diff --git a/packages/db/src/authors.js b/packages/db/src/authors.js
index 98c59f6..049cc09 100644
--- a/packages/db/src/authors.js
+++ b/packages/db/src/authors.js
@@ -190,7 +190,10 @@ export async function upsertAuthor(db, author) {
             (id, slug, identity_key, name, norm_name, bio, avatar_url, site_url,
              email, confidence, created_at, updated_at)
           values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-          on conflict (identity_key) do nothing`,
+          on conflict (identity_key) do nothing
+          -- Same race as creditStatements: the slug was chosen by an earlier
+          -- read, and another writer can take it in between. See there.
+          on conflict (slug) do nothing`,
     args: [
       id,
       author.slug,
@@ -738,7 +741,24 @@ export function creditStatements({ feedId, identityKey, slug, person, authorLink
              or (authors.avatar_url is null and excluded.avatar_url is not null)
              or (authors.site_url is null and excluded.site_url is not null)
              or (authors.email is null and excluded.email is not null)
-             or authors.confidence < excluded.confidence`,
+             or authors.confidence < excluded.confidence
+          -- A different person who happens to have claimed the same slug.
+          --
+          -- claimAuthorSlug reads the slugs already taken and then this insert
+          -- runs later, so two crawls naming the same author can both pick
+          -- jane-doe before either has committed. The second violated the unique
+          -- constraint on authors.slug and, because this statement rides in the
+          -- crawl's own transaction, took the entire crawl down with it -- the
+          -- feed was recorded as uncrawlable and walked up the backoff ladder
+          -- toward dead, for a byline. Two Substack feeds were failing every
+          -- crawl this way for hours.
+          --
+          -- Doing nothing is the right answer rather than merely the safe one.
+          -- The loser of the race is not lost: its slug is taken by the time the
+          -- feed is crawled again, so claimAuthorSlug picks the next free one
+          -- and the credit lands then. A missing byline for one cycle is a far
+          -- smaller thing than a feed marked dead.
+          on conflict (slug) do nothing`,
     args: [
       newId(),
       slug,
diff --git a/packages/db/test/author-slug-race.test.js b/packages/db/test/author-slug-race.test.js
new file mode 100644
index 0000000..23e0a70
--- /dev/null
+++ b/packages/db/test/author-slug-race.test.js
@@ -0,0 +1,155 @@
+import assert from 'node:assert/strict';
+import { test, before, after } from 'node:test';
+import { mkdtemp, rm } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+
+import { connect } from '../src/client.js';
+import { migrate } from '../src/migrate.js';
+import { creditStatements, upsertAuthor } from '../src/authors.js';
+
+/**
+ * Two crawls claiming the same author slug must not fail a feed.
+ *
+ * `claimAuthorSlug` reads the slugs already taken and the insert runs later, so
+ * two feeds naming the same author can both pick `jane-doe` before either has
+ * committed. The loser used to violate `authors.slug` — and because the insert
+ * rides in the crawl's own write transaction, it took the whole crawl with it:
+ * the feed was recorded `could not be crawled` and walked up the backoff ladder
+ * toward `dead`, over a byline.
+ *
+ * Seen in production on 2026-08-19: two Substack feeds failed every crawl for
+ * hours on exactly this.
+ */
+
+let dir;
+let db;
+
+before(async () => {
+  dir = await mkdtemp(join(tmpdir(), 'rssamp-slug-'));
+  db = connect({ url: `file:${join(dir, 'test.db')}` });
+  await migrate(db);
+
+  // feed_authors carries a foreign key to feeds, so the credits have to have
+  // somewhere to land.
+  const now = '2026-01-01T00:00:00.000Z';
+  for (const [id, slug] of [
+    ['feed-1', 'one'],
+    ['feed-2', 'two'],
+  ]) {
+    await db.execute({
+      sql: `insert into feeds (id, slug, title, feed_url, status, next_fetch_at, created_at, updated_at)
+            values (?, ?, ?, ?, 'active', ?, ?, ?)`,
+      args: [id, slug, slug, `https://${slug}.example/feed`, now, now, now],
+    });
+  }
+});
+
+after(async () => {
+  await rm(dir, { recursive: true, force: true });
+});
+
+const person = (name, email) => ({
+  name,
+  normName: name.toLowerCase(),
+  bio: '',
+  avatarUrl: '',
+  siteUrl: '',
+  email,
+  confidence: 0.8,
+  role: 'author',
+  evidence: 'test',
+});
+
+test('a second person claiming a taken slug does not fail the write', async () => {
+  const first = creditStatements({
+    feedId: 'feed-1',
+    identityKey: 'jane@one.example',
+    slug: 'jane-doe',
+    person: person('Jane Doe', 'jane@one.example'),
+  });
+  await db.batch(first, 'write');
+
+  // A different identity — so the identity_key upsert does not catch it — that
+  // raced to the same slug.
+  const second = creditStatements({
+    feedId: 'feed-2',
+    identityKey: 'jane@two.example',
+    slug: 'jane-doe',
+    person: person('Jane Doe', 'jane@two.example'),
+  });
+
+  await assert.doesNotReject(
+    () => db.batch(second, 'write'),
+    'a slug collision must not take the crawl down',
+  );
+});
+
+test('the first claimant keeps the slug, unaltered', async () => {
+  const { rows } = await db.execute({
+    sql: 'select identity_key, email from authors where slug = ?',
+    args: ['jane-doe'],
+  });
+
+  assert.equal(rows.length, 1, 'exactly one author may hold a slug');
+  assert.equal(String(rows[0].identity_key), 'jane@one.example');
+  assert.equal(String(rows[0].email), 'jane@one.example', 'the loser must not overwrite the winner');
+});
+
+test('the loser is not created, so a later crawl can claim a free slug', async () => {
+  // Not lost, deferred. By the next crawl the slug is taken, so
+  // `claimAuthorSlug` picks the next free one and the credit lands then.
+  const { rows } = await db.execute({
+    sql: 'select count(*) as n from authors where identity_key = ?',
+    args: ['jane@two.example'],
+  });
+
+  assert.equal(Number(rows[0].n), 0);
+});
+
+test('the same person crawled twice still updates, rather than being skipped', async () => {
+  // The guard must not swallow the ordinary path: a matching identity_key is an
+  // update, and only a *different* identity colliding on slug is a no-op.
+  const better = creditStatements({
+    feedId: 'feed-1',
+    identityKey: 'jane@one.example',
+    slug: 'jane-doe',
+    person: { ...person('Jane Doe', 'jane@one.example'), bio: 'Writes things.', confidence: 0.95 },
+  });
+  await db.batch(better, 'write');
+
+  const { rows } = await db.execute({
+    sql: 'select bio, confidence from authors where identity_key = ?',
+    args: ['jane@one.example'],
+  });
+
+  assert.equal(String(rows[0].bio), 'Writes things.');
+  assert.equal(Number(rows[0].confidence), 0.95);
+});
+
+test('upsertAuthor survives the same race', async () => {
+  // The enrichment pass takes the other path into this table.
+  await upsertAuthor(db, {
+    identityKey: 'sam@one.example',
+    slug: 'sam-smith',
+    name: 'Sam Smith',
+    normName: 'sam smith',
+    confidence: 0.5,
+  });
+
+  await assert.doesNotReject(() =>
+    upsertAuthor(db, {
+      identityKey: 'sam@two.example',
+      slug: 'sam-smith',
+      name: 'Sam Smith',
+      normName: 'sam smith',
+      confidence: 0.5,
+    }),
+  );
+
+  const { rows } = await db.execute({
+    sql: 'select count(*) as n from authors where slug = ?',
+    args: ['sam-smith'],
+  });
+  assert.equal(Number(rows[0].n), 1);
+});