[jiahuei]

Summary

• Replaced PR feat: support hosted web search across Responses and Messages #74's provider_metadata.anthropic Responses extension with extra_content.anthropic. Search sources retain Anthropic encrypted content and source details; URL citations retain encrypted indices and original excerpts so serialized Responses output can continue against the same Anthropic Messages upstream.
• Updated typed history validation, projection/conversion helpers, route errors, existing cassette-backed SDK parity and continuation tests, and documentation. The colocated Responses-to-IR normalization test asserts complete ordered IR with and without Anthropic extra_content, including source ciphertext/details and citation encrypted indices/excerpts. Reused the existing IR fields; transport-level extra_body is unchanged. The old unmerged envelope is not retained as an alias.
• Targets amer-hosted-web-search (PR feat: support hosted web search across Responses and Messages #74). Implements the Anthropic continuation slice of Establish tested provider compatibility for Bedrock, OpenRouter, Together AI, Gemini, and Fireworks #78; Gemini support remains tracked there.

Problem, symptoms, and diagnosis

Problem

Anthropic hosted-search continuation needs the original source encrypted_content and citation encrypted_index, together with the source details and citation excerpt. Standard Responses URL sources and annotations cannot carry all of that state. PR #74 already preserved it under provider_metadata.anthropic, but the required public extension contract is extra_content.anthropic, following the provider-namespaced convention tracked in #78. This change aligns the existing continuation mechanism with that contract.

Symptoms

• Responses search sources and URL annotations exposed provider_metadata instead of extra_content. Consumers retaining the expected extra_content envelope would not retain the Anthropic continuation state.
• Before the implementation change, the updated cassette-backed output assertions failed in both streaming and non-streaming modes because extra_content was absent.
• History with missing encrypted state, or "N/A" placeholders, cannot restore Anthropic search context and is rejected before an Anthropic follow-up request. Renaming the envelope preserves real state; it does not make placeholders usable. The existing provider_metadata route already supported continuation when clients retained that envelope, so this was a public contract mismatch rather than evidence that all existing continuation was broken.

Steps taken to diagnose

1. Compared Google's documented request-level extra_body and content-level extra_content extension surfaces with Establish tested provider compatibility for Bedrock, OpenRouter, Together AI, Gemini, and Fireworks #78 and PR feat: support hosted web search across Responses and Messages #74 at c55a6b860fc4ff222a5b6e008a11aa1068277614.
2. Traced the existing carrier through local Responses history schemas, source/citation conversion helpers, route validation, streaming projection, SDK serialization, and next-turn ingestion. Confirmed the IR already stored these values directly in WebSearchSource and WebCitation; no new IR container was needed.
3. Changed the output expectations to extra_content and ran the focused recorded-search parity tests before implementation. Both modes failed on the missing field, identifying the Responses boundary as the change location.
4. Renamed the envelope and reran SDK parity and actual-output continuation tests. Verified exact reconstructed Anthropic request bodies, preserved source/citation state and linkage, and continued rejection of missing state or incompatible upstream routes.
5. Extended the existing Responses-to-IR hosted-search test to compare complete ordered IR with and without extra_content.anthropic, directly asserting ciphertext, citation indices, source details, excerpts, and call/result linkage. Verification results are listed below; provider traffic was offline replay only.

Verification

• PYTHONPATH=python /home/akk/jiahuei/molto/.venv/bin/python -m pytest -q tests/core/test_anthropic_web_search.py -k translates_sdk_semantics: both updated assertions failed before implementation because extra_content was absent.

• PYTHONPATH=python /home/akk/jiahuei/molto/.venv/bin/python -m pytest -q tests/core/test_anthropic_web_search.py tests/core/test_web_search.py tests/types/test_openai_responses.py: 405 passed after implementation.

• PYTHONPATH=python /home/akk/jiahuei/molto/.venv/bin/python -m pytest -q -o addopts='': 2,293 passed on Python 3.12.9, offline replay only. No live provider calls or cassette changes.

• uv run --extra lint ruff check --output-format github --config pyproject.toml .: passed.

• uv run --extra lint ruff format --diff --config pyproject.toml .: passed, 99 files already formatted. Initial changed-file formatting check identified two files, corrected with uv run --extra lint ruff format --config pyproject.toml python/molto/types/openai_responses.py tests/core/test_web_search.py.

• npx prettier@3.8 --check .: passed. Initial changed-document check identified docs/web-search.md, corrected with npx prettier@3.8 --write docs/web-search.md.

• git diff --check: passed. git status --short -- tests/cassettes: empty.

• PYTHONPATH=python /home/akk/jiahuei/molto/.venv/bin/python -m pytest -q tests/adapters/test_openai_search.py tests/core/test_anthropic_web_search.py: 55 passed after adding direct IR assertions. Repository-wide Ruff and Prettier checks also passed for this test-only update; the full-suite result above predates this additional parameterized case.