diff --git a/packages/acp-agent/package.json b/packages/acp-agent/package.json
index 4d15703..0a60983 100644
--- a/packages/acp-agent/package.json
+++ b/packages/acp-agent/package.json
@@ -31,7 +31,7 @@
     "@rushstack/heft": "1.2.7",
     "@types/node": "^22.0.0",
     "@vitest/coverage-v8": "^3.1.1",
-    "vitest": "^3.1.1",
+    "vitest": "^4.1.8",
     "typescript": "~5.9.0"
   }
 }
diff --git a/packages/context-builder/package.json b/packages/context-builder/package.json
index 5dc2db3..a655bfa 100644
--- a/packages/context-builder/package.json
+++ b/packages/context-builder/package.json
@@ -21,7 +21,7 @@
     "@rushstack/heft": "1.2.7",
     "@types/node": "^22.0.0",
     "@vitest/coverage-v8": "^3.1.1",
-    "vitest": "^3.1.1",
+    "vitest": "^4.1.8",
     "typescript": "~5.9.0"
   }
 }
diff --git a/rigs/heft-rig/package.json b/rigs/heft-rig/package.json
index 8fcac66..c000f57 100644
--- a/rigs/heft-rig/package.json
+++ b/rigs/heft-rig/package.json
@@ -15,7 +15,7 @@
     "@rushstack/heft-typescript-plugin": "1.3.2",
     "@vitest/coverage-v8": "^3.1.1",
     "eslint": "~9.39.4",
-    "vitest": "^3.1.1",
+    "vitest": "^4.1.8",
     "typescript": "~5.9.0"
   }
 }