diff --git a/.github/scripts/expect-order-scenario-failure.sh b/.github/scripts/expect-order-scenario-failure.sh
new file mode 100755
index 0000000..43ece21
--- /dev/null
+++ b/.github/scripts/expect-order-scenario-failure.sh
@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+#
+# order scenario テストは「リバランス後の Toyopa 保有額が 19,000 円ではなく
+# 20,000 円になる」という既知の不具合を再現したまま残してある。
+# このスクリプトは CI で以下を確認する。
+#
+#   1. order scenario テストが失敗すること(通ってしまったら CI を失敗させる)
+#   2. 期待した箇所(リバランス後の保有額の検証)で失敗していること
+#
+# Usage:
+#   EXPECTED_FAILURE="<substring>" expect-order-scenario-failure.sh <command> [args...]
+#
+# EXPECTED_FAILURE は改行区切りで複数指定でき、そのすべてが出力に含まれている
+# 必要がある。
+set -uo pipefail
+
+if [ $# -eq 0 ]; then
+  echo "usage: EXPECTED_FAILURE=<substring> $0 <command> [args...]" >&2
+  exit 2
+fi
+
+output_file="$(mktemp)"
+trap 'rm -f "${output_file}"' EXIT
+
+echo "::group::order scenario test output (failing on purpose)"
+"$@" 2>&1 | tee "${output_file}"
+status="${PIPESTATUS[0]}"
+echo "::endgroup::"
+
+if [ "${status}" -eq 0 ]; then
+  echo "::error::order scenario test passed unexpectedly. This test is expected to fail at the rebalance assertion (19000 != 20000)."
+  exit 1
+fi
+
+while IFS= read -r expected; do
+  if [ -z "${expected}" ]; then
+    continue
+  fi
+  if ! grep -qF -- "${expected}" "${output_file}"; then
+    echo "::error::order scenario test failed, but not at the expected assertion. Missing message: ${expected}"
+    exit 1
+  fi
+done <<< "${EXPECTED_FAILURE}"
+
+echo "OK: order scenario test failed at the expected assertion (exit status ${status})."
diff --git a/.github/workflows/test-go.yml b/.github/workflows/test-go.yml
index 0a8f867..4bd976a 100644
--- a/.github/workflows/test-go.yml
+++ b/.github/workflows/test-go.yml
@@ -6,6 +6,7 @@ on:
       - '.github/workflows/test-go.yml'
       - 'golang/**.go'
       - 'golang/go.mod'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -37,3 +38,9 @@ jobs:
       - run: go fmt ./...
       - run: go vet ./...
       - run: go test ./test/... -run TestOptimalPortfolioScenario
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            go test ./test/... -run TestOrderScenario
+        env:
+          EXPECTED_FAILURE: 'asset3 Toyopa amount: got 20000, want 19000'
diff --git a/.github/workflows/test-java17.yml b/.github/workflows/test-java17.yml
index 2ec39e8..d631c47 100644
--- a/.github/workflows/test-java17.yml
+++ b/.github/workflows/test-java17.yml
@@ -6,6 +6,7 @@ on:
       - '.github/workflows/test-java17.yml'
       - 'java17/src/**'
       - 'java17/pom.xml'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -37,3 +38,9 @@ jobs:
           java-version: ${{ matrix.java-version }}
           cache: maven
       - run: ./mvnw test -q -Dtest=OptimalPortfolioScenarioTest
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            ./mvnw test -q -Dtest=OrderScenarioTest
+        env:
+          EXPECTED_FAILURE: 'expected 19000 but was 20000'
diff --git a/.github/workflows/test-java8.yml b/.github/workflows/test-java8.yml
index 6ae6e82..f944011 100644
--- a/.github/workflows/test-java8.yml
+++ b/.github/workflows/test-java8.yml
@@ -6,6 +6,7 @@ on:
       - '.github/workflows/test-java8.yml'
       - 'java8/src/**'
       - 'java8/pom.xml'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -34,3 +35,9 @@ jobs:
           java-version: '8'
           cache: maven
       - run: ./mvnw test -q -Dtest=OptimalPortfolioScenarioTest
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            ./mvnw test -q -Dtest=OrderScenarioTest
+        env:
+          EXPECTED_FAILURE: 'expected 19000 but was 20000'
diff --git a/.github/workflows/test-php.yml b/.github/workflows/test-php.yml
index 1595187..6bb8a41 100644
--- a/.github/workflows/test-php.yml
+++ b/.github/workflows/test-php.yml
@@ -6,6 +6,7 @@ on:
       - '.github/workflows/test-php.yml'
       - 'php/src/**'
       - 'php/composer.json'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -34,3 +35,12 @@ jobs:
       - run: composer install --no-interaction --prefer-dist
       - run: find src -name '*.php' -exec php -l {} +
       - run: ./vendor/bin/phpunit tests/OptimalPortfolioScenarioTest.php
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            ./vendor/bin/phpunit tests/OrderScenarioTest.php
+        env:
+          EXPECTED_FAILURE: |
+            Failed asserting that two strings are identical.
+            '19000'
+            '20000'
diff --git a/.github/workflows/test-python.yml b/.github/workflows/test-python.yml
index 12ec909..5e6a0e5 100644
--- a/.github/workflows/test-python.yml
+++ b/.github/workflows/test-python.yml
@@ -6,6 +6,7 @@ on:
       - '.github/workflows/test-python.yml'
       - 'python/src/**'
       - 'python/pyproject.toml'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -35,3 +36,9 @@ jobs:
       - run: pip install ".[dev]"
       - run: find src -name '*.py' -exec python -m py_compile {} +
       - run: python -m pytest tests/test_optimal_portfolio_scenario.py
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            python -m pytest tests/test_order_scenario.py
+        env:
+          EXPECTED_FAILURE: "assert Decimal('20000') == Decimal('19000')"
diff --git a/.github/workflows/test-ruby.yml b/.github/workflows/test-ruby.yml
index 10f46f2..de00e2e 100644
--- a/.github/workflows/test-ruby.yml
+++ b/.github/workflows/test-ruby.yml
@@ -8,6 +8,7 @@ on:
       - 'ruby/spec/**'
       - 'ruby/Gemfile'
       - 'ruby/Gemfile.lock'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -40,3 +41,9 @@ jobs:
           working-directory: ruby
       - run: find lib -name '*.rb' -exec ruby -c {} +
       - run: bundle exec rspec spec/optimal_portfolio_scenario_spec.rb
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            bundle exec rspec spec/order_scenario_spec.rb
+        env:
+          EXPECTED_FAILURE: 'expect(BigDecimal(asset3_toyopa.amount_jpy)).to eq(BigDecimal("19000"))'
diff --git a/.github/workflows/test-scala.yml b/.github/workflows/test-scala.yml
index 85ba58b..9fce94a 100644
--- a/.github/workflows/test-scala.yml
+++ b/.github/workflows/test-scala.yml
@@ -7,6 +7,7 @@ on:
       - 'scala/src/**'
       - 'scala/build.sbt'
       - 'scala/project/**'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -40,3 +41,9 @@ jobs:
       - uses: sbt/setup-sbt@af116cce31c00823d3903ce687f9cda3a4f19f1b # v1
       - run: sbt compile
       - run: sbt "testOnly folio.codinginterview.OptimalPortfolioScenario"
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            sbt "testOnly folio.codinginterview.OrderScenario"
+        env:
+          EXPECTED_FAILURE: 'Expected 19000, but got 20000'
diff --git a/.github/workflows/test-typescript.yml b/.github/workflows/test-typescript.yml
index e4d8ff8..5df5fb6 100644
--- a/.github/workflows/test-typescript.yml
+++ b/.github/workflows/test-typescript.yml
@@ -6,7 +6,9 @@ on:
       - '.github/workflows/test-typescript.yml'
       - 'typescript/src/**'
       - 'typescript/package.json'
+      - 'typescript/tests/**'
       - 'typescript/tsconfig.json'
+      - '.github/scripts/expect-order-scenario-failure.sh'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -37,3 +39,9 @@ jobs:
       - run: npm ci
       - run: npm run build
       - run: npx vitest run tests/optimalPortfolioScenario.test.ts
+      - name: Order scenario test should fail at the rebalance assertion
+        run: |
+          "${GITHUB_WORKSPACE}/.github/scripts/expect-order-scenario-failure.sh" \
+            npx vitest run tests/orderScenario.test.ts
+        env:
+          EXPECTED_FAILURE: 'asset3 Toyopa amount: got 20000, want 19000'
diff --git a/typescript/tests/orderScenario.test.ts b/typescript/tests/orderScenario.test.ts
index ea81bb3..9dd223c 100644
--- a/typescript/tests/orderScenario.test.ts
+++ b/typescript/tests/orderScenario.test.ts
@@ -7,6 +7,19 @@ import { BadRequestException } from "../src/presentation/presentationException.j
 describe("Investment Operation", () => {
   let server: DummyServer;
 
+  // 失敗時に実測値がメッセージへ出るようにする(比較は Decimal 同士のまま)
+  const expectAmount = (label: string, actual: string, expected: string) => {
+    expect(
+      new Decimal(actual).equals(expected),
+      `${label}: got ${actual}, want ${expected}`,
+    ).toBe(true);
+  };
+
+  const totalOf = (asset: { cashAmount: string; stocks: { amountJpy: string }[] }) =>
+    asset.stocks
+      .map((e) => new Decimal(e.amountJpy))
+      .reduce((acc, v) => acc.plus(v), new Decimal(asset.cashAmount));
+
   beforeEach(async () => {
     server = DummyServer.default();
     await server.portfolioController.updateOptimalPortfolio({
@@ -17,57 +30,60 @@ describe("Investment Operation", () => {
     });
   });
 
-  it("存在しないユーザーへのリクエストは BadRequestException を返す", async () => {
+  it("新規注文・追加注文・リバランスの一連の操作が正しく機能する", async () => {
     const userId = randomUUID();
+
+    // Given: 存在しないユーザーで資産を取得しようとする
     let notFound: unknown;
     try {
       await server.assetController.getAsset({ userId });
     } catch (e) {
       notFound = e;
     }
+    // Then: BadRequestException が返される
     expect(notFound instanceof BadRequestException).toBe(true);
-  });
 
-  it("asset1: 新規注文 100,000円 が正しく機能する", async () => {
-    const userId = randomUUID();
-    // cash = floor0(100000 * 0.05) = 5000, investable = 100000 - 5000 = 95000
+    // When: 最適ポートフォリオを Toyopa=40%, Somy=60% に更新する
+    await server.portfolioController.updateOptimalPortfolio({
+      portfolios: [
+        { symbol: "Toyopa", rate: "0.40" },
+        { symbol: "Somy", rate: "0.60" },
+      ],
+    });
+
+    // And: 新規注文を 100,000 円で注文する
     await server.orderController.newOrder({ userId, amount: "100000" });
+
     const asset1 = await server.assetController.getAsset({ userId });
     expect(new Set(asset1.stocks.map((e) => e.symbol))).toEqual(new Set(["Toyopa", "Somy"]));
-    const total1 = asset1.stocks
-      .map((e) => new Decimal(e.amountJpy))
-      .reduce((acc, v) => acc.plus(v), new Decimal(0))
-      .plus(new Decimal(asset1.cashAmount));
+    const total1 = totalOf(asset1);
     expect(total1.minus(100000).abs().lessThanOrEqualTo(2)).toBe(true);
+
+    // Then: 現金比率5%に対して現金が 5,000円、最適ポートフォリオに基づき Toyopa の保有額が 38,000 円(40%)、Somy の保有額が 57,000 円(60%) となる
+    // cash = floor0(100000 * 0.05) = 5000, investable = 100000 - 5000 = 95000
     const asset1Toyopa = asset1.stocks.find((e) => e.symbol === "Toyopa")!;
     const asset1Somy = asset1.stocks.find((e) => e.symbol === "Somy")!;
-    expect(new Decimal(asset1Toyopa.amountJpy).equals("38000")).toBe(true); // floor0(95000 * 0.40) = 38000
-    expect(new Decimal(asset1Somy.amountJpy).equals("57000")).toBe(true);   // floor0(95000 * 0.60) = 57000
-    expect(new Decimal(asset1.cashAmount).equals("5000")).toBe(true);       // 100000 - 38000 - 57000
-  });
+    expectAmount("asset1 Toyopa amount", asset1Toyopa.amountJpy, "38000"); // floor0(95000 * 0.40) = 38000
+    expectAmount("asset1 Somy amount", asset1Somy.amountJpy, "57000");     // floor0(95000 * 0.60) = 57000
+    expectAmount("asset1 cash", asset1.cashAmount, "5000");                // 100000 - 38000 - 57000
 
-  it("asset2: 追加注文 100,000円 が正しく機能する", async () => {
-    const userId = randomUUID();
-    // totalAfter = 200000; investable = 200000 - floor0(200000 * 0.05) = 190000
-    await server.orderController.newOrder({ userId, amount: "100000" });
+    // When: 追加注文を 100,000 円で注文する
     await server.orderController.additionalOrder({ userId, amount: "100000" });
+
+    // Then: 資産合計が約 200,000 円になる
     const asset2 = await server.assetController.getAsset({ userId });
-    const total2 = asset2.stocks
-      .map((e) => new Decimal(e.amountJpy))
-      .reduce((acc, v) => acc.plus(v), new Decimal(0))
-      .plus(new Decimal(asset2.cashAmount));
+    const total2 = totalOf(asset2);
     expect(total2.minus(200000).abs().lessThanOrEqualTo(4)).toBe(true);
+
+    // And: 現金比率5%に対して現金が 10,000円、最適ポートフォリオに基づき Toyopa の保有額が 76,000 円(40%)、Somy の保有額が 114,000 円(60%) となる
+    // totalAfter = 200000; investable = 200000 - floor0(200000 * 0.05) = 190000
     const asset2Toyopa = asset2.stocks.find((e) => e.symbol === "Toyopa")!;
     const asset2Somy = asset2.stocks.find((e) => e.symbol === "Somy")!;
-    expect(new Decimal(asset2Toyopa.amountJpy).equals("76000")).toBe(true); // floor0(190000 * 0.40) = 76000
-    expect(new Decimal(asset2Somy.amountJpy).equals("114000")).toBe(true);  // floor0(190000 * 0.60) = 114000
-    expect(new Decimal(asset2.cashAmount).equals("10000")).toBe(true);      // 200000 - 76000 - 114000
-  });
+    expectAmount("asset2 Toyopa amount", asset2Toyopa.amountJpy, "76000");  // floor0(190000 * 0.40) = 76000
+    expectAmount("asset2 Somy amount", asset2Somy.amountJpy, "114000");     // floor0(190000 * 0.60) = 114000
+    expectAmount("asset2 cash", asset2.cashAmount, "10000");                // 200000 - 76000 - 114000
 
-  it("asset3: リバランス注文が正しく機能する", async () => {
-    const userId = randomUUID();
-    await server.orderController.newOrder({ userId, amount: "100000" });
-    await server.orderController.additionalOrder({ userId, amount: "100000" });
+    // When: 最適ポートフォリオを Toyopa=10%, Somy=90% に変更して、リバランス注文をする
     await server.portfolioController.updateOptimalPortfolio({
       portfolios: [
         { symbol: "Toyopa", rate: "0.10" },
@@ -75,12 +91,18 @@ describe("Investment Operation", () => {
       ],
     });
     await server.orderController.rebalanceOrder({ userId });
-    // total = 200000; investable = 200000 - floor0(200000 * 0.05) = 190000
+
+    // Then: リバランス後も資産合計がほぼ変わらない
     const asset3 = await server.assetController.getAsset({ userId });
+    const total3 = totalOf(asset3);
+    expect(total3.minus(total2).abs().lessThanOrEqualTo(4)).toBe(true);
+
+    // And: 現金比率5%に対して現金が 10,000円、最適ポートフォリオに基づき Toyopa の保有額が 19,000 円(10%)、Somy の保有額が 171,000 円(90%) となる
+    // total = 200000; investable = 200000 - floor0(200000 * 0.05) = 190000
     const asset3Toyopa = asset3.stocks.find((e) => e.symbol === "Toyopa")!;
     const asset3Somy = asset3.stocks.find((e) => e.symbol === "Somy")!;
-    expect(new Decimal(asset3Toyopa.amountJpy).equals("19000")).toBe(true); // floor0(190000 * 0.10) = 19000
-    expect(new Decimal(asset3Somy.amountJpy).equals("171000")).toBe(true);  // floor0(190000 * 0.90) = 171000
-    expect(new Decimal(asset3.cashAmount).equals("10000")).toBe(true);      // 200000 - 19000 - 171000
+    expectAmount("asset3 Toyopa amount", asset3Toyopa.amountJpy, "19000");  // floor0(190000 * 0.10) = 19000
+    expectAmount("asset3 Somy amount", asset3Somy.amountJpy, "171000");     // floor0(190000 * 0.90) = 171000
+    expectAmount("asset3 cash", asset3.cashAmount, "10000");                // 200000 - 19000 - 171000
   });
 });