Maxofpower · Sep 4, 2026 · Sep 4, 2026
diff --git a/AGENTS.md b/AGENTS.md
@@ -22,7 +22,7 @@ Do not treat FeatureFusion as a framework. Install a BuildingBlock only when it
 | `BuildingBlocks.Mediator` | CQRS Send + ordered pipeline | [Mediator](src/BuildingBlocks/Mediator/AGENTS.md) |
 | `BuildingBlocks.Pagination.EntityFrameworkCore` | Keyset (cursor) paging for EF Core (**1.1.0**: any-width Npgsql row comparison, NULLS, `HasKeysetIndex` + `NullOrder`) | [Pagination.EF](src/BuildingBlocks/Pagination.EntityFrameworkCore/AGENTS.md) |
 | `BuildingBlocks.Mcp` | Same logic as HTTP as deny-by-default MCP tools | [Mcp](src/BuildingBlocks/Mcp/AGENTS.md) |
-| `BuildingBlocks.Idempotency` | HTTP Idempotency-Key + optional Redis lock | [Idempotency](src/BuildingBlocks/Idempotency/AGENTS.md) |
+| `BuildingBlocks.Idempotency` | HTTP Idempotency-Key + optional Redis lock (**1.0.1**: System.Text.Json, package icon) | [Idempotency](src/BuildingBlocks/Idempotency/AGENTS.md) |
 | `BuildingBlocks.Telemetry` | Config-driven OpenTelemetry (not a SigNoz SDK) | [Telemetry](src/BuildingBlocks/Telemetry/AGENTS.md) |
 | `BuildingBlocks.Aspire.Hosting.SigNoz` | Local AppHost SigNoz only (net10) | [SigNoz](src/BuildingBlocks/Aspire.Hosting.SigNoz/AGENTS.md) |
 

diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -25,6 +25,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - No hard PackageReference on Npgsql in the nupkg; row comparison requires the host already using Npgsql.EntityFrameworkCore.PostgreSQL.
 - Lab: `NameThenPrice` product sort (3-column keyset) + `AddBuildingBlocksPagination` / `UseBuildingBlocksPagination` on FeatureFusion.
 
+## BuildingBlocks.Idempotency [1.0.1] - 2026-09-04
+
+### Changed
+
+- **System.Text.Json** for cache envelope and MVC `ObjectResult` body capture (dropped `Newtonsoft.Json`). Minimal API path already used STJ. Default property names remain PascalCase.
+- **Package icon** (`idempotency-icon.png`) for NuGet listing parity with other BuildingBlocks.
+
+### Notes
+
+- Cache JSON written by 1.0.0 (Newtonsoft) and 1.0.1 (STJ) are compatible for `IdempotencyCacheEntry` under default options; clear cache if you see odd replay after upgrading mid-flight.
+- Package still depends on `Ulid` and `StackExchange.Redis` (Redis lock); hosts that use the lock must register `IConnectionMultiplexer`.
+
 ## BuildingBlocks.Idempotency [1.0.0] - 2026-09-04
 
 ### Added
@@ -45,7 +57,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Notes
 
 - Distinct from MCP write idempotency (`UseMemoryIdempotency` / `IMcpIdempotencyStore` in BuildingBlocks.Mcp)
-- Package depends on `Newtonsoft.Json` (MVC ObjectResult capture), `Ulid`, and `StackExchange.Redis` (Redis lock); hosts that use the lock must register `IConnectionMultiplexer`
+- Package depended on `Newtonsoft.Json` (MVC ObjectResult capture), `Ulid`, and `StackExchange.Redis` (Redis lock); hosts that use the lock must register `IConnectionMultiplexer`
 
 ## BuildingBlocks.Pagination.EntityFrameworkCore [1.0.0] - 2026-08-29
 

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -46,7 +46,9 @@ Release tags (must match the project `<Version>`): `mediator-v*`, `mcp-v*`, `ide
 
 - HTTP `Idempotency-Key` only — do not fold MCP `IMcpIdempotencyStore` into this package.
 - Host owns `IDistributedCache` (and `IConnectionMultiplexer` when using the Redis lock).
+- Prefer **System.Text.Json** for cache / MVC body capture (no Newtonsoft.Json).
 - Lab provenance: Experiments 3 / 4 / 12 under `tests/Lab/IntegrationTests/Experiments/`.
+- Release tag: `idempotency-v*` must match `<Version>` (current **1.0.1**).
 
 ### BuildingBlocks.Telemetry / SigNoz hosting
 

diff --git a/README.md b/README.md
@@ -60,7 +60,7 @@ NuGet packages you can install in **your** hosts. The FeatureFusion API is a sho
 |---------|---------|------|------|
 | **[BuildingBlocks.Mediator](https://www.nuget.org/packages/BuildingBlocks.Mediator)** | **1.1.0** | CQRS **Send** + ordered pipeline (`ICommand` / `IQuery`, typed behaviors, opt-in traces + metrics) | net8 / net9 / net10 |
 | **[BuildingBlocks.Mcp](https://www.nuget.org/packages/BuildingBlocks.Mcp)** | **1.0.0** | Message types → MCP tools on the official SDK (deny-by-default, `McpResult`, HTTP + opt-in stdio) | net8 / net9 / net10 |
-| **[BuildingBlocks.Idempotency](https://www.nuget.org/packages/BuildingBlocks.Idempotency)** | **1.0.0** | HTTP **Idempotency-Key** — MVC + Minimal API, 2xx envelope replay, ProblemDetails, optional Redis lock, fingerprint, ActivitySource | net8 / net9 / net10 |
+| **[BuildingBlocks.Idempotency](https://www.nuget.org/packages/BuildingBlocks.Idempotency)** | **1.0.1** | HTTP **Idempotency-Key** — MVC + Minimal API, 2xx envelope replay, ProblemDetails, optional Redis lock, fingerprint, ActivitySource | net8 / net9 / net10 |
 | **[BuildingBlocks.Pagination.EntityFrameworkCore](https://www.nuget.org/packages/BuildingBlocks.Pagination.EntityFrameworkCore)** | **1.1.0** | Typed keyset (cursor) pagination for EF Core (IR bundled): any-width Npgsql row comparison, `NULLS FIRST/LAST`, `HasKeysetIndex` + `NullOrder` | net8 / net9 / net10 |
 | **[BuildingBlocks.Telemetry](https://www.nuget.org/packages/BuildingBlocks.Telemetry)** | **1.0.2** | Config-driven OpenTelemetry (traces, metrics, logs) + `IntegrateMediator` / opt-in `IntegrateMcp` | net8 / net9 / net10 |
 | **[BuildingBlocks.Aspire.Hosting.SigNoz](https://www.nuget.org/packages/BuildingBlocks.Aspire.Hosting.SigNoz)** | **1.0.0** | Local-dev Aspire `AddSigNoz()` + `WithSigNozOtlpExporter` | net10 (AppHost) |
@@ -362,7 +362,7 @@ Cursor HTTP:
 
 ASP.NET Core HTTP **Idempotency-Key** for MVC and Minimal API. Host-owned `IDistributedCache`, **2xx** envelope replay, ProblemDetails on conflicts, optional Redis SET NX lock, opt-in method/path/body fingerprint, per-endpoint TTL, optional ActivitySource. Distinct from MCP write idempotency (`UseMemoryIdempotency` / `IMcpIdempotencyStore` above).
 
-**What's new in 1.0.0:** shared `IdempotencyGate` for MVC + Minimal API, 2xx envelope replay, ProblemDetails, optional Redis lock / fingerprint / telemetry. NuGet and release badges resolve after `idempotency-v1.0.0` is tagged and published.
+**What's new in 1.0.1:** NuGet package icon; **System.Text.Json** for cache envelope and MVC `ObjectResult` capture (dropped Newtonsoft.Json). No API surface change from 1.0.0.
 
 ```bash
 dotnet add package BuildingBlocks.Idempotency
@@ -718,7 +718,7 @@ Install the packages above in your own hosts, **or** clone this repo and run **F
 | Telemetry | **`BuildingBlocks.Telemetry`** in ServiceDefaults; **`BuildingBlocks.Aspire.Hosting.SigNoz`** on AppHost |
 | Event bus | RabbitMQ + transactional outbox/inbox, DLQ, dedup hooks |
 | Aspire lab | AppHost orchestration for Postgres, Redis, RabbitMQ, Memcached, SigNoz |
-| HTTP idempotency | **`BuildingBlocks.Idempotency`** — MVC + Minimal API, 2xx envelope replay, optional Redis lock (`POST /api/v2/Order/order`) |
+| HTTP idempotency | **`BuildingBlocks.Idempotency` 1.0.1** — MVC + Minimal API, 2xx envelope replay, System.Text.Json, optional Redis lock (`POST /api/v2/Order/order`) |
 | Feature flags (demo) | ASP.NET Core Feature Management + custom filters (claims / VIP) |
 | API surface | Versioned controllers + Minimal APIs, FluentValidation patterns |
 | Gateway | YARP reverse proxy + Memcached distributed rate limiting |
@@ -943,7 +943,7 @@ Conditional features via Microsoft.FeatureManagement and custom filters (e.g. VI
 
 ### HTTP idempotency (BuildingBlocks.Idempotency)
 
-REST idempotency with `IDistributedCache` status tracking, MVC `[Idempotent]` / Minimal API `WithIdempotency`, and optional Redis lock (`POST /api/v2/Order/order`, smoke `POST /api/v2/idempotency-smoke`). See [BuildingBlocks.Idempotency](#buildingblocksidempotency).
+REST idempotency with `IDistributedCache` status tracking, MVC `[Idempotent]` / Minimal API `WithIdempotency`, optional Redis lock, and **System.Text.Json** cache/body serialization (`POST /api/v2/Order/order`, smoke `POST /api/v2/idempotency-smoke`). Package **1.0.1**. See [BuildingBlocks.Idempotency](#buildingblocksidempotency).
 
 - [Idempotency with CQRS](https://www.linkedin.com/feed/update/urn:li:activity:7303686809891356676/)
 - [IdempotentFusion project](https://www.linkedin.com/feed/update/urn:li:activity:7309149985307029504/) (historical Lab name)
@@ -986,7 +986,7 @@ See [Pagination showcase](#pagination-showcase) for the FeatureFusion catalog (`
 | **Polling publisher** | `OutBoxWorker` background poll → publish |
 | **Dead letter queue** | EventBus DLX / DLQ topology |
 | **Message deduplication** | Inbox + `MessageDeduplicationService` |
-| **Idempotency** | `BuildingBlocks.Idempotency` — `[Idempotent]` / `WithIdempotency`, cache envelope, optional Redis lock |
+| **Idempotency** | `BuildingBlocks.Idempotency` **1.0.1** — `[Idempotent]` / `WithIdempotency`, System.Text.Json cache envelope, optional Redis lock |
 | **Feature toggle** | ASP.NET Core Feature Management + custom filters |
 | **Rate limiting** | ApiGateway Memcached fixed-window limiter |
 | **Circuit breaker / resilience** | Polly `ResiliencePipelineFactory` |

diff --git a/docs/building-blocks/idempotency.md b/docs/building-blocks/idempotency.md
@@ -2,7 +2,15 @@
 
 ASP.NET Core HTTP **Idempotency-Key** for MVC and Minimal API: host-owned `IDistributedCache`, optional Redis lock, opt-in fingerprint, ProblemDetails on conflicts, optional ActivitySource.
 
-Canonical consumer docs: [package README](../../src/BuildingBlocks/Idempotency/PACKAGE_README.md). Agent notes: [AGENTS.md](../../src/BuildingBlocks/Idempotency/AGENTS.md).
+[![NuGet](https://img.shields.io/nuget/v/BuildingBlocks.Idempotency.svg)](https://www.nuget.org/packages/BuildingBlocks.Idempotency)
+[![GitHub Release](https://img.shields.io/github/v/release/Maxofpower/FeatureFusion?filter=idempotency-v*&logo=github&label=GitHub%20Release)](https://github.com/Maxofpower/FeatureFusion/releases?q=idempotency-v)
+
+**Current package version: 1.0.1.** Canonical consumer docs: [package README](../../src/BuildingBlocks/Idempotency/PACKAGE_README.md). Agent notes: [AGENTS.md](../../src/BuildingBlocks/Idempotency/AGENTS.md).
+
+## What's new in 1.0.1
+
+- NuGet package icon
+- **System.Text.Json** for cache envelope and MVC `ObjectResult` capture (no Newtonsoft.Json). No public API change from 1.0.0.
 
 ## Install
 

diff --git a/docs/building-blocks/pagination.md b/docs/building-blocks/pagination.md
@@ -2,6 +2,9 @@
 
 Typed keyset (cursor) pagination. **One NuGet:** `BuildingBlocks.Pagination.EntityFrameworkCore` **1.1.0** (IR + EF Core adapter). Dapper is an in-repo project, not a package.
 
+[![NuGet](https://img.shields.io/nuget/v/BuildingBlocks.Pagination.EntityFrameworkCore.svg)](https://www.nuget.org/packages/BuildingBlocks.Pagination.EntityFrameworkCore)
+[![GitHub Release](https://img.shields.io/github/v/release/Maxofpower/FeatureFusion?filter=pagination-v*&logo=github&label=GitHub%20Release)](https://github.com/Maxofpower/FeatureFusion/releases?q=pagination-v)
+
 See ADR [0003](../adr/0003-pagination-keyset.md), the [test matrix](PAGINATION_TEST_MATRIX.md), and [`PACKAGE_README.md`](../../src/BuildingBlocks/Pagination.EntityFrameworkCore/PACKAGE_README.md).
 
 ## Install

diff --git a/docs/lab/README.md b/docs/lab/README.md
@@ -53,7 +53,7 @@ Aspire: Postgres │ Redis │ RabbitMQ │ Memcached │ SigNoz
 | Family | Experiments | Outcome |
 |--------|-------------|---------|
 | Keyset pagination abuse | 1–2 | Careless HTTP/MCP cursor clients characterized |
-| HTTP Redis idempotency | 3, 4, 12, 15 | Miss/hit, concurrency, fingerprint, ProcessingTtl lease overlap → **BuildingBlocks.Idempotency 1.0.0** |
+| HTTP Redis idempotency | 3, 4, 12, 15 | Miss/hit, concurrency, fingerprint, ProcessingTtl lease overlap → **BuildingBlocks.Idempotency 1.0.1** |
 | MCP write / agent-client semantics | 6, 13, 14, 16 | Confirm+replay, regenerated keys amplify, concurrent same-key safe, **IMcpRateLimiter** bounds distinct-key storms |
 | Outbox → bus → inbox happy path | 5, 8, 10 | HTTP + MCP parity; outbox row lifecycle |
 | Consumer dedup / failure | 7, 9, 11, 17 | Inbox dedup; retry/DLQ; `EnableDeduplication` + `processed_messages` |
@@ -74,7 +74,7 @@ Do **not** extract: Scenario DSL, one-off test gates, fixed-permit rate limiters
 
 ## Package / versioning (current)
 
-- Each packable project owns `<Version>` in its `.csproj` (e.g. `BuildingBlocks.Pagination.EntityFrameworkCore` `1.1.0`, `BuildingBlocks.Mcp` `1.0.0`).
+- Each packable project owns `<Version>` in its `.csproj` (e.g. `BuildingBlocks.Pagination.EntityFrameworkCore` `1.1.0`, `BuildingBlocks.Idempotency` `1.0.1`, `BuildingBlocks.Mcp` `1.0.0`).
 - Release tags are package-prefixed (`mcp-v*`, `mediator-v*`, `telemetry-v*`, …) and must match `<Version>`.
 - Per-package GitHub Actions: `*-yml` CI + `*-release.yml` pack / Trusted Publishing to nuget.org (`idempotency.yml` / `idempotency-release.yml` for this package).
 - IntegrationTests / Exp 1–18 are **not** in CI (local Aspire/Docker).

diff --git a/docs/linkedin-posts.md b/docs/linkedin-posts.md
@@ -15,7 +15,7 @@ Umbrella narrative (lab → packages): [Medium](https://medium.com/@m2hweb86/fea
 | `cursor-pagination` | Reusable generic bidirectional keyset (cursor) pagination | published | https://www.linkedin.com/feed/update/urn:li:activity:7325068550614708225/ | `src/BuildingBlocks/Pagination.EntityFrameworkCore` + lab `ProductService` | `building-blocks-overview` | Typed `SortKey`, opaque cursors, one EF Core nupkg (**1.1.0**: Npgsql row comparison, NULLS interceptor). Optional `QueryHint` (default none). Lab: MVC `POST /api/v2/Product/products`, Minimal API `GET /api/v2/products-page` (POST kept), Dapper `products-dapper`, MCP `products.list` — one `GetProductsQuery`. |
 | `mcp-message-tools` | Message types as MCP tools | published | https://lnkd.in/p/e4-FrM44 | `src/BuildingBlocks/Mcp` + `docs/building-blocks/mcp.md` | `building-blocks-overview` | Deny-by-default `[McpTool]` / `WithMcp` / `MapTool` on the official SDK. Same logic as HTTP. Interim permalink is the umbrella post until a dedicated MCP post ships. Not OpenAPI, not a SOLID linter. |
 | `idempotency-cqrs` | Idempotency with CQRS commands | published | https://www.linkedin.com/feed/update/urn:li:activity:7303686809891356676/ | (pattern lab) | `idempotentfusion` | **Lab only, not NuGet.** Command-level idempotency via reusable `IdentifiedCommand<T,R>` + ULID `Idempotency-Key`, intercepting before handlers. Complementary to Mediator — not core v1. |
-| `idempotentfusion` | IdempotentFusion (REST API) | published | https://www.linkedin.com/feed/update/urn:li:activity:7309149985307029504/ | `src/BuildingBlocks/Idempotency` + Lab `OrderController` | `idempotency-cqrs` | HTTP Idempotency-Key via `BuildingBlocks.Idempotency` (Redis cache host-owned, optional SET NX lock). Lab sets `UserIdFallback = "123"`. |
+| `idempotentfusion` | IdempotentFusion (REST API) | published | https://www.linkedin.com/feed/update/urn:li:activity:7309149985307029504/ | `src/BuildingBlocks/Idempotency` + Lab `OrderController` | `idempotency-cqrs` | HTTP Idempotency-Key via `BuildingBlocks.Idempotency` **1.0.1** (Redis cache host-owned, optional SET NX lock, System.Text.Json). Lab sets `UserIdFallback = "123"`. |
 | `eventbus-outbox-inbox` | Lightweight modular EventBus (outbox, inbox, DLQ) | published | https://www.linkedin.com/posts/mhhoseini_a-lightweight-modular-eventbus-implementation-activity-7316381126535663631-6FiI | `src/Lab/EventBus` | `aspire-integration-testing` | **Lab only, not NuGet.** Sibling of Mediator Send — not `INotification`. |
 | `aspire-integration-testing` | Integration testing microservices with Aspire | published | https://www.linkedin.com/posts/mhhoseini_integration-testing-microservices-with-aspire-activity-7321088554565029888-Z0a8 | `tests/Lab/IntegrationTests` + `src/Lab/FeatureFusion.AppHost` | `building-blocks-overview` | **Lab only, not NuGet.** Aspire-hosted fixture against real Postgres / Redis / RabbitMQ / Memcached. |
 | `ddd-architecture` | Diving into DDD | published | https://www.linkedin.com/posts/mhhoseini_diving-into-ddd-activity-7427983383126896640-Eaaw | lab vertical slices under `src/Lab/FeatureFusion/Features` | `medium-engineering-lab` | **Lab only, not NuGet.** Architecture notes; FeatureFusion is the showcase host, not a DDD framework. |