spec: update SPEC-012 to include both Serial Console + PTY Shell modes

Major update to SPEC-012 adding dual-mode terminal access:

Mode 1: Serial Console Mode (True Remote Console)
- Direct access to system serial console (/dev/ttyS0 or /dev/console)
- Sees GRUB bootloader, kernel boot messages, login prompts, kernel panics
- Boot-time interaction: select GRUB entries, edit kernel parameters, single-user mode
- Requires root privileges or CAP_SYS_TTY_CONFIG capability
- Setup: GRUB + kernel parameters configured for serial console output
- Like KVM-over-IP or IPMI Serial-over-LAN (text-mode equivalent)

Mode 2: PTY Shell Mode (Interactive Shell)
- Spawn pseudo-TTY with bash/zsh shell session
- Normal server management (package updates, log review, etc.)
- Runs as unprivileged agent service user
- Standard interactive shell with full ANSI/VT100 support

Architecture:
- Agent mode selection based on viewer request (console vs. shell)
- Dashboard shows two buttons: "Console" and "Shell" for headless agents
- Same xterm.js viewer handles both modes transparently
- Protobuf extensions: TerminalModeRequest enum, console_mode flag

Security:
- Console mode requires root (boot-level control risk)
- Recommend RBAC: separate console_access and shell_access permissions
- Console sessions should require MFA (Phase 2)
- Audit logging for both modes

Setup Requirements:
- One-time GRUB configuration for serial console
- systemd service with CAP_SYS_TTY_CONFIG for console mode
- serial-getty@ttyS0.service enabled for login prompt

Updated effort: Medium (5-7 weeks, up from 4-6)
Priority remains P2

Addresses user request for "remote console" (as if at the machine)
not just shell access.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/specs/SPEC-012-headless-linux-tty.md

@@ -1,40 +1,63 @@
-# SPEC-012: Headless Linux Mode (Direct TTY Access)
+# SPEC-012: Headless Linux Mode (Serial Console + PTY Shell Access)
 
 **Status:** Proposed
 **Priority:** P2
 **Requested By:** Mike Swanson (2026-05-30)
-**Estimated Effort:** Medium (4-6 weeks)
+**Estimated Effort:** Medium (5-7 weeks)
 
 ## Overview
 
-Enable GuruConnect agent support for headless Linux servers (no X11/Wayland GUI) by providing direct terminal (TTY) access instead of screen capture. This addresses a critical server management use case: remote terminal access to Linux servers, VMs, and containers that run without a graphical desktop environment. Unlike SSH, this integrates with the GuruConnect dashboard for centralized access, audit logging, and support-code workflows. The viewer displays a terminal emulator (xterm.js-based web viewer or native terminal in the desktop viewer) connected to a pseudo-TTY (PTY) on the target server. Success criteria: technician can manage a headless Ubuntu Server 22.04 VM via GuruConnect dashboard with same authentication and session model as GUI agents, full terminal capabilities (colors, cursor control, vim/nano editing), and zero X11/Wayland dependencies on the target.
+Enable GuruConnect agent support for headless Linux servers (no X11/Wayland GUI) by providing two modes of terminal access: **Serial Console Mode** for boot-level access (GRUB, kernel messages, panics) and **PTY Shell Mode** for normal server management. This addresses critical server management use cases—from emergency recovery to routine administration—without requiring SSH. The viewer displays a terminal emulator (xterm.js web viewer) connected to either the system serial console (`/dev/ttyS0`) or a pseudo-TTY shell session. Serial Console Mode provides true "remote console" access like KVM-over-IP or IPMI Serial-over-LAN, seeing everything the physical monitor would show. PTY Shell Mode provides an interactive shell for normal management tasks. Success criteria: technician can access GRUB bootloader, view kernel boot messages, handle kernel panics, AND perform routine server management—all via GuruConnect dashboard with centralized authentication and audit logging.
 
 **Use Cases:**
-- Remote terminal access to headless Linux servers (web hosting, databases, Docker hosts)
+- **Boot-level access:** GRUB menu selection, kernel parameter editing, single-user mode
-- Container debugging (exec into running containers via GuruConnect)
+- **Emergency recovery:** Kernel panic diagnosis, filesystem repair, systemd rescue shell
-- Emergency server recovery (systemd rescue mode, single-user mode)
+- **Server management:** Package updates, configuration changes, log review (normal shell access)
-- MSP consolidation: one tool for both desktop support (GUI) and server management (terminal)
+- **Container debugging:** Exec into running containers via GuruConnect
+- **MSP consolidation:** One tool for desktop support (GUI), server boot recovery (console), and server management (shell)
 
 **Success Criteria:**
+- **Serial Console Mode:** View GRUB bootloader, kernel boot messages, kernel panics, login prompts—as if sitting at physical console
+- **PTY Shell Mode:** Interactive shell (bash/zsh) with full ANSI color, cursor control, vim/nano/htop support
 - GuruConnect agent runs on Ubuntu Server 22.04 minimal install (no desktop packages)
-- Viewer sees full-color, interactive terminal (80x24 or larger, resizable)
+- Dashboard mode selector: "Console" vs. "Shell" per agent (user chooses at connection time)
-- Full terminal capabilities: ANSI colors, cursor positioning, vim/nano/htop work correctly
 - Same protobuf-over-WSS transport, support-code and persistent-agent authentication
-- Audit logging: session recording (terminal output captured to `events` table or file)
+- Audit logging: session recording for both console and shell modes
 
 ## Scope
 
 ### Included in v1
 
-**Headless Agent Mode:**
+**Mode 1: Serial Console Mode (True Remote Console)**
+- Open system serial console device (`/dev/ttyS0` or `/dev/console`) for raw I/O
+- Relay all bytes bidirectionally: console output → `TerminalData` → viewer; viewer input → `TerminalInput` → console
+- **Sees everything:** GRUB bootloader menu, kernel boot messages, systemd startup, login prompts, kernel panics
+- **Boot-time interaction:** Select GRUB entries, edit kernel parameters, boot into single-user mode
+- Requires root privileges (serial console access restricted to root)
+- Requires serial console enabled on target server (GRUB + kernel parameters configured)
+- No PTY spawning—direct device I/O, like `screen /dev/ttyS0 115200`
+- Agent config flag: `console_mode: true` + `console_device: "/dev/ttyS0"`
+
+**Mode 2: PTY Shell Mode (Interactive Shell)**
 - Detect headless environment (no DISPLAY, no X11/Wayland libraries) at runtime
 - Spawn pseudo-TTY (PTY) via `openpty()` + fork/exec shell (`/bin/bash -l` or user's `$SHELL`)
 - Terminal I/O: read PTY output → encode as protobuf `TerminalData` → send via WebSocket
 - Input: receive protobuf `TerminalInput` → write to PTY master
 - Terminal resize: handle `TerminalResize` message → send `SIGWINCH` to PTY
 - Fallback shell selection: `$SHELL` env var → `/bin/bash` → `/bin/sh`
-- Same agent binary as GUI mode: `guruconnect` detects headless and switches mode automatically
 - Graceful PTY cleanup on session end (send exit command, wait for shell exit, close PTY)
+- Standard user privileges (runs as agent service user)
+
+**Mode Selection:**
+- Dashboard shows mode selector when connecting to headless agent: "Console" vs. "Shell"
+- "Console" button: viewer sends `mode: console` in connection request → agent opens `/dev/ttyS0`
+- "Shell" button: viewer sends `mode: shell` in connection request → agent spawns PTY
+- Agent config specifies default mode if serial console unavailable
+- If serial console device doesn't exist or permission denied, fall back to PTY shell mode with warning
+
+**Both Modes Share:**
+- Same agent binary: `guruconnect` detects headless and offers both modes
+- Same xterm.js viewer (handles both serial console and PTY identically)
 
 **Viewer (Web Viewer):**
 - xterm.js-based terminal emulator embedded in `viewer.html`
@@ -66,13 +89,226 @@ Enable GuruConnect agent support for headless Linux servers (no X11/Wayland GUI)
 - **GUI mode on headless agents** — v1 is terminal-only; no attempt to start Xvfb or launch GUI apps
 - **SSH key management** — agent uses GuruConnect auth (support code / agent key), not SSH keys
 - **File transfer via terminal** — defer to SPEC (file transfer is a separate roadmap item for all agent types)
-- **Multi-user terminal sessions** — v1 is single-session PTY; no tmux/screen built-in sharing
+- **Multi-user terminal sessions** — v1 is single-session console/PTY; no tmux/screen built-in sharing
 - **Windows terminal mode** — defer; Windows Server typically has GUI (RDP) or SSH (OpenSSH)
 - **macOS terminal mode** — defer; macOS servers are rare and typically have GUI access
+- **Framebuffer capture (`/dev/fb0`)** — defer; serial console is more reliable and doesn't require framebuffer device
+
+### Serial Console Setup Requirements (Mode 1)
+
+To use Serial Console Mode, the target Linux server must be configured to output to serial console. This is a **one-time setup per server** (typically done during provisioning):
+
+**Step 1: Configure GRUB**
+
+Edit `/etc/default/grub`:
+```bash
+# Enable serial console output at 115200 baud
+GRUB_TERMINAL="serial console"
+GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
+
+# Kernel console output to both VGA (tty0) and serial (ttyS0)
+GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"
+```
+
+Update GRUB and reboot:
+```bash
+sudo update-grub     # Debian/Ubuntu
+# OR
+sudo grub2-mkconfig -o /boot/grub2/grub.cfg  # RHEL/CentOS
+sudo reboot
+```
+
+**Step 2: Enable getty on Serial Console**
+
+Ensure a login prompt appears on serial console after boot:
+```bash
+sudo systemctl enable serial-getty@ttyS0.service
+sudo systemctl start serial-getty@ttyS0.service
+```
+
+**Step 3: Verify**
+
+Test serial console locally before configuring GuruConnect:
+```bash
+sudo screen /dev/ttyS0 115200
+# Should see kernel messages, login prompt
+```
+
+**What This Provides:**
+- ✓ GRUB bootloader menu visible via serial console
+- ✓ Kernel boot messages stream to serial console
+- ✓ Login prompt on `/dev/ttyS0` after boot
+- ✓ Kernel panics output to serial console
+- ✓ systemd rescue shell accessible via serial console
+
+**Compatibility:**
+- Physical servers: Uses hardware serial port (COM1 = ttyS0)
+- Virtual machines: VMware/Proxmox/KVM expose virtual serial port; configure VM to attach serial port
+- Cloud VMs: AWS, GCP, Azure offer "Serial Console" feature (already configured); GuruConnect agent can relay it
 
 ## Architecture
 
-### Agent PTY Handling
+### Agent Mode Selection
+
+**Connection request handling:**
+
+```rust
+// agent/src/session/terminal.rs
+pub async fn handle_terminal_session(
+    ws: WebSocketClient,
+    mode: TerminalMode,  // Console or Shell
+    support_code: String
+) -> Result<()> {
+    match mode {
+        TerminalMode::Console => run_console_session(ws, support_code).await,
+        TerminalMode::Shell => run_shell_session(ws, support_code).await,
+    }
+}
+
+pub enum TerminalMode {
+    Console,  // Serial console (/dev/ttyS0)
+    Shell,    // PTY shell session
+}
+```
+
+### Agent Serial Console Handling (Mode 1)
+
+**Serial device open:**
+
+```rust
+// agent/src/platform/linux/console.rs
+use std::fs::OpenOptions;
+use std::os::unix::io::AsRawFd;
+
+pub struct ConsoleSession {
+    device_fd: RawFd,
+    device_path: String,  // "/dev/ttyS0" or "/dev/console"
+}
+
+impl ConsoleSession {
+    pub fn open(device_path: &str) -> Result<Self> {
+        // Open serial console device for read/write
+        // Requires root privileges
+        let file = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .open(device_path)
+            .context("Failed to open serial console - requires root")?;
+
+        let device_fd = file.as_raw_fd();
+
+        // Configure terminal settings (115200 baud, 8N1)
+        unsafe {
+            let mut termios: libc::termios = std::mem::zeroed();
+            if libc::tcgetattr(device_fd, &mut termios) != 0 {
+                return Err(anyhow!("tcgetattr failed"));
+            }
+
+            // Set baud rate to 115200
+            libc::cfsetispeed(&mut termios, libc::B115200);
+            libc::cfsetospeed(&mut termios, libc::B115200);
+
+            // 8N1 (8 data bits, no parity, 1 stop bit)
+            termios.c_cflag &= !libc::CSIZE;
+            termios.c_cflag |= libc::CS8;
+            termios.c_cflag &= !(libc::PARENB | libc::PARODD);
+            termios.c_cflag &= !libc::CSTOPB;
+
+            // Raw mode (no line buffering, no echo)
+            libc::cfmakeraw(&mut termios);
+
+            if libc::tcsetattr(device_fd, libc::TCSANOW, &termios) != 0 {
+                return Err(anyhow!("tcsetattr failed"));
+            }
+        }
+
+        Ok(ConsoleSession {
+            device_fd,
+            device_path: device_path.to_string(),
+        })
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> Result<usize> {
+        unsafe {
+            let n = libc::read(self.device_fd, buf.as_mut_ptr() as *mut _, buf.len());
+            if n < 0 {
+                Err(anyhow!("Console read failed"))
+            } else {
+                Ok(n as usize)
+            }
+        }
+    }
+
+    pub fn write(&self, data: &[u8]) -> Result<()> {
+        unsafe {
+            let n = libc::write(self.device_fd, data.as_ptr() as *const _, data.len());
+            if n < 0 {
+                Err(anyhow!("Console write failed"))
+            } else {
+                Ok(())
+            }
+        }
+    }
+}
+
+impl Drop for ConsoleSession {
+    fn drop(&mut self) {
+        unsafe { libc::close(self.device_fd); }
+    }
+}
+```
+
+**Console session loop:**
+
+```rust
+// agent/src/session/console.rs
+pub async fn run_console_session(ws: WebSocketClient, support_code: String) -> Result<()> {
+    // Try /dev/ttyS0 first, fall back to /dev/console
+    let console = ConsoleSession::open("/dev/ttyS0")
+        .or_else(|_| ConsoleSession::open("/dev/console"))?;
+
+    // Status update: terminal mode, console
+    ws.send(AgentStatus {
+        terminal_mode: true,
+        console_mode: true,  // NEW flag
+        os: "Linux".to_string(),
+        // ...
+    }).await?;
+
+    let mut buf = vec![0u8; 4096];
+    loop {
+        tokio::select! {
+            // Read console output, send to relay
+            Ok(n) = tokio::task::spawn_blocking({
+                let fd = console.device_fd;
+                move || unsafe { libc::read(fd, buf.as_mut_ptr() as *mut _, buf.len()) }
+            }) => {
+                if n > 0 {
+                    ws.send(TerminalData {
+                        data: buf[..n as usize].to_vec(),
+                    }).await?;
+                }
+            }
+
+            // Receive input from relay, write to console
+            Some(msg) = ws.recv() => {
+                match msg {
+                    Message::TerminalInput(input) => {
+                        console.write(&input.data)?;
+                    }
+                    Message::Disconnect => break,
+                    // Note: Resize ignored for serial console (not applicable)
+                    _ => {}
+                }
+            }
+        }
+    }
+
+    Ok(())
+}
+```
+
+### Agent PTY Handling (Mode 2)
 
 **Headless detection:**
 
@@ -255,11 +491,12 @@ pub async fn run_terminal_session(ws: WebSocketClient, support_code: String) ->
 
 message AgentStatus {
   // Existing fields...
-  optional bool terminal_mode = 21;  // true for headless agents
+  optional bool terminal_mode = 21;   // true for headless agents
+  optional bool console_mode = 22;    // true for serial console mode, false for PTY shell mode
 }
 
 message TerminalData {
-  bytes data = 1;  // PTY raw output (may include ANSI escape sequences)
+  bytes data = 1;  // Raw terminal output (PTY or serial console, includes ANSI escape sequences)
 }
 
 message TerminalInput {
@@ -269,6 +506,17 @@ message TerminalInput {
 message TerminalResize {
   uint32 cols = 1;  // Terminal width (characters)
   uint32 rows = 2;  // Terminal height (lines)
+  // Note: Resize only applies to PTY shell mode; serial console ignores this
+}
+
+enum TerminalModeRequest {
+  SHELL = 0;    // Request PTY shell session
+  CONSOLE = 1;  // Request serial console session
+}
+
+message SessionRequest {
+  // Existing fields...
+  optional TerminalModeRequest terminal_mode_request = 10;  // NEW: viewer specifies console vs. shell
 }
 
 // Update AgentMessage and ViewerMessage unions
@@ -412,7 +660,7 @@ async fn handle_viewer_message(msg: ViewerMessage, session: &Session) {
 </html>
 ```
 
-### Dashboard Detection
+### Dashboard Mode Selector
 
 ```javascript
 // server/static/dashboard.js
@@ -421,27 +669,54 @@ function renderAgentRow(agent) {
         ? '<i class="icon-terminal"></i> Terminal'
         : '<i class="icon-screen"></i> Screen';
 
-    const connectButton = agent.online
+    // For headless agents, show mode selector (Console vs. Shell)
-        ? `<button onclick="connectToAgent('${agent.id}', ${agent.terminal_mode})">Connect</button>`
+    let connectButtons;
-        : '<span>Offline</span>';
+    if (agent.terminal_mode && agent.online) {
+        connectButtons = `
+            <div class="terminal-mode-selector">
+                <button class="btn-console" onclick="connectToTerminal('${agent.id}', 'console')"
+                        title="Serial console access (GRUB, boot, panics)">
+                    Console
+                </button>
+                <button class="btn-shell" onclick="connectToTerminal('${agent.id}', 'shell')"
+                        title="Interactive shell (bash/zsh)">
+                    Shell
+                </button>
+            </div>
+        `;
+    } else if (!agent.terminal_mode && agent.online) {
+        // GUI agent
+        connectButtons = `<button onclick="connectToAgent('${agent.id}')">Connect</button>`;
+    } else {
+        connectButtons = '<span>Offline</span>';
+    }
 
     return `<tr>
         <td>${agent.name}</td>
         <td>${icon}</td>
         <td>${agent.os} ${agent.os_version}</td>
-        <td>${connectButton}</td>
+        <td>${connectButtons}</td>
     </tr>`;
 }
 
-function connectToAgent(agentId, terminalMode) {
+function connectToAgent(agentId) {
-    if (terminalMode) {
+    // GUI agent connection
-        window.open(`/viewer-terminal.html?session=${agentId}&token=${JWT}`, '_blank');
+    window.open(`/viewer.html?session=${agentId}&token=${JWT}`, '_blank');
-    } else {
+}
-        window.open(`/viewer.html?session=${agentId}&token=${JWT}`, '_blank');
+
-    }
+function connectToTerminal(agentId, mode) {
+    // Terminal agent connection with mode parameter
+    window.open(`/viewer-terminal.html?session=${agentId}&token=${JWT}&mode=${mode}`, '_blank');
 }
 ```
 
+**Dashboard UI for headless agents:**
+- Shows two buttons: "Console" and "Shell"
+- "Console" button: opens serial console session (GRUB, boot messages, panics)
+- "Shell" button: opens PTY shell session (normal server management)
+- Tooltip on hover explains each mode
+- Mode parameter passed to viewer via URL query string
+
 ### Database Schema
 
 **Minor addition to `sessions` table:**
@@ -467,9 +742,11 @@ CREATE TABLE IF NOT EXISTS terminal_recordings (
 ### Files to Create
 
 **Agent (Linux-specific):**
+- `agent/src/platform/linux/console.rs` — NEW: Serial console device I/O (`/dev/ttyS0`, termios config)
+- `agent/src/session/console.rs` — NEW: Console session loop (serial device ↔ WebSocket)
 - `agent/src/platform/linux/pty.rs` — PTY spawn, I/O, resize (openpty, fork, exec)
 - `agent/src/platform/linux/headless.rs` — Headless detection logic
-- `agent/src/session/terminal.rs` — Terminal session loop (PTY ↔ WebSocket)
+- `agent/src/session/terminal.rs` — Mode dispatcher (console vs. shell), shell session loop
 
 **Server:**
 - `server/src/relay/terminal.rs` — Terminal message routing (TerminalData/Input/Resize)
@@ -499,10 +776,25 @@ nix = "0.27"  # Safe wrappers for POSIX APIs
 
 ## Security Considerations
 
-### Shell Access Risk
+### Serial Console Access (Mode 1)
 
-- **Privilege escalation:** PTY spawns shell as the agent's user (typically `root` if agent runs as systemd service)
+- **Requires root privileges:** Opening `/dev/ttyS0` or `/dev/console` requires root access
-- **Mitigation 1:** Run agent as unprivileged user (`guruconnect` service user), use `sudo` for privileged commands
+- **Implication:** Agent must run as root for console mode, OR use capabilities (`CAP_SYS_TTY_CONFIG`)
+- **Boot-level control:** Serial console grants full boot-time control (GRUB menu, kernel parameters, single-user mode)
+- **Risk:** Attacker with console access can modify bootloader, disable security features, boot into recovery
+- **Mitigation 1:** Restrict console mode to authorized users only (dashboard RBAC: "console_access" permission)
+- **Mitigation 2:** Require MFA for console mode sessions (stronger auth than shell mode)
+- **Mitigation 3:** Audit logging: record ALL console I/O with immutable timestamps
+- **Mitigation 4:** Alert on console mode connections (notify admin when console session starts)
+
+**Recommended deployment:**
+- Run agent as unprivileged user for shell mode (default)
+- For console mode: either run agent as root OR grant `CAP_SYS_TTY_CONFIG` capability via systemd unit
+
+### Shell Access Risk (Mode 2)
+
+- **Privilege escalation:** PTY spawns shell as the agent's user (typically unprivileged `guruconnect` service user)
+- **Mitigation 1:** Run agent as unprivileged user, use `sudo` for privileged commands
 - **Mitigation 2:** Add `allowed_commands` whitelist (optional Phase 2 feature) — restrict to specific binaries
 - **Mitigation 3:** Audit logging: record all terminal I/O for compliance review
 
@@ -578,17 +870,19 @@ nix = "0.27"  # Safe wrappers for POSIX APIs
 
 ## Effort Estimate & Dependencies
 
-**Size:** Medium (4-6 weeks, 1 developer)
+**Size:** Medium (5-7 weeks, 1 developer)
 
 **Breakdown:**
+- Serial console implementation (Linux agent): 1.5 weeks
 - PTY implementation (Linux agent): 1.5 weeks
-- Protobuf protocol updates: 0.5 weeks
+- Mode selection + dispatcher: 0.5 weeks
+- Protobuf protocol updates (mode enum, console_mode flag): 0.5 weeks
 - Relay server terminal routing: 1 week
 - xterm.js web viewer integration: 1 week
-- Dashboard terminal mode detection + routing: 0.5 weeks
+- Dashboard mode selector UI + routing: 0.5 weeks
-- Session recording + playback: 1 week
+- Session recording + playback (both modes): 1 week
-- Testing, edge cases, systemd integration: 1 week
+- Testing (console + shell modes), edge cases, systemd integration: 1.5 weeks
-- Documentation: 0.5 weeks
+- Documentation (setup guide for serial console): 0.5 weeks
 
 **Dependencies:**
 - **SPEC-010 Linux agent base** — PTY mode extends the Linux agent; can be implemented in parallel with SPEC-010's GUI capture
@@ -597,26 +891,36 @@ nix = "0.27"  # Safe wrappers for POSIX APIs
 - **SPEC-004 per-agent keys** — already shipped for persistent agent auth
 
 **Unblocks:**
-- Server management use case (Linux VMs, containers, bare metal)
+- **Boot-level access** (GRUB menu, kernel parameters, single-user mode) via serial console mode
-- SSH replacement with centralized audit logging
+- **Emergency recovery** (kernel panics, filesystem repair, systemd rescue shell) via serial console
-- Emergency recovery (single-user mode, systemd rescue shell)
+- **Server management** (Linux VMs, containers, bare metal) via shell mode
-- Container debugging (exec into running containers via GuruConnect)
+- **SSH replacement** with centralized audit logging and GuruConnect auth
+- **Container debugging** (exec into running containers via GuruConnect)
+- **KVM-over-IP alternative** (serial console provides text-mode equivalent to IPMI Serial-over-LAN)
 
 ## Open Questions
 
-1. **Run agent as root or unprivileged user?** — Recommend unprivileged `guruconnect` service user + sudo whitelist. Security-sensitive orgs may require root; make configurable.
+1. **Serial console permissions - root vs. capabilities?** — Opening `/dev/ttyS0` requires root. Options: (a) run agent as root for console mode, (b) use Linux capabilities (`CAP_SYS_TTY_CONFIG`), (c) add agent user to `dialout` group (may not work for `/dev/console`). Recommend (b) via systemd unit: `AmbientCapabilities=CAP_SYS_TTY_CONFIG`.
 
-2. **Shell selection?** — v1: `$SHELL` env var → `/bin/bash` → `/bin/sh`. Phase 2: dashboard setting to override shell per agent (`/bin/zsh`, `/bin/fish`).
+2. **Default mode if serial console unavailable?** — If `/dev/ttyS0` doesn't exist or permission denied, fall back to shell mode automatically or show error? Recommend auto-fallback with warning message in viewer.
 
-3. **Concurrent PTY sessions?** — v1: one PTY per agent connection (like SSH). Phase 2: tmux/screen integration for multi-viewer session sharing.
+3. **Serial console baud rate?** — v1 hardcodes 115200 (industry standard). Phase 2: make configurable if slower links needed (9600, 38400).
 
-4. **Terminal recording format?** — Asciicast (JSON, industry standard, xterm.js playback support) vs. raw PTY dump (more compact, custom playback). Recommend asciicast for v1.
+4. **Shell selection (PTY mode)?** — v1: `$SHELL` env var → `/bin/bash` → `/bin/sh`. Phase 2: dashboard setting to override shell per agent (`/bin/zsh`, `/bin/fish`).
 
-5. **Command whitelisting?** — Optional Phase 2 feature. v1 is unrestricted shell access (same as SSH). Add `allowed_commands` array to agent config if compliance requires it.
+5. **Concurrent sessions?** — v1: one console/shell session per agent connection (like SSH). Phase 2: tmux/screen integration for multi-viewer session sharing.
 
-6. **Windows/macOS terminal mode?** — Defer. Windows Server typically uses RDP or SSH (OpenSSH built-in since Server 2019). macOS servers are rare. Linux headless servers are the primary use case.
+6. **Terminal recording format?** — Asciicast (JSON, industry standard, xterm.js playback support) vs. raw dump (more compact, custom playback). Recommend asciicast for v1.
 
-7. **File upload/download via terminal?** — v1: use standard tools (`scp`, `rsync`, `wget`). Phase 2: integrate with SPEC (file transfer) for dashboard-native upload/download.
+7. **Command whitelisting (shell mode)?** — Optional Phase 2 feature. v1 is unrestricted shell access (same as SSH). Add `allowed_commands` array to agent config if compliance requires it.
+
+8. **RBAC for console vs. shell access?** — Should some users only have shell access (not console, which grants boot-level control)? Recommend yes: add `console_access` permission, separate from `shell_access`.
+
+9. **MFA for console mode?** — Given boot-level control risk, require MFA for console mode sessions? Defer to Phase 2 (MFA is a broader GuruConnect feature).
+
+10. **Windows/macOS terminal mode?** — Defer. Windows Server typically uses RDP or SSH (OpenSSH built-in since Server 2019). macOS servers are rare. Linux headless servers are the primary use case.
+
+11. **File upload/download via terminal?** — v1: use standard tools (`scp`, `rsync`, `wget`). Phase 2: integrate with SPEC (file transfer) for dashboard-native upload/download.
 
 ---