diff --git a/tools/push3-evolution/evolve.sh b/tools/push3-evolution/evolve.sh
index 8833080..7595d5b 100755
--- a/tools/push3-evolution/evolve.sh
+++ b/tools/push3-evolution/evolve.sh
@@ -380,7 +380,7 @@ PYEOF
     log "  diverse-seeds: sampling up to $POPULATION candidates from pool ($POOL_COUNT available)"
 
     while IFS= read -r POOL_FILE && [ "$VARIANT_IDX" -lt "$POPULATION" ]; do
-      CAND_FILE="$GEN_DIR/candidate_$(printf '%03d' $VARIANT_IDX).push3"
+      CAND_FILE="$GEN_DIR/candidate_$(printf '%03d' "$VARIANT_IDX").push3"
       cp "$POOL_FILE" "$CAND_FILE"
       printf '0\n' > "${CAND_FILE%.push3}.ops"
       VARIANT_IDX=$((VARIANT_IDX + 1))
@@ -402,7 +402,7 @@ PYEOF
       || fail "seed-gen-cli.ts failed to generate variants"
 
     while IFS= read -r VARIANT_FILE && [ "$VARIANT_IDX" -lt "$POPULATION" ]; do
-      CAND_FILE="$GEN_DIR/candidate_$(printf '%03d' $VARIANT_IDX).push3"
+      CAND_FILE="$GEN_DIR/candidate_$(printf '%03d' "$VARIANT_IDX").push3"
       cp "$VARIANT_FILE" "$CAND_FILE"
       printf '0\n' > "${CAND_FILE%.push3}.ops"
       VARIANT_IDX=$((VARIANT_IDX + 1))
@@ -411,7 +411,7 @@ PYEOF
 
   # Fill any remaining slots with mutations of the seed
   while [ "$VARIANT_IDX" -lt "$POPULATION" ]; do
-    CAND_FILE="$GEN_DIR/candidate_$(printf '%03d' $VARIANT_IDX).push3"
+    CAND_FILE="$GEN_DIR/candidate_$(printf '%03d' "$VARIANT_IDX").push3"
     MUTATED=$(run_mutate_cli mutate "$SEED" "$MUTATION_RATE") \
       || fail "Failed to mutate seed for fallback candidate $VARIANT_IDX"
     printf '%s\n' "$MUTATED" > "$CAND_FILE"
@@ -612,7 +612,7 @@ PYEOF
     done < <(py_top_n "$ELITES" "$SCORES_FILE")
 
     for ELITE_FILE in "${ELITE_FILES[@]}"; do
-      DEST="$NEXT_GEN_DIR/candidate_$(printf '%03d' $NEXT_IDX).push3"
+      DEST="$NEXT_GEN_DIR/candidate_$(printf '%03d' "$NEXT_IDX").push3"
       cp "$ELITE_FILE" "$DEST"
       printf '0\n' > "${DEST%.push3}.ops"
       NEXT_IDX=$((NEXT_IDX + 1))
@@ -629,7 +629,7 @@ PYEOF
   # First half of remaining: mutate random survivors
   for _i in $(seq 1 $HALF); do
     SUR="${SURVIVOR_FILES[$((RANDOM % ${#SURVIVOR_FILES[@]}))]}"
-    DEST="$NEXT_GEN_DIR/candidate_$(printf '%03d' $NEXT_IDX).push3"
+    DEST="$NEXT_GEN_DIR/candidate_$(printf '%03d' "$NEXT_IDX").push3"
     if MUTATED=$(run_mutate_cli mutate "$SUR" "$MUTATION_RATE" 2>/dev/null); then
       printf '%s\n' "$MUTATED" > "$DEST"
       printf '%d\n' "$MUTATION_RATE" > "${DEST%.push3}.ops"
@@ -646,7 +646,7 @@ PYEOF
   for _i in $(seq 1 $REMAINING); do
     SUR_A="${SURVIVOR_FILES[$((RANDOM % ${#SURVIVOR_FILES[@]}))]}"
     SUR_B="${SURVIVOR_FILES[$((RANDOM % ${#SURVIVOR_FILES[@]}))]}"
-    DEST="$NEXT_GEN_DIR/candidate_$(printf '%03d' $NEXT_IDX).push3"
+    DEST="$NEXT_GEN_DIR/candidate_$(printf '%03d' "$NEXT_IDX").push3"
     if CROSSED=$(run_mutate_cli crossover "$SUR_A" "$SUR_B" 2>/dev/null); then
       printf '%s\n' "$CROSSED" > "$DEST"
       printf '0\n' > "${DEST%.push3}.ops"