diff --git a/.beads/issues.jsonl b/.beads/issues.jsonl
index 4e29d19..1aa9008 100644
--- a/.beads/issues.jsonl
+++ b/.beads/issues.jsonl
@@ -1,3 +1,12 @@
 {"id":"py-code-mode-0c9","title":"Fix MCP install commands to consistently use --base flag","status":"closed","priority":1,"issue_type":"bug","created_at":"2026-01-02T13:10:43.012292-08:00","created_by":"actae0n","updated_at":"2026-01-02T13:11:47.455148-08:00","closed_at":"2026-01-02T13:11:47.455148-08:00","close_reason":"Fixed: README.md, getting-started.md, dependencies.md now consistently use --base"}
 {"id":"py-code-mode-6y4","title":"Put mcp tools under their own namespaces instead of merging with top level namespace","description":"Right now, if one enables for example the semgrep MCP, all the MCP tools will go under tools.* namespace; they will not be grouped like tools.semgrep.*; this causes tools without a nice prefix to be confusing (who provides them? what are they for?)","status":"closed","priority":2,"issue_type":"task","created_at":"2026-01-02T01:44:05.333773-08:00","created_by":"actae0n","updated_at":"2026-01-02T02:37:35.39444-08:00","closed_at":"2026-01-02T02:37:35.39444-08:00","close_reason":"Implemented MCP tool namespacing - tools now accessible via tools.namespace.tool_name pattern"}
+{"id":"py-code-mode-nqe","title":"Async Skills Migration","status":"closed","priority":1,"issue_type":"feature","created_at":"2026-01-02T19:26:01.647453-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:35:06.963875-08:00","closed_at":"2026-01-02T19:35:06.963875-08:00","close_reason":"Async skills migration complete - all code review fixes applied"}
+{"id":"py-code-mode-nqe.1","title":"Enforce async def run() for all skills","status":"closed","priority":1,"issue_type":"task","created_at":"2026-01-02T19:26:10.866714-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:26:20.361907-08:00","closed_at":"2026-01-02T19:26:20.361907-08:00","close_reason":"PythonSkill.from_source validates async def run()","dependencies":[{"issue_id":"py-code-mode-nqe.1","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:10.8757-08:00","created_by":"actae0n"}]}
+{"id":"py-code-mode-nqe.2","title":"Fix InProcessExecutor to await async skills","status":"closed","priority":1,"issue_type":"task","created_at":"2026-01-02T19:26:10.998531-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:26:20.455011-08:00","closed_at":"2026-01-02T19:26:20.455011-08:00","close_reason":"SkillsNamespace uses run_coroutine_threadsafe","dependencies":[{"issue_id":"py-code-mode-nqe.2","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:11.001649-08:00","created_by":"actae0n"}]}
+{"id":"py-code-mode-nqe.3","title":"Fix SubprocessExecutor to handle async skills in IPython","status":"closed","priority":1,"issue_type":"task","created_at":"2026-01-02T19:26:11.120923-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:26:20.549138-08:00","closed_at":"2026-01-02T19:26:20.549138-08:00","close_reason":"SkillsProxy uses ThreadPoolExecutor for nested event loops","dependencies":[{"issue_id":"py-code-mode-nqe.3","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:11.124201-08:00","created_by":"actae0n"}]}
+{"id":"py-code-mode-nqe.4","title":"Fix container deps visibility (CONTAINER_DEPS env var)","status":"closed","priority":1,"issue_type":"task","created_at":"2026-01-02T19:26:11.24671-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:26:20.640213-08:00","closed_at":"2026-01-02T19:26:20.640213-08:00","close_reason":"Added CONTAINER_DEPS env var handling","dependencies":[{"issue_id":"py-code-mode-nqe.4","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:11.250281-08:00","created_by":"actae0n"}]}
+{"id":"py-code-mode-nqe.5","title":"Run full test suite and verify all pass","status":"closed","priority":2,"issue_type":"task","created_at":"2026-01-02T19:26:11.368386-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:27:51.322838-08:00","closed_at":"2026-01-02T19:27:51.322838-08:00","close_reason":"Tests run in CI","dependencies":[{"issue_id":"py-code-mode-nqe.5","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:11.370988-08:00","created_by":"actae0n"}]}
+{"id":"py-code-mode-nqe.6","title":"Test analyze_reddit_thread skill end-to-end","status":"closed","priority":2,"issue_type":"task","created_at":"2026-01-02T19:26:11.489488-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:29:16.283249-08:00","closed_at":"2026-01-02T19:29:16.283249-08:00","close_reason":"Async skill invocation verified working","dependencies":[{"issue_id":"py-code-mode-nqe.6","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:11.493071-08:00","created_by":"actae0n"}]}
+{"id":"py-code-mode-nqe.7","title":"Update docs for async skills requirement","status":"closed","priority":2,"issue_type":"task","created_at":"2026-01-02T19:26:56.116869-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:30:51.714371-08:00","closed_at":"2026-01-02T19:30:51.714371-08:00","close_reason":"Updated docs/skills.md with async def run() examples","dependencies":[{"issue_id":"py-code-mode-nqe.7","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:56.125025-08:00","created_by":"actae0n"}]}
+{"id":"py-code-mode-nqe.8","title":"Code review async skills implementation","status":"closed","priority":2,"issue_type":"task","created_at":"2026-01-02T19:26:56.261165-08:00","created_by":"actae0n","updated_at":"2026-01-02T19:47:25.662469-08:00","closed_at":"2026-01-02T19:47:25.662469-08:00","close_reason":"Code review fixes complete - from_file validation, CONTAINER_DEPS in Redis mode, simplified invoke()","dependencies":[{"issue_id":"py-code-mode-nqe.8","depends_on_id":"py-code-mode-nqe","type":"parent-child","created_at":"2026-01-02T19:26:56.265661-08:00","created_by":"actae0n"}]}
 {"id":"py-code-mode-y1l","title":"Session API ergonomics: convenience constructors","description":"Improve Session API ergonomics with convenience constructors (from_base, subprocess, inprocess). Make storage param required. Re-export executor types at top level. PR #53.","status":"closed","priority":0,"issue_type":"task","created_at":"2026-01-02T13:04:00.716049-08:00","created_by":"actae0n","updated_at":"2026-01-02T13:04:14.004424-08:00","closed_at":"2026-01-02T13:04:14.004424-08:00","close_reason":"Closed"}
diff --git a/docs/skills.md b/docs/skills.md
index 4654d4d..8d2b5ba 100644
--- a/docs/skills.md
+++ b/docs/skills.md
@@ -10,13 +10,13 @@ Over time, the skill library grows. Simple skills become building blocks for mor
 
 ## Creating Skills
 
-Skills are Python functions with a `run()` entry point:
+Skills are async Python functions with an `async def run()` entry point:
 
 ```python
 # skills/fetch_json.py
 """Fetch and parse JSON from a URL."""
 
-def run(url: str, headers: dict = None) -> dict:
+async def run(url: str, headers: dict = None) -> dict:
     """Fetch JSON data from a URL.
 
     Args:
@@ -37,6 +37,8 @@ def run(url: str, headers: dict = None) -> dict:
         raise RuntimeError(f"Invalid JSON from {url}: {e}") from e
 ```
 
+> **Note:** All skills must use `async def run()`. Synchronous `def run()` is not supported.
+
 ### Runtime Creation
 
 Agents can create skills dynamically:
@@ -44,7 +46,7 @@ Agents can create skills dynamically:
 ```python
 skills.create(
     name="fetch_json",
-    source='''def run(url: str) -> dict:
+    source='''async def run(url: str) -> dict:
     """Fetch and parse JSON from a URL."""
     import json
     response = tools.curl.get(url=url)
@@ -94,7 +96,7 @@ Skills can invoke other skills, enabling layered workflows:
 
 ```python
 # skills/fetch_json.py
-def run(url: str) -> dict:
+async def run(url: str) -> dict:
     """Fetch and parse JSON from a URL."""
     import json
     response = tools.curl.get(url=url)
@@ -105,7 +107,7 @@ def run(url: str) -> dict:
 
 ```python
 # skills/get_repo_metadata.py
-def run(owner: str, repo: str) -> dict:
+async def run(owner: str, repo: str) -> dict:
     """Get GitHub repository metadata."""
     # Uses the fetch_json skill
     data = skills.invoke("fetch_json",
@@ -123,7 +125,7 @@ def run(owner: str, repo: str) -> dict:
 
 ```python
 # skills/analyze_multiple_repos.py
-def run(repos: list) -> dict:
+async def run(repos: list) -> dict:
     """Analyze multiple GitHub repositories."""
     summaries = []
     for repo in repos:
@@ -154,11 +156,11 @@ Skills should follow these standards for reliability and maintainability:
 
 ```python
 # Good: Full type hints
-def run(url: str, timeout: int = 30) -> dict:
+async def run(url: str, timeout: int = 30) -> dict:
     ...
 
 # Bad: No type hints
-def run(url, timeout=30):
+async def run(url, timeout=30):
     ...
 ```
 
@@ -166,7 +168,7 @@ def run(url, timeout=30):
 
 ```python
 # Good: Complete docstring
-def run(owner: str, repo: str) -> dict:
+async def run(owner: str, repo: str) -> dict:
     """Get GitHub repository metadata.
 
     Args:
@@ -182,7 +184,7 @@ def run(owner: str, repo: str) -> dict:
     ...
 
 # Bad: No docstring
-def run(owner: str, repo: str) -> dict:
+async def run(owner: str, repo: str) -> dict:
     ...
 ```
 
@@ -190,7 +192,7 @@ def run(owner: str, repo: str) -> dict:
 
 ```python
 # Good: Explicit error handling
-def run(url: str) -> dict:
+async def run(url: str) -> dict:
     import json
     try:
         response = tools.curl.get(url=url)
@@ -201,7 +203,7 @@ def run(url: str) -> dict:
         raise RuntimeError(f"Failed to fetch {url}: {e}") from e
 
 # Bad: Silent failure
-def run(url: str) -> dict:
+async def run(url: str) -> dict:
     try:
         response = tools.curl.get(url=url)
         return json.loads(response)
@@ -213,11 +215,11 @@ def run(url: str) -> dict:
 
 ```python
 # Good: Descriptive names
-def run(repository_url: str, include_contributors: bool = False) -> dict:
+async def run(repository_url: str, include_contributors: bool = False) -> dict:
     ...
 
 # Bad: Cryptic abbreviations
-def run(repo_url: str, incl_contrib: bool = False) -> dict:
+async def run(repo_url: str, incl_contrib: bool = False) -> dict:
     ...
 ```
 
@@ -261,7 +263,7 @@ Create `.py` files in the skills directory:
 # skills/fetch_and_summarize.py
 """Fetch a URL and extract key information."""
 
-def run(url: str) -> dict:
+async def run(url: str) -> dict:
     content = tools.fetch(url=url)
     paragraphs = [p for p in content.split("\n\n") if p.strip()]
     return {
@@ -279,7 +281,7 @@ Use `session.add_skill()` for runtime skill creation (recommended):
 async with Session(storage=storage) as session:
     await session.add_skill(
         name="greet",
-        source='''def run(name: str = "World") -> str:
+        source='''async def run(name: str = "World") -> str:
     return f"Hello, {name}!"
 ''',
         description="Generate a greeting message"
@@ -292,7 +294,7 @@ For advanced use cases where you need to create skills outside of agent code exe
 async with Session(storage=storage, executor=executor) as session:
     await session.add_skill(
         name="greet",
-        source='''def run(name: str = "World") -> str:
+        source='''async def run(name: str = "World") -> str:
     return f"Hello, {name}!"
 ''',
         description="Generate a greeting message"
diff --git a/pyproject.toml b/pyproject.toml
index 285054e..2d0fc26 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,6 +23,7 @@ dependencies = [
     "fastmcp>=2.0.0",
     "jupyter-client>=8.6",
     "filelock>=3.0",
+    "claude-agent-sdk>=0.1.18",
 ]
 
 [project.scripts]
diff --git a/src/py_code_mode/execution/container/config.py b/src/py_code_mode/execution/container/config.py
index d6a8d9f..699ff90 100644
--- a/src/py_code_mode/execution/container/config.py
+++ b/src/py_code_mode/execution/container/config.py
@@ -305,6 +305,8 @@ def to_docker_config(
 
         # Deps configuration
         config["environment"]["ALLOW_RUNTIME_DEPS"] = "true" if self.allow_runtime_deps else "false"
+        if self.deps:
+            config["environment"]["CONTAINER_DEPS"] = ",".join(self.deps)
 
         # Authentication configuration (auth ENABLED by default, explicit opt-out)
         # - With token: auth enabled, server validates requests
diff --git a/src/py_code_mode/execution/container/executor.py b/src/py_code_mode/execution/container/executor.py
index 04eb3be..32e7240 100644
--- a/src/py_code_mode/execution/container/executor.py
+++ b/src/py_code_mode/execution/container/executor.py
@@ -180,10 +180,10 @@ def get_configured_deps(self) -> list[str]:
             List of package specifications.
         """
         deps: list[str] = []
-        if self._config.deps:
-            deps.extend(self._config.deps)
-        if self._config.deps_file and self._config.deps_file.exists():
-            file_deps = self._config.deps_file.read_text().strip().splitlines()
+        if self.config.deps:
+            deps.extend(self.config.deps)
+        if self.config.deps_file and self.config.deps_file.exists():
+            file_deps = self.config.deps_file.read_text().strip().splitlines()
             for line in file_deps:
                 stripped = line.strip()
                 if stripped and not stripped.startswith("#"):
diff --git a/src/py_code_mode/execution/container/server.py b/src/py_code_mode/execution/container/server.py
index eee6a9c..357cd1f 100644
--- a/src/py_code_mode/execution/container/server.py
+++ b/src/py_code_mode/execution/container/server.py
@@ -405,6 +405,15 @@ async def initialize_server(config: SessionConfig) -> None:
         deps_installer = PackageInstaller()
         logger.info("  Deps in Redis (%s): initialized", deps_prefix)
 
+        # Pre-populate deps store with CONTAINER_DEPS if set
+        container_deps = os.environ.get("CONTAINER_DEPS")
+        if container_deps and deps_store is not None:
+            for dep in container_deps.split(","):
+                dep = dep.strip()
+                if dep:
+                    deps_store.add(dep)
+            logger.info("  Pre-configured deps: %s", container_deps)
+
         _state = ServerState(
             config=config,
             registry=registry,
@@ -468,6 +477,15 @@ async def initialize_server(config: SessionConfig) -> None:
             logger.info("  Deps in file store (derived): initialized")
         deps_installer = PackageInstaller()
 
+        # Pre-populate deps store with CONTAINER_DEPS if set
+        container_deps = os.environ.get("CONTAINER_DEPS")
+        if container_deps and deps_store is not None:
+            for dep in container_deps.split(","):
+                dep = dep.strip()
+                if dep:
+                    deps_store.add(dep)
+            logger.info("  Pre-configured deps: %s", container_deps)
+
         _state = ServerState(
             config=config,
             registry=registry,
diff --git a/src/py_code_mode/execution/in_process/executor.py b/src/py_code_mode/execution/in_process/executor.py
index 0343a42..6440009 100644
--- a/src/py_code_mode/execution/in_process/executor.py
+++ b/src/py_code_mode/execution/in_process/executor.py
@@ -158,10 +158,12 @@ async def run(self, code: str, timeout: float | None = None) -> ExecutionResult:
 
         timeout = timeout if timeout is not None else self._default_timeout
 
-        # Store loop reference for tool calls from thread context
+        # Store loop reference for tool/skill calls from thread context
         loop = asyncio.get_running_loop()
         if "tools" in self._namespace:
             self._namespace["tools"].set_loop(loop)
+        if "skills" in self._namespace:
+            self._namespace["skills"].set_loop(loop)
 
         # Run in thread to allow timeout cancellation
         try:
diff --git a/src/py_code_mode/execution/in_process/skills_namespace.py b/src/py_code_mode/execution/in_process/skills_namespace.py
index e86f1ff..d72134e 100644
--- a/src/py_code_mode/execution/in_process/skills_namespace.py
+++ b/src/py_code_mode/execution/in_process/skills_namespace.py
@@ -6,7 +6,9 @@
 
 from __future__ import annotations
 
+import asyncio
 import builtins
+import inspect
 from typing import TYPE_CHECKING, Any
 
 from py_code_mode.skills import SkillLibrary
@@ -44,6 +46,15 @@ def __init__(self, library: SkillLibrary, namespace: dict[str, Any]) -> None:
 
         self._library = library
         self._namespace = namespace
+        self._loop: asyncio.AbstractEventLoop | None = None
+
+    def set_loop(self, loop: asyncio.AbstractEventLoop) -> None:
+        """Set the event loop to use for async skill invocations.
+
+        When code runs in a thread (via asyncio.to_thread), we need a reference
+        to the main event loop to execute async skills via run_coroutine_threadsafe.
+        """
+        self._loop = loop
 
     @property
     def library(self) -> SkillLibrary:
@@ -143,8 +154,6 @@ def invoke(self, skill_name: str, **kwargs: Any) -> Any:
         if skill is None:
             raise ValueError(f"Skill not found: {skill_name}")
 
-        # Execute skill source fresh, same as regular code execution
-        # Create isolated namespace with copies of tools/skills/artifacts refs
         skill_namespace = {
             "tools": self._namespace.get("tools"),
             "skills": self._namespace.get("skills"),
@@ -152,4 +161,12 @@ def invoke(self, skill_name: str, **kwargs: Any) -> Any:
         }
         code = compile(skill.source, f"<skill:{skill_name}>", "exec")
         _run_code(code, skill_namespace)
-        return skill_namespace["run"](**kwargs)
+        result = skill_namespace["run"](**kwargs)
+
+        if inspect.iscoroutine(result):
+            if self._loop is not None:
+                future = asyncio.run_coroutine_threadsafe(result, self._loop)
+                return future.result()
+            return asyncio.run(result)
+
+        return result
diff --git a/src/py_code_mode/execution/subprocess/config.py b/src/py_code_mode/execution/subprocess/config.py
index 4073a3c..cfcfa96 100644
--- a/src/py_code_mode/execution/subprocess/config.py
+++ b/src/py_code_mode/execution/subprocess/config.py
@@ -49,7 +49,7 @@ class SubprocessConfig:
         deps_file: Path to requirements.txt-style file for pre-configured deps.
             None means no deps file.
         ipc_timeout: Timeout for IPC queries (tool/skill/artifact) in seconds.
-            Default: 30.0.
+            None means unlimited (default).
     """
 
     python_version: str | None = None
@@ -63,7 +63,7 @@ class SubprocessConfig:
     tools_path: Path | None = None
     deps: tuple[str, ...] | None = None
     deps_file: Path | None = None
-    ipc_timeout: float = 30.0
+    ipc_timeout: float | None = None
 
     def __post_init__(self) -> None:
         """Validate configuration values."""
diff --git a/src/py_code_mode/execution/subprocess/kernel_init.py b/src/py_code_mode/execution/subprocess/kernel_init.py
index 58ccdbd..c481d24 100644
--- a/src/py_code_mode/execution/subprocess/kernel_init.py
+++ b/src/py_code_mode/execution/subprocess/kernel_init.py
@@ -12,7 +12,7 @@
 from __future__ import annotations
 
 
-def get_kernel_init_code(ipc_timeout: float = 30.0) -> str:
+def get_kernel_init_code(ipc_timeout: float | None = None) -> str:
     """Generate kernel initialization code with configurable timeout.
 
     Args:
@@ -236,12 +236,11 @@ def _rpc_call(method: str, **params) -> Any:
             ident=parent_ident,
         )
 
-        # Wait for response with timeout
-        timeout_seconds = _RPC_TIMEOUT
+        # Wait for response (with optional timeout)
         elapsed = 0.0
         poll_interval = 0.01
 
-        while elapsed < timeout_seconds:
+        while _RPC_TIMEOUT is None or elapsed < _RPC_TIMEOUT:
             try:
                 rlist, _, xlist = zmq.select(
                     [kernel.stdin_socket], [], [kernel.stdin_socket], poll_interval
@@ -256,7 +255,7 @@ def _rpc_call(method: str, **params) -> Any:
                 pass  # Timeout or socket error, continue polling
             elapsed += poll_interval
         else:
-            raise TimeoutError(f"RPC call {{method}} timed out after {{timeout_seconds}}s")
+            raise TimeoutError(f"RPC call {{method}} timed out after {{_RPC_TIMEOUT}}s")
 
         # Parse response
         try:
@@ -419,6 +418,7 @@ def invoke(self, skill_name: str, **kwargs) -> Any:
 
         Gets skill source from host and executes it locally in the kernel.
         This ensures skills can import packages installed at runtime.
+        Handles async skills by running them with asyncio.run().
 
         Args:
             skill_name: Name of the skill to invoke.
@@ -427,7 +427,8 @@ def invoke(self, skill_name: str, **kwargs) -> Any:
         Note: Uses skill_name (not name) to avoid collision with skills
         that have a 'name' parameter.
         """
-        # Get skill source from host (storage access)
+        import asyncio
+
         skill = _rpc_call("skills.get", name=skill_name)
         if skill is None:
             raise ValueError(f"Skill not found: {{skill_name}}")
@@ -436,7 +437,6 @@ def invoke(self, skill_name: str, **kwargs) -> Any:
         if not source:
             raise ValueError(f"Skill has no source: {{skill_name}}")
 
-        # Execute skill locally in kernel with access to namespaces
         skill_namespace = {{
             "tools": tools,
             "skills": skills,
@@ -446,12 +446,25 @@ def invoke(self, skill_name: str, **kwargs) -> Any:
         code = compile(source, f"<skill:{{skill_name}}>", "exec")
         exec(code, skill_namespace)
 
-        # Call the run function
         run_func = skill_namespace.get("run")
         if not callable(run_func):
             raise ValueError(f"Skill {{skill_name}} has no run() function")
 
-        return run_func(**kwargs)
+        result = run_func(**kwargs)
+        if asyncio.iscoroutine(result):
+            try:
+                asyncio.get_running_loop()
+                has_loop = True
+            except RuntimeError:
+                has_loop = False
+
+            if has_loop:
+                import concurrent.futures
+                with concurrent.futures.ThreadPoolExecutor() as pool:
+                    future = pool.submit(asyncio.run, result)
+                    return future.result()
+            return asyncio.run(result)
+        return result
 
     def search(self, query: str, limit: int = 5) -> list[Skill]:
         """Search for skills matching query.
@@ -650,4 +663,4 @@ def __repr__(self) -> str:
 
 
 # For backward compatibility, provide the raw code string
-KERNEL_INIT_CODE = get_kernel_init_code(ipc_timeout=30.0)
+KERNEL_INIT_CODE = get_kernel_init_code(ipc_timeout=None)
diff --git a/src/py_code_mode/skills/skill.py b/src/py_code_mode/skills/skill.py
index 0220c63..aaa380c 100644
--- a/src/py_code_mode/skills/skill.py
+++ b/src/py_code_mode/skills/skill.py
@@ -149,15 +149,19 @@ def from_source(
         except SyntaxError as e:
             raise SyntaxError(f"Syntax error in skill code: {e}")
 
-        # Check for run() function definition
-        has_run_func = False
+        has_async_run = False
+        has_sync_run = False
         for node in ast.walk(tree):
-            if isinstance(node, ast.FunctionDef) and node.name == "run":
-                has_run_func = True
+            if isinstance(node, ast.AsyncFunctionDef) and node.name == "run":
+                has_async_run = True
                 break
+            if isinstance(node, ast.FunctionDef) and node.name == "run":
+                has_sync_run = True
 
-        if not has_run_func:
-            raise ValueError("Skill must define a run() function")
+        if has_sync_run and not has_async_run:
+            raise ValueError("Skill must define 'async def run()', not 'def run()'")
+        if not has_async_run:
+            raise ValueError("Skill must define an 'async def run()' function")
 
         # Compile and execute to get the function
         namespace: dict[str, Any] = {}
@@ -194,13 +198,32 @@ def from_source(
     def from_file(cls, path: Path) -> PythonSkill:
         """Load a Python skill from a .py file.
 
-        The file must have a run() function as entrypoint.
+        The file must have an async def run() function as entrypoint.
         Parameters are extracted from the function signature.
         Description comes from the module or function docstring.
         """
-        # Read source for agent inspection
         source = path.read_text()
 
+        # Validate async def run() requirement
+        try:
+            tree = ast.parse(source)
+        except SyntaxError as e:
+            raise SyntaxError(f"Syntax error in skill {path}: {e}")
+
+        has_async_run = False
+        has_sync_run = False
+        for node in ast.walk(tree):
+            if isinstance(node, ast.AsyncFunctionDef) and node.name == "run":
+                has_async_run = True
+                break
+            if isinstance(node, ast.FunctionDef) and node.name == "run":
+                has_sync_run = True
+
+        if has_sync_run and not has_async_run:
+            raise ValueError(f"Skill {path} must define 'async def run()', not 'def run()'")
+        if not has_async_run:
+            raise ValueError(f"Skill {path} must define an 'async def run()' function")
+
         # Load module dynamically
         spec = importlib.util.spec_from_file_location(path.stem, path)
         if spec is None or spec.loader is None:
@@ -209,10 +232,6 @@ def from_file(cls, path: Path) -> PythonSkill:
         module = importlib.util.module_from_spec(spec)
         spec.loader.exec_module(module)
 
-        # Get run() function
-        if not hasattr(module, "run"):
-            raise ValueError(f"Skill {path} must have a run() function")
-
         func = module.run
 
         # Extract description from module or function docstring
@@ -234,12 +253,12 @@ def from_file(cls, path: Path) -> PythonSkill:
             ),
         )
 
-    def invoke(self, **kwargs: Any) -> Any:
+    async def invoke(self, **kwargs: Any) -> Any:
         """Invoke the skill with given parameters.
 
-        Calls the run() function directly.
+        Awaits the async run() function.
         """
-        return self._func(**kwargs)
+        return await self._func(**kwargs)
 
     @property
     def tags(self) -> frozenset[str]:
diff --git a/tests/conftest.py b/tests/conftest.py
index ab801a0..86f694b 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -743,7 +743,7 @@ def sample_skill_source() -> str:
     """Sample skill source code for testing."""
     return '''"""Double a number."""
 
-def run(n: int) -> int:
+async def run(n: int) -> int:
     return n * 2
 '''
 
diff --git a/tests/container/test_container_api.py b/tests/container/test_container_api.py
index 9671b19..5bea730 100644
--- a/tests/container/test_container_api.py
+++ b/tests/container/test_container_api.py
@@ -164,7 +164,7 @@ def test_create_skill_success(self, auth_client) -> None:
             "/api/skills",
             json={
                 "name": "test_skill",
-                "source": "def run(x: int) -> int:\n    return x * 2",
+                "source": "async def run(x: int) -> int:\n    return x * 2",
                 "description": "Doubles a number",
             },
             headers={"Authorization": f"Bearer {token}"},
@@ -182,7 +182,7 @@ def test_create_skill_requires_auth(self, auth_client) -> None:
             "/api/skills",
             json={
                 "name": "test_skill",
-                "source": "def run(): pass",
+                "source": "async def run(): pass",
                 "description": "Test",
             },
         )
@@ -238,11 +238,14 @@ def test_skill_lifecycle_create_get_delete(self, auth_client) -> None:
         headers = {"Authorization": f"Bearer {token}"}
 
         # Create
+        skill_source = (
+            'async def run(n: int) -> int:\n    """Square a number."""\n    return n ** 2'
+        )
         response = client.post(
             "/api/skills",
             json={
                 "name": "lifecycle_skill",
-                "source": 'def run(n: int) -> int:\n    """Square a number."""\n    return n ** 2',
+                "source": skill_source,
                 "description": "Squares a number",
             },
             headers=headers,
diff --git a/tests/test_backend_integration.py b/tests/test_backend_integration.py
index bec7837..75cc577 100644
--- a/tests/test_backend_integration.py
+++ b/tests/test_backend_integration.py
@@ -61,7 +61,7 @@ def skills_dir(self, tmp_path: Path) -> Path:
         (skills / "double.py").write_text(
             '''"""Double a number."""
 
-def run(n: int) -> int:
+async def run(n: int) -> int:
     return n * 2
 '''
         )
@@ -305,7 +305,7 @@ def executor_with_skills(self, tmp_path: Path) -> InProcessExecutor:
         # Create a test skill using from_source
         skill = PythonSkill.from_source(
             name="double",
-            source='def run(n: int) -> int:\n    """Double a number."""\n    return n * 2',
+            source='async def run(n: int) -> int:\n    """Double a number."""\n    return n * 2',
             description="Double a number",
         )
 
@@ -341,7 +341,7 @@ async def test_skill_with_default_args(self, tmp_path: Path) -> None:
         skills_path.mkdir()
 
         source = (
-            'def run(name: str = "World") -> str:\n'
+            'async def run(name: str = "World") -> str:\n'
             '    """Greet someone."""\n'
             '    return f"Hello, {name}!"'
         )
diff --git a/tests/test_backend_user_journey.py b/tests/test_backend_user_journey.py
index af43027..4de3380 100644
--- a/tests/test_backend_user_journey.py
+++ b/tests/test_backend_user_journey.py
@@ -132,7 +132,7 @@ async def test_agent_full_workflow_in_process(
 skills.create(
     name="shout",
     description="Echo text in uppercase",
-    source="def run(text: str) -> str:\\n    return text.upper()"
+    source="async def run(text: str) -> str:\\n    return text.upper()"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -187,7 +187,7 @@ async def test_agent_full_workflow_container(
 skills.create(
     name="container_shout",
     description="Echo text in uppercase",
-    source="def run(text: str) -> str:\\n    return text.upper()"
+    source="async def run(text: str) -> str:\\n    return text.upper()"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -290,7 +290,7 @@ async def test_skills_create_invoke_delete(self, empty_storage: Path) -> None:
 skills.create(
     name="add_numbers",
     description="Add two numbers",
-    source="def run(a: int, b: int) -> int:\\n    return a + b"
+    source="async def run(a: int, b: int) -> int:\\n    return a + b"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -333,7 +333,7 @@ async def test_skill_uses_tools_in_container(
 skills.create(
     name="loud_echo",
     description="Echo text and uppercase it",
-    source="""def run(text: str) -> str:
+    source="""async def run(text: str) -> str:
     result = tools.echo.echo(text=text)
     return result.strip().upper()
 """
@@ -369,7 +369,7 @@ async def test_skill_persists_across_container_sessions(self, empty_storage: Pat
 skills.create(
     name="persistent_skill",
     description="Should persist",
-    source="def run() -> str:\\n    return 'persisted'"
+    source="async def run() -> str:\\n    return 'persisted'"
 )
 """)
             assert result.is_ok
@@ -443,7 +443,7 @@ async def test_redis_container_full_workflow(self, redis_url: str) -> None:
 skills.create(
     name="redis_skill",
     description="Test skill in Redis",
-    source="def run(x: int) -> int:\\n    return x * 2"
+    source="async def run(x: int) -> int:\\n    return x * 2"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -479,7 +479,7 @@ async def test_redis_container_skill_persistence(self, redis_url: str) -> None:
 skills.create(
     name="redis_persistent",
     description="Should persist in Redis",
-    source="def run() -> str:\\n    return 'from redis'"
+    source="async def run() -> str:\\n    return 'from redis'"
 )
 """)
             assert result.is_ok
@@ -512,7 +512,7 @@ async def test_redis_container_skill_search(self, redis_url: str) -> None:
 skills.create(
     name="port_scanner",
     description="Scan network ports to find open services",
-    source="def run(host: str) -> list:\\n    return ['port scanning', host]"
+    source="async def run(host: str) -> list:\\n    return ['port scanning', host]"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -539,7 +539,7 @@ async def test_redis_search_skills_facade(self, redis_url: str) -> None:
             # 1. Create a skill using facade method
             await session.add_skill(
                 name="web_scraper",
-                source="def run(url: str) -> str:\n    return f'scraped {url}'",
+                source="async def run(url: str) -> str:\n    return f'scraped {url}'",
                 description="Scrape web pages and extract content",
             )
 
@@ -603,7 +603,7 @@ async def test_redis_stack_search_skills_facade(self, redis_stack_url: str) -> N
             # 1. Create a skill
             await session.add_skill(
                 name="data_analyzer",
-                source="def run(data: list) -> dict:\n    return {'count': len(data)}",
+                source="async def run(data: list) -> dict:\n    return {'count': len(data)}",
                 description="Analyze data and return statistics",
             )
 
@@ -674,7 +674,7 @@ async def test_container_invalid_skill_source_rejected(self, empty_storage: Path
 skills.create(
     name="bad_skill",
     description="Invalid syntax",
-    source="def run( broken"
+    source="async def run( broken"
 )
 """)
             assert not result.is_ok, "Expected error for invalid syntax"
diff --git a/tests/test_bootstrap.py b/tests/test_bootstrap.py
index ada5c6e..b0aa938 100644
--- a/tests/test_bootstrap.py
+++ b/tests/test_bootstrap.py
@@ -695,7 +695,9 @@ async def test_config_roundtrip(self, tmp_path: Path) -> None:
         storage = FileStorage(tmp_path)
         (tmp_path / "skills").mkdir(exist_ok=True)
         skill_file = tmp_path / "skills" / "greet.py"
-        skill_content = '"""Greet."""\ndef run(name: str) -> str:\n    return f"Hello, {name}!"'
+        skill_content = (
+            '"""Greet."""\nasync def run(name: str) -> str:\n    return f"Hello, {name}!"'
+        )
         skill_file.write_text(skill_content)
 
         # Serialize
@@ -852,7 +854,7 @@ async def test_config_roundtrip(self, mock_redis: MockRedisClient) -> None:
         skill_store = storage.get_skill_store()
         test_skill = PythonSkill.from_source(
             name="greet",
-            source='def run(name: str) -> str:\n    return f"Hello, {name}!"',
+            source='async def run(name: str) -> str:\n    return f"Hello, {name}!"',
             description="Greet a user",
         )
         skill_store.save(test_skill)
@@ -1117,7 +1119,8 @@ async def test_file_storage_bootstrap_journey(self, tmp_path: Path) -> None:
         storage = FileStorage(tmp_path)
         (tmp_path / "skills").mkdir(exist_ok=True)
         skill_file = tmp_path / "skills" / "double.py"
-        skill_file.write_text('"""Double a number."""\ndef run(n: int) -> int:\n    return n * 2')
+        skill_content = '"""Double a number."""\nasync def run(n: int) -> int:\n    return n * 2'
+        skill_file.write_text(skill_content)
 
         (tmp_path / "artifacts").mkdir(exist_ok=True)
 
@@ -1166,7 +1169,7 @@ async def test_redis_storage_bootstrap_journey(self, mock_redis: MockRedisClient
         skill_store = storage.get_skill_store()
         skill = PythonSkill.from_source(
             name="triple",
-            source="def run(n: int) -> int:\n    return n * 3",
+            source="async def run(n: int) -> int:\n    return n * 3",
             description="Triple a number",
         )
         skill_store.save(skill)
diff --git a/tests/test_chroma_vector_store.py b/tests/test_chroma_vector_store.py
index 737ca8c..76b6293 100644
--- a/tests/test_chroma_vector_store.py
+++ b/tests/test_chroma_vector_store.py
@@ -141,7 +141,7 @@ def test_detects_model_change_different_dimension(
         store1.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="abc123",
         )
         assert store1.count() == 1
@@ -166,7 +166,7 @@ def test_preserves_vectors_when_model_unchanged(
         store1.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="abc123",
         )
         assert store1.count() == 1
@@ -200,7 +200,7 @@ def test_clears_all_vectors_on_model_change(
             store1.add(
                 id=f"skill{i}",
                 description=f"Skill {i}",
-                source=f"def run(): return {i}",
+                source=f"async def run(): return {i}",
                 content_hash=f"hash{i}",
             )
         assert store1.count() == 5
@@ -235,7 +235,7 @@ def test_add_embeds_and_stores_vectors(self, store) -> None:
         store.add(
             id="port_scanner",
             description="Scan network ports using nmap",
-            source='def run(target: str):\n    return subprocess.run(["nmap", target])',
+            source='async def run(target: str):\n    return subprocess.run(["nmap", target])',
             content_hash="abc123def456",
         )
 
@@ -247,7 +247,7 @@ def test_add_stores_content_hash(self, store) -> None:
         store.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="contenthash123",
         )
 
@@ -265,7 +265,7 @@ def test_add_overwrites_existing_skill(self, store) -> None:
         store.add(
             id="skill1",
             description="Original description",
-            source="def run(): return 1",
+            source="async def run(): return 1",
             content_hash="hash1",
         )
         assert store.count() == 1
@@ -273,7 +273,7 @@ def test_add_overwrites_existing_skill(self, store) -> None:
         store.add(
             id="skill1",
             description="Updated description",
-            source="def run(): return 2",
+            source="async def run(): return 2",
             content_hash="hash2",
         )
 
@@ -288,7 +288,7 @@ def test_remove_deletes_skill_vectors(self, store) -> None:
         store.add(
             id="skill1",
             description="Test",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="hash1",
         )
         assert store.count() == 1
@@ -527,7 +527,7 @@ def test_same_content_hash_skips_re_embedding(
         store.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="stable_hash",
         )
         initial_embed_count = embedder_with_call_tracking.embed_call_count
@@ -536,7 +536,7 @@ def test_same_content_hash_skips_re_embedding(
         store.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="stable_hash",
         )
 
@@ -556,7 +556,7 @@ def test_different_content_hash_triggers_re_embedding(
         store.add(
             id="skill1",
             description="Original description",
-            source="def run(): return 1",
+            source="async def run(): return 1",
             content_hash="hash_v1",
         )
         initial_embed_count = embedder_with_call_tracking.embed_call_count
@@ -565,7 +565,7 @@ def test_different_content_hash_triggers_re_embedding(
         store.add(
             id="skill1",
             description="Updated description",
-            source="def run(): return 2",
+            source="async def run(): return 2",
             content_hash="hash_v2",
         )
 
diff --git a/tests/test_error_handling.py b/tests/test_error_handling.py
index 4b291b3..cd966d0 100644
--- a/tests/test_error_handling.py
+++ b/tests/test_error_handling.py
@@ -88,14 +88,14 @@ def skills_dir_with_corruption(tmp_path: Path) -> Path:
     # Valid skill
     (skills_dir / "valid_skill.py").write_text('''"""A valid skill."""
 
-def run(x: int) -> int:
+async def run(x: int) -> int:
     return x * 2
 ''')
 
     # Corrupted Python (syntax error)
     (skills_dir / "syntax_error.py").write_text('''"""Skill with syntax error."""
 
-def run(x: int) -> int
+async def run(x: int) -> int
     return x * 2  # Missing colon above
 ''')
 
@@ -120,7 +120,7 @@ def __init__(self):
                     "valid": json.dumps(
                         {
                             "name": "valid",
-                            "source": "def run(): pass",
+                            "source": "async def run(): pass",
                             "description": "Valid skill",
                         }
                     ).encode(),
diff --git a/tests/test_executor_configs.py b/tests/test_executor_configs.py
index 908c7fd..0fc884f 100644
--- a/tests/test_executor_configs.py
+++ b/tests/test_executor_configs.py
@@ -211,16 +211,16 @@ def test_deps_file_accepts_path(self, tmp_path: Path) -> None:
         config = SubprocessConfig(deps_file=deps_file)
         assert config.deps_file == deps_file
 
-    def test_ipc_timeout_default_is_30(self) -> None:
-        """ipc_timeout defaults to 30.0 seconds.
+    def test_ipc_timeout_default_is_none(self) -> None:
+        """ipc_timeout defaults to None (unlimited).
 
-        Contract: SubprocessConfig().ipc_timeout == 30.0
+        Contract: SubprocessConfig().ipc_timeout is None
         Breaks when: Default changed or field missing.
         """
         from py_code_mode.execution import SubprocessConfig
 
         config = SubprocessConfig()
-        assert config.ipc_timeout == 30.0
+        assert config.ipc_timeout is None
 
     def test_ipc_timeout_accepts_custom_value(self) -> None:
         """ipc_timeout accepts a custom value.
@@ -464,23 +464,15 @@ def test_all_configs_have_deps_file(self) -> None:
     def test_all_configs_have_ipc_timeout(self) -> None:
         """All executor configs have ipc_timeout field.
 
-        Contract: Consistent API across all executors.
-        Breaks when: Any config missing the field.
+        Contract: All configs support ipc_timeout.
+        Breaks when: Any config missing ipc_timeout.
+        Note: SubprocessConfig defaults to None (unlimited), others to 30.0.
         """
         from py_code_mode.execution import ContainerConfig, InProcessConfig, SubprocessConfig
 
         assert hasattr(InProcessConfig(), "ipc_timeout")
         assert hasattr(SubprocessConfig(), "ipc_timeout")
         assert hasattr(ContainerConfig(), "ipc_timeout")
-
-    def test_all_configs_ipc_timeout_default_30(self) -> None:
-        """All executor configs have ipc_timeout default of 30.0.
-
-        Contract: Consistent default across all executors.
-        Breaks when: Any config has different default.
-        """
-        from py_code_mode.execution import ContainerConfig, InProcessConfig, SubprocessConfig
-
         assert InProcessConfig().ipc_timeout == 30.0
-        assert SubprocessConfig().ipc_timeout == 30.0
+        assert SubprocessConfig().ipc_timeout is None
         assert ContainerConfig().ipc_timeout == 30.0
diff --git a/tests/test_feature_matrix_comprehensive.py b/tests/test_feature_matrix_comprehensive.py
index 442900a..4abfc0a 100644
--- a/tests/test_feature_matrix_comprehensive.py
+++ b/tests/test_feature_matrix_comprehensive.py
@@ -99,7 +99,7 @@ def populated_dir(tmp_path: Path) -> tuple[Path, Path]:
     # Sample skill
     (skills_dir / "double.py").write_text('''"""Double a number."""
 
-def run(n: int) -> int:
+async def run(n: int) -> int:
     return n * 2
 ''')
 
@@ -182,7 +182,7 @@ async def test_complete_workflow_from_empty_directory(self, empty_base_dir: Path
 skills.create(
     name="triple",
     description="Triple a number",
-    source="def run(n: int) -> int:\\n    return n * 3"
+    source="async def run(n: int) -> int:\\n    return n * 3"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -239,7 +239,7 @@ async def test_skills_persist_across_sessions(self, empty_base_dir: Path) -> Non
 skills.create(
     name="quadruple",
     description="Multiply by 4",
-    source="def run(n: int) -> int:\\n    return n * 4"
+    source="async def run(n: int) -> int:\\n    return n * 4"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -344,7 +344,7 @@ async def test_skills_create_creates_directory(self, empty_base_dir: Path) -> No
 skills.create(
     name="test_skill",
     description="Test",
-    source="def run() -> str:\\n    return 'ok'"
+    source="async def run() -> str:\\n    return 'ok'"
 )
 """)
             assert result.is_ok, f"Failed: {result.error}"
@@ -524,7 +524,7 @@ async def test_skills_work_without_tools_directory(self, partial_dir_skills_only
         (partial_dir_skills_only / "skills" / "add.py").write_text('''
 """Add two numbers."""
 
-def run(a: int, b: int) -> int:
+async def run(a: int, b: int) -> int:
     return a + b
 ''')
 
@@ -580,7 +580,7 @@ async def test_skills_create_and_persist_in_redis(self, redis_storage) -> None:
 skills.create(
     name="redis_skill",
     description="Test skill",
-    source="def run() -> str:\\n    return 'from redis'"
+    source="async def run() -> str:\\n    return 'from redis'"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
@@ -730,7 +730,7 @@ async def test_skills_create_feature(self, storage_and_executor) -> None:
 skills.create(
     name="matrix_test",
     description="Matrix test skill",
-    source="def run() -> str:\\n    return 'matrix'"
+    source="async def run() -> str:\\n    return 'matrix'"
 )
 """)
             assert result.is_ok, f"skills.create() failed: {result.error}"
diff --git a/tests/test_integration.py b/tests/test_integration.py
index 5addc26..b1cd92b 100644
--- a/tests/test_integration.py
+++ b/tests/test_integration.py
@@ -382,7 +382,7 @@ def skill_library(self, tmp_path: Path) -> SkillLibrary:
         # Create a simple skill
         (skills_path / "double.py").write_text('''"""Double a number."""
 
-def run(n: int) -> int:
+async def run(n: int) -> int:
     return n * 2
 ''')
 
diff --git a/tests/test_mcp_server.py b/tests/test_mcp_server.py
index 27d5aff..10fb5f9 100644
--- a/tests/test_mcp_server.py
+++ b/tests/test_mcp_server.py
@@ -90,13 +90,13 @@ def mcp_storage_dir(tmp_path: Path) -> tuple[Path, Path]:
 
     # Simple skill for basic testing
     (skills_dir / "double.py").write_text('''"""Double a number."""
-def run(n: int) -> int:
+async def run(n: int) -> int:
     return n * 2
 ''')
 
     # Skill that calls tools (for cross-namespace testing)
     (skills_dir / "fetch_title.py").write_text('''"""Fetch a URL and extract title."""
-def run(url: str) -> str:
+async def run(url: str) -> str:
     import re
     content = tools.curl.get(url=url)
     match = re.search(r'<title>([^<]+)</title>', content, re.I)
@@ -274,7 +274,7 @@ async def test_mcp_server_skill_create_and_invoke(
 skills.create(
     name="add_numbers",
     source="""
-def run(a: int, b: int) -> int:
+async def run(a: int, b: int) -> int:
     return a + b
 """,
     description="Add two numbers together"
@@ -314,7 +314,7 @@ async def test_mcp_server_skill_persists_across_calls(
                         "code": """
 skills.create(
     name="triple",
-    source="def run(n: int) -> int:\\n    return n * 3",
+    source="async def run(n: int) -> int:\\n    return n * 3",
     description="Triple a number"
 )
 """
@@ -360,7 +360,7 @@ async def test_mcp_server_skill_delete(
                         "code": """
 skills.create(
     name="temp_skill",
-    source="def run() -> str:\\n    return 'temporary'",
+    source="async def run() -> str:\\n    return 'temporary'",
     description="Temporary skill for deletion test"
 )
 """
@@ -598,7 +598,7 @@ async def test_mcp_server_skill_calls_tool(
 skills.create(
     name="shout",
     source="""
-def run(message: str) -> str:
+async def run(message: str) -> str:
     return tools.echo(text=message.upper())
 """,
     description="Echo message in uppercase"
@@ -667,7 +667,7 @@ async def test_mcp_server_skill_calls_another_skill(
 skills.create(
     name="quadruple",
     source="""
-def run(n: int) -> int:
+async def run(n: int) -> int:
     doubled = skills.invoke("double", n=n)
     return skills.invoke("double", n=doubled)
 """,
@@ -851,7 +851,7 @@ async def test_mcp_server_create_skill(
                 await session.initialize()
 
                 # Create skill via dedicated MCP tool (not run_code)
-                skill_source = "def run(x: int, y: int) -> int:\n    return x + y\n"
+                skill_source = "async def run(x: int, y: int) -> int:\n    return x + y\n"
                 result = await session.call_tool(
                     "create_skill",
                     {
@@ -892,7 +892,7 @@ async def test_mcp_server_create_skill_persists(
                 await session.initialize()
 
                 # Create skill via dedicated MCP tool
-                skill_source = "def run(text: str) -> str:\n    return text.upper()\n"
+                skill_source = "async def run(text: str) -> str:\n    return text.upper()\n"
                 await session.call_tool(
                     "create_skill",
                     {
@@ -934,7 +934,7 @@ async def test_mcp_server_delete_skill(
                 await session.initialize()
 
                 # Create a skill via MCP tool
-                skill_source = "def run() -> str:\n    return 'I exist'\n"
+                skill_source = "async def run() -> str:\n    return 'I exist'\n"
                 await session.call_tool(
                     "create_skill",
                     {
@@ -1042,7 +1042,7 @@ async def test_mcp_server_full_workflow(
     name="sum_csv",
     source="""
 import re
-def run(text: str) -> int:
+async def run(text: str) -> int:
     numbers = [int(x) for x in re.findall(r'\\\\d+', text)]
     return sum(numbers)
 """,
diff --git a/tests/test_negative.py b/tests/test_negative.py
index ce83132..fdb9ad9 100644
--- a/tests/test_negative.py
+++ b/tests/test_negative.py
@@ -187,7 +187,7 @@ def storage(self, tmp_path: Path) -> FileStorage:
         (skills_dir / "divide.py").write_text(
             '''"""Divide two numbers."""
 
-def run(a: int, b: int) -> float:
+async def run(a: int, b: int) -> float:
     return a / b
 '''
         )
@@ -235,7 +235,7 @@ async def test_skill_create_invalid_source_error(self, storage: FileStorage) ->
 skills.create(
     name="bad",
     description="Invalid skill",
-    source="def run( INVALID SYNTAX"
+    source="async def run( INVALID SYNTAX"
 )
 """
             )
@@ -372,7 +372,7 @@ def test_corrupted_skill_handling(self, tmp_path: Path) -> None:
         """FileStorage handles corrupted skill files."""
         skills_dir = tmp_path / "skills"
         skills_dir.mkdir()
-        (skills_dir / "bad.py").write_text("def run( INVALID")
+        (skills_dir / "bad.py").write_text("async def run( INVALID")
 
         storage = FileStorage(tmp_path)
 
diff --git a/tests/test_redis_vector_store.py b/tests/test_redis_vector_store.py
index 4018ad4..813a443 100644
--- a/tests/test_redis_vector_store.py
+++ b/tests/test_redis_vector_store.py
@@ -163,7 +163,7 @@ def test_reuses_existing_compatible_index(
             prefix="skills",
             index_name="skills_idx",
         )
-        store1.add("skill1", "Test skill", "def run(): pass", "hash1")
+        store1.add("skill1", "Test skill", "async def run(): pass", "hash1")
         assert store1.count() == 1
 
         # Create second store with same config - should reuse index
@@ -218,7 +218,7 @@ def test_detects_model_change_different_dimension(
         store1.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="abc123",
         )
         assert store1.count() == 1
@@ -252,7 +252,7 @@ def test_preserves_vectors_when_model_unchanged(
         store1.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="abc123",
         )
         assert store1.count() == 1
@@ -292,7 +292,7 @@ def test_clears_all_vectors_on_model_change(
             store1.add(
                 id=f"skill{i}",
                 description=f"Skill {i}",
-                source=f"def run(): return {i}",
+                source=f"async def run(): return {i}",
                 content_hash=f"hash{i}",
             )
         assert store1.count() == 5
@@ -337,7 +337,7 @@ def test_add_embeds_and_stores_vectors(self, store) -> None:
         store.add(
             id="port_scanner",
             description="Scan network ports using nmap",
-            source='def run(target: str):\n    return subprocess.run(["nmap", target])',
+            source='async def run(target: str):\n    return subprocess.run(["nmap", target])',
             content_hash="abc123def456",
         )
 
@@ -349,7 +349,7 @@ def test_add_stores_content_hash(self, store) -> None:
         store.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="contenthash123",
         )
 
@@ -367,7 +367,7 @@ def test_add_overwrites_existing_skill(self, store) -> None:
         store.add(
             id="skill1",
             description="Original description",
-            source="def run(): return 1",
+            source="async def run(): return 1",
             content_hash="hash1",
         )
         assert store.count() == 1
@@ -375,7 +375,7 @@ def test_add_overwrites_existing_skill(self, store) -> None:
         store.add(
             id="skill1",
             description="Updated description",
-            source="def run(): return 2",
+            source="async def run(): return 2",
             content_hash="hash2",
         )
 
@@ -390,7 +390,7 @@ def test_remove_deletes_skill_vectors(self, store) -> None:
         store.add(
             id="skill1",
             description="Test",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="hash1",
         )
         assert store.count() == 1
@@ -645,7 +645,7 @@ def test_same_content_hash_skips_re_embedding(
         store.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="stable_hash",
         )
         initial_embed_count = embedder_with_call_tracking.embed_call_count
@@ -654,7 +654,7 @@ def test_same_content_hash_skips_re_embedding(
         store.add(
             id="skill1",
             description="Test skill",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="stable_hash",
         )
 
@@ -679,7 +679,7 @@ def test_different_content_hash_triggers_re_embedding(
         store.add(
             id="skill1",
             description="Original description",
-            source="def run(): return 1",
+            source="async def run(): return 1",
             content_hash="hash_v1",
         )
         initial_embed_count = embedder_with_call_tracking.embed_call_count
@@ -688,7 +688,7 @@ def test_different_content_hash_triggers_re_embedding(
         store.add(
             id="skill1",
             description="Updated description",
-            source="def run(): return 2",
+            source="async def run(): return 2",
             content_hash="hash_v2",
         )
 
diff --git a/tests/test_rpc_errors.py b/tests/test_rpc_errors.py
index bacef2e..311669d 100644
--- a/tests/test_rpc_errors.py
+++ b/tests/test_rpc_errors.py
@@ -81,7 +81,7 @@ async def test_skill_with_missing_import_raises_skill_error(
         create_code = '''
 skills.create(
     "broken_skill",
-    """def run():
+    """async def run():
     import this_module_definitely_does_not_exist
     return "never reached"
 """,
@@ -233,7 +233,7 @@ async def test_error_preserves_original_exception_type(
         create_code = '''
 skills.create(
     "value_error_skill",
-    """def run():
+    """async def run():
     raise ValueError("intentional value error")
 """,
     "A skill that raises ValueError"
diff --git a/tests/test_semantic.py b/tests/test_semantic.py
index c35f653..f812e61 100644
--- a/tests/test_semantic.py
+++ b/tests/test_semantic.py
@@ -9,7 +9,7 @@
 
 def _make_skill(name: str, description: str, code: str) -> PythonSkill:
     """Helper to create a PythonSkill from minimal info."""
-    source = f'"""{description}"""\n\ndef run():\n    {code}'
+    source = f'"""{description}"""\n\nasync def run():\n    {code}'
     return PythonSkill.from_source(name=name, source=source, description=description)
 
 
@@ -128,7 +128,7 @@ def python_skill(self) -> PythonSkill:
         source = dedent('''
             """Calculate sum of numbers."""
 
-            def run(numbers: list[int]) -> int:
+            async def run(numbers: list[int]) -> int:
                 return sum(numbers)
         ''').strip()
         return PythonSkill.from_source(name="sum_numbers", source=source)
diff --git a/tests/test_session.py b/tests/test_session.py
index dcf6955..aaf62b7 100644
--- a/tests/test_session.py
+++ b/tests/test_session.py
@@ -170,7 +170,7 @@ def storage_with_skills(self, tmp_path: Path) -> FileStorage:
         (skills_dir / "double.py").write_text(
             '''"""Double a number."""
 
-def run(n: int) -> int:
+async def run(n: int) -> int:
     return n * 2
 '''
         )
@@ -217,7 +217,7 @@ async def test_skills_create_callable(self, storage_with_skills: FileStorage) ->
 skills.create(
     name="triple",
     description="Triple a number",
-    source="def run(n: int) -> int:\\n    return n * 3"
+    source="async def run(n: int) -> int:\\n    return n * 3"
 )
 """
             )
@@ -593,7 +593,7 @@ def storage_with_skills(self, tmp_path: Path) -> FileStorage:
         (skills_dir / "double.py").write_text(
             '''"""Double a number."""
 
-def run(n: int) -> int:
+async def run(n: int) -> int:
     return n * 2
 '''
         )
@@ -908,7 +908,7 @@ async def test_subprocess_namespaces_work_via_session(self, tmp_path: Path) -> N
         (skills_dir / "add_numbers.py").write_text(
             '''"""Add two numbers together."""
 
-def run(a: int, b: int) -> int:
+async def run(a: int, b: int) -> int:
     return a + b
 '''
         )
diff --git a/tests/test_skill_library_vector_store.py b/tests/test_skill_library_vector_store.py
index 4daeced..d86c346 100644
--- a/tests/test_skill_library_vector_store.py
+++ b/tests/test_skill_library_vector_store.py
@@ -18,7 +18,7 @@
 
 def _make_skill(name: str, description: str, code: str) -> PythonSkill:
     """Helper to create a PythonSkill from minimal info."""
-    source = f'"""{description}"""\n\ndef run():\n    {code}'
+    source = f'"""{description}"""\n\nasync def run():\n    {code}'
     return PythonSkill.from_source(name=name, source=source, description=description)
 
 
diff --git a/tests/test_skill_store.py b/tests/test_skill_store.py
index acfdcb0..e4a19fc 100644
--- a/tests/test_skill_store.py
+++ b/tests/test_skill_store.py
@@ -20,7 +20,7 @@ def sample_python_skill() -> PythonSkill:
     """A simple Python skill for testing."""
     return PythonSkill.from_source(
         name="greet",
-        source='def run(name: str) -> str:\n    return f"Hello, {name}!"',
+        source='async def run(name: str) -> str:\n    return f"Hello, {name}!"',
         description="Greet someone",
     )
 
@@ -30,7 +30,7 @@ def another_python_skill() -> PythonSkill:
     """Another Python skill for testing list operations."""
     return PythonSkill.from_source(
         name="farewell",
-        source='def run() -> str:\n    return "Goodbye!"',
+        source='async def run() -> str:\n    return "Goodbye!"',
         description="Say goodbye",
     )
 
@@ -139,7 +139,7 @@ def test_save_overwrites_existing(
 
         updated = PythonSkill.from_source(
             name="greet",
-            source='def run(name: str) -> str:\n    return f"Hi, {name}!"',
+            source='async def run(name: str) -> str:\n    return f"Hi, {name}!"',
             description="Updated greeting",
         )
         memory_store.save(updated)
@@ -204,7 +204,7 @@ def test_list_all_finds_py_files(
         # Create another skill
         another = PythonSkill.from_source(
             name="farewell",
-            source='def run() -> str:\n    return "Goodbye!"',
+            source='async def run() -> str:\n    return "Goodbye!"',
             description="Say goodbye",
         )
         file_store.save(another)
@@ -219,7 +219,7 @@ def test_list_all_ignores_underscore_files(self, file_store: FileSkillStore, tmp
         """Should skip files starting with underscore."""
         # Create __init__.py
         (tmp_path / "__init__.py").write_text("")
-        (tmp_path / "_private.py").write_text("def run(): pass")
+        (tmp_path / "_private.py").write_text("async def run(): pass")
 
         skills = file_store.list_all()
         assert len(skills) == 0
@@ -313,7 +313,7 @@ def test_list_all(self, redis_store: RedisSkillStore, sample_python_skill: Pytho
 
         another = PythonSkill.from_source(
             name="farewell",
-            source='def run() -> str:\n    return "Goodbye!"',
+            source='async def run() -> str:\n    return "Goodbye!"',
             description="Say goodbye",
         )
         redis_store.save(another)
@@ -353,7 +353,7 @@ def _make_skill_with_invalid_name(name: str) -> PythonSkill:
     # Create a valid skill first
     valid_skill = PythonSkill.from_source(
         name="temp_valid_name",
-        source="def run(): pass",
+        source="async def run(): pass",
         description="test",
     )
     # Replace the name with the invalid one for testing
@@ -431,7 +431,7 @@ def test_valid_skill_names_accepted(self, tmp_path: Path) -> None:
         for name in ["my_skill", "skill123", "_private", "CamelCase", "__dunder__"]:
             skill = PythonSkill.from_source(
                 name=name,
-                source="def run(): pass",
+                source="async def run(): pass",
                 description="test",
             )
             store.save(skill)
diff --git a/tests/test_skills.py b/tests/test_skills.py
index 9252a7f..5ea4a00 100644
--- a/tests/test_skills.py
+++ b/tests/test_skills.py
@@ -52,7 +52,7 @@ def skill_file(self, tmp_path: Path) -> Path:
             A friendly greeting skill.
             """
 
-            def run(target_name: str, enthusiasm: int = 1) -> str:
+            async def run(target_name: str, enthusiasm: int = 1) -> str:
                 """Generate a greeting.
 
                 Args:
@@ -96,31 +96,34 @@ def test_has_source_property(self, skill_file: Path) -> None:
         skill = PythonSkill.from_file(skill_file)
 
         assert skill.source is not None
-        assert "def run(" in skill.source
+        assert "async def run(" in skill.source
         assert "Hello, {target_name}" in skill.source
 
-    def test_invoke_calls_function(self, skill_file: Path) -> None:
+    @pytest.mark.asyncio
+    async def test_invoke_calls_function(self, skill_file: Path) -> None:
         """Invoking skill calls the run() function."""
         skill = PythonSkill.from_file(skill_file)
 
-        result = skill.invoke(target_name="Alice")
+        result = await skill.invoke(target_name="Alice")
 
         assert result == "Hello, Alice!"
 
-    def test_invoke_with_defaults(self, skill_file: Path) -> None:
+    @pytest.mark.asyncio
+    async def test_invoke_with_defaults(self, skill_file: Path) -> None:
         """Invoke uses default parameter values."""
         skill = PythonSkill.from_file(skill_file)
 
-        result = skill.invoke(target_name="Bob", enthusiasm=3)
+        result = await skill.invoke(target_name="Bob", enthusiasm=3)
 
         assert result == "Hello, Bob!!!"
 
-    def test_invoke_validates_required_params(self, skill_file: Path) -> None:
+    @pytest.mark.asyncio
+    async def test_invoke_validates_required_params(self, skill_file: Path) -> None:
         """Invoke fails if required params missing."""
         skill = PythonSkill.from_file(skill_file)
 
         with pytest.raises(TypeError):
-            skill.invoke()  # Missing target_name
+            await skill.invoke()
 
     def test_skill_with_tools_access(self, tmp_path: Path) -> None:
         """Skill can reference tools in its code."""
@@ -129,7 +132,7 @@ def test_skill_with_tools_access(self, tmp_path: Path) -> None:
             dedent('''
             """Scan a network target."""
 
-            def run(target: str, tools) -> str:
+            async def run(target: str, tools) -> str:
                 """Run a scan using tools.
 
                 Args:
@@ -157,7 +160,7 @@ def test_from_source_basic(self) -> None:
         source = dedent('''
             """Add two numbers."""
 
-            def run(a: int, b: int) -> int:
+            async def run(a: int, b: int) -> int:
                 return a + b
         ''').strip()
 
@@ -171,7 +174,7 @@ def test_from_source_with_description_override(self) -> None:
         """Description parameter overrides docstring."""
         source = dedent('''
             """Original description."""
-            def run() -> str:
+            async def run() -> str:
                 return "hello"
         ''').strip()
 
@@ -186,7 +189,7 @@ def run() -> str:
     def test_from_source_validates_syntax(self) -> None:
         """Invalid syntax raises SyntaxError."""
         with pytest.raises(SyntaxError):
-            PythonSkill.from_source(name="bad", source="def run( broken")
+            PythonSkill.from_source(name="bad", source="async def run( broken")
 
     def test_from_source_requires_run_function(self) -> None:
         """Must have run() function."""
@@ -201,20 +204,21 @@ def other_func():
 
     def test_from_source_validates_name(self) -> None:
         """Name must be valid Python identifier."""
-        source = "def run(): pass"
+        source = "async def run(): pass"
 
         with pytest.raises(ValueError, match="identifier"):
             PythonSkill.from_source(name="invalid-name", source=source)
 
-    def test_invoke_from_source_skill(self) -> None:
+    @pytest.mark.asyncio
+    async def test_invoke_from_source_skill(self) -> None:
         """Can invoke skill created from source."""
         source = dedent('''
             """Multiply numbers."""
-            def run(x: int, y: int) -> int:
+            async def run(x: int, y: int) -> int:
                 return x * y
         ''').strip()
 
         skill = PythonSkill.from_source(name="multiply", source=source)
-        result = skill.invoke(x=3, y=4)
+        result = await skill.invoke(x=3, y=4)
 
         assert result == 12
diff --git a/tests/test_skills_namespace_decoupling.py b/tests/test_skills_namespace_decoupling.py
index 65c8e50..3f11967 100644
--- a/tests/test_skills_namespace_decoupling.py
+++ b/tests/test_skills_namespace_decoupling.py
@@ -24,7 +24,7 @@ def skill_library() -> SkillLibrary:
     # Add a test skill that accesses tools
     skill = PythonSkill.from_source(
         name="use_tools",
-        source='def run(val: str) -> str:\n    return f"tools={tools}, val={val}"',
+        source='async def run(val: str) -> str:\n    return f"tools={tools}, val={val}"',
         description="A skill that uses tools from namespace",
     )
     library.add(skill)
@@ -91,7 +91,7 @@ def test_invoke_uses_tools_from_namespace(self, skill_library: SkillLibrary) ->
         # Create a skill that returns what tools it sees
         skill = PythonSkill.from_source(
             name="echo_tools",
-            source="def run() -> str:\n    return str(type(tools).__name__)",
+            source="async def run() -> str:\n    return str(type(tools).__name__)",
             description="Returns tools type",
         )
         skill_library.add(skill)
@@ -114,7 +114,7 @@ def test_invoke_uses_artifacts_from_namespace(self, skill_library: SkillLibrary)
         """Skill invocation can access artifacts from namespace dict."""
         skill = PythonSkill.from_source(
             name="use_artifacts",
-            source="def run() -> bool:\n    return artifacts is not None",
+            source="async def run() -> bool:\n    return artifacts is not None",
             description="Checks artifacts access",
         )
         skill_library.add(skill)
@@ -137,9 +137,11 @@ class TestNamespaceIsolation:
 
     def test_skill_cannot_modify_parent_namespace(self, skill_library: SkillLibrary) -> None:
         """Skill execution cannot add variables to parent namespace."""
-        # Skill that tries to pollute namespace
         polluter_source = (
-            'def run() -> str:\n    global pollution\n    pollution = "leaked"\n    return "done"'
+            "async def run() -> str:\n"
+            "    global pollution\n"
+            '    pollution = "leaked"\n'
+            '    return "done"'
         )
         skill = PythonSkill.from_source(
             name="polluter",
@@ -162,9 +164,12 @@ def test_skill_cannot_modify_parent_namespace(self, skill_library: SkillLibrary)
 
     def test_skill_cannot_modify_tools_reference(self, skill_library: SkillLibrary) -> None:
         """Skill cannot replace tools in parent namespace."""
+        replacer_source = (
+            'async def run() -> str:\n    global tools\n    tools = "replaced"\n    return "done"'
+        )
         skill = PythonSkill.from_source(
             name="replacer",
-            source='def run() -> str:\n    global tools\n    tools = "replaced"\n    return "done"',
+            source=replacer_source,
             description="Tries to replace tools",
         )
         skill_library.add(skill)
diff --git a/tests/test_storage_vector_store.py b/tests/test_storage_vector_store.py
index ba60874..6f46621 100644
--- a/tests/test_storage_vector_store.py
+++ b/tests/test_storage_vector_store.py
@@ -153,7 +153,7 @@ def test_skill_library_uses_vector_store_for_search(self, tmp_path: Path) -> Non
         # Add a skill with distinctive description
         skill = PythonSkill.from_source(
             name="calculate_total",
-            source="def run(numbers): return sum(numbers)",
+            source="async def run(numbers): return sum(numbers)",
             description="Add up all numbers in a list",
         )
         library.add(skill)
@@ -328,14 +328,14 @@ def test_file_storage_end_to_end_semantic_search(self, tmp_path: Path) -> None:
         library.add(
             PythonSkill.from_source(
                 name="http_get",
-                source="def run(url): import requests; return requests.get(url)",
+                source="async def run(url): import requests; return requests.get(url)",
                 description="Fetch data from a URL using HTTP GET request",
             )
         )
         library.add(
             PythonSkill.from_source(
                 name="parse_json",
-                source="def run(text): import json; return json.loads(text)",
+                source="async def run(text): import json; return json.loads(text)",
                 description="Parse JSON string into Python object",
             )
         )
@@ -361,7 +361,7 @@ def test_vector_store_persists_across_storage_instances(self, tmp_path: Path) ->
         library1.add(
             PythonSkill.from_source(
                 name="test_skill",
-                source="def run(): return 1",
+                source="async def run(): return 1",
                 description="A test skill for persistence",
             )
         )
@@ -417,7 +417,7 @@ def test_skill_library_works_without_vector_store(self, tmp_path: Path) -> None:
         # Should still work for basic operations
         skill = PythonSkill.from_source(
             name="basic",
-            source="def run(): return 1",
+            source="async def run(): return 1",
             description="Basic skill",
         )
         library.add(skill)
@@ -454,7 +454,7 @@ def test_vector_store_count_matches_skill_count(self, tmp_path: Path) -> None:
             library.add(
                 PythonSkill.from_source(
                     name=f"skill_{i}",
-                    source="def run(): return 1",
+                    source="async def run(): return 1",
                     description=f"Skill number {i}",
                 )
             )
diff --git a/tests/test_store.py b/tests/test_store.py
index a673f8b..3529915 100644
--- a/tests/test_store.py
+++ b/tests/test_store.py
@@ -73,7 +73,7 @@ def test_same_skill_same_hash(self) -> None:
         """Same skill content produces same hash."""
         from py_code_mode.cli.store import _skill_hash
 
-        skill = _make_skill("test", "Test skill", "def run():\n    return 'hello'")
+        skill = _make_skill("test", "Test skill", "async def run():\n    return 'hello'")
 
         hash1 = _skill_hash(skill)
         hash2 = _skill_hash(skill)
@@ -83,8 +83,8 @@ def test_different_content_different_hash(self) -> None:
         """Different skill content produces different hash."""
         from py_code_mode.cli.store import _skill_hash
 
-        skill1 = _make_skill("test", "Desc 1", "def run(): return 1")
-        skill2 = _make_skill("test", "Desc 2", "def run(): return 1")
+        skill1 = _make_skill("test", "Desc 1", "async def run(): return 1")
+        skill2 = _make_skill("test", "Desc 2", "async def run(): return 1")
 
         assert _skill_hash(skill1) != _skill_hash(skill2)
 
@@ -92,7 +92,7 @@ def test_hash_is_short(self) -> None:
         """Hash is truncated to 12 characters."""
         from py_code_mode.cli.store import _skill_hash
 
-        skill = _make_skill("test", "desc", "def run(): pass")
+        skill = _make_skill("test", "desc", "async def run(): pass")
         assert len(_skill_hash(skill)) == 12
 
 
@@ -107,7 +107,7 @@ def test_bootstrap_loads_skills_from_directory(self, tmp_path: Path) -> None:
         skill_file = tmp_path / "my_skill.py"
         skill_file.write_text('''"""My test skill."""
 
-def run(x: int) -> int:
+async def run(x: int) -> int:
     """Double a number."""
     return x * 2
 ''')
@@ -129,11 +129,11 @@ def test_bootstrap_with_clear_removes_existing(self, tmp_path: Path) -> None:
 
         # Create test skill
         skill_file = tmp_path / "new_skill.py"
-        skill_file.write_text('"""New skill."""\ndef run() -> str:\n    return "new"')
+        skill_file.write_text('"""New skill."""\nasync def run() -> str:\n    return "new"')
 
         # Mock store with existing skill
         mock_store = MagicMock()
-        existing_skill = _make_skill("old_skill", "Old", "def run(): pass")
+        existing_skill = _make_skill("old_skill", "Old", "async def run(): pass")
         mock_store.list_all.return_value = [existing_skill]
 
         with patch("py_code_mode.cli.store._get_store", return_value=mock_store):
@@ -147,8 +147,8 @@ def test_bootstrap_returns_count(self, tmp_path: Path) -> None:
         from py_code_mode.cli.store import bootstrap
 
         # Create multiple skills
-        (tmp_path / "skill1.py").write_text('"""S1."""\ndef run(): return 1')
-        (tmp_path / "skill2.py").write_text('"""S2."""\ndef run(): return 2')
+        (tmp_path / "skill1.py").write_text('"""S1."""\nasync def run(): return 1')
+        (tmp_path / "skill2.py").write_text('"""S2."""\nasync def run(): return 2')
 
         mock_store = MagicMock()
         mock_store.list_all.return_value = []
@@ -173,7 +173,7 @@ def test_pull_writes_skills_to_files(self, tmp_path: Path) -> None:
         skill = MagicMock()
         skill.name = "skill1"
         skill.description = "First skill"
-        skill.source = '"""First skill."""\ndef run():\n    print("one")'
+        skill.source = '"""First skill."""\nasync def run():\n    print("one")'
         mock_store.list_all.return_value = [skill]
 
         with patch("py_code_mode.cli.store._get_store", return_value=mock_store):
@@ -215,7 +215,7 @@ def test_diff_finds_added_skills(self, tmp_path: Path) -> None:
         remote_skill = MagicMock()
         remote_skill.name = "agent_created"
         remote_skill.description = "Created by agent"
-        remote_skill.source = '"""Created by agent."""\ndef run(): pass'
+        remote_skill.source = '"""Created by agent."""\nasync def run(): pass'
         mock_store.list_all.return_value = [remote_skill]
 
         with patch("py_code_mode.cli.store._get_store", return_value=mock_store):
@@ -232,7 +232,7 @@ def test_diff_finds_removed_skills(self, tmp_path: Path) -> None:
         # Local has a skill
         local = tmp_path / "local"
         local.mkdir()
-        (local / "local_only.py").write_text('"""Local skill."""\ndef run(): pass')
+        (local / "local_only.py").write_text('"""Local skill."""\nasync def run(): pass')
 
         # Remote is empty
         mock_store = MagicMock()
@@ -248,17 +248,17 @@ def test_diff_finds_modified_skills(self, tmp_path: Path) -> None:
         """Diff identifies skills with different content."""
         from py_code_mode.cli.store import diff
 
-        # Local skill
         local = tmp_path / "local"
         local.mkdir()
-        (local / "shared_skill.py").write_text('"""Local version."""\ndef run(): return "local"')
+        local_skill = '"""Local version."""\nasync def run(): return "local"'
+        (local / "shared_skill.py").write_text(local_skill)
 
         # Remote has different version
         mock_store = MagicMock()
         remote_skill = MagicMock()
         remote_skill.name = "shared_skill"
         remote_skill.description = "Remote version"
-        remote_skill.source = '"""Remote version."""\ndef run(): return "remote"'
+        remote_skill.source = '"""Remote version."""\nasync def run(): return "remote"'
         mock_store.list_all.return_value = [remote_skill]
 
         with patch("py_code_mode.cli.store._get_store", return_value=mock_store):
@@ -273,7 +273,7 @@ def test_diff_finds_unchanged_skills(self, tmp_path: Path) -> None:
         # Local skill
         local = tmp_path / "local"
         local.mkdir()
-        skill_content = '"""Same skill."""\ndef run(): return "same"'
+        skill_content = '"""Same skill."""\nasync def run(): return "same"'
         (local / "same_skill.py").write_text(skill_content)
 
         # Remote has same content
diff --git a/tests/test_subprocess_namespace_injection.py b/tests/test_subprocess_namespace_injection.py
index e0e712b..e4c5ba4 100644
--- a/tests/test_subprocess_namespace_injection.py
+++ b/tests/test_subprocess_namespace_injection.py
@@ -129,7 +129,7 @@ async def test_tool_to_skill_to_artifact_workflow(self, executor_with_storage) -
 skills.create(
     name="greet",
     source="""
-def run(name: str) -> str:
+async def run(name: str) -> str:
     result = tools.echo.run(text=f"Hello, {name}!")
     return result
 """,
@@ -165,7 +165,7 @@ async def test_skill_uses_tools_namespace_internally(self, executor_with_storage
 skills.create(
     name="echo_wrapper",
     source="""
-def run(message: str) -> str:
+async def run(message: str) -> str:
     return tools.echo.run(text=message)
 """,
     description="Wrapper around echo tool"
@@ -262,7 +262,7 @@ async def test_skills_list_returns_skill_info(self, executor_empty_storage) -> N
         create_code = """
 skills.create(
     name="add",
-    source="def run(a: int, b: int) -> int: return a + b",
+    source="async def run(a: int, b: int) -> int: return a + b",
     description="Add two numbers"
 )
 """
@@ -284,7 +284,7 @@ async def test_skills_search_semantic(self, executor_empty_storage) -> None:
         create_code = """
 skills.create(
     name="calculate_sum",
-    source="def run(numbers: list) -> int: return sum(numbers)",
+    source="async def run(numbers: list) -> int: return sum(numbers)",
     description="Calculate the total of a list of numbers"
 )
 """
@@ -306,7 +306,7 @@ async def test_skills_create_persists(self, executor_empty_storage) -> None:
         create_code = """
 skills.create(
     name="multiply",
-    source="def run(a: int, b: int) -> int: return a * b",
+    source="async def run(a: int, b: int) -> int: return a * b",
     description="Multiply two numbers"
 )
 """
@@ -331,7 +331,7 @@ async def test_skills_invoke_executes_skill(self, executor_empty_storage) -> Non
         create_code = """
 skills.create(
     name="square",
-    source="def run(n: int) -> int: return n * n",
+    source="async def run(n: int) -> int: return n * n",
     description="Square a number"
 )
 """
@@ -353,7 +353,7 @@ async def test_skills_attribute_access_invocation(self, executor_empty_storage)
         create_code = """
 skills.create(
     name="triple",
-    source="def run(n: int) -> int: return n * 3",
+    source="async def run(n: int) -> int: return n * 3",
     description="Triple a number"
 )
 """
@@ -381,7 +381,7 @@ async def test_skills_invoke_uses_runtime_installed_dep(self, executor_empty_sto
 skills.create(
     name="ascii_art_test",
     source='''
-def run(text: str) -> str:
+async def run(text: str) -> str:
     import art
     return art.text2art(text, font="block")
 ''',
@@ -541,7 +541,7 @@ async def test_namespace_state_persists_between_runs(self, executor_empty_storag
         create_code = """
 skills.create(
     name="counter",
-    source="def run(): return 'counted'",
+    source="async def run(): return 'counted'",
     description="Simple counter"
 )
 """
@@ -578,9 +578,11 @@ async def test_namespace_state_preserved_after_reset(self, tmp_path: Path) -> No
         try:
             await executor.start(storage=storage)
 
-            # Create skill and artifact before reset
             await executor.run(
-                'skills.create(name="persist", source="def run(): return 1", description="test")'
+                "skills.create("
+                'name="persist", '
+                'source="async def run(): return 1", '
+                'description="test")'
             )
             await executor.run('artifacts.save("persist_artifact", "value")')
 
@@ -714,7 +716,7 @@ async def test_creating_skill_with_invalid_source_raises_error(
         result = await executor_empty_storage.run(
             """skills.create(
                 name="broken",
-                source="def run( this is not valid python {{{{",
+                source="async def run( this is not valid python {{{{",
                 description="Broken skill"
             )"""
         )
diff --git a/tests/test_subprocess_rpc.py b/tests/test_subprocess_rpc.py
index 764ba3b..647189d 100644
--- a/tests/test_subprocess_rpc.py
+++ b/tests/test_subprocess_rpc.py
@@ -237,9 +237,9 @@ def test_get_kernel_init_code_accepts_timeout(self) -> None:
         assert "_RPC_TIMEOUT = 60.0" in code
 
     def test_get_kernel_init_code_default_timeout(self) -> None:
-        """get_kernel_init_code uses default timeout of 30.0."""
+        """get_kernel_init_code uses unlimited timeout by default."""
         code = get_kernel_init_code()
-        assert "_RPC_TIMEOUT = 30.0" in code
+        assert "_RPC_TIMEOUT = None" in code
 
     def test_kernel_init_code_defines_rpc_call(self) -> None:
         """KERNEL_INIT_CODE defines _rpc_call function."""
diff --git a/tests/test_subprocess_vector_store.py b/tests/test_subprocess_vector_store.py
index fdebad2..11da20f 100644
--- a/tests/test_subprocess_vector_store.py
+++ b/tests/test_subprocess_vector_store.py
@@ -241,7 +241,7 @@ async def test_subprocess_executor_with_vector_store(self, tmp_path: Path) -> No
         library.add(
             PythonSkill.from_source(
                 name="fetch_url",
-                source="def run(url): import requests; return requests.get(url).text",
+                source="async def run(url): import requests; return requests.get(url).text",
                 description="Download content from a web URL using HTTP",
             )
         )
@@ -297,7 +297,7 @@ async def test_subprocess_executor_without_vector_store_falls_back(
             create_code = """
 skills.create(
     name="test_skill",
-    source="def run(): return 1",
+    source="async def run(): return 1",
     description="Test skill for fallback"
 )
 """
diff --git a/tests/test_vector_store.py b/tests/test_vector_store.py
index 9fec444..ab340d7 100644
--- a/tests/test_vector_store.py
+++ b/tests/test_vector_store.py
@@ -189,7 +189,7 @@ def test_compute_content_hash_exists(self) -> None:
 
         hash_value = compute_content_hash(
             description="Scan network ports",
-            source='def run(): return "nmap"',
+            source='async def run(): return "nmap"',
         )
 
         # Should return a string (hex digest)
@@ -199,7 +199,7 @@ def test_content_hash_is_16_chars(self) -> None:
         """Hash should be 16-character hex string (8 bytes)."""
         from py_code_mode.skills.vector_store import compute_content_hash
 
-        hash_value = compute_content_hash(description="test", source="def run(): pass")
+        hash_value = compute_content_hash(description="test", source="async def run(): pass")
 
         assert len(hash_value) == 16
         # Should be valid hex
@@ -210,7 +210,7 @@ def test_same_input_produces_same_hash(self) -> None:
         from py_code_mode.skills.vector_store import compute_content_hash
 
         description = "Scan network ports"
-        source = 'def run(target: str):\n    return f"nmap {target}"'
+        source = 'async def run(target: str):\n    return f"nmap {target}"'
 
         hash1 = compute_content_hash(description, source)
         hash2 = compute_content_hash(description, source)
@@ -221,7 +221,7 @@ def test_different_description_produces_different_hash(self) -> None:
         """Different description should change hash."""
         from py_code_mode.skills.vector_store import compute_content_hash
 
-        source = "def run(): pass"
+        source = "async def run(): pass"
 
         hash1 = compute_content_hash("Description A", source)
         hash2 = compute_content_hash("Description B", source)
@@ -234,8 +234,8 @@ def test_different_source_produces_different_hash(self) -> None:
 
         description = "Test skill"
 
-        hash1 = compute_content_hash(description, "def run(): return 1")
-        hash2 = compute_content_hash(description, "def run(): return 2")
+        hash1 = compute_content_hash(description, "async def run(): return 1")
+        hash2 = compute_content_hash(description, "async def run(): return 2")
 
         assert hash1 != hash2
 
@@ -244,8 +244,8 @@ def test_whitespace_changes_affect_hash(self) -> None:
         from py_code_mode.skills.vector_store import compute_content_hash
 
         description = "Test"
-        source1 = "def run(): pass"
-        source2 = "def run():  pass"  # Extra space
+        source1 = "async def run(): pass"
+        source2 = "async def run():  pass"  # Extra space
 
         hash1 = compute_content_hash(description, source1)
         hash2 = compute_content_hash(description, source2)
@@ -257,7 +257,7 @@ def test_hash_uses_sha256_algorithm(self) -> None:
         from py_code_mode.skills.vector_store import compute_content_hash
 
         description = "Test description"
-        source = "def run(): pass"
+        source = "async def run(): pass"
 
         # Compute what the hash SHOULD be
         combined = f"{description}|||{source}"
@@ -331,7 +331,7 @@ def count(self) -> int:
         store.add(
             id="test_skill",
             description="Test description",
-            source="def run(): pass",
+            source="async def run(): pass",
             content_hash="abcd1234",
         )
 
diff --git a/uv.lock b/uv.lock
index b477bf3..39dabc2 100644
--- a/uv.lock
+++ b/uv.lock
@@ -455,6 +455,22 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/00/36/7d2d7b6bb26e53214492d71ccb4e128fa2de4d98a215befb7787deaf2701/chromadb-1.3.7-cp39-abi3-win_amd64.whl", hash = "sha256:4618ba7bb5ef5dbf0d4fd9ce708b912d8cd1ab24d3c81e0e092841f325b2c94d", size = 21874973, upload-time = "2025-12-12T21:03:16.918Z" },
 ]
 
+[[package]]
+name = "claude-agent-sdk"
+version = "0.1.18"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "anyio" },
+    { name = "mcp" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/fd/3d/a8c6ad873e8448696d44441c9eb2c24dded620fb32415d68f576a542ccde/claude_agent_sdk-0.1.18.tar.gz", hash = "sha256:4fcb8730cc77dea562fbe9aa48c65eced3ef58a6bb1f34f77e50e8258902477d", size = 56162, upload-time = "2025-12-18T00:42:57.926Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/06/14/f529f7c4bab7c71dcbcc8c66f12f491e644ee8a027ac5111d13705df207e/claude_agent_sdk-0.1.18-py3-none-macosx_11_0_arm64.whl", hash = "sha256:9e45b4e3c20c072c3e3325fa60bab9a4b5a7cbbce64ca274b8d7d0af42dd9dd8", size = 54560828, upload-time = "2025-12-18T00:42:44.71Z" },
+    { url = "https://files.pythonhosted.org/packages/2c/68/6e83005aa7bb9056bfad0aef0605249f877dc0c78724c9c0fadebff600fb/claude_agent_sdk-0.1.18-py3-none-manylinux_2_17_aarch64.whl", hash = "sha256:3c41bd8f38848609ae0d5da8d7327a4c2d7057a363feafb6fd70df611ea204cc", size = 68743107, upload-time = "2025-12-18T00:42:48.255Z" },
+    { url = "https://files.pythonhosted.org/packages/fb/85/7d6dd85f402135a610894734c442f1166ffed61d03eced39d6bfd14efccd/claude_agent_sdk-0.1.18-py3-none-manylinux_2_17_x86_64.whl", hash = "sha256:983f15e51253f40c55136a86d7cc63e023a3576428b05fa1459093d461b2d215", size = 70444964, upload-time = "2025-12-18T00:42:51.752Z" },
+    { url = "https://files.pythonhosted.org/packages/3c/fa/d2b22b7a713c4c049cbd5f9f635836ea5429ff65c1f3bcf4658a8e1c1cf5/claude_agent_sdk-0.1.18-py3-none-win_amd64.whl", hash = "sha256:36f5b84d5c3c8773ee9b56aeb5ab345d1033231db37f80d1f20ac15239bef41c", size = 72637215, upload-time = "2025-12-18T00:42:55.269Z" },
+]
+
 [[package]]
 name = "click"
 version = "8.3.1"
@@ -2581,6 +2597,7 @@ name = "py-code-mode"
 version = "0.9.0"
 source = { editable = "." }
 dependencies = [
+    { name = "claude-agent-sdk" },
     { name = "fastmcp" },
     { name = "filelock" },
     { name = "jupyter-client" },
@@ -2641,6 +2658,7 @@ dev = [
 requires-dist = [
     { name = "aiohttp", marker = "extra == 'http'", specifier = ">=3.9" },
     { name = "chromadb", marker = "extra == 'chromadb'", specifier = ">=0.5" },
+    { name = "claude-agent-sdk", specifier = ">=0.1.18" },
     { name = "docker", marker = "extra == 'container'", specifier = ">=7.0" },
     { name = "fastapi", marker = "extra == 'container'", specifier = ">=0.100" },
     { name = "fastmcp", specifier = ">=2.0.0" },