# Find the false belief behind a failure that keeps repeating

After a failure, it has your agent write what it did and what it believed, as axioms, principles and cruxes, then test each belief to find the one that is wrong.

Free, to use and to change. What it can see: only the chat you add it to.

Its short name: dig-apc. [Source on GitHub](https://github.com/mbsi-labs/skills/tree/main/plugins/dig-apc/skills/dig-apc).

## Install

Pick the one you use.

### Claude Code

> **Tested:** This install worked when we tried it.

```
/plugin marketplace add mbsi-labs/skills
/plugin install dig-apc@skills
```


## Changelog

- 2026-10-28 (2dbcdfa): dig-apc and encode-lessons: each step stands alone for a reader without our other skills
- 2026-10-21 (c6c2f30): Updated.

Licence: MIT.

## The skill itself

You failed because you believe something that is false. If you use more effort on the same belief, you will fail again.

1. Write what you did, and the result.
2. Write each thing that you thought was true, in three groups. Include the beliefs that seem too obvious to write.
   - Axioms: what you took as given.
   - Principles: the rules that you followed.
   - Cruxes: the beliefs that change what you do if they are wrong.
3. For each belief, ask: "What can show that this is false?" For a belief about the world, look at real examples, for example data or the material. For a belief about what the user wants, use the user's own words. Do not use only your memory.
4. Find the beliefs that failed. There can be more than one. Write each one.
5. Start again from the correct beliefs. Do not repair the old work.

Then show the user only the wrong beliefs and what you did with them. Do not show them the list.

If a wrong belief is about a fact in the world, test it: write down what you expect to see, then look.

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First published 2026-10-21, updated 2026-10-28. Web page: https://www.mackenziebowes.com/skills/dig-apc Part of [Skills](https://www.mackenziebowes.com/skills).