cortex-evolve

A tool that saves technical notes and project decisions to a Cortex vault, which is an Obsidian note collection stored as files.

In plain words
What is it for?
Use it when asked to save a how-to or technical explanation as a note, or to record a decision, design detail, or progress update for a specific repository.
Why use it?
It gives session knowledge a consistent place and format, making it easier to find later and link related notes together.

Skill for Claude CodeCodex

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/xbluesky/cortexes/cortex-evolve
Any agent
npx skills add XBlueSky/cortexes --skill cortex-evolve
Clone the repo
git clone --depth 1 https://github.com/XBlueSky/cortexes

Made for: Claude Code, Codex.

Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 953 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 $0.00058 $0.00953
Opus 5 $0.00029 $0.00477
Sonnet 5 $0.00012 $0.00191
Haiku 4.5 $0.00006 $0.00095

Measured 2d ago against content hash 788a4a901324, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

cortex-evolve 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.

skills/cortex-evolve/SKILL.md · 128 lines

How it starts

The opening of the file, as written. The whole thing — 128 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Cortex Evolve — Save to Vault

Save content to the cortex Obsidian vault.

Resolve Vault Path

Read ~/.cortex/config.json to get vault_path. If the file doesn't exist, tell the user to run /cortex:genesis first. All file paths below are relative to the vault root.

Determine Content Type

Ask the user if unclear. Use these heuristics:

Signal Type Target
Technical knowledge, how-to, concept explanation Notes Notes/<category>/<title>.md
Related to a specific repo's design, decision, or progress Projects Projects/<repo-name>/<title>.md

Writing to Notes

  1. Determine category from content (C++, Linux, Nginx, Web, or create new)
  2. Create file at Notes/<category>/<title>.md
  3. Use this template:
---
title: <title>
tags:
  - <relevant-tags>
created: <YYYY-MM-DD>
source: cortex
---

# <title>

<content>

<optional: related wikilinks like [[nginx-cert-renew]] or [[other-note]]>
  1. Use Obsidian wikilinks [[note-name]] for vault-internal references
  2. Use standard markdown links [text](url) for external URLs only

Writing to Projects

  1. Determine repo name (from current session context or ask user)
  2. If Projects/<repo-name>/_index.md doesn't exist, create it:
---
title: <repo-name>
repo: <git-remote-url>
tags:
  - project
---

# <repo-name>

<brief description>
  1. Create topic file at Projects/<repo-name>/<topic>.md

Update _index.md

After writing the file:

  1. Read <vault_path>/_index.md

  2. Append a row under the matching ### sub-section, creating the sub-section (with its table header) if it does not exist yet:

    • Notes → ### <topic> under ## Notes: | [[title]] | tags | one-line summary |
    • Projects → ### <repo-name> under ## Projects: | [[topic-title]] | tags | summary |

    Rows are per-page, not per-repo: a new repo means a new ### sub-section, not a single row standing for the whole repo.

  3. Bump the updated date in frontmatter. There is no entries: count to maintain — the field was removed by design (see /cortex:genesis).

Read the full file on GitHub · 128 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. 2d ago First seen · 128 lines · 58 tokens per session scan A 788a4a901324

Subscribe to this mod's changes

cortex-evolve is a skill published in the GitHub repository XBlueSky/cortexes (20 stars, last pushed 26d ago), licensed Apache-2.0. It adds 58 tokens to every session and 953 once invoked, about $0.0003 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.

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