Preserve native LLM tool context

packages/llm/example/tutorial.ts

@@ -78,7 +78,7 @@ const streamText = LLM.stream(request).pipe(
   Stream.tap((event) =>
     Effect.sync(() => {
       if (event.type === "text-delta") process.stdout.write(`\ntext: ${event.text}`)
-      if (event.type === "request-finish") process.stdout.write(`\nfinish: ${event.reason}\n`)
+      if (event.type === "finish") process.stdout.write(`\nfinish: ${event.reason}\n`)
     }),
   ),
   Stream.runDrain,
@@ -185,7 +185,7 @@ const FakeProtocol = Protocol.make<FakeBody, string, string, void>({
     event: Schema.String,
     initial: () => undefined,
     step: (_, frame) => Effect.succeed([undefined, [{ type: "text-delta", id: "text-0", text: frame }]] as const),
-    onHalt: () => [{ type: "request-finish", reason: "stop" }],
+    onHalt: () => [{ type: "finish", reason: "stop" }],
   },
 })
 

packages/llm/src/index.ts

@@ -17,6 +17,7 @@ export type {
   ExecutableTools,
   Tool as ToolShape,
   ToolExecute,
+  ToolExecuteContext,
   Tools,
   ToolSchema,
 } from "./tool"

packages/llm/src/protocols/openai-responses.ts

@@ -380,7 +380,7 @@ type StepResult = readonly [ParserState, ReadonlyArray<LLMEvent>]
 const NO_EVENTS: StepResult["1"] = []
 
 // `response.completed` / `response.incomplete` are clean finishes that emit a
-// `request-finish` event; `response.failed` is a hard failure that emits a
+// `finish` event; `response.failed` is a hard failure that emits a
 // `provider-error`. All three end the stream — kept in one set so `step` and
 // the protocol's `terminal` predicate stay in sync.
 const TERMINAL_TYPES = new Set(["response.completed", "response.incomplete", "response.failed"])

packages/llm/src/protocols/utils/lifecycle.ts

@@ -80,7 +80,7 @@ export const finish = (
       usage: input.usage,
       providerMetadata: input.providerMetadata,
     }),
-    LLMEvent.requestFinish(input),
+    LLMEvent.finish(input),
   )
   return { ...stepped, stepStarted: false }
 }

packages/llm/src/schema/events.ts

@@ -1,5 +1,5 @@
 import { Schema } from "effect"
-import { ContentBlockID, FinishReason, ProtocolID, ProviderMetadata, ResponseID, RouteID, ToolCallID } from "./ids"
+import { ContentBlockID, FinishReason, ProtocolID, ProviderMetadata, RouteID, ToolCallID } from "./ids"
 import { ModelRef } from "./options"
 import { ToolResultValue } from "./messages"
 
@@ -66,14 +66,13 @@ export class Usage extends Schema.Class<Usage>("LLM.Usage")({
   get visibleOutputTokens() {
     return Math.max(0, (this.outputTokens ?? 0) - (this.reasoningTokens ?? 0))
   }
+
+  static from(input: UsageInput) {
+    return input instanceof Usage ? input : new Usage(input)
+  }
 }
 
-export const RequestStart = Schema.Struct({
-  type: Schema.tag("request-start"),
-  id: ResponseID,
-  model: ModelRef,
-}).annotate({ identifier: "LLM.Event.RequestStart" })
-export type RequestStart = Schema.Schema.Type<typeof RequestStart>
+export type UsageInput = Usage | ConstructorParameters<typeof Usage>[0]
 
 export const StepStart = Schema.Struct({
   type: Schema.tag("step-start"),
@@ -185,13 +184,13 @@ export const StepFinish = Schema.Struct({
 }).annotate({ identifier: "LLM.Event.StepFinish" })
 export type StepFinish = Schema.Schema.Type<typeof StepFinish>
 
-export const RequestFinish = Schema.Struct({
-  type: Schema.tag("request-finish"),
+export const Finish = Schema.Struct({
+  type: Schema.tag("finish"),
   reason: FinishReason,
   usage: Schema.optional(Usage),
   providerMetadata: Schema.optional(ProviderMetadata),
-}).annotate({ identifier: "LLM.Event.RequestFinish" })
-export type RequestFinish = Schema.Schema.Type<typeof RequestFinish>
+}).annotate({ identifier: "LLM.Event.Finish" })
+export type Finish = Schema.Schema.Type<typeof Finish>
 
 export const ProviderErrorEvent = Schema.Struct({
   type: Schema.tag("provider-error"),
@@ -202,7 +201,6 @@ export const ProviderErrorEvent = Schema.Struct({
 export type ProviderErrorEvent = Schema.Schema.Type<typeof ProviderErrorEvent>
 
 const llmEventTagged = Schema.Union([
-  RequestStart,
   StepStart,
   TextStart,
   TextDelta,
@@ -217,13 +215,15 @@ const llmEventTagged = Schema.Union([
   ToolResult,
   ToolError,
   StepFinish,
-  RequestFinish,
+  Finish,
   ProviderErrorEvent,
 ]).pipe(Schema.toTaggedUnion("type"))
 
 type WithID<Event extends { readonly id: unknown }, ID> = Omit<Event, "type" | "id"> & { readonly id: ID | string }
+type WithUsage<Event extends { readonly usage?: Usage }> = Omit<Event, "type" | "usage"> & {
+  readonly usage?: UsageInput
+}
 
-const responseID = (value: ResponseID | string) => ResponseID.make(value)
 const contentBlockID = (value: ContentBlockID | string) => ContentBlockID.make(value)
 const toolCallID = (value: ToolCallID | string) => ToolCallID.make(value)
 
@@ -233,7 +233,6 @@ const toolCallID = (value: ToolCallID | string) => ToolCallID.make(value)
  * `events.filter(LLMEvent.guards["tool-call"])`.
  */
 export const LLMEvent = Object.assign(llmEventTagged, {
-  requestStart: (input: WithID<RequestStart, ResponseID>) => RequestStart.make({ ...input, id: responseID(input.id) }),
   stepStart: StepStart.make,
   textStart: (input: WithID<TextStart, ContentBlockID>) => TextStart.make({ ...input, id: contentBlockID(input.id) }),
   textDelta: (input: WithID<TextDelta, ContentBlockID>) => TextDelta.make({ ...input, id: contentBlockID(input.id) }),
@@ -252,11 +251,18 @@ export const LLMEvent = Object.assign(llmEventTagged, {
   toolCall: (input: WithID<ToolCall, ToolCallID>) => ToolCall.make({ ...input, id: toolCallID(input.id) }),
   toolResult: (input: WithID<ToolResult, ToolCallID>) => ToolResult.make({ ...input, id: toolCallID(input.id) }),
   toolError: (input: WithID<ToolError, ToolCallID>) => ToolError.make({ ...input, id: toolCallID(input.id) }),
-  stepFinish: StepFinish.make,
-  requestFinish: RequestFinish.make,
+  stepFinish: (input: WithUsage<StepFinish>) =>
+    StepFinish.make({
+      ...input,
+      usage: input.usage === undefined ? undefined : Usage.from(input.usage),
+    }),
+  finish: (input: WithUsage<Finish>) =>
+    Finish.make({
+      ...input,
+      usage: input.usage === undefined ? undefined : Usage.from(input.usage),
+    }),
   providerError: ProviderErrorEvent.make,
   is: {
-    requestStart: llmEventTagged.guards["request-start"],
     stepStart: llmEventTagged.guards["step-start"],
     textStart: llmEventTagged.guards["text-start"],
     textDelta: llmEventTagged.guards["text-delta"],
@@ -271,7 +277,7 @@ export const LLMEvent = Object.assign(llmEventTagged, {
     toolResult: llmEventTagged.guards["tool-result"],
     toolError: llmEventTagged.guards["tool-error"],
     stepFinish: llmEventTagged.guards["step-finish"],
-    requestFinish: llmEventTagged.guards["request-finish"],
+    finish: llmEventTagged.guards.finish,
     providerError: llmEventTagged.guards["provider-error"],
   },
 })

packages/llm/src/tool-runtime.ts

@@ -12,6 +12,7 @@ import {
   ToolFailure,
   ToolResultPart,
   type ToolResultValue,
+  Usage,
 } from "./schema"
 import { type AnyTool, type ExecutableTools, type Tools, toDefinitions } from "./tool"
 
@@ -72,19 +73,42 @@ export const stream = <T extends Tools>(options: StreamOptions<T>): Stream.Strea
           tools: [...options.request.tools.filter((tool) => !runtimeToolNames.has(tool.name)), ...runtimeTools],
         })
 
-  const loop = (request: LLMRequest, step: number): Stream.Stream<LLMEvent, LLMError> =>
+  const loop = (
+    request: LLMRequest,
+    step: number,
+    usage: Usage | undefined,
+    providerMetadata: ProviderMetadata | undefined,
+  ): Stream.Stream<LLMEvent, LLMError> =>
     Stream.unwrap(
       Effect.gen(function* () {
-        const state: StepState = { assistantContent: [], toolCalls: [], finishReason: undefined }
+        const state: StepState = {
+          assistantContent: [],
+          toolCalls: [],
+          finishReason: undefined,
+          usage: undefined,
+          providerMetadata: undefined,
+        }
 
         const modelStream = options
           .stream(request)
+          .pipe(Stream.map((event) => indexStep(event, step)))
           .pipe(Stream.tap((event) => Effect.sync(() => accumulate(state, event))))
+          .pipe(Stream.filter((event) => event.type !== "finish"))
 
         const continuation = Stream.unwrap(
           Effect.gen(function* () {
-            if (state.finishReason !== "tool-calls" || state.toolCalls.length === 0) return Stream.empty
-            if (options.toolExecution === "none") return Stream.empty
+            const totalUsage = addUsage(usage, state.usage)
+            const totalProviderMetadata = mergeProviderMetadata(providerMetadata, state.providerMetadata)
+            const finishStream = Stream.fromIterable([
+              LLMEvent.finish({
+                reason: state.finishReason ?? "unknown",
+                usage: totalUsage,
+                providerMetadata: totalProviderMetadata,
+              }),
+            ])
+
+            if (state.finishReason !== "tool-calls" || state.toolCalls.length === 0) return finishStream
+            if (options.toolExecution === "none") return finishStream
 
             const dispatched = yield* Effect.forEach(
               state.toolCalls,
@@ -93,24 +117,36 @@ export const stream = <T extends Tools>(options: StreamOptions<T>): Stream.Strea
             )
             const resultStream = Stream.fromIterable(dispatched.flatMap(([call, result]) => emitEvents(call, result)))
 
-            if (!options.stopWhen) return resultStream
-            if (options.stopWhen({ step, request })) return resultStream
+            if (!options.stopWhen) return resultStream.pipe(Stream.concat(finishStream))
+            if (options.stopWhen({ step, request })) return resultStream.pipe(Stream.concat(finishStream))
 
-            return resultStream.pipe(Stream.concat(loop(followUpRequest(request, state, dispatched), step + 1)))
+            return resultStream.pipe(
+              Stream.concat(
+                loop(followUpRequest(request, state, dispatched), step + 1, totalUsage, totalProviderMetadata),
+              ),
+            )
           }),
         )
 
         return modelStream.pipe(Stream.concat(continuation))
       }),
     )
 
-  return loop(initialRequest, 0)
+  return loop(initialRequest, 0, undefined, undefined)
+}
+
+const indexStep = (event: LLMEvent, index: number): LLMEvent => {
+  if (event.type === "step-start") return LLMEvent.stepStart({ index })
+  if (event.type === "step-finish") return LLMEvent.stepFinish({ ...event, index })
+  return event
 }
 
 interface StepState {
   assistantContent: ContentPart[]
   toolCalls: ToolCallPart[]
   finishReason: FinishReason | undefined
+  usage: Usage | undefined
+  providerMetadata: ProviderMetadata | undefined
 }
 
 const accumulate = (state: StepState, event: LLMEvent) => {
@@ -154,11 +190,45 @@ const accumulate = (state: StepState, event: LLMEvent) => {
     )
     return
   }
-  if (event.type === "step-finish" || event.type === "request-finish") {
+  if (event.type === "step-finish") {
     state.finishReason = event.reason === "stop" && state.toolCalls.length > 0 ? "tool-calls" : event.reason
+    state.usage = addUsage(state.usage, event.usage)
+    state.providerMetadata = mergeProviderMetadata(state.providerMetadata, event.providerMetadata)
+    return
+  }
+  if (event.type === "finish") {
+    state.finishReason ??= event.reason
+    state.usage ??= event.usage
+    state.providerMetadata = mergeProviderMetadata(state.providerMetadata, event.providerMetadata)
   }
 }
 
+const addUsage = (left: Usage | undefined, right: Usage | undefined) => {
+  if (!left) return right
+  if (!right) return left
+  type UsageKey =
+    | "inputTokens"
+    | "outputTokens"
+    | "nonCachedInputTokens"
+    | "cacheReadInputTokens"
+    | "cacheWriteInputTokens"
+    | "reasoningTokens"
+    | "totalTokens"
+  const sum = (key: UsageKey) =>
+    left[key] === undefined && right[key] === undefined ? undefined : Number(left[key] ?? 0) + Number(right[key] ?? 0)
+
+  return new Usage({
+    inputTokens: sum("inputTokens"),
+    outputTokens: sum("outputTokens"),
+    nonCachedInputTokens: sum("nonCachedInputTokens"),
+    cacheReadInputTokens: sum("cacheReadInputTokens"),
+    cacheWriteInputTokens: sum("cacheWriteInputTokens"),
+    reasoningTokens: sum("reasoningTokens"),
+    totalTokens: sum("totalTokens"),
+    providerMetadata: mergeProviderMetadata(left.providerMetadata, right.providerMetadata),
+  })
+}
+
 const sameProviderMetadata = (left: ProviderMetadata | undefined, right: ProviderMetadata | undefined) =>
   left === right || JSON.stringify(left) === JSON.stringify(right)
 
@@ -200,17 +270,17 @@ const dispatch = (tools: Tools, call: ToolCallPart): Effect.Effect<ToolResultVal
   if (!tool.execute)
     return Effect.succeed({ type: "error" as const, value: `Tool has no execute handler: ${call.name}` })
 
-  return decodeAndExecute(tool, call.input).pipe(
+  return decodeAndExecute(tool, call).pipe(
     Effect.catchTag("LLM.ToolFailure", (failure) =>
       Effect.succeed({ type: "error" as const, value: failure.message } satisfies ToolResultValue),
     ),
   )
 }
 
-const decodeAndExecute = (tool: AnyTool, input: unknown): Effect.Effect<ToolResultValue, ToolFailure> =>
-  tool._decode(input).pipe(
+const decodeAndExecute = (tool: AnyTool, call: ToolCallPart): Effect.Effect<ToolResultValue, ToolFailure> =>
+  tool._decode(call.input).pipe(
     Effect.mapError((error) => new ToolFailure({ message: `Invalid tool input: ${error.message}` })),
-    Effect.flatMap((decoded) => tool.execute!(decoded)),
+    Effect.flatMap((decoded) => tool.execute!(decoded, { id: call.id, name: call.name })),
     Effect.flatMap((value) =>
       tool._encode(value).pipe(
         Effect.mapError(

packages/llm/src/tool.ts

@@ -1,5 +1,5 @@
 import { Effect, JsonSchema, Schema } from "effect"
-import type { ToolDefinition as ToolDefinitionClass } from "./schema"
+import type { ToolCallPart, ToolDefinition as ToolDefinitionClass } from "./schema"
 import { ToolDefinition, ToolFailure } from "./schema"
 
 /**
@@ -8,9 +8,14 @@ import { ToolDefinition, ToolFailure } from "./schema"
  * beyond pure data conversion belongs in the handler closure.
  */
 export type ToolSchema<T> = Schema.Codec<T, any, never, never>
+export interface ToolExecuteContext {
+  readonly id: ToolCallPart["id"]
+  readonly name: ToolCallPart["name"]
+}
 
 export type ToolExecute<Parameters extends ToolSchema<any>, Success extends ToolSchema<any>> = (
   params: Schema.Schema.Type<Parameters>,
+  context?: ToolExecuteContext,
 ) => Effect.Effect<Schema.Schema.Type<Success>, ToolFailure>
 
 /**
@@ -61,7 +66,7 @@ type TypedToolConfig = {
 type DynamicToolConfig = {
   readonly description: string
   readonly jsonSchema: JsonSchema.JsonSchema
-  readonly execute?: (params: unknown) => Effect.Effect<unknown, ToolFailure>
+  readonly execute?: (params: unknown, context?: ToolExecuteContext) => Effect.Effect<unknown, ToolFailure>
 }
 
 /**
@@ -110,7 +115,7 @@ export function make<Parameters extends ToolSchema<any>, Success extends ToolSch
 export function make(config: {
   readonly description: string
   readonly jsonSchema: JsonSchema.JsonSchema
-  readonly execute: (params: unknown) => Effect.Effect<unknown, ToolFailure>
+  readonly execute: (params: unknown, context?: ToolExecuteContext) => Effect.Effect<unknown, ToolFailure>
 }): AnyExecutableTool
 export function make(config: {
   readonly description: string

packages/llm/test/adapter.test.ts

@@ -51,7 +51,7 @@ const request = LLM.request({
 
 const raiseEvent = (event: FakeEvent): import("../src/schema").LLMEvent =>
   event.type === "finish"
-    ? { type: "request-finish", reason: event.reason }
+    ? { type: "finish", reason: event.reason }
     : { type: "text-delta", id: "text-0", text: event.text }
 
 const fakeProtocol = Protocol.make<FakeBody, FakeEvent, FakeEvent, void>({
@@ -112,8 +112,8 @@ describe("llm route", () => {
       const events = Array.from(yield* llm.stream(request).pipe(Stream.runCollect))
       const response = yield* llm.generate(request)
 
-      expect(events.map((event) => event.type)).toEqual(["text-delta", "request-finish"])
-      expect(response.events.map((event) => event.type)).toEqual(["text-delta", "request-finish"])
+      expect(events.map((event) => event.type)).toEqual(["text-delta", "finish"])
+      expect(response.events.map((event) => event.type)).toEqual(["text-delta", "finish"])
     }),
   )
 

packages/llm/test/llm.test.ts

@@ -127,7 +127,7 @@ describe("llm constructors", () => {
       LLMResponse.text({
         events: [
           { type: "text-delta", id: "text-0", text: "hi" },
-          { type: "request-finish", reason: "stop" },
+          { type: "finish", reason: "stop" },
         ],
       }),
     ).toBe("hi")