diff --git a/.github/workflows/hole-punch-interop-pr.yml b/.github/workflows/hole-punch-interop-pr.yml
index ba04644..14273d7 100644
--- a/.github/workflows/hole-punch-interop-pr.yml
+++ b/.github/workflows/hole-punch-interop-pr.yml
@@ -128,15 +128,10 @@ jobs:
             # Automatic trigger - use change detection outputs
             echo "test-select=${{ steps.detect.outputs.changed-impls }}" >> $GITHUB_OUTPUT
 
-            # Negate each implementation ID in the pipe-separated list
-            # Always include ~failing to skip known-broken tests
-            CHANGED_IMPLS="${{ steps.detect.outputs.changed-impls }}"
-            if [ -n "$CHANGED_IMPLS" ]; then
-              NEGATED_IMPLS=$(echo "$CHANGED_IMPLS" | sed 's/|/|!/g;s/^/!/')
-              echo "test-ignore=~failing|$NEGATED_IMPLS" >> $GITHUB_OUTPUT
-            else
-              echo "test-ignore=~failing" >> $GITHUB_OUTPUT
-            fi
+            # Always include ~failing to skip known-broken tests.
+            # Do NOT add negated implementation patterns to test-ignore here -
+            # that conflicts with test-select and can result in 0 selected tests.
+            echo "test-ignore=~failing" >> $GITHUB_OUTPUT
 
             echo "relay-select=${{ steps.detect.outputs.changed-relays }}" >> $GITHUB_OUTPUT
 
diff --git a/hole-punch/images.yaml b/hole-punch/images.yaml
index b70d5de..a9ffe5d 100644
--- a/hole-punch/images.yaml
+++ b/hole-punch/images.yaml
@@ -4,6 +4,8 @@
 # Test Aliases - Define reusable patterns for test selection
 # Usage: --test-select "~linux" or --test-ignore "!~linux"
 test-aliases:
+  - alias: "nim"
+    value: "nim-v1.15"
   - alias: "failing"
     value: "rust-v0.56 x rust-v0.56"
 
@@ -40,3 +42,13 @@ implementations:
     transports: [quic-v1, tcp, ws]
     secureChannels: [noise, tls]
     muxers: [yamux, mplex]
+
+  - id: nim-v1.15
+    source:
+      type: github
+      repo: vacp2p/nim-libp2p
+      commit: 1bdf2f67971529e8bee01252230bdb00ab785ef7
+      dockerfile: interop/hole-punching/Dockerfile
+    transports: [tcp]
+    secureChannels: [noise]
+    muxers: [yamux, mplex]
diff --git a/hole-punch/lib/generate-tests.sh b/hole-punch/lib/generate-tests.sh
index 4df055c..275d72e 100755
--- a/hole-punch/lib/generate-tests.sh
+++ b/hole-punch/lib/generate-tests.sh
@@ -359,7 +359,7 @@ for relay_id in "${all_relay_ids[@]}"; do
   relay_secure["${relay_id}"]="${secure}"
   relay_muxers["${relay_id}"]="${muxers}"
   relay_dial_only["${relay_id}"]="${dial_only}"
-  if [ -n "${commit}" ]; then
+  if [ -n "${commit}" ] && [ "${commit}" != "null" ]; then
     relay_commit["${relay_id}"]="${commit}"
   fi
 done
@@ -377,7 +377,7 @@ declare -A router_commit
 for router_id in "${all_router_ids[@]}"; do
   commit=$(yq eval ".routers[] | select (.id == \"${router_id}\") | .source.commit" "${IMAGES_YAML}" 2>/dev/null || echo "")
 
-  if [ -n "${commit}" ]; then
+  if [ -n "${commit}" ] && [ "${commit}" != "null" ]; then
     router_commit["${router_id}"]="${commit}"
   fi
 done
@@ -409,7 +409,7 @@ for image_id in "${all_image_ids[@]}"; do
   image_secure["${image_id}"]="${secure}"
   image_muxers["${image_id}"]="${muxers}"
   image_dial_only["${image_id}"]="${dial_only}"
-  if [ -n "${commit}" ]; then
+  if [ -n "${commit}" ] && [ "${commit}" != "null" ]; then
     image_commit["${image_id}"]="${commit}"
   fi
   image_legacy["${image_id}"]="${legacy}"
@@ -556,8 +556,8 @@ generate_tests_worker() {
 
         print_debug "selecting listener router: ${listener_router_id}"
 
-        # Iterate through all dialers
-        for dialer_id in "${all_image_ids[@]}"; do
+        # Iterate through this worker's chunk of dialers
+        for dialer_id in "${dialer_chunk[@]}"; do
           dialer_transports="${image_transports[$dialer_id]}"
           dialer_secure="${image_secure[$dialer_id]}"
           dialer_muxers="${image_muxers[$dialer_id]}"
@@ -759,7 +759,7 @@ EOF
       imageName: ${relay_image_name}
 EOF
                   if [ -n "${relay_commit}" ]; then
-                    echo "      snapshot: snapshots/${relay_commit}.zip" >> "${worker_selected}"
+                    echo "      snapshot: snapshots/${relay_commit}.zip" >> "${worker_ignored}"
                   fi
                   cat >> "${worker_ignored}" <<EOF
     dialerRouter:
@@ -767,7 +767,7 @@ EOF
       imageName: ${dialer_router_image_name}
 EOF
                   if [ -n "${dialer_router_commit}" ]; then
-                    echo "      snapshot: snapshots/${dialer_router_commit}.zip" >> "${worker_selected}"
+                    echo "      snapshot: snapshots/${dialer_router_commit}.zip" >> "${worker_ignored}"
                   fi
                   cat >> "${worker_ignored}" <<EOF
     listenerRouter:
@@ -775,7 +775,7 @@ EOF
       imageName: ${listener_router_image_name}
 EOF
                   if [ -n "${listener_router_commit}" ]; then
-                    echo "      snapshot: snapshots/${listener_router_commit}.zip" >> "${worker_selected}"
+                    echo "      snapshot: snapshots/${listener_router_commit}.zip" >> "${worker_ignored}"
                   fi
                 fi
 
@@ -939,7 +939,7 @@ EOF
       imageName: ${relay_image_name}
 EOF
                       if [ -n "${relay_commit}" ]; then
-                        echo "      snapshot: snapshots/${relay_commit}.zip" >> "${worker_selected}"
+                        echo "      snapshot: snapshots/${relay_commit}.zip" >> "${worker_ignored}"
                       fi
                       cat >> "${worker_ignored}" <<EOF
     dialerRouter:
@@ -947,7 +947,7 @@ EOF
       imageName: ${dialer_router_image_name}
 EOF
                       if [ -n "${dialer_router_commit}" ]; then
-                        echo "      snapshot: snapshots/${dialer_router_commit}.zip" >> "${worker_selected}"
+                        echo "      snapshot: snapshots/${dialer_router_commit}.zip" >> "${worker_ignored}"
                       fi
                       cat >> "${worker_ignored}" <<EOF
     listenerRouter:
@@ -955,7 +955,7 @@ EOF
       imageName: ${listener_router_image_name}
 EOF
                       if [ -n "${listener_router_commit}" ]; then
-                        echo "      snapshot: snapshots/${listener_router_commit}.zip" >> "${worker_selected}"
+                        echo "      snapshot: snapshots/${listener_router_commit}.zip" >> "${worker_ignored}"
                       fi
                     fi
                   done
diff --git a/lib/lib-test-filtering.sh b/lib/lib-test-filtering.sh
index c040076..af44ebf 100755
--- a/lib/lib-test-filtering.sh
+++ b/lib/lib-test-filtering.sh
@@ -43,6 +43,7 @@ get_common() {
     # For each remaining list, keep only items that appear in it
     for list in "$@"; do
         local -A current_list_map
+        current_list_map=()
 
         # Build a map of items in current list
         for item in ${list}; do