Python: Feat: Add finish_reason support to AgentResponse and AgentResponseUpdate

[LEDazzio01]

Add finish_reason to AgentResponse and AgentResponseUpdate

Motivation

Resolves the gap between ChatResponse/ChatResponseUpdate (which already have finish_reason) and the agent-level response types. This brings the Python SDK into parity with the .NET SDK's AgentResponseItem.FinishReason field.\n\nRelated: Supersedes #4958 (rebased cleanly from current main to resolve merge conflicts).\n\n## Changes\n\n### python/packages/core/agent_framework/_types.py\n\n1. AgentResponse.__init__ — Added finish_reason: FinishReasonLiteral | FinishReason | None = None parameter and self.finish_reason initialization.\n2. AgentResponseUpdate.__init__ — Same addition.\n3. _process_update() — Added an AgentResponse/AgentResponseUpdate isinstance block to propagate finish_reason from updates to the accumulated response (mirrors the existing ChatResponse block).\n4. map_chat_to_agent_update() — Forwards finish_reason from ChatResponseUpdate to AgentResponseUpdate.\n\n### python/packages/core/tests/core/test_finish_reason.py (NEW)\n\nComprehensive unit tests covering:\n- AgentResponse and AgentResponseUpdate initialization with finish_reason\n- map_chat_to_agent_update forwarding\n- _process_update propagation (including None-safety)\n- Serialization round-trip via .to_dict()\n\n## Testing\n\n- [x] All new tests pass locally\n- [x] No changes to existing public API signatures (additive only)\n- [x] Backward compatible — finish_reason defaults to None\n\n## Checklist\n\n- [x] Followed Contribution Guidelines\n- [x] Unit tests added\n- [x] No breaking changes"

[Copilot]

Pull request overview

Adds finish_reason support to agent-level response types in the Python SDK, aligning AgentResponse/AgentResponseUpdate with the existing chat response types and improving parity with the .NET SDK.

Changes:

• Added finish_reason fields to AgentResponse and AgentResponseUpdate.
• Propagated finish_reason during streaming update accumulation (_process_update) and when mapping ChatResponseUpdate -> AgentResponseUpdate.
• Added unit tests validating initialization, mapping, propagation behavior, and serialization.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
python/packages/core/agent_framework/_types.py	Adds finish_reason to agent response types and ensures it is propagated during update processing and chat→agent update mapping.
python/packages/core/tests/core/test_finish_reason.py	New tests covering finish_reason initialization, propagation, and serialization for agent response types.

[eavanvalkenburg]

and please rebase from main, there is a conflict

[LEDazzio01]

@eavanvalkenburg Done — both items addressed:

1. Rebased onto latest main — conflict in _types.py resolved (kept upstream's model → model_id rename alongside the finish_reason propagation logic).

2. Moved tests into test_types.py — deleted the separate test_finish_reason.py file and added all 7 test functions to the test_types.py file under a new # region finish_reason section. Added _process_update and map_chat_to_agent_update to the existing _types import block.

[moonbox3]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework
_types.py	1090	87	92%	58, 67–68, 122, 127, 146, 148, 152, 156, 158, 160, 162, 180, 184, 210, 232, 237, 242, 246, 276, 687–688, 847–848, 1233, 1305, 1340, 1360, 1370, 1422, 1554–1556, 1738, 1841–1846, 1871, 1965, 1973–1975, 1980, 2071, 2083, 2106, 2361, 2385, 2484, 2738, 2947, 3020, 3031, 3033–3037, 3039, 3042–3050, 3060, 3130, 3265, 3270, 3275, 3280, 3284, 3368–3370, 3399, 3476–3480
TOTAL	27693	3201	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
5610	20 💤	0 ❌	0 🔥	1m 30s ⏱️

[moonbox3]

@LEDazzio01 lint is failing in core

[LEDazzio01]

@moonbox3 Fixed in d29c620 — the SIM102 lint error in _process_update() has been resolved by combining the nested if statements. Also addressed @eavanvalkenburg's review feedback (model_id → model) in 3130827.

[eavanvalkenburg]

Another fail, please run the same checks locally. Uv run poe typing -P core

[LEDazzio01]

@eavanvalkenburg Fixed in c134789 — the pyright reportArgumentType error in map_chat_to_agent_update() was caused by pyright widening FinishReason (a NewType of str) back to plain str when reading the attribute. Added a # type: ignore[arg-type] matching the existing pattern used throughout _types.py.

Ran uv run poe typing -P core locally — mypy passes clean, pyright has zero _types.py errors (only pre-existing observability.py import errors remain).