diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9156171..20a1f10 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,18 @@
 cmake_minimum_required(VERSION 3.25)
 
+# Use ccache as the compiler launcher when it is installed — automatic for
+# local dev builds, a no-op where absent. Must be set before project()/
+# enable_language. `NOT DEFINED` respects an explicit -DCMAKE_CXX_COMPILER_LAUNCHER
+# passed by CI, so this only fills the gap for developers.
+if(NOT DEFINED CMAKE_CXX_COMPILER_LAUNCHER)
+    find_program(CCACHE_PROGRAM ccache)
+    if(CCACHE_PROGRAM)
+        set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
+        set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
+        message(STATUS "lci: using ccache compiler launcher (${CCACHE_PROGRAM})")
+    endif()
+endif()
+
 project(lci
     VERSION 0.6.0
     DESCRIPTION "Lightning Code Index - fast semantic code search"
@@ -67,6 +80,23 @@ if(LCI_WARNINGS_AS_ERRORS)
     endif()
 endif()
 
+# Prefer a fast linker (mold > lld) when installed — the link of `lci` and the
+# monolithic `lci_tests` (links all deps + ~1700 tests) is a real slice of
+# build time, more so with debug info. Linux/ELF only: mold targets ELF (no
+# Mach-O), and Apple's default ld64 is fine, so don't override the linker on
+# macOS. No-op if neither is present.
+if(NOT MSVC AND NOT APPLE)
+    find_program(MOLD_LINKER mold)
+    find_program(LLD_LINKER ld.lld)
+    if(MOLD_LINKER)
+        add_link_options(-fuse-ld=mold)
+        message(STATUS "lci: using mold linker (${MOLD_LINKER})")
+    elseif(LLD_LINKER)
+        add_link_options(-fuse-ld=lld)
+        message(STATUS "lci: using lld linker")
+    endif()
+endif()
+
 # Version header generation
 configure_file(
     "${CMAKE_CURRENT_SOURCE_DIR}/cmake/version.h.in"
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index b21b197..94e026c 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -184,3 +184,19 @@ target_link_libraries(lci PRIVATE
 # Project warning flags (target-scoped, do not leak into FetchContent libs).
 target_compile_options(lci_lib PRIVATE ${LCI_WARNING_FLAGS})
 target_compile_options(lci PRIVATE ${LCI_WARNING_FLAGS})
+
+# Precompiled headers. The heaviest, most widely-included headers — nlohmann/json
+# (~25k lines, in 26 TUs) and absl flat_hash_map (39 TUs) — are parsed once into
+# the PCH instead of per translation unit. Largest clean-build compile-time win
+# for the library. Both deps are linked PUBLIC above, so their include dirs are
+# already on lci_lib's compile line; the std headers are ubiquitous (<string> in
+# 134 TUs, <vector> in 100).
+target_precompile_headers(lci_lib PRIVATE
+    <string>
+    <string_view>
+    <vector>
+    <memory>
+    <unordered_map>
+    <nlohmann/json.hpp>
+    <absl/container/flat_hash_map.h>
+)