diff --git a/CHANGELOG.md b/CHANGELOG.md
index 935f383..9e977fd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,11 @@ Details: [foreman changelog](plugins/foreman/CHANGELOG.md).
 - CI pins Claude Code 2.1.295, the minimum version the README requires (#151)
 - `/axis-new-branch` asks whether to start fixing the issue right after creating its branch (#174)
 
+#### Fixed
+
+- `release.js prepare` restores its files and exits 1 when the release notes fail (#171)
+- `context-budget.js --base` works on revisions from before the vcs reference files (#171)
+
 ## [1.7.0] - 2026-10-17
 
 ### Marketplace
diff --git a/scripts/context-budget.js b/scripts/context-budget.js
index 3cc43cd..4edc6bc 100644
--- a/scripts/context-budget.js
+++ b/scripts/context-budget.js
@@ -85,7 +85,8 @@ function gitReader(ref, repo = REPO) {
 function measure(r) {
   const size = (rel) => Buffer.byteLength(r.text(rel));
   const vcs = ['vcs-git.md', 'vcs-tfvc.md', 'vcs-none.md'].map((f) => `reference/${f}`).filter(r.exists);
-  const largestVcs = vcs.reduce((a, b) => (size(a) >= size(b) ? a : b));
+  // null on a base revision from before the vcs files (#171): nothing to add for them.
+  const largestVcs = vcs.reduce((a, b) => (a && size(a) >= size(b) ? a : b), null);
   const templates = r.list('templates');
 
   // Every plugin file a text names: ${CLAUDE_PLUGIN_ROOT}/... paths, `vcs-<value>.md` or
@@ -101,10 +102,11 @@ function measure(r) {
       return out;
     }
     for (const m of body.matchAll(/\$\{CLAUDE_PLUGIN_ROOT\}\/([\w./<>-]+\.(?:md|json))/g)) {
-      if (m[1].includes('<value>')) out.add(largestVcs);
-      else if (r.exists(m[1])) out.add(m[1]);
+      if (m[1].includes('<value>')) {
+        if (largestVcs) out.add(largestVcs);
+      } else if (r.exists(m[1])) out.add(m[1]);
     }
-    if (/the vcs file/.test(body)) out.add(largestVcs);
+    if (largestVcs && /the vcs file/.test(body)) out.add(largestVcs);
     if (/template/i.test(body)) for (const t of templates) if (body.includes(`\`${t}\``)) out.add(`templates/${t}`);
     return out;
   }
diff --git a/scripts/release.js b/scripts/release.js
index 197ccc8..db7ee4a 100644
--- a/scripts/release.js
+++ b/scripts/release.js
@@ -12,7 +12,8 @@
 //     table, plugin README Version line), renames Unreleased to `[X.Y.Z] - date` in the
 //     root and those plugins' changelogs (new empty Unreleased above), and sets the
 //     root `### <plugin> X.Y.Z` headings. Every plugin with Unreleased entries needs a
-//     version. All files or none; each keeps its line endings.
+//     version. All files or none (also when the release notes then fail); each keeps
+//     its line endings.
 //   node scripts/release.js tag X.Y.Z
 //     On a clean `main` equal to GitHub's, with no open milestone issues and valid
 //     release notes: creates the annotated tag vX.Y.Z and pushes only that tag to the
@@ -322,7 +323,9 @@ function status(arg) {
   return lines;
 }
 
-function prepare(args) {
+// Writes the release edits into `root`; on a write or release notes error, restores the files and throws.
+function prepare(args, root = ROOT, notesOf = releaseNotes) {
+  const read = (rel) => fs.readFileSync(path.join(root, rel), 'utf8');
   let date = today();
   const versions = {};
   const rest = [];
@@ -335,20 +338,32 @@ function prepare(args) {
   }
   if (rest.length !== 1) throw new Error('usage: prepare X.Y.Z [<plugin>=X.Y.Z ...] [--date YYYY-MM-DD]');
   const version = rest[0];
-  const result = prepareEdits(readRel, version, versions, date);
+  const result = prepareEdits(read, version, versions, date);
   if (result.error) throw new Error(result.error);
   const before = {};
+  const restore = () => {
+    for (const [rel, text] of Object.entries(before)) fs.writeFileSync(path.join(root, rel), text);
+  };
   try {
     for (const [rel, text] of Object.entries(result.files)) {
-      before[rel] = readRel(rel);
-      fs.writeFileSync(path.join(ROOT, rel), text);
+      before[rel] = read(rel);
+      fs.writeFileSync(path.join(root, rel), text);
     }
   } catch (e) {
-    for (const [rel, text] of Object.entries(before)) fs.writeFileSync(path.join(ROOT, rel), text);
+    restore();
     throw e;
   }
-  const notes = releaseNotes(`v${version}`, ROOT);
-  return [...Object.keys(result.files).map((rel) => `changed: ${rel}`), notes.error ? `notes: ${notes.error}` : `notes: v${version} ok`];
+  let notes;
+  try {
+    notes = notesOf(`v${version}`, root);
+  } catch (e) {
+    notes = { error: e.message };
+  }
+  if (notes.error) {
+    restore();
+    throw new Error(`notes: ${notes.error} (files restored)`);
+  }
+  return [...Object.keys(result.files).map((rel) => `changed: ${rel}`), `notes: v${version} ok`];
 }
 
 function tag(version) {
@@ -415,4 +430,4 @@ function main(argv) {
 
 if (require.main === module) process.exitCode = main(process.argv.slice(2));
 
-module.exports = { unreleasedLines, rootAreas, pluginTypes, bumpOf, bump, compare, milestoneVersion, kindOf, phaseOf, propose, releaseChangelog, setJsonVersion, setReadmeRow, setVersionLine, prepareEdits, pushRemote };
+module.exports = { unreleasedLines, rootAreas, pluginTypes, bumpOf, bump, compare, milestoneVersion, kindOf, phaseOf, propose, releaseChangelog, setJsonVersion, setReadmeRow, setVersionLine, prepareEdits, prepare, pushRemote };
diff --git a/tests/foreman/context-budget.test.js b/tests/foreman/context-budget.test.js
index f2ffca0..917093b 100644
--- a/tests/foreman/context-budget.test.js
+++ b/tests/foreman/context-budget.test.js
@@ -52,6 +52,20 @@ test('report: only commands near budget or changed, with the changed files', ()
   assert.deepStrictEqual(report(small, small), ['context budget: ok']);
 });
 
+test('measure works on a plugin without vcs files (a base revision from before them)', () => {
+  const files = {
+    'commands/run.md': '---\ndescription: Run\n---\nRead `${CLAUDE_PLUGIN_ROOT}/reference/vcs-<value>.md`, then the vcs file.\n',
+    'templates/claude-md.md': 'block',
+  };
+  const r = {
+    text: (rel) => files[rel],
+    exists: (rel) => rel in files,
+    list: (rel) => (rel === 'commands' ? ['run.md'] : []),
+  };
+  const m = measure(r);
+  assert.deepStrictEqual(Object.keys(m.commands.run.files), ['commands/run.md']);
+});
+
 test('the git reader on HEAD measures what the tree measures when nothing is changed', () => {
   // A throwaway clone of HEAD: the working tree there is HEAD, so both readers must agree.
   const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'axis-context-budget-'));
diff --git a/tests/release-script.test.js b/tests/release-script.test.js
index a9c4088..33c847c 100644
--- a/tests/release-script.test.js
+++ b/tests/release-script.test.js
@@ -6,7 +6,7 @@ const test = require('node:test');
 const assert = require('node:assert');
 const fs = require('fs');
 const path = require('path');
-const { unreleasedLines, rootAreas, pluginTypes, bumpOf, bump, compare, milestoneVersion, kindOf, phaseOf, propose, releaseChangelog, setJsonVersion, setReadmeRow, setVersionLine, prepareEdits, pushRemote } = require('../scripts/release.js');
+const { unreleasedLines, rootAreas, pluginTypes, bumpOf, bump, compare, milestoneVersion, kindOf, phaseOf, propose, releaseChangelog, setJsonVersion, setReadmeRow, setVersionLine, prepareEdits, prepare, pushRemote } = require('../scripts/release.js');
 
 const ROOT_LOG = [
   '# Changelog',
@@ -164,6 +164,30 @@ test('prepareEdits: every file, or an error', () => {
   assert.deepStrictEqual(Object.keys(prepareEdits(noPluginEntries, '1.6.1', {}, '2026-10-13').files).sort(), ['.claude-plugin/marketplace.json', 'CHANGELOG.md', 'README.md']);
 });
 
+test('prepare: writes every file, or restores them all when the release notes fail', () => {
+  const os = require('os');
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'axis-release-'));
+  const write = () => {
+    for (const [rel, text] of Object.entries(FILES)) {
+      fs.mkdirSync(path.dirname(path.join(dir, rel)), { recursive: true });
+      fs.writeFileSync(path.join(dir, rel), text);
+    }
+  };
+  const snapshot = () => Object.fromEntries(Object.keys(FILES).map((rel) => [rel, fs.readFileSync(path.join(dir, rel), 'utf8')]));
+  try {
+    write();
+    assert.throws(() => prepare(['1.7.0', 'foreman=1.6.1', '--date', '2026-10-13'], dir, () => ({ error: 'broken' })), /notes: broken \(files restored\)/);
+    assert.deepStrictEqual(snapshot(), FILES);
+    assert.throws(() => prepare(['1.7.0', 'foreman=1.6.1', '--date', '2026-10-13'], dir, () => { throw new Error('unreadable'); }), /notes: unreadable \(files restored\)/);
+    assert.deepStrictEqual(snapshot(), FILES);
+    const lines = prepare(['1.7.0', 'foreman=1.6.1', '--date', '2026-10-13'], dir);
+    assert.strictEqual(lines[lines.length - 1], 'notes: v1.7.0 ok');
+    assert.match(fs.readFileSync(path.join(dir, 'CHANGELOG.md'), 'utf8'), /## \[1\.7\.0\] - 2026-10-13/);
+  } finally {
+    fs.rmSync(dir, { recursive: true, force: true });
+  }
+});
+
 test('pushRemote: by Black-Axis/axis-hub URL, never by name', () => {
   const v = [
     'fork\thttps://github.com/someone/axis-hub.git (fetch)',