Merge release/v0.3.0: Phase 3 - Participant Self-Management

Implement Phase 3 participant self-management features:

Story 6.3 - Reminder Preferences:
- Add ReminderPreferenceForm to participant forms
- Add update_preferences route for preference updates
- Update dashboard template with reminder preference toggle
- Participants can enable/disable reminder emails at any time

Story 6.2 - Withdrawal from Exchange:
- Add can_withdraw utility function for state validation
- Create WithdrawalService to handle withdrawal process
- Add WithdrawForm with explicit confirmation requirement
- Add withdraw route with GET (confirmation) and POST (process)
- Add withdrawal confirmation email template
- Update dashboard to show withdraw link when allowed
- Withdrawal only allowed before registration closes
- Session cleared after withdrawal, user redirected to registration

All acceptance criteria met for both stories.
Test coverage: 90.02% (156 tests passing)
Linting and type checking: passed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/agents/architect.md

@@ -37,6 +37,41 @@ You are an expert in:
 3. **AI-consumable output**: Your designs will be read and implemented by an AI developer subagent, not a human—structure your output for clarity and unambiguous interpretation
 4. **Explicit over implicit**: State assumptions clearly; avoid ambiguity
 5. **Security by default**: Design with security in mind from the start
+6. **Clean upgrade paths**: All designs must support existing installations upgrading seamlessly
+
+## Upgrade Path Requirements
+
+**CRITICAL**: Sneaky Klaus is now deployed in production. All designs must include:
+
+1. **Migration Strategy**: How will database schema changes be applied to existing data?
+2. **Data Preservation**: Existing exchanges, participants, and settings must never be lost
+3. **Backward Compatibility**: Consider whether old clients/data can work with new code
+4. **Rollback Plan**: What happens if an upgrade fails? Can users revert?
+
+### Database Changes
+
+- All schema changes MUST use Alembic migrations (never `db.create_all()`)
+- Migrations MUST be reversible (`upgrade()` and `downgrade()` functions)
+- New columns on existing tables MUST have defaults or be nullable
+- Column renames or type changes require careful data migration
+- Document migration steps in design documents
+
+### Breaking Changes
+
+If a breaking change is unavoidable:
+1. Document it clearly in the design
+2. Provide a migration path for existing data
+3. Consider a multi-step migration if needed
+4. Increment the MAJOR version number
+
+### Design Document Requirements
+
+Each design MUST include an **Upgrade Considerations** section covering:
+- Required database migrations
+- Data migration requirements
+- Configuration changes
+- Breaking changes (if any)
+- Rollback procedure
 
 ## Output Locations
 

.claude/agents/developer.md

@@ -26,6 +26,55 @@ You implement features based on designs provided by the architect. You write pro
 4. **Stop on errors**: When you encounter failing tests, design inconsistencies, or blockers, stop and report to the coordinator immediately
 5. **Clean code**: Follow Python best practices and PEP standards
 6. **Mandatory docstrings**: All modules, classes, and functions must have docstrings
+7. **Clean upgrade paths**: All changes must support existing production installations
+
+## Upgrade Path Requirements
+
+**CRITICAL**: Sneaky Klaus is deployed in production with real user data. All changes must:
+
+1. **Preserve existing data**: Never lose exchanges, participants, or settings
+2. **Use Alembic migrations**: All database schema changes MUST use Alembic
+3. **Be reversible**: Migrations must have working `downgrade()` functions
+4. **Handle existing data**: New columns must have defaults or be nullable
+
+### Database Migration Rules
+
+```bash
+# NEVER use db.create_all() for schema changes
+# ALWAYS create migrations with:
+uv run alembic revision --autogenerate -m "description of change"
+
+# Review generated migration before committing
+# Ensure both upgrade() and downgrade() work correctly
+
+# Test migration on a copy of production data if possible
+```
+
+### Migration Best Practices
+
+1. **New columns on existing tables**:
+   - Must be nullable OR have a server_default
+   - Example: `sa.Column('new_field', sa.String(100), nullable=True)`
+
+2. **Renaming columns**:
+   - Use `op.alter_column()` with proper data preservation
+   - Never drop and recreate
+
+3. **Changing column types**:
+   - Create new column, migrate data, drop old column
+   - Or use `op.alter_column()` if type is compatible
+
+4. **Adding constraints**:
+   - Ensure existing data satisfies the constraint
+   - May need data cleanup migration first
+
+### Testing Migrations
+
+Before merging, verify:
+- [ ] Migration applies cleanly to fresh database
+- [ ] Migration applies cleanly to database with existing data
+- [ ] Downgrade works correctly
+- [ ] Application functions correctly after migration
 
 ## Code Style & Standards
 

.env.example

@@ -0,0 +1,27 @@
+# Sneaky Klaus Environment Configuration
+#
+# Copy this file to .env and customize for your environment.
+# NEVER commit .env to version control!
+
+# Required: Secret key for session signing and CSRF protection
+# Generate with: python -c "import secrets; print(secrets.token_hex(32))"
+SECRET_KEY=your-secret-key-here
+
+# Required for production: Resend API key for sending emails
+# Get your API key at https://resend.com
+# Leave empty for development mode (emails logged to stdout)
+RESEND_API_KEY=
+
+# Email sender address (must be from a verified domain in Resend)
+EMAIL_FROM=noreply@example.com
+
+# Public URL of your application (used in email links)
+# Include protocol, no trailing slash
+APP_URL=https://secretsanta.example.com
+
+# Environment mode: 'production' or 'development'
+# In development mode:
+#   - Emails are logged to stdout instead of sent
+#   - Debug mode is enabled
+#   - Session cookies don't require HTTPS
+FLASK_ENV=production

docker-compose.example.yml

@@ -0,0 +1,72 @@
+# Sneaky Klaus - Example Docker Compose Configuration
+#
+# Copy this file to docker-compose.yml and customize for your environment.
+#
+# Quick Start:
+#   1. cp docker-compose.example.yml docker-compose.yml
+#   2. Create .env file with your configuration (see .env.example)
+#   3. docker compose up -d
+#   4. Visit http://localhost:8000 to set up your admin account
+#
+# Upgrading:
+#   docker compose pull
+#   docker compose up -d
+#   (Migrations run automatically on container start)
+
+version: "3.8"
+
+services:
+  sneaky-klaus:
+    image: git.thesatelliteoflove.com/phil/sneakyklaus:latest
+    container_name: sneaky-klaus
+    restart: unless-stopped
+    ports:
+      - "8000:8000"
+    environment:
+      # Required: Generate a secure secret key
+      # Example: python -c "import secrets; print(secrets.token_hex(32))"
+      - SECRET_KEY=${SECRET_KEY:?SECRET_KEY is required}
+
+      # Required for production email sending via Resend
+      # Get your API key at https://resend.com
+      - RESEND_API_KEY=${RESEND_API_KEY:-}
+
+      # Email sender address (must be verified domain with Resend)
+      - EMAIL_FROM=${EMAIL_FROM:-noreply@example.com}
+
+      # Public URL of your application (used in magic link emails)
+      - APP_URL=${APP_URL:-http://localhost:8000}
+
+      # Environment: 'production' or 'development'
+      # In development mode, emails are logged to stdout instead of sent
+      - FLASK_ENV=${FLASK_ENV:-production}
+    volumes:
+      # Persistent storage for SQLite database and session files
+      # Database migrations are applied automatically on container start
+      - sneaky-klaus-data:/app/data
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8000/health')"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 10s
+
+volumes:
+  sneaky-klaus-data:
+    driver: local
+
+# Optional: Add a reverse proxy for HTTPS
+# Example with Traefik:
+#
+# services:
+#   sneaky-klaus:
+#     labels:
+#       - "traefik.enable=true"
+#       - "traefik.http.routers.sneaky-klaus.rule=Host(`secretsanta.example.com`)"
+#       - "traefik.http.routers.sneaky-klaus.tls.certresolver=letsencrypt"
+#     networks:
+#       - traefik
+#
+# networks:
+#   traefik:
+#     external: true

docker-compose.yml

@@ -0,0 +1,38 @@
+version: "3.8"
+
+services:
+  sneaky-klaus:
+    image: git.thesatelliteoflove.com/phil/sneakyklaus:latest
+    container_name: sneaky-klaus
+    restart: unless-stopped
+    ports:
+      - "8000:8000"
+    environment:
+      # Required: Generate a secure secret key
+      # Example: python -c "import secrets; print(secrets.token_hex(32))"
+      - SECRET_KEY=${SECRET_KEY:?SECRET_KEY is required}
+
+      # Required for production email sending
+      - RESEND_API_KEY=${RESEND_API_KEY:-}
+
+      # Email sender address (must be verified with Resend)
+      - EMAIL_FROM=${EMAIL_FROM:-noreply@example.com}
+
+      # Public URL of your application (used for magic links)
+      - APP_URL=${APP_URL:-http://localhost:8000}
+
+      # Set to 'development' for testing (logs emails instead of sending)
+      - FLASK_ENV=${FLASK_ENV:-production}
+    volumes:
+      # Persistent storage for SQLite database and sessions
+      - sneaky-klaus-data:/app/data
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8000/health')"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 10s
+
+volumes:
+  sneaky-klaus-data:
+    driver: local

docs/decisions/0006-participant-state-management.md

@@ -0,0 +1,252 @@
+# ADR-0006: Participant State Management
+
+**Status**: Accepted
+**Date**: 2025-12-22
+**Deciders**: Architect
+**Phase**: v0.3.0
+
+## Context
+
+Participants need to manage their own profiles and potentially withdraw from exchanges. We need to decide:
+
+1. When can participants update their profiles (name, gift ideas)?
+2. When can participants withdraw from an exchange?
+3. How should withdrawals be implemented (hard delete vs soft delete)?
+4. Should withdrawn participants be visible in any context?
+5. Can withdrawn participants re-join the same exchange?
+
+These decisions impact data integrity, user experience, and admin workflows.
+
+## Decision
+
+### 1. Profile Update Rules
+
+**Profile updates are allowed until matching occurs.**
+
+Participants can update their name and gift ideas when the exchange is in:
+- `draft` state
+- `registration_open` state
+- `registration_closed` state
+
+Profile updates are **locked** when the exchange is in:
+- `matched` state
+- `completed` state
+
+**Rationale**:
+- Gift ideas are sent to Secret Santas during match notification
+- Allowing changes after matching would create inconsistency (giver sees old version in email)
+- Name changes after matching could confuse participants about who they're buying for
+- Registration close is admin's signal to finalize participant list, not to lock profiles
+- Locking happens at matching, which is the point where profile data is "consumed" by the system
+
+### 2. Withdrawal Rules
+
+**Withdrawals are allowed until registration closes.**
+
+Participants can withdraw when the exchange is in:
+- `draft` state
+- `registration_open` state
+
+Withdrawals require admin intervention when the exchange is in:
+- `registration_closed` state (admin may be configuring exclusions)
+- `matched` state (would require re-matching)
+- `completed` state (historical record)
+
+**Rationale**:
+- Before registration closes: minimal impact, just removes one participant
+- After registration closes: admin is likely configuring exclusions or preparing to match
+- After matching: re-matching is a significant operation that should be admin-controlled
+- Clear deadline (registration close) sets expectations for participants
+- Prevents last-minute dropouts that could disrupt matching
+
+### 3. Withdrawal Implementation (Soft Delete)
+
+**Withdrawals use soft delete via `withdrawn_at` timestamp.**
+
+Technical implementation:
+- Set `participant.withdrawn_at = datetime.utcnow()` on withdrawal
+- Keep participant record in database
+- Filter out withdrawn participants in queries: `Participant.withdrawn_at.is_(None)`
+- Cascade rules remain unchanged (deleting exchange deletes all participants)
+
+**Rationale**:
+- **Audit trail**: Preserves record of who registered and when they withdrew
+- **Email uniqueness**: Prevents re-registration with same email in same exchange (see Decision 5)
+- **Admin visibility**: Admins can see withdrawal history for troubleshooting
+- **Simplicity**: No cascade delete complexity or foreign key violations
+- **Existing pattern**: Data model already includes `withdrawn_at` field (v0.2.0 design)
+
+Alternative considered: Hard delete participants on withdrawal
+- Rejected: Loses audit trail, allows immediate re-registration (see Decision 5)
+- Rejected: Requires careful cascade handling for tokens, exclusions
+- Rejected: Complicates participant count tracking
+
+### 4. Withdrawn Participant Visibility
+
+**Withdrawn participants are visible only to admin.**
+
+Visibility rules:
+- **Participant list (participant view)**: Withdrawn participants excluded
+- **Participant list (admin view)**: Withdrawn participants shown with indicator (e.g., grayed out, "Withdrawn" badge)
+- **Participant count**: Counts exclude withdrawn participants
+- **Matching algorithm**: Withdrawn participants excluded from matching pool
+
+**Rationale**:
+- **Privacy**: Respects participant's decision to withdraw (no public record)
+- **Admin needs**: Admin may need to see who withdrew (for follow-up, re-invites, etc.)
+- **Clean UX**: Participants see only active participants (less confusing)
+- **Data integrity**: Admin view preserves audit trail
+
+### 5. Re-Registration After Withdrawal
+
+**Withdrawn participants cannot re-join the same exchange (with same email).**
+
+Technical enforcement:
+- Unique constraint on `(exchange_id, email)` remains in place
+- Soft delete doesn't remove the record, so email remains "taken"
+- Participant must use a different email to re-register
+
+**Rationale**:
+- **Prevents gaming**: Stops participants from withdrawing to see participant list changes, then re-joining
+- **Simplifies logic**: No need to handle "re-activation" of withdrawn participants
+- **Clear consequence**: Withdrawal is final (as warned in UI)
+- **Data integrity**: Each participant registration is a distinct record
+
+Alternative considered: Allow re-activation of withdrawn participants
+- Rejected: Complex state transitions (withdrawn → active → withdrawn → active)
+- Rejected: Unclear UX (does re-joining restore old profile or create new?)
+- Rejected: Enables abuse (withdraw/rejoin cycle)
+
+If participant genuinely needs to rejoin:
+- Use a different email address (e.g., alias like user+exchange@example.com)
+- Or: Contact admin, who can manually delete the withdrawn record (future admin feature)
+
+### 6. Reminder Preferences After Withdrawal
+
+**Withdrawn participants do not receive reminder emails.**
+
+Technical implementation:
+- Reminder job queries exclude withdrawn participants: `withdrawn_at IS NULL`
+- Reminder preference persists in database (for audit) but is not used
+
+**Rationale**:
+- Withdrawn participants have no match to be reminded about
+- Sending reminders would be confusing and violate withdrawal expectations
+- Simple filter in reminder job handles this naturally
+
+## Consequences
+
+### Positive
+
+1. **Clear rules**: Participants know when they can update profiles or withdraw
+2. **Data integrity**: Matching always uses consistent profile data
+3. **Audit trail**: System preserves record of all registrations and withdrawals
+4. **Simple implementation**: Soft delete is easier than hard delete + cascades
+5. **Privacy**: Withdrawn participants not visible to other participants
+6. **Admin control**: Admin retains visibility for troubleshooting
+
+### Negative
+
+1. **No re-join**: Participants who withdraw accidentally must use different email
+2. **Email "wastage"**: Withdrawn participants' emails remain "taken" in that exchange
+3. **Database growth**: Withdrawn participants remain in database (minimal impact given small datasets)
+
+### Mitigations
+
+1. **Clear warnings**: UI prominently warns that withdrawal is permanent and cannot be undone
+2. **Confirmation required**: Withdrawal requires explicit checkbox confirmation
+3. **Confirmation email**: Withdrawn participants receive email confirming withdrawal
+4. **Admin override** (future): Admin can manually delete withdrawn participants if needed
+
+## Implementation Notes
+
+### State Check Function
+
+```python
+def can_update_profile(participant: Participant) -> bool:
+    """Check if participant can update their profile."""
+    exchange = participant.exchange
+    allowed_states = ['draft', 'registration_open', 'registration_closed']
+    return exchange.state in allowed_states
+
+
+def can_withdraw(participant: Participant) -> bool:
+    """Check if participant can withdraw from the exchange."""
+    if participant.withdrawn_at is not None:
+        return False  # Already withdrawn
+
+    exchange = participant.exchange
+    allowed_states = ['draft', 'registration_open']
+    return exchange.state in allowed_states
+```
+
+### Query Pattern for Active Participants
+
+```python
+# Get active participants only
+active_participants = Participant.query.filter(
+    Participant.exchange_id == exchange_id,
+    Participant.withdrawn_at.is_(None)
+).all()
+
+# Count active participants
+active_count = Participant.query.filter(
+    Participant.exchange_id == exchange_id,
+    Participant.withdrawn_at.is_(None)
+).count()
+```
+
+### Admin View Enhancement (Future)
+
+```python
+# Admin can see all participants including withdrawn
+all_participants = Participant.query.filter(
+    Participant.exchange_id == exchange_id
+).all()
+
+# Template can check: participant.withdrawn_at is not None
+```
+
+## Related Decisions
+
+- [ADR-0002: Authentication Strategy](0002-authentication-strategy.md) - Participant session management
+- [ADR-0003: Participant Session Scoping](0003-participant-session-scoping.md) - Session behavior on withdrawal
+- [v0.2.0 Data Model](../designs/v0.2.0/data-model.md) - `withdrawn_at` field design
+- [v0.3.0 Participant Self-Management](../designs/v0.3.0/participant-self-management.md) - Implementation details
+
+## Future Considerations
+
+### Phase 6: Admin Participant Management
+
+When implementing admin participant removal (Epic 9):
+- Admin should be able to hard delete withdrawn participants (cleanup)
+- Admin should be able to remove active participants (sets withdrawn_at + sends notification)
+- Admin should see withdrawal history in participant list
+
+### Phase 8: Matching
+
+Matching algorithm must:
+- Filter participants by `withdrawn_at IS NULL`
+- Validate participant count >= 3 (after filtering)
+- Handle case where withdrawals reduce count below minimum
+
+### Potential Future Enhancement: Re-Activation
+
+If user demand requires allowing re-join:
+- Add `reactivated_at` timestamp
+- Track withdrawal/reactivation history (audit log)
+- Clear `withdrawn_at` on re-activation
+- Send re-activation email
+- Complexity: High, defer until proven necessary
+
+## References
+
+- [Product Backlog](../BACKLOG.md) - Epic 6: Participant Self-Management
+- [Project Overview](../PROJECT_OVERVIEW.md) - Self-management principles
+- [v0.2.0 Data Model](../designs/v0.2.0/data-model.md) - Participant table schema
+
+---
+
+**Decision Date**: 2025-12-22
+**Architect**: Claude Opus 4.5
+**Status**: Accepted for v0.3.0

docs/designs/v0.3.0/README.md

@@ -0,0 +1,278 @@
+# Phase 3 (v0.3.0) Design Documentation
+
+**Version**: 0.3.0
+**Date**: 2025-12-22
+**Status**: Ready for Implementation
+
+## Quick Start
+
+Phase 3 implements participant self-management features, building on the authentication foundation from Phase 2.
+
+**Core Features**:
+- Participant list view (see who else registered)
+- Profile updates (name and gift ideas)
+- Reminder email preferences
+- Participant withdrawal (before registration closes)
+
+## Document Index
+
+### 1. [System Overview](overview.md)
+High-level architecture, goals, and design decisions for Phase 3.
+
+**Read this first** to understand:
+- What's in scope for v0.3.0
+- Key design decisions (profile locks, withdrawal rules)
+- Data flow diagrams
+- State machine changes
+
+**Key sections**:
+- Phase Goals (page 1)
+- Key Design Decisions (page 2)
+- State Machine Impact (page 4)
+
+### 2. [Participant Self-Management Component Design](participant-self-management.md)
+Detailed component specifications for all Phase 3 features.
+
+**Use this for**:
+- Exact function signatures and implementations
+- Form definitions
+- Route specifications
+- Template structures
+- Email templates
+
+**Key sections**:
+- Business Logic Functions (page 1)
+- Forms (page 6)
+- Routes (page 8)
+- Templates (page 11)
+- Security Checklist (page 19)
+
+### 3. [Test Plan](test-plan.md)
+Comprehensive testing specifications for Phase 3.
+
+**Use this for**:
+- Unit test cases and fixtures
+- Integration test scenarios
+- Acceptance test procedures
+- Manual QA steps
+- Coverage requirements
+
+**Key sections**:
+- Unit Tests (page 1)
+- Integration Tests (page 4)
+- Acceptance Tests (page 9)
+- Edge Cases (page 11)
+
+### 4. [Implementation Guide](implementation-guide.md)
+Step-by-step implementation instructions using TDD.
+
+**Follow this to**:
+- Implement features in correct order
+- Write tests first, then code
+- Verify each feature before moving on
+- Create proper commits and PRs
+
+**Key sections**:
+- Implementation Order (page 1)
+- Phase 3.1: Participant List (page 2)
+- Phase 3.2: Profile Updates (page 4)
+- Phase 3.3: Reminder Preferences (page 7)
+- Phase 3.4: Withdrawal (page 9)
+- Final Steps (page 14)
+
+## Architecture Decision Records
+
+### [ADR-0006: Participant State Management](../../decisions/0006-participant-state-management.md)
+Documents key decisions about when participants can update profiles, withdraw, and how withdrawals are implemented.
+
+**Key decisions**:
+- Profile updates allowed until matching
+- Withdrawals allowed until registration closes
+- Soft delete implementation (withdrawn_at timestamp)
+- Withdrawn participants visible only to admin
+- No re-registration with same email
+
+## User Stories Implemented
+
+Phase 3 completes these backlog items:
+
+### Epic 4: Participant Registration
+- ✅ **Story 4.5**: View Participant List (Pre-Matching)
+
+### Epic 6: Participant Self-Management
+- ✅ **Story 6.1**: Update Profile
+- ✅ **Story 6.2**: Withdraw from Exchange
+- ✅ **Story 6.3**: Update Reminder Preferences
+
+## Dependencies
+
+### Prerequisites (from Phase 2)
+- ✅ Participant model with `withdrawn_at` field
+- ✅ Participant authentication (@participant_required decorator)
+- ✅ Participant dashboard route
+- ✅ Email service for sending emails
+
+### No New Dependencies
+Phase 3 requires **no new**:
+- Python packages
+- Database migrations
+- Environment variables
+- External services
+
+## Technical Highlights
+
+### New Files Created
+```
+src/
+  utils/participant.py              # Business logic functions
+  services/withdrawal.py            # Withdrawal service
+
+templates/
+  participant/
+    profile_edit.html               # Profile edit page
+    withdraw.html                   # Withdrawal confirmation
+  emails/
+    participant/
+      withdrawal_confirmation.html  # Withdrawal email
+      withdrawal_confirmation.txt   # Plain text version
+
+tests/
+  unit/
+    test_participant_utils.py       # Unit tests for business logic
+    test_withdrawal_service.py      # Unit tests for withdrawal
+  integration/
+    test_profile_update.py          # Profile update integration tests
+    test_withdrawal.py              # Withdrawal integration tests
+    test_participant_list.py        # Participant list tests
+    test_reminder_preferences.py    # Preference update tests
+```
+
+### Modified Files
+```
+src/
+  routes/participant.py             # New routes added
+  forms/participant.py              # New forms added
+  services/email.py                 # Withdrawal email method added
+
+templates/
+  participant/dashboard.html        # Enhanced with participant list
+```
+
+## Design Principles Applied
+
+Phase 3 adheres to project principles:
+
+1. **Simplicity First**
+   - No new database tables (uses existing fields)
+   - No new external dependencies
+   - Soft delete instead of complex cascade handling
+
+2. **State-Based Permissions**
+   - Clear rules about when operations are allowed
+   - Based on exchange state (draft, open, closed, matched)
+   - Easy to test and reason about
+
+3. **TDD Approach**
+   - Implementation guide follows test-first methodology
+   - Every feature has unit and integration tests
+   - 80%+ coverage maintained
+
+4. **Security by Design**
+   - All routes require authentication
+   - State validation prevents unauthorized operations
+   - CSRF protection on all POST operations
+   - Input sanitization via WTForms and Jinja2
+
+5. **Privacy-Conscious**
+   - Participant list shows names only (no emails)
+   - Withdrawn participants hidden from other participants
+   - Gift ideas not revealed until matching
+
+## Implementation Checklist
+
+Use this to track progress:
+
+- [ ] **Phase 3.1: Participant List View**
+  - [ ] Create `src/utils/participant.py`
+  - [ ] Write unit tests for utility functions
+  - [ ] Update dashboard route
+  - [ ] Update dashboard template
+  - [ ] Write integration tests
+  - [ ] Manual QA
+
+- [ ] **Phase 3.2: Profile Updates**
+  - [ ] Add `can_update_profile()` function
+  - [ ] Write unit tests for state validation
+  - [ ] Create `ProfileUpdateForm`
+  - [ ] Create profile edit route
+  - [ ] Create profile edit template
+  - [ ] Update dashboard with edit link
+  - [ ] Write integration tests
+  - [ ] Manual QA
+
+- [ ] **Phase 3.3: Reminder Preferences**
+  - [ ] Create `ReminderPreferenceForm`
+  - [ ] Create preference update route
+  - [ ] Update dashboard with preference form
+  - [ ] Write integration tests
+  - [ ] Manual QA
+
+- [ ] **Phase 3.4: Withdrawal**
+  - [ ] Add `can_withdraw()` function
+  - [ ] Create `src/services/withdrawal.py`
+  - [ ] Write unit tests for withdrawal service
+  - [ ] Create `WithdrawForm`
+  - [ ] Create withdrawal route
+  - [ ] Create email templates
+  - [ ] Update email service
+  - [ ] Create withdrawal template
+  - [ ] Update dashboard with withdraw link
+  - [ ] Write integration tests
+  - [ ] Manual QA
+
+- [ ] **Final Steps**
+  - [ ] Run all tests (≥ 80% coverage)
+  - [ ] Run linting and type checking
+  - [ ] Complete manual QA from test plan
+  - [ ] Update documentation if needed
+  - [ ] Create feature branch
+  - [ ] Commit changes
+  - [ ] Create pull request
+
+## Success Criteria
+
+Phase 3 is complete when:
+
+1. ✅ All user stories have passing acceptance tests
+2. ✅ Code coverage ≥ 80%
+3. ✅ All linting and type checking passes
+4. ✅ Manual QA completed
+5. ✅ Security checklist verified
+6. ✅ Accessibility tests pass
+7. ✅ Browser compatibility verified
+8. ✅ Phase 2 regression tests still pass
+9. ✅ Documentation updated
+10. ✅ Pull request approved and merged
+
+## What's Next: Phase 4
+
+After Phase 3 is complete, the next logical phase is:
+
+**Phase 4 (v0.4.0)**: Post-Matching Participant Experience (Epic 11)
+- View assigned recipient (match assignment)
+- View recipient's gift ideas
+- View exchange information post-matching
+- Participant list (post-matching version)
+
+This builds on Phase 3's participant dashboard foundation and enables the core Secret Santa experience after admin has matched participants.
+
+## Questions?
+
+- Review the [Project Overview](../../PROJECT_OVERVIEW.md) for product vision
+- Check the [Backlog](../../BACKLOG.md) for user stories
+- See [v0.2.0 Design](../v0.2.0/overview.md) for foundation architecture
+- Consult existing [ADRs](../../decisions/) for architectural context
+
+---
+
+**Phase 3 Design Status**: ✅ Complete and Ready for Implementation

docs/designs/v0.3.0/overview.md

@@ -0,0 +1,566 @@
+# System Overview - v0.3.0
+
+**Version**: 0.3.0
+**Date**: 2025-12-22
+**Status**: Phase 3 Design
+
+## Introduction
+
+This document describes the design for Phase 3 of Sneaky Klaus, building on the participant authentication foundation established in v0.2.0. This phase focuses on participant self-management capabilities and pre-matching participant experience.
+
+**Phase 3 Scope**: Implement Epic 6 (Participant Self-Management) and Epic 4.5 (View Participant List Pre-Matching), enabling participants to manage their own profiles and see who else has registered before matching occurs.
+
+## Phase Goals
+
+The primary goals for v0.3.0 are:
+
+1. **Enable participant self-service**: Allow participants to update their profiles without admin intervention
+2. **Support graceful withdrawals**: Handle participants who need to drop out before matching
+3. **Build social engagement**: Let participants see who else is participating (pre-matching only)
+4. **Maintain data integrity**: Ensure profile changes and withdrawals don't break the exchange flow
+
+## User Stories in Scope
+
+### Epic 6: Participant Self-Management
+
+- **6.1 Update Profile**: Participants can edit their name and gift ideas before matching
+- **6.2 Withdraw from Exchange**: Participants can opt out before registration closes
+- **6.3 Update Reminder Preferences**: Participants can toggle reminder emails on/off
+
+### Epic 4: Participant Registration (Continuation)
+
+- **4.5 View Participant List (Pre-Matching)**: Registered participants can see who else has joined
+
+## Out of Scope for v0.3.0
+
+The following features are explicitly **not** included in this phase:
+
+- Post-matching participant experience (Epic 11) - deferred to Phase 4
+- Matching system (Epic 8) - deferred to Phase 5
+- Admin exchange management beyond what v0.1.0 provided
+- Participant removal by admin (Epic 9) - deferred to Phase 6
+- Notification emails beyond registration confirmation (Epic 10) - partial in Phase 2, remainder in Phase 7
+
+## Architecture Overview
+
+Phase 3 builds incrementally on the v0.2.0 architecture with no new infrastructure components:
+
+```mermaid
+graph TB
+    subgraph "Phase 3 Additions"
+        ProfileUpdate[Profile Update UI]
+        WithdrawUI[Withdraw UI]
+        ParticipantList[Participant List View]
+
+        ProfileUpdate --> ParticipantRoutes
+        WithdrawUI --> ParticipantRoutes
+        ParticipantList --> ParticipantRoutes
+    end
+
+    subgraph "Existing v0.2.0 Foundation"
+        ParticipantRoutes[Participant Routes]
+        ParticipantAuth[Participant Auth Decorator]
+        ParticipantModel[Participant Model]
+        ExchangeModel[Exchange Model]
+        Database[(SQLite)]
+
+        ParticipantRoutes --> ParticipantAuth
+        ParticipantRoutes --> ParticipantModel
+        ParticipantRoutes --> ExchangeModel
+        ParticipantModel --> Database
+        ExchangeModel --> Database
+    end
+```
+
+## Technical Design Principles
+
+This phase adheres to the project's core principles established in v0.1.0 and v0.2.0:
+
+1. **No new database tables**: All features use existing Participant and Exchange models
+2. **No new external dependencies**: Pure Flask/SQLAlchemy implementation
+3. **Soft deletes**: Withdrawals use `withdrawn_at` timestamp rather than hard deletes
+4. **State-based permissions**: Operations restricted based on exchange state
+5. **TDD approach**: Write tests first, implement to pass
+
+## Key Design Decisions
+
+### 1. Profile Update Restrictions
+
+**Decision**: Profile updates are only allowed when exchange is in `draft`, `registration_open`, or `registration_closed` states. After matching, profiles are locked.
+
+**Rationale**:
+- Gift ideas are sent to givers during match notification - changes after matching would create inconsistency
+- Name changes after matching could confuse participants
+- Clear state transition prevents data inconsistency
+
+**Implementation**:
+```python
+def can_update_profile(participant: Participant) -> bool:
+    """Check if participant can update their profile."""
+    exchange = participant.exchange
+    return exchange.state in ['draft', 'registration_open', 'registration_closed']
+```
+
+### 2. Withdrawal Rules
+
+**Decision**: Withdrawals are only allowed before registration closes. After registration closes, admin intervention required.
+
+**Rationale**:
+- Pre-closure: minimal impact, just removes one participant
+- Post-closure: admin likely already configuring exclusions or has matched
+- Post-matching: requires re-match, admin should make this decision
+- Clear deadline prevents last-minute dropouts
+
+**Implementation**:
+```python
+def can_withdraw(participant: Participant) -> bool:
+    """Check if participant can withdraw themselves."""
+    exchange = participant.exchange
+    return exchange.state in ['draft', 'registration_open']
+```
+
+### 3. Withdrawal Implementation (Soft Delete)
+
+**Decision**: Use existing `withdrawn_at` timestamp field, don't delete participant records.
+
+**Rationale**:
+- Data model already supports soft deletes (v0.2.0 design)
+- Preserves audit trail of who registered
+- Prevents re-use of email during same exchange
+- Allows admin to see withdrawal history
+- Simplifies database constraints (no cascade delete issues)
+
+**Implementation**:
+```python
+def withdraw_participant(participant: Participant):
+    """Mark participant as withdrawn."""
+    participant.withdrawn_at = datetime.utcnow()
+    db.session.commit()
+```
+
+### 4. Participant List Visibility
+
+**Decision**: Show participant list to all registered participants, but only show names (not emails or gift ideas).
+
+**Rationale**:
+- Social aspect: participants want to know who's participating
+- Privacy: emails are admin-only
+- Security: gift ideas are for givers only (post-matching)
+- Pre-matching only: post-matching handled in Phase 4
+
+**Display Rules**:
+- Show: participant names, count
+- Hide: emails, gift ideas, withdrawn participants
+- Filter: exclude withdrawn participants from list
+
+### 5. Reminder Preference Changes
+
+**Decision**: Allow reminder preference changes at any time before exchange completes.
+
+**Rationale**:
+- Low-impact change (doesn't affect matching or other participants)
+- User preference should be flexible
+- No technical reason to restrict after matching
+- Allows opting out if circumstances change
+
+**Implementation**: Simple boolean toggle, no state restrictions.
+
+### 6. Form Validation Strategy
+
+**Decision**: Use server-side validation with WTForms, add client-side hints for UX.
+
+**Rationale**:
+- Consistent with Phase 2 implementation decisions
+- Security: never trust client-side validation
+- UX: client-side provides immediate feedback
+- Progressive enhancement: works without JavaScript
+
+## Data Flow
+
+### Profile Update Flow
+
+```mermaid
+sequenceDiagram
+    participant P as Participant Browser
+    participant F as Flask App
+    participant DB as SQLite Database
+
+    P->>F: GET /participant/profile/edit
+    F->>F: Check @participant_required
+    F->>DB: Load participant & exchange
+    F->>F: Check can_update_profile()
+    F-->>P: Render edit form (or error)
+
+    P->>F: POST /participant/profile/edit (name, gift_ideas)
+    F->>F: Validate form
+    F->>F: Check can_update_profile()
+    F->>DB: Update participant record
+    DB-->>F: Success
+    F-->>P: Redirect to dashboard with success message
+```
+
+### Withdrawal Flow
+
+```mermaid
+sequenceDiagram
+    participant P as Participant Browser
+    participant F as Flask App
+    participant DB as SQLite Database
+    participant E as Email Service
+
+    P->>F: POST /participant/withdraw (with confirmation)
+    F->>F: Check @participant_required
+    F->>DB: Load participant & exchange
+    F->>F: Check can_withdraw()
+    F->>DB: Set withdrawn_at timestamp
+    DB-->>F: Success
+    F->>E: Send withdrawal confirmation email
+    E-->>F: Email sent
+    F->>F: Clear session (log out participant)
+    F-->>P: Redirect to public page with confirmation
+```
+
+### Participant List Flow
+
+```mermaid
+sequenceDiagram
+    participant P as Participant Browser
+    participant F as Flask App
+    participant DB as SQLite Database
+
+    P->>F: GET /participant/dashboard
+    F->>F: Check @participant_required
+    F->>DB: Load participant's exchange
+    F->>DB: Query active participants (withdrawn_at IS NULL)
+    DB-->>F: Participant list (names only)
+    F-->>P: Render dashboard with participant list
+```
+
+## State Machine Impact
+
+Phase 3 doesn't add new exchange states, but adds participant-level state:
+
+```mermaid
+stateDiagram-v2
+    [*] --> Registered: Registration
+    Registered --> UpdatedProfile: Edit profile
+    UpdatedProfile --> UpdatedProfile: Edit again
+    UpdatedProfile --> Withdrawn: Withdraw
+    Registered --> Withdrawn: Withdraw
+    UpdatedProfile --> Matched: Admin matches
+    Registered --> Matched: Admin matches
+    Withdrawn --> [*]
+
+    note right of Withdrawn
+        Soft delete: withdrawn_at set
+        Cannot re-activate
+        Must re-register with new email
+    end note
+
+    note right of UpdatedProfile
+        Only before matching
+        Name and gift_ideas editable
+    end note
+```
+
+## Component Design
+
+### Routes (participant_bp)
+
+New routes added to existing `src/routes/participant.py`:
+
+| Route | Method | Auth | Description |
+|-------|--------|------|-------------|
+| `/participant/profile/edit` | GET, POST | @participant_required | Edit profile (name, gift ideas) |
+| `/participant/preferences` | POST | @participant_required | Update reminder preference |
+| `/participant/withdraw` | POST | @participant_required | Withdraw from exchange |
+
+Existing routes used:
+- `/participant/dashboard` - enhanced to show participant list
+
+### Forms (src/forms/participant.py)
+
+New forms:
+
+**ProfileUpdateForm**:
+```python
+class ProfileUpdateForm(FlaskForm):
+    name = StringField('Name', validators=[DataRequired(), Length(max=255)])
+    gift_ideas = TextAreaField('Gift Ideas', validators=[Length(max=10000)])
+    submit = SubmitField('Save Changes')
+```
+
+**ReminderPreferenceForm**:
+```python
+class ReminderPreferenceForm(FlaskForm):
+    reminder_enabled = BooleanField('Send me reminders')
+    submit = SubmitField('Update Preferences')
+```
+
+**WithdrawForm**:
+```python
+class WithdrawForm(FlaskForm):
+    confirm = BooleanField('I understand this cannot be undone',
+                           validators=[DataRequired()])
+    submit = SubmitField('Withdraw from Exchange')
+```
+
+### Templates
+
+New templates in `templates/participant/`:
+
+- `profile_edit.html` - Profile update form
+- `withdraw.html` - Withdrawal confirmation page (with warnings)
+- `participant_list.html` - Reusable component for displaying participant names
+
+Enhanced templates:
+- `dashboard.html` - Add participant list section
+
+### Email Templates
+
+New email template in `templates/emails/participant/`:
+
+- `withdrawal_confirmation.html` - Sent when participant withdraws
+- `withdrawal_confirmation.txt` - Plain text version
+
+## Security Considerations
+
+### 1. Authorization Checks
+
+Every participant operation must verify:
+- User is authenticated as participant (@participant_required)
+- User owns the resource (participant_id matches session)
+- Exchange state allows the operation (can_update_profile, can_withdraw)
+
+### 2. CSRF Protection
+
+All POST operations require CSRF tokens (WTForms automatic).
+
+### 3. Input Validation
+
+- Name: 1-255 characters, required
+- Gift ideas: 0-10,000 characters, optional
+- All inputs sanitized via Jinja2 auto-escaping
+
+### 4. Privacy
+
+Participant list shows:
+- Names only (public within exchange)
+- Not emails (admin-only)
+- Not gift ideas (giver-only post-matching)
+- Not withdrawn participants (respect withdrawal privacy)
+
+### 5. Rate Limiting
+
+No new rate limiting needed:
+- Profile updates: legitimate user operation, no abuse vector
+- Withdrawals: self-limiting (can only withdraw once)
+- Participant list: read-only, authenticated
+
+## Testing Strategy
+
+### Unit Tests
+
+Test business logic in isolation:
+- `can_update_profile()` logic for each exchange state
+- `can_withdraw()` logic for each exchange state
+- Soft delete implementation (withdrawn_at timestamp)
+- Participant list filtering (exclude withdrawn)
+
+### Integration Tests
+
+Test full request/response cycles:
+- Profile update happy path
+- Profile update when locked (post-matching)
+- Withdrawal happy path
+- Withdrawal when not allowed
+- Participant list rendering
+
+### Test Data Setup
+
+Reuse existing test fixtures from Phase 2, add:
+- Multiple participants in same exchange
+- Participants in different states (registered, withdrawn)
+- Exchanges in different states
+
+### Coverage Target
+
+Maintain 80%+ coverage established in previous phases.
+
+## Error Handling
+
+### Expected Errors
+
+| Scenario | HTTP Status | User Message | Action |
+|----------|-------------|--------------|--------|
+| Update profile after matching | 400 | "Your profile is locked after matching" | Redirect to dashboard |
+| Withdraw after registration closes | 400 | "Withdrawal deadline has passed. Contact admin." | Redirect to dashboard |
+| Invalid form data | 400 | Field-specific errors | Re-render form with errors |
+| Already withdrawn | 400 | "You have already withdrawn" | Redirect to public page |
+
+### Unexpected Errors
+
+- Database errors: Log, flash generic error, redirect safely
+- Missing participant record: Clear session, redirect to landing page
+- Orphaned session: Clear session, redirect to landing page
+
+## Performance Considerations
+
+### Database Queries
+
+**Participant List Query**:
+```python
+# Efficient query with single DB hit
+participants = Participant.query.filter(
+    Participant.exchange_id == exchange_id,
+    Participant.withdrawn_at.is_(None)
+).order_by(Participant.name).all()
+```
+
+**Profile Load**:
+- Already loaded by @participant_required decorator (uses `g.participant`)
+- No additional query needed
+
+### Caching
+
+Not needed for v0.3.0:
+- Participant counts are small (3-100 typical)
+- Updates are infrequent
+- Reads are authenticated (no public caching)
+
+## Migration Requirements
+
+**No database migrations required for v0.3.0.**
+
+All fields already exist:
+- `participant.name` - editable
+- `participant.gift_ideas` - editable
+- `participant.reminder_enabled` - editable
+- `participant.withdrawn_at` - set on withdrawal
+
+## Deployment Impact
+
+### Breaking Changes
+
+None. v0.3.0 is fully backward compatible with v0.2.0.
+
+### Configuration Changes
+
+None. No new environment variables or configuration needed.
+
+### Data Migration
+
+None. Existing data fully compatible.
+
+## User Experience Flow
+
+### Participant Journey (Pre-Matching)
+
+1. **Register** (Phase 2)
+   - Receive confirmation email with magic link
+
+2. **View Dashboard** (Phase 2 + Phase 3)
+   - See own information
+   - **NEW**: See list of other participants (names only)
+
+3. **Update Profile** (Phase 3)
+   - Click "Edit Profile" from dashboard
+   - Update name or gift ideas
+   - Save changes
+   - See confirmation message
+
+4. **Change Reminder Preference** (Phase 3)
+   - Toggle reminder checkbox on dashboard
+   - See confirmation message
+
+5. **Withdraw (if needed)** (Phase 3)
+   - Click "Withdraw" from dashboard
+   - See warning about permanence
+   - Confirm withdrawal
+   - Receive confirmation email
+   - Logged out and redirected to public page
+
+## Admin Experience Impact
+
+Phase 3 adds visibility for admins:
+
+### Exchange Detail View (Enhancement)
+
+Add to existing exchange detail page:
+- Show participant list with withdrawn indicator
+- Display: "5 active, 1 withdrawn"
+- Allow admin to see withdrawn participants (grayed out)
+
+**Implementation Note**: This is a minor enhancement to existing admin routes, not a major feature. Can be implemented alongside participant features or deferred to Phase 6 (Admin Participant Management).
+
+## Future Considerations
+
+### Phase 4 Dependencies
+
+Phase 3 sets up foundations for Phase 4 (Post-Matching Experience):
+- Participant list already implemented (will be reused post-matching)
+- Profile lock logic (can_update_profile) prevents changes after matching
+- Dashboard structure ready to show match assignment
+
+### Potential Enhancements (Out of Scope)
+
+Not included in v0.3.0 but possible future additions:
+- Email notification to admin when participant withdraws (Epic 10.5)
+- Allow participants to indicate dietary restrictions or allergies
+- Allow participants to add profile pictures
+- Allow participants to message admin (anonymous contact form)
+
+## Acceptance Criteria
+
+Phase 3 is complete when:
+
+1. ✅ Participants can update their name and gift ideas before matching
+2. ✅ Participants cannot update profile after matching occurs
+3. ✅ Participants can withdraw before registration closes
+4. ✅ Participants cannot withdraw after registration closes
+5. ✅ Withdrawn participants receive confirmation email
+6. ✅ Withdrawn participants are logged out and removed from participant list
+7. ✅ Participants can view list of other registered participants (names only)
+8. ✅ Participant list excludes withdrawn participants
+9. ✅ Participants can toggle reminder preferences at any time
+10. ✅ All operations require participant authentication
+11. ✅ All operations validate exchange state appropriately
+12. ✅ All user stories have passing integration tests
+13. ✅ Code coverage remains at 80%+
+
+## Implementation Phases
+
+Recommended implementation order (TDD, vertical slices):
+
+### Phase 3.1: Participant List View
+- Story 4.5: View Participant List (Pre-Matching)
+- Simplest feature, no state changes
+- Sets up dashboard enhancements
+
+### Phase 3.2: Profile Updates
+- Story 6.1: Update Profile
+- Core self-management feature
+- Tests state-based permissions
+
+### Phase 3.3: Reminder Preferences
+- Story 6.3: Update Reminder Preferences
+- Simple toggle, low risk
+- Quick win
+
+### Phase 3.4: Withdrawal
+- Story 6.2: Withdraw from Exchange
+- Most complex (state changes, email, logout)
+- Benefits from previous features being solid
+
+## References
+
+- [v0.2.0 System Overview](../v0.2.0/overview.md)
+- [v0.2.0 Data Model](../v0.2.0/data-model.md)
+- [Product Backlog](../../BACKLOG.md)
+- [Project Overview](../../PROJECT_OVERVIEW.md)
+- [ADR-0002: Authentication Strategy](../../decisions/0002-authentication-strategy.md)
+- [ADR-0003: Participant Session Scoping](../../decisions/0003-participant-session-scoping.md)
+
+---
+
+**End of Phase 3 Design Overview**

docs/designs/v0.3.0/test-plan.md

@@ -0,0 +1,545 @@
+# Test Plan - v0.3.0
+
+**Version**: 0.3.0
+**Date**: 2025-12-22
+**Status**: Test Specification
+
+## Overview
+
+This document defines the comprehensive test plan for Phase 3 (Participant Self-Management). It covers unit tests, integration tests, and acceptance criteria for all user stories in scope.
+
+## Test Pyramid
+
+```
+         ╱╲
+        ╱  ╲        E2E Tests (Manual QA)
+       ╱────╲       - Full user journeys
+      ╱      ╲      - Cross-browser testing
+     ╱────────╲
+    ╱          ╲    Integration Tests (pytest)
+   ╱────────────╲   - Route handlers
+  ╱              ╲  - Database operations
+ ╱────────────────╲ - Email sending
+╱──────────────────╲
+                    Unit Tests (pytest)
+                    - Business logic functions
+                    - Form validation
+                    - State checks
+```
+
+## Test Coverage Goals
+
+- **Overall coverage**: 80%+ (maintain Phase 2 level)
+- **Business logic**: 95%+ (pure functions)
+- **Route handlers**: 80%+ (integration tests)
+- **Templates**: Manual testing (not measured by coverage)
+
+## 1. Unit Tests
+
+### 1.1 Participant Utility Functions
+
+**File**: `tests/unit/test_participant_utils.py`
+
+| Test Case | Description | Assertions |
+|-----------|-------------|------------|
+| `test_can_update_profile_draft_state` | Profile updates allowed in draft | `can_update_profile() == True` |
+| `test_can_update_profile_registration_open` | Profile updates allowed when open | `can_update_profile() == True` |
+| `test_can_update_profile_registration_closed` | Profile updates allowed when closed | `can_update_profile() == True` |
+| `test_can_update_profile_matched_state` | Profile updates blocked after matching | `can_update_profile() == False` |
+| `test_can_update_profile_completed_state` | Profile updates blocked when completed | `can_update_profile() == False` |
+| `test_can_withdraw_draft_state` | Withdrawal allowed in draft | `can_withdraw() == True` |
+| `test_can_withdraw_registration_open` | Withdrawal allowed when open | `can_withdraw() == True` |
+| `test_can_withdraw_registration_closed` | Withdrawal blocked when closed | `can_withdraw() == False` |
+| `test_can_withdraw_matched_state` | Withdrawal blocked after matching | `can_withdraw() == False` |
+| `test_can_withdraw_already_withdrawn` | Withdrawal blocked if already withdrawn | `can_withdraw() == False` |
+| `test_get_active_participants` | Returns only non-withdrawn participants | Count and names match |
+| `test_get_active_participants_empty` | Returns empty list when all withdrawn | `len(participants) == 0` |
+| `test_get_active_participants_ordered` | Participants ordered by name | Names in alphabetical order |
+| `test_is_withdrawn_true` | Detects withdrawn participant | `is_withdrawn() == True` |
+| `test_is_withdrawn_false` | Detects active participant | `is_withdrawn() == False` |
+
+**Fixtures needed**:
+```python
+@pytest.fixture
+def exchange_factory(db):
+    """Factory for creating exchanges in different states."""
+    def _create(state='draft'):
+        exchange = Exchange(
+            slug=generate_slug(),
+            name='Test Exchange',
+            budget='$25-50',
+            max_participants=50,
+            registration_close_date=datetime.utcnow() + timedelta(days=7),
+            exchange_date=datetime.utcnow() + timedelta(days=14),
+            timezone='UTC',
+            state=state
+        )
+        db.session.add(exchange)
+        db.session.commit()
+        return exchange
+    return _create
+
+@pytest.fixture
+def participant_factory(db):
+    """Factory for creating participants."""
+    def _create(exchange=None, withdrawn_at=None):
+        if not exchange:
+            exchange = Exchange(...)  # Create default exchange
+            db.session.add(exchange)
+
+        participant = Participant(
+            exchange_id=exchange.id,
+            name='Test Participant',
+            email='test@example.com',
+            gift_ideas='Test ideas',
+            reminder_enabled=True,
+            withdrawn_at=withdrawn_at
+        )
+        db.session.add(participant)
+        db.session.commit()
+        return participant
+    return _create
+```
+
+### 1.2 Withdrawal Service
+
+**File**: `tests/unit/test_withdrawal_service.py`
+
+| Test Case | Description | Assertions |
+|-----------|-------------|------------|
+| `test_withdraw_participant_success` | Happy path withdrawal | `withdrawn_at` is set, email called |
+| `test_withdraw_participant_already_withdrawn` | Raises error if already withdrawn | `WithdrawalError` raised |
+| `test_withdraw_participant_wrong_state_closed` | Raises error if registration closed | `WithdrawalError` with specific message |
+| `test_withdraw_participant_wrong_state_matched` | Raises error if already matched | `WithdrawalError` with specific message |
+| `test_withdraw_participant_database_error` | Handles DB error gracefully | `WithdrawalError` raised, rollback called |
+| `test_withdraw_participant_email_failure` | Continues if email fails | `withdrawn_at` set, error logged |
+
+**Mocking strategy**:
+```python
+@pytest.fixture
+def mock_email_service(monkeypatch):
+    """Mock EmailService for withdrawal tests."""
+    mock = Mock()
+    monkeypatch.setattr('src.services.withdrawal.EmailService', lambda: mock)
+    return mock
+```
+
+### 1.3 Form Validation
+
+**File**: `tests/unit/test_participant_forms.py`
+
+| Test Case | Description | Assertions |
+|-----------|-------------|------------|
+| `test_profile_form_valid_data` | Valid name and gift ideas | `form.validate() == True` |
+| `test_profile_form_name_required` | Name is required | Validation error on name field |
+| `test_profile_form_name_too_long` | Name max 255 chars | Validation error on name field |
+| `test_profile_form_gift_ideas_optional` | Gift ideas can be empty | `form.validate() == True` |
+| `test_profile_form_gift_ideas_too_long` | Gift ideas max 10,000 chars | Validation error on gift_ideas field |
+| `test_reminder_form_boolean_field` | Accepts boolean value | `form.validate() == True` |
+| `test_withdraw_form_confirmation_required` | Confirmation required | Validation error on confirm field |
+| `test_withdraw_form_confirmation_true` | Accepts confirmation | `form.validate() == True` |
+
+## 2. Integration Tests
+
+### 2.1 Profile Update Tests
+
+**File**: `tests/integration/test_profile_update.py`
+
+| Test Case | Description | Setup | Action | Expected Result |
+|-----------|-------------|-------|--------|-----------------|
+| `test_profile_update_get_shows_form` | GET shows edit form | Auth'd participant | GET /participant/profile/edit | 200, form with current values |
+| `test_profile_update_post_success` | POST updates profile | Auth'd participant | POST with valid data | 302 redirect, flash success, DB updated |
+| `test_profile_update_name_change` | Name updates in DB | Auth'd participant | POST with new name | Participant.name updated |
+| `test_profile_update_gift_ideas_change` | Gift ideas update in DB | Auth'd participant | POST with new ideas | Participant.gift_ideas updated |
+| `test_profile_update_clears_whitespace` | Strips leading/trailing spaces | Auth'd participant | POST with "  Name  " | Stored as "Name" |
+| `test_profile_update_locked_after_matching` | Blocked when matched | Matched exchange | GET profile edit | 302 redirect, flash error |
+| `test_profile_update_form_validation_error` | Invalid data shows errors | Auth'd participant | POST with empty name | 200, form with errors |
+| `test_profile_update_csrf_required` | CSRF token required | Auth'd participant | POST without CSRF | 400 error |
+| `test_profile_update_requires_auth` | Auth required | No session | GET profile edit | 302 to login |
+| `test_profile_update_database_error` | Handles DB failure | Auth'd participant, mock DB error | POST valid data | Flash error, no DB change |
+
+**Test helpers**:
+```python
+@pytest.fixture
+def participant_session(client, participant_factory):
+    """Create authenticated participant session."""
+    participant = participant_factory()
+
+    with client.session_transaction() as session:
+        session['user_id'] = participant.id
+        session['user_type'] = 'participant'
+        session['exchange_id'] = participant.exchange_id
+
+    return participant
+
+def get_csrf_token(client, url='/participant/dashboard'):
+    """Extract CSRF token from page."""
+    response = client.get(url)
+    # Parse HTML and extract token
+    return extract_csrf_token(response.data)
+```
+
+### 2.2 Withdrawal Tests
+
+**File**: `tests/integration/test_withdrawal.py`
+
+| Test Case | Description | Setup | Action | Expected Result |
+|-----------|-------------|-------|--------|-----------------|
+| `test_withdrawal_get_shows_form` | GET shows confirmation page | Auth'd participant | GET /participant/withdraw | 200, form with warnings |
+| `test_withdrawal_post_success` | POST withdraws participant | Auth'd participant | POST with confirmation | 302 redirect, withdrawn_at set, session cleared |
+| `test_withdrawal_sends_email` | Email sent on withdrawal | Auth'd participant, mock email | POST with confirmation | Email service called |
+| `test_withdrawal_clears_session` | Session cleared after withdrawal | Auth'd participant | POST with confirmation | Session empty |
+| `test_withdrawal_redirects_to_public` | Redirects to registration page | Auth'd participant | POST with confirmation | Redirect to /exchange/{slug}/register |
+| `test_withdrawal_already_withdrawn` | Detects already withdrawn | Withdrawn participant | GET withdraw | Flash info, redirect |
+| `test_withdrawal_blocked_after_close` | Blocked when registration closed | Closed exchange | GET withdraw | Flash error, redirect to dashboard |
+| `test_withdrawal_blocked_after_matching` | Blocked when matched | Matched exchange | GET withdraw | Flash error, redirect to dashboard |
+| `test_withdrawal_requires_confirmation` | Confirmation checkbox required | Auth'd participant | POST without confirm=True | Form errors |
+| `test_withdrawal_csrf_required` | CSRF token required | Auth'd participant | POST without CSRF | 400 error |
+| `test_withdrawal_requires_auth` | Auth required | No session | GET withdraw | 302 to login |
+| `test_withdrawal_database_error` | Handles DB failure gracefully | Auth'd participant, mock DB error | POST valid data | Flash error, not withdrawn |
+
+### 2.3 Reminder Preference Tests
+
+**File**: `tests/integration/test_reminder_preferences.py`
+
+| Test Case | Description | Setup | Action | Expected Result |
+|-----------|-------------|-------|--------|-----------------|
+| `test_update_preferences_enable` | Enable reminders | Auth'd participant (disabled) | POST reminder_enabled=True | Flash success, DB updated |
+| `test_update_preferences_disable` | Disable reminders | Auth'd participant (enabled) | POST reminder_enabled=False | Flash success, DB updated |
+| `test_update_preferences_csrf_required` | CSRF token required | Auth'd participant | POST without CSRF | 400 error |
+| `test_update_preferences_requires_auth` | Auth required | No session | POST preferences | 302 to login |
+| `test_update_preferences_database_error` | Handles DB failure | Auth'd participant, mock DB error | POST valid data | Flash error, no change |
+
+### 2.4 Participant List Tests
+
+**File**: `tests/integration/test_participant_list.py`
+
+| Test Case | Description | Setup | Action | Expected Result |
+|-----------|-------------|-------|--------|-----------------|
+| `test_participant_list_shows_all_active` | Shows all active participants | 3 active participants | GET dashboard | All 3 names displayed |
+| `test_participant_list_excludes_withdrawn` | Hides withdrawn participants | 2 active, 1 withdrawn | GET dashboard | Only 2 names displayed |
+| `test_participant_list_shows_self_badge` | Marks current user | Auth'd participant | GET dashboard | "You" badge on own name |
+| `test_participant_list_ordered_by_name` | Alphabetical order | Participants: Zoe, Alice, Bob | GET dashboard | Order: Alice, Bob, Zoe |
+| `test_participant_list_count_excludes_withdrawn` | Count shows active only | 3 active, 1 withdrawn | GET dashboard | "Participants (3)" |
+| `test_participant_list_empty_state` | Message when alone | Only current participant | GET dashboard | "No other participants yet" |
+| `test_participant_list_requires_auth` | Auth required | No session | GET dashboard | 302 to login |
+
+## 3. Acceptance Tests
+
+### 3.1 Story 4.5: View Participant List (Pre-Matching)
+
+**Acceptance Criteria**:
+- ✅ Participant list visible after logging in via magic link
+- ✅ Shows display names only
+- ✅ Does not show email addresses
+- ✅ Does not indicate any match information
+- ✅ Updates as new participants register
+
+**Manual Test Steps**:
+
+1. **Setup**: Create exchange, register 3 participants (Alice, Bob, Charlie)
+2. **Login as Alice**: Request magic link, login
+3. **View Dashboard**: Participant list shows "Bob" and "Charlie" (not Alice's own name in list)
+4. **Verify No Emails**: Inspect HTML, confirm no email addresses visible
+5. **Register New Participant (Dave)**: Have Dave register
+6. **Refresh Dashboard**: Dave now appears in Alice's participant list
+7. **Bob Withdraws**: Have Bob withdraw
+8. **Refresh Dashboard**: Bob no longer appears in participant list
+
+**Expected Results**: Pass all criteria
+
+### 3.2 Story 6.1: Update Profile
+
+**Acceptance Criteria**:
+- ✅ Edit option available when logged in
+- ✅ Can update name and gift ideas
+- ✅ Cannot change email (request admin help)
+- ✅ Only available before matching occurs
+- ✅ Confirmation after save
+
+**Manual Test Steps**:
+
+1. **Login as Participant**: Use magic link to access dashboard
+2. **Click "Edit Profile"**: Navigate to profile edit page
+3. **Verify Pre-Population**: Name and gift ideas fields show current values
+4. **Update Name**: Change name from "Alice" to "Alice Smith"
+5. **Update Gift Ideas**: Add new gift idea
+6. **Verify Email Not Editable**: Email field not present in form
+7. **Save Changes**: Submit form
+8. **Verify Success Message**: "Your profile has been updated successfully"
+9. **Verify Dashboard Updated**: Dashboard shows new name and gift ideas
+10. **Admin Matches Exchange**: Admin triggers matching
+11. **Try to Edit Profile**: Click "Edit Profile" (if visible)
+12. **Verify Locked**: Error message "Your profile is locked after matching"
+
+**Expected Results**: Pass all criteria
+
+### 3.3 Story 6.2: Withdraw from Exchange
+
+**Acceptance Criteria**:
+- ✅ "Withdraw" option available before registration closes
+- ✅ Confirmation required
+- ✅ Participant removed from exchange
+- ✅ Confirmation email sent
+- ✅ Admin notified (if notifications enabled) - **Deferred to Phase 7**
+
+**Manual Test Steps**:
+
+1. **Login as Participant**: Use magic link
+2. **Click "Withdraw from Exchange"**: Navigate to withdrawal page
+3. **Verify Warning**: Warning box shows consequences
+4. **Try Submit Without Confirmation**: Leave checkbox unchecked, submit
+5. **Verify Error**: Form error requires confirmation
+6. **Check Confirmation Box**: Check "I understand..." box
+7. **Submit Withdrawal**: Click "Withdraw from Exchange"
+8. **Verify Success Message**: "You have been withdrawn..."
+9. **Verify Logged Out**: Session cleared, redirected to public page
+10. **Check Email**: Withdrawal confirmation email received
+11. **Login as Different Participant**: Login as Bob
+12. **Check Participant List**: Withdrawn participant (Alice) not in list
+13. **Admin Closes Registration**: Admin closes registration
+14. **Try to Withdraw as Bob**: Navigate to withdrawal page
+15. **Verify Blocked**: Error message "Registration has closed"
+
+**Expected Results**: Pass all criteria (except admin notification - Phase 7)
+
+### 3.4 Story 6.3: Update Reminder Preferences
+
+**Acceptance Criteria**:
+- ✅ Option to enable/disable reminder emails
+- ✅ Available before exchange completes
+- ✅ Changes take effect immediately
+
+**Manual Test Steps**:
+
+1. **Login as Participant**: Use magic link
+2. **View Dashboard**: Reminder preference checkbox visible
+3. **Verify Current State**: Checkbox checked (enabled by default)
+4. **Uncheck Reminder Box**: Uncheck "Send me reminders"
+5. **Click "Update Preferences"**: Submit form
+6. **Verify Success Message**: "Reminder emails disabled"
+7. **Refresh Page**: Checkbox remains unchecked
+8. **Re-Enable Reminders**: Check box, submit
+9. **Verify Success Message**: "Reminder emails enabled"
+10. **Admin Matches Exchange**: Trigger matching
+11. **Verify Still Available**: Reminder preference form still available post-matching
+
+**Expected Results**: Pass all criteria
+
+## 4. Edge Cases and Error Scenarios
+
+### 4.1 Race Conditions
+
+| Scenario | Expected Behavior | Test Method |
+|----------|-------------------|-------------|
+| Participant withdraws while admin is matching | Withdrawal succeeds if submitted before matching, blocked if submitted after | Manual timing test |
+| Two participants update profiles simultaneously | Both succeed (no conflicts, different records) | Concurrent requests test |
+| Participant updates profile while admin closes registration | Both succeed (profile lock is at matching, not close) | Manual timing test |
+
+### 4.2 Data Validation
+
+| Scenario | Expected Behavior | Test Method |
+|----------|-------------------|-------------|
+| Name with only whitespace | Validation error "Name is required" | Integration test |
+| Gift ideas exactly 10,000 characters | Accepted | Integration test |
+| Gift ideas 10,001 characters | Validation error | Integration test |
+| Name with special characters (é, ñ, 中) | Accepted, displayed correctly | Manual test |
+| XSS attempt in gift ideas | Escaped in display | Manual test |
+
+### 4.3 Session Handling
+
+| Scenario | Expected Behavior | Test Method |
+|----------|-------------------|-------------|
+| Session expires during profile edit | Redirect to login on submit | Manual test (wait for expiry) |
+| Withdraw from different browser tab | Both tabs see withdrawal (one succeeds, one sees "already withdrawn") | Manual test |
+| Participant deleted by admin while logged in | Next request clears session, redirects to login | Integration test |
+
+## 5. Performance Tests
+
+### 5.1 Query Optimization
+
+| Test | Query Count | Execution Time |
+|------|-------------|----------------|
+| Load dashboard with 50 participants | 3 queries max (exchange, participant, participant list) | < 100ms |
+| Update profile | 2 queries (load participant, update) | < 50ms |
+| Withdraw participant | 3 queries (load, update, email) | < 100ms |
+
+**Testing Method**: Use Flask-DebugToolbar or SQLAlchemy query logging
+
+### 5.2 Concurrent Operations
+
+| Test | Concurrent Requests | Expected Result |
+|------|---------------------|-----------------|
+| 10 participants updating profiles | 10 simultaneous | All succeed, no deadlocks |
+| 5 participants viewing participant list | 5 simultaneous | All succeed, consistent data |
+
+**Testing Method**: Use locust or manual concurrent curl requests
+
+## 6. Browser Compatibility
+
+**Supported Browsers** (per project requirements):
+- Chrome (last 2 versions)
+- Firefox (last 2 versions)
+- Safari (last 2 versions)
+- Edge (last 2 versions)
+
+**Manual Tests**:
+- Profile edit form renders correctly
+- Character counter works (progressive enhancement)
+- Withdrawal confirmation checkbox works
+- CSRF tokens submitted correctly
+- Flash messages display correctly
+
+## 7. Accessibility Tests
+
+**WCAG 2.1 AA Compliance**:
+
+| Test | Tool | Expected Result |
+|------|------|-----------------|
+| Form labels | axe DevTools | All inputs have associated labels |
+| Keyboard navigation | Manual | All actions accessible via keyboard |
+| Screen reader | NVDA/JAWS | Forms and messages announced correctly |
+| Color contrast | axe DevTools | All text meets 4.5:1 contrast ratio |
+| Error messages | Manual | Errors linked to fields via ARIA |
+
+## 8. Security Tests
+
+### 8.1 Authentication
+
+| Test | Method | Expected Result |
+|------|--------|-----------------|
+| Access profile edit without login | GET /participant/profile/edit | 302 redirect to login |
+| Access withdrawal without login | GET /participant/withdraw | 302 redirect to login |
+| Use expired session | Set session to past timestamp | Session cleared, redirect to login |
+
+### 8.2 Authorization
+
+| Test | Method | Expected Result |
+|------|--------|-----------------|
+| Edit another participant's profile | Manipulate user_id in session | Decorator uses session, not URL param - not vulnerable |
+| Withdraw another participant | Manipulate user_id in session | Decorator uses session, not URL param - not vulnerable |
+
+### 8.3 Input Validation
+
+| Test | Method | Expected Result |
+|------|--------|-----------------|
+| SQL injection in name field | Submit `'; DROP TABLE participants; --` | Escaped, no SQL execution |
+| XSS in gift ideas | Submit `<script>alert('XSS')</script>` | Escaped, rendered as text |
+| CSRF attack | POST without token | 400 error |
+
+## 9. Test Automation
+
+### 9.1 CI Pipeline
+
+```yaml
+# .github/workflows/test.yml (example)
+name: Tests
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install uv
+        run: pip install uv
+      - name: Install dependencies
+        run: uv sync
+      - name: Run unit tests
+        run: uv run pytest tests/unit -v --cov
+      - name: Run integration tests
+        run: uv run pytest tests/integration -v --cov --cov-append
+      - name: Coverage report
+        run: uv run coverage report --fail-under=80
+```
+
+### 9.2 Pre-Commit Hooks
+
+```yaml
+# .pre-commit-config.yaml
+repos:
+  - repo: local
+    hooks:
+      - id: pytest
+        name: pytest
+        entry: uv run pytest tests/unit
+        language: system
+        pass_filenames: false
+        always_run: true
+```
+
+## 10. Test Data Management
+
+### 10.1 Fixtures
+
+**Location**: `tests/conftest.py`
+
+```python
+@pytest.fixture
+def app():
+    """Create test Flask app."""
+    app = create_app('testing')
+    with app.app_context():
+        db.create_all()
+        yield app
+        db.drop_all()
+
+@pytest.fixture
+def client(app):
+    """Create test client."""
+    return app.test_client()
+
+@pytest.fixture
+def exchange(db):
+    """Create test exchange."""
+    exchange = Exchange(...)
+    db.session.add(exchange)
+    db.session.commit()
+    return exchange
+
+@pytest.fixture
+def participant(db, exchange):
+    """Create test participant."""
+    participant = Participant(exchange=exchange, ...)
+    db.session.add(participant)
+    db.session.commit()
+    return participant
+```
+
+### 10.2 Test Database
+
+- Use in-memory SQLite for speed: `sqlite:///:memory:`
+- Reset between tests: `db.drop_all()` + `db.create_all()`
+- Factories for generating test data with variations
+
+## 11. Regression Tests
+
+Tests from Phase 2 that must still pass:
+
+- ✅ Participant registration still works
+- ✅ Magic link authentication still works
+- ✅ Participant dashboard loads (now with participant list)
+- ✅ Admin login still works
+- ✅ Exchange creation still works
+
+## 12. Success Criteria
+
+Phase 3 tests are complete when:
+
+1. ✅ All unit tests pass (100% pass rate)
+2. ✅ All integration tests pass (100% pass rate)
+3. ✅ Code coverage ≥ 80%
+4. ✅ All acceptance criteria manually verified
+5. ✅ No security vulnerabilities found
+6. ✅ Accessibility tests pass
+7. ✅ All edge cases handled gracefully
+8. ✅ Performance benchmarks met
+9. ✅ Browser compatibility verified
+10. ✅ Phase 2 regression tests pass
+
+---
+
+**Test Plan Version**: 1.0
+**Last Updated**: 2025-12-22
+**Status**: Ready for Implementation

entrypoint.sh

@@ -4,6 +4,22 @@ set -e  # Exit on any error
 # Ensure data directory exists
 mkdir -p /app/data
 
+echo "=== Sneaky Klaus Container Startup ==="
+echo "Data directory: /app/data"
+echo "Database path: /app/data/sneaky-klaus.db"
+
+# Check if database exists
+if [ -f /app/data/sneaky-klaus.db ]; then
+    echo "Existing database found ($(ls -lh /app/data/sneaky-klaus.db | awk '{print $5}'))"
+else
+    echo "No existing database - will be created by migrations"
+fi
+
+# List contents of data directory
+echo "Data directory contents:"
+ls -la /app/data/ || echo "(empty)"
+
+echo ""
 echo "Running database migrations..."
 if uv run alembic upgrade head; then
     echo "Database migrations completed successfully"
@@ -13,5 +29,6 @@ else
     exit 1
 fi
 
+echo ""
 echo "Starting application server..."
 exec gunicorn --bind 0.0.0.0:8000 --workers 2 --threads 4 main:app

migrations/env.py

@@ -24,7 +24,8 @@ if config.config_file_name is not None:
 # Create minimal Flask app for migrations (without session initialization)
 # This avoids Flask-Session trying to create tables before migrations run
 app = Flask(__name__)
-BASE_DIR = Path(__file__).parent.parent
+# Use resolve() to ensure absolute paths - critical for database persistence
+BASE_DIR = Path(__file__).parent.parent.resolve()
 DATA_DIR = BASE_DIR / "data"
 DATA_DIR.mkdir(parents=True, exist_ok=True)
 

src/app.py

@@ -144,6 +144,9 @@ def register_setup_check(app: Flask) -> None:
             "participant.magic_login",
             "participant.dashboard",
             "participant.logout",
+            "participant.profile_edit",
+            "participant.update_preferences",
+            "participant.withdraw",
         ]:
             return
 

src/config.py

@@ -12,8 +12,8 @@ from pathlib import Path
 class Config:
     """Base configuration class with common settings."""
 
-    # Base paths
-    BASE_DIR = Path(__file__).parent.parent
+    # Base paths - use resolve() to ensure absolute paths
+    BASE_DIR = Path(__file__).parent.parent.resolve()
     DATA_DIR = BASE_DIR / "data"
 
     # Security

src/forms/participant.py

@@ -1,7 +1,7 @@
 """Forms for participant registration and management."""
 
 from flask_wtf import FlaskForm
-from wtforms import BooleanField, EmailField, StringField, TextAreaField
+from wtforms import BooleanField, EmailField, StringField, SubmitField, TextAreaField
 from wtforms.validators import DataRequired, Email, Length
 
 
@@ -48,3 +48,48 @@ class MagicLinkRequestForm(FlaskForm):
             Length(max=255, message="Email must be less than 255 characters"),
         ],
     )
+
+
+class ProfileUpdateForm(FlaskForm):
+    """Form for updating participant profile."""
+
+    name = StringField(
+        "Name",
+        validators=[
+            DataRequired(message="Name is required"),
+            Length(min=1, max=255, message="Name must be 1-255 characters"),
+        ],
+        description="Your display name (visible to other participants)",
+    )
+
+    gift_ideas = TextAreaField(
+        "Gift Ideas",
+        validators=[
+            Length(max=10000, message="Gift ideas must be less than 10,000 characters")
+        ],
+        description="Optional wishlist or gift preferences for your Secret Santa",
+        render_kw={"rows": 6, "maxlength": 10000},
+    )
+
+
+class ReminderPreferenceForm(FlaskForm):
+    """Form for updating reminder email preferences."""
+
+    reminder_enabled = BooleanField(
+        "Send me reminder emails before the exchange date",
+        description="You can change this at any time",
+    )
+
+
+class WithdrawForm(FlaskForm):
+    """Form for confirming withdrawal from exchange.
+
+    Requires explicit confirmation to prevent accidental withdrawals.
+    """
+
+    confirm = BooleanField(
+        "I understand this cannot be undone and I will need to re-register to rejoin",
+        validators=[DataRequired(message="You must confirm to withdraw")],
+    )
+
+    submit = SubmitField("Withdraw from Exchange")

src/routes/participant.py

@@ -17,7 +17,13 @@ from flask import (
 
 from src.app import db
 from src.decorators.auth import participant_required
-from src.forms.participant import MagicLinkRequestForm, ParticipantRegistrationForm
+from src.forms.participant import (
+    MagicLinkRequestForm,
+    ParticipantRegistrationForm,
+    ProfileUpdateForm,
+    ReminderPreferenceForm,
+    WithdrawForm,
+)
 from src.models.exchange import Exchange
 from src.models.magic_token import MagicToken
 from src.models.participant import Participant
@@ -341,10 +347,198 @@ def dashboard(id: int):  # noqa: A002
     if not participant:
         abort(404)
 
+    # Get list of active participants
+    from src.utils.participant import (
+        can_update_profile,
+        can_withdraw,
+        get_active_participants,
+    )
+
+    participants = get_active_participants(exchange.id)
+    can_edit = can_update_profile(participant)
+    can_leave = can_withdraw(participant)
+
+    # Create reminder preference form
+    reminder_form = ReminderPreferenceForm(
+        reminder_enabled=participant.reminder_enabled
+    )
+
     return render_template(
         "participant/dashboard.html",
         exchange=exchange,
         participant=participant,
+        participants=participants,
+        participant_count=len(participants),
+        can_edit_profile=can_edit,
+        can_withdraw=can_leave,
+        reminder_form=reminder_form,
+    )
+
+
+@participant_bp.route("/participant/profile/edit", methods=["GET", "POST"])
+@participant_required
+def profile_edit():
+    """Edit participant profile (name and gift ideas).
+
+    Only allowed before matching occurs.
+
+    Returns:
+        GET: Profile edit form
+        POST: Redirect to dashboard on success, or re-render form on error
+    """
+    from flask import current_app
+
+    # Get participant from session
+    participant = db.session.query(Participant).filter_by(id=session["user_id"]).first()
+    if not participant:
+        abort(404)
+
+    # Check if profile editing is allowed
+    from src.utils.participant import can_update_profile
+
+    if not can_update_profile(participant):
+        flash(
+            "Your profile is locked after matching. Contact the admin for changes.",
+            "error",
+        )
+        return redirect(url_for("participant.dashboard", id=participant.exchange_id))
+
+    # Create form with current values
+    form = ProfileUpdateForm(obj=participant)
+
+    if form.validate_on_submit():
+        try:
+            # Update participant
+            participant.name = form.name.data.strip()
+            participant.gift_ideas = (
+                form.gift_ideas.data.strip() if form.gift_ideas.data else None
+            )
+
+            db.session.commit()
+
+            flash("Your profile has been updated successfully.", "success")
+            return redirect(
+                url_for("participant.dashboard", id=participant.exchange_id)
+            )
+
+        except Exception as e:
+            db.session.rollback()
+            current_app.logger.error(f"Failed to update participant profile: {e}")
+            flash("Failed to update profile. Please try again.", "error")
+
+    return render_template(
+        "participant/profile_edit.html",
+        form=form,
+        participant=participant,
+        exchange=participant.exchange,
+    )
+
+
+@participant_bp.route("/participant/preferences", methods=["POST"])
+@participant_required
+def update_preferences():
+    """Update participant reminder email preferences.
+
+    Returns:
+        Redirect to dashboard
+    """
+    from flask import current_app
+
+    participant = db.session.query(Participant).filter_by(id=session["user_id"]).first()
+    if not participant:
+        abort(404)
+
+    form = ReminderPreferenceForm()
+
+    if form.validate_on_submit():
+        try:
+            participant.reminder_enabled = form.reminder_enabled.data
+            db.session.commit()
+
+            if form.reminder_enabled.data:
+                flash("Reminder emails enabled.", "success")
+            else:
+                flash("Reminder emails disabled.", "success")
+
+        except Exception as e:
+            db.session.rollback()
+            current_app.logger.error(f"Failed to update preferences: {e}")
+            flash("Failed to update preferences. Please try again.", "error")
+    else:
+        flash("Invalid request.", "error")
+
+    return redirect(url_for("participant.dashboard", id=participant.exchange_id))
+
+
+@participant_bp.route("/participant/withdraw", methods=["GET", "POST"])
+@participant_required
+def withdraw():
+    """Withdraw from exchange (soft delete).
+
+    GET: Show confirmation page with warnings
+    POST: Process withdrawal, log out, redirect to public page
+
+    Returns:
+        GET: Withdrawal confirmation page
+        POST: Redirect to exchange registration page
+    """
+    from flask import current_app
+
+    participant = db.session.query(Participant).filter_by(id=session["user_id"]).first()
+    if not participant:
+        abort(404)
+
+    exchange = participant.exchange
+
+    # Check if withdrawal is allowed
+    from src.utils.participant import can_withdraw, is_withdrawn
+
+    if is_withdrawn(participant):
+        flash("You have already withdrawn from this exchange.", "info")
+        return redirect(url_for("participant.register", slug=exchange.slug))
+
+    if not can_withdraw(participant):
+        if exchange.state == "registration_closed":
+            message = "Registration has closed. Please contact the admin to withdraw."
+        else:
+            message = "Withdrawal is no longer available. Please contact the admin."
+        flash(message, "error")
+        return redirect(url_for("participant.dashboard", id=exchange.id))
+
+    # Create withdrawal confirmation form
+    form = WithdrawForm()
+
+    if form.validate_on_submit():
+        try:
+            # Perform withdrawal
+            from src.services.withdrawal import WithdrawalError, withdraw_participant
+
+            withdraw_participant(participant)
+
+            # Log out participant
+            session.clear()
+
+            flash(
+                "You have been withdrawn from the exchange. "
+                "A confirmation email has been sent.",
+                "success",
+            )
+            return redirect(url_for("participant.register", slug=exchange.slug))
+
+        except WithdrawalError as e:
+            flash(str(e), "error")
+            return redirect(url_for("participant.dashboard", id=exchange.id))
+
+        except Exception as e:
+            current_app.logger.error(f"Unexpected error during withdrawal: {e}")
+            flash("An unexpected error occurred. Please try again.", "error")
+
+    # GET request: show confirmation page
+    return render_template(
+        "participant/withdraw.html",
+        form=form,
+        participant=participant,
+        exchange=exchange,
     )
 
 

src/services/email.py

@@ -174,3 +174,53 @@ class EmailService:
         """
 
         return self.send_email(to=to, subject=subject, html_body=html_body)
+
+    def send_withdrawal_confirmation(self, participant: Any) -> Any:
+        """Send withdrawal confirmation email to participant.
+
+        Args:
+            participant: The participant who withdrew
+
+        Returns:
+            Response from email service
+        """
+        exchange = participant.exchange
+
+        subject = f"Withdrawal Confirmed - {exchange.name}"
+        html_body = f"""
+        <html>
+            <body>
+                <h2>Withdrawal Confirmed</h2>
+                <p>Hello {participant.name},</p>
+                <p>
+                    This email confirms that you have withdrawn from the
+                    Secret Santa exchange <strong>{exchange.name}</strong>.
+                </p>
+                <div style="background-color: #f8f9fa;
+                    border-left: 4px solid #e74c3c;
+                    padding: 15px; margin: 20px 0;">
+                    <p style="margin: 0;"><strong>What happens now:</strong></p>
+                    <ul style="margin: 10px 0;">
+                        <li>You have been removed from the participant list</li>
+                        <li>Your profile information has been archived</li>
+                        <li>
+                            You will not receive further emails about this exchange
+                        </li>
+                    </ul>
+                </div>
+                <p>
+                    If you withdrew by mistake, you can re-register using a
+                    different email address while registration is still open.
+                </p>
+                <hr style="border: none; border-top: 1px solid #ddd;
+                    margin: 30px 0;">
+                <p style="font-size: 12px; color: #666;">
+                    This is an automated message from Sneaky Klaus.
+                </p>
+            </body>
+        </html>
+        """
+
+        return self.send_email(
+            to=participant.email, subject=subject, html_body=html_body
+        )

src/services/withdrawal.py

@@ -0,0 +1,73 @@
+"""Participant withdrawal service."""
+
+from datetime import UTC, datetime
+
+from flask import current_app
+
+from src.app import db
+from src.models.participant import Participant
+from src.services.email import EmailService
+from src.utils.participant import can_withdraw
+
+
+class WithdrawalError(Exception):
+    """Raised when withdrawal operation fails."""
+
+    pass
+
+
+def withdraw_participant(participant: Participant) -> None:
+    """Withdraw a participant from their exchange.
+
+    This performs a soft delete by setting withdrawn_at timestamp.
+    Participant record is retained for audit trail.
+
+    Args:
+        participant: The participant to withdraw
+
+    Raises:
+        WithdrawalError: If withdrawal is not allowed
+
+    Side effects:
+        - Sets participant.withdrawn_at to current UTC time
+        - Commits database transaction
+        - Sends withdrawal confirmation email
+    """
+    # Validate withdrawal is allowed
+    if not can_withdraw(participant):
+        if participant.withdrawn_at is not None:
+            raise WithdrawalError("You have already withdrawn from this exchange.")
+
+        exchange = participant.exchange
+        if exchange.state == "registration_closed":
+            raise WithdrawalError(
+                "Registration has closed. Please contact the admin to withdraw."
+            )
+        elif exchange.state in ["matched", "completed"]:
+            raise WithdrawalError(
+                "Matching has already occurred. Please contact the admin."
+            )
+        else:
+            raise WithdrawalError("Withdrawal is not allowed at this time.")
+
+    # Perform withdrawal
+    participant.withdrawn_at = datetime.now(UTC)
+
+    try:
+        db.session.commit()
+        current_app.logger.info(
+            f"Participant {participant.id} withdrawn from "
+            f"exchange {participant.exchange_id}"
+        )
+    except Exception as e:
+        db.session.rollback()
+        current_app.logger.error(f"Failed to withdraw participant: {e}")
+        raise WithdrawalError("Failed to process withdrawal. Please try again.") from e
+
+    # Send confirmation email
+    try:
+        email_service = EmailService()
+        email_service.send_withdrawal_confirmation(participant)
+    except Exception as e:
+        current_app.logger.error(f"Failed to send withdrawal email: {e}")
+        # Don't raise - withdrawal already committed

src/templates/admin/dashboard.html

@@ -51,7 +51,7 @@
             <tr>
                 <td>{{ exchange.name }}</td>
                 <td><mark>{{ exchange.state }}</mark></td>
-                <td>0 / {{ exchange.max_participants }}</td>
+                <td>{{ exchange.participants|selectattr('withdrawn_at', 'none')|list|length }} / {{ exchange.max_participants }}</td>
                 <td>{{ exchange.exchange_date.strftime('%Y-%m-%d') }}</td>
                 <td>
                     <a href="{{ url_for('admin.view_exchange', exchange_id=exchange.id) }}">View</a>

src/templates/admin/exchange_detail.html

@@ -37,8 +37,30 @@
         </div>
 
         <div class="detail-section">
-            <h2>Participants</h2>
+            <h2>Participants ({{ exchange.participants|selectattr('withdrawn_at', 'none')|list|length }} / {{ exchange.max_participants }})</h2>
+            {% set active_participants = exchange.participants|selectattr('withdrawn_at', 'none')|list %}
+            {% if active_participants %}
+            <table>
+                <thead>
+                    <tr>
+                        <th>Name</th>
+                        <th>Email</th>
+                        <th>Registered</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    {% for participant in active_participants|sort(attribute='name') %}
+                    <tr>
+                        <td>{{ participant.name }}</td>
+                        <td>{{ participant.email }}</td>
+                        <td>{{ participant.created_at.strftime('%Y-%m-%d %H:%M') }}</td>
+                    </tr>
+                    {% endfor %}
+                </tbody>
+            </table>
+            {% else %}
             <p>No participants yet.</p>
+            {% endif %}
         </div>
 
         <div class="actions">

src/templates/participant/dashboard.html

@@ -37,8 +37,58 @@
             <dd>{{ participant.gift_ideas }}</dd>
             {% endif %}
         </dl>
+
+        {% if can_edit_profile %}
+        <a href="{{ url_for('participant.profile_edit') }}">Edit Profile</a>
+        {% endif %}
     </section>
 
+    <section>
+        <h2>Participants ({{ participant_count }})</h2>
+        {% if participants %}
+        <ul>
+            {% for p in participants %}
+            <li>
+                {{ p.name }}
+                {% if p.id == participant.id %}
+                <span class="badge">You</span>
+                {% endif %}
+            </li>
+            {% endfor %}
+        </ul>
+        {% else %}
+        <p>No other participants yet. Share the registration link!</p>
+        {% endif %}
+    </section>
+
+    <section>
+        <h2>Email Reminders</h2>
+        <form method="POST" action="{{ url_for('participant.update_preferences') }}">
+            {{ reminder_form.hidden_tag() }}
+            <div>
+                {{ reminder_form.reminder_enabled() }}
+                {{ reminder_form.reminder_enabled.label }}
+            </div>
+            {% if reminder_form.reminder_enabled.description %}
+            <small>{{ reminder_form.reminder_enabled.description }}</small>
+            {% endif %}
+            <button type="submit">Update Preferences</button>
+        </form>
+    </section>
+
+    {% if can_withdraw %}
+    <section>
+        <h2>Withdraw from Exchange</h2>
+        <p>
+            If you can no longer participate, you can withdraw from this exchange.
+            This cannot be undone.
+        </p>
+        <a href="{{ url_for('participant.withdraw') }}" role="button" class="secondary">
+            Withdraw from Exchange
+        </a>
+    </section>
+    {% endif %}
+
     <section>
         <form method="POST" action="{{ url_for('participant.logout') }}">
             <input type="hidden" name="csrf_token" value="{{ csrf_token() }}">

src/templates/participant/profile_edit.html

@@ -0,0 +1,64 @@
+{% extends "layouts/base.html" %}
+
+{% block title %}Edit Profile - {{ exchange.name }}{% endblock %}
+
+{% block content %}
+<article>
+    <header>
+        <h1>Edit Your Profile</h1>
+        <p>Update your display name and gift ideas. Your Secret Santa will see this information after matching.</p>
+    </header>
+
+    <form method="POST" action="{{ url_for('participant.profile_edit') }}">
+        {{ form.hidden_tag() }}
+
+        <div>
+            {{ form.name.label }}
+            {{ form.name(class="form-control") }}
+            {% if form.name.errors %}
+            <ul class="field-errors">
+                {% for error in form.name.errors %}
+                <li>{{ error }}</li>
+                {% endfor %}
+            </ul>
+            {% endif %}
+            <small>{{ form.name.description }}</small>
+        </div>
+
+        <div>
+            {{ form.gift_ideas.label }}
+            {{ form.gift_ideas(class="form-control") }}
+            {% if form.gift_ideas.errors %}
+            <ul class="field-errors">
+                {% for error in form.gift_ideas.errors %}
+                <li>{{ error }}</li>
+                {% endfor %}
+            </ul>
+            {% endif %}
+            <small>{{ form.gift_ideas.description }}</small>
+            <small id="gift-ideas-count">
+                {{ (form.gift_ideas.data or '')|length }} / 10,000 characters
+            </small>
+        </div>
+
+        <div>
+            <button type="submit">Save Changes</button>
+            <a href="{{ url_for('participant.dashboard', id=exchange.id) }}">Cancel</a>
+        </div>
+    </form>
+</article>
+
+<script>
+// Character counter (progressive enhancement)
+document.addEventListener('DOMContentLoaded', function() {
+    const textarea = document.querySelector('textarea[name="gift_ideas"]');
+    const counter = document.getElementById('gift-ideas-count');
+
+    if (textarea && counter) {
+        textarea.addEventListener('input', function() {
+            counter.textContent = this.value.length + ' / 10,000 characters';
+        });
+    }
+});
+</script>
+{% endblock %}

src/templates/participant/withdraw.html

@@ -0,0 +1,47 @@
+{% extends "layouts/base.html" %}
+
+{% block title %}Withdraw from {{ exchange.name }}{% endblock %}
+
+{% block content %}
+<article>
+    <header>
+        <h1>Withdraw from Exchange</h1>
+    </header>
+
+    <div role="alert" style="background-color: #fff3cd; border-left: 4px solid #ffc107; padding: 1rem; margin: 1rem 0;">
+        <h2 style="margin-top: 0;">⚠️ Are you sure?</h2>
+        <p>Withdrawing from this exchange means:</p>
+        <ul>
+            <li>Your registration will be cancelled</li>
+            <li>You will be removed from the participant list</li>
+            <li>You cannot undo this action</li>
+            <li>You will need to re-register with a different email to rejoin</li>
+        </ul>
+    </div>
+
+    <form method="POST" action="{{ url_for('participant.withdraw') }}">
+        {{ form.hidden_tag() }}
+
+        <div>
+            <label>
+                {{ form.confirm() }}
+                {{ form.confirm.label.text }}
+            </label>
+            {% if form.confirm.errors %}
+            <ul style="color: #dc3545; list-style: none; padding: 0;">
+                {% for error in form.confirm.errors %}
+                <li>{{ error }}</li>
+                {% endfor %}
+            </ul>
+            {% endif %}
+        </div>
+
+        <div>
+            {{ form.submit(class="contrast") }}
+            <a href="{{ url_for('participant.dashboard', id=exchange.id) }}" role="button" class="secondary">
+                Cancel
+            </a>
+        </div>
+    </form>
+</article>
+{% endblock %}

src/utils/participant.py

@@ -0,0 +1,76 @@
+"""Participant business logic utilities."""
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from src.models import Participant
+
+
+def get_active_participants(exchange_id: int) -> list["Participant"]:
+    """Get all active (non-withdrawn) participants for an exchange.
+
+    Args:
+        exchange_id: ID of the exchange
+
+    Returns:
+        List of active participants, ordered by name
+    """
+    from src.models.participant import Participant
+
+    result: list[Participant] = (
+        Participant.query.filter(
+            Participant.exchange_id == exchange_id, Participant.withdrawn_at.is_(None)
+        )
+        .order_by(Participant.name)
+        .all()
+    )
+    return result
+
+
+def is_withdrawn(participant: "Participant") -> bool:
+    """Check if participant has withdrawn.
+
+    Args:
+        participant: The participant to check
+
+    Returns:
+        True if withdrawn, False otherwise
+    """
+    return participant.withdrawn_at is not None
+
+
+def can_update_profile(participant: "Participant") -> bool:
+    """Check if participant can update their profile.
+
+    Profile updates are allowed until matching occurs.
+
+    Args:
+        participant: The participant to check
+
+    Returns:
+        True if profile updates are allowed, False otherwise
+    """
+    exchange = participant.exchange
+    allowed_states = ["draft", "registration_open", "registration_closed"]
+    return exchange.state in allowed_states
+
+
+def can_withdraw(participant: "Participant") -> bool:
+    """Check if participant can withdraw from the exchange.
+
+    Withdrawals are only allowed before registration closes.
+    After that, admin intervention is required.
+
+    Args:
+        participant: The participant to check
+
+    Returns:
+        True if withdrawal is allowed, False otherwise
+    """
+    # Already withdrawn
+    if participant.withdrawn_at is not None:
+        return False
+
+    exchange = participant.exchange
+    allowed_states = ["draft", "registration_open"]
+    return exchange.state in allowed_states

tests/conftest.py

@@ -75,3 +75,97 @@ def admin(db):
     db.session.add(admin)
     db.session.commit()
     return admin
+
+
+@pytest.fixture
+def exchange_factory(db):
+    """Factory for creating test exchanges.
+
+    Args:
+        db: Database instance.
+
+    Returns:
+        Function that creates and returns Exchange instances.
+    """
+    from datetime import UTC, datetime, timedelta
+
+    from src.models.exchange import Exchange
+
+    def _create(state="draft", **kwargs):
+        exchange = Exchange(
+            slug=kwargs.get("slug", Exchange.generate_slug()),
+            name=kwargs.get("name", "Test Exchange"),
+            budget=kwargs.get("budget", "$25-50"),
+            max_participants=kwargs.get("max_participants", 50),
+            registration_close_date=kwargs.get(
+                "registration_close_date", datetime.now(UTC) + timedelta(days=7)
+            ),
+            exchange_date=kwargs.get(
+                "exchange_date", datetime.now(UTC) + timedelta(days=14)
+            ),
+            timezone=kwargs.get("timezone", "UTC"),
+            state=state,
+        )
+        db.session.add(exchange)
+        db.session.commit()
+        return exchange
+
+    return _create
+
+
+@pytest.fixture
+def participant_factory(db, exchange_factory):
+    """Factory for creating test participants.
+
+    Args:
+        db: Database instance.
+        exchange_factory: Exchange factory fixture.
+
+    Returns:
+        Function that creates and returns Participant instances.
+    """
+    from src.models.participant import Participant
+
+    counter = {"value": 0}
+
+    def _create(exchange=None, **kwargs):
+        if not exchange:
+            exchange = exchange_factory()
+
+        counter["value"] += 1
+        participant = Participant(
+            exchange_id=exchange.id,
+            name=kwargs.get("name", f"Test Participant {counter['value']}"),
+            email=kwargs.get("email", f"test{counter['value']}@example.com"),
+            gift_ideas=kwargs.get("gift_ideas", "Test ideas"),
+            reminder_enabled=kwargs.get("reminder_enabled", True),
+            withdrawn_at=kwargs.get("withdrawn_at"),
+        )
+        db.session.add(participant)
+        db.session.commit()
+        return participant
+
+    return _create
+
+
+@pytest.fixture
+def auth_participant(client, exchange_factory, participant_factory):
+    """Create an authenticated participant session.
+
+    Args:
+        client: Flask test client.
+        exchange_factory: Exchange factory fixture.
+        participant_factory: Participant factory fixture.
+
+    Returns:
+        Authenticated participant instance.
+    """
+    exchange = exchange_factory(state="registration_open")
+    participant = participant_factory(exchange=exchange)
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    return participant

tests/integration/test_participant_list.py

@@ -0,0 +1,135 @@
+"""Integration tests for participant list functionality."""
+
+from datetime import UTC, datetime
+
+from flask import url_for
+
+
+def test_participant_list_shows_all_active(
+    client, auth_participant, participant_factory
+):
+    """Test participant list shows all active participants."""
+    # auth_participant fixture creates session and one participant
+    exchange = auth_participant.exchange
+
+    # Create 2 more active participants
+    participant_factory(exchange=exchange, name="Bob")
+    participant_factory(exchange=exchange, name="Charlie")
+
+    response = client.get(url_for("participant.dashboard", id=exchange.id))
+
+    assert response.status_code == 200
+    assert b"Bob" in response.data
+    assert b"Charlie" in response.data
+    assert b"Participants (3)" in response.data
+
+
+def test_participant_list_excludes_withdrawn(
+    client, auth_participant, participant_factory
+):
+    """Test withdrawn participants are not shown."""
+    exchange = auth_participant.exchange
+
+    # Create active and withdrawn participants
+    participant_factory(exchange=exchange, name="Active")
+    participant_factory(
+        exchange=exchange, name="Withdrawn", withdrawn_at=datetime.now(UTC)
+    )
+
+    response = client.get(url_for("participant.dashboard", id=exchange.id))
+
+    assert response.status_code == 200
+    assert b"Active" in response.data
+    assert b"Withdrawn" not in response.data
+    # Count should be 2 (auth_participant + Active)
+    assert b"Participants (2)" in response.data
+
+
+def test_participant_list_shows_self_badge(client, auth_participant):
+    """Test participant list marks current user with badge."""
+    exchange = auth_participant.exchange
+
+    response = client.get(url_for("participant.dashboard", id=exchange.id))
+
+    assert response.status_code == 200
+    # Should show the participant's name
+    assert auth_participant.name.encode() in response.data
+    # Should show "You" badge
+    assert b"You" in response.data
+
+
+def test_participant_list_ordered_by_name(
+    client, auth_participant, participant_factory
+):
+    """Test participants are shown in alphabetical order."""
+    exchange = auth_participant.exchange
+
+    # Create participants with names that should be sorted
+    participant_factory(exchange=exchange, name="Zoe")
+    participant_factory(exchange=exchange, name="Alice")
+    participant_factory(exchange=exchange, name="Bob")
+
+    response = client.get(url_for("participant.dashboard", id=exchange.id))
+
+    assert response.status_code == 200
+    # Check order by finding positions in response
+    data = response.data.decode()
+    alice_pos = data.find("Alice")
+    bob_pos = data.find("Bob")
+    zoe_pos = data.find("Zoe")
+
+    # All should be present
+    assert alice_pos > 0
+    assert bob_pos > 0
+    assert zoe_pos > 0
+
+    # Should be in alphabetical order
+    assert alice_pos < bob_pos < zoe_pos
+
+
+def test_participant_list_empty_state(client, exchange_factory, participant_factory):
+    """Test message shown when only one participant."""
+    exchange = exchange_factory(state="registration_open")
+    participant = participant_factory(exchange=exchange)
+
+    # Create session for the only participant
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    response = client.get(url_for("participant.dashboard", id=exchange.id))
+
+    assert response.status_code == 200
+    assert b"Participants (1)" in response.data
+    # Should show participant's own name
+    assert participant.name.encode() in response.data
+
+
+def test_participant_list_requires_auth(client, exchange_factory):
+    """Test participant list requires authentication."""
+    exchange = exchange_factory()
+
+    response = client.get(
+        url_for("participant.dashboard", id=exchange.id), follow_redirects=False
+    )
+
+    # Should redirect to login (or show error)
+    assert response.status_code in [302, 403]
+
+
+def test_participant_list_different_exchange(
+    client, auth_participant, exchange_factory, participant_factory
+):
+    """Test participants filtered by exchange."""
+    exchange1 = auth_participant.exchange
+    exchange2 = exchange_factory(state="registration_open")
+
+    # Create participant in different exchange
+    participant_factory(exchange=exchange2, name="Other Exchange")
+
+    response = client.get(url_for("participant.dashboard", id=exchange1.id))
+
+    assert response.status_code == 200
+    # Should not show participant from other exchange
+    assert b"Other Exchange" not in response.data

tests/integration/test_profile_update.py

@@ -0,0 +1,125 @@
+"""Integration tests for profile update functionality."""
+
+from flask import url_for
+
+
+def test_profile_update_get_shows_form(client, auth_participant):
+    """GET shows edit form with current values."""
+    response = client.get(url_for("participant.profile_edit"))
+
+    assert response.status_code == 200
+    assert auth_participant.name.encode() in response.data
+    assert b"Edit Your Profile" in response.data
+
+
+def test_profile_update_post_success(client, auth_participant, db):
+    """POST updates profile successfully."""
+    response = client.post(
+        url_for("participant.profile_edit"),
+        data={"name": "Updated Name", "gift_ideas": "Updated ideas"},
+        follow_redirects=True,
+    )
+
+    assert response.status_code == 200
+    assert b"profile has been updated" in response.data
+
+    # Verify database
+    db.session.refresh(auth_participant)
+    assert auth_participant.name == "Updated Name"
+    assert auth_participant.gift_ideas == "Updated ideas"
+
+
+def test_profile_update_name_change(client, auth_participant, db):
+    """Name updates in database."""
+    original_name = auth_participant.name
+
+    client.post(
+        url_for("participant.profile_edit"),
+        data={"name": "New Name", "gift_ideas": ""},
+        follow_redirects=True,
+    )
+
+    db.session.refresh(auth_participant)
+    assert auth_participant.name == "New Name"
+    assert auth_participant.name != original_name
+
+
+def test_profile_update_locked_after_matching(
+    client, exchange_factory, participant_factory
+):
+    """Profile edit blocked after matching."""
+    exchange = exchange_factory(state="matched")
+    participant = participant_factory(exchange=exchange)
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    response = client.get(url_for("participant.profile_edit"), follow_redirects=True)
+
+    assert b"profile is locked" in response.data
+
+
+def test_profile_update_form_validation_empty_name(client, auth_participant):
+    """Empty name shows validation error."""
+    # auth_participant fixture sets up the session
+    _ = auth_participant  # Mark as used
+    response = client.post(
+        url_for("participant.profile_edit"), data={"name": "", "gift_ideas": "Test"}
+    )
+
+    assert response.status_code == 200
+    assert (
+        b"Name is required" in response.data
+        or b"This field is required" in response.data
+    )
+
+
+def test_profile_update_requires_auth(client):
+    """Profile edit requires authentication."""
+    response = client.get(url_for("participant.profile_edit"), follow_redirects=False)
+
+    assert response.status_code == 403
+
+
+def test_profile_update_strips_whitespace(client, auth_participant, db):
+    """Whitespace is stripped from name and gift ideas."""
+    client.post(
+        url_for("participant.profile_edit"),
+        data={"name": "  Spaces  ", "gift_ideas": "  Gift  "},
+        follow_redirects=True,
+    )
+
+    db.session.refresh(auth_participant)
+    assert auth_participant.name == "Spaces"
+    assert auth_participant.gift_ideas == "Gift"
+
+
+def test_dashboard_shows_edit_link_when_allowed(client, auth_participant):
+    """Dashboard shows edit profile link when editing is allowed."""
+    response = client.get(
+        url_for("participant.dashboard", id=auth_participant.exchange_id)
+    )
+
+    assert response.status_code == 200
+    assert b"Edit Profile" in response.data
+
+
+def test_dashboard_hides_edit_link_after_matching(
+    client, exchange_factory, participant_factory
+):
+    """Dashboard hides edit profile link after matching."""
+    exchange = exchange_factory(state="matched")
+    participant = participant_factory(exchange=exchange)
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    response = client.get(url_for("participant.dashboard", id=exchange.id))
+
+    assert response.status_code == 200
+    # Edit link should not be present
+    assert b"Edit Profile" not in response.data

tests/integration/test_reminder_preferences.py

@@ -0,0 +1,83 @@
+"""Integration tests for reminder preferences."""
+
+from flask import url_for
+
+
+def get_csrf_token(client, url):
+    """Extract CSRF token from a page.
+
+    Args:
+        client: Flask test client.
+        url: URL to fetch the CSRF token from.
+
+    Returns:
+        CSRF token string.
+    """
+    response = client.get(url)
+    # Extract CSRF token from the form
+    data = response.data.decode()
+    start = data.find('name="csrf_token" value="') + len('name="csrf_token" value="')
+    end = data.find('"', start)
+    return data[start:end]
+
+
+def test_dashboard_shows_reminder_preference_form(client, auth_participant):
+    """Test that dashboard shows reminder preference form."""
+    response = client.get(
+        url_for("participant.dashboard", id=auth_participant.exchange_id)
+    )
+
+    assert response.status_code == 200
+    assert b"Email Reminders" in response.data or b"Send me reminders" in response.data
+
+
+def test_update_preferences_enable(client, auth_participant, db):
+    """Enable reminder emails."""
+    auth_participant.reminder_enabled = False
+    db.session.commit()
+
+    csrf_token = get_csrf_token(
+        client, url_for("participant.dashboard", id=auth_participant.exchange_id)
+    )
+
+    response = client.post(
+        url_for("participant.update_preferences"),
+        data={"reminder_enabled": True, "csrf_token": csrf_token},
+        follow_redirects=True,
+    )
+
+    assert response.status_code == 200
+    assert b"Reminder emails enabled" in response.data
+
+    db.session.refresh(auth_participant)
+    assert auth_participant.reminder_enabled is True
+
+
+def test_update_preferences_disable(client, auth_participant, db):
+    """Disable reminder emails."""
+    auth_participant.reminder_enabled = True
+    db.session.commit()
+
+    csrf_token = get_csrf_token(
+        client, url_for("participant.dashboard", id=auth_participant.exchange_id)
+    )
+
+    response = client.post(
+        url_for("participant.update_preferences"),
+        data={"csrf_token": csrf_token},
+        follow_redirects=True,
+    )
+
+    assert response.status_code == 200
+    assert b"Reminder emails disabled" in response.data
+
+    db.session.refresh(auth_participant)
+    assert auth_participant.reminder_enabled is False
+
+
+def test_update_preferences_requires_login(client):
+    """Test that update_preferences requires login."""
+    response = client.post(url_for("participant.update_preferences"))
+
+    # Should redirect to login or show error
+    assert response.status_code in [302, 401, 403]

tests/integration/test_withdrawal.py

@@ -0,0 +1,172 @@
+"""Integration tests for withdrawal functionality."""
+
+from datetime import datetime
+
+from flask import url_for
+
+from src.models.participant import Participant
+
+
+def get_csrf_token(client, url):
+    """Extract CSRF token from a page.
+
+    Args:
+        client: Flask test client.
+        url: URL to fetch the CSRF token from.
+
+    Returns:
+        CSRF token string.
+    """
+    response = client.get(url)
+    # Extract CSRF token from the form
+    data = response.data.decode()
+    start = data.find('name="csrf_token" value="') + len('name="csrf_token" value="')
+    end = data.find('"', start)
+    return data[start:end]
+
+
+def test_withdrawal_get_shows_confirmation_page(client, auth_participant):  # noqa: ARG001
+    """Test GET shows withdrawal confirmation page."""
+    response = client.get(url_for("participant.withdraw"))
+
+    assert response.status_code == 200
+    assert b"Withdraw from Exchange" in response.data
+    assert b"Are you sure" in response.data or b"cannot be undone" in response.data
+
+
+def test_withdrawal_post_success(client, auth_participant, db):
+    """Test successful withdrawal flow."""
+    participant_id = auth_participant.id
+
+    csrf_token = get_csrf_token(client, url_for("participant.withdraw"))
+
+    response = client.post(
+        url_for("participant.withdraw"),
+        data={"confirm": True, "csrf_token": csrf_token},
+        follow_redirects=True,
+    )
+
+    assert response.status_code == 200
+    assert b"withdrawn from the exchange" in response.data
+
+    # Verify database
+    participant = db.session.query(Participant).filter_by(id=participant_id).first()
+    assert participant.withdrawn_at is not None
+
+    # Verify session cleared
+    with client.session_transaction() as session:
+        assert "user_id" not in session
+
+
+def test_withdrawal_requires_confirmation(client, auth_participant):  # noqa: ARG001
+    """Test withdrawal requires checkbox confirmation."""
+    csrf_token = get_csrf_token(client, url_for("participant.withdraw"))
+
+    response = client.post(
+        url_for("participant.withdraw"),
+        data={"csrf_token": csrf_token},
+        follow_redirects=False,
+    )
+
+    # Should re-render form with validation error
+    assert response.status_code == 200
+    assert b"confirm" in response.data.lower()
+
+
+def test_withdrawal_blocked_after_registration_closes(
+    client, exchange_factory, participant_factory
+):
+    """Test withdrawal blocked after registration closes."""
+    exchange = exchange_factory(state="registration_closed")
+    participant = participant_factory(exchange=exchange)
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    response = client.get(url_for("participant.withdraw"), follow_redirects=True)
+
+    assert (
+        b"Registration has closed" in response.data
+        or b"Contact the admin" in response.data
+    )
+
+
+def test_withdrawal_blocked_after_matching(
+    client, exchange_factory, participant_factory
+):
+    """Test withdrawal blocked after matching occurs."""
+    exchange = exchange_factory(state="matched")
+    participant = participant_factory(exchange=exchange)
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    response = client.get(url_for("participant.withdraw"), follow_redirects=True)
+
+    assert (
+        b"Withdrawal is no longer available" in response.data
+        or b"Contact the admin" in response.data
+    )
+
+
+def test_withdrawal_requires_login(client):
+    """Test that withdrawal requires login."""
+    response = client.get(url_for("participant.withdraw"))
+
+    # Should redirect or show error
+    assert response.status_code in [302, 401, 403]
+
+
+def test_dashboard_shows_withdraw_link_when_allowed(client, auth_participant):
+    """Dashboard shows withdraw link when withdrawal is allowed."""
+    response = client.get(
+        url_for("participant.dashboard", id=auth_participant.exchange_id)
+    )
+
+    assert response.status_code == 200
+    assert b"Withdraw" in response.data
+
+
+def test_dashboard_hides_withdraw_link_after_close(
+    client, exchange_factory, participant_factory
+):
+    """Dashboard hides withdraw link after registration closes."""
+    exchange = exchange_factory(state="registration_closed")
+    participant = participant_factory(exchange=exchange)
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    response = client.get(url_for("participant.dashboard", id=exchange.id))
+
+    assert response.status_code == 200
+    # Withdraw link should not be present
+    assert b"Withdraw from Exchange" not in response.data
+
+
+def test_already_withdrawn_redirects_to_register(
+    client,
+    exchange_factory,
+    participant_factory,
+    db,  # noqa: ARG001
+):
+    """Test that already withdrawn participants are redirected to register page."""
+    exchange = exchange_factory(state="registration_open")
+    participant = participant_factory(exchange=exchange, withdrawn_at=datetime.utcnow())
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    response = client.get(url_for("participant.withdraw"), follow_redirects=True)
+
+    assert b"already withdrawn" in response.data
+    # Should be on registration page
+    assert exchange.name.encode() in response.data

tests/unit/test_participant_utils.py

@@ -0,0 +1,158 @@
+"""Unit tests for participant utility functions."""
+
+from datetime import UTC, datetime
+
+from src.utils.participant import (
+    can_update_profile,
+    can_withdraw,
+    get_active_participants,
+    is_withdrawn,
+)
+
+
+def test_get_active_participants_excludes_withdrawn(
+    exchange_factory, participant_factory
+):
+    """Test that get_active_participants excludes withdrawn participants."""
+    exchange = exchange_factory()
+
+    # Create 2 active, 1 withdrawn
+    active1 = participant_factory(exchange=exchange, name="Alice")
+    active2 = participant_factory(exchange=exchange, name="Bob")
+    withdrawn = participant_factory(
+        exchange=exchange, name="Charlie", withdrawn_at=datetime.now(UTC)
+    )
+
+    participants = get_active_participants(exchange.id)
+
+    assert len(participants) == 2
+    assert active1 in participants
+    assert active2 in participants
+    assert withdrawn not in participants
+
+
+def test_get_active_participants_ordered_by_name(exchange_factory, participant_factory):
+    """Test that participants are ordered alphabetically."""
+    exchange = exchange_factory()
+
+    participant_factory(exchange=exchange, name="Zoe")
+    participant_factory(exchange=exchange, name="Alice")
+    participant_factory(exchange=exchange, name="Bob")
+
+    participants = get_active_participants(exchange.id)
+
+    assert len(participants) == 3
+    assert participants[0].name == "Alice"
+    assert participants[1].name == "Bob"
+    assert participants[2].name == "Zoe"
+
+
+def test_get_active_participants_empty_when_all_withdrawn(
+    exchange_factory, participant_factory
+):
+    """Test that empty list returned when all participants withdrawn."""
+    exchange = exchange_factory()
+
+    participant_factory(exchange=exchange, withdrawn_at=datetime.now(UTC))
+    participant_factory(exchange=exchange, withdrawn_at=datetime.now(UTC))
+
+    participants = get_active_participants(exchange.id)
+
+    assert len(participants) == 0
+
+
+def test_get_active_participants_different_exchanges(
+    exchange_factory, participant_factory
+):
+    """Test that participants are filtered by exchange_id."""
+    exchange1 = exchange_factory()
+    exchange2 = exchange_factory()
+
+    participant_factory(exchange=exchange1, name="Alice")
+    participant_factory(exchange=exchange2, name="Bob")
+
+    participants = get_active_participants(exchange1.id)
+
+    assert len(participants) == 1
+    assert participants[0].name == "Alice"
+
+
+def test_is_withdrawn_true(participant_factory):
+    """Test is_withdrawn returns True for withdrawn participant."""
+    participant = participant_factory(withdrawn_at=datetime.now(UTC))
+    assert is_withdrawn(participant) is True
+
+
+def test_is_withdrawn_false(participant_factory):
+    """Test is_withdrawn returns False for active participant."""
+    participant = participant_factory()
+    assert is_withdrawn(participant) is False
+
+
+def test_can_update_profile_draft_state(participant_factory, exchange_factory):
+    """Profile updates allowed in draft state."""
+    exchange = exchange_factory(state="draft")
+    participant = participant_factory(exchange=exchange)
+    assert can_update_profile(participant) is True
+
+
+def test_can_update_profile_registration_open(participant_factory, exchange_factory):
+    """Profile updates allowed when registration open."""
+    exchange = exchange_factory(state="registration_open")
+    participant = participant_factory(exchange=exchange)
+    assert can_update_profile(participant) is True
+
+
+def test_can_update_profile_registration_closed(participant_factory, exchange_factory):
+    """Profile updates allowed when registration closed."""
+    exchange = exchange_factory(state="registration_closed")
+    participant = participant_factory(exchange=exchange)
+    assert can_update_profile(participant) is True
+
+
+def test_can_update_profile_matched_state(participant_factory, exchange_factory):
+    """Profile updates blocked after matching."""
+    exchange = exchange_factory(state="matched")
+    participant = participant_factory(exchange=exchange)
+    assert can_update_profile(participant) is False
+
+
+def test_can_update_profile_completed_state(participant_factory, exchange_factory):
+    """Profile updates blocked when completed."""
+    exchange = exchange_factory(state="completed")
+    participant = participant_factory(exchange=exchange)
+    assert can_update_profile(participant) is False
+
+
+def test_can_withdraw_draft_state(participant_factory, exchange_factory):
+    """Withdrawal allowed in draft state."""
+    exchange = exchange_factory(state="draft")
+    participant = participant_factory(exchange=exchange)
+    assert can_withdraw(participant) is True
+
+
+def test_can_withdraw_registration_open(participant_factory, exchange_factory):
+    """Withdrawal allowed when registration open."""
+    exchange = exchange_factory(state="registration_open")
+    participant = participant_factory(exchange=exchange)
+    assert can_withdraw(participant) is True
+
+
+def test_can_withdraw_registration_closed(participant_factory, exchange_factory):
+    """Withdrawal blocked when registration closed."""
+    exchange = exchange_factory(state="registration_closed")
+    participant = participant_factory(exchange=exchange)
+    assert can_withdraw(participant) is False
+
+
+def test_can_withdraw_matched_state(participant_factory, exchange_factory):
+    """Withdrawal blocked after matching."""
+    exchange = exchange_factory(state="matched")
+    participant = participant_factory(exchange=exchange)
+    assert can_withdraw(participant) is False
+
+
+def test_can_withdraw_already_withdrawn(participant_factory):
+    """Withdrawal blocked if already withdrawn."""
+    participant = participant_factory(withdrawn_at=datetime.now(UTC))
+    assert can_withdraw(participant) is False

tests/unit/test_withdrawal_service.py

@@ -0,0 +1,67 @@
+"""Unit tests for withdrawal service."""
+
+from datetime import datetime
+from unittest.mock import patch
+
+import pytest
+
+from src.services.withdrawal import WithdrawalError, withdraw_participant
+
+
+def test_withdraw_participant_success(participant_factory, db, app):  # noqa: ARG001
+    """Test successful withdrawal."""
+    with app.app_context():
+        participant = participant_factory()
+
+        with patch("src.services.withdrawal.EmailService") as mock_email_service:
+            withdraw_participant(participant)
+
+            assert participant.withdrawn_at is not None
+            mock_email_service.return_value.send_withdrawal_confirmation.assert_called_once()
+
+
+def test_withdraw_participant_already_withdrawn(participant_factory, app):
+    """Test error when already withdrawn."""
+    with app.app_context():
+        participant = participant_factory(withdrawn_at=datetime.utcnow())
+
+        with pytest.raises(WithdrawalError, match="already withdrawn"):
+            withdraw_participant(participant)
+
+
+def test_withdraw_participant_registration_closed(
+    exchange_factory, participant_factory, app
+):
+    """Test error when registration is closed."""
+    with app.app_context():
+        exchange = exchange_factory(state="registration_closed")
+        participant = participant_factory(exchange=exchange)
+
+        with pytest.raises(WithdrawalError, match="Registration has closed"):
+            withdraw_participant(participant)
+
+
+def test_withdraw_participant_after_matching(
+    exchange_factory, participant_factory, app
+):
+    """Test error when matching has occurred."""
+    with app.app_context():
+        exchange = exchange_factory(state="matched")
+        participant = participant_factory(exchange=exchange)
+
+        with pytest.raises(WithdrawalError, match="Matching has already occurred"):
+            withdraw_participant(participant)
+
+
+def test_withdraw_participant_sets_timestamp(participant_factory, db, app):  # noqa: ARG001
+    """Test that withdrawal sets timestamp correctly."""
+    with app.app_context():
+        participant = participant_factory()
+
+        with patch("src.services.withdrawal.EmailService"):
+            before = datetime.utcnow()
+            withdraw_participant(participant)
+            after = datetime.utcnow()
+
+            assert participant.withdrawn_at is not None
+            assert before <= participant.withdrawn_at <= after