diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f3e875..a96efc8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,13 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Security
+
+- The minimum `claude-agent-sdk` is raised to 0.2.121. Earlier versions
+  are affected by an argument-injection advisory in the `resume` option
+  (GHSA-h4mw-j7qp-8mwm, CRITICAL). Installs that resolved an older SDK
+  now resolve a patched one.
+
 ### Fixed
 
 - A pipeline stage naming a gate the engine does not hold in its
diff --git a/pyproject.toml b/pyproject.toml
index 61aebb1..26dac4b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,7 +24,7 @@ classifiers = [
     "Typing :: Typed",
 ]
 dependencies = [
-    "claude-agent-sdk>=0.1",
+    "claude-agent-sdk>=0.2.121",
     "pydantic>=2.0",
     "pydantic-settings>=2.0",
     "typer>=0.15",
diff --git a/tests/unit/test_no_persona_names_in_public_docs.py b/tests/unit/test_no_persona_names_in_public_docs.py
index 699bb9c..fbab6e6 100644
--- a/tests/unit/test_no_persona_names_in_public_docs.py
+++ b/tests/unit/test_no_persona_names_in_public_docs.py
@@ -194,22 +194,22 @@
         # under [Unreleased]. Anchors only; expected text is unchanged.
         (
             "CHANGELOG.md",
-            677,
+            684,
             "predecessor persona (Passelewe, the Chamberlain) was retired; the",
         ),
         (
             "CHANGELOG.md",
-            679,
+            686,
             "`docs/_lore/passelewe.md`. The persona builtins directory",
         ),
         (
             "CHANGELOG.md",
-            680,
+            687,
             "`src/bonfire/persona/builtins/passelewe/` was deleted; a new",
         ),
         (
             "CHANGELOG.md",
-            697,
+            704,
             'to ban `"passelewe"` in src/ (the predecessor persona is gone, so',
         ),
         # --- CLAUDE.md — constellation-pointer breadcrumbs --------------