diff --git a/bun.lock b/bun.lock
index e8ff7adafb..3341e3f480 100644
--- a/bun.lock
+++ b/bun.lock
@@ -394,6 +394,7 @@
         "@octokit/graphql": "9.0.2",
         "@octokit/rest": "catalog:",
         "@openauthjs/openauth": "catalog:",
+        "@opencode-ai/llm": "workspace:*",
         "@opencode-ai/plugin": "workspace:*",
         "@opencode-ai/script": "workspace:*",
         "@opencode-ai/sdk": "workspace:*",
diff --git a/packages/opencode/package.json b/packages/opencode/package.json
index 48cb7b3450..46f7fc3606 100644
--- a/packages/opencode/package.json
+++ b/packages/opencode/package.json
@@ -105,6 +105,7 @@
     "@octokit/graphql": "9.0.2",
     "@octokit/rest": "catalog:",
     "@openauthjs/openauth": "catalog:",
+    "@opencode-ai/llm": "workspace:*",
     "@opencode-ai/plugin": "workspace:*",
     "@opencode-ai/script": "workspace:*",
     "@opencode-ai/sdk": "workspace:*",
diff --git a/packages/opencode/src/session/llm-ai-sdk.ts b/packages/opencode/src/session/llm-ai-sdk.ts
new file mode 100644
index 0000000000..3c1b38cda5
--- /dev/null
+++ b/packages/opencode/src/session/llm-ai-sdk.ts
@@ -0,0 +1,234 @@
+import { FinishReason, LLMEvent, ProviderMetadata, ToolResultValue } from "@opencode-ai/llm"
+import { Effect, Schema } from "effect"
+import { type streamText } from "ai"
+import { errorMessage } from "@/util/error"
+
+type Result = Awaited<ReturnType<typeof streamText>>
+type AISDKEvent = Result["fullStream"] extends AsyncIterable<infer T> ? T : never
+
+export function adapterState() {
+  return {
+    step: 0,
+    text: 0,
+    reasoning: 0,
+    currentTextID: undefined as string | undefined,
+    currentReasoningID: undefined as string | undefined,
+    toolNames: {} as Record<string, string>,
+  }
+}
+
+function finishReason(value: string | undefined): FinishReason {
+  return Schema.is(FinishReason)(value) ? value : "unknown"
+}
+
+function providerMetadata(value: unknown): ProviderMetadata | undefined {
+  return Schema.is(ProviderMetadata)(value) ? value : undefined
+}
+
+function usage(value: unknown) {
+  if (!value || typeof value !== "object") return undefined
+  const item = value as {
+    inputTokens?: number
+    outputTokens?: number
+    totalTokens?: number
+    reasoningTokens?: number
+    cachedInputTokens?: number
+    inputTokenDetails?: { cacheReadTokens?: number; cacheWriteTokens?: number }
+    outputTokenDetails?: { reasoningTokens?: number }
+  }
+  const result = Object.fromEntries(
+    Object.entries({
+      inputTokens: item.inputTokens,
+      outputTokens: item.outputTokens,
+      totalTokens: item.totalTokens,
+      reasoningTokens: item.outputTokenDetails?.reasoningTokens ?? item.reasoningTokens,
+      cacheReadInputTokens: item.inputTokenDetails?.cacheReadTokens ?? item.cachedInputTokens,
+      cacheWriteInputTokens: item.inputTokenDetails?.cacheWriteTokens,
+    }).filter((entry) => entry[1] !== undefined),
+  )
+  return result
+}
+
+function currentTextID(state: ReturnType<typeof adapterState>, id: string | undefined) {
+  state.currentTextID = id ?? state.currentTextID ?? `text-${state.text++}`
+  return state.currentTextID
+}
+
+function currentReasoningID(state: ReturnType<typeof adapterState>, id: string | undefined) {
+  state.currentReasoningID = id ?? state.currentReasoningID ?? `reasoning-${state.reasoning++}`
+  return state.currentReasoningID
+}
+
+export function toLLMEvents(
+  state: ReturnType<typeof adapterState>,
+  event: AISDKEvent,
+): Effect.Effect<ReadonlyArray<LLMEvent>, unknown> {
+  switch (event.type) {
+    case "start":
+      return Effect.succeed([])
+
+    case "start-step":
+      return Effect.succeed([LLMEvent.stepStart({ index: state.step })])
+
+    case "finish-step":
+      return Effect.sync(() => [
+        LLMEvent.stepFinish({
+          index: state.step++,
+          reason: finishReason(event.finishReason),
+          usage: usage(event.usage),
+          providerMetadata: providerMetadata(event.providerMetadata),
+        }),
+      ])
+
+    case "finish":
+      return Effect.sync(() => {
+        state.toolNames = {}
+        return [
+          LLMEvent.finish({
+            reason: finishReason(event.finishReason),
+            usage: usage(event.totalUsage),
+          }),
+        ]
+      })
+
+    case "text-start":
+      return Effect.sync(() => {
+        state.currentTextID = currentTextID(state, event.id)
+        return [
+          LLMEvent.textStart({
+            id: state.currentTextID,
+            providerMetadata: providerMetadata(event.providerMetadata),
+          }),
+        ]
+      })
+
+    case "text-delta":
+      return Effect.succeed([
+        LLMEvent.textDelta({
+          id: currentTextID(state, event.id),
+          text: event.text,
+        }),
+      ])
+
+    case "text-end":
+      return Effect.sync(() => {
+        const id = currentTextID(state, event.id)
+        state.currentTextID = undefined
+        return [
+          LLMEvent.textEnd({
+            id,
+            providerMetadata: providerMetadata(event.providerMetadata),
+          }),
+        ]
+      })
+
+    case "reasoning-start":
+      return Effect.sync(() => {
+        state.currentReasoningID = currentReasoningID(state, event.id)
+        return [
+          LLMEvent.reasoningStart({
+            id: state.currentReasoningID,
+            providerMetadata: providerMetadata(event.providerMetadata),
+          }),
+        ]
+      })
+
+    case "reasoning-delta":
+      return Effect.succeed([
+        LLMEvent.reasoningDelta({
+          id: currentReasoningID(state, event.id),
+          text: event.text,
+        }),
+      ])
+
+    case "reasoning-end":
+      return Effect.sync(() => {
+        const id = currentReasoningID(state, event.id)
+        state.currentReasoningID = undefined
+        return [
+          LLMEvent.reasoningEnd({
+            id,
+            providerMetadata: providerMetadata(event.providerMetadata),
+          }),
+        ]
+      })
+
+    case "tool-input-start":
+      return Effect.sync(() => {
+        state.toolNames[event.id] = event.toolName
+        return [
+          LLMEvent.toolInputStart({
+            id: event.id,
+            name: event.toolName,
+            providerMetadata: providerMetadata(event.providerMetadata),
+          }),
+        ]
+      })
+
+    case "tool-input-delta":
+      return Effect.succeed([
+        LLMEvent.toolInputDelta({
+          id: event.id,
+          name: state.toolNames[event.id] ?? "unknown",
+          text: event.delta ?? "",
+        }),
+      ])
+
+    case "tool-input-end":
+      return Effect.succeed([
+        LLMEvent.toolInputEnd({
+          id: event.id,
+          name: state.toolNames[event.id] ?? "unknown",
+        }),
+      ])
+
+    case "tool-call":
+      return Effect.sync(() => {
+        state.toolNames[event.toolCallId] = event.toolName
+        return [
+          LLMEvent.toolCall({
+            id: event.toolCallId,
+            name: event.toolName,
+            input: event.input,
+            providerExecuted: "providerExecuted" in event ? event.providerExecuted : undefined,
+            providerMetadata: providerMetadata(event.providerMetadata),
+          }),
+        ]
+      })
+
+    case "tool-result":
+      return Effect.sync(() => {
+        const name = state.toolNames[event.toolCallId] ?? "unknown"
+        delete state.toolNames[event.toolCallId]
+        return [
+          LLMEvent.toolResult({
+            id: event.toolCallId,
+            name,
+            result: ToolResultValue.make(event.output),
+            providerExecuted: "providerExecuted" in event ? event.providerExecuted : undefined,
+          }),
+        ]
+      })
+
+    case "tool-error":
+      return Effect.sync(() => {
+        const name = state.toolNames[event.toolCallId] ?? "unknown"
+        delete state.toolNames[event.toolCallId]
+        return [
+          LLMEvent.toolError({
+            id: event.toolCallId,
+            name,
+            message: errorMessage(event.error),
+          }),
+        ]
+      })
+
+    case "error":
+      return Effect.fail(event.error)
+
+    default:
+      return Effect.succeed([])
+  }
+}
+
+export * as LLMAISDK from "./llm-ai-sdk"
diff --git a/packages/opencode/src/session/llm-native.ts b/packages/opencode/src/session/llm-native.ts
new file mode 100644
index 0000000000..22725e9e76
--- /dev/null
+++ b/packages/opencode/src/session/llm-native.ts
@@ -0,0 +1,188 @@
+import type { JsonSchema, LLMRequest, ProviderMetadata } from "@opencode-ai/llm"
+import { LLM, Message, SystemPart, ToolCallPart, ToolDefinition, ToolResultPart } from "@opencode-ai/llm"
+import "@opencode-ai/llm/providers"
+import type { ModelMessage } from "ai"
+import type { Provider } from "@/provider/provider"
+import { isRecord } from "@/util/record"
+
+type ToolInput = {
+  readonly description?: string
+  readonly inputSchema?: unknown
+}
+
+export type RequestInput = {
+  readonly model: Provider.Model
+  readonly apiKey?: string
+  readonly baseURL?: string
+  readonly system?: readonly string[]
+  readonly messages: readonly ModelMessage[]
+  readonly tools?: Record<string, ToolInput>
+  readonly toolChoice?: "auto" | "required" | "none"
+  readonly temperature?: number
+  readonly topP?: number
+  readonly topK?: number
+  readonly maxOutputTokens?: number
+  readonly providerOptions?: LLMRequest["providerOptions"]
+  readonly headers?: Record<string, string>
+}
+
+const DEFAULT_BASE_URL: Record<string, string> = {
+  "@ai-sdk/openai": "https://api.openai.com/v1",
+  "@ai-sdk/anthropic": "https://api.anthropic.com/v1",
+  "@ai-sdk/google": "https://generativelanguage.googleapis.com/v1beta",
+  "@ai-sdk/amazon-bedrock": "https://bedrock-runtime.us-east-1.amazonaws.com",
+  "@openrouter/ai-sdk-provider": "https://openrouter.ai/api/v1",
+}
+
+const ROUTE: Record<string, string> = {
+  "@ai-sdk/openai": "openai-responses",
+  "@ai-sdk/azure": "azure-openai-responses",
+  "@ai-sdk/anthropic": "anthropic-messages",
+  "@ai-sdk/google": "gemini",
+  "@ai-sdk/amazon-bedrock": "bedrock-converse",
+  "@ai-sdk/openai-compatible": "openai-compatible-chat",
+  "@openrouter/ai-sdk-provider": "openrouter",
+}
+
+const providerMetadata = (value: unknown): ProviderMetadata | undefined => {
+  if (!isRecord(value)) return undefined
+  const result = Object.fromEntries(
+    Object.entries(value).filter((entry): entry is [string, Record<string, unknown>] => isRecord(entry[1])),
+  )
+  return Object.keys(result).length === 0 ? undefined : result
+}
+
+const textPart = (part: Record<string, unknown>) => ({
+  type: "text" as const,
+  text: typeof part.text === "string" ? part.text : "",
+  providerMetadata: providerMetadata(part.providerOptions),
+})
+
+const mediaPart = (part: Record<string, unknown>) => {
+  if (typeof part.data !== "string" && !(part.data instanceof Uint8Array))
+    throw new Error("Native LLM request adapter only supports file parts with string or Uint8Array data")
+  return {
+    type: "media" as const,
+    mediaType: typeof part.mediaType === "string" ? part.mediaType : "application/octet-stream",
+    data: part.data,
+    filename: typeof part.filename === "string" ? part.filename : undefined,
+  }
+}
+
+const toolResult = (part: Record<string, unknown>) => {
+  const output = isRecord(part.output) ? part.output : { type: "json", value: part.output }
+  const type = output.type === "text" ? "text" : output.type === "error-text" ? "error" : "json"
+  return ToolResultPart.make({
+    id: typeof part.toolCallId === "string" ? part.toolCallId : "",
+    name: typeof part.toolName === "string" ? part.toolName : "",
+    result: "value" in output ? output.value : output,
+    resultType: type,
+    providerExecuted: typeof part.providerExecuted === "boolean" ? part.providerExecuted : undefined,
+    providerMetadata: providerMetadata(part.providerOptions),
+  })
+}
+
+const contentPart = (part: unknown) => {
+  if (!isRecord(part)) throw new Error("Native LLM request adapter only supports object content parts")
+  if (part.type === "text") return textPart(part)
+  if (part.type === "file") return mediaPart(part)
+  if (part.type === "reasoning")
+    return {
+      type: "reasoning" as const,
+      text: typeof part.text === "string" ? part.text : "",
+      providerMetadata: providerMetadata(part.providerOptions),
+    }
+  if (part.type === "tool-call")
+    return ToolCallPart.make({
+      id: typeof part.toolCallId === "string" ? part.toolCallId : "",
+      name: typeof part.toolName === "string" ? part.toolName : "",
+      input: part.input,
+      providerExecuted: typeof part.providerExecuted === "boolean" ? part.providerExecuted : undefined,
+      providerMetadata: providerMetadata(part.providerOptions),
+    })
+  if (part.type === "tool-result") return toolResult(part)
+  throw new Error(`Native LLM request adapter does not support ${String(part.type)} content parts`)
+}
+
+const content = (value: ModelMessage["content"]) =>
+  typeof value === "string" ? [{ type: "text" as const, text: value }] : value.map(contentPart)
+
+const messages = (input: readonly ModelMessage[]) => {
+  const system = input.flatMap((message) => (message.role === "system" ? [SystemPart.make(message.content)] : []))
+  const messages = input.flatMap((message) => {
+    if (message.role === "system") return []
+    return [
+      Message.make({
+        role: message.role,
+        content: content(message.content),
+        native: isRecord(message.providerOptions) ? { providerOptions: message.providerOptions } : undefined,
+      }),
+    ]
+  })
+  return { system, messages }
+}
+
+const schema = (value: unknown): JsonSchema => {
+  if (!isRecord(value)) return { type: "object", properties: {} }
+  if (isRecord(value.jsonSchema)) return value.jsonSchema
+  return value
+}
+
+const tools = (input: Record<string, ToolInput> | undefined): ToolDefinition[] =>
+  Object.entries(input ?? {}).map(([name, item]) =>
+    ToolDefinition.make({
+      name,
+      description: item.description ?? "",
+      inputSchema: schema(item.inputSchema),
+    }),
+  )
+
+const generation = (input: RequestInput) => {
+  const result = {
+    temperature: input.temperature,
+    topP: input.topP,
+    topK: input.topK,
+    maxTokens: input.maxOutputTokens,
+  }
+  return Object.values(result).some((value) => value !== undefined) ? result : undefined
+}
+
+const baseURL = (model: Provider.Model) => {
+  if (model.api.url) return model.api.url
+  const fallback = DEFAULT_BASE_URL[model.api.npm]
+  if (fallback) return fallback
+  throw new Error(`Native LLM request adapter requires a base URL for ${model.providerID}/${model.id}`)
+}
+
+export const model = (input: Provider.Model | RequestInput, headers?: Record<string, string>) => {
+  const model = "model" in input ? input.model : input
+  const route = ROUTE[model.api.npm]
+  if (!route) throw new Error(`Native LLM request adapter does not support provider package ${model.api.npm}`)
+  return LLM.model({
+    id: model.api.id,
+    provider: model.providerID,
+    route,
+    baseURL: "model" in input && input.baseURL ? input.baseURL : baseURL(model),
+    apiKey: "model" in input ? input.apiKey : undefined,
+    headers: Object.keys({ ...model.headers, ...headers }).length === 0 ? undefined : { ...model.headers, ...headers },
+    limits: {
+      context: model.limit.context,
+      output: model.limit.output,
+    },
+  })
+}
+
+export const request = (input: RequestInput) => {
+  const converted = messages(input.messages)
+  return LLM.request({
+    model: model(input, input.headers),
+    system: [...(input.system ?? []).map(SystemPart.make), ...converted.system],
+    messages: converted.messages,
+    tools: tools(input.tools),
+    toolChoice: input.toolChoice,
+    generation: generation(input),
+    providerOptions: input.providerOptions,
+  })
+}
+
+export * as LLMNative from "./llm-native"
diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index c7990d1b35..29de530112 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -2,7 +2,10 @@ import { Provider } from "@/provider/provider"
 import * as Log from "@opencode-ai/core/util/log"
 import { Context, Effect, Layer, Record } from "effect"
 import * as Stream from "effect/Stream"
-import { streamText, wrapLanguageModel, type ModelMessage, type Tool, tool, jsonSchema } from "ai"
+import { streamText, wrapLanguageModel, type ModelMessage, type Tool, tool as aiTool, jsonSchema, asSchema } from "ai"
+import { tool as nativeTool, ToolFailure, type JsonSchema, type LLMEvent } from "@opencode-ai/llm"
+import { LLMClient, RequestExecutor } from "@opencode-ai/llm/route"
+import type { LLMClientService } from "@opencode-ai/llm/route"
 import { mergeDeep } from "remeda"
 import { GitLabWorkflowLanguageModel } from "gitlab-ai-provider"
 import { ProviderTransform } from "@/provider/transform"
@@ -16,23 +19,26 @@ import { Flag } from "@opencode-ai/core/flag/flag"
 import { Permission } from "@/permission"
 import { PermissionID } from "@/permission/schema"
 import { Bus } from "@/bus"
+import { errorMessage } from "@/util/error"
 import { Wildcard } from "@/util/wildcard"
 import { SessionID } from "@/session/schema"
 import { Auth } from "@/auth"
-import { Installation } from "@/installation"
 import { InstallationVersion } from "@opencode-ai/core/installation/version"
 import { EffectBridge } from "@/effect/bridge"
 import * as Option from "effect/Option"
 import * as OtelTracer from "@effect/opentelemetry/Tracer"
+import { LLMAISDK } from "./llm-ai-sdk"
+import { LLMNative } from "./llm-native"
 
 const log = Log.create({ service: "llm" })
 export const OUTPUT_TOKEN_MAX = ProviderTransform.OUTPUT_TOKEN_MAX
-type Result = Awaited<ReturnType<typeof streamText>>
 
 // Avoid re-instantiating remeda's deep merge types in this hot LLM path; the runtime behavior is still mergeDeep.
 const mergeOptions = (target: Record<string, any>, source: Record<string, any> | undefined): Record<string, any> =>
   mergeDeep(target, source ?? {}) as Record<string, any>
 
+const runtime = () => (process.env.OPENCODE_LLM_RUNTIME === "native" ? "native" : "ai-sdk")
+
 export type StreamInput = {
   user: MessageV2.User
   sessionID: string
@@ -52,10 +58,8 @@ export type StreamRequest = StreamInput & {
   abort: AbortSignal
 }
 
-export type Event = Result["fullStream"] extends AsyncIterable<infer T> ? T : never
-
 export interface Interface {
-  readonly stream: (input: StreamInput) => Stream.Stream<Event, unknown>
+  readonly stream: (input: StreamInput) => Stream.Stream<LLMEvent, unknown>
 }
 
 export class Service extends Context.Service<Service, Interface>()("@opencode/LLM") {}
@@ -63,7 +67,7 @@ export class Service extends Context.Service<Service, Interface>()("@opencode/LL
 const live: Layer.Layer<
   Service,
   never,
-  Auth.Service | Config.Service | Provider.Service | Plugin.Service | Permission.Service
+  Auth.Service | Config.Service | Provider.Service | Plugin.Service | Permission.Service | LLMClientService
 > = Layer.effect(
   Service,
   Effect.gen(function* () {
@@ -72,6 +76,7 @@ const live: Layer.Layer<
     const provider = yield* Provider.Service
     const plugin = yield* Plugin.Service
     const perm = yield* Permission.Service
+    const llmClient = yield* LLMClient.Service
 
     const run = Effect.fn("LLM.run")(function* (input: StreamRequest) {
       const l = log
@@ -214,7 +219,7 @@ const live: Layer.Layer<
         Object.keys(tools).length === 0 &&
         hasToolCalls(input.messages)
       ) {
-        tools["_noop"] = tool({
+        tools["_noop"] = aiTool({
           description: "Do not call this tool. It exists only for API compatibility and must never be invoked.",
           inputSchema: jsonSchema({
             type: "object",
@@ -334,86 +339,119 @@ const live: Layer.Layer<
         ? (yield* InstanceState.context).project.id
         : undefined
 
-      return streamText({
-        onError(error) {
-          l.error("stream error", {
-            error,
-          })
-        },
-        async experimental_repairToolCall(failed) {
-          const lower = failed.toolCall.toolName.toLowerCase()
-          if (lower !== failed.toolCall.toolName && sortedTools[lower]) {
-            l.info("repairing tool call", {
-              tool: failed.toolCall.toolName,
-              repaired: lower,
+      const requestHeaders = {
+        ...(input.model.providerID.startsWith("opencode")
+          ? {
+              ...(opencodeProjectID ? { "x-opencode-project": opencodeProjectID } : {}),
+              "x-opencode-session": input.sessionID,
+              "x-opencode-request": input.user.id,
+              "x-opencode-client": Flag.OPENCODE_CLIENT,
+              "User-Agent": `opencode/${InstallationVersion}`,
+            }
+          : {
+              "x-session-affinity": input.sessionID,
+              ...(input.parentSessionID ? { "x-parent-session-id": input.parentSessionID } : {}),
+              "User-Agent": `opencode/${InstallationVersion}`,
+            }),
+        ...input.model.headers,
+        ...headers,
+      }
+
+      if (runtime() === "native") {
+        if (input.model.providerID !== "openai" || input.model.api.npm !== "@ai-sdk/openai") {
+          return yield* Effect.fail(new Error("Native LLM runtime currently only supports OpenAI models"))
+        }
+        const apiKey =
+          info?.type === "api" ? info.key : typeof item.options.apiKey === "string" ? item.options.apiKey : undefined
+        if (!apiKey) return yield* Effect.fail(new Error("Native LLM runtime requires API key auth for OpenAI"))
+        const baseURL = typeof item.options.baseURL === "string" ? item.options.baseURL : undefined
+        const request = LLMNative.request({
+          model: input.model,
+          apiKey,
+          baseURL,
+          system: isOpenaiOauth ? system : [],
+          messages: ProviderTransform.message(messages, input.model, options),
+          toolChoice: input.toolChoice,
+          temperature: params.temperature,
+          topP: params.topP,
+          topK: params.topK,
+          maxOutputTokens: params.maxOutputTokens,
+          providerOptions: ProviderTransform.providerOptions(input.model, params.options),
+          headers: requestHeaders,
+        })
+        return {
+          type: "native" as const,
+          stream: llmClient.stream({ request, tools: nativeTools(sortedTools, input) }),
+        }
+      }
+
+      return {
+        type: "ai-sdk" as const,
+        result: streamText({
+          onError(error) {
+            l.error("stream error", {
+              error,
             })
+          },
+          async experimental_repairToolCall(failed) {
+            const lower = failed.toolCall.toolName.toLowerCase()
+            if (lower !== failed.toolCall.toolName && sortedTools[lower]) {
+              l.info("repairing tool call", {
+                tool: failed.toolCall.toolName,
+                repaired: lower,
+              })
+              return {
+                ...failed.toolCall,
+                toolName: lower,
+              }
+            }
             return {
               ...failed.toolCall,
-              toolName: lower,
-            }
-          }
-          return {
-            ...failed.toolCall,
-            input: JSON.stringify({
-              tool: failed.toolCall.toolName,
-              error: failed.error.message,
-            }),
-            toolName: "invalid",
-          }
-        },
-        temperature: params.temperature,
-        topP: params.topP,
-        topK: params.topK,
-        providerOptions: ProviderTransform.providerOptions(input.model, params.options),
-        activeTools: Object.keys(sortedTools).filter((x) => x !== "invalid"),
-        tools: sortedTools,
-        toolChoice: input.toolChoice,
-        maxOutputTokens: params.maxOutputTokens,
-        abortSignal: input.abort,
-        headers: {
-          ...(input.model.providerID.startsWith("opencode")
-            ? {
-                "x-opencode-project": opencodeProjectID,
-                "x-opencode-session": input.sessionID,
-                "x-opencode-request": input.user.id,
-                "x-opencode-client": Flag.OPENCODE_CLIENT,
-                "User-Agent": `opencode/${InstallationVersion}`,
-              }
-            : {
-                "x-session-affinity": input.sessionID,
-                ...(input.parentSessionID ? { "x-parent-session-id": input.parentSessionID } : {}),
-                "User-Agent": `opencode/${InstallationVersion}`,
+              input: JSON.stringify({
+                tool: failed.toolCall.toolName,
+                error: failed.error.message,
               }),
-          ...input.model.headers,
-          ...headers,
-        },
-        maxRetries: input.retries ?? 0,
-        messages,
-        model: wrapLanguageModel({
-          model: language,
-          middleware: [
-            {
-              specificationVersion: "v3" as const,
-              async transformParams(args) {
-                if (args.type === "stream") {
-                  // @ts-expect-error
-                  args.params.prompt = ProviderTransform.message(args.params.prompt, input.model, options)
-                }
-                return args.params
-              },
-            },
-          ],
-        }),
-        experimental_telemetry: {
-          isEnabled: cfg.experimental?.openTelemetry,
-          functionId: "session.llm",
-          tracer: telemetryTracer,
-          metadata: {
-            userId: cfg.username ?? "unknown",
-            sessionId: input.sessionID,
+              toolName: "invalid",
+            }
           },
-        },
-      })
+          temperature: params.temperature,
+          topP: params.topP,
+          topK: params.topK,
+          providerOptions: ProviderTransform.providerOptions(input.model, params.options),
+          activeTools: Object.keys(sortedTools).filter((x) => x !== "invalid"),
+          tools: sortedTools,
+          toolChoice: input.toolChoice,
+          maxOutputTokens: params.maxOutputTokens,
+          abortSignal: input.abort,
+          headers: requestHeaders,
+          maxRetries: input.retries ?? 0,
+          messages,
+          model: wrapLanguageModel({
+            model: language,
+            middleware: [
+              {
+                specificationVersion: "v3" as const,
+                async transformParams(args) {
+                  if (args.type === "stream") {
+                    // @ts-expect-error
+                    args.params.prompt = ProviderTransform.message(args.params.prompt, input.model, options)
+                  }
+                  return args.params
+                },
+              },
+            ],
+          }),
+          experimental_telemetry: {
+            isEnabled: cfg.experimental?.openTelemetry,
+            functionId: "session.llm",
+            tracer: telemetryTracer,
+            metadata: {
+              userId: cfg.username ?? "unknown",
+              sessionId: input.sessionID,
+            },
+          },
+        }),
+      }
     })
 
     const stream: Interface["stream"] = (input) =>
@@ -427,7 +465,15 @@ const live: Layer.Layer<
 
             const result = yield* run({ ...input, abort: ctrl.signal })
 
-            return Stream.fromAsyncIterable(result.fullStream, (e) => (e instanceof Error ? e : new Error(String(e))))
+            if (result.type === "native") return result.stream
+
+            const state = LLMAISDK.adapterState()
+            return Stream.fromAsyncIterable(result.result.fullStream, (e) =>
+              e instanceof Error ? e : new Error(String(e)),
+            ).pipe(
+              Stream.mapEffect((event) => LLMAISDK.toLLMEvents(state, event)),
+              Stream.flatMap((events) => Stream.fromIterable(events)),
+            )
           }),
         ),
       )
@@ -444,6 +490,7 @@ export const defaultLayer = Layer.suspend(() =>
     Layer.provide(Config.defaultLayer),
     Layer.provide(Provider.defaultLayer),
     Layer.provide(Plugin.defaultLayer),
+    Layer.provide(LLMClient.layer.pipe(Layer.provide(RequestExecutor.defaultLayer))),
   ),
 )
 
@@ -455,6 +502,37 @@ function resolveTools(input: Pick<StreamInput, "tools" | "agent" | "permission"
   return Record.filter(input.tools, (_, k) => input.user.tools?.[k] !== false && !disabled.has(k))
 }
 
+function nativeSchema(value: unknown): JsonSchema {
+  if (!value || typeof value !== "object") return { type: "object", properties: {} }
+  if ("jsonSchema" in value && value.jsonSchema && typeof value.jsonSchema === "object")
+    return value.jsonSchema as JsonSchema
+  return asSchema(value as Parameters<typeof asSchema>[0]).jsonSchema as JsonSchema
+}
+
+function nativeTools(tools: Record<string, Tool>, input: StreamRequest) {
+  return Object.fromEntries(
+    Object.entries(tools).map(([name, item]) => [
+      name,
+      nativeTool({
+        description: item.description ?? "",
+        jsonSchema: nativeSchema(item.inputSchema),
+        execute: (args: unknown, ctx?: { readonly id: string; readonly name: string }) =>
+          Effect.tryPromise({
+            try: () => {
+              if (!item.execute) throw new Error(`Tool has no execute handler: ${name}`)
+              return item.execute(args, {
+                toolCallId: ctx?.id ?? name,
+                messages: input.messages,
+                abortSignal: input.abort,
+              })
+            },
+            catch: (error) => new ToolFailure({ message: errorMessage(error) }),
+          }),
+      }),
+    ]),
+  )
+}
+
 // Check if messages contain any tool-call content
 // Used to determine if a dummy tool should be added for LiteLLM proxy compatibility
 export function hasToolCalls(messages: ModelMessage[]): boolean {
diff --git a/packages/opencode/src/session/processor.ts b/packages/opencode/src/session/processor.ts
index c731239b62..aeab6c0bfd 100644
--- a/packages/opencode/src/session/processor.ts
+++ b/packages/opencode/src/session/processor.ts
@@ -1,4 +1,4 @@
-import { Cause, Deferred, Effect, Exit, Layer, Context, Scope } from "effect"
+import { Cause, Deferred, Effect, Exit, Layer, Context, Scope, Schema } from "effect"
 import * as Stream from "effect/Stream"
 import { Agent } from "@/agent/agent"
 import { Bus } from "@/bus"
@@ -26,14 +26,13 @@ import { SessionEvent } from "@/v2/session-event"
 import { Modelv2 } from "@/v2/model"
 import * as DateTime from "effect/DateTime"
 import { RuntimeFlags } from "@/effect/runtime-flags"
+import { Usage, type LLMEvent } from "@opencode-ai/llm"
 
 const DOOM_LOOP_THRESHOLD = 3
 const log = Log.create({ service: "session.processor" })
 
 export type Result = "compact" | "stop" | "continue"
 
-export type Event = LLM.Event
-
 export interface Handle {
   readonly message: MessageV2.Assistant
   readonly updateToolCall: (
@@ -67,6 +66,7 @@ type ToolCall = {
   messageID: MessageV2.ToolPart["messageID"]
   sessionID: MessageV2.ToolPart["sessionID"]
   done: Deferred.Deferred<void>
+  inputEnded: boolean
 }
 
 interface ProcessorContext extends Input {
@@ -79,7 +79,7 @@ interface ProcessorContext extends Input {
   reasoningMap: Record<string, MessageV2.ReasoningPart>
 }
 
-type StreamEvent = Event
+type StreamEvent = LLMEvent
 
 export class Service extends Context.Service<Service, Interface>()("@opencode/SessionProcessor") {}
 
@@ -225,12 +225,84 @@ export const layer: Layer.Layer<
         return true
       })
 
+      const finishReasoning = Effect.fn("SessionProcessor.finishReasoning")(function* (reasoningID: string) {
+        if (!(reasoningID in ctx.reasoningMap)) return
+        // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
+        if (flags.experimentalEventSystem) {
+          yield* sync.run(SessionEvent.Reasoning.Ended.Sync, {
+            sessionID: ctx.sessionID,
+            reasoningID,
+            text: ctx.reasoningMap[reasoningID].text,
+            timestamp: DateTime.makeUnsafe(Date.now()),
+          })
+        }
+        // oxlint-disable-next-line no-self-assign -- reactivity trigger
+        ctx.reasoningMap[reasoningID].text = ctx.reasoningMap[reasoningID].text
+        ctx.reasoningMap[reasoningID].time = { ...ctx.reasoningMap[reasoningID].time, end: Date.now() }
+        yield* session.updatePart(ctx.reasoningMap[reasoningID])
+        delete ctx.reasoningMap[reasoningID]
+      })
+
+      const ensureToolCall = Effect.fn("SessionProcessor.ensureToolCall")(function* (input: {
+        id: string
+        name: string
+        providerExecuted?: boolean
+      }) {
+        const existing = yield* readToolCall(input.id)
+        if (existing) return existing
+        // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
+        if (flags.experimentalEventSystem) {
+          yield* sync.run(SessionEvent.Tool.Input.Started.Sync, {
+            sessionID: ctx.sessionID,
+            callID: input.id,
+            name: input.name,
+            timestamp: DateTime.makeUnsafe(Date.now()),
+          })
+        }
+        const part = yield* session.updatePart({
+          id: PartID.ascending(),
+          messageID: ctx.assistantMessage.id,
+          sessionID: ctx.assistantMessage.sessionID,
+          type: "tool",
+          tool: input.name,
+          callID: input.id,
+          state: { status: "pending", input: {}, raw: "" },
+          metadata: input.providerExecuted ? { providerExecuted: true } : undefined,
+        } satisfies MessageV2.ToolPart)
+        ctx.toolcalls[input.id] = {
+          done: yield* Deferred.make<void>(),
+          partID: part.id,
+          messageID: part.messageID,
+          sessionID: part.sessionID,
+          inputEnded: false,
+        }
+        return { call: ctx.toolcalls[input.id], part }
+      })
+
+      const isFilePart = Schema.is(MessageV2.FilePart)
+
+      const toolResultOutput = (value: Extract<StreamEvent, { type: "tool-result" }>) => {
+        if (isRecord(value.result.value) && typeof value.result.value.output === "string") {
+          return {
+            title: typeof value.result.value.title === "string" ? value.result.value.title : value.name,
+            metadata: isRecord(value.result.value.metadata) ? value.result.value.metadata : {},
+            output: value.result.value.output,
+            attachments: Array.isArray(value.result.value.attachments)
+              ? value.result.value.attachments.filter(isFilePart)
+              : undefined,
+          }
+        }
+        return {
+          title: value.name,
+          metadata: value.result.type === "json" && isRecord(value.result.value) ? value.result.value : {},
+          output: typeof value.result.value === "string" ? value.result.value : (JSON.stringify(value.result.value) ?? ""),
+        }
+      }
+
+      const toolInput = (value: unknown): Record<string, any> => (isRecord(value) ? value : { value })
+
       const handleEvent = Effect.fnUntraced(function* (value: StreamEvent) {
         switch (value.type) {
-          case "start":
-            yield* status.set(ctx.sessionID, { type: "busy" })
-            return
-
           case "reasoning-start":
             if (value.id in ctx.reasoningMap) return
             // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
@@ -253,116 +325,132 @@ export const layer: Layer.Layer<
             yield* session.updatePart(ctx.reasoningMap[value.id])
             return
 
-          case "reasoning-delta":
-            if (!(value.id in ctx.reasoningMap)) return
-            ctx.reasoningMap[value.id].text += value.text
-            if (value.providerMetadata) ctx.reasoningMap[value.id].metadata = value.providerMetadata
+          case "reasoning-delta": {
+            const reasoningID = value.id ?? "reasoning"
+            if (!(reasoningID in ctx.reasoningMap)) {
+              // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
+              if (flags.experimentalEventSystem) {
+                yield* sync.run(SessionEvent.Reasoning.Started.Sync, {
+                  sessionID: ctx.sessionID,
+                  reasoningID,
+                  timestamp: DateTime.makeUnsafe(Date.now()),
+                })
+              }
+              ctx.reasoningMap[reasoningID] = {
+                id: PartID.ascending(),
+                messageID: ctx.assistantMessage.id,
+                sessionID: ctx.assistantMessage.sessionID,
+                type: "reasoning",
+                text: "",
+                time: { start: Date.now() },
+              }
+              yield* session.updatePart(ctx.reasoningMap[reasoningID])
+            }
+            ctx.reasoningMap[reasoningID].text += value.text
             yield* session.updatePartDelta({
-              sessionID: ctx.reasoningMap[value.id].sessionID,
-              messageID: ctx.reasoningMap[value.id].messageID,
-              partID: ctx.reasoningMap[value.id].id,
+              sessionID: ctx.reasoningMap[reasoningID].sessionID,
+              messageID: ctx.reasoningMap[reasoningID].messageID,
+              partID: ctx.reasoningMap[reasoningID].id,
               field: "text",
               delta: value.text,
             })
             return
+          }
 
           case "reasoning-end":
-            if (!(value.id in ctx.reasoningMap)) return
-            // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
-            if (flags.experimentalEventSystem) {
-              yield* sync.run(SessionEvent.Reasoning.Ended.Sync, {
-                sessionID: ctx.sessionID,
-                reasoningID: value.id,
-                text: ctx.reasoningMap[value.id].text,
-                timestamp: DateTime.makeUnsafe(Date.now()),
-              })
+            if (value.providerMetadata && value.id in ctx.reasoningMap) {
+              ctx.reasoningMap[value.id].metadata = value.providerMetadata
             }
-            // oxlint-disable-next-line no-self-assign -- reactivity trigger
-            ctx.reasoningMap[value.id].text = ctx.reasoningMap[value.id].text
-            ctx.reasoningMap[value.id].time = { ...ctx.reasoningMap[value.id].time, end: Date.now() }
-            if (value.providerMetadata) ctx.reasoningMap[value.id].metadata = value.providerMetadata
-            yield* session.updatePart(ctx.reasoningMap[value.id])
-            delete ctx.reasoningMap[value.id]
+            yield* finishReasoning(value.id)
             return
 
           case "tool-input-start":
             if (ctx.assistantMessage.summary) {
-              throw new Error(`Tool call not allowed while generating summary: ${value.toolName}`)
-            }
-            // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
-            if (flags.experimentalEventSystem) {
-              yield* sync.run(SessionEvent.Tool.Input.Started.Sync, {
-                sessionID: ctx.sessionID,
-                callID: value.id,
-                name: value.toolName,
-                timestamp: DateTime.makeUnsafe(Date.now()),
-              })
-            }
-            const part = yield* session.updatePart({
-              id: ctx.toolcalls[value.id]?.partID ?? PartID.ascending(),
-              messageID: ctx.assistantMessage.id,
-              sessionID: ctx.assistantMessage.sessionID,
-              type: "tool",
-              tool: value.toolName,
-              callID: value.id,
-              state: { status: "pending", input: {}, raw: "" },
-              metadata: value.providerExecuted ? { providerExecuted: true } : undefined,
-            } satisfies MessageV2.ToolPart)
-            ctx.toolcalls[value.id] = {
-              done: yield* Deferred.make<void>(),
-              partID: part.id,
-              messageID: part.messageID,
-              sessionID: part.sessionID,
+              throw new Error(`Tool call not allowed while generating summary: ${value.name}`)
             }
+            yield* ensureToolCall(value)
             return
 
-          case "tool-input-delta":
+          case "tool-input-delta": {
+            if (ctx.assistantMessage.summary) {
+              throw new Error(`Tool call not allowed while generating summary: ${value.name}`)
+            }
+            yield* ensureToolCall(value)
+            if (value.text) {
+              yield* updateToolCall(value.id, (match) => ({
+                ...match,
+                state:
+                  match.state.status === "pending"
+                    ? { ...match.state, raw: match.state.raw + value.text }
+                    : match.state,
+              }))
+            }
             return
+          }
 
           case "tool-input-end": {
+            const toolCall = yield* ensureToolCall(value)
             // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
             if (flags.experimentalEventSystem) {
               yield* sync.run(SessionEvent.Tool.Input.Ended.Sync, {
                 sessionID: ctx.sessionID,
                 callID: value.id,
-                text: "",
+                text: toolCall.part.state.status === "pending" ? toolCall.part.state.raw : "",
                 timestamp: DateTime.makeUnsafe(Date.now()),
               })
             }
+            ctx.toolcalls[value.id] = { ...toolCall.call, inputEnded: true }
             return
           }
 
           case "tool-call": {
             if (ctx.assistantMessage.summary) {
-              throw new Error(`Tool call not allowed while generating summary: ${value.toolName}`)
+              throw new Error(`Tool call not allowed while generating summary: ${value.name}`)
+            }
+            const toolCall = yield* ensureToolCall(value)
+            const input = toolInput(value.input)
+            const raw = toolCall.part.state.status === "pending" ? toolCall.part.state.raw : ""
+            if (!toolCall.call.inputEnded) {
+              // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
+              if (flags.experimentalEventSystem) {
+                yield* sync.run(SessionEvent.Tool.Input.Ended.Sync, {
+                  sessionID: ctx.sessionID,
+                  callID: value.id,
+                  text: raw,
+                  timestamp: DateTime.makeUnsafe(Date.now()),
+                })
+              }
             }
-            const toolCall = yield* readToolCall(value.toolCallId)
             // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
             if (flags.experimentalEventSystem) {
               yield* sync.run(SessionEvent.Tool.Called.Sync, {
                 sessionID: ctx.sessionID,
-                callID: value.toolCallId,
-                tool: value.toolName,
-                input: value.input,
+                callID: value.id,
+                tool: value.name,
+                input,
                 provider: {
-                  executed: toolCall?.part.metadata?.providerExecuted === true,
+                  executed: toolCall.part.metadata?.providerExecuted === true,
                   ...(value.providerMetadata ? { metadata: value.providerMetadata } : {}),
                 },
                 timestamp: DateTime.makeUnsafe(Date.now()),
               })
             }
-            yield* updateToolCall(value.toolCallId, (match) => ({
+            yield* updateToolCall(value.id, (match) => ({
               ...match,
-              tool: value.toolName,
-              state: {
-                ...match.state,
-                status: "running",
-                input: value.input,
-                time: { start: Date.now() },
+              tool: value.name,
+              state:
+                match.state.status === "running"
+                  ? { ...match.state, input }
+                  : {
+                      status: "running",
+                      input,
+                      time: { start: Date.now() },
+                    },
+              metadata: {
+                ...match.metadata,
+                ...value.providerMetadata,
+                ...(match.metadata?.providerExecuted ? { providerExecuted: true } : {}),
               },
-              metadata: match.metadata?.providerExecuted
-                ? { ...value.providerMetadata, providerExecuted: true }
-                : value.providerMetadata,
             }))
 
             const parts = MessageV2.parts(ctx.assistantMessage.id)
@@ -373,9 +461,9 @@ export const layer: Layer.Layer<
               !recentParts.every(
                 (part) =>
                   part.type === "tool" &&
-                  part.tool === value.toolName &&
+                  part.tool === value.name &&
                   part.state.status !== "pending" &&
-                  JSON.stringify(part.state.input) === JSON.stringify(value.input),
+                  JSON.stringify(part.state.input) === JSON.stringify(input),
               )
             ) {
               return
@@ -384,50 +472,42 @@ export const layer: Layer.Layer<
             const agent = yield* agents.get(ctx.assistantMessage.agent)
             yield* permission.ask({
               permission: "doom_loop",
-              patterns: [value.toolName],
+              patterns: [value.name],
               sessionID: ctx.assistantMessage.sessionID,
-              metadata: { tool: value.toolName, input: value.input },
-              always: [value.toolName],
+              metadata: { tool: value.name, input },
+              always: [value.name],
               ruleset: agent.permission,
             })
             return
           }
 
           case "tool-result": {
-            const toolCall = yield* readToolCall(value.toolCallId)
-            const toolAttachments: MessageV2.FilePart[] = (
-              Array.isArray(value.output.attachments) ? value.output.attachments : []
-            ).filter(
-              (attachment: unknown): attachment is MessageV2.FilePart =>
-                isRecord(attachment) &&
-                attachment.type === "file" &&
-                typeof attachment.mime === "string" &&
-                typeof attachment.url === "string",
-            )
+            const toolCall = yield* readToolCall(value.id)
+            const rawOutput = toolResultOutput(value)
             // temporarily disabled
-            // const normalized = yield* Effect.forEach(toolAttachments, (attachment) =>
+            // const normalized = yield* Effect.forEach(rawOutput.attachments ?? [], (attachment) =>
             //   attachment.mime.startsWith("image/")
             //     ? image.normalize(attachment).pipe(Effect.exit)
             //     : Effect.succeed(Exit.succeed<MessageV2.FilePart>(attachment)),
             // )
-            const normalized = yield* Effect.forEach(toolAttachments, (attachment) =>
+            const normalized = yield* Effect.forEach(rawOutput.attachments ?? [], (attachment) =>
               Effect.succeed(Exit.succeed<MessageV2.FilePart>(attachment)),
             )
             const omitted = normalized.filter(Exit.isFailure).length
             const attachments = normalized.filter(Exit.isSuccess).map((item) => item.value)
             const output = {
-              ...value.output,
+              ...rawOutput,
               output:
                 omitted === 0
-                  ? value.output.output
-                  : `${value.output.output}\n\n[${omitted} image${omitted === 1 ? "" : "s"} omitted: could not be resized below the image size limit.]`,
-              attachments: attachments?.length ? attachments : undefined,
+                  ? rawOutput.output
+                  : `${rawOutput.output}\n\n[${omitted} image${omitted === 1 ? "" : "s"} omitted: could not be resized below the image size limit.]`,
+              attachments: attachments.length ? attachments : undefined,
             }
             // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
             if (flags.experimentalEventSystem) {
               yield* sync.run(SessionEvent.Tool.Success.Sync, {
                 sessionID: ctx.sessionID,
-                callID: value.toolCallId,
+                callID: value.id,
                 structured: output.metadata,
                 content: [
                   {
@@ -435,32 +515,32 @@ export const layer: Layer.Layer<
                     text: output.output,
                   },
                   ...(output.attachments?.map((item: MessageV2.FilePart) => ({
-                    type: "file",
+                    type: "file" as const,
                     uri: item.url,
                     mime: item.mime,
                     name: item.filename,
                   })) ?? []),
                 ],
                 provider: {
-                  executed: toolCall?.part.metadata?.providerExecuted === true,
+                  executed: value.providerExecuted === true || toolCall?.part.metadata?.providerExecuted === true,
                 },
                 timestamp: DateTime.makeUnsafe(Date.now()),
               })
             }
-            yield* completeToolCall(value.toolCallId, output)
+            yield* completeToolCall(value.id, output)
             return
           }
 
           case "tool-error": {
-            const toolCall = yield* readToolCall(value.toolCallId)
+            const toolCall = yield* readToolCall(value.id)
             // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
             if (flags.experimentalEventSystem) {
               yield* sync.run(SessionEvent.Tool.Failed.Sync, {
                 sessionID: ctx.sessionID,
-                callID: value.toolCallId,
+                callID: value.id,
                 error: {
                   type: "unknown",
-                  message: errorMessage(value.error),
+                  message: value.message,
                 },
                 provider: {
                   executed: toolCall?.part.metadata?.providerExecuted === true,
@@ -468,14 +548,14 @@ export const layer: Layer.Layer<
                 timestamp: DateTime.makeUnsafe(Date.now()),
               })
             }
-            yield* failToolCall(value.toolCallId, value.error)
+            yield* failToolCall(value.id, new Error(value.message))
             return
           }
 
-          case "error":
-            throw value.error
+          case "provider-error":
+            throw new Error(value.message)
 
-          case "start-step":
+          case "step-start":
             if (!ctx.snapshot) ctx.snapshot = yield* snapshot.track()
             if (!ctx.assistantMessage.summary) {
               // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
@@ -502,11 +582,12 @@ export const layer: Layer.Layer<
             })
             return
 
-          case "finish-step": {
+          case "step-finish": {
             const completedSnapshot = yield* snapshot.track()
+            yield* Effect.forEach(Object.keys(ctx.reasoningMap), finishReasoning)
             const usage = Session.getUsage({
               model: ctx.model,
-              usage: value.usage,
+              usage: value.usage ?? new Usage({}),
               metadata: value.providerMetadata,
             })
             if (!ctx.assistantMessage.summary) {
@@ -514,7 +595,7 @@ export const layer: Layer.Layer<
               if (flags.experimentalEventSystem) {
                 yield* sync.run(SessionEvent.Step.Ended.Sync, {
                   sessionID: ctx.sessionID,
-                  finish: value.finishReason,
+                  finish: value.reason,
                   cost: usage.cost,
                   tokens: usage.tokens,
                   snapshot: completedSnapshot,
@@ -522,12 +603,12 @@ export const layer: Layer.Layer<
                 })
               }
             }
-            ctx.assistantMessage.finish = value.finishReason
+            ctx.assistantMessage.finish = value.reason
             ctx.assistantMessage.cost += usage.cost
             ctx.assistantMessage.tokens = usage.tokens
             yield* session.updatePart({
               id: PartID.ascending(),
-              reason: value.finishReason,
+              reason: value.reason,
               snapshot: completedSnapshot,
               messageID: ctx.assistantMessage.id,
               sessionID: ctx.assistantMessage.sessionID,
@@ -590,7 +671,6 @@ export const layer: Layer.Layer<
           case "text-delta":
             if (!ctx.currentText) return
             ctx.currentText.text += value.text
-            if (value.providerMetadata) ctx.currentText.metadata = value.providerMetadata
             yield* session.updatePartDelta({
               sessionID: ctx.currentText.sessionID,
               messageID: ctx.currentText.messageID,
@@ -635,9 +715,6 @@ export const layer: Layer.Layer<
           case "finish":
             return
 
-          default:
-            slog.info("unhandled", { event: value.type, value })
-            return
         }
       })
 
@@ -739,6 +816,7 @@ export const layer: Layer.Layer<
           yield* Effect.gen(function* () {
             ctx.currentText = undefined
             ctx.reasoningMap = {}
+            yield* status.set(ctx.sessionID, { type: "busy" })
             const stream = llm.stream(streamInput)
 
             yield* stream.pipe(
@@ -822,12 +900,12 @@ export const defaultLayer = Layer.suspend(() =>
     Layer.provide(LLM.defaultLayer),
     Layer.provide(Permission.defaultLayer),
     Layer.provide(Plugin.defaultLayer),
+    Layer.provide(Image.defaultLayer),
     Layer.provide(SessionSummary.defaultLayer),
     Layer.provide(SessionStatus.defaultLayer),
-    Layer.provide(Image.defaultLayer),
+    Layer.provide(SyncEvent.defaultLayer),
     Layer.provide(Bus.layer),
     Layer.provide(Config.defaultLayer),
-    Layer.provide(SyncEvent.defaultLayer),
     Layer.provide(RuntimeFlags.defaultLayer),
   ),
 )
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index cae0dd3845..062620a4d3 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -60,6 +60,7 @@ import * as DateTime from "effect/DateTime"
 import { eq } from "@/storage/db"
 import * as Database from "@/storage/db"
 import { SessionTable } from "./session.sql"
+import { LLMEvent } from "@opencode-ai/llm"
 
 // @ts-ignore
 globalThis.AI_SDK_LOG_WARNINGS = false
@@ -360,7 +361,7 @@ export const layer = Layer.effect(
           messages: [{ role: "user", content: "Generate a title for this conversation:\n" }, ...msgs],
         })
         .pipe(
-          Stream.filter((e): e is Extract<LLM.Event, { type: "text-delta" }> => e.type === "text-delta"),
+          Stream.filter(LLMEvent.is.textDelta),
           Stream.map((e) => e.text),
           Stream.mkString,
           Effect.orDie,
diff --git a/packages/opencode/src/session/session.ts b/packages/opencode/src/session/session.ts
index df173e895b..b6df745084 100644
--- a/packages/opencode/src/session/session.ts
+++ b/packages/opencode/src/session/session.ts
@@ -3,7 +3,7 @@ import path from "path"
 import { BusEvent } from "@/bus/bus-event"
 import { Bus } from "@/bus"
 import { Decimal } from "decimal.js"
-import { type ProviderMetadata, type LanguageModelUsage } from "ai"
+import type { ProviderMetadata, Usage } from "@opencode-ai/llm"
 import { Flag } from "@opencode-ai/core/flag/flag"
 import { InstallationVersion } from "@opencode-ai/core/installation/version"
 
@@ -373,21 +373,19 @@ export function plan(input: { slug: string; time: { created: number } }, instanc
   return path.join(base, [input.time.created, input.slug].join("-") + ".md")
 }
 
-export const getUsage = (input: { model: Provider.Model; usage: LanguageModelUsage; metadata?: ProviderMetadata }) => {
+export const getUsage = (input: { model: Provider.Model; usage: Usage; metadata?: ProviderMetadata }) => {
   const safe = (value: number) => {
     if (!Number.isFinite(value)) return 0
     return Math.max(0, value)
   }
   const inputTokens = safe(input.usage.inputTokens ?? 0)
   const outputTokens = safe(input.usage.outputTokens ?? 0)
-  const reasoningTokens = safe(input.usage.outputTokenDetails?.reasoningTokens ?? input.usage.reasoningTokens ?? 0)
+  const reasoningTokens = safe(input.usage.reasoningTokens ?? 0)
 
-  const cacheReadInputTokens = safe(
-    input.usage.inputTokenDetails?.cacheReadTokens ?? input.usage.cachedInputTokens ?? 0,
-  )
+  const cacheReadInputTokens = safe(input.usage.cacheReadInputTokens ?? 0)
   const cacheWriteInputTokens = safe(
     Number(
-      input.usage.inputTokenDetails?.cacheWriteTokens ??
+      input.usage.cacheWriteInputTokens ??
         input.metadata?.["anthropic"]?.["cacheCreationInputTokens"] ??
         // google-vertex-anthropic returns metadata under "vertex" key
         // (AnthropicMessagesLanguageModel custom provider key from 'vertex.anthropic.messages')
diff --git a/packages/opencode/test/session/compaction.test.ts b/packages/opencode/test/session/compaction.test.ts
index d8a4167902..3c276d84dc 100644
--- a/packages/opencode/test/session/compaction.test.ts
+++ b/packages/opencode/test/session/compaction.test.ts
@@ -29,6 +29,7 @@ import { CrossSpawnSpawner } from "@opencode-ai/core/cross-spawn-spawner"
 import { TestConfig } from "../fixture/config"
 import { SyncEvent } from "@/sync"
 import { RuntimeFlags } from "@/effect/runtime-flags"
+import { LLMEvent, Usage } from "@opencode-ai/llm"
 
 void Log.init({ print: false })
 
@@ -46,6 +47,10 @@ const ref = {
   modelID: ModelID.make("test-model"),
 }
 
+const usage = (input: ConstructorParameters<typeof Usage>[0]) => new Usage(input)
+
+const basicUsage = () => usage({ inputTokens: 1, outputTokens: 1, totalTokens: 2 })
+
 afterEach(() => {
   mock.restore()
 })
@@ -293,11 +298,11 @@ function readCompactionPart(sessionID: SessionID) {
 
 function llm() {
   const queue: Array<
-    Stream.Stream<LLM.Event, unknown> | ((input: LLM.StreamInput) => Stream.Stream<LLM.Event, unknown>)
+    Stream.Stream<LLMEvent, unknown> | ((input: LLM.StreamInput) => Stream.Stream<LLMEvent, unknown>)
   > = []
 
   return {
-    push(stream: Stream.Stream<LLM.Event, unknown> | ((input: LLM.StreamInput) => Stream.Stream<LLM.Event, unknown>)) {
+    push(stream: Stream.Stream<LLMEvent, unknown> | ((input: LLM.StreamInput) => Stream.Stream<LLMEvent, unknown>)) {
       queue.push(stream)
     },
     layer: Layer.succeed(
@@ -316,54 +321,22 @@ function llm() {
 function reply(
   text: string,
   capture?: (input: LLM.StreamInput) => void,
-): (input: LLM.StreamInput) => Stream.Stream<LLM.Event, unknown> {
+): (input: LLM.StreamInput) => Stream.Stream<LLMEvent, unknown> {
   return (input) => {
     capture?.(input)
     return Stream.make(
-      { type: "start" } satisfies LLM.Event,
-      { type: "text-start", id: "txt-0" } satisfies LLM.Event,
-      { type: "text-delta", id: "txt-0", delta: text, text } as LLM.Event,
-      { type: "text-end", id: "txt-0" } satisfies LLM.Event,
-      {
-        type: "finish-step",
-        finishReason: "stop",
-        rawFinishReason: "stop",
-        response: { id: "res", modelId: "test-model", timestamp: new Date() },
-        providerMetadata: undefined,
-        usage: {
-          inputTokens: 1,
-          outputTokens: 1,
-          totalTokens: 2,
-          inputTokenDetails: {
-            noCacheTokens: undefined,
-            cacheReadTokens: undefined,
-            cacheWriteTokens: undefined,
-          },
-          outputTokenDetails: {
-            textTokens: undefined,
-            reasoningTokens: undefined,
-          },
-        },
-      } satisfies LLM.Event,
-      {
-        type: "finish",
-        finishReason: "stop",
-        rawFinishReason: "stop",
-        totalUsage: {
-          inputTokens: 1,
-          outputTokens: 1,
-          totalTokens: 2,
-          inputTokenDetails: {
-            noCacheTokens: undefined,
-            cacheReadTokens: undefined,
-            cacheWriteTokens: undefined,
-          },
-          outputTokenDetails: {
-            textTokens: undefined,
-            reasoningTokens: undefined,
-          },
-        },
-      } satisfies LLM.Event,
+      LLMEvent.textStart({ id: "txt-0" }),
+      LLMEvent.textDelta({ id: "txt-0", text }),
+      LLMEvent.textEnd({ id: "txt-0" }),
+      LLMEvent.stepFinish({
+        index: 0,
+        reason: "stop",
+        usage: basicUsage(),
+      }),
+      LLMEvent.finish({
+        reason: "stop",
+        usage: basicUsage(),
+      }),
     )
   }
 }
@@ -1201,7 +1174,7 @@ describe("session.compaction.process", () => {
         Stream.fromAsyncIterable(
           {
             async *[Symbol.asyncIterator]() {
-              yield { type: "start" } as LLM.Event
+              yield LLMEvent.stepStart({ index: 0 })
               throw new APICallError({
                 message: "boom",
                 url: "https://example.com/v1/chat/completions",
@@ -1293,49 +1266,16 @@ describe("session.compaction.process", () => {
       const stub = llm()
       stub.push(
         Stream.make(
-          { type: "start" } satisfies LLM.Event,
-          { type: "tool-input-start", id: "call-1", toolName: "_noop" } satisfies LLM.Event,
-          { type: "tool-call", toolCallId: "call-1", toolName: "_noop", input: {} } satisfies LLM.Event,
-          {
-            type: "finish-step",
-            finishReason: "tool-calls",
-            rawFinishReason: "tool_calls",
-            response: { id: "res", modelId: "test-model", timestamp: new Date() },
-            providerMetadata: undefined,
-            usage: {
-              inputTokens: 1,
-              outputTokens: 1,
-              totalTokens: 2,
-              inputTokenDetails: {
-                noCacheTokens: undefined,
-                cacheReadTokens: undefined,
-                cacheWriteTokens: undefined,
-              },
-              outputTokenDetails: {
-                textTokens: undefined,
-                reasoningTokens: undefined,
-              },
-            },
-          } satisfies LLM.Event,
-          {
-            type: "finish",
-            finishReason: "tool-calls",
-            rawFinishReason: "tool_calls",
-            totalUsage: {
-              inputTokens: 1,
-              outputTokens: 1,
-              totalTokens: 2,
-              inputTokenDetails: {
-                noCacheTokens: undefined,
-                cacheReadTokens: undefined,
-                cacheWriteTokens: undefined,
-              },
-              outputTokenDetails: {
-                textTokens: undefined,
-                reasoningTokens: undefined,
-              },
-            },
-          } satisfies LLM.Event,
+          LLMEvent.toolCall({ id: "call-1", name: "_noop", input: {} }),
+          LLMEvent.stepFinish({
+            index: 0,
+            reason: "tool-calls",
+            usage: basicUsage(),
+          }),
+          LLMEvent.finish({
+            reason: "tool-calls",
+            usage: basicUsage(),
+          }),
         ),
       )
       return Effect.gen(function* () {
@@ -1541,20 +1481,7 @@ describe("SessionNs.getUsage", () => {
     const model = createModel({ context: 100_000, output: 32_000 })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 1000,
-        outputTokens: 500,
-        totalTokens: 1500,
-        inputTokenDetails: {
-          noCacheTokens: undefined,
-          cacheReadTokens: undefined,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      },
+      usage: usage({ inputTokens: 1000, outputTokens: 500, totalTokens: 1500 }),
     })
 
     expect(result.tokens.input).toBe(1000)
@@ -1568,20 +1495,7 @@ describe("SessionNs.getUsage", () => {
     const model = createModel({ context: 100_000, output: 32_000 })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 1000,
-        outputTokens: 500,
-        totalTokens: 1500,
-        inputTokenDetails: {
-          noCacheTokens: 800,
-          cacheReadTokens: 200,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      },
+      usage: usage({ inputTokens: 1000, outputTokens: 500, totalTokens: 1500, cacheReadInputTokens: 200 }),
     })
 
     expect(result.tokens.input).toBe(800)
@@ -1592,20 +1506,7 @@ describe("SessionNs.getUsage", () => {
     const model = createModel({ context: 100_000, output: 32_000 })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 1000,
-        outputTokens: 500,
-        totalTokens: 1500,
-        inputTokenDetails: {
-          noCacheTokens: undefined,
-          cacheReadTokens: undefined,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      },
+      usage: usage({ inputTokens: 1000, outputTokens: 500, totalTokens: 1500 }),
       metadata: {
         anthropic: {
           cacheCreationInputTokens: 300,
@@ -1621,20 +1522,7 @@ describe("SessionNs.getUsage", () => {
     // AI SDK v6 normalizes inputTokens to include cached tokens for all providers
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 1000,
-        outputTokens: 500,
-        totalTokens: 1500,
-        inputTokenDetails: {
-          noCacheTokens: 800,
-          cacheReadTokens: 200,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      },
+      usage: usage({ inputTokens: 1000, outputTokens: 500, totalTokens: 1500, cacheReadInputTokens: 200 }),
       metadata: {
         anthropic: {},
       },
@@ -1648,20 +1536,7 @@ describe("SessionNs.getUsage", () => {
     const model = createModel({ context: 100_000, output: 32_000 })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 1000,
-        outputTokens: 500,
-        totalTokens: 1500,
-        inputTokenDetails: {
-          noCacheTokens: undefined,
-          cacheReadTokens: undefined,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: 400,
-          reasoningTokens: 100,
-        },
-      },
+      usage: usage({ inputTokens: 1000, outputTokens: 500, reasoningTokens: 100, totalTokens: 1500 }),
     })
 
     expect(result.tokens.input).toBe(1000)
@@ -1682,20 +1557,7 @@ describe("SessionNs.getUsage", () => {
     })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 0,
-        outputTokens: 1_000_000,
-        totalTokens: 1_000_000,
-        inputTokenDetails: {
-          noCacheTokens: undefined,
-          cacheReadTokens: undefined,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: 750_000,
-          reasoningTokens: 250_000,
-        },
-      },
+      usage: usage({ inputTokens: 0, outputTokens: 1_000_000, reasoningTokens: 250_000, totalTokens: 1_000_000 }),
     })
 
     expect(result.tokens.output).toBe(750_000)
@@ -1707,20 +1569,7 @@ describe("SessionNs.getUsage", () => {
     const model = createModel({ context: 100_000, output: 32_000 })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 0,
-        outputTokens: 0,
-        totalTokens: 0,
-        inputTokenDetails: {
-          noCacheTokens: undefined,
-          cacheReadTokens: undefined,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      },
+      usage: usage({ inputTokens: 0, outputTokens: 0, totalTokens: 0 }),
     })
 
     expect(result.tokens.input).toBe(0)
@@ -1743,20 +1592,7 @@ describe("SessionNs.getUsage", () => {
     })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 1_000_000,
-        outputTokens: 100_000,
-        totalTokens: 1_100_000,
-        inputTokenDetails: {
-          noCacheTokens: undefined,
-          cacheReadTokens: undefined,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      },
+      usage: usage({ inputTokens: 1_000_000, outputTokens: 100_000, totalTokens: 1_100_000 }),
     })
 
     expect(result.cost).toBe(3 + 1.5)
@@ -1862,24 +1698,16 @@ describe("SessionNs.getUsage", () => {
     (npm) => {
       const model = createModel({ context: 100_000, output: 32_000, npm })
       // AI SDK v6: inputTokens includes cached tokens for all providers
-      const usage = {
+      const item = usage({
         inputTokens: 1000,
         outputTokens: 500,
         totalTokens: 1500,
-        inputTokenDetails: {
-          noCacheTokens: 800,
-          cacheReadTokens: 200,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      }
+        cacheReadInputTokens: 200,
+      })
       if (npm === "@ai-sdk/amazon-bedrock") {
         const result = SessionNs.getUsage({
           model,
-          usage,
+          usage: item,
           metadata: {
             bedrock: {
               usage: {
@@ -1900,7 +1728,7 @@ describe("SessionNs.getUsage", () => {
 
       const result = SessionNs.getUsage({
         model,
-        usage,
+        usage: item,
         metadata: {
           anthropic: {
             cacheCreationInputTokens: 300,
@@ -1921,20 +1749,7 @@ describe("SessionNs.getUsage", () => {
     const model = createModel({ context: 100_000, output: 32_000, npm: "@ai-sdk/google-vertex/anthropic" })
     const result = SessionNs.getUsage({
       model,
-      usage: {
-        inputTokens: 1000,
-        outputTokens: 500,
-        totalTokens: 1500,
-        inputTokenDetails: {
-          noCacheTokens: 800,
-          cacheReadTokens: 200,
-          cacheWriteTokens: undefined,
-        },
-        outputTokenDetails: {
-          textTokens: undefined,
-          reasoningTokens: undefined,
-        },
-      },
+      usage: usage({ inputTokens: 1000, outputTokens: 500, totalTokens: 1500, cacheReadInputTokens: 200 }),
       metadata: {
         vertex: {
           cacheCreationInputTokens: 300,
diff --git a/packages/opencode/test/session/llm-native.test.ts b/packages/opencode/test/session/llm-native.test.ts
new file mode 100644
index 0000000000..40aa71df4d
--- /dev/null
+++ b/packages/opencode/test/session/llm-native.test.ts
@@ -0,0 +1,262 @@
+import { describe, expect, test } from "bun:test"
+import { LLMClient, RequestExecutor } from "@opencode-ai/llm/route"
+import { jsonSchema, tool, type ModelMessage } from "ai"
+import { Effect } from "effect"
+import { LLMNative } from "@/session/llm-native"
+import type { Provider } from "@/provider/provider"
+import { ModelID, ProviderID } from "@/provider/schema"
+
+const baseModel: Provider.Model = {
+  id: ModelID.make("gpt-5-mini"),
+  providerID: ProviderID.make("openai"),
+  api: {
+    id: "gpt-5-mini",
+    url: "https://api.openai.com/v1",
+    npm: "@ai-sdk/openai",
+  },
+  name: "GPT-5 Mini",
+  capabilities: {
+    temperature: true,
+    reasoning: true,
+    attachment: true,
+    toolcall: true,
+    input: {
+      text: true,
+      audio: false,
+      image: true,
+      video: false,
+      pdf: false,
+    },
+    output: {
+      text: true,
+      audio: false,
+      image: false,
+      video: false,
+      pdf: false,
+    },
+    interleaved: false,
+  },
+  cost: {
+    input: 0,
+    output: 0,
+    cache: {
+      read: 0,
+      write: 0,
+    },
+  },
+  limit: {
+    context: 128_000,
+    input: 128_000,
+    output: 32_000,
+  },
+  status: "active",
+  options: {},
+  headers: {
+    "x-model": "model-header",
+  },
+  release_date: "2026-01-01",
+}
+
+describe("session.llm-native.request", () => {
+  test("maps normalized stream inputs to a native LLM request", () => {
+    const messages: ModelMessage[] = [
+      {
+        role: "system",
+        content: "system from messages",
+      },
+      {
+        role: "user",
+        content: [
+          { type: "text", text: "hello", providerOptions: { openai: { cacheControl: { type: "ephemeral" } } } },
+          { type: "file", mediaType: "image/png", filename: "img.png", data: "data:image/png;base64,Zm9v" },
+        ],
+      },
+      {
+        role: "assistant",
+        content: [
+          { type: "reasoning", text: "thinking", providerOptions: { openai: { encryptedContent: "secret" } } },
+          { type: "text", text: "I'll run it" },
+          {
+            type: "tool-call",
+            toolCallId: "call-1",
+            toolName: "bash",
+            input: { command: "ls" },
+            providerOptions: { openai: { itemId: "item-1" } },
+          },
+        ],
+      },
+      {
+        role: "tool",
+        content: [
+          {
+            type: "tool-result",
+            toolCallId: "call-1",
+            toolName: "bash",
+            output: { type: "text", value: "ok" },
+            providerOptions: { openai: { outputId: "output-1" } },
+          },
+        ],
+      },
+    ]
+
+    const request = LLMNative.request({
+      model: baseModel,
+      system: ["agent system"],
+      messages,
+      tools: {
+        bash: tool({
+          description: "Run a shell command",
+          inputSchema: jsonSchema({
+            type: "object",
+            properties: {
+              command: { type: "string" },
+            },
+            required: ["command"],
+          }),
+        }),
+      },
+      toolChoice: "required",
+      temperature: 0.2,
+      topP: 0.9,
+      topK: 40,
+      maxOutputTokens: 1024,
+      providerOptions: { openai: { store: false } },
+      headers: { "x-request": "request-header" },
+    })
+
+    expect(request.model).toMatchObject({
+      id: "gpt-5-mini",
+      provider: "openai",
+      route: "openai-responses",
+      baseURL: "https://api.openai.com/v1",
+      headers: {
+        "x-model": "model-header",
+        "x-request": "request-header",
+      },
+      limits: {
+        context: 128_000,
+        output: 32_000,
+      },
+    })
+    expect(request.system).toEqual([
+      { type: "text", text: "agent system" },
+      { type: "text", text: "system from messages" },
+    ])
+    expect(request.generation).toMatchObject({
+      temperature: 0.2,
+      topP: 0.9,
+      topK: 40,
+      maxTokens: 1024,
+    })
+    expect(request.providerOptions).toEqual({ openai: { store: false } })
+    expect(request.toolChoice).toMatchObject({ type: "required" })
+    expect(request.tools).toMatchObject([
+      {
+        name: "bash",
+        description: "Run a shell command",
+        inputSchema: {
+          type: "object",
+          properties: {
+            command: { type: "string" },
+          },
+          required: ["command"],
+        },
+      },
+    ])
+    expect(request.messages).toMatchObject([
+      {
+        role: "user",
+        content: [
+          { type: "text", text: "hello", providerMetadata: { openai: { cacheControl: { type: "ephemeral" } } } },
+          { type: "media", mediaType: "image/png", filename: "img.png", data: "data:image/png;base64,Zm9v" },
+        ],
+      },
+      {
+        role: "assistant",
+        content: [
+          { type: "reasoning", text: "thinking", providerMetadata: { openai: { encryptedContent: "secret" } } },
+          { type: "text", text: "I'll run it" },
+          {
+            type: "tool-call",
+            id: "call-1",
+            name: "bash",
+            input: { command: "ls" },
+            providerMetadata: { openai: { itemId: "item-1" } },
+          },
+        ],
+      },
+      {
+        role: "tool",
+        content: [
+          {
+            type: "tool-result",
+            id: "call-1",
+            name: "bash",
+            result: { type: "text", value: "ok" },
+            providerMetadata: { openai: { outputId: "output-1" } },
+          },
+        ],
+      },
+    ])
+  })
+
+  test("selects native routes from existing provider packages", () => {
+    expect(
+      LLMNative.model({ ...baseModel, api: { ...baseModel.api, url: "", npm: "@ai-sdk/anthropic" } }),
+    ).toMatchObject({
+      route: "anthropic-messages",
+      baseURL: "https://api.anthropic.com/v1",
+    })
+    expect(LLMNative.model({ ...baseModel, api: { ...baseModel.api, url: "", npm: "@ai-sdk/google" } })).toMatchObject({
+      route: "gemini",
+      baseURL: "https://generativelanguage.googleapis.com/v1beta",
+    })
+    expect(
+      LLMNative.model({ ...baseModel, api: { ...baseModel.api, npm: "@ai-sdk/openai-compatible" } }),
+    ).toMatchObject({
+      route: "openai-compatible-chat",
+      baseURL: "https://api.openai.com/v1",
+    })
+    expect(
+      LLMNative.model({ ...baseModel, api: { ...baseModel.api, url: "", npm: "@openrouter/ai-sdk-provider" } }),
+    ).toMatchObject({
+      route: "openrouter",
+      baseURL: "https://openrouter.ai/api/v1",
+    })
+  })
+
+  test("fails fast for unsupported provider packages", () => {
+    expect(() =>
+      LLMNative.request({
+        model: { ...baseModel, api: { ...baseModel.api, npm: "unknown-provider" } },
+        messages: [],
+      }),
+    ).toThrow("Native LLM request adapter does not support provider package unknown-provider")
+  })
+
+  test("compiles through the native OpenAI Responses route", async () => {
+    const prepared = await Effect.runPromise(
+      LLMClient.prepare(
+        LLMNative.request({
+          model: baseModel,
+          messages: [{ role: "user", content: "hello" }],
+          providerOptions: { openai: { store: false } },
+          maxOutputTokens: 512,
+          headers: { "x-request": "request-header" },
+        }),
+      ).pipe(Effect.provide(LLMClient.layer), Effect.provide(RequestExecutor.defaultLayer)),
+    )
+
+    expect(prepared).toMatchObject({
+      route: "openai-responses",
+      protocol: "openai-responses",
+      body: {
+        model: "gpt-5-mini",
+        input: [{ role: "user", content: [{ type: "input_text", text: "hello" }] }],
+        max_output_tokens: 512,
+        store: false,
+        stream: true,
+      },
+    })
+  })
+})
diff --git a/packages/opencode/test/session/llm.test.ts b/packages/opencode/test/session/llm.test.ts
index 4a6b1e8b7f..6744362a71 100644
--- a/packages/opencode/test/session/llm.test.ts
+++ b/packages/opencode/test/session/llm.test.ts
@@ -1,15 +1,19 @@
 import { afterAll, beforeAll, beforeEach, describe, expect, test } from "bun:test"
 import path from "path"
 import { tool, type ModelMessage } from "ai"
-import { Cause, Effect, Exit, Stream } from "effect"
+import { Cause, Effect, Exit, Layer, Stream } from "effect"
+import { HttpClientRequest, HttpClientResponse } from "effect/unstable/http"
 import z from "zod"
-import { makeRuntime } from "../../src/effect/run-service"
+import { attach, makeRuntime } from "../../src/effect/run-service"
 import { LLM } from "../../src/session/llm"
-import { Instance } from "../../src/project/instance"
+import { LLMClient, RequestExecutor } from "@opencode-ai/llm/route"
 import { WithInstance } from "../../src/project/with-instance"
+import { Auth } from "@/auth"
+import { Config } from "@/config/config"
 import { Provider } from "@/provider/provider"
 import { ProviderTransform } from "@/provider/transform"
 import { ModelsDev } from "@/provider/models"
+import { Plugin } from "@/plugin"
 import { ProviderID, ModelID } from "../../src/provider/schema"
 import { Filesystem } from "@/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
@@ -18,6 +22,29 @@ import { MessageV2 } from "../../src/session/message-v2"
 import { SessionID, MessageID } from "../../src/session/schema"
 import { AppRuntime } from "../../src/effect/app-runtime"
 
+const openAIConfig = (model: ModelsDev.Provider["models"][string], baseURL: string): Partial<Config.Info> => {
+  const { experimental: _experimental, ...configModel } = model
+  type ConfigModel = NonNullable<NonNullable<Config.Info["provider"]>[string]["models"]>[string]
+  return {
+    enabled_providers: ["openai"],
+    provider: {
+      openai: {
+        name: "OpenAI",
+        env: ["OPENAI_API_KEY"],
+        npm: "@ai-sdk/openai",
+        api: "https://api.openai.com/v1",
+        models: {
+          [model.id]: JSON.parse(JSON.stringify(configModel)) as ConfigModel,
+        },
+        options: {
+          apiKey: "test-openai-key",
+          baseURL,
+        },
+      },
+    },
+  }
+}
+
 async function getModel(providerID: ProviderID, modelID: ModelID) {
   return AppRuntime.runPromise(
     Effect.gen(function* () {
@@ -33,6 +60,22 @@ async function drain(input: LLM.StreamInput) {
   return llm.runPromise((svc) => svc.stream(input).pipe(Stream.runDrain))
 }
 
+async function drainWith(layer: Layer.Layer<LLM.Service>, input: LLM.StreamInput) {
+  return Effect.runPromise(
+    attach(LLM.Service.use((svc) => svc.stream(input).pipe(Stream.runDrain))).pipe(Effect.provide(layer)),
+  )
+}
+
+function llmLayerWithExecutor(executor: Layer.Layer<RequestExecutor.Service>) {
+  return LLM.layer.pipe(
+    Layer.provide(Auth.defaultLayer),
+    Layer.provide(Config.defaultLayer),
+    Layer.provide(Provider.defaultLayer),
+    Layer.provide(Plugin.defaultLayer),
+    Layer.provide(LLMClient.layer.pipe(Layer.provide(executor))),
+  )
+}
+
 describe("session.llm.hasToolCalls", () => {
   test("returns false for empty messages array", () => {
     expect(LLM.hasToolCalls([])).toBe(false)
@@ -600,6 +643,18 @@ describe("session.llm.stream", () => {
           service_tier: null,
         },
       },
+      {
+        type: "response.output_item.added",
+        output_index: 0,
+        item: { type: "message", id: "item-1", status: "in_progress", role: "assistant", content: [] },
+      },
+      {
+        type: "response.content_part.added",
+        item_id: "item-1",
+        output_index: 0,
+        content_index: 0,
+        part: { type: "output_text", text: "", annotations: [] },
+      },
       {
         type: "response.output_text.delta",
         item_id: "item-1",
@@ -622,32 +677,7 @@ describe("session.llm.stream", () => {
     ]
     const request = waitRequest("/responses", createEventResponse(responseChunks, true))
 
-    await using tmp = await tmpdir({
-      init: async (dir) => {
-        await Bun.write(
-          path.join(dir, "opencode.json"),
-          JSON.stringify({
-            $schema: "https://opencode.ai/config.json",
-            enabled_providers: ["openai"],
-            provider: {
-              openai: {
-                name: "OpenAI",
-                env: ["OPENAI_API_KEY"],
-                npm: "@ai-sdk/openai",
-                api: "https://api.openai.com/v1",
-                models: {
-                  [model.id]: configModel(model),
-                },
-                options: {
-                  apiKey: "test-openai-key",
-                  baseURL: `${server.url.origin}/v1`,
-                },
-              },
-            },
-          }),
-        )
-      },
-    })
+    await using tmp = await tmpdir({ config: openAIConfig(model, `${server.url.origin}/v1`) })
 
     await WithInstance.provide({
       directory: tmp.path,
@@ -695,6 +725,333 @@ describe("session.llm.stream", () => {
     })
   })
 
+  test("streams OpenAI through native runtime when opted in", async () => {
+    const server = state.server
+    if (!server) {
+      throw new Error("Server not initialized")
+    }
+
+    const source = await loadFixture("openai", "gpt-5.2")
+    const model = source.model
+    const chunks = [
+      {
+        type: "response.created",
+        response: {
+          id: "resp-native",
+        },
+      },
+      {
+        type: "response.output_item.added",
+        item: { type: "message", id: "item-native", status: "in_progress" },
+      },
+      {
+        type: "response.output_text.delta",
+        item_id: "item-native",
+        delta: "Hello native",
+      },
+      {
+        type: "response.completed",
+        response: {
+          incomplete_details: null,
+          usage: {
+            input_tokens: 1,
+            input_tokens_details: null,
+            output_tokens: 1,
+            output_tokens_details: null,
+          },
+        },
+      },
+    ]
+    const request = waitRequest("/responses", createEventResponse(chunks, true))
+
+    await using tmp = await tmpdir({ config: openAIConfig(model, `${server.url.origin}/v1`) })
+
+    await WithInstance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const previous = process.env.OPENCODE_LLM_RUNTIME
+        process.env.OPENCODE_LLM_RUNTIME = "native"
+        try {
+          const resolved = await getModel(ProviderID.openai, ModelID.make(model.id))
+          const sessionID = SessionID.make("session-test-native")
+          const agent = {
+            name: "test",
+            mode: "primary",
+            options: {},
+            permission: [{ permission: "*", pattern: "*", action: "allow" }],
+            temperature: 0.2,
+          } satisfies Agent.Info
+
+          await drain({
+            user: {
+              id: MessageID.make("msg_user-native"),
+              sessionID,
+              role: "user",
+              time: { created: Date.now() },
+              agent: agent.name,
+              model: { providerID: ProviderID.make("openai"), modelID: resolved.id, variant: "high" },
+            } satisfies MessageV2.User,
+            sessionID,
+            model: resolved,
+            agent,
+            system: ["You are a helpful assistant."],
+            messages: [{ role: "user", content: "Hello" }],
+            tools: {},
+          })
+        } finally {
+          if (previous === undefined) delete process.env.OPENCODE_LLM_RUNTIME
+          else process.env.OPENCODE_LLM_RUNTIME = previous
+        }
+
+        const capture = await request
+        expect(capture.url.pathname.endsWith("/responses")).toBe(true)
+        expect(capture.headers.get("Authorization")).toBe("Bearer test-openai-key")
+        expect(capture.body.model).toBe(model.id)
+        expect(capture.body.stream).toBe(true)
+        expect((capture.body.reasoning as { effort?: string } | undefined)?.effort).toBe("high")
+        expect(JSON.stringify(capture.body.input)).toContain("You are a helpful assistant.")
+        expect(capture.body.input).toContainEqual({ role: "user", content: [{ type: "input_text", text: "Hello" }] })
+      },
+    })
+  })
+
+  test("uses injected native request executor for tool calls", async () => {
+    const source = await loadFixture("openai", "gpt-5.2")
+    const model = source.model
+    const chunks = [
+      {
+        type: "response.output_item.added",
+        item: { type: "function_call", id: "item-injected-tool", call_id: "call-injected-tool", name: "lookup" },
+      },
+      {
+        type: "response.function_call_arguments.delta",
+        item_id: "item-injected-tool",
+        delta: '{"query":"weather"}',
+      },
+      {
+        type: "response.output_item.done",
+        item: {
+          type: "function_call",
+          id: "item-injected-tool",
+          call_id: "call-injected-tool",
+          name: "lookup",
+          arguments: '{"query":"weather"}',
+        },
+      },
+      {
+        type: "response.completed",
+        response: { incomplete_details: null, usage: { input_tokens: 1, output_tokens: 1 } },
+      },
+    ]
+    let captured: Record<string, unknown> | undefined
+    let executed: unknown
+    const executor = Layer.succeed(
+      RequestExecutor.Service,
+      RequestExecutor.Service.of({
+        execute: (request) =>
+          Effect.gen(function* () {
+            const web = yield* HttpClientRequest.toWeb(request).pipe(Effect.orDie)
+            captured = (yield* Effect.promise(() => web.json())) as Record<string, unknown>
+            return HttpClientResponse.fromWeb(request, createEventResponse(chunks, true))
+          }),
+      }),
+    )
+
+    await using tmp = await tmpdir({ config: openAIConfig(model, "https://injected-openai.test/v1") })
+
+    await WithInstance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const previous = process.env.OPENCODE_LLM_RUNTIME
+        process.env.OPENCODE_LLM_RUNTIME = "native"
+        try {
+          const resolved = await getModel(ProviderID.openai, ModelID.make(model.id))
+          const sessionID = SessionID.make("session-test-native-injected-tool")
+          const agent = {
+            name: "test",
+            mode: "primary",
+            options: {},
+            permission: [{ permission: "*", pattern: "*", action: "allow" }],
+          } satisfies Agent.Info
+
+          await drainWith(llmLayerWithExecutor(executor), {
+            user: {
+              id: MessageID.make("msg_user-native-injected-tool"),
+              sessionID,
+              role: "user",
+              time: { created: Date.now() },
+              agent: agent.name,
+              model: { providerID: ProviderID.make("openai"), modelID: resolved.id },
+            } satisfies MessageV2.User,
+            sessionID,
+            model: resolved,
+            agent,
+            system: [],
+            messages: [{ role: "user", content: "Use lookup" }],
+            tools: {
+              lookup: tool({
+                description: "Lookup data",
+                inputSchema: z.object({ query: z.string() }),
+                execute: async (args, options) => {
+                  executed = { args, toolCallId: options.toolCallId }
+                  return { output: "looked up" }
+                },
+              }),
+            },
+          })
+        } finally {
+          if (previous === undefined) delete process.env.OPENCODE_LLM_RUNTIME
+          else process.env.OPENCODE_LLM_RUNTIME = previous
+        }
+
+        expect(captured?.model).toBe(model.id)
+        expect(captured?.tools).toEqual([
+          {
+            type: "function",
+            name: "lookup",
+            description: "Lookup data",
+            parameters: {
+              type: "object",
+              properties: { query: { type: "string" } },
+              required: ["query"],
+              additionalProperties: false,
+              $schema: "http://json-schema.org/draft-07/schema#",
+            },
+          },
+        ])
+        expect(executed).toEqual({ args: { query: "weather" }, toolCallId: "call-injected-tool" })
+      },
+    })
+  })
+
+  test("executes OpenAI tool calls through native runtime", async () => {
+    const server = state.server
+    if (!server) {
+      throw new Error("Server not initialized")
+    }
+
+    const source = await loadFixture("openai", "gpt-5.2")
+    const model = source.model
+    const chunks = [
+      {
+        type: "response.output_item.added",
+        item: { type: "function_call", id: "item-native-tool", call_id: "call-native-tool", name: "lookup" },
+      },
+      {
+        type: "response.function_call_arguments.delta",
+        item_id: "item-native-tool",
+        delta: '{"query":"weather"}',
+      },
+      {
+        type: "response.output_item.done",
+        item: {
+          type: "function_call",
+          id: "item-native-tool",
+          call_id: "call-native-tool",
+          name: "lookup",
+          arguments: '{"query":"weather"}',
+        },
+      },
+      {
+        type: "response.completed",
+        response: { incomplete_details: null, usage: { input_tokens: 1, output_tokens: 1 } },
+      },
+    ]
+    const request = waitRequest("/responses", createEventResponse(chunks, true))
+    let executed: unknown
+
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(
+          path.join(dir, "opencode.json"),
+          JSON.stringify({
+            $schema: "https://opencode.ai/config.json",
+            enabled_providers: ["openai"],
+            provider: {
+              openai: {
+                name: "OpenAI",
+                env: ["OPENAI_API_KEY"],
+                npm: "@ai-sdk/openai",
+                api: "https://api.openai.com/v1",
+                models: {
+                  [model.id]: model,
+                },
+                options: {
+                  apiKey: "test-openai-key",
+                  baseURL: `${server.url.origin}/v1`,
+                },
+              },
+            },
+          }),
+        )
+      },
+    })
+
+    await WithInstance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const previous = process.env.OPENCODE_LLM_RUNTIME
+        process.env.OPENCODE_LLM_RUNTIME = "native"
+        try {
+          const resolved = await getModel(ProviderID.openai, ModelID.make(model.id))
+          const sessionID = SessionID.make("session-test-native-tool")
+          const agent = {
+            name: "test",
+            mode: "primary",
+            options: {},
+            permission: [{ permission: "*", pattern: "*", action: "allow" }],
+          } satisfies Agent.Info
+
+          await drain({
+            user: {
+              id: MessageID.make("msg_user-native-tool"),
+              sessionID,
+              role: "user",
+              time: { created: Date.now() },
+              agent: agent.name,
+              model: { providerID: ProviderID.make("openai"), modelID: resolved.id },
+            } satisfies MessageV2.User,
+            sessionID,
+            model: resolved,
+            agent,
+            system: [],
+            messages: [{ role: "user", content: "Use lookup" }],
+            tools: {
+              lookup: tool({
+                description: "Lookup data",
+                inputSchema: z.object({ query: z.string() }),
+                execute: async (args, options) => {
+                  executed = { args, toolCallId: options.toolCallId }
+                  return { output: "looked up" }
+                },
+              }),
+            },
+          })
+        } finally {
+          if (previous === undefined) delete process.env.OPENCODE_LLM_RUNTIME
+          else process.env.OPENCODE_LLM_RUNTIME = previous
+        }
+
+        const capture = await request
+        expect(capture.body.tools).toEqual([
+          {
+            type: "function",
+            name: "lookup",
+            description: "Lookup data",
+            parameters: {
+              type: "object",
+              properties: { query: { type: "string" } },
+              required: ["query"],
+              additionalProperties: false,
+              $schema: "http://json-schema.org/draft-07/schema#",
+            },
+          },
+        ])
+        expect(executed).toEqual({ args: { query: "weather" }, toolCallId: "call-native-tool" })
+      },
+    })
+  })
+
   test("accepts user image attachments as data URLs for OpenAI models", async () => {
     const server = state.server
     if (!server) {
@@ -713,6 +1070,18 @@ describe("session.llm.stream", () => {
           service_tier: null,
         },
       },
+      {
+        type: "response.output_item.added",
+        output_index: 0,
+        item: { type: "message", id: "item-data-url", status: "in_progress", role: "assistant", content: [] },
+      },
+      {
+        type: "response.content_part.added",
+        item_id: "item-data-url",
+        output_index: 0,
+        content_index: 0,
+        part: { type: "output_text", text: "", annotations: [] },
+      },
       {
         type: "response.output_text.delta",
         item_id: "item-data-url",