fix(pet): a member's pet chat starts in <their folder>/sagi

POST /api/lanes/ensure without a cwd defaulted to the dashboard's own
home, outside a member's folder, so every member's pet chat failed with
"a workspace must be inside your own folder" (EFOLDER). A member now
gets <their folder>/sagi, made as them (write-as mkdir) on first use.

docs/API.md

@@ -197,9 +197,11 @@ POST /api/lanes/ensure
 ```
 
 `cwd` is optional — when missing or empty the server falls back to
-`os.homedir()` (the user's home directory). This is how the Sagi mascot
-adopts its dedicated workspace without the client needing to know an absolute
-path. Existing cwd values still pass through unchanged. `pipeline` is
+`os.homedir()` (the user's home directory) — or, for a server-mode member
+with an own folder, `<their folder>/sagi`, made as them on first use (the
+host's home lies outside their folder and would be `403 EFOLDER`). This is
+how the Sagi mascot adopts its dedicated workspace without the client
+needing to know an absolute path. Existing cwd values still pass through unchanged. `pipeline` is
 optional and, like `title`, applies **only when a workspace is actually created**
 — an existing workspace is returned untouched. Omitted, the workspace gets `default`.
 `POST /api/lanes/worktree` and `POST /api/lanes` take the same optional

server/__tests__/server-s3-lanes.test.js

@@ -192,3 +192,31 @@ describe("a member's new project folder", () => {
     assert.equal(fs.existsSync(path.join(TMP, "host-new")), false);
   });
 });
+
+describe("the pet chat's workspace for a member", () => {
+  it("is <their folder>/sagi, made as them — never the host's home (EFOLDER)", async () => {
+    const { fakeSudo } = require("./fixtures/fake-sudo");
+    const sudo = fakeSudo();
+    runAs.__setExecImpl(sudo.exec);
+    const login = await fetch(`${BASE}/api/auth/login`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ username: "mia", password: "member-pass-1" }),
+    });
+    const cm = login.headers.get("set-cookie").split(";")[0];
+    const ensure = () =>
+      fetch(`${BASE}/api/lanes/ensure`, {
+        method: "POST",
+        headers: { "Content-Type": "application/json", cookie: cm },
+        body: JSON.stringify({ title: "Sagi" }),
+      }).then(async (r) => ({ status: r.status, body: await r.json() }));
+    const first = await ensure();
+    assert.equal(first.status, 201, JSON.stringify(first.body));
+    const want = fs.realpathSync(path.join(USERS, "mia", "sagi"));
+    assert.equal(first.body.lane.cwd, want);
+    const mk = sudo.calls.find((c) => c.includes("/opt/agenthub/libexec/write-as"));
+    assert.ok(mk && mk.includes("ah-mia") && mk.includes("mkdir"));
+    const again = await ensure();
+    assert.equal(again.body.lane.id, first.body.lane.id, "the same workspace next time");
+  });
+});

server/routes/lanes.js

@@ -436,6 +436,23 @@ function refuseFolder(res) {
   });
 }
 
+/**
+ * A member's folder for a workspace no caller picked a directory for (the
+ * pet chat): `<own folder>/sagi`, made AS the member under S3 (`mkdirAs`,
+ * never a host write in their home). The caller still runs it through
+ * `folderAllowed`, so a link planted there cannot lead outside.
+ */
+function ownDefaultFolder(own) {
+  const target = path.join(own, "sagi");
+  if (!fs.existsSync(target)) {
+    const runAs = require("../lib/run-as");
+    const acct = runAs.accountForPath(target);
+    if (acct) runAs.mkdirAs(acct, target);
+    else fs.mkdirSync(target, { recursive: true });
+  }
+  return target;
+}
+
 /**
  * Idempotent "which lane owns this directory?" — the Workspace page opens on a
  * cwd, not on a lane id, so it needs one lane to exist for that cwd without
@@ -447,10 +464,24 @@ router.post("/ensure", sameOriginGuard, (req, res) => {
   // specific directory (e.g. Sagi's mascot companion) get a real, existing
   // path and lane uniqueness stays meaningful. Callers that do care pass one
   // through unchanged.
+  // A member's default is NOT the host's home (outside their folder: EFOLDER,
+  // the pet chat could never start) nor their own home (no workspace under
+  // S3), but `<their folder>/sagi`, made as them on first use.
   // Canonical before the lookup, so the lookup and createLane's insert agree.
-  const cwd = lanesLib.canonicalCwd(
-    typeof body.cwd === "string" && body.cwd.trim() ? body.cwd.trim() : os.homedir()
-  );
+  let cwd;
+  if (typeof body.cwd === "string" && body.cwd.trim()) {
+    cwd = lanesLib.canonicalCwd(body.cwd.trim());
+  } else if (scope.ownFolder(req)) {
+    try {
+      cwd = lanesLib.canonicalCwd(ownDefaultFolder(scope.ownFolder(req)));
+    } catch (err) {
+      return res.status(err.code === "EMEMBERGONE" ? 409 : 500).json({
+        error: { code: err.code || "EMKDIR", message: err.message },
+      });
+    }
+  } else {
+    cwd = lanesLib.canonicalCwd(os.homedir());
+  }
 
   if (body.tool !== undefined && !aiTools.has(body.tool)) {
     return res.status(400).json({ error: { code: "EBADTOOL", message: "unknown tool" } });