Proposer Sub-Agent

Create change proposals with intent, scope, and approach

The sdd-propose sub-agent creates structured change proposals. It takes exploration analysis (or direct user input) and produces a proposal.md document that defines what will be built and why.

Metadata

name · string

sdd-propose

version · string

2.0

author · string

gentleman-programming

license · string

MIT

When It’s Triggered

The orchestrator launches sdd-propose when:

• User runs /sdd-new <change-name> (after exploration)
• User wants to create or update a proposal
• Exploration is complete and ready for formalization

What It Does

Step 1: Create Change Directory

Creates the change folder structure:

openspec/changes/{change-name}/
└── proposal.md

Or, in engram mode, prepares to save with topic_key: sdd/{change-name}/proposal

Step 2: Read Existing Specs

If openspec/specs/ has relevant specs, reads them to understand current behavior that this change might affect.

Step 3: Write proposal.md

Creates a structured proposal with these sections:

Proposal Format

# Proposal: {Change Title}

## Intent

{What problem are we solving? Why does this change need to happen?
Be specific about the user need or technical debt being addressed.}

## Scope

### In Scope
- {Concrete deliverable 1}
- {Concrete deliverable 2}
- {Concrete deliverable 3}

### Out of Scope
- {What we're explicitly NOT doing}
- {Future work that's related but deferred}

## Approach

{High-level technical approach. How will we solve this?
Reference the recommended approach from exploration if available.}

## Affected Areas

| Area | Impact | Description |
|------|--------|-------------|
| `path/to/area` | New/Modified/Removed | {What changes} |

## Risks

| Risk | Likelihood | Mitigation |
|------|------------|------------|
| {Risk description} | Low/Med/High | {How we mitigate} |

## Rollback Plan

{How to revert if something goes wrong. Be specific.}

## Dependencies

- {External dependency or prerequisite, if any}

## Success Criteria

- [ ] {How do we know this change succeeded?}
- [ ] {Measurable outcome}

Step 4: Return Summary

Returns a result envelope with proposal summary.

Result Envelope Example

## Proposal Created

**Change**: add-dark-mode
**Location**: openspec/changes/add-dark-mode/proposal.md

### Summary
- **Intent**: Enable users to switch between light and dark themes for reduced eye strain
- **Scope**: 3 deliverables in (theme toggle, CSS variables, persistence), 2 items deferred (per-component overrides, theme preview)
- **Approach**: CSS variables + React Context pattern
- **Risk Level**: Low

### Next Step
Ready for specs (sdd-spec) or design (sdd-design).

Proposal Example

Here’s a real proposal document:

# Proposal: Add Dark Mode

## Intent

Users have requested the ability to switch between light and dark color schemes to reduce eye strain in low-light environments. Currently, the app only supports a light theme with no way for users to customize the appearance.

This change will introduce a theme toggle that persists the user's preference.

## Scope

### In Scope
- Theme toggle button in the app header
- CSS variable system for color theming
- React Context for theme state management
- LocalStorage persistence of theme choice
- Dark theme color palette

### Out of Scope
- Per-component theme overrides (deferred to future)
- Theme preview during selection (not in MVP)
- Automatic theme based on system preference (could be added later)

## Approach

Use CSS custom properties (CSS variables) for all color values, managed by a React Context. When the user toggles the theme:

1. React Context updates the active theme
2. Root element gets `data-theme="dark"` attribute
3. CSS variables switch to dark palette
4. Choice saved to `localStorage`

On page load, read from `localStorage` and apply theme before first render to avoid flash.

## Affected Areas

| Area | Impact | Description |
|------|--------|-------------|
| `src/styles/theme.css` | Modified | Convert hardcoded colors to CSS variables |
| `src/contexts/ThemeContext.tsx` | New | Theme state management with Context |
| `src/hooks/useTheme.ts` | New | Hook to consume theme context |
| `src/components/Header.tsx` | Modified | Add theme toggle button |
| `src/components/App.tsx` | Modified | Wrap with ThemeProvider |
| `localStorage` | Modified | Store theme preference |

## Risks

| Risk | Likelihood | Mitigation |
|------|------------|------------|
| SSR theme flash (dark → light or vice versa) | Medium | Inject inline script before hydration to apply theme immediately |
| Missing color variables (some hardcoded colors remain) | Low | Audit all `.css` files during implementation |
| Browser compatibility with CSS variables | Very Low | CSS variables supported in all modern browsers (IE11 not a target) |

## Rollback Plan

If the feature needs to be reverted:
1. Remove `data-theme` attribute from root
2. Revert `theme.css` to use hardcoded light colors
3. Remove `ThemeProvider` from `App.tsx`
4. Remove toggle button from `Header.tsx`

No data migration needed — localStorage entry can remain without side effects.

## Dependencies

None. This change is self-contained.

## Success Criteria

- [ ] User can toggle between light and dark themes via header button
- [ ] Theme choice persists across page reloads
- [ ] All UI components render correctly in both themes
- [ ] No color contrast accessibility violations (WCAG AA)
- [ ] No SSR flash (theme applied before first paint)

Rules

• In openspec mode, ALWAYS create the proposal.md file
• If the change directory already exists with a proposal, READ it first and UPDATE it
• Keep the proposal CONCISE — it’s a thinking tool, not a novel
• Every proposal MUST have a rollback plan
• Every proposal MUST have success criteria
• Use concrete file paths in “Affected Areas” when possible
• Apply any rules.proposal from openspec/config.yaml
• Return a structured envelope with: status, executive_summary, detailed_report, artifacts, next_recommended, and risks

Related

• Explorer — Provides the exploration analysis
• Spec Writer — Next phase after proposal
• OpenSpec Convention