diff --git a/.gitea/scripts/build-plan.sh b/.gitea/scripts/build-plan.sh
new file mode 100755
index 0000000..9e87613
--- /dev/null
+++ b/.gitea/scripts/build-plan.sh
@@ -0,0 +1,127 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# build-plan.sh
+# Calculates whether to build from scratch, skip tests, or retag an existing image.
+#
+# Inputs (via env or arguments):
+#   REF: Git reference (e.g. refs/heads/dev, refs/heads/main, refs/tags/v0.10.0)
+#   COMMIT: Commit SHA or HEAD (defaults to HEAD)
+#   IMAGE: Docker image repository name (e.g. git.dsit.me/sandrodach/mindsift)
+#   PKG_VERSION: Package version from package.json (optional, auto-detected)
+#   CHECK_IMAGE_CMD: Command to check image existence in registry (default: "docker manifest inspect")
+
+REF="${REF:-${1:-}}"
+COMMIT="${COMMIT:-${2:-HEAD}}"
+IMAGE="${IMAGE:-${3:-}}"
+PKG_VERSION="${PKG_VERSION:-${4:-}}"
+CHECK_CMD="${CHECK_IMAGE_CMD:-docker manifest inspect}"
+
+if [ -z "${REF}" ]; then
+  REF="$(git symbolic-ref -q HEAD 2>/dev/null || git describe --tags --exact-match 2>/dev/null || echo "refs/heads/dev")"
+fi
+
+if [ -z "${PKG_VERSION}" ] && [ -f "frontend/package.json" ]; then
+  PKG_VERSION="$(sed -nE 's/^  "version": "([^"]+)".*/\1/p' frontend/package.json | head -n1)"
+fi
+
+SHORT_SHA="$(git rev-parse --short=8 "${COMMIT}^{commit}" 2>/dev/null || echo "unknown")"
+SHORT_TREE="$(git rev-parse --short=12 "${COMMIT}^{tree}" 2>/dev/null || echo "unknown")"
+
+image_exists() {
+  local target="$1"
+  ${CHECK_CMD} "${target}" >/dev/null 2>&1
+}
+
+ACTION="build"
+SKIP_TESTS="0"
+APP_VERSION=""
+TAGS=""
+SOURCE_IMAGE=""
+REASON=""
+
+case "${REF}" in
+  refs/heads/dev|dev)
+    ACTION="build"
+    SKIP_TESTS="0"
+    APP_VERSION=""
+    TAGS="dev tree-${SHORT_TREE}"
+    REASON="Dev branch push: running full frontend and backend tests, tagging :dev and :tree-${SHORT_TREE}"
+    ;;
+
+  refs/heads/main|main)
+    ACTION="build"
+    APP_VERSION="v${PKG_VERSION}"
+    TAGS="latest sha-${SHORT_SHA} tree-${SHORT_TREE}"
+
+    # Check if this exact tree was already successfully tested on dev
+    if [ -n "${IMAGE}" ] && image_exists "${IMAGE}:tree-${SHORT_TREE}"; then
+      SKIP_TESTS="1"
+      REASON="Main branch merge/push: tree :tree-${SHORT_TREE} was already tested on dev. Skipping tests (SKIP_TESTS=1)."
+    else
+      SKIP_TESTS="0"
+      REASON="Main branch merge/push: tree :tree-${SHORT_TREE} not found in registry. Running full tests (SKIP_TESTS=0)."
+    fi
+    ;;
+
+  refs/tags/v*|v*)
+    TAG_NAME="${REF#refs/tags/}"
+    # If pre-release (contains hyphen like v1.0.0-rc.1), do not tag :stable
+    if [[ "${TAG_NAME}" == *-* ]]; then
+      TARGET_TAGS="${TAG_NAME}"
+    else
+      TARGET_TAGS="${TAG_NAME} stable"
+    fi
+
+    # Check if a main image was already built for this exact commit
+    if [ -n "${IMAGE}" ] && image_exists "${IMAGE}:sha-${SHORT_SHA}"; then
+      ACTION="retag"
+      SOURCE_IMAGE="${IMAGE}:sha-${SHORT_SHA}"
+      SKIP_TESTS="1"
+      TAGS="${TARGET_TAGS}"
+      REASON="Release tag ${TAG_NAME} points to commit with existing image (${IMAGE}:sha-${SHORT_SHA}). Retagging without rebuild."
+    else
+      ACTION="build"
+      APP_VERSION="${TAG_NAME}"
+      TAGS="${TARGET_TAGS}"
+      if [ -n "${IMAGE}" ] && image_exists "${IMAGE}:tree-${SHORT_TREE}"; then
+        SKIP_TESTS="1"
+        REASON="Release tag ${TAG_NAME}: :sha-${SHORT_SHA} not found, but tree was tested on dev. Building with SKIP_TESTS=1."
+      else
+        SKIP_TESTS="0"
+        REASON="Release tag ${TAG_NAME}: :sha-${SHORT_SHA} not found and tree not verified. Building with full tests (SKIP_TESTS=0)."
+      fi
+    fi
+    ;;
+
+  *)
+    REF_SLUG="$(echo "${REF#refs/heads/}" | sed 's#/#-#g' | tr '[:upper:]' '[:lower:]')"
+    ACTION="build"
+    SKIP_TESTS="0"
+    APP_VERSION=""
+    TAGS="${REF_SLUG}"
+    REASON="Feature/other branch (${REF}): building with full tests"
+    ;;
+esac
+
+# Output to stdout
+echo "ACTION=${ACTION}"
+echo "SKIP_TESTS=${SKIP_TESTS}"
+echo "APP_VERSION=${APP_VERSION}"
+echo "TAGS=${TAGS}"
+echo "SOURCE_IMAGE=${SOURCE_IMAGE}"
+echo "SHORT_SHA=${SHORT_SHA}"
+echo "SHORT_TREE=${SHORT_TREE}"
+echo "REASON=${REASON}"
+
+# Output to GITHUB_OUTPUT if present
+if [ -n "${GITHUB_OUTPUT:-}" ] && [ -w "${GITHUB_OUTPUT}" ]; then
+  echo "action=${ACTION}" >> "${GITHUB_OUTPUT}"
+  echo "skip_tests=${SKIP_TESTS}" >> "${GITHUB_OUTPUT}"
+  echo "app_version=${APP_VERSION}" >> "${GITHUB_OUTPUT}"
+  echo "tags=${TAGS}" >> "${GITHUB_OUTPUT}"
+  echo "source_image=${SOURCE_IMAGE}" >> "${GITHUB_OUTPUT}"
+  echo "short_sha=${SHORT_SHA}" >> "${GITHUB_OUTPUT}"
+  echo "short_tree=${SHORT_TREE}" >> "${GITHUB_OUTPUT}"
+  echo "reason=${REASON}" >> "${GITHUB_OUTPUT}"
+fi
diff --git a/.gitea/scripts/test-build-plan.sh b/.gitea/scripts/test-build-plan.sh
new file mode 100755
index 0000000..c0a387d
--- /dev/null
+++ b/.gitea/scripts/test-build-plan.sh
@@ -0,0 +1,76 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PLAN_SCRIPT="${SCRIPT_DIR}/build-plan.sh"
+IMAGE="git.dsit.me/sandrodach/mindsift"
+
+COMMIT_SHA="$(git rev-parse --short=8 HEAD)"
+COMMIT_TREE="$(git rev-parse --short=12 HEAD^{tree})"
+
+# Helper mock check script
+MOCK_BIN="${SCRIPT_DIR}/.mock_check.sh"
+cat << 'EOF' > "${MOCK_BIN}"
+#!/usr/bin/env bash
+TARGET="$1"
+if [ "${MOCK_MODE}" = "tree_only" ] && [[ "${TARGET}" == *":tree-"* ]]; then
+  exit 0
+fi
+if [ "${MOCK_MODE}" = "sha_only" ] && [[ "${TARGET}" == *":sha-"* ]]; then
+  exit 0
+fi
+if [ "${MOCK_MODE}" = "all" ]; then
+  exit 0
+fi
+exit 1
+EOF
+chmod +x "${MOCK_BIN}"
+trap 'rm -f "${MOCK_BIN}"' EXIT
+
+echo "============================================================"
+echo "TEST 1: Push to dev"
+echo "============================================================"
+export MOCK_MODE="none"
+REF="refs/heads/dev" COMMIT="HEAD" IMAGE="${IMAGE}" CHECK_IMAGE_CMD="${MOCK_BIN}" "${PLAN_SCRIPT}"
+
+echo ""
+echo "============================================================"
+echo "TEST 2: Push/Merge to main (Tree ALREADY tested on dev)"
+echo "============================================================"
+export MOCK_MODE="tree_only"
+REF="refs/heads/main" COMMIT="HEAD" IMAGE="${IMAGE}" CHECK_IMAGE_CMD="${MOCK_BIN}" "${PLAN_SCRIPT}"
+
+echo ""
+echo "============================================================"
+echo "TEST 3: Push to main (Tree NOT yet tested)"
+echo "============================================================"
+export MOCK_MODE="none"
+REF="refs/heads/main" COMMIT="HEAD" IMAGE="${IMAGE}" CHECK_IMAGE_CMD="${MOCK_BIN}" "${PLAN_SCRIPT}"
+
+echo ""
+echo "============================================================"
+echo "TEST 4: Release Tag v0.10.0 (Main sha image ALREADY exists)"
+echo "============================================================"
+export MOCK_MODE="sha_only"
+REF="refs/tags/v0.10.0" COMMIT="HEAD" IMAGE="${IMAGE}" CHECK_IMAGE_CMD="${MOCK_BIN}" "${PLAN_SCRIPT}"
+
+echo ""
+echo "============================================================"
+echo "TEST 5: Release Tag v0.10.0 (Sha NOT found, but Tree exists)"
+echo "============================================================"
+export MOCK_MODE="tree_only"
+REF="refs/tags/v0.10.0" COMMIT="HEAD" IMAGE="${IMAGE}" CHECK_IMAGE_CMD="${MOCK_BIN}" "${PLAN_SCRIPT}"
+
+echo ""
+echo "============================================================"
+echo "TEST 6: Release Tag v0.10.0 (Sha NOT found, Tree NOT found)"
+echo "============================================================"
+export MOCK_MODE="none"
+REF="refs/tags/v0.10.0" COMMIT="HEAD" IMAGE="${IMAGE}" CHECK_IMAGE_CMD="${MOCK_BIN}" "${PLAN_SCRIPT}"
+
+echo ""
+echo "============================================================"
+echo "TEST 7: Pre-release Tag v0.10.0-rc.1 (Sha image exists)"
+echo "============================================================"
+export MOCK_MODE="sha_only"
+REF="refs/tags/v0.10.0-rc.1" COMMIT="HEAD" IMAGE="${IMAGE}" CHECK_IMAGE_CMD="${MOCK_BIN}" "${PLAN_SCRIPT}"
diff --git a/.gitea/workflows/build-and-publish.yaml b/.gitea/workflows/build-and-publish.yaml
index 0943af5..da67ce6 100644
--- a/.gitea/workflows/build-and-publish.yaml
+++ b/.gitea/workflows/build-and-publish.yaml
@@ -1,10 +1,5 @@
 name: MindSift CI & Docker Release
 
-# Image tags:
-#   push to dev      -> :dev
-#   push/merge main  -> :latest
-#   git tag v1.2.0   -> :v1.2.0 and :stable
-#   git tag v1.2.0-rc.1 (pre-release) -> :v1.2.0-rc.1 only, :stable stays
 on:
   push:
     branches:
@@ -21,59 +16,54 @@ jobs:
       - name: Checkout Code
         uses: actions/checkout@v4
 
-      - name: Determine Registry & Docker Tag
-        id: prep
-        run: |
-          SERVER_URL="${GITHUB_SERVER_URL:-https://git.dsit.me}"
-          REGISTRY_HOST=$(echo "${SERVER_URL}" | sed -E 's#^https?://##' | sed 's#/$##')
-          if [ -z "${REGISTRY_HOST}" ]; then
-            REGISTRY_HOST="git.dsit.me"
-          fi
-
-          REPO_PATH="${GITHUB_REPOSITORY:-sandrodach/mindsift}"
-          IMAGE_NAME=$(echo "${REGISTRY_HOST}/${REPO_PATH}" | tr '[:upper:]' '[:lower:]')
-          REF_NAME="${GITHUB_REF_NAME:-latest}"
-          ACTOR_NAME="${GITHUB_ACTOR:-sandrodach}"
-
-          # Ersetze evtl. Slashes in Branch-Namen (z.B. rc/1.1 -> rc-1.1) für valide Docker-Tags
-          DOCKER_TAG=$(echo "${REF_NAME}" | sed 's#/#-#g' | tr '[:upper:]' '[:lower:]')
-
-          # All tags of this run (space separated)
-          case "${GITHUB_REF:-}" in
-            refs/tags/*-*) TAGS="${DOCKER_TAG}" ;;
-            refs/tags/*)  TAGS="${DOCKER_TAG} stable" ;;
-            refs/heads/main) TAGS="latest" ;;
-            *)            TAGS="${DOCKER_TAG}" ;;
-          esac
-
-          echo "registry=${REGISTRY_HOST}" >> "$GITHUB_OUTPUT"
-          echo "image=${IMAGE_NAME}" >> "$GITHUB_OUTPUT"
-          echo "tag=${TAGS%% *}" >> "$GITHUB_OUTPUT"
-          echo "tags=${TAGS}" >> "$GITHUB_OUTPUT"
-          echo "actor=${ACTOR_NAME}" >> "$GITHUB_OUTPUT"
-          # Version in the app header: tags show the tag, main the package version, everything else
-          # (dev, feature branches) keeps the "-dev" suffix from vite.config.ts
-          APP_VERSION=""
-          case "${GITHUB_REF:-}" in
-            refs/tags/*) APP_VERSION="${REF_NAME}" ;;
-            refs/heads/main) APP_VERSION="v$(sed -nE 's/^  "version": "([^"]+)".*/\1/p' frontend/package.json | head -n1)" ;;
-          esac
-          echo "app_version=${APP_VERSION}" >> "$GITHUB_OUTPUT"
-          echo "Target Docker image: ${IMAGE_NAME} tags: ${TAGS} (Registry: ${REGISTRY_HOST}, Actor: ${ACTOR_NAME})"
-
       - name: Login to Gitea Container Registry
         uses: docker/login-action@v3
         with:
-          registry: ${{ steps.prep.outputs.registry }}
-          username: ${{ steps.prep.outputs.actor }}
+          registry: ${{ vars.REGISTRY_HOST || 'git.dsit.me' }}
+          username: ${{ github.actor }}
           password: ${{ secrets.PUSH_TOKEN || secrets.GITEA_TOKEN || github.token }}
 
-      - name: Build & Run All Checks in Container, then Push
+      - name: Calculate Build Plan
+        id: plan
         run: |
-          IMAGE="${{ steps.prep.outputs.image }}"
-          TAG_ARGS=""
-          for t in ${{ steps.prep.outputs.tags }}; do TAG_ARGS="${TAG_ARGS} -t ${IMAGE}:${t}"; done
-          echo "🚀 Building container & executing Frontend/Backend checks inside image: ${IMAGE} (tags: ${{ steps.prep.outputs.tags }})"
-          DOCKER_BUILDKIT=1 docker build --progress=plain --build-arg APP_VERSION="${{ steps.prep.outputs.app_version }}" ${TAG_ARGS} .
-          echo "✅ All checks & tests passed inside container! Pushing..."
-          for t in ${{ steps.prep.outputs.tags }}; do docker push "${IMAGE}:${t}"; done
+          SERVER_URL="${GITHUB_SERVER_URL:-https://git.dsit.me}"
+          REGISTRY_HOST=$(echo "${SERVER_URL}" | sed -E 's#^https?://##' | sed 's#/$##')
+          [ -z "${REGISTRY_HOST}" ] && REGISTRY_HOST="git.dsit.me"
+          REPO_PATH="${GITHUB_REPOSITORY:-sandrodach/mindsift}"
+          IMAGE_NAME=$(echo "${REGISTRY_HOST}/${REPO_PATH}" | tr '[:upper:]' '[:lower:]')
+
+          echo "registry=${REGISTRY_HOST}" >> "$GITHUB_OUTPUT"
+          echo "image=${IMAGE_NAME}" >> "$GITHUB_OUTPUT"
+
+          REF="${GITHUB_REF:-}" COMMIT="${GITHUB_SHA:-HEAD}" IMAGE="${IMAGE_NAME}" .gitea/scripts/build-plan.sh
+
+      - name: Execute Build or Retag & Push
+        run: |
+          IMAGE="${{ steps.plan.outputs.image }}"
+          ACTION="${{ steps.plan.outputs.action }}"
+          TAGS="${{ steps.plan.outputs.tags }}"
+
+          if [ "${ACTION}" = "retag" ]; then
+            SOURCE="${{ steps.plan.outputs.source_image }}"
+            echo "🏷️ Re-tagging existing image ${SOURCE} without rebuilding (Reason: ${{ steps.plan.outputs.reason }})"
+            docker pull "${SOURCE}"
+            for t in ${TAGS}; do
+              docker tag "${SOURCE}" "${IMAGE}:${t}"
+              docker push "${IMAGE}:${t}"
+            done
+          else
+            SKIP_TESTS="${{ steps.plan.outputs.skip_tests }}"
+            APP_VERSION="${{ steps.plan.outputs.app_version }}"
+            TAG_ARGS=""
+            for t in ${TAGS}; do TAG_ARGS="${TAG_ARGS} -t ${IMAGE}:${t}"; done
+
+            echo "🚀 Building container (SKIP_TESTS=${SKIP_TESTS}, APP_VERSION=${APP_VERSION}) for tags: ${TAGS}"
+            echo "ℹ️ Reason: ${{ steps.plan.outputs.reason }}"
+            DOCKER_BUILDKIT=1 docker build --progress=plain \
+              --build-arg APP_VERSION="${APP_VERSION}" \
+              --build-arg SKIP_TESTS="${SKIP_TESTS}" \
+              ${TAG_ARGS} .
+
+            echo "✅ Build complete! Pushing..."
+            for t in ${TAGS}; do docker push "${IMAGE}:${t}"; done
+          fi
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6c006ca..1cd9887 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,11 @@ Das Format folgt [Keep a Changelog](https://keepachangelog.com/de/1.1.0/), die V
 - „Über MindSift“-Dialog und Versionsanzeige im mobilen Profil-Menü (Avatar-Menü oben rechts).
 - PWA Web Share Target: Text, Links und Bilder können über den nativen Teilen-Dialog des Smartphones direkt in den MindSift-Posteingang geteilt werden (`share_target` im Manifest, Abfangen im Service Worker via IndexedDB und Übernahme beim App-Start; Fallback-Route `POST /share-target` im Server).
 
+### Changed
+- CI/CD & Pipeline: Schlankere Builds ohne Dreifach-Kompilierung. Bei Release-Tags wird das bestehende `main`-Image (`:sha-<commit>`) per Umtaggen direkt als `:vX.Y.Z` und `:stable` weiterverwendet.
+- CI/CD: Bedingte Testausführung über `ARG SKIP_TESTS=0` im Dockerfile; überspringt Frontend- und Backend-Tests auf `main`, wenn der Git-Tree (`:tree-<hash>`) bereits auf `dev` getestet wurde.
+- Build-Caching: BuildKit-Caches für Go-Module (`/go/pkg/mod`, `/root/.cache/go-build`) und npm (`/root/.npm`) im Dockerfile aktiviert.
+
 ## [0.10.0] - 2026-10-30
 
 ### Added
diff --git a/Dockerfile b/Dockerfile
index 04f7a85..530d168 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,11 +4,17 @@
 FROM node:22-alpine AS frontend-builder
 WORKDIR /app/frontend
 COPY frontend/package*.json ./
-RUN npm install --no-audit --no-fund
+RUN --mount=type=cache,target=/root/.npm npm install --no-audit --no-fund
 COPY frontend/ ./
 # Version shown in the header: the git tag for releases (set by CI), otherwise "<package version>-dev"
 ARG APP_VERSION=""
-RUN npx tsc --noEmit && npm run lint && npm run test:run && APP_VERSION="${APP_VERSION}" npm run build
+ARG SKIP_TESTS=0
+RUN if [ "$SKIP_TESTS" != "1" ]; then \
+      npx tsc --noEmit && npm run lint && npm run test:run; \
+    else \
+      echo "Skipping frontend tests (SKIP_TESTS=1)"; \
+    fi && \
+    APP_VERSION="${APP_VERSION}" npm run build
 
 # ==============================================================================
 # Stage 2: Go Backend Lint, Unit Tests & Binary Build (Cached Go module & sqlite layer)
@@ -19,7 +25,8 @@ RUN apk add --no-cache git ca-certificates
 
 # Cache Go modules & pre-compile heavy dependencies (modernc.org/sqlite) in a dedicated layer
 COPY go.mod ./
-RUN go get github.com/go-chi/chi/v5@v5.2.0 \
+RUN --mount=type=cache,target=/go/pkg/mod --mount=type=cache,target=/root/.cache/go-build \
+    go get github.com/go-chi/chi/v5@v5.2.0 \
     github.com/go-chi/cors@v1.2.1 \
     github.com/golang-jwt/jwt/v5@v5.2.1 \
     github.com/gorilla/websocket@v1.5.3 \
@@ -38,10 +45,16 @@ COPY cmd/ ./cmd/
 COPY internal/ ./internal/
 COPY --from=frontend-builder /app/frontend/dist ./cmd/server/dist
 
+ARG SKIP_TESTS=0
 # Run go mod tidy, static analysis (go vet), unit tests (go test), and compile final binary
-RUN go mod tidy && \
-    CGO_ENABLED=0 go vet ./... && \
-    CGO_ENABLED=0 go test -v ./... && \
+RUN --mount=type=cache,target=/go/pkg/mod --mount=type=cache,target=/root/.cache/go-build \
+    go mod tidy && \
+    if [ "$SKIP_TESTS" != "1" ]; then \
+      CGO_ENABLED=0 go vet ./... && \
+      CGO_ENABLED=0 go test -v ./...; \
+    else \
+      echo "Skipping backend tests (SKIP_TESTS=1)"; \
+    fi && \
     CGO_ENABLED=0 go build -ldflags="-s -w" -o /app/mindsift ./cmd/server
 
 # ==============================================================================