Remember selected sessions and reveal selections

src/client/src/components/SessionList.ts

@@ -48,6 +48,12 @@ export class SessionList extends LitElement {
   protected override updated(changed: PropertyValues<this>): void {
     if (changed.has("sessions") && this.openMenuSessionId !== undefined && !this.sessions.some((session) => session.id === this.openMenuSessionId)) this.openMenuSessionId = undefined;
     if (changed.has("sessions") && !this.sessions.some((session) => session.archived === true)) this.archivedExpanded = false;
+    if (this.selected?.archived === true && !this.archivedExpanded) {
+      this.archivedExpanded = true;
+      void this.updateComplete.then(() => { this.scrollSelectedIntoView(); });
+      return;
+    }
+    if (changed.has("selected") || changed.has("sessions")) this.scrollSelectedIntoView();
   }
 
   override render() {
@@ -113,6 +119,10 @@ export class SessionList extends LitElement {
     if (!this.archivedExpanded) this.openMenuSessionId = undefined;
   }
 
+  private scrollSelectedIntoView(): void {
+    this.renderRoot.querySelector<HTMLElement>(".action-row.selected")?.scrollIntoView({ block: "nearest" });
+  }
+
   private renderStatus(session: SessionInfo) {
     if (session.archived === true) return "read-only · ";
     const status = this.statuses[session.id];

src/client/src/components/WorkspaceList.ts

@@ -1,4 +1,4 @@
-import { LitElement, html } from "lit";
+import { LitElement, html, type PropertyValues } from "lit";
 import { customElement, property } from "lit/decorators.js";
 import type { Workspace } from "../api";
 import type { WorkspaceLabelItem } from "../plugins/types";
@@ -13,6 +13,10 @@ export class WorkspaceList extends LitElement {
   @property({ attribute: false }) workspaceLabelItems: (workspace: Workspace) => WorkspaceLabelItem[] = () => [];
   @property({ attribute: false }) onSelect?: (workspace: Workspace) => void;
 
+  protected override updated(changed: PropertyValues<this>): void {
+    if (changed.has("selected") || changed.has("workspaces")) this.scrollSelectedIntoView();
+  }
+
   override render() {
     return html`
       <section>
@@ -41,5 +45,9 @@ export class WorkspaceList extends LitElement {
     `;
   }
 
+  private scrollSelectedIntoView(): void {
+    this.renderRoot.querySelector<HTMLElement>(".action-row.selected")?.scrollIntoView({ block: "nearest" });
+  }
+
   static override styles = listStyles;
 }

src/client/src/controllers/sessionController.ts

@@ -6,7 +6,7 @@ import { readChatHistoryCache, mergeChatHistory, writeChatHistoryCache, type Raw
 import { applyTranscriptEvent } from "../chatTranscript";
 import { isShellInput } from "../inputModes";
 import { SessionSocket, type GlobalSessionEvent, type SessionUiEvent } from "../sessionSocket";
-import { markSessionArchived, selectionAfterArchivingSession } from "./sessionSelection";
+import { InMemorySessionSelectionMemory, markSessionArchived, selectPreferredSession, selectionAfterArchivingSession, type SessionSelectionMemory } from "./sessionSelection";
 import type { GetState, SetState, UpdateUrl } from "./types";
 
 export class SessionController {
@@ -16,7 +16,12 @@ export class SessionController {
   private pendingTranscriptEvents: SessionUiEvent[] = [];
   private pendingTranscriptFrame: number | undefined;
 
-  constructor(private readonly getState: GetState, private readonly setState: SetState, private readonly updateUrl: UpdateUrl) {}
+  constructor(
+    private readonly getState: GetState,
+    private readonly setState: SetState,
+    private readonly updateUrl: UpdateUrl,
+    private readonly sessionSelection: SessionSelectionMemory = new InMemorySessionSelectionMemory(),
+  ) {}
 
   applyGlobalEvent(event: GlobalSessionEvent): void {
     if (event.type === "status.update") this.applyStatus(event.status);
@@ -48,7 +53,12 @@ export class SessionController {
     }
   }
 
+  preferredSession(cwd: string, sessions: SessionInfo[], targetSessionId: string | undefined): SessionInfo | undefined {
+    return selectPreferredSession(sessions, { targetSessionId, latestSessionId: this.sessionSelection.latestSessionId(cwd) });
+  }
+
   async selectSession(session: SessionInfo, options?: { updateUrl?: boolean | undefined }) {
+    this.sessionSelection.rememberSession(session);
     const seq = ++this.selectionSeq;
     this.socket.close();
     this.catchupStreamSessionId = undefined;

src/client/src/controllers/sessionSelection.test.ts

@@ -1,6 +1,61 @@
 import { describe, expect, it } from "vitest";
 import type { SessionInfo } from "../api";
-import { markSessionArchived, selectionAfterArchivingSession } from "./sessionSelection";
+import { InMemorySessionSelectionMemory, markSessionArchived, selectPreferredSession, selectionAfterArchivingSession } from "./sessionSelection";
+
+describe("selectPreferredSession", () => {
+  it("prefers an explicit target session by id", () => {
+    const sessions = [testSession("s1"), testSession("s2")];
+
+    expect(selectPreferredSession(sessions, { targetSessionId: "s2", latestSessionId: "s1" })?.id).toBe("s2");
+  });
+
+  it("matches explicit target sessions by id prefix", () => {
+    const session = testSession("abcdef");
+
+    expect(selectPreferredSession([session], { targetSessionId: "abc" })).toBe(session);
+  });
+
+  it("remembers the latest selected session when no explicit target is provided", () => {
+    const sessions = [testSession("s1"), testSession("s2")];
+
+    expect(selectPreferredSession(sessions, { latestSessionId: "s2" })?.id).toBe("s2");
+  });
+
+  it("can remember an archived selected session", () => {
+    const sessions = [{ ...testSession("s1"), archived: true }, testSession("s2")];
+
+    expect(selectPreferredSession(sessions, { latestSessionId: "s1" })?.id).toBe("s1");
+  });
+
+  it("falls back to the first active session when the remembered session no longer exists", () => {
+    const sessions = [{ ...testSession("s1"), archived: true }, testSession("s2")];
+
+    expect(selectPreferredSession(sessions, { latestSessionId: "old" })?.id).toBe("s2");
+  });
+
+  it("returns undefined for an invalid explicit target", () => {
+    const sessions = [testSession("s1"), testSession("s2")];
+
+    expect(selectPreferredSession(sessions, { targetSessionId: "old", latestSessionId: "s2" })).toBeUndefined();
+  });
+});
+
+describe("InMemorySessionSelectionMemory", () => {
+  it("remembers and forgets the latest selected session per cwd", () => {
+    const memory = new InMemorySessionSelectionMemory();
+
+    memory.rememberSession({ ...testSession("s1"), cwd: "/tmp/one" });
+    memory.rememberSession({ ...testSession("s2"), cwd: "/tmp/two" });
+
+    expect(memory.latestSessionId("/tmp/one")).toBe("s1");
+    expect(memory.latestSessionId("/tmp/two")).toBe("s2");
+
+    memory.forgetWorkspace("/tmp/one");
+
+    expect(memory.latestSessionId("/tmp/one")).toBeUndefined();
+    expect(memory.latestSessionId("/tmp/two")).toBe("s2");
+  });
+});
 
 describe("markSessionArchived", () => {
   it("marks the matching session archived without mutating the original", () => {

src/client/src/controllers/sessionSelection.ts

@@ -1,5 +1,41 @@
 import type { SessionInfo } from "../api";
 
+export interface SessionSelectionMemory {
+  latestSessionId(cwd: string): string | undefined;
+  rememberSession(session: SessionInfo): void;
+  forgetWorkspace(cwd: string): void;
+}
+
+export class InMemorySessionSelectionMemory implements SessionSelectionMemory {
+  private readonly sessionIdsByCwd = new Map<string, string>();
+
+  latestSessionId(cwd: string): string | undefined {
+    return this.sessionIdsByCwd.get(cwd);
+  }
+
+  rememberSession(session: SessionInfo): void {
+    this.sessionIdsByCwd.set(session.cwd, session.id);
+  }
+
+  forgetWorkspace(cwd: string): void {
+    this.sessionIdsByCwd.delete(cwd);
+  }
+}
+
+export function selectPreferredSession(sessions: SessionInfo[], options?: { targetSessionId?: string | undefined; latestSessionId?: string | undefined }): SessionInfo | undefined {
+  const targetSessionId = options?.targetSessionId;
+  if (targetSessionId !== undefined && targetSessionId !== "") return sessionByIdOrPrefix(sessions, targetSessionId);
+
+  const latestSessionId = options?.latestSessionId;
+  if (latestSessionId !== undefined && latestSessionId !== "") return sessions.find((session) => session.id === latestSessionId) ?? sessions.find((session) => session.archived !== true);
+
+  return sessions.find((session) => session.archived !== true);
+}
+
+function sessionByIdOrPrefix(sessions: SessionInfo[], sessionId: string): SessionInfo | undefined {
+  return sessions.find((session) => session.id === sessionId || session.id.startsWith(sessionId));
+}
+
 export type ArchiveSelectionChange =
   | { type: "unchanged" }
   | { type: "select"; session: SessionInfo }

src/client/src/controllers/workspaceController.ts

@@ -43,8 +43,7 @@ export class WorkspaceController {
     try {
       const sessions = await api.sessions(workspace.path);
       this.setState({ sessions });
-      const sessionId = target?.sessionId;
+      const session = this.sessions.preferredSession(workspace.path, sessions, target?.sessionId);
-      const session = sessionId !== undefined && sessionId !== "" ? sessions.find((s) => s.id === sessionId || s.id.startsWith(sessionId)) : sessions.find((s) => s.archived !== true);
       if (session) await this.sessions.selectSession(session, { updateUrl: target?.updateUrl });
       else if (target?.updateUrl !== false) this.updateUrl();
     } catch (error) {