brain-log

brain-log is a skill for Claude Code, Codex from ARCASSystems/FounderOS. It costs 187 tokens per session (1,995 once invoked), scanned A, original, MIT.

A note-taking tool for recording thoughts, decisions, flags, and ideas in a local brain log, with optional links to related files.

In plain words
What is it for?
Use it to capture a thought, journal entry, decision, reminder, or idea, either for later reference or immediate action.
Why use it?
It keeps important context from being forgotten and can connect a note to follow-up work or an existing topic.

Skill for Claude CodeCodex

Part of the founder-os plugin — 9 skills, 45 commands, 6 hooks shipped together

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 skills/arcassystems/founderos/brain-log
Any agent
npx skills add ARCASSystems/FounderOS --skill brain-log
Clone the repo
git clone --depth 1 https://github.com/ARCASSystems/FounderOS

Made for: Claude Code, Codex.

Or install founder-os, the plugin that ships this one along with the rest of its 9 skills, 45 commands, 6 hooks.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for brain-log

README.md
[![agentmods](https://agentmods.dev/badge/skills/arcassystems/founderos/brain-log.svg)](https://agentmods.dev/skills/arcassystems/founderos/brain-log)
Your own site
<a href="https://agentmods.dev/skills/arcassystems/founderos/brain-log"><img src="https://agentmods.dev/badge/skills/arcassystems/founderos/brain-log.svg" alt="Measured on agentmods" height="20"></a>
Per session 187 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,995 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 $0.00187 $0.01995
Opus 5 $0.00093 $0.00997
Sonnet 5 $0.00037 $0.00399
Haiku 4.5 $0.00019 $0.00199

Measured 3d ago against content hash 43fcc8fe63b5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

brain-log 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 3d 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.

skills/brain-log/SKILL.md · 179 lines

How it starts

The opening of the file, as written. The whole thing — 179 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Brain Log

Runs on: local-writes - creates or edits files in your OS folder; needs an agent with write access.

Three modes for incoming thoughts, plus flags and parked decisions.

Routing

When the founder gives you something to capture, determine which mode:

Mode A: Log and Move On

The thought is worth recording but doesn't connect to anything specific right now.

  • Append to brain/log.md with timestamp and a stamped ID (see ID Stamping below)
  • Tag: #context
  • No follow-up

Mode B: Log and Cross-Reference

The thought connects to an existing file or topic.

  • Append to brain/log.md with timestamp and a stamped ID
  • Tag: #xref:[target-file]
  • Insert a dated note into the referenced file
  • Examples: "This changes my priorities" -> xref to priorities.md. "This affects the deal with X" -> xref to clients.md

Mode C: Log and Act

The thought requires immediate action.

  • Append to brain/log.md with timestamp and a stamped ID
  • Tag: #acted
  • Take the action (update a file, create a task, move a priority)
  • Note what was done in the log entry

Default: Infer the mode from context. The founder can override: "just log it" (Mode A), "tie this to priorities" (Mode B), "act on this now" (Mode C).

Brain context (default)

Before producing output, read brain/.snapshot.md. If it is missing, or its date: line is more than 3 days old, run python scripts/brain-snapshot.py --write first and read the fresh one - a stale snapshot read as current presents last week's flags and must-dos as today's, which is worse than no memory at all. If Python is unavailable, proceed without it and say so.

If the snapshot is missing, run:

python scripts/brain-snapshot.py --write

Then read it. If the snapshot script is also missing (older install), proceed using only the profile files. Do not block.

The snapshot tells you what flags are open, what the user is working on this week, and what the latest staleness state is. Apply this context to your output where it is relevant. Do not surface every snapshot field in every output - use judgment. For brain logging, recent decisions and open flags help you choose the right tag - if a thought connects to an active flag or recent decision, prefer Mode B (cross-reference) over Mode A (log in isolation).

Read the full file on GitHub · 179 lines

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. 3d ago First seen · 179 lines · 187 tokens per session scan A 43fcc8fe63b5

Subscribe to this mod's changes

brain-log is a skill published in the GitHub repository ARCASSystems/FounderOS (5 stars, last pushed 20d ago), licensed MIT. It adds 187 tokens to every session and 1,995 once invoked, about $0.0009 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 2026-08-31.

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