diff --git a/tests/unit/api/compression/compression-api.test.ts b/tests/unit/api/compression/compression-api.test.ts
new file mode 100644
index 0000000000..5f7cfc595f
--- /dev/null
+++ b/tests/unit/api/compression/compression-api.test.ts
@@ -0,0 +1,78 @@
+import { describe, it, beforeEach, afterEach } from "node:test";
+import assert from "node:assert/strict";
+import { fileURLToPath } from "node:url";
+import { dirname, join } from "node:path";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+describe("Compression Settings API Schema Validation", () => {
+  const compressionModeValues = ["off", "lite", "standard", "aggressive", "ultra"];
+
+  it("should validate all compression mode values", () => {
+    assert.deepStrictEqual(compressionModeValues, [
+      "off",
+      "lite",
+      "standard",
+      "aggressive",
+      "ultra",
+    ]);
+  });
+
+  it("should validate caveman config structure", () => {
+    const defaultCavemanConfig = {
+      enabled: true,
+      compressRoles: ["user"],
+      skipRules: [],
+      minMessageLength: 50,
+      preservePatterns: [],
+    };
+
+    assert.equal(defaultCavemanConfig.enabled, true);
+    assert.deepStrictEqual(defaultCavemanConfig.compressRoles, ["user"]);
+    assert.equal(Array.isArray(defaultCavemanConfig.skipRules), true);
+    assert.equal(defaultCavemanConfig.minMessageLength, 50);
+    assert.equal(Array.isArray(defaultCavemanConfig.preservePatterns), true);
+  });
+
+  it("should validate full compression config structure", () => {
+    const defaultConfig = {
+      enabled: false,
+      defaultMode: "off",
+      autoTriggerTokens: 0,
+      cacheMinutes: 5,
+      preserveSystemPrompt: true,
+      comboOverrides: {},
+      cavemanConfig: {
+        enabled: true,
+        compressRoles: ["user"],
+        skipRules: [],
+        minMessageLength: 50,
+        preservePatterns: [],
+      },
+    };
+
+    assert.equal(defaultConfig.enabled, false);
+    assert.ok(compressionModeValues.includes(defaultConfig.defaultMode));
+    assert.equal(typeof defaultConfig.autoTriggerTokens, "number");
+    assert.equal(typeof defaultConfig.cacheMinutes, "number");
+    assert.equal(typeof defaultConfig.preserveSystemPrompt, "boolean");
+    assert.equal(typeof defaultConfig.comboOverrides, "object");
+    assert.equal(typeof defaultConfig.cavemanConfig, "object");
+  });
+
+  it("should validate all 30 caveman compression rules are defined", async () => {
+    const { CAVEMAN_RULES } =
+      await import("../../../../open-sse/services/compression/cavemanRules.ts");
+    assert.ok(Array.isArray(CAVEMAN_RULES));
+    assert.ok(CAVEMAN_RULES.length >= 30, `Expected >= 30 rules, got ${CAVEMAN_RULES.length}`);
+  });
+
+  it("should validate compression modes cover all CavemanConfig roles", () => {
+    const validRoles = ["user", "assistant", "system"];
+    for (const role of validRoles) {
+      assert.ok(validRoles.includes(role), `Role ${role} should be valid`);
+    }
+    assert.equal(validRoles.length, 3);
+  });
+});