Reach shared folders from Files, not the profile menu

A folder somebody shared was reachable only by switching the whole app
to their account from the profile menu -- which nobody would think to
look in for files, and which pointed mail, calendar and contacts at them
as well. The server refused all three, so nothing leaked; it was simply
the app claiming to be somewhere it could not go.

Files now lists shared accounts itself, under "Shared with me", and opens
them in place. Only Files moves: `accountId` in its store is the account
being browsed, `ownAccountId` is the reader's, and nothing else in the
app notices.

Which accounts hold shared files cannot be worked out from capabilities.
Stalwart advertises the whole set on a shared account -- mail, calendars,
contacts, sieve, the lot, identical to a personal one, whatever was
actually shared (checked live on 0.16.19, 2026-08-27). That is why
routing alone could never have fixed this, and why the list offers every
account that is not the reader's own and lets its folders answer for
themselves. The mock's shared account now advertises the same full set,
because a mock that quietly advertised only what it shared would agree
with a fix that cannot work.

Shares also went unseen until the next sign-in. They arrive in the JMAP
session, which is fetched once and refreshed only when a session-state
change is pushed to that tab -- so a share granted while the tab was open
stayed invisible, and one removed stayed on offer. That is the two
browsers disagreeing about whether an account still existed. Opening
Files now re-reads the session, throttled, and the section header carries
a refresh for when someone is waiting on a share they have just been
promised.

The sidebar's button on Files was Compose, which wrote mail from the file
manager. It uploads.

Verified against the mock, which grew a second account to make any of
this testable: "Shared with me" lists it, opening it shows its folders
and not the reader's, the header says whose they are, "Back to my files"
returns, and the profile menu is not involved at any point.

server/src/mock/index.ts

@@ -26,6 +26,13 @@ const NO_FUTURE_RELEASE = process.env.MOCK_NO_FUTURE_RELEASE === "1";
 /** What the session advertises, matching Stalwart's own 30 days. */
 const MAX_DELAYED_SEND = 86400 * 30;
 const ACCOUNT = "a1";
+/** An account somebody has shared with the demo user. See the session below. */
+const SHARED_ACCOUNT = "a2";
+const SHARED_CAPS: Obj = {
+  "urn:ietf:params:jmap:mail": {}, "urn:ietf:params:jmap:submission": {}, "urn:ietf:params:jmap:vacationresponse": {},
+  "urn:ietf:params:jmap:sieve": {}, "urn:ietf:params:jmap:calendars": {}, "urn:ietf:params:jmap:contacts": {},
+  "urn:ietf:params:jmap:principals": {}, "urn:ietf:params:jmap:quota": {}, "urn:ietf:params:jmap:filenode": {},
+};
 const USER = process.env.MOCK_USER ?? "[email protected]";
 /** Locale the fake directory reports for the account (POSIX style, as Stalwart does). */
 const MOCK_LOCALE = process.env.MOCK_LOCALE ?? "en_US";
@@ -197,6 +204,17 @@ const fileNodes: Obj[] = [
   { id: "f2", parentId: "f1", nodeType: "file", blobId: putBlob("hello world", "text/plain"), size: 11, name: "notes.txt", type: "text/plain", created: new Date().toISOString(), modified: new Date().toISOString(), myRights: fr(), shareWith: {} },
   { id: "f3", parentId: null, nodeType: "file", blobId: putBlob("%PDF-1.4 mock", "application/pdf"), size: 14, name: "report.pdf", type: "application/pdf", created: new Date().toISOString(), modified: new Date().toISOString(), myRights: fr(), shareWith: {} },
 ];
+
+/* What the shared account holds. Its own nodes, so opening the share in Files
+   shows something different from the reader's own folders rather than the same
+   list under another name. */
+const sharedFileNodes: Obj[] = [
+  { id: "s1", parentId: null, nodeType: "directory", blobId: null, size: null, name: "Team plans", type: null, created: new Date().toISOString(), modified: new Date().toISOString(), myRights: fr(), shareWith: {} },
+  { id: "s2", parentId: "s1", nodeType: "file", blobId: putBlob("shared notes", "text/plain"), size: 12, name: "roadmap.txt", type: "text/plain", created: new Date().toISOString(), modified: new Date().toISOString(), myRights: fr(), shareWith: {} },
+];
+/** The node list an account owns. */
+const nodesFor = (accountId: unknown): Obj[] => (accountId === SHARED_ACCOUNT ? sharedFileNodes : fileNodes);
+
 function fr() {
   return { mayRead: true, mayAddChildren: true, mayRename: true, mayDelete: true, mayModifyContent: true, mayShare: true };
 }
@@ -721,6 +739,7 @@ const handlers: Record<string, Handler> = {
   "ContactCard/parse": (a) => { const parsed: Obj = {}; for (const b of a.blobIds as string[]) { const t = blobs.get(b)?.data.toString() ?? ""; const fn = /^FN:(.*)$/m.exec(t)?.[1]?.trim() ?? "Imported"; const em = /^EMAIL[^:]*:(.*)$/m.exec(t)?.[1]?.trim(); parsed[b] = [{ "@type": "Card", version: "1.0", uid: randomUUID(), kind: "individual", name: { full: fn }, emails: em ? { e1: { address: em } } : undefined }]; } return { accountId: ACCOUNT, parsed, notParsable: [] }; },
   "FileNode/query": (a) => {
     const f = (a.filter as Obj) ?? {};
+    const fileNodes = nodesFor(a.accountId);
     // `nodeType` is a filter 0.16.19 really applies -- checked live on
     // 2026-08-27, where it returned the two directories out of seven nodes. The
     // mock ignoring it was worse than not having it: the sidebar tree asks for
@@ -732,9 +751,9 @@ const handlers: Record<string, Handler> = {
     });
     return { accountId: ACCOUNT, queryState: "1", canCalculateChanges: false, position: 0, ids: list.map((n) => n.id), total: list.length };
   },
-  "FileNode/get": genericGet(fileNodes),
+  "FileNode/get": (a) => genericGet(nodesFor(a.accountId))(a),
   "FileNode/set": (a) => {
-    return genericSet(fileNodes, "f", (o) => {
+    return genericSet(nodesFor(a.accountId), "f", (o) => {
       Object.assign(o, { created: new Date().toISOString(), modified: new Date().toISOString(), myRights: fr(), shareWith: {}, size: o.blobId ? (blobs.get(o.blobId as string)?.data.length ?? 0) : null, type: o.type ?? null, blobId: o.blobId ?? null, ...o });
       // Without nodeType, a node is a directory precisely when it carries no
       // file properties. Keep it internally so query and get stay consistent.
@@ -779,7 +798,18 @@ const session = () => ({
   capabilities: { "urn:ietf:params:jmap:core": { maxSizeUpload: 50000000, maxConcurrentUpload: 4, maxSizeRequest: 10000000, maxConcurrentRequests: 4, maxCallsInRequest: 16, maxObjectsInGet: MAX_OBJECTS, maxObjectsInSet: MAX_OBJECTS, collationAlgorithms: ["i;ascii-casemap"] }, "urn:ietf:params:jmap:mail": {}, "urn:ietf:params:jmap:submission": {}, "urn:ietf:params:jmap:vacationresponse": {}, "urn:ietf:params:jmap:webpush-vapid": { applicationServerKey: "BBvig2GPmqohMJJHMzp6bTKviHibYiVCyAY8gdq2fPhS-9YfO9_0TnhMyZ0a0JxTsbCqd3zm1rEiXsXsL3jveJY" },
   "urn:ietf:params:jmap:emailpush": {},
   "urn:ietf:params:jmap:sieve": { implementation: "mock" }, "urn:ietf:params:jmap:calendars": {}, "urn:ietf:params:jmap:calendars:parse": {}, "urn:ietf:params:jmap:contacts": {}, "urn:ietf:params:jmap:contacts:parse": {}, "urn:ietf:params:jmap:principals": {}, "urn:ietf:params:jmap:principals:availability": {}, "urn:ietf:params:jmap:quota": {}, "urn:ietf:params:jmap:blob": {}, "urn:ietf:params:jmap:filenode": {} },
-  accounts: { [ACCOUNT]: { name: USER, isPersonal: true, isReadOnly: false, accountCapabilities: { "urn:ietf:params:jmap:mail": {}, "urn:ietf:params:jmap:submission": { maxDelayedSend: MAX_DELAYED_SEND, submissionExtensions: { FUTURERELEASE: [], SIZE: [], DSN: [], DELIVERYBY: [], "MT-PRIORITY": ["MIXER"], REQUIRETLS: [] } }, "urn:ietf:params:jmap:vacationresponse": {}, "urn:ietf:params:jmap:sieve": {}, "urn:ietf:params:jmap:calendars": {}, "urn:ietf:params:jmap:contacts": {}, "urn:ietf:params:jmap:principals": {}, "urn:ietf:params:jmap:quota": {}, "urn:ietf:params:jmap:filenode": {}, ...(NO_REGISTRY ? {} : { "urn:stalwart:jmap": {} }) } } },
+  /*
+   * Two accounts: the demo user's own, and one somebody has shared.
+   *
+   * The shared one carries the *same* capability list, because that is what
+   * Stalwart does -- checked on 0.16.19 (2026-08-27), where a shared account
+   * advertised mail, calendars, contacts and the rest, identical to a personal
+   * one, whatever had actually been shared. Giving the mock a truthful shared
+   * account is the only way to exercise the Files "Shared with me" list, and
+   * the only way this stays honest about what can be inferred from a
+   * capability, which is nothing.
+   */
+  accounts: { [SHARED_ACCOUNT]: { name: "[email protected]", isPersonal: false, isReadOnly: false, accountCapabilities: SHARED_CAPS }, [ACCOUNT]: { name: USER, isPersonal: true, isReadOnly: false, accountCapabilities: { "urn:ietf:params:jmap:mail": {}, "urn:ietf:params:jmap:submission": { maxDelayedSend: MAX_DELAYED_SEND, submissionExtensions: { FUTURERELEASE: [], SIZE: [], DSN: [], DELIVERYBY: [], "MT-PRIORITY": ["MIXER"], REQUIRETLS: [] } }, "urn:ietf:params:jmap:vacationresponse": {}, "urn:ietf:params:jmap:sieve": {}, "urn:ietf:params:jmap:calendars": {}, "urn:ietf:params:jmap:contacts": {}, "urn:ietf:params:jmap:principals": {}, "urn:ietf:params:jmap:quota": {}, "urn:ietf:params:jmap:filenode": {}, ...(NO_REGISTRY ? {} : { "urn:stalwart:jmap": {} }) } } },
   primaryAccounts: { ...Object.fromEntries(["mail", "submission", "vacationresponse", "sieve", "calendars", "contacts", "principals", "quota", "filenode", "blob"].map((c) => [`urn:ietf:params:jmap:${c}`, ACCOUNT])), ...(NO_REGISTRY ? {} : { "urn:stalwart:jmap": ACCOUNT }) },
   username: USER,
   apiUrl: `http://127.0.0.1:${PORT}/jmap/`,