Read documents through an ellmer chat

Uses an ellmer Chat object as the transport, so every provider ellmer supports (Anthropic, Google, Bedrock, Azure, Ollama, Hugging Face, and the rest) becomes available to every reading strategy here, with this package's context budgeting, cost rails, traces, caching and replay unchanged around it.

Usage

gr_ellmer_client(chat, embed = NULL, model = NULL)

Arguments

chat: An ellmer Chat, e.g. from ellmer::chat_anthropic() or ellmer::chat_ollama().
embed: Optional function of (texts, params) returning one row per input, for example a thin wrapper around ragnar::embed_ollama(). Without it, retrieve and the semantic segmenter fall back to lexical vectors and warn.
model: Model id reported to this package. Defaults to the chat's own model. Register it with gr_register_model() if it is not already known. The context window is what sizes your chunks, so a wrong one is not cosmetic.

Value

A gr_backend_client().

Details

ellmer is a suggested dependency: this function is the only thing in the package that needs it.

Requirements on the chat

The adapter calls $chat(), $chat_structured(), $clone(), $set_turns() and $set_system_prompt(), and refuses a chat missing any of them (gr_bad_backend). $chat_structured() is used by every schema-bearing call (each rerank score and each iterative round), so a chat without it would have failed mid-run rather than at construction. The last two are not conveniences: this package puts its instructions in the system prompt, and it clears turns so that one chunk's call cannot leak into the next. A chat that silently dropped either would produce unconstrained answers with nothing to show for it.

What does not carry over

Two things, both worth knowing before you rely on them.

temperature belongs to the chat object, not to the call. ellmer fixes sampling parameters when the chat is constructed, so a temperature in a gr_read_spec() cannot be honoured per-call; it is ignored and warned about once (gr_ellmer_temperature). Build a second chat if you need a second temperature.

Each call is independent. An ellmer chat accumulates turns, and this package issues many unrelated calls per run, so every call runs against a fresh deep clone with its turns cleared. Your chat object is never mutated, and no conversation history leaks from one chunk's call into the next.

Examples

if (FALSE) { # \dontrun{
library(ellmer)

# Any provider ellmer speaks to, with any reading strategy here.
cl <- gr_ellmer_client(chat_anthropic(model = "claude-sonnet-4-5"))
ans <- answer_document("report.pdf", "What was revenue?", "thorough", client = cl)

# Locally, for nothing:
local <- gr_ellmer_client(chat_ollama(model = "llama3.1"))
gr_compare("report.pdf", "What was revenue?",
           c("fast", "thorough"), client = local)$summary
} # }