feat: add OpenSpec change proposal for archive command

feat: add diff command to view spec changes

openspec/README.md

@@ -10,6 +10,23 @@ OpenSpec is an AI-native system for change-driven development where:
 - **AI drives the process** - You generate proposals, humans review and approve
 - **Specs are living documentation** - Always kept in sync with deployed code
 
+## Start Simple
+
+**Default to minimal implementations:**
+- New features should be <100 lines of code initially
+- Use the simplest solution that works
+- Avoid premature optimization (no caching, parallelization, or complex patterns without proven need)
+- Choose boring technology over cutting-edge solutions
+
+**Complexity triggers** - Only add complexity when you have:
+- **Performance data** showing current solution is too slow
+- **Scale requirements** with specific numbers (>1000 users, >100MB data)
+- **Multiple use cases** requiring the same abstraction
+- **Regulatory compliance** mandating specific patterns
+- **Security threats** that simple solutions cannot address
+
+When triggered, document the specific justification in your change proposal.
+
 ## Directory Structure
 
 ```
@@ -72,6 +89,11 @@ Before any task:
 - Adding tests for existing behavior
 - Documentation fixes
 
+**Complexity assessment:**
+- If your solution requires >100 lines of new code, justify the complexity
+- If adding dependencies, frameworks, or architectural patterns, document why simpler alternatives won't work
+- Default to single-file implementations until proven insufficient
+
 ### 3. Creating a Change Proposal
 
 When a user requests a significant change:
@@ -383,10 +405,12 @@ Progress communication:
 - "Implementing approved changes..."
 
 ### For AI Assistants
+- **Bias toward simplicity** - Propose the minimal solution that works
 - Use your exploration tools liberally before proposing
 - Batch operations for efficiency
 - Communicate your progress
 - It's OK to revise proposals based on discoveries
+- **Question complexity** - If your solution feels complex, simplify first
 
 ## Edge Case Handling
 
@@ -442,6 +466,7 @@ Proposal REQUIRED if:
 - Specs must always reflect deployed reality
 - Changes are proposed, not imposed
 - Impact analysis prevents surprises
-- The simplicity is the power - just markdown files
+- Simplicity is the power - just markdown files, minimal solutions
+- Start simple, add complexity only when justified
 
 By following these conventions, you enable true spec-driven development where documentation stays current, changes are traceable, and evolution is intentional.

openspec/changes/add-archive-command/proposal.md

@@ -0,0 +1,12 @@
+## Why
+Need a command to archive completed changes to the archive folder with proper date prefixing, following OpenSpec conventions. Currently changes must be manually moved and renamed.
+
+## What Changes
+- Add new `archive` command to CLI that moves changes to `changes/archive/YYYY-MM-DD-[change-name]/`
+- Check for incomplete tasks before archiving and warn user
+- Allow interactive selection of change to archive
+- Prevent archiving if target directory already exists
+
+## Impact
+- Affected specs: cli-archive (new)
+- Affected code: src/cli/index.ts, src/core/archive.ts (new)

openspec/changes/add-archive-command/specs/cli-archive/spec.md

@@ -0,0 +1,60 @@
+# CLI Archive Command Specification
+
+## Purpose
+The archive command moves completed changes from the active changes directory to the archive folder with date-based naming, following OpenSpec conventions.
+
+## Command Syntax
+```bash
+openspec archive [change-name]
+```
+
+## Behavior
+
+### Change Selection
+WHEN no change-name is provided
+THEN display interactive list of available changes (excluding archive/)
+AND allow user to select one
+
+WHEN change-name is provided
+THEN use that change directly
+AND validate it exists
+
+### Task Completion Check
+The command SHALL scan the change's tasks.md file for incomplete tasks (marked with `- [ ]`)
+
+WHEN incomplete tasks are found
+THEN display all incomplete tasks to the user
+AND prompt for confirmation to continue
+AND default to "No" for safety
+
+WHEN all tasks are complete OR no tasks.md exists
+THEN proceed with archiving without prompting
+
+### Archive Process
+The archive operation SHALL:
+1. Create archive/ directory if it doesn't exist
+2. Generate target name as `YYYY-MM-DD-[change-name]` using current date
+3. Check if target directory already exists
+4. Move the entire change directory to the archive location
+
+WHEN target archive already exists
+THEN fail with error message
+AND do not overwrite existing archive
+
+WHEN move succeeds
+THEN display success message with archived name
+
+## Error Handling
+
+SHALL handle the following error conditions:
+- Missing openspec/changes/ directory
+- Change not found
+- Archive target already exists
+- File system permissions issues
+
+## Why These Decisions
+
+**Interactive selection**: Reduces typing and helps users see available changes
+**Task checking**: Prevents accidental archiving of incomplete work
+**Date prefixing**: Maintains chronological order and prevents naming conflicts
+**No overwrite**: Preserves historical archives and prevents data loss

openspec/changes/add-archive-command/tasks.md

@@ -0,0 +1,30 @@
+# Implementation Tasks
+
+## 1. Core Implementation
+- [ ] 1.1 Create `src/core/archive.ts` with ArchiveCommand class
+  - [ ] 1.1.1 Implement change selection (interactive if not provided)
+  - [ ] 1.1.2 Implement incomplete task checking from tasks.md
+  - [ ] 1.1.3 Implement confirmation prompt for incomplete tasks
+  - [ ] 1.1.4 Implement archive move with date prefixing
+
+## 2. CLI Integration
+- [ ] 2.1 Add archive command to `src/cli/index.ts`
+  - [ ] 2.1.1 Import ArchiveCommand
+  - [ ] 2.1.2 Register command with commander
+  - [ ] 2.1.3 Add proper error handling
+
+## 3. Error Handling
+- [ ] 3.1 Handle missing openspec/changes/ directory
+- [ ] 3.2 Handle change not found
+- [ ] 3.3 Handle archive target already exists
+- [ ] 3.4 Handle user cancellation
+
+## 4. Testing
+- [ ] 4.1 Test with fully completed change
+- [ ] 4.2 Test with incomplete tasks (warning shown)
+- [ ] 4.3 Test interactive selection mode
+- [ ] 4.4 Test duplicate archive prevention
+
+## 5. Build and Validation
+- [ ] 5.1 Ensure TypeScript compilation succeeds
+- [ ] 5.2 Test command execution

openspec/changes/add-complexity-guidelines/tasks.md

@@ -1,9 +0,0 @@
-# Implementation Tasks
-
-## 1. Update OpenSpec README
-- [ ] 1.1 Add "Start Simple" section after Core Principle
-- [ ] 1.2 Add complexity triggers to "When to Create Change Proposals" section
-- [ ] 1.3 Update AI workflow guidance to emphasize minimal implementations
-
-## 2. Update CLAUDE.md
-- [ ] 2.1 Add complexity management rules to project instructions

openspec/changes/add-diff-command/proposal.md

@@ -0,0 +1,19 @@
+# Add Diff Command to OpenSpec CLI
+
+## Why
+
+Developers need to easily view differences between proposed spec changes and current specs without manually comparing files.
+
+## What Changes
+
+- Add `openspec diff [change-name]` command that shows differences between change specs and current specs
+- Compare files in `changes/[change-name]/specs/` with corresponding files in `specs/`
+- Display unified diff output showing added/removed/modified lines
+- Support colored output for better readability
+
+## Impact
+
+- Affected specs: New capability `cli-diff` will be added
+- Affected code:
+  - `src/cli/index.ts` - Add diff command
+  - `src/core/diff.ts` - New file with diff logic (~80 lines)

openspec/changes/add-diff-command/specs/cli-diff/spec.md

@@ -0,0 +1,77 @@
+# CLI Diff Command Specification
+
+## Purpose
+
+The `openspec diff` command provides developers with a visual comparison between proposed spec changes and the current deployed specs.
+
+## Command Syntax
+
+```bash
+openspec diff [change-name]
+```
+
+## Behavior
+
+### Without Arguments
+
+WHEN running `openspec diff` without arguments
+THEN list all available changes in the `changes/` directory (excluding archive)
+AND prompt user to select a change
+
+### With Change Name
+
+WHEN running `openspec diff <change-name>`
+THEN compare all spec files in `changes/<change-name>/specs/` with corresponding files in `specs/`
+
+### Diff Output
+
+FOR each spec file in the change:
+- IF file exists in both locations THEN show unified diff
+- IF file only exists in change THEN show as new file (all lines with +)
+- IF file only exists in current specs THEN show as deleted (all lines with -)
+
+### Display Format
+
+The diff SHALL use standard unified diff format:
+- Lines prefixed with `-` for removed content
+- Lines prefixed with `+` for added content
+- Lines without prefix for unchanged context
+- File headers showing the paths being compared
+
+### Color Support
+
+WHEN terminal supports colors:
+- Removed lines displayed in red
+- Added lines displayed in green
+- File headers displayed in bold
+- Context lines in default color
+
+### Error Handling
+
+WHEN specified change doesn't exist THEN display error "Change '<name>' not found"
+WHEN no specs directory in change THEN display "No spec changes found for '<name>'"
+WHEN changes directory doesn't exist THEN display "No OpenSpec changes directory found"
+
+## Examples
+
+```bash
+# View diff for specific change
+$ openspec diff add-auth-feature
+
+--- specs/user-auth/spec.md
++++ changes/add-auth-feature/specs/user-auth/spec.md
+@@ -10,6 +10,8 @@
+ Users SHALL authenticate with email and password.
+ 
++Users MAY authenticate with OAuth providers.
++
+ WHEN credentials are valid THEN issue JWT token.
+
+# List all changes and select
+$ openspec diff
+Available changes:
+  1. add-auth-feature
+  2. update-payment-flow
+  3. add-status-command
+Select a change (1-3): 
+```

openspec/changes/add-diff-command/tasks.md

@@ -0,0 +1,23 @@
+# Implementation Tasks
+
+## 1. Core Implementation
+- [x] 1.1 Create `src/core/diff.ts` with diff logic
+- [x] 1.2 Implement change directory scanning
+- [x] 1.3 Implement file comparison using unified diff format
+- [x] 1.4 Add color support for terminal output
+
+## 2. CLI Integration
+- [x] 2.1 Add diff command to `src/cli/index.ts`
+- [x] 2.2 Implement interactive change selection when no argument provided
+- [x] 2.3 Add error handling for missing changes
+
+## 3. Enhancements
+- [x] 3.1 Replace with jest-diff for professional diff output
+- [x] 3.2 Improve file headers with status and statistics
+- [x] 3.3 Add summary view with file counts and line changes
+
+## 4. Testing
+- [ ] 4.1 Test diff generation for modified files
+- [ ] 4.2 Test handling of new files
+- [ ] 4.3 Test handling of deleted files
+- [ ] 4.4 Test interactive mode

openspec/changes/add-list-command/proposal.md

@@ -0,0 +1,20 @@
+# Add List Command to OpenSpec CLI
+
+## Why
+
+Developers need visibility into available changes and their status to understand the project's evolution and pending work.
+
+## What Changes
+
+- Add `openspec list` command that displays all changes in the changes/ directory
+- Show each change name with task completion count (e.g., "add-auth: 3/5 tasks")
+- Display completion status indicator (✓ for fully complete, progress for partial)
+- Skip the archive/ subdirectory to focus on active changes
+- Simple table output for easy scanning
+
+## Impact
+
+- Affected specs: New capability `cli-list` will be added
+- Affected code:
+  - `src/cli/index.ts` - Add list command
+  - `src/core/list.ts` - New file with directory scanning and task parsing (~60 lines)

openspec/changes/add-list-command/specs/cli-list/spec.md

@@ -0,0 +1,69 @@
+# List Command Specification
+
+## Purpose
+
+The `openspec list` command SHALL provide developers with a quick overview of all active changes in the project, showing their names and task completion status.
+
+## Behavior
+
+### Command Execution
+
+WHEN `openspec list` is executed
+THEN scan the `openspec/changes/` directory for change directories
+AND exclude the `archive/` subdirectory from results
+AND parse each change's `tasks.md` file to count task completion
+
+### Task Counting
+
+WHEN parsing a `tasks.md` file
+THEN count tasks matching these patterns:
+- Completed: Lines containing `- [x]`
+- Incomplete: Lines containing `- [ ]`
+AND calculate total tasks as the sum of completed and incomplete
+
+### Output Format
+
+WHEN displaying the list
+THEN show a table with columns:
+- Change name (directory name)
+- Task progress (e.g., "3/5 tasks" or "✓ Complete")
+- Status indicator:
+  - `✓` for fully completed changes (all tasks done)
+  - Progress fraction for partial completion
+
+Example output:
+```
+Changes:
+  add-auth-feature     3/5 tasks
+  update-api-docs      ✓ Complete
+  fix-validation       0/2 tasks
+  add-list-command     1/4 tasks
+```
+
+### Empty State
+
+WHEN no active changes exist (only archive/ or empty changes/)
+THEN display: "No active changes found."
+
+### Error Handling
+
+IF a change directory has no `tasks.md` file
+THEN display the change with "No tasks" status
+
+IF `openspec/changes/` directory doesn't exist
+THEN display error: "No OpenSpec changes directory found. Run 'openspec init' first."
+AND exit with code 1
+
+### Sorting
+
+Changes SHALL be displayed in alphabetical order by change name for consistency.
+
+## Why
+
+Developers need a quick way to:
+- See what changes are in progress
+- Identify which changes are ready to archive
+- Understand the overall project evolution status
+- Get a bird's-eye view without opening multiple files
+
+This command provides that visibility with minimal effort, following OpenSpec's philosophy of simplicity and clarity.

openspec/changes/add-list-command/tasks.md

@@ -0,0 +1,26 @@
+# Implementation Tasks
+
+## 1. Core Implementation
+- [ ] 1.1 Create `src/core/list.ts` with list logic
+  - [ ] 1.1.1 Implement directory scanning (exclude archive/)
+  - [ ] 1.1.2 Implement task counting from tasks.md files
+  - [ ] 1.1.3 Format output as simple table
+- [ ] 1.2 Add list command to CLI in `src/cli/index.ts`
+  - [ ] 1.2.1 Register `openspec list` command
+  - [ ] 1.2.2 Connect to list.ts implementation
+
+## 2. Error Handling
+- [ ] 2.1 Handle missing openspec/changes/ directory
+- [ ] 2.2 Handle changes without tasks.md files
+- [ ] 2.3 Handle empty changes directory
+
+## 3. Testing
+- [ ] 3.1 Add tests for list functionality
+  - [ ] 3.1.1 Test with multiple changes
+  - [ ] 3.1.2 Test with completed changes
+  - [ ] 3.1.3 Test with no changes
+  - [ ] 3.1.4 Test error conditions
+
+## 4. Documentation
+- [ ] 4.1 Update CLI help text with list command
+- [ ] 4.2 Add list command to README if applicable

openspec/changes/add-requirement-markers/proposal.md

@@ -0,0 +1,15 @@
+# Add @requirement Markers for Requirement Identification
+
+## Why
+Specs contain WHEN/THEN patterns that define system requirements, but extracting these programmatically requires brittle regex parsing that may miss edge cases or break with formatting changes.
+
+## What Changes
+- Define @requirement marker convention for identifying key requirements in specs
+- Each marker includes a brief identifier (e.g., @requirement user-register)
+- Markers appear directly before their WHEN/THEN blocks
+- Document convention in openspec-conventions spec
+
+## Impact
+- Affected specs: openspec-conventions (new)
+- Affected code: None initially - enables future tooling
+- Breaking changes: None - additive convention only

openspec/changes/add-requirement-markers/specs/openspec-conventions/spec.md

@@ -0,0 +1,219 @@
+# OpenSpec Conventions Specification
+
+## Purpose
+
+OpenSpec conventions SHALL define how system capabilities are documented, how changes are proposed and tracked, and how specifications evolve over time. This meta-specification serves as the source of truth for OpenSpec's own conventions.
+
+## Core Principles
+
+The system SHALL follow these principles:
+- Specs reflect what IS currently built and deployed
+- Changes contain proposals for what SHOULD be changed
+- AI drives the documentation process
+- Specs are living documentation kept in sync with deployed code
+
+## Directory Structure
+
+WHEN an OpenSpec project is initialized
+THEN it SHALL have this structure:
+```
+openspec/
+├── project.md              # Project-specific context
+├── README.md               # AI assistant instructions
+├── specs/                  # Current deployed capabilities
+│   └── [capability]/       # Single, focused capability
+│       ├── spec.md         # WHAT and WHY
+│       └── design.md       # HOW (optional, for established patterns)
+└── changes/                # Proposed changes
+    ├── [change-name]/      # Descriptive change identifier
+    │   ├── proposal.md     # Why, what, and impact
+    │   ├── tasks.md        # Implementation checklist
+    │   ├── design.md       # Technical decisions (optional)
+    │   └── specs/          # Complete future state
+    │       └── [capability]/
+    │           └── spec.md # Clean markdown (no diff syntax)
+    └── archive/            # Completed changes
+        └── YYYY-MM-DD-[name]/
+```
+
+## Change Storage Convention
+
+### Future State Storage
+
+WHEN creating a change proposal
+THEN store the complete future state of affected specs
+AND use clean markdown without diff syntax
+
+The `changes/[name]/specs/` directory SHALL contain:
+- Complete spec files as they will exist after the change
+- Clean markdown without `+` or `-` prefixes
+- All formatting and structure of the final intended state
+
+### Proposal Format
+
+WHEN documenting what changes
+THEN the proposal SHALL explicitly describe each change:
+
+```markdown
+**[Section or Behavior Name]**
+- From: [current state/requirement]
+- To: [future state/requirement]
+- Reason: [why this change is needed]
+- Impact: [breaking/non-breaking, who's affected]
+```
+
+This explicit format compensates for not having inline diffs and ensures reviewers understand exactly what will change.
+
+## Change Lifecycle
+
+The change process SHALL follow these states:
+
+1. **Propose**: AI creates change with future state specs and explicit proposal
+2. **Review**: Humans review proposal and future state
+3. **Approve**: Change is approved for implementation
+4. **Implement**: Follow tasks.md checklist (can span multiple PRs)
+5. **Deploy**: Changes are deployed to production
+6. **Update**: Specs in `specs/` are updated to match deployed reality
+7. **Archive**: Change is moved to `archive/YYYY-MM-DD-[name]/`
+
+## Viewing Changes
+
+WHEN reviewing proposed changes
+THEN reviewers can compare using:
+- GitHub PR diff view when changes are committed
+- Command line: `diff -u specs/[capability]/spec.md changes/[name]/specs/[capability]/spec.md`
+- Any visual diff tool comparing current vs future state
+
+The system relies on tools to generate diffs rather than storing them.
+
+## Capability Naming
+
+Capabilities SHALL use:
+- Verb-noun patterns (e.g., `user-auth`, `payment-capture`)
+- Hyphenated lowercase names
+- Singular focus (one responsibility per capability)
+- No nesting (flat structure under `specs/`)
+
+## When Changes Require Proposals
+
+A proposal SHALL be created for:
+- New features or capabilities
+- Breaking changes to existing behavior
+- Architecture or pattern changes
+- Performance optimizations that change behavior
+- Security updates affecting access patterns
+
+A proposal is NOT required for:
+- Bug fixes restoring intended behavior
+- Typos or formatting fixes
+- Non-breaking dependency updates
+- Adding tests for existing behavior
+- Documentation clarifications
+
+## Requirement Markers
+
+### Marker Syntax
+
+@requirement marker-syntax
+WHEN writing a requirement in a spec
+THEN prefix it with @requirement followed by a brief kebab-case identifier
+AND place the marker on the line immediately before the WHEN statement
+
+@requirement marker-identifier
+WHEN choosing an identifier for @requirement
+THEN use kebab-case (lowercase with hyphens)
+AND keep it brief but descriptive (2-4 words)
+AND ensure it's unique within the spec
+
+@requirement marker-placement
+WHEN adding @requirement markers to a spec
+THEN place them in the ## Behavior or ## Behaviors section
+AND ensure each WHEN/THEN block has exactly one marker
+AND maintain a blank line after each THEN block for readability
+
+### Examples
+
+@requirement valid-marker-example
+WHEN a spec includes properly formatted markers
+THEN tools can extract and identify requirements programmatically
+AND the spec remains human-readable
+
+Example of correct usage:
+```markdown
+## Behavior
+
+@requirement user-register
+WHEN user registers with valid email
+THEN create account and send confirmation
+
+@requirement user-login
+WHEN user logs in with correct credentials
+THEN return JWT token with user data
+
+@requirement invalid-credentials
+WHEN user provides invalid credentials
+THEN return 401 unauthorized error
+```
+
+@requirement invalid-marker-detection
+WHEN a requirement lacks an @requirement marker
+THEN tools should gracefully skip it
+AND optionally warn about unmarked requirements
+
+### Edge Cases
+
+@requirement multiline-when-then
+WHEN a WHEN or THEN clause spans multiple lines
+THEN the @requirement marker still goes on the line before WHEN
+AND the entire block is considered part of that requirement
+
+@requirement multiple-then-clauses
+WHEN a requirement has multiple THEN clauses using AND
+THEN treat them as part of the same requirement
+AND use a single @requirement marker for the entire block
+
+@requirement nested-conditions
+WHEN requirements have nested conditions or complex logic
+THEN keep the @requirement marker simple
+AND let the WHEN/THEN content contain the complexity
+
+## Spec Structure
+
+@requirement spec-file-location
+WHEN creating a spec file
+THEN place it in openspec/specs/[capability-name]/spec.md
+AND use kebab-case for the capability name
+
+@requirement spec-sections
+WHEN structuring a spec
+THEN include these sections in order:
+- # [Capability Name] Specification
+- ## Purpose (brief description)
+- ## Behavior or ## Behaviors (with @requirement markers)
+- ## Examples (optional, for complex requirements)
+
+## Benefits of Requirement Markers
+
+@requirement tooling-extraction
+WHEN tools need to extract requirements from specs
+THEN they can parse @requirement markers reliably
+AND avoid complex regex patterns for WHEN/THEN extraction
+
+@requirement requirement-counting
+WHEN displaying change summaries
+THEN tools can count requirements by counting @requirement markers
+AND show accurate requirement counts per spec
+
+@requirement requirement-referencing
+WHEN documenting or discussing specific requirements
+THEN use the @requirement identifier for clear reference
+AND maintain consistency across documentation
+
+## Why This Approach
+
+Clean future state storage provides:
+- **Readability**: No diff syntax pollution
+- **AI-compatibility**: Standard markdown that AI tools understand
+- **Simplicity**: No special parsing or processing needed
+- **Tool-agnostic**: Any diff tool can show changes
+- **Clear intent**: Explicit proposals document reasoning

openspec/changes/add-requirement-markers/tasks.md

@@ -0,0 +1,24 @@
+# Implementation Tasks
+
+## 1. Define Convention
+- [ ] 1.1 Document @requirement marker syntax
+- [ ] 1.2 Define identifier naming guidelines
+- [ ] 1.3 Specify marker placement rules
+- [ ] 1.4 Add examples of proper usage
+
+## 2. Create Specification
+- [ ] 2.1 Write openspec-conventions spec
+- [ ] 2.2 Include requirement marker section
+- [ ] 2.3 Add good and bad examples
+- [ ] 2.4 Document edge cases
+
+## 3. Update Existing Specs
+- [ ] 3.1 Add @requirement markers to cli-init spec
+- [ ] 3.2 Add @requirement markers to cli-update spec
+- [ ] 3.3 Add @requirement markers to cli-view spec
+- [ ] 3.4 Review and update any other existing specs
+
+## 4. Documentation
+- [ ] 4.1 Update README with marker convention
+- [ ] 4.2 Add marker usage to CLAUDE.md
+- [ ] 4.3 Create examples for AI assistants

openspec/changes/archive/2025-08-11-add-complexity-guidelines/tasks.md

@@ -0,0 +1,9 @@
+# Implementation Tasks
+
+## 1. Update OpenSpec README
+- [x] 1.1 Add "Start Simple" section after Core Principle
+- [x] 1.2 Add complexity triggers to "When to Create Change Proposals" section
+- [x] 1.3 Update AI workflow guidance to emphasize minimal implementations
+
+## 2. Update CLAUDE.md
+- [x] 2.1 Add complexity management rules to project instructions

openspec/specs/cli-update/spec.md

@@ -0,0 +1,59 @@
+# Update Command Specification
+
+## Purpose
+
+As a developer using OpenSpec, I want to update the OpenSpec instructions in my project when new versions are released, so that I can benefit from improvements to AI agent instructions.
+
+## Core Requirements
+
+### Update Behavior
+
+The update command SHALL update OpenSpec instruction files to the latest templates.
+
+WHEN a user runs `openspec update` THEN the command SHALL:
+- Check if the `openspec` directory exists
+- Replace `openspec/README.md` with the latest template (complete replacement)
+- Update the OpenSpec-managed block in `CLAUDE.md` using markers
+  - Preserve user content outside markers
+  - Create `CLAUDE.md` if missing
+- Display ASCII-safe success message: "Updated OpenSpec instructions"
+
+### Prerequisites
+
+The command SHALL require:
+- An existing `openspec` directory (created by `openspec init`)
+
+IF the `openspec` directory does not exist THEN:
+- Display error: "No OpenSpec directory found. Run 'openspec init' first."
+- Exit with code 1
+
+### File Handling
+
+The update command SHALL:
+- Completely replace `openspec/README.md` with the latest template
+- Update only the OpenSpec-managed block in `CLAUDE.md` using markers
+- Use the default directory name `openspec`
+- Be idempotent (repeated runs have no additional effect)
+
+## Edge Cases
+
+### File Permissions
+IF file write fails THEN let the error bubble up naturally with file path.
+
+### Missing CLAUDE.md
+IF CLAUDE.md doesn't exist THEN create it with the template content.
+
+### Custom Directory Name
+Not supported in this change. The default directory name `openspec` SHALL be used.
+
+## Success Criteria
+
+Users SHALL be able to:
+- Update OpenSpec instructions with a single command
+- Get the latest AI agent instructions
+- See clear confirmation of the update
+
+The update process SHALL be:
+- Simple and fast (no version checking)
+- Predictable (same result every time)
+- Self-contained (no network required)

package.json

@@ -53,7 +53,9 @@
   },
   "dependencies": {
     "@inquirer/prompts": "^7.8.0",
+    "chalk": "^5.5.0",
     "commander": "^14.0.0",
+    "jest-diff": "^30.0.5",
     "ora": "^8.2.0"
   }
 }

pnpm-lock.yaml

@@ -11,9 +11,15 @@ importers:
       '@inquirer/prompts':
         specifier: ^7.8.0
         version: 7.8.0(@types/node@24.2.0)
+      chalk:
+        specifier: ^5.5.0
+        version: 5.5.0
       commander:
         specifier: ^14.0.0
         version: 14.0.0
+      jest-diff:
+        specifier: ^30.0.5
+        version: 30.0.5
       ora:
         specifier: ^8.2.0
         version: 8.2.0
@@ -310,6 +316,18 @@ packages:
       '@types/node':
         optional: true
 
+  '@jest/diff-sequences@30.0.1':
+    resolution: {integrity: sha512-n5H8QLDJ47QqbCNn5SuFjCRDrOLEZ0h8vAHCK5RL9Ls7Xa8AQLa/YxAc9UjFqoEDM48muwtBGjtMY5cr0PLDCw==}
+    engines: {node: ^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0}
+
+  '@jest/get-type@30.0.1':
+    resolution: {integrity: sha512-AyYdemXCptSRFirI5EPazNxyPwAL0jXt3zceFjaj8NFiKP9pOi0bfXonf6qkf82z2t3QWPeLCWWw4stPBzctLw==}
+    engines: {node: ^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0}
+
+  '@jest/schemas@30.0.5':
+    resolution: {integrity: sha512-DmdYgtezMkh3cpU8/1uyXakv3tJRcmcXxBOcO0tbaozPwpmh4YMsnWrQm9ZmZMfa5ocbxzbFk6O4bDPEc/iAnA==}
+    engines: {node: ^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0}
+
   '@jridgewell/sourcemap-codec@1.5.4':
     resolution: {integrity: sha512-VT2+G1VQs/9oz078bLrYbecdZKs912zQlkelYpuf+SXF+QvZDYJlbx/LSx+meSAwdDFnF8FVXW92AVjjkVmgFw==}
 
@@ -416,6 +434,9 @@ packages:
     cpu: [x64]
     os: [win32]
 
+  '@sinclair/typebox@0.34.38':
+    resolution: {integrity: sha512-HpkxMmc2XmZKhvaKIZZThlHmx1L0I/V1hWK1NubtlFnr6ZqdiOpV72TKudZUNQjZNsyDBay72qFEhEvb+bcwcA==}
+
   '@types/chai@5.2.2':
     resolution: {integrity: sha512-8kB30R7Hwqf40JPiKhVzodJs2Qc1ZJ5zuT3uzw5Hq/dhNCl3G3l83jfpdI1e20BP348+fV7VIL/+FxaXkqBmWg==}
 
@@ -478,6 +499,10 @@ packages:
     resolution: {integrity: sha512-zbB9rCJAT1rbjiVDb2hqKFHNYLxgtk8NURxZ3IZwD3F6NtxbXZQCnnSi1Lkx+IDohdPlFp222wVALIheZJQSEg==}
     engines: {node: '>=8'}
 
+  ansi-styles@5.2.0:
+    resolution: {integrity: sha512-Cxwpt2SfTzTtXcfOlzGEee8O+c+MmUgGrNiBcXnuWxuFJHe6a5Hz7qwhwe5OgaSYI0IJvkLqWX1ASG+cJOkEiA==}
+    engines: {node: '>=10'}
+
   assertion-error@2.0.1:
     resolution: {integrity: sha512-Izi8RQcffqCeNVgFigKli1ssklIbpHnCYc6AknXGYoB6grJqyeby7jv12JUQgmTAnIDnbck1uxksT4dzN3PWBA==}
     engines: {node: '>=12'}
@@ -490,6 +515,10 @@ packages:
     resolution: {integrity: sha512-5nFxhUrX0PqtyogoYOA8IPswy5sZFTOsBFl/9bNsmDLgsxYTzSZQJDPppDnZPTQbzSEm0hqGjWPzRemQCYbD6A==}
     engines: {node: '>=18'}
 
+  chalk@4.1.2:
+    resolution: {integrity: sha512-oKnbhFyRIXpUuez8iBMmyEa4nbj4IOQyuhc/wy9kY7/WVPcwIO9VA668Pu8RkO7+0G76SLROeyw9CpQ061i4mA==}
+    engines: {node: '>=10'}
+
   chalk@5.5.0:
     resolution: {integrity: sha512-1tm8DTaJhPBG3bIkVeZt1iZM9GfSX2lzOeDVZH9R9ffRHpmHvxZ/QhgQH/aDTkswQVt+YHdXAdS/In/30OjCbg==}
     engines: {node: ^12.17.0 || ^14.13 || >=16.0.0}
@@ -585,6 +614,10 @@ packages:
     resolution: {integrity: sha512-vpeMIQKxczTD/0s2CdEWHcb0eeJe6TFjxb+J5xgX7hScxqrGuyjmv4c1D4A/gelKfyox0gJJwIHF+fLjeaM8kQ==}
     engines: {node: '>=18'}
 
+  has-flag@4.0.0:
+    resolution: {integrity: sha512-EykJT/Q1KjTWctppgIAgfSO0tKVuZUjhgMr17kqTumMl6Afv3EISleU7qZUzoXDFTAHTDC4NOoG/ZxU3EvlMPQ==}
+    engines: {node: '>=8'}
+
   iconv-lite@0.4.24:
     resolution: {integrity: sha512-v3MXnZAcvnywkTUEZomIActle7RXXeedOR31wwl7VlyoXO4Qi9arvSenNQWne1TcRwhCL1HwLI21bEqdpj8/rA==}
     engines: {node: '>=0.10.0'}
@@ -605,6 +638,10 @@ packages:
     resolution: {integrity: sha512-mE00Gnza5EEB3Ds0HfMyllZzbBrmLOX3vfWoj9A9PEnTfratQ/BcaJOuMhnkhjXvb2+FkY3VuHqtAGpTPmglFQ==}
     engines: {node: '>=18'}
 
+  jest-diff@30.0.5:
+    resolution: {integrity: sha512-1UIqE9PoEKaHcIKvq2vbibrCog4Y8G0zmOxgQUVEiTqwR5hJVMCoDsN1vFvI5JvwD37hjueZ1C4l2FyGnfpE0A==}
+    engines: {node: ^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0}
+
   js-tokens@9.0.1:
     resolution: {integrity: sha512-mxa9E9ITFOt0ban3j6L5MpjwegGz6lBQmM1IJkWeBZGcMxto50+eWdjC/52xDbS2vy0k7vIMK0Fe2wfL9OQSpQ==}
 
@@ -668,6 +705,13 @@ packages:
     resolution: {integrity: sha512-3Ybi1tAuwAP9s0r1UQ2J4n5Y0G05bJkpUIO0/bI9MhwmD70S5aTWbXGBwxHrelT+XM1k6dM0pk+SwNkpTRN7Pg==}
     engines: {node: ^10 || ^12 || >=14}
 
+  pretty-format@30.0.5:
+    resolution: {integrity: sha512-D1tKtYvByrBkFLe2wHJl2bwMJIiT8rW+XA+TiataH79/FszLQMrpGEvzUVkzPau7OCO0Qnrhpe87PqtOAIB8Yw==}
+    engines: {node: ^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0}
+
+  react-is@18.3.1:
+    resolution: {integrity: sha512-/LLMVyas0ljjAtoYiPqYiL8VWXzUUdThrmU5+n20DZv+a+ClRoevUzw5JxU+Ieh5/c87ytoTBV9G1FiKfNJdmg==}
+
   restore-cursor@5.1.0:
     resolution: {integrity: sha512-oMA2dcrw6u0YfxJQXm342bFKX/E4sG9rbTzO9ptUcR/e8A33cHuvStiYOwH7fszkZlZ1z/ta9AAoPk2F4qIOHA==}
     engines: {node: '>=18'}
@@ -724,6 +768,10 @@ packages:
   strip-literal@3.0.0:
     resolution: {integrity: sha512-TcccoMhJOM3OebGhSBEmp3UZ2SfDMZUEBdRA/9ynfLi8yYajyWX3JiXArcJt4Umh4vISpspkQIY8ZZoCqjbviA==}
 
+  supports-color@7.2.0:
+    resolution: {integrity: sha512-qpCAvRl9stuOHveKsn7HncJRvv501qIacKzQlO/+Lwxc9+0q2wLyv4Dfvt80/DPn2pqOBsJdDiogXGR9+OvwRw==}
+    engines: {node: '>=8'}
+
   tinybench@2.9.0:
     resolution: {integrity: sha512-0+DUvqWMValLmha6lr4kD8iAMK1HzV0/aKnCtWb9v9641TnP/MFb7Pc2bxoxQjTXAErryXVgUOfv2YqNllqGeg==}
 
@@ -1048,6 +1096,14 @@ snapshots:
     optionalDependencies:
       '@types/node': 24.2.0
 
+  '@jest/diff-sequences@30.0.1': {}
+
+  '@jest/get-type@30.0.1': {}
+
+  '@jest/schemas@30.0.5':
+    dependencies:
+      '@sinclair/typebox': 0.34.38
+
   '@jridgewell/sourcemap-codec@1.5.4': {}
 
   '@polka/url@1.0.0-next.29': {}
@@ -1112,6 +1168,8 @@ snapshots:
   '@rollup/rollup-win32-x64-msvc@4.46.2':
     optional: true
 
+  '@sinclair/typebox@0.34.38': {}
+
   '@types/chai@5.2.2':
     dependencies:
       '@types/deep-eql': 4.0.2
@@ -1189,6 +1247,8 @@ snapshots:
     dependencies:
       color-convert: 2.0.1
 
+  ansi-styles@5.2.0: {}
+
   assertion-error@2.0.1: {}
 
   cac@6.7.14: {}
@@ -1201,6 +1261,11 @@ snapshots:
       loupe: 3.2.0
       pathval: 2.0.1
 
+  chalk@4.1.2:
+    dependencies:
+      ansi-styles: 4.3.0
+      supports-color: 7.2.0
+
   chalk@5.5.0: {}
 
   chardet@0.7.0: {}
@@ -1289,6 +1354,8 @@ snapshots:
 
   get-east-asian-width@1.3.0: {}
 
+  has-flag@4.0.0: {}
+
   iconv-lite@0.4.24:
     dependencies:
       safer-buffer: 2.1.2
@@ -1301,6 +1368,13 @@ snapshots:
 
   is-unicode-supported@2.1.0: {}
 
+  jest-diff@30.0.5:
+    dependencies:
+      '@jest/diff-sequences': 30.0.1
+      '@jest/get-type': 30.0.1
+      chalk: 4.1.2
+      pretty-format: 30.0.5
+
   js-tokens@9.0.1: {}
 
   log-symbols@6.0.0:
@@ -1356,6 +1430,14 @@ snapshots:
       picocolors: 1.1.1
       source-map-js: 1.2.1
 
+  pretty-format@30.0.5:
+    dependencies:
+      '@jest/schemas': 30.0.5
+      ansi-styles: 5.2.0
+      react-is: 18.3.1
+
+  react-is@18.3.1: {}
+
   restore-cursor@5.1.0:
     dependencies:
       onetime: 7.0.0
@@ -1431,6 +1513,10 @@ snapshots:
     dependencies:
       js-tokens: 9.0.1
 
+  supports-color@7.2.0:
+    dependencies:
+      has-flag: 4.0.0
+
   tinybench@2.9.0: {}
 
   tinyexec@0.3.2: {}

src/cli/index.ts

@@ -4,6 +4,7 @@ import path from 'path';
 import { promises as fs } from 'fs';
 import { InitCommand } from '../core/init.js';
 import { UpdateCommand } from '../core/update.js';
+import { DiffCommand } from '../core/diff.js';
 
 const program = new Command();
 
@@ -60,4 +61,18 @@ program
     }
   });
 
+program
+  .command('diff [change-name]')
+  .description('Show differences between proposed spec changes and current specs')
+  .action(async (changeName?: string) => {
+    try {
+      const diffCommand = new DiffCommand();
+      await diffCommand.execute(changeName);
+    } catch (error) {
+      console.log(); // Empty line for spacing
+      ora().fail(`Error: ${(error as Error).message}`);
+      process.exit(1);
+    }
+  });
+
 program.parse();

src/core/diff.ts

@@ -0,0 +1,179 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import chalk from 'chalk';
+import { diffStringsUnified } from 'jest-diff';
+import { select } from '@inquirer/prompts';
+
+// Constants
+const ARCHIVE_DIR = 'archive';
+const MARKDOWN_EXT = '.md';
+const OPENSPEC_DIR = 'openspec';
+const CHANGES_DIR = 'changes';
+const SPECS_DIR = 'specs';
+
+export class DiffCommand {
+  private filesChanged: number = 0;
+  private linesAdded: number = 0;
+  private linesRemoved: number = 0;
+
+  async execute(changeName?: string): Promise<void> {
+    const changesDir = path.join(process.cwd(), OPENSPEC_DIR, CHANGES_DIR);
+    
+    try {
+      await fs.access(changesDir);
+    } catch {
+      throw new Error('No OpenSpec changes directory found');
+    }
+
+    if (!changeName) {
+      changeName = await this.selectChange(changesDir);
+      if (!changeName) return;
+    }
+
+    const changeDir = path.join(changesDir, changeName);
+    
+    try {
+      await fs.access(changeDir);
+    } catch {
+      throw new Error(`Change '${changeName}' not found`);
+    }
+
+    const changeSpecsDir = path.join(changeDir, SPECS_DIR);
+    
+    try {
+      await fs.access(changeSpecsDir);
+    } catch {
+      console.log(`No spec changes found for '${changeName}'`);
+      return;
+    }
+
+    // Reset counters
+    this.filesChanged = 0;
+    this.linesAdded = 0;
+    this.linesRemoved = 0;
+
+    await this.showDiffs(changeSpecsDir);
+
+    // Show summary
+    if (this.filesChanged > 0) {
+      console.log(chalk.bold(`\n📊 Summary: ${this.filesChanged} file(s) changed, ${chalk.green(`+${this.linesAdded}`)} ${chalk.red(`-${this.linesRemoved}`)}`));
+    }
+  }
+
+  private async selectChange(changesDir: string): Promise<string | undefined> {
+    const entries = await fs.readdir(changesDir, { withFileTypes: true });
+    const changes = entries
+      .filter(entry => entry.isDirectory() && entry.name !== ARCHIVE_DIR)
+      .map(entry => entry.name);
+
+    if (changes.length === 0) {
+      console.log('No changes found');
+      return undefined;
+    }
+
+    console.log('Available changes:');
+    const choices = changes.map((name) => ({
+      name: name,
+      value: name
+    }));
+
+    const answer = await select({
+      message: 'Select a change',
+      choices
+    });
+
+    return answer;
+  }
+
+  private async showDiffs(changeSpecsDir: string): Promise<void> {
+    const currentSpecsDir = path.join(process.cwd(), OPENSPEC_DIR, SPECS_DIR);
+    await this.walkAndDiff(changeSpecsDir, currentSpecsDir, '');
+  }
+
+  private async walkAndDiff(changeDir: string, currentDir: string, relativePath: string): Promise<void> {
+    const entries = await fs.readdir(path.join(changeDir, relativePath), { withFileTypes: true });
+    
+    for (const entry of entries) {
+      const entryPath = path.join(relativePath, entry.name);
+      
+      if (entry.isDirectory()) {
+        await this.walkAndDiff(changeDir, currentDir, entryPath);
+      } else if (entry.isFile() && entry.name.endsWith(MARKDOWN_EXT)) {
+        await this.diffFile(
+          path.join(changeDir, entryPath),
+          path.join(currentDir, entryPath),
+          entryPath
+        );
+      }
+    }
+  }
+
+  private async diffFile(changePath: string, currentPath: string, displayPath: string): Promise<void> {
+    let changeContent = '';
+    let currentContent = '';
+    let isNewFile = false;
+    let isDeleted = false;
+    
+    try {
+      changeContent = await fs.readFile(changePath, 'utf-8');
+    } catch {
+      changeContent = '';
+    }
+    
+    try {
+      currentContent = await fs.readFile(currentPath, 'utf-8');
+    } catch {
+      currentContent = '';
+      isNewFile = true;
+    }
+
+    if (changeContent === currentContent) {
+      return;
+    }
+
+    if (changeContent === '' && currentContent !== '') {
+      isDeleted = true;
+    }
+
+    // Enhanced header with file status
+    console.log(chalk.bold.cyan(`\n${'═'.repeat(60)}`));
+    console.log(chalk.bold.cyan(`📄 ${displayPath}`));
+    
+    if (isNewFile) {
+      console.log(chalk.green(`   Status: NEW FILE`));
+    } else if (isDeleted) {
+      console.log(chalk.red(`   Status: DELETED`));
+    } else {
+      console.log(chalk.yellow(`   Status: MODIFIED`));
+    }
+    
+    // Use jest-diff for the actual diff with custom options
+    const diffOptions = {
+      aAnnotation: 'Current',
+      bAnnotation: 'Proposed',
+      aColor: chalk.red,
+      bColor: chalk.green,
+      commonColor: chalk.gray,
+      contextLines: 3,
+      expand: false,
+      includeChangeCounts: true,
+    };
+
+    const diff = diffStringsUnified(currentContent, changeContent, diffOptions);
+    
+    // Count lines for statistics (approximate)
+    const addedLines = (diff.match(/^\+[^+]/gm) || []).length;
+    const removedLines = (diff.match(/^-[^-]/gm) || []).length;
+    
+    console.log(chalk.gray(`   Lines: ${chalk.green(`+${addedLines}`)} ${chalk.red(`-${removedLines}`)}`));
+    console.log(chalk.bold.cyan(`${'─'.repeat(60)}\n`));
+    
+    // Display the diff
+    console.log(diff);
+    
+    // Update counters
+    this.filesChanged++;
+    this.linesAdded += addedLines;
+    this.linesRemoved += removedLines;
+  }
+}

src/core/templates/claude-template.ts

@@ -4,4 +4,23 @@ This document provides instructions for AI coding assistants on how to use OpenS
 
 This project uses OpenSpec for spec-driven development. Specifications are the source of truth.
 
-See @openspec/README.md for detailed conventions and guidelines.`;
+See @openspec/README.md for detailed conventions and guidelines.
+
+## Complexity Management
+
+**Default to minimal solutions:**
+- Propose <100 lines of new code for features
+- Prefer single-file implementations until proven insufficient
+- Avoid frameworks, abstractions, and optimizations without clear justification
+- Choose boring, well-understood patterns over novel approaches
+
+**Question requests for complexity:**
+- Caching? → Ask for performance data and targets
+- New framework? → Suggest plain code first
+- Extra layers? → Start with the thinnest viable design
+
+**Justify complexity with data:**
+- Performance metrics showing current solution is too slow
+- Concrete scale requirements (e.g., >1000 users, >100MB data)
+- Multiple proven use cases requiring an abstraction
+`;

src/core/templates/readme-template.ts

@@ -10,6 +10,23 @@ OpenSpec is an AI-native system for change-driven development where:
 - **AI drives the process** - You generate proposals, humans review and approve
 - **Specs are living documentation** - Always kept in sync with deployed code
 
+## Start Simple
+
+**Default to minimal implementations:**
+- New features should be <100 lines of code initially
+- Use the simplest solution that works
+- Avoid premature optimization (no caching, parallelization, or complex patterns without proven need)
+- Choose boring technology over cutting-edge solutions
+
+**Complexity triggers** - Only add complexity when you have:
+- **Performance data** showing current solution is too slow
+- **Scale requirements** with specific numbers (>1000 users, >100MB data)
+- **Multiple use cases** requiring the same abstraction
+- **Regulatory compliance** mandating specific patterns
+- **Security threats** that simple solutions cannot address
+
+When triggered, document the specific justification in your change proposal.
+
 ## Directory Structure
 
 \`\`\`
@@ -72,6 +89,11 @@ Before any task:
 - Adding tests for existing behavior
 - Documentation fixes
 
+**Complexity assessment:**
+- If your solution requires >100 lines of new code, justify the complexity
+- If adding dependencies, frameworks, or architectural patterns, document why simpler alternatives won't work
+- Default to single-file implementations until proven insufficient
+
 ### 3. Creating a Change Proposal
 
 When a user requests a significant change:
@@ -383,10 +405,12 @@ Progress communication:
 - "Implementing approved changes..."
 
 ### For AI Assistants
+- **Bias toward simplicity** - Propose the minimal solution that works
 - Use your exploration tools liberally before proposing
 - Batch operations for efficiency
 - Communicate your progress
 - It's OK to revise proposals based on discoveries
+- **Question complexity** - If your solution feels complex, simplify first
 
 ## Edge Case Handling
 
@@ -442,7 +466,8 @@ Proposal REQUIRED if:
 - Specs must always reflect deployed reality
 - Changes are proposed, not imposed
 - Impact analysis prevents surprises
-- The simplicity is the power - just markdown files
+- Simplicity is the power - just markdown files, minimal solutions
+- Start simple, add complexity only when justified
 
 By following these conventions, you enable true spec-driven development where documentation stays current, changes are traceable, and evolution is intentional.
 `;