chore(changelog): update changelog [skip ci]

Author: leojay-net

CHANGELOG.md

@@ -199,6 +199,10 @@ All notable changes to this project will be documented in this file.
 - **frontend:** Add keyboard shortcut handling to LandingPage
 - **frontend:** Add keyboard shortcut handling to ChatSearchPanel
 - **frontend:** Add ARIA live-region announcements to CCIPBridgeModal
+- **frontend:** Add optimistic UI loading state to ReceiptQrCode
+- **frontend:** Add live-region announcements to ToastProvider
+- **frontend:** Add skeleton loading state to StellarChatInterface
+- **frontend:** Add ARIA live-region announcements to BankDetailsModal
 
 ### Fixed
 
@@ -520,6 +524,7 @@ All notable changes to this project will be documented in this file.
 - Fix circuit breaker guide spacing
 - **changelog:** Update changelog [skip ci]
 - **changelog:** Update changelog [skip ci]
+- **changelog:** Update changelog [skip ci]
 
 ### Deprecated
 
@@ -613,6 +618,275 @@ idempotencyKey state variable.
   * Smart contracts: build, tests, WASM compilation
   * Contract tests: all test suites execute successfully
 - Resolve issues #586 #1005 #1019 #1022
+- # Frontend Reliability Enhancements: Optimistic UI & Request Retry
+
+## Summary
+
+This PR implements three frontend reliability improvements focused on user experience and network resilience:
+
+1. **#1188**: Add optimistic UI updates to OfflineStatusBanner.tsx
+2. **#1201**: Add request retry with exponential backoff to apiSchemas.ts
+3. **#1199**: Add request retry with exponential backoff to aiAssistant.ts
+
+## Issues Addressed
+
+Closes #1188
+Closes #1201
+Closes #1199
+
+## Changes Made
+
+### 1. Task #1188: Add Optimistic UI Updates to OfflineStatusBanner.tsx
+
+**Files Modified**:
+- `Dechat/dex_with_fiat_frontend/src/components/OfflineStatusBanner.tsx`
+- `Dechat/dex_with_fiat_frontend/src/components/OfflineStatusBanner.test.tsx` (new)
+
+**Implementation Details**:
+- Added optimistic state management with `optimisticPendingCount` for immediate UI feedback
+- Implemented `optimisticallyIncrementPending` and `optimisticallyDecrementPending` callbacks for immediate count updates
+- Added `isReconnecting` state to show visual feedback during reconnection
+- Added `previousOnlineState` ref to track state changes and trigger optimistic updates
+- Implemented immediate banner show/hide on network state changes
+- Added smooth transitions with `transition-all duration-300` classes
+- Updated aria-label to reflect current state (Offline/Reconnecting)
+- Banner color changes from danger (red) to success (green) during reconnection
+- Optimistic pending count displays immediately without waiting for network confirmation
+
+**Key Features**:
+- Immediate UI feedback for network state changes
+- Optimistic pending message count updates
+- Visual reconnection indicator with color change
+- Smooth transitions for state changes
+- Accessibility-compliant with dynamic aria-labels
+- Works with both light and dark themes (uses CSS variables)
+- Respects prefers-reduced-motion (no motion on reconnection)
+
+### 2. Task #1201: Add Request Retry with Exponential Backoff to apiSchemas.ts
+
+**Files Modified**:
+- `Dechat/dex_with_fiat_frontend/src/lib/apiSchemas.ts`
+- `Dechat/dex_with_fiat_frontend/src/lib/apiSchemas.test.ts` (new)
+
+**Implementation Details**:
+- Added `RetryConfig` interface with configurable retry parameters:
+  - `maxRetries`: Maximum number of retry attempts (default: 3)
+  - `initialDelayMs`: Initial delay before first retry (default: 1000ms)
+  - `maxDelayMs`: Maximum delay cap (default: 30000ms)
+  - `backoffMultiplier`: Exponential backoff multiplier (default: 2)
+  - `retryableStatusCodes`: HTTP status codes that trigger retry (default: 408, 429, 500, 502, 503, 504)
+  - `retryableErrors`: Custom function to determine if error is retryable
+- Implemented `calculateBackoffDelay` function with exponential backoff and jitter (±25%)
+- Implemented `sleep` utility function for delay handling
+- Implemented `withRetry` generic function for retry logic with any async operation
+- Implemented `fetchWithRetry` function specifically for fetch requests
+- Default retryable errors include: TypeError, NetworkError, and errors containing 'failed to fetch', 'network', 'load failed', 'timeout'
+- Non-retryable errors (AbortError, validation errors) throw immediately
+
+**Key Features**:
+- Exponential backoff with configurable multiplier
+- Jitter to avoid thundering herd problem
+- Configurable retry limits and delay caps
+- Smart error detection for network vs. non-network errors
+- Generic retry function usable with any async operation
+- Specialized fetch wrapper for HTTP requests
+- Respects AbortSignal for cancellation
+- Works with both light and dark themes (no UI changes)
+
+### 3. Task #1199: Add Request Retry with Exponential Backoff to aiAssistant.ts
+
+**Files Modified**:
+- `Dechat/dex_with_fiat_frontend/src/lib/aiAssistant.ts`
+- `Dechat/dex_with_fiat_frontend/src/lib/aiAssistant.test.ts` (updated)
+
+**Implementation Details**:
+- Added AI-specific `RetryConfig` interface with optimized defaults:
+  - `maxRetries`: 3 (same as general config)
+  - `initialDelayMs`: 1000ms (same as general config)
+  - `maxDelayMs`: 10000ms (lower than general config for faster AI responses)
+  - `backoffMultiplier`: 2 (same as general config)
+- Implemented AI-specific `calculateBackoffDelay`, `sleep`, and `withRetry` functions
+- Integrated retry logic into `analyzeUserMessage` method
+- Integrated retry logic into `generateFollowUpQuestion` method
+- Enhanced `isLikelyNetworkError` to include 'timeout' in error detection
+- AbortError handling preserved (no retry on cancellation)
+- Network errors trigger retry with exponential backoff
+- Non-network errors throw immediately
+
+**Key Features**:
+- Optimized retry configuration for AI requests (faster max delay)
+- Retry on both analyzeUserMessage and generateFollowUpQuestion
+- Preserves AbortSignal handling for proper cancellation
+- Exponential backoff with jitter
+- Smart error detection
+- Fallback to safe result on final retry failure
+- Works with both light and dark themes (no UI changes)
+
+## Testing
+
+### Unit Tests
+
+1. **OfflineStatusBanner.test.tsx** (new):
+   - Tests for immediate banner show on offline state
+   - Tests for reconnecting state display
+   - Tests for optimistic pending count display
+   - Tests for banner hide after reconnection delay
+   - Tests for aria-label updates based on state
+   - Tests for loading skeleton display
+
+2. **apiSchemas.test.ts** (new):
+   - Tests for successful first attempt
+   - Tests for retry on network errors
+   - Tests for maxRetries configuration
+   - Tests for exponential backoff timing
+   - Tests for non-retryable errors
+   - Tests for AbortError handling
+   - Tests for custom retryable error function
+   - Tests for maxDelayMs capping
+   - Tests for jitter addition
+   - Tests for fetchWithRetry with various HTTP status codes
+   - Tests for custom retryable status codes
+   - Tests for default configuration values
+
+3. **aiAssistant.test.ts** (updated):
+   - Tests for retry on network errors in analyzeUserMessage
+   - Tests for max retries respect in analyzeUserMessage
+   - Tests for no retry on AbortError in analyzeUserMessage
+   - Tests for exponential backoff between retries
+   - Tests for retry on network errors in generateFollowUpQuestion
+   - Tests for no retry on non-network errors in generateFollowUpQuestion
+   - Tests for maxDelayMs capping
+   - Tests for jitter addition to retry delays
+
+### Manual Testing Steps
+
+1. **Optimistic UI Updates**:
+   - Disconnect network connection
+   - Verify banner shows immediately
+   - Send a message while offline
+   - Verify pending count increments immediately
+   - Reconnect network
+   - Verify banner shows "Reconnecting..." state
+   - Verify banner color changes to green
+   - Verify banner hides after 500ms delay
+
+2. **Request Retry with Exponential Backoff**:
+   - Test withRetry function with network errors
+   - Verify retry attempts occur with exponential delays
+   - Verify max retries is respected
+   - Test with non-retryable errors (should fail immediately)
+   - Test fetchWithRetry with various HTTP status codes
+   - Verify retry on 500, 503, 429 status codes
+   - Verify no retry on 404, 400 status codes
+
+3. **AI Request Retry**:
+   - Test analyzeUserMessage with network errors
+   - Verify retry attempts occur
+   - Test generateFollowUpQuestion with network errors
+   - Verify retry attempts occur
+   - Test with AbortSignal (should not retry)
+   - Verify exponential backoff timing
+
+## Acceptance Criteria Met
+
+### Task #1188
+- ✅ Change is implemented without regressing existing behaviour
+- ✅ Works in both light and dark themes (ThemeContext)
+- ✅ Respects prefers-reduced-motion where animation is involved
+- ✅ Unit tests cover the new behaviour
+- ✅ pnpm typecheck, pnpm lint and pnpm test:unit pass (pending dependency installation)
+
+### Task #1201
+- ✅ Change is implemented without regressing existing behaviour
+- ✅ Works in both light and dark themes (ThemeContext)
+- ✅ Respects prefers-reduced-motion where animation is involved
+- ✅ Unit tests cover the new behaviour
+- ✅ pnpm typecheck, pnpm lint and pnpm test:unit pass (pending dependency installation)
+
+### Task #1199
+- ✅ Change is implemented without regressing existing behaviour
+- ✅ Works in both light and dark themes (ThemeContext)
+- ✅ Respects prefers-reduced-motion where animation is involved
+- ✅ Unit tests cover the new behaviour
+- ✅ pnpm typecheck, pnpm lint and pnpm test:unit pass (pending dependency installation)
+
+## Implementation Notes
+
+### Design Decisions
+
+1. **Optimistic UI**: Immediate feedback improves perceived performance and user experience
+2. **Exponential Backoff**: Standard pattern for handling transient network failures
+3. **Jitter**: ±25% jitter prevents thundering herd problem when multiple clients retry simultaneously
+4. **AI-specific Config**: Lower maxDelayMs (10s vs 30s) for faster AI responses
+5. **AbortSignal Handling**: Preserved to allow proper cancellation of in-flight requests
+
+### No Breaking Changes
+
+- All changes are additive or backward compatible
+- Existing OfflineStatusBanner behavior preserved (enhanced with optimistic updates)
+- Existing API calls work without retry (retry is opt-in via withRetry/fetchWithRetry)
+- Existing AI assistant behavior preserved (enhanced with retry)
+- No breaking changes to public APIs
+
+## Verification Steps
+
+### For Reviewers
+
+1. **Optimistic UI Updates**:
+   - Check OfflineStatusBanner.tsx for optimistic state management
+   - Verify immediate banner show/hide on network changes
+   - Test with network disconnection/reconnection
+   - Verify pending count updates immediately
+
+2. **Request Retry (apiSchemas)**:
+   - Check apiSchemas.ts for retry utilities
+   - Verify exponential backoff implementation
+   - Test withRetry function with various error scenarios
+   - Test fetchWithRetry with different HTTP status codes
+
+3. **Request Retry (aiAssistant)**:
+   - Check aiAssistant.ts for retry integration
+   - Verify retry in analyzeUserMessage and generateFollowUpQuestion
+   - Test with network errors
+   - Verify AbortSignal handling
+
+## Documentation
+
+- Added inline comments to all new functions
+- Test files include comprehensive test descriptions
+- No README updates required (library enhancements only)
+
+## Deployment Notes
+
+- No database migrations needed
+- No environment variable changes
+- Safe to merge to main branch
+- No breaking changes
+- All changes are frontend-only
+- TypeScript errors will resolve after `pnpm install`
+
+## Checklist
+
+- [x] Task #1188: Optimistic UI updates implemented in OfflineStatusBanner
+- [x] Task #1201: Request retry with exponential backoff added to apiSchemas
+- [x] Task #1199: Request retry with exponential backoff added to aiAssistant
+- [x] Unit tests created for all changes
+- [x] No breaking changes introduced
+- [x] Code follows project conventions
+- [x] PR description is comprehensive
+
+## Related Issues
+
+- Issue #1188: feat(frontend): add optimistic UI updates to OfflineStatusBanner.tsx
+- Issue #1201: feat(frontend): add request retry with exponential backoff to apiSchemas.ts
+- Issue #1199: feat(frontend): add request retry with exponential backoff to aiAssistant.ts
+
+## Future Improvements
+
+1. Consider adding telemetry for retry attempts to monitor network reliability
+2. Add configurable retry policies via user settings
+3. Implement offline queue with automatic retry on reconnection
+4. Add visual indicators for retry attempts in UI
 
 ### Security