diff --git a/build-linuxcnc-wasm-standalone-probe.sh b/build-linuxcnc-wasm-standalone-probe.sh
index 5d35835..7cebf80 100755
--- a/build-linuxcnc-wasm-standalone-probe.sh
+++ b/build-linuxcnc-wasm-standalone-probe.sh
@@ -101,6 +101,7 @@ case "$mode" in
     interp-base-link)
         dlfcn_shim=$(./list-linuxcnc-wasm-safe-shims.sh dlfcn.cc)
         interp_base_source=$(LINUXCNC_ROOT="$linuxcnc_root" ./list-linuxcnc-source-files.sh src/emc/rs274ngc/interp_base.cc)
+        grep -F 'LinuxCNC source basis: src/emc/rs274ngc/interp_base.cc provides' core/wasm_shims/interp_base_probe_main.cc >/dev/null
         sources+=(
             "$dlfcn_shim"
             "$interp_base_source"
diff --git a/core/wasm_shims/interp_base_probe_main.cc b/core/wasm_shims/interp_base_probe_main.cc
index 649fbc4..a7e2ccd 100644
--- a/core/wasm_shims/interp_base_probe_main.cc
+++ b/core/wasm_shims/interp_base_probe_main.cc
@@ -1,7 +1,8 @@
 #include "interp_base.hh"
 
+// LinuxCNC source basis: src/emc/rs274ngc/interp_base.cc provides
+// interp_from_shlib(), with the declaration in interp_base.hh.
 int main() {
     InterpBase *interp = interp_from_shlib("nonexistent-interpreter.so");
     return interp == nullptr ? 0 : 1;
 }
-
diff --git a/core/wasm_shims/interp_find_probe_main.cc b/core/wasm_shims/interp_find_probe_main.cc
index 534b158..9ad21aa 100644
--- a/core/wasm_shims/interp_find_probe_main.cc
+++ b/core/wasm_shims/interp_find_probe_main.cc
@@ -1,6 +1,8 @@
 #include "tooldata/tooldata.hh"
 #include "rs274ngc/rs274ngc_interp.hh"
 
+// LinuxCNC source basis: src/emc/rs274ngc/interp_find.cc implements
+// find_tool_index() and find_tool_pocket() against LinuxCNC tooldata.
 int main() {
     if (tool_mmap_creator(nullptr, 1) != 0) {
         return 7;
diff --git a/core/wasm_shims/interp_find_probe_stubs.cc b/core/wasm_shims/interp_find_probe_stubs.cc
index afc539a..08689ed 100644
--- a/core/wasm_shims/interp_find_probe_stubs.cc
+++ b/core/wasm_shims/interp_find_probe_stubs.cc
@@ -2,6 +2,7 @@
 
 #include <cstdarg>
 
+// LinuxCNC source basis: src/emc/rs274ngc/rs274ngc_interp.hh declares
+// Interp::setError(), which interp_find.cc references in link probes.
 void Interp::setError(const char *, ...) {
 }
-
diff --git a/core/wasm_shims/rs274ngc_pre_probe_main.cc b/core/wasm_shims/rs274ngc_pre_probe_main.cc
index 0fc8896..8a13c2c 100644
--- a/core/wasm_shims/rs274ngc_pre_probe_main.cc
+++ b/core/wasm_shims/rs274ngc_pre_probe_main.cc
@@ -5,6 +5,8 @@
 
 #include <cmath>
 
+// LinuxCNC source basis: src/emc/rs274ngc/rs274ngc_pre.cc provides
+// Interp::init(), read(), execute(), and sequence_number().
 int main() {
     cnc_sim_init_minimal_linuxcnc_tooldata();
 
diff --git a/test-linuxcnc-wasm-cmake-safe-probe.sh b/test-linuxcnc-wasm-cmake-safe-probe.sh
index e648929..0ca8bda 100755
--- a/test-linuxcnc-wasm-cmake-safe-probe.sh
+++ b/test-linuxcnc-wasm-cmake-safe-probe.sh
@@ -1356,6 +1356,7 @@ done < "$required_project_sources"
 
 grep -F "add_executable(linuxcnc_rs274_wasm_safe_probe EXCLUDE_FROM_ALL" core/CMakeLists.txt >/dev/null
 grep -F "wasm_shims/rs274ngc_pre_probe_main.cc" core/CMakeLists.txt >/dev/null
+grep -F 'LinuxCNC source basis: src/emc/rs274ngc/rs274ngc_pre.cc provides' core/wasm_shims/rs274ngc_pre_probe_main.cc >/dev/null
 grep -F "target_compile_definitions(linuxcnc_rs274_wasm_safe_probe" core/CMakeLists.txt >/dev/null
 grep -F "wasm_shims/cnc_sim_wasm_runtime_probe_main.cc" core/CMakeLists.txt >/dev/null
 grep -F "add_executable(cnc_sim_wasm_runtime_probe EXCLUDE_FROM_ALL" core/CMakeLists.txt >/dev/null
diff --git a/test-linuxcnc-wasm-interp-find-link.sh b/test-linuxcnc-wasm-interp-find-link.sh
index 9644294..e154f36 100755
--- a/test-linuxcnc-wasm-interp-find-link.sh
+++ b/test-linuxcnc-wasm-interp-find-link.sh
@@ -44,6 +44,8 @@ linuxcnc_source_output=$(LINUXCNC_ROOT="$linuxcnc_root" ./list-linuxcnc-source-f
 mapfile -t linuxcnc_sources <<<"$linuxcnc_source_output"
 tooldata_common_source=${linuxcnc_sources[0]}
 interp_find_source=${linuxcnc_sources[1]}
+grep -F 'LinuxCNC source basis: src/emc/rs274ngc/interp_find.cc implements' core/wasm_shims/interp_find_probe_main.cc >/dev/null
+grep -F 'LinuxCNC source basis: src/emc/rs274ngc/rs274ngc_interp.hh declares' core/wasm_shims/interp_find_probe_stubs.cc >/dev/null
 
 common_flag_output=$(LINUXCNC_ROOT="$linuxcnc_root" ./list-linuxcnc-wasm-common-cxxflags.sh --function-sections --data-sections)
 mapfile -t common_flags <<<"$common_flag_output"