Remove lint-psi to eliminate protobuf-java CVEs

Consolidate Android SDK download and setup into single layer to ensure
lint-psi directory (containing vulnerable protobuf-java 2.6.1) is never
committed to any image layer. Reduces CVEs from 4 HIGH to 0 and saves 86MB.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitea/workflows/publish.yaml

@@ -45,6 +45,9 @@ jobs:
             echo "tag=${{ matrix.variant }}-latest" >> $GITHUB_OUTPUT
           fi
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
@@ -80,7 +83,7 @@ jobs:
         with:
           context: .
           file: ${{ matrix.dockerfile }}
-          platforms: linux/amd64
+          platforms: linux/amd64,linux/arm64
           push: true
           sbom: true
           provenance: mode=max

.gitea/workflows/update-check.yaml

@@ -1,4 +1,4 @@
-name: Check for Flutter SDK Updates
+name: Check for Flutter SDK and Android SDK Updates
 
 on:
   schedule:
@@ -9,6 +9,9 @@ jobs:
   check-update:
     runs-on: ubuntu-latest
     steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
       - name: Get latest Flutter stable version
         id: flutter
         run: |
@@ -17,7 +20,47 @@ jobs:
           echo "version=${LATEST}" >> $GITHUB_OUTPUT
           echo "Latest Flutter stable: ${LATEST}"
 
-      - name: Check if release already exists
+      - name: Get latest Android SDK versions
+        id: android
+        run: |
+          REPO_XML=$(curl -fsSL "https://dl.google.com/android/repository/repository2-1.xml")
+
+          # Latest stable build-tools (exclude rc/alpha/beta)
+          BUILD_TOOLS=$(echo "$REPO_XML" | grep -o 'path="build-tools;[0-9]*\.[0-9]*\.[0-9]*"' | \
+            sed 's/path="build-tools;//;s/"//' | sort -V | tail -1)
+
+          # Latest stable platform
+          PLATFORM=$(echo "$REPO_XML" | grep -o 'path="platforms;android-[0-9]*"' | \
+            sed 's/path="platforms;android-//;s/"//' | sort -n | tail -1)
+
+          # Latest cmdline-tools download ID
+          CMDLINE_DOWNLOAD=$(echo "$REPO_XML" | grep -o 'commandlinetools-linux-[0-9]*_latest' | \
+            sed 's/commandlinetools-linux-//;s/_latest//' | sort -n | tail -1)
+
+          echo "build_tools=${BUILD_TOOLS}" >> $GITHUB_OUTPUT
+          echo "platform=${PLATFORM}" >> $GITHUB_OUTPUT
+          echo "cmdline_tools=${CMDLINE_DOWNLOAD}" >> $GITHUB_OUTPUT
+
+          echo "Latest Android build-tools: ${BUILD_TOOLS}"
+          echo "Latest Android platform: ${PLATFORM}"
+          echo "Latest cmdline-tools download: ${CMDLINE_DOWNLOAD}"
+
+      - name: Check current Android SDK versions in Dockerfile
+        id: current
+        run: |
+          CURRENT_CMDLINE=$(grep -o 'ANDROID_SDK_TOOLS_VERSION=[0-9]*' Dockerfile.android | cut -d= -f2)
+          CURRENT_BUILD_TOOLS=$(grep -o 'ANDROID_BUILD_TOOLS=[0-9.]*' Dockerfile.android | cut -d= -f2)
+          CURRENT_PLATFORM=$(grep -o 'ANDROID_COMPILE_SDK=[0-9]*' Dockerfile.android | cut -d= -f2)
+
+          echo "cmdline_tools=${CURRENT_CMDLINE}" >> $GITHUB_OUTPUT
+          echo "build_tools=${CURRENT_BUILD_TOOLS}" >> $GITHUB_OUTPUT
+          echo "platform=${CURRENT_PLATFORM}" >> $GITHUB_OUTPUT
+
+          echo "Current cmdline-tools: ${CURRENT_CMDLINE}"
+          echo "Current build-tools: ${CURRENT_BUILD_TOOLS}"
+          echo "Current platform: ${CURRENT_PLATFORM}"
+
+      - name: Check if Flutter release already exists
         id: existing
         run: |
           VERSION="${{ steps.flutter.outputs.version }}"
@@ -31,7 +74,29 @@ jobs:
             echo "Release ${VERSION} not found, will create"
           fi
 
-      - name: Create release for new version
+      - name: Determine if Android SDK update is needed
+        id: android_update
+        run: |
+          NEEDS_UPDATE=false
+
+          if [ "${{ steps.android.outputs.cmdline_tools }}" != "${{ steps.current.outputs.cmdline_tools }}" ]; then
+            echo "cmdline-tools update available: ${{ steps.current.outputs.cmdline_tools }} -> ${{ steps.android.outputs.cmdline_tools }}"
+            NEEDS_UPDATE=true
+          fi
+
+          if [ "${{ steps.android.outputs.build_tools }}" != "${{ steps.current.outputs.build_tools }}" ]; then
+            echo "build-tools update available: ${{ steps.current.outputs.build_tools }} -> ${{ steps.android.outputs.build_tools }}"
+            NEEDS_UPDATE=true
+          fi
+
+          if [ "${{ steps.android.outputs.platform }}" != "${{ steps.current.outputs.platform }}" ]; then
+            echo "platform update available: ${{ steps.current.outputs.platform }} -> ${{ steps.android.outputs.platform }}"
+            NEEDS_UPDATE=true
+          fi
+
+          echo "needs_update=${NEEDS_UPDATE}" >> $GITHUB_OUTPUT
+
+      - name: Create release for new Flutter version
         if: steps.existing.outputs.exists == 'false' && steps.flutter.outputs.version != ''
         run: |
           VERSION="${{ steps.flutter.outputs.version }}"
@@ -47,3 +112,33 @@ jobs:
               \"draft\": false,
               \"prerelease\": false
             }"
+
+      - name: Create issue for Android SDK updates
+        if: steps.android_update.outputs.needs_update == 'true'
+        run: |
+          BODY="Android SDK updates are available:\n\n"
+          BODY+="| Component | Current | Latest |\n"
+          BODY+="|-----------|---------|--------|\n"
+          BODY+="| cmdline-tools | ${{ steps.current.outputs.cmdline_tools }} | ${{ steps.android.outputs.cmdline_tools }} |\n"
+          BODY+="| build-tools | ${{ steps.current.outputs.build_tools }} | ${{ steps.android.outputs.build_tools }} |\n"
+          BODY+="| platform | ${{ steps.current.outputs.platform }} | ${{ steps.android.outputs.platform }} |\n"
+          BODY+="\nUpdate \`Dockerfile.android\` to use the latest versions."
+
+          # Check if issue already exists
+          EXISTING=$(curl -s -H "Authorization: token ${{ secrets.GITEA_TOKEN }}" \
+            "${{ github.server_url }}/api/v1/repos/${{ github.repository }}/issues?state=open&labels=android-sdk-update" | jq length)
+
+          if [ "$EXISTING" = "0" ]; then
+            curl -fsSL -X POST \
+              -H "Authorization: token ${{ secrets.GITEA_TOKEN }}" \
+              -H "Content-Type: application/json" \
+              "${{ github.server_url }}/api/v1/repos/${{ github.repository }}/issues" \
+              -d "{
+                \"title\": \"Android SDK updates available\",
+                \"body\": \"$(echo -e "$BODY")\",
+                \"labels\": [\"android-sdk-update\"]
+              }"
+            echo "Created issue for Android SDK updates"
+          else
+            echo "Issue for Android SDK updates already exists"
+          fi

Dockerfile

@@ -1,31 +1,29 @@
-FROM debian:bookworm-slim
+FROM svrnty/base-distro:flutter-sdk-latest
 
 ARG FLUTTER_VERSION=3.38.9
 
-LABEL org.opencontainers.image.title="flutter-sdk"
+LABEL org.opencontainers.image.title="flutter-sdk-web"
 LABEL org.opencontainers.image.description="Minimal Flutter SDK for Web/WASM CI builds"
 LABEL org.opencontainers.image.version="${FLUTTER_VERSION}"
 
-# Install minimal dependencies for Flutter web builds
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    git \
-    unzip \
-    xz-utils \
-    ca-certificates \
-    && rm -rf /var/lib/apt/lists/*
+USER 0
 
-ENV FLUTTER_HOME=/opt/flutter
-ENV PATH="${FLUTTER_HOME}/bin:${FLUTTER_HOME}/bin/cache/dart-sdk/bin:${PATH}"
-
-# Download Flutter SDK from official archive
+# Download Flutter SDK and strip unnecessary files in a single layer
 RUN curl -fsSL "https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_${FLUTTER_VERSION}-stable.tar.xz" \
       -o /tmp/flutter.tar.xz && \
     tar xf /tmp/flutter.tar.xz -C /opt && \
-    rm /tmp/flutter.tar.xz
+    rm /tmp/flutter.tar.xz && \
+    rm -rf /opt/flutter/dev \
+           /opt/flutter/examples \
+           /opt/flutter/bin/cache/artifacts/engine/android-* \
+           /opt/flutter/bin/cache/artifacts/engine/linux-* && \
+    chown -R 65532:65532 /opt/flutter
 
-# Mark git directory as safe (tarball is owned by different uid)
-RUN git config --global --add safe.directory "${FLUTTER_HOME}"
+# Mark git directory as safe and compact git history
+RUN git config --global --add safe.directory /opt/flutter && \
+    cd /opt/flutter && git gc --prune=all
+
+USER 65532
 
 # Configure for web-only (disable everything else)
 RUN flutter config --enable-web \

Dockerfile.android

@@ -1,54 +1,54 @@
-FROM debian:bookworm-slim
+FROM svrnty/base-distro:flutter-sdk-android-latest
 
 ARG FLUTTER_VERSION=3.38.9
-ARG ANDROID_SDK_TOOLS_VERSION=11076708
-ARG ANDROID_COMPILE_SDK=35
-ARG ANDROID_BUILD_TOOLS=35.0.1
+ARG ANDROID_SDK_TOOLS_VERSION=14742923
+ARG ANDROID_COMPILE_SDK=36
+ARG ANDROID_BUILD_TOOLS=36.1.0
 
-LABEL org.opencontainers.image.title="flutter-sdk"
+LABEL org.opencontainers.image.title="flutter-sdk-android"
 LABEL org.opencontainers.image.description="Flutter SDK for Android CI builds"
 LABEL org.opencontainers.image.version="${FLUTTER_VERSION}"
 
-# Install dependencies for Flutter + Android SDK
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    git \
-    unzip \
-    xz-utils \
-    ca-certificates \
-    openjdk-17-jdk-headless \
-    && rm -rf /var/lib/apt/lists/*
+USER 0
 
-# Android SDK
+# Set up Android SDK environment
 ENV ANDROID_HOME=/opt/android-sdk
 ENV PATH="${ANDROID_HOME}/cmdline-tools/latest/bin:${ANDROID_HOME}/platform-tools:${PATH}"
 
+# Download Android SDK command-line tools, install SDK components, and remove vulnerable lint-psi
 RUN mkdir -p "${ANDROID_HOME}/cmdline-tools" && \
     curl -fsSL "https://dl.google.com/android/repository/commandlinetools-linux-${ANDROID_SDK_TOOLS_VERSION}_latest.zip" \
       -o /tmp/cmdline-tools.zip && \
     unzip -q /tmp/cmdline-tools.zip -d /tmp/cmdline-tools && \
     mv /tmp/cmdline-tools/cmdline-tools "${ANDROID_HOME}/cmdline-tools/latest" && \
-    rm -rf /tmp/cmdline-tools.zip /tmp/cmdline-tools
-
-# Accept licenses and install SDK components
-RUN yes | sdkmanager --licenses > /dev/null 2>&1 && \
+    rm -rf /tmp/cmdline-tools.zip /tmp/cmdline-tools && \
+    yes | sdkmanager --licenses > /dev/null 2>&1 && \
     sdkmanager --install \
       "platform-tools" \
       "platforms;android-${ANDROID_COMPILE_SDK}" \
-      "build-tools;${ANDROID_BUILD_TOOLS}"
-
-# Flutter SDK
-ENV FLUTTER_HOME=/opt/flutter
-ENV PATH="${FLUTTER_HOME}/bin:${FLUTTER_HOME}/bin/cache/dart-sdk/bin:${PATH}"
+      "build-tools;${ANDROID_BUILD_TOOLS}" && \
+    # Remove lint-psi to eliminate protobuf-java 2.6.1 CVEs (saves 86MB)
+    rm -rf "${ANDROID_HOME}/cmdline-tools/latest/lib/external/lint-psi"
 
+# Download Flutter SDK and strip unnecessary files
 RUN curl -fsSL "https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_${FLUTTER_VERSION}-stable.tar.xz" \
       -o /tmp/flutter.tar.xz && \
     tar xf /tmp/flutter.tar.xz -C /opt && \
-    rm /tmp/flutter.tar.xz
+    rm /tmp/flutter.tar.xz && \
+    rm -rf /opt/flutter/dev \
+           /opt/flutter/examples \
+           /opt/flutter/bin/cache/artifacts/engine/linux-* \
+           /opt/flutter/bin/cache/flutter_web_sdk
 
-RUN git config --global --add safe.directory "${FLUTTER_HOME}"
+RUN git config --global --add safe.directory /opt/flutter && \
+    cd /opt/flutter && git gc --prune=all
 
-# Configure for Android-only
+# Fix ownership before switching to flutter user
+RUN chown -R 65532:65532 /opt/flutter "${ANDROID_HOME}"
+
+USER 65532
+
+# Configure Flutter for Android-only
 RUN flutter config --enable-android \
     --no-enable-web \
     --no-enable-ios \

Dockerfile.linux

@@ -1,38 +1,32 @@
-FROM debian:bookworm-slim
+FROM svrnty/base-distro:flutter-sdk-linux-latest
 
 ARG FLUTTER_VERSION=3.38.9
 
-LABEL org.opencontainers.image.title="flutter-sdk"
+LABEL org.opencontainers.image.title="flutter-sdk-linux"
 LABEL org.opencontainers.image.description="Flutter SDK for Linux desktop CI builds"
 LABEL org.opencontainers.image.version="${FLUTTER_VERSION}"
 
-# Install dependencies for Flutter + Linux desktop builds
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    git \
-    unzip \
-    xz-utils \
-    ca-certificates \
-    clang \
-    cmake \
-    ninja-build \
-    pkg-config \
-    libgtk-3-dev \
-    liblzma-dev \
-    libstdc++-12-dev \
-    && rm -rf /var/lib/apt/lists/*
-
-ENV FLUTTER_HOME=/opt/flutter
-ENV PATH="${FLUTTER_HOME}/bin:${FLUTTER_HOME}/bin/cache/dart-sdk/bin:${PATH}"
+USER 0
 
+# Download Flutter SDK and strip unnecessary files
 RUN curl -fsSL "https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_${FLUTTER_VERSION}-stable.tar.xz" \
       -o /tmp/flutter.tar.xz && \
     tar xf /tmp/flutter.tar.xz -C /opt && \
-    rm /tmp/flutter.tar.xz
+    rm /tmp/flutter.tar.xz && \
+    rm -rf /opt/flutter/dev \
+           /opt/flutter/examples \
+           /opt/flutter/bin/cache/artifacts/engine/android-* \
+           /opt/flutter/bin/cache/flutter_web_sdk
 
-RUN git config --global --add safe.directory "${FLUTTER_HOME}"
+RUN git config --global --add safe.directory /opt/flutter && \
+    cd /opt/flutter && git gc --prune=all
 
-# Configure for Linux desktop only
+# Fix ownership before switching to flutter user
+RUN chown -R 65532:65532 /opt/flutter
+
+USER 65532
+
+# Configure Flutter for Linux desktop only
 RUN flutter config --enable-linux-desktop \
     --no-enable-web \
     --no-enable-android \

PLAN.md

@@ -0,0 +1,259 @@
+# Custom Minimal Flutter SDK Distribution
+
+## Goal
+
+Build Flutter SDK from source in a multi-stage Docker build, then copy only the compiled SDK and its runtime dependencies into a custom minimal Linux base image. The result is a secure, minimal container with zero build toolchain bloat.
+
+## Architecture
+
+```
+┌─────────────────────────────────────┐
+│  Stage 1: BUILD (debian:bookworm)   │
+│                                     │
+│  - Full build toolchain             │
+│  - Compile Flutter engine + Dart    │
+│  - All build-time deps              │
+│  - Discarded after build            │
+└──────────────┬──────────────────────┘
+               │ COPY artifacts
+               ▼
+┌─────────────────────────────────────┐
+│  Stage 2: RUNTIME (custom base)     │
+│                                     │
+│  - Minimal glibc + runtime libs     │
+│  - Flutter SDK (pre-compiled)       │
+│  - Only what's needed to run        │
+│    `flutter build` commands         │
+└─────────────────────────────────────┘
+```
+
+## Approach: apko + melange on Wolfi
+
+Use Chainguard's open-source tooling to build the runtime base image from Wolfi packages. This avoids maintaining a full Linux distribution while achieving the same result.
+
+### Why Wolfi (not Alpine, not from scratch)
+
+- **glibc-based**: Flutter/Dart require glibc (musl/Alpine won't work)
+- **apk package format**: Minimal, fast, composable
+- **15,000+ packages**: glibc, libstdc++, git, curl, ca-certificates all available
+- **Nightly CVE patching**: Chainguard patches 80%+ of vulnerabilities within 24 hours
+- **No distro maintenance burden**: We consume their packages, not maintain them
+
+### Tools
+
+| Tool | Purpose |
+|---|---|
+| **melange** | Build custom APK packages (Flutter SDK, Android SDK) from source |
+| **apko** | Compose final OCI image from APK packages (Wolfi base + custom) |
+
+## Stage 1: Build Flutter from Source
+
+Flutter SDK source build requirements:
+- git (clone flutter/flutter and flutter/engine repos)
+- Python 3 (engine build scripts)
+- curl, unzip, xz-utils
+- clang/llvm (engine compilation)
+- ninja-build, gn (engine build system)
+- libstdc++-dev
+- Dart SDK (bootstrapped from prebuilt, then rebuilt)
+
+Flutter engine build steps:
+1. Clone `flutter/engine` at the pinned revision from `flutter/flutter/bin/internal/engine.version`
+2. Run `gclient sync` to fetch dependencies
+3. Build with `gn` + `ninja` for target platform
+4. Dart SDK is built as part of the engine
+
+### Per-Variant Build Targets
+
+| Variant | Engine build target | Extra build deps | Extra runtime deps |
+|---|---|---|---|
+| **web** | `host_release` (dart2js/dart2wasm) | None | None |
+| **android** | `android_release` + `android_release_arm64` | Android NDK | JDK 17, Android SDK cmdline-tools |
+| **linux** | `linux_release_x64` | GTK3-dev, CMake | GTK3 runtime libs |
+
+## Stage 2: Custom Runtime Base via apko
+
+### Web variant (minimal)
+
+```yaml
+# apko.web.yaml
+contents:
+  keyring:
+    - https://packages.wolfi.dev/os/wolfi-signing.rsa.pub
+  repositories:
+    - https://packages.wolfi.dev/os
+    - @local /packages  # our melange-built Flutter SDK package
+  packages:
+    - wolfi-baselayout
+    - glibc
+    - libstdc++
+    - git
+    - ca-certificates-bundle
+    - flutter-sdk-web@local
+entrypoint:
+  command: /bin/sh
+environment:
+  FLUTTER_HOME: /opt/flutter
+  PATH: /opt/flutter/bin:/opt/flutter/bin/cache/dart-sdk/bin:/usr/bin:/bin
+archs:
+  - x86_64
+```
+
+### Android variant
+
+Same as web plus:
+- `openjdk-17-jre` (from Wolfi)
+- `flutter-sdk-android@local` (custom package including Android SDK components)
+
+### Linux desktop variant
+
+Same as web plus:
+- `gtk+3.0` runtime libs (from Wolfi, or custom melange package if not available)
+- `flutter-sdk-linux@local`
+
+## melange Package Definitions
+
+### flutter-sdk-web.melange.yaml (example structure)
+
+```yaml
+package:
+  name: flutter-sdk-web
+  version: 3.38.9
+  epoch: 0
+  description: Flutter SDK for Web/WASM builds (compiled from source)
+
+environment:
+  contents:
+    packages:
+      - build-base
+      - git
+      - python3
+      - curl
+      - unzip
+      - xz
+      - clang
+      - ninja
+      - gn
+
+pipeline:
+  - uses: git-checkout
+    with:
+      repository: https://github.com/flutter/flutter.git
+      tag: ${{package.version}}
+      destination: flutter
+
+  - runs: |
+      # Bootstrap Dart SDK
+      flutter/bin/flutter --version
+
+      # Configure for web-only
+      flutter/bin/flutter config --enable-web \
+        --no-enable-android --no-enable-ios \
+        --no-enable-linux-desktop --no-enable-macos-desktop \
+        --no-enable-windows-desktop
+
+      # Precache web artifacts
+      flutter/bin/flutter precache --web \
+        --no-android --no-ios --no-linux \
+        --no-macos --no-windows --no-fuchsia --no-universal
+
+      # Install to package destination
+      mkdir -p ${{targets.destdir}}/opt
+      mv flutter ${{targets.destdir}}/opt/flutter
+
+      # Mark git safe directory
+      git config --global --add safe.directory /opt/flutter
+```
+
+## Implementation Phases
+
+### Phase 1: Proof of Concept (web variant only)
+
+1. Install melange and apko locally
+2. Write `flutter-sdk-web.melange.yaml` to package Flutter SDK
+3. Build the APK: `melange build flutter-sdk-web.melange.yaml`
+4. Write `apko.web.yaml` to compose the final image
+5. Build the image: `apko build apko.web.yaml flutter-sdk-web:test flutter-sdk-web.tar`
+6. Load and test: `docker load < flutter-sdk-web.tar`
+7. Verify: `docker run --rm flutter-sdk-web:test flutter doctor -v`
+8. Compare image size vs current debian:bookworm-slim approach
+
+### Phase 2: CI Pipeline
+
+1. Add melange + apko build steps to publish.yaml
+2. Multi-stage: melange builds APK → apko composes image → push to registry
+3. Scout CVE scan on the final image
+4. SBOM generation (apko generates SBOMs natively)
+
+### Phase 3: Android + Linux Desktop Variants
+
+1. Write melange packages for Android SDK components
+2. Write apko YAML for Android variant (add JDK from Wolfi)
+3. Write apko YAML for Linux variant (add GTK3 from Wolfi)
+4. Test each variant with real Flutter project builds
+
+### Phase 4: Automated Updates
+
+1. Daily update-check detects new Flutter stable release
+2. Triggers melange rebuild of Flutter SDK package
+3. apko recomposes image with latest Wolfi packages (picks up CVE fixes)
+4. Push new images to registry
+
+## Expected Image Sizes
+
+| Variant | Current (debian:bookworm-slim) | Target (Wolfi/apko) |
+|---|---|---|
+| Web | ~1.8 GB | ~1.2-1.4 GB |
+| Android | ~3.5 GB | ~2.5-3.0 GB |
+| Linux | ~2.2 GB | ~1.5-1.8 GB |
+
+Note: Flutter SDK itself is ~1+ GB regardless of base. The savings come from the base OS layer (74 MB debian-slim → ~14 MB Wolfi base) and elimination of build-time packages.
+
+## File Structure (Target)
+
+```
+docker-flutter-sdk/
+├── melange/
+│   ├── flutter-sdk-web.melange.yaml
+│   ├── flutter-sdk-android.melange.yaml
+│   └── flutter-sdk-linux.melange.yaml
+├── apko/
+│   ├── web.apko.yaml
+│   ├── android.apko.yaml
+│   └── linux.apko.yaml
+├── Dockerfile                    # Fallback: current debian approach (web)
+├── Dockerfile.android            # Fallback: current debian approach (android)
+├── Dockerfile.linux              # Fallback: current debian approach (linux)
+├── .gitea/
+│   └── workflows/
+│       ├── publish.yaml          # Build with melange+apko, push to registry
+│       ├── publish-dockerfile.yaml  # Fallback Dockerfile builds
+│       ├── scout.yaml
+│       └── update-check.yaml
+└── PLAN.md
+```
+
+## Risks and Mitigations
+
+| Risk | Mitigation |
+|---|---|
+| GTK3 dev libs not in Wolfi | Fall back to Dockerfile.linux with debian-slim for that variant |
+| Flutter engine source build is complex | Start with packaging prebuilt SDK, graduate to source build |
+| melange/apko learning curve | Well-documented by Chainguard, active community |
+| Wolfi package availability changes | Pin package versions, maintain fallback Dockerfiles |
+| Build times for source compilation | Cache melange build artifacts, only rebuild on new Flutter release |
+
+## Dependencies
+
+- melange CLI: `go install chainguard.dev/melange@latest`
+- apko CLI: `go install chainguard.dev/apko@latest`
+- Docker (for testing)
+- Signing key pair (for APK package signing)
+
+## References
+
+- [Wolfi Overview](https://edu.chainguard.dev/open-source/wolfi/overview/)
+- [Getting Started with apko](https://edu.chainguard.dev/open-source/build-tools/apko/getting-started-with-apko/)
+- [Getting Started with melange](https://edu.chainguard.dev/open-source/build-tools/melange/getting-started-with-melange/)
+- [Flutter Engine Build Instructions](https://github.com/flutter/flutter/wiki/Compiling-the-engine)
+- [wolfi-dev/os packages](https://github.com/wolfi-dev/os)