feat: archive session descendants

.changeset/archive-session-descendants.md

@@ -0,0 +1,5 @@
+---
+"@jmfederico/pi-web": patch
+---
+
+Add a session list action to archive a session together with its descendant sessions in the same workspace.

src/client/src/api.ts

@@ -1,3 +1,3 @@
 export { activityApi, api, filesApi, gitApi, piWebApi, projectsApi, sessionsApi, terminalsApi, workspacesApi } from "./api/clients";
 export { globalSessionEvents, realtimeEvents, sessionEvents, terminalSocket } from "./api/sockets";
-export type { AuthProviderOption, AuthProviderStatus, AuthProvidersResponse, AuthStatusSource, AuthType, CommandOption, CommandResult, FileContentMediaType, FileContentResponse, FileSuggestion, FileTreeEntry, FileTreeResponse, GitDiffResponse, GitFileState, GitStatusFile, GitStatusResponse, MessagePage, ModelSelectionResponse, OAuthFlowState, PiWebComponentStatus, PiWebInstallationInfo, PiWebReleaseStatus, PiWebStatusMessage, PiWebStatusResponse, Project, QueuedSessionMessage, RealtimeEvent, SessionActivity, SessionInfo, SessionModel, SessionStatus, SlashCommand, SessionUiEvent, TerminalInfo, TerminalUiEvent, ThinkingLevel, ThinkingLevelsResponse, Workspace, WorkspaceActivity, WorkspaceActivityResponse, WorkspaceActivityUiEvent } from "../../shared/apiTypes";
+export type { ArchiveSessionsResponse, AuthProviderOption, AuthProviderStatus, AuthProvidersResponse, AuthStatusSource, AuthType, CommandOption, CommandResult, FileContentMediaType, FileContentResponse, FileSuggestion, FileTreeEntry, FileTreeResponse, GitDiffResponse, GitFileState, GitStatusFile, GitStatusResponse, MessagePage, ModelSelectionResponse, OAuthFlowState, PiWebComponentStatus, PiWebInstallationInfo, PiWebReleaseStatus, PiWebStatusMessage, PiWebStatusResponse, Project, QueuedSessionMessage, RealtimeEvent, SessionActivity, SessionInfo, SessionModel, SessionStatus, SlashCommand, SessionUiEvent, TerminalInfo, TerminalUiEvent, ThinkingLevel, ThinkingLevelsResponse, Workspace, WorkspaceActivity, WorkspaceActivityResponse, WorkspaceActivityUiEvent } from "../../shared/apiTypes";

src/client/src/api/clients.ts

@@ -71,6 +71,7 @@ export const sessionsApi = {
   abort: (sessionId: string) => request(`/api/sessions/${sessionId}/abort`, parseAborted, { method: "POST" }),
   stop: (sessionId: string) => request(`/api/sessions/${sessionId}/stop`, parseStopped, { method: "POST" }),
   archive: (sessionId: string) => request(`/api/sessions/${sessionId}/archive`, parseArchived, { method: "POST" }),
+  archiveWithDescendants: (sessionId: string) => request(`/api/sessions/${sessionId}/archive-tree`, parseArchived, { method: "POST" }),
   restore: (sessionId: string) => request(`/api/sessions/${sessionId}/restore`, parseRestored, { method: "POST" }),
   detachParent: (sessionId: string) => request(`/api/sessions/${sessionId}/detach-parent`, parseDetached, { method: "POST" }),
   authProviders: (options?: { mode?: "login" | "logout"; authType?: "oauth" | "api_key" }) => {

src/client/src/api/parsers.ts

@@ -1,4 +1,4 @@
-import type { AuthProviderOption, AuthProviderStatus, AuthProvidersResponse, AuthStatusSource, AuthType, CommandOption, CommandResult, FileContentResponse, FileSuggestion, FileTreeEntry, FileTreeResponse, GitDiffResponse, GitFileState, GitStatusFile, GitStatusResponse, MessagePage, ModelSelectionResponse, OAuthFlowState, PiWebComponentStatus, PiWebInstallationInfo, PiWebReleaseStatus, PiWebServiceComponent, PiWebStatusMessage, PiWebStatusResponse, PiWebStatusSeverity, Project, QueuedSessionMessage, SessionInfo, SessionModel, SessionStatus, SlashCommand, TerminalInfo, ThinkingLevel, ThinkingLevelsResponse, Workspace, WorkspaceActivity, WorkspaceActivityResponse } from "../../../shared/apiTypes";
+import type { ArchiveSessionsResponse, AuthProviderOption, AuthProviderStatus, AuthProvidersResponse, AuthStatusSource, AuthType, CommandOption, CommandResult, FileContentResponse, FileSuggestion, FileTreeEntry, FileTreeResponse, GitDiffResponse, GitFileState, GitStatusFile, GitStatusResponse, MessagePage, ModelSelectionResponse, OAuthFlowState, PiWebComponentStatus, PiWebInstallationInfo, PiWebReleaseStatus, PiWebServiceComponent, PiWebStatusMessage, PiWebStatusResponse, PiWebStatusSeverity, Project, QueuedSessionMessage, SessionInfo, SessionModel, SessionStatus, SlashCommand, TerminalInfo, ThinkingLevel, ThinkingLevelsResponse, Workspace, WorkspaceActivity, WorkspaceActivityResponse } from "../../../shared/apiTypes";
 
 function isRecord(value: unknown): value is Record<string, unknown> {
   return typeof value === "object" && value !== null;
@@ -46,6 +46,11 @@ function parseUnknownArray(value: unknown): unknown[] {
   return value;
 }
 
+function arrayOfString(value: unknown, key: string): string[] {
+  if (!Array.isArray(value) || !value.every((item) => typeof item === "string")) throw new Error(`Expected string array field: ${key}`);
+  return value;
+}
+
 export function parseMessagePage(value: unknown): MessagePage {
   if (Array.isArray(value)) return { messages: value, start: 0, total: value.length };
   const record = requireRecord(value);
@@ -446,10 +451,18 @@ export function parseStopped(value: unknown): { stopped: true } {
   return { stopped: true };
 }
 
-export function parseArchived(value: unknown): { archived: true } {
+export function parseArchived(value: unknown): ArchiveSessionsResponse {
   const record = requireRecord(value);
   if (record["archived"] !== true) throw new Error("Expected archived response");
-  return { archived: true };
+  const sessionIds = record["sessionIds"] === undefined ? undefined : arrayOfString(record["sessionIds"], "sessionIds");
+  const archivedCount = optionalNumber(record, "archivedCount");
+  const skippedAlreadyArchivedCount = optionalNumber(record, "skippedAlreadyArchivedCount");
+  return {
+    archived: true,
+    ...(sessionIds === undefined ? {} : { sessionIds }),
+    ...(archivedCount === undefined ? {} : { archivedCount }),
+    ...(skippedAlreadyArchivedCount === undefined ? {} : { skippedAlreadyArchivedCount }),
+  };
 }
 
 export function parseRestored(value: unknown): { restored: true } {

src/client/src/components/PiWebApp.ts

@@ -474,6 +474,7 @@ export class PiWebApp extends LitElement {
         .onStart=${() => openChatAfter(() => this.sessions.startSession())}
         .onSelect=${(session: SessionInfo) => openChatAfter(() => this.sessions.selectSession(session))}
         .onArchive=${(session: SessionInfo) => this.sessions.archiveSession(session)}
+        .onArchiveWithDescendants=${(session: SessionInfo) => this.sessions.archiveSessionWithDescendants(session)}
         .onRestore=${(session: SessionInfo) => openChatAfter(() => this.sessions.restoreSession(session))}
         .onDelete=${(session: SessionInfo) => this.sessions.deleteCachedNewSession(session)}
         .onDetachParent=${(session: SessionInfo) => this.sessions.detachParent(session)}

src/client/src/components/SessionList.ts

@@ -40,6 +40,7 @@ export class SessionList extends LitElement {
     this.openMenuSessionId = undefined;
   };
   @property({ attribute: false }) onArchive?: (session: SessionInfo) => void;
+  @property({ attribute: false }) onArchiveWithDescendants?: (session: SessionInfo) => void;
   @property({ attribute: false }) onRestore?: (session: SessionInfo) => void;
   @property({ attribute: false }) onDelete?: (session: SessionInfo) => void;
   @property({ attribute: false }) onDetachParent?: (session: SessionInfo) => void;
@@ -71,13 +72,14 @@ export class SessionList extends LitElement {
     const activeRows = sessionRowsForActiveTree(this.sessions);
     const activeIds = new Set(activeRows.map((row) => row.session.id));
     const archivedRows = sessionRows(this.sessions.filter((session) => session.archived === true && !activeIds.has(session.id)));
+    const descendantCounts = unarchivedDescendantCounts(this.sessions);
     return html`
       <section>
         ${this.renderHeading(activeRows.length + archivedRows.length)}
-        ${this.collapsed ? null : activeRows.map((row) => this.renderSession(row))}
+        ${this.collapsed ? null : activeRows.map((row) => this.renderSession(row, descendantCounts.get(row.session.id) ?? 0))}
         ${this.collapsed ? null : archivedRows.length > 0 ? html`
           <h2 class="subheading"><button class="section-toggle" aria-expanded=${String(this.archivedExpanded)} @click=${() => { this.toggleArchived(); }}><span>${this.archivedExpanded ? "▾" : "▸"} Archived</span><small>${archivedRows.length}</small></button></h2>
-          ${this.archivedExpanded ? archivedRows.map((row) => this.renderSession(row)) : null}
+          ${this.archivedExpanded ? archivedRows.map((row) => this.renderSession(row, descendantCounts.get(row.session.id) ?? 0)) : null}
         ` : null}
       </section>
     `;
@@ -95,7 +97,7 @@ export class SessionList extends LitElement {
     `;
   }
 
-  private renderSession(row: SessionRow) {
+  private renderSession(row: SessionRow, descendantCount: number) {
     const { session } = row;
     const cappedDepth = Math.min(row.depth, 2);
     return html`
@@ -119,7 +121,10 @@ export class SessionList extends LitElement {
                 ? html`<button title="Delete browser-cached new session" @click=${() => { this.openMenuSessionId = undefined; this.onDelete?.(session); }}>Delete</button>`
                 : session.archived === true
                   ? html`<button title="Restore session" @click=${() => { this.openMenuSessionId = undefined; this.onRestore?.(session); }}>Restore</button>`
-                  : html`<button title="Archive session" @click=${() => { this.openMenuSessionId = undefined; this.onArchive?.(session); }}>Archive</button>`}
+                  : html`
+                    <button title="Archive session" @click=${() => { this.openMenuSessionId = undefined; this.onArchive?.(session); }}>Archive</button>
+                    ${descendantCount > 0 ? html`<button title="Archive this session and its descendants" @click=${() => { this.openMenuSessionId = undefined; this.confirmArchiveWithDescendants(session, descendantCount); }}>Archive with descendants (${descendantCount})</button>` : null}
+                  `}
             </div>
           ` : null}
         </div>
@@ -127,6 +132,11 @@ export class SessionList extends LitElement {
     `;
   }
 
+  private confirmArchiveWithDescendants(session: SessionInfo, descendantCount: number): void {
+    const noun = descendantCount === 1 ? "descendant session" : "descendant sessions";
+    if (confirm(`Archive “${sessionLabel(session)}” and ${String(descendantCount)} ${noun}?`)) this.onArchiveWithDescendants?.(session);
+  }
+
   private toggleMenu(sessionId: string, target: EventTarget | null) {
     if (this.openMenuSessionId === sessionId) {
       this.openMenuSessionId = undefined;
@@ -157,6 +167,31 @@ export class SessionList extends LitElement {
   static override styles = listStyles;
 }
 
+function unarchivedDescendantCounts(sessions: SessionInfo[]): Map<string, number> {
+  const childrenByParentPath = new Map<string, SessionInfo[]>();
+  for (const session of sessions) {
+    if (session.parentSessionPath === undefined) continue;
+    const children = childrenByParentPath.get(session.parentSessionPath) ?? [];
+    children.push(session);
+    childrenByParentPath.set(session.parentSessionPath, children);
+  }
+
+  const countFor = (session: SessionInfo, seenPaths: Set<string>): number => {
+    if (seenPaths.has(session.path)) return 0;
+    const nextSeenPaths = new Set(seenPaths);
+    nextSeenPaths.add(session.path);
+    let count = 0;
+    for (const child of childrenByParentPath.get(session.path) ?? []) {
+      if (nextSeenPaths.has(child.path)) continue;
+      if (child.archived !== true) count += 1;
+      count += countFor(child, nextSeenPaths);
+    }
+    return count;
+  };
+
+  return new Map(sessions.map((session) => [session.id, countFor(session, new Set())]));
+}
+
 function sessionRowsForActiveTree(sessions: SessionInfo[]): SessionRow[] {
   const byPath = new Map(sessions.map((session) => [session.path, session]));
   const visible = new Set<string>();

src/client/src/controllers/sessionController.test.ts

@@ -193,6 +193,32 @@ describe("SessionController", () => {
     expect(urlUpdates).toEqual([undefined]);
   });
 
+  it("archives selected session descendants and selects the next active session", async () => {
+    const childSession = { ...oldSession, id: "child-session", path: "/tmp/child-session.jsonl", parentSessionPath: oldSession.path };
+    const nextSession = { ...oldSession, id: "next-session", path: "/tmp/next-session.jsonl" };
+    let state: AppState = { ...initialAppState(), selectedWorkspace: workspace, sessions: [oldSession, childSession, nextSession] };
+    const api: typeof defaultApi = {
+      ...defaultApi,
+      archiveWithDescendants: () => Promise.resolve({ archived: true, sessionIds: [oldSession.id, childSession.id], archivedCount: 2, skippedAlreadyArchivedCount: 0 }),
+      messages: () => Promise.resolve(emptyPage),
+      status: (sessionId) => Promise.resolve(status(sessionId)),
+    };
+    const controller = new SessionController(
+      () => state,
+      (patch) => { state = { ...state, ...patch }; },
+      () => undefined,
+      new InMemorySessionSelectionMemory(),
+      { api, socket: new FakeSocket() },
+    );
+
+    await controller.selectSession(oldSession, { updateUrl: false });
+    await controller.archiveSessionWithDescendants(oldSession);
+
+    expect(state.sessions.find((session) => session.id === oldSession.id)).toMatchObject({ archived: true });
+    expect(state.sessions.find((session) => session.id === childSession.id)).toMatchObject({ archived: true });
+    expect(state.selectedSession?.id).toBe(nextSession.id);
+  });
+
   it("forgets archived selections when the archived section collapse clears selection", async () => {
     const archivedSession = { ...oldSession, archived: true, archivedAt: "later" };
     let state: AppState = { ...initialAppState(), selectedWorkspace: workspace, sessions: [archivedSession] };

src/client/src/controllers/sessionController.ts

@@ -5,7 +5,7 @@ import { clearDraft, moveDraft, saveDraft } from "../promptDraftStorage";
 import { ChatTranscriptStore } from "../chatTranscriptStore";
 import { isShellInput } from "../inputModes";
 import { SessionSocket, type GlobalSessionEvent, type SessionUiEvent } from "../sessionSocket";
-import { InMemorySessionSelectionMemory, markSessionArchived, selectPreferredSession, selectionAfterArchivingSession, shouldDeselectAfterArchivedCollapse, type SessionSelectionMemory } from "./sessionSelection";
+import { InMemorySessionSelectionMemory, markSessionArchived, markSessionsArchived, selectPreferredSession, selectionAfterArchivingSession, selectionAfterArchivingSessions, shouldDeselectAfterArchivedCollapse, type SessionSelectionMemory } from "./sessionSelection";
 import type { GetState, SetState, UpdateUrl } from "./types";
 
 const MESSAGE_PAGE_SIZE = 100;
@@ -238,6 +238,23 @@ export class SessionController {
     }
   }
 
+  async archiveSessionWithDescendants(session = this.getState().selectedSession) {
+    if (!session || isCachedNewSessionInfo(session)) return;
+    try {
+      const response = await this.api.archiveWithDescendants(session.id);
+      const archivedIds = response.sessionIds !== undefined && response.sessionIds.length > 0 ? response.sessionIds : [session.id];
+      const state = this.getState();
+      const sessions = markSessionsArchived(state.sessions, archivedIds, new Date().toISOString());
+      const selectionChange = selectionAfterArchivingSessions(sessions, state.selectedSession?.id, archivedIds);
+      this.setState({ sessions });
+
+      if (selectionChange.type === "select") await this.selectSession(selectionChange.session);
+      else if (selectionChange.type === "clear") this.deselectSession({ forgetRememberedSelection: true });
+    } catch (error) {
+      this.setState({ error: String(error) });
+    }
+  }
+
   async deleteCachedNewSession(session = this.getState().selectedSession) {
     if (!isCachedNewSessionInfo(session)) return;
     void this.api.stop(session.id).catch(() => {

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

@@ -1,6 +1,6 @@
 import { describe, expect, it } from "vitest";
 import type { SessionInfo } from "../api";
-import { InMemorySessionSelectionMemory, markSessionArchived, selectPreferredSession, selectionAfterArchivingSession, shouldDeselectAfterArchivedCollapse } from "./sessionSelection";
+import { InMemorySessionSelectionMemory, markSessionArchived, markSessionsArchived, selectPreferredSession, selectionAfterArchivingSession, selectionAfterArchivingSessions, shouldDeselectAfterArchivedCollapse } from "./sessionSelection";
 
 describe("selectPreferredSession", () => {
   it("prefers an explicit target session by id", () => {
@@ -78,6 +78,14 @@ describe("markSessionArchived", () => {
     expect(next).toEqual([{ ...sessions[0], archived: true, archivedAt: "later" }, sessions[1]]);
     expect(sessions[0]?.archived).toBeUndefined();
   });
+
+  it("marks multiple matching sessions archived", () => {
+    const sessions = [testSession("s1"), testSession("s2"), testSession("s3")];
+
+    const next = markSessionsArchived(sessions, ["s1", "s3"], "later");
+
+    expect(next).toEqual([{ ...sessions[0], archived: true, archivedAt: "later" }, sessions[1], { ...sessions[2], archived: true, archivedAt: "later" }]);
+  });
 });
 
 describe("shouldDeselectAfterArchivedCollapse", () => {
@@ -112,6 +120,10 @@ describe("selectionAfterArchivingSession", () => {
   it("clears selection when no active session remains", () => {
     expect(selectionAfterArchivingSession([testSession("s1")], "s1", "s1")).toEqual({ type: "clear" });
   });
+
+  it("clears selection when archiving a selected subtree with no active sessions left", () => {
+    expect(selectionAfterArchivingSessions([testSession("s1"), testSession("s2")], "s2", ["s1", "s2"])).toEqual({ type: "clear" });
+  });
 });
 
 function testSession(id: string): SessionInfo {

src/client/src/controllers/sessionSelection.ts

@@ -47,12 +47,22 @@ export type ArchiveSelectionChange =
   | { type: "clear" };
 
 export function markSessionArchived(sessions: SessionInfo[], sessionId: string, archivedAt: string): SessionInfo[] {
-  return sessions.map((session) => session.id === sessionId ? { ...session, archived: true, archivedAt } : session);
+  return markSessionsArchived(sessions, [sessionId], archivedAt);
+}
+
+export function markSessionsArchived(sessions: SessionInfo[], sessionIds: readonly string[], archivedAt: string): SessionInfo[] {
+  const archivedIds = new Set(sessionIds);
+  return sessions.map((session) => archivedIds.has(session.id) ? { ...session, archived: true, archivedAt } : session);
 }
 
 export function selectionAfterArchivingSession(sessions: SessionInfo[], selectedSessionId: string | undefined, archivedSessionId: string): ArchiveSelectionChange {
-  if (selectedSessionId !== archivedSessionId) return { type: "unchanged" };
+  return selectionAfterArchivingSessions(sessions, selectedSessionId, [archivedSessionId]);
+}
 
-  const nextSession = sessions.find((session) => session.id !== archivedSessionId && session.archived !== true);
+export function selectionAfterArchivingSessions(sessions: SessionInfo[], selectedSessionId: string | undefined, archivedSessionIds: readonly string[]): ArchiveSelectionChange {
+  if (selectedSessionId === undefined || !archivedSessionIds.includes(selectedSessionId)) return { type: "unchanged" };
+
+  const archivedIds = new Set(archivedSessionIds);
+  const nextSession = sessions.find((session) => !archivedIds.has(session.id) && session.archived !== true);
   return nextSession === undefined ? { type: "clear" } : { type: "select", session: nextSession };
 }

src/server/sessions/piSessionService.test.ts

@@ -206,6 +206,46 @@ describe("PiSessionService", () => {
     await service.dispose();
   });
 
+  it("archives a session subtree within the root workspace", async () => {
+    const archivedInputs: string[] = [];
+    const root = sessionRecord("root");
+    const directChild = { ...sessionRecord("direct-child"), path: "/sessions/direct-child.jsonl", parentSessionPath: root.path };
+    const archivedChild = { ...sessionRecord("archived-child"), path: "/sessions/archived-child.jsonl", parentSessionPath: root.path };
+    const grandchild = { ...sessionRecord("grandchild"), path: "/sessions/grandchild.jsonl", parentSessionPath: archivedChild.path };
+    const otherWorkspaceChild = { ...sessionRecord("other-child", "/other"), path: "/sessions/other-child.jsonl", parentSessionPath: root.path };
+    const fake = fakeRuntime("root", { sessionFile: root.path });
+    const service = new PiSessionService(new CapturingSessionEventHub(), {
+      createAgentRuntime: runtimeCreator(fake.runtime),
+      archiveStore: {
+        list: () => Promise.resolve([{ sessionId: "archived-child", cwd: "/workspace", archivedAt: "2026-01-02T00:00:00.000Z", originalPath: archivedChild.path, archivePath: "/archive/archived-child.jsonl", created: "2026-01-01T00:00:00.000Z", modified: "2026-01-01T00:01:00.000Z", messageCount: 1, firstMessage: "archived", parentSessionPath: root.path }]),
+        get: () => Promise.resolve(undefined),
+        archive: (input) => {
+          archivedInputs.push(input.sessionId);
+          return Promise.resolve({ sessionId: input.sessionId, cwd: input.cwd, archivedAt: "2026-01-03T00:00:00.000Z" });
+        },
+        restore: () => Promise.resolve(),
+        isArchived: () => Promise.resolve(false),
+      },
+      sessionManager: {
+        create: () => fakeSessionManager(),
+        list: (cwd) => Promise.resolve(cwd === "/workspace" ? [root, directChild, archivedChild, grandchild] : [otherWorkspaceChild]),
+        listAll: () => Promise.resolve([root, directChild, archivedChild, grandchild, otherWorkspaceChild]),
+        open: () => fakeSessionManager(),
+      },
+      heartbeatIntervalMs: 60_000,
+    });
+
+    await expect(service.archiveTree("root")).resolves.toEqual({
+      archived: true,
+      sessionIds: ["root", "direct-child", "grandchild"],
+      archivedCount: 3,
+      skippedAlreadyArchivedCount: 1,
+    });
+    expect(archivedInputs).toEqual(["root", "direct-child", "grandchild"]);
+
+    await service.dispose();
+  });
+
   it("reconciles workspace activity when listing only archived sessions", async () => {
     const reconciliations: { cwd: string; sessionIds: string[] }[] = [];
     const service = new PiSessionService(new CapturingSessionEventHub(), {

src/server/sessions/piSessionService.ts

@@ -13,12 +13,13 @@ import {
   type CreateAgentSessionRuntimeFactory,
   type EditToolDetails,
 } from "@earendil-works/pi-coding-agent";
-import type { ClientCommand, ClientCommandResult, ClientMessagePage, ClientSession, ClientSessionModel, ClientSessionStatus, ClientThinkingLevel, SessionUiEvent } from "../types.js";
+import type { ClientArchiveSessionsResponse, ClientCommand, ClientCommandResult, ClientMessagePage, ClientSession, ClientSessionModel, ClientSessionStatus, ClientThinkingLevel, SessionUiEvent } from "../types.js";
 import { pageMessagesAtSafeBoundary } from "./messagePaging.js";
 import type { SessionEventHub } from "../realtime/sessionEventHub.js";
 import { BUILTIN_COMMANDS } from "./builtinCommands.js";
 import { SessionCommandService } from "./sessionCommandService.js";
 import { SessionArchiveStore, type ArchivedSessionRecord, type ArchiveSessionInput } from "./sessionArchiveStore.js";
+import { findArchiveCandidateByIdOrPrefix, planSessionArchiveTree, type SessionArchiveTreeCandidate } from "./sessionArchiveTree.js";
 import type { ActiveSession } from "./sessionRuntimeStore.js";
 import type { AuthChange } from "./authService.js";
 import { fallbackSessionName, generateShortSessionName } from "./sessionNameGenerator.js";
@@ -46,6 +47,13 @@ interface PiSessionListEntry {
   name?: string;
   parentSessionPath?: string;
 }
+
+interface WorkspaceArchiveCandidate extends SessionArchiveTreeCandidate {
+  cwd: string;
+  listEntry?: PiSessionListEntry;
+  activeSession?: PiAgentSession;
+}
+
 type AgentModel = Model<Api>;
 type ModelRegistryInstance = ReturnType<typeof ModelRegistry.create>;
 
@@ -408,12 +416,32 @@ export class PiSessionService {
 
   async archive(sessionId: string): Promise<void> {
     const session = await this.getOrOpen(sessionId);
-    if (session.isStreaming || session.isCompacting || session.isBashRunning || session.pendingMessageCount > 0) throw new Error("Stop current session activity before archiving");
+    if (sessionHasActiveWork(session)) throw new Error("Stop current session activity before archiving");
     const archiveInput = await this.archiveInputForSession(session);
     await this.closeActive(session.sessionId);
     await this.archiveStore.archive(archiveInput);
   }
 
+  async archiveTree(sessionId: string): Promise<ClientArchiveSessionsResponse> {
+    const session = await this.getOrOpen(sessionId);
+    const catalog = await this.workspaceArchiveCandidates(session.sessionManager.getCwd());
+    const root = findArchiveCandidateByIdOrPrefix(catalog, session.sessionId) ?? archiveCandidateFromActiveSession(session, false);
+    const plan = planSessionArchiveTree(root, catalog);
+    const busy = plan.targets.map((target) => target.activeSession).find((target) => target !== undefined && sessionHasActiveWork(target));
+    if (busy !== undefined) throw new Error(`Stop current session activity before archiving ${sessionDisplayName(busy)}`);
+
+    const archiveInputs = plan.unarchivedTargets.map((target) => archiveInputFromCandidate(target));
+    for (const input of archiveInputs) await this.closeActive(input.sessionId);
+    for (const input of archiveInputs) await this.archiveStore.archive(input);
+
+    return {
+      archived: true,
+      sessionIds: archiveInputs.map((input) => input.sessionId),
+      archivedCount: archiveInputs.length,
+      skippedAlreadyArchivedCount: plan.skippedAlreadyArchivedCount,
+    };
+  }
+
   async restore(sessionId: string): Promise<void> {
     await this.closeActive(sessionId);
     await this.archiveStore.restore(sessionId);
@@ -465,16 +493,41 @@ export class PiSessionService {
     if (sessionFile === undefined || sessionFile === "") throw new Error("Session is not persisted");
     const listed = (await this.sessionManager.list(cwd)).find((candidate) => candidate.id === session.sessionId);
     if (listed !== undefined) return archiveInputFromListEntry(listed);
-    return {
-      sessionId: session.sessionId,
-      cwd,
-      path: sessionFile,
-      created: new Date().toISOString(),
-      modified: new Date().toISOString(),
-      messageCount: session.messages.length,
-      firstMessage: "",
-      ...(session.sessionName === undefined ? {} : { name: session.sessionName }),
-    };
+    return archiveInputFromActiveSession(session);
+  }
+
+  private async workspaceArchiveCandidates(cwd: string): Promise<WorkspaceArchiveCandidate[]> {
+    const [sessions, archivedRecords] = await Promise.all([this.sessionManager.list(cwd), this.archiveStore.list()]);
+    const candidates = new Map<string, WorkspaceArchiveCandidate>();
+    const archivedById = new Map<string, ArchivedSessionRecord>();
+
+    for (const record of archivedRecords) {
+      if (record.cwd === cwd) archivedById.set(record.sessionId, record);
+    }
+
+    for (const session of sessions) {
+      const archived = archivedById.get(session.id);
+      if (archived === undefined) candidates.set(session.id, archiveCandidateFromListEntry(session));
+      else {
+        const candidate = archiveCandidateFromArchivedRecord(archived, session);
+        if (candidate !== undefined) candidates.set(candidate.id, candidate);
+      }
+    }
+
+    for (const record of archivedById.values()) {
+      if (candidates.has(record.sessionId)) continue;
+      const candidate = archiveCandidateFromArchivedRecord(record, undefined);
+      if (candidate !== undefined) candidates.set(candidate.id, candidate);
+    }
+
+    for (const active of new Set(this.active.values())) {
+      const session = active.runtime.session;
+      if (session.sessionManager.getCwd() !== cwd || archivedById.has(session.sessionId)) continue;
+      const existing = candidates.get(session.sessionId);
+      candidates.set(session.sessionId, { ...(existing ?? archiveCandidateFromActiveSession(session, false)), activeSession: session });
+    }
+
+    return [...candidates.values()];
   }
 
   private async listSessionNames(cwd: string): Promise<string[]> {
@@ -742,6 +795,76 @@ function archiveInputFromListEntry(session: PiSessionListEntry): ArchiveSessionI
   };
 }
 
+function archiveInputFromActiveSession(session: PiAgentSession): ArchiveSessionInput {
+  const sessionFile = session.sessionFile;
+  if (sessionFile === undefined || sessionFile === "") throw new Error("Session is not persisted");
+  const parentSessionPath = session.sessionManager.getHeader?.()?.parentSession;
+  return {
+    sessionId: session.sessionId,
+    cwd: session.sessionManager.getCwd(),
+    path: sessionFile,
+    created: new Date().toISOString(),
+    modified: new Date().toISOString(),
+    messageCount: session.messages.length,
+    firstMessage: "",
+    ...(session.sessionName === undefined ? {} : { name: session.sessionName }),
+    ...(parentSessionPath === undefined ? {} : { parentSessionPath }),
+  };
+}
+
+function archiveCandidateFromListEntry(session: PiSessionListEntry): WorkspaceArchiveCandidate {
+  return {
+    id: session.id,
+    path: session.path,
+    cwd: session.cwd,
+    archived: false,
+    listEntry: session,
+    ...(session.parentSessionPath === undefined ? {} : { parentSessionPath: session.parentSessionPath }),
+  };
+}
+
+function archiveCandidateFromArchivedRecord(record: ArchivedSessionRecord, fallback: PiSessionListEntry | undefined): WorkspaceArchiveCandidate | undefined {
+  const path = record.originalPath ?? fallback?.path;
+  if (path === undefined) return undefined;
+  const parentSessionPath = record.parentSessionPath ?? fallback?.parentSessionPath;
+  return {
+    id: record.sessionId,
+    path,
+    cwd: record.cwd,
+    archived: true,
+    ...(fallback === undefined ? {} : { listEntry: fallback }),
+    ...(parentSessionPath === undefined ? {} : { parentSessionPath }),
+  };
+}
+
+function archiveCandidateFromActiveSession(session: PiAgentSession, archived: boolean): WorkspaceArchiveCandidate {
+  const sessionFile = session.sessionFile;
+  if (sessionFile === undefined || sessionFile === "") throw new Error("Session is not persisted");
+  const parentSessionPath = session.sessionManager.getHeader?.()?.parentSession;
+  return {
+    id: session.sessionId,
+    path: sessionFile,
+    cwd: session.sessionManager.getCwd(),
+    archived,
+    activeSession: session,
+    ...(parentSessionPath === undefined ? {} : { parentSessionPath }),
+  };
+}
+
+function archiveInputFromCandidate(candidate: WorkspaceArchiveCandidate): ArchiveSessionInput {
+  if (candidate.listEntry !== undefined) return archiveInputFromListEntry(candidate.listEntry);
+  if (candidate.activeSession !== undefined) return archiveInputFromActiveSession(candidate.activeSession);
+  throw new Error(`Session is not available for archiving: ${candidate.id}`);
+}
+
+function sessionHasActiveWork(session: PiAgentSession): boolean {
+  return session.isStreaming || session.isCompacting || session.isBashRunning || session.pendingMessageCount > 0;
+}
+
+function sessionDisplayName(session: PiAgentSession): string {
+  return session.sessionName ?? session.sessionId;
+}
+
 function clientSessionFromArchivedRecord(record: ArchivedSessionRecord, fallback: PiSessionListEntry | undefined): ClientSession | undefined {
   const path = record.originalPath ?? fallback?.path;
   const created = record.created ?? fallback?.created.toISOString();

src/server/sessions/sessionArchiveTree.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from "vitest";
+import { findArchiveCandidateByIdOrPrefix, planSessionArchiveTree, type SessionArchiveTreeCandidate } from "./sessionArchiveTree.js";
+
+function candidate(id: string, options: Partial<SessionArchiveTreeCandidate> = {}): SessionArchiveTreeCandidate {
+  return {
+    id,
+    path: `/sessions/${id}.jsonl`,
+    archived: false,
+    ...options,
+  };
+}
+
+describe("session archive tree planning", () => {
+  it("finds candidates by full id or prefix", () => {
+    const candidates = [candidate("abcdef"), candidate("xyz")];
+
+    expect(findArchiveCandidateByIdOrPrefix(candidates, "abcdef")?.id).toBe("abcdef");
+    expect(findArchiveCandidateByIdOrPrefix(candidates, "abc")?.id).toBe("abcdef");
+    expect(findArchiveCandidateByIdOrPrefix(candidates, "missing")).toBeUndefined();
+  });
+
+  it("plans recursive descendants and separates already archived targets", () => {
+    const root = candidate("root");
+    const child = candidate("child", { parentSessionPath: root.path });
+    const archivedChild = candidate("archived-child", { parentSessionPath: root.path, archived: true });
+    const grandchild = candidate("grandchild", { parentSessionPath: archivedChild.path });
+    const unrelated = candidate("unrelated");
+
+    const plan = planSessionArchiveTree(root, [root, child, archivedChild, grandchild, unrelated]);
+
+    expect(plan.targets.map((target) => target.id)).toEqual(["root", "child", "archived-child", "grandchild"]);
+    expect(plan.unarchivedTargets.map((target) => target.id)).toEqual(["root", "child", "grandchild"]);
+    expect(plan.skippedAlreadyArchivedCount).toBe(1);
+  });
+
+  it("stops traversal across cycles", () => {
+    const root = candidate("root");
+    const child = candidate("child", { parentSessionPath: root.path });
+    const cycle = candidate("cycle", { path: root.path, parentSessionPath: child.path });
+
+    const plan = planSessionArchiveTree(root, [root, child, cycle]);
+
+    expect(plan.targets.map((target) => target.id)).toEqual(["root", "child"]);
+  });
+});

src/server/sessions/sessionArchiveTree.ts

@@ -0,0 +1,47 @@
+export interface SessionArchiveTreeCandidate {
+  id: string;
+  path: string;
+  archived: boolean;
+  parentSessionPath?: string;
+}
+
+export interface SessionArchiveTreePlan<T extends SessionArchiveTreeCandidate> {
+  targets: T[];
+  unarchivedTargets: T[];
+  skippedAlreadyArchivedCount: number;
+}
+
+export function findArchiveCandidateByIdOrPrefix<T extends SessionArchiveTreeCandidate>(candidates: readonly T[], sessionId: string): T | undefined {
+  return candidates.find((candidate) => candidate.id === sessionId) ?? candidates.find((candidate) => candidate.id.startsWith(sessionId));
+}
+
+export function planSessionArchiveTree<T extends SessionArchiveTreeCandidate>(root: T, candidates: readonly T[]): SessionArchiveTreePlan<T> {
+  const targets = sessionArchiveSubtree(root, candidates);
+  const unarchivedTargets = targets.filter((target) => !target.archived);
+  return {
+    targets,
+    unarchivedTargets,
+    skippedAlreadyArchivedCount: targets.length - unarchivedTargets.length,
+  };
+}
+
+function sessionArchiveSubtree<T extends SessionArchiveTreeCandidate>(root: T, candidates: readonly T[]): T[] {
+  const childrenByParentPath = new Map<string, T[]>();
+  for (const candidate of candidates) {
+    if (candidate.parentSessionPath === undefined) continue;
+    const children = childrenByParentPath.get(candidate.parentSessionPath) ?? [];
+    children.push(candidate);
+    childrenByParentPath.set(candidate.parentSessionPath, children);
+  }
+
+  const result: T[] = [];
+  const visit = (candidate: T, seenPaths: Set<string>) => {
+    if (seenPaths.has(candidate.path)) return;
+    result.push(candidate);
+    const nextSeenPaths = new Set(seenPaths);
+    nextSeenPaths.add(candidate.path);
+    for (const child of childrenByParentPath.get(candidate.path) ?? []) visit(child, nextSeenPaths);
+  };
+  visit(root, new Set());
+  return result;
+}

src/server/sessions/sessionRoutes.ts

@@ -142,6 +142,14 @@ export function registerSessionRoutes(app: FastifyInstance, sessions: PiSessionS
     }
   });
 
+  app.post<{ Params: { sessionId: string } }>(`${prefix}/sessions/:sessionId/archive-tree`, async (request, reply) => {
+    try {
+      return await sessions.archiveTree(request.params.sessionId);
+    } catch (error) {
+      return reply.code(400).send({ error: error instanceof Error ? error.message : String(error) });
+    }
+  });
+
   app.post<{ Params: { sessionId: string } }>(`${prefix}/sessions/:sessionId/restore`, async (request, reply) => {
     try {
       await sessions.restore(request.params.sessionId);

src/server/types.ts

@@ -2,6 +2,7 @@ export type {
   Project,
   Workspace,
   SessionInfo as ClientSession,
+  ArchiveSessionsResponse as ClientArchiveSessionsResponse,
   MessagePage as ClientMessagePage,
   SessionStatus as ClientSessionStatus,
   SessionModel as ClientSessionModel,

src/shared/apiTypes.ts

@@ -30,6 +30,13 @@ export interface SessionInfo {
   archivedAt?: string;
 }
 
+export interface ArchiveSessionsResponse {
+  archived: true;
+  sessionIds?: string[];
+  archivedCount?: number;
+  skippedAlreadyArchivedCount?: number;
+}
+
 export interface SessionActivity {
   sessionId: string;
   phase: "active" | "idle" | "error";