diff --git a/ai_client.py b/ai_client.py
index a84db52..42cba1c 100644
--- a/ai_client.py
+++ b/ai_client.py
@@ -89,6 +89,9 @@ comms_log_callback: Callable[[dict[str, Any]], None] | None = None
 # Signature: (script: str, result: str) -> None
 tool_log_callback: Callable[[str, str], None] | None = None
 
+# Set by caller tiers before ai_client.send(); cleared in finally.
+# Safe — ai_client.send() calls are serialized by the MMA engine executor.
+current_tier: str | None = None
 # Increased to allow thorough code exploration before forcing a summary
 MAX_TOOL_ROUNDS: int = 10
 
@@ -134,12 +137,13 @@ COMMS_CLAMP_CHARS: int = 300
 
 def _append_comms(direction: str, kind: str, payload: dict[str, Any]) -> None:
  entry = {
-  "ts":        datetime.datetime.now().strftime("%H:%M:%S"),
-  "direction": direction,
-  "kind":      kind,
-  "provider":  _provider,
-  "model":     _model,
-  "payload":   payload,
+  "ts":          datetime.datetime.now().strftime("%H:%M:%S"),
+  "direction":   direction,
+  "kind":        kind,
+  "provider":    _provider,
+  "model":       _model,
+  "payload":     payload,
+  "source_tier": current_tier,  # set/cleared by caller tiers; None for main-session calls
  }
  _comms_log.append(entry)
  if comms_log_callback is not None:
diff --git a/conductor_tech_lead.py b/conductor_tech_lead.py
index 9d3d3cf..1346e25 100644
--- a/conductor_tech_lead.py
+++ b/conductor_tech_lead.py
@@ -19,6 +19,7 @@ def generate_tickets(track_brief: str, module_skeletons: str) -> list[dict]:
  # Set custom system prompt for this call
  old_system_prompt = ai_client._custom_system_prompt
  ai_client.set_custom_system_prompt(system_prompt)
+ ai_client.current_tier = "Tier 2"
  try:
  # 3. Call Tier 2 Model
   response = ai_client.send(
@@ -41,11 +42,11 @@ def generate_tickets(track_brief: str, module_skeletons: str) -> list[dict]:
   return tickets
  except Exception as e:
   print(f"Error parsing Tier 2 response: {e}")
-  # print(f"Raw response: {response}")
   return []
  finally:
- # Restore old system prompt
+ # Restore old system prompt and clear tier tag
   ai_client.set_custom_system_prompt(old_system_prompt)
+  ai_client.current_tier = None
 
 from dag_engine import TrackDAG
 from models import Ticket
diff --git a/gui_2.py b/gui_2.py
index 25a2edb..15b1a5f 100644
--- a/gui_2.py
+++ b/gui_2.py
@@ -276,10 +276,10 @@ class App:
    "Tier 3": {"input": 0, "output": 0, "model": "gemini-2.5-flash-lite"},
    "Tier 4": {"input": 0, "output": 0, "model": "gemini-2.5-flash-lite"},
   }
-  self._tool_log: list[tuple[str, str, float]] = []
+  self._tool_log: list[dict] = []
   self._comms_log: list[dict[str, Any]] = []
   self._pending_comms: list[dict[str, Any]] = []
-  self._pending_tool_calls: list[tuple[str, str, float]] = []
+  self._pending_tool_calls: list[dict] = []
   self._pending_history_adds: list[dict[str, Any]] = []
   self._trigger_blink = False
   self._is_blinking = False
@@ -891,8 +891,9 @@ class App:
 
  def _on_tool_log(self, script: str, result: str) -> None:
   session_logger.log_tool_call(script, result, None)
+  source_tier = ai_client.current_tier
   with self._pending_tool_calls_lock:
-   self._pending_tool_calls.append((script, result, time.time()))
+   self._pending_tool_calls.append({"script": script, "result": result, "ts": time.time(), "source_tier": source_tier})
 
  def _on_api_event(self, *args, **kwargs) -> None:
   payload = kwargs.get("payload", {})
@@ -1488,8 +1489,8 @@ class App:
     return True
   return False
 
- def _append_tool_log(self, script: str, result: str) -> None:
-  self._tool_log.append((script, result, time.time()))
+ def _append_tool_log(self, script: str, result: str, source_tier: str | None = None) -> None:
+  self._tool_log.append({"script": script, "result": result, "ts": time.time(), "source_tier": source_tier})
   self.ui_last_script_text = script
   self.ui_last_script_output = result
   self._trigger_script_blink = True
diff --git a/multi_agent_conductor.py b/multi_agent_conductor.py
index ba21456..e6fc9f6 100644
--- a/multi_agent_conductor.py
+++ b/multi_agent_conductor.py
@@ -308,6 +308,7 @@ def run_worker_lifecycle(ticket: Ticket, context: WorkerContext, context_files:
    old_comms_cb(entry)
 
  ai_client.comms_log_callback = worker_comms_callback
+ ai_client.current_tier = "Tier 3"
  try:
   comms_baseline = len(ai_client.get_comms_log())
   response = ai_client.send(
@@ -320,7 +321,7 @@ def run_worker_lifecycle(ticket: Ticket, context: WorkerContext, context_files:
   )
  finally:
   ai_client.comms_log_callback = old_comms_cb
-
+  ai_client.current_tier = None
  if event_queue:
   # Push via "response" event type — _process_event_queue wraps this
   # as {"action": "handle_ai_response", "payload": ...} for the GUI.
diff --git a/tests/test_mma_agent_focus_phase1.py b/tests/test_mma_agent_focus_phase1.py
new file mode 100644
index 0000000..62bcd31
--- /dev/null
+++ b/tests/test_mma_agent_focus_phase1.py
@@ -0,0 +1,131 @@
+"""
+Tests for mma_agent_focus_ux_20260302 — Phase 1: Tier Tagging at Emission.
+These tests are written RED-first: they fail before implementation.
+"""
+from typing import Generator
+import pytest
+from unittest.mock import patch
+import ai_client
+from gui_2 import App
+
+
+@pytest.fixture
+def app_instance() -> Generator[App, None, None]:
+ with (
+  patch('gui_2.load_config', return_value={'gui': {'show_windows': {}}}),
+  patch('gui_2.save_config'),
+  patch('gui_2.project_manager'),
+  patch('gui_2.session_logger'),
+  patch('gui_2.immapp.run'),
+  patch.object(App, '_load_active_project'),
+  patch.object(App, '_fetch_models'),
+  patch.object(App, '_load_fonts'),
+  patch.object(App, '_post_init')
+ ):
+  yield App()
+
+
+@pytest.fixture(autouse=True)
+def reset_tier():
+ """Reset current_tier before and after each test."""
+ if hasattr(ai_client, "current_tier"):
+  ai_client.current_tier = None
+ yield
+ if hasattr(ai_client, "current_tier"):
+  ai_client.current_tier = None
+
+
+# ---------------------------------------------------------------------------
+# Task 1.1 / 1.2: current_tier variable and source_tier in _append_comms
+# ---------------------------------------------------------------------------
+
+def test_current_tier_variable_exists():
+ """ai_client must expose a module-level current_tier variable."""
+ assert hasattr(ai_client, "current_tier"), (
+  "ai_client.current_tier does not exist — Task 1.1 not implemented"
+ )
+
+
+def test_append_comms_has_source_tier_key():
+ """_append_comms entries must contain a 'source_tier' key."""
+ ai_client.clear_comms_log()
+ ai_client._append_comms("OUT", "request", {"text": "hello"})
+ log = ai_client.get_comms_log()
+ assert len(log) >= 1, "comms log is empty after _append_comms"
+ last_entry = log[-1]
+ assert "source_tier" in last_entry, (
+  f"'source_tier' key missing from comms entry: {last_entry}"
+ )
+
+
+def test_append_comms_source_tier_none_when_unset():
+ """source_tier must be None when current_tier is not set."""
+ ai_client.clear_comms_log()
+ ai_client.current_tier = None
+ ai_client._append_comms("OUT", "request", {"text": "hello"})
+ log = ai_client.get_comms_log()
+ last_entry = log[-1]
+ assert last_entry["source_tier"] is None, (
+  f"Expected source_tier=None, got {last_entry['source_tier']}"
+ )
+
+
+def test_append_comms_source_tier_set_when_current_tier_set():
+ """source_tier must reflect current_tier when it is set."""
+ ai_client.clear_comms_log()
+ ai_client.current_tier = "Tier 3"
+ ai_client._append_comms("OUT", "request", {"text": "hello"})
+ log = ai_client.get_comms_log()
+ last_entry = log[-1]
+ assert last_entry["source_tier"] == "Tier 3", (
+  f"Expected source_tier='Tier 3', got {last_entry['source_tier']}"
+ )
+
+
+def test_append_comms_source_tier_tier2():
+ """source_tier must reflect Tier 2 when current_tier = 'Tier 2'."""
+ ai_client.clear_comms_log()
+ ai_client.current_tier = "Tier 2"
+ ai_client._append_comms("IN", "response", {"text": "result"})
+ log = ai_client.get_comms_log()
+ last_entry = log[-1]
+ assert last_entry["source_tier"] == "Tier 2", (
+  f"Expected source_tier='Tier 2', got {last_entry['source_tier']}"
+ )
+
+
+# ---------------------------------------------------------------------------
+# Task 1.5: _tool_log stores dicts with source_tier
+# ---------------------------------------------------------------------------
+
+def test_append_tool_log_stores_dict(app_instance):
+ """_append_tool_log must store a dict, not a tuple."""
+ app = app_instance
+ initial_len = len(app._tool_log)
+ app._append_tool_log("echo hello", "output", "Tier 3")
+ assert len(app._tool_log) == initial_len + 1, "_tool_log length did not increase"
+ entry = app._tool_log[-1]
+ assert isinstance(entry, dict), (
+  f"_tool_log entry is a {type(entry).__name__}, expected dict"
+ )
+
+
+def test_append_tool_log_dict_has_source_tier(app_instance):
+ """Dict entry must have 'source_tier' key."""
+ app = app_instance
+ app._append_tool_log("ls", "file1\nfile2", "Tier 3")
+ entry = app._tool_log[-1]
+ assert "source_tier" in entry, f"'source_tier' missing from tool log dict: {entry}"
+ assert entry["source_tier"] == "Tier 3"
+
+
+def test_append_tool_log_dict_keys(app_instance):
+ """Dict entry must have script, result, ts, source_tier keys."""
+ app = app_instance
+ app._append_tool_log("pwd", "/projects", None)
+ entry = app._tool_log[-1]
+ for key in ("script", "result", "ts", "source_tier"):
+  assert key in entry, f"key '{key}' missing from tool log entry: {entry}"
+ assert entry["script"] == "pwd"
+ assert entry["result"] == "/projects"
+ assert entry["source_tier"] is None