diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2360209..6a3d8db 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- **`list_sbir_topics(cycle_name=...)`** filters topics by their DSIP solicitation cycle (e.g. `DOD_SBIR_2026_P1_CBZ`), and `SbirTopic` gains a `cycle_name` field (Tango API 5.3.1). The vendored API contract is refreshed to 5.3.1.
+
 ## [1.9.0] - 2026-09-28
 
 ### Added
diff --git a/contracts/filter_shape_contract.json b/contracts/filter_shape_contract.json
index a1fe295..3e0f0ca 100644
--- a/contracts/filter_shape_contract.json
+++ b/contracts/filter_shape_contract.json
@@ -1,6 +1,6 @@
 {
   "meta": {
-    "api_version": "5.3.0",
+    "api_version": "5.3.1",
     "description": "Canonical API filter/shape contract. Downstream consumers (SDK, MCP) should validate their conformance against this manifest.",
     "generated_from": "scripts/filter_shape_conformance.py",
     "schema_version": 2
@@ -13990,6 +13990,7 @@
           "agency",
           "close_date_after",
           "close_date_before",
+          "cycle_name",
           "doc_source",
           "open_date_after",
           "open_date_before",
@@ -14025,6 +14026,10 @@
             "lookup": "lte",
             "type": "date"
           },
+          "cycle_name": {
+            "filter_class": "CharFilter",
+            "type": "string"
+          },
           "doc_source": {
             "filter_class": "CharFilter",
             "lookup": "iexact",
@@ -14134,6 +14139,7 @@
             "activity",
             "agency",
             "close_date",
+            "cycle_name",
             "description",
             "doc_source",
             "due_dates_text",
@@ -14156,6 +14162,7 @@
           "activity",
           "agency",
           "close_date",
+          "cycle_name",
           "description",
           "doc_source",
           "due_dates_text",
diff --git a/tango/client.py b/tango/client.py
index 64854d1..9691e5d 100644
--- a/tango/client.py
+++ b/tango/client.py
@@ -3733,6 +3733,7 @@ def list_sbir_topics(
         flat_lists: bool = False,
         topic_number: str | None = None,
         solicitation_number: str | None = None,
+        cycle_name: str | None = None,
         agency: str | None = None,
         activity: str | None = None,
         year: int | None = None,
@@ -3759,6 +3760,7 @@ def list_sbir_topics(
             flat_lists: If True, flatten arrays using indexed keys
             topic_number: Filter by topic number
             solicitation_number: Filter by solicitation number
+            cycle_name: Filter by DSIP solicitation cycle, exact (e.g. "DOD_SBIR_2026_P1_CBZ"; requires Tango API 5.3.1)
             agency: Filter by agency
             activity: Filter by activity (component/branch)
             year: Filter by solicitation year
@@ -3786,6 +3788,7 @@ def list_sbir_topics(
         for key, val in (
             ("topic_number", topic_number),
             ("solicitation_number", solicitation_number),
+            ("cycle_name", cycle_name),
             ("agency", agency),
             ("activity", activity),
             ("year", year),
diff --git a/tango/models.py b/tango/models.py
index 56f0e6c..b1097e9 100644
--- a/tango/models.py
+++ b/tango/models.py
@@ -1000,6 +1000,7 @@ class SbirTopic:
     activity: str | None = None
     year: int | None = None
     solicitation_number: str | None = None
+    cycle_name: str | None = None
     solicitation_status: str | None = None
     release_date: str | None = None
     open_date: str | None = None
diff --git a/tango/shapes/generated_overlay.py b/tango/shapes/generated_overlay.py
index c781166..eddbccd 100644
--- a/tango/shapes/generated_overlay.py
+++ b/tango/shapes/generated_overlay.py
@@ -2731,6 +2731,7 @@
         "activity": FieldSchema(name="activity", type=str, is_optional=True, is_list=False),
         "agency": FieldSchema(name="agency", type=str, is_optional=True, is_list=False),
         "close_date": FieldSchema(name="close_date", type=date, is_optional=True, is_list=False),
+        "cycle_name": FieldSchema(name="cycle_name", type=str, is_optional=True, is_list=False),
         "description": FieldSchema(name="description", type=str, is_optional=True, is_list=False),
         "doc_source": FieldSchema(name="doc_source", type=str, is_optional=True, is_list=False),
         "due_dates_text": FieldSchema(
diff --git a/tests/test_dibbs_exclusions_sbir.py b/tests/test_dibbs_exclusions_sbir.py
index c9edf54..a6ce47f 100644
--- a/tests/test_dibbs_exclusions_sbir.py
+++ b/tests/test_dibbs_exclusions_sbir.py
@@ -141,6 +141,12 @@ def test_list_sbir_topics_filters(self, mock_request):
         assert params["year"] == 2026
         assert params["topic_number"] == "A26-001"
 
+    @patch("tango.client.httpx.Client.request")
+    def test_list_sbir_topics_cycle_name(self, mock_request):
+        _mock(mock_request)
+        TangoClient(api_key="k").list_sbir_topics(cycle_name="DOD_SBIR_2026_P1_CBZ")
+        assert _call_params(mock_request)["cycle_name"] == "DOD_SBIR_2026_P1_CBZ"
+
     @patch("tango.client.httpx.Client.request")
     def test_get_sbir_topic_uses_topic_id_route(self, mock_request):
         _mock(mock_request, {"topic_id": "t1"})