Archive durable previous-session cache files with session state

internal/stage/archive.go

@@ -118,6 +118,10 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 		return nil, fmt.Errorf("archive: collect run files: %w", err)
 	}
 	sessionPaths := archiveSessionPaths(env, m)
+	previousFiles, err := collectArchivePreviousFiles(sessionPaths.PreviousDir)
+	if err != nil {
+		return nil, fmt.Errorf("archive: collect previous files: %w", err)
+	}
 	runtimeCatalog, err := buildArchiveRuntimeArtifactCatalog(sessionPaths, env.Config.Pipeline.Scriptorium)
 	if err != nil {
 		return nil, fmt.Errorf("archive: build runtime artifact catalog: %w", err)
@@ -144,6 +148,15 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 		promotedUploaded = append(promotedUploaded, promotion.Dest)
 	}
 
+	previousUploaded := make([]string, 0, len(previousFiles))
+	for _, file := range previousFiles {
+		key := artifacts.S3PromotedArtifactKey(sessionPrefix, file.RelativePath)
+		if _, err := env.ObjectStore.Upload(ctx, file.LocalPath, key, storage.UploadOptions{}); err != nil {
+			return nil, fmt.Errorf("archive: upload previous file %q to %q: %w", file.RelativePath, key, err)
+		}
+		previousUploaded = append(previousUploaded, file.RelativePath)
+	}
+
 	currentManifestKey, currentRunPointerKey := artifacts.ResolveArchiveCurrentStateKeys(sessionPrefix)
 	manifestTempPath, err := writeCurrentManifestSnapshot(m, archiveMetadataPreview(
 		bucket,
@@ -151,6 +164,7 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 		sessionPrefix,
 		runUploaded,
 		promotedUploaded,
+		previousUploaded,
 		skippedOptional,
 		currentManifestKey,
 	))
@@ -187,6 +201,8 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 			"run_uploaded_paths":          runUploaded,
 			"promoted_files_uploaded":     len(promotedUploaded),
 			"promoted_paths":              promotedUploaded,
+			"previous_files_uploaded":     len(previousUploaded),
+			"previous_uploaded_paths":     previousUploaded,
 			"skipped_optional_promotions": skippedOptional,
 			"current_manifest_key":        currentManifestKey,
 			"current_run_id_key":          currentRunPointerKey,
@@ -497,6 +513,51 @@ func collectArchiveRunFiles(runRoot, manifestPath string) ([]archiveUploadFile,
 	return files, nil
 }
 
+func collectArchivePreviousFiles(previousDir string) ([]archiveUploadFile, error) {
+	previousDir = filepath.Clean(strings.TrimSpace(previousDir))
+	if previousDir == "" {
+		return nil, fmt.Errorf("previous directory is required")
+	}
+	info, err := os.Stat(previousDir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("stat %q: %w", previousDir, err)
+	}
+	if !info.IsDir() {
+		return nil, fmt.Errorf("previous path %q is not a directory", previousDir)
+	}
+
+	files := make([]archiveUploadFile, 0, 16)
+	err = filepath.WalkDir(previousDir, func(path string, d fs.DirEntry, walkErr error) error {
+		if walkErr != nil {
+			return walkErr
+		}
+		if d.IsDir() {
+			return nil
+		}
+		rel, err := filepath.Rel(previousDir, path)
+		if err != nil {
+			return fmt.Errorf("relative path from %q to %q: %w", previousDir, path, err)
+		}
+		rel = filepath.ToSlash(rel)
+		files = append(files, archiveUploadFile{
+			RelativePath: filepath.ToSlash(filepath.Join(config.PathPreviousDirSegment, rel)),
+			LocalPath:    path,
+		})
+		return nil
+	})
+	if err != nil {
+		return nil, fmt.Errorf("walk %q: %w", previousDir, err)
+	}
+
+	sort.Slice(files, func(i, j int) bool {
+		return files[i].RelativePath < files[j].RelativePath
+	})
+	return files, nil
+}
+
 func resolveArchiveRunManifestSource(runRoot string) (string, error) {
 	path := filepath.Join(filepath.Clean(runRoot), "manifest.json")
 	info, err := os.Stat(path)
@@ -600,6 +661,7 @@ func archiveMetadataPreview(
 	bucket, runPrefix, sessionPrefix string,
 	runUploaded []string,
 	promotedUploaded []string,
+	previousUploaded []string,
 	skippedOptional []string,
 	currentManifestKey string,
 ) map[string]any {
@@ -612,6 +674,8 @@ func archiveMetadataPreview(
 		"run_uploaded_paths":          append([]string(nil), runUploaded...),
 		"promoted_files_uploaded":     len(promotedUploaded),
 		"promoted_paths":              append([]string(nil), promotedUploaded...),
+		"previous_files_uploaded":     len(previousUploaded),
+		"previous_uploaded_paths":     append([]string(nil), previousUploaded...),
 		"skipped_optional_promotions": append([]string(nil), skippedOptional...),
 		"current_manifest_key":        currentManifestKey,
 		"current_run_id_key":          artifacts.S3CurrentRunPointerKey(sessionPrefix),

internal/stage/archive_test.go

@@ -130,6 +130,50 @@ func TestArchiveUploadsRunRecordPromotionsAndCurrentPointer(t *testing.T) {
 	if result.Metadata["promoted_files_uploaded"] != 2 {
 		t.Fatalf("metadata promoted_files_uploaded = %#v, want 2", result.Metadata["promoted_files_uploaded"])
 	}
+	if result.Metadata["previous_files_uploaded"] != 0 {
+		t.Fatalf("metadata previous_files_uploaded = %#v, want 0", result.Metadata["previous_files_uploaded"])
+	}
+}
+
+func TestArchiveUploadsPreviousCacheWhenPresent(t *testing.T) {
+	env, m, _ := archiveFixture(t)
+	fake := env.ObjectStore.(*storage.FakeBackend)
+	sessionRoot := artifacts.SessionWorkDirForCampaign(
+		env.Config.Pipeline.Workspace.Root,
+		env.Config.Session.Campaign,
+		env.Config.Session.SessionID,
+	)
+	writeStageTestFile(t, filepath.Join(sessionRoot, "previous", "manifest.json"), "{\"session_id\":\"2026-04-12\"}\n")
+	writeStageTestFile(t, filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md"), "# previous recap\n")
+
+	result, err := archiveStage{}.Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+
+	previousManifestKey := m.S3SessionPrefix + "previous/manifest.json"
+	previousRecapKey := m.S3SessionPrefix + "previous/artifacts/session_recap.md"
+	if _, ok := fake.Objects[previousManifestKey]; !ok {
+		t.Fatalf("missing archived previous manifest key %q", previousManifestKey)
+	}
+	if _, ok := fake.Objects[previousRecapKey]; !ok {
+		t.Fatalf("missing archived previous artifact key %q", previousRecapKey)
+	}
+	if result.Metadata["previous_files_uploaded"] != 2 {
+		t.Fatalf("metadata previous_files_uploaded = %#v, want 2", result.Metadata["previous_files_uploaded"])
+	}
+}
+
+func TestArchiveToleratesMissingPreviousCache(t *testing.T) {
+	env, m, _ := archiveFixture(t)
+
+	result, err := archiveStage{}.Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if result.Metadata["previous_files_uploaded"] != 0 {
+		t.Fatalf("metadata previous_files_uploaded = %#v, want 0", result.Metadata["previous_files_uploaded"])
+	}
 }
 
 func TestArchiveUsesCustomPromotionRules(t *testing.T) {