Documentation Index
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weave / LLM
An LLM call. Emits a chat span with gen_ai.* attributes.
Created by weave.startLLM() (or turn.startLLM()) and terminated with
end(). Only one LLM may be active in an async context at a time; nest
tool/subagent calls under it via startTool / startSubagent.
Populate inputMessages / outputMessages / usage / reasoning directly,
or via the helper functions (output, think, attachMedia, record).
All recorded data is flushed to the span at end().
Example
const llm = weave.startLLM({model: 'gpt-4o-mini', providerName: 'openai'});
try {
llm.inputMessages = [{role: 'user', content: prompt}];
const resp = await openai.chat.completions.create({...});
llm.output(resp.choices[0].message.content ?? '');
llm.record({usage: {inputTokens: resp.usage?.prompt_tokens}});
} finally {
llm.end();
}
Table of contents
Properties
Methods
Properties
• inputMessages: Message[] = []
Input messages sent to the model. Flushed to gen_ai.input.messages on
end().
Defined in
genai/llm.ts:78
model
• Readonly model: string
Defined in
genai/llm.ts:98
outputMessages
• outputMessages: Message[] = []
Assistant messages returned by the model. Flushed to
gen_ai.output.messages on end().
Defined in
genai/llm.ts:83
providerName
• Readonly providerName: string
Defined in
genai/llm.ts:99
reasoning
• Optional reasoning: Reasoning
Chain-of-thought content. Folded into the last assistant message as a
ReasoningPart at serialization time.
Defined in
genai/llm.ts:90
usage
• usage: Usage = {}
Token counts and cache stats. Flushed to gen_ai.usage.* on end().
Defined in
genai/llm.ts:85
Methods
▸ attachMedia(opts): this
Attach a media part to the last input message. Pick exactly one of
content (inline base64 bytes), uri (URI reference), or fileId
(pre-uploaded file id).
Parameters
| Name | Type |
|---|
opts | AttachMediaOpts |
Returns
this
Defined in
genai/llm.ts:168
▸ attachMediaUrl(url, opts): this
Convenience for attachMedia({uri, modality}).
Parameters
| Name | Type |
|---|
url | string |
opts | Object |
opts.modality | Modality |
Returns
this
Defined in
genai/llm.ts:186
end
▸ end(opts?): void
Flush accumulated state to the span and close it. Idempotent. Pass
error to mark the span as failed.
Parameters
| Name | Type |
|---|
opts? | Object |
opts.error? | Error |
Returns
void
Defined in
genai/llm.ts:246
output
▸ output(content): this
Append an assistant message to the response.
Parameters
Returns
this
Defined in
genai/llm.ts:141
record
▸ record(opts): this
Bulk-set any subset of the mutable fields. Replaces (does not merge).
Useful for assigning everything at once after a provider call returns.
Parameters
| Name | Type |
|---|
opts | LLMRecordOpts |
Returns
this
Defined in
genai/llm.ts:197
startSubagent
▸ startSubagent(opts): SubAgent
Start a child SubAgent span nested under this LLM.
Parameters
Returns
SubAgent
Defined in
genai/llm.ts:230
▸ startTool(opts): Tool
Start a child Tool span nested under this LLM.
Parameters
Returns
Tool
Defined in
genai/llm.ts:221
think
▸ think(content): this
Set or extend the model’s reasoning/chain-of-thought content. Accumulates
into this.reasoning.content. Folded into the last assistant message as
a ReasoningPart at serialization time, matching the Python SDK’s
on-the-wire shape.
Parameters
Returns
this
Defined in
genai/llm.ts:153
create
▸ create(opts): LLM
Parameters
| Name | Type |
|---|
opts | LLMInit & ChildSpanContext |
Returns
LLM
Defined in
genai/llm.ts:102
