diff --git a/agents/runner.py b/agents/runner.py
index 1182cbe..b8d02e8 100644
--- a/agents/runner.py
+++ b/agents/runner.py
@@ -1612,6 +1612,14 @@ def run_pipeline(
                 if agent_error:
                     error_msg += f": {agent_error}"
                 models.update_task(conn, task_id, status="blocked", blocked_reason=error_msg)
+                # Worktree cleanup on step failure (KIN-103)
+                if worktree_path and not dry_run:
+                    try:
+                        from core.worktree import cleanup_worktree
+                        p_path = str(Path(project_for_wt["path"]).expanduser())
+                        cleanup_worktree(worktree_path, p_path)
+                    except Exception:
+                        pass
                 return {
                     "success": False,
                     "error": error_msg,
@@ -1652,14 +1660,6 @@ def run_pipeline(
                 cleanup_worktree(worktree_path, p_path)
             except Exception:
                 pass  # Worktree errors must never block pipeline
-        elif worktree_path and not dry_run:
-            # Step failed — cleanup worktree without merging
-            try:
-                from core.worktree import cleanup_worktree
-                p_path = str(Path(project_for_wt["path"]).expanduser())
-                cleanup_worktree(worktree_path, p_path)
-            except Exception:
-                pass
 
         results.append(result)
 
diff --git a/tests/test_kin_103_worktrees.py b/tests/test_kin_103_worktrees.py
new file mode 100644
index 0000000..ed0f0d5
--- /dev/null
+++ b/tests/test_kin_103_worktrees.py
@@ -0,0 +1,457 @@
+"""KIN-103 — Regression + unit tests for worktrees_enabled feature.
+
+Covers:
+  1. core/worktree.py — create_worktree, merge_worktree, cleanup_worktree, ensure_gitignore
+  2. agents/runner.py run_pipeline — worktree lifecycle (create, merge, cleanup)
+     - eligible role + worktrees_enabled=True → worktree created
+     - non-eligible role → no worktree
+     - worktrees_enabled=False → no worktree
+     - success path → merge + cleanup called
+     - failure path → cleanup called without merge
+     - create_worktree returns None → graceful fallback, no crash
+     - non-git directory (create_worktree fails) → pipeline continues normally
+"""
+
+import subprocess
+from pathlib import Path
+from unittest.mock import MagicMock, call, patch
+
+import pytest
+
+from core.db import init_db
+from core import models
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# Shared fixtures
+# ─────────────────────────────────────────────────────────────────────────────
+
+@pytest.fixture
+def conn():
+    c = init_db(":memory:")
+    models.create_project(c, "wt1", "WT Project", "/projects/wtproject",
+                          tech_stack=["python"])
+    models.create_task(c, "WT1-001", "wt1", "Fix worktree bug",
+                       brief={"route_type": "debug"})
+    yield c
+    c.close()
+
+
+@pytest.fixture
+def conn_wt_enabled(conn):
+    """Project with worktrees_enabled=1."""
+    conn.execute("UPDATE projects SET worktrees_enabled=1 WHERE id='wt1'")
+    conn.commit()
+    return conn
+
+
+def _ok_run():
+    m = MagicMock()
+    m.returncode = 0
+    m.stdout = ""
+    m.stderr = ""
+    return m
+
+
+def _fail_run(stderr="git error"):
+    m = MagicMock()
+    m.returncode = 1
+    m.stdout = ""
+    m.stderr = stderr
+    return m
+
+
+def _claude_ok():
+    import json
+    m = MagicMock()
+    m.returncode = 0
+    m.stdout = json.dumps({"result": "done"})
+    m.stderr = ""
+    return m
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 1. core/worktree.py — create_worktree
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestCreateWorktree:
+    @patch("subprocess.run")
+    def test_create_worktree_success_returns_path(self, mock_run, tmp_path):
+        """create_worktree вызывает git worktree add и возвращает путь."""
+        from core.worktree import create_worktree
+        mock_run.return_value = _ok_run()
+
+        result = create_worktree(str(tmp_path), "WT1-001", "backend_dev")
+
+        assert result is not None
+        assert "WT1-001" in result
+        assert "backend_dev" in result
+
+    @patch("subprocess.run")
+    def test_create_worktree_calls_git_worktree_add(self, mock_run, tmp_path):
+        """create_worktree вызывает git worktree add с корректными аргументами."""
+        from core.worktree import create_worktree
+        mock_run.return_value = _ok_run()
+
+        create_worktree(str(tmp_path), "WT1-001", "debugger")
+
+        cmd = mock_run.call_args[0][0]
+        assert "worktree" in cmd
+        assert "add" in cmd
+
+    @patch("subprocess.run")
+    def test_create_worktree_git_fail_returns_none(self, mock_run, tmp_path):
+        """Если git возвращает non-zero returncode — create_worktree возвращает None."""
+        from core.worktree import create_worktree
+        mock_run.return_value = _fail_run("fatal: not a git repo")
+
+        result = create_worktree(str(tmp_path), "WT1-001", "debugger")
+
+        assert result is None
+
+    @patch("subprocess.run", side_effect=Exception("git not found"))
+    def test_create_worktree_exception_returns_none(self, mock_run, tmp_path):
+        """При исключении create_worktree возвращает None, не поднимает."""
+        from core.worktree import create_worktree
+
+        result = create_worktree(str(tmp_path), "WT1-001", "debugger")
+
+        assert result is None
+
+    @patch("subprocess.run")
+    def test_create_worktree_sanitizes_step_name(self, mock_run, tmp_path):
+        """Слэши и пробелы в step_name заменяются на _ в branch name."""
+        from core.worktree import create_worktree
+        mock_run.return_value = _ok_run()
+
+        result = create_worktree(str(tmp_path), "WT1-001", "role/with spaces")
+
+        assert result is not None
+        assert "/" not in Path(result).name
+        assert "role_with_spaces" in Path(result).name
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 2. core/worktree.py — merge_worktree
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestMergeWorktree:
+    @patch("subprocess.run")
+    def test_merge_worktree_success_returns_dict(self, mock_run, tmp_path):
+        """Успешный merge возвращает {success: True, conflicts: [], merged_files: [...]}."""
+        from core.worktree import merge_worktree
+
+        worktree_path = tmp_path / ".kin_worktrees" / "WT1-001-debugger"
+        worktree_path.mkdir(parents=True)
+
+        # First call: merge succeeds; second: diff
+        mock_run.side_effect = [
+            _ok_run(),                            # git merge --no-ff
+            _ok_run(),                            # git diff HEAD~1 HEAD --name-only
+        ]
+
+        result = merge_worktree(str(worktree_path), str(tmp_path))
+
+        assert result["success"] is True
+        assert result["conflicts"] == []
+
+    @patch("subprocess.run")
+    def test_merge_worktree_conflict_returns_conflicts(self, mock_run, tmp_path):
+        """При конфликте merge возвращает {success: False, conflicts: [...]}."""
+        from core.worktree import merge_worktree
+
+        worktree_path = tmp_path / ".kin_worktrees" / "WT1-001-debugger"
+        worktree_path.mkdir(parents=True)
+
+        conflict_diff = MagicMock()
+        conflict_diff.returncode = 0
+        conflict_diff.stdout = "src/app.py\nsrc/utils.py\n"
+        conflict_diff.stderr = ""
+
+        abort_result = _ok_run()
+
+        merge_fail = _fail_run("CONFLICT (content)")
+
+        mock_run.side_effect = [merge_fail, conflict_diff, abort_result]
+
+        result = merge_worktree(str(worktree_path), str(tmp_path))
+
+        assert result["success"] is False
+        assert "src/app.py" in result["conflicts"]
+
+    @patch("subprocess.run", side_effect=Exception("git gone"))
+    def test_merge_worktree_exception_returns_failure(self, mock_run, tmp_path):
+        """При исключении merge возвращает {success: False}, не поднимает."""
+        from core.worktree import merge_worktree
+
+        worktree_path = tmp_path / ".kin_worktrees" / "WT1-001-debugger"
+        worktree_path.mkdir(parents=True)
+
+        result = merge_worktree(str(worktree_path), str(tmp_path))
+
+        assert result["success"] is False
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 3. core/worktree.py — cleanup_worktree
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestCleanupWorktree:
+    @patch("subprocess.run")
+    def test_cleanup_calls_worktree_remove_and_branch_delete(self, mock_run, tmp_path):
+        """cleanup_worktree вызывает git worktree remove и git branch -D."""
+        from core.worktree import cleanup_worktree
+
+        worktree_path = tmp_path / ".kin_worktrees" / "WT1-001-debugger"
+        mock_run.return_value = _ok_run()
+
+        cleanup_worktree(str(worktree_path), str(tmp_path))
+
+        assert mock_run.call_count == 2
+        cmds = [call[0][0] for call in mock_run.call_args_list]
+        worktree_remove_cmd = cmds[0]
+        branch_delete_cmd = cmds[1]
+        assert "worktree" in worktree_remove_cmd and "remove" in worktree_remove_cmd
+        assert "branch" in branch_delete_cmd and "-D" in branch_delete_cmd
+
+    @patch("subprocess.run", side_effect=Exception("permission denied"))
+    def test_cleanup_worktree_exception_does_not_raise(self, mock_run, tmp_path):
+        """cleanup_worktree никогда не поднимает исключение."""
+        from core.worktree import cleanup_worktree
+
+        worktree_path = tmp_path / ".kin_worktrees" / "WT1-001-debugger"
+
+        # Must not raise
+        cleanup_worktree(str(worktree_path), str(tmp_path))
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 4. core/worktree.py — ensure_gitignore
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestEnsureGitignore:
+    def test_ensure_gitignore_creates_file_if_not_exists(self, tmp_path):
+        """ensure_gitignore создаёт .gitignore с .kin_worktrees/ если файла нет."""
+        from core.worktree import ensure_gitignore
+
+        ensure_gitignore(str(tmp_path))
+
+        gitignore = tmp_path / ".gitignore"
+        assert gitignore.exists()
+        assert ".kin_worktrees/" in gitignore.read_text()
+
+    def test_ensure_gitignore_appends_entry_if_file_exists(self, tmp_path):
+        """ensure_gitignore добавляет .kin_worktrees/ в существующий .gitignore."""
+        from core.worktree import ensure_gitignore
+
+        gitignore = tmp_path / ".gitignore"
+        gitignore.write_text("*.pyc\n__pycache__/\n")
+
+        ensure_gitignore(str(tmp_path))
+
+        content = gitignore.read_text()
+        assert ".kin_worktrees/" in content
+        assert "*.pyc" in content  # existing entries preserved
+
+    def test_ensure_gitignore_no_duplicate_if_entry_exists(self, tmp_path):
+        """ensure_gitignore не дублирует запись если уже есть."""
+        from core.worktree import ensure_gitignore
+
+        gitignore = tmp_path / ".gitignore"
+        gitignore.write_text(".kin_worktrees/\n")
+
+        ensure_gitignore(str(tmp_path))
+
+        content = gitignore.read_text()
+        assert content.count(".kin_worktrees/") == 1
+
+    def test_ensure_gitignore_exception_does_not_raise(self, tmp_path):
+        """ensure_gitignore не поднимает исключение при любых ошибках."""
+        from core.worktree import ensure_gitignore
+
+        # Read-only path trick: pass a file as path (not a dir)
+        fake_path = tmp_path / "not_a_dir.txt"
+        fake_path.write_text("content")
+
+        # Must not raise — function is defensive
+        try:
+            ensure_gitignore(str(fake_path))
+        except Exception as e:
+            pytest.fail(f"ensure_gitignore raised unexpectedly: {e}")
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 5. runner — worktree lifecycle в run_pipeline
+# ─────────────────────────────────────────────────────────────────────────────
+
+class TestRunPipelineWorktrees:
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.cleanup_worktree")
+    @patch("core.worktree.merge_worktree",
+           return_value={"success": True, "conflicts": [], "merged_files": []})
+    @patch("core.worktree.create_worktree", return_value="/tmp/fake-worktree")
+    @patch("core.worktree.ensure_gitignore")
+    def test_worktrees_enabled_eligible_role_creates_worktree(
+        self, mock_gitignore, mock_create, mock_merge, mock_cleanup, mock_runner_run,
+        conn_wt_enabled
+    ):
+        """worktrees_enabled=True + роль debugger → create_worktree вызывается."""
+        from agents.runner import run_pipeline
+
+        mock_runner_run.return_value = _claude_ok()
+
+        result = run_pipeline(conn_wt_enabled, "WT1-001",
+                              [{"role": "debugger", "brief": "fix"}])
+
+        assert result["success"] is True
+        mock_create.assert_called_once()
+        call_args = mock_create.call_args[0]
+        assert "WT1-001" in call_args[1]
+        assert "debugger" in call_args[2]
+
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.subprocess.run")
+    def test_worktrees_disabled_no_worktree_created(
+        self, mock_wt_run, mock_runner_run, conn
+    ):
+        """worktrees_enabled=False → create_worktree НЕ вызывается."""
+        from agents.runner import run_pipeline
+
+        mock_runner_run.return_value = _claude_ok()
+        mock_wt_run.return_value = _ok_run()
+
+        with patch("core.worktree._git", return_value="git"):
+            result = run_pipeline(conn, "WT1-001",
+                                  [{"role": "debugger", "brief": "fix"}])
+
+        assert result["success"] is True
+        # git worktree add must NOT have been called
+        cmds = [c[0][0] for c in mock_wt_run.call_args_list]
+        worktree_add_calls = [cmd for cmd in cmds if "worktree" in cmd and "add" in cmd]
+        assert len(worktree_add_calls) == 0
+
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.subprocess.run")
+    def test_non_eligible_role_no_worktree(
+        self, mock_wt_run, mock_runner_run, conn_wt_enabled
+    ):
+        """Роль tester не входит в _WORKTREE_ROLES → worktree не создаётся."""
+        from agents.runner import run_pipeline
+
+        mock_runner_run.return_value = _claude_ok()
+        mock_wt_run.return_value = _ok_run()
+
+        with patch("core.worktree._git", return_value="git"):
+            result = run_pipeline(conn_wt_enabled, "WT1-001",
+                                  [{"role": "tester", "brief": "test"}])
+
+        assert result["success"] is True
+        cmds = [c[0][0] for c in mock_wt_run.call_args_list]
+        worktree_add_calls = [cmd for cmd in cmds if "worktree" in cmd and "add" in cmd]
+        assert len(worktree_add_calls) == 0
+
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.create_worktree", return_value=None)
+    @patch("core.worktree.ensure_gitignore")
+    def test_create_worktree_returns_none_fallback_no_crash(
+        self, mock_gitignore, mock_create, mock_runner_run, conn_wt_enabled
+    ):
+        """Если create_worktree возвращает None (не-git dir) — pipeline продолжается нормально."""
+        from agents.runner import run_pipeline
+
+        mock_runner_run.return_value = _claude_ok()
+
+        result = run_pipeline(conn_wt_enabled, "WT1-001",
+                              [{"role": "debugger", "brief": "fix"}])
+
+        assert result["success"] is True
+        assert result["steps_completed"] == 1
+
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.cleanup_worktree")
+    @patch("core.worktree.merge_worktree", return_value={"success": True, "conflicts": [], "merged_files": []})
+    @patch("core.worktree.create_worktree", return_value="/tmp/WT1-001-debugger")
+    @patch("core.worktree.ensure_gitignore")
+    def test_successful_step_calls_merge_then_cleanup(
+        self, mock_gitignore, mock_create, mock_merge, mock_cleanup, mock_runner_run, conn_wt_enabled
+    ):
+        """После успешного шага: merge_worktree вызывается, затем cleanup_worktree."""
+        from agents.runner import run_pipeline
+
+        mock_runner_run.return_value = _claude_ok()
+
+        result = run_pipeline(conn_wt_enabled, "WT1-001",
+                              [{"role": "debugger", "brief": "fix"}])
+
+        assert result["success"] is True
+        mock_merge.assert_called_once()
+        mock_cleanup.assert_called_once()
+
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.cleanup_worktree")
+    @patch("core.worktree.merge_worktree")
+    @patch("core.worktree.create_worktree", return_value="/tmp/WT1-001-debugger")
+    @patch("core.worktree.ensure_gitignore")
+    def test_failed_step_calls_cleanup_without_merge(
+        self, mock_gitignore, mock_create, mock_merge, mock_cleanup, mock_runner_run, conn_wt_enabled
+    ):
+        """После неудачного шага: cleanup_worktree вызывается, merge_worktree — нет."""
+        from agents.runner import run_pipeline
+
+        fail = MagicMock()
+        fail.returncode = 1
+        fail.stdout = ""
+        fail.stderr = "compilation error"
+        mock_runner_run.return_value = fail
+
+        result = run_pipeline(conn_wt_enabled, "WT1-001",
+                              [{"role": "debugger", "brief": "fix"}])
+
+        assert result["success"] is False
+        mock_merge.assert_not_called()
+        mock_cleanup.assert_called_once()
+
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.cleanup_worktree")
+    @patch("core.worktree.merge_worktree",
+           return_value={"success": False, "conflicts": ["src/app.py"], "merged_files": []})
+    @patch("core.worktree.create_worktree", return_value="/tmp/WT1-001-debugger")
+    @patch("core.worktree.ensure_gitignore")
+    def test_merge_conflict_sets_task_blocked(
+        self, mock_gitignore, mock_create, mock_merge, mock_cleanup, mock_runner_run, conn_wt_enabled
+    ):
+        """При конфликте merge: задача переходит в blocked с корректной причиной."""
+        from agents.runner import run_pipeline
+
+        mock_runner_run.return_value = _claude_ok()
+
+        result = run_pipeline(conn_wt_enabled, "WT1-001",
+                              [{"role": "debugger", "brief": "fix"}])
+
+        # pipeline fails due to merge conflict
+        assert result["success"] is False
+        task = models.get_task(conn_wt_enabled, "WT1-001")
+        assert task["status"] == "blocked"
+        assert "src/app.py" in (task.get("blocked_reason") or "")
+        # cleanup still called after conflict
+        mock_cleanup.assert_called_once()
+
+    @patch("agents.runner.subprocess.run")
+    @patch("core.worktree.cleanup_worktree", side_effect=Exception("disk error"))
+    @patch("core.worktree.merge_worktree",
+           return_value={"success": True, "conflicts": [], "merged_files": []})
+    @patch("core.worktree.create_worktree", return_value="/tmp/WT1-001-debugger")
+    @patch("core.worktree.ensure_gitignore")
+    def test_cleanup_exception_does_not_propagate(
+        self, mock_gitignore, mock_create, mock_merge, mock_cleanup, mock_runner_run, conn_wt_enabled
+    ):
+        """Исключение в cleanup_worktree не блокирует pipeline — он завершается успешно."""
+        from agents.runner import run_pipeline
+
+        mock_runner_run.return_value = _claude_ok()
+
+        # Must not raise
+        result = run_pipeline(conn_wt_enabled, "WT1-001",
+                              [{"role": "debugger", "brief": "fix"}])
+
+        assert result["success"] is True