diff --git a/diagram.js b/diagram.js
new file mode 100644
index 00000000..db638edb
--- /dev/null
+++ b/diagram.js
@@ -0,0 +1,124 @@
+import { exec } from "node:child_process";
+import * as path from "node:path";
+
+import { readFile, writeFile } from "node:fs/promises";
+
+const findMarkdownFilesInGit = async () => {
+  return await new Promise((resolve, reject) => {
+    exec("git ls-files -z", (error, stdout, stderr) => {
+      if (error) reject(error);
+      else resolve(stdout.split("\0").filter((s) => s.endsWith(".md")));
+    });
+  });
+};
+
+const findMarkdownFiles = async () => {
+  const ignorePattern = /^(README|LICENSE|contributing\/)/;
+  return (await findMarkdownFilesInGit()).filter((f) => !ignorePattern.test(f));
+};
+
+const findLinks = async (content) => {
+  // Dirty, inaccurate markdown parse
+  const all = content.matchAll(
+    /(?<bang>!)?\[(?<text>.*?)\]\((?<target>.*?)\)/g,
+  );
+  return [...all].map((m) => ({
+    isImage: !!m.groups.bang,
+    text: m.groups.text,
+    target: m.groups.target,
+  }));
+};
+
+const scanForLinks = async (filenames) => {
+  return Promise.all(
+    filenames.map((filename) =>
+      readFile(filename, "utf-8").then((content) =>
+        findLinks(content).then((links) => ({ filename, links })),
+      ),
+    ),
+  );
+};
+
+const localMarkdownToMarkdownLinks = (links) => {
+  return links
+    .map((l) => ({
+      ...l,
+      links: l.links.filter(
+        (t) => !t.isImage && !t.target.startsWith("https:"),
+      ),
+    }))
+    .filter((f) => f.links.length > 0);
+};
+
+const makeResolver = (filenameToNodeId) => {
+  // TODO: could make this case-insensitive, but it's probably both
+  // easier and more helpful to be more strict.
+  return (fromFile, target) => {
+    let resolved = path.join(path.dirname(fromFile), target);
+    let id = filenameToNodeId.get(resolved);
+    if (id) return { id, resolved, isNew: false };
+
+    resolved = path.join(path.dirname(fromFile), target) + "/README.md";
+    id = filenameToNodeId.get(resolved);
+    if (id) return { id, resolved, isNew: false };
+
+    resolved = path.join(path.dirname(fromFile), target) + "/readme.md";
+    id = filenameToNodeId.get(resolved);
+    if (id) return { id, resolved, isNew: false };
+
+    const newId = `id${filenameToNodeId.size + 1}`;
+    const unresolved = path.join(path.dirname(fromFile), target);
+    filenameToNodeId.set(unresolved, newId);
+    return { id: newId, resolved: unresolved, isNew: true };
+  };
+};
+
+const main = async () => {
+  const markdownFilenames = await findMarkdownFiles();
+  const links = await scanForLinks(markdownFilenames);
+  const trimmed = localMarkdownToMarkdownLinks(links);
+
+  const filenameToNodeId = new Map(
+    markdownFilenames.map((filename, index) => [filename, `id${index}`]),
+  );
+  //   console.dir([...filenameToNodeId.entries()]);
+
+  const targetResolver = makeResolver(filenameToNodeId);
+  const seenEdges = new Set();
+
+  console.log("```mermaid");
+  //   console.log("graph TD;"); // top-down
+  console.log("graph LR;"); // left-right
+
+  for (const [filename, nodeId] of filenameToNodeId.entries()) {
+    console.log(`  ${nodeId}[${JSON.stringify(filename)}]`);
+  }
+
+  for (const links of trimmed) {
+    const fromNodeId = filenameToNodeId.get(links.filename);
+
+    for (const l of links.links) {
+      const r = targetResolver(links.filename, l.target);
+
+      if (r.isNew) {
+        const label = `?? ${r.resolved} ??`;
+        console.log(`  ${r.id}[${JSON.stringify(label)}]`);
+      }
+
+      const edgeKey = `${fromNodeId} to ${r.id}`;
+      if (!seenEdges.has(edgeKey)) {
+        console.log(`  ${fromNodeId}-->${r.id}`);
+        seenEdges.add(edgeKey);
+      }
+    }
+  }
+
+  console.log("```");
+
+  //   console.dir({ trimmed, e: [...m.entries()] }, { depth: 5 });
+};
+
+main().catch((error) => {
+  console.error(error);
+  process.exit(1);
+});
diff --git a/package.json b/package.json
index 0a53eb70..68fe2fa8 100644
--- a/package.json
+++ b/package.json
@@ -2,5 +2,6 @@
   "dependencies": {
     "markdownlint-cli": "^0.44.0",
     "prettier": "^3.5.3"
-  }
+  },
+  "type": "module"
 }