diff --git a/.agents/plugins/marketplace.json b/.agents/plugins/marketplace.json
index a9b4e66..8a2f91b 100644
--- a/.agents/plugins/marketplace.json
+++ b/.agents/plugins/marketplace.json
@@ -43,7 +43,7 @@
         "source": "url",
         "url": "https://gitea.jsc.idv.tw/plugins/hooks.git"
       },
-      "description": "跨 CLI hooks：STE100 語言強制、工時計時、技能用量記錄"
+      "description": "跨 CLI hooks：STE100 語言強制、工時計時、技能用量記錄、SDLC 模型鎖、版本前置檢查"
     },
     {
       "name": "jsc-log",
@@ -75,7 +75,7 @@
         "source": "url",
         "url": "https://gitea.jsc.idv.tw/plugins/review.git"
       },
-      "description": "程式碼審查：Refactoring 壞味道六組 + 註解規範 + 淺模組"
+      "description": "程式碼審查：Refactoring 壞味道六組、註解規範、淺模組"
     },
     {
       "name": "jsc-sdlc",
@@ -83,7 +83,7 @@
         "source": "url",
         "url": "https://gitea.jsc.idv.tw/plugins/sdlc.git"
       },
-      "description": "開發生命週期：規劃/分析/實作/維護（wiki 追蹤）"
+      "description": "開發生命週期：規劃、分析、實作、維護（wiki 追蹤）"
     }
   ]
 }
diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
index a9b4e66..8a2f91b 100644
--- a/.claude-plugin/marketplace.json
+++ b/.claude-plugin/marketplace.json
@@ -43,7 +43,7 @@
         "source": "url",
         "url": "https://gitea.jsc.idv.tw/plugins/hooks.git"
       },
-      "description": "跨 CLI hooks：STE100 語言強制、工時計時、技能用量記錄"
+      "description": "跨 CLI hooks：STE100 語言強制、工時計時、技能用量記錄、SDLC 模型鎖、版本前置檢查"
     },
     {
       "name": "jsc-log",
@@ -75,7 +75,7 @@
         "source": "url",
         "url": "https://gitea.jsc.idv.tw/plugins/review.git"
       },
-      "description": "程式碼審查：Refactoring 壞味道六組 + 註解規範 + 淺模組"
+      "description": "程式碼審查：Refactoring 壞味道六組、註解規範、淺模組"
     },
     {
       "name": "jsc-sdlc",
@@ -83,7 +83,7 @@
         "source": "url",
         "url": "https://gitea.jsc.idv.tw/plugins/sdlc.git"
       },
-      "description": "開發生命週期：規劃/分析/實作/維護（wiki 追蹤）"
+      "description": "開發生命週期：規劃、分析、實作、維護（wiki 追蹤）"
     }
   ]
 }
diff --git a/.claude-plugin/plugin.json b/.claude-plugin/plugin.json
index 3f65887..3f02e63 100644
--- a/.claude-plugin/plugin.json
+++ b/.claude-plugin/plugin.json
@@ -1,6 +1,6 @@
 {
   "name": "jsc-pkg",
-  "version": "0.0.3",
+  "version": "0.0.5",
   "description": "套件批次更新（nodejs/python/dotnet），失敗還原",
   "skills": "./skills",
   "author": {
diff --git a/.codex-plugin/plugin.json b/.codex-plugin/plugin.json
index 26561ef..14f0d74 100644
--- a/.codex-plugin/plugin.json
+++ b/.codex-plugin/plugin.json
@@ -1,6 +1,6 @@
 {
   "name": "jsc-pkg",
-  "version": "0.0.3",
+  "version": "0.0.5",
   "description": "套件批次更新（nodejs/python/dotnet），失敗還原",
   "skills": "./skills"
 }
diff --git a/README.md b/README.md
index 6e3b7f1..93d7b23 100644
--- a/README.md
+++ b/README.md
@@ -20,11 +20,36 @@ Marketplace 統一為 `jsc`（https://gitea.jsc.idv.tw/plugins/meta.git），安
 
 ## 工具
 
-| 工具 | 用途 |
-| --- | --- |
-| `tools/list-packages.sh` | 偵測專案類型並列出所有外部套件與目前版本（TSV：ecosystem / name / current） |
-| `tools/latest-version.sh` | `latest-version.sh <ecosystem> <name>` 查最新穩定版（npm / pypi / nuget），查無 exit 4 |
-| `tools/apply-version.sh` | `apply-version.sh <ecosystem> <project dir> <name> <version>` 改寫版本來源檔案，把套件釘選到指定版本 |
+五支工具都靠 python3 解析或改寫檔案。少了 python3，每一支都回報「需要的指令不存在」，不會裝成查無套件。
+
+| 工具 | 用途 | 需要的指令 |
+| --- | --- | --- |
+| `tools/list-packages.sh` | `list-packages.sh [專案目錄]` 偵測專案類型並列出所有外部套件與目前版本（TSV：ecosystem / name / current） | python3 |
+| `tools/latest-version.sh` | `latest-version.sh <ecosystem> <name>` 查最新穩定版（npm / pypi / nuget） | curl、python3 |
+| `tools/apply-version.sh` | `apply-version.sh <ecosystem> <project dir> <name> <version>` 改寫版本來源檔案，把套件釘選到指定版本 | python3 |
+| `tools/install-deps.sh` | `install-deps.sh <ecosystem> <project dir>` 重新解析並安裝相依套件（npm install、pip install、dotnet restore） | npm、pip、dotnet |
+| `tools/build-test.sh` | `build-test.sh <ecosystem> <project dir>` 偵測並執行建置與測試 | npm、python3、pytest、dotnet |
+
+### 結束碼總表
+
+一個數字只有一個意思，五支工具共用。新增工具請沿用這張表，不要自己編號。
+
+| 碼 | 意思 | 呼叫方的動作 |
+| --- | --- | --- |
+| 0 | 成功 | 繼續 |
+| 1 | 參數個數不對 | 停手 |
+| 2 | ecosystem 不認識 | 停手 |
+| 3 | 該 ecosystem 沒有來源檔案 | 跳過這個 ecosystem 或套件 |
+| 4 | 依工具而定：`list-packages.sh`、`build-test.sh`、`install-deps.sh` 是指令不存在（停手）；`latest-version.sh`、`apply-version.sh` 是查不到該套件（跳過） | 見左欄 |
+| 5 | 依工具而定：`latest-version.sh`、`apply-version.sh` 是指令不存在（停手）；`build-test.sh` 是推不出建置或測試指令（改問使用者） | 見左欄 |
+| 6 | 找不到專案目錄 | 停手 |
+| 其他 | 底層指令的結束碼 | 只有 `install-deps.sh`、`build-test.sh` 會走還原 |
+
+6 不與 3 合併：找不到專案目錄是輸入壞了，併進 3 會被當成跳過藏起來。`latest-version.sh` 不收專案目錄，所以沒有 6。
+
+4 與 5 在各工具間意思不同，是為了保住既有的跳過路由；新增工具請優先用 4 表示指令不存在。
+
+回 1、回 2、回 6 與回「指令不存在」時，技能只回報並停手，不還原工作樹——工具鏈壞了不是套件壞了，還原只會白白刪掉檔案。
 
 ## Skills 目錄
 
diff --git a/plugin.json b/plugin.json
index 923fddf..e4e2e85 100644
--- a/plugin.json
+++ b/plugin.json
@@ -1,6 +1,6 @@
 {
   "name": "jsc-pkg",
-  "version": "0.0.3",
+  "version": "0.0.5",
   "description": "套件批次更新（nodejs/python/dotnet），失敗還原",
   "skills": "./skills/"
 }
diff --git a/skills/pkg-update/SKILL.md b/skills/pkg-update/SKILL.md
index 839d2a5..345cdff 100644
--- a/skills/pkg-update/SKILL.md
+++ b/skills/pkg-update/SKILL.md
@@ -5,18 +5,49 @@ description: Update every external package of a project to its latest stable ver
 
 # pkg-update — batch-update packages
 
+## Exit-code routes
+
+Every tool exit code below has exactly one route. Three routes exist:
+
+- **skip** — record the reason, keep going.
+- **stop** — report and end the run. Change no file, and never enter step 5.
+- **revert** — go to step 5, which reverts the working tree.
+
+Only a real install, build or test failure takes the revert route. A missing input, a bad argument, an unknown ecosystem or a missing command is a broken call or a broken toolchain, so it takes the stop route.
+
+One number carries one meaning across all five tools. Exit 6 is always a missing project directory and always stops the run — never fold it into the exit 3 skip, or a bad path hides as "nothing to do".
+
+| Tool | 0 | 1 (bad argument count) | 2 (unknown ecosystem) | 3 (no source file) | 4 | 5 | 6 (project dir not found) | other |
+| --- | --- | --- | --- | --- | --- | --- | --- | --- |
+| `list-packages.sh` | continue | stop | — | — | stop (python3 missing) | — | stop | stop |
+| `latest-version.sh` | continue | stop | stop | — | skip (not in registry) | stop (curl or python3 missing) | — (takes no project dir) | stop |
+| `apply-version.sh` | continue | stop | stop | skip | skip (package absent from the file) | stop (python3 missing) | stop | stop |
+| `install-deps.sh` | continue | stop | stop | skip | stop (npm, pip or dotnet missing) | — | stop | **revert** |
+| `build-test.sh` | continue | stop | stop | — (uses 5 instead) | stop (npm, python3, pytest or dotnet missing) | ask the user | stop | **revert** |
+
+Exit 4 and exit 5 are the two codes whose meaning depends on the tool, so read them off this table rather than from memory.
+
 ## Steps
 
-1. Run `tools/list-packages.sh {project dir}` to get every external package (ecosystem, name, current version).
-2. Confirm the working tree is clean: stop and report when uncommitted changes exist, so the revert cannot destroy them.
+1. Run `tools/list-packages.sh {project dir}` to get every external package (ecosystem, name, current version). Route the exit code per the table above. Step 1 is done only when the tool exited 0 and at least one row came back, with an ecosystem, a name and a current version in every row. Zero rows → stop and report the project directory you scanned plus the supported ecosystems (nodejs / python / dotnet), and run no further step.
+2. Prove the project directory is a git repository with a clean tree. Run this before any step changes a file:
+   1. Run `git -C {project dir} rev-parse --git-dir`. Exit 0 is required to continue, because step 5's revert is impossible outside a git repository. Any other exit code → stop and report the directory, and run no further step.
+   2. Run `git -C {project dir} status --porcelain`. Continuing requires that it prints **nothing at all**. Any output stops the run and reports that output, **including `??` untracked lines**: step 5 runs `git clean -fd`, which deletes untracked files with no reflog and no way back.
+   3. Step 2 is done only when `rev-parse --git-dir` exited 0 and `status --porcelain` printed zero bytes. Report both results, then enter step 3.
 3. Update ecosystem by ecosystem. This step **MUST run as a sub agent** (one sub agent per ecosystem):
-   1. For every package, run `tools/latest-version.sh {ecosystem} {name}` to get the latest stable version.
-   2. Run `tools/apply-version.sh {ecosystem} {project dir} {name} {version}` to rewrite the version source file (package.json / requirements.txt / pyproject.toml / *.csproj).
-   3. Re-resolve and install (`npm install` / `pip install -r` / `dotnet restore`).
-4. Run build and tests:
-   - nodejs: `npm run build` (if present) plus `npm test` (if present).
-   - python: `pytest` (when tests exist).
-   - dotnet: `dotnet build` plus `dotnet test`.
-   - When the commands cannot be inferred, ask the user per the `jsc-ask:ask` rules.
-5. Build or tests fail → revert every change (`git checkout -- .` and clean untracked lock changes), then report the failing packages with an error summary.
-6. Success → report the update list (package, old version, new version) and hand off to `jsc-git:commit`.
+   1. For every package, run `tools/latest-version.sh {ecosystem} {name}` for the latest stable version, then `tools/apply-version.sh {ecosystem} {project dir} {name} {version}` to rewrite the version source file (package.json / requirements.txt / pyproject.toml / *.csproj). This substep is done when every package of the ecosystem carries either an applied version or a skip reason from substep 2.
+   2. Route every exit code per the table above. The skip route covers `latest-version.sh` exit 4 (package not found in the registry), `apply-version.sh` exit 3 (no version source file) and `apply-version.sh` exit 4 (package absent from the file): record the package and the reason, move on to the next package, and never abort the whole ecosystem. The stop route covers exit 1, exit 2, `latest-version.sh` or `apply-version.sh` exit 5 (a required command is missing) and `apply-version.sh` exit 6 (project directory not found): report the code and end the run without entering step 5. This substep is done when every exit code seen has taken exactly one route.
+   3. Run `tools/install-deps.sh {ecosystem} {project dir}` once, after every package of that ecosystem is applied. Exit 0 means the install finished. Exit 3 means this ecosystem has no dependency source file, which is the same documented skip as substep 2: record the ecosystem and the reason, and install nothing. Exit 1, exit 2, exit 4 and exit 6 take the stop route — exit 6 is a missing project directory, so report it instead of skipping it. Only another non-zero code is a real install failure and goes to step 5. This substep is done when the exit code is recorded together with the route it took.
+   4. The sub agent returns one row per package from substep 1: name, old version, new version — or `skipped` plus the reason. It also returns the `install-deps.sh` exit code and its route. The ecosystem is done only when every package appears in exactly one row.
+4. Run `tools/build-test.sh {ecosystem} {project dir}` for every ecosystem and route on the exit code:
+   - 0 → this ecosystem passed.
+   - 1, 2, 4 or 6 → stop route. Report the code and the missing argument, ecosystem, command or directory, and enter no further step. Exit 4 means the toolchain is broken, not that the packages are broken, so reverting would destroy files for nothing.
+   - 5 → no build or test command could be inferred. Ask the user for the build command and the test command per the `jsc-ask:ask` rules, run the answers in that order, and take their exit codes as this ecosystem's result: all 0 → passed; any non-zero → step 5.
+   - any other code → a real build or test failure. Go to step 5.
+
+   Step 4 is done only when every ecosystem reached exit 0, from the tool or from the user's own commands.
+5. A real install, build or test failure reached this step → revert:
+   1. Run `git -C {project dir} checkout -- .` to restore every tracked file to HEAD.
+   2. Run `git -C {project dir} clean -fd` to remove the untracked files and directories this run created, such as a new lock file. Gitignored paths survive `-fd` on purpose: `node_modules`, `__pycache__`, `bin/` and `obj/` stay behind, so restoring install output is out of scope for this skill. Do not reach for `-fdx` — it deletes far more than this run created.
+   3. The revert is done only when `git -C {project dir} status --porcelain` prints nothing. Report the failing packages with an error summary after that check passes.
+6. Success → report the update list (package, old version, new version), plus every skip and its reason, and hand off to `jsc-git:commit`. Step 6 is done when the hand-off is made and every package from step 1 appears either as an update or as a skip.
diff --git a/tools/apply-version.sh b/tools/apply-version.sh
index c519d8c..d8605dc 100755
--- a/tools/apply-version.sh
+++ b/tools/apply-version.sh
@@ -1,17 +1,36 @@
 #!/usr/bin/env sh
 # apply-version.sh — 改寫版本來源檔案，把套件釘選到指定版本。
-# 用法: apply-version.sh <ecosystem> <project-dir> <name> <version>
-#   ecosystem: nodejs | python | dotnet
-# 對應檔案（與 list-packages.sh 相同的解析邏輯）:
+# 用法：apply-version.sh <ecosystem> <project-dir> <name> <version>
+#   ecosystem：nodejs | python | dotnet
+# 對應檔案（與 list-packages.sh 相同的解析邏輯）：
 #   nodejs → package.json（dependencies / devDependencies）
 #   python → requirements.txt（優先）或 pyproject.toml 的 [project] dependencies
 #   dotnet → *.csproj 的 PackageReference
-# 找不到對應檔案 exit 3；檔案中找不到該套件 exit 4
+# 結束碼（慣例見 README「工具」章的結束碼總表）：
+#   0 改寫成功
+#   1 參數個數不對
+#   2 ecosystem 不認識
+#   3 找不到對應的版本來源檔案——呼叫方跳過這個套件
+#   4 檔案中找不到該套件——呼叫方跳過這個套件
+#   5 需要的指令不存在（python3）
+#   6 找不到專案目錄——呼叫方停手，不要當成跳過
 set -u
-eco="${1:?ecosystem required (nodejs|python|dotnet)}"
-DIR="${2:?project dir required}"
-name="${3:?package name required}"
-version="${4:?version required}"
+
+if [ "$#" -ne 4 ]; then
+  echo "用法：apply-version.sh <ecosystem> <project-dir> <name> <version>" >&2
+  exit 1
+fi
+
+eco="$1"
+DIR="$2"
+name="$3"
+version="$4"
+
+# 先擋找不到專案目錄。少了這道，壞路徑會被報成「沒有版本來源檔案」，然後被當成跳過藏起來。
+[ -d "$DIR" ] || { echo "project dir not found: $DIR" >&2; exit 6; }
+
+# 三種來源檔案都靠 python3 改寫。少了 python3 會被誤判成檔案中找不到該套件，所以先擋。
+command -v python3 >/dev/null 2>&1 || { echo "python3 not found" >&2; exit 5; }
 
 case "$eco" in
   nodejs)
diff --git a/tools/build-test.sh b/tools/build-test.sh
new file mode 100755
index 0000000..d7fcfea
--- /dev/null
+++ b/tools/build-test.sh
@@ -0,0 +1,91 @@
+#!/usr/bin/env sh
+# build-test.sh — 偵測並執行專案的建置與測試，先建置再測試。
+# 用法：build-test.sh <ecosystem> <project-dir>
+#   ecosystem：nodejs | python | dotnet
+# 偵測方式：
+#   nodejs → package.json 的 scripts.build 與 scripts.test（npm init 產生的佔位 test 視為沒有）
+#   python → pytest 設定（pytest.ini、setup.cfg、tox.ini、pyproject.toml）或 tests 目錄與 test_*.py
+#   dotnet → *.sln 或 *.csproj，建置與測試都用 dotnet
+# 輸出：底層指令的原始輸出。
+# 結束碼（慣例見 README「工具」章的結束碼總表）：
+#   0 建置與測試都通過
+#   1 參數個數不對
+#   2 ecosystem 不認識
+#   4 需要的指令不存在（npm、python3、pytest、dotnet）
+#   5 推不出任何建置或測試指令——呼叫方要改問使用者
+#   6 找不到專案目錄——呼叫方停手
+#   其他 建置或測試失敗，帶回失敗指令的結束碼
+# 本工具不用 3：3 保留給「該 ecosystem 沒有來源檔案」，這支改用 5 表達推不出指令。
+set -u
+
+if [ "$#" -ne 2 ]; then
+  echo "用法：build-test.sh <ecosystem> <project-dir>" >&2
+  exit 1
+fi
+
+eco="$1"
+DIR="$2"
+
+NO_COMMAND=5
+
+[ -d "$DIR" ] || { echo "project dir not found: $DIR" >&2; exit 6; }
+
+case "$eco" in
+  nodejs)
+    [ -f "$DIR/package.json" ] || { echo "no build or test command inferred for $DIR" >&2; exit "$NO_COMMAND"; }
+    # package.json 靠 python3 解析。少了 python3 會解出空字串，被誤判成推不出指令，所以先擋。
+    command -v python3 >/dev/null 2>&1 || { echo "python3 not found" >&2; exit 4; }
+    scripts=$(python3 - "$DIR/package.json" <<'EOF'
+import json,sys
+try:
+    d=json.load(open(sys.argv[1],encoding="utf-8"))
+except Exception:
+    sys.exit(0)
+s=(d.get("scripts") or {})
+if s.get("build"): print("build")
+t=s.get("test") or ""
+if t and "no test specified" not in t: print("test")
+EOF
+)
+    [ -n "$scripts" ] || { echo "no build or test command inferred for $DIR" >&2; exit "$NO_COMMAND"; }
+    command -v npm >/dev/null 2>&1 || { echo "npm not found" >&2; exit 4; }
+    for s in $scripts; do
+      ( cd "$DIR" && npm run --if-present "$s" ) || exit $?
+    done
+    exit 0
+    ;;
+
+  python)
+    has_tests=0
+    for f in pytest.ini setup.cfg tox.ini pyproject.toml; do
+      if [ -f "$DIR/$f" ] && grep -q 'pytest' "$DIR/$f" 2>/dev/null; then has_tests=1; fi
+    done
+    [ -d "$DIR/tests" ] && has_tests=1
+    if [ "$has_tests" -eq 0 ]; then
+      found=$(find "$DIR" -maxdepth 3 -name 'test_*.py' 2>/dev/null | head -n 1)
+      [ -n "$found" ] && has_tests=1
+    fi
+    [ "$has_tests" -eq 1 ] || { echo "no build or test command inferred for $DIR" >&2; exit "$NO_COMMAND"; }
+    if command -v pytest >/dev/null 2>&1; then
+      ( cd "$DIR" && pytest )
+      exit $?
+    elif command -v python3 >/dev/null 2>&1 && python3 -m pytest --version >/dev/null 2>&1; then
+      ( cd "$DIR" && python3 -m pytest )
+      exit $?
+    else
+      echo "pytest not found" >&2
+      exit 4
+    fi
+    ;;
+
+  dotnet)
+    projs=$(find "$DIR" -maxdepth 3 \( -name '*.sln' -o -name '*.csproj' \) 2>/dev/null)
+    [ -n "$projs" ] || { echo "no build or test command inferred for $DIR" >&2; exit "$NO_COMMAND"; }
+    command -v dotnet >/dev/null 2>&1 || { echo "dotnet not found" >&2; exit 4; }
+    ( cd "$DIR" && dotnet build ) || exit $?
+    ( cd "$DIR" && dotnet test ) || exit $?
+    exit 0
+    ;;
+
+  *) echo "unknown ecosystem: $eco" >&2; exit 2 ;;
+esac
diff --git a/tools/install-deps.sh b/tools/install-deps.sh
new file mode 100755
index 0000000..48027b5
--- /dev/null
+++ b/tools/install-deps.sh
@@ -0,0 +1,73 @@
+#!/usr/bin/env sh
+# install-deps.sh — 重新解析並安裝專案的相依套件。
+# 用法：install-deps.sh <ecosystem> <project-dir>
+#   ecosystem：nodejs | python | dotnet
+# 對應動作：
+#   nodejs → npm install
+#   python → pip install -r requirements.txt（優先）或 pip install -e .（pyproject.toml）
+#   dotnet → dotnet restore
+# 輸出：底層指令的原始輸出。
+# 檢查順序：先確認相依來源檔案存在，才檢查指令存在。順序顛倒會把「沒有來源檔案」報成「指令不存在」。
+# 結束碼（慣例見 README「工具」章的結束碼總表）：
+#   0 安裝成功
+#   1 參數個數不對
+#   2 ecosystem 不認識
+#   3 該 ecosystem 沒有相依來源檔案——呼叫方跳過這個 ecosystem
+#   4 需要的指令不存在（npm、pip、dotnet）
+#   6 找不到專案目錄——呼叫方停手，不要當成跳過
+#   其他 底層指令的結束碼，代表安裝失敗
+set -u
+
+if [ "$#" -ne 2 ]; then
+  echo "用法：install-deps.sh <ecosystem> <project-dir>" >&2
+  exit 1
+fi
+
+eco="$1"
+DIR="$2"
+
+[ -d "$DIR" ] || { echo "project dir not found: $DIR" >&2; exit 6; }
+
+case "$eco" in
+  nodejs)
+    [ -f "$DIR/package.json" ] || { echo "package.json not found in $DIR" >&2; exit 3; }
+    command -v npm >/dev/null 2>&1 || { echo "npm not found" >&2; exit 4; }
+    ( cd "$DIR" && npm install )
+    exit $?
+    ;;
+
+  python)
+    if [ -f "$DIR/requirements.txt" ]; then
+      target="-r requirements.txt"
+    elif [ -f "$DIR/pyproject.toml" ]; then
+      target="-e ."
+    else
+      echo "requirements.txt or pyproject.toml not found in $DIR" >&2
+      exit 3
+    fi
+    pip=""
+    for c in pip3 pip; do
+      if command -v "$c" >/dev/null 2>&1; then pip="$c"; break; fi
+    done
+    if [ -z "$pip" ]; then
+      if command -v python3 >/dev/null 2>&1 && python3 -m pip --version >/dev/null 2>&1; then
+        pip="python3 -m pip"
+      else
+        echo "pip not found" >&2
+        exit 4
+      fi
+    fi
+    ( cd "$DIR" && $pip install $target )
+    exit $?
+    ;;
+
+  dotnet)
+    projs=$(find "$DIR" -maxdepth 3 \( -name '*.csproj' -o -name '*.sln' \) 2>/dev/null)
+    [ -n "$projs" ] || { echo "*.csproj or *.sln not found in $DIR" >&2; exit 3; }
+    command -v dotnet >/dev/null 2>&1 || { echo "dotnet not found" >&2; exit 4; }
+    ( cd "$DIR" && dotnet restore )
+    exit $?
+    ;;
+
+  *) echo "unknown ecosystem: $eco" >&2; exit 2 ;;
+esac
diff --git a/tools/latest-version.sh b/tools/latest-version.sh
index 81a3e98..01a82b3 100755
--- a/tools/latest-version.sh
+++ b/tools/latest-version.sh
@@ -1,11 +1,29 @@
 #!/usr/bin/env sh
 # latest-version.sh — 查詢套件最新且穩定的版本號。
-# 用法: latest-version.sh <ecosystem> <name>
-#   ecosystem: nodejs | python | dotnet
-# 輸出: 版本號一行；查不到 exit 4
+# 用法：latest-version.sh <ecosystem> <name>
+#   ecosystem：nodejs | python | dotnet
+# 輸出：版本號一行。
+# 結束碼（慣例見 README「工具」章的結束碼總表）：
+#   0 查到版本號
+#   1 參數個數不對
+#   2 ecosystem 不認識
+#   4 登錄站上查不到這個套件——呼叫方跳過這個套件
+#   5 需要的指令不存在（curl、python3）
+# 本工具不收專案目錄，所以沒有 6。
 set -u
-eco="${1:?ecosystem required (nodejs|python|dotnet)}"
-name="${2:?package name required}"
+
+if [ "$#" -ne 2 ]; then
+  echo "用法：latest-version.sh <ecosystem> <name>" >&2
+  exit 1
+fi
+
+eco="$1"
+name="$2"
+
+# 回應靠 curl 取得、靠 python3 解析。少了任一支會解出空字串，被誤判成查不到套件，所以先擋。
+for c in curl python3; do
+  command -v "$c" >/dev/null 2>&1 || { echo "$c not found" >&2; exit 5; }
+done
 
 case "$eco" in
   nodejs)
diff --git a/tools/list-packages.sh b/tools/list-packages.sh
index ee12fc1..7488f71 100755
--- a/tools/list-packages.sh
+++ b/tools/list-packages.sh
@@ -1,11 +1,28 @@
 #!/usr/bin/env sh
 # list-packages.sh — 列出專案的所有外部套件與目前版本。
-# 用法: list-packages.sh [專案目錄]（預設目前目錄）
-# 輸出（TSV）: ecosystem<TAB>name<TAB>current
-# 支援: nodejs（package.json）、python（requirements.txt / pyproject.toml）、dotnet（*.csproj）
+# 用法：list-packages.sh [專案目錄]（預設目前目錄）
+# 輸出（TSV）：ecosystem<TAB>name<TAB>current
+# 支援：nodejs（package.json）、python（requirements.txt / pyproject.toml）、dotnet（*.csproj）
+# 結束碼（慣例見 README「工具」章的結束碼總表）：
+#   0 掃描完成（沒有套件時輸出零行）
+#   1 參數個數不對
+#   4 需要的指令不存在（python3）
+#   6 找不到專案目錄——呼叫方停手
 set -u
+
+if [ "$#" -gt 1 ]; then
+  echo "用法：list-packages.sh [專案目錄]" >&2
+  exit 1
+fi
+
 DIR="${1:-.}"
 
+# 先擋找不到專案目錄。少了這道，壞路徑會輸出零行，被誤判成專案沒有套件。
+[ -d "$DIR" ] || { echo "project dir not found: $DIR" >&2; exit 6; }
+
+# 四種來源檔案都靠 python3 解析。少了 python3 會輸出零行，被誤判成專案沒有套件，所以先擋。
+command -v python3 >/dev/null 2>&1 || { echo "python3 not found" >&2; exit 4; }
+
 # nodejs: package.json 的 dependencies / devDependencies
 if [ -f "$DIR/package.json" ]; then
   python3 - "$DIR/package.json" <<'EOF'