diff --git a/AGENTS.md b/AGENTS.md
index 96daa64..0740320 100644
--- 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
index 1362956..77b4fba 100644
--- 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
index 3ab853b..257fa1e 100644
--- 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
index 104d8bf..8d602d2 100644
--- 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
index 8f4dfe1..751d555 100644
--- 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
index a10a805..5d4b558 100644
--- 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
index 272a112..3a8d7c1 100644
--- 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
index 63e72f9..979d753 100644
--- 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. |
diff --git a/llms.txt b/llms.txt
index 5f0a9ba..23ae73c 100644
--- a/llms.txt
+++ b/llms.txt
@@ -4,11 +4,26 @@
 
 ## Canonical
 
-- [README](https://github.com/Maxofpower/FeatureFusion/blob/main/README.md): lab + package overview
+- [README](https://github.com/Maxofpower/FeatureFusion/blob/main/README.md): lab + package overview (versions below)
 - [AGENTS.md](https://github.com/Maxofpower/FeatureFusion/blob/main/AGENTS.md): repo map for coding agents
+- [CHANGELOG](https://github.com/Maxofpower/FeatureFusion/blob/main/CHANGELOG.md): BuildingBlocks release notes
 - [Medium](https://medium.com/@m2hweb86/featurefusion-an-engineering-lab-that-extracts-reusable-net-building-blocks-28152cafafb9): lab-to-package narrative
 - [Writing catalog](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/linkedin-posts.md): LinkedIn / Medium post ↔ code map
 - [CONTRIBUTING](https://github.com/Maxofpower/FeatureFusion/blob/main/CONTRIBUTING.md)
+- [web/README](https://github.com/Maxofpower/FeatureFusion/blob/main/web/README.md): reserved Next.js frontend root (not in the .NET solution)
+
+## Packages (current versions)
+
+| Package | Version | NuGet | GitHub releases |
+|---------|---------|-------|-----------------|
+| BuildingBlocks.Mediator | 1.1.0 | [nuget.org](https://www.nuget.org/packages/BuildingBlocks.Mediator/1.1.0) | [mediator-v*](https://github.com/Maxofpower/FeatureFusion/releases?q=mediator-v) |
+| BuildingBlocks.Mcp | 1.0.0 | [nuget.org](https://www.nuget.org/packages/BuildingBlocks.Mcp/1.0.0) | [mcp-v*](https://github.com/Maxofpower/FeatureFusion/releases?q=mcp-v) |
+| BuildingBlocks.Idempotency | 1.0.1 | [nuget.org](https://www.nuget.org/packages/BuildingBlocks.Idempotency/1.0.1) | [idempotency-v*](https://github.com/Maxofpower/FeatureFusion/releases?q=idempotency-v) |
+| BuildingBlocks.Pagination.EntityFrameworkCore | 1.1.0 | [nuget.org](https://www.nuget.org/packages/BuildingBlocks.Pagination.EntityFrameworkCore/1.1.0) | [pagination-v*](https://github.com/Maxofpower/FeatureFusion/releases?q=pagination-v) |
+| BuildingBlocks.Telemetry | 1.0.2 | [nuget.org](https://www.nuget.org/packages/BuildingBlocks.Telemetry/1.0.2) | [telemetry-v*](https://github.com/Maxofpower/FeatureFusion/releases?q=telemetry-v) |
+| BuildingBlocks.Aspire.Hosting.SigNoz | 1.0.0 | [nuget.org](https://www.nuget.org/packages/BuildingBlocks.Aspire.Hosting.SigNoz/1.0.0) | [signoz-v*](https://github.com/Maxofpower/FeatureFusion/releases?q=signoz-v) |
+
+**Highlights:** Pagination **1.1.0** — any-width Npgsql row comparison, `NULLS FIRST/LAST` interceptor, `HasKeysetIndex` + `NullOrder`. Idempotency **1.0.1** — package icon, System.Text.Json only (no Newtonsoft).
 
 ## BuildingBlocks — NuGet READMEs
 
@@ -33,13 +48,17 @@
 ## Guides
 
 - [Getting started](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/getting-started.md)
+- [Cookbook](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/cookbook.md)
 - [Mediator](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/mediator.md)
-- [Idempotency](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/idempotency.md)
-- [Pagination](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/pagination.md)
+- [Pipeline behaviors](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/pipeline-behaviors.md)
+- [Idempotency](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/idempotency.md) (1.0.1)
+- [Pagination](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/pagination.md) (1.1.0)
+- [Pagination test matrix](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/PAGINATION_TEST_MATRIX.md)
 - [MCP](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/mcp.md)
 - [Telemetry](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/building-blocks/telemetry.md)
+- [ADR 0003 — pagination keyset](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/adr/0003-pagination-keyset.md)
 
 ## Lab integration experiments
 
 - [Lab charter](https://github.com/Maxofpower/FeatureFusion/blob/main/docs/lab/README.md): evidence families, extraction rules, roadmap
-- [Experiments README](https://github.com/Maxofpower/FeatureFusion/blob/main/tests/Lab/IntegrationTests/Experiments/README.md): behavioral experiment catalog Exp 1–18 + MAF prototype, evidence model, conventions
+- [Experiments README](https://github.com/Maxofpower/FeatureFusion/blob/main/tests/Lab/IntegrationTests/Experiments/README.md): behavioral experiment catalog Exp 1–18 + MAF prototype, evidence model, conventions (HTTP Idempotency Exp 3/4/12/15 → package 1.0.1)
diff --git a/src/BuildingBlocks/Aspire.Hosting.SigNoz/PACKAGE_README.md b/src/BuildingBlocks/Aspire.Hosting.SigNoz/PACKAGE_README.md
index 47c3128..1025437 100644
--- a/src/BuildingBlocks/Aspire.Hosting.SigNoz/PACKAGE_README.md
+++ b/src/BuildingBlocks/Aspire.Hosting.SigNoz/PACKAGE_README.md
@@ -5,6 +5,7 @@ Local Aspire AppHost integration for SigNoz. Production telemetry belongs in `Bu
 **TFM:** net10.0 (Aspire 13.4.6 AppHost). Docker required.
 
 [![NuGet](https://img.shields.io/nuget/v/BuildingBlocks.Aspire.Hosting.SigNoz.svg)](https://www.nuget.org/packages/BuildingBlocks.Aspire.Hosting.SigNoz)
+[![GitHub Release](https://img.shields.io/github/v/release/Maxofpower/FeatureFusion?filter=signoz-v*&logo=github&label=GitHub%20Release)](https://github.com/Maxofpower/FeatureFusion/releases?q=signoz-v)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
 | API | Role |
diff --git a/src/BuildingBlocks/Idempotency/AGENTS.md b/src/BuildingBlocks/Idempotency/AGENTS.md
index f6050bb..efade0b 100644
--- a/src/BuildingBlocks/Idempotency/AGENTS.md
+++ b/src/BuildingBlocks/Idempotency/AGENTS.md
@@ -1,6 +1,6 @@
 # BuildingBlocks.Idempotency — agent notes
 
-**Status: COMPLETE — 1.0.0**
+**Status: COMPLETE — 1.0.1**
 
 HTTP **Idempotency-Key** for ASP.NET Core. Consumer docs: [PACKAGE_README.md](PACKAGE_README.md). Lab guide: [docs/building-blocks/idempotency.md](../../../docs/building-blocks/idempotency.md).
 
@@ -35,7 +35,7 @@ app.MapPost("/path", handler).WithIdempotency(useLock: true);
 - Errors: ProblemDetails (`https://buildingblocks.dev/errors/idempotency/...`)
 - Fingerprint default **off** (Exp 3); on → method+path+body SHA-256 (Exp 12)
 - Lock only around GetOrCreate when `UseLock` (Exp 4)
-- MVC ObjectResult body: Newtonsoft.Json; Minimal API `IResult`: System.Text.Json
+- MVC ObjectResult body and cache envelope: System.Text.Json; Minimal API `IResult`: System.Text.Json
 - Telemetry optional; no cache-key tag by default; no BuildingBlocks.Telemetry package ref
 
 ## Lab evidence
diff --git a/src/BuildingBlocks/Idempotency/AspNetCore/IdempotentAttributeFilter.cs b/src/BuildingBlocks/Idempotency/AspNetCore/IdempotentAttributeFilter.cs
index 1cd12f1..c219850 100644
--- a/src/BuildingBlocks/Idempotency/AspNetCore/IdempotentAttributeFilter.cs
+++ b/src/BuildingBlocks/Idempotency/AspNetCore/IdempotentAttributeFilter.cs
@@ -1,9 +1,9 @@
+using System.Text.Json;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.Filters;
 using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.Logging;
-using Newtonsoft.Json;
 
 namespace BuildingBlocks.Idempotency.AspNetCore;
 
@@ -121,7 +121,7 @@ await _gate
 
 	/// <summary>
 	/// Captures a successful action result for cache storage.
-	/// Keeps Newtonsoft serialization for ObjectResult values (same representation as historical Lab/Exp 3).
+	/// Serializes <see cref="ObjectResult"/> values with <see cref="JsonSerializer"/> (System.Text.Json).
 	/// Caches all HTTP 2xx results (including null StatusCode meaning 200).
 	/// </summary>
 	internal static bool TryCaptureSuccessfulResponse(
@@ -138,7 +138,7 @@ internal static bool TryCaptureSuccessfulResponse(
 		{
 			statusCode = obj.StatusCode ?? StatusCodes.Status200OK;
 			contentType = "application/json";
-			body = JsonConvert.SerializeObject(obj.Value);
+			body = JsonSerializer.Serialize(obj.Value);
 			return true;
 		}
 
diff --git a/src/BuildingBlocks/Idempotency/BuildingBlocks.Idempotency.csproj b/src/BuildingBlocks/Idempotency/BuildingBlocks.Idempotency.csproj
index c7b1a3b..8c418e4 100644
--- a/src/BuildingBlocks/Idempotency/BuildingBlocks.Idempotency.csproj
+++ b/src/BuildingBlocks/Idempotency/BuildingBlocks.Idempotency.csproj
@@ -12,11 +12,11 @@
     <IsPackable>true</IsPackable>
     <PackageId>BuildingBlocks.Idempotency</PackageId>
     <Title>BuildingBlocks.Idempotency</Title>
-    <Version>1.0.0</Version>
+    <Version>1.0.1</Version>
     <Authors>Mohammad Hasan Hosseini</Authors>
     <Company>Mohammad Hasan Hosseini</Company>
     <Copyright>Copyright (c) 2026 Mohammad Hasan Hosseini</Copyright>
-    <Description>ASP.NET Core HTTP Idempotency-Key filter (MVC + Minimal API): shared IdempotencyGate over IDistributedCache, 2xx response envelope replay, RFC 9457 ProblemDetails errors, optional Redis SET NX lock, ProcessingTtl abandoned recovery, opt-in method+path+body fingerprinting, per-endpoint TTL, and optional ActivitySource instrumentation. Host owns cache registration. No MCP or Telemetry package coupling.</Description>
+    <Description>ASP.NET Core HTTP Idempotency-Key filter (MVC + Minimal API): shared IdempotencyGate over IDistributedCache, 2xx response envelope replay, RFC 9457 ProblemDetails errors, optional Redis SET NX lock, ProcessingTtl abandoned recovery, opt-in method+path+body fingerprinting, per-endpoint TTL, and optional ActivitySource instrumentation. Host owns cache registration. Uses System.Text.Json. No MCP or Telemetry package coupling.</Description>
     <PackageTags>idempotency;idempotency-key;aspnetcore;minimal-api;redis;distributed-lock;distributed-cache;fingerprint;problemdetails;opentelemetry;net8;net9;net10</PackageTags>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/Maxofpower/FeatureFusion</PackageProjectUrl>
@@ -24,7 +24,7 @@
     <RepositoryType>git</RepositoryType>
     <PackageReadmeFile>PACKAGE_README.md</PackageReadmeFile>
     <PackageIcon>idempotency-icon.png</PackageIcon>
-    <PackageReleaseNotes>1.0.0: IdempotencyGate; MVC + Minimal API; 2xx envelope replay; ProblemDetails errors; ProcessingTtl / EntryTtl + per-endpoint overrides; optional Redis lock; opt-in method+path+body fingerprint; fluent UseRedisLock/UseTelemetry. Host owns IDistributedCache. https://github.com/Maxofpower/FeatureFusion/blob/main/CHANGELOG.md</PackageReleaseNotes>
+    <PackageReleaseNotes>1.0.1: package icon; System.Text.Json for cache + MVC ObjectResult (drop Newtonsoft.Json). https://github.com/Maxofpower/FeatureFusion/blob/main/CHANGELOG.md</PackageReleaseNotes>
     <PublishRepositoryUrl>true</PublishRepositoryUrl>
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
     <IncludeSymbols>true</IncludeSymbols>
@@ -43,7 +43,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageReference Include="StackExchange.Redis" Version="2.8.16" />
     <PackageReference Include="Ulid" Version="1.3.4" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All" />
diff --git a/src/BuildingBlocks/Idempotency/Core/IdempotencyGate.cs b/src/BuildingBlocks/Idempotency/Core/IdempotencyGate.cs
index 4711028..6259824 100644
--- a/src/BuildingBlocks/Idempotency/Core/IdempotencyGate.cs
+++ b/src/BuildingBlocks/Idempotency/Core/IdempotencyGate.cs
@@ -1,8 +1,8 @@
 using System.Text;
+using System.Text.Json;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.Logging;
-using Newtonsoft.Json;
 
 namespace BuildingBlocks.Idempotency;
 
@@ -166,7 +166,7 @@ public async Task CompleteAsync(
 			RequestFingerprint = requestFingerprint,
 			ProcessingExpiresAtUtc = null
 		};
-		var cacheEntryData = JsonConvert.SerializeObject(cacheEntry);
+		var cacheEntryData = JsonSerializer.Serialize(cacheEntry);
 		var entryTtl = endpoint.EntryTtl ?? _options.EntryTtl;
 
 		await _distributedCache.SetAsync(
@@ -289,7 +289,7 @@ await _idempotencyLock.ReleaseAsync(lockKey, lockValue, CancellationToken.None)
 		var cacheData = await _distributedCache.GetAsync(cacheKey, cancellationToken).ConfigureAwait(false);
 		if (cacheData != null)
 		{
-			var existing = JsonConvert.DeserializeObject<IdempotencyCacheEntry>(Encoding.UTF8.GetString(cacheData));
+			var existing = JsonSerializer.Deserialize<IdempotencyCacheEntry>(Encoding.UTF8.GetString(cacheData));
 			if (existing is not null
 				&& existing.Status == "Processing"
 				&& IsProcessingExpired(existing))
@@ -310,7 +310,7 @@ await _idempotencyLock.ReleaseAsync(lockKey, lockValue, CancellationToken.None)
 			RequestFingerprint = requestFingerprint,
 			ProcessingExpiresAtUtc = expiresAt
 		};
-		var cacheEntryData = JsonConvert.SerializeObject(cacheEntry);
+		var cacheEntryData = JsonSerializer.Serialize(cacheEntry);
 
 		await _distributedCache.SetAsync(
 			cacheKey,
@@ -345,7 +345,7 @@ private async Task MarkRequestAsProcessingAsync(
 			RequestFingerprint = requestFingerprint,
 			ProcessingExpiresAtUtc = DateTimeOffset.UtcNow.Add(processingTtl)
 		};
-		var cacheEntryData = JsonConvert.SerializeObject(cacheEntry);
+		var cacheEntryData = JsonSerializer.Serialize(cacheEntry);
 
 		await _distributedCache.SetAsync(
 			cacheKey,
diff --git a/src/BuildingBlocks/Idempotency/PACKAGE_README.md b/src/BuildingBlocks/Idempotency/PACKAGE_README.md
index b10130e..0ac1804 100644
--- a/src/BuildingBlocks/Idempotency/PACKAGE_README.md
+++ b/src/BuildingBlocks/Idempotency/PACKAGE_README.md
@@ -3,18 +3,24 @@
 ASP.NET Core **Idempotency-Key** for MVC and Minimal API. Host-owned `IDistributedCache`, optional Redis lock, opt-in request fingerprint, RFC 9457 ProblemDetails on conflicts, optional ActivitySource.
 
 [![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)
 [![.NET](https://img.shields.io/badge/.NET-8%20%7C%209%20%7C%2010-512BD4)](https://dotnet.microsoft.com/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
 Requires **.NET 8**, **.NET 9**, or **.NET 10**.
 
+## What's new in 1.0.1
+
+- **Package icon** for NuGet listing parity with other BuildingBlocks
+- **System.Text.Json** for the cache envelope and MVC `ObjectResult` body capture (dropped `Newtonsoft.Json`). Minimal API already used STJ. No public API change from 1.0.0.
+
 ## Install
 
 ```bash
 dotnet add package BuildingBlocks.Idempotency
 ```
 
-## Features (1.0.0)
+## Features
 
 - Shared gate for **MVC** (`[Idempotent]`) and **Minimal API** (`WithIdempotency`)
 - Cache **HTTP 2xx** envelopes (status, content-type, body) and replay them
@@ -26,6 +32,7 @@ dotnet add package BuildingBlocks.Idempotency
 - `DuplicateCompletedBehavior`: Replay (default) or Conflict
 - ProblemDetails errors with stable `type` URIs
 - Optional telemetry (`.UseTelemetry()`); host `AddSource("BuildingBlocks.Idempotency")`
+- **System.Text.Json** only (cache + MVC + Minimal API)
 
 ## Quick start
 
diff --git a/src/BuildingBlocks/Mcp/PACKAGE_README.md b/src/BuildingBlocks/Mcp/PACKAGE_README.md
index ecf800c..40f5c1a 100644
--- a/src/BuildingBlocks/Mcp/PACKAGE_README.md
+++ b/src/BuildingBlocks/Mcp/PACKAGE_README.md
@@ -3,6 +3,7 @@
 Map **application message types** (commands, queries, DTOs) and **public static Minimal API methods** to MCP tools on the official C# SDK. Deny-by-default catalog, typed `McpResult`, HTTP by default (stdio opt-in). Does not require BuildingBlocks.Mediator.
 
 [![NuGet](https://img.shields.io/nuget/v/BuildingBlocks.Mcp.svg)](https://www.nuget.org/packages/BuildingBlocks.Mcp)
+[![GitHub Release](https://img.shields.io/github/v/release/Maxofpower/FeatureFusion?filter=mcp-v*&logo=github&label=GitHub%20Release)](https://github.com/Maxofpower/FeatureFusion/releases?q=mcp-v)
 [![.NET](https://img.shields.io/badge/.NET-8%20%7C%209%20%7C%2010-512BD4)](https://dotnet.microsoft.com/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
diff --git a/src/BuildingBlocks/Mediator/PACKAGE_README.md b/src/BuildingBlocks/Mediator/PACKAGE_README.md
index e8e8cad..84a9f26 100644
--- a/src/BuildingBlocks/Mediator/PACKAGE_README.md
+++ b/src/BuildingBlocks/Mediator/PACKAGE_README.md
@@ -3,6 +3,7 @@
 CQRS-first **Send** + ordered **pipeline** for .NET 8+. Commands and queries, host-owned behaviors, optional traces and metrics, startup handler checks.
 
 [![NuGet](https://img.shields.io/nuget/v/BuildingBlocks.Mediator.svg)](https://www.nuget.org/packages/BuildingBlocks.Mediator)
+[![GitHub Release](https://img.shields.io/github/v/release/Maxofpower/FeatureFusion?filter=mediator-v*&logo=github&label=GitHub%20Release)](https://github.com/Maxofpower/FeatureFusion/releases?q=mediator-v)
 [![.NET](https://img.shields.io/badge/.NET-8%20%7C%209%20%7C%2010-512BD4)](https://dotnet.microsoft.com/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
diff --git a/src/BuildingBlocks/Pagination.EntityFrameworkCore/PACKAGE_README.md b/src/BuildingBlocks/Pagination.EntityFrameworkCore/PACKAGE_README.md
index 99148b0..af36f53 100644
--- a/src/BuildingBlocks/Pagination.EntityFrameworkCore/PACKAGE_README.md
+++ b/src/BuildingBlocks/Pagination.EntityFrameworkCore/PACKAGE_README.md
@@ -3,6 +3,7 @@
 Typed **keyset (cursor)** pagination for EF Core: `SortKey`, opaque versioned cursors, and `IQueryable.ToCursorPageAsync`. One NuGet — the IR assembly is bundled; you do not install a second Pagination 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)
 [![.NET](https://img.shields.io/badge/.NET-8%20%7C%209%20%7C%2010-512BD4)](https://dotnet.microsoft.com/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
diff --git a/src/BuildingBlocks/Telemetry/PACKAGE_README.md b/src/BuildingBlocks/Telemetry/PACKAGE_README.md
index ae034a3..5e312e5 100644
--- a/src/BuildingBlocks/Telemetry/PACKAGE_README.md
+++ b/src/BuildingBlocks/Telemetry/PACKAGE_README.md
@@ -3,6 +3,7 @@
 Config-driven OpenTelemetry traces, metrics, and logs for ASP.NET Core from one `AddTelemetry` call. Export **OTLP to any backend**. Requires `IHostApplicationBuilder`.
 
 [![NuGet](https://img.shields.io/nuget/v/BuildingBlocks.Telemetry.svg)](https://www.nuget.org/packages/BuildingBlocks.Telemetry)
+[![GitHub Release](https://img.shields.io/github/v/release/Maxofpower/FeatureFusion?filter=telemetry-v*&logo=github&label=GitHub%20Release)](https://github.com/Maxofpower/FeatureFusion/releases?q=telemetry-v)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
 ## What's new in 1.0.2
diff --git a/tests/BuildingBlocks/Idempotency.Tests/IdempotentAttributeFilterTests.cs b/tests/BuildingBlocks/Idempotency.Tests/IdempotentAttributeFilterTests.cs
index dd27423..7264403 100644
--- a/tests/BuildingBlocks/Idempotency.Tests/IdempotentAttributeFilterTests.cs
+++ b/tests/BuildingBlocks/Idempotency.Tests/IdempotentAttributeFilterTests.cs
@@ -1,6 +1,7 @@
 using System.Diagnostics;
 using System.Security.Claims;
 using System.Text;
+using System.Text.Json;
 using BuildingBlocks.Idempotency;
 using BuildingBlocks.Idempotency.AspNetCore;
 using BuildingBlocks.Idempotency.DependencyInjection;
@@ -15,7 +16,6 @@
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 using Moq;
-using Newtonsoft.Json;
 using Xunit;
 
 namespace BuildingBlocks.Idempotency.Tests;
@@ -179,7 +179,7 @@ public async Task FirstRequest_CachesEnvelope()
 		var cachedData = await _distributedCache.GetAsync(cacheKey);
 		Assert.NotNull(cachedData);
 
-		var cachedEntry = JsonConvert.DeserializeObject<IdempotencyCacheEntry>(Encoding.UTF8.GetString(cachedData));
+		var cachedEntry = JsonSerializer.Deserialize<IdempotencyCacheEntry>(Encoding.UTF8.GetString(cachedData));
 		Assert.Equal("Completed", cachedEntry?.Status);
 		Assert.Equal(200, cachedEntry?.StatusCode);
 		Assert.Equal("application/json", cachedEntry?.ContentType);
@@ -220,7 +220,7 @@ public async Task DuplicateRequest_ReplaysStoredStatusAndContentType()
 			StatusCode = 200,
 			ContentType = "application/json"
 		};
-		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(cacheEntry)));
+		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonSerializer.Serialize(cacheEntry)));
 
 		var filter = CreateFilter();
 		var context = CreateActionContext(httpContext);
@@ -243,7 +243,7 @@ public async Task DuplicateCompleted_ConflictStrategy_Returns409Problem()
 		};
 		var idempotencyKey = Ulid.NewUlid().ToString();
 		var cacheKey = $"Idempotency_1_{idempotencyKey}";
-		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(new IdempotencyCacheEntry
+		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonSerializer.Serialize(new IdempotencyCacheEntry
 		{
 			Status = "Completed",
 			Response = "{}",
@@ -268,7 +268,7 @@ public async Task ProcessingRequest_ReturnsConflictProblem()
 			Status = "Processing",
 			ProcessingExpiresAtUtc = DateTimeOffset.UtcNow.AddMinutes(1)
 		};
-		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(cacheEntry)));
+		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonSerializer.Serialize(cacheEntry)));
 
 		var filter = CreateFilter();
 		var context = CreateActionContext(httpContext);
@@ -289,7 +289,7 @@ public async Task ExpiredProcessing_AllowsNewExecution()
 			Status = "Processing",
 			ProcessingExpiresAtUtc = DateTimeOffset.UtcNow.AddMinutes(-1)
 		};
-		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(stale)));
+		await _distributedCache.SetAsync(cacheKey, Encoding.UTF8.GetBytes(JsonSerializer.Serialize(stale)));
 
 		var filter = CreateFilter();
 		var context = CreateActionContext(httpContext);
@@ -304,7 +304,7 @@ await filter.OnActionExecutionAsync(context, () =>
 
 		Assert.True(ran);
 		var cachedData = await _distributedCache.GetAsync(cacheKey);
-		var entry = JsonConvert.DeserializeObject<IdempotencyCacheEntry>(Encoding.UTF8.GetString(cachedData!));
+		var entry = JsonSerializer.Deserialize<IdempotencyCacheEntry>(Encoding.UTF8.GetString(cachedData!));
 		Assert.Equal("Completed", entry?.Status);
 	}
 
@@ -449,7 +449,7 @@ public async Task PerEndpointProcessingTtl_IsApplied()
 		var cacheKey = $"Idempotency_7_{idempotencyKey}";
 		var raw = await _distributedCache.GetAsync(cacheKey);
 		Assert.NotNull(raw);
-		var entry = JsonConvert.DeserializeObject<IdempotencyCacheEntry>(Encoding.UTF8.GetString(raw));
+		var entry = JsonSerializer.Deserialize<IdempotencyCacheEntry>(Encoding.UTF8.GetString(raw));
 		Assert.NotNull(entry?.ProcessingExpiresAtUtc);
 		var remaining = entry!.ProcessingExpiresAtUtc!.Value - DateTimeOffset.UtcNow;
 		Assert.True(remaining <= TimeSpan.FromSeconds(30) + TimeSpan.FromSeconds(2));
diff --git a/tests/Lab/IntegrationTests/Experiments/CacheVsProduction/CacheVsProductionExperimentTests.cs b/tests/Lab/IntegrationTests/Experiments/CacheVsProduction/CacheVsProductionExperimentTests.cs
index 0d4b4f2..e967e92 100644
--- a/tests/Lab/IntegrationTests/Experiments/CacheVsProduction/CacheVsProductionExperimentTests.cs
+++ b/tests/Lab/IntegrationTests/Experiments/CacheVsProduction/CacheVsProductionExperimentTests.cs
@@ -152,7 +152,7 @@ public async Task Order_create_redis_idempotency_cache_vs_production_is_observed
 		miss.Body.Should().Contain("\"orderId\"",
 			"production MVC serialization is camelCase System.Text.Json");
 		hit.Body.Should().Contain("\"OrderId\"",
-			"the cached replay is Newtonsoft.Json from BuildingBlocks.Idempotency, which defaults to PascalCase");
+			"the cached replay is System.Text.Json from BuildingBlocks.Idempotency, which defaults to PascalCase");
 
 		mutatedBody.HttpStatus.Should().Be(200);
 		mutatedBody.OrderId.Should().Be(miss.OrderId);
diff --git a/tests/Lab/IntegrationTests/Experiments/IdempotencyProcessingLease/IdempotencyProcessingLeaseExperimentTests.cs b/tests/Lab/IntegrationTests/Experiments/IdempotencyProcessingLease/IdempotencyProcessingLeaseExperimentTests.cs
index 8db8541..bb06785 100644
--- a/tests/Lab/IntegrationTests/Experiments/IdempotencyProcessingLease/IdempotencyProcessingLeaseExperimentTests.cs
+++ b/tests/Lab/IntegrationTests/Experiments/IdempotencyProcessingLease/IdempotencyProcessingLeaseExperimentTests.cs
@@ -14,7 +14,6 @@
 using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
-using Newtonsoft.Json;
 using Xunit.Abstractions;
 using static FeatureFusion.Features.Orders.Commands.CreateOrderCommandHandler;
 using static IntegrationTests.Infrastructure.Telemetry.LabTrace;
@@ -269,7 +268,7 @@ private async Task<LeaseObservation> WaitForProcessingLeaseExpiredAsync(
 		if (bytes is null || bytes.Length == 0)
 			return null;
 
-		return JsonConvert.DeserializeObject<IdempotencyCacheEntry>(Encoding.UTF8.GetString(bytes));
+		return JsonSerializer.Deserialize<IdempotencyCacheEntry>(Encoding.UTF8.GetString(bytes));
 	}
 
 	private async Task<LeaseCall> SendAsync(
diff --git a/tests/Lab/IntegrationTests/Experiments/README.md b/tests/Lab/IntegrationTests/Experiments/README.md
index 269c600..827a535 100644
--- a/tests/Lab/IntegrationTests/Experiments/README.md
+++ b/tests/Lab/IntegrationTests/Experiments/README.md
@@ -102,7 +102,7 @@ This is research infrastructure only — not Exp 15 and not a BuildingBlock.
 
 ### Workstream status — HTTP Redis idempotency (Exp 3, 4, 12)
 
-**COMPLETE — BuildingBlocks.Idempotency 1.0.0**
+**COMPLETE — BuildingBlocks.Idempotency 1.0.1** (extraction evidence from 1.0.0; packaging/STJ polish in 1.0.1)
 
 Reusable implementation: [`src/BuildingBlocks/Idempotency`](../../../../src/BuildingBlocks/Idempotency). Lab hosts the package on `POST /api/v2/Order/order`; these three experiments are the **evidence / provenance trail**, not unfinished extraction work. Package unit tests live under `tests/BuildingBlocks/Idempotency.Tests`. MCP `orders.create` idempotency (Exp 6) is a separate in-memory store and is **not** part of this BuildingBlock.
 
@@ -123,16 +123,16 @@ Reusable implementation: [`src/BuildingBlocks/Idempotency`](../../../../src/Buil
 ### Experiment 3 — HTTP Redis idempotency vs production (CacheVsProduction)
 
 - **Role:** Originally characterized Lab HTTP idempotency; now **regression / provenance** that extracted `BuildingBlocks.Idempotency` preserves the intended miss/hit workflow (fingerprint **off**, Lab default).
-- **Workstream:** COMPLETE — BuildingBlocks.Idempotency 1.0.0 (extraction proof set).
+- **Workstream:** COMPLETE — BuildingBlocks.Idempotency 1.0.1 (extraction proof set).
 - **Hypothesis / problem:** Package filter (Redis `IDistributedCache`) separates cache replay from production execution on `POST /api/v2/Order/order`.
 - **Surface:** HTTP order create → `[Idempotent(useLock: true)]` → `CreateOrderCommandHandler` (Mediator + catalog SaveChanges + outbox insert on miss).
-- **Primary behavior:** Miss runs production (Mediator + Npgsql); hit replays with `X-Idempotent-Response`; same key + different body keeps original order (body not part of key when fingerprint off); new key runs production again. Replay body casing reflects package Newtonsoft cache serialization.
+- **Primary behavior:** Miss runs production (Mediator + Npgsql); hit replays with `X-Idempotent-Response`; same key + different body keeps original order (body not part of key when fingerprint off); new key runs production again. Replay body casing reflects package System.Text.Json cache serialization (PascalCase by default).
 - **Limitation / non-goal:** Does not cover MCP `orders.create` (Exp 6). Does not assert async handler delivery (Exp 5). Does not prove concurrency lock races (Exp 4) or opt-in fingerprinting (Exp 12).
 
 ### Experiment 4 — HTTP idempotency concurrency (ConcurrencyRace)
 
 - **Role:** Originally proved the Redis same-key concurrency problem and lock behavior; now **regression / provenance** for `RedisIdempotencyLock` + Processing/Completed coordination under concurrent clients.
-- **Workstream:** COMPLETE — BuildingBlocks.Idempotency 1.0.0 (extraction proof set).
+- **Workstream:** COMPLETE — BuildingBlocks.Idempotency 1.0.1 (extraction proof set).
 - **Hypothesis / problem:** Concurrent clients with the **same** `Idempotency-Key` coordinate through Redis lock/status; different keys run independently.
 - **Surface:** Same HTTP order-create path as Exp 3 (`BuildingBlocks.Idempotency`).
 - **Primary behavior:** Three concurrent same-key requests → exactly one production winner, one unique `orderId`; losers are cached replay, HTTP 409, or lock-failure HTTP 500 (as observed). Two different keys both run production.
@@ -193,7 +193,7 @@ Reusable implementation: [`src/BuildingBlocks/Idempotency`](../../../../src/Buil
 ### Experiment 12 — HTTP idempotency request fingerprint (opt-in)
 
 - **Role:** Proves the **opt-in request fingerprint** capability added in richer BuildingBlocks.Idempotency v1 (not part of the original extraction proof set). Remains a **regression / proof gate** for that feature.
-- **Workstream:** COMPLETE — BuildingBlocks.Idempotency 1.0.0 (richer v1 evidence).
+- **Workstream:** COMPLETE — BuildingBlocks.Idempotency 1.0.1 (richer v1 evidence).
 - **Hypothesis / problem:** With `EnableRequestFingerprint=true`, same key + same body replays; same key + different body conflicts (422) without production.
 - **Surface:** Same order-create path as Exp 3; fingerprint enabled via test-host `PostConfigure<IdempotencyOptions>` only (Lab app default stays off).
 - **Primary behavior:** Miss runs production; same-body replay sets `X-Idempotent-Response`; different quantity → HTTP 422, no Mediator.
@@ -220,6 +220,7 @@ Reusable implementation: [`src/BuildingBlocks/Idempotency`](../../../../src/Buil
 ### Experiment 15 — HTTP idempotency ProcessingTtl lease overlap
 
 - **Role:** Closes the lease-expiry gap deferred by Exp 4 / package docs: what happens when the first same-key request stays in `Processing` longer than `ProcessingTtl`.
+- **Workstream:** COMPLETE — BuildingBlocks.Idempotency 1.0.1 (lease-overlap characterization; unchanged in STJ packaging polish).
 - **Hypothesis / problem:** After the Processing lease expires, a second client with the same `Idempotency-Key` may run production while the first handler is still in flight → duplicate orders/outbox.
 - **Surface:** HTTP `POST /api/v2/Order/order` → `BuildingBlocks.Idempotency` (`useLock: true`) → Mediator `CreateOrderCommand` → outbox. Test host only: short `ProcessingTtl` via `PostConfigure` + test-only gated handler wrapper (production handler unchanged).
 - **Primary behavior (characterized by this experiment):** Probe while first held → HTTP 409; after lease expiry → second request executes production; both complete with distinct `orderId`s and outbox rows when the packaged lease tradeoff admits overlap.