diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1af2b88
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,25 @@
+# Build trees: build/<preset>/ for every preset.
+/build/
+
+# clangd's per-project index and cache.
+/.cache/
+
+# A compile_commands.json in the root means someone copied or symlinked it.
+# .clangd points at build/debug instead; a root copy is stale by construction.
+/compile_commands.json
+
+# IDE leftovers. Committing these is what made PaulDB's history noisy.
+/.idea/
+/.vscode/
+*.iml
+.project
+.cproject
+/.settings/
+
+# Sanitizer and profiling output
+*.profraw
+*.profdata
+/callgrind.out.*
+
+.DS_Store
+*.bak-*