diff --git a/CHANGELOG.md b/CHANGELOG.md
index 72970ffa3..e0be630fb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,24 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Fixed
 
+- **ACMS Default Pipeline Wiring** (#9169): `ACMSExecutePhaseContextAssembler` now
+  defaults to `ContextAssemblyPipeline()` instead of the base `ACMSPipeline()` when
+  no pipeline is injected. This ensures plan execution context assembly uses the full
+  production pipeline with `ConfidenceWeightedSelector`, `ProportionalBudgetAllocator`,
+  and `ParallelStrategyExecutor`. The DI container's `acms_pipeline` singleton and
+  `plan.py`'s `_get_plan_executor()` are updated accordingly. BDD coverage added to
+  verify `ContextAssemblyPipeline` is the default.
+
+
+- **ACMS Default Pipeline Wiring** (#9169): `ACMSExecutePhaseContextAssembler` now
+  defaults to `ContextAssemblyPipeline()` instead of the base `ACMSPipeline()` when
+  no pipeline is injected. This ensures plan execution context assembly uses the full
+  production pipeline with `ConfidenceWeightedSelector`, `ProportionalBudgetAllocator`,
+  and `ParallelStrategyExecutor`. The DI container's `acms_pipeline` singleton and
+  `plan.py`'s `_get_plan_executor()` are updated accordingly. BDD coverage added to
+  verify `ContextAssemblyPipeline` is the default.
+
+
 - **TDD Non-AssertionError Guard Visibility** (#8294): `apply_tdd_inversion` in
   `features/environment.py` now emits its non-assertion exception guard warning to
   both the structured logger and `stderr` via a new `_warning_with_stderr` helper.
diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 60ee6fb1d..c930315da 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -21,3 +21,4 @@ Below are some of the specific details of various contributions.
 * HAL 9000 has contributed the plugin entry point security hardening fix (#7476): enforced entry point allowlist validation before importing plugin modules to prevent malicious plugin loading.
 * This project was made possible thanks to considerable donation of time, money, and resources by CleverThis, Inc.
 * HAL 9000 has contributed automated bug fixes, CLI output formatting improvements, and ongoing maintenance as part of the CleverAgents automation system.
+* HAL 9000 has contributed the ACMS default pipeline wiring fix (#9169): wired `ContextAssemblyPipeline` as the default pipeline in `ACMSExecutePhaseContextAssembler`, ensuring plan execution context assembly uses the full production pipeline with confidence-weighted selection, proportional budget allocation, and parallel strategy execution.
diff --git a/features/steps/execute_phase_context_assembler_coverage_steps.py b/features/steps/execute_phase_context_assembler_coverage_steps.py
index 203f6ae09..1490c5795 100644
--- a/features/steps/execute_phase_context_assembler_coverage_steps.py
+++ b/features/steps/execute_phase_context_assembler_coverage_steps.py
@@ -947,15 +947,19 @@ def step_epcov_assembled_has_data(context: Context) -> None:
 @given("epcov an assembler created without explicit pipeline")
 def step_epcov_assembler_no_pipeline(context: Context) -> None:
     """Create assembler without injecting a pipeline — should default to ContextAssemblyPipeline."""
-    from unittest.mock import MagicMock
-
     tier_service = MagicMock()
     repo = MagicMock()
     repo.get_context_policy.return_value = None
-    from cleveragents.application.services.execute_phase_context_assembler import (
-        ACMSExecutePhaseContextAssembler,
-    )
     context.epcov_assembler = ACMSExecutePhaseContextAssembler(
         context_tier_service=tier_service,
         project_repository=repo,
     )
+
+
+@then("epcov the assembler pipeline should be a ContextAssemblyPipeline instance")
+def step_epcov_pipeline_is_context_assembly(context: Context) -> None:
+    from cleveragents.application.services.acms_pipeline import ContextAssemblyPipeline
+
+    assert isinstance(context.epcov_assembler._pipeline, ContextAssemblyPipeline), (
+        f"Expected ContextAssemblyPipeline, got {type(context.epcov_assembler._pipeline)}"
+    )