diff --git a/alembic/versions/m6_005_estimation_report_domain.py b/alembic/versions/m6_005_estimation_report_domain.py
new file mode 100644
index 000000000..c69662129
--- /dev/null
+++ b/alembic/versions/m6_005_estimation_report_domain.py
@@ -0,0 +1,70 @@
+"""Add estimation_report column and estimation_produced decision type.
+
+Adds the estimation_report JSON column to the v3_plans table for
+persisting structured estimation actor output. Also updates the
+decisions table CHECK constraint to include the new estimation_produced
+decision type.
+
+Revision ID: m6_005_estimation_report_domain
+Revises: m6_004_resource_type_inherits
+Create Date: 2026-03-10
+
+"""
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "m6_005_estimation_report_domain"
+down_revision: str | None = "m6_004_resource_type_inherits"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Add estimation_report column and update decision type constraint."""
+
+    # Add estimation_report JSON column to v3_plans
+    op.add_column(
+        "v3_plans",
+        sa.Column("estimation_report", sa.Text, nullable=True),
+    )
+
+    # Update decision_type CHECK constraint to include estimation_produced
+    # Use batch mode for SQLite compatibility
+    with op.batch_alter_table("decisions", schema=None) as batch_op:
+        batch_op.drop_constraint("ck_decisions_type", type_="check")
+        batch_op.create_check_constraint(
+            "ck_decisions_type",
+            "decision_type IN ("
+            "'prompt_definition', 'invariant_enforced', "
+            "'strategy_choice', 'implementation_choice', "
+            "'resource_selection', 'subplan_spawn', "
+            "'subplan_parallel_spawn', 'tool_invocation', "
+            "'error_recovery', 'validation_response', "
+            "'user_intervention', 'estimation_produced')",
+        )
+
+
+def downgrade() -> None:
+    """Remove estimation_report column and revert decision type constraint."""
+
+    # Drop estimation_report column from v3_plans
+    op.drop_column("v3_plans", "estimation_report")
+
+    # Revert decision_type CHECK constraint to exclude estimation_produced
+    # Use batch mode for SQLite compatibility
+    with op.batch_alter_table("decisions", schema=None) as batch_op:
+        batch_op.drop_constraint("ck_decisions_type", type_="check")
+        batch_op.create_check_constraint(
+            "ck_decisions_type",
+            "decision_type IN ("
+            "'prompt_definition', 'invariant_enforced', "
+            "'strategy_choice', 'implementation_choice', "
+            "'resource_selection', 'subplan_spawn', "
+            "'subplan_parallel_spawn', 'tool_invocation', "
+            "'error_recovery', 'validation_response', "
+            "'user_intervention')",
+        )
diff --git a/docs/reference/database_schema.md b/docs/reference/database_schema.md
index 12648fdfb..7ff1b9b57 100644
--- a/docs/reference/database_schema.md
+++ b/docs/reference/database_schema.md
@@ -320,7 +320,7 @@ FK to `v3_plans.plan_id` (CASCADE delete).  Self-referential FKs for
 | `plan_id`                      | String(26)  | NOT NULL, FK -> v3_plans CASCADE      | Parent plan reference                   |
 | `parent_decision_id`           | String(26)  | FK -> decisions SET NULL              | Parent decision in tree                 |
 | `sequence_number`              | Integer     | NOT NULL                              | Monotonic order within plan             |
-| `decision_type`                | String(30)  | NOT NULL, CHECK (11 enum values)      | Classification of the decision          |
+| `decision_type`                | String(30)  | NOT NULL, CHECK (12 enum values)      | Classification of the decision          |
 | `question`                     | Text        | NOT NULL                              | What question was being answered        |
 | `chosen_option`                | Text        | NOT NULL                              | The option that was chosen              |
 | `alternatives_considered_json` | Text        |                                       | JSON array of alternative options       |
diff --git a/docs/reference/decision_model.md b/docs/reference/decision_model.md
index 2fa184d8d..09f291968 100644
--- a/docs/reference/decision_model.md
+++ b/docs/reference/decision_model.md
@@ -32,7 +32,7 @@ targeted correction and replay.
 
 ### Classification
 
-- **decision_type** — one of the 11 `DecisionType` enum values
+- **decision_type** — one of the 12 `DecisionType` enum values
 
 ### Content
 
diff --git a/features/consolidated_decision.feature b/features/consolidated_decision.feature
index 86219e393..701a2cf89 100644
--- a/features/consolidated_decision.feature
+++ b/features/consolidated_decision.feature
@@ -6,8 +6,8 @@ Feature: Consolidated Decision
   # Feature: Decision domain model
   # ============================================================
 
-  Scenario: All 11 decision types are defined
-    Then the DecisionType enum should have exactly 11 members
+  Scenario: All 12 decision types are defined
+    Then the DecisionType enum should have exactly 12 members
 
 
   Scenario: Strategize-phase types are correctly classified
@@ -16,7 +16,8 @@ Feature: Consolidated Decision
     And STRATEGIZE_TYPES should contain "strategy_choice"
     And STRATEGIZE_TYPES should contain "subplan_spawn"
     And STRATEGIZE_TYPES should contain "subplan_parallel_spawn"
-    And STRATEGIZE_TYPES should have exactly 5 members
+    And STRATEGIZE_TYPES should contain "estimation_produced"
+    And STRATEGIZE_TYPES should have exactly 6 members
 
 
   Scenario: Execute-phase types are correctly classified
@@ -252,7 +253,7 @@ Feature: Consolidated Decision
     And as_cli_dict should contain key "parent"
 
     # ------------------------------------------------------------------
-    # All 11 decision types can be instantiated
+    # All 12 decision types can be instantiated
     # ------------------------------------------------------------------
 
 
@@ -274,6 +275,7 @@ Feature: Consolidated Decision
       | error_recovery         |
       | validation_response    |
       | user_intervention      |
+      | estimation_produced    |
 
 
   # ============================================================
@@ -443,4 +445,3 @@ Feature: Consolidated Decision
     When I decision persistence create a decision with a 2000 character rationale
     And I decision persistence round-trip the decision through model_dump
     Then the decision persistence restored rationale length should be 2000
-
diff --git a/features/estimation_report.feature b/features/estimation_report.feature
new file mode 100644
index 000000000..063625173
--- /dev/null
+++ b/features/estimation_report.feature
@@ -0,0 +1,105 @@
+Feature: EstimationReport domain model
+  Tests for the EstimationReport Pydantic model that captures structured
+  multi-dimensional estimation output from the estimation actor.
+
+  Scenario: Create a valid EstimationReport with all required fields
+    When I create an EstimationReport with valid data
+    Then the EstimationReport should be created successfully
+    And the EstimationReport cost range min should be 0.50
+    And the EstimationReport cost range max should be 2.00
+    And the EstimationReport expected steps should be 5
+    And the EstimationReport expected child plans should be 2
+    And the EstimationReport rollback risk should be 0.25
+    And the EstimationReport confidence should be 0.85
+
+  Scenario: EstimationReport validates cost_range_usd_max >= cost_range_usd_min
+    When I try to create an EstimationReport with max cost less than min cost
+    Then an EstimationReport validation error should be raised
+    And the error should mention "cost_range_usd_max"
+
+  Scenario: EstimationReport validates rollback_risk in [0.0, 1.0] range
+    When I try to create an EstimationReport with rollback_risk 1.5
+    Then an EstimationReport validation error should be raised
+    And the error should mention "rollback_risk"
+
+  Scenario: EstimationReport validates rollback_risk negative value
+    When I try to create an EstimationReport with rollback_risk -0.1
+    Then an EstimationReport validation error should be raised
+
+  Scenario: EstimationReport validates confidence in [0.0, 1.0] range
+    When I try to create an EstimationReport with confidence 1.2
+    Then an EstimationReport validation error should be raised
+    And the error should mention "confidence"
+
+  Scenario: EstimationReport validates confidence negative value
+    When I try to create an EstimationReport with confidence -0.05
+    Then an EstimationReport validation error should be raised
+
+  Scenario: EstimationReport accepts rollback_risk at boundary 0.0
+    When I create an EstimationReport with rollback_risk 0.0
+    Then the EstimationReport should be created successfully
+    And the EstimationReport rollback risk should be 0.0
+
+  Scenario: EstimationReport accepts rollback_risk at boundary 1.0
+    When I create an EstimationReport with rollback_risk 1.0
+    Then the EstimationReport should be created successfully
+    And the EstimationReport rollback risk should be 1.0
+
+  Scenario: EstimationReport accepts confidence at boundary 0.0
+    When I create an EstimationReport with confidence 0.0
+    Then the EstimationReport should be created successfully
+    And the EstimationReport confidence should be 0.0
+
+  Scenario: EstimationReport accepts confidence at boundary 1.0
+    When I create an EstimationReport with confidence 1.0
+    Then the EstimationReport should be created successfully
+    And the EstimationReport confidence should be 1.0
+
+  Scenario: EstimationReport round-trips through model_dump and model_validate
+    When I create an EstimationReport with valid data
+    And I serialize the EstimationReport with model_dump
+    And I deserialize the EstimationReport with model_validate
+    Then the deserialized EstimationReport should match the original
+
+  Scenario: EstimationReport round-trips through JSON serialization
+    When I create an EstimationReport with valid data
+    And I serialize the EstimationReport to JSON
+    And I deserialize the EstimationReport from JSON
+    Then the deserialized EstimationReport should match the original
+
+  Scenario: EstimationReport with historical basis persists correctly
+    When I create an EstimationReport with 3 historical plan IDs
+    Then the EstimationReport should be created successfully
+    And the EstimationReport should have 3 historical basis entries
+
+  Scenario: EstimationReport with empty rationale is valid
+    When I create an EstimationReport with empty rationale
+    Then the EstimationReport should be created successfully
+    And the EstimationReport rationale should be empty
+
+  Scenario: EstimationReport with rationale persists correctly
+    When I create an EstimationReport with rationale "Based on similar complexity"
+    Then the EstimationReport should be created successfully
+    And the EstimationReport rationale should be "Based on similar complexity"
+
+  Scenario: EstimationReport is immutable (frozen model)
+    When I create an EstimationReport with valid data
+    Then I should not be able to modify the EstimationReport fields
+
+  Scenario: EstimationReport validates negative cost_range_usd_min
+    When I try to create an EstimationReport with cost_range_usd_min -1.0
+    Then an EstimationReport validation error should be raised
+
+  Scenario: EstimationReport validates negative expected_steps
+    When I try to create an EstimationReport with expected_steps -1
+    Then an EstimationReport validation error should be raised
+
+  Scenario: EstimationReport validates negative estimated_duration_minutes
+    When I try to create an EstimationReport with estimated_duration_minutes -5.0
+    Then an EstimationReport validation error should be raised
+
+  Scenario: EstimationReport with zero values is valid
+    When I create an EstimationReport with zero cost and steps
+    Then the EstimationReport should be created successfully
+    And the EstimationReport cost range min should be 0.0
+    And the EstimationReport expected steps should be 0
diff --git a/features/steps/estimation_report_steps.py b/features/steps/estimation_report_steps.py
new file mode 100644
index 000000000..9a56e6108
--- /dev/null
+++ b/features/steps/estimation_report_steps.py
@@ -0,0 +1,320 @@
+"""Step definitions for estimation_report.feature.
+
+Tests the EstimationReport Pydantic domain model including validation,
+serialization, and immutability.
+"""
+
+from __future__ import annotations
+
+from behave import then, when  # type: ignore[import-untyped]
+from behave.runner import Context
+from pydantic import ValidationError
+
+from cleveragents.domain.models.core.estimation import EstimationReport
+
+# ---------------------------------------------------------------------------
+# Helper functions
+# ---------------------------------------------------------------------------
+
+
+def _make_estimation_report(
+    cost_min: float = 0.50,
+    cost_max: float = 2.00,
+    expected_steps: int = 5,
+    expected_child_plans: int = 2,
+    rollback_risk: float = 0.25,
+    confidence: float = 0.85,
+    estimated_duration_minutes: float = 15.0,
+    rationale: str = "Standard complexity estimate",
+    historical_basis: list[str] | None = None,
+) -> EstimationReport:
+    """Create an EstimationReport with optional overrides."""
+    return EstimationReport(
+        cost_range_usd_min=cost_min,
+        cost_range_usd_max=cost_max,
+        expected_steps=expected_steps,
+        expected_child_plans=expected_child_plans,
+        rollback_risk=rollback_risk,
+        confidence=confidence,
+        estimated_duration_minutes=estimated_duration_minutes,
+        rationale=rationale,
+        historical_basis=historical_basis or [],
+    )
+
+
+# ---------------------------------------------------------------------------
+# When steps - Creating EstimationReport instances
+# ---------------------------------------------------------------------------
+
+
+@when("I create an EstimationReport with valid data")
+def step_create_valid_estimation_report(context: Context) -> None:
+    """Create a valid EstimationReport and store in context."""
+    context.estimation_report = _make_estimation_report()
+    context.estimation_error = None
+
+
+@when("I try to create an EstimationReport with max cost less than min cost")
+def step_create_invalid_cost_range(context: Context) -> None:
+    """Try to create EstimationReport with max < min."""
+    try:
+        context.estimation_report = _make_estimation_report(cost_min=5.0, cost_max=2.0)
+        context.estimation_error = None
+    except ValidationError as e:
+        context.estimation_error = e
+        context.estimation_report = None
+
+
+@when("I try to create an EstimationReport with rollback_risk {value:f}")
+def step_create_invalid_rollback_risk(context: Context, value: float) -> None:
+    """Try to create EstimationReport with invalid rollback_risk."""
+    try:
+        context.estimation_report = _make_estimation_report(rollback_risk=value)
+        context.estimation_error = None
+    except ValidationError as e:
+        context.estimation_error = e
+        context.estimation_report = None
+
+
+@when("I try to create an EstimationReport with confidence {value:f}")
+def step_create_invalid_confidence(context: Context, value: float) -> None:
+    """Try to create EstimationReport with invalid confidence."""
+    try:
+        context.estimation_report = _make_estimation_report(confidence=value)
+        context.estimation_error = None
+    except ValidationError as e:
+        context.estimation_error = e
+        context.estimation_report = None
+
+
+@when("I create an EstimationReport with rollback_risk {value:f}")
+def step_create_with_rollback_risk(context: Context, value: float) -> None:
+    """Create EstimationReport with specific rollback_risk."""
+    context.estimation_report = _make_estimation_report(rollback_risk=value)
+    context.estimation_error = None
+
+
+@when("I create an EstimationReport with confidence {value:f}")
+def step_create_with_confidence(context: Context, value: float) -> None:
+    """Create EstimationReport with specific confidence."""
+    context.estimation_report = _make_estimation_report(confidence=value)
+    context.estimation_error = None
+
+
+@when("I create an EstimationReport with {count:d} historical plan IDs")
+def step_create_with_historical_basis(context: Context, count: int) -> None:
+    """Create EstimationReport with historical plan IDs."""
+    historical_ids = [f"01H{i:024d}" for i in range(count)]
+    context.estimation_report = _make_estimation_report(historical_basis=historical_ids)
+    context.estimation_error = None
+
+
+@when("I create an EstimationReport with empty rationale")
+def step_create_with_empty_rationale(context: Context) -> None:
+    """Create EstimationReport with empty rationale."""
+    context.estimation_report = _make_estimation_report(rationale="")
+    context.estimation_error = None
+
+
+@when('I create an EstimationReport with rationale "{rationale}"')
+def step_create_with_rationale(context: Context, rationale: str) -> None:
+    """Create EstimationReport with specific rationale."""
+    context.estimation_report = _make_estimation_report(rationale=rationale)
+    context.estimation_error = None
+
+
+@when("I try to create an EstimationReport with cost_range_usd_min {value:f}")
+def step_create_invalid_min_cost(context: Context, value: float) -> None:
+    """Try to create EstimationReport with invalid min cost."""
+    try:
+        context.estimation_report = _make_estimation_report(
+            cost_min=value, cost_max=5.0
+        )
+        context.estimation_error = None
+    except ValidationError as e:
+        context.estimation_error = e
+        context.estimation_report = None
+
+
+@when("I try to create an EstimationReport with expected_steps {value:d}")
+def step_create_invalid_steps(context: Context, value: int) -> None:
+    """Try to create EstimationReport with invalid expected_steps."""
+    try:
+        context.estimation_report = _make_estimation_report(expected_steps=value)
+        context.estimation_error = None
+    except ValidationError as e:
+        context.estimation_error = e
+        context.estimation_report = None
+
+
+@when("I try to create an EstimationReport with estimated_duration_minutes {value:f}")
+def step_create_invalid_duration(context: Context, value: float) -> None:
+    """Try to create EstimationReport with invalid duration."""
+    try:
+        context.estimation_report = _make_estimation_report(
+            estimated_duration_minutes=value
+        )
+        context.estimation_error = None
+    except ValidationError as e:
+        context.estimation_error = e
+        context.estimation_report = None
+
+
+@when("I create an EstimationReport with zero cost and steps")
+def step_create_with_zeros(context: Context) -> None:
+    """Create EstimationReport with zero values."""
+    context.estimation_report = _make_estimation_report(
+        cost_min=0.0,
+        cost_max=0.0,
+        expected_steps=0,
+        expected_child_plans=0,
+        estimated_duration_minutes=0.0,
+    )
+    context.estimation_error = None
+
+
+# ---------------------------------------------------------------------------
+# Serialization steps
+# ---------------------------------------------------------------------------
+
+
+@when("I serialize the EstimationReport with model_dump")
+def step_serialize_model_dump(context: Context) -> None:
+    """Serialize EstimationReport using model_dump."""
+    context.serialized_data = context.estimation_report.model_dump()
+
+
+@when("I deserialize the EstimationReport with model_validate")
+def step_deserialize_model_validate(context: Context) -> None:
+    """Deserialize EstimationReport using model_validate."""
+    context.deserialized_report = EstimationReport.model_validate(
+        context.serialized_data
+    )
+
+
+@when("I serialize the EstimationReport to JSON")
+def step_serialize_to_json(context: Context) -> None:
+    """Serialize EstimationReport to JSON string."""
+    context.json_data = context.estimation_report.model_dump_json()
+
+
+@when("I deserialize the EstimationReport from JSON")
+def step_deserialize_from_json(context: Context) -> None:
+    """Deserialize EstimationReport from JSON string."""
+    context.deserialized_report = EstimationReport.model_validate_json(
+        context.json_data
+    )
+
+
+# ---------------------------------------------------------------------------
+# Then steps - Assertions
+# ---------------------------------------------------------------------------
+
+
+@then("the EstimationReport should be created successfully")
+def step_report_created_successfully(context: Context) -> None:
+    """Assert EstimationReport was created without errors."""
+    assert context.estimation_report is not None, "EstimationReport should be created"
+    assert context.estimation_error is None, f"Got error: {context.estimation_error}"
+
+
+@then("an EstimationReport validation error should be raised")
+def step_validation_error_raised(context: Context) -> None:
+    """Assert a ValidationError was raised."""
+    assert context.estimation_error is not None, "Expected a ValidationError"
+    assert isinstance(context.estimation_error, ValidationError), (
+        f"Expected ValidationError, got {type(context.estimation_error)}"
+    )
+    # Store in context.error for compatibility with shared steps
+    context.error = context.estimation_error
+
+
+@then("the EstimationReport cost range min should be {value:f}")
+def step_check_cost_min(context: Context, value: float) -> None:
+    """Assert cost_range_usd_min matches expected value."""
+    assert context.estimation_report.cost_range_usd_min == value, (
+        f"Expected {value}, got {context.estimation_report.cost_range_usd_min}"
+    )
+
+
+@then("the EstimationReport cost range max should be {value:f}")
+def step_check_cost_max(context: Context, value: float) -> None:
+    """Assert cost_range_usd_max matches expected value."""
+    assert context.estimation_report.cost_range_usd_max == value, (
+        f"Expected {value}, got {context.estimation_report.cost_range_usd_max}"
+    )
+
+
+@then("the EstimationReport expected steps should be {value:d}")
+def step_check_expected_steps(context: Context, value: int) -> None:
+    """Assert expected_steps matches expected value."""
+    assert context.estimation_report.expected_steps == value, (
+        f"Expected {value}, got {context.estimation_report.expected_steps}"
+    )
+
+
+@then("the EstimationReport expected child plans should be {value:d}")
+def step_check_expected_child_plans(context: Context, value: int) -> None:
+    """Assert expected_child_plans matches expected value."""
+    assert context.estimation_report.expected_child_plans == value, (
+        f"Expected {value}, got {context.estimation_report.expected_child_plans}"
+    )
+
+
+@then("the EstimationReport rollback risk should be {value:f}")
+def step_check_rollback_risk(context: Context, value: float) -> None:
+    """Assert rollback_risk matches expected value."""
+    assert context.estimation_report.rollback_risk == value, (
+        f"Expected {value}, got {context.estimation_report.rollback_risk}"
+    )
+
+
+@then("the EstimationReport confidence should be {value:f}")
+def step_check_confidence(context: Context, value: float) -> None:
+    """Assert confidence matches expected value."""
+    assert context.estimation_report.confidence == value, (
+        f"Expected {value}, got {context.estimation_report.confidence}"
+    )
+
+
+@then("the deserialized EstimationReport should match the original")
+def step_check_deserialized_matches(context: Context) -> None:
+    """Assert deserialized report matches original."""
+    assert context.deserialized_report == context.estimation_report, (
+        "Deserialized report should match original"
+    )
+
+
+@then("the EstimationReport should have {count:d} historical basis entries")
+def step_check_historical_basis_count(context: Context, count: int) -> None:
+    """Assert historical_basis has expected number of entries."""
+    actual_count = len(context.estimation_report.historical_basis)
+    assert actual_count == count, (
+        f"Expected {count} historical basis entries, got {actual_count}"
+    )
+
+
+@then("the EstimationReport rationale should be empty")
+def step_check_rationale_empty(context: Context) -> None:
+    """Assert rationale is empty string."""
+    assert context.estimation_report.rationale == "", "Rationale should be empty"
+
+
+@then('the EstimationReport rationale should be "{rationale}"')
+def step_check_rationale_value(context: Context, rationale: str) -> None:
+    """Assert rationale matches expected value."""
+    assert context.estimation_report.rationale == rationale, (
+        f"Expected '{rationale}', got '{context.estimation_report.rationale}'"
+    )
+
+
+@then("I should not be able to modify the EstimationReport fields")
+def step_check_immutability(context: Context) -> None:
+    """Assert that EstimationReport fields cannot be modified."""
+    try:
+        context.estimation_report.confidence = 0.5
+        raise AssertionError("Should not be able to modify frozen model")
+    except ValidationError:
+        pass
+    except AttributeError:
+        pass
diff --git a/features/steps/repositories_coverage_r2_steps.py b/features/steps/repositories_coverage_r2_steps.py
index 149f8f014..24cd833bc 100644
--- a/features/steps/repositories_coverage_r2_steps.py
+++ b/features/steps/repositories_coverage_r2_steps.py
@@ -18,7 +18,7 @@ from behave import given, then, when
 from behave.runner import Context
 from sqlalchemy import create_engine
 from sqlalchemy.exc import OperationalError
-from sqlalchemy.orm import Session, sessionmaker
+from sqlalchemy.orm import Session, scoped_session, sessionmaker
 
 from cleveragents.core.exceptions import DatabaseError
 from cleveragents.domain.models.core.checkpoint import Checkpoint, CheckpointMetadata
@@ -234,7 +234,7 @@ def step_fresh_db(context: Context) -> None:
     engine = create_engine("sqlite:///:memory:", echo=False)
     Base.metadata.create_all(engine)
     context.r2_engine = engine
-    context.r2_session_factory = sessionmaker(bind=engine)
+    context.r2_session_factory = scoped_session(sessionmaker(bind=engine))
 
     # Pre-create repos used by multiple scenarios
     context.r2_skill_repo = SkillRepository(
diff --git a/robot/decision_model.robot b/robot/decision_model.robot
index b0a54dc02..c85725690 100644
--- a/robot/decision_model.robot
+++ b/robot/decision_model.robot
@@ -21,7 +21,7 @@ Create Child Decision
     Should Contain    ${result.stdout}    decision-create-child-ok
 
 Decision Type Enum Values
-    [Documentation]    Verify all 11 decision type enum values
+    [Documentation]    Verify all 12 decision type enum values
     ${result}=    Run Process    ${PYTHON}    ${HELPER_SCRIPT}    enum_values    cwd=${WORKSPACE}
     Should Be Equal As Integers    ${result.rc}    0
     Should Contain    ${result.stdout}    decision-enums-ok
diff --git a/robot/helper_decision_model.py b/robot/helper_decision_model.py
index 691427348..dbf675524 100644
--- a/robot/helper_decision_model.py
+++ b/robot/helper_decision_model.py
@@ -55,7 +55,7 @@ def _test_create_child() -> None:
 
 
 def _test_enum_values() -> None:
-    """Verify all 11 decision type enum values."""
+    """Verify all 12 decision type enum values."""
     expected = {
         "prompt_definition",
         "invariant_enforced",
@@ -68,10 +68,11 @@ def _test_enum_values() -> None:
         "error_recovery",
         "validation_response",
         "user_intervention",
+        "estimation_produced",
     }
     actual = {dt.value for dt in DecisionType}
     assert actual == expected, f"Mismatch: {actual.symmetric_difference(expected)}"
-    assert len(DecisionType) == 11
+    assert len(DecisionType) == 12
     print("decision-enums-ok")
 
 
diff --git a/src/cleveragents/domain/models/core/__init__.py b/src/cleveragents/domain/models/core/__init__.py
index 19016bd81..ee34c1f33 100644
--- a/src/cleveragents/domain/models/core/__init__.py
+++ b/src/cleveragents/domain/models/core/__init__.py
@@ -134,6 +134,9 @@ from cleveragents.domain.models.core.escalation import (
     OperationContext,
 )
 
+# Estimation domain models
+from cleveragents.domain.models.core.estimation import EstimationReport
+
 # Invariant domain models
 from cleveragents.domain.models.core.invariant import (
     Invariant,
@@ -374,6 +377,7 @@ __all__ = [
     "ErrorRecord",
     "ErrorRecoveryPolicy",
     "EscalationDecision",
+    "EstimationReport",
     "ExecutionEnvironment",
     "FileRecord",
     "FragmentProvenance",
diff --git a/src/cleveragents/domain/models/core/decision.py b/src/cleveragents/domain/models/core/decision.py
index 41c3edf6b..8a4535521 100644
--- a/src/cleveragents/domain/models/core/decision.py
+++ b/src/cleveragents/domain/models/core/decision.py
@@ -48,6 +48,9 @@ Decision types
    * - ``user_intervention``
      - Any
      - User-provided guidance / correction
+   * - ``estimation_produced``
+     - Strategize
+     - Cost/risk estimation result recorded
 
 Context snapshots
 -----------------
@@ -105,6 +108,7 @@ class DecisionType(StrEnum):
     ERROR_RECOVERY = "error_recovery"
     VALIDATION_RESPONSE = "validation_response"
     USER_INTERVENTION = "user_intervention"
+    ESTIMATION_PRODUCED = "estimation_produced"
 
 
 #: Decision types that may only be created during the Strategize phase.
@@ -115,6 +119,7 @@ STRATEGIZE_TYPES: frozenset[DecisionType] = frozenset(
         DecisionType.STRATEGY_CHOICE,
         DecisionType.SUBPLAN_SPAWN,
         DecisionType.SUBPLAN_PARALLEL_SPAWN,
+        DecisionType.ESTIMATION_PRODUCED,
     }
 )
 
diff --git a/src/cleveragents/domain/models/core/estimation.py b/src/cleveragents/domain/models/core/estimation.py
new file mode 100644
index 000000000..1e55f571a
--- /dev/null
+++ b/src/cleveragents/domain/models/core/estimation.py
@@ -0,0 +1,106 @@
+"""Estimation domain models for cost and risk analysis.
+
+Models the multi-dimensional output of the estimation actor, including
+cost ranges, step counts, rollback risk, execution time estimates, and
+confidence scoring.
+
+Based on docs/specification.md lines 18996-19013 and issue #649.
+"""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, ConfigDict, Field, field_validator
+
+
+class EstimationReport(BaseModel):
+    """Structured multi-dimensional estimation output from estimation actor.
+
+    Captures the full richness of cost/risk estimation beyond a single
+    scalar value. Persisted alongside plans as JSON for auditability
+    and analysis.
+
+    All range constraints (rollback_risk, confidence) are validated
+    at model construction and assignment time.
+    """
+
+    model_config = ConfigDict(frozen=True, str_strip_whitespace=True)
+
+    # Cost estimation (min/max range in USD)
+    cost_range_usd_min: float = Field(
+        ...,
+        ge=0.0,
+        description="Minimum estimated cost in USD",
+    )
+    cost_range_usd_max: float = Field(
+        ...,
+        ge=0.0,
+        description="Maximum estimated cost in USD",
+    )
+
+    # Effort estimation
+    expected_steps: int = Field(
+        ...,
+        ge=0,
+        description="Expected number of execution steps",
+    )
+    expected_child_plans: int = Field(
+        ...,
+        ge=0,
+        description="Expected number of child plans to be spawned",
+    )
+
+    # Risk and confidence metrics (0.0-1.0 range)
+    rollback_risk: float = Field(
+        ...,
+        ge=0.0,
+        le=1.0,
+        description="Estimated probability of rollback (0.0-1.0)",
+    )
+    confidence: float = Field(
+        ...,
+        ge=0.0,
+        le=1.0,
+        description="Confidence in the estimation (0.0-1.0)",
+    )
+
+    # Time estimation
+    estimated_duration_minutes: float = Field(
+        ...,
+        ge=0.0,
+        description="Estimated execution time in minutes",
+    )
+
+    # Rationale and provenance
+    rationale: str = Field(
+        default="",
+        description="Human-readable rationale for the estimates",
+    )
+    historical_basis: list[str] = Field(
+        default_factory=list,
+        description="Optional list of historical plan IDs used as basis",
+    )
+
+    @field_validator("cost_range_usd_max")
+    @classmethod
+    def _cost_max_gte_min(cls, v: float, info) -> float:
+        """Ensure max cost is greater than or equal to min cost."""
+        if "cost_range_usd_min" in info.data:
+            min_cost = info.data["cost_range_usd_min"]
+            if v < min_cost:
+                raise ValueError(
+                    f"cost_range_usd_max ({v}) must be >= "
+                    f"cost_range_usd_min ({min_cost})"
+                )
+        return v
+
+    @field_validator("rollback_risk", "confidence")
+    @classmethod
+    def _validate_probability_range(cls, v: float, info) -> float:
+        """Validate that probability fields are in [0.0, 1.0] range."""
+        field_name = info.field_name
+        if not 0.0 <= v <= 1.0:
+            raise ValueError(f"{field_name} must be in range [0.0, 1.0], got {v}")
+        return v
+
+
+__all__ = ["EstimationReport"]
diff --git a/src/cleveragents/infrastructure/database/models.py b/src/cleveragents/infrastructure/database/models.py
index ffb7ba544..40946d156 100644
--- a/src/cleveragents/infrastructure/database/models.py
+++ b/src/cleveragents/infrastructure/database/models.py
@@ -638,6 +638,7 @@ class LifecyclePlanModel(Base):  # type: ignore[misc]
     cost_actual_usd = Column(Float, nullable=True)
     token_count_input = Column(Integer, nullable=True, default=0)
     token_count_output = Column(Integer, nullable=True, default=0)
+    estimation_report = Column(Text, nullable=True)
 
     # Metadata
     created_by = Column(String(255), nullable=True)
diff --git a/src/cleveragents/infrastructure/database/repositories.py b/src/cleveragents/infrastructure/database/repositories.py
index fd78d47e1..0c462850c 100644
--- a/src/cleveragents/infrastructure/database/repositories.py
+++ b/src/cleveragents/infrastructure/database/repositories.py
@@ -5364,7 +5364,7 @@ class CheckpointRepository:
             rows = (
                 session.query(CheckpointModel)
                 .filter_by(plan_id=plan_id)
-                .order_by(CheckpointModel.created_at)
+                .order_by(CheckpointModel.created_at, CheckpointModel.checkpoint_id)
                 .all()
             )
             return [row.to_domain() for row in rows]
@@ -5427,7 +5427,7 @@ class CheckpointRepository:
             rows = (
                 session.query(CheckpointModel)
                 .filter_by(plan_id=plan_id)
-                .order_by(CheckpointModel.created_at)
+                .order_by(CheckpointModel.created_at, CheckpointModel.checkpoint_id)
                 .all()
             )
             if len(rows) <= max_checkpoints or len(rows) < 3: