diff --git a/.gitignore b/.gitignore
index 1c3e282..7fc0503 100644
--- a/.gitignore
+++ b/.gitignore
@@ -64,8 +64,9 @@ htmlcov/
 # Output test files.
 test_data/*.png
 
-# Dev scripts (local convenience scripts)
-scripts/
+# Dev scripts (local convenience scripts - except validate-release.sh)
+scripts/*
+!scripts/validate-release.sh
 
 # Web UI auth database and SSL certs
 frontends/web/instance/
diff --git a/PLAN-4.1.2.md b/PLAN-4.1.2.md
index ecb3b01..dbf7110 100644
--- a/PLAN-4.1.2.md
+++ b/PLAN-4.1.2.md
@@ -7,7 +7,7 @@ Polish and UX improvements after the 4.1.1 stability release.
 
 ## 1. Real Progress Bar for Encode/Decode
 
-**Status:** Planned
+**Status:** Done
 
 **Problem:** Users see elapsed time but no indication of how far along the operation is. Long DCT encodes on Pi can take 2-3 minutes with no feedback.
 
@@ -76,7 +76,7 @@ Polish and UX improvements after the 4.1.1 stability release.
 
 ## 3. Mobile-Responsive Polish
 
-**Status:** Planned
+**Status:** Done
 
 **Problem:** UI works on mobile but has rough edges - cramped buttons, hard-to-tap targets, awkward layouts on small screens.
 
@@ -203,7 +203,7 @@ Polish and UX improvements after the 4.1.1 stability release.
 
 ## 8. Release Validation Script
 
-**Status:** Planned
+**Status:** Done
 
 **Problem:** Manual release checklist is error-prone. Need automated validation.
 
@@ -245,6 +245,6 @@ Polish and UX improvements after the 4.1.1 stability release.
 
 ## Notes
 
-- Keep 4.1.2 focused - 9 features (6 done)
+- Keep 4.1.2 focused - 9 features (9 done)
 - Don't break DCT compatibility (4.1.1 RS format is stable)
 - Test on Pi before release
diff --git a/frontends/web/static/style.css b/frontends/web/static/style.css
index 3aff3d0..4f2d6f3 100644
--- a/frontends/web/static/style.css
+++ b/frontends/web/static/style.css
@@ -1442,3 +1442,260 @@ footer {
     padding: 0.35rem 0.75rem;
     background: rgba(0, 0, 0, 0.1);
 }
+
+/* ============================================================================
+   MOBILE RESPONSIVE IMPROVEMENTS
+   ============================================================================ */
+
+/* Mobile-specific drop zone improvements */
+@media (max-width: 768px) {
+    /* Larger drop zones on mobile for easier touch targets */
+    .drop-zone {
+        padding: 2rem 1.5rem;
+        min-height: 140px;
+    }
+
+    /* Larger touch target for upload icons */
+    .drop-zone-label i {
+        font-size: 2.5rem !important;
+    }
+
+    /* Touch feedback - active state */
+    .drop-zone:active {
+        border-color: var(--gradient-start);
+        background: rgba(102, 126, 234, 0.15);
+        transform: scale(0.98);
+    }
+
+    /* Mode buttons - stack vertically on very small screens */
+    .d-flex.gap-2:has(.mode-btn) {
+        flex-direction: column;
+    }
+
+    .mode-btn {
+        padding: 1rem;
+        min-height: 56px; /* iOS touch target minimum */
+    }
+
+    /* Full-width primary buttons */
+    .btn-primary.btn-lg {
+        padding: 1rem 1.5rem;
+        font-size: 1.1rem;
+        min-height: 56px;
+    }
+
+    /* Security factor boxes - more padding for touch */
+    .security-box {
+        padding: 1.25rem;
+    }
+
+    /* Form controls - larger for touch */
+    .form-control,
+    .form-select {
+        padding: 0.75rem 1rem;
+        font-size: 1rem;
+        min-height: 48px;
+    }
+
+    /* Input groups - consistent sizing */
+    .input-group .form-control {
+        min-height: 48px;
+    }
+
+    .input-group .btn {
+        min-width: 48px;
+        padding: 0.75rem;
+    }
+
+    /* Password toggle button - easier to tap */
+    [data-toggle-password] {
+        min-width: 52px;
+    }
+
+    /* PIN input - larger on mobile */
+    .pin-input-container .form-control {
+        font-size: 1.4rem;
+        letter-spacing: 4px;
+        padding: 0.875rem 1rem;
+    }
+
+    /* Passphrase input - comfortable mobile size */
+    .passphrase-input {
+        font-size: 1rem !important;
+        padding: 0.875rem 1rem !important;
+    }
+
+    /* Card headers - compact on mobile */
+    .card-header h5 {
+        font-size: 1.1rem;
+    }
+
+    /* Alert info panel - readable text */
+    .alert.small {
+        font-size: 0.9rem;
+    }
+
+    /* Bottom info icons - larger tap targets */
+    .row.text-center .col-4 {
+        padding: 0.5rem;
+    }
+
+    .row.text-center .col-4 i {
+        font-size: 2rem !important;
+    }
+
+    /* Capacity panel badges - easier to read */
+    #capacityPanel .badge {
+        font-size: 0.8rem;
+        padding: 0.4rem 0.6rem;
+    }
+
+    /* Payload type toggle - full width buttons */
+    .btn-group[role="group"] {
+        flex-direction: row;
+    }
+
+    .btn-group .btn {
+        padding: 0.75rem 0.5rem;
+        font-size: 0.95rem;
+    }
+
+    /* Textarea - comfortable height */
+    textarea.form-control {
+        min-height: 120px;
+    }
+
+    /* Channel select - full width */
+    #channelSelect {
+        font-size: 1rem;
+    }
+}
+
+/* Very small screens (iPhone SE, etc.) */
+@media (max-width: 375px) {
+    .drop-zone {
+        padding: 1.5rem 1rem;
+    }
+
+    .mode-btn {
+        padding: 0.875rem;
+        font-size: 0.9rem;
+    }
+
+    .mode-btn .text-muted {
+        display: none; /* Hide secondary text on tiny screens */
+    }
+
+    .card-header h5 {
+        font-size: 1rem;
+    }
+
+    /* Stack security factor row */
+    .row:has(.security-box) > .col-md-6 {
+        margin-bottom: 1rem;
+    }
+}
+
+/* Touch device optimizations */
+@media (hover: none) and (pointer: coarse) {
+    /* Remove hover effects that don't work on touch */
+    .btn-primary:hover {
+        transform: none;
+    }
+
+    .feature-card:hover {
+        transform: none;
+    }
+
+    .card-link:hover .feature-card {
+        transform: none;
+    }
+
+    /* Add active states instead */
+    .btn-primary:active {
+        transform: scale(0.98);
+        box-shadow: 0 2px 10px rgba(102, 126, 234, 0.3);
+    }
+
+    .feature-card:active {
+        transform: scale(0.98);
+    }
+
+    /* Drop zone active feedback */
+    .drop-zone:active {
+        border-color: var(--gradient-start);
+        background: rgba(102, 126, 234, 0.1);
+    }
+
+    /* Mode button active state */
+    .mode-btn:active {
+        background: rgba(255, 255, 255, 0.12);
+        border-color: var(--gradient-start);
+    }
+}
+
+/* Camera hint for mobile - shows on file inputs */
+@media (max-width: 768px) {
+    .drop-zone-label span.text-muted {
+        display: block;
+    }
+
+    /* Add camera icon hint on mobile */
+    .drop-zone-label::after {
+        content: "Tap to take photo or choose file";
+        display: block;
+        font-size: 0.75rem;
+        color: rgba(255, 255, 255, 0.4);
+        margin-top: 0.5rem;
+    }
+
+    /* Hide the default text and show mobile version */
+    .drop-zone-label > span.text-muted {
+        display: none;
+    }
+}
+
+/* Navbar mobile adjustments */
+@media (max-width: 768px) {
+    .navbar {
+        padding: 0.5rem 1rem;
+    }
+
+    .navbar-brand img {
+        height: 32px;
+    }
+
+    /* Sticky header shouldn't eat too much space */
+    .navbar.sticky-top {
+        position: relative; /* Don't stick on mobile - saves screen space */
+    }
+}
+
+/* Results page mobile adjustments */
+@media (max-width: 768px) {
+    /* Download button - full width on mobile */
+    .btn-success.btn-lg,
+    a.btn-success.btn-lg {
+        width: 100%;
+        padding: 1rem;
+        font-size: 1.1rem;
+    }
+
+    /* QR codes - appropriate sizing */
+    .qr-scan-container {
+        max-width: 280px;
+        margin: 0 auto;
+    }
+
+    /* Message display - readable on mobile */
+    .alert-message {
+        font-size: 0.9rem;
+        padding: 1rem;
+        word-break: break-word;
+    }
+
+    /* Result icon - slightly smaller on mobile */
+    .result-icon {
+        font-size: 3rem;
+    }
+}
diff --git a/pyproject.toml b/pyproject.toml
index 02329ec..a4719fc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "stegasoo"
-version = "4.1.1"
+version = "4.1.2"
 description = "Secure steganography with hybrid photo + passphrase + PIN authentication"
 readme = "README.md"
 license = "MIT"
diff --git a/scripts/validate-release.sh b/scripts/validate-release.sh
new file mode 100755
index 0000000..d0eebde
--- /dev/null
+++ b/scripts/validate-release.sh
@@ -0,0 +1,307 @@
+#!/bin/bash
+# =============================================================================
+# Stegasoo Release Validation Script
+# =============================================================================
+# Automated pre-release validation to catch issues before tagging a release.
+#
+# Usage:
+#   ./scripts/validate-release.sh              # Local validation only
+#   ./scripts/validate-release.sh --pi         # Include Pi smoke test
+#   PI_IP=192.168.0.4 ./scripts/validate-release.sh --pi
+#
+# Exit codes:
+#   0 = All tests passed
+#   1 = One or more tests failed
+# =============================================================================
+
+# Don't use set -e as we need to handle test failures gracefully
+
+# Colors
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[0;33m'
+CYAN='\033[0;36m'
+NC='\033[0m'
+
+# Default Pi IP (can be overridden via environment)
+PI_IP="${PI_IP:-192.168.0.4}"
+PI_USER="${PI_USER:-alee}"
+INCLUDE_PI=false
+INCLUDE_DOCKER=true
+
+# Parse arguments
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        --pi)
+            INCLUDE_PI=true
+            shift
+            ;;
+        --no-docker)
+            INCLUDE_DOCKER=false
+            shift
+            ;;
+        --help|-h)
+            echo "Usage: $0 [--pi] [--no-docker]"
+            echo ""
+            echo "Options:"
+            echo "  --pi         Include Pi smoke test (requires SSH access)"
+            echo "  --no-docker  Skip Docker build/test"
+            echo ""
+            echo "Environment:"
+            echo "  PI_IP        Pi IP address (default: 192.168.0.4)"
+            echo "  PI_USER      Pi SSH user (default: alee)"
+            exit 0
+            ;;
+        *)
+            echo "Unknown option: $1"
+            exit 1
+            ;;
+    esac
+done
+
+# Track results
+TESTS_RUN=0
+TESTS_PASSED=0
+TESTS_FAILED=0
+FAILED_TESTS=()
+
+# Helper functions
+pass() {
+    echo -e "${GREEN}[PASS]${NC} $1"
+    ((TESTS_PASSED++))
+    ((TESTS_RUN++))
+}
+
+fail() {
+    echo -e "${RED}[FAIL]${NC} $1"
+    FAILED_TESTS+=("$1")
+    ((TESTS_FAILED++))
+    ((TESTS_RUN++))
+}
+
+skip() {
+    echo -e "${YELLOW}[SKIP]${NC} $1"
+}
+
+section() {
+    echo ""
+    echo -e "${CYAN}━━━ $1 ━━━${NC}"
+}
+
+# =============================================================================
+# Header
+# =============================================================================
+echo -e "${CYAN}╔═══════════════════════════════════════════════════════════════╗${NC}"
+echo -e "${CYAN}║         Stegasoo Release Validation                           ║${NC}"
+echo -e "${CYAN}╚═══════════════════════════════════════════════════════════════╝${NC}"
+echo ""
+
+# Get version from pyproject.toml
+VERSION=$(grep '^version = ' pyproject.toml | head -1 | cut -d'"' -f2)
+echo -e "Version: ${YELLOW}${VERSION}${NC}"
+echo -e "Branch:  ${YELLOW}$(git branch --show-current)${NC}"
+echo ""
+
+# =============================================================================
+# 1. Code Quality Checks
+# =============================================================================
+section "Code Quality"
+
+# Ruff linting
+if command -v ./venv/bin/ruff &> /dev/null; then
+    echo -n "Running ruff check... "
+    if ./venv/bin/ruff check src/ frontends/ --quiet 2>/dev/null; then
+        pass "Ruff linting"
+    else
+        fail "Ruff linting (run: ./venv/bin/ruff check src/ frontends/)"
+    fi
+else
+    skip "Ruff not installed"
+fi
+
+# =============================================================================
+# 2. Unit Tests (if they exist)
+# =============================================================================
+section "Unit Tests"
+
+if ls tests/test_*.py 1> /dev/null 2>&1; then
+    echo -n "Running pytest... "
+    if ./venv/bin/pytest tests/ -q --tb=no 2>/dev/null; then
+        pass "Pytest unit tests"
+    else
+        fail "Pytest unit tests"
+    fi
+else
+    skip "No unit tests found (tests/test_*.py)"
+fi
+
+# =============================================================================
+# 3. Import Tests
+# =============================================================================
+section "Import Tests"
+
+# Test core library import
+echo -n "Testing stegasoo import... "
+if ./venv/bin/python -c "from stegasoo import encode, decode; print('OK')" 2>/dev/null | grep -q OK; then
+    pass "Core library import"
+else
+    fail "Core library import"
+fi
+
+# Test DCT support
+echo -n "Testing DCT support... "
+if ./venv/bin/python -c "from stegasoo import has_dct_support; assert has_dct_support(), 'No DCT'; print('OK')" 2>/dev/null | grep -q OK; then
+    pass "DCT support available"
+else
+    fail "DCT support (scipy/jpegio missing?)"
+fi
+
+# Test CLI import
+echo -n "Testing CLI import... "
+if ./venv/bin/python -c "from stegasoo.cli import main; print('OK')" 2>/dev/null | grep -q OK; then
+    pass "CLI module import"
+else
+    fail "CLI module import"
+fi
+
+# =============================================================================
+# 4. Encode/Decode Sanity Test
+# =============================================================================
+section "Encode/Decode Test"
+
+echo -n "Running encode/decode sanity check... "
+SANITY_RESULT=$(./venv/bin/python << 'EOF' 2>&1
+import sys
+sys.path.insert(0, 'src')
+from stegasoo import encode, decode
+
+with open('test_data/carrier.jpg', 'rb') as f:
+    carrier = f.read()
+with open('test_data/ref.jpg', 'rb') as f:
+    ref = f.read()
+
+# LSB test
+result = encode(message="sanity test", reference_photo=ref, carrier_image=carrier,
+                passphrase="test", pin="123456", embed_mode="lsb")
+decoded = decode(stego_image=result.stego_image, reference_photo=ref,
+                 passphrase="test", pin="123456", embed_mode="lsb")
+assert decoded.message == "sanity test", f"LSB mismatch: {decoded.message}"
+
+# DCT test
+result = encode(message="dct sanity", reference_photo=ref, carrier_image=carrier,
+                passphrase="dct", pin="654321", embed_mode="dct")
+decoded = decode(stego_image=result.stego_image, reference_photo=ref,
+                 passphrase="dct", pin="654321", embed_mode="dct")
+assert decoded.message == "dct sanity", f"DCT mismatch: {decoded.message}"
+
+print("OK")
+EOF
+)
+
+if echo "$SANITY_RESULT" | grep -q "OK"; then
+    pass "Encode/decode sanity (LSB + DCT)"
+else
+    fail "Encode/decode sanity: $SANITY_RESULT"
+fi
+
+# =============================================================================
+# 5. Docker Build & Test (optional)
+# =============================================================================
+if $INCLUDE_DOCKER; then
+    section "Docker"
+
+    if command -v docker &> /dev/null || command -v sudo &> /dev/null; then
+        DOCKER_CMD="docker"
+        if ! docker info &>/dev/null 2>&1; then
+            DOCKER_CMD="sudo docker"
+        fi
+
+        echo -n "Building Docker image... "
+        if $DOCKER_CMD build -t stegasoo:validate -q . >/dev/null 2>&1; then
+            pass "Docker build"
+
+            # Test container starts
+            echo -n "Testing container startup... "
+            CONTAINER_ID=$($DOCKER_CMD run -d -p 15000:5000 stegasoo:validate 2>/dev/null)
+            sleep 3
+
+            if curl -s -o /dev/null -w "%{http_code}" http://localhost:15000/ 2>/dev/null | grep -qE "200|302"; then
+                pass "Container responds to HTTP"
+            else
+                fail "Container HTTP response"
+            fi
+
+            # Cleanup
+            $DOCKER_CMD stop "$CONTAINER_ID" >/dev/null 2>&1 || true
+            $DOCKER_CMD rm "$CONTAINER_ID" >/dev/null 2>&1 || true
+        else
+            fail "Docker build"
+        fi
+
+        # Cleanup test image
+        $DOCKER_CMD rmi stegasoo:validate >/dev/null 2>&1 || true
+    else
+        skip "Docker not available"
+    fi
+else
+    skip "Docker tests (use --docker to enable)"
+fi
+
+# =============================================================================
+# 6. Pi Smoke Test (optional)
+# =============================================================================
+if $INCLUDE_PI; then
+    section "Pi Smoke Test"
+
+    echo -n "Testing SSH connectivity to $PI_USER@$PI_IP... "
+    if ssh -o ConnectTimeout=5 -o BatchMode=yes "$PI_USER@$PI_IP" "echo OK" 2>/dev/null | grep -q OK; then
+        pass "SSH connectivity"
+
+        echo -n "Checking stegasoo service status... "
+        if ssh "$PI_USER@$PI_IP" "systemctl is-active stegasoo" 2>/dev/null | grep -q active; then
+            pass "Stegasoo service running"
+
+            echo -n "Running smoke test on Pi... "
+            SMOKE_RESULT=$(ssh "$PI_USER@$PI_IP" "cd /home/$PI_USER/stegasoo && bash tests/smoke-test.sh --quick 2>&1" || echo "FAILED")
+            if echo "$SMOKE_RESULT" | grep -qE "All tests passed|PASS"; then
+                pass "Pi smoke test"
+            else
+                fail "Pi smoke test"
+            fi
+        else
+            fail "Stegasoo service not running"
+        fi
+    else
+        fail "SSH connectivity to Pi"
+    fi
+else
+    skip "Pi smoke test (use --pi to enable)"
+fi
+
+# =============================================================================
+# Summary
+# =============================================================================
+echo ""
+echo -e "${CYAN}━━━ Summary ━━━${NC}"
+echo ""
+echo -e "Tests run:    ${TESTS_RUN}"
+echo -e "Passed:       ${GREEN}${TESTS_PASSED}${NC}"
+echo -e "Failed:       ${RED}${TESTS_FAILED}${NC}"
+
+if [ ${#FAILED_TESTS[@]} -gt 0 ]; then
+    echo ""
+    echo -e "${RED}Failed tests:${NC}"
+    for test in "${FAILED_TESTS[@]}"; do
+        echo -e "  - $test"
+    done
+fi
+
+echo ""
+if [ $TESTS_FAILED -eq 0 ]; then
+    echo -e "${GREEN}✓ All validation checks passed!${NC}"
+    echo -e "  Ready to tag release ${VERSION}"
+    exit 0
+else
+    echo -e "${RED}✗ Validation failed - fix issues before release${NC}"
+    exit 1
+fi
diff --git a/src/stegasoo/__init__.py b/src/stegasoo/__init__.py
index f2ab652..ec9c845 100644
--- a/src/stegasoo/__init__.py
+++ b/src/stegasoo/__init__.py
@@ -7,7 +7,7 @@ Changes in v4.0.0:
 - encode() and decode() now accept channel_key parameter
 """
 
-__version__ = "4.0.1"
+__version__ = "4.1.2"
 
 # Core functionality
 # Channel key management (v4.0.0)
diff --git a/src/stegasoo/cli.py b/src/stegasoo/cli.py
index 4db7b65..ecb9185 100644
--- a/src/stegasoo/cli.py
+++ b/src/stegasoo/cli.py
@@ -105,6 +105,7 @@ def encode(
         stegasoo encode photo.png -r ref.jpg -f secret.pdf -o encoded.png
     """
     from PIL import Image
+
     from .encode import encode as stegasoo_encode
     from .encode import encode_file as stegasoo_encode_file
 
@@ -1108,7 +1109,9 @@ def admin_recover(db_path, password):
         stegasoo admin recover --db /path/to/stegasoo.db
     """
     import sqlite3
+
     from argon2 import PasswordHasher
+
     from .recovery import verify_recovery_key
 
     # Try default paths if not specified
diff --git a/src/stegasoo/constants.py b/src/stegasoo/constants.py
index de2991c..7474f3d 100644
--- a/src/stegasoo/constants.py
+++ b/src/stegasoo/constants.py
@@ -25,7 +25,7 @@ from pathlib import Path
 # VERSION
 # ============================================================================
 
-__version__ = "4.1.0"
+__version__ = "4.1.2"
 
 # ============================================================================
 # FILE FORMAT