diff --git a/packages/server/src/utils/federationOriginResolve.test.ts b/packages/server/src/utils/federationOriginResolve.test.ts
new file mode 100644
index 00000000..998ab1d8
--- /dev/null
+++ b/packages/server/src/utils/federationOriginResolve.test.ts
@@ -0,0 +1,91 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import Database from 'better-sqlite3';
+import { drizzle } from 'drizzle-orm/better-sqlite3';
+import fs from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import * as schema from '../db/schema.js';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+let sqlite: Database.Database;
+let testDb: ReturnType<typeof drizzle<typeof schema>>;
+let mockOurOrigin = 'https://home.test';
+
+vi.mock('../db/index.js', () => ({
+  getDb: () => testDb,
+  getRawDb: () => sqlite,
+  schema,
+}));
+
+vi.mock('./federationAuth.js', async (importActual) => {
+  const actual = await importActual<typeof import('./federationAuth.js')>();
+  return { ...actual, getOurOrigin: () => mockOurOrigin };
+});
+
+function applyMigrations(db: Database.Database): void {
+  const dir = path.resolve(__dirname, '../../drizzle');
+  for (const f of fs.readdirSync(dir).filter(f => f.endsWith('.sql')).sort()) {
+    const sqlText = fs.readFileSync(path.join(dir, f), 'utf8');
+    for (const stmt of sqlText.split(/-->\s*statement-breakpoint/)) {
+      const clean = stmt.trim();
+      if (clean) db.exec(clean);
+    }
+  }
+}
+
+function seedPeer(origin: string): void {
+  testDb.insert(schema.federationPeers).values({
+    id: `peer-${origin}`,
+    origin,
+    hmacSecret: 'a'.repeat(64),
+    status: 'active',
+    nonceSupported: 1,
+    createdAt: Date.now(),
+    consecutiveFailures: 0,
+    consecutiveAuthFailures: 0,
+  } as typeof schema.federationPeers.$inferInsert).run();
+}
+
+beforeEach(() => {
+  sqlite = new Database(':memory:');
+  testDb = drizzle(sqlite, { schema });
+  applyMigrations(sqlite);
+  mockOurOrigin = 'https://home.test';
+});
+
+describe('resolveOriginFromHostname', () => {
+  it('returns stored peer origin on exact host match', async () => {
+    seedPeer('https://orbit.test');
+    const { resolveOriginFromHostname } = await import('./federationOriginResolve.js');
+    expect(resolveOriginFromHostname('orbit.test')).toBe('https://orbit.test');
+  });
+
+  it('matches peer origin case-insensitively', async () => {
+    seedPeer('https://orbit.test');
+    const { resolveOriginFromHostname } = await import('./federationOriginResolve.js');
+    expect(resolveOriginFromHostname('ORBIT.TEST')).toBe('https://orbit.test');
+  });
+
+  it('mirrors https scheme when no peer matches', async () => {
+    mockOurOrigin = 'https://home.test';
+    const { resolveOriginFromHostname } = await import('./federationOriginResolve.js');
+    expect(resolveOriginFromHostname('newpeer.example')).toBe('https://newpeer.example');
+  });
+
+  it('mirrors http scheme for localhost targets', async () => {
+    mockOurOrigin = 'http://localhost:3005';
+    const { resolveOriginFromHostname } = await import('./federationOriginResolve.js');
+    expect(resolveOriginFromHostname('localhost:3006')).toBe('http://localhost:3006');
+  });
+
+  it('returns null when validateOrigin rejects http for non-localhost', async () => {
+    mockOurOrigin = 'http://localhost:3005';
+    const { resolveOriginFromHostname } = await import('./federationOriginResolve.js');
+    expect(resolveOriginFromHostname('newpeer.example')).toBeNull();
+  });
+
+  it('returns null for empty input', async () => {
+    const { resolveOriginFromHostname } = await import('./federationOriginResolve.js');
+    expect(resolveOriginFromHostname('')).toBeNull();
+  });
+});
diff --git a/packages/server/src/utils/federationOriginResolve.ts b/packages/server/src/utils/federationOriginResolve.ts
new file mode 100644
index 00000000..e04713f3
--- /dev/null
+++ b/packages/server/src/utils/federationOriginResolve.ts
@@ -0,0 +1,51 @@
+import { getDb } from '../db/index.js';
+import * as schema from '../db/schema.js';
+import { getOurOrigin } from './federationAuth.js';
+import { validateOrigin } from '../routes/federation.js';
+
+/**
+ * Resolve a typed hostname (e.g., the part after `@` in `alice@orbit.test`)
+ * into a full peer origin URL suitable for ensurePeered() / fetch().
+ *
+ * Resolution order:
+ *   1. If a federation_peers row exists whose URL host matches (case-insensitive),
+ *      return that peer's stored origin verbatim. (Authoritative for any peer the
+ *      admin has explicitly configured.)
+ *   2. Otherwise, mirror getOurOrigin()'s scheme:
+ *        - https://...  →  https://${hostname}
+ *        - http://...   →  http://${hostname}   (covers dev: localhost:3006)
+ *      Validate via validateOrigin (which rejects http for non-localhost).
+ *
+ * Returns null if the result fails validation (e.g., http for a public domain
+ * when our scheme is http — caller should surface as 'invalid target').
+ *
+ * Stale-scheme edge case: if a stored peer row points at the wrong scheme
+ * (peer migrated http↔https since the row was written), ensurePeered will
+ * surface a connectivity failure via the standard 'unreachable' path. Scheme
+ * migration of an existing peer is an admin operation outside this code's
+ * scope (delete + re-peer).
+ */
+export function resolveOriginFromHostname(hostnameOrHostPort: string): string | null {
+  if (!hostnameOrHostPort) return null;
+  const target = hostnameOrHostPort.trim().toLowerCase();
+  if (!target) return null;
+
+  const db = getDb();
+  const peers = db
+    .select({ origin: schema.federationPeers.origin })
+    .from(schema.federationPeers)
+    .all();
+
+  for (const p of peers) {
+    try {
+      const u = new URL(p.origin);
+      if (u.host.toLowerCase() === target) return p.origin;
+    } catch {
+      // skip malformed origin
+    }
+  }
+
+  const ourScheme = getOurOrigin().startsWith('https://') ? 'https://' : 'http://';
+  const candidate = `${ourScheme}${target}`;
+  return validateOrigin(candidate);
+}