---
title: "Use strict types and linters · Agent Wranglers"
url: https://agentwranglers.se/playbook/ai-assisted-development/rules-the-agent-cannot-break/strict-tooling
updated: 2026-10-20
licence: "All rights reserved"
---

# Use strict types and linters

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Required
- Chapter: [Rules the agent cannot break](https://agentwranglers.se/playbook/ai-assisted-development/rules-the-agent-cannot-break)
- Rule: Run the strictest type checker and linter settings the project can pass, so mistakes fail fast instead of reaching review.
- How: Turn on strict modes, such as TypeScript `strict`, mypy `--strict` or PHPStan's highest level the code passes. Forbid untyped escapes such as `any`. Agents fix tool errors well, so strict tools turn many silent bugs into quick fixes.
- Check: The configuration files set the strict options, and the check command fails on a deliberate type error.

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers ai development playbook: https://agentwranglers.se/playbook/ai-assisted-development/rules-the-agent-cannot-break/strict-tooling`.

- Next: [Block dangerous actions with hooks](https://agentwranglers.se/playbook/ai-assisted-development/rules-the-agent-cannot-break/blocking-hooks)
- [Rules the agent cannot break](https://agentwranglers.se/playbook/ai-assisted-development/rules-the-agent-cannot-break)