diff --git a/internal/scaffold/fullsend-repo/.github/workflows/dispatch.yml b/internal/scaffold/fullsend-repo/.github/workflows/dispatch.yml
index a2c7164cc4..f47dfd4e2d 100644
--- a/internal/scaffold/fullsend-repo/.github/workflows/dispatch.yml
+++ b/internal/scaffold/fullsend-repo/.github/workflows/dispatch.yml
@@ -1,4 +1,4 @@
-# lint-workflow-size: max-lines=390
+# lint-workflow-size: max-lines=415
 # Dispatcher workflow that routes events to agent workflows based on stage.
 # Routing logic determines the stage from event context — the shim only
 # forwards the raw event.  Adding a new stage requires only a case branch
@@ -324,6 +324,29 @@ jobs:
             comment: (.comment // null | if . then {body: .body[:4096]} else null end)
           }' "$GITHUB_EVENT_PATH")
 
+          # Deduplicate retro dispatches — if a retro workflow run is
+          # already queued or in-progress for the same source repo + PR,
+          # skip this dispatch.  Multiple shim runs for the same PR close
+          # event each call dispatch independently; this check prevents
+          # all but the first from launching a redundant retro run.
+          if [[ "$STAGE" == "retro" ]]; then
+            RETRO_PR=$(echo "$EVENT_PAYLOAD" | jq -r '(.pull_request.number // .issue.number) | tostring')
+            if [[ -n "$RETRO_PR" && "$RETRO_PR" != "null" ]]; then
+              ACTIVE_IDS=$(gh api "repos/${DISPATCH_REPO}/actions/workflows/retro.yml/runs?per_page=10" \
+                --jq '[.workflow_runs[] | select(.status == "queued" or .status == "in_progress") | .id] | .[]' 2>/dev/null || true)
+              for rid in $ACTIVE_IDS; do
+                RUN_INPUTS=$(gh api "repos/${DISPATCH_REPO}/actions/runs/${rid}" --jq '.inputs' 2>/dev/null || echo '{}')
+                RUN_SRC=$(echo "$RUN_INPUTS" | jq -r '.source_repo // empty')
+                RUN_PR=$(echo "$RUN_INPUTS" | jq -r '.event_payload' 2>/dev/null \
+                  | jq -r '(.pull_request.number // .issue.number) | tostring' 2>/dev/null || true)
+                if [[ "$RUN_SRC" == "$SOURCE_REPO" && "$RUN_PR" == "$RETRO_PR" ]]; then
+                  echo "::notice::Retro already active for ${SOURCE_REPO}#${RETRO_PR} (run ${rid}) — skipping duplicate dispatch"
+                  exit 0
+                fi
+              done
+            fi
+          fi
+
           echo "Scanning for workflows with stage: $STAGE"
 
           dispatched=0