diff --git a/features/steps/decision_dependency_basic_steps.py b/features/steps/decision_dependency_basic_steps.py
new file mode 100644
index 000000000..4740c26cf
--- /dev/null
+++ b/features/steps/decision_dependency_basic_steps.py
@@ -0,0 +1,350 @@
+"""Basic steps for decision dependency persistence feature."""
+
+from __future__ import annotations
+
+from behave import given, then, when
+from behave.runner import Context
+
+from cleveragents.core.exceptions import DatabaseError
+from cleveragents.infrastructure.database.models import DecisionDependencyModel
+
+from features.steps.helpers.decision_dependency_helpers import (
+    PLAN_ID_1,
+    PLAN_ID_2,
+    create_child,
+    create_prerequisite_action,
+    create_prerequisite_plan,
+    create_root,
+    get_edges,
+    record_dependency,
+    setup_db,
+)
+
+
+@given("a fresh database for decision dependencies")
+def step_fresh_db(context: Context) -> None:
+    """Set up a fresh database."""
+    setup_db(context)
+
+
+@given('a prerequisite action "{action_name}" exists for dependencies')
+def step_prereq_action(context: Context, action_name: str) -> None:
+    """Create a prerequisite action."""
+    create_prerequisite_action(context, action_name)
+
+
+@given("a prerequisite plan exists for dependencies")
+def step_prereq_plan(context: Context) -> None:
+    """Create a prerequisite plan."""
+    create_prerequisite_plan(context, PLAN_ID_1)
+
+
+@given("a persisted root decision for dependencies")
+def step_persisted_root_dep(context: Context) -> None:
+    """Create and persist a root decision."""
+    root = create_root(context)
+    context._ddp_root_id = root.decision_id
+    context._ddp_root_decision = root
+
+
+@given("a persisted child decision for dependencies")
+def step_persisted_child_dep(context: Context) -> None:
+    """Create and persist a child decision."""
+    root_id = getattr(context, "_ddp_root_id", None)
+    if root_id is None:
+        root_id = context._ddp_root_ids[0]
+    child = create_child(context, root_id)
+    context._ddp_child_id = child.decision_id
+    context._ddp_child_decision = child
+
+
+@given("{count:d} persisted sibling decisions for dependencies")
+def step_persisted_siblings_dep(context: Context, count: int) -> None:
+    """Create and persist multiple sibling decisions."""
+    context._ddp_sibling_ids = []
+    for index in range(count):
+        sibling = create_child(
+            context,
+            context._ddp_root_id,
+            sequence_number=index + 1,
+        )
+        context._ddp_sibling_ids.append(sibling.decision_id)
+
+
+@given("{count:d} persisted root decisions for dependencies")
+def step_persisted_roots_dep(context: Context, count: int) -> None:
+    """Create and persist multiple root decisions."""
+    context._ddp_root_ids = []
+    for index in range(count):
+        root = create_root(context, index=index)
+        context._ddp_root_ids.append(root.decision_id)
+    context._ddp_root_id = context._ddp_root_ids[0]
+
+
+@given("{count:d} persisted plans for dependencies")
+def step_persisted_plans_dep(context: Context, count: int) -> None:
+    """Create and persist multiple plans."""
+    context._ddp_plan_ids = [PLAN_ID_1]
+    if count > 1:
+        create_prerequisite_plan(context, PLAN_ID_2)
+        context._ddp_plan_ids.append(PLAN_ID_2)
+
+
+@given("a decision tree in plan 1 with dependencies")
+def step_decision_tree_plan1_dep(context: Context) -> None:
+    """Create a decision tree in plan 1 with dependencies."""
+    root = create_root(context, PLAN_ID_1)
+    child = create_child(context, root.decision_id, PLAN_ID_1)
+    record_dependency(context, root.decision_id, child.decision_id)
+    context._ddp_plan1_root_id = root.decision_id
+    context._ddp_plan1_child_id = child.decision_id
+
+
+@given("a decision tree in plan 2 with dependencies")
+def step_decision_tree_plan2_dep(context: Context) -> None:
+    """Create a decision tree in plan 2 with dependencies."""
+    root = create_root(context, PLAN_ID_2)
+    child = create_child(context, root.decision_id, PLAN_ID_2)
+    record_dependency(context, root.decision_id, child.decision_id)
+    context._ddp_plan2_root_id = root.decision_id
+    context._ddp_plan2_child_id = child.decision_id
+
+
+@given("a decision in plan 1 and a decision in plan 2")
+def step_cross_plan_decisions_dep(context: Context) -> None:
+    """Create decisions in different plans."""
+    d1 = create_root(context, PLAN_ID_1)
+    d2 = create_root(context, PLAN_ID_2)
+    context._ddp_cross_plan_id1 = d1.decision_id
+    context._ddp_cross_plan_id2 = d2.decision_id
+
+
+@given("a recorded dependency from root to child")
+def step_given_recorded_dependency_root_child(context: Context) -> None:
+    """Record a dependency from root to child during scenario setup."""
+    record_dependency(context, context._ddp_root_id, context._ddp_child_id)
+
+
+@given("recorded dependencies from root to both siblings")
+def step_given_recorded_dependencies_root_siblings(context: Context) -> None:
+    """Record dependencies from root to all siblings during setup."""
+    for sibling_id in context._ddp_sibling_ids:
+        record_dependency(context, context._ddp_root_id, sibling_id)
+
+
+@given("recorded dependencies from both roots to the child")
+def step_given_recorded_dependencies_both_roots(context: Context) -> None:
+    """Record dependencies from each root to the child during setup."""
+    for root_id in context._ddp_root_ids:
+        record_dependency(context, root_id, context._ddp_child_id)
+
+
+@when("I record a dependency from the root to the child")
+def step_record_dependency_root_child(context: Context) -> None:
+    """Record a dependency from root to child."""
+    record_dependency(context, context._ddp_root_id, context._ddp_child_id)
+
+
+@when("I record dependencies from the root to both siblings")
+def step_record_dependencies_root_siblings(context: Context) -> None:
+    """Record dependencies from root to all siblings."""
+    for sibling_id in context._ddp_sibling_ids:
+        record_dependency(context, context._ddp_root_id, sibling_id)
+
+
+@when('I record a dependency with relationship_type "{rel_type}"')
+def step_record_dependency_custom_type(context: Context, rel_type: str) -> None:
+    """Record a dependency with custom relationship type."""
+    record_dependency(
+        context,
+        context._ddp_root_id,
+        context._ddp_child_id,
+        relationship_type=rel_type,
+    )
+    context._ddp_custom_rel_type = rel_type
+
+
+@when("I try to record a self-loop dependency")
+def step_try_self_loop_dependency(context: Context) -> None:
+    """Try to record a self-loop dependency."""
+    try:
+        record_dependency(context, context._ddp_root_id, context._ddp_root_id)
+        context._ddp_self_loop_error = None
+    except DatabaseError as exc:
+        context._ddp_self_loop_error = exc
+
+
+@when("I try to record the same dependency again")
+def step_try_duplicate_dependency(context: Context) -> None:
+    """Try to record the same dependency again."""
+    try:
+        record_dependency(context, context._ddp_root_id, context._ddp_child_id)
+        context._ddp_duplicate_error = None
+    except DatabaseError as exc:
+        context._ddp_duplicate_error = exc
+
+
+@when("I try to record a cross-plan dependency")
+def step_try_cross_plan_dependency(context: Context) -> None:
+    """Try to record a cross-plan dependency."""
+    try:
+        record_dependency(
+            context,
+            context._ddp_cross_plan_id1,
+            context._ddp_cross_plan_id2,
+        )
+        context._ddp_cross_plan_error = None
+    except DatabaseError as exc:
+        context._ddp_cross_plan_error = exc
+
+
+@when("I get influence edges for the plan")
+def step_get_influence_edges(context: Context) -> None:
+    """Get influence edges for the plan."""
+    context._ddp_influence_edges = get_edges(context, PLAN_ID_1)
+
+
+@when("I get influence edges for plan 1")
+def step_get_influence_edges_plan1(context: Context) -> None:
+    """Get influence edges for plan 1."""
+    context._ddp_influence_edges_plan1 = get_edges(context, PLAN_ID_1)
+
+
+@when("I get influence edges for plan 2")
+def step_get_influence_edges_plan2(context: Context) -> None:
+    """Get influence edges for plan 2."""
+    context._ddp_influence_edges_plan2 = get_edges(context, PLAN_ID_2)
+
+
+@then("the dependency should be persisted to the database")
+def step_assert_dependency_persisted(context: Context) -> None:
+    """Assert that the dependency was persisted."""
+    edges = get_edges(context)
+    target_id = getattr(context, "_ddp_new_decision_id", None)
+    if target_id is None:
+        target_id = context._ddp_child_id
+    assert context._ddp_root_id in edges, "Root should be in edges"
+    assert target_id in edges[context._ddp_root_id], "Child should be in root's targets"
+
+
+@then('the dependency should have relationship_type "{rel_type}"')
+def step_assert_dependency_rel_type(context: Context, rel_type: str) -> None:
+    """Assert that the dependency has the correct relationship type."""
+    _assert_dependency_relationship_type(context, rel_type)
+
+
+@then('the dependency should be persisted with relationship_type "{rel_type}"')
+def step_assert_dependency_persisted_with_type(context: Context, rel_type: str) -> None:
+    """Assert that the dependency was persisted with the correct type."""
+    _assert_dependency_relationship_type(context, rel_type)
+
+
+@then("both dependencies should be persisted to the database")
+def step_assert_both_dependencies_persisted(context: Context) -> None:
+    """Assert that both dependencies were persisted."""
+    edges = get_edges(context)
+    if hasattr(context, "_ddp_new_decision_id"):
+        for root_id in context._ddp_root_ids:
+            assert root_id in edges, f"Root {root_id} should be in edges"
+            assert context._ddp_new_decision_id in edges[root_id], (
+                f"New decision should be in {root_id}'s targets"
+            )
+        return
+
+    assert context._ddp_root_id in edges, "Root should be in edges"
+    assert len(edges[context._ddp_root_id]) == 2, "Root should have 2 targets"
+    for sibling_id in context._ddp_sibling_ids:
+        assert sibling_id in edges[context._ddp_root_id], (
+            f"Sibling {sibling_id} should be in root's targets"
+        )
+
+
+@then("the influence edges should be empty")
+def step_assert_influence_edges_empty(context: Context) -> None:
+    """Assert that influence edges are empty."""
+    assert context._ddp_influence_edges == {}, "Influence edges should be empty"
+
+
+@then("the influence edges should contain {count:d} source")
+def step_assert_influence_edges_source_count(context: Context, count: int) -> None:
+    """Assert the number of sources in influence edges."""
+    assert len(context._ddp_influence_edges) == count, (
+        f"Should have {count} source(s), got {len(context._ddp_influence_edges)}"
+    )
+
+
+@then("the influence edges should contain {count:d} sources")
+def step_assert_influence_edges_sources_count(context: Context, count: int) -> None:
+    """Assert the number of sources in influence edges."""
+    step_assert_influence_edges_source_count(context, count)
+
+
+@then("the influence edges should map root to {targets}")
+def step_assert_influence_edges_mapping(context: Context, targets: str) -> None:
+    """Assert that influence edges map root to the specified targets."""
+    if targets == "[child]":
+        expected = [context._ddp_child_id]
+    elif targets == "[sibling1, sibling2]":
+        expected = context._ddp_sibling_ids
+    else:
+        expected = []
+
+    assert context._ddp_root_id in context._ddp_influence_edges, (
+        "Root should be in edges"
+    )
+    actual = context._ddp_influence_edges[context._ddp_root_id]
+    assert set(actual) == set(expected), f"Expected {expected}, got {actual}"
+
+
+@then("the influence edges should only include decisions from plan 1")
+def step_assert_influence_edges_plan1_only(context: Context) -> None:
+    """Assert that influence edges only include plan 1 decisions."""
+    edges = context._ddp_influence_edges_plan1
+    plan1_ids = {
+        context._ddp_plan1_root_id,
+        context._ddp_plan1_child_id,
+    }
+    for source, targets in edges.items():
+        assert source in plan1_ids, f"Source {source} should be in plan 1"
+        for target in targets:
+            assert target in plan1_ids, f"Target {target} should be in plan 1"
+
+
+@then("the cross-plan dependency should not appear in influence edges")
+def step_assert_no_cross_plan_dependency(context: Context) -> None:
+    """Assert that cross-plan dependencies don't appear in edges."""
+    edges = get_edges(context)
+    if context._ddp_cross_plan_id1 in edges:
+        assert context._ddp_cross_plan_id2 not in edges[context._ddp_cross_plan_id1], (
+            "Cross-plan dependency should not appear"
+        )
+
+
+@then("a database constraint error should be raised")
+def step_assert_constraint_error(context: Context) -> None:
+    """Assert that a constraint error was raised."""
+    assert context._ddp_self_loop_error is not None, (
+        "Should have raised a constraint error"
+    )
+
+
+@then("the operation should complete without error")
+def step_assert_no_error(context: Context) -> None:
+    """Assert that the operation completed without error."""
+    assert context._ddp_duplicate_error is None, "Should not have raised an error"
+
+
+def _assert_dependency_relationship_type(context: Context, rel_type: str) -> None:
+    session = context._ddp_factory()
+    dep = (
+        session.query(DecisionDependencyModel)
+        .filter_by(
+            source_decision_id=context._ddp_root_id,
+            target_decision_id=context._ddp_child_id,
+        )
+        .first()
+    )
+    assert dep is not None, "Dependency should exist"
+    assert dep.relationship_type == rel_type, (
+        f"Relationship type should be {rel_type}, got {dep.relationship_type}"
+    )
diff --git a/features/steps/decision_dependency_integration_steps.py b/features/steps/decision_dependency_integration_steps.py
new file mode 100644
index 000000000..3704287ca
--- /dev/null
+++ b/features/steps/decision_dependency_integration_steps.py
@@ -0,0 +1,184 @@
+"""DecisionService and correction workflow steps for dependency persistence."""
+
+from __future__ import annotations
+
+from behave import given, then, when
+from behave.runner import Context
+
+from cleveragents.application.services.decision_service import DecisionService
+from cleveragents.domain.models.core.decision import DecisionType
+
+from features.steps.helpers.decision_dependency_helpers import (
+    PLAN_ID_1,
+    affected_subtree,
+    create_child,
+    create_three_level_tree,
+    get_edges,
+    record_dependency,
+    record_three_level_edges,
+)
+
+
+@given("a persisted decision tree with 3 levels for dependencies")
+def step_decision_tree_3levels_dep(context: Context) -> None:
+    """Create a 3-level decision tree."""
+    create_three_level_tree(context)
+
+
+@given("recorded dependencies forming a DAG")
+def step_recorded_dag_dep(context: Context) -> None:
+    """Record dependencies forming a DAG."""
+    record_three_level_edges(context)
+
+
+@given("a persisted decision tree with dependencies")
+def step_persisted_decision_tree_with_dependencies(context: Context) -> None:
+    """Create a persisted decision tree and matching dependency edges."""
+    create_three_level_tree(context)
+    record_three_level_edges(context)
+    context._ddp_root_id = context._ddp_tree_root_id
+    context._ddp_child_id = context._ddp_tree_child_id
+
+
+@given("a persisted child decision depending on the root")
+def step_persisted_child_decision_depending_on_root(context: Context) -> None:
+    """Create a child decision and persist a root -> child dependency."""
+    child = create_child(context, context._ddp_root_id)
+    context._ddp_child_id = child.decision_id
+    context._ddp_child_decision = child
+    record_dependency(context, context._ddp_root_id, context._ddp_child_id)
+
+
+@when("I create a new DecisionService instance with the same database")
+def step_new_decision_service(context: Context) -> None:
+    """Create a new DecisionService with the same database."""
+    context._ddp_new_service = DecisionService(unit_of_work=context._ddp_uow)
+
+
+@when("I record a new decision with dependency_decision_ids={deps}")
+def step_record_decision_with_deps(context: Context, deps: str) -> None:
+    """Record a new decision with dependencies."""
+    service = DecisionService(unit_of_work=context._ddp_uow)
+
+    if deps == "[]":
+        dep_ids = []
+    elif deps == "[root]":
+        dep_ids = [context._ddp_root_id]
+    elif deps == "[root1, root2]":
+        dep_ids = context._ddp_root_ids
+    else:
+        raise AssertionError(f"Unsupported dependency list literal: {deps}")
+
+    decision = service.record_decision(
+        plan_id=PLAN_ID_1,
+        decision_type=DecisionType.STRATEGY_CHOICE,
+        question="What strategy?",
+        chosen_option="Strategy A",
+        dependency_decision_ids=dep_ids,
+    )
+    context._ddp_new_decision_id = decision.decision_id
+    context._ddp_new_decision = decision
+
+
+@when("I compute affected subtree using influence edges")
+def step_compute_affected_subtree(context: Context) -> None:
+    """Compute all downstream decisions from the persisted influence DAG."""
+    context._ddp_influence_edges = get_edges(context)
+    context._ddp_affected_subtree = affected_subtree(
+        context._ddp_tree_root_id,
+        context._ddp_influence_edges,
+    )
+
+
+@when("I record a correction decision with the same dependencies")
+def step_record_correction_decision_same_dependencies(context: Context) -> None:
+    """Record a correction decision that depends on the same root."""
+    service = DecisionService(unit_of_work=context._ddp_uow)
+    correction = service.record_decision(
+        plan_id=PLAN_ID_1,
+        decision_type=DecisionType.USER_INTERVENTION,
+        question="How should the previous decision be corrected?",
+        chosen_option="Apply corrected approach",
+        parent_decision_id=context._ddp_child_id,
+        dependency_decision_ids=[context._ddp_root_id],
+    )
+    context._ddp_correction_decision_id = correction.decision_id
+
+
+@then("the new service should retrieve the same dependency edges")
+def step_assert_new_service_same_edges(context: Context) -> None:
+    """Assert that a new service retrieves the same edges."""
+    new_edges = context._ddp_new_service.get_influence_edges(PLAN_ID_1)
+    assert context._ddp_root_id in new_edges, "Root should be in new edges"
+    assert context._ddp_child_id in new_edges[context._ddp_root_id], (
+        "Child should be in new root's targets"
+    )
+
+
+@then("the new service should retrieve all dependency edges")
+def step_assert_new_service_all_edges(context: Context) -> None:
+    """Assert that a new service retrieves all edges."""
+    new_edges = context._ddp_new_service.get_influence_edges(PLAN_ID_1)
+    assert len(new_edges) == 2, f"Should have 2 sources, got {len(new_edges)}"
+    assert context._ddp_tree_root_id in new_edges, "Root should be in edges"
+    assert context._ddp_tree_child_id in new_edges, "Child should be in edges"
+
+
+@then("no dependencies should be created")
+def step_assert_no_dependencies_created(context: Context) -> None:
+    """Assert that no dependencies were created."""
+    edges = get_edges(context)
+    assert edges == {}, "No dependencies should be created"
+
+
+@then("get_influence_edges should return the dependency")
+def step_assert_get_influence_edges_returns_dep(context: Context) -> None:
+    """Assert that get_influence_edges returns the dependency."""
+    edges = get_edges(context)
+    assert context._ddp_root_id in edges, "Root should be in edges"
+    assert context._ddp_new_decision_id in edges[context._ddp_root_id], (
+        "New decision should be in root's targets"
+    )
+
+
+@then("get_influence_edges should return both dependencies")
+def step_assert_get_influence_edges_returns_both(context: Context) -> None:
+    """Assert that get_influence_edges returns both dependencies."""
+    edges = get_edges(context)
+    for root_id in context._ddp_root_ids:
+        assert root_id in edges, f"Root {root_id} should be in edges"
+        assert context._ddp_new_decision_id in edges[root_id], (
+            f"New decision should be in {root_id}'s targets"
+        )
+
+
+@then("get_influence_edges should be empty")
+def step_assert_get_influence_edges_empty(context: Context) -> None:
+    """Assert that get_influence_edges returns empty dict."""
+    edges = get_edges(context)
+    assert edges == {}, "Influence edges should be empty"
+
+
+@then("the affected subtree should include all transitive dependents")
+def step_assert_affected_subtree_transitive(context: Context) -> None:
+    """Assert transitive dependents are included in the affected subtree."""
+    expected = {
+        context._ddp_tree_child_id,
+        context._ddp_tree_grandchild_id,
+    }
+    assert expected <= context._ddp_affected_subtree, (
+        f"Expected {expected}, got {context._ddp_affected_subtree}"
+    )
+
+
+@then("the correction decision should have the same influence edges")
+def step_assert_correction_decision_has_same_edges(context: Context) -> None:
+    """Assert the correction decision is linked to the same upstream root."""
+    edges = get_edges(context)
+    assert context._ddp_root_id in edges, "Root should be in influence edges"
+    assert context._ddp_child_id in edges[context._ddp_root_id], (
+        "Original child dependency should remain"
+    )
+    assert context._ddp_correction_decision_id in edges[context._ddp_root_id], (
+        "Correction decision should depend on the same root"
+    )
diff --git a/features/steps/decision_dependency_persistence_steps.py b/features/steps/decision_dependency_persistence_steps.py
deleted file mode 100644
index b85401de7..000000000
--- a/features/steps/decision_dependency_persistence_steps.py
+++ /dev/null
@@ -1,670 +0,0 @@
-"""Step definitions for decision_dependency_persistence.feature.
-
-Tests decision dependency persistence, influence DAG retrieval,
-and integration with DecisionService.
-"""
-
-from __future__ import annotations
-
-from datetime import UTC, datetime
-
-from behave import given, then, when
-from behave.runner import Context
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker
-
-from cleveragents.application.services.decision_service import DecisionService
-from cleveragents.core.exceptions import DatabaseError
-from cleveragents.domain.models.core.action import Action, ActionState
-from cleveragents.domain.models.core.decision import Decision, DecisionType
-from cleveragents.domain.models.core.plan import (
-    NamespacedName,
-    Plan,
-    PlanIdentity,
-    PlanPhase,
-    PlanTimestamps,
-    ProcessingState,
-)
-from cleveragents.infrastructure.database.models import Base
-from cleveragents.infrastructure.database.repositories import (
-    ActionRepository,
-    DecisionRepository,
-    LifecyclePlanRepository,
-)
-from cleveragents.infrastructure.database.unit_of_work import UnitOfWork
-
-# ---------------------------------------------------------------------------
-# Helpers
-# ---------------------------------------------------------------------------
-
-_PLAN_ID_1 = "01HV000000000000000000DP01"
-_PLAN_ID_2 = "01HV000000000000000000DP02"
-
-
-def _setup_db(context: Context) -> None:
-    """Create an in-memory SQLite DB and attach repos."""
-    engine = create_engine("sqlite:///:memory:", echo=False)
-    Base.metadata.create_all(engine)
-    sm = sessionmaker(bind=engine)
-    session = sm()
-    context._ddp_engine = engine
-    context._ddp_session = session
-    context._ddp_factory = lambda: session
-    context._ddp_repo = DecisionRepository(session_factory=context._ddp_factory)
-    context._ddp_action_repo = ActionRepository(session_factory=context._ddp_factory)
-    context._ddp_plan_repo = LifecyclePlanRepository(
-        session_factory=context._ddp_factory,
-    )
-    context._ddp_uow = UnitOfWork(
-        engine=engine,
-        session_factory=context._ddp_factory,
-    )
-
-
-def _make_decision(
-    plan_id: str = _PLAN_ID_1,
-    parent_decision_id: str | None = None,
-    sequence_number: int = 0,
-    decision_type: DecisionType = DecisionType.PROMPT_DEFINITION,
-    question: str = "What approach should we take?",
-    chosen_option: str = "Build a REST API",
-) -> Decision:
-    """Create a Decision domain model."""
-    return Decision(
-        plan_id=plan_id,
-        sequence_number=sequence_number,
-        decision_type=decision_type,
-        question=question,
-        chosen_option=chosen_option,
-        parent_decision_id=parent_decision_id,
-    )
-
-
-def _create_prerequisite_action(context: Context, action_name: str) -> None:
-    """Create a prerequisite action for testing."""
-    ns = NamespacedName.parse(action_name)
-    action = Action(
-        namespaced_name=ns,
-        description="Prerequisite action for dependency tests",
-        definition_of_done="Done",
-        strategy_actor="local/s",
-        execution_actor="local/e",
-        state=ActionState.AVAILABLE,
-        created_at=datetime(2026, 1, 1, tzinfo=UTC),
-        updated_at=datetime(2026, 1, 1, tzinfo=UTC),
-    )
-    context._ddp_action_repo.create(action)
-    context._ddp_session.commit()
-
-
-def _create_prerequisite_plan(context: Context, plan_id: str) -> None:
-    """Create a prerequisite plan for testing."""
-    now = datetime(2026, 3, 1, tzinfo=UTC)
-    plan = Plan(
-        identity=PlanIdentity(plan_id=plan_id, attempt=1),
-        namespaced_name=NamespacedName(namespace="local", name="decision-plan"),
-        action_name="local/decision-action",
-        description="Decision test plan",
-        definition_of_done="All assertions pass",
-        phase=PlanPhase.STRATEGIZE,
-        processing_state=ProcessingState.PROCESSING,
-        strategy_actor="local/s",
-        execution_actor="local/e",
-        timestamps=PlanTimestamps(created_at=now, updated_at=now),
-        created_by="test-dependency",
-        tags=[],
-        reusable=True,
-        read_only=False,
-    )
-    context._ddp_plan_repo.create(plan)
-    context._ddp_session.commit()
-
-
-# ---------------------------------------------------------------------------
-# Background
-# ---------------------------------------------------------------------------
-
-
-@given("a fresh database for decision dependencies")
-def step_fresh_db(context: Context) -> None:
-    """Set up a fresh in-memory database."""
-    _setup_db(context)
-
-
-@given('a prerequisite action "{action_name}" exists for dependencies')
-def step_prereq_action(context: Context, action_name: str) -> None:
-    """Create a prerequisite action."""
-    _create_prerequisite_action(context, action_name)
-
-
-@given("a prerequisite plan exists for dependencies")
-def step_prereq_plan(context: Context) -> None:
-    """Create a prerequisite plan."""
-    _create_prerequisite_plan(context, _PLAN_ID_1)
-
-
-# ---------------------------------------------------------------------------
-# Decision creation
-# ---------------------------------------------------------------------------
-
-
-@given("a persisted root decision for dependencies")
-def step_persisted_root_dep(context: Context) -> None:
-    """Create and persist a root decision."""
-    d = _make_decision(plan_id=_PLAN_ID_1, sequence_number=0)
-    context._ddp_repo.create(d)
-    context._ddp_session.commit()
-    context._ddp_root_id = d.decision_id
-    context._ddp_root_decision = d
-
-
-@given("a persisted child decision for dependencies")
-def step_persisted_child_dep(context: Context) -> None:
-    """Create and persist a child decision."""
-    d = _make_decision(
-        plan_id=_PLAN_ID_1,
-        parent_decision_id=context._ddp_root_id,
-        sequence_number=1,
-        decision_type=DecisionType.STRATEGY_CHOICE,
-    )
-    context._ddp_repo.create(d)
-    context._ddp_session.commit()
-    context._ddp_child_id = d.decision_id
-    context._ddp_child_decision = d
-
-
-@given("{count:d} persisted sibling decisions for dependencies")
-def step_persisted_siblings_dep(context: Context, count: int) -> None:
-    """Create and persist multiple sibling decisions."""
-    context._ddp_sibling_ids = []
-    for i in range(count):
-        d = _make_decision(
-            plan_id=_PLAN_ID_1,
-            parent_decision_id=context._ddp_root_id,
-            sequence_number=i + 1,
-            decision_type=DecisionType.STRATEGY_CHOICE,
-        )
-        context._ddp_repo.create(d)
-        context._ddp_sibling_ids.append(d.decision_id)
-    context._ddp_session.commit()
-
-
-@given("{count:d} persisted root decisions for dependencies")
-def step_persisted_roots_dep(context: Context, count: int) -> None:
-    """Create and persist multiple root decisions."""
-    context._ddp_root_ids = []
-    for i in range(count):
-        d = _make_decision(
-            plan_id=_PLAN_ID_1,
-            sequence_number=i,
-        )
-        context._ddp_repo.create(d)
-        context._ddp_root_ids.append(d.decision_id)
-    context._ddp_session.commit()
-
-
-@given("{count:d} persisted plans for dependencies")
-def step_persisted_plans_dep(context: Context, count: int) -> None:
-    """Create and persist multiple plans."""
-    context._ddp_plan_ids = [_PLAN_ID_1]
-    if count > 1:
-        _create_prerequisite_plan(context, _PLAN_ID_2)
-        context._ddp_plan_ids.append(_PLAN_ID_2)
-
-
-@given("a decision tree in plan 1 with dependencies")
-def step_decision_tree_plan1_dep(context: Context) -> None:
-    """Create a decision tree in plan 1 with dependencies."""
-    # Create root
-    root = _make_decision(plan_id=_PLAN_ID_1, sequence_number=0)
-    context._ddp_repo.create(root)
-    context._ddp_session.commit()
-    root_id = root.decision_id
-
-    # Create child
-    child = _make_decision(
-        plan_id=_PLAN_ID_1,
-        parent_decision_id=root_id,
-        sequence_number=1,
-        decision_type=DecisionType.STRATEGY_CHOICE,
-    )
-    context._ddp_repo.create(child)
-    context._ddp_session.commit()
-
-    # Record dependency
-    context._ddp_repo.record_dependency(root_id, child.decision_id)
-    context._ddp_session.commit()
-
-    context._ddp_plan1_root_id = root_id
-    context._ddp_plan1_child_id = child.decision_id
-
-
-@given("a decision tree in plan 2 with dependencies")
-def step_decision_tree_plan2_dep(context: Context) -> None:
-    """Create a decision tree in plan 2 with dependencies."""
-    # Create root
-    root = _make_decision(plan_id=_PLAN_ID_2, sequence_number=0)
-    context._ddp_repo.create(root)
-    context._ddp_session.commit()
-    root_id = root.decision_id
-
-    # Create child
-    child = _make_decision(
-        plan_id=_PLAN_ID_2,
-        parent_decision_id=root_id,
-        sequence_number=1,
-        decision_type=DecisionType.STRATEGY_CHOICE,
-    )
-    context._ddp_repo.create(child)
-    context._ddp_session.commit()
-
-    # Record dependency
-    context._ddp_repo.record_dependency(root_id, child.decision_id)
-    context._ddp_session.commit()
-
-    context._ddp_plan2_root_id = root_id
-    context._ddp_plan2_child_id = child.decision_id
-
-
-@given("a decision in plan 1 and a decision in plan 2")
-def step_cross_plan_decisions_dep(context: Context) -> None:
-    """Create decisions in different plans."""
-    d1 = _make_decision(plan_id=_PLAN_ID_1, sequence_number=0)
-    context._ddp_repo.create(d1)
-
-    d2 = _make_decision(plan_id=_PLAN_ID_2, sequence_number=0)
-    context._ddp_repo.create(d2)
-    context._ddp_session.commit()
-
-    context._ddp_cross_plan_id1 = d1.decision_id
-    context._ddp_cross_plan_id2 = d2.decision_id
-
-
-@given("a persisted decision tree with 3 levels for dependencies")
-def step_decision_tree_3levels_dep(context: Context) -> None:
-    """Create a 3-level decision tree."""
-    # Level 0: root
-    root = _make_decision(plan_id=_PLAN_ID_1, sequence_number=0)
-    context._ddp_repo.create(root)
-    context._ddp_session.commit()
-    root_id = root.decision_id
-
-    # Level 1: child
-    child = _make_decision(
-        plan_id=_PLAN_ID_1,
-        parent_decision_id=root_id,
-        sequence_number=1,
-        decision_type=DecisionType.STRATEGY_CHOICE,
-    )
-    context._ddp_repo.create(child)
-    context._ddp_session.commit()
-    child_id = child.decision_id
-
-    # Level 2: grandchild
-    grandchild = _make_decision(
-        plan_id=_PLAN_ID_1,
-        parent_decision_id=child_id,
-        sequence_number=2,
-        decision_type=DecisionType.IMPLEMENTATION_CHOICE,
-    )
-    context._ddp_repo.create(grandchild)
-    context._ddp_session.commit()
-    grandchild_id = grandchild.decision_id
-
-    context._ddp_tree_root_id = root_id
-    context._ddp_tree_child_id = child_id
-    context._ddp_tree_grandchild_id = grandchild_id
-
-
-@given("recorded dependencies forming a DAG")
-def step_recorded_dag_dep(context: Context) -> None:
-    """Record dependencies forming a DAG."""
-    context._ddp_repo.record_dependency(
-        context._ddp_tree_root_id,
-        context._ddp_tree_child_id,
-    )
-    context._ddp_repo.record_dependency(
-        context._ddp_tree_child_id,
-        context._ddp_tree_grandchild_id,
-    )
-    context._ddp_session.commit()
-
-
-# ---------------------------------------------------------------------------
-# Dependency recording
-# ---------------------------------------------------------------------------
-
-
-@when("I record a dependency from the root to the child")
-def step_record_dependency_root_child(context: Context) -> None:
-    """Record a dependency from root to child."""
-    context._ddp_repo.record_dependency(
-        context._ddp_root_id,
-        context._ddp_child_id,
-    )
-    context._ddp_session.commit()
-
-
-@when("I record dependencies from the root to both siblings")
-def step_record_dependencies_root_siblings(context: Context) -> None:
-    """Record dependencies from root to all siblings."""
-    for sibling_id in context._ddp_sibling_ids:
-        context._ddp_repo.record_dependency(
-            context._ddp_root_id,
-            sibling_id,
-        )
-    context._ddp_session.commit()
-
-
-@when("I record a dependency with relationship_type {rel_type}")
-def step_record_dependency_custom_type(context: Context, rel_type: str) -> None:
-    """Record a dependency with custom relationship type."""
-    context._ddp_repo.record_dependency(
-        context._ddp_root_id,
-        context._ddp_child_id,
-        relationship_type=rel_type,
-    )
-    context._ddp_session.commit()
-    context._ddp_custom_rel_type = rel_type
-
-
-@when("I try to record a self-loop dependency")
-def step_try_self_loop_dependency(context: Context) -> None:
-    """Try to record a self-loop dependency."""
-    try:
-        context._ddp_repo.record_dependency(
-            context._ddp_root_id,
-            context._ddp_root_id,
-        )
-        context._ddp_session.commit()
-        context._ddp_self_loop_error = None
-    except DatabaseError as e:
-        context._ddp_self_loop_error = e
-
-
-@when("I try to record the same dependency again")
-def step_try_duplicate_dependency(context: Context) -> None:
-    """Try to record the same dependency again."""
-    try:
-        context._ddp_repo.record_dependency(
-            context._ddp_root_id,
-            context._ddp_child_id,
-        )
-        context._ddp_session.commit()
-        context._ddp_duplicate_error = None
-    except DatabaseError as e:
-        context._ddp_duplicate_error = e
-
-
-@when("I try to record a cross-plan dependency")
-def step_try_cross_plan_dependency(context: Context) -> None:
-    """Try to record a cross-plan dependency."""
-    try:
-        context._ddp_repo.record_dependency(
-            context._ddp_cross_plan_id1,
-            context._ddp_cross_plan_id2,
-        )
-        context._ddp_session.commit()
-        context._ddp_cross_plan_error = None
-    except DatabaseError as e:
-        context._ddp_cross_plan_error = e
-
-
-# ---------------------------------------------------------------------------
-# Influence edges retrieval
-# ---------------------------------------------------------------------------
-
-
-@when("I get influence edges for the plan")
-def step_get_influence_edges(context: Context) -> None:
-    """Get influence edges for the plan."""
-    context._ddp_influence_edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-
-
-@when("I get influence edges for plan 1")
-def step_get_influence_edges_plan1(context: Context) -> None:
-    """Get influence edges for plan 1."""
-    context._ddp_influence_edges_plan1 = context._ddp_repo.get_influence_edges(
-        _PLAN_ID_1
-    )
-
-
-@when("I get influence edges for plan 2")
-def step_get_influence_edges_plan2(context: Context) -> None:
-    """Get influence edges for plan 2."""
-    context._ddp_influence_edges_plan2 = context._ddp_repo.get_influence_edges(
-        _PLAN_ID_2
-    )
-
-
-# ---------------------------------------------------------------------------
-# DecisionService integration
-# ---------------------------------------------------------------------------
-
-
-@when("I create a new DecisionService instance with the same database")
-def step_new_decision_service(context: Context) -> None:
-    """Create a new DecisionService with the same database."""
-    context._ddp_new_service = DecisionService(
-        unit_of_work=context._ddp_uow,
-    )
-
-
-@when("I record a new decision with dependency_decision_ids={deps}")
-def step_record_decision_with_deps(context: Context, deps: str) -> None:
-    """Record a new decision with dependencies."""
-    # Parse the deps string (e.g., "[root]" or "[root1, root2]")
-    service = DecisionService(unit_of_work=context._ddp_uow)
-
-    if deps == "[]":
-        dep_ids = []
-    elif deps == "[root]":
-        dep_ids = [context._ddp_root_id]
-    elif deps == "[root1, root2]":
-        dep_ids = context._ddp_root_ids
-    else:
-        dep_ids = []
-
-    decision = service.record_decision(
-        plan_id=_PLAN_ID_1,
-        decision_type=DecisionType.STRATEGY_CHOICE,
-        question="What strategy?",
-        chosen_option="Strategy A",
-        dependency_decision_ids=dep_ids,
-    )
-    context._ddp_new_decision_id = decision.decision_id
-    context._ddp_new_decision = decision
-
-
-# ---------------------------------------------------------------------------
-# Assertions
-# ---------------------------------------------------------------------------
-
-
-@then("the dependency should be persisted to the database")
-def step_assert_dependency_persisted(context: Context) -> None:
-    """Assert that the dependency was persisted."""
-    edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-    assert context._ddp_root_id in edges, "Root should be in edges"
-    assert context._ddp_child_id in edges[context._ddp_root_id], (
-        "Child should be in root's targets"
-    )
-
-
-@then("the dependency should have relationship_type {rel_type}")
-def step_assert_dependency_rel_type(context: Context, rel_type: str) -> None:
-    """Assert that the dependency has the correct relationship type."""
-    # Note: The current implementation doesn't return relationship_type,
-    # but we can verify it was stored by checking the database directly
-    from cleveragents.infrastructure.database.models import DecisionDependencyModel
-
-    session = context._ddp_factory()
-    dep = (
-        session.query(DecisionDependencyModel)
-        .filter_by(
-            source_decision_id=context._ddp_root_id,
-            target_decision_id=context._ddp_child_id,
-        )
-        .first()
-    )
-    assert dep is not None, "Dependency should exist"
-    assert dep.relationship_type == rel_type, (
-        f"Relationship type should be {rel_type}, got {dep.relationship_type}"
-    )
-
-
-@then("the dependency should be persisted with relationship_type {rel_type}")
-def step_assert_dependency_persisted_with_type(context: Context, rel_type: str) -> None:
-    """Assert that the dependency was persisted with the correct type."""
-    from cleveragents.infrastructure.database.models import DecisionDependencyModel
-
-    session = context._ddp_factory()
-    dep = (
-        session.query(DecisionDependencyModel)
-        .filter_by(
-            source_decision_id=context._ddp_root_id,
-            target_decision_id=context._ddp_child_id,
-        )
-        .first()
-    )
-    assert dep is not None, "Dependency should exist"
-    assert dep.relationship_type == rel_type, (
-        f"Relationship type should be {rel_type}, got {dep.relationship_type}"
-    )
-
-
-@then("both dependencies should be persisted to the database")
-def step_assert_both_dependencies_persisted(context: Context) -> None:
-    """Assert that both dependencies were persisted."""
-    edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-    assert context._ddp_root_id in edges, "Root should be in edges"
-    assert len(edges[context._ddp_root_id]) == 2, "Root should have 2 targets"
-    for sibling_id in context._ddp_sibling_ids:
-        assert sibling_id in edges[context._ddp_root_id], (
-            f"Sibling {sibling_id} should be in root's targets"
-        )
-
-
-@then("the influence edges should be empty")
-def step_assert_influence_edges_empty(context: Context) -> None:
-    """Assert that influence edges are empty."""
-    assert context._ddp_influence_edges == {}, "Influence edges should be empty"
-
-
-@then("the influence edges should contain {count:d} source")
-def step_assert_influence_edges_source_count(context: Context, count: int) -> None:
-    """Assert the number of sources in influence edges."""
-    assert len(context._ddp_influence_edges) == count, (
-        f"Should have {count} source(s), got {len(context._ddp_influence_edges)}"
-    )
-
-
-@then("the influence edges should map root to {targets}")
-def step_assert_influence_edges_mapping(context: Context, targets: str) -> None:
-    """Assert that influence edges map root to the specified targets."""
-    # Parse targets string (e.g., "[child]" or "[sibling1, sibling2]")
-    if targets == "[child]":
-        expected = [context._ddp_child_id]
-    elif targets == "[sibling1, sibling2]":
-        expected = context._ddp_sibling_ids
-    else:
-        expected = []
-
-    assert context._ddp_root_id in context._ddp_influence_edges, (
-        "Root should be in edges"
-    )
-    actual = context._ddp_influence_edges[context._ddp_root_id]
-    assert set(actual) == set(expected), f"Expected {expected}, got {actual}"
-
-
-@then("the influence edges should only include decisions from plan 1")
-def step_assert_influence_edges_plan1_only(context: Context) -> None:
-    """Assert that influence edges only include plan 1 decisions."""
-    edges = context._ddp_influence_edges_plan1
-    plan1_ids = {
-        context._ddp_plan1_root_id,
-        context._ddp_plan1_child_id,
-    }
-    for source, targets in edges.items():
-        assert source in plan1_ids, f"Source {source} should be in plan 1"
-        for target in targets:
-            assert target in plan1_ids, f"Target {target} should be in plan 1"
-
-
-@then("the cross-plan dependency should not appear in influence edges")
-def step_assert_no_cross_plan_dependency(context: Context) -> None:
-    """Assert that cross-plan dependencies don't appear in edges."""
-    edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-    # The cross-plan dependency should not appear because the target is in a different plan
-    if context._ddp_cross_plan_id1 in edges:
-        assert context._ddp_cross_plan_id2 not in edges[context._ddp_cross_plan_id1], (
-            "Cross-plan dependency should not appear"
-        )
-
-
-@then("the new service should retrieve the same dependency edges")
-def step_assert_new_service_same_edges(context: Context) -> None:
-    """Assert that a new service retrieves the same edges."""
-    new_edges = context._ddp_new_service.get_influence_edges(_PLAN_ID_1)
-    assert context._ddp_root_id in new_edges, "Root should be in new edges"
-    assert context._ddp_child_id in new_edges[context._ddp_root_id], (
-        "Child should be in new root's targets"
-    )
-
-
-@then("the new service should retrieve all dependency edges")
-def step_assert_new_service_all_edges(context: Context) -> None:
-    """Assert that a new service retrieves all edges."""
-    new_edges = context._ddp_new_service.get_influence_edges(_PLAN_ID_1)
-    assert len(new_edges) == 2, f"Should have 2 sources, got {len(new_edges)}"
-    assert context._ddp_tree_root_id in new_edges, "Root should be in edges"
-    assert context._ddp_tree_child_id in new_edges, "Child should be in edges"
-
-
-@then("a database constraint error should be raised")
-def step_assert_constraint_error(context: Context) -> None:
-    """Assert that a constraint error was raised."""
-    assert context._ddp_self_loop_error is not None, (
-        "Should have raised a constraint error"
-    )
-
-
-@then("the operation should complete without error")
-def step_assert_no_error(context: Context) -> None:
-    """Assert that the operation completed without error."""
-    assert context._ddp_duplicate_error is None, "Should not have raised an error"
-
-
-@then("no dependencies should be created")
-def step_assert_no_dependencies_created(context: Context) -> None:
-    """Assert that no dependencies were created."""
-    edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-    assert edges == {}, "No dependencies should be created"
-
-
-@then("get_influence_edges should return the dependency")
-def step_assert_get_influence_edges_returns_dep(context: Context) -> None:
-    """Assert that get_influence_edges returns the dependency."""
-    edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-    assert context._ddp_root_id in edges, "Root should be in edges"
-    assert context._ddp_new_decision_id in edges[context._ddp_root_id], (
-        "New decision should be in root's targets"
-    )
-
-
-@then("get_influence_edges should return both dependencies")
-def step_assert_get_influence_edges_returns_both(context: Context) -> None:
-    """Assert that get_influence_edges returns both dependencies."""
-    edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-    for root_id in context._ddp_root_ids:
-        assert root_id in edges, f"Root {root_id} should be in edges"
-        assert context._ddp_new_decision_id in edges[root_id], (
-            f"New decision should be in {root_id}'s targets"
-        )
-
-
-@then("get_influence_edges should be empty")
-def step_assert_get_influence_edges_empty(context: Context) -> None:
-    """Assert that get_influence_edges returns empty dict."""
-    edges = context._ddp_repo.get_influence_edges(_PLAN_ID_1)
-    assert edges == {}, "Influence edges should be empty"
diff --git a/features/steps/helpers/__init__.py b/features/steps/helpers/__init__.py
new file mode 100644
index 000000000..103aa2187
--- /dev/null
+++ b/features/steps/helpers/__init__.py
@@ -0,0 +1 @@
+"""Shared Behave step helpers."""
diff --git a/features/steps/helpers/decision_dependency_helpers.py b/features/steps/helpers/decision_dependency_helpers.py
new file mode 100644
index 000000000..f5ec2336d
--- /dev/null
+++ b/features/steps/helpers/decision_dependency_helpers.py
@@ -0,0 +1,224 @@
+"""Shared helpers for decision dependency persistence Behave steps."""
+
+from __future__ import annotations
+
+import tempfile
+from collections import deque
+from datetime import UTC, datetime
+from pathlib import Path
+
+from behave.runner import Context
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from cleveragents.domain.models.core.action import Action, ActionState
+from cleveragents.domain.models.core.decision import Decision, DecisionType
+from cleveragents.domain.models.core.plan import (
+    NamespacedName,
+    Plan,
+    PlanIdentity,
+    PlanPhase,
+    PlanTimestamps,
+    ProcessingState,
+)
+from cleveragents.infrastructure.database.models import Base
+from cleveragents.infrastructure.database.repositories import (
+    ActionRepository,
+    DecisionRepository,
+    LifecyclePlanRepository,
+)
+from cleveragents.infrastructure.database.unit_of_work import UnitOfWork
+
+PLAN_ID_1 = "01HV000000000000000000DP01"
+PLAN_ID_2 = "01HV000000000000000000DP02"
+
+
+def setup_db(context: Context) -> None:
+    """Create a per-scenario SQLite database and attach repositories."""
+    tmp_dir = Path(tempfile.mkdtemp(prefix="ddp-", dir="/tmp"))
+    db_path = tmp_dir / "decision-dependencies.sqlite"
+    engine = create_engine(f"sqlite:///{db_path}", echo=False)
+    Base.metadata.create_all(engine)
+    session_factory = sessionmaker(
+        bind=engine,
+        expire_on_commit=False,
+        autoflush=False,
+        autocommit=False,
+    )
+    session = session_factory()
+
+    context._ddp_tmp_dir = tmp_dir
+    context._ddp_db_url = f"sqlite:///{db_path}"
+    context._ddp_engine = engine
+    context._ddp_session = session
+    context._ddp_uow_session_factory = session_factory
+    context._ddp_factory = lambda: session
+    context._ddp_repo = DecisionRepository(session_factory=context._ddp_factory)
+    context._ddp_action_repo = ActionRepository(session_factory=context._ddp_factory)
+    context._ddp_plan_repo = LifecyclePlanRepository(
+        session_factory=context._ddp_factory,
+    )
+    context._ddp_uow = UnitOfWork(
+        context._ddp_db_url,
+        require_confirmation=False,
+    )
+    context._ddp_uow._engine = engine
+    context._ddp_uow._session_factory = session_factory
+
+
+def make_decision(
+    plan_id: str = PLAN_ID_1,
+    parent_decision_id: str | None = None,
+    sequence_number: int = 0,
+    decision_type: DecisionType = DecisionType.PROMPT_DEFINITION,
+    question: str = "What approach should we take?",
+    chosen_option: str = "Build a REST API",
+) -> Decision:
+    """Create a Decision domain model."""
+    return Decision(
+        plan_id=plan_id,
+        sequence_number=sequence_number,
+        decision_type=decision_type,
+        question=question,
+        chosen_option=chosen_option,
+        parent_decision_id=parent_decision_id,
+    )
+
+
+def create_prerequisite_action(context: Context, action_name: str) -> None:
+    """Create a prerequisite action for testing."""
+    ns = NamespacedName.parse(action_name)
+    action = Action(
+        namespaced_name=ns,
+        description="Prerequisite action for dependency tests",
+        definition_of_done="Done",
+        strategy_actor="local/s",
+        execution_actor="local/e",
+        state=ActionState.AVAILABLE,
+        created_at=datetime(2026, 1, 1, tzinfo=UTC),
+        updated_at=datetime(2026, 1, 1, tzinfo=UTC),
+    )
+    context._ddp_action_repo.create(action)
+    context._ddp_session.commit()
+
+
+def create_prerequisite_plan(context: Context, plan_id: str) -> None:
+    """Create a prerequisite plan for testing."""
+    now = datetime(2026, 3, 1, tzinfo=UTC)
+    plan = Plan(
+        identity=PlanIdentity(plan_id=plan_id, attempt=1),
+        namespaced_name=NamespacedName(namespace="local", name="decision-plan"),
+        action_name="local/decision-action",
+        description="Decision test plan",
+        definition_of_done="All assertions pass",
+        phase=PlanPhase.STRATEGIZE,
+        processing_state=ProcessingState.PROCESSING,
+        strategy_actor="local/s",
+        execution_actor="local/e",
+        timestamps=PlanTimestamps(created_at=now, updated_at=now),
+        created_by="test-dependency",
+        tags=[],
+        reusable=True,
+        read_only=False,
+    )
+    context._ddp_plan_repo.create(plan)
+    context._ddp_session.commit()
+
+
+def persist_decision(context: Context, decision: Decision) -> Decision:
+    """Persist one decision and commit it."""
+    context._ddp_repo.create(decision)
+    context._ddp_session.commit()
+    return decision
+
+
+def create_root(context: Context, plan_id: str = PLAN_ID_1, index: int = 0) -> Decision:
+    """Create a persisted root decision."""
+    return persist_decision(
+        context,
+        make_decision(plan_id=plan_id, sequence_number=index),
+    )
+
+
+def create_child(
+    context: Context,
+    root_id: str,
+    plan_id: str = PLAN_ID_1,
+    sequence_number: int = 1,
+) -> Decision:
+    """Create a persisted child decision."""
+    return persist_decision(
+        context,
+        make_decision(
+            plan_id=plan_id,
+            parent_decision_id=root_id,
+            sequence_number=sequence_number,
+            decision_type=DecisionType.STRATEGY_CHOICE,
+        ),
+    )
+
+
+def record_dependency(
+    context: Context,
+    source_id: str,
+    target_id: str,
+    relationship_type: str = "influences",
+) -> None:
+    """Persist one dependency edge and commit it."""
+    context._ddp_repo.record_dependency(
+        source_id,
+        target_id,
+        relationship_type=relationship_type,
+    )
+    context._ddp_session.commit()
+
+
+def get_edges(context: Context, plan_id: str = PLAN_ID_1) -> dict[str, list[str]]:
+    """Read influence edges after expiring the assertion session cache."""
+    context._ddp_session.expire_all()
+    return context._ddp_repo.get_influence_edges(plan_id)
+
+
+def create_three_level_tree(context: Context) -> None:
+    """Create a root -> child -> grandchild tree."""
+    root = create_root(context)
+    child = create_child(context, root.decision_id, sequence_number=1)
+    grandchild = persist_decision(
+        context,
+        make_decision(
+            plan_id=PLAN_ID_1,
+            parent_decision_id=child.decision_id,
+            sequence_number=2,
+            decision_type=DecisionType.IMPLEMENTATION_CHOICE,
+        ),
+    )
+    context._ddp_tree_root_id = root.decision_id
+    context._ddp_tree_child_id = child.decision_id
+    context._ddp_tree_grandchild_id = grandchild.decision_id
+
+
+def record_three_level_edges(context: Context) -> None:
+    """Record root -> child and child -> grandchild dependencies."""
+    record_dependency(
+        context,
+        context._ddp_tree_root_id,
+        context._ddp_tree_child_id,
+    )
+    record_dependency(
+        context,
+        context._ddp_tree_child_id,
+        context._ddp_tree_grandchild_id,
+    )
+
+
+def affected_subtree(start_id: str, edges: dict[str, list[str]]) -> set[str]:
+    """Return all transitive dependents reachable from start_id."""
+    affected: set[str] = set()
+    queue: deque[str] = deque(edges.get(start_id, []))
+    while queue:
+        decision_id = queue.popleft()
+        if decision_id in affected:
+            continue
+        affected.add(decision_id)
+        queue.extend(edges.get(decision_id, []))
+    return affected
diff --git a/src/cleveragents/infrastructure/database/repositories.py b/src/cleveragents/infrastructure/database/repositories.py
index 6064b06b0..90e8de06f 100644
--- a/src/cleveragents/infrastructure/database/repositories.py
+++ b/src/cleveragents/infrastructure/database/repositories.py
@@ -111,6 +111,7 @@ from cleveragents.infrastructure.database.models import (
     ContextModel,
     CorrectionAttemptModel,
     DebugAttemptModel,
+    DecisionDependencyModel,
     DecisionModel,
     LifecycleActionModel,
     LifecyclePlanModel,
@@ -5754,10 +5755,8 @@ class DecisionRepository(DecisionRepositoryProtocol):
         Raises:
             DatabaseError: On constraint violation or transient DB errors.
         """
-        from cleveragents.infrastructure.database.models import (
-            DecisionDependencyModel,
-        )
-
+        if source_decision_id == target_decision_id:
+            raise DatabaseError("Decision dependency self-loops are not allowed")
         session = self._session()
         try:
             now_iso = datetime.now(UTC).isoformat()
@@ -5795,11 +5794,6 @@ class DecisionRepository(DecisionRepositoryProtocol):
         Raises:
             DatabaseError: On transient or unexpected DB errors.
         """
-        from cleveragents.infrastructure.database.models import (
-            DecisionDependencyModel,
-            DecisionModel,
-        )
-
         session = self._session()
         try:
             # Get all decision IDs for the plan