diff --git a/config.go b/config.go
index 302df8e..23998a8 100644
--- a/config.go
+++ b/config.go
@@ -74,6 +74,7 @@ type ConfigScope[C any] struct {
 }
 
 // Selector binds one typed command flag to selected configuration scopes.
+// A required binding is required only when a selected scope uses it.
 type Selector[C any] struct {
 	Binding Flag[C]
 	Scopes  []string
@@ -101,6 +102,8 @@ type configScopesInput struct {
 }
 
 type selectorState[C any] struct {
+	name     string
+	required bool
 	scopes   []string
 	supplied bool
 	apply    func(*C)
diff --git a/config_test.go b/config_test.go
index 8d44e5b..c6b5005 100644
--- a/config_test.go
+++ b/config_test.go
@@ -217,3 +217,41 @@ func TestConfigPreflightRejectsUnsupportedAggregateAndInapplicableSelector(t *te
 func noopConfigAcquire[C any](context.Context, ConfigRequest, C) (Acquired[ConfigView], error) {
 	return Acquired[ConfigView]{}, nil
 }
+
+func TestRequiredConfigSelectorOnlyAppliesToSelectedScopes(t *testing.T) {
+	app, _ := New(Identity{Name: "example"})
+	calls := 0
+	acquire := func(context.Context, ConfigRequest, string) (Acquired[ConfigView], error) {
+		calls++
+		return Acquired[ConfigView]{}, nil
+	}
+	err := RegisterConfig(app, ConfigSuite[string]{
+		Selectors: []Selector[string]{{Scopes: []string{"app"}, Binding: ValueFlag[string](FlagMeta{Name: "campaign", Required: true}, nil, parseString, func(c *string, v Supplied[string]) { *c = v.Value })}},
+		Scopes:    []ConfigScope[string]{{Name: "app", Operations: []ConfigOperation{ConfigValidate}, Acquire: acquire}, {Name: "promptkit", Operations: []ConfigOperation{ConfigValidate}, Acquire: acquire}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, tc := range []struct {
+		args  []string
+		kind  OutcomeKind
+		calls int
+	}{
+		{[]string{"--scope", "promptkit"}, OutcomeSuccess, 1},
+		{nil, OutcomeUsage, 0},
+		{[]string{"--scope", "all"}, OutcomeUsage, 0},
+		{[]string{"--scope", "all", "--campaign", "spring"}, OutcomeSuccess, 2},
+		{[]string{"--scope", "promptkit", "--campaign", "spring"}, OutcomeUsage, 0},
+		{[]string{"--help"}, OutcomeSuccess, 0},
+	} {
+		calls = 0
+		var out bytes.Buffer
+		result := app.Execute(context.Background(), append([]string{"config", "validate"}, tc.args...), Streams{Out: &out})
+		if result.Kind != tc.kind || calls != tc.calls {
+			t.Fatalf("%v: result=%#v calls=%d", tc.args, result, calls)
+		}
+		if len(tc.args) > 0 && tc.args[0] == "--help" && !strings.Contains(out.String(), "required where applicable") {
+			t.Fatalf("help=%q", out.String())
+		}
+	}
+}
diff --git a/docs/roadmap/remediation.md b/docs/roadmap/remediation.md
index 144a981..974ce93 100644
--- a/docs/roadmap/remediation.md
+++ b/docs/roadmap/remediation.md
@@ -1,6 +1,6 @@
 # Initial implementation review and remediation
 
-Status: findings recorded; implementation fixes pending.
+Status: remediation in progress.
 
 Date: 2026-10-07.
 
@@ -17,7 +17,13 @@ review; prior completion notes are historical evidence, not a new validation
 result. The triggering cases below follow from the current code paths. Focused
 regression checks are proposed completion evidence for subsequent fixes.
 
-This document records remediation work only. Implementation remains unchanged.
+The findings below describe the review baseline. Completion is tracked here as
+implementation fixes land.
+
+## Remediation progress
+
+- R-01 complete: required selectors are checked after scope selection; unrelated
+  scopes remain usable, and help describes conditional requiredness.
 
 ## Architecture assessment
 
diff --git a/selectors.go b/selectors.go
index 3611971..b564986 100644
--- a/selectors.go
+++ b/selectors.go
@@ -27,10 +27,15 @@ func configInputFlags[C any](suite ConfigSuite[C], formatDefault string) []Flag[
 }
 
 func adaptSelector[C any](selector Selector[C]) Flag[configInput[C]] {
-	return adaptContextSelector(selector,
+	flag := adaptContextSelector(selector,
 		func(input *configInput[C]) *C { return &input.SelectorContext },
 		func(input *configInput[C], state selectorState[C]) { input.selectors = append(input.selectors, state) },
 	)
+	if flag.binding.meta.Required {
+		flag.binding.meta.Required = false // Scope-aware preflight enforces this requirement.
+		flag.binding.meta.Usage += " (required where applicable)"
+	}
+	return flag
 }
 
 func adaptContextSelector[C any, I any](selector Selector[C], selectContext func(*I) *C, record func(*I, selectorState[C])) Flag[I] {
@@ -53,6 +58,8 @@ func adaptContextSelector[C any, I any](selector Selector[C], selectContext func
 				return nil, err
 			}
 			state := selectorState[C]{
+				name:     binding.meta.Name,
+				required: binding.meta.Required,
 				scopes:   append([]string(nil), selector.Scopes...),
 				supplied: len(values) > 0,
 				apply:    apply,
@@ -128,9 +135,6 @@ func selectConfigScopes[C any](suite ConfigSuite[C], input configInput[C], opera
 		}
 	}
 	for _, selector := range input.selectors {
-		if !selector.supplied {
-			continue
-		}
 		applies := false
 		for _, scopeName := range scopes {
 			if selectorApplies(selector.scopes, scopeName) {
@@ -138,7 +142,10 @@ func selectConfigScopes[C any](suite ConfigSuite[C], input configInput[C], opera
 				break
 			}
 		}
-		if !applies {
+		if applies && selector.required && !selector.supplied {
+			return nil, fmt.Errorf("required flag --%s was not supplied", selector.name)
+		}
+		if selector.supplied && !applies {
 			return nil, fmt.Errorf("selector is not applicable to configuration scope %q", input.Scope)
 		}
 	}