diff --git a/.changeset/import-undo-preserveaudit.md b/.changeset/import-undo-preserveaudit.md
new file mode 100644
index 0000000000..ec45d9a1a6
--- /dev/null
+++ b/.changeset/import-undo-preserveaudit.md
@@ -0,0 +1,17 @@
+---
+"@objectstack/rest": patch
+---
+
+fix(rest): undo of a historical import now preserves the audit timeline (#3549)
+
+A `treatAsHistorical` import writes with `preserveAudit` (#3493), keeping the
+original `updated_at`/`updated_by` and business `readonly` fields instead of
+stamping-now / stripping them. Its undo route, however, restored the captured
+pre-import snapshot with a plain write context — so the audit auto-stamp
+re-wrote `updated_at`/`updated_by` to "now", silently corrupting the very
+timeline the historical import had preserved.
+
+The undo write context now mirrors the import's own: it carries
+`preserveAudit` iff the job row is flagged `treat_as_historical`, so restoring
+`u.before` re-writes the snapshotted audit/timestamp values verbatim. A normal
+import's undo is unchanged (default stamp/strip).
diff --git a/packages/rest/src/import-job-integration.test.ts b/packages/rest/src/import-job-integration.test.ts
index 097f64e7a8..66b6e6bc4a 100644
--- a/packages/rest/src/import-job-integration.test.ts
+++ b/packages/rest/src/import-job-integration.test.ts
@@ -96,6 +96,7 @@ const SYS_IMPORT_JOB = {
     write_mode: { name: 'write_mode', type: 'text' as const },
     dry_run: { name: 'dry_run', type: 'boolean' as const },
     run_automations: { name: 'run_automations', type: 'boolean' as const },
+    treat_as_historical: { name: 'treat_as_historical', type: 'boolean' as const },
     error: { name: 'error', type: 'textarea' as const },
     results: { name: 'results', type: 'json' as const },
     started_at: { name: 'started_at', type: 'text' as const },
@@ -387,4 +388,66 @@ describe('async import job — real engine + protocol integration', () => {
     const res = await callJob(ctx.undo, 'imp_nope');
     expect(res._status).toBe(404);
   });
+
+  // #3549 — the undo write context must mirror the import's own write context.
+  // A historical import carries `preserveAudit` (#3493) so it keeps the original
+  // `updated_at`/`updated_by` (and business `readonly` fields) instead of
+  // stamping-now / stripping them. The undo restores the captured pre-import
+  // snapshot; if that restore write does NOT also carry `preserveAudit`, the
+  // audit auto-stamp re-writes `updated_at`/`updated_by` to "now" — silently
+  // corrupting the very timeline the historical import preserved. So undo of a
+  // historical import must set `preserveAudit`, and undo of a normal import
+  // must not. We assert on the write context the route hands the protocol.
+  function spyUpdateContexts() {
+    const seen: Array<{ object: string; context: any }> = [];
+    const orig = (ctx.protocol as any).updateData.bind(ctx.protocol);
+    (ctx.protocol as any).updateData = async (args: any) => {
+      seen.push({ object: args.object, context: args.context });
+      return orig(args);
+    };
+    return seen;
+  }
+
+  it('undo of a historical import carries preserveAudit on the restore write (#3549)', async () => {
+    // Seed an existing row so the historical upsert updates it (populates the undo log).
+    await ctx.protocol.createData({ object: 'task', data: { id: 'h_existing', title: 'orig', score: 1 } });
+
+    const created = await callCreate(ctx.create, {
+      format: 'json', writeMode: 'upsert', matchFields: ['id'], treatAsHistorical: true,
+      rows: [{ id: 'h_existing', title: 'historical', score: 42 }],
+    });
+    const jobId = created._json.jobId;
+    const done = await waitForTerminal(ctx.progress, jobId);
+    expect(done).toMatchObject({ status: 'succeeded', updated: 1 });
+    expect(done.undoable).toBe(true);
+
+    // Observe only the undo phase.
+    const seen = spyUpdateContexts();
+    const u = await callJob(ctx.undo, jobId);
+    expect(u._json).toMatchObject({ success: true, restored: 1 });
+
+    const restoreWrites = seen.filter((s) => s.object === 'task');
+    expect(restoreWrites.length).toBeGreaterThan(0);
+    for (const w of restoreWrites) expect(w.context?.preserveAudit).toBe(true);
+  });
+
+  it('undo of a normal import does NOT set preserveAudit — default stamp/strip (#3549)', async () => {
+    await ctx.protocol.createData({ object: 'task', data: { id: 'n_existing', title: 'orig', score: 1 } });
+
+    const created = await callCreate(ctx.create, {
+      format: 'json', writeMode: 'upsert', matchFields: ['id'], // treatAsHistorical omitted
+      rows: [{ id: 'n_existing', title: 'updated', score: 7 }],
+    });
+    const jobId = created._json.jobId;
+    const done = await waitForTerminal(ctx.progress, jobId);
+    expect(done).toMatchObject({ status: 'succeeded', updated: 1 });
+
+    const seen = spyUpdateContexts();
+    const u = await callJob(ctx.undo, jobId);
+    expect(u._json).toMatchObject({ success: true, restored: 1 });
+
+    const restoreWrites = seen.filter((s) => s.object === 'task');
+    expect(restoreWrites.length).toBeGreaterThan(0);
+    for (const w of restoreWrites) expect(w.context?.preserveAudit).toBeUndefined();
+  });
 });
diff --git a/packages/rest/src/rest-server.ts b/packages/rest/src/rest-server.ts
index 78f87a2acb..c3dd61de0b 100644
--- a/packages/rest/src/rest-server.ts
+++ b/packages/rest/src/rest-server.ts
@@ -4049,7 +4049,20 @@ export class RestServer {
                     // re-writes the row's earlier state, which need not be a legal
                     // transition from where it is now — an undo reinstates an established
                     // fact, it does not walk the FSM.
-                    const writeCtx = { ...(context ?? {}), skipAutomations: true, skipStateMachine: true };
+                    //
+                    // For a historical import (#3493/#3549), the undo write must mirror
+                    // the import's own write context: carry `preserveAudit` so restoring
+                    // `u.before` re-writes the captured `updated_at`/`updated_by` (and any
+                    // business `readonly` fields in the snapshot) verbatim, rather than
+                    // stamping-now / stripping them. Without this, undoing a historical
+                    // import would silently rewrite the audit timeline the import took
+                    // pains to preserve. A normal import keeps the default (stamp/strip).
+                    const writeCtx = {
+                        ...(context ?? {}),
+                        skipAutomations: true,
+                        skipStateMachine: true,
+                        ...(row.treat_as_historical ? { preserveAudit: true } : {}),
+                    };
                     let deleted = 0, restored = 0, failed = 0;
 
                     // Delete created records first (they didn't exist before).