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v0.3 JSON-RPC and REST GetTask return no history when history_length is 0 #1311
Description
What happens
A v0.3 JSON-RPC or REST client that sends historyLength: 0 gets the task back with empty history. In v0.3, 0 means unlimited, and the gRPC path returns the full history.
Why
to_core_send_message_configuration (compat/v0_3/conversions.py:320) and to_core_get_task_request (:1077) pass 0 through as a limit, and the core reads 0 as no history. FromProto already maps 0 to None for gRPC since #1306.
Version
main @ e649325
Activity
rohityan commentedon Oct 8, 2026
Hi @ConnorMoss02, thanks for reporting this.
In the
v0.3protocol specification,history_length = 0signifies unlimited history. However, in the v1.0 core protobuf models,history_length = 0explicitly tells the engine to truncate history to 0 items; unlimited history requires the field to remain unset.In
src/a2a/compat/v0_3/conversions.py,to_core_get_task_requestandto_core_send_message_configurationcheckif history_length is not None:. Because0 is not NoneisTrue,0is set on the protobuf request rather than being omitted.As a workaround you can omit
history_lengthor passNoneinstead of0.Your implementation of an upstream fix in PR #1312 is the right approach. Assigning the issue to you till it gets reviewed.
ConnorMoss02 commentedon Oct 8, 2026
Thanks for confirming. Happy to adjust #1312 if the reviewers want anything changed.