diff --git a/package-lock.json b/package-lock.json
index 42f7677..c80ad25 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "getbased-relay",
-  "version": "1.1.0",
+  "version": "1.2.2",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "getbased-relay",
-      "version": "1.1.0",
+      "version": "1.2.2",
       "license": "AGPL-3.0-or-later",
       "dependencies": {
         "@evolu/common": "^7.4.0",
diff --git a/src/lib/admin-server.ts b/src/lib/admin-server.ts
index 25b2533..71fdb63 100644
--- a/src/lib/admin-server.ts
+++ b/src/lib/admin-server.ts
@@ -17,6 +17,7 @@ import type { RelayConfig } from "./config.js";
 import type { Logger } from "./logger.js";
 import type { Metrics } from "./metrics.js";
 import type { OwnerTracker } from "./owner-tracker.js";
+import { compactOwner } from "./compact-owner.js";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const pkg = JSON.parse(
@@ -105,51 +106,15 @@ export function createAdminServer(
       // is too short for a busy relay where the writer holds the lock during
       // a large batch ingest.
       db.pragma("busy_timeout = 30000");
-      // Run the SELECTs inside the same transaction so the deletedMessages
-      // count + before/after storedBytes are consistent with the DELETE/UPDATE
-      // — without this, a concurrent push between the SELECT and the write
-      // would yield a slightly stale count in the response.
-      let before: { storedBytes: number } | undefined;
-      let after: { storedBytes: number } | undefined;
-      let deletedMessages = 0;
-      const tx = db.transaction(() => {
-        before = db!
-          .prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?')
-          .get(ownerId) as { storedBytes: number } | undefined;
-        const cnt = db!
-          .prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?')
-          .get(ownerId) as { c: number };
-        deletedMessages = cnt.c;
-        db!
-          .prepare('DELETE FROM evolu_message WHERE "ownerId" = ?')
-          .run(ownerId);
-        db!
-          .prepare('UPDATE evolu_usage SET "storedBytes" = 0 WHERE "ownerId" = ?')
-          .run(ownerId);
-        after = db!
-          .prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?')
-          .get(ownerId) as { storedBytes: number } | undefined;
-      });
-      tx();
+      // Shared transaction with /self/compact-owner — single source of
+      // truth for what "compact this owner" means (see compact-owner.ts).
+      const result = compactOwner(db, ownerId);
       logger.emit("info", "admin.compact_owner", {
         ownerId: ownerIdStr,
-        deletedMessages,
-        beforeStoredBytes: before?.storedBytes ?? 0,
-        afterStoredBytes: after?.storedBytes ?? 0,
+        ...result,
       });
       res.writeHead(200, { "Content-Type": "application/json" });
-      res.end(
-        JSON.stringify(
-          {
-            ownerId: ownerIdStr,
-            deletedMessages,
-            beforeStoredBytes: before?.storedBytes ?? 0,
-            afterStoredBytes: after?.storedBytes ?? 0,
-          },
-          null,
-          2,
-        ),
-      );
+      res.end(JSON.stringify({ ownerId: ownerIdStr, ...result }, null, 2));
     } catch (e) {
       logger.emit("warn", "admin.compact_owner_failed", {
         ownerId: ownerIdStr,
diff --git a/src/lib/compact-owner.ts b/src/lib/compact-owner.ts
new file mode 100644
index 0000000..84c5b50
--- /dev/null
+++ b/src/lib/compact-owner.ts
@@ -0,0 +1,63 @@
+// Shared compact-owner transaction used by both /admin/compact-owner and
+// /self/compact-owner. Lives here so the two endpoints can't drift on what
+// "compact" actually wipes — every cleanup step (evolu_message rows,
+// evolu_timestamp merkle/fingerprint rows, evolu_usage bookkeeping) runs
+// inside one transaction so a partial failure can't strand the owner in
+// a half-cleaned state where the next client push gets rejected as
+// "already-seen" (see fix history at PR #10 for the production repro).
+
+import type Database from "better-sqlite3";
+
+export interface CompactOwnerResult {
+  deletedMessages: number;
+  beforeStoredBytes: number;
+  afterStoredBytes: number;
+}
+
+/**
+ * Atomically drops every relay-side trace of `ownerId`:
+ *  - evolu_message rows (the encrypted CRDT log)
+ *  - evolu_timestamp rows (the merkle/fingerprint table feeding negentropy
+ *    reconciliation — leaving these populated after evolu_message is gone
+ *    makes the relay report fingerprints for timestamps without payloads,
+ *    so peers' subsequent per-row pushes get rejected as "you already have
+ *    it" and silently disappear)
+ *  - evolu_usage.storedBytes / firstTimestamp / lastTimestamp (zeroed so
+ *    quota tracking matches reality and getOwnerUsage doesn't fall back
+ *    to stale bookkeeping pointing at deleted message rows)
+ *
+ * Caller passes an open `Database` handle with `busy_timeout` already set
+ * to whatever they want (admin and self both use 30s). The transaction is
+ * synchronous via better-sqlite3.
+ */
+export function compactOwner(
+  db: Database.Database,
+  ownerId: Buffer,
+): CompactOwnerResult {
+  let before: { storedBytes: number } | undefined;
+  let after: { storedBytes: number } | undefined;
+  let deletedMessages = 0;
+  const tx = db.transaction(() => {
+    before = db
+      .prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?')
+      .get(ownerId) as { storedBytes: number } | undefined;
+    const cnt = db
+      .prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?')
+      .get(ownerId) as { c: number };
+    deletedMessages = cnt.c;
+    db.prepare('DELETE FROM evolu_message WHERE "ownerId" = ?').run(ownerId);
+    db.prepare('DELETE FROM evolu_timestamp WHERE "ownerId" = ?').run(ownerId);
+    db.prepare(
+      'UPDATE evolu_usage SET "storedBytes" = 0, "firstTimestamp" = NULL, "lastTimestamp" = NULL WHERE "ownerId" = ?',
+    ).run(ownerId);
+    after = db
+      .prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?')
+      .get(ownerId) as { storedBytes: number } | undefined;
+  });
+  tx();
+  return {
+    deletedMessages,
+    beforeStoredBytes: before?.storedBytes ?? 0,
+    afterStoredBytes: after?.storedBytes ?? 0,
+  };
+}
diff --git a/src/lib/self-server.ts b/src/lib/self-server.ts
index f565bbd..9e9fa38 100644
--- a/src/lib/self-server.ts
+++ b/src/lib/self-server.ts
@@ -38,6 +38,7 @@ import { join } from "path";
 import Database from "better-sqlite3";
 import type { RelayConfig } from "./config.js";
 import type { Logger } from "./logger.js";
+import { compactOwner } from "./compact-owner.js";
 
 const TIMESTAMP_WINDOW_MS = 5 * 60 * 1000;
 const MAX_BODY_BYTES = 4096;
@@ -350,7 +351,8 @@ export function createSelfServer(
       return;
     }
 
-    // Run the same DELETE/UPDATE transaction as /admin/compact-owner.
+    // Shared transaction with /admin/compact-owner — single source of
+    // truth for what "compact this owner" means (see compact-owner.ts).
     // Open a fresh write-handle so we don't hold the lookup-DB hostage
     // during the WAL wait.
     const dbPath = join(config.dataDir, `${config.relayName}.db`);
@@ -358,40 +360,12 @@ export function createSelfServer(
     try {
       db = new Database(dbPath, { fileMustExist: true });
       db.pragma("busy_timeout = 30000");
-      let before: { storedBytes: number } | undefined;
-      let after: { storedBytes: number } | undefined;
-      let deletedMessages = 0;
-      const tx = db.transaction(() => {
-        before = db!
-          .prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?')
-          .get(ownerId) as { storedBytes: number } | undefined;
-        const cnt = db!
-          .prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?')
-          .get(ownerId) as { c: number };
-        deletedMessages = cnt.c;
-        db!
-          .prepare('DELETE FROM evolu_message WHERE "ownerId" = ?')
-          .run(ownerId);
-        db!
-          .prepare('UPDATE evolu_usage SET "storedBytes" = 0 WHERE "ownerId" = ?')
-          .run(ownerId);
-        after = db!
-          .prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?')
-          .get(ownerId) as { storedBytes: number } | undefined;
-      });
-      tx();
+      const result = compactOwner(db, ownerId);
       logger.emit("info", "self.compact_owner", {
         ownerId: ownerIdStr,
-        deletedMessages,
-        beforeStoredBytes: before?.storedBytes ?? 0,
-        afterStoredBytes: after?.storedBytes ?? 0,
-      });
-      jsonResponse(res, 200, {
-        ownerId: ownerIdStr,
-        deletedMessages,
-        beforeStoredBytes: before?.storedBytes ?? 0,
-        afterStoredBytes: after?.storedBytes ?? 0,
+        ...result,
       });
+      jsonResponse(res, 200, { ownerId: ownerIdStr, ...result });
     } catch (e) {
       logger.emit("warn", "self.compact_owner_failed", {
         ownerId: ownerIdStr,
diff --git a/test/compact-owner.test.mjs b/test/compact-owner.test.mjs
new file mode 100644
index 0000000..ae43a9f
--- /dev/null
+++ b/test/compact-owner.test.mjs
@@ -0,0 +1,138 @@
+// Unit test for the shared compactOwner helper. Both /admin/compact-owner
+// and /self/compact-owner call this function — testing it directly means
+// either route's coverage is automatic by construction.
+//
+// The self-server integration test (self-server.integration.test.mjs)
+// exercises the same helper end-to-end via the HTTP path. This file
+// covers the helper's contract in isolation: schema cleanup happens,
+// before/after counts are correct, idempotent on already-empty owners,
+// other owners' state is untouched.
+
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { randomBytes } from "node:crypto";
+import Database from "better-sqlite3";
+
+import { compactOwner } from "../dist/lib/compact-owner.js";
+
+function setup() {
+  const dbPath = join(mkdtempSync(join(tmpdir(), "compact-owner-test-")), "relay.db");
+  const db = new Database(dbPath);
+  db.exec(`
+    CREATE TABLE evolu_usage (
+      "ownerId" blob primary key,
+      "storedBytes" integer not null,
+      "firstTimestamp" blob,
+      "lastTimestamp" blob
+    ) strict;
+    CREATE TABLE evolu_message (
+      "ownerId" blob not null,
+      "timestamp" blob not null,
+      "change" blob not null,
+      primary key ("ownerId", "timestamp")
+    ) strict;
+    CREATE TABLE evolu_timestamp (
+      "ownerId" blob not null,
+      "t" blob not null,
+      "h1" integer, "h2" integer, "c" integer,
+      "l" integer not null,
+      primary key ("ownerId", "t")
+    ) strict;
+  `);
+  return { db };
+}
+
+function seedOwner(db, ownerIdBytes, { messageCount = 5, payloadBytes = 1000 } = {}) {
+  db.prepare('INSERT INTO evolu_usage ("ownerId", "storedBytes", "firstTimestamp", "lastTimestamp") VALUES (?, ?, ?, ?)')
+    .run(ownerIdBytes, messageCount * payloadBytes,
+         Buffer.from("ts-0", "utf8"), Buffer.from(`ts-${messageCount - 1}`, "utf8"));
+  const insertMsg = db.prepare('INSERT INTO evolu_message ("ownerId", "timestamp", "change") VALUES (?, ?, ?)');
+  const insertTs = db.prepare('INSERT INTO evolu_timestamp ("ownerId", "t", "h1", "h2", "c", "l") VALUES (?, ?, ?, ?, ?, ?)');
+  for (let i = 0; i < messageCount; i++) {
+    const ts = Buffer.from(`ts-${i}`, "utf8");
+    insertMsg.run(ownerIdBytes, ts, Buffer.alloc(payloadBytes));
+    insertTs.run(ownerIdBytes, ts, 0, 0, 0, 1);
+  }
+}
+
+test("compactOwner deletes evolu_message rows for the target owner", () => {
+  const { db } = setup();
+  const ownerIdBytes = randomBytes(16);
+  seedOwner(db, ownerIdBytes);
+
+  const result = compactOwner(db, ownerIdBytes);
+
+  assert.equal(result.deletedMessages, 5);
+  const after = db.prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?').get(ownerIdBytes);
+  assert.equal(after.c, 0);
+});
+
+test("compactOwner deletes evolu_timestamp rows (the merkle/fingerprint table)", () => {
+  // This is the regression guard for the production wedge: pre-fix,
+  // these rows survived compact, fed stale fingerprints to the negentropy
+  // reconciliation, and stranded every subsequent peer push.
+  const { db } = setup();
+  const ownerIdBytes = randomBytes(16);
+  seedOwner(db, ownerIdBytes);
+
+  const before = db.prepare('SELECT COUNT(*) as c FROM evolu_timestamp WHERE "ownerId" = ?').get(ownerIdBytes);
+  assert.equal(before.c, 5, "fixture sanity");
+
+  compactOwner(db, ownerIdBytes);
+
+  const after = db.prepare('SELECT COUNT(*) as c FROM evolu_timestamp WHERE "ownerId" = ?').get(ownerIdBytes);
+  assert.equal(after.c, 0, "evolu_timestamp must be empty post-compact (else fresh pushes get stranded)");
+});
+
+test("compactOwner zeroes storedBytes + clears first/lastTimestamp on evolu_usage", () => {
+  const { db } = setup();
+  const ownerIdBytes = randomBytes(16);
+  seedOwner(db, ownerIdBytes);
+
+  const result = compactOwner(db, ownerIdBytes);
+
+  assert.equal(result.beforeStoredBytes, 5000);
+  assert.equal(result.afterStoredBytes, 0);
+  const usage = db.prepare('SELECT * FROM evolu_usage WHERE "ownerId" = ?').get(ownerIdBytes);
+  assert.equal(usage.storedBytes, 0);
+  assert.equal(usage.firstTimestamp, null, "firstTimestamp pointed at a deleted message");
+  assert.equal(usage.lastTimestamp, null, "lastTimestamp pointed at a deleted message");
+});
+
+test("compactOwner is idempotent (deletedMessages=0 on already-empty owner)", () => {
+  const { db } = setup();
+  const ownerIdBytes = randomBytes(16);
+  seedOwner(db, ownerIdBytes);
+
+  compactOwner(db, ownerIdBytes);
+  const second = compactOwner(db, ownerIdBytes);
+
+  assert.equal(second.deletedMessages, 0);
+  assert.equal(second.beforeStoredBytes, 0);
+  assert.equal(second.afterStoredBytes, 0);
+});
+
+test("compactOwner does not touch other owners' state", () => {
+  // Defence-in-depth: a buggy WHERE clause refactor would silently wipe
+  // the wrong owner. This test confirms the helper is properly scoped.
+  const { db } = setup();
+  const ownerA = randomBytes(16);
+  const ownerB = randomBytes(16);
+  seedOwner(db, ownerA, { messageCount: 5 });
+  seedOwner(db, ownerB, { messageCount: 3 });
+
+  compactOwner(db, ownerA);
+
+  const aMsgs = db.prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?').get(ownerA);
+  const bMsgs = db.prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?').get(ownerB);
+  const bTs = db.prepare('SELECT COUNT(*) as c FROM evolu_timestamp WHERE "ownerId" = ?').get(ownerB);
+  const bUsage = db.prepare('SELECT * FROM evolu_usage WHERE "ownerId" = ?').get(ownerB);
+  assert.equal(aMsgs.c, 0, "compact target wiped");
+  assert.equal(bMsgs.c, 3, "other owner's messages untouched");
+  assert.equal(bTs.c, 3, "other owner's timestamps untouched");
+  assert.equal(bUsage.storedBytes, 3000, "other owner's storedBytes untouched");
+  assert.notEqual(bUsage.firstTimestamp, null, "other owner's first/lastTimestamp untouched");
+});
diff --git a/test/self-server.integration.test.mjs b/test/self-server.integration.test.mjs
index 908247e..122b371 100644
--- a/test/self-server.integration.test.mjs
+++ b/test/self-server.integration.test.mjs
@@ -64,8 +64,18 @@ before(async () => {
   for (let i = 0; i < 5; i++) {
     insertMsg.run(ownerIdBytes, Buffer.from(`ts-${i}`, "utf8"), Buffer.alloc(1000));
   }
-  // Manually set storedBytes to match what a real relay would have.
-  db.prepare('UPDATE evolu_usage SET "storedBytes" = 5000 WHERE "ownerId" = ?').run(ownerIdBytes);
+  // Seed the merkle/fingerprint table the way a real relay populates it
+  // alongside evolu_message. Compact must wipe these too — leaving them
+  // strands the owner because negentropy reports stale fingerprints for
+  // timestamps whose underlying messages we just deleted.
+  const insertTs = db.prepare('INSERT INTO evolu_timestamp ("ownerId", "t", "h1", "h2", "c", "l") VALUES (?, ?, ?, ?, ?, ?)');
+  for (let i = 0; i < 5; i++) {
+    insertTs.run(ownerIdBytes, Buffer.from(`ts-${i}`, "utf8"), 0, 0, 0, 1);
+  }
+  // Manually set storedBytes + first/lastTimestamp to match what a real
+  // relay would have written alongside the messages.
+  db.prepare('UPDATE evolu_usage SET "storedBytes" = 5000, "firstTimestamp" = ?, "lastTimestamp" = ? WHERE "ownerId" = ?')
+    .run(Buffer.from("ts-0", "utf8"), Buffer.from("ts-4", "utf8"), ownerIdBytes);
   db.close();
 
   // Boot the relay listener on a random port (let OS pick).
@@ -127,10 +137,14 @@ test("compact drops every evolu_message row and zeroes storedBytes", async () =>
   // Sanity: precondition.
   const db = new Database(dbPath, { readonly: true });
   const before = db.prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?').get(ownerIdBytes);
-  const beforeUsage = db.prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?').get(ownerIdBytes);
+  const beforeTs = db.prepare('SELECT COUNT(*) as c FROM evolu_timestamp WHERE "ownerId" = ?').get(ownerIdBytes);
+  const beforeUsage = db.prepare('SELECT "storedBytes", "firstTimestamp", "lastTimestamp" FROM evolu_usage WHERE "ownerId" = ?').get(ownerIdBytes);
   db.close();
   assert.equal(before.c, 5, "should have 5 message rows before compact");
+  assert.equal(beforeTs.c, 5, "should have 5 timestamp/fingerprint rows before compact");
   assert.equal(beforeUsage.storedBytes, 5000, "should have 5000 storedBytes before");
+  assert.notEqual(beforeUsage.firstTimestamp, null, "firstTimestamp should be seeded");
+  assert.notEqual(beforeUsage.lastTimestamp, null, "lastTimestamp should be seeded");
 
   // Sign + send compact.
   const ts = Date.now();
@@ -150,10 +164,19 @@ test("compact drops every evolu_message row and zeroes storedBytes", async () =>
   // Verify the actual DB state matches the response.
   const db2 = new Database(dbPath, { readonly: true });
   const after = db2.prepare('SELECT COUNT(*) as c FROM evolu_message WHERE "ownerId" = ?').get(ownerIdBytes);
-  const afterUsage = db2.prepare('SELECT "storedBytes" FROM evolu_usage WHERE "ownerId" = ?').get(ownerIdBytes);
+  const afterTs = db2.prepare('SELECT COUNT(*) as c FROM evolu_timestamp WHERE "ownerId" = ?').get(ownerIdBytes);
+  const afterUsage = db2.prepare('SELECT "storedBytes", "firstTimestamp", "lastTimestamp" FROM evolu_usage WHERE "ownerId" = ?').get(ownerIdBytes);
   db2.close();
   assert.equal(after.c, 0, "should have 0 message rows after compact");
+  // Critical regression guard: leaving evolu_timestamp populated after
+  // evolu_message is empty makes the negentropy reconciliation report
+  // fingerprints for timestamps that no longer have a payload, so
+  // peers' fresh per-row pushes get rejected as "already have it" and
+  // disappear. Verified in production 2026-05-06.
+  assert.equal(afterTs.c, 0, "should have 0 timestamp/fingerprint rows after compact (else fresh pushes get stranded)");
   assert.equal(afterUsage.storedBytes, 0, "should have 0 storedBytes after");
+  assert.equal(afterUsage.firstTimestamp, null, "firstTimestamp should be cleared (pointed at deleted messages)");
+  assert.equal(afterUsage.lastTimestamp, null, "lastTimestamp should be cleared (pointed at deleted messages)");
 });
 
 test("compact is idempotent (second call returns deletedMessages=0)", async () => {