fix(cli): stop sending UI notices to the provider as system messages

extensions/cli/src/services/ChatHistoryService.ts

@@ -2,6 +2,7 @@ import type { ChatHistoryItem, ToolStatus } from "core/index.js";
 import { createHistoryItem } from "core/util/messageConversion.js";
 
 import { loadSessionById, updateSessionHistory } from "../session.js";
+import type { ChatHistoryItemWithType } from "../uiNotices.js";
 import { logger } from "../util/logger.js";
 
 import { BaseService } from "./BaseService.js";
@@ -205,13 +206,23 @@ export class ChatHistoryService extends BaseService<ChatHistoryState> {
   }
 
   /**
-   * Add a system message to the history
+   * Add a system message to the history.
+   *
+   * Everything that reaches this method is a notice addressed to the user —
+   * "Remote environment is shutting down…", `WARNING: Tool … requires
+   * permission`, command output, diffs — so the item is marked as a UI notice
+   * and is dropped before the history is converted to wire format. Callers that
+   * ever need to add a real system *instruction* should build the item
+   * themselves rather than reach for this.
    */
   addSystemMessage(content: string): ChatHistoryItem {
-    const newMessage = createHistoryItem({
-      role: "system",
-      content,
-    });
+    const newMessage: ChatHistoryItemWithType = {
+      ...createHistoryItem({
+        role: "system",
+        content,
+      }),
+      messageType: "system",
+    };
 
     const newHistory = [...this.currentState.history, newMessage];
     this.setHistoryInternal(newHistory);

extensions/cli/src/stream/streamChatResponse.autoCompaction.ts

@@ -10,6 +10,7 @@ import {
   shouldAutoCompact,
 } from "../compaction.js";
 import { updateSessionHistory } from "../session.js";
+import { uiNotice } from "../uiNotices.js";
 import { formatError } from "../util/formatError.js";
 import { logger } from "../util/logger.js";
 
@@ -74,13 +75,7 @@ function handleCompactionSuccess(
     callbacks.setCompactionIndex(result.compactionIndex);
     callbacks.setMessages((prev: ChatHistoryItem[]) => [
       ...prev,
-      {
-        message: {
-          role: "system",
-          content: successMessage,
-        },
-        contextItems: [],
-      },
+      uiNotice(successMessage),
     ]);
   }
 }
@@ -105,13 +100,7 @@ function handleCompactionError(
   } else if (callbacks?.setMessages) {
     callbacks.setMessages((prev: ChatHistoryItem[]) => [
       ...prev,
-      {
-        message: {
-          role: "system",
-          content: warningMessage,
-        },
-        contextItems: [],
-      },
+      uiNotice(warningMessage),
     ]);
   }
 }

extensions/cli/src/stream/streamChatResponse.systemMessage.test.ts

@@ -4,6 +4,7 @@ import type { ChatHistoryItem } from "core/index.js";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 
 import { services } from "../services/index.js";
+import { uiNotice } from "../uiNotices.js";
 
 import { processStreamingResponse } from "./streamChatResponse.js";
 
@@ -160,6 +161,112 @@ describe("streamChatResponse system message validation", () => {
     expect(services.systemMessage.getSystemMessage).not.toHaveBeenCalled();
   });
 
+  it("should not send UI notices to the provider as extra system messages", async () => {
+    const model = {
+      model: "test-model",
+      defaultCompletionOptions: {
+        contextLength: 1000,
+        maxTokens: 100,
+      },
+    } as ModelConfig;
+
+    const systemMessage = "System instructions";
+
+    // A `/model` notice recorded in the history. It is role:"system" for
+    // rendering, and carries the messageType discriminator from
+    // spec/wire-format.md marking it as display-only.
+    const chatHistory: ChatHistoryItem[] = [
+      { message: { role: "user", content: "hello" }, contextItems: [] },
+      {
+        message: { role: "system", content: "Switched to model: gpt-4o" },
+        contextItems: [],
+        messageType: "system",
+      } as ChatHistoryItem,
+      { message: { role: "user", content: "and now?" }, contextItems: [] },
+    ];
+
+    const mockStream = {
+      [Symbol.asyncIterator]: async function* () {
+        yield { choices: [{ delta: { content: "ok" } }] };
+      },
+    };
+    mockLlmApi.chatCompletionStream = vi.fn().mockResolvedValue(mockStream);
+
+    await processStreamingResponse({
+      chatHistory,
+      model,
+      llmApi: mockLlmApi,
+      abortController,
+      systemMessage,
+    });
+
+    const sent = vi.mocked(mockLlmApi.chatCompletionStream).mock.calls[0]?.[0];
+    const systemMessages = sent!.messages.filter((m) => m.role === "system");
+
+    // Exactly one system message, and it is first — otherwise providers reject
+    // the request with "System message must be at the beginning".
+    expect(systemMessages).toHaveLength(1);
+    expect(sent!.messages[0]?.role).toBe("system");
+    expect(sent!.messages[0]?.content).toBe(systemMessage);
+    expect(
+      sent!.messages.some((m) =>
+        typeof m.content === "string"
+          ? m.content.includes("Switched to model")
+          : false,
+      ),
+    ).toBe(false);
+  });
+
+  it("should not send notices from the non-selector sites either", async () => {
+    const model = {
+      model: "test-model",
+      defaultCompletionOptions: { contextLength: 1000, maxTokens: 100 },
+    } as ModelConfig;
+
+    const systemMessage = "System instructions";
+
+    // The shape reported in #13026: an error banner sitting next to a /model
+    // notice. The banner comes from useChat.ts, a site that does not go through
+    // the selector hooks, so it is only filtered because every notice site now
+    // builds its item with uiNotice().
+    const chatHistory: ChatHistoryItem[] = [
+      { message: { role: "user", content: "hello" }, contextItems: [] },
+      uiNotice("Switched to model: qwen/qwen3.6-35b-a3b") as ChatHistoryItem,
+      uiNotice("Error: Connection error.") as ChatHistoryItem,
+      uiNotice(
+        "[Tool canceled - please tell Continue what to do differently]",
+      ) as ChatHistoryItem,
+      uiNotice("Chat history compacted successfully.") as ChatHistoryItem,
+      uiNotice("Session exported to /tmp/x.json") as ChatHistoryItem,
+      { message: { role: "user", content: "and now?" }, contextItems: [] },
+    ];
+
+    const mockStream = {
+      [Symbol.asyncIterator]: async function* () {
+        yield { choices: [{ delta: { content: "ok" } }] };
+      },
+    };
+    mockLlmApi.chatCompletionStream = vi.fn().mockResolvedValue(mockStream);
+
+    await processStreamingResponse({
+      chatHistory,
+      model,
+      llmApi: mockLlmApi,
+      abortController,
+      systemMessage,
+    });
+
+    const sent = vi.mocked(mockLlmApi.chatCompletionStream).mock.calls[0]?.[0];
+
+    expect(sent!.messages.filter((m) => m.role === "system")).toHaveLength(1);
+    expect(sent!.messages[0]?.content).toBe(systemMessage);
+    expect(sent!.messages.map((m) => m.content)).toEqual([
+      systemMessage,
+      "hello",
+      "and now?",
+    ]);
+  });
+
   it("should use safety buffer in validation", async () => {
     const model = {
       model: "test-model",

extensions/cli/src/stream/streamChatResponse.ts

@@ -13,6 +13,7 @@ import { services } from "../services/index.js";
 import { telemetryService } from "../telemetry/telemetryService.js";
 import { applyChatCompletionToolOverrides } from "../tools/applyToolOverrides.js";
 import { ToolCall } from "../tools/index.js";
+import { withoutUiNotices } from "../uiNotices.js";
 import {
   chatCompletionStreamWithBackoff,
   isContextLengthError,
@@ -249,9 +250,12 @@ export async function processStreamingResponse(
     throw new Error(`Context length validation failed: ${validation.error}`);
   }
 
-  // Create OpenAI format history with validated system message
+  // Create OpenAI format history with validated system message. UI notices are
+  // dropped first: they are `role: "system"` items the TUI added for display
+  // only, and sending them would put a second system message at a non-zero
+  // index, which providers reject.
   const openaiChatHistory = convertFromUnifiedHistoryWithSystemMessage(
-    chatHistory,
+    withoutUiNotices(chatHistory),
     systemMessage,
   ) as ChatCompletionMessageParam[];
   const requestStartTime = Date.now();

extensions/cli/src/ui/TUIChat.tsx

@@ -19,6 +19,7 @@ import {
   UpdateServiceState,
 } from "../services/types.js";
 import { getTotalSessionCost } from "../session.js";
+import { uiNotice } from "../uiNotices.js";
 import { bashToolEvents } from "../util/cli.js";
 import { logger } from "../util/logger.js";
 
@@ -302,13 +303,7 @@ const TUIChat: React.FC<TUIChatProps> = ({
         if (!session) {
           setChatHistory((prev) => [
             ...prev,
-            {
-              message: {
-                role: "system",
-                content: `Failed to export: Session ${sessionId} not found`,
-              },
-              contextItems: [],
-            },
+            uiNotice(`Failed to export: Session ${sessionId} not found`),
           ]);
           closeCurrentScreen();
           return;
@@ -329,25 +324,13 @@ const TUIChat: React.FC<TUIChatProps> = ({
 
         setChatHistory((prev) => [
           ...prev,
-          {
-            message: {
-              role: "system",
-              content: `Session exported to ${defaultPath}`,
-            },
-            contextItems: [],
-          },
+          uiNotice(`Session exported to ${defaultPath}`),
         ]);
         closeCurrentScreen();
       } catch (error: any) {
         setChatHistory((prev) => [
           ...prev,
-          {
-            message: {
-              role: "system",
-              content: `Failed to export session: ${error.message}`,
-            },
-            contextItems: [],
-          },
+          uiNotice(`Failed to export session: ${error.message}`),
         ]);
         closeCurrentScreen();
       }

extensions/cli/src/ui/hooks/useChat.clear.test.ts

@@ -59,14 +59,16 @@ describe("useChat clear command", () => {
       chatHistory[0], // The system message ChatHistoryItem
     ]);
 
-    // Second call should be with the "Chat history cleared" message
+    // Second call should be with the "Chat history cleared" message, marked as
+    // a UI notice so it is shown to the user but not sent to the model.
     expect(mockSetChatHistory).toHaveBeenLastCalledWith([
       {
         message: {
           role: "system",
           content: "Chat history cleared",
         },
         contextItems: [],
+        messageType: "system",
       },
     ]);
   });

extensions/cli/src/ui/hooks/useChat.compaction.ts

@@ -3,6 +3,7 @@ import type { ChatHistoryItem, Session } from "core/index.js";
 import { compactChatHistory } from "../../compaction.js";
 import { updateSessionHistory } from "../../session.js";
 import { handleAutoCompaction as coreHandleAutoCompaction } from "../../stream/streamChatResponse.autoCompaction.js";
+import { uiNotice } from "../../uiNotices.js";
 import { formatError } from "../../util/formatError.js";
 import { logger } from "../../util/logger.js";
 
@@ -68,39 +69,18 @@ export async function handleCompactCommand({
     // Add success message to chat
     setChatHistory((prev) => [
       ...prev,
-      {
-        message: {
-          role: "system",
-          content: "Chat history compacted successfully.",
-        },
-        contextItems: [],
-      },
+      uiNotice("Chat history compacted successfully."),
     ]);
   } catch (error) {
     // Check if the error was due to abortion
     if (compactionController.signal.aborted) {
       logger.info("Manual compaction was cancelled by user");
-      setChatHistory((prev) => [
-        ...prev,
-        {
-          message: {
-            role: "system",
-            content: "Compaction cancelled.",
-          },
-          contextItems: [],
-        },
-      ]);
+      setChatHistory((prev) => [...prev, uiNotice("Compaction cancelled.")]);
     } else {
       logger.error("Compaction failed:", error);
       setChatHistory((prev) => [
         ...prev,
-        {
-          message: {
-            role: "system",
-            content: `Compaction failed: ${formatError(error)}`,
-          },
-          contextItems: [],
-        },
+        uiNotice(`Compaction failed: ${formatError(error)}`),
       ]);
     }
   } finally {

extensions/cli/src/ui/hooks/useChat.helpers.ts

@@ -9,6 +9,7 @@ import { logger } from "src/util/logger.js";
 import { DEFAULT_SESSION_TITLE } from "../../constants/session.js";
 import { loadSession, startNewSession } from "../../session.js";
 import { telemetryService } from "../../telemetry/telemetryService.js";
+import { uiNotice } from "../../uiNotices.js";
 
 import { processImagePlaceholder } from "./useChat.imageProcessing.js";
 import { SlashCommandResult } from "./useChat.types.js";
@@ -124,42 +125,19 @@ export function processSlashCommandResult({
     }
 
     if (result.output) {
-      setChatHistory([
-        {
-          message: {
-            role: "system",
-            content: result.output,
-          },
-          contextItems: [],
-        },
-      ]);
+      setChatHistory([uiNotice(result.output)]);
     }
     return null;
   }
 
   if (result.diffContent) {
     setChatHistory((prev) => [
       ...prev,
-      {
-        message: {
-          role: "system",
-          content: `Diff:\n${result.diffContent}`,
-        },
-        contextItems: [],
-      },
+      uiNotice(`Diff:\n${result.diffContent}`),
     ]);
     return null;
   } else if (result.output) {
-    setChatHistory((prev) => [
-      ...prev,
-      {
-        message: {
-          role: "system",
-          content: result.output || "",
-        },
-        contextItems: [],
-      },
-    ]);
+    setChatHistory((prev) => [...prev, uiNotice(result.output || "")]);
     return null;
   }