diff --git a/CHANGELOG.md b/CHANGELOG.md
index 387e9146..d6e516d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,7 +26,10 @@ Status of the `main` branch. Changes prior to the next official version change w
     (which does not correctly unpack structured output) #1042
   - Fix: Project-specific filtering of files for source files ignored the language backend. 
     The check is really only possible for LSP. 
-  - Fix: File system permission errors during gitignore scanning were not caught #1624 
+  - Fix: File system permission errors during gitignore scanning were not caught #1624
+  - During project creation, language composition percentages are now computed relative to the total number 
+    of recognised source files instead of all files, i.e. unrecognised files are ignored in the percentage 
+    computation.
 
 * CLI:
   - Fix `--project-from-cwd` hijacking git worktrees nested under a Serena project. `find_project_root`
diff --git a/src/serena/util/inspection.py b/src/serena/util/inspection.py
index a0e3e96a..440d7c5b 100644
--- a/src/serena/util/inspection.py
+++ b/src/serena/util/inspection.py
@@ -31,36 +31,40 @@ def determine_programming_language_composition(repo_path: str) -> dict[Language,
     """
     Determine the programming language composition of a repository.
 
-    :param repo_path: Path to the repository to analyze
+    Percentages are computed relative to the number of files that match at least
+    one supported language, not the total file count.  This prevents files that
+    belong to no supported language (images, plain text, licenses, lock files, etc.)
+    from diluting language percentages in repositories where such files dominate.
 
-    :return: Dictionary mapping languages to percentages of files matching each language
+    :param repo_path: Path to the repository to analyze
+    :return: Dictionary mapping languages to percentages of recognised source files
+        matching each language (denominator = files matched by at least one language)
     """
     all_files = find_all_non_ignored_files(repo_path)
 
     if not all_files:
         return {}
 
-    # Count files for each language
+    # collect all language matchers once
+    all_languages = list(Language.iter_all(include_experimental=False))
+    matchers = {lang: lang.get_source_fn_matcher() for lang in all_languages}
+
+    # count files per language in a single pass over the files
     language_counts: dict[Language, int] = {}
-    total_files = len(all_files)
-
-    for language in Language.iter_all(include_experimental=False):
-        matcher = language.get_source_fn_matcher()
-        count = 0
-
-        for file_path in all_files:
-            # Use just the filename for matching, not the full path
-            filename = os.path.basename(file_path)
+    recognised_files = 0
+    for file_path in all_files:
+        # Use just the filename for matching, not the full path
+        filename = os.path.basename(file_path)
+        matched_any = False
+        for lang, matcher in matchers.items():
             if matcher.is_relevant_filename(filename):
-                count += 1
+                language_counts[lang] = language_counts.get(lang, 0) + 1
+                matched_any = True
+        if matched_any:
+            recognised_files += 1
 
-        if count > 0:
-            language_counts[language] = count
+    if recognised_files == 0:
+        return {}
 
-    # Convert counts to percentages
-    language_percentages: dict[Language, float] = {}
-    for language, count in language_counts.items():
-        percentage = (count / total_files) * 100
-        language_percentages[language] = round(percentage, 2)
-
-    return language_percentages
+    # convert to percentages relative to recognised source files only
+    return {lang: round(count / recognised_files * 100, 2) for lang, count in language_counts.items()}
diff --git a/test/serena/util/test_inspection.py b/test/serena/util/test_inspection.py
new file mode 100644
index 00000000..90378aac
--- /dev/null
+++ b/test/serena/util/test_inspection.py
@@ -0,0 +1,45 @@
+"""Unit tests for :func:`serena.util.inspection.determine_programming_language_composition`."""
+
+from pathlib import Path
+
+from serena.util.inspection import determine_programming_language_composition
+from solidlsp.ls_config import Language
+
+
+def _touch(directory: Path, *names: str) -> None:
+    for name in names:
+        (directory / name).write_text("content", encoding="utf-8")
+
+
+class TestDetermineProgrammingLanguageComposition:
+    def test_single_language_repo(self, tmp_path: Path) -> None:
+        _touch(tmp_path, "a.py", "b.py", "c.py")
+        composition = determine_programming_language_composition(str(tmp_path))
+        assert composition[Language.PYTHON] == 100.0
+
+    def test_unrecognised_files_do_not_dilute_percentages(self, tmp_path: Path) -> None:
+        # 2 source files vs many files that belong to no supported language
+        _touch(tmp_path, "main.py", "util.py")
+        _touch(tmp_path, *[f"note_{i}.txt" for i in range(20)])
+        _touch(tmp_path, "logo.png", "LICENSE", "data.csv")
+
+        composition = determine_programming_language_composition(str(tmp_path))
+
+        # previously: 2 / 25 files = 8% — now the denominator is recognised source files only
+        assert composition[Language.PYTHON] == 100.0
+
+    def test_mixed_language_percentages_relative_to_recognised_files(self, tmp_path: Path) -> None:
+        _touch(tmp_path, "a.py", "b.py", "c.py", "d.go")
+        _touch(tmp_path, *[f"asset_{i}.dat" for i in range(50)])
+
+        composition = determine_programming_language_composition(str(tmp_path))
+
+        assert composition[Language.PYTHON] == 75.0
+        assert composition[Language.GO] == 25.0
+
+    def test_repo_without_recognised_files(self, tmp_path: Path) -> None:
+        _touch(tmp_path, "readme.txt", "logo.png")
+        assert determine_programming_language_composition(str(tmp_path)) == {}
+
+    def test_empty_repo(self, tmp_path: Path) -> None:
+        assert determine_programming_language_composition(str(tmp_path)) == {}