diff --git a/chaincode/src/contracts/GalaContract.spec.ts b/chaincode/src/contracts/GalaContract.spec.ts
index a4c7abd9d2..fcb40c7826 100644
--- a/chaincode/src/contracts/GalaContract.spec.ts
+++ b/chaincode/src/contracts/GalaContract.spec.ts
@@ -403,7 +403,9 @@ describe("GalaContract.DryRun", () => {
           Message: "DTO validation failed: (1) isPositive: age must be a positive number"
         },
         reads: { [callerProfileKey]: "" },
-        writes: {},
+        writes: {
+          [`\u0000UNTX\u0000${dto.uniqueKey}\u0000`]: expect.any(String)
+        },
         deletes: {}
       }
     });
diff --git a/chaincode/src/contracts/GalaTransaction.ts b/chaincode/src/contracts/GalaTransaction.ts
index 750482789c..96c1fb8b10 100644
--- a/chaincode/src/contracts/GalaTransaction.ts
+++ b/chaincode/src/contracts/GalaTransaction.ts
@@ -35,7 +35,7 @@ import {
 import { Object as DTOObject, Transaction } from "fabric-contract-api";
 import { inspect } from "util";
 
-import { UniqueTransactionService } from "../services";
+import { UniqueTransactionConflictError, UniqueTransactionService } from "../services";
 import { GalaChainContext } from "../types";
 import { GalaContract } from "./GalaContract";
 import { updateApi } from "./GalaContractApi";
@@ -112,6 +112,48 @@ function isArrayOut<Out>(x: OutType<Out> | OutArrType<Out> | undefined): x is Ou
   return typeof x === "object" && "arrayOf" in x;
 }
 
+/** uniqueKey is a global nonce; read it from the raw submit, not the method DTO. */
+function readUniqueKeyFromPlain(dtoPlain: unknown): string | undefined {
+  if (dtoPlain == null) {
+    return undefined;
+  }
+
+  let plain: unknown = dtoPlain;
+  if (typeof dtoPlain === "string") {
+    try {
+      plain = JSON.parse(dtoPlain);
+    } catch {
+      return undefined;
+    }
+  }
+
+  if (typeof plain !== "object" || plain === null || Array.isArray(plain)) {
+    return undefined;
+  }
+
+  const uniqueKey = (plain as { uniqueKey?: unknown }).uniqueKey;
+  return typeof uniqueKey === "string" && uniqueKey.length > 0 ? uniqueKey : undefined;
+}
+
+function isUniqueTransactionConflict(err: unknown): boolean {
+  return ChainError.matches(ChainError.from(err as object), UniqueTransactionConflictError);
+}
+
+async function persistUniqueKeyOnFailure(
+  ctx: GalaChainContext,
+  uniqueKey: string | undefined
+): Promise<void> {
+  if (!uniqueKey) {
+    return;
+  }
+
+  try {
+    await UniqueTransactionService.ensureUniqueTransaction(ctx, uniqueKey);
+  } catch (e) {
+    ChainError.recover(e, UniqueTransactionConflictError);
+  }
+}
+
 function Submit<In extends SubmitCallDTO, Out>(
   options: GalaSubmitOptions<In, Out>
 ): GalaTransactionDecoratorFunction {
@@ -192,6 +234,8 @@ function GalaTransaction<In extends ChainCallDTO, Out>(
 
       // ALS = SERVER so nested batch EVALUATE does not parent to batch.operation.
       return ctx.otel.run(async () => {
+        let uniqueKey: string | undefined;
+
         try {
           const metadata = [{ dto: dtoPlain }];
           ctx?.logger?.logTimeline("Begin Transaction", loggingContext, metadata);
@@ -217,6 +261,7 @@ function GalaTransaction<In extends ChainCallDTO, Out>(
                     dtoPlain as string | Record<string, unknown>,
                     validationOptions
                   );
+              uniqueKey = dto?.uniqueKey;
 
               if (dto?.dtoExpiresAt !== undefined && dto.dtoExpiresAt < ctx.txUnixTime) {
                 throw new ExpiredError(`DTO expired at ${new Date(dto.dtoExpiresAt).toISOString()}`);
@@ -251,12 +296,11 @@ function GalaTransaction<In extends ChainCallDTO, Out>(
                 // Record uniqueKey before the handler so a later business failure
                 // still consumes the key (flushed on error by afterTransaction).
                 if (options.enforceUniqueKey) {
-                  if (dto?.uniqueKey) {
-                    await UniqueTransactionService.ensureUniqueTransaction(ctx, dto.uniqueKey);
-                  } else {
+                  if (!uniqueKey) {
                     const message = `Missing uniqueKey in transaction dto for method '${method.name}'`;
                     throw new RuntimeError(message);
                   }
+                  await UniqueTransactionService.ensureUniqueTransaction(ctx, uniqueKey);
                 }
               });
 
@@ -290,6 +334,10 @@ function GalaTransaction<In extends ChainCallDTO, Out>(
             }
           );
         } catch (err) {
+          if (options.enforceUniqueKey && !isUniqueTransactionConflict(err)) {
+            await persistUniqueKeyOnFailure(ctx, uniqueKey ?? readUniqueKeyFromPlain(dtoPlain));
+          }
+
           const chainError = ChainError.from(err);
           ctx.otel.recordError(err);
 
diff --git a/chaincode/src/services/UniqueTransactionService.spec.ts b/chaincode/src/services/UniqueTransactionService.spec.ts
index 2428ca82d5..a51da454f6 100644
--- a/chaincode/src/services/UniqueTransactionService.spec.ts
+++ b/chaincode/src/services/UniqueTransactionService.spec.ts
@@ -12,7 +12,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { createValidDTO } from "@gala-chain/api";
+import { createValidDTO, signatures } from "@gala-chain/api";
 import { TestChaincode, transactionError, transactionErrorKey, transactionSuccess } from "@gala-chain/test";
 
 import TestGalaContract, { KVDto, SuperheroDto } from "../__test__/TestGalaContract";
@@ -49,6 +49,49 @@ describe("UniqueTransactionService", () => {
     expect(saveResponse).toEqual(transactionError());
   });
 
+  it("should consume uniqueKey when this endpoint rejects the DTO", async () => {
+    // Given a submit that fails CreateSuperhero validation but is valid for PutKv
+    const chaincode = new TestChaincode([TestGalaContract]);
+    const uniqueKey = "failed-parse-uk";
+
+    // When
+    const first = await chaincode.invoke("TestGalaContract:CreateSuperhero", JSON.stringify({ uniqueKey }));
+    const second = await chaincode.invoke(
+      "TestGalaContract:PutKv",
+      JSON.stringify({ uniqueKey, key: "should-not-persist", value: "robot" })
+    );
+
+    // Then the first endpoint rejects the DTO, but the uniqueKey is still consumed
+    expect(first).toEqual(transactionErrorKey("DTO_VALIDATION_FAILED"));
+    expect(second).toEqual(transactionErrorKey("UNIQUE_TRANSACTION_CONFLICT"));
+    expect(chaincode.getStateAll()["should-not-persist"]).toBeUndefined();
+  });
+
+  it("should consume uniqueKey when authentication fails", async () => {
+    // Given a signed submit DTO whose signature cannot recover a public key
+    const chaincode = new TestChaincode([TestGalaContract]);
+    const dto = await createValidDTO(SuperheroDto, {
+      name: "foo",
+      age: 2,
+      uniqueKey: "failed-auth-uk"
+    });
+    dto.signature = signatures.getDERSignature(
+      dto,
+      signatures.normalizePrivateKey(signatures.genKeyPair().privateKey)
+    );
+
+    // When
+    const first = await chaincode.invoke("TestGalaContract:CreateSuperhero", dto.serialize());
+    const second = await chaincode.invoke(
+      "TestGalaContract:PutKv",
+      JSON.stringify({ uniqueKey: dto.uniqueKey, key: "should-not-persist", value: "robot" })
+    );
+
+    // Then the first attempt fails auth, but the uniqueKey is still consumed
+    expect(first).toEqual(transactionErrorKey("MISSING_SIGNER"));
+    expect(second).toEqual(transactionErrorKey("UNIQUE_TRANSACTION_CONFLICT"));
+  });
+
   it("should consume uniqueKey when the submit handler fails", async () => {
     // Given
     const chaincode = new TestChaincode([TestGalaContract]);