[Zakaria Khchiche (Zakariakhchiche)]

Motivation & Context

Citations returned by Anthropic are lost or broken in two cases:

1. Streaming: each citation arrives as a citations_delta event on the open text block. _parse_contents_from_anthropic has no case for it, so streamed responses come back without any annotations, while the same request without streaming has them.
2. char_location citations: the parser reads citation.title, but BetaCitationCharLocation exposes document_title. Document citations therefore have no title. This is the field issue raised in the review of Python: Surface Anthropic citations_delta annotations when streaming #8978.

Description & Review Guide

• What are the major changes?
  • New citations_delta case: it emits an empty text content with merge_mode="append" when streaming, carrying the parsed annotation, so it merges into the text it belongs to.
  • _parse_citations_from_anthropic accepts a citations_delta block, reading its single citation.
  • The char_location branch reads document_title.
  • Two tests: one builds a real BetaCitationCharLocation and checks the title, snippet and span; one streams a text block with a char_location and a web_search_result_location citation and checks that both end up as annotations on the final text.
• What is the impact of these changes? Streaming and non-streaming responses now expose the same citations. There is no API change.
• What do you want reviewers to focus on? Whether an empty appended text is the preferred way to attach a streamed annotation to the open text block.

Related Issue

Fixes #8977.

No other open PR addresses this issue (#8978 was closed).

AI Assistance

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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 links to an agreed issue with no competing open PR, or the Related Issue section documents a trivial-change or repository-automation exception.
• 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.

[Copilot]

🟢 Approval recommended

There are no active review issues for the streamed-citation and document-title changes.

No open issues 🎉

What changed in this PR

This PR addresses #8977 by preserving Anthropic citations in streamed responses and correcting document citation titles in the Python client, without changing the public API.

Changes:

• Handles citations_delta events using empty appended text content to carry annotations.
• Reads document_title for char_location citations.
• Adds regression tests for document citation metadata and streamed document/web citations.

File	Description
python/​packages/​anthropic/​tests/​test_anthropic_client.py	Adds regression coverage for citation titles and streamed annotations.
python/​packages/​anthropic/​agent_framework_anthropic/​_chat_client.py	Parses streamed citation deltas and corrects document title extraction.

_{Review effort: Balanced}