diff --git a/.gitignore b/.gitignore
index 9989634..ea391f5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,7 @@ dist/
 .env.*
 !.env.example
 coverage/
+
+# local agent/machine config (personal hostnames — never commit)
+AGENTS.md
+.serena/
diff --git a/src/broker/server.ts b/src/broker/server.ts
index 775d039..a837337 100644
--- a/src/broker/server.ts
+++ b/src/broker/server.ts
@@ -15,7 +15,7 @@ import type { TunnelProvider } from "../tunnel/provider.js";
 import { Logger, nullLogger } from "../logger/index.js";
 import { DEFAULT_HOST, DEFAULT_PORT, getStateDir } from "../config/paths.js";
 import { SERVICE_NAME, VERSION } from "../version.js";
-import { writeRuntimeState, clearRuntimeState, type RuntimeState } from "../bridge/runtime.js";
+import { writeRuntimeState, clearRuntimeState, probeBridge, type RuntimeState } from "../bridge/runtime.js";
 import { createAdminGuard } from "../bridge/admin-guard.js";
 import {
   loadOrCreateInstallation,
@@ -333,6 +333,19 @@ export async function startBroker(opts: BrokerOptions = {}): Promise<Broker> {
   });
 
   const { server, port } = await listen(app, host, opts.port ?? DEFAULT_PORT);
+  // Duplicate-daemon guard: if the preferred port was taken and we fell back
+  // to an ephemeral one, refuse to shadow an already-running broker for the
+  // same installation (it would split the CLI from the tunnel-bearing broker).
+  const preferredPort = opts.port ?? DEFAULT_PORT;
+  if (port !== preferredPort) {
+    const occupant = await probeBridge(preferredPort);
+    if (occupant && occupant.workspaceId === installation.installationId) {
+      server.close();
+      throw new Error(
+        `A broker for this installation is already running on port ${preferredPort}; not starting a duplicate.`
+      );
+    }
+  }
   const startedAt = new Date().toISOString();
   logger.info(
     `Broker listening on ${host}:${port} for installation ${installation.installationId} ` +
diff --git a/src/cli/index.ts b/src/cli/index.ts
index c1fd476..940cbb2 100644
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -161,6 +161,11 @@ program
   .name("c2c")
   .description(`${PRODUCT_NAME} — Claude thinks. Codex works.`)
   .version(VERSION, "-v, --version")
+  .option("--profile <name>", "operate an isolated installation (~/.c2c/profiles/<name>)")
+  .hook("preAction", () => {
+    const profile = (program.opts().profile as string | undefined)?.trim();
+    if (profile) process.env.C2C_PROFILE = profile;
+  })
   .configureHelp({ sortSubcommands: true });
 
 // ---------------------------------------------------------------- serve (internal)
diff --git a/src/config/paths.ts b/src/config/paths.ts
index 3642a29..2c936c4 100644
--- a/src/config/paths.ts
+++ b/src/config/paths.ts
@@ -40,6 +40,10 @@ export function getStateDir(): string {
   const override = process.env.C2C_STATE_DIR;
   if (override && override.trim() !== "") return path.resolve(override);
 
+  // 1b. named profile: an isolated installation (~/.c2c/profiles/<name>)
+  const profile = process.env.C2C_PROFILE?.trim();
+  if (profile) return path.join(getC2cHome(), "profiles", profile);
+
   // 2. the systemwide installation home, once `c2c install` has created it
   const homeState = path.join(getC2cHome(), "state");
   if (fs.existsSync(homeState)) return homeState;
diff --git a/src/tunnel/installation.ts b/src/tunnel/installation.ts
index ad158e6..e04e555 100644
--- a/src/tunnel/installation.ts
+++ b/src/tunnel/installation.ts
@@ -95,11 +95,15 @@ export async function resolveInstallationTunnel(
         message: "Tell me your Cloudflare domain, e.g. example.com",
       });
     }
+    // Named profiles need their own Cloudflare tunnel; reusing the default
+    // name would route both profiles' hostnames at one installation.
+    const profile = process.env.C2C_PROFILE?.trim();
     const result = await provisionNamedTunnel({
       workspaceId: INSTALLATION_TUNNEL_ID,
-      workspaceName: "installation",
+      workspaceName: profile ? `installation-${profile}` : "installation",
       zone,
       hostname: opts.hostname,
+      tunnelName: profile ? `c2c-installation-${profile}` : undefined,
     });
     state = result.state;
     const { url } = await restartBrokerTunnel();
diff --git a/src/tunnel/named-provision.ts b/src/tunnel/named-provision.ts
index 235cfaa..6264ec4 100644
--- a/src/tunnel/named-provision.ts
+++ b/src/tunnel/named-provision.ts
@@ -188,6 +188,7 @@ export async function provisionNamedTunnel(opts: {
   workspaceName: string;
   zone: string;
   hostname?: string;
+  tunnelName?: string;
   account?: CloudflaredAccount;
 }): Promise<ProvisionNamedResult> {
   const account = opts.account ?? new ProcessCloudflaredAccount();
@@ -200,7 +201,7 @@ export async function provisionNamedTunnel(opts: {
     return fallbackState(opts.workspaceId, "invalid_hostname", (error as Error).message);
   }
 
-  const tunnelName = `c2c-${opts.workspaceId}`;
+  const tunnelName = opts.tunnelName ?? `c2c-${opts.workspaceId}`;
   try {
     if (!account.hasCert()) await account.login();
     const tunnel = await account.createTunnel(tunnelName);
diff --git a/tests/workspaces-domain.test.ts b/tests/workspaces-domain.test.ts
index 6c70a94..029e4c9 100644
--- a/tests/workspaces-domain.test.ts
+++ b/tests/workspaces-domain.test.ts
@@ -263,3 +263,29 @@ describe("state dir precedence", () => {
     }
   });
 });
+
+describe("profile state resolution", () => {
+  it("routes state to ~/.c2c/profiles/<name> via C2C_PROFILE", async () => {
+    const { getStateDir, getC2cHome } = await import("../src/config/paths.js");
+    delete process.env.C2C_STATE_DIR;
+    process.env.C2C_PROFILE = "wiriawan-gmail";
+    try {
+      expect(getStateDir()).toBe(path.join(getC2cHome(), "profiles", "wiriawan-gmail"));
+    } finally {
+      delete process.env.C2C_PROFILE;
+    }
+  });
+
+  it("keeps C2C_STATE_DIR stronger than C2C_PROFILE", async () => {
+    const { getStateDir } = await import("../src/config/paths.js");
+    const scratch = makeTmpDir("profile-scratch");
+    process.env.C2C_STATE_DIR = scratch;
+    process.env.C2C_PROFILE = "wiriawan-gmail";
+    try {
+      expect(getStateDir()).toBe(scratch);
+    } finally {
+      delete process.env.C2C_STATE_DIR;
+      delete process.env.C2C_PROFILE;
+    }
+  });
+});