diff --git a/src/app/api/quota/plans/[connectionId]/route.ts b/src/app/api/quota/plans/[connectionId]/route.ts
index 517db505dc..54bbd55577 100644
--- a/src/app/api/quota/plans/[connectionId]/route.ts
+++ b/src/app/api/quota/plans/[connectionId]/route.ts
@@ -5,7 +5,7 @@
  *
  * Auth: requireManagementAuth
  * Zod:  PlanUpsertSchema from @/shared/schemas/quota (PUT only)
- * Audit: quota.plan.updated on PUT (B26)
+ * Audit: quota.plan.updated on PUT and DELETE (B26 — DELETE reverts override to auto/catalog)
  * Sanitization: all error responses via buildErrorBody (Hard Rule #12, B25)
  *
  * For PUT: provider is derived from the connectionId via getProviderConnectionById.
@@ -115,9 +115,21 @@ export async function DELETE(request: Request, { params }: RouteParams): Promise
 
   try {
     const { connectionId } = await params;
-    // deleteProviderPlan returns true if a row was deleted, false if not found
-    // We return 204 either way (idempotent delete)
+
+    const existing = getProviderPlan(connectionId);
+    const provider = existing?.provider ?? (await resolveProvider(connectionId));
+
     deleteProviderPlan(connectionId);
+
+    const ctx = getAuditRequestContext(request);
+    logAuditEvent({
+      action: "quota.plan.updated",
+      target: connectionId,
+      metadata: { provider, source: "auto", reverted: true },
+      ipAddress: ctx.ipAddress ?? undefined,
+      requestId: ctx.requestId,
+    });
+
     return new Response(null, { status: 204 });
   } catch (err) {
     const message = err instanceof Error ? err.message : "Failed to delete plan";
diff --git a/src/i18n/messages/pt-BR.json b/src/i18n/messages/pt-BR.json
index 2341b3494d..91a5e25613 100644
--- a/src/i18n/messages/pt-BR.json
+++ b/src/i18n/messages/pt-BR.json
@@ -819,7 +819,7 @@
     "agentsAiSection": "Agents & AI",
     "cacheContextSection": "Cache & Context",
     "analyticsSection": "Analytics",
-    "costsSection": "Costs",
+    "costsSection": "Custos",
     "monitoringSection": "Monitoring",
     "auditSecuritySection": "Audit & Security",
     "devtoolsSection": "Dev Tools",
diff --git a/src/i18n/messages/pt.json b/src/i18n/messages/pt.json
index 2935420b9e..beb976af8c 100644
--- a/src/i18n/messages/pt.json
+++ b/src/i18n/messages/pt.json
@@ -819,7 +819,7 @@
     "agentsAiSection": "Agents & AI",
     "cacheContextSection": "Cache & Context",
     "analyticsSection": "Analytics",
-    "costsSection": "Costs",
+    "costsSection": "Custos",
     "monitoringSection": "Monitoring",
     "auditSecuritySection": "Audit & Security",
     "devtoolsSection": "Dev Tools",
diff --git a/tests/integration/quota-plans-crud.test.ts b/tests/integration/quota-plans-crud.test.ts
index 8f603e5ade..c580c3613d 100644
--- a/tests/integration/quota-plans-crud.test.ts
+++ b/tests/integration/quota-plans-crud.test.ts
@@ -238,6 +238,19 @@ test("DELETE /api/quota/plans/[connectionId] clears override → 204; GET revert
   // After delete, should fall back to catalog or empty (source=auto or manual-empty)
   // For a connectionId with no catalog match, source=manual + dimensions=[]
   assert.ok(["auto", "manual"].includes(body.plan.source));
+
+  // B26: DELETE must emit logAuditEvent with quota.plan.updated + metadata.reverted=true
+  const logs = compliance.getAuditLog({ action: "quota.plan.updated", limit: 20 });
+  const events = Array.isArray(logs) ? logs : [];
+  const deleteEvt = events.find(
+    (e) =>
+      typeof e === "object" &&
+      e !== null &&
+      (e as Record<string, unknown>).action === "quota.plan.updated" &&
+      (e as Record<string, unknown>).target === connectionId &&
+      (e as { metadata?: { reverted?: boolean } }).metadata?.reverted === true
+  );
+  assert.ok(deleteEvt, "quota.plan.updated audit event (reverted=true) must be present after DELETE");
 });
 
 test("DELETE /api/quota/plans/[connectionId] is idempotent → 204 even when not found", async () => {