Modernized and streamlined default LLMs

[jamesbraza]

This PR:

• Removes some one-off defaulted LLMs from the code base, keeping us centered on Settings
• Updates LLM defaults to match the latest Anthropic OpenAI model
  • Went with OpenAI to stick to one provider

Previously we used gpt-4o-2024-11-20 for our models. From https://platform.openai.com/docs/models/gpt-4o, https://platform.openai.com/docs/models/gpt-5, and https://docs.claude.com/en/docs/about-claude/models/overview as of 10/20/2025:

Model	Input Price (USD/M tokens)	Output Price (USD/M tokens)	Context Window (tokens)	Data Cutoff
gpt-4o-2024-11-20	$2	$10	128k	October 2023
gpt-5-2025-08-07	$1.25	$10	400k	September 2024
claude-sonnet-4-5-20250929	$3	$15	200k	July 2025

[Copilot]

Pull Request Overview

This PR modernizes default LLM selections by:

• Migrating from OpenAI's GPT-4 to Anthropic's Claude Sonnet 4-5 as the default model
• Removing hardcoded model defaults in function signatures to rely on centralized settings
• Updating test cassettes to reflect the model changes

Reviewed Changes

Copilot reviewed 5 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/cassettes/test_partly_embedded_texts[True].yaml	Updated test cassette reflecting API interactions with the new default model and updated library versions
src/paperqa/settings.py	Changed default LLM from gpt-4o-2024-11-20 to claude-sonnet-4-5-20250929 for agent_llm, llm, and summary_llm; removed unused CommonLLMNames import
src/paperqa/agents/models.py	Removed hardcoded default model from get_summary method signature
src/paperqa/agents/helpers.py	Made llm parameter required by removing default value and reordering parameters in litellm_get_search_query
README.md	Updated documentation to reflect new default models

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[whitead]

For simplicity, it would be nice to only require one provider. If we change to Anthropic a user needs OpenAI keys and Anthropic keys, right? Because if the embeddings?

[jamesbraza]

For simplicity, it would be nice to only require one provider. If we change to Anthropic a user needs OpenAI keys and Anthropic keys, right? Because if the embeddings?

Yeah makes sense, so I just updated to GPT-5. Why I hadn't originally was, GPT-5 requires updating our default temperature to 1.

[mskarlin]

thank you for this!