diff --git a/src/seedpass/cli/__init__.py b/src/seedpass/cli/__init__.py
index 9aaa81f6..140f1b76 100644
--- a/src/seedpass/cli/__init__.py
+++ b/src/seedpass/cli/__init__.py
@@ -13,6 +13,7 @@ from .common import _get_entry_service, _get_services
 from seedpass.core.errors import SeedPassError
 from constants import GUI_BACKEND_CONFIG
 from seedpass.tui_v2.app import check_tui2_runtime, launch_tui2
+from seedpass.tui_v3 import launch_tui3
 
 app = typer.Typer(
     help=(
@@ -50,6 +51,12 @@ legacy_tui_option = typer.Option(
     help="Use legacy interactive TUI (temporary fallback during TUI v2 cutover)",
 )
 
+tui_version_option = typer.Option(
+    "v2",
+    "--tui",
+    help="Select TUI version: legacy, v2, v3",
+)
+
 # Sub command groups
 from . import entry, vault, nostr, config, fingerprint, util, api, agent, semantic
 from .capabilities import register_capabilities_command
@@ -131,6 +138,7 @@ def main(
     no_clipboard: bool = no_clipboard_option,
     deterministic_totp: bool = deterministic_totp_option,
     legacy_tui: bool = legacy_tui_option,
+    tui_version: str = tui_version_option,
 ) -> None:
     """SeedPass CLI entry point.
 
@@ -143,19 +151,34 @@ def main(
         "no_clipboard": no_clipboard,
         "deterministic_totp": deterministic_totp,
         "legacy_tui": legacy_tui,
+        "tui_version": tui_version,
     }
     if ctx.invoked_subcommand is None:
-        if legacy_tui:
+        if legacy_tui or tui_version == "legacy":
             raise _launch_legacy_tui(fingerprint=fingerprint)
 
         services, preflight_error = _prime_tui2_service(ctx)
         if preflight_error is not None:
             typer.echo(
-                "TUI v2 preflight failed; falling back to legacy TUI. "
+                f"TUI {tui_version} preflight failed; falling back to legacy TUI. "
                 f"Details: {preflight_error}"
             )
             raise _launch_legacy_tui(fingerprint=fingerprint)
 
+        if tui_version == "v3":
+            launch_tui3(
+                fingerprint=fingerprint,
+                entry_service_factory=lambda: services["entry"],
+                profile_service_factory=lambda: services["profile"],
+                config_service_factory=lambda: services["config"],
+                nostr_service_factory=lambda: services["nostr"],
+                sync_service_factory=lambda: services["sync"],
+                utility_service_factory=lambda: services["utility"],
+                vault_service_factory=lambda: services["vault"],
+                semantic_service_factory=lambda: services["semantic"],
+            )
+            return
+
         launched = launch_tui2(
             fingerprint=fingerprint,
             entry_service_factory=lambda: services["entry"],
@@ -171,7 +194,7 @@ def main(
             return
 
         typer.echo(
-            "TUI v2 runtime unavailable; falling back to legacy TUI. "
+            f"TUI {tui_version} runtime unavailable; falling back to legacy TUI. "
             "Run `seedpass tui2 --check` for diagnostics."
         )
         raise _launch_legacy_tui(fingerprint=fingerprint)
@@ -247,6 +270,28 @@ def tui2(
     raise typer.Exit(1)
 
 
+@app.command("tui3")
+def tui3(ctx: typer.Context) -> None:
+    """Launch the experimental TUI v3 scratch architecture."""
+    fingerprint = (ctx.obj or {}).get("fingerprint")
+    services, preflight_error = _prime_tui2_service(ctx)
+    if preflight_error is not None:
+        typer.echo(f"TUI v3 preflight failed: {preflight_error}", err=True)
+        raise typer.Exit(1)
+
+    launch_tui3(
+        fingerprint=fingerprint,
+        entry_service_factory=lambda: services["entry"],
+        profile_service_factory=lambda: services["profile"],
+        config_service_factory=lambda: services["config"],
+        nostr_service_factory=lambda: services["nostr"],
+        sync_service_factory=lambda: services["sync"],
+        utility_service_factory=lambda: services["utility"],
+        vault_service_factory=lambda: services["vault"],
+        semantic_service_factory=lambda: services["semantic"],
+    )
+
+
 @app.command("legacy")
 def legacy_tui(ctx: typer.Context) -> None:
     """Launch the legacy interactive TUI explicitly."""
diff --git a/src/seedpass/tui_v3/__init__.py b/src/seedpass/tui_v3/__init__.py
new file mode 100644
index 00000000..b7dd0e2a
--- /dev/null
+++ b/src/seedpass/tui_v3/__init__.py
@@ -0,0 +1,56 @@
+from __future__ import annotations
+import importlib.util
+from typing import Any
+
+def check_tui3_runtime() -> dict[str, Any]:
+    """Return runtime capability diagnostics for TUI v3."""
+    textual_available = importlib.util.find_spec("textual") is not None
+    return {
+        "status": "ok" if textual_available else "unavailable",
+        "backend": "textual-v3",
+        "textual_available": textual_available,
+        "message": (
+            "Textual runtime available."
+            if textual_available
+            else "Textual is not installed. Install `textual` to run tui3."
+        ),
+    }
+
+def launch_tui3(
+    *,
+    fingerprint: str | None = None,
+    entry_service_factory: Any | None = None,
+    profile_service_factory: Any | None = None,
+    config_service_factory: Any | None = None,
+    nostr_service_factory: Any | None = None,
+    sync_service_factory: Any | None = None,
+    utility_service_factory: Any | None = None,
+    vault_service_factory: Any | None = None,
+    semantic_service_factory: Any | None = None,
+    app_hook: Any | None = None,
+) -> bool:
+    """Launch TUI v3 from scratch architecture."""
+    runtime = check_tui3_runtime()
+    if not runtime["textual_available"]:
+        return False
+
+    from .app import SeedPassTuiV3
+    
+    app = SeedPassTuiV3(
+        fingerprint=fingerprint,
+        entry_service_factory=entry_service_factory,
+        profile_service_factory=profile_service_factory,
+        config_service_factory=config_service_factory,
+        nostr_service_factory=nostr_service_factory,
+        sync_service_factory=sync_service_factory,
+        utility_service_factory=utility_service_factory,
+        vault_service_factory=vault_service_factory,
+        semantic_service_factory=semantic_service_factory,
+    )
+    
+    if callable(app_hook):
+        app_hook(app)
+        return True
+        
+    app.run()
+    return True
diff --git a/src/seedpass/tui_v3/app.py b/src/seedpass/tui_v3/app.py
new file mode 100644
index 00000000..bc051249
--- /dev/null
+++ b/src/seedpass/tui_v3/app.py
@@ -0,0 +1,158 @@
+from __future__ import annotations
+import time
+from typing import Any, Callable
+
+from textual.app import App, ComposeResult
+from textual.binding import Binding
+from textual.reactive import reactive
+from textual.screen import Screen
+from textual.widgets import Header, Footer, Static
+from textual.containers import Horizontal, Vertical
+
+from .widgets.header import RibbonHeader
+from .widgets.sidebar import SidebarContainer
+from .widgets.grid import GridContainer
+from .widgets.inspector import BoardContainer
+from .screens.settings import SettingsScreen
+from .screens.inspector import MaximizedInspectorScreen
+
+class MainScreen(Screen):
+    def compose(self) -> ComposeResult:
+        yield Static("SeedPass ◈ UI v3", id="brand-strip")
+        yield RibbonHeader(id="top-ribbon")
+        with Vertical(id="body"):
+            with Horizontal(id="top-work"):
+                yield SidebarContainer(id="left")
+                with Vertical(id="center"):
+                    yield GridContainer(id="grid-work")
+            with Vertical(id="right"):
+                yield Static("Inspector Board", id="inspector-heading")
+                yield BoardContainer(id="board-container")
+        yield Static("Ready", id="status")
+        yield Footer()
+
+class SeedPassTuiV3(App[None]):
+    """
+    SeedPass TUI v3 - Rebuilt from scratch for modularity and mockup fidelity.
+    """
+    CSS = """
+    #brand-strip {
+        background: #0b0f13;
+        color: #58f29d;
+        text-style: bold;
+        border: solid #2abf75;
+        margin: 0 1;
+        padding: 0 1;
+        height: 3;
+        content-align: center middle;
+    }
+    #body { height: 1fr; margin: 0 1; }
+    #top-work { height: 6fr; }
+    #left { width: 31; border: solid #1a3024; background: #0d1114; }
+    #center { width: 1fr; border: solid #1a3024; background: #0d1114; margin-left: 1; }
+    #right { height: 5fr; border: heavy #3ce79c; background: #0d1114; margin-top: 1; }
+    #status {
+        height: 3;
+        padding: 0 1;
+        border: heavy #58f29d;
+        background: #11191f;
+        color: #e4fff2;
+        margin: 0 1;
+    }
+    #sidebar-placeholder, #grid-placeholder, #inspector-placeholder {
+        height: 1fr;
+        content-align: center middle;
+        color: #3ce79c;
+    }
+    """
+    
+    BINDINGS = [
+        Binding("q", "quit", "Quit", show=True),
+        Binding("ctrl+p", "open_palette", "Palette", show=True),
+        Binding("shift+s", "toggle_settings", "Settings", show=True),
+        Binding("z", "maximize_inspector", "Maximize", show=True),
+    ]
+
+    # Shared Reactive State
+    active_fingerprint = reactive("")
+    selected_entry_id = reactive[int | None](None)
+    session_locked = reactive(True)
+
+    def __init__(
+        self,
+        fingerprint: str | None = None,
+        entry_service_factory: Callable | None = None,
+        profile_service_factory: Callable | None = None,
+        config_service_factory: Callable | None = None,
+        nostr_service_factory: Callable | None = None,
+        sync_service_factory: Callable | None = None,
+        utility_service_factory: Callable | None = None,
+        vault_service_factory: Callable | None = None,
+        semantic_service_factory: Callable | None = None,
+    ) -> None:
+        super().__init__()
+        # Store factories
+        self.factories = {
+            "entry": entry_service_factory,
+            "profile": profile_service_factory,
+            "config": config_service_factory,
+            "nostr": nostr_service_factory,
+            "sync": sync_service_factory,
+            "utility": utility_service_factory,
+            "vault": vault_service_factory,
+            "semantic": semantic_service_factory,
+        }
+        # Initialized services
+        self.services: dict[str, Any] = {}
+        self._initial_fingerprint = fingerprint
+
+    def on_mount(self) -> None:
+        """Initialize services and push the main screen."""
+        for name, factory in self.factories.items():
+            if factory:
+                try:
+                    self.services[name] = factory()
+                except Exception as e:
+                    self.log(f"Failed to init service {name}: {e}")
+        
+        self.active_fingerprint = self._initial_fingerprint or ""
+        self.push_screen(MainScreen())
+
+    def watch_active_fingerprint(self, old_fp: str, new_fp: str) -> None:
+        """Refresh components when the profile changes."""
+        if not new_fp:
+            return
+        # Notify sidebar and grid to refresh
+        try:
+            self.query_one("#profile-tree")._refresh_tree()
+            self.query_one("#entry-data-table")._refresh_data()
+        except Exception:
+            pass
+
+    def watch_selected_entry_id(self, old_id: int | None, new_id: int | None) -> None:
+        """Update inspectors when an entry is selected."""
+        try:
+            self.query_one("#board-container").update_entry(new_id)
+        except Exception:
+            pass
+
+    def action_refresh(self) -> None:
+        """Force a global UI refresh."""
+        self.query_one("#profile-tree")._refresh_tree()
+        self.query_one("#entry-data-table")._refresh_data()
+        self.notify("UI Refreshed")
+
+    def action_open_palette(self) -> None:
+        # Placeholder for unified command palette
+        self.notify("Palette coming soon in v3")
+
+    def action_toggle_settings(self) -> None:
+        """Push the full-screen settings screen."""
+        self.push_screen(SettingsScreen())
+
+    def action_maximize_inspector(self) -> None:
+        """Push the full-screen maximized entry detail screen."""
+        if self.selected_entry_id is None:
+            self.notify("Select an entry to maximize", severity="warning")
+            return
+        self.push_screen(MaximizedInspectorScreen())
diff --git a/src/seedpass/tui_v3/screens/inspector.py b/src/seedpass/tui_v3/screens/inspector.py
new file mode 100644
index 00000000..01d21dc6
--- /dev/null
+++ b/src/seedpass/tui_v3/screens/inspector.py
@@ -0,0 +1,108 @@
+from __future__ import annotations
+from typing import Any
+from textual.app import ComposeResult
+from textual.screen import Screen
+from textual.widgets import Static, Footer
+from textual.containers import Vertical, Horizontal
+
+class MaximizedInspectorScreen(Screen):
+    """
+    Full-screen detailed view for a single entry.
+    Optimized for long documents, SSH keys, or PGP blocks.
+    """
+    
+    BINDINGS = [
+        ("escape", "app.pop_screen", "Back to Vault"),
+        ("v", "reveal", "Reveal Secret"),
+        ("g", "qr", "Show QR"),
+    ]
+
+    DEFAULT_CSS = """
+    MaximizedInspectorScreen {
+        background: #080a0c;
+    }
+    #max-inspector-title {
+        background: #0b0f13;
+        color: #58f29d;
+        text-style: bold;
+        text-align: center;
+        height: 3;
+        border: double #2abf75;
+        padding: 0 1;
+        margin: 1 2;
+    }
+    #max-inspector-container {
+        height: 1fr;
+        margin: 0 2;
+        border: solid #1a3024;
+        padding: 1;
+        overflow: auto;
+    }
+    #max-inspector-footer {
+        height: 3;
+        background: #11191f;
+        color: #daf2e5;
+        text-align: center;
+        border: double #2abf75;
+        padding: 0 1;
+        margin: 1 2;
+    }
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Static("SeedPass ◈ Detailed Inspection", id="max-inspector-title")
+        with Vertical(id="max-inspector-container"):
+            yield Static("Loading details...", id="max-inspector-content")
+        yield Static("ESC: Back | v: Reveal | g: QR", id="max-inspector-footer")
+
+    def on_mount(self) -> None:
+        self._refresh_detail()
+
+    def _refresh_detail(self) -> None:
+        app = self.app
+        eid = app.selected_entry_id
+        if eid is None:
+            self.query_one("#max-inspector-content", Static).update("No entry selected.")
+            return
+
+        if "entry" not in app.services:
+            return
+
+        entry = app.services["entry"].retrieve_entry(eid)
+        if not entry:
+            return
+
+        # Simple render for the full screen view
+        label = entry.get('label', 'Unknown')
+        kind = entry.get('kind', 'Unknown')
+        
+        # Build a large detail view
+        header = f"[b]ENTRY #{eid} - {label.upper()} ({kind})[/b]
+"
+        divider = "=" * 60 + "
+"
+        
+        # Meta info
+        meta_lines = [
+            f"Username : {entry.get('username', '(none)')}",
+            f"URL      : {entry.get('url', '(none)')}",
+            f"Created  : {entry.get('created_at', '(unknown)')}",
+            f"Modified : {entry.get('modified_at', '(unknown)')}",
+        ]
+        
+        # Content (if note/doc)
+        content = entry.get('content', '')
+        content_block = f"
+[b]CONTENT / NOTES:[/b]
+{divider}{content}
+" if content else ""
+        
+        final_text = header + divider + "
+".join(meta_lines) + content_block
+        self.query_one("#max-inspector-content", Static).update(final_text)
+
+    def action_reveal(self) -> None:
+        self.app.notify("Reveal triggered (Coming Soon in v3)")
+
+    def action_qr(self) -> None:
+        self.app.notify("QR triggered (Coming Soon in v3)")
diff --git a/src/seedpass/tui_v3/screens/settings.py b/src/seedpass/tui_v3/screens/settings.py
new file mode 100644
index 00000000..3228409d
--- /dev/null
+++ b/src/seedpass/tui_v3/screens/settings.py
@@ -0,0 +1,118 @@
+from __future__ import annotations
+from typing import Any
+from textual.app import ComposeResult
+from textual.screen import Screen
+from textual.widgets import Static, Footer
+from textual.containers import Vertical
+
+class SettingsScreen(Screen):
+    """
+    A dedicated, full-screen settings management interface.
+    Categorizes configuration into Security, Storage, and Connectivity.
+    """
+    
+    BINDINGS = [
+        ("escape", "app.pop_screen", "Back to Vault"),
+        ("r", "refresh", "Refresh Settings"),
+    ]
+
+    DEFAULT_CSS = """
+    SettingsScreen {
+        background: #080a0c;
+    }
+    #settings-title {
+        background: #0b0f13;
+        color: #58f29d;
+        text-style: bold;
+        text-align: center;
+        height: 3;
+        border: double #2abf75;
+        padding: 0 1;
+        margin: 1 2;
+    }
+    #settings-container {
+        height: 1fr;
+        margin: 0 2;
+        border: solid #1a3024;
+        padding: 1;
+        overflow: auto;
+    }
+    #settings-footer {
+        height: 3;
+        background: #11191f;
+        color: #daf2e5;
+        text-align: center;
+        border: double #2abf75;
+        padding: 0 1;
+        margin: 1 2;
+    }
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Static("SeedPass ◈ System Configuration", id="settings-title")
+        with Vertical(id="settings-container"):
+            yield Static("Loading configuration...", id="settings-content")
+        yield Static("ESC: Exit Settings | R: Reload | Use Palette (Ctrl+P) to change values", id="settings-footer")
+
+    def on_mount(self) -> None:
+        self.action_refresh()
+
+    def action_refresh(self) -> None:
+        """Fetch live settings and render them into the content panel."""
+        app = self.app
+        if "config" not in app.services:
+            self.query_one("#settings-content", Static).update("[red]Config Service Offline[/red]")
+            return
+
+        service = app.services["config"]
+        
+        def get_val(key, default=""):
+            try:
+                val = service.get(key)
+                return val if val is not None else default
+            except Exception:
+                return "[red](error)[/red]"
+
+        # Categorized Rows
+        security_rows = [
+            f"Secret Mode    : {get_val('secret_mode_enabled', False)}  [dim](setting-secret on|off)[/dim]",
+            f"Quick Unlock   : {get_val('quick_unlock', False)}  [dim](setting-quick-unlock on|off)[/dim]",
+            f"KDF Iterations : {get_val('kdf_iterations', 100000)}  [dim](setting-kdf-iterations <n>)[/dim]",
+            f"KDF Mode       : {get_val('kdf_mode', 'argon2id')}  [dim](setting-kdf-mode <mode>)[/dim]",
+            f"Lock Timeout   : {get_val('inactivity_timeout', 300)}s  [dim](setting-timeout <s>)[/dim]",
+        ]
+        
+        backup_rows = [
+            f"Backup Path    : {get_val('additional_backup_path', '(none)')}  [dim](db-export <path>)[/dim]",
+            f"Backup Interval: {get_val('backup_interval', 3600)}s",
+        ]
+
+        nostr_rows = [
+            f"Sync Mode      : {get_val('semantic_search_mode', 'keyword')}  [dim](search-mode ...)[/dim]",
+            f"Relays         : {len(get_val('relays', []))} connected  [dim](relay-list)[/dim]",
+        ]
+
+        # Use the app's card rendering utility if available, or fallback
+        # In v3, we keep card logic in a central place or widget.
+        # For now, we'll implement a clean local version.
+        def render_card(title: str, rows: list[str]) -> str:
+            width = 60
+            top = f"┌─ {title} " + "─" * (width - len(title) - 4) + "┐"
+            lines = [top]
+            for row in rows:
+                lines.append(f"│ {row:<{width-4}} │")
+            lines.append("└" + "─" * (width - 2) + "┘")
+            return "
+".join(lines)
+
+        rendered_lines = [
+            render_card("SECURITY & AUTHENTICATION", security_rows),
+            "",
+            render_card("STORAGE & BACKUP POLICY", backup_rows),
+            "",
+            render_card("CONNECTIVITY & NOSTR SYNC", nostr_rows),
+        ]
+        
+        self.query_one("#settings-content", Static).update("
+".join(rendered_lines))
+        self.app.notify("Settings reloaded")
diff --git a/src/seedpass/tui_v3/widgets/grid.py b/src/seedpass/tui_v3/widgets/grid.py
new file mode 100644
index 00000000..58afe37b
--- /dev/null
+++ b/src/seedpass/tui_v3/widgets/grid.py
@@ -0,0 +1,108 @@
+from __future__ import annotations
+from typing import Any
+from textual.app import ComposeResult
+from textual.widgets import Static, DataTable
+from textual.reactive import reactive
+
+class GridMetrics(Static):
+    """
+    Displays pagination, row counts, and search mode state.
+    Matches the 'Entry Grid | Pg X/X ...' line in the mockups.
+    """
+    DEFAULT_CSS = """
+    GridMetrics {
+        height: 1;
+        background: #0b0f13;
+        color: #daf2e5;
+        padding: 0 1;
+    }
+    """
+    
+    def render(self) -> str:
+        # These would eventually come from App reactives
+        pg = "1/1"
+        rows = "0/0"
+        density = "compact"
+        # Search mode highlighting
+        search = "[b](KEYWORD)[/b] hybrid semantic"
+        
+        return f"Entry Grid  |  Pg {pg}  Rows {rows}  Density {density}  Search {search}"
+
+class EntryDataTable(DataTable):
+    """
+    High-fidelity data table for entry browsing.
+    """
+    def on_mount(self) -> None:
+        self.cursor_type = "row"
+        self.add_columns(
+            "Sel", "Id", "Entry#", "Label", "Kind", "Meta", "Arch"
+        )
+        self._refresh_data()
+
+    def _refresh_data(self) -> None:
+        self.clear()
+        app = self.app
+        if "entry" not in app.services:
+            return
+
+        # Fetch real data from service
+        entries = app.services["entry"].search_entries("")
+        for i, (eid, label, user, url, arch, kind) in enumerate(entries):
+            marker = "▶" if eid == app.selected_entry_id else " "
+            arch_status = "🔒" if arch else " "
+            # 'Meta' column logic from mockup
+            meta = user or url or ""
+            
+            self.add_row(
+                marker,
+                str(i+1),
+                f"#{eid}",
+                label,
+                kind.value,
+                meta,
+                arch_status,
+                key=str(eid)
+            )
+
+    def on_data_table_row_selected(self, event: DataTable.RowSelected) -> None:
+        """Handle entry selection."""
+        if event.row_key.value:
+            self.app.selected_entry_id = int(event.row_key.value)
+            self.app.notify(f"Selected Entry #{event.row_key.value}")
+
+class GridContainer(Static):
+    """
+    The central workspace container.
+    """
+    def compose(self) -> ComposeResult:
+        yield GridMetrics()
+        # Header divider
+        yield Static("-" * 120, id="grid-divider")
+        yield EntryDataTable(id="entry-data-table")
+
+    DEFAULT_CSS = """
+    GridContainer {
+        height: 1fr;
+        background: #0d1114;
+    }
+    #grid-divider {
+        color: #1a3024;
+        height: 1;
+        padding: 0 1;
+    }
+    #entry-data-table {
+        background: transparent;
+        color: #97b8a6;
+        border: none;
+        height: 1fr;
+    }
+    #entry-data-table > .datatable--header {
+        background: #0b0f13;
+        color: #58f29d;
+        text-style: bold;
+    }
+    #entry-data-table > .datatable--cursor {
+        background: #122019;
+        color: #58f29d;
+    }
+    """
diff --git a/src/seedpass/tui_v3/widgets/header.py b/src/seedpass/tui_v3/widgets/header.py
new file mode 100644
index 00000000..f5903913
--- /dev/null
+++ b/src/seedpass/tui_v3/widgets/header.py
@@ -0,0 +1,50 @@
+from __future__ import annotations
+from textual.app import ComposeResult
+from textual.widgets import Static
+from textual.reactive import reactive
+
+class RibbonHeader(Static):
+    """
+    A high-density status ribbon that displays active profile, 
+    session state, and vault metrics.
+    
+    Matches the 'UI Board' mockup top ribbon layout.
+    """
+    
+    DEFAULT_CSS = """
+    RibbonHeader {
+        height: 3;
+        background: #10181f;
+        color: #daf2e5;
+        border: heavy #2abf75;
+        padding: 0 1;
+        margin: 0 1;
+        text-style: bold;
+    }
+    """
+
+    def render(self) -> str:
+        app = self.app
+        fp = app.active_fingerprint or "No Profile"
+        lock_icon = "🔒" if app.session_locked else "🔓"
+        status = "LOCKED" if app.session_locked else "UNLOCKED"
+        
+        # In a real app, we'd fetch stats from the service. 
+        # For the shell, we'll use placeholders that look like the mockup.
+        stats = "Entries: 0 | PWD: 0 | 2FA: 0 | Keys: 0"
+        sync = "Sync: Never"
+        
+        # Layout: [Icon] Status | Fingerprint | Stats | Sync
+        left = f"{lock_icon} {status} | Seed: {fp}"
+        right = f"{stats} | {sync}"
+        
+        # Calculate spacing to push sync to the right
+        available_width = self.size.width - len(left) - len(right) - 4
+        spacer = " " * max(1, available_width)
+        
+        return f"{left}{spacer}{right}"
+
+    def on_mount(self) -> None:
+        # Refresh the header whenever important app state changes
+        self.watch(self.app, "active_fingerprint", self.refresh)
+        self.watch(self.app, "session_locked", self.refresh)
diff --git a/src/seedpass/tui_v3/widgets/inspector.py b/src/seedpass/tui_v3/widgets/inspector.py
new file mode 100644
index 00000000..355078c0
--- /dev/null
+++ b/src/seedpass/tui_v3/widgets/inspector.py
@@ -0,0 +1,133 @@
+from __future__ import annotations
+from typing import Any
+from textual.app import ComposeResult
+from textual.widgets import Static, Label
+from textual.containers import Vertical, Horizontal
+from textual.reactive import reactive
+
+class BaseBoard(Static):
+    """Base class for all specialized entry boards."""
+    entry_data = reactive[dict[str, Any]]({})
+
+    def _render_card(self, title: str, rows: list[str]) -> str:
+        """Utility to render ASCII cards matching mockup style."""
+        width = 40
+        top = f"┌─ {title} " + "─" * (width - len(title) - 4) + "┐"
+        bottom = "└" + "─" * (width - 2) + "┘"
+        lines = [top]
+        for row in rows:
+            lines.append(f"│ {row:<{width-4}} │")
+        lines.append(bottom)
+        return "
+".join(lines)
+
+class IdleBoard(Static):
+    """Shown when no entry is selected."""
+    def render(self) -> str:
+        return "
+
+
+[b]Inspector Idle[/b]
+
+Select an entry from the grid
+to view details."
+
+class PasswordBoard(BaseBoard):
+    """Matches 'Password Board.png' mockup."""
+    def render(self) -> str:
+        d = self.entry_data
+        cred_rows = [
+            f"Label    : {d.get('label', '')}",
+            f"Username : {d.get('username', '')}",
+            f"URL      : {d.get('url', '')}",
+            "Password : [HIDDEN]",
+        ]
+        action_rows = [
+            "▣ Reveal (v)  ▣ QR (g)",
+            "▣ Edit (e)    ▣ Archive (a)",
+        ]
+        
+        return "
+".join([
+            self._render_card("Credentials", cred_rows),
+            "",
+            self._render_card("Quick Actions", action_rows)
+        ])
+
+class NoteBoard(BaseBoard):
+    """Matches 'Note Board.png' mockup."""
+    def render(self) -> str:
+        d = self.entry_data
+        content = d.get('content', '')
+        # Truncate for preview
+        preview = (content[:200] + '...') if len(content) > 200 else content
+        
+        content_rows = preview.splitlines()[:10]
+        action_rows = [
+            "▣ Edit Doc (e)  ▣ Export",
+            "▣ Archive (a)",
+        ]
+        
+        return "
+".join([
+            self._render_card("Content", content_rows),
+            "",
+            self._render_card("Quick Actions", action_rows)
+        ])
+
+class BoardContainer(Vertical):
+    """
+    Reactive container that swaps specialized boards based on entry kind.
+    """
+    DEFAULT_CSS = """
+    BoardContainer {
+        height: 1fr;
+        padding: 1;
+        content-align: center top;
+    }
+    """
+
+    def on_mount(self) -> None:
+        self._show_board("idle")
+
+    def update_entry(self, entry_id: int | None) -> None:
+        if entry_id is None:
+            self._show_board("idle")
+            return
+
+        app = self.app
+        if "entry" not in app.services:
+            return
+
+        entry = app.services["entry"].retrieve_entry(entry_id)
+        if not entry:
+            self._show_board("idle")
+            return
+
+        kind = str(entry.get("kind") or entry.get("type") or "").lower()
+        
+        # Select appropriate board
+        if kind in {"password", "stored_password"}:
+            board = self._show_board("password")
+            board.entry_data = entry
+        elif kind in {"document", "note"}:
+            board = self._show_board("note")
+            board.entry_data = entry
+        else:
+            # Fallback for now
+            board = self._show_board("password")
+            board.entry_data = entry
+
+    def _show_board(self, board_type: str) -> Any:
+        self.remove_children()
+        if board_type == "idle":
+            new_board = IdleBoard()
+        elif board_type == "password":
+            new_board = PasswordBoard()
+        elif board_type == "note":
+            new_board = NoteBoard()
+        else:
+            new_board = IdleBoard()
+            
+        self.mount(new_board)
+        return new_board
diff --git a/src/seedpass/tui_v3/widgets/sidebar.py b/src/seedpass/tui_v3/widgets/sidebar.py
new file mode 100644
index 00000000..40a5256e
--- /dev/null
+++ b/src/seedpass/tui_v3/widgets/sidebar.py
@@ -0,0 +1,85 @@
+from __future__ import annotations
+from typing import Any
+from textual.app import ComposeResult
+from textual.widgets import Tree, Static
+from textual.widgets.tree import TreeNode
+
+class ProfileTree(Tree):
+    """
+    A hierarchical sidebar that manages Seed Profiles, Managed Accounts, and Agents.
+    
+    Structure:
+    Root (Hidden)
+    ├── Fingerprint (Parent Seed)
+    │   ├── Managed Account 1
+    │   │   └── Agent 1
+    │   └── Managed Account 2
+    └── External Fingerprint
+    """
+    
+    def on_mount(self) -> None:
+        self.root.expand()
+        self._refresh_tree()
+
+    def _refresh_tree(self) -> None:
+        self.clear()
+        app = self.app
+        if "profile" not in app.services:
+            self.root.add_leaf("Profile Service Offline")
+            return
+
+        service = app.services["profile"]
+        profiles = service.list_profiles()
+        
+        # In v3, we will properly fetch nested accounts. 
+        # For this initial scaffold, we populate the top-level fingerprints.
+        for fp in profiles:
+            icon = "■ " if fp == app.active_fingerprint else "□ "
+            label = f"{icon}{fp[:12]}..." if len(fp) > 12 else f"{icon}{fp}"
+            node = self.root.add(label, data=fp, expand=True)
+            
+            # Placeholder for child accounts - in a real run, 
+            # we would query the service for sub-entries of this FP.
+            # node.add_leaf("  ├─ Managed Account 1")
+
+    def on_tree_node_selected(self, event: Tree.NodeSelected) -> None:
+        """Handle profile selection."""
+        fp = event.node.data
+        if fp and isinstance(fp, str):
+            self.app.active_fingerprint = fp
+            self.app.notify(f"Switched to profile: {fp[:8]}")
+
+class SidebarContainer(Static):
+    """Container for the sidebar tree and toggle."""
+    def compose(self) -> ComposeResult:
+        yield Static("PROFILES", id="sidebar-title")
+        yield ProfileTree("Profiles", id="profile-tree")
+
+    DEFAULT_CSS = """
+    SidebarContainer {
+        width: 31;
+        background: #0d1114;
+        border-right: solid #1a3024;
+    }
+    #sidebar-title {
+        background: #1a3024;
+        color: #58f29d;
+        text-style: bold;
+        padding: 0 1;
+        height: 1;
+    }
+    #profile-tree {
+        background: transparent;
+        color: #97b8a6;
+        border: none;
+        padding: 0;
+    }
+    #profile-tree > .tree--guides {
+        color: #1a3024;
+    }
+    #profile-tree > .tree--cursor {
+        background: #122019;
+        color: #58f29d;
+        text-style: bold;
+    }
+    """