semi implemented and features implemented save checkpoint

docs/features/unchecked/gateway/gateway-connection-lifecycle-management.md

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+# Gateway Connection Lifecycle Management
+
+## Module
+Gateway
+
+## Status
+IMPLEMENTED
+
+## Description
+HELLO frame processing for microservice registration, connection lifecycle management with cleanup on disconnect, and `ConnectionManager` hosted service for monitoring active connections.
+
+## Implementation Details
+- **Gateway hosted service**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayHostedService.cs` -- connection lifecycle management background service
+- **Health monitoring**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayHealthMonitorService.cs` -- monitors active connections, detects stale instances
+- **Metrics**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayMetrics.cs` -- connection metrics tracking
+- **Configuration**: `src/Gateway/StellaOps.Gateway.WebService/Configuration/GatewayOptions.cs`, `GatewayOptionsValidator.cs`
+- **Source**: batch_51/file_22.md
+
+## E2E Test Plan
+- [ ] Verify HELLO frame processing registers new microservice connections
+- [ ] Test connection cleanup on client disconnect
+- [ ] Verify GatewayHealthMonitorService detects stale connections
+- [ ] Verify edge cases and error handling

docs/features/unchecked/gateway/gateway-http-middleware-pipeline.md

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+# Gateway HTTP Middleware Pipeline
+
+## Module
+Gateway
+
+## Status
+IMPLEMENTED
+
+## Description
+Full HTTP middleware pipeline for the Gateway WebService including endpoint resolution, authorization with claims propagation, routing decision, transport dispatch, correlation ID tracking, tenant isolation, health checks, and global error handling.
+
+## Implementation Details
+- **Authorization**: `src/Gateway/StellaOps.Gateway.WebService/Authorization/AuthorizationMiddleware.cs` -- endpoint authorization
+- **Claims propagation**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/ClaimsPropagationMiddleware.cs` -- propagates authenticated claims to downstream services
+- **Correlation ID**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/CorrelationIdMiddleware.cs` -- request correlation tracking
+- **Routing**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/RequestRoutingMiddleware.cs` -- route resolution and dispatch
+- **Routes**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/GatewayRoutes.cs` -- route definitions
+- **Health checks**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/HealthCheckMiddleware.cs`
+- **Identity header policy**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/IdentityHeaderPolicyMiddleware.cs` -- identity header enforcement
+- **Sender constraints**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/SenderConstraintMiddleware.cs`
+- **Tenant isolation**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/TenantMiddleware.cs`
+- **Context keys**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/GatewayContextKeys.cs`
+- **Security**: `src/Gateway/StellaOps.Gateway.WebService/Security/AllowAllAuthenticationHandler.cs`
+- **Source**: batch_51/file_21.md
+
+## E2E Test Plan
+- [ ] Verify middleware pipeline executes in correct order
+- [ ] Test authorization middleware blocks unauthorized requests
+- [ ] Verify correlation IDs propagate through gateway to downstream services
+- [ ] Test tenant isolation prevents cross-tenant access
+- [ ] Verify edge cases and error handling

docs/features/unchecked/gateway/gateway-identity-header-strip-and-overwrite-policy-middleware.md

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+# Gateway Identity Header Strip-and-Overwrite Policy Middleware
+
+## Module
+Gateway
+
+## Status
+IMPLEMENTED
+
+## Description
+Security middleware that enforces identity header integrity at the Gateway/Router level. Strips incoming identity headers from external requests and overwrites them with verified claims from the authenticated session, preventing header spoofing attacks in service-to-service communication.
+
+## Implementation Details
+- **Identity header middleware**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/IdentityHeaderPolicyMiddleware.cs` -- strips incoming identity headers and overwrites with verified claims
+- **Claims store**: `src/Gateway/StellaOps.Gateway.WebService/Authorization/EffectiveClaimsStore.cs`, `IEffectiveClaimsStore.cs` -- manages effective claims after header processing
+- **Authorization middleware**: `src/Gateway/StellaOps.Gateway.WebService/Authorization/AuthorizationMiddleware.cs` -- enforces authorization after identity header processing
+- **Sender constraints**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/SenderConstraintMiddleware.cs` -- validates sender identity
+- **Source**: SPRINT_8100_0011_0002_gateway_identity_header_hardening.md
+
+## E2E Test Plan
+- [ ] Verify incoming identity headers are stripped from external requests
+- [ ] Test verified claims replace stripped headers correctly
+- [ ] Verify header spoofing attempts are blocked
+- [ ] Test service-to-service communication uses verified identity headers
+- [ ] Verify edge cases and error handling

docs/features/unchecked/gateway/router-authority-claims-integration.md

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+# Router Authority Claims Integration
+
+## Module
+Gateway
+
+## Status
+IMPLEMENTED
+
+## Description
+`IAuthorityClaimsProvider` integration enabling centralized Authority service to override endpoint claim requirements. Three-tier precedence: Code attributes < YAML config < Authority overrides. EffectiveClaimsStore caches resolved claims.
+
+## Implementation Details
+- **Effective claims store**: `src/Gateway/StellaOps.Gateway.WebService/Authorization/EffectiveClaimsStore.cs`, `IEffectiveClaimsStore.cs` -- caches resolved claims with three-tier precedence
+- **Authorization middleware**: `src/Gateway/StellaOps.Gateway.WebService/Authorization/AuthorizationMiddleware.cs` -- enforces Authority-provided claim requirements
+- **Claims propagation**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/ClaimsPropagationMiddleware.cs` -- propagates resolved claims downstream
+- **Gateway value parser**: `src/Gateway/StellaOps.Gateway.WebService/Configuration/GatewayValueParser.cs` -- parses configuration values for claims
+- **Source**: batch_52/file_09.md
+
+## E2E Test Plan
+- [ ] Verify three-tier precedence: code attributes < YAML config < Authority overrides
+- [ ] Test EffectiveClaimsStore caching behaves correctly
+- [ ] Verify Authority-provided claim overrides take highest priority
+- [ ] Test claims propagation to downstream services

docs/features/unchecked/gateway/router-heartbeat-and-health-monitoring.md

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+# Router Heartbeat and Health Monitoring
+
+## Module
+Gateway
+
+## Status
+IMPLEMENTED
+
+## Description
+Heartbeat protocol with configurable intervals, `HealthMonitorService` for stale instance detection, ping latency tracking with exponential moving average, Draining health status for graceful shutdown, and automatic instance removal on missed heartbeats.
+
+## Implementation Details
+- **Health monitor service**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayHealthMonitorService.cs` -- stale instance detection, heartbeat tracking
+- **Health check middleware**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/HealthCheckMiddleware.cs` -- health endpoint processing
+- **Gateway metrics**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayMetrics.cs` -- latency tracking, connection metrics
+- **Gateway hosted service**: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayHostedService.cs` -- connection lifecycle management
+- **Options**: `src/Gateway/StellaOps.Gateway.WebService/Configuration/GatewayOptions.cs` -- configurable heartbeat intervals
+- **Source**: batch_51/file_23.md
+
+## E2E Test Plan
+- [ ] Verify heartbeat protocol detects stale instances
+- [ ] Test configurable heartbeat intervals
+- [ ] Verify Draining status for graceful shutdown
+- [ ] Test automatic instance removal on missed heartbeats

docs/features/unchecked/gateway/router-payload-size-enforcement.md

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+# Router Payload Size Enforcement
+
+## Module
+Gateway
+
+## Status
+IMPLEMENTED
+
+## Description
+PayloadLimitsMiddleware with per-request, per-connection, and aggregate byte limits using `ByteCountingStream`. Returns HTTP 413 (payload too large), 429 (rate limited), or 503 (service unavailable) with configurable thresholds.
+
+## Implementation Details
+- **Gateway options**: `src/Gateway/StellaOps.Gateway.WebService/Configuration/GatewayOptions.cs` -- configurable payload size thresholds
+- **Options validator**: `src/Gateway/StellaOps.Gateway.WebService/Configuration/GatewayOptionsValidator.cs` -- validates payload limit configuration
+- **Routing middleware**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/RequestRoutingMiddleware.cs` -- request routing with size checks
+- **Sender constraints**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/SenderConstraintMiddleware.cs` -- sender-level enforcement
+- **Source**: batch_52/file_02.md
+
+## E2E Test Plan
+- [ ] Verify HTTP 413 returned for oversized payloads
+- [ ] Test per-request, per-connection, and aggregate limits independently
+- [ ] Verify configurable thresholds are respected
+- [ ] Test HTTP 429 and 503 responses for rate limiting and service unavailability