diff --git a/openfut-adapter-fifa17/mutation-battery.sh b/openfut-adapter-fifa17/mutation-battery.sh
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+++ b/openfut-adapter-fifa17/mutation-battery.sh
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+#!/usr/bin/env bash
+# FIFA 17 squad-adapter mutation battery.
+#
+# Each mutation injects a specific WRONG behaviour into the committed source,
+# runs the one test that defends the invariant, and requires that test to FAIL
+# (non-zero exit) — i.e. the mutant is killed. The source is reverted via
+# `git checkout` after every mutation, so the tree is left untouched.
+#
+# A mutant that SURVIVES (its guard test still passes) means the invariant is
+# not actually defended; the battery then exits non-zero.
+#
+# Run from the adapter crate root:  bash mutation-battery.sh
+set -u
+cd "$(dirname "$0")"
+
+FUT=src/fut
+PASS=0
+FAIL=0
+declare -a SURVIVORS=()
+
+# mutate <file> <literal-old> <literal-new>  (literal, multiline-safe)
+mutate() {
+  OLD="$2" NEW="$3" perl -0777 -pi -e \
+    's/\Q$ENV{OLD}\E/$ENV{NEW}/g or die "MUTATION PATTERN NOT FOUND in '"$1"'\n"' "$1"
+}
+
+# kill <n> <label> <test-filter> <file> <old> <new>
+kill_test() {
+  local n="$1" label="$2" filter="$3" file="$4" old="$5" new="$6"
+  git checkout -- "$file"
+  mutate "$file" "$old" "$new" || { echo "  [#$n] SETUP ERROR"; FAIL=$((FAIL+1)); SURVIVORS+=("#$n $label (setup)"); return; }
+  if cargo test --quiet "$filter" >/dev/null 2>&1; then
+    echo "  [#$n] SURVIVED  — $label  (test '$filter' still passed)"
+    FAIL=$((FAIL+1)); SURVIVORS+=("#$n $label")
+  else
+    echo "  [#$n] killed    — $label"
+    PASS=$((PASS+1))
+  fi
+  git checkout -- "$file"
+}
+
+echo "== FIFA17 squad adapter mutation battery =="
+
+kill_test 1 "kitNumber keyed by slot index, not owned item" \
+  kit_number_is_keyed_by_owned_item_not_slot "$FUT/squad_ext.rs" \
+  '(s.owned_card_id.clone(), s.kit_number)' '(s.index.to_string(), s.kit_number)'
+
+kill_test 2 "captain emitted using resourceId (asset), not wire id" \
+  fresh_projects_full_23_slot_array_with_captain_wire_id "$FUT/squad_projection.rs" \
+  'captain_wire = id.item_id as i64;' 'captain_wire = id.asset_id as i64;'
+
+kill_test 3 "client chemistry silently reconciled (shadow lost)" \
+  swap_moves_two_players_with_their_kits_and_round_trips "$FUT/squad_projection.rs" \
+  '"chemistry": ext.client_reported.chemistry,' '"chemistry": 0,'
+
+kill_test 4 "custom[] regenerated instead of round-tripped verbatim" \
+  custom_is_preserved_byte_for_byte "$FUT/squad_ext.rs" \
+  'custom: put.custom.clone(),' 'custom: Some("[]".to_string()),'
+
+kill_test 5 "index derived (zeroed) instead of round-tripped" \
+  baseline_projects_the_known_squad_round_trip "$FUT/squad.rs" \
+  'index: p.index,' 'index: 0,'
+
+kill_test 6 "stale extension accepted and projected" \
+  stale_is_never_applied "$FUT/squad_projection.rs" \
+  'SquadExtInput::Stale(_) => return Ok(SquadProjection::Stale),' 'SquadExtInput::Stale(ext) => ext,'
+
+kill_test 7 "missing extension fabricates default fields" \
+  missing_is_explicit_never_fabricated "$FUT/squad_projection.rs" \
+  'SquadExtInput::Missing => return Ok(SquadProjection::Missing),' \
+  'SquadExtInput::Missing => return Ok(SquadProjection::Projected(json!({"custom":"[]","manager":[]}))),'
+
+kill_test 8 "shaper fabricates asset id, bypassing real FIFA identity" \
+  shapes_real_identity_and_reverse_entity_ids "$FUT/item.rs" \
+  'let asset = id.asset_id;' 'let asset = 0;'
+
+kill_test 9 "duplicate definition collapses owned instances (id=asset)" \
+  two_owned_copies_of_one_definition_stay_distinct_on_the_wire "$FUT/item.rs" \
+  '"id": id.item_id,' '"id": id.asset_id,'
+
+kill_test 10 "PUT treated as a partial slot diff (drops slots)" \
+  full_replacement_carries_every_occupied_slot_no_diff "$FUT/squad.rs" \
+  'if p.item_data.id == 0 {' 'if p.item_data.id == 0 || p.index > 1 {'
+
+kill_test 11 "FIFA wire item id stored in canonical replacement" \
+  full_replacement_carries_every_occupied_slot_no_diff "$FUT/squad.rs" \
+  'ProposedSlot {
+                owned_card_id,' 'ProposedSlot {
+                owned_card_id: p.item_data.id.to_string(),'
+
+kill_test 12 "projector rebuilds items independently of shared shaper" \
+  persisted_read_round_trips_via_reconstructed_canonical_and_extension "$FUT/squad_projection.rs" \
+  '"itemData": shape_item(item, id, ent),' '"itemData": json!({"id": id.item_id}),'
+
+kill_test 13 "extension schema version ignored on read" \
+  unknown_schema_version_is_rejected_not_coerced "$FUT/squad_ext.rs" \
+  'if schema_version != EXT_SCHEMA_VERSION {' 'if false {'
+
+kill_test 14 "player state keyed by CardDefinitionId not OwnedItemId" \
+  two_owned_copies_of_one_definition_project_as_distinct_players "$FUT/squad_projection.rs" \
+  'ext.kit_numbers.get(&slot.owned_card_id)' 'ext.kit_numbers.get(&item.card_id)'
+
+echo "== mutants killed: $PASS / $((PASS+FAIL)) =="
+if [ "$FAIL" -ne 0 ]; then
+  printf 'SURVIVORS:\n'; printf '  - %s\n' "${SURVIVORS[@]}"
+  exit 1
+fi
+echo "all mutants killed"