diff --git a/tools/deno/api-diff.ts b/tools/deno/api-diff.ts
new file mode 100755
index 000000000..80c89c8f7
--- /dev/null
+++ b/tools/deno/api-diff.ts
@@ -0,0 +1,77 @@
+#! /usr/bin/env -S deno run --allow-run --allow-net --allow-read --allow-write --allow-env
+
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * Copyright Oxide Computer Company
+ */
+import { $, CommandBuilder } from 'https://deno.land/x/dax@0.35.0/mod.ts'
+
+// inspired by: https://github.com/dsherret/dax/issues/137#issuecomment-1603848769
+declare module 'https://deno.land/x/dax@0.35.0/mod.ts' {
+  interface CommandBuilder {
+    pipe(next: CommandBuilder): CommandBuilder
+  }
+}
+
+CommandBuilder.prototype.pipe = function (next: CommandBuilder): CommandBuilder {
+  const p = this.stdout('piped').spawn()
+  return next.stdin(p.stdout())
+}
+
+// have to do this this way because I couldn't figure out how to get
+// my stupid bash function to show up here. I'm sure it's possible
+async function pickPr() {
+  const listPRs = () =>
+    $`gh pr list -R oxidecomputer/omicron --limit 100 --json number,title,updatedAt,author --template  '{{range .}}{{tablerow .number .title .author.name (timeago .updatedAt)}}{{end}}'`
+  const picker = () => $`fzf --height 25% --reverse`
+  const cut = () => $`cut -f1 -d ' '`
+
+  return listPRs().pipe(picker()).pipe(cut()).text()
+}
+
+async function getPrRange(prNum: string) {
+  const pr = await $`gh api graphql -f query='{ 
+      repository(owner: "oxidecomputer", name: "omicron") { 
+        pullRequest(number: ${prNum}) { 
+          baseRefOid
+          headRefOid
+        }
+      }
+    }'`.json()
+  const { baseRefOid: base, headRefOid: head } = pr.data.repository.pullRequest
+  return { base, head } as { base: string; head: string }
+}
+
+async function genForCommit(commit: string) {
+  const tmpDir = `/tmp/api-diff/${commit}`
+  await $`rm -rf ${tmpDir}`
+  await $`mkdir -p ${tmpDir}`
+  await $`npm run --silent --prefix ../oxide.ts gen-from ${commit} ${tmpDir}`
+  await $`npx prettier --write --log-level error ${tmpDir}`
+  return tmpDir
+}
+
+//////////////////////////////
+// ACTUAL SCRIPT FOLLOWS
+//////////////////////////////
+
+if (!$.commandExistsSync('gh')) throw Error('Need gh (GitHub CLI)')
+
+const diffTool = $.commandExistsSync('difft') ? 'difft' : 'diff'
+
+const prNum = await pickPr()
+
+if (!/^\d+$/.test(prNum)) {
+  console.error(`Error picking PR. Expected number, got '${prNum}'`)
+  Deno.exit()
+}
+
+const { base, head } = await getPrRange(prNum)
+
+const tmpDirBase = await genForCommit(base)
+const tmpDirHead = await genForCommit(head)
+
+await $`${diffTool} ${tmpDirBase} ${tmpDirHead} || true`