hooks_session-start · Claude Flow MCP: Risk & Policy

WHAT IT DOES

What hooks_session-start does on Claude Flow

AI agents invoke hooks_session-start to trigger actions in Claude Flow. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why hooks_session-start needs a policy

This tool triggers initialization and daemon startup—external operations whose effects depend on configuration and runtime state. While not destructive per se, it executes background processes which can alter system state, consume resources, or enable further actions. Classified as Execute rather than Write because it runs code/processes rather than just creating reversible data artifacts.

From the tool's definition Tool name 'hooks_session-start' with description 'Initialize a new session and auto-start daemon' indicates launching background processes or daemon initialization. The mention of 'native Bash hooks' and 'Claude Code' confirms command execution capabilities.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

hooks_session-start Rate-limited

hooks_session-start stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "hooks_session-start": {
      "limits": [
        {
          "counter": "hooks_session-start_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Claude Flow, so you can run agents against it safely.

FAQ

Questions about hooks_session-start

What does the hooks_session-start tool do? +

Initialize a new session and auto-start daemon Use when native Bash hooks (via Claude Code\. It is categorised as a Execute tool in the Claude Flow MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on hooks_session-start? +

Register the Claude Flow MCP server in PolicyLayer and add a rule for hooks_session-start: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Claude Flow. Nothing to install.

What risk level is hooks_session-start? +

hooks_session-start is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit hooks_session-start? +

Yes. Add a rate_limit block to the hooks_session-start rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block hooks_session-start completely? +

Set action: deny in the PolicyLayer policy for hooks_session-start. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides hooks_session-start? +

hooks_session-start is provided by the Claude Flow MCP server (claude-flow). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.