feat(webui): add lightweight session messaging via mentions

docs/configuration.md

@@ -2082,6 +2082,7 @@ For API keys, tokens, and other secrets, see [Environment Variables for Secrets]
 | Option | Default | Description |
 |--------|---------|-------------|
 | `tools.restrictToWorkspace` | `false` | When `true`, enables nanobot's application-level workspace guards for workspace-aware tools. File tools resolve paths under the active workspace; selected internal roots can be added as read-only or explicitly write-enabled roots, and media uploads are read-only by default. Shell execution rejects workspace-external `working_dir` values and applies best-effort command path checks, but this is not an OS sandbox. |
+| `tools.maxSessionMessagesPerMinute` | `6` | Maximum messages one WebUI session may send to other sessions during any rolling 60-second window. Additional sends are rejected to stop runaway agent loops. |
 | `tools.exec.sandbox` | `""` | Sandbox backend for shell commands. Set to `"bwrap"` to wrap exec calls in a [bubblewrap](https://github.com/containers/bubblewrap) sandbox — the process can only see the workspace (read-write) and media directory (read-only); config files and API keys are hidden. Automatically enables workspace restriction for file tools. **Linux only** — requires `bwrap` installed (`apt install bubblewrap`; pre-installed in the Docker image). Not available on macOS or Windows (bwrap depends on Linux kernel namespaces). |
 | `tools.exec.enable` | `true` | When `false`, the shell `exec` tool is not registered at all. Use this to completely disable shell command execution. |
 | `tools.exec.timeout` | `60` | Default hard timeout in seconds for shell commands. Config values may exceed the per-call tool cap; set `0` to disable the hard timeout for trusted long-running commands. |