diff --git a/src/app_controller.py b/src/app_controller.py
index 46d6e293..a0c05b6c 100644
--- a/src/app_controller.py
+++ b/src/app_controller.py
@@ -27,6 +27,7 @@ from src.module_loader import _require_warmed
 from src import conductor_tech_lead
 from src import events
 from src import mcp_client
+from src import mcp_tool_specs
 from src import multi_agent_conductor
 from src import orchestrator_pm
 from src import paths
@@ -2106,7 +2107,7 @@ class AppController:
   saved = self.config.get("gui", {}).get("show_windows", {})
   self.show_windows = {k: saved.get(k, v) for k, v in _default_windows.items()}
   agent_tools_cfg = self.project.get("agent", {}).get("tools", {})
-  self.ui_agent_tools = {t: agent_tools_cfg.get(t, True) for t in models.AGENT_TOOL_NAMES}
+  self.ui_agent_tools = {t: agent_tools_cfg.get(t, True) for t in mcp_tool_specs.tool_names()}
   label = self.project.get("project", {}).get("name", "")
   session_logger.reset_session(label=label)
   # Trigger auto-start of MCP servers
@@ -2968,7 +2969,7 @@ class AppController:
   proj["project"]["auto_scroll_tool_calls"] = self.ui_auto_scroll_tool_calls
   proj.setdefault("gemini_cli", {})["binary_path"] = self.ui_gemini_cli_path
   proj.setdefault("agent", {}).setdefault("tools", {})
-  for t_name in models.AGENT_TOOL_NAMES:
+  for t_name in mcp_tool_specs.tool_names():
    proj["agent"]["tools"][t_name] = self.ui_agent_tools.get(t_name, True)
   self._flush_disc_entries_to_project()
   disc_sec = proj.setdefault("discussion", {})
@@ -3268,7 +3269,7 @@ class AppController:
   self.ui_auto_scroll_tool_calls = proj.get("project", {}).get("auto_scroll_tool_calls", True)
   self.ui_word_wrap = proj.get("project", {}).get("word_wrap", True)
   agent_tools_cfg = proj.get("agent", {}).get("tools", {})
-  self.ui_agent_tools = {t: agent_tools_cfg.get(t, True) for t in models.AGENT_TOOL_NAMES}
+  self.ui_agent_tools = {t: agent_tools_cfg.get(t, True) for t in mcp_tool_specs.tool_names()}
   # MMA Tracks
   self.tracks = project_manager.get_all_tracks(self.active_project_root)
   # Restore MMA state
diff --git a/src/models.py b/src/models.py
index 4a097324..683dae34 100644
--- a/src/models.py
+++ b/src/models.py
@@ -28,7 +28,7 @@ Thread Safety:
 
 Configuration Integration:
  - load_config() / save_config() read/write the global config.toml
- - AGENT_TOOL_NAMES defines the canonical list of MCP tools available to agents
+ - DEFAULT_TOOL_CATEGORIES groups the canonical tool list for UI display
 See Also:
  - docs/guide_mma.md for MMA orchestration documentation
  - src/dag_engine.py for TrackDAG and ExecutionEngine
@@ -117,67 +117,15 @@ from src.project_files import (
 # src.models; if we eagerly imported Tool from src.tool_presets, the
 # cycle would deadlock on initial load). Phase 5 will move the BiasProfile
 # re-export to a similar lazy mechanism, then we can drop these too.
-
-
 #region: Constants
 
-# PROVIDERS is the source of truth in src/ai_client.py (per the
-# follow-up track's Naming Convention HARD RULE). Lazy-loaded
-# via the __getattr__ defined later in this module to break the
-# circular import (src.ai_client imports ToolPreset/BiasProfile/
-# Tool from this module at line 50, so a top-level 'from
-# src.ai_client import PROVIDERS' here would deadlock). The
-# audit script scripts/audit_providers_source_of_truth.py
-# verifies PROVIDERS is declared in src/ai_client.py and not here.
-
-AGENT_TOOL_NAMES: List[str] = [
- "run_powershell",
- "read_file",
- "list_directory",
- "search_files",
- "get_file_summary",
- "get_file_slice",
- "set_file_slice",
- "edit_file",
- "get_tree",
- "get_git_diff",
- "web_search",
- "fetch_url",
- "get_ui_performance",
- "py_get_skeleton",
- "py_get_code_outline",
- "py_get_definition",
- "py_update_definition",
- "py_get_signature",
- "py_set_signature",
- "py_get_class_summary",
- "py_get_var_declaration",
- "py_set_var_declaration",
- "py_get_docstring",
- "py_find_usages",
- "py_get_imports",
- "py_check_syntax",
- "py_get_hierarchy",
- "py_remove_def",
- "py_add_def",
- "py_move_def",
- "py_region_wrap",
- "ts_c_get_skeleton",
- "ts_cpp_get_skeleton",
- "ts_c_get_code_outline",
- "ts_cpp_get_code_outline",
- "ts_c_get_definition",
- "ts_cpp_get_definition",
- "ts_c_get_signature",
- "ts_cpp_get_signature",
- "ts_c_update_definition",
- "ts_cpp_update_definition",
- "derive_code_path",
- "bd_create",
- "bd_update",
- "bd_list",
- "bd_ready",
-]
+# AGENT_TOOL_NAMES was deleted in module_taxonomy_refactor_20260627 Phase 4.
+# It was a hardcoded snapshot of mcp_tool_specs.tool_names() that was
+# effectively redundant (the existing test
+# test_tool_names_subset_of_models_agent_tool_names literally asserted
+# tool_names() ⊆ AGENT_TOOL_NAMES, proving the redundancy). Consumers
+# must now use mcp_tool_specs.tool_names() directly. See the v2 spec
+# for the migration rationale.
 
 DEFAULT_TOOL_CATEGORIES: Dict[str, List[str]] = {
  "General": ["read_file", "list_directory", "search_files", "get_tree", "get_file_summary"],
diff --git a/tests/test_arch_boundary_phase2.py b/tests/test_arch_boundary_phase2.py
index 235e9cdf..e04e4c2f 100644
--- a/tests/test_arch_boundary_phase2.py
+++ b/tests/test_arch_boundary_phase2.py
@@ -13,24 +13,25 @@ class TestArchBoundaryPhase2(unittest.TestCase):
 
  def test_toml_exposes_all_dispatch_tools(self) -> None:
   """manual_slop.toml [agent.tools] must list every tool in mcp_client.dispatch()."""
-  from src import models
-    
+  from src import mcp_tool_specs
+
   # We check the tool names in the source of mcp_client.dispatch
   import inspect
   import src.mcp_client as mcp
   source = inspect.getsource(mcp.dispatch)
   # This is a bit dynamic, but we can check if it covers our core tool names
-  for tool in models.AGENT_TOOL_NAMES:
+  for tool in mcp_tool_specs.tool_names():
    if tool not in ("set_file_slice", "py_update_definition", "py_set_signature", "py_set_var_declaration"):
     # Non-mutating tools should definitely be handled
     pass
  def test_toml_mutating_tools_disabled_by_default(self) -> None:
   """Verify that the core set of read-only tools is present."""
-  from src.models import AGENT_TOOL_NAMES
+  from src import mcp_tool_specs
+  tool_names = mcp_tool_specs.tool_names()
   # Our architecture now uses a fixed set of high-signal tools
-  self.assertIn("read_file", AGENT_TOOL_NAMES)
-  self.assertIn("list_directory", AGENT_TOOL_NAMES)
-  self.assertIn("py_get_skeleton", AGENT_TOOL_NAMES)
+  self.assertIn("read_file", tool_names)
+  self.assertIn("list_directory", tool_names)
+  self.assertIn("py_get_skeleton", tool_names)
 
  def test_mcp_client_dispatch_completeness(self) -> None:
   """Verify that all tools in tool_schemas are handled by dispatch()."""
diff --git a/tests/test_mcp_tool_specs.py b/tests/test_mcp_tool_specs.py
index 2212d5f5..79ccf5e2 100644
--- a/tests/test_mcp_tool_specs.py
+++ b/tests/test_mcp_tool_specs.py
@@ -7,7 +7,6 @@ Phase 1 of any_type_componentization_20260621. Verifies:
 - get_tool_schemas() returns the expected list
 - ToolParameter / ToolSpec dataclasses have correct frozen=True semantics
 - to_dict() round-trip preserves the legacy dict shape
-- Cross-module invariant: tool_names() == models.AGENT_TOOL_NAMES subset
 
 CONVENTION: 1-space indentation. NO COMMENTS.
 """
@@ -15,7 +14,6 @@ from __future__ import annotations
 
 import pytest
 from src import mcp_tool_specs
-from src import models
 
 
 EXPECTED_TOOLS: set[str] = {
@@ -107,14 +105,6 @@ def test_tool_parameter_to_dict_includes_enum() -> None:
  assert 'before' in d['enum']
 
 
-def test_tool_names_subset_of_models_agent_tool_names() -> None:
- """Cross-module invariant: every MCP tool is also an agent tool."""
- native_names = mcp_tool_specs.tool_names()
- agent_names = set(models.AGENT_TOOL_NAMES)
- missing_in_agent = native_names - agent_names
- assert not missing_in_agent, f"Native tools not in AGENT_TOOL_NAMES: {missing_in_agent}"
-
-
 def test_register_idempotent_replaces_existing() -> None:
  """register() should overwrite (idempotent for hot-reload scenarios)."""
  from src.mcp_tool_specs import ToolSpec, ToolParameter, register