diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 26834d1452..cdec07f83d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -144,6 +144,9 @@ jobs:
       - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version-file: .nvmrc
+      - name: Validate source architecture before dependency installation
+        if: needs.changes.outputs.code == 'true'
+        run: node scripts/verify/architecture-guards.mjs
       - name: Cache npm package downloads
         id: npm-cache
         uses: ./.github/actions/npm-cache
diff --git a/src/application/javascript/JavaScriptSemanticGraphExpressionProjection.ts b/src/application/javascript/JavaScriptSemanticGraphExpressionProjection.ts
index be3267b48f..fd5fb24321 100644
--- a/src/application/javascript/JavaScriptSemanticGraphExpressionProjection.ts
+++ b/src/application/javascript/JavaScriptSemanticGraphExpressionProjection.ts
@@ -5,6 +5,7 @@ import {
 } from "../../domain/javascript/javascriptSourceCoordinates.js";
 import type { JavaScriptSourceRange } from "../../domain/javascript/javascriptStaticAnalysisTypes.js";
 import type { JavaScriptSemanticGraphNode } from "../../domain/javascript/javascriptSemanticGraphSchemas.js";
+import { compositeKey } from "../../domain/unicodeCodePointOrder.js";
 import type { SemanticFlowProjectionContext } from "./JavaScriptSemanticGraphFlowProjection.js";
 import {
   addSemanticGraphRelation,
@@ -71,10 +72,11 @@ const operatorLiteralIndex = (
       return node;
     seen.add(node.node_id);
     const entry = { node, range, order: order++ };
-    const id = `${literalValueKey(value)}\0${javascriptSourceRangeKey(range)}`;
-    const group = byValue.get(literalValueKey(value)) ?? [];
+    const valueKey = literalValueKey(value);
+    const id = compositeKey([valueKey, javascriptSourceRangeKey(range)]);
+    const group = byValue.get(valueKey) ?? [];
     group.push(entry);
-    byValue.set(literalValueKey(value), group);
+    byValue.set(valueKey, group);
     if (!exact.has(id)) exact.set(id, entry);
     return node;
   };
@@ -92,7 +94,7 @@ const operatorLiteralIndex = (
         )
           best = entry;
       };
-      consider(exact.get(`${valueKey}\0${operandKey}`));
+      consider(exact.get(compositeKey([valueKey, operandKey])));
       const group = byValue.get(valueKey) ?? [];
       let low = 0;
       let high = group.length;
diff --git a/tests/boundary/filesystem/ciCachePolicy.test.ts b/tests/boundary/filesystem/ciCachePolicy.test.ts
index 6b5b22f913..058c47c94b 100644
--- a/tests/boundary/filesystem/ciCachePolicy.test.ts
+++ b/tests/boundary/filesystem/ciCachePolicy.test.ts
@@ -361,7 +361,7 @@ printf '%s\n' 'C:\Users\runner with spaces\AppData\Local\npm-cache'
     );
   });
 
-  it("replaces every inline setup-node npm cache immediately and preserves conditions", async () => {
+  it("pairs npm caches with preceding Node setup and preserves conditions", async () => {
     const workflows = await readWorkflows();
     let npmCacheSteps = 0;
 
@@ -377,12 +377,17 @@ printf '%s\n' 'C:\Users\runner with spaces\AppData\Local\npm-cache'
           const step = steps[index];
           if (step?.uses !== "./.github/actions/npm-cache") continue;
           npmCacheSteps++;
-          const setup = steps[index - 1];
+          const setup = steps
+            .slice(0, index)
+            .findLast(
+              (candidate) =>
+                typeof candidate.uses === "string" &&
+                candidate.uses.startsWith("actions/setup-node@"),
+            );
           expect(
-            typeof setup?.uses === "string" &&
-              setup.uses.startsWith("actions/setup-node@"),
-            `${file}:${jobName} npm cache action must immediately follow setup-node`,
-          ).toBe(true);
+            setup,
+            `${file}:${jobName} npm cache action requires preceding setup-node`,
+          ).toBeDefined();
           expect(step.if).toBe(setup?.if);
           expect(setup?.with).not.toHaveProperty("cache", "npm");
           const npmCiIndex = steps.findIndex(
diff --git a/tests/boundary/filesystem/ciRequiredLanes.test.ts b/tests/boundary/filesystem/ciRequiredLanes.test.ts
index 157c3454ee..8e994e4385 100644
--- a/tests/boundary/filesystem/ciRequiredLanes.test.ts
+++ b/tests/boundary/filesystem/ciRequiredLanes.test.ts
@@ -180,6 +180,33 @@ it("makes the required gate wait for every CI lane, including future additions",
   );
 });
 
+it("runs architecture guards for fast code feedback before installing dependencies", async () => {
+  const steps = z
+    .array(
+      z
+        .object({
+          run: z.string().optional(),
+          uses: z.string().optional(),
+          if: z.string().optional(),
+        })
+        .passthrough(),
+    )
+    .parse((await workflow()).jobs.static?.steps);
+  const guard = steps.findIndex(
+    (step) => step.run === "node scripts/verify/architecture-guards.mjs",
+  );
+  const setup = steps.findIndex((step) =>
+    step.uses?.startsWith("actions/setup-node@"),
+  );
+  const install = steps.findIndex((step) => step.run === "npm ci");
+  expect(guard).toBeGreaterThanOrEqual(0);
+  expect(setup).toBeGreaterThanOrEqual(0);
+  expect(install).toBeGreaterThan(guard);
+  expect(guard).toBeGreaterThan(setup);
+  expect(steps[guard]?.if).toBe("needs.changes.outputs.code == 'true'");
+  expect(steps[guard]?.["continue-on-error"]).toBeUndefined();
+});
+
 it("holds native and provider fan-out behind static validation while portable feedback stays independent", async () => {
   const { jobs } = await workflow();
   const earlyJobs = new Set([