# P3 Design: Performance, Observability & Developer Experience

**Purpose:** Defines scope, boundaries, and acceptance criteria for P3 work before implementation begins.  
**Owner:** Development Team  
**Last Updated:** 2025-12-22  
**Status:** design-only (no implementation)  
**Baseline:** `v1.0.11-p2.3-p1.5b-complete`

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## Purpose

This document defines the **scope, boundaries, and acceptance criteria** for P3 work **before any implementation begins**. It ensures P3:

- Does not violate established invariants
- Has clear "done" criteria
- Can be executed incrementally
- Maintains the stability achieved in P0/P1/P2
- Focuses on polish, performance, and developer experience

---

## P3 Scope Definition

### What P3 Includes

**P3.1 — Performance Optimization & Metrics**
- Add performance metrics collection (timing, memory, database operations)
- Optimize critical paths (scheduling, recovery, database queries)
- Document performance characteristics and benchmarks
- Add performance regression tests

**P3.2 — Enhanced Observability**
- Expand event logging coverage (missing edge cases)
- Add structured metrics export (for dashboards/monitoring)
- Improve error context (stack traces, state snapshots)
- Add diagnostic mode for troubleshooting

**P3.3 — Developer Experience Improvements**
- Improve error messages (actionable, context-rich)
- Add development mode helpers (debug logging, state inspection)
- Enhance TypeScript types (better IntelliSense, stricter contracts)
- Add integration examples and quick-start guides

**P3.4 — Documentation Polish**
- API documentation improvements (JSDoc completeness)
- Add troubleshooting guides (common issues, solutions)
- Improve onboarding documentation (getting started, architecture overview)
- Add migration guides (version upgrades, breaking changes)

### What P3 Excludes

- **No new features** — P3 is polish, not expansion
- **No architectural changes** — Core structure remains unchanged
- **No breaking API changes** — Backward compatibility required
- **No new platforms** — Focus on existing iOS/Android/Web
- **No new dependencies** — Minimize external additions (prefer built-in solutions)

---

## Invariants That Must Not Be Violated

All invariants from P0/P1/P2 remain in force:

1. **Packaging Invariants (P0)** — No forbidden files, exports correct
2. **Core Module Purity (P1.4)** — No platform imports in `src/core/`
3. **CI Authority (P0)** — `./ci/run.sh` remains authoritative
4. **Export Correctness (P0)** — All exports match artifacts
5. **Documentation Structure (P1.5)** — Index-first rule followed
6. **Baseline Tag Integrity** — Tags represent known-good states

**Enforcement:** All P3 work must pass `./ci/run.sh` before merging.

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## P3 Work Items

### P3.1: Performance Optimization & Metrics

**Goal:** Measure, optimize, and document performance characteristics.

**Current State:**
- No explicit performance metrics collection
- No performance regression tests
- Performance characteristics undocumented

**Scope:**
- Add timing metrics for critical operations:
  - Schedule creation/update
  - Notification delivery
  - Recovery operations
  - Database queries
- Add memory usage tracking (optional, platform-specific)
- Optimize identified bottlenecks:
  - Database query patterns
  - Notification scheduling overhead
  - Recovery path efficiency
- Document performance characteristics:
  - Expected operation times
  - Memory footprint
  - Platform-specific considerations
- Add performance regression tests:
  - Baseline metrics collection
  - CI integration (warn on regressions)

**Constraints:**
- Must not add significant overhead (metrics collection must be lightweight)
- Must be opt-in or development-only (production impact minimal)
- Must not break existing functionality
- Must be cross-platform compatible

**Acceptance Criteria:**
- [ ] Performance metrics collection implemented (timing, optional memory)
- [ ] Critical paths optimized (at least 2 identified bottlenecks addressed)
- [ ] Performance characteristics documented (expected times, memory footprint)
- [ ] Performance regression tests added (baseline + CI integration)
- [ ] No performance regressions introduced (verified via tests)

**Estimated Effort:** Medium (2-3 days)

---

### P3.2: Enhanced Observability

**Goal:** Improve visibility into plugin behavior for debugging and monitoring.

**Current State:**
- Event logging exists but may have gaps
- No structured metrics export
- Error context could be richer
- No diagnostic mode

**Scope:**
- Expand event logging coverage:
  - Missing edge cases (if any)
  - Background task execution
  - Recovery operations
  - State transitions
- Add structured metrics export:
  - JSON export of metrics
  - Integration with monitoring systems (optional)
  - Historical metrics (if storage available)
- Improve error context:
  - Stack traces (where available)
  - State snapshots (relevant context)
  - Operation context (what was happening)
- Add diagnostic mode:
  - Verbose logging toggle
  - State inspection helpers
  - Debug information export

**Constraints:**
- Must not expose sensitive data (user content, tokens)
- Must be opt-in (diagnostic mode)
- Must not impact production performance
- Must be cross-platform compatible

**Acceptance Criteria:**
- [ ] Event logging coverage expanded (all critical paths covered)
- [ ] Structured metrics export implemented (JSON format)
- [ ] Error context improved (stack traces, state snapshots)
- [ ] Diagnostic mode added (verbose logging, state inspection)
- [ ] Documentation updated (how to use observability features)

**Estimated Effort:** Medium (2-3 days)

---

### P3.3: Developer Experience Improvements

**Goal:** Make the plugin easier to use, debug, and integrate.

**Current State:**
- Error messages could be more actionable
- TypeScript types are good but could be stricter
- Limited development helpers
- Integration examples exist but could be expanded

**Scope:**
- Improve error messages:
  - Actionable guidance (what to do next)
  - Context-rich (what went wrong, why)
  - Platform-specific hints (iOS vs Android differences)
- Add development mode helpers:
  - Debug logging toggle
  - State inspection methods
  - Test data injection helpers
- Enhance TypeScript types:
  - Stricter contracts (discriminated unions where appropriate)
  - Better IntelliSense (JSDoc improvements)
  - Type guards for runtime validation
- Add integration examples:
  - Quick-start guide (minimal working example)
  - Common patterns (scheduling, recovery, error handling)
  - Platform-specific examples (iOS, Android, Web)

**Constraints:**
- Must maintain backward compatibility
- Must not add production overhead (development helpers only)
- Must be cross-platform compatible
- Must not break existing integrations

**Acceptance Criteria:**
- [ ] Error messages improved (actionable, context-rich)
- [ ] Development mode helpers added (debug logging, state inspection)
- [ ] TypeScript types enhanced (stricter contracts, better IntelliSense)
- [ ] Integration examples expanded (quick-start, common patterns)
- [ ] Documentation updated (developer experience improvements)

**Estimated Effort:** Medium (2-3 days)

---

### P3.4: Documentation Polish

**Goal:** Improve documentation completeness, clarity, and discoverability.

**Current State:**
- API documentation exists but may have gaps
- Troubleshooting guides are minimal
- Onboarding documentation could be improved
- Migration guides may be missing

**Scope:**
- API documentation improvements:
  - JSDoc completeness (all public APIs documented)
  - Parameter descriptions (types, constraints, examples)
  - Return value documentation (types, possible values)
  - Error documentation (when errors occur, what they mean)
- Add troubleshooting guides:
  - Common issues (with solutions)
  - Platform-specific issues (iOS vs Android)
  - Debugging steps (how to diagnose problems)
  - FAQ (frequently asked questions)
- Improve onboarding documentation:
  - Getting started guide (step-by-step)
  - Architecture overview (high-level design)
  - Key concepts (scheduling, recovery, persistence)
  - Integration checklist
- Add migration guides:
  - Version upgrade guides (breaking changes)
  - API migration (deprecated → new APIs)
  - Configuration migration (old → new config)

**Constraints:**
- Must maintain accuracy (docs must match code)
- Must be discoverable (linked from index)
- Must be maintainable (drift guards, review process)
- Must not duplicate existing content

**Acceptance Criteria:**
- [ ] API documentation complete (all public APIs have JSDoc)
- [ ] Troubleshooting guides added (common issues, solutions)
- [ ] Onboarding documentation improved (getting started, architecture)
- [ ] Migration guides added (version upgrades, API changes)
- [ ] Documentation index updated (all new docs linked)

**Estimated Effort:** Medium (2-3 days)

---

## P3 Execution Strategy

### Phase Ordering

**Recommended sequence:**

1. **P3.1 First (Performance)**
   - Measure first (add metrics collection)
   - Identify bottlenecks
   - Optimize critical paths
   - Document characteristics
   - **Checkpoint:** Run `./ci/run.sh`, update progress docs

2. **P3.2 Second (Observability)**
   - Expand event logging
   - Add metrics export
   - Improve error context
   - Add diagnostic mode
   - **Checkpoint:** Run `./ci/run.sh`, update progress docs

3. **P3.3 Third (Developer Experience)**
   - Improve error messages
   - Add development helpers
   - Enhance TypeScript types
   - Expand examples
   - **Checkpoint:** Run `./ci/run.sh`, update progress docs

4. **P3.4 Fourth (Documentation)**
   - Complete API docs
   - Add troubleshooting guides
   - Improve onboarding
   - Add migration guides
   - **Checkpoint:** Run `./ci/run.sh`, update progress docs

### Incremental Approach

- Each P3 item can be completed independently
- No strict dependencies between items
- Each item has its own acceptance criteria
- Can pause/resume at any item boundary

### Testing Strategy

- **P3.1:** Performance regression tests required
- **P3.2:** Observability features must be testable
- **P3.3:** Developer helpers must not break existing functionality
- **P3.4:** Documentation review (no code changes, but accuracy checks)

---

## P3 "Done" Criteria

### Overall P3 Completion

P3 is complete when:

1. **All P3 items completed** (P3.1, P3.2, P3.3, P3.4)
2. **All invariants preserved** (verified by CI)
3. **All acceptance criteria met** (per item)
4. **Documentation updated** (progress docs, index, changelog)
5. **Baseline tag created** (if desired: `v1.0.11-p3-complete`)

### Individual Item Completion

Each P3 item is complete when:

- [ ] Acceptance criteria met
- [ ] CI passes (`./ci/run.sh`)
- [ ] No invariant violations
- [ ] Documentation updated (if applicable)
- [ ] Performance tests pass (for P3.1)

---

## Risk Mitigation

### Performance Overhead

**Risk:** Metrics collection adds overhead  
**Mitigation:** Make metrics opt-in or development-only, use lightweight collection

### Breaking Changes

**Risk:** Developer experience improvements break existing code  
**Mitigation:** Maintain backward compatibility, add deprecation warnings

### Documentation Drift

**Risk:** Documentation becomes outdated  
**Mitigation:** Drift guards, review process, link from index

### Scope Creep

**Risk:** P3 expands beyond polish into features  
**Mitigation:** Strict scope definition, "what P3 excludes" section

---

## Success Metrics

### Performance (P3.1)

- Critical operations complete within expected timeframes
- No performance regressions introduced
- Performance characteristics documented

### Observability (P3.2)

- All critical paths have event logging
- Error context is actionable
- Diagnostic mode is useful for troubleshooting

### Developer Experience (P3.3)

- Error messages are actionable
- TypeScript types provide good IntelliSense
- Integration examples are clear and helpful

### Documentation (P3.4)

- All public APIs are documented
- Troubleshooting guides are comprehensive
- Onboarding is smooth for new developers

---

## Next Steps After P3

Potential future phases (not in scope for P3):

- **P4.x:** New features (if needed)
- **P5.x:** Platform expansion (if needed)
- **P6.x:** Major architectural changes (if needed)

**Decision:** Defer until P3 completion and review.

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**Last Updated:** 2025-12-22  
**Status:** Design-only (awaiting approval before implementation)

