fix: avoid faulty duplicate detection

adapters/humamux/humamux_test.go

@@ -133,3 +133,63 @@ func BenchmarkHumaGorillaMux(b *testing.B) {
 		}
 	}
 }
+
+func TestOperationWithoutIDAndInlineRequestTypeDefinitionNotPanics(t *testing.T) {
+	r := mux.NewRouter()
+	api := New(r, huma.DefaultConfig("Test", "1.0.0"))
+
+	var (
+		op1 = huma.Operation{Method: http.MethodGet, Path: "/1"} // no OperationID
+		op2 = huma.Operation{Method: http.MethodGet, Path: "/2"} // no OperationID
+	)
+
+	huma.Register(api, op1, func(ctx context.Context, i *struct { // inline request input type definition
+		Body struct {
+			Test1 string // field name varying
+		}
+	},
+	) (*struct{}, error,
+	) {
+		return nil, nil
+	})
+
+	huma.Register(api, op2, func(ctx context.Context, i *struct { // inline request input type definition
+		Body struct {
+			Test2 string // field name varying
+		}
+	},
+	) (*struct{}, error,
+	) {
+		return nil, nil
+	})
+}
+
+func TestOperationWithoutIDAndInlineResponseTypeDefinitionNotPanics(t *testing.T) {
+	r := mux.NewRouter()
+	api := New(r, huma.DefaultConfig("", ""))
+
+	var (
+		op1 = huma.Operation{Method: http.MethodGet, Path: "/1"} // no OperationID
+		op2 = huma.Operation{Method: http.MethodGet, Path: "/2"} // no OperationID
+	)
+
+	huma.Register(api, op1, func(ctx context.Context, i *struct{},
+	) (*struct { // inline response output type definition
+		Body struct {
+			Test1 string // field name varying
+		}
+	}, error,
+	) {
+		return nil, nil
+	})
+
+	huma.Register(api, op2, func(ctx context.Context, i *struct{},
+	) (*struct { // inline response output type definition
+		Body struct {
+			Test2 string // field name varying
+		}
+	}, error,
+	) {
+		return nil, nil
+	})
+}

registry.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"reflect"
+	"strconv"
 	"strings"
 	"unicode/utf8"
 )
@@ -124,17 +125,30 @@ func (r *mapRegistry) Schema(t reflect.Type, allowRef bool, hint string) *Schema
 
 	if getsRef {
 		if s, ok := r.schemas[name]; ok {
-			if _, ok = r.seen[t]; !ok {
-				// The name matches but the type is different, so we have a dupe.
+			if _, seen := r.seen[t]; seen {
+				// The name and type both match, so reuse the existing schema.
+				if allowRef {
+					return &Schema{Ref: r.prefix + name}
+				}
 
-				panic(fmt.Errorf("duplicate name: %s, new type: %s, existing type: %s", name, t, r.types[name]))
+				return s
 			}
 
-			if allowRef {
-				return &Schema{Ref: r.prefix + name}
+			// The name matches but the type is different. Named types are a
+			// genuine duplicate the caller must resolve (e.g. with a custom
+			// namer), but unnamed inline types share a hint-derived name by
+			// design, so disambiguate them with an incrementing numeric suffix.
+			if t.Name() != "" {
+				panic(fmt.Errorf("duplicate name: %s, new type: %s, existing type: %s", name, t, r.types[name]))
 			}
 
-			return s
+			base := name
+			for i := 1; ; i++ {
+				name = base + strconv.Itoa(i)
+				if _, exists := r.schemas[name]; !exists {
+					break
+				}
+			}
 		}
 	}
 

registry_test.go

@@ -98,6 +98,53 @@ func TestAllowAdditionalPropertiesByDefault(t *testing.T) {
 	})
 }
 
+func TestInlineTypeDisambiguation(t *testing.T) {
+	// Distinct inline (unnamed) structs share the same hint-derived name and
+	// must be disambiguated rather than panic. See issue reproduced in #893.
+	r := NewMapRegistry("#/components/schemas/", DefaultSchemaNamer)
+
+	first := r.Schema(reflect.TypeOf(struct {
+		Field1 string `json:"field1"`
+	}{}), true, "Request")
+	second := r.Schema(reflect.TypeOf(struct {
+		Field2 string `json:"field2"`
+	}{}), true, "Request")
+
+	assert.Equal(t, "#/components/schemas/Request", first.Ref)
+	assert.Equal(t, "#/components/schemas/Request1", second.Ref)
+	assert.Len(t, r.Map(), 2)
+}
+
+func TestInlineTypeDeduplication(t *testing.T) {
+	// Identical inline structs are the same reflect.Type and must still
+	// deduplicate to a single schema.
+	r := NewMapRegistry("#/components/schemas/", DefaultSchemaNamer)
+
+	first := r.Schema(reflect.TypeOf(struct {
+		Field string `json:"field"`
+	}{}), true, "Request")
+	second := r.Schema(reflect.TypeOf(struct {
+		Field string `json:"field"`
+	}{}), true, "Request")
+
+	assert.Equal(t, "#/components/schemas/Request", first.Ref)
+	assert.Equal(t, first.Ref, second.Ref)
+	assert.Len(t, r.Map(), 1)
+}
+
+func TestDuplicateNamedTypePanics(t *testing.T) {
+	// Genuinely different named types that collide on a name remain a hard
+	// error, directing the caller to a custom namer.
+	r := NewMapRegistry("#/components/schemas/", func(reflect.Type, string) string {
+		return "Collision"
+	})
+
+	r.Schema(reflect.TypeFor[S](), true, "")
+	assert.Panics(t, func() {
+		r.Schema(reflect.TypeFor[Output[int]](), true, "")
+	})
+}
+
 func TestRegistryConfigValue(t *testing.T) {
 	r := NewMapRegistry("/schemas", DefaultSchemaNamer)