deepset-ai/haystack · error · TypeError

Hook registered for hook point '{hook_point}' must have a ca

Error message

Hook registered for hook point '{hook_point}' must have a callable 'run(state)', got an object of type '{type(h).__name__}'.

What it means

FileSystemSkillStore.warm_up() scans self.skills_dir to build the skill catalog; before the first scan it verifies the configured path exists and is a directory. This ValueError is raised when skills_dir is missing, a file instead of a directory, or otherwise not listable. warm_up is idempotent and is called lazily by _skill_dir and list_skills, so most store operations fail with this if the directory is bad.

Source

Thrown at haystack/components/agents/agent.py:133

    Validate a hooks mapping: known hook points, real Hook objects, and hook-point restrictions.

    :param hooks: Mapping of hook point to the hooks registered under it.
    :raises ValueError: If a hook point is unknown, or a hook is registered under a hook point it does not support.
    :raises TypeError: If a registered hook has no callable `run(state)`.
    """
    for hook_point, hook_list in hooks.items():
        if hook_point not in VALID_HOOK_POINTS:
            raise ValueError(
                f"Invalid hook point '{hook_point}'. Valid hook points are: {', '.join(VALID_HOOK_POINTS)}."
            )
        for h in hook_list:
            if not callable(getattr(h, "run", None)):
                if callable(h):
                    raise TypeError(
                        f"Hook registered for hook point '{hook_point}' is callable but is not a Hook object. "
                        "If it is a function, wrap it with the @hook decorator."
                    )
                raise TypeError(
                    f"Hook registered for hook point '{hook_point}' must have a callable 'run(state)', "
                    f"got an object of type '{type(h).__name__}'."
                )
            # A hook may declare `allowed_hook_points` to restrict where it can run (e.g. ConfirmationHook only
            # makes sense at "before_tool"). Hooks without it can be registered under any hook point.
            allowed_points = getattr(h, "allowed_hook_points", None)
            if allowed_points is not None and hook_point not in allowed_points:
                raise ValueError(
                    f"Hook of type '{type(h).__name__}' is registered under hook point '{hook_point}' but only "
                    f"supports: {', '.join(allowed_points)}."
                )


def _consume_continue_run(state: State) -> bool:
    """Return the `continue_run` control flag and reset it so it does not carry over to the next exit attempt."""
    should_continue = state.data["continue_run"]
    state.set("continue_run", False)
    return should_continue

View on GitHub (pinned to e318778c9b)

Solutions

Create the directory or correct the skills_dir value passed to FileSystemSkillStore to an existing directory.
Use an absolute path (Path(...).resolve()) so it doesn't depend on the process working directory.
Verify with Path(skills_dir).is_dir() before constructing the store, and ensure the path is mounted/copied into containers.

Example fix

// before
store = FileSystemSkillStore(skills_dir="./skills")
// after
from pathlib import Path
skills_dir = Path("./skills").resolve()
if not skills_dir.is_dir():
    skills_dir.mkdir(parents=True)
store = FileSystemSkillStore(skills_dir=skills_dir)

Defensive patterns

Strategy: validation

Validate before calling

from pathlib import Path

def ensure_skills_dir(skills_dir) -> Path:
    path = Path(skills_dir).resolve()
    if not path.is_dir():
        raise NotADirectoryError(f"skills_dir does not exist or is not a directory: {path}")
    return path

store = FileSystemSkillStore(skills_dir=ensure_skills_dir("./skills"))

Try / catch

try:
    skills = store.list_skills()
except ValueError as e:
    if "does not exist or is not a directory" in str(e):
        Path(skills_dir).mkdir(parents=True, exist_ok=True)
        skills = store.list_skills()
    else:
        raise

Prevention

Use absolute resolved paths for skills_dir, independent of the working directory
Create the directory at deployment/startup time (mkdir parents=True, exist_ok=True)
In containers, ensure the skills volume is mounted before constructing the store
Check path existence in a startup health check

When it happens

Trigger: Constructing FileSystemSkillStore(skills_dir=...) with a nonexistent path, a file path, a deleted/renamed directory, or an unreachable mount; then calling list_skills(), load_skill(), or any read that triggers warm_up.

Common situations: Typoed or relative path resolved from the wrong working directory; env var/setting pointing at a path that doesn't exist in the deployment container; skills directory removed after startup; path pointing to a zip archive or file.

Related errors

AI-assisted analysis of deepset-ai/haystack@e318778c9b (2026-08-30). Data as JSON: /api/errors/32666cd41f22eca8. Report an issue: GitHub.