diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
new file mode 100644
index 0000000..abbbdb3
--- /dev/null
+++ b/.github/CODEOWNERS
@@ -0,0 +1,15 @@
+# MIZAN Code Owners
+# These users will be automatically requested for review on PRs.
+
+# Default owner for everything
+* @CodeWithJuber
+
+# Backend core
+/backend/core/ @CodeWithJuber
+/backend/security/ @CodeWithJuber
+/backend/api/main.py @CodeWithJuber
+
+# Infrastructure
+/docker-compose.yml @CodeWithJuber
+/.github/workflows/ @CodeWithJuber
+/scripts/ @CodeWithJuber
diff --git a/.github/workflows/pr-check.yml b/.github/workflows/pr-check.yml
new file mode 100644
index 0000000..b35260d
--- /dev/null
+++ b/.github/workflows/pr-check.yml
@@ -0,0 +1,42 @@
+name: Branch Protection Check
+
+# Enforces quality gates on all PRs to main/master.
+# Complement this with GitHub branch protection rules (see scripts/setup-branch-protection.sh).
+
+on:
+  pull_request:
+    branches: [main, master]
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - run: pip install ruff
+      - run: ruff check backend/ tests/
+      - run: ruff format --check backend/ tests/
+
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - run: pip install -e ".[dev]"
+      - run: pytest tests/ -v --tb=short
+
+  frontend-build:
+    name: Frontend Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+      - run: cd frontend && npm ci && npx tsc --noEmit && npx vite build
diff --git a/Makefile b/Makefile
index 3835c5d..3c62ee8 100644
--- a/Makefile
+++ b/Makefile
@@ -108,3 +108,6 @@ release-major: ## Full release: bump major, changelog, tag, push
 
 release-dry: ## Dry run of a patch release (no changes)
 	./scripts/release.sh patch --dry-run
+
+protect: ## Setup GitHub branch protection rules for main
+	./scripts/setup-branch-protection.sh
diff --git a/scripts/setup-branch-protection.sh b/scripts/setup-branch-protection.sh
new file mode 100755
index 0000000..f968602
--- /dev/null
+++ b/scripts/setup-branch-protection.sh
@@ -0,0 +1,112 @@
+#!/usr/bin/env bash
+# ═══════════════════════════════════════════════════════════════
+# MIZAN Branch Protection Setup
+#
+# Sets up GitHub branch protection rules for main branch.
+# Requires: gh CLI authenticated with repo admin access.
+#
+# Usage:
+#   ./scripts/setup-branch-protection.sh
+#   ./scripts/setup-branch-protection.sh --branch master
+# ═══════════════════════════════════════════════════════════════
+
+set -euo pipefail
+
+GOLD='\033[0;33m'
+GREEN='\033[0;32m'
+BLUE='\033[0;34m'
+RED='\033[0;31m'
+BOLD='\033[1m'
+NC='\033[0m'
+
+info()    { echo -e "  ${BLUE}➜${NC} $1"; }
+success() { echo -e "  ${GREEN}✓${NC} $1"; }
+error()   { echo -e "  ${RED}✗${NC} $1"; exit 1; }
+step()    { echo -e "\n  ${GOLD}━━━${NC} ${BOLD}$1${NC}"; }
+
+BRANCH="${1:---branch}"
+if [ "$BRANCH" = "--branch" ]; then
+    BRANCH="${2:-main}"
+fi
+
+# Detect repo from git remote
+REPO=$(gh repo view --json nameWithOwner -q '.nameWithOwner' 2>/dev/null) || true
+if [ -z "$REPO" ]; then
+    REPO=$(git remote get-url origin | sed -E 's|.*github\.com[:/](.+)(\.git)?$|\1|' | sed 's/\.git$//')
+fi
+
+if [ -z "$REPO" ]; then
+    error "Could not detect repository. Run from within a git repo with a GitHub remote."
+fi
+
+echo ""
+echo -e "  ${GOLD}═══════════════════════════════════════════════════${NC}"
+echo -e "  ${BOLD}  MIZAN Branch Protection Setup${NC}"
+echo -e "  ${GOLD}═══════════════════════════════════════════════════${NC}"
+echo ""
+info "Repository: $REPO"
+info "Branch: $BRANCH"
+
+# ───── Check prerequisites ─────
+
+step "Checking prerequisites"
+
+if ! command -v gh &>/dev/null; then
+    error "GitHub CLI (gh) not installed. Install: https://cli.github.com"
+fi
+success "gh CLI found"
+
+if ! gh auth status &>/dev/null; then
+    error "Not authenticated. Run: gh auth login"
+fi
+success "Authenticated with GitHub"
+
+# ───── Apply branch protection rules ─────
+
+step "Applying branch protection rules"
+
+gh api \
+  --method PUT \
+  -H "Accept: application/vnd.github+json" \
+  "/repos/$REPO/branches/$BRANCH/protection" \
+  -f "required_status_checks[strict]=true" \
+  -f "required_status_checks[contexts][]=Lint" \
+  -f "required_status_checks[contexts][]=Test" \
+  -f "required_status_checks[contexts][]=Frontend Build" \
+  -f "enforce_admins=true" \
+  -f "required_pull_request_reviews[dismiss_stale_reviews]=true" \
+  -f "required_pull_request_reviews[require_code_owner_reviews]=false" \
+  -f "required_pull_request_reviews[required_approving_review_count]=1" \
+  -F "restrictions=null" \
+  -F "allow_force_pushes=false" \
+  -F "allow_deletions=false" \
+  -F "block_creations=false" \
+  -F "required_linear_history=false" \
+  -F "required_conversation_resolution=true" \
+  > /dev/null 2>&1
+
+success "Branch protection rules applied"
+
+# ───── Summary ─────
+
+echo ""
+echo -e "  ${GOLD}═══════════════════════════════════════════════════${NC}"
+echo -e "  ${GREEN}${BOLD}  Branch protection enabled for $BRANCH${NC}"
+echo -e "  ${GOLD}═══════════════════════════════════════════════════${NC}"
+echo ""
+echo -e "  ${BOLD}Rules applied:${NC}"
+echo -e "    ${GREEN}✓${NC} Require PR before merging (1 approval)"
+echo -e "    ${GREEN}✓${NC} Dismiss stale reviews on new pushes"
+echo -e "    ${GREEN}✓${NC} Require status checks to pass:"
+echo -e "      • Lint (ruff check + format)"
+echo -e "      • Test (pytest)"
+echo -e "      • Frontend Build (tsc + vite)"
+echo -e "    ${GREEN}✓${NC} Require branches to be up to date"
+echo -e "    ${GREEN}✓${NC} Require conversations resolved"
+echo -e "    ${GREEN}✓${NC} Enforce for admins too"
+echo -e "    ${GREEN}✓${NC} Block force pushes"
+echo -e "    ${GREEN}✓${NC} Block branch deletion"
+echo ""
+echo -e "  ${BOLD}To verify:${NC}"
+echo -e "    ${BLUE}https://github.com/$REPO/settings/branches${NC}"
+echo ""