fix(grpc): make history_length optional

[yarolegovich]

Description

Both fields are optional in types.ts and jsonrpc schema.
For both cases it might be useful to differentiate 0 and unset. For example:

1. A client calls GetTask and doesn't want History to be fetched / included in the response.
2. A client calls SendMessage and doesn't want history to be persisted at all.

The change is backward-compatible and makes it possible for a2a servers to provide consistent behavior regardless of the selected transport.

Fixes #1072

[gemini-code-assist]

Summary of Changes

Hello @yarolegovich, 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 enhances the flexibility of history management within the a2a system by making the history_length field optional in key gRPC message definitions: SendMessageConfiguration and GetTaskRequest. This update allows clients to precisely control whether history is fetched or persisted, differentiating between a zero value and an unset state. The change ensures consistency across various communication transports, including gRPC and JSON-RPC, and is fully backward-compatible.

Highlights

• gRPC Field Optionality: The history_length field in both SendMessageConfiguration and GetTaskRequest gRPC messages has been updated from a required int32 to an optional int32. This allows for explicit differentiation between a zero value (e.g., unlimited history) and an unset value (e.g., no history desired).
• Consistency Across Transports: This change aligns the gRPC specification with existing types.ts and JSON-RPC schemas, where history_length is already optional. This ensures a2a servers can provide consistent behavior regarding history handling, regardless of the communication transport used.
• Backward Compatibility: The modification is backward-compatible, meaning existing clients will continue to function without issues, while new clients can leverage the enhanced control offered by the optional field.

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[gemini-code-assist]

Code Review

This pull request makes the history_length field optional in SendMessageConfiguration and GetTaskRequest to align with the JSON-RPC specification and provide more flexibility. The change is logical and well-justified. My review includes suggestions to improve the comments for these fields to clearly document the behavior when the field is unset, which is important for API consumers.

[ToddSegal]

cleanup for 1.0 needs this.

recommend we vote

/vote

[git-vote]

Vote created

@ToddSegal has called for a vote on fix(grpc): make history_length optional (#1071).

The members of the following teams have binding votes:

Team
@a2aproject/a2a-tsc

Non-binding votes are also appreciated as a sign of support!

How to vote

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[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
ToddSegal	In favor	2025-11-10 21:42:05.0 +00:00:00
darrelmiller	In favor	2025-11-10 22:13:44.0 +00:00:00
muscariello	In favor	2025-11-10 23:01:30.0 +00:00:00
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
ToddSegal	In favor	2025-11-10 21:42:05.0 +00:00:00
darrelmiller	In favor	2025-11-10 22:13:44.0 +00:00:00
muscariello	In favor	2025-11-10 23:01:30.0 +00:00:00
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
ToddSegal	In favor	2025-11-10 21:42:05.0 +00:00:00
darrelmiller	In favor	2025-11-10 22:13:44.0 +00:00:00
muscariello	In favor	2025-11-10 23:01:30.0 +00:00:00
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
ToddSegal	In favor	2025-11-10 21:42:05.0 +00:00:00
darrelmiller	In favor	2025-11-10 22:13:44.0 +00:00:00
muscariello	In favor	2025-11-10 23:01:30.0 +00:00:00
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
ToddSegal	In favor	2025-11-10 21:42:05.0 +00:00:00
darrelmiller	In favor	2025-11-10 22:13:44.0 +00:00:00
muscariello	In favor	2025-11-10 23:01:30.0 +00:00:00
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
ToddSegal	In favor	2025-11-10 21:42:05.0 +00:00:00
darrelmiller	In favor	2025-11-10 22:13:44.0 +00:00:00
muscariello	In favor	2025-11-10 23:01:30.0 +00:00:00
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

[git-vote]

Vote closed

The vote did not pass.

37.50% of the users with binding vote were in favor and 0.00% were against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
@ToddSegal	In favor	2025-11-10 21:42:05.0 +00:00:00
@darrelmiller	In favor	2025-11-10 22:13:44.0 +00:00:00
@muscariello	In favor	2025-11-10 23:01:30.0 +00:00:00

[amye]

/vote

[git-vote]

Vote created

@amye has called for a vote on fix(grpc): make history_length optional (#1071).

The members of the following teams have binding votes:

Team
@a2aproject/a2a-tsc

Non-binding votes are also appreciated as a sign of support!

How to vote

You can cast your vote by reacting to this comment. The following reactions are supported:

In favor	Against	Abstain
👍	👎	👀

Please note that voting for multiple options is not allowed and those votes won't be counted.

The vote will be open for 7days. It will pass if at least 51% of the users with binding votes vote In favor 👍. Once it's closed, results will be published here as a new comment.

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
000-000-000-000-000	In favor	2025-11-18 17:06:02.0 +00:00:00
geneknit	In favor	2025-11-18 17:06:51.0 +00:00:00
hughesthe1st	In favor	2025-11-18 17:10:20.0 +00:00:00
@muscariello	Pending
@darrelmiller	Pending
@lerhaupt	Pending
@ToddSegal	Pending
@SivaNSAP	Pending

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
000-000-000-000-000	In favor	2025-11-18 17:06:02.0 +00:00:00
geneknit	In favor	2025-11-18 17:06:51.0 +00:00:00
hughesthe1st	In favor	2025-11-18 17:10:20.0 +00:00:00
@muscariello	Pending
@darrelmiller	Pending
@lerhaupt	Pending
@ToddSegal	Pending
@SivaNSAP	Pending

[holtskinner]

@yarolegovich Be sure to rebase to main after the recent refactoring

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
000-000-000-000-000	In favor	2025-11-18 17:06:02.0 +00:00:00
geneknit	In favor	2025-11-18 17:06:51.0 +00:00:00
hughesthe1st	In favor	2025-11-18 17:10:20.0 +00:00:00
@muscariello	Pending
@darrelmiller	Pending
@lerhaupt	Pending
@ToddSegal	Pending
@SivaNSAP	Pending

[amye]

Ping for this particular comment: #1071 (comment)

@muscariello
@darrelmiller
@lerhaupt
@ToddSegal
@SivaNSAP