brain

A session control for claudectl’s automatic decisions about tool calls. It lets you turn that checking on, off, or into a more automatic mode.

In plain words
What is it for?
Use it to check the current mode or change how claudectl approves and denies tool calls while you work.
Why use it?
It lets you choose how much control you keep over tool use during the current session. You can require normal permission prompts or allow safe calls to proceed automatically.

Command

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add commands/mercurialsolo/claudectl/brain
Clone the repo
git clone --depth 1 https://github.com/mercurialsolo/claudectl
Per session 16 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 312 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00016 $0.00312
Opus 5 $0.00008 $0.00156
Sonnet 5 $0.00003 $0.00062
Haiku 4.5 $0.00002 $0.00031

Measured 2d ago against content hash 030807b5a59a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

brain scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

claude-plugin/commands/brain.md · 24 lines

What it actually says

Control the claudectl brain's auto-approve/deny behavior for tool calls in this session.

Modes

  • on (default) — brain evaluates every tool call, auto-approves safe ones, denies dangerous ones. Low-confidence decisions fall through to normal permission prompts.
  • off — brain is disabled. All tool calls go through Claude Code's normal permission flow. Use this when you want full manual control.
  • auto — brain auto-approves all tool calls it considers safe, even with lower confidence. Use this when you trust the brain's judgment and want maximum speed.
  • status — show the current mode without changing it.

What to do

Run claudectl --mode {{mode}} where {{mode}} is the argument the user provided (on, off, auto, or status). If no argument was provided, run claudectl --mode status.

After running the command, confirm the mode change to the user and briefly explain what it means:

  • off: "Brain disabled. Tool calls will go through normal permission prompts."
  • on: "Brain active. Safe tool calls will be auto-approved, dangerous ones auto-denied."
  • auto: "Brain in full auto mode. All decisions above the confidence threshold will execute without prompts."
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 24 lines · 16 tokens per session scan A 030807b5a59a

Subscribe to this mod's changes

brain is a command published in the GitHub repository mercurialsolo/claudectl (197 stars, last pushed 1mo ago), licensed MIT. It adds 16 tokens to every session and 312 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.