feat: Add write operations to MCP server (v0.4.0)

[vscarpenter]

Summary

This PR transforms the GSD MCP server from read-only access to full CRUD capabilities with maintained end-to-end encryption. This is a major feature release (v0.2.1 → v0.4.0) that enables Claude Desktop to create, update, and delete tasks using natural language.

🔥 Breaking Changes

• Requires GSD_ENCRYPTION_PASSPHRASE for all write operations
• Security model updated from read-only to read-write with encryption
• Users must run npx gsd-mcp-server --setup to configure encryption

✨ New Features

Write Operations (5 New Tools)

• create_task - Create new tasks with all properties (title, description, quadrant, tags, subtasks, recurrence, dependencies)
• update_task - Update existing tasks (any property, automatic quadrant moves)
• complete_task - Quick toggle for task completion status
• delete_task - Permanently delete tasks (cannot be undone)
• bulk_update_tasks - Update up to 50 tasks at once with 6 operation types:
  • Complete/uncomplete multiple tasks
  • Move tasks between quadrants
  • Add/remove tags from multiple tasks
  • Set due dates for multiple tasks
  • Batch delete tasks

Enhanced Encryption (crypto.ts)

• Added encrypt() method for encrypting task data before push
• Updated deriveKey() to support both encrypt and decrypt capabilities
• Secure random nonce generation for each encryption operation
• Full AES-256-GCM encryption/decryption round-trip support

Interactive CLI (v0.3.0)

• Setup wizard (--setup) - Step-by-step guided configuration with API testing
• Configuration validator (--validate) - Comprehensive diagnostics and troubleshooting
• Help system (--help) - Detailed usage documentation

Analytics & Insights (v0.3.0)

• 6 analytics MCP tools: productivity metrics, quadrant analysis, tag analytics, deadlines, insights, config validation
• Ported from frontend lib/analytics.ts with full metrics calculation

MCP Prompts (v0.3.2)

• 6 pre-configured conversation starters (daily-standup, weekly-review, focus-mode, etc.)
• get_help tool with topic-based filtering

🐛 Bug Fixes

• Critical: Fixed hardcoded device ID in tools.ts:223 causing multi-device sync issues
• Now dynamically parses device ID from JWT token via new jwt.ts module

🔒 Security

• End-to-end encryption maintained for all write operations
• Zero-knowledge server (Worker cannot decrypt task changes)
• Local passphrase never sent to server
• Same PBKDF2 key derivation (600k iterations)
• Transactional API push (all-or-nothing)

📦 Technical Details

New Modules

• src/write-ops.ts (447 lines) - Write operation functions with encryption
• src/cli.ts - Interactive CLI utilities
• src/jwt.ts - JWT parsing and token utilities
• src/analytics.ts - Productivity metrics calculation

Modified Files

• src/crypto.ts - Added encrypt() method, updated deriveKey capabilities
• src/index.ts - Added 5 write tool definitions and handlers (v0.2.0 → v0.4.0)
• src/tools.ts - Fixed device ID bug, enhanced error messages
• package.json - Version bump, description update
• README.md - Comprehensive write operation documentation
• CHANGELOG.md - Detailed version history (NEW)

API Integration

• Calls /api/sync/push endpoint with encrypted task blobs
• Handles vector clocks for conflict resolution
• Supports batch push for bulk operations
• Proper error handling for network failures

Encryption Details

• Uses Node.js Web Crypto API (webcrypto)
• AES-256-GCM with 128-bit authentication tag
• 96-bit (12-byte) random nonce per encryption
• Base64 encoding for ciphertext and nonce
• PBKDF2 with 600,000 iterations (OWASP 2023)

📊 Stats

• Tool count: 6 → 18 (added 12 tools across 3 versions)
• Lines added: ~3,095 lines (447 in write-ops.ts alone)
• New files: 5 (write-ops, cli, jwt, analytics, CHANGELOG)
• Version progression: v0.2.1 → v0.3.0 → v0.3.2 → v0.4.0

🧪 Testing

• ✅ TypeScript compilation successful
• ✅ All dist files generated (30 files)
• ✅ Build output verified
• ✅ Package ready for npm publication

📋 Checklist

• Version bumped to 0.4.0
• TypeScript build successful
• README updated with new features
• CHANGELOG added with detailed release notes
• All dist files present
• Package.json metadata updated
• Breaking changes documented
• Security model updated

🚀 Post-Merge

After merge, publish to npm:

cd packages/mcp-server
npm publish

🤖 Generated with Claude Code

[claude]

PR Review: Add write operations to MCP server (v0.4.0)

🎯 Overall Assessment

This is a major feature release that transforms the MCP server from read-only to full CRUD capabilities. The implementation is well-structured, maintains end-to-end encryption, and follows the project's coding standards. However, there are several critical areas that need attention before merging.

Recommendation: ⚠️ Request Changes - Address critical security and testing issues before merge.

---

✅ Strengths

1. Excellent Code Organization

• Clean separation of concerns (write-ops.ts, crypto.ts, jwt.ts, analytics.ts)
• Clear module boundaries with well-defined interfaces
• Consistent naming conventions and TypeScript types
• Good use of helper functions (generateTaskId(), deriveQuadrantId())

2. Security Model

• ✅ End-to-end encryption maintained for write operations
• ✅ Proper PBKDF2 key derivation (600k iterations per OWASP 2023)
• ✅ Secure random nonce generation per encryption (96-bit)
• ✅ AES-256-GCM with 128-bit auth tag
• ✅ Zero-knowledge architecture preserved

3. User Experience

• Clear error messages with actionable guidance
• Safety limits on bulk operations (50 task max)
• Good validation and input checking
• Comprehensive CLI tools (--setup, --validate, --help)

4. Documentation

• Excellent README with usage examples
• Comprehensive CHANGELOG following Keep a Changelog format
• Clear API documentation for all tools
• Good inline code comments

---

🚨 Critical Issues

1. Missing Test Coverage (Blocker)

Issue: No tests found for 3,095 lines of new code.

# No test files found:
packages/mcp-server/**/*.test.ts  # 0 files
packages/mcp-server/**/*.spec.ts  # 0 files

Risk: High - Write operations directly modify user data. Without tests:

• No validation of encryption/decryption round-trip
• No verification of bulk operation safety limits
• No testing of error handling paths
• Regression risk for future changes

Required Actions:

1. Add unit tests for write-ops.ts:

   • createTask() - verify encryption and ID generation
   • updateTask() - verify partial updates and quadrant recalculation
   • deleteTask() - verify deletion flag
   • bulkUpdateTasks() - verify safety limits (50 task max), operation types, error handling

2. Add unit tests for crypto.ts:

   • encrypt() - verify ciphertext format, nonce generation
   • decrypt() - verify round-trip encryption
   • Key derivation with various passphrases

3. Add unit tests for jwt.ts:

   • parseJWT() - handle malformed tokens
   • isTokenExpired() - edge cases (already expired, far future)
   • getDeviceIdFromToken() - verify extraction

4. Add integration tests:

   • Full create → encrypt → push → pull → decrypt flow
   • Bulk operations with API mocking

Target Coverage: ≥80% per CLAUDE.md guidelines

2. Vector Clock Simplification (High Risk)

Issue: write-ops.ts:135 - Vector clock set to empty object

body: JSON.stringify({
  deviceId,
  tasks,
  vectorClock: {}, // Simplified: let server handle vector clock
}),

Risk: This defeats the purpose of vector clocks for conflict resolution:

• Concurrent edits from multiple devices will be unpredictable
• Last-write-wins without proper causality tracking
• Potential data loss in multi-device scenarios

Questions:

1. Does the Worker API actually handle vector clock generation server-side?
2. What happens when two devices push simultaneously with empty vector clocks?
3. Is there client-side vector clock tracking that should be used here?

Required Action:

• Review Worker API implementation for vector clock handling
• Either implement proper vector clock tracking or document the trade-offs
• Add integration tests for concurrent write scenarios

3. Error Handling: Silent Conflicts (Medium Risk)

Issue: write-ops.ts:153-156 - Conflicts logged to console, not surfaced to user

if (result.conflicts && result.conflicts.length > 0) {
  console.warn(`⚠️  Warning: ${result.conflicts.length} conflict(s) detected`);
  console.warn('Last-write-wins strategy applied - your changes took precedence');
}

Risk: Users won't know their changes conflicted with other devices. Claude Desktop won't see these console warnings.

Required Action:

• Return conflicts in the response object
• Update tool handlers to surface conflict warnings to the user
• Consider allowing user to review conflicts before accepting last-write-wins

4. Hardcoded Device ID Fixed, But No Validation (Medium)

Good: The critical bug fix in tools.ts:223 (hardcoded device ID) is addressed by using getDeviceIdFromToken().

Concern: No validation that the device ID in the token matches the device making the request.

Recommendation:

• Add device ID validation in write operations
• Consider caching device ID after first parse (performance)

---

⚠️ Security Concerns

1. Encryption Key Lifecycle (Medium)

Issue: Singleton CryptoManager persists in memory for the entire MCP server session.

Crypto.ts:161-171:

let cryptoManagerInstance: CryptoManager | null = null;

export function getCryptoManager(): CryptoManager {
  if (!cryptoManagerInstance) {
    cryptoManagerInstance = new CryptoManager();
  }
  return cryptoManagerInstance;
}

Concerns:

1. Encryption key stays in memory indefinitely
2. No session timeout or key rotation
3. If MCP server process is compromised, keys are exposed

Recommendations:

• Consider key expiration after inactivity period
• Add clearCryptoManager() calls after operations (tradeoff: performance vs security)
• Document key lifecycle in security documentation

2. Input Validation (Low-Medium)

Observation: Limited input validation for write operations.

Missing Validations:

• Task title length limits (prevent excessive storage)
• Description length limits
• Tag count/length limits
• Subtask count limits
• Dependency circular reference validation (should call frontend's wouldCreateCircularDependency())

Recommendation:

• Add Zod schemas for CreateTaskInput and UpdateTaskInput
• Validate before encryption (cheaper than encrypting invalid data)
• Match frontend validation rules from lib/schema.ts

3. Bulk Delete Safety (Low)

Issue: Bulk delete has 50-task limit, but no confirmation or undo.

Write-ops.ts:391-399:

case 'delete':
  updatedTasks.push({
    id: task.id,
    encryptedBlob: '',
    nonce: '',
    deleted: true,
  });
  continue;

Recommendations:

• Consider requiring explicit confirmation for bulk deletes >10 tasks
• Log bulk deletes for audit trail
• Document that deletes are permanent (already in README ✓)

---

🔍 Code Quality Issues

1. Inconsistent Error Messages (Low)

Good: Most error messages are clear and actionable.

Inconsistency: Some use emoji prefixes (❌), others don't.

Examples:

// With emoji (good):
throw new Error(`❌ Task not found: ${input.id}\n\nThe task may have been deleted.`);

// Without emoji (inconsistent):
throw new Error('Invalid JWT format'); // jwt.ts:28

Recommendation: Standardize on emoji prefixes for user-facing errors throughout.

2. Type Safety: any Usage (Low)

Write-ops.ts:402:

default:
  throw new Error(`Unknown operation type: ${(operation as any).type}`);

Better approach:

default:
  const _exhaustive: never = operation;
  throw new Error(`Unknown operation type`);

This provides compile-time exhaustiveness checking for the BulkOperation union type.

3. Magic Numbers (Low)

Write-ops.ts:320:

const maxTasks = options?.maxTasks || 50;

Recommendation:

const DEFAULT_BULK_LIMIT = 50;
const maxTasks = options?.maxTasks || DEFAULT_BULK_LIMIT;

Extract to named constant at module level.

---

📊 Performance Considerations

1. Bulk Operations Efficiency (Medium)

Issue: bulkUpdateTasks() fetches ALL tasks, then filters.

Write-ops.ts:337-338:

const allTasks = await listTasks(config);
const tasksToUpdate = allTasks.filter((t) => taskIds.includes(t.id));

Problem: If user has 1000 tasks but only updating 5, still decrypts all 1000.

Recommendation:

• Add listTasksByIds(config, taskIds) function that only decrypts requested tasks
• Use Set for taskIds lookup (O(1) instead of O(n))

2. Encryption Overhead (Low)

Observation: Each task encrypted individually in bulk operations (write-ops.ts:406-407).

Current:

for (const task of tasksToUpdate) {
  const { ciphertext, nonce } = await cryptoManager.encrypt(taskJson);
}

Impact: Minimal for 50 tasks, but worth noting.

Note: This is probably optimal given the API expects per-task encryption. No change needed unless API supports bulk encryption.

---

🧪 Testing Recommendations

Based on CLAUDE.md (≥80% coverage):

Unit Tests (Priority: High)

// packages/mcp-server/tests/write-ops.test.ts
describe('createTask', () => {
  it('generates unique task IDs', () => {});
  it('derives correct quadrant from urgent/important flags', () => {});
  it('encrypts task before push', () => {});
  it('throws error when passphrase not set', () => {});
});

describe('bulkUpdateTasks', () => {
  it('enforces 50-task limit', () => {});
  it('handles partial failures gracefully', () => {});
  it('returns error for each failed task', () => {});
});

Integration Tests (Priority: High)

// packages/mcp-server/tests/integration.test.ts
describe('encryption round-trip', () => {
  it('can decrypt what it encrypted', async () => {});
  it('matches frontend encryption format', async () => {});
});

describe('API integration', () => {
  it('pushes encrypted tasks to /api/sync/push', () => {});
  it('handles conflicts from server', () => {});
});

Security Tests (Priority: Medium)

describe('security', () => {
  it('rejects tasks without encryption passphrase', () => {});
  it('validates JWT token format', () => {});
  it('prevents circular dependencies', () => {});
  it('enforces bulk operation limits', () => {});
});

---

📝 Documentation Issues

1. Missing Migration Guide (Medium)

Issue: Users upgrading from v0.3.2 need to know:

• New passphrase requirement for all operations
• How to update Claude Desktop config
• What happens to existing read-only setups

Recommendation: Add "Upgrading from v0.3.x" section to README.

2. Security Documentation (Low)

README.md references DECRYPTION.md:

See DECRYPTION.md for detailed security documentation.

Issue: This file doesn't exist in the diff or repo.

Recommendation: Either create DECRYPTION.md or remove the reference.

---

🎯 Breaking Changes - Well Documented ✅

The breaking changes are clearly documented:

• ✅ CHANGELOG.md has "⚠️ BREAKING CHANGES" section
• ✅ PR description calls out breaking changes
• ✅ README updated with new requirements
• ✅ Version bump follows semver (0.3.2 → 0.4.0)

---

📋 Recommendations Summary

Before Merge (Blockers):

1. Add test coverage for all new code (target: ≥80%)

   • Unit tests for write-ops.ts, crypto.ts, jwt.ts
   • Integration tests for encryption round-trip
   • Security tests for validation and limits

2. Review vector clock handling

   • Verify Worker API handles empty vector clocks correctly
   • Document trade-offs or implement proper tracking
   • Add tests for concurrent write scenarios

3. Surface conflicts to users

   • Return conflicts in tool responses
   • Don't just log to console (MCP won't see it)

Before Merge (High Priority):

4. Add input validation

   • Zod schemas for CreateTaskInput/UpdateTaskInput
   • Length limits for title, description, tags
   • Circular dependency validation

5. Add migration guide for v0.3.x → v0.4.0 users

Post-Merge (Nice to Have):

6. Performance optimization for bulk operations (fetch only needed tasks)
7. Key lifecycle management (expiration, rotation)
8. Bulk delete confirmation for >10 tasks

---

🏆 Final Thoughts

This PR represents a significant and well-executed enhancement to the GSD MCP server. The code quality is high, the security model is sound, and the user experience is thoughtfully designed. However, the lack of test coverage for 3,000+ lines of write operations is a critical gap that must be addressed before merge.

The vector clock simplification also needs clarification - if the Worker doesn't properly handle empty vector clocks, this could lead to data loss in multi-device scenarios.

Once tests are added and the vector clock concern is addressed, this will be a solid release that maintains the project's high standards.

Estimated effort to address blockers: 1-2 days

• Test writing: ~4-6 hours
• Vector clock investigation: ~2-4 hours
• Input validation: ~2-3 hours

---

Reviewed with reference to:

• /home/runner/work/gsd-task-manager/gsd-task-manager/CLAUDE.md
• /home/runner/work/gsd-task-manager/gsd-task-manager/coding-standards.md
• GSD Task Manager architecture and security model

🤖 Generated with Claude Code

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[claude]

Code Review: MCP Server Write Operations

Overall Assessment

This is a major feature release (v0.4.0) that adds full CRUD capabilities to the MCP server while maintaining end-to-end encryption. The implementation is well-structured, but there are critical issues that must be addressed before merging.

---

CRITICAL ISSUES (BLOCKERS)

1. Missing Test Coverage

• Issue: Zero test files in packages/mcp-server/ (3,123 new lines untested)
• Risk: High regression probability, especially in crypto logic
• Requirement: Minimum 80% coverage per CLAUDE.md
• BLOCKER: Violates project testing standards

2. Hardcoded Vector Clock Strategy

• Location: write-ops.ts:143, 218, 274
• Code: clientVectorClock: {} (empty object passed to all operations)
• Risk: Defeats conflict resolution, potential data loss in multi-device scenarios
• BLOCKER: Could cause data corruption

3. Incomplete Bulk Error Handling

• Location: write-ops.ts:420-424
• Issue: Partial failures in bulk ops are logged but other tasks still pushed
• Risk: Silent failures, inconsistent state
• Need: True transactional behavior (all-or-nothing)

---

MAJOR CONCERNS

4. No Rollback Mechanism

• Bulk delete is permanent - user error causes data loss
• Recommendation: Soft-delete with 30-day recovery OR backup warnings

5. Rate Limiting Missing

• No client throttling for bulk ops
• Could hit server limit (100 req/min per CLAUDE.md)
• Need: Client-side rate limiting with exponential backoff

6. JWT Parsing Without Validation

• jwt.ts:23 parses without signature validation
• Server validates, but local parsing could cause bugs
• Recommendation: Document this is convenience-only OR add local validation

7. Version Inconsistency

• package.json says 0.4.1, PR title says v0.4.0
• Clarify which version this represents

---

STRENGTHS

Architecture

• Clean module separation (crypto, jwt, write-ops, analytics)
• Proper TypeScript + Zod validation
• Single responsibility principle throughout

Security

• E2E encryption maintained
• PBKDF2 600k iterations (OWASP 2023)
• AES-256-GCM with per-op nonces
• Zero-knowledge server
• Passphrase never transmitted

Developer Experience

• Interactive setup wizard (--setup)
• Validation tool (--validate)
• Comprehensive error messages
• 6 built-in prompts
• Excellent JSDoc comments

---

CODE QUALITY ISSUES

1. Magic numbers: maxTasks = 50 should be constant (write-ops.ts:330)
2. Duplicate code: Encryption logic repeated 3x - extract helper
3. Long function: bulkUpdateTasks 120 lines (exceeds 30-line limit)
4. Deep nesting: 4 levels in bulkUpdateTasks (exceeds 3-level max)

---

PERFORMANCE ISSUES

1. Serial encryption: Bulk ops encrypt sequentially - use Promise.all()
2. Inefficient lookup: updateTask fetches ALL tasks to find one
   • write-ops.ts:234: const tasks = await listTasks(config)
   • Should use: await getTask(config, input.id)
3. No caching: Encryption salt fetched every time (static data)

---

SPECIFIC FIXES NEEDED

write-ops.ts:234

Change from listTasks to getTask for single task lookup

write-ops.ts:143

Document why empty vector clock is acceptable OR implement properly

write-ops.ts:330

Extract MAX_BULK_OPERATION_TASKS constant

---

TESTING GAPS

Need tests for:

1. Encryption round-trip (verify data preserved)
2. Concurrent modifications (multi-device conflict)
3. Bulk edge cases (51 tasks, empty array, all fail)
4. JWT parsing (valid, expired, malformed)
5. Error handling (network fail, wrong passphrase, missing task)
6. Vector clock conflict resolution

---

BEFORE MERGING CHECKLIST

BLOCKERS:

• Add comprehensive test suite (80% coverage minimum)
• Fix or document vector clock strategy

HIGH PRIORITY:

• Make bulk ops transactional
• Fix updateTask performance (use getTask)
• Add rate limiting

MEDIUM:

• Document JWT parsing security
• Extract MAX_BULK_OPERATION_TASKS
• Refactor bulkUpdateTasks (too long)
• Document rollback procedures
• Clarify version (0.4.0 vs 0.4.1)

REFACTORING:

• Extract encryption helper
• Parallelize bulk encryption
• Cache encryption salt

---

RECOMMENDATION

Status: CHANGES REQUESTED

Excellent work adding critical functionality, but lack of tests and incomplete vector clock are blockers. High code quality otherwise, but these gaps pose significant risks.

Priority Actions:

1. Add test coverage (80% minimum)
2. Fix/document vector clock strategy
3. Address bulk transactionality
4. Fix updateTask performance

Once tests and vector clock are addressed, ready to merge.

---

Reviewed with: CLAUDE.md, coding-standards.md
Date: 2025-10-26
Reviewer: Claude Code