diff --git a/.env.example b/.env.example
index 9ca59fd..f759171 100644
--- a/.env.example
+++ b/.env.example
@@ -350,6 +350,28 @@ OLLAMA_MODEL=llama3.1:latest
 # Get your API key from: https://platform.openai.com/api-keys
 # OPENAI_API_KEY=sk-...
 
+# ======================
+# Matrix Dev Environment (docker-compose.matrix.yml overlay)
+# ======================
+# These variables configure the local Matrix dev environment.
+# Only used when running: docker compose -f docker/docker-compose.yml -f docker/docker-compose.matrix.yml up
+#
+# Synapse homeserver
+# SYNAPSE_CLIENT_PORT=8008
+# SYNAPSE_FEDERATION_PORT=8448
+# SYNAPSE_POSTGRES_DB=synapse
+# SYNAPSE_POSTGRES_USER=synapse
+# SYNAPSE_POSTGRES_PASSWORD=synapse_dev_password
+#
+# Element Web client
+# ELEMENT_PORT=8501
+#
+# Matrix bridge connection (set after running docker/matrix/scripts/setup-bot.sh)
+# MATRIX_HOMESERVER_URL=http://localhost:8008
+# MATRIX_ACCESS_TOKEN=<obtained from setup-bot.sh>
+# MATRIX_BOT_USER_ID=@mosaic-bot:localhost
+# MATRIX_SERVER_NAME=localhost
+
 # ======================
 # Logging & Debugging
 # ======================
diff --git a/Makefile b/Makefile
index 3375fee..ac2718b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-.PHONY: help install dev build test docker-up docker-down docker-logs docker-ps docker-build docker-restart docker-test clean
+.PHONY: help install dev build test docker-up docker-down docker-logs docker-ps docker-build docker-restart docker-test clean matrix-up matrix-down matrix-logs matrix-setup-bot
 
 # Default target
 help:
@@ -24,6 +24,12 @@ help:
 	@echo "  make docker-test            Run Docker smoke test"
 	@echo "  make docker-test-traefik    Run Traefik integration tests"
 	@echo ""
+	@echo "Matrix Dev Environment:"
+	@echo "  make matrix-up              Start Matrix services (Synapse + Element)"
+	@echo "  make matrix-down            Stop Matrix services"
+	@echo "  make matrix-logs            View Matrix service logs"
+	@echo "  make matrix-setup-bot       Create bot account and get access token"
+	@echo ""
 	@echo "Database:"
 	@echo "  make db-migrate       Run database migrations"
 	@echo "  make db-seed          Seed development data"
@@ -85,6 +91,19 @@ docker-test:
 docker-test-traefik:
 	./tests/integration/docker/traefik.test.sh all
 
+# Matrix Dev Environment
+matrix-up:
+	docker compose -f docker/docker-compose.yml -f docker/docker-compose.matrix.yml up -d
+
+matrix-down:
+	docker compose -f docker/docker-compose.yml -f docker/docker-compose.matrix.yml down
+
+matrix-logs:
+	docker compose -f docker/docker-compose.yml -f docker/docker-compose.matrix.yml logs -f synapse element-web
+
+matrix-setup-bot:
+	docker/matrix/scripts/setup-bot.sh
+
 # Database operations
 db-migrate:
 	cd apps/api && pnpm prisma:migrate
diff --git a/docker/docker-compose.matrix.yml b/docker/docker-compose.matrix.yml
new file mode 100644
index 0000000..b850458
--- /dev/null
+++ b/docker/docker-compose.matrix.yml
@@ -0,0 +1,129 @@
+# ==============================================
+# Matrix Dev Environment (Synapse + Element Web)
+# ==============================================
+#
+# Development-only overlay for testing the Matrix bridge locally.
+# NOT for production — use docker-compose.sample.matrix.yml for production.
+#
+# Usage:
+#   docker compose -f docker/docker-compose.yml -f docker/docker-compose.matrix.yml up -d
+#
+# Or with Makefile:
+#   make matrix-up
+#
+# This overlay:
+#   - Adds Synapse homeserver (localhost:8008) using shared PostgreSQL
+#   - Adds Element Web client (localhost:8501)
+#   - Creates a separate 'synapse' database in the shared PostgreSQL instance
+#   - Enables open registration for easy dev testing
+#
+# After first startup, create the bot account:
+#   docker/matrix/scripts/setup-bot.sh
+#
+# ==============================================
+
+services:
+  # ======================
+  # Synapse Database Init
+  # ======================
+  # Creates the 'synapse' database and user in the shared PostgreSQL instance.
+  # Runs once and exits — idempotent, safe to run repeatedly.
+  synapse-db-init:
+    image: postgres:17-alpine
+    container_name: mosaic-synapse-db-init
+    restart: "no"
+    environment:
+      PGHOST: postgres
+      PGPORT: 5432
+      PGUSER: ${POSTGRES_USER:-mosaic}
+      PGPASSWORD: ${POSTGRES_PASSWORD:-mosaic_dev_password}
+      SYNAPSE_DB: ${SYNAPSE_POSTGRES_DB:-synapse}
+      SYNAPSE_USER: ${SYNAPSE_POSTGRES_USER:-synapse}
+      SYNAPSE_PASSWORD: ${SYNAPSE_POSTGRES_PASSWORD:-synapse_dev_password}
+    entrypoint: ["sh", "-c"]
+    command:
+      - |
+        until pg_isready -h postgres -p 5432 -U $${PGUSER}; do
+          echo "Waiting for PostgreSQL..."
+          sleep 2
+        done
+        echo "PostgreSQL is ready. Creating Synapse database and user..."
+
+        psql -h postgres -U $${PGUSER} -tc "SELECT 1 FROM pg_roles WHERE rolname='$${SYNAPSE_USER}'" | grep -q 1 || \
+          psql -h postgres -U $${PGUSER} -c "CREATE USER $${SYNAPSE_USER} WITH PASSWORD '$${SYNAPSE_PASSWORD}';"
+
+        psql -h postgres -U $${PGUSER} -tc "SELECT 1 FROM pg_database WHERE datname='$${SYNAPSE_DB}'" | grep -q 1 || \
+          psql -h postgres -U $${PGUSER} -c "CREATE DATABASE $${SYNAPSE_DB} OWNER $${SYNAPSE_USER} ENCODING 'UTF8' LC_COLLATE='C' LC_CTYPE='C' TEMPLATE template0;"
+
+        echo "Synapse database ready: $${SYNAPSE_DB}"
+    depends_on:
+      postgres:
+        condition: service_healthy
+    networks:
+      - mosaic-network
+
+  # ======================
+  # Synapse (Matrix Homeserver)
+  # ======================
+  synapse:
+    image: matrixdotorg/synapse:latest
+    container_name: mosaic-synapse
+    restart: unless-stopped
+    environment:
+      SYNAPSE_CONFIG_DIR: /data
+      SYNAPSE_CONFIG_PATH: /data/homeserver.yaml
+    ports:
+      - "${SYNAPSE_CLIENT_PORT:-8008}:8008"
+      - "${SYNAPSE_FEDERATION_PORT:-8448}:8448"
+    volumes:
+      - ./matrix/synapse/homeserver.yaml:/data/homeserver.yaml:ro
+      - synapse_data:/data/media_store
+      - synapse_signing_key:/data/keys
+    depends_on:
+      postgres:
+        condition: service_healthy
+      synapse-db-init:
+        condition: service_completed_successfully
+    healthcheck:
+      test: ["CMD-SHELL", "curl -fSs http://localhost:8008/health || exit 1"]
+      interval: 15s
+      timeout: 5s
+      retries: 5
+      start_period: 30s
+    networks:
+      - mosaic-network
+    labels:
+      com.mosaic.service: "matrix-synapse"
+      com.mosaic.description: "Matrix homeserver (dev)"
+
+  # ======================
+  # Element Web (Matrix Client)
+  # ======================
+  element-web:
+    image: vectorim/element-web:latest
+    container_name: mosaic-element-web
+    restart: unless-stopped
+    ports:
+      - "${ELEMENT_PORT:-8501}:80"
+    volumes:
+      - ./matrix/element/config.json:/app/config.json:ro
+    depends_on:
+      synapse:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD-SHELL", "wget --no-verbose --tries=1 --spider http://localhost:80 || exit 1"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 10s
+    networks:
+      - mosaic-network
+    labels:
+      com.mosaic.service: "matrix-element"
+      com.mosaic.description: "Element Web client (dev)"
+
+volumes:
+  synapse_data:
+    name: mosaic-synapse-data
+  synapse_signing_key:
+    name: mosaic-synapse-signing-key
diff --git a/docker/matrix/element/config.json b/docker/matrix/element/config.json
new file mode 100644
index 0000000..509f013
--- /dev/null
+++ b/docker/matrix/element/config.json
@@ -0,0 +1,30 @@
+{
+  "default_server_config": {
+    "m.homeserver": {
+      "base_url": "http://localhost:8008",
+      "server_name": "localhost"
+    }
+  },
+  "brand": "Mosaic Stack Dev",
+  "default_theme": "dark",
+  "room_directory": {
+    "servers": ["localhost"]
+  },
+  "features": {
+    "feature_video_rooms": false,
+    "feature_group_calls": false
+  },
+  "show_labs_settings": true,
+  "piwik": false,
+  "posthog": {
+    "enabled": false
+  },
+  "privacy_policy_url": null,
+  "terms_and_conditions_links": [],
+  "setting_defaults": {
+    "breadcrumbs": true,
+    "custom_themes": []
+  },
+  "disable_guests": true,
+  "disable_3pid_login": true
+}
diff --git a/docker/matrix/scripts/setup-bot.sh b/docker/matrix/scripts/setup-bot.sh
new file mode 100755
index 0000000..59c541c
--- /dev/null
+++ b/docker/matrix/scripts/setup-bot.sh
@@ -0,0 +1,210 @@
+#!/usr/bin/env bash
+# ==============================================
+# Matrix Bot Account Setup Script
+# ==============================================
+#
+# Creates the Mosaic bot user on the local Synapse instance and retrieves
+# an access token. Idempotent — safe to run multiple times.
+#
+# Usage:
+#   docker/matrix/scripts/setup-bot.sh
+#   docker/matrix/scripts/setup-bot.sh --username custom-bot --password custom-pass
+#
+# Prerequisites:
+#   - Synapse must be running (docker compose -f ... up synapse)
+#   - Synapse must be healthy (check with: curl http://localhost:8008/health)
+#
+# Output:
+#   Prints the environment variables needed for MatrixService configuration.
+#
+# ==============================================
+
+set -euo pipefail
+
+# Defaults
+SYNAPSE_URL="${SYNAPSE_URL:-http://localhost:8008}"
+BOT_USERNAME="${BOT_USERNAME:-mosaic-bot}"
+BOT_PASSWORD="${BOT_PASSWORD:-mosaic-bot-dev-password}"
+BOT_DISPLAY_NAME="${BOT_DISPLAY_NAME:-Mosaic Bot}"
+ADMIN_USERNAME="${ADMIN_USERNAME:-admin}"
+ADMIN_PASSWORD="${ADMIN_PASSWORD:-admin-dev-password}"
+
+# Parse arguments
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --username) BOT_USERNAME="$2"; shift 2 ;;
+    --password) BOT_PASSWORD="$2"; shift 2 ;;
+    --synapse-url) SYNAPSE_URL="$2"; shift 2 ;;
+    --admin-username) ADMIN_USERNAME="$2"; shift 2 ;;
+    --admin-password) ADMIN_PASSWORD="$2"; shift 2 ;;
+    --help|-h)
+      echo "Usage: $0 [OPTIONS]"
+      echo ""
+      echo "Options:"
+      echo "  --username NAME        Bot username (default: mosaic-bot)"
+      echo "  --password PASS        Bot password (default: mosaic-bot-dev-password)"
+      echo "  --synapse-url URL      Synapse URL (default: http://localhost:8008)"
+      echo "  --admin-username NAME  Admin username (default: admin)"
+      echo "  --admin-password PASS  Admin password (default: admin-dev-password)"
+      echo "  --help, -h             Show this help"
+      exit 0
+      ;;
+    *) echo "Unknown option: $1"; exit 1 ;;
+  esac
+done
+
+echo "=== Mosaic Stack — Matrix Bot Setup ==="
+echo ""
+echo "Synapse URL: ${SYNAPSE_URL}"
+echo "Bot username: ${BOT_USERNAME}"
+echo ""
+
+# Wait for Synapse to be ready
+echo "Checking Synapse health..."
+for i in $(seq 1 30); do
+  if curl -fsSo /dev/null "${SYNAPSE_URL}/health" 2>/dev/null; then
+    echo "Synapse is healthy."
+    break
+  fi
+  if [ "$i" -eq 30 ]; then
+    echo "ERROR: Synapse is not responding at ${SYNAPSE_URL}/health after 30 attempts."
+    echo "Make sure Synapse is running:"
+    echo "  docker compose -f docker/docker-compose.yml -f docker/docker-compose.matrix.yml up -d"
+    exit 1
+  fi
+  echo "  Waiting for Synapse... (attempt ${i}/30)"
+  sleep 2
+done
+
+echo ""
+
+# Step 1: Register admin account (if not exists)
+echo "Step 1: Registering admin account '${ADMIN_USERNAME}'..."
+ADMIN_REGISTER_RESPONSE=$(curl -sS -X POST "${SYNAPSE_URL}/_synapse/admin/v1/register" \
+  -H "Content-Type: application/json" \
+  -d "{}" 2>/dev/null || true)
+
+NONCE=$(echo "${ADMIN_REGISTER_RESPONSE}" | python3 -c "import sys,json; print(json.load(sys.stdin).get('nonce',''))" 2>/dev/null || true)
+
+if [ -n "${NONCE}" ]; then
+  # Generate HMAC for admin registration using the nonce
+  # For dev, we use register_new_matrix_user via docker exec instead
+  echo "  Using docker exec to register admin via Synapse CLI..."
+  docker exec mosaic-synapse register_new_matrix_user \
+    -u "${ADMIN_USERNAME}" \
+    -p "${ADMIN_PASSWORD}" \
+    -a \
+    -c /data/homeserver.yaml \
+    http://localhost:8008 2>/dev/null && echo "  Admin account created." || echo "  Admin account already exists (or registration failed — continuing)."
+else
+  echo "  Attempting registration via docker exec..."
+  docker exec mosaic-synapse register_new_matrix_user \
+    -u "${ADMIN_USERNAME}" \
+    -p "${ADMIN_PASSWORD}" \
+    -a \
+    -c /data/homeserver.yaml \
+    http://localhost:8008 2>/dev/null && echo "  Admin account created." || echo "  Admin account already exists (or registration failed — continuing)."
+fi
+
+echo ""
+
+# Step 2: Get admin access token
+echo "Step 2: Obtaining admin access token..."
+ADMIN_LOGIN_RESPONSE=$(curl -sS -X POST "${SYNAPSE_URL}/_matrix/client/v3/login" \
+  -H "Content-Type: application/json" \
+  -d "{
+    \"type\": \"m.login.password\",
+    \"identifier\": {
+      \"type\": \"m.id.user\",
+      \"user\": \"${ADMIN_USERNAME}\"
+    },
+    \"password\": \"${ADMIN_PASSWORD}\"
+  }" 2>/dev/null)
+
+ADMIN_TOKEN=$(echo "${ADMIN_LOGIN_RESPONSE}" | python3 -c "import sys,json; print(json.load(sys.stdin).get('access_token',''))" 2>/dev/null || true)
+
+if [ -z "${ADMIN_TOKEN}" ]; then
+  echo "ERROR: Could not obtain admin access token."
+  echo "Response: ${ADMIN_LOGIN_RESPONSE}"
+  echo ""
+  echo "Try registering the admin account manually:"
+  echo "  docker exec -it mosaic-synapse register_new_matrix_user -u ${ADMIN_USERNAME} -p ${ADMIN_PASSWORD} -a -c /data/homeserver.yaml http://localhost:8008"
+  exit 1
+fi
+echo "  Admin token obtained."
+
+echo ""
+
+# Step 3: Register bot account via admin API (idempotent)
+echo "Step 3: Registering bot account '${BOT_USERNAME}'..."
+BOT_REGISTER_RESPONSE=$(curl -sS -X PUT "${SYNAPSE_URL}/_synapse/admin/v2/users/@${BOT_USERNAME}:localhost" \
+  -H "Authorization: Bearer ${ADMIN_TOKEN}" \
+  -H "Content-Type: application/json" \
+  -d "{
+    \"password\": \"${BOT_PASSWORD}\",
+    \"displayname\": \"${BOT_DISPLAY_NAME}\",
+    \"admin\": false,
+    \"deactivated\": false
+  }" 2>/dev/null)
+
+BOT_EXISTS=$(echo "${BOT_REGISTER_RESPONSE}" | python3 -c "import sys,json; d=json.load(sys.stdin); print('yes' if d.get('name') else 'no')" 2>/dev/null || echo "no")
+
+if [ "${BOT_EXISTS}" = "yes" ]; then
+  echo "  Bot account '@${BOT_USERNAME}:localhost' is ready."
+else
+  echo "  WARNING: Bot registration response unexpected: ${BOT_REGISTER_RESPONSE}"
+  echo "  Continuing anyway — bot may already exist."
+fi
+
+echo ""
+
+# Step 4: Get bot access token
+echo "Step 4: Obtaining bot access token..."
+BOT_LOGIN_RESPONSE=$(curl -sS -X POST "${SYNAPSE_URL}/_matrix/client/v3/login" \
+  -H "Content-Type: application/json" \
+  -d "{
+    \"type\": \"m.login.password\",
+    \"identifier\": {
+      \"type\": \"m.id.user\",
+      \"user\": \"${BOT_USERNAME}\"
+    },
+    \"password\": \"${BOT_PASSWORD}\"
+  }" 2>/dev/null)
+
+BOT_TOKEN=$(echo "${BOT_LOGIN_RESPONSE}" | python3 -c "import sys,json; print(json.load(sys.stdin).get('access_token',''))" 2>/dev/null || true)
+
+if [ -z "${BOT_TOKEN}" ]; then
+  echo "ERROR: Could not obtain bot access token."
+  echo "Response: ${BOT_LOGIN_RESPONSE}"
+  exit 1
+fi
+
+echo "  Bot token obtained."
+echo ""
+
+# Step 5: Output configuration
+echo "============================================"
+echo "  Matrix Bot Setup Complete"
+echo "============================================"
+echo ""
+echo "Add the following to your .env file:"
+echo ""
+echo "  # Matrix Bridge Configuration"
+echo "  MATRIX_HOMESERVER_URL=http://localhost:8008"
+echo "  MATRIX_ACCESS_TOKEN=${BOT_TOKEN}"
+echo "  MATRIX_BOT_USER_ID=@${BOT_USERNAME}:localhost"
+echo "  MATRIX_SERVER_NAME=localhost"
+echo ""
+echo "Or, if running the API inside Docker (same compose network):"
+echo ""
+echo "  MATRIX_HOMESERVER_URL=http://synapse:8008"
+echo "  MATRIX_ACCESS_TOKEN=${BOT_TOKEN}"
+echo "  MATRIX_BOT_USER_ID=@${BOT_USERNAME}:localhost"
+echo "  MATRIX_SERVER_NAME=localhost"
+echo ""
+echo "Element Web is available at: http://localhost:8501"
+echo "  Login with any registered user to test messaging."
+echo ""
+echo "Admin account: ${ADMIN_USERNAME} / ${ADMIN_PASSWORD}"
+echo "Bot account:   ${BOT_USERNAME} / ${BOT_PASSWORD}"
+echo "============================================"
diff --git a/docker/matrix/synapse/homeserver.yaml b/docker/matrix/synapse/homeserver.yaml
new file mode 100644
index 0000000..304387c
--- /dev/null
+++ b/docker/matrix/synapse/homeserver.yaml
@@ -0,0 +1,131 @@
+# ==============================================
+# Synapse Homeserver Configuration — Development Only
+# ==============================================
+#
+# This config is for LOCAL DEVELOPMENT with the Mosaic Stack docker-compose overlay.
+# Do NOT use this in production. See docker-compose.sample.matrix.yml for production.
+#
+# Server name is set to 'localhost' — this is permanent and cannot be changed
+# after the database has been initialized.
+#
+# ==============================================
+
+server_name: "localhost"
+pid_file: /data/homeserver.pid
+public_baseurl: "http://localhost:8008/"
+
+# ======================
+# Network Listeners
+# ======================
+listeners:
+  # Client API (used by Element Web, Mosaic bridge, etc.)
+  - port: 8008
+    tls: false
+    type: http
+    x_forwarded: true
+    bind_addresses: ["0.0.0.0"]
+    resources:
+      - names: [client, federation]
+        compress: false
+
+# ======================
+# Database (Shared PostgreSQL)
+# ======================
+database:
+  name: psycopg2
+  txn_limit: 10000
+  args:
+    user: "synapse"
+    password: "synapse_dev_password"
+    database: "synapse"
+    host: "postgres"
+    port: 5432
+    cp_min: 5
+    cp_max: 10
+
+# ======================
+# Media Storage
+# ======================
+media_store_path: /data/media_store
+max_upload_size: 50M
+url_preview_enabled: true
+url_preview_ip_range_blacklist:
+  - "127.0.0.0/8"
+  - "10.0.0.0/8"
+  - "172.16.0.0/12"
+  - "192.168.0.0/16"
+  - "100.64.0.0/10"
+  - "192.0.0.0/24"
+  - "169.254.0.0/16"
+  - "198.18.0.0/15"
+  - "::1/128"
+  - "fe80::/10"
+  - "fc00::/7"
+  - "2001:db8::/32"
+  - "ff00::/8"
+  - "fec0::/10"
+
+# ======================
+# Registration (Dev Only)
+# ======================
+enable_registration: true
+enable_registration_without_verification: true
+
+# ======================
+# Signing Keys
+# ======================
+# Auto-generated on first startup and persisted in the signing_key volume
+signing_key_path: "/data/keys/localhost.signing.key"
+
+# Suppress warning about trusted key servers in dev
+suppress_key_server_warning: true
+trusted_key_servers: []
+
+# ======================
+# Room Configuration
+# ======================
+enable_room_list_search: true
+allow_public_rooms_over_federation: false
+
+# ======================
+# Rate Limiting (Relaxed for Dev)
+# ======================
+rc_message:
+  per_second: 100
+  burst_count: 200
+
+rc_registration:
+  per_second: 10
+  burst_count: 50
+
+rc_login:
+  address:
+    per_second: 10
+    burst_count: 50
+  account:
+    per_second: 10
+    burst_count: 50
+
+# ======================
+# Logging
+# ======================
+log_config: "/data/localhost.log.config"
+
+# Inline log config — write to stdout for docker logs
+# Synapse falls back to a basic console logger if the log_config file is missing,
+# so we leave log_config pointing to a non-existent file intentionally.
+# Override: mount a custom log config file at /data/localhost.log.config
+
+# ======================
+# Miscellaneous
+# ======================
+report_stats: false
+macaroon_secret_key: "dev-macaroon-secret-change-in-production"
+form_secret: "dev-form-secret-change-in-production"
+
+# Enable presence for dev
+use_presence: true
+
+# Retention policy (optional, keep messages for 180 days in dev)
+retention:
+  enabled: false