refactor(core): narrow v2 context epoch scope

packages/llm/src/protocols/anthropic-messages.ts

@@ -386,7 +386,6 @@ const lowerMessages = Effect.fn("AnthropicMessages.lowerMessages")(function* (
 
   for (const [index, message] of request.messages.entries()) {
     if (message.role === "system") {
-      yield* ProviderShared.guardSystemUpdatePlacement("Anthropic Messages", request.messages, index)
       if (supportsNativeSystemUpdates(request) && canUseNativeSystemUpdate(request.messages, index)) {
         messages.push(yield* lowerNativeSystemUpdate(message, breakpoints))
         continue

packages/llm/src/protocols/bedrock-converse.ts

@@ -292,9 +292,8 @@ const lowerMessages = Effect.fn("BedrockConverse.lowerMessages")(function* (
 ) {
   const messages: BedrockMessage[] = []
 
-  for (const [index, message] of request.messages.entries()) {
+  for (const message of request.messages) {
     if (message.role === "system") {
-      yield* ProviderShared.guardSystemUpdatePlacement("Bedrock Converse", request.messages, index)
       const part = yield* ProviderShared.wrappedSystemUpdate("Bedrock Converse", message)
       const content = textWithCache(breakpoints, part.text, part.cache)
       const previous = messages.at(-1)

packages/llm/src/protocols/gemini.ts

@@ -200,9 +200,8 @@ const lowerToolCall = (part: ToolCallPart) => ({
 const lowerMessages = Effect.fn("Gemini.lowerMessages")(function* (request: LLMRequest) {
   const contents: GeminiContent[] = []
 
-  for (const [index, message] of request.messages.entries()) {
+  for (const message of request.messages) {
     if (message.role === "system") {
-      yield* ProviderShared.guardSystemUpdatePlacement("Gemini", request.messages, index)
       const part = yield* ProviderShared.wrappedSystemUpdate("Gemini", message)
       const previous = contents.at(-1)
       if (previous?.role === "user")

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

@@ -252,9 +252,8 @@ const lowerMessages = Effect.fn("OpenAIChat.lowerMessages")(function* (request:
   const system: OpenAIChatMessage[] =
     request.system.length === 0 ? [] : [{ role: "system", content: ProviderShared.joinText(request.system) }]
   const messages = [...system]
-  for (const [index, message] of request.messages.entries()) {
+  for (const message of request.messages) {
     if (message.role === "system") {
-      yield* ProviderShared.guardSystemUpdatePlacement("OpenAI Chat", request.messages, index)
       const part = yield* ProviderShared.wrappedSystemUpdate("OpenAI Chat", message)
       const previous = messages.at(-1)
       if (previous?.role === "user")

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

@@ -338,9 +338,8 @@ const lowerMessages = Effect.fn("OpenAIResponses.lowerMessages")(function* (requ
   const input: OpenAIResponsesInputItem[] = [...system]
   const store = OpenAIOptions.store(request)
 
-  for (const [index, message] of request.messages.entries()) {
+  for (const message of request.messages) {
     if (message.role === "system") {
-      yield* ProviderShared.guardSystemUpdatePlacement("OpenAI Responses", request.messages, index)
       const part = yield* ProviderShared.wrappedSystemUpdate("OpenAI Responses", message)
       const previous = input.at(-1)
       if (previous && "role" in previous && previous.role === "user")

packages/llm/src/protocols/shared.ts

@@ -177,26 +177,6 @@ export const wrappedSystemUpdate = Effect.fn("ProviderShared.wrappedSystemUpdate
   return { type: "text" as const, text: wrapSystemUpdate(content), cache: content.at(-1)?.cache }
 })
 
-export const guardSystemUpdatePlacement = Effect.fn("ProviderShared.guardSystemUpdatePlacement")(function* (
-  route: string,
-  messages: LLMRequest["messages"],
-  index: number,
-) {
-  const pending = new Set<string>()
-  for (const message of messages.slice(0, index)) {
-    for (const part of message.content) {
-      if (message.role === "assistant" && part.type === "tool-call" && part.providerExecuted !== true)
-        pending.add(part.id)
-      if (message.role === "tool" && part.type === "tool-result") pending.delete(part.id)
-    }
-  }
-  if (pending.size > 0)
-    return yield* invalidRequest(
-      `${route} chronological system updates cannot appear between a local tool call and its tool result`,
-    )
-  return yield* Effect.void
-})
-
 /**
  * Parse the streamed JSON input of a tool call. Treats an empty string as
  * `"{}"` — providers occasionally finish a tool call without ever emitting

packages/llm/test/provider/anthropic-messages.test.ts

@@ -127,9 +127,6 @@ describe("Anthropic Messages route", () => {
 
   it.effect("falls back for unsupported native chronological system update placement", () =>
     Effect.gen(function* () {
-      const placementError = (messages: Parameters<typeof LLM.request>[0]["messages"]) =>
-        LLMClient.prepare(LLM.request({ model: opus48, messages, cache: "none" })).pipe(Effect.flip)
-
       expect(
         (yield* LLMClient.prepare<AnthropicMessages.AnthropicMessagesBody>(
           LLM.request({
@@ -168,17 +165,6 @@ describe("Anthropic Messages route", () => {
           ],
         },
       ])
-      expect(
-        (yield* placementError([
-          Message.user("Use the tool."),
-          Message.assistant([
-            ToolCallPart.make({ id: "call_1", name: "lookup", input: {} }),
-            { type: "text", text: "Waiting." },
-          ]),
-          Message.system("Too early."),
-          Message.tool({ id: "call_1", name: "lookup", result: "Done." }),
-        ])).message,
-      ).toContain("cannot appear between a local tool call and its tool result")
     }),
   )
 

packages/llm/test/schema.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test"
-import { Effect, Schema } from "effect"
+import { Schema } from "effect"
 import * as OpenAIChat from "../src/protocols/openai-chat"
 import * as OpenAIResponses from "../src/protocols/openai-responses"
 import {
@@ -10,7 +10,6 @@ import {
   Model,
   ModelID,
   ProviderID,
-  ToolCallPart,
   Usage,
 } from "../src/schema"
 import { ProviderShared } from "../src/protocols/shared"
@@ -64,33 +63,6 @@ describe("llm schema", () => {
     expect(decoded.messages[0]).toMatchObject({ role: "system", content: [{ type: "text", text: "Operator update." }] })
   })
 
-  test("rejects chronological system updates between a local tool call and its result", async () => {
-    const messages = [
-      Message.assistant([
-        ToolCallPart.make({ id: "call_1", name: "lookup", input: {} }),
-        { type: "text", text: "Waiting." },
-      ]),
-    ]
-
-    await expect(Effect.runPromise(ProviderShared.guardSystemUpdatePlacement("Test", messages, 1))).rejects.toThrow(
-      "Test chronological system updates cannot appear between a local tool call and its tool result",
-    )
-  })
-
-  test("rejects chronological system updates between results for multiple local tool calls", async () => {
-    const messages = [
-      Message.assistant([
-        ToolCallPart.make({ id: "call_1", name: "lookup", input: {} }),
-        ToolCallPart.make({ id: "call_2", name: "lookup", input: {} }),
-      ]),
-      Message.tool({ id: "call_1", name: "lookup", result: "first" }),
-    ]
-
-    await expect(Effect.runPromise(ProviderShared.guardSystemUpdatePlacement("Test", messages, 2))).rejects.toThrow(
-      "Test chronological system updates cannot appear between a local tool call and its tool result",
-    )
-  })
-
   test("rejects invalid event type", () => {
     expect(() => decodeLLMEvent({ type: "bogus" })).toThrow()
   })