diff --git a/src/society.ts b/src/society.ts
index 51b4b87a1..5760a2750 100644
--- a/src/society.ts
+++ b/src/society.ts
@@ -5728,6 +5728,20 @@ export async function createPayoutReceipt(env: Env, submitter: Citizen, bindingI
   const existing = await env.DB.prepare("SELECT id FROM payout_receipts WHERE binding_id = ?")
     .bind(bindingId).first<{ id: number }>();
   if (existing) throw new SocietyError(409, `binding ${bindingId} already has payout receipt ${existing.id}; one scoped authorization settles once`);
+  // AND IT SETTLES ONCE ACROSS BOTH SETTLEMENT FACTS. The observer can settle
+  // this binding's award from an on-chain transfer, which cuts no receipt row,
+  // so the check above cannot see it. The settler already refuses the mirror
+  // case (a transfer that is already a receipt, auditor P6 in settleOneObserved);
+  // without this guard a receipt filed after an observed settlement — for the
+  // same transfer or another — stands beside it, and the binding carries two
+  // settlement facts for one authorization. GET /api/payout-bindings/:id then
+  // serves settled_by:"receipt" with the observed transfer hidden, so the record
+  // of how the award was actually paid is overwritten by the later filing.
+  const observedSettlement = await env.DB.prepare(
+    "SELECT id, settled_award_id FROM observed_transfers WHERE binding_id = ? AND settled_award_id IS NOT NULL LIMIT 1",
+  ).bind(bindingId).first<{ id: number; settled_award_id: number }>();
+  if (observedSettlement)
+    throw new SocietyError(409, `binding ${bindingId} was already settled by observed transfer ${observedSettlement.id} (award ${observedSettlement.settled_award_id}); one scoped authorization settles once`);
 
   // MAKE THE #188 ROWS INERT, not merely labelled. Bindings 163 and 164
   // authorize six-decimal USDC against a listing priced in eighteen-decimal
diff --git a/test/payout-receipt-after-observed.test.ts b/test/payout-receipt-after-observed.test.ts
new file mode 100644
index 000000000..b91b2f3e2
--- /dev/null
+++ b/test/payout-receipt-after-observed.test.ts
@@ -0,0 +1,72 @@
+// A binding settles once, across both settlement facts. The observer settles an
+// award from an on-chain transfer without cutting a payout_receipts row, and
+// createPayoutReceipt only checked payout_receipts for an earlier settlement.
+// So a receipt filed after an observed settlement was recorded beside it: one
+// binding, one award, two settlement facts, and GET /api/payout-bindings/:id
+// switched to settled_by:"receipt" with the observed transfer hidden. The
+// settler already refused the mirror order (a transfer already receipted,
+// auditor P6); this pins the receipt side.
+//
+// Killing mutation: delete the observed_transfers guard in createPayoutReceipt
+// -> the observed-settled binding gets past it to body validation, which
+// refuses with a 400 rather than the 409 naming the observed transfer, and the
+// first test goes red. The second test (an unsettled binding must NOT get that
+// 409) keeps the guard from being written as a blanket refusal.
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { createPayoutReceipt, SocietyError, type Env } from "../src/society.ts";
+import { sqliteTestEnv } from "./helpers/sqlite-d1.ts";
+
+const SCHEMA = readFileSync(fileURLToPath(new URL("../schema.sql", import.meta.url)), "utf8");
+const TOKEN = "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913";
+const ADDR = "0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+const PAYEE = { id: 1, handle: "payee", model: "test-model" };
+
+function bindRow(id: number, docket: string): string {
+  // Column order matches schema.sql payout_bindings; wallet_signature set,
+  // wallet_proof_id null (the one-proof CHECK). expiry far in the future.
+  return `(${id}, 1, '${docket}', '1f916.payout.v1', '1000000', 8453, '${TOKEN}', '${ADDR}', 9999999999, '0xsig', NULL, 'pk', 'csig', 'tp-${id}', 'self', 100, 'valid-at-binding-event', 100, '{}', '2026-01-01', '{}', 'pre-${id}', 'ah-${id}', 'ph-${id}', 'cn-${id}', 200)`;
+}
+
+function seeded(): Env {
+  const { env, db } = sqliteTestEnv(SCHEMA);
+  // The settling observed transfer names an award row this test does not seed;
+  // D1 does not enforce foreign keys, and the guard reads observed_transfers only.
+  db.exec("PRAGMA foreign_keys = OFF");
+  db.exec(`
+    INSERT INTO citizens (id, handle, model, secret_hash, created_at, last_seen_at)
+      VALUES (1, 'payee', 'test-model', 'h1', 100, 100);
+    INSERT INTO payout_bindings (
+      id, citizen_id, docket_id, version, amount_atomic, chain_id, token, payout_address, expiry,
+      wallet_signature, wallet_proof_id, citizen_public_key, citizen_signature, citizen_key_thumbprint,
+      citizen_key_custody, citizen_key_bound_at, authorization_verification, authorization_verified_at,
+      docket_acceptance, docket_updated, docket_snapshot, preimage, authorization_hash, payload_hash,
+      commit_nonce, created_at
+    ) VALUES ${bindRow(2, "listing-91")}, ${bindRow(3, "listing-92")};
+    -- Binding 2: its award settled by an observed transfer; no receipt row.
+    INSERT INTO observed_transfers (funder_address, to_address, token, amount_atomic, tx_hash, log_index, block_number, kind, binding_id, listing_id, citizen_id, sources, observed_at, settled_award_id, settlement_checked_at, block_timestamp)
+      VALUES ('${ADDR}', '${ADDR}', '${TOKEN}', '1000000', '0xobservedtx', 0, 51480102, 'payment', 2, 91, 1, 2, 100, 11, 100, 100);
+    -- Binding 3: an observed payment the settler declined (settled_award_id null)
+    -- is not a settlement, so it must not block a receipt.
+    INSERT INTO observed_transfers (funder_address, to_address, token, amount_atomic, tx_hash, log_index, block_number, kind, binding_id, listing_id, citizen_id, sources, observed_at, settled_award_id, settlement_checked_at, block_timestamp)
+      VALUES ('${ADDR}', '${ADDR}', '${TOKEN}', '1000000', '0xdeclinedtx', 0, 51480103, 'payment', 3, 92, 1, 2, 100, NULL, 100, 100);
+  `);
+  return env;
+}
+
+test("a receipt on a binding already settled by an observed transfer is refused 409, naming the transfer and award", async () => {
+  await assert.rejects(
+    createPayoutReceipt(seeded(), PAYEE as never, 2, {} as never),
+    (e: SocietyError) => e.status === 409 && /settled by observed transfer 1 \(award 11\)/.test(e.message),
+  );
+});
+
+test("a binding whose observed payment settled nothing is not refused by the observed-settlement guard", async () => {
+  await assert.rejects(
+    createPayoutReceipt(seeded(), PAYEE as never, 3, {} as never),
+    (e: SocietyError) => !/settled by observed transfer/.test(e.message),
+  );
+});