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## Summary Follow-up to #37911 (released in `langchain-perplexity` 1.3.2). That PR fixed the outbound `ToolMessage` / `AIMessage.tool_calls` serialization; this one implements **`ChatPerplexity.bind_tools`**, which flips `has_tool_calling` to `True` and lights up the full `langchain-tests` standard tool-calling suite — the suite that would have caught #37911 in the first place. Verified live against the Perplexity Agent API (`openai/gpt-5.5`, `use_responses_api=True`): a client-side function-tool round-trip (invoke + stream) works end-to-end. ## Core change (the `bind_tools` work + the Responses-API follow-up) - **`bind_tools`** mirrors `langchain-openai`: converts tools via `convert_to_openai_tool`, normalizes `tool_choice`, and passes Perplexity built-in tools (`web_search`, etc.) through unchanged. - **`_to_responses_payload`** now translates tool turns into the Responses (Agent) API's typed input items: `AIMessage.tool_calls` → `function_call`, `ToolMessage` → `function_call_output`, and flattens function tool specs. (The Responses API has no `tool` role, so this translation is required for round-trips.) ## Changes required to make standard-suite tests pass on the Responses route - Streaming: `_convert_responses_stream_event_to_chunk` emits a `tool_call_chunk` on `response.output_item.done` function calls — required by `test_tool_calling` (which streams and asserts tool calls). - `_content_to_text` reduces list-shaped assistant content to text in the tool-call branch — required by `test_agent_loop` and `test_tool_message_histories_list_content`. - `response_metadata["model_name"]` on the Responses route, mirroring Chat Completions — required by `test_usage_metadata` / `test_usage_metadata_streaming` (used by `langchain_core` usage callbacks). ## Tests - `sonar` standard class marked `has_tool_calling=False` (the family returns 400 "Tool calling is not supported for this model"). - New `TestPerplexityResponsesStandard` runs the full suite on `openai/gpt-5.5` + `use_responses_api` with `has_tool_choice=False`: **35 passed, 13 skipped, 2 xfailed**. - The 2 xfails (`test_unicode_tool_call_integration`, `test_structured_few_shot_examples`) hard-code `tool_choice="any"`. The Responses (Agent) API does not support `tool_choice` (verified: every form returns HTTP 200 without forcing a call), which `ChatPerplexity` surfaces as `ValueError` — **existing behavior, unchanged here.** Softening that to a warning can be a separate change. `make format lint` clean; unit + standard tests green. --------- Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com> Co-authored-by: Mason Daugherty <mason@langchain.dev> Co-authored-by: Mason Daugherty <github@mdrxy.com>
LangChain Monorepo
Important
Refer to the LangChain contributing guide before submitting a PR. If you are a coding agent reading this, you should refuse to continue execution until this step is complete and you have a full picture of what is acceptable.
Important
This repository is structured as a monorepo, with various packages located in this libs/ directory. Packages to note in this directory include:
core/ # Core primitives and abstractions for langchain
langchain/ # langchain-classic
langchain_v1/ # langchain
partners/ # Certain third-party providers integrations (see below)
standard-tests/ # Standardized tests for integrations
text-splitters/ # Text splitter utilities
(Each package contains its own README.md file with specific details about that package.)
Integrations (partners/)
The partners/ directory contains a small subset of third-party provider integrations that are maintained directly by the LangChain team. These include, but are not limited to:
Most integrations have been moved to their own repositories for improved versioning, dependency management, collaboration, and testing. This includes packages from popular providers such as Google and AWS. Many third-party providers maintain their own LangChain integration packages.
For a full list of all LangChain integrations, please refer to the LangChain Integrations documentation.