diff --git a/Dockerfile b/Dockerfile
index 4001cf7..1af1bb6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -45,9 +45,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 
 ARG BRIDGE_FILE="bridge.yaml"
 
-COPY --chmod=0755 script/entrypoint.sh /entrypoint.sh
-COPY --chmod=0755 script/ros_entrypoint.sh /ros_entrypoint.sh
+COPY --chmod=0755 script/ /
 COPY --chmod=0644 "${BRIDGE_FILE}" /bridge.yaml
+COPY --chmod=0644 config/demo_bridge.yaml /demo_bridge.yaml
 
 ENTRYPOINT ["/ros_entrypoint.sh"]
 CMD ["bash"]
diff --git a/README.md b/README.md
index d928419..67db8a1 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@
 - [Quick Start](#quick-start)
 - [Usage](#usage)
 - [Bridge Configuration](#bridge-configuration)
+- [Demo](#demo)
 - [Architecture](#architecture)
 - [Directory Structure](#directory-structure)
 
@@ -127,6 +128,41 @@ services_2_to_1:
     type: rcl_interfaces/GetParameters
 ```
 
+## Demo
+
+Two-terminal end-to-end bridge demo using `std_msgs/String`. Both demos
+use the same pattern: a **server** terminal that owns `roscore` +
+`parameter_bridge` (loaded from the baked-in `/demo_bridge.yaml`), and a
+**client** terminal that just subscribes.
+
+| Demo | Terminal 1 (server) | Terminal 2 (client) |
+|------|---------------------|---------------------|
+| A — ROS 1 → ROS 2 | `./exec.sh /ros1_server.sh` | `./exec.sh /ros2_client.sh` |
+| B — ROS 2 → ROS 1 | `./exec.sh /ros2_server.sh` | `./exec.sh /ros1_client.sh` |
+
+Steps (assuming the container is up via `./run.sh -d`):
+
+```bash
+# Terminal 1 (server) — pick one demo
+./exec.sh /ros1_server.sh    # Demo A
+./exec.sh /ros2_server.sh    # Demo B
+
+# Terminal 2 (client) — matching pair
+./exec.sh /ros2_client.sh    # Demo A
+./exec.sh /ros1_client.sh    # Demo B
+```
+
+Server scripts log every step (`[ros1_server] step N/5: ...`) so it's
+clear when `roscore` and `parameter_bridge` are up. Override the
+published string with `MESSAGE`:
+
+```bash
+./exec.sh env MESSAGE="hi from ROS 1" /ros1_server.sh
+```
+
+`Ctrl+C` on the server terminal tears down `parameter_bridge` and
+`roscore`; the client terminal then EOFs.
+
 ## Architecture
 
 ```mermaid
@@ -169,11 +205,16 @@ ros1_bridge/
 ├── template/                    # Shared scripts, tests, CI (git subtree)
 ├── script/
 │   ├── entrypoint.sh            # Sources ROS 1 + ROS 2, loads bridge config
-│   └── ros_entrypoint.sh        # ROS env only (osrf-compatible)
+│   ├── ros_entrypoint.sh        # ROS env only (osrf-compatible)
+│   ├── ros1_server.sh           # Demo A publisher (bootstraps roscore + bridge)
+│   ├── ros1_client.sh           # Demo B subscriber
+│   ├── ros2_server.sh           # Demo B publisher (bootstraps roscore + bridge)
+│   └── ros2_client.sh           # Demo A subscriber
 ├── bridge.yaml                  # Default bridge configuration
 ├── config/                      # Additional bridge configs
 │   ├── scan_bridge.yaml         # LaserScan bridge
-│   └── release_bridge.yaml      # Camera + depth bridge
+│   ├── release_bridge.yaml      # Camera + depth bridge
+│   └── demo_bridge.yaml         # Demo bidirectional std_msgs/String
 ├── doc/                         # Translated READMEs
 │   ├── README.zh-TW.md          # Traditional Chinese
 │   ├── README.zh-CN.md          # Simplified Chinese
diff --git a/config/demo_bridge.yaml b/config/demo_bridge.yaml
new file mode 100644
index 0000000..1dff798
--- /dev/null
+++ b/config/demo_bridge.yaml
@@ -0,0 +1,9 @@
+# Demo bridge config — std_msgs/String, both directions.
+# Used by script/ros{1,2}_server.sh via parameter_bridge.
+topics:
+  - topic: /chatter_1to2
+    type: std_msgs/msg/String
+    queue_size: 10
+  - topic: /chatter_2to1
+    type: std_msgs/msg/String
+    queue_size: 10
diff --git a/doc/README.ja.md b/doc/README.ja.md
index 2576eae..1adcc1e 100644
--- a/doc/README.ja.md
+++ b/doc/README.ja.md
@@ -16,6 +16,7 @@
 - [クイックスタート](#クイックスタート)
 - [使い方](#使い方)
 - [ブリッジ設定](#ブリッジ設定)
+- [Demo](#demo)
 - [アーキテクチャ](#アーキテクチャ)
 - [ディレクトリ構成](#ディレクトリ構成)
 
@@ -127,6 +128,43 @@ services_2_to_1:
     type: rcl_interfaces/GetParameters
 ```
 
+## Demo
+
+2 つの terminal でエンドツーエンドの bridge デモを実行します。
+メッセージ型は `std_msgs/String`。パターンは対称で、**server**
+terminal が `roscore` + `parameter_bridge`(ビルド時にイメージへ
+焼き込まれた `/demo_bridge.yaml` を読み込む)を起動し、**client**
+terminal は subscribe するだけです。
+
+| Demo | Terminal 1 (server) | Terminal 2 (client) |
+|------|---------------------|---------------------|
+| A — ROS 1 → ROS 2 | `./exec.sh /ros1_server.sh` | `./exec.sh /ros2_client.sh` |
+| B — ROS 2 → ROS 1 | `./exec.sh /ros2_server.sh` | `./exec.sh /ros1_client.sh` |
+
+実際の手順(コンテナを `./run.sh -d` で起動済みとして):
+
+```bash
+# Terminal 1 (server) — どちらかを選択
+./exec.sh /ros1_server.sh    # Demo A
+./exec.sh /ros2_server.sh    # Demo B
+
+# Terminal 2 (client) — 対応するもう一方
+./exec.sh /ros2_client.sh    # Demo A
+./exec.sh /ros1_client.sh    # Demo B
+```
+
+Server スクリプトは各ステップを明示的にログ出力します
+(`[ros1_server] step N/5: ...`)。`roscore` と `parameter_bridge` が
+いつ準備完了になったかが一目で分かります。Publish するメッセージは
+`MESSAGE` 環境変数で上書き可能です:
+
+```bash
+./exec.sh env MESSAGE="hi from ROS 1" /ros1_server.sh
+```
+
+Server terminal で `Ctrl+C` を押すと `parameter_bridge` と `roscore`
+を停止し、client terminal も EOF になります。
+
 ## アーキテクチャ
 
 ```mermaid
@@ -169,11 +207,16 @@ ros1_bridge/
 ├── template/                    # 共有スクリプト、テスト、CI（git subtree）
 ├── script/
 │   ├── entrypoint.sh            # ROS 1 + ROS 2 を source、bridge 設定を読み込み
-│   └── ros_entrypoint.sh        # ROS 環境のみ source（osrf 互換）
+│   ├── ros_entrypoint.sh        # ROS 環境のみ source（osrf 互換）
+│   ├── ros1_server.sh           # Demo A publisher（roscore + bridge を自起動）
+│   ├── ros1_client.sh           # Demo B subscriber
+│   ├── ros2_server.sh           # Demo B publisher（roscore + bridge を自起動）
+│   └── ros2_client.sh           # Demo A subscriber
 ├── bridge.yaml                  # デフォルト bridge 設定
 ├── config/                      # 追加 bridge 設定
 │   ├── scan_bridge.yaml         # LaserScan bridge
-│   └── release_bridge.yaml      # Camera + depth bridge
+│   ├── release_bridge.yaml      # Camera + depth bridge
+│   └── demo_bridge.yaml         # Demo 双方向 std_msgs/String
 ├── doc/                         # 翻訳版 README
 │   ├── README.zh-TW.md          # 繁体字中国語
 │   ├── README.zh-CN.md          # 簡体字中国語
diff --git a/doc/README.zh-CN.md b/doc/README.zh-CN.md
index 2508cdf..206972d 100644
--- a/doc/README.zh-CN.md
+++ b/doc/README.zh-CN.md
@@ -16,6 +16,7 @@
 - [快速开始](#快速开始)
 - [使用方式](#使用方式)
 - [Bridge 设置](#bridge-设置)
+- [Demo](#demo)
 - [架构](#架构)
 - [目录结构](#目录结构)
 
@@ -126,6 +127,40 @@ services_2_to_1:
     type: rcl_interfaces/GetParameters
 ```
 
+## Demo
+
+两个 terminal 跑 end-to-end bridge demo，消息类型 `std_msgs/String`。
+规则对称:**server** terminal 负责起 `roscore` + `parameter_bridge`
+(读 build 时烤进 image 的 `/demo_bridge.yaml`)，**client** terminal 只订阅。
+
+| Demo | Terminal 1 (server) | Terminal 2 (client) |
+|------|---------------------|---------------------|
+| A — ROS 1 → ROS 2 | `./exec.sh /ros1_server.sh` | `./exec.sh /ros2_client.sh` |
+| B — ROS 2 → ROS 1 | `./exec.sh /ros2_server.sh` | `./exec.sh /ros1_client.sh` |
+
+实际操作(假设容器已用 `./run.sh -d` 起好):
+
+```bash
+# Terminal 1 (server) — 二选一
+./exec.sh /ros1_server.sh    # Demo A
+./exec.sh /ros2_server.sh    # Demo B
+
+# Terminal 2 (client) — 对应的另一半
+./exec.sh /ros2_client.sh    # Demo A
+./exec.sh /ros1_client.sh    # Demo B
+```
+
+Server 脚本每一步都打印进度(`[ros1_server] step N/5: ...`)，所以
+`roscore` 跟 `parameter_bridge` 何时就绪一目了然。要换消息字串用
+`MESSAGE` 环境变量:
+
+```bash
+./exec.sh env MESSAGE="hi from ROS 1" /ros1_server.sh
+```
+
+Server terminal 按 `Ctrl+C` 会收掉 `parameter_bridge` 跟 `roscore`，
+client terminal 接着就 EOF。
+
 ## 架构
 
 ```mermaid
@@ -168,11 +203,16 @@ ros1_bridge/
 ├── template/                    # 共用脚本、测试、CI（git subtree）
 ├── script/
 │   ├── entrypoint.sh            # Source ROS 1 + ROS 2，载入 bridge 设置
-│   └── ros_entrypoint.sh        # 仅 source ROS 环境（兼容 osrf）
+│   ├── ros_entrypoint.sh        # 仅 source ROS 环境（兼容 osrf）
+│   ├── ros1_server.sh           # Demo A publisher（自起 roscore + bridge）
+│   ├── ros1_client.sh           # Demo B subscriber
+│   ├── ros2_server.sh           # Demo B publisher（自起 roscore + bridge）
+│   └── ros2_client.sh           # Demo A subscriber
 ├── bridge.yaml                  # 默认 bridge 设置
 ├── config/                      # 额外 bridge 设置
 │   ├── scan_bridge.yaml         # LaserScan bridge
-│   └── release_bridge.yaml      # Camera + depth bridge
+│   ├── release_bridge.yaml      # Camera + depth bridge
+│   └── demo_bridge.yaml         # Demo 双向 std_msgs/String
 ├── doc/                         # 翻译版 README
 │   ├── README.zh-TW.md          # 繁体中文
 │   ├── README.zh-CN.md          # 简体中文
diff --git a/doc/README.zh-TW.md b/doc/README.zh-TW.md
index 101c129..6526256 100644
--- a/doc/README.zh-TW.md
+++ b/doc/README.zh-TW.md
@@ -16,6 +16,7 @@
 - [快速開始](#快速開始)
 - [使用方式](#使用方式)
 - [Bridge 設定](#bridge-設定)
+- [Demo](#demo)
 - [架構](#架構)
 - [目錄結構](#目錄結構)
 
@@ -126,6 +127,40 @@ services_2_to_1:
     type: rcl_interfaces/GetParameters
 ```
 
+## Demo
+
+兩個 terminal 跑 end-to-end bridge demo，訊息型別 `std_msgs/String`。
+規則對稱:**server** terminal 負責起 `roscore` + `parameter_bridge`
+(讀 build 時烤進 image 的 `/demo_bridge.yaml`)，**client** terminal 只訂閱。
+
+| Demo | Terminal 1 (server) | Terminal 2 (client) |
+|------|---------------------|---------------------|
+| A — ROS 1 → ROS 2 | `./exec.sh /ros1_server.sh` | `./exec.sh /ros2_client.sh` |
+| B — ROS 2 → ROS 1 | `./exec.sh /ros2_server.sh` | `./exec.sh /ros1_client.sh` |
+
+實際操作(假設容器已用 `./run.sh -d` 起好):
+
+```bash
+# Terminal 1 (server) — 二選一
+./exec.sh /ros1_server.sh    # Demo A
+./exec.sh /ros2_server.sh    # Demo B
+
+# Terminal 2 (client) — 對應的另一半
+./exec.sh /ros2_client.sh    # Demo A
+./exec.sh /ros1_client.sh    # Demo B
+```
+
+Server 腳本每一步都印出進度(`[ros1_server] step N/5: ...`)，所以
+`roscore` 跟 `parameter_bridge` 何時就緒一目了然。要換訊息字串用
+`MESSAGE` 環境變數:
+
+```bash
+./exec.sh env MESSAGE="hi from ROS 1" /ros1_server.sh
+```
+
+Server terminal 按 `Ctrl+C` 會收掉 `parameter_bridge` 跟 `roscore`，
+client terminal 接著就 EOF。
+
 ## 架構
 
 ```mermaid
@@ -168,11 +203,16 @@ ros1_bridge/
 ├── template/                    # 共用腳本、測試、CI（git subtree）
 ├── script/
 │   ├── entrypoint.sh            # Source ROS 1 + ROS 2，載入 bridge 設定
-│   └── ros_entrypoint.sh        # 僅 source ROS 環境（相容 osrf）
+│   ├── ros_entrypoint.sh        # 僅 source ROS 環境（相容 osrf）
+│   ├── ros1_server.sh           # Demo A publisher（自起 roscore + bridge）
+│   ├── ros1_client.sh           # Demo B subscriber
+│   ├── ros2_server.sh           # Demo B publisher（自起 roscore + bridge）
+│   └── ros2_client.sh           # Demo A subscriber
 ├── bridge.yaml                  # 預設 bridge 設定
 ├── config/                      # 額外 bridge 設定
 │   ├── scan_bridge.yaml         # LaserScan bridge
-│   └── release_bridge.yaml      # Camera + depth bridge
+│   ├── release_bridge.yaml      # Camera + depth bridge
+│   └── demo_bridge.yaml         # Demo 雙向 std_msgs/String
 ├── doc/                         # 翻譯版 README
 │   ├── README.zh-TW.md          # 繁體中文
 │   ├── README.zh-CN.md          # 簡體中文
diff --git a/doc/changelog/CHANGELOG.md b/doc/changelog/CHANGELOG.md
index 2f4ed23..cda6992 100644
--- a/doc/changelog/CHANGELOG.md
+++ b/doc/changelog/CHANGELOG.md
@@ -19,12 +19,20 @@ versioning follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - Rebuild `devel` stage from `ros:foxy-ros-base-focal` (multi-arch) plus the ROS 1 snapshot apt repo instead of the amd64-only `osrf/ros:foxy-ros1-bridge`. Enables Jetson (arm64) support.
 - `ENV ROS1_DISTRO=noetic` / `ENV ROS2_DISTRO=foxy` now baked into the image so downstream scripts can reference the distro names without hardcoding.
 - Test stage lint target uses `COPY script/*.sh /lint/` (glob) to pick up new scripts automatically.
+- Dockerfile `COPY` for `script/` switched from per-file (`entrypoint.sh`, `ros_entrypoint.sh`) to directory glob (`COPY --chmod=0755 script/ /`) so new helpers (the four demo scripts) are picked up without further Dockerfile edits.
 - Bridge YAML examples now document the full `parameter_bridge` schema: `bridge.yaml` ships `services_1_to_2` / `services_2_to_1` entries and an inline QoS block on `/scan`; `config/scan_bridge.yaml` and `config/release_bridge.yaml` set sensor-data QoS (BEST_EFFORT for image streams, RELIABLE for `camera_info`). READMEs in all four languages note the topic (ROS 2) vs service (ROS 1) `type` format asymmetry.
 - **Split `devel` and `runtime` into separate stages (USER-VISIBLE BEHAVIOR CHANGE).** `devel` CMD is now `bash` — `./run.sh` drops into an interactive shell instead of auto-launching `parameter_bridge`. `devel` ENTRYPOINT is `/ros_entrypoint.sh` (sources ROS1+ROS2 env only, no `rosparam load`) so the shell is usable immediately. The new `runtime` stage (`FROM devel`) keeps `CMD ["ros2", "run", "ros1_bridge", "parameter_bridge"]` and switches ENTRYPOINT back to `/entrypoint.sh` (which does `rosparam load /bridge.yaml` before launch) for production-style auto-bridge deployments. CI builds both (`build_runtime: true` in `main.yaml`). Note: `./run.sh runtime` does not yet work because the auto-generated `compose.yaml` does not emit a `runtime` service (tracked upstream in template); invoke runtime via direct `docker build --target runtime && docker run` until template provides this.
 
 ### Added
 - `script/ros_entrypoint.sh` — osrf-compatible entrypoint that only sources both ROS distros (no `rosparam load`), available at `/ros_entrypoint.sh` in the image. `devel` stage uses this as its `ENTRYPOINT`; `runtime` stage keeps `/entrypoint.sh` (with `rosparam load`).
-- Smoke tests: `ROS1_DISTRO`/`ROS2_DISTRO` env vars, `/ros_entrypoint.sh` existence + ability to source both ROS envs + expose `ros2`.
+- **Demo scripts** — symmetric server/client pairs that run a 2-terminal end-to-end bridge demo with std_msgs/String. Each `*_server.sh` self-bootstraps `roscore` + `parameter_bridge` (loading `/demo_bridge.yaml`) before publishing, with explicit step-by-step logs (`[ros1_server] step N/5: ...`); each `*_client.sh` only sources the relevant distro and subscribes. Trap on the server tears down `roscore` + bridge on Ctrl+C.
+  - `script/ros1_server.sh` — Demo A publisher: bootstraps + `rostopic pub /chatter_1to2 std_msgs/String`. Pair with `ros2_client.sh`.
+  - `script/ros2_client.sh` — Demo A subscriber: `ros2 topic echo /chatter_1to2`.
+  - `script/ros2_server.sh` — Demo B publisher: bootstraps + `ros2 topic pub /chatter_2to1 std_msgs/msg/String`. Pair with `ros1_client.sh`.
+  - `script/ros1_client.sh` — Demo B subscriber: `rostopic echo /chatter_2to1`.
+  - `MESSAGE` env var overrides the published string on either server.
+- `config/demo_bridge.yaml` — bidirectional `std_msgs/msg/String` bridge for `/chatter_1to2` and `/chatter_2to1`, baked into the image as `/demo_bridge.yaml` so the demo scripts pick it up without env overrides.
+- Smoke tests: `ROS1_DISTRO`/`ROS2_DISTRO` env vars, `/ros_entrypoint.sh` existence + ability to source both ROS envs + expose `ros2`, plus 9 new demo-helper tests (4 scripts exist+executable, 4 `-h` prints `Usage:`, `/demo_bridge.yaml` exists). Total: 28 → 37.
 
 ### Removed
 - `COPY config/ /config/` from Dockerfile and the `config directory exists` smoke test — the `/config/` directory was never read at runtime (entrypoint only loads `/bridge.yaml`). `config/*.yaml` files remain in the repo as reference examples and can still be consumed via `--build-arg BRIDGE_FILE=config/<file>.yaml`.
diff --git a/doc/test/TEST.md b/doc/test/TEST.md
index ff6b26d..655fb28 100644
--- a/doc/test/TEST.md
+++ b/doc/test/TEST.md
@@ -1,6 +1,6 @@
 # TEST.md
 
-**29 tests** total.
+**38 tests** total.
 
 ## test/smoke/ros_env.bats
 
@@ -21,7 +21,7 @@
 |------|-------------|
 | `ros1_bridge package is available` | `ros2 pkg list` includes ros1_bridge |
 
-### Bridge config (5)
+### Bridge config (6)
 
 | Test | Description |
 |------|-------------|
@@ -32,6 +32,20 @@
 | `ros_entrypoint.sh exposes ros2 command` | `ros2` binary is on `PATH` after entrypoint |
 | `entrypoint.sh skips rosparam load when roscore unreachable` | `timeout 2 rosparam list` guards the `rosparam load` so a missing roscore doesn't hang container boot |
 
+### Demo helpers (9)
+
+| Test | Description |
+|------|-------------|
+| `demo_bridge.yaml exists` | `/demo_bridge.yaml` exists (built into image from `config/demo_bridge.yaml`) |
+| `ros1_server.sh exists and is executable` | `/ros1_server.sh` is executable |
+| `ros1_client.sh exists and is executable` | `/ros1_client.sh` is executable |
+| `ros2_server.sh exists and is executable` | `/ros2_server.sh` is executable |
+| `ros2_client.sh exists and is executable` | `/ros2_client.sh` is executable |
+| `ros1_server.sh -h prints usage` | Help exits 0 with "Usage:" |
+| `ros1_client.sh -h prints usage` | Help exits 0 with "Usage:" |
+| `ros2_server.sh -h prints usage` | Help exits 0 with "Usage:" |
+| `ros2_client.sh -h prints usage` | Help exits 0 with "Usage:" |
+
 ## test/smoke/script_help.bats
 
 ### build.sh (3)
diff --git a/script/ros1_client.sh b/script/ros1_client.sh
new file mode 100755
index 0000000..76d9e86
--- /dev/null
+++ b/script/ros1_client.sh
@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+#
+# Demo B — ROS 1 client (subscriber).
+#
+# Subscribes to /chatter_2to1 from ROS 1. Run ros2_server.sh on the other
+# terminal first — it owns roscore + parameter_bridge.
+
+set -e
+
+readonly TOPIC="/chatter_2to1"
+
+usage() {
+    cat >&2 <<EOF
+Usage: ros1_client.sh [-h|--help]
+
+Demo B (ROS 2 -> ROS 1) — client / subscriber side.
+
+Subscribes to ${TOPIC} from ROS 1. Start ros2_server.sh on a second
+terminal first — it owns roscore + parameter_bridge.
+EOF
+}
+
+log() {
+    printf '[ros1_client] %s\n' "$*"
+}
+
+main() {
+    case "${1:-}" in
+        -h|--help) usage; exit 0 ;;
+    esac
+
+    log "step 1/2: sourcing ROS 1 (${ROS1_DISTRO})"
+    unset ROS_DISTRO
+    # shellcheck source=/dev/null
+    source "/opt/ros/${ROS1_DISTRO}/setup.bash"
+
+    log "step 2/2: subscribing to ${TOPIC} (Ctrl+C to stop)"
+    rostopic echo "${TOPIC}"
+}
+
+main "$@"
diff --git a/script/ros1_server.sh b/script/ros1_server.sh
new file mode 100755
index 0000000..4609d56
--- /dev/null
+++ b/script/ros1_server.sh
@@ -0,0 +1,102 @@
+#!/usr/bin/env bash
+#
+# Demo A — ROS 1 server (publisher).
+#
+# Bootstraps roscore + parameter_bridge (using /demo_bridge.yaml), then
+# publishes std_msgs/String "${MESSAGE}" on /chatter_1to2 at 1 Hz from ROS 1.
+# Pair with ros2_client.sh on a second terminal.
+#
+# Each command runs in its own subshell so ROS 1 and ROS 2 envs never
+# collide — sourcing both into one shell breaks roscore (Python imports
+# ROS 2's rosgraph_msgs.Log instead of ROS 1's).
+
+set -e
+
+readonly TOPIC="/chatter_1to2"
+readonly BRIDGE_YAML="/demo_bridge.yaml"
+readonly DEFAULT_MESSAGE="hello from ROS 1"
+
+usage() {
+    cat >&2 <<EOF
+Usage: ros1_server.sh [-h|--help]
+
+Demo A (ROS 1 -> ROS 2) — server / publisher side.
+
+Bootstraps roscore + parameter_bridge from ${BRIDGE_YAML}, then publishes
+std_msgs/String on ${TOPIC} at 1 Hz from ROS 1.
+
+Pair with ros2_client.sh on a second terminal.
+
+Environment:
+  MESSAGE   Override the published string (default: "${DEFAULT_MESSAGE}").
+EOF
+}
+
+log() {
+    printf '[ros1_server] %s\n' "$*"
+}
+
+# Source ROS 1 only (for roscore, rostopic, rosparam).
+ros1_env() {
+    unset ROS_DISTRO
+    # shellcheck source=/dev/null
+    source "/opt/ros/${ROS1_DISTRO}/setup.bash" >/dev/null 2>&1
+}
+
+# Source ROS 1 then ROS 2 (for parameter_bridge — needs both).
+both_env() {
+    ros1_env
+    unset ROS_DISTRO
+    # shellcheck source=/dev/null
+    source "/opt/ros/${ROS2_DISTRO}/setup.bash" >/dev/null 2>&1
+}
+
+cleanup() {
+    log "shutting down (parameter_bridge + roscore)..."
+    [[ -n "${BRIDGE_PID:-}" ]] && kill "${BRIDGE_PID}" 2>/dev/null || true
+    [[ -n "${ROSCORE_PID:-}" ]] && kill "${ROSCORE_PID}" 2>/dev/null || true
+    wait 2>/dev/null || true
+    log "done."
+}
+
+main() {
+    case "${1:-}" in
+        -h|--help) usage; exit 0 ;;
+    esac
+
+    local message="${MESSAGE:-${DEFAULT_MESSAGE}}"
+
+    log "step 1/4: starting roscore in background — ROS 1 only env (log: /tmp/roscore.log)"
+    ( ros1_env; exec roscore ) >/tmp/roscore.log 2>&1 &
+    ROSCORE_PID="${!}"
+    trap cleanup EXIT INT TERM
+
+    log "        waiting for rosmaster..."
+    until ( ros1_env; rostopic list ) >/dev/null 2>&1; do sleep 0.2; done
+    log "        rosmaster ready (pid=${ROSCORE_PID})"
+
+    log "step 2/4: loading bridge config from ${BRIDGE_YAML} — ROS 1 env"
+    ( ros1_env; exec rosparam load "${BRIDGE_YAML}" )
+
+    log "step 3/4: starting parameter_bridge in background — ROS 1 + ROS 2 env (log: /tmp/bridge.log)"
+    ( both_env; exec ros2 run ros1_bridge parameter_bridge ) >/tmp/bridge.log 2>&1 &
+    BRIDGE_PID="${!}"
+
+    log "        waiting for bridge to expose ${TOPIC} (timeout 10s)..."
+    local i=0
+    until ( ros1_env; rostopic list ) 2>/dev/null | grep -qx "${TOPIC}"; do
+        i=$((i + 1))
+        if [[ "${i}" -gt 50 ]]; then
+            log "        WARNING: ${TOPIC} not seen after 10s — continuing anyway."
+            break
+        fi
+        sleep 0.2
+    done
+    log "        bridge ready (pid=${BRIDGE_PID})"
+
+    log "step 4/4: publishing on ${TOPIC} at 1 Hz: \"${message}\" — ROS 1 env"
+    log "        Ctrl+C to stop everything."
+    ( ros1_env; exec rostopic pub -r 1 "${TOPIC}" std_msgs/String "data: '${message}'" )
+}
+
+main "$@"
diff --git a/script/ros2_client.sh b/script/ros2_client.sh
new file mode 100755
index 0000000..76f2462
--- /dev/null
+++ b/script/ros2_client.sh
@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+#
+# Demo A — ROS 2 client (subscriber).
+#
+# Subscribes to /chatter_1to2 from ROS 2. Run ros1_server.sh on the other
+# terminal first — it owns roscore + parameter_bridge.
+
+set -e
+
+readonly TOPIC="/chatter_1to2"
+
+usage() {
+    cat >&2 <<EOF
+Usage: ros2_client.sh [-h|--help]
+
+Demo A (ROS 1 -> ROS 2) — client / subscriber side.
+
+Subscribes to ${TOPIC} from ROS 2. Start ros1_server.sh on a second
+terminal first — it owns roscore + parameter_bridge.
+EOF
+}
+
+log() {
+    printf '[ros2_client] %s\n' "$*"
+}
+
+main() {
+    case "${1:-}" in
+        -h|--help) usage; exit 0 ;;
+    esac
+
+    log "step 1/2: sourcing ROS 2 (${ROS2_DISTRO})"
+    unset ROS_DISTRO
+    # shellcheck source=/dev/null
+    source "/opt/ros/${ROS2_DISTRO}/setup.bash"
+
+    log "step 2/2: subscribing to ${TOPIC} (Ctrl+C to stop)"
+    ros2 topic echo "${TOPIC}" std_msgs/msg/String
+}
+
+main "$@"
diff --git a/script/ros2_server.sh b/script/ros2_server.sh
new file mode 100755
index 0000000..46a5736
--- /dev/null
+++ b/script/ros2_server.sh
@@ -0,0 +1,107 @@
+#!/usr/bin/env bash
+#
+# Demo B — ROS 2 server (publisher).
+#
+# Bootstraps roscore + parameter_bridge (using /demo_bridge.yaml), then
+# publishes std_msgs/msg/String "${MESSAGE}" on /chatter_2to1 at 1 Hz from
+# ROS 2. Pair with ros1_client.sh on a second terminal.
+#
+# Each command runs in its own subshell so ROS 1 and ROS 2 envs never
+# collide — sourcing both into one shell breaks roscore (Python imports
+# ROS 2's rosgraph_msgs.Log instead of ROS 1's).
+
+set -e
+
+readonly TOPIC="/chatter_2to1"
+readonly BRIDGE_YAML="/demo_bridge.yaml"
+readonly DEFAULT_MESSAGE="hello from ROS 2"
+
+usage() {
+    cat >&2 <<EOF
+Usage: ros2_server.sh [-h|--help]
+
+Demo B (ROS 2 -> ROS 1) — server / publisher side.
+
+Bootstraps roscore + parameter_bridge from ${BRIDGE_YAML}, then publishes
+std_msgs/msg/String on ${TOPIC} at 1 Hz from ROS 2.
+
+Pair with ros1_client.sh on a second terminal.
+
+Environment:
+  MESSAGE   Override the published string (default: "${DEFAULT_MESSAGE}").
+EOF
+}
+
+log() {
+    printf '[ros2_server] %s\n' "$*"
+}
+
+# Source ROS 1 only (for roscore, rostopic, rosparam).
+ros1_env() {
+    unset ROS_DISTRO
+    # shellcheck source=/dev/null
+    source "/opt/ros/${ROS1_DISTRO}/setup.bash" >/dev/null 2>&1
+}
+
+# Source ROS 2 only (for ros2 CLI).
+ros2_env() {
+    unset ROS_DISTRO
+    # shellcheck source=/dev/null
+    source "/opt/ros/${ROS2_DISTRO}/setup.bash" >/dev/null 2>&1
+}
+
+# Source ROS 1 then ROS 2 (for parameter_bridge — needs both).
+both_env() {
+    ros1_env
+    ros2_env
+}
+
+cleanup() {
+    log "shutting down (parameter_bridge + roscore)..."
+    [[ -n "${BRIDGE_PID:-}" ]] && kill "${BRIDGE_PID}" 2>/dev/null || true
+    [[ -n "${ROSCORE_PID:-}" ]] && kill "${ROSCORE_PID}" 2>/dev/null || true
+    wait 2>/dev/null || true
+    log "done."
+}
+
+main() {
+    case "${1:-}" in
+        -h|--help) usage; exit 0 ;;
+    esac
+
+    local message="${MESSAGE:-${DEFAULT_MESSAGE}}"
+
+    log "step 1/4: starting roscore in background — ROS 1 only env (log: /tmp/roscore.log)"
+    ( ros1_env; exec roscore ) >/tmp/roscore.log 2>&1 &
+    ROSCORE_PID="${!}"
+    trap cleanup EXIT INT TERM
+
+    log "        waiting for rosmaster..."
+    until ( ros1_env; rostopic list ) >/dev/null 2>&1; do sleep 0.2; done
+    log "        rosmaster ready (pid=${ROSCORE_PID})"
+
+    log "step 2/4: loading bridge config from ${BRIDGE_YAML} — ROS 1 env"
+    ( ros1_env; exec rosparam load "${BRIDGE_YAML}" )
+
+    log "step 3/4: starting parameter_bridge in background — ROS 1 + ROS 2 env (log: /tmp/bridge.log)"
+    ( both_env; exec ros2 run ros1_bridge parameter_bridge ) >/tmp/bridge.log 2>&1 &
+    BRIDGE_PID="${!}"
+
+    log "        waiting for bridge to expose ${TOPIC} (timeout 10s)..."
+    local i=0
+    until ( ros2_env; ros2 topic list ) 2>/dev/null | grep -qx "${TOPIC}"; do
+        i=$((i + 1))
+        if [[ "${i}" -gt 50 ]]; then
+            log "        WARNING: ${TOPIC} not seen after 10s — continuing anyway."
+            break
+        fi
+        sleep 0.2
+    done
+    log "        bridge ready (pid=${BRIDGE_PID})"
+
+    log "step 4/4: publishing on ${TOPIC} at 1 Hz: \"${message}\" — ROS 2 env"
+    log "        Ctrl+C to stop everything."
+    ( ros2_env; exec ros2 topic pub -r 1 "${TOPIC}" std_msgs/msg/String "{data: '${message}'}" )
+}
+
+main "$@"
diff --git a/test/smoke/ros_env.bats b/test/smoke/ros_env.bats
index 077c1aa..5b47a9c 100644
--- a/test/smoke/ros_env.bats
+++ b/test/smoke/ros_env.bats
@@ -79,3 +79,49 @@ setup() {
     assert_output --partial "roscore not reachable"
     assert_output --partial "hello"
 }
+
+# -------------------- Demo helpers --------------------
+
+@test "demo_bridge.yaml exists" {
+    assert [ -f "/demo_bridge.yaml" ]
+}
+
+@test "ros1_server.sh exists and is executable" {
+    assert [ -x "/ros1_server.sh" ]
+}
+
+@test "ros1_client.sh exists and is executable" {
+    assert [ -x "/ros1_client.sh" ]
+}
+
+@test "ros2_server.sh exists and is executable" {
+    assert [ -x "/ros2_server.sh" ]
+}
+
+@test "ros2_client.sh exists and is executable" {
+    assert [ -x "/ros2_client.sh" ]
+}
+
+@test "ros1_server.sh -h prints usage" {
+    run bash /ros1_server.sh -h
+    assert_success
+    assert_line --partial "Usage:"
+}
+
+@test "ros1_client.sh -h prints usage" {
+    run bash /ros1_client.sh -h
+    assert_success
+    assert_line --partial "Usage:"
+}
+
+@test "ros2_server.sh -h prints usage" {
+    run bash /ros2_server.sh -h
+    assert_success
+    assert_line --partial "Usage:"
+}
+
+@test "ros2_client.sh -h prints usage" {
+    run bash /ros2_client.sh -h
+    assert_success
+    assert_line --partial "Usage:"
+}