Correct artifact file and empty input handling

engine_test.go

@@ -1049,6 +1049,59 @@ func TestArtifactReaderReceivesPublicReferenceAndPreparesArtifact(t *testing.T)
 	}
 }
 
+func TestPrepareAcceptsExplicitEmptyInlineInputs(t *testing.T) {
+	promptSource := fstest.MapFS{
+		"prompt.yaml": &fstest.MapFile{Data: []byte(`id: empty-inline
+version: "1"
+default_profile: profile
+inputs:
+  - name: transcript
+    required: true
+session_id: 'session-{{input "transcript"}}'
+messages:
+  - role: user
+    content: 'before{{input "transcript"}}after'
+output:
+  format: text
+  validation_mode: none
+`)},
+	}
+	engine, err := promptkit.NewEngine(
+		promptkit.Config{},
+		promptkit.WithPromptFS(promptSource, "."),
+		promptkit.WithProfiles(promptkit.Profile{
+			ID: "profile", Endpoint: "http://example.test/v1", Model: "model",
+		}),
+	)
+	if err != nil {
+		t.Fatalf("construct engine: %v", err)
+	}
+
+	for name, ref := range map[string]promptkit.ArtifactRef{
+		"without URI": promptkit.Inline(""),
+		"with URI":    promptkit.InlineWithURI("memory://empty", ""),
+	} {
+		t.Run(name, func(t *testing.T) {
+			prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{
+				PromptID: "empty-inline",
+				Inputs:   map[string]promptkit.ArtifactRef{"transcript": ref},
+			})
+			if err != nil {
+				t.Fatalf("prepare empty input: %v", err)
+			}
+			if prepared.SessionID != "session-" {
+				t.Fatalf("session ID = %q, want session-", prepared.SessionID)
+			}
+			if len(prepared.Messages) != 1 || prepared.Messages[0].Content != "beforeafter" {
+				t.Fatalf("messages = %#v, want empty input rendered between markers", prepared.Messages)
+			}
+			if prepared.InputHashes["transcript"] == "" {
+				t.Fatalf("empty input did not retain an equality value: %#v", prepared.InputHashes)
+			}
+		})
+	}
+}
+
 func TestArtifactReaderFailuresPreserveArtifactLoadErrors(t *testing.T) {
 	readerErr := errors.New("artifact reader failed")