@cuzfrog/pi-module-gates

pi-module-gates - Constraints liberate, liberties constrain.

Experimental pi cli extension that controls the entropy of the codebase by enforcing code module boundaries. It helps combat slop generation and code architecture degradation.

• Claude Code supported via a hook, see below.

Problem

AI coding agents produce edits with limited context knowledge (myopia) — their changes may leak implementation details, and break architectural contracts (slop).

Approach

Module contracts as guardrails. Each directory can contain a descriptor file that declares:

• readonly — files and directories the agent must not touch
• no-new-exports — files where no new exports are allowed (body still editable)
• visible — the set of exports allowed to be added or modified in that module

The extension intercepts agent write/edit operations and enforces these contracts. Violations are blocked with a clear reason.

The attempt to add 2 public helper functions is blocked, forcing the agent to re-think the design.

How it works

• Indexing — On session start, scans the project tree for descriptor files and builds a module index.
• System prompt — Injects a hint so the agent knows to respect descriptor file conventions.
• Gating — On every write/edit, checks:
  • Readonly gate — is the target file locked? No-new-exports gate — would the change add new exports to a file in the no-new-exports list?
  • Export gate — would the change introduce an export not in the visible list?
  • Module interface import gate — external files can only import from the module not internal files, i.e. re-exports from index.ts or mod.rs. A child module may import from a parent module's internal files (not recommended but allowed). (Only Typescript/JavaScript and Rust are supported)
  • Import gate (not implemented yet) — would the change introduce an import violating visibility scope?

• System prompt: system-prompt.md
• Currently supported languages: TypeScript/JavaScript, Rust, Java, Go, Kotlin, Scala

Installation

pi install npm:@cuzfrog/pi-module-gates

Or load directly for a single session:

pi -e npm:@cuzfrog/pi-module-gates

Module Descriptor Semantics

A module descriptor is a Markdown file (default name: MODULE.md) placed in a directory. You can piggy-back on your module context file for example CONTEXT.md.

Readonly constraints

---
readonly: [mod.rs]
---

Any prose for the agent to better understand the module.

No-new-exports constraints

no-new-exports: [mod.rs]

No-new-exports files cannot change their surface size: no new exports or public entries are allowed. The file body is still editable.

A skill module-no-new-exports-all has been included to populate no-new-exports entries in modules.

Visibility whitelist (under redesign)

visible:
  - greet # equivalent to `path: ./greet`
  - sub/mod1/Foo

or:

visible:
  - path: my_function
    modifier: pub(crate) # (optional) demands an exact match

Scenario	Behavior
visible key absent or no MODULE.md	Module is unconstrained — exports are not gated. Equivalent to null internally.
visible: []	Module is fully closed — no new exports may be added. Editing existing exports is still allowed.
Malformed YAML frontmatter	The module is left unguarded and an info notification is emitted.

Export gating

project/
  MODULE.md          visible: [Foo, Bar]
  src/
    MODULE.md        visible: [Bar, Baz]
    app.ts           ← checked against `src/MODULE.md` only

A MODULE.md only enforces exports within its immediate directory.

Import gating (not implemented yet)

# parent/MODULE.md
visible:
  - sub/Tool # type Tool is allowed to be imported from parent

# parent/sub/MODULE.md (before complement pass)
visible:
  - Bar # type Bar is allowed to be imported from parent/sub within parent, but not outside parent

A MODULE.md semantically gates exposures at the module level it resides.

Configuration

Add a module-gates entry to .pi/settings.json:

{
  "module-gates": {
    "moduleDescriptorFileName": "MODULE.md",
    "moduleDescriptorReadonly": "file",
    "sourceRoots": ["src/"],
    "outputModuleProseOnBlock": false
  }
}

Option	Default	Description
moduleDescriptorFileName	MODULE.md	File name used for module descriptors (case-insensitive)
moduleDescriptorReadonly	"frontmatter"	"file" makes the whole descriptor readonly; "frontmatter" locks only the YAML frontmatter (body prose stays editable); "off" disables descriptor readonly. true/false are also accepted for backward compatibility.
sourceRoots	["src/"]	Directories to scan for descriptor files and enforce gates. Pass a single string for one root, or an array for multiple roots (e.g. monorepos with ["packages/app/src/", "packages/lib/src/"]). Use [""] to scan from the project root. Legacy singular sourceRoot (string) is still accepted.
disableModuleInterfaceImportGate	false	When true, imports will not be forced to be from module interface.
disableSystemPrompt	false	When true, skip injecting the module-gates hint into the agent's system prompt.
outputModuleProseOnBlock	false	When true, the violating module descriptor's prose is appended to the block message so the agent sees the contract context. Disabled by default to keep the error message concise.

When no settings file exists or no module-gates key is present, defaults apply.

Claude Code Support

Install

Add the following to .claude/settings.json in the current project, pointing the PreToolUse hook at the installed binary.

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Edit|MultiEdit|Write",
        "hooks": [
          {
            "type": "command",
            "command": "bun ${CLAUDE_PROJECT_DIR}/node_modules/@cuzfrog/pi-module-gates/src/claude/pre-tool-use.ts",
            "statusMessage": "Module gate checking edit..."
          }
        ]
      }
    ]
  }
}

If pi-module-gates is already installed in pi global dir, you can use below path instead:

~/.pi/agent/npm/node_modules/@cuzfrog/pi-module-gates/src/claude/pre-tool-use.ts

System prompt

You need to add system-prompt.md manually to your context.

Configuration

Claude Code uses the same .pi/settings.json#module-gates block as the pi extension. See the Configuration section above.

Troubleshooting

Prompt:

Check if PreToolUse hook `pi-module-gates` is triggered and runs expectedly.

License

MIT

Author

Cause Chung ([e-mail])