ReqLLM.
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Shared streaming-chunk reducer used by both ReqLLM.StreamServer (the
hot path, one chunk at a time) and
ReqLLM.Provider.Defaults.ResponseBuilder (batch, full chunk list at
end-of-stream).
Maintains running iodata buffers for text/thinking, a running tool-call
list, and per-index argument-fragment buffers. Reasoning details and
logprobs are also collected from :meta chunks.
Finalizers
Two different finalizers exist because StreamServer and ResponseBuilder consume the accumulator differently:
finalize_tool_calls_for_response/1— preserves the historicalResponseBuildercontract: returns raw maps with:id,:name,:arguments(decoded JSON when fragments are present, else the raw args from the tool_call chunk). Used to feedResponseBuilder.normalize_tool_calls/1.finalize_message/1— preserves the historicalStreamServercontract: returns eithernil(empty acc) or an assistant%ReqLLM.Message{}ready to attach to OTel content-capture metadata. Text content becomes a single:textContentPart; tool calls become%ReqLLM.ToolCall{}structs (with builtin flag preserved).
Reasoning text is intentionally not surfaced through finalize_message/1
— OTel content capture redacts it anyway and the canonical response
message is built separately by ResponseBuilder with full reasoning
details.
Performance notes
The accumulator is on the streaming hot path. To keep push/2 O(1) per
chunk we prepend list entries (tool calls, reasoning details, logprobs)
and reverse them at finalize time. Text and thinking buffers are iodata
— also O(1) per chunk. Argument fragments are iodata buffers keyed by
tool-call index, joined only at finalize time. A stream with N chunks
costs O(N) total work, not O(N²).
Summary
Functions
Returns the most recently observed finish_reason from meta chunks, or
nil if no meta chunk surfaced one. The value is returned raw (atom or
string) — callers normalize.
Returns logprob tokens in arrival order.
Returns a partial assistant %ReqLLM.Message{} for OTel content
capture, or nil when the accumulator has no text and no tool calls.
Reasoning is intentionally nil — OTel content capture redacts it.
Returns reasoning details in arrival order.
Returns the concatenated text content as a binary.
Returns the concatenated thinking content as a binary.
Returns tool calls in the format ResponseBuilder.normalize_tool_calls/1
expects: maps with :id, :name, :arguments, and optionally a
:builtin? flag. If argument fragments were observed and decode
successfully, arguments are the decoded JSON; otherwise they fall back
to the raw arguments captured from the tool_call chunk.
Returns the merged usage map (or nil if no meta chunk surfaced usage).
Returns an empty accumulator.
Folds a single chunk into the accumulator. Hot path — O(1) per chunk.
Folds a list of chunks through push/2. Convenience wrapper for the
batch path (ResponseBuilder).
Types
@type t() :: %ReqLLM.Provider.ChunkAccumulator{ arg_fragments: %{optional(non_neg_integer()) => iodata()}, finish_reason: atom() | String.t() | nil, logprobs: [term()], reasoning_details: [term()], text_content: iodata(), thinking_content: iodata(), tool_calls: [tool_call_record()], usage: map() | nil }
@type tool_call_record() :: %{ id: String.t(), name: String.t(), arguments: term(), index: non_neg_integer() }
Functions
Returns the most recently observed finish_reason from meta chunks, or
nil if no meta chunk surfaced one. The value is returned raw (atom or
string) — callers normalize.
Returns logprob tokens in arrival order.
@spec finalize_message(t()) :: ReqLLM.Message.t() | nil
Returns a partial assistant %ReqLLM.Message{} for OTel content
capture, or nil when the accumulator has no text and no tool calls.
Reasoning is intentionally nil — OTel content capture redacts it.
Returns reasoning details in arrival order.
Returns the concatenated text content as a binary.
Returns the concatenated thinking content as a binary.
Returns tool calls in the format ResponseBuilder.normalize_tool_calls/1
expects: maps with :id, :name, :arguments, and optionally a
:builtin? flag. If argument fragments were observed and decode
successfully, arguments are the decoded JSON; otherwise they fall back
to the raw arguments captured from the tool_call chunk.
Returns the merged usage map (or nil if no meta chunk surfaced usage).
@spec new() :: t()
Returns an empty accumulator.
@spec push(t(), ReqLLM.StreamChunk.t()) :: t()
Folds a single chunk into the accumulator. Hot path — O(1) per chunk.
@spec reduce(t(), [ReqLLM.StreamChunk.t()]) :: t()
Folds a list of chunks through push/2. Convenience wrapper for the
batch path (ResponseBuilder).