diff --git a/go-services/inventory-go/spell_filter.go b/go-services/inventory-go/spell_filter.go
new file mode 100644
index 00000000..b85056e5
--- /dev/null
+++ b/go-services/inventory-go/spell_filter.go
@@ -0,0 +1,60 @@
+package main
+
+import (
+	"sort"
+	"strings"
+)
+
+// Spell-filter support for /search/items: implements the has_spell /
+// spell_contains / legendary_cantrips params the Go port had ignored
+// (design doc 2026-07-14; legacy inventory-service/main.py:3345-3452).
+// Names are matched against the in-memory enum-DB spell map; the resulting
+// IDs are filtered in SQL against the item_spells table.
+
+// spellIDsContaining returns the IDs of all spells whose name contains q,
+// case-insensitively, in ascending order (deterministic SQL args).
+func spellIDsContaining(spells map[int]map[string]any, q string) []int {
+	q = strings.ToLower(strings.TrimSpace(q))
+	var ids []int
+	for id, sp := range spells {
+		name, _ := sp["name"].(string)
+		if name != "" && strings.Contains(strings.ToLower(name), q) {
+			ids = append(ids, id)
+		}
+	}
+	sort.Ints(ids)
+	return ids
+}
+
+// spellIDsForCantrip matches one cantrip display name using the legacy
+// flexible rule: spell name contains the label OR the label contains the
+// spell name (both case-insensitive).
+func spellIDsForCantrip(spells map[int]map[string]any, cantrip string) []int {
+	c := strings.ToLower(strings.TrimSpace(cantrip))
+	var ids []int
+	for id, sp := range spells {
+		name, _ := sp["name"].(string)
+		n := strings.ToLower(name)
+		if n == "" {
+			continue
+		}
+		if strings.Contains(n, c) || strings.Contains(c, n) {
+			ids = append(ids, id)
+		}
+	}
+	sort.Ints(ids)
+	return ids
+}
+
+// exactSpellID returns the lowest ID whose name equals q case-insensitively.
+func exactSpellID(spells map[int]map[string]any, q string) (int, bool) {
+	q = strings.ToLower(strings.TrimSpace(q))
+	best := -1
+	for id, sp := range spells {
+		name, _ := sp["name"].(string)
+		if strings.ToLower(name) == q && (best == -1 || id < best) {
+			best = id
+		}
+	}
+	return best, best != -1
+}
diff --git a/go-services/inventory-go/spell_filter_test.go b/go-services/inventory-go/spell_filter_test.go
new file mode 100644
index 00000000..f556dee7
--- /dev/null
+++ b/go-services/inventory-go/spell_filter_test.go
@@ -0,0 +1,52 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+// Minimal stand-in for the enum-DB spell map (Server.spells).
+var testSpells = map[int]map[string]any{
+	1: {"name": "Legendary Invulnerability"},
+	2: {"name": "Epic Invulnerability"},
+	3: {"name": "Legendary Summoning Prowess"},
+	4: {"name": "Strength Other VI"},
+	5: {"name": "Summoning"}, // shorter name CONTAINED IN a cantrip label
+	6: {"name": ""},          // malformed entry must never match
+}
+
+func TestSpellIDsContaining(t *testing.T) {
+	if got := spellIDsContaining(testSpells, "invulnerability"); !reflect.DeepEqual(got, []int{1, 2}) {
+		t.Errorf("substring match = %v, want [1 2]", got)
+	}
+	if got := spellIDsContaining(testSpells, "INVULN"); !reflect.DeepEqual(got, []int{1, 2}) {
+		t.Errorf("case-insensitive match = %v, want [1 2]", got)
+	}
+	if got := spellIDsContaining(testSpells, "frostbite"); got != nil {
+		t.Errorf("no-match = %v, want nil", got)
+	}
+}
+
+func TestSpellIDsForCantrip(t *testing.T) {
+	// Forward direction: spell name contains the cantrip label.
+	if got := spellIDsForCantrip(testSpells, "Invulnerability"); !reflect.DeepEqual(got, []int{1, 2}) {
+		t.Errorf("forward contains = %v, want [1 2]", got)
+	}
+	// Both directions (legacy flexible rule): "Legendary Summoning Prowess"
+	// matches spell 3 (equal) AND spell 5 ("Summoning" is contained in the label).
+	if got := spellIDsForCantrip(testSpells, "Legendary Summoning Prowess"); !reflect.DeepEqual(got, []int{3, 5}) {
+		t.Errorf("both-direction = %v, want [3 5]", got)
+	}
+	if got := spellIDsForCantrip(testSpells, "Piercing Bane"); got != nil {
+		t.Errorf("no-match = %v, want nil", got)
+	}
+}
+
+func TestExactSpellID(t *testing.T) {
+	if id, ok := exactSpellID(testSpells, "legendary invulnerability"); !ok || id != 1 {
+		t.Errorf("exact case-insensitive = (%d,%v), want (1,true)", id, ok)
+	}
+	if _, ok := exactSpellID(testSpells, "Invulnerability"); ok {
+		t.Error("partial name must not exact-match")
+	}
+}