iframe-proxy

kabir · 2026-03-17T12:50:05Z

Fixes #754

gemini-code-assist · 2026-03-17T12:50:26Z

Summary of Changes

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This pull request resolves an issue where task event streams were prematurely closed when a task entered an interrupted state, such as INPUT_REQUIRED. By refining the TaskState classification and updating the stream termination logic to align with the A2A Protocol Specification, streams will now correctly persist through interrupted states, allowing for subsequent updates, and will only terminate when a task reaches a definitive final state. This ensures a more robust and compliant event streaming experience.

Highlights

Stream Termination Logic Refined: The logic for terminating task event streams was updated to strictly adhere to the A2A Protocol Specification, ensuring streams only close when a task reaches a truly terminal state.
TaskState Classification Enhanced: The TaskState enum was extended with an isInterrupted property and corresponding method, allowing for explicit identification of states where a task is paused awaiting external action.
INPUT_REQUIRED State Handling Corrected: The isStreamTerminatingTask method in EventConsumer no longer treats TASK_STATE_INPUT_REQUIRED as a stream-terminating condition, preventing premature stream closure.
New Test Coverage Added: A comprehensive test case was introduced to validate that event streams correctly remain open for interrupted states and only terminate upon reaching a final task state.

Changelog

server-common/src/main/java/io/a2a/server/events/EventConsumer.java
- Modified isStreamTerminatingTask to remove TASK_STATE_INPUT_REQUIRED from the conditions that trigger stream termination, now relying solely on isFinal().
- Updated Javadoc for isStreamTerminatingTask to reflect the A2A Protocol Specification regarding stream termination.
spec/src/main/java/io/a2a/spec/TaskState.java
- Introduced a new isInterrupted boolean field to the TaskState enum constructor.
- Updated all TaskState enum instances to initialize the new isInterrupted field.
- Added a new public method isInterrupted() to determine if a state is interrupted.
- Revised Javadoc to categorize states into "Active Transitional States" and "Interrupted States" and to explain the purpose of isInterrupted().
tests/server-common/src/test/java/io/a2a/server/apps/common/AbstractA2AServerTest.java
- Added testSubscribeToTaskWithInterruptedStateKeepsStreamOpen, a new integration test to verify that event streams correctly remain open for INPUT_REQUIRED and WORKING states, and only terminate when a task reaches a COMPLETED state.

Activity

kabir opened this pull request to fix issue [Bug]: SubscribeToTask stream closes immediately instead of staying open for state updates #754.

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Code Review

This pull request correctly resolves an issue where event streams were prematurely closing for tasks in an interrupted state, such as INPUT_REQUIRED. The fix aligns the stream termination logic in EventConsumer with the A2A protocol specification, ensuring streams only terminate when a task reaches a final state. The refactoring of the TaskState enum to explicitly define and track isInterrupted states is a solid design improvement that enhances code clarity. Additionally, the new integration test, testSubscribeToTaskWithInterruptedStateKeepsStreamOpen, provides excellent coverage and validation for the corrected behavior. The changes are well-implemented and I have no further suggestions.

jmesnil · 2026-03-17T14:43:55Z

@kabir The JSON-RPC reproducer still fails:

 # Step 1: Create a non-terminal task (input_required state)
   RESPONSE=$(curl -s -X POST http://localhost:9999 \
     -H "Content-Type: application/json" \
     -d '{
       "jsonrpc":"2.0","id":1,"method":"SendMessage",
       "params":{"message":{"role":"ROLE_USER","parts":[{"text":"test"}],"messageId":"tck-input-required-repro"}}
     }')
   TASK_ID=$(echo "$RESPONSE" | python3 -c "import sys,json; r=json.load(sys.stdin); print(r['result']['task']['id'])")
   echo "Task ID: $TASK_ID  State: TASK_STATE_INPUT_REQUIRED"

At this point, the task is in TASK_STATE_INPUT_REQUIRED.
But when I subscribe to the task, the HTTP POST request returns immediately:

$ curl -s -N -X POST http://localhost:9999 \
     -H "Content-Type: application/json" \
     -H "Accept: text/event-stream" \
     -d "{\"jsonrpc\":\"2.0\",\"id\":2,\"method\":\"SubscribeToTask\",\"params\":{\"id\":\"$TASK_ID\"}}"

data: {"jsonrpc":"2.0","id":2,"result":{"task":{"id":"938089f1-9ce5-4bff-8cc8-8d092f3e5c84","contextId":"ba5beadd-cd73-4188-ad1f-f011dec726a9","status":{"state":"TASK_STATE_INPUT_REQUIRED","timestamp":"2026-03-17T14:40:49.748656Z"},"artifacts":[],"history":[],"metadata":{}}}}
id: 0

BTW, the id: 0 looks very suspicious in the event stream...

At this point, I was expecting the request to stay open until I complete the task with another message such as:

 curl -s -X POST http://localhost:9999 \
     -H "Content-Type: application/json" \
     -d "{
       \"jsonrpc\":\"2.0\",\"id\":3,\"method\":\"SendMessage\",
       \"params\":{\"message\":{\"role\":\"ROLE_USER\",\"parts\":[{\"text\":\"done\"}],\"messageId\":\"tck-complete-task-repro\",\"taskId\":\"$TASK_ID\"}}
     }"

The EventConsumer grace period logic was incorrectly closing the queue after agent completion, even when the task was in an interrupted state (INPUT_REQUIRED or AUTH_REQUIRED). Per A2A Protocol Specification 3.1.6, streams must remain open for interrupted states to receive future state updates, regardless of whether the agent has completed. Changes: - Track last seen task state in EventConsumer - Prevent grace period queue close if task is in interrupted state - Add logging for interrupted state detection This fixes the issue where SubscribeToTask would close immediately after delivering the initial Task snapshot for INPUT_REQUIRED tasks. Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

kabir · 2026-03-17T16:20:22Z

@jmesnil I've tried to make the test do what the reproducer does

kabir · 2026-03-17T16:28:38Z

/gemini review

gemini-code-assist

Code Review

This pull request provides a critical fix to ensure that event streams remain open for tasks in an interrupted state (like INPUT_REQUIRED), adhering to the A2A specification. The changes are well-implemented across several files. In EventConsumer, the logic for closing the stream is corrected to check for interrupted states. The TaskState enum is refactored to explicitly include the concept of an "interrupted" state, which is a great design improvement that enhances clarity and maintainability. The isStreamTerminatingTask method is also corrected. The changes are supported by excellent tests, including an updated unit test and a new, comprehensive integration test that thoroughly validates the end-to-end behavior. The code quality is high, and the fix appears robust and correct.

kabir · 2026-03-23T15:45:49Z

Fixes a2aproject#754

gemini-code-assist Bot reviewed Mar 17, 2026

View reviewed changes

fix: Keep stream open on interrupted state changes

556b28b

kabir force-pushed the issue-754 branch from 7f11b49 to 556b28b Compare March 17, 2026 14:52

kabir and others added 2 commits March 17, 2026 15:06

Fix test to work like the reproducer

8adc284

gemini-code-assist Bot reviewed Mar 17, 2026

View reviewed changes

kabir merged commit f668b77 into a2aproject:main Mar 23, 2026
11 checks passed

salaboy pushed a commit to salaboy/a2a-java that referenced this pull request Jun 19, 2026

fix: Keep stream open on interrupted state changes (a2aproject#756)

e2c7a2e

Fixes a2aproject#754

bianjp mentioned this pull request Jul 9, 2026

[Bug]: AgentEmitter#requiresInput(..., isFinal=true) does not close the event stream #975

Closed

1 task done

chopmob-cloud mentioned this pull request Jul 13, 2026

fix(server): close event stream when requiresInput/requiresAuth force isFinal #980

Closed

bianjp mentioned this pull request Jul 22, 2026

Provide an API/hook to close streams after INPUT_REQUIRED / AUTH_REQUIRED #990

Closed

Lirons01 mentioned this pull request Sep 30, 2026

[Bug]: REST transport never signals normal stream completion to the client (SSE hangs until timeout) #1194

Open

1 task done

Sunbelt Computer Software

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fix: Keep stream open on interrupted state changes - #756

fix: Keep stream open on interrupted state changes#756
kabir merged 3 commits into
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kabir:issue-754

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kabir commented Mar 17, 2026

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