diff --git a/.fullsend/config.yaml b/.fullsend/config.yaml
index ad0e2b3bc..ac7d99dbd 100644
--- a/.fullsend/config.yaml
+++ b/.fullsend/config.yaml
@@ -10,12 +10,12 @@ roles:
     - coder
     - review
     - fix
-    - retro:
-        trigger: >
-          event.transition.kind == "comment_added"
-          && has(event.transition.comment.command)
-          && event.transition.comment.command == "/fs-retro"
-          && event.actor.kind == "human"
+    - retro
+agents:
+    # Retro: run only on an explicit /fs-retro comment from a human, not on
+    # every closed PR. 
+    - name: retro
+      source: harness/retro.yaml
 allowed_remote_resources:
     - https://raw.githubusercontent.com/fullsend-ai/fullsend/
     - https://raw.githubusercontent.com/fullsend-ai/agents/
diff --git a/.fullsend/harness/retro.yaml b/.fullsend/harness/retro.yaml
new file mode 100644
index 000000000..d5c2451cb
--- /dev/null
+++ b/.fullsend/harness/retro.yaml
@@ -0,0 +1,13 @@
+# Retro harness overlay for lightspeed-core/lightspeed-stack
+#
+# Extends the upstream fullsend-ai/agents retro harness (pinned to the v0.51.0
+# commit with a SHA-256 integrity fragment) and restricts dispatch to an
+# explicit /fs-retro comment from a human. By default retro runs on every
+# closed pull request; this overlay makes it opt-in only.
+base: https://raw.githubusercontent.com/fullsend-ai/agents/16657d540187b16743c8693dc2ccc40366334430/harness/retro.yaml#sha256=97771fd79ad7f4095b5fc9d92dc9d447487c19482018d2c9ccce1c4398608fd5
+
+trigger: >-
+  event.transition.kind == "comment_added"
+  && has(event.transition.comment.command)
+  && event.transition.comment.command == "/fs-retro"
+  && event.actor.kind == "human"