak from the published deb
         env:
diff --git a/docs/release.md b/docs/release.md
index fc5277d..06be920 100644
--- a/docs/release.md
+++ b/docs/release.md
@@ -105,6 +105,11 @@ against. The sandbox gets the network, the notification service and the download
 nothing else. CI builds the same manifest on every push to main, against a deb built there, which
 is the only way a break in it gets found before a release.
 
+On Linux, `just flatpak` builds the deb and repackages it locally. Install `flatpak` first; the
+build script installs the GNOME runtime and `org.flatpak.Builder` from Flathub for your user.
+Both CI and local builds use that builder because Ubuntu 22.04's `flatpak-builder` calls the old
+`appstream-compose` tool, which the GNOME 48 SDK no longer includes.
+
 The **nix** job runs after the publish, so the flake can only ever point at a release that survived
 the manifest check. It hashes the published deb into `nix/release.json`, builds the package to
 prove the pin works, and commits the pin to main. `NIXPKGS_ALLOW_UNFREE` and `--impure` are in that
diff --git a/flatpak/build.sh b/flatpak/build.sh
index d2ffd32..a326710 100755
--- a/flatpak/build.sh
+++ b/flatpak/build.sh
@@ -18,11 +18,14 @@ runtime_version=$(sed -n "s/^runtime-version: *'\(.*\)'/\1/p" "$id.yml")
 # --user so nothing here needs root, and --if-not-exists so a second run is free.
 flatpak remote-add --user --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
 flatpak install --user --noninteractive flathub \
+  org.flatpak.Builder \
   "org.gnome.Platform//$runtime_version" \
   "org.gnome.Sdk//$runtime_version"
 
 rm -rf build repo
-flatpak-builder --user --disable-rofiles-fuse --force-clean --repo=repo build "$id.yml"
+# Ubuntu 22.04's builder calls appstream-compose, which GNOME 48 no longer ships.
+# Use the Flathub builder for its current AppStream support on CI and local builds alike.
+flatpak run org.flatpak.Builder --user --disable-rofiles-fuse --force-clean --repo=repo build "$id.yml"
 flatpak build-bundle repo "$bundle" "$id"
 
 echo "Wrote $bundle"
diff --git a/flatpak/studio.margin.mail.metainfo.xml b/flatpak/studio.margin.mail.metainfo.xml
index de8d4bf..656f0b0 100644
--- a/flatpak/studio.margin.mail.metainfo.xml
+++ b/flatpak/studio.margin.mail.metainfo.xml
@@ -5,7 +5,7 @@
   <summary>A calm, keyboard-first mail client for Gmail</summary>
 
   <metadata_license>CC0-1.0</metadata_license>
-  <project_license>LicenseRef-proprietary=https://github.com/priyanshujain/margin-mail/blob/main/LICENSE</project_license>
+  <project_license>LicenseRef-FSL-1.1-MIT=https://github.com/priyanshujain/margin-mail/blob/main/LICENSE</project_license>
 
   <developer id="studio.margin">
     <name>Margin</name>
diff --git a/flatpak/studio.margin.mail.yml b/flatpak/studio.margin.mail.yml
index 311c06f..7e48109 100644
--- a/flatpak/studio.margin.mail.yml
+++ b/flatpak/studio.margin.mail.yml
@@ -39,9 +39,13 @@ modules:
       # after the product and the binary, so both are renamed on the way in.
       - install -Dm644 "deb/usr/share/applications/Margin Mail.desktop" /app/share/applications/studio.margin.mail.desktop
       - desktop-file-edit --set-icon=studio.margin.mail /app/share/applications/studio.margin.mail.desktop
+      # Only the plainly named sizes. Tauri also writes a `256x256@2` directory, and hicolor spells
+      # a scaled one `256x256@2x`, so flatpak would be exporting an icon at a size that is not a
+      # size.
       - |
-        for src in deb/usr/share/icons/hicolor/*/apps/margin-mail.png; do
-          size=$(basename "$(dirname "$(dirname "$src")")")
+        for size in 32x32 128x128; do
+          src="deb/usr/share/icons/hicolor/$size/apps/margin-mail.png"
+          [ -f "$src" ] || continue
           install -Dm644 "$src" "/app/share/icons/hicolor/$size/apps/studio.margin.mail.png"
         done
 
diff --git a/justfile b/justfile
index 9f64545..8c0f39f 100644
--- a/justfile
+++ b/justfile
@@ -58,6 +58,18 @@ build:
       *)      echo "just: no local build for $(uname -s); macOS and Linux are the desktop targets." >&2; exit 1 ;;
     esac
 
+# Wants flatpak, and pulls the Flathub builder and GNOME runtime if they are not installed.
+# The release workflow runs the same script over the deb it published.
+# Build the flatpak, which is the deb repackaged. Linux only.
+flatpak:
+    #!/usr/bin/env bash
+    set -euo pipefail
+    [ "$(uname -s)" = Linux ] || { echo "just: the flatpak builds on Linux only." >&2; exit 1; }
+    pnpm install
+    pnpm tauri build --bundles deb
+    cp {{bundle}}/deb/*.deb flatpak/margin-mail.deb
+    flatpak/build.sh
+
 # Build, install over whatever version is already installed, and start the new one.
 install: build
     #!/usr/bin/env bash