diff --git a/.Rbuildignore b/.Rbuildignore
index 8fd6c54..bbc651a 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -15,3 +15,4 @@ pkgdown/
 ^pkgdown$
 ^vignettes/articles$
 ^_docs$
+^\.claude$
diff --git a/.github/workflows/R-CMD-check.yaml b/.github/workflows/R-CMD-check.yaml
index a3ac618..21efb73 100644
--- a/.github/workflows/R-CMD-check.yaml
+++ b/.github/workflows/R-CMD-check.yaml
@@ -29,7 +29,7 @@ jobs:
       R_KEEP_PKG_SOURCE: yes
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v5
 
       - uses: r-lib/actions/setup-pandoc@v2
 
diff --git a/.github/workflows/pkgdown.yaml b/.github/workflows/pkgdown.yaml
index ed7650c..4360b25 100644
--- a/.github/workflows/pkgdown.yaml
+++ b/.github/workflows/pkgdown.yaml
@@ -22,7 +22,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v5
 
       - uses: r-lib/actions/setup-pandoc@v2
 
diff --git a/inst/COPYRIGHTS b/inst/COPYRIGHTS
new file mode 100644
index 0000000..f552348
--- /dev/null
+++ b/inst/COPYRIGHTS
@@ -0,0 +1,12 @@
+The file src/nanoflann.h is a copy of the nanoflann C++ library
+(https://github.com/jlblancoc/nanoflann), used for nearest-neighbour search
+in edge_bundle_mingle().
+
+nanoflann is distributed under the 2-clause BSD license:
+
+  Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
+  Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
+  Copyright 2011-2026  Jose Luis Blanco (joseluisblancoc@gmail.com).
+  All rights reserved.
+
+The full license text is retained in the header of src/nanoflann.h.
diff --git a/src/mingle.cpp b/src/mingle.cpp
index ef97cb6..92f29e6 100644
--- a/src/mingle.cpp
+++ b/src/mingle.cpp
@@ -10,7 +10,7 @@
 // is built once with a kd-tree (vendored nanoflann), giving O(E log E); the
 // graph is then coarsened combinatorially level by level.
 #include <Rcpp.h>
-#include "nanoflann.hpp"
+#include "nanoflann.h"
 #include <set>
 #include <array>
 using namespace Rcpp;
diff --git a/src/nanoflann.hpp b/src/nanoflann.h
similarity index 100%
rename from src/nanoflann.hpp
rename to src/nanoflann.h