A2A: Standardize Kagent's human in the loop with A2A Extension by supreme-gg-gg · Pull Request #2396 · kagent-dev/kagent

supreme-gg-gg · 2026-08-05T16:58:25Z

Move Kagent's human in the loop (HITL) to an A2A Extension that is framework-neutral and standardized. Previously, we relied on ADK-specific parts from its request confirmation flow and a lot of custom metadata.
Redesigned the HITL payload following the Extension migration since it's framework neutral now. This redesign means UI and extension becomes simpler, and defers more processing logic to the upstream executor and each framework
Upgrade Python ADK to 2.0 so that we can reuse upstream A2A agent executor to handle request confirmation flow internally and remove duplicated code introduced in the last HITL PR when upstream does not support it back then
Added e2e test for HITL (ask user tool)

Core changes are documented in docs/architecture/human-in-the-loop.md, see the diff for the design changes.

This is breaking so old clients without the A2A extension negotiation capability will stop receiving HITL events properly. To upgrade your custom client / agents, please refer to changes in the above doc.

As before, only ADK and Langgraph (BYO) supports HITL. However, this redesign enables users to easily develop their own adapter for other BYO frameworks / harness since HITL over A2A itself is framework-neutral.

chromatic-com · 2026-08-06T01:21:25Z

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supreme-gg-gg · 2026-08-06T02:28:34Z

Note for reviewer: Also added UI option to set and show toggle for isolating subagent sessions added in #2153 (SelectToolsDialog.tsx, ToolsSection.tsx, AgentDetailsSidebar.tsx)

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supreme-gg-gg · 2026-08-06T15:32:42Z

        a2a_part.metadata.update({get_kagent_metadata_key(A2A_DATA_PART_METADATA_IS_LONG_RUNNING_KEY): True})


-def _process_subagent_session_id(a2a_part: A2APart, subagent_session_ids: Dict[str, str]) -> None:


Note for reviewer: cleaning up these unnecessary event converters and utils for stamping subagent session ID as #2153 removed it for Go

supreme-gg-gg · 2026-08-06T15:33:57Z

Note for reviewer: removed sandbox code executor no longer in use

The merge-base changed after approval.

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

…l to a2a extension Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

…r changes Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

…ted UI code refactor Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

…sions for subagents Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

supreme-gg-gg changed the title ~~[WIP] A2A: Standardize Kagent's human in the loop with A2A Extension~~ A2A: Standardize Kagent's human in the loop with A2A Extension Aug 5, 2026

supreme-gg-gg force-pushed the jetc/feat/a2a-hitl-extension branch from e5e1bfc to 00203f0 Compare August 6, 2026 01:20

supreme-gg-gg commented Aug 6, 2026

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supreme-gg-gg force-pushed the jetc/feat/a2a-hitl-extension branch 2 times, most recently from 7726578 to 8dfdc4e Compare August 6, 2026 02:45

supreme-gg-gg requested a lite review from Copilot August 6, 2026 02:45

Copilot AI reviewed Aug 6, 2026

supreme-gg-gg force-pushed the jetc/feat/a2a-hitl-extension branch from dce2b6b to 5e9d177 Compare August 6, 2026 15:28

supreme-gg-gg commented Aug 6, 2026

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supreme-gg-gg marked this pull request as ready for review August 6, 2026 15:36

supreme-gg-gg requested review from a team, Charlesthebird and peterj as code owners August 6, 2026 15:36

supreme-gg-gg force-pushed the jetc/feat/a2a-hitl-extension branch from 1894a93 to f06e3ec Compare August 6, 2026 15:52

EItanya force-pushed the jetc/feat/a2a-hitl-extension branch from f06e3ec to 911bea9 Compare August 6, 2026 20:38

EItanya previously approved these changes Aug 6, 2026

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supreme-gg-gg mentioned this pull request Aug 6, 2026

A2A: Various usage cleanups in Kagent harness #2385

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supreme-gg-gg force-pushed the jetc/feat/a2a-hitl-extension branch from 911bea9 to d8c6e91 Compare August 7, 2026 14:20

peterj approved these changes Aug 7, 2026

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Base automatically changed from jetc/feat/a2a-cleanup to main August 7, 2026 15:01

ui and go tui updates

60b3392

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

supreme-gg-gg added 17 commits August 7, 2026 11:01

initial python refactor and go agentcard extension

312c114

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

migrate python adk to 2.0, reuse upstream agent executor, migrate hit…

9ecc3cd

…l to a2a extension Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

include extension in go a2a proxy

69bfed7

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

migrate go adk hitl interface to a2a extensions

c2f43d1

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

ui changes to use framework-neutral a2a extension for HITL and refactors

7f21bba

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

updated hitl docs

c71ad08

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

update translator agent card wording

ded8be6

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

improve go/adk, remove unused code, make payload strongly typed, othe…

ab74a2b

…r changes Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

python: docs and langgraph hitl

0532139

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

ui: routers only attach extension header when present, more hitl rela…

4fb699f

…ted UI code refactor Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

ui: fix a subagent hitl display bug and also add UI for isolating ses…

df6e9be

…sions for subagents Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

fix(langgraph): hitl and refactor part of utils to hitl/core

b412a4e

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

hitl e2e test

dd94bca

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

remove run code test and unused sandbox code executor

b58be4c

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

cleanup file

193ccb2

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

remove unused code more

8f528fa

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

fix lint and tests from rebasing

1f9538e

Signed-off-by: Jet Chiang <pokyuen.jetchiang-ext@solo.io>

EItanya force-pushed the jetc/feat/a2a-hitl-extension branch from 5f924c6 to 1f9538e Compare August 7, 2026 15:01

EItanya approved these changes Aug 7, 2026

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EItanya merged commit b58666b into main Aug 7, 2026
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EItanya deleted the jetc/feat/a2a-hitl-extension branch August 7, 2026 16:38

vramahandry mentioned this pull request Sep 15, 2026

fix(go-adk): surface the sub-agent's ask_user question in RemoteHitlHint #2475

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A2A: Standardize Kagent's human in the loop with A2A Extension - #2396

A2A: Standardize Kagent's human in the loop with A2A Extension#2396
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		a2a_part.metadata.update({get_kagent_metadata_key(A2A_DATA_PART_METADATA_IS_LONG_RUNNING_KEY): True})


		def _process_subagent_session_id(a2a_part: A2APart, subagent_session_ids: Dict[str, str]) -> None:

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