feat(pool): pin a user to one Claude/Codex pool account

An admin pins a server-mode user to one pool account per tool
(account_pins; PUT /api/accounts/pins with the password step-up and audit,
the Users page's Pin a user, agenthub accounts pin|unpin). The workspace
owner's pin wins over the balancer whenever the pane may use the account;
a pinned login still waits while another pool login holds the home.

server/__tests__/claude-pool-login.test.js

@@ -9,7 +9,8 @@
  * same account; removing the account takes it out of those homes; and the
  * Users-page route moves a saved switch-user profile in — the one this
  * machine's own Claude Code is logged into with its LIVE login, the host's
- * home then being one more placement the server refreshes.
+ * home then being one more placement the server refreshes. A pin of the
+ * owner to another login waits while a live pane holds the first.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -188,6 +189,38 @@ describe("a pool login", () => {
     assert.equal(pool.__read("team"), null);
   });
 
+  it("follows the owner's pin, but never over another login a live pane holds", () => {
+    const { db } = require("../db");
+    const pins = require("../lib/account-pins");
+    const miaId = db.prepare("SELECT id FROM users WHERE username = 'mia'").get().id;
+    pool.addLoginAccount("alpha", { oauth: oauth("a"), account: ACCOUNT });
+    pool.addLoginAccount("beta", {
+      oauth: oauth("b"),
+      account: { accountUuid: "uuid-beta", emailAddress: "beta@example.com" },
+    });
+    assert.equal(pool.forSpawn(acct, miaId).name, "alpha", "unpinned: the balancer's pick");
+    pins.setPin(miaId, "claude", "beta");
+    assert.equal(pool.forSpawn(acct, miaId).name, "beta");
+    assert.equal(pool.forSpawn(acct, null).name, "alpha", "another owner is not pinned");
+    // A pane of mia's runs on alpha: beta waits until it ends.
+    pool.forSpawn(acct).place();
+    fs.mkdirSync(path.join(HOME, "proj"), { recursive: true });
+    const lane = db
+      .prepare("INSERT INTO lanes (cwd, owner_id) VALUES (?, ?)")
+      .run(path.join(HOME, "proj"), miaId).lastInsertRowid;
+    db.prepare(
+      `INSERT INTO dashboard_runs (id, mode, cwd, status, started_at, account, lane_id, tool)
+       VALUES ('pin-run', 'interactive', ?, 'running', ?, 'alpha', ?, 'claude')`
+    ).run(path.join(HOME, "proj"), new Date().toISOString(), lane);
+    assert.equal(pool.forSpawn(acct, miaId).name, "alpha");
+    db.prepare("UPDATE dashboard_runs SET status = 'completed' WHERE id = 'pin-run'").run();
+    assert.equal(pool.forSpawn(acct, miaId).name, "beta");
+    pool.removeAccount("beta");
+    assert.equal(pins.pinFor(miaId, "claude"), null, "a removed account drops its pins");
+    db.prepare("DELETE FROM dashboard_runs WHERE id = 'pin-run'").run();
+    db.prepare("DELETE FROM lanes WHERE id = ?").run(lane);
+  });
+
   it("refuses a second copy of one Claude account", () => {
     pool.addLoginAccount("team", { oauth: oauth("a"), account: ACCOUNT });
     assert.throws(() => pool.addLoginAccount("team-2", { oauth: oauth("b"), account: ACCOUNT }), {

server/__tests__/server-mode-account-pool.test.js

@@ -4,7 +4,8 @@
  * admin may add or remove an account, each change needs the admin's OWN
  * password again (EREAUTH), the token only goes in — no answer (the add, the
  * list) ever carries it — the audit log names the account, not its secret, and
- * in local mode the routes refuse.
+ * in local mode the routes refuse. An admin pins a user to one account
+ * (`PUT /api/accounts/pins`): that user's new panes skip the balancer.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -144,3 +145,75 @@ describe("the account pool from the Users page", () => {
     assert.ok(claudePool.pickAccount(), "team-1 is still there");
   });
 });
+
+describe("pinning a user to one account", () => {
+  const pins = require("../lib/account-pins");
+  const pin = (cookie, body) =>
+    call("PUT", "/api/accounts/pins", {
+      cookie,
+      body: { tool: "claude", currentPassword: BOSS_PASS, ...body },
+    });
+
+  it("lets an admin pin and unpin, audited, and new panes follow the pin", async () => {
+    const boss = await login("boss", BOSS_PASS);
+    const miaId = db.prepare("SELECT id FROM users WHERE username = 'mia'").get().id;
+    claudePool.addAccount("team-z", `sk-ant-oat01-${"z".repeat(40)}`);
+    assert.equal(claudePool.pickAccount(null, miaId).name, "team-1", "the balancer's pick");
+    const r = await pin(boss, { userId: miaId, account: "team-z" });
+    assert.equal(r.status, 200);
+    assert.deepEqual(r.body.pin, { userId: miaId, username: "mia", account: "team-z" });
+    assert.equal(claudePool.pickAccount(null, miaId).name, "team-z");
+    assert.equal(claudePool.pickAccount(null, null).name, "team-1", "nobody else moves");
+    const audit = db.prepare("SELECT owner_id, path FROM audit_log ORDER BY id DESC LIMIT 1").get();
+    assert.equal(audit.owner_id, miaId);
+    assert.match(audit.path, /pin mia to claude account team-z/);
+    const list = await call("GET", "/api/accounts", { cookie: boss });
+    assert.deepEqual(
+      list.body.pins.claude.map((p) => [p.username, p.account]),
+      [["mia", "team-z"]]
+    );
+    assert.deepEqual(list.body.pins.codex, []);
+    const off = await pin(boss, { userId: miaId, account: null });
+    assert.equal(off.body.pin.account, null);
+    assert.equal(claudePool.pickAccount(null, miaId).name, "team-1");
+    claudePool.removeAccount("team-z");
+  });
+
+  it("refuses an unknown account or user, a wrong password, and a non-admin", async () => {
+    const boss = await login("boss", BOSS_PASS);
+    const miaId = db.prepare("SELECT id FROM users WHERE username = 'mia'").get().id;
+    assert.equal(
+      (await pin(boss, { userId: miaId, account: "nope" })).body.error.code,
+      "ENOACCOUNT"
+    );
+    assert.equal((await pin(boss, { userId: 9999, account: "team-1" })).body.error.code, "ENOUSER");
+    assert.equal(
+      (await pin(boss, { userId: miaId, account: "team-1", currentPassword: "x" })).body.error.code,
+      "EREAUTH"
+    );
+    const ana = await login("ana", "analyst-pass-1");
+    const w = await call("PUT", "/api/accounts/pins", {
+      cookie: ana,
+      body: { tool: "claude", userId: miaId, account: "team-1", currentPassword: "analyst-pass-1" },
+    });
+    assert.equal(w.status, 403);
+    assert.equal(pins.pinFor(miaId, "claude"), null);
+  });
+
+  it("is ignored in local mode and dropped with its user", async () => {
+    const miaId = db.prepare("SELECT id FROM users WHERE username = 'mia'").get().id;
+    pins.setPin(miaId, "claude", "team-1");
+    delete process.env.AGENTHUB_MODE;
+    try {
+      assert.equal(pins.pinFor(miaId, "claude"), null);
+    } finally {
+      process.env.AGENTHUB_MODE = "server";
+    }
+    assert.equal(pins.pinFor(miaId, "claude"), "team-1");
+    db.prepare("DELETE FROM users WHERE id = ?").run(miaId);
+    assert.equal(
+      db.prepare("SELECT COUNT(*) AS n FROM account_pins WHERE user_id = ?").get(miaId).n,
+      0
+    );
+  });
+});

server/db.js

@@ -1873,6 +1873,18 @@ for (const col of ["display_name", "email", "avatar_at"]) {
     db.prepare(`ALTER TABLE users ADD COLUMN ${col} TEXT`).run();
   }
 }
+// An admin's pin of one server-mode user to one pool account per tool
+// (server/lib/account-pins.js): that user's new sessions skip the balancer.
+// The account is named, not referenced — the pool lives in files.
+db.exec(`
+  CREATE TABLE IF NOT EXISTS account_pins (
+    user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    tool TEXT NOT NULL CHECK(tool IN ('claude','codex')),
+    account TEXT NOT NULL,
+    pinned_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
+    PRIMARY KEY (user_id, tool)
+  );
+`);
 
 // An existing database made before auto_vacuum: the setting is stored only by
 // a VACUUM, which rewrites the whole file under an exclusive lock. Done here,

server/lib/account-pins.js

@@ -0,0 +1,91 @@
+/**
+ * @file account-pins.js
+ * @description Account pins: an admin's choice that one server-mode user's
+ * new sessions of a tool run on one named pool account instead of the one the
+ * balancer would pick (claude-pool.js / codex-pool.js `pick`). One pin per
+ * user and tool (`account_pins`); the user is the workspace's OWNER
+ * (`lanes.owner_id`), never whoever clicked Start. A pin is a preference the
+ * pool still bounds: an account a pane may not use (expired, or a login the
+ * pane's home cannot take) falls back to the balancer, and a login never
+ * replaces another one a live pane in the same home runs on.
+ *
+ * Server mode only: in local mode there are no users and nothing is pinned.
+ * Removing the account drops its pins (`dropAccount`); deleting the user drops
+ * theirs (ON DELETE CASCADE, and `auth.deleteUser`).
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const TOOLS = ["claude", "codex"];
+
+const err = (code, message) => Object.assign(new Error(message), { code });
+const db = () => require("../db").db;
+const poolOf = (tool) => require(tool === "codex" ? "./codex-pool" : "./claude-pool");
+
+function validTool(tool) {
+  if (!TOOLS.includes(tool)) throw err("EBADTOOL", "tool: claude or codex");
+  return tool;
+}
+
+/** The account name `ownerId`'s new `tool` sessions are pinned to, or null. */
+function pinFor(ownerId, tool) {
+  if (!require("./auth").isServerMode() || !Number.isInteger(ownerId)) return null;
+  try {
+    return (
+      db()
+        .prepare("SELECT account FROM account_pins WHERE user_id = ? AND tool = ?")
+        .get(ownerId, tool)?.account ?? null
+    );
+  } catch {
+    return null; // a spawn never fails over a pin
+  }
+}
+
+/** Every pin of `tool`, with its user's name: `[{userId, username, account, pinnedAt}]`. */
+function listPins(tool) {
+  return db()
+    .prepare(
+      `SELECT p.user_id AS userId, u.username, p.account, p.pinned_at AS pinnedAt
+         FROM account_pins p JOIN users u ON u.id = p.user_id
+        WHERE p.tool = ? ORDER BY u.username`
+    )
+    .all(validTool(tool));
+}
+
+/**
+ * Pin `userId`'s new `tool` sessions to `account`, or unpin them (`account`
+ * null). Returns `{userId, username, account}`.
+ */
+function setPin(userId, tool, account) {
+  validTool(tool);
+  const user = Number.isInteger(userId)
+    ? db().prepare("SELECT id, username FROM users WHERE id = ?").get(userId)
+    : null;
+  if (!user) throw err("ENOUSER", `no user ${userId}`);
+  if (account == null || account === "") {
+    db().prepare("DELETE FROM account_pins WHERE user_id = ? AND tool = ?").run(user.id, tool);
+    return { userId: user.id, username: user.username, account: null };
+  }
+  const name = String(account);
+  if (!poolOf(tool).hasAccount(name)) {
+    throw err("ENOACCOUNT", `no ${tool} account ${name} in the pool`);
+  }
+  db()
+    .prepare(
+      `INSERT INTO account_pins (user_id, tool, account) VALUES (?, ?, ?)
+       ON CONFLICT(user_id, tool) DO UPDATE SET account = excluded.account,
+         pinned_at = strftime('%Y-%m-%dT%H:%M:%fZ', 'now')`
+    )
+    .run(user.id, tool, name);
+  return { userId: user.id, username: user.username, account: name };
+}
+
+/** A removed account takes its pins with it. */
+function dropAccount(tool, account) {
+  try {
+    db().prepare("DELETE FROM account_pins WHERE tool = ? AND account = ?").run(tool, account);
+  } catch {
+    /* no database (a bare CLI test): nothing pinned */
+  }
+}
+
+module.exports = { TOOLS, pinFor, listPins, setPin, dropAccount };

server/lib/auth.js

@@ -367,6 +367,7 @@ function deleteUser(username) {
   } catch {
     /* no personal profiles */
   }
+  sql("DELETE FROM account_pins WHERE user_id = ?").run(u.id);
   sql("DELETE FROM users WHERE id = ?").run(u.id);
   return { id: u.id, username: u.username, workspaces: lanes.length };
 }

server/lib/claude-pool.js

@@ -18,6 +18,8 @@
  *   3. least $ spent in the last 5 hours, then in the last 7 days — the
  *      sessions its runs (`dashboard_runs.account`) held, over the hours they
  *      held them (pool-usage.js).
+ * An admin may pin a user to one account (account-pins.js): that user's
+ * panes skip the ranking whenever they may use it.
  * The quota is read with the account's own token in the background, at most
  * every `QUOTA_TTL_MS`; a token the usage endpoint refuses simply has no
  * reading, and ranking falls back to spend.
@@ -193,6 +195,7 @@ function removeAccount(name) {
     }
   }
   fs.rmSync(fileOf(n));
+  require("./account-pins").dropAccount("claude", n);
   quotaCache.delete(n);
 }
 
@@ -434,10 +437,15 @@ function liveInHome(name, member) {
     });
 }
 
-/** The full record a new Claude pane should run on, or null. `member` = run-as account. */
-function pick(member) {
+/**
+ * The full record a new Claude pane should run on, or null. `member` = run-as
+ * account; `ownerId` = the workspace owner, whose pin (account-pins.js) wins
+ * over the ranking when this pane may use that account.
+ */
+function pick(member, ownerId = null) {
   let usable = allAccounts().filter((a) => !expired(a));
   if (usable.length === 0) return null;
+  let live = null;
   if (!member) {
     // A host pane's home holds the host's own login — a pool account only when
     // it was moved in from there (`hostHolds`) and is still the pair on disk:
@@ -453,10 +461,15 @@ function pick(member) {
     } else {
       // One .credentials.json per home: while a pane of theirs runs on a
       // pool login, the next pane stays on that one.
-      const live = usable.find((a) => a.kind === "login" && liveInHome(a.name, member));
-      if (live) return live;
+      live = usable.find((a) => a.kind === "login" && liveInHome(a.name, member)) || null;
     }
   }
+  // A pinned token goes in by env and wins outright; a pinned login waits
+  // while another login holds this home.
+  const pin = require("./account-pins").pinFor(ownerId, "claude");
+  const pinned = pin ? usable.find((a) => a.name === pin) : null;
+  if (pinned && (pinned.kind === "token" || !live || live === pinned)) return pinned;
+  if (live) return live;
   if (usable.length === 0) return null;
   refreshQuotas().catch(() => {});
   const ranked = usable
@@ -489,8 +502,8 @@ function pick(member) {
  * background re-read. A `login` is offered for a member, and for a host pane
  * only when it is the host's own login (`hostHolds`), which stays as it is.
  */
-function pickAccount(member = null) {
-  const a = pick(member);
+function pickAccount(member = null, ownerId = null) {
+  const a = pick(member, ownerId);
   if (!a) return null;
   return a.kind === "login"
     ? { name: a.name, kind: "login" }
@@ -502,8 +515,8 @@ function pickAccount(member = null) {
  * `env` goes through tmux `-e` (a member's launch file); `place()` runs just
  * before the pane starts and writes a login into the member's home.
  */
-function forSpawn(member = null) {
-  const a = pick(member);
+function forSpawn(member = null, ownerId = null) {
+  const a = pick(member, ownerId);
   if (!a) return null;
   if (a.kind === "token") {
     return { name: a.name, env: { CLAUDE_CODE_OAUTH_TOKEN: a.token }, place: () => {} };
@@ -524,8 +537,12 @@ function forSpawn(member = null) {
   };
 }
 
+/** Is `name` an account in the pool (any state)? */
+const hasAccount = (name) => NAME_RE.test(String(name)) && Boolean(readAccount(String(name)));
+
 module.exports = {
   BLOCK_PERCENT,
+  hasAccount,
   REFRESH_AHEAD_MS,
   addAccount,
   addLoginAccount,

server/lib/codex-pool.js

@@ -29,6 +29,7 @@
  * the last 5 h, then 7 d. The reading is the newest `rate_limits` in the
  * rollouts of the sessions that account's runs started (no network), each
  * from the CODEX_HOME of the account its workspace runs as.
+ * A user an admin pinned to one account (account-pins.js) skips the ranking.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -139,6 +140,7 @@ function removeAccount(name) {
   const n = validName(name);
   if (!readAccount(n)) throw err("ENOACCOUNT", `no account ${n} in the pool`);
   fs.rmSync(fileOf(n));
+  require("./account-pins").dropAccount("codex", n);
   quotaCache = null;
 }
 
@@ -332,10 +334,15 @@ function syncBack() {
 
 // ── Picking ────────────────────────────────────────────────────────────────
 
-/** The full record a new Codex pane should run on, or null. `member` = run-as account. */
-function pick(member) {
+/**
+ * The full record a new Codex pane should run on, or null. `member` = run-as
+ * account; `ownerId` = the workspace owner, whose pin (account-pins.js) wins
+ * over the ranking when this pane may use that account.
+ */
+function pick(member, ownerId = null) {
   let usable = allAccounts();
   if (usable.length === 0) return null;
+  let live = null;
   if (!member) {
     // A host pane's CODEX_HOME holds the host's own login.
     usable = usable.filter((a) => a.kind === "apikey");
@@ -348,10 +355,15 @@ function pick(member) {
     } else {
       // One auth.json per home: while a pane of theirs runs on a pool
       // login, the next pane stays on that one.
-      const live = usable.find((a) => a.kind === "chatgpt" && liveInHome(a.name, member));
-      if (live) return live;
+      live = usable.find((a) => a.kind === "chatgpt" && liveInHome(a.name, member)) || null;
     }
   }
+  // A pinned API key goes in by env and wins outright; a pinned ChatGPT login
+  // waits while another login holds this home.
+  const pin = require("./account-pins").pinFor(ownerId, "codex");
+  const pinned = pin ? usable.find((a) => a.name === pin) : null;
+  if (pinned && (pinned.kind === "apikey" || !live || live === pinned)) return pinned;
+  if (live) return live;
   if (usable.length === 0) return null;
   const ranked = usable
     .map((a) => {
@@ -395,8 +407,8 @@ function liveInHome(name, member) {
 }
 
 /** `{name, kind}` of the account a new Codex pane would get, or null. */
-function pickAccount(member = null) {
-  const a = pick(member);
+function pickAccount(member = null, ownerId = null) {
+  const a = pick(member, ownerId);
   return a ? { name: a.name, kind: a.kind } : null;
 }
 
@@ -405,8 +417,8 @@ function pickAccount(member = null) {
  * this pane may use): `{name, argv, env, place}`. `env` goes through tmux `-e`
  * (a member's launch file); `place()` runs just before the pane starts.
  */
-function forSpawn(member = null) {
-  const a = pick(member);
+function forSpawn(member = null, ownerId = null) {
+  const a = pick(member, ownerId);
   if (!a) return null;
   if (a.kind === "apikey") {
     const provider = `{name="OpenAI (AgentHub pool)",base_url="https://api.openai.com/v1",env_key="${KEY_ENV}",wire_api="responses"}`;
@@ -439,8 +451,12 @@ function forSpawn(member = null) {
   };
 }
 
+/** Is `name` an account in the pool? */
+const hasAccount = (name) => NAME_RE.test(String(name)) && Boolean(readAccount(String(name)));
+
 module.exports = {
   BLOCK_PERCENT,
+  hasAccount,
   addAccount,
   removeAccount,
   poolStatus,

server/lib/pty-run.js

@@ -461,19 +461,20 @@ function spawnRun(args) {
   assertCwdAccount(laneId, cwd); // ECWDACCOUNT
   const proxyProfile = resolveProxy(tool, proxy, laneOwner); // EBADPROXY, EUNSUPPORTED
   // A Claude session on the vendor's own API runs on the least-loaded pool
-  // account, if the admin added any (claude-pool.js); an AI Proxy brings its
+  // account, if the admin added any (claude-pool.js) — or the one the
+  // workspace owner is pinned to (account-pins.js); an AI Proxy brings its
   // own key, and an empty pool leaves the machine's login in charge.
   // A real login (kind `login`) is written into a MEMBER's home by place();
   // a setup-token goes in as CLAUDE_CODE_OAUTH_TOKEN.
   const poolAccount =
     entry.launcher === "claude" && !proxyProfile
-      ? require("./claude-pool").forSpawn(require("./run-as").accountForLane(laneId))
+      ? require("./claude-pool").forSpawn(require("./run-as").accountForLane(laneId), laneOwner)
       : null;
   // Codex likewise, from its own pool (codex-pool.js): an API key through
   // `-e`, or a ChatGPT login written into the member's CODEX_HOME by place().
   const codexPool =
     entry.launcher === "codex" && !proxyProfile
-      ? require("./codex-pool").forSpawn(require("./run-as").accountForLane(laneId))
+      ? require("./codex-pool").forSpawn(require("./run-as").accountForLane(laneId), laneOwner)
       : null;
   const paneCred = require("./auth").newPaneToken();
   if (forkSession === true) {

server/openapi-extra/auth.js

@@ -5,6 +5,7 @@
  *   - POST /api/auth/logout  (Auth)
  *   - GET  /api/accounts     (Auth) — the Claude and Codex account pools, no keys or tokens
  *   - POST /api/accounts, DELETE /api/accounts/{name} (Auth) — an admin adds/removes one
+ *   - PUT  /api/accounts/pins (Auth) — an admin pins a user to one pool account
  *   - GET  /api/users        (Auth) — every account's usage (admin/analyst)
  *   - GET  /api/users/audit  (Auth) — staff reads of developers' sessions
  *   - GET/PUT /api/me/prefs, POST /api/me/onboarded (Auth) — the account's own UI preferences
@@ -30,6 +31,16 @@ const tags = [
 ];
 
 const schemas = {
+  AccountPin: {
+    type: "object",
+    required: ["userId", "username", "account"],
+    properties: {
+      userId: { type: "integer" },
+      username: { type: "string" },
+      account: { type: "string", description: "The pool account's name" },
+      pinnedAt: { type: "string" },
+    },
+  },
   UserPrefs: {
     type: "object",
     required: ["prefs", "onboardedAt"],
@@ -633,6 +644,15 @@ const paths = {
                       },
                     },
                   },
+                  pins: {
+                    type: "object",
+                    description:
+                      "Per tool, the users an admin pinned to one account (empty in local mode)",
+                    properties: {
+                      claude: { type: "array", items: { $ref: "#/components/schemas/AccountPin" } },
+                      codex: { type: "array", items: { $ref: "#/components/schemas/AccountPin" } },
+                    },
+                  },
                   codex: {
                     type: "array",
                     description:
@@ -706,6 +726,38 @@ const paths = {
       },
     },
   },
+  "/api/accounts/pins": {
+    put: {
+      tags: ["Auth"],
+      operationId: "pinPoolAccount",
+      summary:
+        "Admin: pin one user's new sessions of a tool to one pool account (`account: null` unpins), with their own password again",
+      requestBody: {
+        required: true,
+        content: {
+          "application/json": {
+            schema: {
+              type: "object",
+              required: ["tool", "userId", "currentPassword"],
+              properties: {
+                tool: { type: "string", enum: ["claude", "codex"] },
+                userId: { type: "integer" },
+                account: { type: "string", nullable: true },
+                currentPassword: { type: "string" },
+              },
+            },
+          },
+        },
+      },
+      responses: {
+        200: { description: "`{pin: {userId, username, account}}` — `account` null when unpinned" },
+        400: err("EBADTOOL"),
+        403: err("EREAUTH — wrong password; EADMIN — not an admin; ELOCALMODE"),
+        404: err("ENOUSER, ENOACCOUNT"),
+        429: err("ETOOMANY — too many wrong passwords"),
+      },
+    },
+  },
   "/api/accounts/profiles": {
     get: {
       tags: ["Auth"],

server/routes/accounts.js

@@ -16,6 +16,9 @@
  * refreshes); `credentials` — the text of a `.credentials.json` (or a macOS
  * Keychain item's JSON); or `token` — a `claude setup-token` token. A Codex
  * one is an OpenAI API key or the text of an `auth.json` (`token`).
+ * `PUT /pins` (`{tool, userId, account}`, `account: null` unpins) pins one
+ * user's new sessions of a tool to one pool account (account-pins.js); `GET /`
+ * lists the pins under `pins`.
  * `GET /profiles` lists the saved profiles that can be moved in (identity only). Like every Users-page change
  * they need the admin's own password again (`currentPassword`), are audited
  * (the account NAME only), and refuse in local mode. The secret only goes IN:
@@ -29,6 +32,7 @@ const codexPool = require("../lib/codex-pool");
 const auth = require("../lib/auth");
 const { recordAccountChange } = require("../lib/audit");
 const profiles = require("../lib/cc-profiles");
+const pins = require("../lib/account-pins");
 
 const router = Router();
 
@@ -39,6 +43,9 @@ router.get("/", async (req, res) => {
     res.json({
       accounts: pool.poolStatus(),
       codex: codexPool.poolStatus(),
+      pins: auth.isServerMode()
+        ? { claude: pins.listPins("claude"), codex: pins.listPins("codex") }
+        : { claude: [], codex: [] },
       blockPercent: pool.BLOCK_PERCENT,
     });
   } catch (e) {
@@ -72,6 +79,7 @@ const STATUS = {
   EBADNAME: 400,
   EBADTOKEN: 400,
   ENOACCOUNT: 404,
+  ENOUSER: 404,
   EEXISTS: 409,
   ETOOMANY: 429,
   ESTALE: 409, // a pasted login whose refresh token was already spent
@@ -93,7 +101,7 @@ function poolChange(handler) {
       }
       await auth.confirmPassword(req.user, body.currentPassword);
       const out = await handler(req, body);
-      recordAccountChange(req.user.id, null, req.method, out.action);
+      recordAccountChange(req.user.id, out.target ?? null, req.method, out.action);
       res.status(out.status || 200).json(out.json);
     } catch (e) {
       const status = STATUS[e.code];
@@ -203,6 +211,20 @@ router.post(
   })
 );
 
+router.put(
+  "/pins",
+  poolChange((_req, body) => {
+    const pin = pins.setPin(Number(body.userId), body.tool, body.account ?? null);
+    return {
+      json: { pin },
+      target: pin.userId,
+      action: pin.account
+        ? `pool: pin ${pin.username} to ${body.tool} account ${pin.account}`
+        : `pool: unpin ${pin.username} from ${body.tool}`,
+    };
+  })
+);
+
 router.delete(
   "/:name",
   poolChange((req, body) => {