Comet vs ellmer

ellmer is R's provider-agnostic LLM client, covering Anthropic, OpenAI, Gemini, Bedrock, Databricks, Snowflake, Ollama, Groq and more behind one Chat object with structured output, tool calling and streaming. The last year moved it well past request plumbing: API keys are now fetched through a credentials function rather than stored in the object, provider-native web search and fetch are first-class tools, and every call emits OpenTelemetry spans when a tracer is active. Releases land roughly every six to ten weeks with meaningful content each time.

The arc runs from breadth to depth. Early releases raced to add providers; recent ones assume you already picked one and are trying to run it in production — tracing with the gen_ai semantic conventions, prompt caching on by default, parallel and batch chat graduating out of experimental with configurable error handling, and truncated or filtered responses raising warnings instead of passing silently. The credentials rework and automatic key redaction on save show the same instinct applied to secrets.

Batch processing has been picking up one provider per release — Gemini and Groq most recently — so the next releases likely continue filling in batch and built-in-tool coverage across the provider list rather than adding new provider integrations.