diff --git a/bot_bottle/backend/resolve_common.py b/bot_bottle/backend/resolve_common.py
index c316173..549a466 100644
--- a/bot_bottle/backend/resolve_common.py
+++ b/bot_bottle/backend/resolve_common.py
@@ -33,8 +33,18 @@ from . import BottleSpec
 
 def mint_slug(spec: BottleSpec) -> str:
     """Return the bottle identity: the recorded identity for a resume,
-    or a freshly minted one for a new start."""
-    return spec.identity or bottle_identity(spec.agent_name)
+    or a freshly minted one for a new start.
+
+    When a label is provided it becomes the full slug (no random suffix),
+    so two launches with the same label collide by design.  When no label
+    is given the identity is minted with a random suffix to avoid
+    collisions between anonymous launches of the same agent."""
+    if spec.identity:
+        return spec.identity
+    if spec.label:
+        from .docker import util as docker_mod
+        return docker_mod.slugify(spec.label)
+    return bottle_identity(spec.agent_name)
 
 
 def write_launch_metadata(
diff --git a/bot_bottle/cli/start.py b/bot_bottle/cli/start.py
index a658b56..55a47ac 100644
--- a/bot_bottle/cli/start.py
+++ b/bot_bottle/cli/start.py
@@ -20,9 +20,11 @@ from ..agent_provider import runtime_for
 from ..backend import (
     Bottle,
     BottleSpec,
+    enumerate_active_agents,
     get_bottle_backend,
     known_backend_names,
 )
+from ..backend.docker import util as docker_mod
 from ..backend.docker.bottle_plan import DockerBottlePlan
 from ..bottle_state import (
     cleanup_state,
@@ -74,6 +76,7 @@ def cmd_start(argv: list[str]) -> int:
     backend_name: str | None = args.backend
 
     label, color = tui.name_color_modal(default_label=agent_name)
+    label, color = _resolve_unique_label(label, color)
 
     spec = BottleSpec(
         manifest=manifest,
@@ -191,6 +194,21 @@ def _identity_from_plan(plan: object) -> str:
     return getattr(plan, "slug", "")
 
 
+def _resolve_unique_label(label: str, color: str) -> tuple[str, str]:
+    """Re-prompt with a disclaimer until the label's slug is not already
+    in use among running bottles.  Passes through unchanged when no
+    collision is found on the first check."""
+    while True:
+        slug_candidate = docker_mod.slugify(label)
+        active_slugs = {a.slug for a in enumerate_active_agents()}
+        if slug_candidate not in active_slugs:
+            return label, color
+        label, color = tui.name_color_modal(
+            default_label=label,
+            disclaimer=f'"{label}" is already in use',
+        )
+
+
 def _text_prompt_yes() -> bool:
     """Default `prompt_yes` for CLI use: reads y/N from the
     controlling tty via stderr prompt + tty-line read."""
diff --git a/bot_bottle/cli/tui.py b/bot_bottle/cli/tui.py
index 4ecac36..57cced3 100644
--- a/bot_bottle/cli/tui.py
+++ b/bot_bottle/cli/tui.py
@@ -243,11 +243,15 @@ _COLOR_NONE = "(none)"
 def name_color_modal(
     default_label: str,
     *,
+    disclaimer: str = "",
     tty_path: str = "/dev/tty",
 ) -> tuple[str, str]:
     """Present a two-step curses modal: first edit the agent label,
     then optionally pick a color.
 
+    ``disclaimer`` is shown below the input field — use it to surface
+    an error from a previous attempt (e.g. name already in use).
+
     Returns ``(label, color)`` where ``color`` is one of the 16 ANSI
     color name strings or ``""`` for no color. Falls back to
     ``(default_label, "")`` on any error (terminal too small, not a tty).
@@ -259,14 +263,14 @@ def name_color_modal(
 
     try:
         fd_dup = os.dup(tty_fd.fileno())
-        return _run_name_color(default_label, tty_fd=fd_dup)
+        return _run_name_color(default_label, tty_fd=fd_dup, disclaimer=disclaimer)
     except Exception:  # noqa: BLE001  # pylint: disable=broad-exception-caught
         return default_label, ""
     finally:
         tty_fd.close()
 
 
-def _run_name_color(default_label: str, *, tty_fd: int) -> tuple[str, str]:
+def _run_name_color(default_label: str, *, tty_fd: int, disclaimer: str = "") -> tuple[str, str]:
     import io
     orig_stdin = sys.__stdin__
     orig_stdout = sys.__stdout__
@@ -281,7 +285,7 @@ def _run_name_color(default_label: str, *, tty_fd: int) -> tuple[str, str]:
         curses.cbreak()
         screen.keypad(True)
         try:
-            label = _label_step(screen, default_label)
+            label = _label_step(screen, default_label, disclaimer=disclaimer)
             color = _color_step(screen, label)
         finally:
             screen.keypad(False)
@@ -294,14 +298,14 @@ def _run_name_color(default_label: str, *, tty_fd: int) -> tuple[str, str]:
     return label, color
 
 
-def _label_step(screen: Any, default_label: str) -> str:
+def _label_step(screen: Any, default_label: str, *, disclaimer: str = "") -> str:
     """Step 1: edit the label. First printable key replaces the
     pre-fill; subsequent keys append. Enter confirms."""
     text = default_label
     replaced = False  # True once the user has typed their first char
 
     while True:
-        _render_label(screen, text)
+        _render_label(screen, text, disclaimer=disclaimer)
         try:
             key = screen.getch()
         except KeyboardInterrupt:
@@ -325,7 +329,7 @@ def _label_step(screen: Any, default_label: str) -> str:
                 text += chr(key)
 
 
-def _render_label(screen: Any, text: str) -> None:
+def _render_label(screen: Any, text: str, *, disclaimer: str = "") -> None:
     screen.erase()
     rows, cols = screen.getmaxyx()
     sep = "─" * min(cols - 1, 40)
@@ -333,8 +337,12 @@ def _render_label(screen: Any, text: str) -> None:
     _addstr_safe(screen, 1, 0, sep)
     _addstr_safe(screen, 2, 0, text[:cols - 1], curses.A_REVERSE)
     _addstr_safe(screen, 3, 0, sep)
-    if rows > 5:
-        _addstr_safe(screen, 5, 0, "[any key] edit  [Enter] confirm", curses.A_DIM)
+    row = 4
+    if disclaimer and rows > row + 1:
+        _addstr_safe(screen, row, 0, disclaimer[:cols - 1], curses.A_BOLD)
+        row += 1
+    if rows > row + 1:
+        _addstr_safe(screen, row, 0, "[any key] edit  [Enter] confirm", curses.A_DIM)
     screen.refresh()
 
 
diff --git a/tests/unit/test_backend_prepare.py b/tests/unit/test_backend_prepare.py
index 3fab237..ee673a1 100644
--- a/tests/unit/test_backend_prepare.py
+++ b/tests/unit/test_backend_prepare.py
@@ -16,6 +16,7 @@ from bot_bottle import bottle_state
 from bot_bottle import supervise
 from bot_bottle.backend import BottleSpec
 from bot_bottle.backend.docker import DockerBottleBackend
+from bot_bottle.backend.resolve_common import mint_slug
 from bot_bottle.backend.smolmachines import SmolmachinesBottleBackend
 from bot_bottle.manifest import Manifest
 
@@ -115,5 +116,36 @@ class TestSmolmachinesPrepare(_FakeStateMixin, unittest.TestCase):
         )
 
 
+class TestMintSlug(unittest.TestCase):
+    def _spec(self, *, label: str = "", identity: str = "") -> BottleSpec:
+        manifest = _manifest()
+        return BottleSpec(
+            manifest=manifest,
+            agent_name="demo",
+            copy_cwd=False,
+            user_cwd="/tmp",
+            label=label,
+            identity=identity,
+        )
+
+    def test_no_label_uses_agent_name_with_random_suffix(self) -> None:
+        slug = mint_slug(self._spec(label=""))
+        self.assertTrue(slug.startswith("demo-"), slug)
+        # random suffix present — slug is longer than just "demo"
+        self.assertGreater(len(slug), len("demo-"))
+
+    def test_label_becomes_exact_slug(self) -> None:
+        slug = mint_slug(self._spec(label="my-run"))
+        self.assertEqual("my-run", slug)
+
+    def test_label_with_spaces_slugified_no_suffix(self) -> None:
+        slug = mint_slug(self._spec(label="My Feature Run"))
+        self.assertEqual("my-feature-run", slug)
+
+    def test_identity_takes_precedence_over_label(self) -> None:
+        slug = mint_slug(self._spec(label="my-run", identity="fixed-id"))
+        self.assertEqual("fixed-id", slug)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/tests/unit/test_cli_start_selector.py b/tests/unit/test_cli_start_selector.py
index d34ee0e..d0876a1 100644
--- a/tests/unit/test_cli_start_selector.py
+++ b/tests/unit/test_cli_start_selector.py
@@ -14,6 +14,7 @@ from unittest.mock import MagicMock, patch
 
 import bot_bottle.cli.start as start_mod
 import bot_bottle.cli.tui as tui_mod
+from bot_bottle.backend import ActiveAgent
 
 
 def _make_manifest(agent_names: list[str]):
@@ -133,5 +134,63 @@ class TestCmdStartSelector(unittest.TestCase):
         self._launch_mock.assert_not_called()
 
 
+def _active_agent(slug: str) -> ActiveAgent:
+    return ActiveAgent(
+        backend_name="docker",
+        slug=slug,
+        agent_name="demo",
+        started_at="2026-01-01T00:00:00+00:00",
+        services=(),
+    )
+
+
+class TestCmdStartLabelCollision(unittest.TestCase):
+    """cmd_start re-prompts when the label's slug is already running."""
+
+    def setUp(self):
+        self._manifest = _make_manifest(["researcher"])
+        patch("bot_bottle.cli.start.Manifest.resolve", return_value=self._manifest).start()
+        self._launch_mock = patch(
+            "bot_bottle.cli.start._launch_bottle", return_value=0,
+        ).start()
+        self.addCleanup(patch.stopall)
+
+    def test_no_collision_proceeds_without_reprompt(self):
+        with (
+            patch.object(tui_mod, "name_color_modal", return_value=("researcher", "")) as modal,
+            patch("bot_bottle.cli.start.enumerate_active_agents", return_value=[]),
+        ):
+            rc = start_mod.cmd_start(["researcher"])
+        self.assertEqual(0, rc)
+        modal.assert_called_once()
+        self._launch_mock.assert_called_once()
+
+    def test_collision_reprompts_with_disclaimer(self):
+        collision_agent = _active_agent("researcher")
+        call_count = 0
+
+        def _modal(default_label: str, *, disclaimer: str = "", **_kw: object) -> tuple[str, str]:
+            nonlocal call_count
+            call_count += 1
+            if call_count == 1:
+                return "researcher", ""
+            return "researcher-2", ""
+
+        with (
+            patch.object(tui_mod, "name_color_modal", side_effect=_modal) as modal,
+            patch(
+                "bot_bottle.cli.start.enumerate_active_agents",
+                side_effect=[[collision_agent], []],
+            ),
+        ):
+            rc = start_mod.cmd_start(["researcher"])
+
+        self.assertEqual(0, rc)
+        self.assertEqual(2, modal.call_count)
+        second_call_kwargs = modal.call_args_list[1][1]
+        self.assertIn("researcher", second_call_kwargs.get("disclaimer", ""))
+        self.assertIn("already in use", second_call_kwargs.get("disclaimer", ""))
+
+
 if __name__ == "__main__":
     unittest.main()