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fix(grpc): missing field in gRPC spec - state_transition_history #1138

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darrelmiller merged 2 commits intoa2aproject:mainfrom
madankumarpichamuthu:feature/sync-grpc-spec-with-json
Oct 19, 2025
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fix(grpc): missing field in gRPC spec - state_transition_history #1138
darrelmiller merged 2 commits intoa2aproject:mainfrom
madankumarpichamuthu:feature/sync-grpc-spec-with-json

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@madankumarpichamuthu madankumarpichamuthu commented Oct 10, 2025

Add missing fields to align gRPC specification with JSON specification:

  • Add reference_task_ids field to Message to support cross-task context references, matching the referenceTaskIds field in JSON spec
  • Add state_transition_history capability flag to AgentCapabilities to indicate support for task state transition history tracking

These changes ensure feature parity between gRPC and JSON-RPC implementations of the A2A protocol. Both additions are optional fields and maintain backward compatibility with existing implementations.

Fixes #1139
Closes #1139

@madankumarpichamuthu madankumarpichamuthu requested a review from a team as a code owner October 10, 2025 23:07
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Summary of Changes

Hello @madankumarpichamuthu, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request synchronizes the gRPC specification with its JSON counterpart by introducing two new optional fields. These additions, "reference_task_ids" within the "Message" structure and "state_transition_history" in "AgentCapabilities", ensure feature parity for cross-task context referencing and state transition history tracking in the A2A protocol, while maintaining full backward compatibility.

Highlights

  • Message structure enhancement: The "Message" message now includes a "reference_task_ids" field, a repeated string, to support cross-task context references, aligning with the "referenceTaskIds" field in the JSON specification.
  • Agent capability reporting: The "AgentCapabilities" message has been updated with a "state_transition_history" boolean flag, indicating whether an agent supports tracking task state transition history, thereby matching the JSON spec.
Ignored Files
  • Ignored by pattern: CHANGELOG.md (1)
    • CHANGELOG.md
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Code Review

This pull request brings the gRPC specification in sync with the JSON specification by adding two missing fields. The reference_task_ids field is added to the Message message, and the state_transition_history flag is added to AgentCapabilities. The implementation is correct, using appropriate field numbers and following Protobuf style conventions. The changes are backward-compatible and ensure feature parity between the gRPC and JSON-RPC protocols. Overall, this is a good fix and I approve of the changes.

@madankumarpichamuthu madankumarpichamuthu changed the title fix(grpc): Sync gRPC spec with JSON spec - state_transition_history missing in gRPC fix(grpc): missing field in gRPC spec - state_transition_history Oct 10, 2025
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I am going to approve this but want to note that "state_transition_history" currently has no defined way of exposing that history. See #1158

@darrelmiller darrelmiller added the TSC Review To be reviewed by the Technical Steering Committee label Oct 18, 2025
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LGTM

@madankumarpichamuthu madankumarpichamuthu force-pushed the feature/sync-grpc-spec-with-json branch 2 times, most recently from 086aee4 to 7ba4dc2 Compare October 18, 2025 22:30
@madankumarpichamuthu madankumarpichamuthu requested a review from a team as a code owner October 18, 2025 22:30
@madankumarpichamuthu madankumarpichamuthu force-pushed the feature/sync-grpc-spec-with-json branch from 7ba4dc2 to ac12630 Compare October 18, 2025 22:34
Add missing fields to align gRPC specification with JSON specification:

- Add reference_task_ids field to Message to support cross-task context
  references, matching the referenceTaskIds field in JSON spec
- Add state_transition_history capability flag to AgentCapabilities to
  indicate support for task state transition history tracking

These changes ensure feature parity between gRPC and JSON-RPC
implementations of the A2A protocol. All additions are optional fields
and maintain backward compatibility with existing implementations.
@madankumarpichamuthu madankumarpichamuthu force-pushed the feature/sync-grpc-spec-with-json branch from ac12630 to 0d7d34b Compare October 18, 2025 22:38
@darrelmiller darrelmiller merged commit a2de798 into a2aproject:main Oct 19, 2025
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mikeas1 commented Oct 20, 2025

This also addresses #1107

@madankumarpichamuthu madankumarpichamuthu deleted the feature/sync-grpc-spec-with-json branch October 20, 2025 17:37
darrelmiller pushed a commit that referenced this pull request Mar 12, 2026
🤖 I have created a release *beep* *boop*
---


## [1.0.0](v0.3.0...v1.0.0)
(2026-03-12)


### ⚠ BREAKING CHANGES

* **spec:** Combine `TaskPushNotificationConfig` and
`PushNotificationConfig`
([#1500](#1500))
* **spec:** remove duplicated ID from the create task push config
request ([#1487](#1487))
* **spec:** pluralize configs in `ListTaskPushNotificationConfigs`
([#1486](#1486))
* **spec:** Add LF prefix to the package.
([#1474](#1474))
* **spec:** Switch to non-complex IDs in requests
([#1389](#1389))
* **spec:** Standardize spelling of "canceled" to use American Spelling
throughout ([#1283](#1283))
* **spec:** Align enum format with ADR-001 ProtoJSON specification
([#1384](#1384))
* **spec:** Remove redundant `final` field from `TaskStatusUpdateEvent`
([#1308](#1308))
* **spec:** Move `extendedAgentCard` field to `AgentCapabilities`
([#1307](#1307))
* **spec:** Fixes for the last_updated_after field
([#1358](#1358))
* **spec:** modernize oauth 2.0 flows - remove implicit/password, add
device code / pkce
([#1303](#1303))
* **spec:** Make "message" field name consistent between protocol
bindings ([#1302](#1302))
* **spec:** Remove deprecated fields from a2a.proto for v1.0 release
([#1301](#1301))
* **spec:** Rename `supportsAuthenticatedExtendedCard` to
`supportsExtendedAgentCard`
([#1222](#1222))
* **spec:** Remove v1s from a2a url http bindings
* **spec:** Large refactor of specification to separate application
protocol definition from mapping to transports

### Features

* **spec:** Add `tasks/list` method with filtering and pagination to the
specification
([0a9f629](0a9f629))
* **spec:** modernize oauth 2.0 flows - remove implicit/password, add
device code / pkce
([#1303](#1303))
([525ff38](525ff38))
* **spec:** Natively Support Multi-tenancy on gRPC through an additional
scope field on the request.
([#1195](#1195))
([cfbce32](cfbce32)),
closes [#1148](#1148)
* **spec:** Provide ability for SDKs to be backwards compatible.
([#1401](#1401))
([227e249](227e249))
* **spec:** Remove v1s from a2a url http bindings
([1bd263f](1bd263f))


### Bug Fixes

* Add missing metadata field to Part message in gRPC specification
([#1019](#1019))
([b3b266d](b3b266d)),
closes [#1005](#1005)
* Add name field to FilePart protobuf message
([#983](#983))
([2b7cb6f](2b7cb6f)),
closes [#984](#984)
* Clarify blocking calls return on interrupted states
([#1403](#1403))
([0655ff3](0655ff3))
* **doc:** Makes JSON-RPC SendMessage response clearer
([#1241](#1241))
([5792804](5792804))
* **docs:** Clearer wording around context id.
([#1588](#1588))
([dec790a](dec790a))
* **grpc:** Fix inconsistent property name between gRPC and JSON-RPC in
Message object ([#1100](#1100))
([2a1f819](2a1f819))
* **grpc:** missing field in gRPC spec - state_transition_history
([#1138](#1138))
([a2de798](a2de798)),
closes [#1139](#1139)
* **grpc:** Update `CreateTaskPushNotificationConfig` endpoint to
`/v1/{parent=tasks/*/pushNotificationConfigs}`
([#979](#979))
([911f9b0](911f9b0))
* **proto:** Add icon_url to a2a.proto
([#986](#986))
([17e7f62](17e7f62))
* **proto:** Adds metadata field to A2A DataPart proto
([#1004](#1004))
([a8b45dc](a8b45dc))
* Remove unimplemented state_transition_history capability field
([#1396](#1396))
([c768a44](c768a44)),
closes [#1228](#1228)
* Restore CreateTaskPushNotificationConfig method naming
([#1402](#1402))
([d14f410](d14f410))
* Revert "chore(gRPC): Update a2a.proto to include metadata on
GetTaskRequest" ([#1000](#1000))
([e6b8c65](e6b8c65))
* Simplify Part message structure by flattening FilePart and DataPart
([#1411](#1411))
([bfae8f7](bfae8f7))
* **spec:** Add LF prefix to the package.
([#1474](#1474))
([a54e809](a54e809))
* **spec:** add metadata to `CancelTaskRequest`
([#1485](#1485))
([c441b91](c441b91)),
closes [#1484](#1484)
* **spec:** Added clarification on timestamps in HTTP query params
([#1425](#1425))
([6292104](6292104))
* **spec:** Added clarifying text around messages and artifacts
([#1424](#1424))
([b03d141](b03d141))
* **spec:** Adjust field number for `ListTasksRequest.tenant` to prevent
missing number ([#1470](#1470))
([cd16c52](cd16c52))
* **spec:** Clarify contextId behavior when message is sent with taskId
but without contextId
([#1309](#1309))
([a336a5a](a336a5a))
* **spec:** Clarify versioning strategy and client responsibilities in
protocol specification
([#1259](#1259))
([a4afeea](a4afeea))
* **spec:** Fix/1251 clarify authentication scheme
([#1256](#1256))
([3e6c7db](3e6c7db))
* **spec:** Fixes for the last_updated_after field
([#1358](#1358))
([0e204bf](0e204bf))
* **spec:** Make "message" field name consistent between protocol
bindings ([#1302](#1302))
([1e5f462](1e5f462)),
closes [#1230](#1230)
* **spec:** make `history_length` optional
([#1071](#1071))
([0572953](0572953))
* **spec:** pluralize configs in `ListTaskPushNotificationConfigs`
([#1486](#1486))
([cf735cb](cf735cb))
* **spec:** Remove config from binding.
([#1587](#1587))
([010b9cc](010b9cc))
* **spec:** Remove deprecated fields from a2a.proto for v1.0 release
([#1301](#1301))
([60f83c3](60f83c3)),
closes [#1227](#1227)
* **spec:** remove duplicated ID from the create task push config
request ([#1487](#1487))
([393898d](393898d))
* **spec:** Remove metadata field from ListTasksRequest
([#1235](#1235))
([b6ef9ee](b6ef9ee))
* **spec:** Remove reserved and fix tags ordering
([#1494](#1494))
([1997c9d](1997c9d))
* **spec:** Rename `supportsAuthenticatedExtendedCard` to
`supportsExtendedAgentCard`
([#1222](#1222))
([c196824](c196824)),
closes [#1215](#1215)
* **spec:** Standardize spelling of "canceled" to use American Spelling
throughout ([#1283](#1283))
([4dd980f](4dd980f))
* **spec:** Suggest Unique Identifier fields to be UUID
([#966](#966))
([00cf76e](00cf76e))
* **spec:** Switch to non-complex IDs in requests
([#1389](#1389))
([2596c1c](2596c1c)),
closes [#1390](#1390)
* **spec:** Update security schemes example
([#1364](#1364))
([f9a8f5b](f9a8f5b))
* Update the Java tutorials and descriptions
([#1181](#1181))
([202aa06](202aa06))


### Documentation

* **spec:** Align enum format with ADR-001 ProtoJSON specification
([#1384](#1384))
([810eaa1](810eaa1)),
closes [#1344](#1344)


### Code Refactoring

* **spec:** Combine `TaskPushNotificationConfig` and
`PushNotificationConfig`
([#1500](#1500))
([d1ed0da](d1ed0da))
* **spec:** Large refactor of specification to separate application
protocol definition from mapping to transports
([b078419](b078419))
* **spec:** Move `extendedAgentCard` field to `AgentCapabilities`
([#1307](#1307))
([40d6286](40d6286))
* **spec:** Remove redundant `final` field from `TaskStatusUpdateEvent`
([#1308](#1308))
([5b101cc](5b101cc))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: Amye Scavarda Perrin <amye@amye.org>
Co-authored-by: Holt Skinner <13262395+holtskinner@users.noreply.github.com>
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[Bug]: gRPC spec missing state_transition_history field in AgentCapabilities

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