aiderdesk-conditional-rules

AiderDesk extension that loads rule files only when the current task is working on files that match the rule's globs. Cursor-style on-demand rule selection for AiderDesk.

If you've ever wished AiderDesk would load your Go style rules only when you're editing Go code, and your Docker rules only when you're touching a Dockerfile, this is that.

How it works

AiderDesk's native rule loader reads every .md file in ~/.aider-desk/rules/ and <project>/.aider-desk/rules/ into the system prompt on every turn. This extension layers conditional loading on top by handling .mdc files in the same directories (the native loader ignores them).

Each .mdc file declares its activation condition via YAML frontmatter:

---
description: Go coding conventions
globs:
  - '**/*.go'
  - '**/go.mod'
  - '**/go.sum'
alwaysApply: false
---
# Go Rule: Core Style
…body of the rule…

On every agent turn, the extension:

1. Scans ~/.aider-desk/rules/ and <project>/.aider-desk/rules/ for .mdc files.
2. Parses each one's YAML frontmatter.
3. Asks AiderDesk for the files currently in the task's context.
4. Includes a rule when:
   • alwaysApply: true, or
   • at least one globs: entry matches at least one context file.
5. Returns the augmented rule list. AiderDesk's prompt manager reads each included rule from disk verbatim and injects it.

The decision is file-glob-driven, not agent-decision-driven. For a polyglot task (Go + Dockerfile in context), Go and Docker rules both load. For a Go-only task, only the Go rules load.

Frontmatter schema

All fields optional.

Field	Type	Default	Behaviour
description	string	—	Human-readable. Not used for matching; appears in the prompt so the agent sees a one-liner explaining why the rule loaded.
globs	string | string[]	—	Patterns matched against context file paths. A single string is treated as comma-separated ("**/*.go, **/go.mod").
alwaysApply	boolean	false	When true, the rule loads on every turn regardless of globs.

Frontmatter state	Result
alwaysApply: true	always include
no frontmatter at all	include (defensive default)
globs: present, ≥ 1 glob matches ≥ 1 context file	include
globs: present, no glob matches	exclude

Glob matching

• Globs are matched against two forms of each context file path: project-relative and absolute. So **/*.go matches both src/foo.go and /abs/path/src/foo.go.
• Implementation uses picomatch with { dot: true } so .env-style filenames work.
• No glob negation in v0.1.0. Patterns like !**/*_test.go are ignored. Use the body of the rule to handle exclusions.
• No subdirectory recursion in v0.1.0. Only top-level .mdc files in each rules directory are scanned.

File layout

Put .mdc files alongside your .md rules:

~/.aider-desk/rules/
├── SECURITY-01-SECRETS.md          # always-on (native loader)
├── GIT-01-COMMIT-MESSAGES.md       # always-on (native loader)
├── GOLANG-01-STYLE.mdc             # globs: ["**/*.go"]
├── GOLANG-08-TESTING.mdc           # globs: ["**/*.go"]
├── DOCKER-01-HOST-ACCESS.mdc       # globs: ["**/Dockerfile*", …]
└── PYTHON-01-STYLE.mdc             # globs: ["**/*.py"]

The .md files keep their existing always-on behaviour. The .mdc files are handled exclusively by this extension.

Install

One-off (current user)

npx @aiderdesk/extensions install https://github.com/neumachen/aiderdesk-conditional-rules \
  --directory ~/.aider-desk/extensions

Restart AiderDesk.

Inside the shiki container image

Add the GitHub URL to AIDER_DESK_EXTENSIONS_DEFAULT in your private_dot_config/exact_shiki/shiki.Dockerfile:

ARG AIDER_DESK_EXTENSIONS_DEFAULT="…, \
    https://github.com/neumachen/aiderdesk-conditional-rules"

Then rebuild:

shiki --rebuild

Every new shiki session will have the extension active.

Configuration

The extension creates <extensionDir>/config.json on first save. Schema:

{
  "scanProjectRules": true,
  "scanGlobalRules": true,
  "extraRuleDirs": ""
}

• scanProjectRules — whether to scan <project>/.aider-desk/rules/. Default true.
• scanGlobalRules — whether to scan ~/.aider-desk/rules/. Default true.
• extraRuleDirs — comma-separated additional directories to scan. Paths are absolute, ~-expanded, or relative to the project dir.

There is no UI config component in v0.1.0; edit the JSON directly if you need to tweak.

What this does NOT do

• It does not change how .md files are loaded. Those remain always-on.
• It does not change content of any rule file. Frontmatter will appear in the prompt.
• It does not handle Cursor's agent_requested / manual modes. Only alwaysApply and globs: are honoured. (Future v0.2 candidate.)
• It does not de-duplicate rules with the same basename across global + project dirs. If you have ~/.aider-desk/rules/GOLANG-01.mdc AND <project>/.aider-desk/rules/GOLANG-01.mdc, both will load. The project rule wins by virtue of appearing later in the list and getting the last word in the prompt.

Status & roadmap

• v0.1.0 (current draft): core hook, .mdc scanning, frontmatter parsing, glob matching, three test suites, working stub implementation.
• v0.2 (tentative): glob negation, subdirectory recursion, config UI component, possibly augmenting the context match set with files explicitly named in the user's prompt.

Development

nvm use
npm install

npm run typecheck    # tsc --noEmit
npm run lint         # eslint
npm run format:check # prettier --check
npm test             # vitest run
npm run check        # all of the above

Node 22 (see .nvmrc).

License

MIT. See LICENSE.

Related projects

• neumachen/aiderdesk-codex-extension — sibling extension; same packaging conventions.
• hotovo/aider-desk — the host application this extension plugs into.
• Cursor rules docs — the convention this extension implements.