diff --git a/cli/watch.go b/cli/watch.go
index ccd47175..aceff00f 100644
--- a/cli/watch.go
+++ b/cli/watch.go
@@ -987,7 +987,8 @@ func watchProjectWithEventObserver(ctx context.Context, projectRoot string, emb
 	}
 
 	// Initialize scanner
-	scanner := indexer.NewScanner(projectRoot, ignoreMatcher)
+	scanner := indexer.NewScanner(projectRoot, ignoreMatcher).
+		WithCustomExtensions(cfg.Chunking.CustomExtensions)
 
 	// Initialize chunker
 	chunker := indexer.NewChunker(cfg.Chunking.Size, cfg.Chunking.Overlap)
@@ -2752,7 +2753,9 @@ func initializeWorkspaceRuntime(ctx context.Context, ws *config.Workspace, proje
 		return nil, nil, fmt.Errorf("failed to initialize ignore matcher: %w", err)
 	}
 
-	scanner := indexer.NewScanner(project.Path, ignoreMatcher)
+	scanner := indexer.NewScanner(project.Path, ignoreMatcher).
+		WithCustomExtensions(ws.Chunking.CustomExtensions).
+		WithCustomExtensions(projectCfg.Chunking.CustomExtensions)
 	chunker := indexer.NewChunker(projectCfg.Chunking.Size, projectCfg.Chunking.Overlap)
 	processorRegistry := buildFrameworkRegistry(projectCfg)
 	vectorStore := &projectPrefixStore{
diff --git a/config/config.go b/config/config.go
index 2ca67996..c0733a42 100644
--- a/config/config.go
+++ b/config/config.go
@@ -203,6 +203,12 @@ type QdrantConfig struct {
 type ChunkingConfig struct {
 	Size    int `yaml:"size"`
 	Overlap int `yaml:"overlap"`
+	// CustomExtensions extends the built-in SupportedExtensions list with
+	// additional file extensions to index (e.g. [".tengo", ".el"]). Each
+	// entry must include the leading dot and is matched case-insensitively.
+	// Binary detection (UTF-8 + null-byte check) still applies, so adding
+	// a binary extension here is safe.
+	CustomExtensions []string `yaml:"custom_extensions,omitempty"`
 }
 
 func DefaultStoreForBackend(backend string) StoreConfig {
diff --git a/config/workspace.go b/config/workspace.go
index 4a919e9d..59fe19aa 100644
--- a/config/workspace.go
+++ b/config/workspace.go
@@ -25,6 +25,10 @@ type Workspace struct {
 	Name     string         `yaml:"name"`
 	Store    StoreConfig    `yaml:"store"`
 	Embedder EmbedderConfig `yaml:"embedder"`
+	// Chunking provides workspace-level defaults. Currently only
+	// CustomExtensions is consumed; Size/Overlap are taken from the
+	// per-project config.
+	Chunking ChunkingConfig `yaml:"chunking,omitempty"`
 	Projects []ProjectEntry `yaml:"projects"`
 }
 
diff --git a/docs/src/content/docs/configuration.md b/docs/src/content/docs/configuration.md
index 55e4b14e..3c0b2f6b 100644
--- a/docs/src/content/docs/configuration.md
+++ b/docs/src/content/docs/configuration.md
@@ -53,6 +53,13 @@ chunking:
   size: 512
   # Overlap between chunks (for context continuity)
   overlap: 50
+  # Optional: index extra extensions beyond the built-in supported set.
+  # Entries must include the leading dot, are matched case-insensitively,
+  # and still go through the binary-file and minified-file filters.
+  # Examples: ".tengo" (Tengo scripts), ".el" (Emacs Lisp), ".prisma".
+  # custom_extensions:
+  #   - .tengo
+  #   - .prisma
 
 # File watching configuration
 watch:
diff --git a/docs/src/content/docs/workspace.md b/docs/src/content/docs/workspace.md
index 067bcc0a..7e0d4d50 100644
--- a/docs/src/content/docs/workspace.md
+++ b/docs/src/content/docs/workspace.md
@@ -278,6 +278,7 @@ When indexing via workspace, settings come from different sources:
 | `store` (backend, DSN) | **Workspace** | Shared store required |
 | `embedder` (provider, model) | **Workspace** | Ensures compatible vectors |
 | `chunking` (size, overlap) | **Project** | Can vary per project/language |
+| `chunking.custom_extensions` | **Workspace** + **Project** | Both lists are merged when scanning a project |
 | `ignore` patterns | **Project** | Project-specific exclusions |
 | `external_gitignore` | **Project** | Project-specific gitignore |
 
diff --git a/indexer/scanner.go b/indexer/scanner.go
index 373a9bdc..790ff2e7 100644
--- a/indexer/scanner.go
+++ b/indexer/scanner.go
@@ -112,8 +112,9 @@ type FileMeta struct {
 }
 
 type Scanner struct {
-	root   string
-	ignore *IgnoreMatcher
+	root      string
+	ignore    *IgnoreMatcher
+	extraExts map[string]bool
 }
 
 func NewScanner(root string, ignore *IgnoreMatcher) *Scanner {
@@ -123,6 +124,31 @@ func NewScanner(root string, ignore *IgnoreMatcher) *Scanner {
 	}
 }
 
+// WithCustomExtensions returns the scanner with the given extensions added to
+// the set of extensions it will index, on top of SupportedExtensions. Entries
+// must include the leading dot ("." e.g., ".tengo"); they are normalized to
+// lowercase and entries missing the dot or empty are silently dropped.
+func (s *Scanner) WithCustomExtensions(exts []string) *Scanner {
+	for _, raw := range exts {
+		ext := strings.ToLower(strings.TrimSpace(raw))
+		if ext == "" || !strings.HasPrefix(ext, ".") {
+			continue
+		}
+		if s.extraExts == nil {
+			s.extraExts = make(map[string]bool)
+		}
+		s.extraExts[ext] = true
+	}
+	return s
+}
+
+func (s *Scanner) isSupported(ext string) bool {
+	if SupportedExtensions[ext] {
+		return true
+	}
+	return s.extraExts[ext]
+}
+
 // ScanMetadata scans indexable files and returns only file metadata.
 // It avoids reading file contents and hash computation for a faster first pass.
 func (s *Scanner) ScanMetadata() ([]FileMeta, []string, error) {
@@ -154,7 +180,7 @@ func (s *Scanner) ScanMetadata() ([]FileMeta, []string, error) {
 
 		// Check extension
 		ext := strings.ToLower(filepath.Ext(path))
-		if !SupportedExtensions[ext] {
+		if !s.isSupported(ext) {
 			return nil
 		}
 
@@ -216,7 +242,7 @@ func (s *Scanner) Scan() ([]FileInfo, []string, error) {
 
 		// Check extension
 		ext := strings.ToLower(filepath.Ext(path))
-		if !SupportedExtensions[ext] {
+		if !s.isSupported(ext) {
 			return nil
 		}
 
diff --git a/indexer/scanner_test.go b/indexer/scanner_test.go
index 85b641bd..5feb388c 100644
--- a/indexer/scanner_test.go
+++ b/indexer/scanner_test.go
@@ -352,3 +352,141 @@ func TestScanner_ScanFile_SkipsMinified(t *testing.T) {
 		t.Error("expected nil for minified file, got file info")
 	}
 }
+
+func TestScanner_CustomExtensions(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// File with a custom extension that's not in SupportedExtensions.
+	tengoFile := filepath.Join(tmpDir, "workflow.tengo")
+	if err := os.WriteFile(tengoFile, []byte(`fmt := import("fmt")` + "\n" + `fmt.println("hello")` + "\n"), 0644); err != nil {
+		t.Fatalf("failed to create tengo file: %v", err)
+	}
+
+	// File with an unrecognized extension that should remain unsupported.
+	unknownFile := filepath.Join(tmpDir, "data.xyz")
+	if err := os.WriteFile(unknownFile, []byte("ignored"), 0644); err != nil {
+		t.Fatalf("failed to create xyz file: %v", err)
+	}
+
+	// File with a built-in supported extension to confirm coexistence.
+	goFile := filepath.Join(tmpDir, "main.go")
+	if err := os.WriteFile(goFile, []byte("package main"), 0644); err != nil {
+		t.Fatalf("failed to create go file: %v", err)
+	}
+
+	ignoreMatcher, err := NewIgnoreMatcher(tmpDir, []string{}, "")
+	if err != nil {
+		t.Fatalf("failed to create ignore matcher: %v", err)
+	}
+
+	// Without custom extensions: only main.go indexed.
+	scanner := NewScanner(tmpDir, ignoreMatcher)
+	files, _, err := scanner.Scan()
+	if err != nil {
+		t.Fatalf("scan failed: %v", err)
+	}
+	if len(files) != 1 || filepath.Base(files[0].Path) != "main.go" {
+		t.Errorf("baseline scan expected only main.go, got %+v", files)
+	}
+
+	// With ".tengo" added: main.go + workflow.tengo (xyz still skipped).
+	scanner = NewScanner(tmpDir, ignoreMatcher).
+		WithCustomExtensions([]string{".tengo"})
+	files, _, err = scanner.Scan()
+	if err != nil {
+		t.Fatalf("scan with custom ext failed: %v", err)
+	}
+	got := make(map[string]bool)
+	for _, f := range files {
+		got[filepath.Base(f.Path)] = true
+	}
+	if !got["main.go"] || !got["workflow.tengo"] {
+		t.Errorf("expected main.go + workflow.tengo, got %v", got)
+	}
+	if got["data.xyz"] {
+		t.Errorf("data.xyz should not have been indexed")
+	}
+}
+
+func TestScanner_WithCustomExtensions_Normalizes(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Both uppercase and lowercase variants of the file extension.
+	upper := filepath.Join(tmpDir, "module.TENGO")
+	if err := os.WriteFile(upper, []byte("upper"), 0644); err != nil {
+		t.Fatalf("failed to create upper file: %v", err)
+	}
+
+	ignoreMatcher, err := NewIgnoreMatcher(tmpDir, []string{}, "")
+	if err != nil {
+		t.Fatalf("failed to create ignore matcher: %v", err)
+	}
+
+	scanner := NewScanner(tmpDir, ignoreMatcher).
+		WithCustomExtensions([]string{"  .TENGO  "})
+	files, _, err := scanner.Scan()
+	if err != nil {
+		t.Fatalf("scan failed: %v", err)
+	}
+	if len(files) != 1 {
+		t.Fatalf("expected 1 file, got %d: %+v", len(files), files)
+	}
+}
+
+func TestScanner_WithCustomExtensions_RejectsInvalidEntries(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Files exercising the various invalid-entry forms.
+	if err := os.WriteFile(filepath.Join(tmpDir, "bad1"), []byte("x"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(tmpDir, "bad2.foo"), []byte("x"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	ignoreMatcher, err := NewIgnoreMatcher(tmpDir, []string{}, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// All these inputs should be silently dropped: empty, missing dot, just whitespace.
+	scanner := NewScanner(tmpDir, ignoreMatcher).
+		WithCustomExtensions([]string{"", "foo", "   ", ".."})
+	files, _, err := scanner.Scan()
+	if err != nil {
+		t.Fatal(err)
+	}
+	// ".." is a valid extension-with-dot, so .foo files might match if treated wrong.
+	// But filepath.Ext("bad2.foo") == ".foo", which we did NOT add. Should be 0 files.
+	if len(files) != 0 {
+		t.Errorf("expected no files indexed from invalid extensions, got %+v", files)
+	}
+}
+
+func TestScanner_CustomExtensions_BinaryStillSkipped(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// A "tengo" file that is actually binary (null bytes) — should be skipped
+	// even with the extension whitelisted.
+	binFile := filepath.Join(tmpDir, "blob.tengo")
+	if err := os.WriteFile(binFile, []byte{0x00, 0x01, 0x02, 0x03}, 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	ignoreMatcher, err := NewIgnoreMatcher(tmpDir, []string{}, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	scanner := NewScanner(tmpDir, ignoreMatcher).
+		WithCustomExtensions([]string{".tengo"})
+
+	// Scan reads content + binary check; should drop the binary blob.
+	files, _, err := scanner.Scan()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 0 {
+		t.Errorf("expected binary .tengo to be skipped, got %+v", files)
+	}
+}