[KG-4] Initial version of A2A SDK and integration #875

EugeneTheDev · 2025-09-29T13:08:48Z

Introduce initial version of A2A SDK and Koog agent A2A integration:

Multiplatform Kotlin A2A SDK, including server and client. Only JSON-RPC HTTP for now.
Integration tests for A2A SDK using A2A Protocol Technology Compatibility Kit (TCK). All tests pass.

kpavlov

just notes

kpavlov · 2025-09-30T06:09:32Z

a2a/a2a-client/src/commonMain/kotlin/ai/koog/a2a/client/A2AClient.kt

+     * Retrieves [AgentCard] by calling [AgentCardResolver.resolve].
+     * Saves it to the cache.
+     */
+    public open suspend fun getAgentCard(): AgentCard {


nit: As a User, I would expect this method to use cache transparently.
Maybe use cache TTL and/or introduce refreshAgentCard()?

Regular getAgentCard already refreshes the cache, because it uses resoslver every time. And so is get authenticated card. cached card is a convenience method to get local version of the card without fetching it

kpavlov · 2025-09-30T06:09:57Z

a2a/a2a-client/src/commonMain/kotlin/ai/koog/a2a/client/A2AClient.kt

+        request: Request<Nothing?>,
+        ctx: ClientCallContext = ClientCallContext.Default
+    ): Response<AgentCard> {
+        check(getAgentCard().supportsAuthenticatedExtendedCard == true) {


this method bypasses cache

kpavlov · 2025-09-30T06:10:55Z

a2a/a2a-client/src/commonMain/kotlin/ai/koog/a2a/client/A2AClient.kt

+        request: Request<MessageSendParams>,
+        ctx: ClientCallContext = ClientCallContext.Default
+    ): Response<CommunicationEvent> {
+        return transport.sendMessage(request, ctx)


future improvement: check supported features and fail when operation is not supported

I already do this, e.g. streaming and push notifications

kpavlov · 2025-09-30T06:14:16Z

a2a/a2a-client/src/commonMain/kotlin/ai/koog/a2a/client/AgentCardResolver.kt

+            contentType(ContentType.Application.Json)
+        }
+
+        install(ContentNegotiation) {


nit: Needs logging also

Logging is definitely needed everywhere in A2A, will add this separately later

kpavlov · 2025-09-30T06:17:18Z

a2a/a2a-core/src/commonMain/kotlin/ai/koog/a2a/model/AgentCard.kt

@@ -0,0 +1,476 @@
+package ai.koog.a2a.model


nit: annotations, consts, and utils packages are plural, model and transport are single. Maybe rename for consistency?

kpavlov · 2025-09-30T06:18:03Z

a2a/a2a-core/src/commonMain/kotlin/ai/koog/a2a/model/AgentCard.kt

+@JvmInline
+@Serializable
+public value class TransportProtocol(public val value: String) {
+    @Suppress("MissingKDocForPublicAPI")


maybe, let's generate the KDoc

Ololoshechkin

🗿

kpavlov · 2025-10-01T15:47:54Z

a2a/a2a-client/src/commonMain/kotlin/ai/koog/a2a/client/A2AClient.kt

        ctx: ClientCallContext = ClientCallContext.Default
    ): Response<AgentCard> {
-        check(getAgentCard().supportsAuthenticatedExtendedCard == true) {
+        check(cachedAgentCard().supportsAuthenticatedExtendedCard == true) {


github-actions · 2025-10-01T17:47:29Z

Qodana for JVM

1003 new problems were found

Inspection name	Severity	Problems
`Check Kotlin and Java source code coverage`	🔶 Warning	958
`Vulnerable imported dependency`	🔶 Warning	30
`Missing KDoc for public API declaration`	🔶 Warning	9
`Unused import directive`	🔶 Warning	6

@@ Code coverage @@
+ 71% total lines covered
14234 lines analyzed, 10107 lines covered
# Calculated according to the filters of your coverage tool

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…port

…dencies in build.gradle.kts

EugeneTheDev force-pushed the a2a-support branch 4 times, most recently from 9128245 to ea01449 Compare September 30, 2025 13:40

kpavlov reviewed Sep 30, 2025

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EugeneTheDev force-pushed the a2a-support branch 2 times, most recently from 910e9b2 to cefa010 Compare September 30, 2025 16:18

Ololoshechkin self-requested a review October 1, 2025 13:56

Ololoshechkin approved these changes Oct 1, 2025

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EugeneTheDev force-pushed the a2a-support branch from 041444c to 438ef9e Compare October 1, 2025 14:50

EugeneTheDev marked this pull request as ready for review October 1, 2025 15:16

kpavlov approved these changes Oct 1, 2025

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kpavlov reviewed Oct 1, 2025

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EugeneTheDev force-pushed the a2a-support branch from 35611e4 to 2b9f211 Compare October 1, 2025 17:57

EugeneTheDev and others added 15 commits October 1, 2025 20:20

[a2a] Add JSON-RPC protocol foundation and module structure

7e71851

[a2a] Implement AgentCard and core A2A data models

ab98cf2

[a2a] Add client and server transport abstractions

d208bfb

[a2a] Implement HTTP JSON-RPC client transport with tests

2ae67f0

[a2a] Implement HTTP JSON-RPC server transport with full protocol sup…

becbf37

…port

Add integration tests for HttpJSONRPCClientTransport and update depen…

b536450

…dencies in build.gradle.kts

[a2a] Implement A2AClient foundation with AgentCardResolver

757964f

[a2a] Update A2A models for spec compliance and add client methods

4dc50ae

[a2a] Add comprehensive A2A client test suite with Python test server

a998dea

[a2a] Improve agent card loading and resolution

2ac63dd

[a2a] Implement A2AServer core with session management and storage

0ac934c

[a2a] Implement session management with push notifications

ad7c61a

[a2a] Add comprehensive documentation for server components

f63824a

[a2a] Introduce a2a-test module, create BaseA2AProtocolTest

e934cf3

[a2a] Fix SessionEventProcessor concurrency and event management

da87a8f

EugeneTheDev added 11 commits October 1, 2025 20:26

[a2a] Refine AgentExecutor interface and add test utilities

13dd663

[a2a] Add task locking, add A2A server integration tests

64bfafd

[a2a] Implement full TCK compliance with all tests passing

8e98faa

[a2a] Add CORS configuration

43ab8fa

[a2a] Add A2A server and A2A client agent features

9d5927c

[a2a] Fix compilation issues and build configuration

1fd35d1

[a2a] Add module documentation and metadata field support

0c9fc72

[a2a] Add interactive joke agent example

6768b42

[agents] Fix EventHandlerTest

3b2c9e2

[agents] Update simple joke a2a example

80abf56

[a2a] Add stress tests, fix race conditions, and refine testing approach

1a80d6c

EugeneTheDev force-pushed the a2a-support branch from 2b9f211 to 1a80d6c Compare October 1, 2025 18:29

EugeneTheDev changed the title ~~[KG-4] A2A~~ [KG-4] Initial version of A2A SDK and integration Oct 1, 2025

EugeneTheDev merged commit d9ed920 into develop Oct 1, 2025
36 of 44 checks passed

EugeneTheDev deleted the a2a-support branch October 1, 2025 20:40

[KG-4] Initial version of A2A SDK and integration #875

[KG-4] Initial version of A2A SDK and integration #875

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EugeneTheDev commented Sep 29, 2025 •

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