diff --git a/tools/deno/api-diff.ts b/tools/deno/api-diff.ts
index a7f4337c2..fa8f74a7f 100755
--- a/tools/deno/api-diff.ts
+++ b/tools/deno/api-diff.ts
@@ -7,22 +7,11 @@
  *
  * Copyright Oxide Computer Company
  */
-import { exists } from 'https://deno.land/std@0.208.0/fs/mod.ts'
-import { $ } from 'https://deno.land/x/dax@0.39.1/mod.ts'
 import { Command, ValidationError } from 'jsr:@cliffy/command@1.0.0'
+import { $ } from 'jsr:@david/dax@0.41.0'
+import { exists } from 'jsr:@std/fs@1.0'
 
-// fzf picker keeps UX quick without requiring people to wire up shell helpers
-async function pickPr(): Promise<number> {
-  const prNum = await $`gh pr list -R oxidecomputer/omicron --limit 100
-        --json number,title,updatedAt,author
-        --template '{{range .}}{{tablerow .number .title .author.name (timeago .updatedAt)}}{{end}}'`
-    .pipe($`fzf --height 25% --reverse`)
-    .pipe($`cut -f1 -d ' '`)
-    .text()
-  if (!/^\d+$/.test(prNum))
-    throw new Error(`Error picking PR. Expected number, got '${prNum}'`)
-  return parseInt(prNum, 10)
-}
+import { isJjRepository, pickPr, resolveLocalCommit } from './common.ts'
 
 // because the schema files change, in order to specify a schema you need both a
 // commit and a filename
@@ -40,7 +29,7 @@ const SPEC_RAW_URL = (ref: string, path: string) =>
   `https://raw.githubusercontent.com/oxidecomputer/omicron/${ref}/${path}`
 
 async function resolveCommit(ref?: string | number): Promise<string> {
-  if (ref === undefined) return resolveCommit(await pickPr())
+  if (ref === undefined) return resolveCommit(await pickPr('oxidecomputer/omicron'))
   if (typeof ref === 'number') {
     console.error(`Resolving PR #${ref} to commit...`)
     const query = `{
@@ -133,32 +122,13 @@ const remoteSource: Source = {
 /** Read schemas from the git repo in the current directory (run from an omicron checkout) */
 async function createLocalSource(): Promise<Source> {
   if (!$.commandExistsSync('git')) throw new Error('--local requires git')
+  const repoRoot = Deno.cwd()
   // jj's working copy is always a commit, so in a jj repo @ is the natural
   // default and reflects in-progress (even uncommitted) work. Plain git uses HEAD.
-  const isJj =
-    $.commandExistsSync('jj') &&
-    (await $`jj root`.noThrow().stdout('null').stderr('null')).code === 0
+  const isJj = await isJjRepository(repoRoot)
 
   const gitShow = (target: string) => $`git show ${target}`.text()
 
-  const resolveOne = async (ref: string): Promise<string> => {
-    try {
-      if (isJj) {
-        const out = (
-          await $`jj log -r ${ref} --no-graph -T commit_id`.stderr('null').text()
-        ).trim()
-        if (out.includes('\n')) throw new Error(`Revset '${ref}' matches multiple commits`)
-        return out
-      }
-      // pass the peel as a single arg so ^{commit} isn't brace-expanded
-      const rev = `${ref}^{commit}`
-      return (await $`git rev-parse --verify ${rev}`.stderr('null').text()).trim()
-    } catch (e) {
-      if (e instanceof Error && e.message.startsWith('Revset')) throw e
-      throw new Error(`Could not resolve '${ref}' in local ${isJj ? 'jj' : 'git'} repo`)
-    }
-  }
-
   return {
     resolveCommit: async (ref) => {
       if (typeof ref === 'number')
@@ -168,9 +138,9 @@ async function createLocalSource(): Promise<Source> {
       if (ref === undefined) {
         const def = isJj ? '@' : 'HEAD'
         console.error(`No ref given, defaulting to ${def} (comparing against its parent)`)
-        return resolveOne(def)
+        return resolveLocalCommit(repoRoot, def, isJj)
       }
-      return resolveOne(ref)
+      return resolveLocalCommit(repoRoot, ref, isJj)
     },
     listSchemaNames: async (commit) => {
       const out = (
diff --git a/tools/deno/bump-omicron.ts b/tools/deno/bump-omicron.ts
index 2e8437766..ebd4237f8 100755
--- a/tools/deno/bump-omicron.ts
+++ b/tools/deno/bump-omicron.ts
@@ -7,11 +7,11 @@
  *
  * Copyright Oxide Computer Company
  */
-import * as path from 'https://deno.land/std@0.159.0/path/mod.ts'
-import $ from 'https://deno.land/x/dax@0.39.2/mod.ts'
 import { Command } from 'jsr:@cliffy/command@1.0.0'
 import { Confirm, Input } from 'jsr:@cliffy/prompt@1.0.0'
+import $ from 'jsr:@david/dax@0.41.0'
 import { existsSync } from 'jsr:@std/fs@1.0'
+import * as path from 'jsr:@std/path@1.1.6'
 
 const OMICRON_DIR = path.resolve('../omicron')
 const GH_MISSING = 'GitHub CLI not found. Please install it and try again.'
diff --git a/tools/deno/bundle-size-diff.ts b/tools/deno/bundle-size-diff.ts
new file mode 100755
index 000000000..4b7d734f7
--- /dev/null
+++ b/tools/deno/bundle-size-diff.ts
@@ -0,0 +1,290 @@
+#! /usr/bin/env -S deno run --allow-run=gh,git,jj,npm,diff,delta,fzf --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 { Command, ValidationError } from 'jsr:@cliffy/command@1.0.0'
+import { $ } from 'jsr:@david/dax@0.41.0'
+import { exists } from 'jsr:@std/fs@1.0'
+
+import { pickPr, resolveLocalCommit } from './common.ts'
+
+const REPO = 'oxidecomputer/console'
+const CACHE_ROOT = '/tmp/bundle-size-diff'
+const SMALL_CHANGE_KB = 0.05
+
+type Pr = {
+  baseRefOid: string
+  headRefOid: string
+  number: number
+}
+
+type DiffTarget = {
+  baseCommit: string
+  headCommit: string
+}
+
+async function getPr(number: number): Promise<Pr> {
+  const result: unknown = await $`gh pr view ${number} --repo ${REPO}
+      --json number,baseRefOid,headRefOid`.json()
+
+  if (
+    typeof result !== 'object' ||
+    result === null ||
+    !('number' in result) ||
+    typeof result.number !== 'number' ||
+    !('baseRefOid' in result) ||
+    typeof result.baseRefOid !== 'string' ||
+    !('headRefOid' in result) ||
+    typeof result.headRefOid !== 'string'
+  ) {
+    throw new Error(`Unexpected response while resolving PR #${number}`)
+  }
+
+  return {
+    number: result.number,
+    baseRefOid: result.baseRefOid,
+    headRefOid: result.headRefOid,
+  }
+}
+
+async function hasCommit(repoRoot: string, commit: string): Promise<boolean> {
+  const rev = `${commit}^{commit}`
+  return (
+    (await $`git cat-file -e ${rev}`.cwd(repoRoot).noThrow().stdout('null').stderr('null'))
+      .code === 0
+  )
+}
+
+async function fetchMissingCommits(repoRoot: string, pr: Pr): Promise<void> {
+  if (!(await hasCommit(repoRoot, pr.baseRefOid))) {
+    console.error(`Fetching base ${pr.baseRefOid.slice(0, 8)}...`)
+    await $`git fetch --quiet origin ${pr.baseRefOid}`.cwd(repoRoot)
+  }
+
+  if (!(await hasCommit(repoRoot, pr.headRefOid))) {
+    console.error(`Fetching head ${pr.headRefOid.slice(0, 8)}...`)
+    const pullRef = `refs/pull/${pr.number}/head`
+    await $`git fetch --quiet origin ${pullRef}`.cwd(repoRoot)
+  }
+}
+
+async function resolveTarget(
+  repoRoot: string,
+  ref1?: string,
+  ref2?: string
+): Promise<DiffTarget> {
+  const firstRef = ref1 ?? String(await pickPr(REPO))
+
+  if (ref2 === undefined) {
+    if (!/^\d+$/.test(firstRef)) {
+      throw new ValidationError(
+        'A single argument must be a console PR number; pass two arguments to compare revisions'
+      )
+    }
+    if (!$.commandExistsSync('gh')) throw new Error('Need gh (GitHub CLI)')
+
+    const pr = await getPr(Number(firstRef))
+    await fetchMissingCommits(repoRoot, pr)
+    return { baseCommit: pr.baseRefOid, headCommit: pr.headRefOid }
+  }
+
+  // jj may snapshot the working copy while resolving a revision, so avoid
+  // running two jj processes against it concurrently.
+  const baseCommit = await resolveLocalCommit(repoRoot, firstRef)
+  const headCommit = await resolveLocalCommit(repoRoot, ref2)
+  return { baseCommit, headCommit }
+}
+
+async function addWorktree(repoRoot: string, dir: string, commit: string): Promise<void> {
+  await $`git worktree add --detach --quiet ${dir} ${commit}`.cwd(repoRoot)
+}
+
+function extractBundleSizes(output: string): string {
+  const lines = output.split('\n')
+  const start = lines.findIndex((line) => line === 'computing gzip size...')
+  const end = lines.findIndex(
+    (line, index) => index > start && line.startsWith('✓ built in')
+  )
+
+  if (start === -1 || end === -1) {
+    throw new Error('Could not find the bundle size table in npm run build output')
+  }
+
+  return (
+    lines
+      .slice(start + 1, end)
+      // Content changes cascade new hashes through importing chunks. Keep a
+      // fixed-width placeholder so hash-only changes disappear from the diff.
+      .map((line) => line.replace(/-[\w-]{8}(?=\.[a-z0-9]+(?:\s|$))/i, '-HASHHASH'))
+      // Vite sorts by size, which makes unchanged rows look moved when a
+      // nearby chunk changes. Filename order is stable across builds.
+      .sort()
+      .join('\n')
+      .trimEnd() + '\n'
+  )
+}
+
+type BundleRow = {
+  file: string
+  line: string
+  sizes: number[]
+}
+
+function parseBundleRow(line: string): BundleRow | undefined {
+  const file = line.match(/^\S+/)?.[0]
+  const sizes = [...line.matchAll(/([\d,]+\.\d+) kB/g)].map((match) =>
+    Number(match[1].replaceAll(',', ''))
+  )
+  return file && sizes.length > 0 ? { file, line, sizes } : undefined
+}
+
+function suppressSmallChanges(base: string, head: string): string {
+  const baseRows = new Map<string, BundleRow[]>()
+  for (const line of base.trimEnd().split('\n')) {
+    const row = parseBundleRow(line)
+    if (!row) continue
+    const rows = baseRows.get(row.file) ?? []
+    rows.push(row)
+    baseRows.set(row.file, rows)
+  }
+
+  const lines = head.trimEnd().split('\n')
+  return (
+    lines
+      .map((line) => {
+        const headRow = parseBundleRow(line)
+        const baseRow = headRow && baseRows.get(headRow.file)?.shift()
+        const isSmallChange =
+          baseRow &&
+          baseRow.sizes.length === headRow.sizes.length &&
+          baseRow.sizes.every(
+            (size, index) => Math.abs(size - headRow.sizes[index]) <= SMALL_CHANGE_KB + 1e-9
+          )
+        return isSmallChange ? baseRow.line : line
+      })
+      .join('\n') + '\n'
+  )
+}
+
+async function ensureBuild(
+  repoRoot: string,
+  dir: string,
+  commit: string,
+  label: string,
+  force: boolean
+): Promise<string> {
+  const cacheDir = `${CACHE_ROOT}/${commit}`
+  const outputPath = `${cacheDir}/build-output.txt`
+  if (!force && (await exists(outputPath))) {
+    console.error(`Using cached ${label} build...`)
+    return extractBundleSizes(await Deno.readTextFile(outputPath))
+  }
+
+  await addWorktree(repoRoot, dir, commit)
+  try {
+    console.error(`Installing ${label} dependencies...`)
+    await $`npm ci --no-audit --no-fund`.cwd(dir).env('HUSKY', '0').stdout('null')
+
+    console.error(`Building ${label}...`)
+    const output = await $`npm run build`.cwd(dir).text()
+    const sizes = extractBundleSizes(output)
+    await Deno.mkdir(cacheDir, { recursive: true })
+    await Deno.writeTextFile(outputPath, output)
+    return sizes
+  } finally {
+    console.error(`Cleaning up ${label} worktree...`)
+    await $`git worktree remove --force ${dir}`.cwd(repoRoot).noThrow().quiet()
+  }
+}
+
+async function runDiff(base: string, head: string, baseLabel: string, headLabel: string) {
+  const dir = await Deno.makeTempDir({ prefix: 'bundle-size-diff-output-' })
+  const basePath = `${dir}/base.txt`
+  const headPath = `${dir}/head.txt`
+
+  try {
+    await Promise.all([
+      Deno.writeTextFile(basePath, base),
+      Deno.writeTextFile(headPath, head),
+    ])
+
+    // Match api-diff: render through delta for interactive use and leave plain
+    // unified output intact when piping the result elsewhere.
+    const useDelta = $.commandExistsSync('delta') && Deno.stdout.isTerminal()
+    const diff =
+      $`diff -u -L ${baseLabel} -L ${headLabel} ${basePath} ${headPath}`.noThrow()
+    await (useDelta ? diff.pipe($`delta`) : diff)
+  } finally {
+    await Deno.remove(dir, { recursive: true })
+  }
+}
+
+await new Command()
+  .name('bundle-size-diff')
+  .description(
+    `Build two console revisions and display a unified diff of Vite's
+bundle size table.
+
+Arguments:
+  No args         Pick a console PR with fzf
+  <pr>            Compare the base and head of a console PR
+  <base> <head>   Compare two local git or jj revisions
+
+Dependencies:
+  - Deno
+  - GitHub CLI (gh) for PRs
+  - Git
+  - Node.js and npm
+  - Optional: delta diff pager https://dandavison.github.io/delta/
+  - Optional: fzf for PR picker https://github.com/junegunn/fzf`
+  )
+  .helpOption('-h, --help', 'Show help')
+  .option('--force', 'Rebuild even if output is cached')
+  .arguments('[ref1:string] [ref2:string]')
+  .action(async (options, ref1?: string, ref2?: string) => {
+    let tempRoot: string | undefined
+
+    try {
+      const repoRoot = (await $`git rev-parse --show-toplevel`.text()).trim()
+      const target = await resolveTarget(repoRoot, ref1, ref2)
+
+      tempRoot = await Deno.makeTempDir({ prefix: 'bundle-size-diff-' })
+      const baseDir = `${tempRoot}/base`
+      const headDir = `${tempRoot}/head`
+
+      const baseShort = target.baseCommit.slice(0, 8)
+      const headShort = target.headCommit.slice(0, 8)
+      const force = options.force ?? false
+      const base = await ensureBuild(
+        repoRoot,
+        baseDir,
+        target.baseCommit,
+        `base (${baseShort})`,
+        force
+      )
+      const head = await ensureBuild(
+        repoRoot,
+        headDir,
+        target.headCommit,
+        `head (${headShort})`,
+        force
+      )
+      await runDiff(
+        base,
+        suppressSmallChanges(base, head),
+        `a/${baseShort}/bundle-size`,
+        `b/${headShort}/bundle-size`
+      )
+    } catch (e) {
+      console.error(`error: ${e instanceof Error ? e.message : String(e)}`)
+      Deno.exitCode = 1
+    } finally {
+      if (tempRoot) await Deno.remove(tempRoot, { recursive: true }).catch(() => {})
+    }
+  })
+  .parse(Deno.args)
diff --git a/tools/deno/common.ts b/tools/deno/common.ts
new file mode 100644
index 000000000..56464e670
--- /dev/null
+++ b/tools/deno/common.ts
@@ -0,0 +1,70 @@
+/*
+ * 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 { $ } from 'jsr:@david/dax@0.41.0'
+
+export async function pickPr(repo: string): Promise<number> {
+  if (!$.commandExistsSync('gh')) throw new Error('Need gh (GitHub CLI)')
+  if (!$.commandExistsSync('fzf')) throw new Error('Need fzf to pick a PR')
+
+  const selection = await $`gh pr list --repo ${repo} --limit 100
+      --json number,title,updatedAt,author
+      --template '{{range .}}{{tablerow .number .title .author.name (timeago .updatedAt)}}{{end}}'`
+    .pipe($`fzf --height 25% --reverse`)
+    .text()
+  const prNumber = selection.match(/^\d+/)?.[0]
+  if (!prNumber) {
+    throw new Error('Expected the selected row to start with a PR number')
+  }
+  return Number(prNumber)
+}
+
+export async function isJjRepository(repoRoot: string): Promise<boolean> {
+  return (
+    $.commandExistsSync('jj') &&
+    (await $`jj root`.cwd(repoRoot).noThrow().stdout('null').stderr('null')).code === 0
+  )
+}
+
+export async function resolveLocalCommit(
+  repoRoot: string,
+  ref: string,
+  isJj?: boolean
+): Promise<string> {
+  const useJj = isJj ?? (await isJjRepository(repoRoot))
+  if (useJj) {
+    try {
+      const template = 'commit_id ++ "\\n"'
+      const commits = (
+        await $`jj log --revisions ${ref} --no-graph --template ${template}`
+          .cwd(repoRoot)
+          .stderr('null')
+          .text()
+      )
+        .trim()
+        .split('\n')
+        .filter(Boolean)
+      if (commits.length !== 1) {
+        throw new Error(`Revision '${ref}' resolved to ${commits.length} commits`)
+      }
+      return commits[0]
+    } catch (e) {
+      if (e instanceof Error && e.message.startsWith('Revision')) throw e
+      // A newly fetched Git commit may not have been imported into jj yet.
+    }
+  }
+
+  try {
+    // Pass the peel as a single argument so ^{commit} isn't brace-expanded.
+    const rev = `${ref}^{commit}`
+    return (
+      await $`git rev-parse --verify ${rev}`.cwd(repoRoot).stderr('null').text()
+    ).trim()
+  } catch {
+    throw new Error(`Could not resolve revision '${ref}'`)
+  }
+}