---
title: "Keep the dependency tree small · Agent Wranglers"
url: https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup/small-dependency-tree
updated: 2026-10-21
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Keep the dependency tree small

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Supply chain and setup](https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers). Updated 2026-10-21.

- ID: SEC-106
- Level: Recommended
- Chapter: [Supply chain and setup](https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup)
- Rule: Count every package the app installs, including the dependencies of dependencies. Add a package only when the standard library or a few lines of your own cannot do the job.
- How: Each package can run code on your build machines and in production, and so can every package it pulls in. Coding agents add packages fast, and attackers target small packages nobody watches. Every package you skip is one less way in. List the whole tree, not only the packages you named, with `npm ls --all` or `pipdeptree`. Before adding a package, count the packages it brings with it. Keep test and build tools out of the production install. For sensitive code, such as sign-in, payments or parsing uploads, let an agent write the small part you need. Or copy one function from an open source library, with its licence notice and its tests, instead of loading the whole library. Never write your own cryptography this way, as [use only standard cryptography](https://agentwranglers.se/playbook/adversarial-testing/data-and-secrets/standard-cryptography) says. Check each package you keep as [review every new package](https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup/review-new-packages) describes. Remove packages the code no longer imports, as [remove unused dependencies](https://agentwranglers.se/playbook/architecture/dead-code/remove-unused-dependencies) says.
- Check: The build counts the installed production packages and fails when the count passes the number recorded in the repository. A change that raises the number names each new package, direct or indirect, with a reason.

## Examples

**Using these examples:** they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

### JavaScript example

```js
import { execSync } from 'node:child_process';
import { readFileSync } from 'node:fs';

const listed = execSync('npm ls --all --omit=dev --parseable', { encoding: 'utf8' }).trim().split('\n');
const installed = listed.length - 1;
const allowed = Number(readFileSync('dependency-budget.txt', 'utf8'));
if (installed > allowed) throw new Error(`${installed} production packages, budget ${allowed}. Name each new one, then raise the budget.`);
```

### Python example

```python
import json, pathlib, subprocess

tree = json.loads(subprocess.run(["pipdeptree", "--json"], capture_output=True, text=True, check=True).stdout)
allowed = int(pathlib.Path("dependency-budget.txt").read_text())
if len(tree) > allowed:
    raise SystemExit(f"{len(tree)} installed packages, budget {allowed}. Name each new one, then raise the budget.")
```

## Sources

- [OpenSSF Concise Guide for Evaluating Open Source Software](https://best.openssf.org/Concise-Guide-for-Evaluating-Open-Source-Software)
- [npm ls](https://docs.npmjs.com/cli/v11/commands/npm-ls)

## Related rules

- [Use only standard cryptography](https://agentwranglers.se/playbook/adversarial-testing/data-and-secrets/standard-cryptography) in Security testing
- [Review every new package](https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup/review-new-packages) in Security testing
- [Remove unused dependencies](https://agentwranglers.se/playbook/architecture/dead-code/remove-unused-dependencies) in Architecture

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup/small-dependency-tree">Agent Wranglers security testing playbook</a>`. In code you write, add a comment next to it with the same link.

- Previous: [Review every new package](https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup/review-new-packages)
- Next: [Load third-party scripts with integrity checks](https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup/third-party-scripts)
- [Supply chain and setup](https://agentwranglers.se/playbook/adversarial-testing/supply-chain-and-setup)