diff --git a/src/adm_cli/gates.py b/src/adm_cli/gates.py
index 9e26451..9f1e687 100644
--- a/src/adm_cli/gates.py
+++ b/src/adm_cli/gates.py
@@ -81,7 +81,7 @@ def can_advance(
     if missing:
         return False, f"Missing required artefacts in {phase_dir_name}/: {', '.join(missing)}"
 
-    # Ratchet gate: zero PENDING/OPEN resolutions
+    # Ratchet gate: zero PENDING/OPEN resolutions + stability window
     if target_phase == 6:
         open_clrs = [
             k for k, v in domain_state.resolutions.items()
@@ -90,6 +90,15 @@ def can_advance(
         if open_clrs:
             return False, f"Cannot ratchet: {len(open_clrs)} open clarifications ({', '.join(open_clrs)})"
 
+        if domain_state.stability_window_days > 0 and domain_state.last_thesis_change:
+            from datetime import date
+
+            last_change = date.fromisoformat(domain_state.last_thesis_change)
+            days_elapsed = (date.today() - last_change).days
+            if days_elapsed < domain_state.stability_window_days:
+                remaining = domain_state.stability_window_days - days_elapsed
+                return False, f"Stability window: {remaining} days remaining (need {domain_state.stability_window_days}, elapsed {days_elapsed})"
+
     return True, "Gate passed"
 
 
diff --git a/src/adm_cli/schema.py b/src/adm_cli/schema.py
index 9ada3e2..066b7b0 100644
--- a/src/adm_cli/schema.py
+++ b/src/adm_cli/schema.py
@@ -21,6 +21,8 @@ class DomainState(BaseModel):
     iteration: Annotated[int, Field(ge=1)] = 1
     contract_version: str | None = None
     source_path: str | None = None
+    stability_window_days: Annotated[int, Field(ge=0)] = 0
+    last_thesis_change: str | None = None
     resolutions: dict[str, ResolutionStatus] = Field(default_factory=dict)
 
     @field_validator("contract_version")
diff --git a/tests/test_gates.py b/tests/test_gates.py
index 299b766..a2c653f 100644
--- a/tests/test_gates.py
+++ b/tests/test_gates.py
@@ -94,6 +94,47 @@ def test_ratchet_gate_passes_when_all_resolved(self, tmp_path: Path):
         allowed, reason = can_advance("holdings", 6, state, tmp_path)
         assert allowed is True
 
+    def test_stability_window_blocks_when_too_recent(self, tmp_path: Path):
+        from datetime import date
+
+        state = _setup_project(
+            tmp_path,
+            phase=5,
+            stability_window_days=7,
+            last_thesis_change=date.today().isoformat(),
+        )
+        _create_phase_artefacts(tmp_path, "holdings", 5)
+        allowed, reason = can_advance("holdings", 6, state, tmp_path)
+        assert allowed is False
+        assert "stability window" in reason.lower()
+
+    def test_stability_window_passes_when_elapsed(self, tmp_path: Path):
+        from datetime import date, timedelta
+
+        past = (date.today() - timedelta(days=10)).isoformat()
+        state = _setup_project(
+            tmp_path,
+            phase=5,
+            stability_window_days=7,
+            last_thesis_change=past,
+        )
+        _create_phase_artefacts(tmp_path, "holdings", 5)
+        allowed, reason = can_advance("holdings", 6, state, tmp_path)
+        assert allowed is True
+
+    def test_stability_window_zero_allows_immediate(self, tmp_path: Path):
+        from datetime import date
+
+        state = _setup_project(
+            tmp_path,
+            phase=5,
+            stability_window_days=0,
+            last_thesis_change=date.today().isoformat(),
+        )
+        _create_phase_artefacts(tmp_path, "holdings", 5)
+        allowed, reason = can_advance("holdings", 6, state, tmp_path)
+        assert allowed is True
+
 
 class TestAdvancePhase:
     def test_increments_phase(self, tmp_path: Path):