fix(multiuser): close cross-user web-layer scoping holes found in review

The opt-in multi-user feature's only enforcement is web-layer scoping
(all sessions share one OS account). An adversarial review found 8 critical
+ 7 high cross-user holes that defeated it, plus mediums; all fixed here.
Single-user (flag-off) behavior stays byte-identical apart from documented
consistency deltas.

Ownership / confinement:
- DELETE /api/sessions (bulk) + /:id now owner-scope / findSessionOrFail
- quick-start, cron (create+fire), scheduled runs confine workingDir to the
  owner's space; case link/docker-link/docker-import confine the host path
- resolveCasePath no longer resolves linked cases for non-admins; foreign
  remote/docker cases are skipped (fall through to the caller's own local case)
- history, subagents/workflows, mux-sessions, orchestrator, cron run-history,
  away-digest, and remote/docker host reads are owner- or admin-scoped

Permission policy (section 6.3):
- non-granted users are downgraded at every spawn site incl. legacy
  /api/scheduled, PlanOrchestrator one-shots, remote launch, and the cron-fire
  gemini/codex bypass switches; resolveClaudeModeForUsername now fails closed

Auth / store:
- verify-first login throttle (a correct password is never locked out),
  /ws terminal subject to the change-password lockbox, cookie fast-path
  re-validates identity live, role/grant changes revoke sessions, admin delete
  runs the last-admin guard before any teardown
- users.json: distinguish missing (ENOENT) from corrupt/unreadable so a bad
  read can't overwrite all accounts; unique per-process temp write path

Event streams:
- debounced session:updated + batched task:updated, clipboard, and push
  notifications route by owner (fail closed); getLightState hides machine-wide
  globalStats from non-admins

Tests: two suites updated to assert the fixed (secure) behavior. tsc, eslint,
and test:ci all green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/web/routes/system-routes.ts

@@ -17,7 +17,7 @@ import { ApiErrorCode, createErrorResponse, getErrorMessage, type NiceConfig } f
 import { isUnauthenticatedNetworkAcknowledged } from '../network-auth-policy.js';
 import { isMultiUserMode } from '../../config/multiuser.js';
 import { findUser } from '../../user-store.js';
-import { getAuthUser } from '../route-helpers.js';
+import { getAuthUser, requireAdmin, canAccessOwned } from '../route-helpers.js';
 import {
   ConfigUpdateSchema,
   SettingsUpdateSchema,
@@ -224,14 +224,16 @@ export function registerSystemRoutes(
     }
 
     // Resolve the role for the bound user (disabled/deleted users fail closed).
-    let identity: { username: string; role: 'admin' | 'user' } | undefined;
+    // Carry the bound user's real mustChangePassword flag out of this block so the
+    // minted cookie enforces the lockbox instead of hardcoding false.
+    let identity: { username: string; role: 'admin' | 'user'; mustChangePassword: boolean } | undefined;
     if (multiUser && consumed.username) {
       const user = await findUser(consumed.username);
       if (!user || user.disabled) {
         ctx.qrAuthFailures?.set(clientIp, qrFailures + 1);
         return reply.code(401).send('Invalid or expired QR code');
       }
-      identity = { username: user.username, role: user.role };
+      identity = { username: user.username, role: user.role, mustChangePassword: !!user.mustChangePassword };
     }
 
     // Issue session cookie (same pattern as Basic Auth success path)
@@ -244,7 +246,7 @@ export function registerSystemRoutes(
       method: 'qr',
       username: identity?.username,
       role: identity?.role,
-      mustChangePassword: false,
+      mustChangePassword: !!identity?.mustChangePassword,
     });
     ctx.qrAuthFailures?.delete(clientIp);
 
@@ -493,23 +495,52 @@ export function registerSystemRoutes(
       limit: 1000,
     });
 
-    const sessions: AwayDigestSession[] = Array.from(ctx.sessions.values()).map((session) => ({
-      id: session.id,
-      name: session.name,
-      status: session.status,
-      inputTokens: session.inputTokens,
-      outputTokens: session.outputTokens,
-      totalCost: session.totalCost,
-    }));
+    // Multi-user: scope the digest's aggregated activity to sessions the caller
+    // owns (canAccessOwned is a no-op allow-all for admins/single-user).
+    const user = getAuthUser(req);
+    const sessions: AwayDigestSession[] = Array.from(ctx.sessions.values())
+      .filter((session) => canAccessOwned(user, session.owner))
+      .map((session) => ({
+        id: session.id,
+        name: session.name,
+        status: session.status,
+        inputTokens: session.inputTokens,
+        outputTokens: session.outputTokens,
+        totalCost: session.totalCost,
+      }));
 
-    const runSummaries = Array.from(ctx.runSummaryTrackers.values()).map((tracker) => tracker.getSummary());
+    // Run-summary trackers are keyed by Codeman session id → filter by that session's owner.
+    const runSummaries = Array.from(ctx.runSummaryTrackers.entries())
+      .filter(([id]) => canAccessOwned(user, ctx.sessions.get(id)?.owner))
+      .map(([, tracker]) => tracker.getSummary());
+
+    // Map each subagent's Claude conversation id back to its owning session so the
+    // recent-subagent lookback is owner-scoped too (fails closed when unattributable).
+    const ownerByClaudeSessionId = new Map<string, string | undefined>();
+    for (const s of ctx.sessions.values()) {
+      if (s.claudeSessionId) ownerByClaudeSessionId.set(s.claudeSessionId, s.owner);
+    }
+    const subagents = subagentWatcher
+      .getRecentSubagents(60)
+      .filter((sa) => canAccessOwned(user, ownerByClaudeSessionId.get(sa.sessionId))) as AwayDigestSubagent[];
+
+    // Multi-user: the lifecycle log and daily token stats carry no owner, so scope them
+    // for a non-admin: keep only lifecycle entries attributable to an owned LIVE session
+    // (fail closed — an ended session's owner can't be resolved, so it is dropped rather
+    // than leaked), and withhold the machine-wide daily token totals entirely (they can't
+    // be per-user attributed, same as globalStats in #29). Admins/single-user keep all
+    // (canAccessOwned allow-all, role check false → byte-identical).
+    const scopedLifecycle = lifecycleEntries.filter((e) =>
+      canAccessOwned(user, ctx.sessions.get(e.sessionId ?? '')?.owner)
+    );
+    const nonAdminScoped = isMultiUserMode() && user.role !== 'admin';
     const digest = buildAwayDigest({
       range,
-      lifecycleEntries,
+      lifecycleEntries: scopedLifecycle,
       runSummaries,
       sessions,
-      dailyTokenStats: ctx.store.getDailyStats(30),
-      subagents: subagentWatcher.getRecentSubagents(60) as AwayDigestSubagent[],
+      dailyTokenStats: nonAdminScoped ? [] : ctx.store.getDailyStats(30),
+      subagents,
       now: range.until,
     });
 
@@ -827,7 +858,10 @@ export function registerSystemRoutes(
   // ========== Workflow Run Monitoring (ultracode) ==========
 
   // LEFT-pane list: lightweight run summaries (no agents[]).
-  app.get('/api/workflows', async (req) => {
+  app.get('/api/workflows', async (req, reply) => {
+    // Multi-user stopgap: these aggregates are process-wide (no owner concept), so
+    // restrict cross-user reads to admins (no-op allow-all in single-user mode).
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const { minutes } = req.query as { minutes?: string };
     const runs = minutes
       ? workflowRunWatcher.getRecentRunSummaries(parseInt(minutes, 10))
@@ -836,7 +870,9 @@ export function registerSystemRoutes(
   });
 
   // RIGHT-pane detail: full run incl. agents[] (tokens/toolCalls/state per agent).
-  app.get('/api/workflows/:runId', async (req) => {
+  app.get('/api/workflows/:runId', async (req, reply) => {
+    // Multi-user stopgap: cross-user run detail is admin-only (no-op in single-user).
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const { runId } = req.params as { runId: string };
     const run = workflowRunWatcher.getRun(runId);
     if (!run) {
@@ -847,7 +883,10 @@ export function registerSystemRoutes(
 
   // ========== Subagent Monitoring ==========
 
-  app.get('/api/subagents', async (req) => {
+  app.get('/api/subagents', async (req, reply) => {
+    // Multi-user stopgap: the global subagent list spans all users → admin-only
+    // (no-op allow-all in single-user mode). Per-session variant below stays scoped.
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const { minutes } = req.query as { minutes?: string };
     const subagents = minutes
       ? subagentWatcher.getRecentSubagents(parseInt(minutes, 10))
@@ -862,7 +901,9 @@ export function registerSystemRoutes(
     return { success: true, data: subagents };
   });
 
-  app.get('/api/subagents/:agentId', async (req) => {
+  app.get('/api/subagents/:agentId', async (req, reply) => {
+    // Multi-user stopgap: cross-user subagent metadata is admin-only (no-op single-user).
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const { agentId } = req.params as { agentId: string };
     const info = subagentWatcher.getSubagent(agentId);
     if (!info) {
@@ -871,7 +912,10 @@ export function registerSystemRoutes(
     return { success: true, data: info };
   });
 
-  app.get('/api/subagents/:agentId/transcript', async (req) => {
+  app.get('/api/subagents/:agentId/transcript', async (req, reply) => {
+    // Multi-user stopgap: transcript CONTENT of any user's subagent is admin-only
+    // (no-op allow-all in single-user mode).
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const { agentId } = req.params as { agentId: string };
     const { limit, format } = req.query as { limit?: string; format?: 'raw' | 'formatted' };
     const limitNum = limit ? parseInt(limit, 10) : undefined;
@@ -885,7 +929,10 @@ export function registerSystemRoutes(
     return { success: true, data: transcript };
   });
 
-  app.delete('/api/subagents/:agentId', async (req) => {
+  app.delete('/api/subagents/:agentId', async (req, reply) => {
+    // Multi-user stopgap: killing any user's subagent is a cross-user write → admin-only
+    // (no-op allow-all in single-user mode).
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const { agentId } = req.params as { agentId: string };
     const info = subagentWatcher.getSubagent(agentId);
     if (!info) {
@@ -899,12 +946,16 @@ export function registerSystemRoutes(
     return createErrorResponse(ApiErrorCode.OPERATION_FAILED, 'Subagent not found or already completed');
   });
 
-  app.post('/api/subagents/cleanup', async () => {
+  app.post('/api/subagents/cleanup', async (req, reply) => {
+    // Multi-user stopgap: process-wide cleanup affects every user → admin-only (no-op single-user).
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const removed = subagentWatcher.cleanupNow();
     return { success: true, data: { removed, remaining: subagentWatcher.getSubagents().length } };
   });
 
-  app.delete('/api/subagents', async () => {
+  app.delete('/api/subagents', async (req, reply) => {
+    // Multi-user stopgap: clearing ALL users' subagents is a cross-user write → admin-only (no-op single-user).
+    if (isMultiUserMode() && !requireAdmin(req, reply)) return;
     const cleared = subagentWatcher.clearAll();
     return { success: true, data: { cleared } };
   });