Preserve transcript destinations that change type

docs/operations.md

@@ -27,8 +27,10 @@ consumed application and PromptKit sources, and effective host message files. An
 intentional in-place transcript replacement is allowed. A regular transcript
 output is prepared in a sibling temporary file, leaving the final destination
 untouched until successful publication. Pipes and devices are opened only for
-delivery; a pipe can wait for its reader. Parent directories for required outputs
-must already exist.
+delivery, and a pipe can wait for its reader. If a transcript destination changes
+between a regular file and a pipe or device during processing, Audita can report a
+delivery failure while preserving the new destination. Parent directories for
+required outputs must already exist.
 
 Enabled reports are initialized as `in_progress` before processing. The
 transcript is published before final reports; the files do not form a single

docs/roadmap/remediation.md

@@ -384,6 +384,8 @@ keep their native behavior.
 
 ## R11 — P2: Preserve Pipes That Appear After Output Preparation
 
+**Status:** Completed. Delivery checks the destination type before opening a prepared stream or replacing a file. Tests cover both type changes, preservation of the replacement destination, and cleanup of staged output.
+
 **Category**
 
 The new Stage 7 preparation changes the existing special-file delivery behavior.

internal/core/diagnostics/output_session.go

@@ -327,6 +327,13 @@ func (s *OutputSession) writeTranscript(payload []byte) error {
 		return err
 	}
 	if s.direct {
+		info, err := os.Stat(s.transcript)
+		if err != nil {
+			return err
+		}
+		if info.IsDir() || info.Mode().IsRegular() {
+			return fmt.Errorf("transcript output is no longer a stream destination")
+		}
 		file, err := os.OpenFile(s.transcript, os.O_WRONLY, 0)
 		if err != nil {
 			return err
@@ -349,6 +356,13 @@ func (s *OutputSession) writeTranscript(payload []byte) error {
 	if err := errors.Join(writeErr, closeErr); err != nil {
 		return err
 	}
+	info, err := os.Stat(s.publishPath)
+	if err == nil && !info.Mode().IsRegular() {
+		return fmt.Errorf("transcript output changed type after preparation")
+	}
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return err
+	}
 	if err := os.Rename(s.tempPath, s.publishPath); err != nil {
 		return err
 	}

internal/core/diagnostics/output_session_test.go

@@ -418,14 +418,8 @@ func TestTranscriptWriteFailureCleansTemporaryResource(t *testing.T) {
 }
 
 func TestNamedPipeIsNotOpenedDuringPreparation(t *testing.T) {
-	tool, err := exec.LookPath("mkfifo")
-	if err != nil {
-		t.Skip("mkfifo is unavailable")
-	}
 	pipe := filepath.Join(t.TempDir(), "output-pipe")
-	if output, err := exec.Command(tool, pipe).CombinedOutput(); err != nil {
-		t.Fatalf("mkfifo: %v %s", err, output)
-	}
+	makeNamedPipe(t, pipe)
 	session, err := PrepareOutput(OutputSelection{TranscriptPath: pipe})
 	if err != nil {
 		t.Fatal(err)
@@ -437,3 +431,60 @@ func TestNamedPipeIsNotOpenedDuringPreparation(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestLateNamedPipeIsPreserved(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "output")
+	session, err := PrepareOutput(OutputSelection{TranscriptPath: path})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer session.Close()
+	makeNamedPipe(t, path)
+	err = session.Finish(nil, []byte("transcript"), ReportBundle{}, nil)
+	if err == nil || !strings.Contains(err.Error(), "changed type") {
+		t.Fatalf("expected clear delivery failure, got %v", err)
+	}
+	info, err := os.Stat(path)
+	if err != nil || info.Mode()&os.ModeNamedPipe == 0 {
+		t.Fatalf("late pipe was lost: %v %v", info, err)
+	}
+	entries, err := os.ReadDir(dir)
+	if err != nil || len(entries) != 1 {
+		t.Fatalf("unpublished output resources remain: %v %v", entries, err)
+	}
+}
+
+func TestStreamChangedToRegularFileIsPreserved(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "output")
+	makeNamedPipe(t, path)
+	session, err := PrepareOutput(OutputSelection{TranscriptPath: path})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer session.Close()
+	if err := os.Remove(path); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, []byte("existing content"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	err = session.Finish(nil, []byte("new"), ReportBundle{}, nil)
+	if err == nil || !strings.Contains(err.Error(), "no longer a stream") {
+		t.Fatalf("expected clear delivery failure, got %v", err)
+	}
+	if data, err := os.ReadFile(path); err != nil || string(data) != "existing content" {
+		t.Fatalf("replacement file changed: %q %v", data, err)
+	}
+}
+
+func makeNamedPipe(t *testing.T, path string) {
+	t.Helper()
+	tool, err := exec.LookPath("mkfifo")
+	if err != nil {
+		t.Skip("mkfifo is unavailable")
+	}
+	if output, err := exec.Command(tool, path).CombinedOutput(); err != nil {
+		t.Fatalf("mkfifo: %v %s", err, output)
+	}
+}