diff --git a/claude_bottle/backend/docker/bottle_state.py b/claude_bottle/backend/docker/bottle_state.py
index 912a794..19b1bf2 100644
--- a/claude_bottle/backend/docker/bottle_state.py
+++ b/claude_bottle/backend/docker/bottle_state.py
@@ -45,6 +45,10 @@ _STATE_SUBDIR = "state"
 _PER_BOTTLE_DOCKERFILE_NAME = "Dockerfile"
 _TRANSCRIPT_SUBDIR = "transcript"
 _METADATA_NAME = "metadata.json"
+# Empty marker file. capability_apply writes it before teardown so
+# cli.py's session-end cleanup knows to preserve the state dir for
+# `cli.py resume <identity>`. Absent = clean up.
+_PRESERVE_MARKER = ".preserve"
 
 # 5 chars of base36 alphabet ≈ 60M combinations. Plenty for human
 # operators starting bottles by hand; collision-free in practice.
@@ -155,14 +159,61 @@ def transcript_snapshot_dir(identity: str) -> Path:
     return bottle_state_dir(identity) / _TRANSCRIPT_SUBDIR
 
 
+# --- Preserve-on-close marker ----------------------------------------------
+
+
+def preserve_marker_path(identity: str) -> Path:
+    return bottle_state_dir(identity) / _PRESERVE_MARKER
+
+
+def mark_preserved(identity: str) -> Path:
+    """Mark this bottle's state for preservation across session
+    teardown. Written by capability_apply.apply_capability_change so
+    cli.py's session-end cleanup leaves the state dir intact for a
+    subsequent `cli.py resume`."""
+    path = preserve_marker_path(identity)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.touch()
+    return path
+
+
+def is_preserved(identity: str) -> bool:
+    return preserve_marker_path(identity).exists()
+
+
+def clear_preserve_marker(identity: str) -> None:
+    """Idempotent removal. Called at fresh launch (start or resume)
+    so a marker left from a prior capability-block doesn't keep
+    state alive past the next normal session-end."""
+    try:
+        preserve_marker_path(identity).unlink()
+    except FileNotFoundError:
+        pass
+
+
+def cleanup_state(identity: str) -> None:
+    """Remove the per-bottle state dir entirely. Called by cli.py
+    when a bottle session ends and is_preserved(identity) is False.
+    Idempotent — missing dir is success."""
+    import shutil
+    state_dir = bottle_state_dir(identity)
+    if state_dir.is_dir():
+        shutil.rmtree(state_dir, ignore_errors=True)
+
+
 __all__ = [
     "BottleMetadata",
     "bottle_identity",
     "bottle_state_dir",
+    "cleanup_state",
+    "clear_preserve_marker",
+    "is_preserved",
+    "mark_preserved",
     "metadata_path",
     "per_bottle_dockerfile",
     "per_bottle_dockerfile_path",
     "per_bottle_image_tag",
+    "preserve_marker_path",
     "read_metadata",
     "transcript_snapshot_dir",
     "write_metadata",
diff --git a/claude_bottle/backend/docker/capability_apply.py b/claude_bottle/backend/docker/capability_apply.py
index 414e59f..1a8b96a 100644
--- a/claude_bottle/backend/docker/capability_apply.py
+++ b/claude_bottle/backend/docker/capability_apply.py
@@ -37,6 +37,7 @@ from pathlib import Path
 
 from ...log import info, warn
 from .bottle_state import (
+    mark_preserved,
     per_bottle_dockerfile,
     per_bottle_dockerfile_path,
     transcript_snapshot_dir,
@@ -114,9 +115,14 @@ def apply_capability_change(slug: str, new_dockerfile: str) -> tuple[str, str]:
         raise CapabilityApplyError("proposed Dockerfile is empty")
     before = fetch_current_dockerfile(slug)
 
-    _snapshot_transcript(slug)
+    snapshot_transcript(slug)
     _push_working_tree(slug)
     write_per_bottle_dockerfile(slug, new_dockerfile)
+    # Set the preserve marker BEFORE teardown so cli.py's session-end
+    # cleanup sees it and keeps the state dir intact for the
+    # operator's `cli.py resume <identity>`. Without the marker the
+    # state dir would be deleted as part of normal session end.
+    mark_preserved(slug)
     _teardown_bottle(slug)
 
     return before, new_dockerfile
@@ -133,12 +139,19 @@ def _repo_dockerfile_path() -> Path:
     return Path(__file__).resolve().parent.parent.parent.parent / "Dockerfile"
 
 
-def _snapshot_transcript(slug: str) -> None:
+def snapshot_transcript(slug: str) -> None:
     """`docker cp` /home/node/.claude out of the agent container into
     ~/.claude-bottle/state/<slug>/transcript/. Best-effort: missing
     container, missing dir, or cp error all log a warning and return.
     The transcript is what `claude --resume` reads to pick up where
-    the agent left off."""
+    the agent left off.
+
+    Called from two places:
+      - capability-apply, before tearing the bottle down.
+      - cli.py's session-end path, before the launch context closes,
+        so a crash or normal exit also leaves a transcript on disk
+        (deleted along with the state dir on clean exit, kept on
+        crash or capability-block per the preserve marker)."""
     container = _agent_container_name(slug)
     dest = transcript_snapshot_dir(slug)
     if dest.exists():
@@ -151,11 +164,11 @@ def _snapshot_transcript(slug: str) -> None:
     )
     if r.returncode != 0:
         warn(
-            f"capability-apply: transcript snapshot skipped "
+            f"transcript snapshot skipped "
             f"({(r.stderr or '').strip() or 'no transcript dir in container?'})"
         )
         return
-    info(f"capability-apply: transcript snapshotted to {dest}")
+    info(f"transcript snapshotted to {dest}")
 
 
 def _push_working_tree(slug: str) -> None:
@@ -207,4 +220,5 @@ __all__ = [
     "CapabilityApplyError",
     "apply_capability_change",
     "fetch_current_dockerfile",
+    "snapshot_transcript",
 ]
diff --git a/claude_bottle/backend/docker/prepare.py b/claude_bottle/backend/docker/prepare.py
index d3ba481..d4e8bf7 100644
--- a/claude_bottle/backend/docker/prepare.py
+++ b/claude_bottle/backend/docker/prepare.py
@@ -30,6 +30,7 @@ from .git_gate import DockerGitGate, git_gate_container_name
 from .bottle_state import (
     BottleMetadata,
     bottle_identity,
+    clear_preserve_marker,
     per_bottle_dockerfile,
     per_bottle_dockerfile_path,
     per_bottle_image_tag,
@@ -73,6 +74,10 @@ def resolve_plan(
         copy_cwd=spec.copy_cwd,
         started_at=datetime.now(timezone.utc).isoformat(),
     ))
+    # Clear any leftover preserve marker from a prior capability-block
+    # so this fresh launch can be cleaned up at session-end unless
+    # the agent triggers another capability-block.
+    clear_preserve_marker(slug)
 
     # PRD 0016 capability-block: if a per-bottle Dockerfile has been
     # written (via apply_capability_change), the base image becomes
diff --git a/claude_bottle/cli/cleanup.py b/claude_bottle/cli/cleanup.py
index cfaafa1..52b861b 100644
--- a/claude_bottle/cli/cleanup.py
+++ b/claude_bottle/cli/cleanup.py
@@ -1,10 +1,19 @@
 """cleanup: stop and remove all orphaned claude-bottle resources
-(containers + networks) left behind by previous bottles."""
+(containers + networks) left behind by previous bottles, plus
+optionally the per-bottle state dirs under ~/.claude-bottle/state/.
+
+State cleanup is prompted separately from container cleanup because
+the trade-off is different: containers + networks are pure debris,
+but a state dir may carry a resumable bottle (capability-block
+rebuild + transcript snapshot) the operator still wants."""
 
 from __future__ import annotations
 
+import shutil
 import sys
+from pathlib import Path
 
+from .. import supervise as _supervise
 from ..backend import get_bottle_backend
 from ..log import info
 from ._common import read_tty_line
@@ -13,19 +22,76 @@ from ._common import read_tty_line
 def cmd_cleanup(_argv: list[str]) -> int:
     backend = get_bottle_backend()
     plan = backend.prepare_cleanup()
+    state_dirs = _enumerate_state_dirs()
 
-    if plan.empty:
+    if plan.empty and not state_dirs:
         info("no claude-bottle resources to clean up")
         return 0
 
-    plan.print()
-    sys.stderr.write("claude-bottle: remove all of the above? [y/N] ")
+    if not plan.empty:
+        plan.print()
+        if _prompt_yes("remove all of the above?"):
+            backend.cleanup(plan)
+            info("containers + networks: cleaned")
+        else:
+            info("containers + networks: skipped")
+
+    if state_dirs:
+        _print_state(state_dirs)
+        if _prompt_yes(
+            "remove per-bottle state? (loses resumable bottles)",
+        ):
+            for d in state_dirs:
+                shutil.rmtree(d, ignore_errors=True)
+            info(f"state: removed {len(state_dirs)} dir(s)")
+        else:
+            info("state: skipped")
+
+    return 0
+
+
+# --- State enumeration + display ------------------------------------------
+
+
+def _enumerate_state_dirs() -> list[Path]:
+    """All per-bottle state dirs under ~/.claude-bottle/state/.
+    Sorted for stable preflight output."""
+    state_root = _supervise.claude_bottle_root() / "state"
+    if not state_root.is_dir():
+        return []
+    return sorted(p for p in state_root.iterdir() if p.is_dir())
+
+
+def _state_summary(path: Path) -> str:
+    """One-line description suitable for the cleanup prompt. Calls
+    out resumability so the operator can decide whether removing it
+    loses anything they care about."""
+    flags: list[str] = []
+    if (path / "metadata.json").is_file():
+        flags.append("resumable")
+    else:
+        flags.append("no metadata.json (orphan)")
+    if (path / "Dockerfile").is_file():
+        flags.append("rebuilt Dockerfile")
+    if (path / "transcript").is_dir():
+        flags.append("transcript snapshot")
+    if (path / ".preserve").is_file():
+        flags.append("preserve marker")
+    return f"state:     {path.name} ({', '.join(flags)})"
+
+
+def _print_state(dirs: list[Path]) -> None:
+    print(file=sys.stderr)
+    for d in dirs:
+        info(_state_summary(d))
+    print(file=sys.stderr)
+
+
+# --- Prompt ----------------------------------------------------------------
+
+
+def _prompt_yes(message: str) -> bool:
+    sys.stderr.write(f"claude-bottle: {message} [y/N] ")
     sys.stderr.flush()
     reply = read_tty_line()
-    if reply not in ("y", "Y", "yes", "YES"):
-        info("aborted")
-        return 0
-
-    backend.cleanup(plan)
-    info("done")
-    return 0
+    return reply in ("y", "Y", "yes", "YES")
diff --git a/claude_bottle/cli/start.py b/claude_bottle/cli/start.py
index 81fdbfc..45b5c74 100644
--- a/claude_bottle/cli/start.py
+++ b/claude_bottle/cli/start.py
@@ -17,6 +17,12 @@ import tempfile
 from pathlib import Path
 
 from ..backend import BottleSpec, get_bottle_backend
+from ..backend.docker.bottle_state import (
+    cleanup_state,
+    is_preserved,
+    mark_preserved,
+)
+from ..backend.docker.capability_apply import snapshot_transcript
 from ..log import die, info
 from ..manifest import Manifest
 from ._common import PROG, USER_CWD, read_tty_line
@@ -97,15 +103,51 @@ def _launch_bottle(
             claude_args = ["--dangerously-skip-permissions"]
             if remote_control:
                 claude_args.append("--remote-control")
-            bottle.exec_claude(claude_args, tty=True)
-            info(f"session ended; container {bottle.name} will be removed")
-            if identity:
-                info(f"to resume this bottle: ./cli.py resume {identity}")
-            return 0
+            exit_code = bottle.exec_claude(claude_args, tty=True)
+            info(
+                f"session ended (exit {exit_code}); "
+                f"container {bottle.name} will be removed"
+            )
+            # While the container is still alive: always snapshot the
+            # transcript and — if the agent exited non-zero — mark
+            # the state for preservation. Capability-block already
+            # did both before triggering teardown from the dashboard;
+            # this picks up crashes / Ctrl-Cs / OOM kills the same
+            # way. snapshot_transcript is best-effort so the
+            # capability-block path's prior snapshot isn't clobbered
+            # when the container is already gone.
+            _capture_session_state(identity, exit_code)
+        # Context exited → containers + networks gone. Now decide
+        # what to do with the per-bottle state dir on the host: any
+        # preserve marker (capability-block OR crash) keeps it; a
+        # clean exit cleans it up so ~/.claude-bottle/state/ doesn't
+        # accumulate per-launch debris.
+        _settle_state(identity)
+        return 0
     finally:
         shutil.rmtree(stage_dir, ignore_errors=True)
 
 
+def _capture_session_state(identity: str, exit_code: int) -> None:
+    """Inside the launch context, while the container is still
+    alive: snapshot the transcript and mark for preservation if
+    claude crashed. Pure-function-ish; tests stub the helpers."""
+    if not identity:
+        return
+    snapshot_transcript(identity)
+    if exit_code != 0:
+        mark_preserved(identity)
+
+
+def _settle_state(identity: str) -> None:
+    if not identity:
+        return
+    if is_preserved(identity):
+        info(f"to resume this bottle: ./cli.py resume {identity}")
+        return
+    cleanup_state(identity)
+
+
 def _identity_from_plan(plan: object) -> str:
     """Backend-specific: the docker plan exposes the identity as
     `.slug`. Other backends in the future would expose their own
diff --git a/tests/unit/test_bottle_state.py b/tests/unit/test_bottle_state.py
index 4fe2287..858b8b4 100644
--- a/tests/unit/test_bottle_state.py
+++ b/tests/unit/test_bottle_state.py
@@ -114,6 +114,60 @@ class TestBottleIdentity(unittest.TestCase):
         self.assertTrue(identity.startswith("my-agent-"))
 
 
+class TestPreserveMarker(_FakeHomeMixin, unittest.TestCase):
+    """The .preserve marker is how capability_apply tells cli.py's
+    session-end cleanup to keep the state dir instead of removing it."""
+
+    def setUp(self):
+        self._setup_fake_home()
+
+    def tearDown(self):
+        self._teardown_fake_home()
+
+    def test_default_is_unpreserved(self):
+        self.assertFalse(bottle_state.is_preserved("dev-x"))
+
+    def test_mark_then_is_preserved(self):
+        bottle_state.mark_preserved("dev-x")
+        self.assertTrue(bottle_state.is_preserved("dev-x"))
+
+    def test_clear_removes_marker(self):
+        bottle_state.mark_preserved("dev-x")
+        bottle_state.clear_preserve_marker("dev-x")
+        self.assertFalse(bottle_state.is_preserved("dev-x"))
+
+    def test_clear_is_idempotent(self):
+        # No marker present — should not raise.
+        bottle_state.clear_preserve_marker("never-existed")
+        self.assertFalse(bottle_state.is_preserved("never-existed"))
+
+    def test_marker_path_under_state_dir(self):
+        path = bottle_state.preserve_marker_path("dev-x")
+        self.assertTrue(str(path).endswith("/.claude-bottle/state/dev-x/.preserve"))
+
+
+class TestCleanupState(_FakeHomeMixin, unittest.TestCase):
+    """cleanup_state removes the entire per-bottle state dir.
+    Called by cli.py when a session ends without the preserve marker."""
+
+    def setUp(self):
+        self._setup_fake_home()
+
+    def tearDown(self):
+        self._teardown_fake_home()
+
+    def test_removes_state_dir_and_contents(self):
+        bottle_state.write_per_bottle_dockerfile("dev-x", "FROM x\n")
+        d = bottle_state.bottle_state_dir("dev-x")
+        self.assertTrue(d.is_dir())
+        bottle_state.cleanup_state("dev-x")
+        self.assertFalse(d.exists())
+
+    def test_idempotent_when_dir_missing(self):
+        # Never created — should not raise.
+        bottle_state.cleanup_state("never-existed")
+
+
 class TestBottleMetadata(_FakeHomeMixin, unittest.TestCase):
     def setUp(self):
         self._setup_fake_home()
diff --git a/tests/unit/test_capability_apply.py b/tests/unit/test_capability_apply.py
index e3fca9f..bcef7fb 100644
--- a/tests/unit/test_capability_apply.py
+++ b/tests/unit/test_capability_apply.py
@@ -63,7 +63,7 @@ class TestApplyCapabilityChange(_FakeHomeMixin, unittest.TestCase):
         # job is to sequence write + snapshot + push + teardown; we
         # validate that sequence here, not the docker primitives.
         self._calls: list[str] = []
-        self._orig_snapshot = capability_apply._snapshot_transcript
+        self._orig_snapshot = capability_apply.snapshot_transcript
         self._orig_push = capability_apply._push_working_tree
         self._orig_teardown = capability_apply._teardown_bottle
 
@@ -76,12 +76,12 @@ class TestApplyCapabilityChange(_FakeHomeMixin, unittest.TestCase):
         def stub_teardown(slug):
             self._calls.append(f"teardown:{slug}")
 
-        capability_apply._snapshot_transcript = stub_snapshot  # type: ignore[assignment]
+        capability_apply.snapshot_transcript = stub_snapshot  # type: ignore[assignment]
         capability_apply._push_working_tree = stub_push  # type: ignore[assignment]
         capability_apply._teardown_bottle = stub_teardown  # type: ignore[assignment]
 
     def tearDown(self):
-        capability_apply._snapshot_transcript = self._orig_snapshot  # type: ignore[assignment]
+        capability_apply.snapshot_transcript = self._orig_snapshot  # type: ignore[assignment]
         capability_apply._push_working_tree = self._orig_push  # type: ignore[assignment]
         capability_apply._teardown_bottle = self._orig_teardown  # type: ignore[assignment]
         self._teardown_fake_home()
@@ -107,6 +107,14 @@ class TestApplyCapabilityChange(_FakeHomeMixin, unittest.TestCase):
             self._calls,
         )
 
+    def test_marks_preserved_before_teardown(self):
+        # cli.py's session-end cleanup reads the marker after the
+        # bottle is torn down. The marker must therefore be written
+        # before teardown — otherwise the cleanup would see no
+        # marker and rm the state dir we just populated.
+        apply_capability_change("dev", "FROM new\n")
+        self.assertTrue(bottle_state.is_preserved("dev"))
+
     def test_first_change_falls_back_to_repo_dockerfile_for_before(self):
         # No per-bottle override yet — before-diff comes from the
         # repo's Dockerfile.
diff --git a/tests/unit/test_cli_cleanup.py b/tests/unit/test_cli_cleanup.py
new file mode 100644
index 0000000..97c04ac
--- /dev/null
+++ b/tests/unit/test_cli_cleanup.py
@@ -0,0 +1,102 @@
+"""Unit: cli/cleanup.py state-dir enumeration + summary.
+
+The end-to-end cleanup-with-prompt flow is exercised manually;
+here we cover the state-dir display logic so a regression in the
+resumable / orphan / rebuild flags surfaces in unit CI."""
+
+import tempfile
+import unittest
+from pathlib import Path
+
+from claude_bottle import supervise
+from claude_bottle.backend.docker import bottle_state
+from claude_bottle.cli.cleanup import _enumerate_state_dirs, _state_summary
+
+
+class _FakeHomeMixin:
+    def _setup_fake_home(self):
+        self._tmp = tempfile.TemporaryDirectory(prefix="cli-cleanup-test.")
+        original = supervise.claude_bottle_root
+
+        def fake_root() -> Path:
+            return Path(self._tmp.name) / ".claude-bottle"
+
+        supervise.claude_bottle_root = fake_root  # type: ignore[assignment]
+        self._restore = lambda: setattr(supervise, "claude_bottle_root", original)
+
+    def _teardown_fake_home(self):
+        self._restore()
+        self._tmp.cleanup()
+
+
+class TestEnumerateStateDirs(_FakeHomeMixin, unittest.TestCase):
+    def setUp(self):
+        self._setup_fake_home()
+
+    def tearDown(self):
+        self._teardown_fake_home()
+
+    def test_empty_when_no_state_root(self):
+        self.assertEqual([], _enumerate_state_dirs())
+
+    def test_lists_each_identity_dir(self):
+        bottle_state.write_per_bottle_dockerfile("dev-aaa", "FROM x\n")
+        bottle_state.write_per_bottle_dockerfile("api-bbb", "FROM y\n")
+        dirs = _enumerate_state_dirs()
+        self.assertEqual(
+            ["api-bbb", "dev-aaa"],
+            [p.name for p in dirs],
+        )
+
+    def test_sorted_for_stable_preflight(self):
+        for name in ("z", "a", "m"):
+            bottle_state.write_per_bottle_dockerfile(name, "FROM x\n")
+        names = [p.name for p in _enumerate_state_dirs()]
+        self.assertEqual(["a", "m", "z"], names)
+
+
+class TestStateSummary(_FakeHomeMixin, unittest.TestCase):
+    def setUp(self):
+        self._setup_fake_home()
+
+    def tearDown(self):
+        self._teardown_fake_home()
+
+    def _path(self, name: str) -> Path:
+        return bottle_state.bottle_state_dir(name)
+
+    def test_orphan_state_dir(self):
+        # Only a Dockerfile, no metadata.json — the "api / dev" shape
+        # that comes from pre-identity-fix code.
+        bottle_state.write_per_bottle_dockerfile("orphan", "FROM old\n")
+        s = _state_summary(self._path("orphan"))
+        self.assertIn("orphan", s)
+        self.assertIn("no metadata.json", s)
+        self.assertIn("rebuilt Dockerfile", s)
+
+    def test_resumable_state_dir(self):
+        bottle_state.write_metadata(bottle_state.BottleMetadata(
+            identity="dev-aaa", agent_name="dev",
+            cwd="/proj/A", copy_cwd=True, started_at="t",
+        ))
+        s = _state_summary(self._path("dev-aaa"))
+        self.assertIn("resumable", s)
+        self.assertNotIn("rebuilt Dockerfile", s)
+
+    def test_resumable_with_capability_rebuild_and_preserve_marker(self):
+        bottle_state.write_metadata(bottle_state.BottleMetadata(
+            identity="dev-bbb", agent_name="dev",
+            cwd="", copy_cwd=False, started_at="t",
+        ))
+        bottle_state.write_per_bottle_dockerfile("dev-bbb", "FROM rebuilt\n")
+        bottle_state.transcript_snapshot_dir("dev-bbb").mkdir(parents=True)
+        bottle_state.mark_preserved("dev-bbb")
+        s = _state_summary(self._path("dev-bbb"))
+        self.assertIn("resumable", s)
+        self.assertIn("rebuilt Dockerfile", s)
+        self.assertIn("transcript snapshot", s)
+        self.assertIn("preserve marker", s)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/unit/test_cli_start_settle.py b/tests/unit/test_cli_start_settle.py
new file mode 100644
index 0000000..f6fad89
--- /dev/null
+++ b/tests/unit/test_cli_start_settle.py
@@ -0,0 +1,93 @@
+"""Unit: cli/start.py session-end state capture (crash preservation).
+
+The launch-context machinery is covered by integration; this isolates
+the post-exec_claude decision: snapshot transcript + mark for
+preservation if non-zero exit, no-op for clean exit."""
+
+import tempfile
+import unittest
+from pathlib import Path
+
+from claude_bottle import supervise
+from claude_bottle.backend.docker import bottle_state
+from claude_bottle.cli import start as start_mod
+
+
+class _FakeHomeMixin:
+    def _setup_fake_home(self):
+        self._tmp = tempfile.TemporaryDirectory(prefix="cli-start-settle.")
+        self._original = supervise.claude_bottle_root
+
+        def fake_root() -> Path:
+            return Path(self._tmp.name) / ".claude-bottle"
+
+        supervise.claude_bottle_root = fake_root  # type: ignore[assignment]
+
+    def _teardown_fake_home(self):
+        supervise.claude_bottle_root = self._original  # type: ignore[assignment]
+        self._tmp.cleanup()
+
+
+class TestCaptureSessionState(_FakeHomeMixin, unittest.TestCase):
+    def setUp(self):
+        self._setup_fake_home()
+        # Stub the docker-dependent snapshot call so this stays a
+        # unit test. apply_capability_change's integration test
+        # covers the real docker cp path.
+        self._snap_calls: list[str] = []
+        self._orig_snap = start_mod.snapshot_transcript
+        start_mod.snapshot_transcript = lambda identity: (
+            self._snap_calls.append(identity)
+        )
+
+    def tearDown(self):
+        start_mod.snapshot_transcript = self._orig_snap
+        self._teardown_fake_home()
+
+    def test_clean_exit_snapshots_but_does_not_mark(self):
+        start_mod._capture_session_state("dev-abc", exit_code=0)
+        self.assertEqual(["dev-abc"], self._snap_calls)
+        self.assertFalse(bottle_state.is_preserved("dev-abc"))
+
+    def test_crash_snapshots_and_marks(self):
+        start_mod._capture_session_state("dev-abc", exit_code=137)
+        self.assertEqual(["dev-abc"], self._snap_calls)
+        self.assertTrue(bottle_state.is_preserved("dev-abc"))
+
+    def test_ctrl_c_treated_as_crash(self):
+        # SIGINT delivers exit 130; the operator may have Ctrl-C'd
+        # because something went wrong, so we preserve.
+        start_mod._capture_session_state("dev-abc", exit_code=130)
+        self.assertTrue(bottle_state.is_preserved("dev-abc"))
+
+    def test_empty_identity_is_noop(self):
+        # Backends without an identity field shouldn't crash this
+        # path (the _identity_from_plan helper falls back to "").
+        start_mod._capture_session_state("", exit_code=137)
+        self.assertEqual([], self._snap_calls)
+
+
+class TestSettleState(_FakeHomeMixin, unittest.TestCase):
+    def setUp(self):
+        self._setup_fake_home()
+
+    def tearDown(self):
+        self._teardown_fake_home()
+
+    def test_preserved_state_survives(self):
+        bottle_state.write_per_bottle_dockerfile("dev-abc", "FROM x\n")
+        bottle_state.mark_preserved("dev-abc")
+        start_mod._settle_state("dev-abc")
+        self.assertTrue(bottle_state.bottle_state_dir("dev-abc").is_dir())
+
+    def test_unpreserved_state_is_cleaned(self):
+        bottle_state.write_per_bottle_dockerfile("dev-abc", "FROM x\n")
+        start_mod._settle_state("dev-abc")
+        self.assertFalse(bottle_state.bottle_state_dir("dev-abc").exists())
+
+    def test_empty_identity_is_noop(self):
+        start_mod._settle_state("")  # should not raise
+
+
+if __name__ == "__main__":
+    unittest.main()