diff --git a/.changeset/witty-yaks-munch.md b/.changeset/witty-yaks-munch.md
new file mode 100644
index 000000000..458bf18eb
--- /dev/null
+++ b/.changeset/witty-yaks-munch.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 3095
+---
+**Local `lint:changeset` and `lint:docs-required` now diff against `next` instead of `main`** — the local fallback was the release branch (`main`), which lags far behind the integration branch (`next`), so the lint always passed by finding fragments from other already-merged PRs in the oversized diff range. The local invocation now matches the base CI uses. (#2988)
diff --git a/scripts/changeset/lint.cjs b/scripts/changeset/lint.cjs
index 9fe975093..933d5fe55 100755
--- a/scripts/changeset/lint.cjs
+++ b/scripts/changeset/lint.cjs
@@ -12,6 +12,10 @@
  * Tests assert on the typed verdict, never on free text.
  */
 
+// #2988: the repo's integration/default branch — the base every PR targets.
+// Used as the local fallback when GITHUB_BASE_REF is unset (CI sets it).
+const DEFAULT_BASE = 'next';
+
 const LINT_REASON = Object.freeze({
   OK_FRAGMENT_PRESENT: 'ok_fragment_present',
   OK_OPT_OUT_LABEL: 'ok_opt_out_label',
@@ -80,7 +84,10 @@ function main() {
       labels = (event.pull_request?.labels || []).map((l) => l.name);
     } catch { /* fall through */ }
   }
-  const base = process.env.GITHUB_BASE_REF || 'main';
+  // #2988: local fallback must match the repo's integration branch (`next`),
+  // not the release branch (`main`). CI sets GITHUB_BASE_REF explicitly; the
+  // fallback only fires locally, where `next` is the base every PR targets.
+  const base = process.env.GITHUB_BASE_REF || DEFAULT_BASE;
   let changedFiles = [];
   try {
     // Use execFileSync with an argv array — the base ref is interpolated
@@ -145,4 +152,4 @@ function main() {
 
 if (require.main === module) runMain(main);
 
-module.exports = { evaluateLint, LINT_REASON, OPT_OUT_LABEL, isUserFacing, isFragment };
+module.exports = { evaluateLint, LINT_REASON, OPT_OUT_LABEL, isUserFacing, isFragment, DEFAULT_BASE };
diff --git a/scripts/lint-docs-required.cjs b/scripts/lint-docs-required.cjs
index a6580cb4a..3bcce28ca 100755
--- a/scripts/lint-docs-required.cjs
+++ b/scripts/lint-docs-required.cjs
@@ -16,6 +16,10 @@
 const { parseFragment, FRAGMENT_ERROR } = require('./changeset/parse.cjs');
 const { ExitError, runMain } = require('./lib/cli-exit.cjs');
 
+// #2988: the repo's integration/default branch — the base every PR targets.
+// Used as the local fallback when GITHUB_BASE_REF is unset (CI sets it).
+const DEFAULT_BASE = 'next';
+
 const LINT_REASON = Object.freeze({
   OK_NO_TRIGGERING_FRAGMENTS: 'ok_no_triggering_fragments',
   OK_DOCS_UPDATED: 'ok_docs_updated',
@@ -149,7 +153,10 @@ function main() {
     } catch { /* fall through */ }
   }
 
-  const base = process.env.GITHUB_BASE_REF || 'main';
+  // #2988: local fallback must match the repo's integration branch (`next`),
+  // not the release branch (`main`). CI sets GITHUB_BASE_REF explicitly; the
+  // fallback only fires locally, where `next` is the base every PR targets.
+  const base = process.env.GITHUB_BASE_REF || DEFAULT_BASE;
   let changedFiles = [];
   try {
     // execFileSync with argv — no shell, so a malicious GITHUB_BASE_REF
@@ -216,6 +223,7 @@ module.exports = {
   OPT_OUT_LABEL,
   TRIGGERING_TYPES,
   FRAGMENT_ERROR,
+  DEFAULT_BASE,
   isFragmentPath,
   isDocsFile,
   isExemptFragment,
diff --git a/tests/changeset-lint.test.cjs b/tests/changeset-lint.test.cjs
index dff7ab16a..6775d142d 100644
--- a/tests/changeset-lint.test.cjs
+++ b/tests/changeset-lint.test.cjs
@@ -8,7 +8,8 @@ const fs = require('node:fs');
 const os = require('node:os');
 const cp = require('node:child_process');
 
-const { evaluateLint, LINT_REASON } = require(path.join(__dirname, '..', 'scripts', 'changeset', 'lint.cjs'));
+const { evaluateLint, LINT_REASON, DEFAULT_BASE: CHANGESET_DEFAULT_BASE } = require(path.join(__dirname, '..', 'scripts', 'changeset', 'lint.cjs'));
+const { DEFAULT_BASE: DOCS_DEFAULT_BASE } = require(path.join(__dirname, '..', 'scripts', 'lint-docs-required.cjs'));
 
 const ROOT = path.join(__dirname, '..');
 const LINT_SCRIPT = path.join(ROOT, 'scripts', 'changeset', 'lint.cjs');
@@ -297,3 +298,19 @@ describe('changeset lint: main() end-to-end wiring (#1006)', () => {
     assert.ok(!deletedEntry, `deleted fragment must not appear in failures, got: ${JSON.stringify(failures)}`);
   });
 });
+
+// ─── #2988: local base fallback parity ──────────────────────────────────────
+
+describe('#2988: changeset + docs lints resolve the same local base fallback', () => {
+  test('both lints default to `next` (the integration branch), not `main`', () => {
+    assert.strictEqual(CHANGESET_DEFAULT_BASE, 'next',
+      `changeset lint DEFAULT_BASE must be 'next', got '${CHANGESET_DEFAULT_BASE}'`);
+    assert.strictEqual(DOCS_DEFAULT_BASE, 'next',
+      `docs lint DEFAULT_BASE must be 'next', got '${DOCS_DEFAULT_BASE}'`);
+  });
+
+  test('both lints resolve the same base given the same environment (parity)', () => {
+    assert.strictEqual(CHANGESET_DEFAULT_BASE, DOCS_DEFAULT_BASE,
+      `the two lints must not diverge on base resolution: changeset='${CHANGESET_DEFAULT_BASE}' docs='${DOCS_DEFAULT_BASE}'`);
+  });
+});