diff --git a/layers/registry/server/utils/sync-repo.ts b/layers/registry/server/utils/sync-repo.ts
index 2dd6f87c..7a8427b3 100644
--- a/layers/registry/server/utils/sync-repo.ts
+++ b/layers/registry/server/utils/sync-repo.ts
@@ -148,6 +148,17 @@ export const EXISTING_SKILL_ASSET_CHUNK = 15
  */
 export const D1_BATCH_CHAR_BUDGET = 8_000_000
 
+/**
+ * Revisions kept per Skill, newest first (ADR-0019).
+ *
+ * One sync reads a Skill's last 30 commits, and every reader wants the
+ * newest: the page shows the latest sha, the digest reads a month back, and
+ * the feed joins the revision at or before an activity row. Rows beyond
+ * that were a commit message each, 146,515 of them on 2026-11-12, and
+ * nothing deleted one.
+ */
+export const SKILL_REVISION_RETAIN = 30
+
 /** A prepared write and the bound payload size that decides which batch it joins. */
 export interface WeightedWrite {
   statement: D1PreparedStatement
@@ -1399,6 +1410,20 @@ export async function syncRepo(
             [owner, repo, parsed.name, c.sha, occurredAt, c.author?.login ?? null, c.commit.message],
           ))
         }
+        if (commits.length > 0) {
+          writes.push(weighWrite(
+            db,
+            `DELETE FROM skill_revisions
+             WHERE owner = ? AND repo = ? AND name = ?
+               AND sha NOT IN (
+                 SELECT sha FROM skill_revisions
+                 WHERE owner = ? AND repo = ? AND name = ?
+                 ORDER BY modified_at DESC, sha DESC
+                 LIMIT ?
+               )`,
+            [owner, repo, parsed.name, owner, repo, parsed.name, SKILL_REVISION_RETAIN],
+          ))
+        }
       }
 
       writes.push(weighWrite(
diff --git a/test/unit/sync-repo-revision-retention.test.ts b/test/unit/sync-repo-revision-retention.test.ts
new file mode 100644
index 00000000..14039d72
--- /dev/null
+++ b/test/unit/sync-repo-revision-retention.test.ts
@@ -0,0 +1,217 @@
+import Database from 'better-sqlite3'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { SKILL_REVISION_RETAIN, syncRepo } from '../../layers/registry/server/utils/sync-repo'
+
+/**
+ * ADR-0019: `skill_revisions` keeps the newest `SKILL_REVISION_RETAIN` rows per
+ * Skill. A changed body inserts its commits and then drops what falls past
+ * the window, in the same batch.
+ */
+
+const github = vi.hoisted(() => ({
+  getBlobsBatch: vi.fn(),
+  getCommitsBatch: vi.fn(),
+  getRepoSummary: vi.fn(),
+  getTree: vi.fn(),
+  logRateLimit: vi.fn(),
+}))
+const renderer = vi.hoisted(() => ({
+  parseSkillMd: vi.fn(async (raw: string) => ({ frontmatter: {}, body: raw, html: `<p>${raw}</p>` })),
+}))
+
+vi.mock('../../layers/registry/server/utils/github-client', () => github)
+vi.mock('../../layers/registry/server/utils/skill-md-render', () => renderer)
+
+const rawSkill = (name: string) => `---\nname: ${name}\ndescription: ${name} description\n---\n# ${name}`
+
+function commit(index: number) {
+  return {
+    sha: `sha-${String(index).padStart(3, '0')}`,
+    author: { login: 'author' },
+    commit: { message: `commit ${index}`, author: { date: new Date(Date.UTC(2026, 0, 1) + index * 86_400_000).toISOString() } },
+  }
+}
+
+describe('syncRepo revision retention', () => {
+  let sqlite: Database.Database
+  let db: D1Database
+
+  beforeEach(() => {
+    vi.useFakeTimers()
+    vi.setSystemTime(new Date('2026-11-12T00:00:00Z'))
+    vi.clearAllMocks()
+    sqlite = createDatabase()
+    db = wrapSqlite(sqlite)
+    github.getRepoSummary.mockResolvedValue({
+      status: 200,
+      data: {
+        repositoryId: 1,
+        headTreeSha: 'new-tree',
+        meta: {
+          name: 'skills',
+          full_name: 'acme/skills',
+          html_url: 'https://github.com/acme/skills',
+          owner: { login: 'acme' },
+          default_branch: 'main',
+          description: 'Skills',
+          stargazers_count: 1,
+          forks_count: 0,
+          pushed_at: '2026-11-11T12:00:00Z',
+          created_at: '2025-01-01T00:00:00Z',
+        },
+      },
+      rateLimit: null,
+      notModified: false,
+    })
+    github.getTree.mockResolvedValue({
+      status: 200,
+      data: { sha: 'new-tree', tree: [{ path: 'skills/one/SKILL.md', sha: 'one-new', type: 'blob' }] },
+      rateLimit: null,
+      notModified: false,
+    })
+    github.getBlobsBatch.mockResolvedValue({
+      status: 200,
+      data: new Map([['skills/one/SKILL.md', rawSkill('One')]]),
+      unreadable: new Set(),
+      rateLimit: null,
+      notModified: false,
+    })
+    sqlite.prepare(`INSERT INTO repos (owner, repo, default_branch, pushed_at, last_tree_sha) VALUES ('acme', 'skills', 'main', 0, 'old-tree')`).run()
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+    sqlite.close()
+  })
+
+  it('keeps only the newest revisions per Skill after a sync', async () => {
+    // Older rows from earlier syncs, below the window once new commits land.
+    const insert = sqlite.prepare(`INSERT INTO skill_revisions (owner, repo, name, sha, modified_at, author_login, message) VALUES ('acme', 'skills', 'one', ?, ?, 'author', ?)`)
+    for (let i = 0; i < 10; i += 1)
+      insert.run(`old-${i}`, 1_000 + i, `old ${i}`)
+    const newest = Array.from({ length: SKILL_REVISION_RETAIN }, (_, i) => commit(100 + i)).reverse()
+    github.getCommitsBatch.mockResolvedValue({
+      status: 200,
+      data: new Map([['skills/one/SKILL.md', newest]]),
+      rateLimit: null,
+      notModified: false,
+    })
+
+    const result = await syncRepo('acme', 'skills', {}, db, { ownerVerified: true })
+
+    expect(result.status).toBe('indexed')
+    const shas = sqlite.prepare(`SELECT sha FROM skill_revisions WHERE name = 'one' ORDER BY modified_at DESC`).pluck().all()
+    expect(shas).toHaveLength(SKILL_REVISION_RETAIN)
+    expect(shas[0]).toBe(newest[0]!.sha)
+    expect(shas.some(sha => String(sha).startsWith('old-'))).toBe(false)
+  })
+
+  it('leaves a Skill with few revisions alone', async () => {
+    github.getCommitsBatch.mockResolvedValue({
+      status: 200,
+      data: new Map([['skills/one/SKILL.md', [commit(2), commit(1)]]]),
+      rateLimit: null,
+      notModified: false,
+    })
+
+    await syncRepo('acme', 'skills', {}, db, { ownerVerified: true })
+
+    expect(sqlite.prepare(`SELECT sha FROM skill_revisions ORDER BY modified_at DESC`).pluck().all()).toEqual(['sha-002', 'sha-001'])
+  })
+})
+
+function createDatabase(): Database.Database {
+  const sqlite = new Database(':memory:')
+  sqlite.exec(`
+    CREATE TABLE repos (
+      owner TEXT NOT NULL, repo TEXT NOT NULL, default_branch TEXT, stars INTEGER NOT NULL DEFAULT 0,
+      forks INTEGER NOT NULL DEFAULT 0, pushed_at INTEGER, repo_created_at INTEGER,
+      repo_meta_synced_at INTEGER, description TEXT, last_tree_sha TEXT, repo_kind TEXT NOT NULL DEFAULT 'creator',
+      repo_kind_source TEXT NOT NULL DEFAULT 'computed', repo_skill_count INTEGER NOT NULL DEFAULT 0,
+      broken_since INTEGER, tree_truncated_at INTEGER, source_owner TEXT, source_repo TEXT, repository_id INTEGER, is_fork INTEGER, PRIMARY KEY (owner, repo)
+    );
+    CREATE TABLE skills (
+      name TEXT NOT NULL, owner TEXT NOT NULL, repo TEXT NOT NULL, display_name TEXT NOT NULL,
+      installs INTEGER NOT NULL DEFAULT 0, slug TEXT NOT NULL, description TEXT, current_sha TEXT,
+      modified_at INTEGER, first_seen_at INTEGER, references_count INTEGER NOT NULL DEFAULT 0,
+      assets TEXT NOT NULL DEFAULT '[]', last_synced_at INTEGER, sync_status TEXT,
+      is_official INTEGER NOT NULL DEFAULT 0, source_resolved INTEGER NOT NULL DEFAULT 0,
+      seo_index_score INTEGER NOT NULL DEFAULT 0, seo_indexable INTEGER NOT NULL DEFAULT 0,
+      seo_index_reasons TEXT NOT NULL DEFAULT '[]', seo_index_synced_at INTEGER,
+      trust_tier TEXT NOT NULL DEFAULT 'untrusted', trust_source TEXT NOT NULL DEFAULT 'computed',
+      trust_score INTEGER NOT NULL DEFAULT 0, trust_reasons TEXT NOT NULL DEFAULT '[]', trust_synced_at INTEGER,
+      rendered_skill_path TEXT, rendered_commit_sha TEXT, rendered_status TEXT, rendered_raw TEXT, rendered_raw_sha256 TEXT, rendered_frontmatter TEXT,
+      rendered_html TEXT, rendered_at INTEGER, owner_verified INTEGER NOT NULL DEFAULT 0,
+      PRIMARY KEY (owner, repo, name)
+    );
+    CREATE TABLE skill_revisions (
+      owner TEXT NOT NULL, repo TEXT NOT NULL, name TEXT NOT NULL, sha TEXT NOT NULL,
+      modified_at INTEGER NOT NULL, author_login TEXT, message TEXT,
+      PRIMARY KEY (owner, repo, name, sha)
+    );
+    CREATE TABLE activity (
+      type TEXT NOT NULL, owner TEXT NOT NULL, repo TEXT, name TEXT NOT NULL,
+      occurred_at INTEGER NOT NULL, ingested_at INTEGER NOT NULL, sha TEXT
+    );
+    CREATE TABLE skill_dirty (
+      owner TEXT NOT NULL, repo TEXT NOT NULL, name TEXT NOT NULL, reason TEXT NOT NULL,
+      queued_at INTEGER NOT NULL, attempts INTEGER NOT NULL DEFAULT 0,
+      PRIMARY KEY (owner, repo, name, reason)
+    );
+    CREATE TABLE repo_trust_overrides (
+      owner TEXT NOT NULL, repo TEXT NOT NULL, tier TEXT NOT NULL, reason TEXT,
+      PRIMARY KEY (owner, repo)
+    );
+    CREATE TABLE repo_kind_overrides (
+      owner TEXT NOT NULL, repo TEXT NOT NULL, kind TEXT NOT NULL,
+      PRIMARY KEY (owner, repo)
+    );
+    CREATE TABLE skill_repo_eligibility (
+      owner TEXT NOT NULL, repo TEXT NOT NULL,
+      status TEXT NOT NULL CHECK (status IN ('eligible', 'rejected')),
+      reason TEXT NOT NULL, reviewed_by TEXT NOT NULL,
+      reviewed_at INTEGER NOT NULL DEFAULT (unixepoch()),
+      PRIMARY KEY (owner, repo)
+    );
+    CREATE TABLE repo_star_observations (
+      owner TEXT NOT NULL, repo TEXT NOT NULL, observed_day INTEGER NOT NULL,
+      stars INTEGER NOT NULL, PRIMARY KEY (owner, repo, observed_day)
+    );
+  `)
+  return sqlite
+}
+
+interface BoundStatement {
+  executeSync: () => D1Result<unknown>
+  run: () => Promise<D1Result<unknown>>
+  all: <T>() => Promise<D1Result<T>>
+  first: <T>() => Promise<T | null>
+}
+
+function wrapSqlite(sqlite: Database.Database): D1Database {
+  const prepare = (sql: string) => ({
+    bind(...params: unknown[]): BoundStatement {
+      const executeSync = () => {
+        const result = sqlite.prepare(sql).run(...params)
+        return { meta: { changes: result.changes } } as D1Result<unknown>
+      }
+      return {
+        executeSync,
+        run: async () => executeSync(),
+        async all<T>() {
+          return { results: sqlite.prepare(sql).all(...params) as T[] } as D1Result<T>
+        },
+        async first<T>() {
+          return (sqlite.prepare(sql).get(...params) as T | undefined) ?? null
+        },
+      }
+    },
+  })
+  return {
+    prepare,
+    async batch<T>(statements: D1PreparedStatement[]) {
+      const run = sqlite.transaction(() => statements.map(statement => (statement as unknown as BoundStatement).executeSync()))
+      return run() as D1Result<T>[]
+    },
+  } as unknown as D1Database
+}