diff --git a/.envrc b/.envrc
index af2fd92..72baf23 100644
--- a/.envrc
+++ b/.envrc
@@ -8,5 +8,9 @@
 # Ensures that flake.nix gets evaluated.
 use flake
 
+# Flutter via FVM — .fvmrc pins the version; fvm use creates .fvm/flutter_sdk.
+# This must come after `use flake` so FVM Flutter takes precedence.
+PATH_add .fvm/flutter_sdk/bin
+
 # Load variables from .env
 dotenv_if_exists
diff --git a/.fvmrc b/.fvmrc
new file mode 100644
index 0000000..19e8577
--- /dev/null
+++ b/.fvmrc
@@ -0,0 +1,3 @@
+{
+  "flutter": "3.41.6"
+}
\ No newline at end of file
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bcaf171..38c16a5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -37,8 +37,7 @@ jobs:
   integration:
     name: Integration tests (Stalwart)
     runs-on: ubuntu-latest
-    # Run integration tests only on push to main, not on every PR,
-    # since they require downloading the Stalwart binary via Nix.
+    # Run integration tests only on push to main, not on every PR.
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
 
     steps:
@@ -54,7 +53,7 @@ jobs:
           channel: stable
           cache: true
 
-      - name: Enter Nix shell and run integration tests
+      - name: Run integration tests
         run: |
           nix develop --command bash -c "
             flutter pub get &&
diff --git a/.gitignore b/.gitignore
index 0e15fd7..89e9e5c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -51,3 +51,6 @@ linux/flutter/generated_plugins.cmake
 
 # direnv cache
 .direnv/
+
+# FVM — .fvmrc is committed; .fvm/ contains the downloaded SDK (not committed)
+.fvm/
diff --git a/LATER.md b/LATER.md
index ccba6de..c52ada2 100644
--- a/LATER.md
+++ b/LATER.md
@@ -1,6 +1,14 @@
 # Later
 
-is there a e2e test tool in Flutter like Playwright? Application should launch, create screenshots...
+Flutter best practices?
+
+---
+
+Flutter/Dart Linters?
+
+---
+
+integration_test (similar to Playwright)
 
 ---
 
diff --git a/README.md b/README.md
index 38342cb..ffa6f32 100644
--- a/README.md
+++ b/README.md
@@ -51,14 +51,17 @@ Run the app, tap **+**, and enter your IMAP/SMTP server details. The app syncs y
 
 ### Prerequisites
 
-[Nix](https://nixos.org/download) with flakes enabled, and [direnv](https://direnv.net/).
+[Nix](https://nixos.org/download) with flakes enabled and [direnv](https://direnv.net/).
 
 ```bash
-# One-time: allow direnv in this directory
+# One-time: allow direnv to load the Nix dev shell
 direnv allow
+
+# One-time: install the pinned Flutter version (fvm is provided by Nix)
+fvm install
 ```
 
-`direnv` loads the Nix flake automatically — no manual `nix develop` needed after that. The flake pins **Flutter 3.41.6**, Android SDK, Stalwart mail server (for integration tests), and all Linux desktop build tools (GTK3, clang, cmake).
+`direnv` loads the Nix flake automatically — it provides go-task, fvm, Android SDK, Stalwart, and Linux build tools. Flutter itself is managed by FVM (pinned in `.fvmrc`) rather than Nix, which avoids glibc compatibility issues on non-NixOS hosts. `task check` also runs `fvm install` automatically if Flutter is missing.
 
 ### First-time setup
 
diff --git a/Taskfile.yml b/Taskfile.yml
index 15131a9..38f5155 100644
--- a/Taskfile.yml
+++ b/Taskfile.yml
@@ -13,10 +13,17 @@ tasks:
       - sh: test "${DIRENV_DIR#-}" = "{{.TASKFILE_DIR}}"
         msg: "Not in nix dev shell. Run: nix develop"
 
-  _pub-get:
+  _flutter-check:
     internal: true
     run: once
     deps: [_nix-check]
+    cmds:
+      - cmd: command -v flutter >/dev/null 2>&1 || fvm install
+
+  _pub-get:
+    internal: true
+    run: once
+    deps: [_flutter-check]
     cmds:
       - flutter pub get --suppress-analytics 2>/dev/null
 
@@ -63,7 +70,7 @@ tasks:
 
   integration:
     desc: Integration tests against a local Stalwart mail server
-    deps: [_nix-check]
+    deps: [_flutter-check]
     cmds:
       - stalwart-dev/test.sh
 
@@ -77,18 +84,26 @@ tasks:
           echo "Error: libsecret-1-dev is installed but pkg-config cannot find it."
           echo "Your nix shell was opened before the package was installed."
           echo "Fix: exit the nix shell and re-enter with: nix develop"
-          exit 1
         else
           echo "Error: libsecret-1-dev is not installed."
           echo "Fix: sudo apt install libsecret-1-dev"
-          exit 1
         fi
+        exit 1
 
   build-linux:
     desc: Build the Linux desktop app (debug)
     deps: [_nix-check, _pub-get, _check-libsecret]
     cmds:
       - flutter build linux --debug --no-pub
+      - |
+        binary=build/linux/x64/debug/bundle/sharedinbox
+        missing=$(LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu:/lib/x86_64-linux-gnu ldd "$binary" 2>/dev/null | grep 'not found' || true)
+        if [ -n "$missing" ]; then
+          echo "Error: built binary has unresolvable runtime dependencies:"
+          echo "$missing"
+          echo "Fix: sudo apt install libsecret-1-0"
+          exit 1
+        fi
 
   build-android:
     desc: Build a release APK (output in build/app/outputs/flutter-apk/)
diff --git a/flake.nix b/flake.nix
index a361e86..f65356f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -31,9 +31,6 @@
       in {
         devShells.default = pkgs.mkShell {
           buildInputs = with pkgs; [
-            # Flutter / Dart toolchain
-            flutter
-
             # Android
             androidSdk
 
@@ -60,6 +57,9 @@
             # Task runner
             go-task
 
+            # Flutter version manager (fvm install downloads the pinned Flutter SDK)
+            fvm
+
             # Utilities
             git
             curl