diff --git a/skills/hyperlight-codeact/SKILL.md b/skills/hyperlight-codeact/SKILL.md
index 72234a7..dd401e3 100644
--- a/skills/hyperlight-codeact/SKILL.md
+++ b/skills/hyperlight-codeact/SKILL.md
@@ -49,11 +49,11 @@ Sandboxed code can only reach the outside world through `call_tool()` bridges.
 ## Quick start
 
 ```bash
-# 1. Discover tools (matches Copilot CLI tool names)
+# 1. Discover tools (works without any packages installed)
 python3 scripts/codeact.py --discover
 
-# 2. Run code with auto-discovered tools
-python3 scripts/codeact.py --auto --workspace . --code '
+# 2. Run code (uv auto-installs hyperlight-sandbox into an ephemeral env)
+uv run --with 'hyperlight-sandbox[wasm,python_guest]' python3 scripts/codeact.py --auto --workspace . --code '
 content = call_tool("view", path="README.md")
 print(f"README has {len(content.splitlines())} lines")
 '
@@ -100,15 +100,20 @@ content = call_tool('view', path=call_tool('glob', pattern='config.json')[0])
 
 ### Step 3 -- Execute
 
+Use `uv run --with` to auto-install the dependency:
+
 ```bash
 # Auto-discover + workspace scoping (recommended)
-python3 scripts/codeact.py --auto --workspace . --code '...'
+uv run --with 'hyperlight-sandbox[wasm,python_guest]' python3 scripts/codeact.py --auto --workspace . --code '...'
 
 # With saved manifest
-python3 scripts/codeact.py --manifest tools.json --code-file script.py
+uv run --with 'hyperlight-sandbox[wasm,python_guest]' python3 scripts/codeact.py --manifest tools.json --code-file script.py
+```
 
-# Via stdin
-echo '{"tools": [...], "code": "..."}' | python3 scripts/codeact.py --stdin
+If `hyperlight-sandbox` is already installed, plain `python3` works too:
+
+```bash
+python3 scripts/codeact.py --auto --workspace . --code '...'
 ```
 
 Output is always JSON: `{"stdout": "...", "stderr": "...", "exit_code": 0, "success": true}`
@@ -130,4 +135,5 @@ Main executor. Key flags:
 ## Prerequisites
 
 - Python 3.10+
-- `hyperlight-sandbox[wasm,python_guest]` or build via `just python-build`
+- `uv` (recommended — auto-installs `hyperlight-sandbox` with no side effects)
+- Or: `pip install 'hyperlight-sandbox[wasm,python_guest]'`
diff --git a/skills/hyperlight-codeact/scripts/codeact.py b/skills/hyperlight-codeact/scripts/codeact.py
index d54161c..5f81db5 100644
--- a/skills/hyperlight-codeact/scripts/codeact.py
+++ b/skills/hyperlight-codeact/scripts/codeact.py
@@ -499,7 +499,20 @@ def main() -> None:
         return
 
     # ---- execution ----
-    from hyperlight_sandbox import Sandbox
+    try:
+        from hyperlight_sandbox import Sandbox
+    except ImportError:
+        print(json.dumps({
+            "stdout": "",
+            "stderr": (
+                "hyperlight-sandbox is not installed.\n"
+                "Run this script with: uv run --with 'hyperlight-sandbox[wasm,python_guest]' python3 scripts/codeact.py ...\n"
+                "Or install manually: pip install 'hyperlight-sandbox[wasm,python_guest]'"
+            ),
+            "exit_code": 1,
+            "success": False,
+        }, indent=2))
+        sys.exit(1)
 
     global _WORKSPACE_ROOT
     if args.workspace:
diff --git a/skills/monty-codeact/SKILL.md b/skills/monty-codeact/SKILL.md
index 11c7e6d..8db7ef9 100644
--- a/skills/monty-codeact/SKILL.md
+++ b/skills/monty-codeact/SKILL.md
@@ -65,7 +65,11 @@ or need full Python (classes, third-party libs).
 ## Quick start
 
 ```bash
-python3 scripts/codeact.py --auto --workspace . --code '
+# Discovery works without any packages installed
+python3 scripts/codeact.py --discover
+
+# Execute code (uv auto-installs pydantic-monty into an ephemeral env)
+uv run --with pydantic-monty python3 scripts/codeact.py --auto --workspace . --code '
 files = glob(pattern="**/*.py", paths="src")
 print("Found " + str(len(files)) + " Python files")
 for f in files[:3]:
@@ -113,10 +117,17 @@ but it must be imported explicitly).
 
 ### Step 3 -- Execute
 
+Use `uv run --with pydantic-monty` to auto-install the dependency:
+
+```bash
+uv run --with pydantic-monty python3 scripts/codeact.py --auto --workspace . --code '...'
+uv run --with pydantic-monty python3 scripts/codeact.py --manifest tools.json --code-file script.py
+```
+
+If `pydantic-monty` is already installed, plain `python3` works too:
+
 ```bash
 python3 scripts/codeact.py --auto --workspace . --code '...'
-python3 scripts/codeact.py --manifest tools.json --code-file script.py
-echo '{"tools": [...], "code": "..."}' | python3 scripts/codeact.py --stdin
 ```
 
 Output is JSON:
@@ -140,4 +151,5 @@ Key flags:
 ## Prerequisites
 
 - Python 3.10+
-- `pip install pydantic-monty` (~4.5MB, no other dependencies)
+- `uv` (recommended — auto-installs `pydantic-monty` with no side effects)
+- Or: `pip install pydantic-monty` (~4.5MB, no other dependencies)
diff --git a/skills/monty-codeact/scripts/codeact.py b/skills/monty-codeact/scripts/codeact.py
index fb2337a..c107cb9 100644
--- a/skills/monty-codeact/scripts/codeact.py
+++ b/skills/monty-codeact/scripts/codeact.py
@@ -453,7 +453,20 @@ def main() -> None:
         return
 
     # ---- execution ----
-    import pydantic_monty
+    try:
+        import pydantic_monty
+    except ImportError:
+        print(json.dumps({
+            "stdout": "",
+            "stderr": (
+                "pydantic-monty is not installed.\n"
+                "Run this script with: uv run --with pydantic-monty python3 scripts/codeact.py ...\n"
+                "Or install manually: pip install pydantic-monty"
+            ),
+            "return_value": None,
+            "success": False,
+        }, indent=2))
+        sys.exit(1)
 
     global _WORKSPACE_ROOT
     if args.workspace: