diff --git a/docs/design/iter-slm257-lot4-01-not-authorized-20260725.json b/docs/design/iter-slm257-lot4-01-not-authorized-20260725.json
new file mode 100644
index 000000000..e2645cc5a
--- /dev/null
+++ b/docs/design/iter-slm257-lot4-01-not-authorized-20260725.json
@@ -0,0 +1,26 @@
+{
+  "contract_hash": "3840a7e57f9829623bd91f26ff0bf8c3d4388c830a82f720f86395702b00bf06",
+  "contract_id": "lotus-openui-compute-frontier-v1",
+  "issue": {
+    "activation_requirement": "SLM-251 supplies faithful treatment and continued explicit checkpoints with fairness manifests; SLM-252/253/256 select the objective/readout/workspace or explicitly close those branches; SLM-254 defines allowed causal-use language; SLM-255 defines accepted-equivalence evaluation.",
+    "alias": "LOT4-01",
+    "gate_contract_id": "lotus-openui-compute-frontier-v1",
+    "linear_issue": "SLM-257",
+    "slug": "lot4-01-compute-frontier",
+    "title": "Measure the equal-quality end-to-end accuracy, throughput, FLOPs, memory, energy, and training-cost frontier"
+  },
+  "lot1_01_disposition": "not_authorized",
+  "lot1_02_disposition": "not_authorized",
+  "schema_version": "lot_downstream_gate/v1",
+  "verdict": "not_authorized",
+  "verdict_rationale": "LOT4-01 (SLM-257) activation requires: SLM-251 supplies faithful treatment and continued explicit checkpoints with fairness manifests; SLM-252/253/256 select the objective/readout/workspace or explicitly close those branches; SLM-254 defines allowed causal-use language; SLM-255 defines accepted-equivalence evaluation. The LOT1-02 launch gate reports 'not_authorized' (LOT1-01 disposition 'not_authorized'): no faithful K x c model path, curriculum, Stage 0 parent, or continued-explicit control exists, and SLM-249's oracle ceiling is not positive. Closing not_authorized in plan-only/bounded-diagnostic mode; no training, factorial, intervention, or systems code is added by this disposition.",
+  "version_stamp": {
+    "code_commit": "d2ee54dc7bd95dd59a0e4181d0a0b095b36c4178",
+    "code_dirty": true,
+    "components": {
+      "harness.experiments": "v116"
+    },
+    "stamp_schema": "version_stamp/v1",
+    "stamped_at": "2026-07-25T16:19:43.618388+00:00"
+  }
+}
diff --git a/docs/design/iter-slm257-lot4-01-not-authorized-20260725.md b/docs/design/iter-slm257-lot4-01-not-authorized-20260725.md
new file mode 100644
index 000000000..d5f8fdace
--- /dev/null
+++ b/docs/design/iter-slm257-lot4-01-not-authorized-20260725.md
@@ -0,0 +1,15 @@
+# SLM-257 LOT4-01 — Downstream-gate disposition (lotus-openui-compute-frontier-v1)
+
+Verdict: **not_authorized**
+
+LOT4-01 (SLM-257) activation requires: SLM-251 supplies faithful treatment and continued explicit checkpoints with fairness manifests; SLM-252/253/256 select the objective/readout/workspace or explicitly close those branches; SLM-254 defines allowed causal-use language; SLM-255 defines accepted-equivalence evaluation. The LOT1-02 launch gate reports 'not_authorized' (LOT1-01 disposition 'not_authorized'): no faithful K x c model path, curriculum, Stage 0 parent, or continued-explicit control exists, and SLM-249's oracle ceiling is not positive. Closing not_authorized in plan-only/bounded-diagnostic mode; no training, factorial, intervention, or systems code is added by this disposition.
+
+## Upstream chain
+
+- LOT1-02 launch gate (SLM-251): `not_authorized`
+- LOT1-01 activation gate (SLM-250): `not_authorized`
+- Activation requirement: SLM-251 supplies faithful treatment and continued explicit checkpoints with fairness manifests; SLM-252/253/256 select the objective/readout/workspace or explicitly close those branches; SLM-254 defines allowed causal-use language; SLM-255 defines accepted-equivalence evaluation.
+
+## Non-goals honored
+
+No training campaign, factorial, readout/decoder, intervention, systems measurement, or production default change. This disposition is itself the deliverable while the upstream activation gate is unmet.
diff --git a/src/slm_training/harnesses/experiments/lot_downstream_gate.py b/src/slm_training/harnesses/experiments/lot_downstream_gate.py
index fdd7edfd8..00196e911 100644
--- a/src/slm_training/harnesses/experiments/lot_downstream_gate.py
+++ b/src/slm_training/harnesses/experiments/lot_downstream_gate.py
@@ -134,6 +134,20 @@ def to_dict(self) -> dict[str, Any]:
             "selected supervision routing/timing/grounding contract."
         ),
     ),
+    "SLM-257": DownstreamIssueSpec(
+        linear_issue="SLM-257",
+        alias="LOT4-01",
+        title="Measure the equal-quality end-to-end accuracy, throughput, FLOPs, memory, energy, and training-cost frontier",
+        gate_contract_id="lotus-openui-compute-frontier-v1",
+        slug="lot4-01-compute-frontier",
+        activation_requirement=(
+            "SLM-251 supplies faithful treatment and continued explicit "
+            "checkpoints with fairness manifests; SLM-252/253/256 select "
+            "the objective/readout/workspace or explicitly close those "
+            "branches; SLM-254 defines allowed causal-use language; "
+            "SLM-255 defines accepted-equivalence evaluation."
+        ),
+    ),
 }
 
 
diff --git a/src/slm_training/resources/versions.json b/src/slm_training/resources/versions.json
index 2c145ed8d..7498e42a1 100644
--- a/src/slm_training/resources/versions.json
+++ b/src/slm_training/resources/versions.json
@@ -1912,7 +1912,7 @@
       ]
     },
     "harness.experiments": {
-      "version": "v122",
+      "version": "v123",
       "kind": "harness",
       "paths": [
         "scripts/run_slm298_capacity_context_curriculum.py",
@@ -1921,6 +1921,11 @@
         "tests/test_scripts/test_run_slm298_capacity_context_curriculum.py"
       ],
       "history": [
+        {
+          "version": "v123",
+          "date": "2026-07-25",
+          "note": "register SLM-257 LOT4-01 in the LOT downstream gate registry; closes not_authorized off the unmet LOT1/LOT2/LOT3 chain"
+        },
         {
           "version": "v122",
           "date": "2026-07-25",
@@ -2001,6 +2006,11 @@
           "date": "2026-07-25",
           "note": "add SLM-300 AP-015 self-context exposure-bias curriculum manifest, policy-origin-mixture wiring/fixture harness, and mixture-zero legacy-equivalence invariant"
         },
+        {
+          "version": "v116",
+          "date": "2026-07-25",
+          "note": "register SLM-257 LOT4-01 in the LOT downstream gate registry; closes not_authorized off the unmet LOT1/LOT2/LOT3 chain"
+        },
         {
           "version": "v115",
           "date": "2026-07-25",
@@ -9836,7 +9846,7 @@
       ]
     },
     "harness.experiments.lot_downstream_gate": {
-      "version": "v5",
+      "version": "v6",
       "kind": "gate",
       "paths": [
         "docs/design/iter-slm252-lot2-01-not-authorized-20260725.json",
@@ -9849,6 +9859,8 @@
         "docs/design/iter-slm255-lot3-02-not-authorized-20260725.md",
         "docs/design/iter-slm256-lot2-03-not-authorized-20260725.json",
         "docs/design/iter-slm256-lot2-03-not-authorized-20260725.md",
+        "docs/design/iter-slm257-lot4-01-not-authorized-20260725.json",
+        "docs/design/iter-slm257-lot4-01-not-authorized-20260725.md",
         "scripts/evaluate_lot_downstream_gate.py",
         "src/slm_training/harnesses/experiments/lot_downstream_gate.py",
         "tests/test_harnesses/experiments/test_lot_downstream_gate.py",
@@ -9856,9 +9868,14 @@
       ],
       "history": [
         {
-          "version": "v5",
+          "version": "v6",
           "date": "2026-07-25",
-          "note": "add SLM-256 LOT2-03 registry entry + not_authorized iter docs (latent-workspace-capacity-gate-v1)"
+          "note": "add SLM-257 LOT4-01 registry entry + not_authorized iter docs (lotus-openui-compute-frontier-v1)"
+        },
+        {
+          "version": "v6",
+          "date": "2026-07-25",
+          "note": "add SLM-257 LOT4-01 registry entry + not_authorized iter docs (lotus-openui-compute-frontier-v1)"
         },
         {
           "version": "v5",
diff --git a/tests/test_harnesses/experiments/test_lot_downstream_gate.py b/tests/test_harnesses/experiments/test_lot_downstream_gate.py
index 4336ebc8b..668152371 100644
--- a/tests/test_harnesses/experiments/test_lot_downstream_gate.py
+++ b/tests/test_harnesses/experiments/test_lot_downstream_gate.py
@@ -140,3 +140,11 @@ def test_slm256_real_contracts_are_not_authorized() -> None:
 
     assert contract.verdict == NOT_AUTHORIZED
     assert contract.contract_id == "latent-workspace-capacity-gate-v1"
+
+
+def test_slm257_real_contracts_are_not_authorized() -> None:
+    fidelity, trace = _real_contracts()
+    contract = evaluate_downstream_gate(DOWNSTREAM_ISSUES["SLM-257"], fidelity, trace)
+
+    assert contract.verdict == NOT_AUTHORIZED
+    assert contract.contract_id == "lotus-openui-compute-frontier-v1"
diff --git a/tests/test_scripts/test_evaluate_lot_downstream_gate.py b/tests/test_scripts/test_evaluate_lot_downstream_gate.py
index c218b4fc5..d16ce80fd 100644
--- a/tests/test_scripts/test_evaluate_lot_downstream_gate.py
+++ b/tests/test_scripts/test_evaluate_lot_downstream_gate.py
@@ -73,3 +73,12 @@ def test_slm256_run_reports_not_authorized(tmp_path: Path) -> None:
     data = json.loads((out / "lot2_03_workspace_capacity_gate.json").read_text())
     assert data["verdict"] == "not_authorized"
     assert data["issue"]["alias"] == "LOT2-03"
+
+
+def test_slm257_run_reports_not_authorized(tmp_path: Path) -> None:
+    out = tmp_path / "gate257"
+    rc = evaluate_lot_downstream_gate.main(["--issue", "SLM-257", "--out", str(out)])
+    assert rc == 0
+    data = json.loads((out / "lot4_01_compute_frontier_gate.json").read_text())
+    assert data["verdict"] == "not_authorized"
+    assert data["issue"]["alias"] == "LOT4-01"