Tighten prepared execution credential handling

internal/usecase/prepared_execution_test.go

@@ -210,6 +210,48 @@ func TestRunnerRunPreparedRechecksEnvironmentCredentialBeforeAdmission(t *testin
 	}
 }
 
+func TestRunnerRunPreparedKeepsDirectCredentialOutOfMetadata(t *testing.T) {
+	const directKey = "direct-prepared-test-key"
+
+	profile := defaultExecutionProfile()
+	profile.APIKeyRequired = true
+	client := &fakeLLM{resp: &domain.GenerateResponse{Content: "ok"}}
+	runner := NewRunner(
+		&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)},
+		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": profile}},
+		nil,
+		defaultArtifactReader(),
+		defaultRenderer(),
+		client,
+		&recordingValidationPreparer{plan: &recordingPreparedValidation{}},
+		nil,
+	)
+
+	prepared, err := runner.PrepareExecution(context.Background(), domain.RunRequest{
+		PromptID:  "p",
+		ProfileID: "exec",
+		APIKey:    directKey,
+		Inputs:    singleInputRef(),
+	})
+	if err != nil {
+		t.Fatalf("prepare execution: %v", err)
+	}
+	if details := prepared.Details(); details.EffectiveModelParams.APIKey != "" {
+		t.Fatal("prepared details retained direct credential")
+	}
+
+	result, err := runner.RunPrepared(context.Background(), prepared)
+	if err != nil {
+		t.Fatalf("run prepared: %v", err)
+	}
+	if client.lastReq.Target.APIKey != directKey {
+		t.Fatal("generation did not receive direct credential")
+	}
+	if result.EffectiveModelParams.APIKey != "" {
+		t.Fatal("run result retained direct credential")
+	}
+}
+
 func TestRunnerRunPreparedUsesFrozenValidationForInitialAndRepairOutputs(t *testing.T) {
 	validator := &recordingValidationPreparer{
 		plan: &recordingPreparedValidation{