diff --git a/scripts/lib/removal-fixture.ts b/scripts/lib/removal-fixture.ts
index 3d9bf58..87ee028 100644
--- a/scripts/lib/removal-fixture.ts
+++ b/scripts/lib/removal-fixture.ts
@@ -78,6 +78,9 @@ export async function runtimeImportGraph(
   const files = (await filesBelow(root))
     .filter((file) => /\.(?:[cm]?ts|tsx)$/u.test(file))
     .map((file) => path.resolve(file));
+  if (files.length === 0) {
+    throw new Error("removal fixture scanned module universe is empty");
+  }
   const sourceSet = new Set(files);
   const runtimeRoots = runtimeSourceRoots.map((entry) => path.resolve(root, entry));
   const imports = new Map<string, readonly string[]>();
@@ -124,6 +127,9 @@ export async function removeRuntimeDependentTests(
   runtimeSourceRoots: readonly string[],
 ): Promise<number> {
   const graph = await runtimeImportGraph(root, runtimeSourceRoots);
+  if (graph.dependentTests.length === 0) {
+    throw new Error("removal fixture: no runtime-dependent tests discovered");
+  }
   await Promise.all(graph.dependentTests.map((file) => rm(file, { force: true })));
   return graph.dependentTests.length;
 }
diff --git a/tests/unit/ci-workflow-generation.test.ts b/tests/unit/ci-workflow-generation.test.ts
index 5b65a2c..e0f9e48 100644
--- a/tests/unit/ci-workflow-generation.test.ts
+++ b/tests/unit/ci-workflow-generation.test.ts
@@ -195,7 +195,26 @@ describe("CI gate contract", () => {
     await writeFile(path.join(root, "package.json"), await readFile("package.json"));
 
     await expect(loadCiGateContract(root)).rejects.toThrow(
-      /canonical gate semantic shape|lacks a bound producer command/i,
+      /lacks a bound producer command/i,
+    );
+  });
+
+  it("rejects canonical gate name drift through the semantic-shape digest", async () => {
+    const root = await mkdtemp(path.join(tmpdir(), "ci-contract-gate-name-shape-"));
+    temporaryRoots.push(root);
+    await mkdir(path.join(root, "config/ci"), { recursive: true });
+    const contract = JSON.parse(
+      JSON.stringify(await loadCiGateContract(process.cwd())),
+    ) as Record<string, any>;
+    const gate = contract.gates.find(
+      (candidate: Record<string, any>) => candidate.id === "FE-GATE-013",
+    );
+    gate.name = `${gate.name}-renamed`;
+    await writeFile(path.join(root, "config/ci/gates.json"), `${JSON.stringify(contract)}\n`);
+    await writeFile(path.join(root, "package.json"), await readFile("package.json"));
+
+    await expect(loadCiGateContract(root)).rejects.toThrow(
+      /canonical gate semantic shape/i,
     );
   });
 
diff --git a/tests/unit/removal-fixture.test.ts b/tests/unit/removal-fixture.test.ts
index b88155b..9e303be 100644
--- a/tests/unit/removal-fixture.test.ts
+++ b/tests/unit/removal-fixture.test.ts
@@ -6,7 +6,10 @@ import { afterEach, expect, it } from "vitest";
 
 import { loadCiGateContract } from "../../scripts/contracts/ci-gates.ts";
 import {
+  assertNoRuntimeImports,
   pruneRemovalFixtureCiContract,
+  removeRuntimeDependentTests,
+  runtimeImportGraph,
 } from "../../scripts/lib/removal-fixture.ts";
 
 const temporaryRoots: string[] = [];
@@ -17,6 +20,39 @@ afterEach(async () => {
   );
 });
 
+it("rejects an empty scanned module universe", async () => {
+  const root = await mkdtemp(path.join(tmpdir(), "removal-fixture-empty-modules-"));
+  temporaryRoots.push(root);
+
+  await expect(runtimeImportGraph(root, ["src/runtime"])).rejects.toThrow(
+    /scanned module universe is empty/i,
+  );
+});
+
+it("rejects a runtime removal scan that discovers no dependent tests", async () => {
+  const root = await mkdtemp(path.join(tmpdir(), "removal-fixture-zero-dependent-tests-"));
+  temporaryRoots.push(root);
+  await mkdir(path.join(root, "src/runtime"), { recursive: true });
+  await mkdir(path.join(root, "tests"), { recursive: true });
+  await writeFile(path.join(root, "src/runtime/index.ts"), "export const runtime = true;\n");
+  await writeFile(path.join(root, "tests/unrelated.test.ts"), "export const unrelated = true;\n");
+
+  await expect(removeRuntimeDependentTests(root, ["src/runtime"])).rejects.toThrow(
+    /no runtime-dependent tests discovered/i,
+  );
+});
+
+it("allows zero runtime imports after the runtime has been removed", async () => {
+  const root = await mkdtemp(path.join(tmpdir(), "removal-fixture-post-removal-"));
+  temporaryRoots.push(root);
+  await mkdir(path.join(root, "tests"), { recursive: true });
+  await writeFile(path.join(root, "tests/unrelated.test.ts"), "export const unrelated = true;\n");
+
+  await expect(
+    assertNoRuntimeImports(root, ["src/runtime"], "fixture runtime"),
+  ).resolves.toBeUndefined();
+});
+
 it("prunes removed command and evidence references from a reduced CI contract", async () => {
   const root = await mkdtemp(path.join(tmpdir(), "removal-fixture-contract-"));
   temporaryRoots.push(root);