Python: Enhance _OutputItemTracker to prevent duplicate function call streaming

[cecheta]

Motivation & Context

Fixes bug where function call was duplicated when streaming response from declaration-only tool,

Description & Review Guide

When the agent invokes the declaration-only tool, there is a second function call emitted containing just metadata. Both of these tools were being streamed to the user.

Related Issue

Fixes #7485

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change. If it is a breaking change, add the breaking change label (or add "[BREAKING]" to the title prefix, before or after any language prefix) — a workflow keeps the label and title prefix in sync automatically.

[github-actions]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/foundry_hosting/agent_framework_foundry_hosting
_responses.py	930	91	90%	199–202, 270, 275, 299, 354–355, 369, 372–373, 405–406, 440, 456, 518, 639, 653, 701, 761, 764, 770, 772, 849, 936–937, 1058, 1289, 1302, 1793–1795, 1797, 1844–1845, 1847–1848, 1850–1851, 1853–1854, 1859, 1868, 1871–1873, 1875, 1885, 1889, 1902, 1993–1994, 2009–2010, 2012, 2017–2021, 2023, 2030–2031, 2033–2034, 2040, 2042–2046, 2053, 2059, 2081, 2087, 2093, 2095, 2097–2100, 2108, 2110, 2171–2173, 2187–2188, 2191–2192
TOTAL	44559	4127	90%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
9128	34 💤	0 ❌	0 🔥	2m 4s ⏱️

[Copilot]

Pull request overview

Fixes a Foundry Hosting streaming bug in the Python implementation where a declaration-only tool invocation can result in a duplicate function_call output item being streamed to the client. The change extends the streaming output-item tracker to recognize and suppress the metadata-only duplicate call, and adds a regression test covering the scenario.

Changes:

• Track previously-streamed function call call_ids during a streaming response.
• Suppress streaming of metadata-only duplicate function-call updates for already-seen call_ids.
• Add a regression test ensuring only one function_call output item is emitted for declaration-only metadata follow-ups.

Show a summary per file

File	Description
python/packages/foundry_hosting/agent_framework_foundry_hosting/_responses.py	Adds duplicate-detection logic in _OutputItemTracker to prevent streaming a second metadata-only function call item.
python/packages/foundry_hosting/tests/test_responses.py	Adds a regression test reproducing the declaration-only metadata duplication scenario in streaming mode.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Lite

[moonbox3]

Could we scope this suppression to the current logical occurrence instead of retaining every call_id for the full response? call_id reuse after completion is supported, so a later zero-argument user_input_request with that ID is silently dropped here as metadata. In a workflow, the request remains pending but the client never receives it and cannot resume. How about we retire the ID on its matching terminal result or otherwise distinguish the metadata replay?