diff --git a/.mike.yml b/.mike.yml
index 973a18d..9557b23 100644
--- a/.mike.yml
+++ b/.mike.yml
@@ -2,6 +2,7 @@ version_selector: true
 title_switch: true
 versions_file: docs/versions/versions.json
 versions:
+  - 4.3.1
   - 4.3.0
   - 4.2.0
   - 4.1.0
@@ -17,4 +18,4 @@ versions:
   - 0.1.0
   - latest
 aliases:
-  latest: 4.3.0
+  latest: 4.3.1
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fc9d833..236158d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,17 @@ Changelog
 
 ___
 
+v4.3.1 (2026-09-23)
+-------------------
+
+guard-core 4.0.x tracking: dependency floor to >=4.0.0, agent docs (v4.3.1)
+---------------------------------------------------------------------------
+
+- **Compatibility** - The `guard-core` floor moves from `>=3.15.0` to `>=4.0.0` in `pyproject.toml` (no upper bound), so this adapter tracks the guard-core 4.0.x engine line and is verified against guard-core 4.0.4. No adapter code changed: the delta since 4.3.0 is docs and CI only, hence the patch bump. Since the adapter delegates all security behavior to the engine, no other change is required for the 4.0.x line; guard-core 4.0.0's own breaking changes (grammar-based secret redaction, exact-value `require_headers()` enforcement, `excluded_detection_headers` semantics) are documented in the guard-core changelog.
+- **Documentation** - Added `AGENTS.md`/`CLAUDE.md` agent guidance and the flaskapi-guard package skill, and noted in the access-control decorator docs that an unknown bypass token now warns.
+
+___
+
 v4.3.0 (2026-08-31)
 -------------------
 
diff --git a/docs/index.md b/docs/index.md
index 11f8796..5c23020 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -106,7 +106,7 @@ You can also download the example app as a Docker container from [GitHub Contain
 docker pull ghcr.io/rennf93/flaskapi-guard-example:latest
 
 # Or pull a specific version (matches library releases)
-docker pull ghcr.io/rennf93/flaskapi-guard-example:v4.3.0
+docker pull ghcr.io/rennf93/flaskapi-guard-example:v4.3.1
 ```
 
 ___
diff --git a/docs/release-notes.md b/docs/release-notes.md
index 5c8fd40..e329357 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -3,6 +3,17 @@ Release Notes
 
 ___
 
+v4.3.1 (2026-09-23)
+-------------------
+
+guard-core 4.0.x tracking: dependency floor to >=4.0.0, agent docs (v4.3.1)
+---------------------------------------------------------------------------
+
+- **Compatibility** - The `guard-core` floor moves from `>=3.15.0` to `>=4.0.0` in `pyproject.toml` (no upper bound), so this adapter tracks the guard-core 4.0.x engine line and is verified against guard-core 4.0.4. No adapter code changed: the delta since 4.3.0 is docs and CI only, hence the patch bump. Since the adapter delegates all security behavior to the engine, no other change is required for the 4.0.x line; guard-core 4.0.0's own breaking changes (grammar-based secret redaction, exact-value `require_headers()` enforcement, `excluded_detection_headers` semantics) are documented in the guard-core changelog.
+- **Documentation** - Added `AGENTS.md`/`CLAUDE.md` agent guidance and the flaskapi-guard package skill, and noted in the access-control decorator docs that an unknown bypass token now warns.
+
+___
+
 v4.3.0 (2026-08-31)
 -------------------
 
diff --git a/docs/versions/versions.json b/docs/versions/versions.json
index 26813f3..1ed07f9 100644
--- a/docs/versions/versions.json
+++ b/docs/versions/versions.json
@@ -1,4 +1,5 @@
 {
+    "4.3.1": "4.3.1",
     "4.3.0": "4.3.0",
     "4.2.0": "4.2.0",
     "4.1.0": "4.1.0",
@@ -12,5 +13,5 @@
     "1.1.0": "1.1.0",
     "1.0.0": "1.0.0",
     "0.1.0": "0.1.0",
-    "latest": "4.3.0"
+    "latest": "4.3.1"
 }
diff --git a/pyproject.toml b/pyproject.toml
index 9547213..26714b9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "flaskapi_guard"
-version = "4.3.0"
+version = "4.3.1"
 description = "A security library for Flask to control IPs, log requests, and detect penetration attempts."
 authors = [
     {name = "Renzo Franceschini", email = "rennf93@users.noreply.github.com"}
@@ -23,7 +23,7 @@ classifiers = [
 ]
 dependencies = [
     "flask",
-    "guard-core>=3.15.0",
+    "guard-core>=4.0.0",
     "gunicorn",
     "werkzeug",
 ]