Move thread title derivations to view model

src/features/chat/view-model.ts

@@ -15,7 +15,7 @@ import { readRuntimeConfig } from "../../runtime/config";
 import { sortedAvailableModels } from "../../runtime/model";
 import { compactContextLabel } from "../../runtime/settings";
 import { contextSummary, effectiveConfigSections, rateLimitSummary } from "../../runtime/view";
-import { getThreadTitle } from "../../domain/threads/model";
+import { codexPanelDisplayTitle, explicitThreadName, getThreadTitle } from "../../domain/threads/model";
 import { connectionDiagnosticSections, diagnosticAlertLevel } from "./diagnostics";
 import type { ChatState } from "./chat-state";
 import { statusValue, usageLimitStatusLines } from "./status-lines";
@@ -52,6 +52,12 @@ export interface RuntimeToolbarChoicesInput {
   setRequestedReasoningEffort: (effort: ReasoningEffort | null) => void;
 }
 
+export interface RestoredThreadTitleSnapshot {
+  threadId: string;
+  title: string | null;
+  explicitName: string | null;
+}
+
 export function runtimeSnapshotForChatState({ state }: RuntimeSnapshotInput): RuntimeSnapshot {
   return {
     effectiveConfig: state.effectiveConfig,
@@ -106,6 +112,30 @@ export function runtimeToolbarChoices(input: RuntimeToolbarChoicesInput): Pick<T
   return { modelChoices, effortChoices };
 }
 
+export function chatViewDisplayTitle(state: ChatState, restoredThreadTitle: string | null): string {
+  return codexPanelDisplayTitle(state.activeThreadId, state.listedThreads, restoredThreadTitle);
+}
+
+export function activeThreadTitle(state: ChatState): string | null {
+  const threadId = state.activeThreadId;
+  if (!threadId) return null;
+  const thread = state.listedThreads.find((item) => item.id === threadId);
+  return thread ? getThreadTitle(thread) : null;
+}
+
+export function activeComposerThreadName(state: ChatState, restoredThread: RestoredThreadTitleSnapshot | null): string | null {
+  const threadId = state.activeThreadId;
+  if (!threadId) return null;
+  const thread = state.listedThreads.find((item) => item.id === threadId);
+  const listedName = thread ? explicitThreadName(thread) : null;
+  if (listedName) return listedName;
+  return restoredThread?.threadId === threadId ? restoredThread.explicitName : null;
+}
+
+export function composerPlaceholder(threadName: string | null): string {
+  return threadName ? `Ask Codex to work on “${threadName}”...` : "Ask Codex to work on this task...";
+}
+
 export function toolbarViewModel(input: ToolbarViewModelInput): ToolbarViewModel {
   const { state, snapshot } = input;
   const config = readRuntimeConfig(state.effectiveConfig);

src/features/chat/view.ts

@@ -30,7 +30,6 @@ import {
   type ChatAction,
   type ChatState,
 } from "./chat-state";
-import { codexPanelDisplayTitle, explicitThreadName, getThreadTitle } from "../../domain/threads/model";
 import {
   referencedThreadDisplay,
   referencedThreadPrompt,
@@ -50,7 +49,11 @@ import { ChatRuntimeSettingsController } from "./runtime-settings-controller";
 import { RestoredThreadController } from "./restored-thread-controller";
 import { unmountReactRoot } from "../../shared/ui/react-root";
 import {
+  activeComposerThreadName as buildActiveComposerThreadName,
+  activeThreadTitle as buildActiveThreadTitle,
+  chatViewDisplayTitle,
   connectionDiagnosticsModel,
+  composerPlaceholder as buildComposerPlaceholder,
   effortStatusLines as buildEffortStatusLines,
   modelStatusLines as buildModelStatusLines,
   runtimeToolbarChoices,
@@ -366,7 +369,7 @@ export class CodexChatView extends ItemView {
   }
 
   override getDisplayText(): string {
-    return codexPanelDisplayTitle(this.state.activeThreadId, this.state.listedThreads, this.restoredThreadTitle());
+    return chatViewDisplayTitle(this.state, this.restoredThreadTitle());
   }
 
   override getIcon(): string {
@@ -1026,10 +1029,7 @@ export class CodexChatView extends ItemView {
   }
 
   private activeThreadTitle(): string | null {
-    const threadId = this.state.activeThreadId;
-    if (!threadId) return null;
-    const thread = this.state.listedThreads.find((item) => item.id === threadId);
-    return thread ? getThreadTitle(thread) : null;
+    return buildActiveThreadTitle(this.state);
   }
 
   private restoredThreadPlaceholder() {
@@ -1045,18 +1045,11 @@ export class CodexChatView extends ItemView {
   }
 
   private composerPlaceholder(): string {
-    const threadName = this.activeComposerThreadName();
-    return threadName ? `Ask Codex to work on “${threadName}”...` : "Ask Codex to work on this task...";
+    return buildComposerPlaceholder(this.activeComposerThreadName());
   }
 
   private activeComposerThreadName(): string | null {
-    const threadId = this.state.activeThreadId;
-    if (!threadId) return null;
-    const thread = this.state.listedThreads.find((item) => item.id === threadId);
-    const listedName = thread ? explicitThreadName(thread) : null;
-    if (listedName) return listedName;
-    const restoredThread = this.restoredThreadPlaceholder();
-    return restoredThread?.threadId === threadId ? restoredThread.explicitName : null;
+    return buildActiveComposerThreadName(this.state, this.restoredThreadPlaceholder());
   }
 
   private readonly renderToolbarSlot = (toolbar: HTMLElement): void => {

tests/features/chat/view-model.test.ts

@@ -3,6 +3,10 @@ import { describe, expect, it } from "vitest";
 import { createAppServerDiagnostics } from "../../../src/app-server/compatibility";
 import { createChatState } from "../../../src/features/chat/chat-state";
 import {
+  activeComposerThreadName,
+  activeThreadTitle,
+  chatViewDisplayTitle,
+  composerPlaceholder,
   effortStatusLines,
   runtimeToolbarChoices,
   modelStatusLines,
@@ -94,6 +98,21 @@ describe("chat view model", () => {
     expect(selectedModels).toEqual(["gpt-5-mini"]);
     expect(selectedEfforts).toEqual(["high"]);
   });
+
+  it("derives active thread titles and composer placeholders", () => {
+    const state = createChatState();
+    state.activeThreadId = "thread-1";
+    state.listedThreads = [threadFixture("thread-1", "Active")];
+
+    expect(chatViewDisplayTitle(state, null)).toBe("Codex: Active");
+    expect(activeThreadTitle(state)).toBe("Active");
+    expect(activeComposerThreadName(state, null)).toBe("Active");
+    expect(composerPlaceholder("Active")).toBe("Ask Codex to work on “Active”...");
+    expect(composerPlaceholder(null)).toBe("Ask Codex to work on this task...");
+
+    state.listedThreads = [threadFixture("thread-1", null)];
+    expect(activeComposerThreadName(state, { threadId: "thread-1", title: "Restored", explicitName: "Restored" })).toBe("Restored");
+  });
 });
 
 function effectiveConfigFixture(config: Record<string, unknown>): ConfigReadResponse {
@@ -104,7 +123,7 @@ function effectiveConfigFixture(config: Record<string, unknown>): ConfigReadResp
   };
 }
 
-function threadFixture(id: string, name: string): Thread {
+function threadFixture(id: string, name: string | null): Thread {
   return {
     id,
     sessionId: "session",