feat(layout_optimizer): default cardinal snap and alignment to off

align_weight defaults to 0 (was DEFAULT_WEIGHT_ANGLE=60).
snap_theta_safe is opt-in via snap_cardinal=True (was always-on).
Both remain available when explicitly requested.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

unilabos/layout_optimizer/server.py

@@ -368,6 +368,7 @@ class OptimizeRequest(BaseModel):
     workflow_edges: list[list[str]] = []
     maxiter: int = 200
     seed: int | None = None
+    snap_cardinal: bool = False
 
 
 class PositionXYZ(BaseModel):
@@ -459,8 +460,8 @@ async def run_optimize(request: OptimizeRequest):
                 params={"mode": orientation_mode},
                 weight=request.seeder_overrides.get("orientation_weight", DEFAULT_WEIGHT_ANGLE),
             ))
-        # prefer_aligned: penalize non-cardinal angles
+        # prefer_aligned: penalize non-cardinal angles（默认关闭，用户可通过 align_cardinal intent 或 seeder_overrides 开启）
-        align_weight = request.seeder_overrides.get("align_weight", DEFAULT_WEIGHT_ANGLE)
+        align_weight = request.seeder_overrides.get("align_weight", 0)
         if align_weight > 0:
             constraints.append(Constraint(
                 type="soft",
@@ -486,8 +487,9 @@ async def run_optimize(request: OptimizeRequest):
     else:
         result_placements = seed_placements
 
-    # 5. θ snap post-processing（碰撞安全：snap 后验证，失败则回退）
+    # 5. θ snap post-processing（opt-in，默认关闭）
-    result_placements = snap_theta_safe(result_placements, devices, lab, checker)
+    if request.snap_cardinal:
+        result_placements = snap_theta_safe(result_placements, devices, lab, checker)
 
     # 6. Evaluate final cost (binary mode for pass/fail reporting)
     final_cost = evaluate_default_hard_constraints(

unilabos/layout_optimizer/tests/test_bugfixes_v2.py

@@ -376,3 +376,58 @@ class TestScenarios:
         assert not _has_collision(devices, result)
         for i, p in enumerate(result):
             assert _facing_dot(p, devices[i], lab) > 0
+
+
+# ── V2 Stage 1: 默认关闭 cardinal snap/alignment ────────
+
+class TestV2Stage1Bugfixes:
+    """align_weight 默认为 0，snap_cardinal 默认关闭。"""
+
+    def test_default_align_weight_is_zero(self):
+        """Default request (no seeder_overrides) should NOT inject prefer_aligned."""
+        from fastapi.testclient import TestClient
+        from ..server import app
+
+        client = TestClient(app)
+        resp = client.post("/optimize", json={
+            "devices": [{"id": "opentrons_liquid_handler", "uuid": "u1"}],
+            "lab": {"width": 3, "depth": 3},
+            "seeder": "compact_outward",
+            "run_de": True,
+            "maxiter": 50,
+            "seed": 42,
+        })
+        assert resp.status_code == 200
+
+    def test_snap_cardinal_off_by_default(self):
+        """Default request should NOT snap theta to cardinal."""
+        from fastapi.testclient import TestClient
+        from ..server import app
+
+        client = TestClient(app)
+        resp = client.post("/optimize", json={
+            "devices": [{"id": "opentrons_liquid_handler", "uuid": "u1"}],
+            "lab": {"width": 3, "depth": 3},
+            "seeder": "compact_outward",
+            "run_de": True,
+            "maxiter": 10,
+            "seed": 42,
+        })
+        assert resp.status_code == 200
+
+    def test_snap_cardinal_opt_in(self):
+        """snap_cardinal=True should be accepted and snap angles."""
+        from fastapi.testclient import TestClient
+        from ..server import app
+
+        client = TestClient(app)
+        resp = client.post("/optimize", json={
+            "devices": [{"id": "opentrons_liquid_handler", "uuid": "u1"}],
+            "lab": {"width": 3, "depth": 3},
+            "seeder": "compact_outward",
+            "snap_cardinal": True,
+            "run_de": True,
+            "maxiter": 10,
+            "seed": 42,
+        })
+        assert resp.status_code == 200

unilabos/layout_optimizer/tests/test_e2e_pcr_pipeline.py

@@ -199,6 +199,8 @@ class TestStage3VerifyPlacements:
             "run_de": True,
             "maxiter": 100,
             "seed": 42,
+            "snap_cardinal": True,
+            "seeder_overrides": {"align_weight": 60},
         })
         data = optimize_resp.json()
         assert data["success"] is True