[ENHANCEMENT] Add mode argument that allows it to ignore default rules, only specific mode rules are loaded

[anderrom]

Problem (one or two sentences)

While most rules applies to almost all modes, some specifics modes do not need these default set of rules. It is important to remove the rules in that case, because models are more likely to stick to the rules if there are less rules for it to follow.
Because of this, almost all rules needs to be duplicated in almost all modes.
Adding an argument would allow to have most of the rules in the default folder, and an specific model to ignore this default folder entirely.

Context (who is affected and when)

Users are affected when models don't properly follow the rules because there are too many

or

With increased maintenance, because a lot of rules are duplicated in the modes folders, when it could easily be kept only in the main rules folder, and the very specific modes ignoring it entirely.

Desired behavior (conceptual, not technical)

Add an argument to custom_modes.yaml that defines the mode to only use the rules assigned direct for it, and not include the default rules folder.

Constraints / preferences (optional)

No response

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Roo Code Task Links (optional)

No response

Acceptance criteria (optional)

No response

Proposed approach (optional)

No response

Trade-offs / risks (optional)

No response

[roomote]

I've analyzed this issue and here's my proposed implementation plan:

Summary

Add a disableDefaultRules option to ModeConfig that, when set to true, causes a mode to skip loading the generic/default rules (from .roo/rules/, .roorules, .clinerules, and AGENTS.md). Only mode-specific rules (from .roo/rules-{mode}/) would be loaded.

Changes

1. Update ModeConfig schema (packages/types/src/mode.ts)

Add an optional disableDefaultRules boolean field to modeConfigSchema. This means it can be set in custom_modes.yaml like:

customModes:
  - slug: my-focused-mode
    name: My Focused Mode
    roleDefinition: ...
    groups: [read]
    disableDefaultRules: true

2. Pass mode config into addCustomInstructions (src/core/prompts/sections/custom-instructions.ts)

The addCustomInstructions function currently receives just the mode slug string. Add a disableDefaultRules field to the options parameter since the caller in generatePrompt (src/core/prompts/system.ts) already has access to the resolved modeConfig object.

3. Conditionally skip generic rules and AGENTS.md loading (src/core/prompts/sections/custom-instructions.ts)

In the addCustomInstructions function, wrap the generic rules loading and AGENTS.md loading in a conditional that checks options.disableDefaultRules. Mode-specific rules (.roo/rules-{mode}/) would still be loaded regardless of this setting.

4. Pass the flag from generatePrompt (src/core/prompts/system.ts)

Update the call to addCustomInstructions to pass the disableDefaultRules flag from the resolved mode config.

5. Add tests

• Update tests in src/core/prompts/sections/__tests__/custom-instructions.spec.ts to verify that when disableDefaultRules: true, generic rules and AGENTS.md are not loaded but mode-specific rules still are.
• Update schema validation tests in src/core/config/__tests__/ModeConfig.spec.ts to validate the new field.

Benefits

• Minimal, non-breaking change -- the field is optional and defaults to false (current behavior)
• Works with both custom_modes.yaml and .roomodes project-level configs
• Clear naming that describes the behavior
• Mode-specific rules (.roo/rules-{mode}/) still work, giving focused modes exactly the rules they need

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.

[anderrom]

@roomote plan approved!

[roomote]

Thanks for the approval @anderrom! I've seen your comment and will now implement the plan. I'll open a draft PR to share progress shortly.

[roomote]

Opened a draft PR with my attempt at addressing this: #11614

The implementation adds a disableDefaultRules boolean to ModeConfig. When set to true, only mode-specific rules (.roo/rules-{mode}/) are loaded -- generic rules, AGENTS.md, and legacy rule files are skipped. A UI toggle is also included in the mode settings panel for custom modes.

Feedback welcome!

[anderrom]

Waiting for PR #11614 to be merged before closing issue. @roomote

[roomote]

I've seen your comment -- PR #11614 is open and I'm currently working on adding the missing translations so the check-translation CI passes. Will update here once that's pushed.