Add tri-state reasoning overrides

internal/usecase/runner.go

@@ -442,8 +442,8 @@ func mergeExecutionTargetOverride(base domain.ExecutionTarget, override domain.E
 	if strings.TrimSpace(override.ServiceTier) != "" {
 		out.ServiceTier = override.ServiceTier
 	}
-	if strings.TrimSpace(override.ReasoningEffort) != "" {
-		out.ReasoningEffort = override.ReasoningEffort
+	if override.ReasoningEffort != nil {
+		out.ReasoningEffort = strings.TrimSpace(*override.ReasoningEffort)
 	}
 	if strings.TrimSpace(override.APIKeyEnv) != "" {
 		out.APIKeyEnv = override.APIKeyEnv

internal/usecase/runner_test.go

@@ -1710,7 +1710,7 @@ func TestResolveExecutionTargetRuntimeOverridesBeatProfileForAllOverrideableFiel
 		TopP:            float64Ptr(0.5),
 		TimeoutSeconds:  intPtr(30),
 		ServiceTier:     "flex",
-		ReasoningEffort: "high",
+		ReasoningEffort: stringPtr("high"),
 		APIKeyEnv:       "RUNTIME_KEY",
 		ExtraParams: map[string]any{
 			"runtime_only": "yes",
@@ -1731,7 +1731,7 @@ func TestResolveExecutionTargetRuntimeOverridesBeatProfileForAllOverrideableFiel
 		target.TopP != *override.TopP ||
 		target.TimeoutSeconds != *override.TimeoutSeconds ||
 		target.ServiceTier != override.ServiceTier ||
-		target.ReasoningEffort != override.ReasoningEffort ||
+		target.ReasoningEffort != *override.ReasoningEffort ||
 		target.APIKeyEnv != override.APIKeyEnv {
 		t.Fatalf("expected runtime overrides to win for all fields, got %+v", target)
 	}
@@ -1740,6 +1740,46 @@ func TestResolveExecutionTargetRuntimeOverridesBeatProfileForAllOverrideableFiel
 	}
 }
 
+func TestResolveExecutionTargetReasoningOverrideStates(t *testing.T) {
+	profileValue := &domain.ExecutionProfile{
+		ReasoningEffort: "medium",
+	}
+	tests := []struct {
+		name     string
+		override *string
+		want     string
+	}{
+		{
+			name: "nil inherits profile value",
+			want: "medium",
+		},
+		{
+			name:     "nonblank replaces and trims profile value",
+			override: stringPtr(" high "),
+			want:     "high",
+		},
+		{
+			name:     "blank clears profile value",
+			override: stringPtr(" \t "),
+			want:     "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			target, _, err := resolveExecutionTarget(nil, profileValue, &domain.ExecutionTargetOverride{
+				ReasoningEffort: tt.override,
+			})
+			if err != nil {
+				t.Fatalf("resolve execution target: %v", err)
+			}
+			if target.ReasoningEffort != tt.want {
+				t.Fatalf("reasoning effort = %q, want %q", target.ReasoningEffort, tt.want)
+			}
+		})
+	}
+}
+
 func TestMergeExecutionTargetEmptyStringOverridesDoNotErase(t *testing.T) {
 	base := domain.ExecutionTarget{
 		Endpoint:        "http://base/v1",
@@ -1970,6 +2010,10 @@ func float64Ptr(v float64) *float64 {
 	return &v
 }
 
+func stringPtr(v string) *string {
+	return &v
+}
+
 func intPtr(v int) *int {
 	return &v
 }