docs: Adding the release note for 1.4.0.Final (#1195)

Signed-off-by: Emmanuel Hugonnet <ehugonne@redhat.com>

Author: ehsavoie

docs/content/posts/2026-09-28-a2a-java-sdk-1-4-0-final-released/announce.png

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+---
+layout: post
+title: 'A2A Java SDK 1.4.0.Final Released'
+date: 2026-09-28
+tags: ai a2a
+synopsis: 'A2A Java SDK 1.4.0.Final is now available -- with SSE configuration improvements, a breaking change in the multi-tenancy @Tenant qualifier, ITK enhancements, and a comprehensive wave of bug fixes.'
+author: ehsavoie
+image: announce.png
+---
+
+image::announce.png[A2A Java SDK 1.4.0.Final announcement]
+
+I am happy to announce the release of link:https://github.com/a2aproject/a2a-java/releases/tag/v1.4.0.Final[A2A Java SDK 1.4.0.Final]. This release consolidates the multi-tenancy API with an important breaking change, brings SSE configuration improvements, strengthens interoperability testing, and delivers a large set of bug fixes across all transports.
+
+NOTE: This release contains a **breaking change** affecting the `@Tenant` qualifier. See the <<migration>> section for details.
+
+== What's New
+
+=== Multi-Tenancy: `@Tenant` Qualifier Consolidation
+
+The `@Tenant` qualifier annotation has been moved **from** `a2a-java-extras-multitenancy` **into** `server-common` (link:https://github.com/a2aproject/a2a-java/pull/1176[\#1176]). This is a **breaking change** -- see <<migration>> below.
+
+Moving the qualifier into `server-common` means the CDI runtime can now correctly filter out tenant-qualified beans at all `@PublicAgentCard` and `@ExtendedAgentCard` injection points. Previously, annotating a tenant card with both `@Tenant("x")` and `@PublicAgentCard` would cause CDI ambiguity and result in 404 errors on the default route.
+
+Additional improvements in this area:
+
+* Tenant cards annotated with both `@Tenant("x")` and `@PublicAgentCard` now take precedence over bare `@Tenant` cards at the public card endpoint.
+* Duplicate `@ExtendedAgentCard` registrations for the same tenant are now rejected at startup instead of silently winning arbitrarily.
+* Missing default `AgentExecutor` beans now throw an explicit exception at startup rather than causing silent runtime failures.
+* Agent card resolution now correctly falls back to the router even when no default bean is present (link:https://github.com/a2aproject/a2a-java/pull/1184[\#1184]).
+
+=== SSE Configuration
+
+A new `SSEParserConfig` class (link:https://github.com/a2aproject/a2a-java/pull/1149[\#1149]) makes Server-Sent Events parsing configurable per client. The default per-line size limit has been raised to 1 MB, resolving issues where large message payloads were rejected by the SSE parser.
+
+=== `application/a2a+json` Content-Type Support
+
+The server transports now recognize `application/a2a+json` as a valid content type alongside `application/json` (link:https://github.com/a2aproject/a2a-java/pull/1181[\#1181]), improving out-of-the-box interoperability with clients that send this media type.
+
+=== ITK Enhancements
+
+The ITK test agent gains ACTS SUT behavior support via YAML configuration (link:https://github.com/a2aproject/a2a-java/pull/1150[\#1150]), along with CI workflow integration and an auth precondition implementation (link:https://github.com/a2aproject/a2a-java/pull/1157[\#1157]). These additions make it easier to configure and run interoperability tests against the upstream ACTS test harness.
+
+=== Documentation Improvements
+
+* A complete `TaskAuthorizationProvider` implementation example has been added to the documentation (link:https://github.com/a2aproject/a2a-java/pull/1146[\#1146]).
+* Security advisory link:https://github.com/a2aproject/a2a-java/security/advisories/GHSA-4fpj-g9jf-9rgg[GHSA-4fpj-g9jf-9rgg] has been incorporated into the threat model (link:https://github.com/a2aproject/a2a-java/pull/1148[\#1148]).
+* JDK HttpClient's restricted `Host` header behavior and the Vert.x HTTP client as an alternative are now documented (link:https://github.com/a2aproject/a2a-java/pull/1180[\#1180]).
+
+== Bug Fixes
+
+* **Task history** -- current status messages are no longer incorrectly included in task history (link:https://github.com/a2aproject/a2a-java/pull/1122[\#1122])
+* **Push notification config** -- omitted push config IDs are now accepted in both HTTP (link:https://github.com/a2aproject/a2a-java/pull/1092[\#1092]) and gRPC (link:https://github.com/a2aproject/a2a-java/pull/1163[\#1163]) transports
+* **Push notification ordering** -- delivery order of push notifications per task is now preserved (link:https://github.com/a2aproject/a2a-java/pull/1156[\#1156])
+* **gRPC `Part.metadata`** -- the `metadata` field is now correctly mapped in 0.3 gRPC classes (link:https://github.com/a2aproject/a2a-java/pull/1169[\#1169])
+* **Blank task/context IDs** -- blank `taskId` and `contextId` values in `messages/send` are treated as absent (link:https://github.com/a2aproject/a2a-java/pull/1172[\#1172])
+* **JSON null preservation** -- explicit JSON nulls in value mappings are now preserved correctly (link:https://github.com/a2aproject/a2a-java/pull/1174[\#1174])
+* **Relative redirects** -- relative `Location` header values in HTTP redirects are now resolved against the request URI (link:https://github.com/a2aproject/a2a-java/pull/1162[\#1162])
+* **SSE terminal callback** -- exactly one terminal SSE callback is now guaranteed (link:https://github.com/a2aproject/a2a-java/pull/1173[\#1173])
+* **`A2ACardResolver` fallback URL** -- a fallback URL is now always provided (link:https://github.com/a2aproject/a2a-java/pull/1179[\#1179])
+* **Event bus processor** -- the event bus processor now starts correctly when using manual (non-CDI) wiring (link:https://github.com/a2aproject/a2a-java/pull/997[\#997])
+* **Terminal enqueue recovery** -- failed terminal enqueue operations are now recovered (link:https://github.com/a2aproject/a2a-java/pull/1185[\#1185])
+
+[[migration]]
+== Migration from 1.3.x
+
+Update your BOM version:
+
+[source,xml]
+----
+<dependencyManagement>
+    <dependencies>
+        <dependency>
+            <groupId>org.a2aproject.sdk</groupId>
+            <artifactId>a2a-java-sdk-bom</artifactId>
+            <version>1.4.0.Final</version>
+            <type>pom</type>
+            <scope>import</scope>
+        </dependency>
+    </dependencies>
+</dependencyManagement>
+----
+
+[[tenant-migration]]
+=== `@Tenant` Import Change (Breaking)
+
+The `@Tenant` qualifier has moved from the `a2a-java-extras-multitenancy` module into `server-common`, and its package has changed accordingly. Any class that imports `@Tenant` must be updated:
+
+[source,java]
+----
+// Before (1.3.x) -- from the extras module
+import org.a2aproject.sdk.extras.multitenancy.Tenant;
+
+// After (1.4.0) -- from server-common
+import org.a2aproject.sdk.server.multitenancy.Tenant;
+----
+
+The annotation's semantics are unchanged. No other code modifications are required.
+
+=== Missing Default `AgentExecutor` Now Throws
+
+If a CDI-based multi-tenant deployment has no default `AgentExecutor` bean, the server will now throw an explicit exception at startup. Previously this would compile and deploy successfully but fail silently at runtime. Ensure a default `AgentExecutor` bean is always registered, or supply an `AgentExecutorRouter` programmatically via the builder:
+
+[source,java]
+----
+AgentExecutorRouter router = tenant ->
+    executors.getOrDefault(tenant, defaultExecutor);
+
+DefaultRequestHandler handler = DefaultRequestHandler.builder()
+    .agentExecutorRouter(router)
+    .taskStore(taskStore)
+    .queueManager(queueManager)
+    // ...
+    .build();
+----
+
+== Contributors
+
+A big thank you to all contributors of this release -- and a warm welcome to those joining for the first time!
+
+link:https://github.com/ehsavoie[@ehsavoie], link:https://github.com/kabir[@kabir], link:https://github.com/JakubWorek[@JakubWorek], link:https://github.com/014-code[@014-code], link:https://github.com/1fanwang[@1fanwang], link:https://github.com/hutiefang76[@hutiefang76], link:https://github.com/serhiy-bzhezytskyy[@serhiy-bzhezytskyy], link:https://github.com/56wj[@56wj], link:https://github.com/paulrutter[@paulrutter], link:https://github.com/girishkvs[@girishkvs], link:https://github.com/chopmob-cloud[@chopmob-cloud]
+
+== Resources
+
+* link:https://github.com/a2aproject/a2a-java/releases/tag/v1.4.0.Final[Release Notes on GitHub]
+* link:https://central.sonatype.com/artifact/org.a2aproject.sdk/a2a-java-sdk-parent/1.4.0.Final[Maven Central]
+* link:https://javadoc.io/doc/org.a2aproject.sdk/[JavaDoc]
+* link:https://a2a-protocol.org/v1.0.0/specification/[A2A Specification]
+* link:https://a2aproject.github.io/a2a-java/[Project Website]
+* link:https://github.com/a2aproject/a2a-java/tree/main/examples[Examples]
+
+== Come Join Us
+
+We value your feedback a lot so please report bugs, ask for improvements etc. Let's build something great together!
+
+If you are an A2A Java SDK user or just curious, don't be shy and join our welcoming community:
+
+* provide feedback on link:https://github.com/a2aproject/a2a-java/issues[GitHub];
+* craft some code and link:https://github.com/a2aproject/a2a-java/pulls[push a PR];
+* discuss with us in the `#a2a-java` channel on link:https://discord.gg/jTtSkJB74Q[Discord];