diff --git a/src/sdk/requestTimeout.ts b/src/sdk/requestTimeout.ts
index 87f28f0..f408aa2 100644
--- a/src/sdk/requestTimeout.ts
+++ b/src/sdk/requestTimeout.ts
@@ -97,7 +97,7 @@ export function wrapFetchWithTimeout(
   };
 }
 
-function combineAbortSignals(
+export function combineAbortSignals(
   timeoutSignal: AbortSignal,
   upstreamSignal: AbortSignal | null | undefined,
 ): { cleanup: () => void; signal: AbortSignal } {
diff --git a/test/requestTimeout.combineAbortSignals.test.ts b/test/requestTimeout.combineAbortSignals.test.ts
new file mode 100644
index 0000000..14d0334
--- /dev/null
+++ b/test/requestTimeout.combineAbortSignals.test.ts
@@ -0,0 +1,95 @@
+import { describe, expect, it } from "vitest";
+
+import { combineAbortSignals } from "../src/sdk/requestTimeout.js";
+
+describe("combineAbortSignals", () => {
+  it("returns timeout signal directly when upstream is undefined", () => {
+    const tc = new AbortController();
+    const { signal, cleanup } = combineAbortSignals(tc.signal, undefined);
+
+    expect(signal).toBe(tc.signal);
+    cleanup();
+  });
+
+  it("returns timeout signal directly when upstream is null", () => {
+    const tc = new AbortController();
+    const { signal, cleanup } = combineAbortSignals(tc.signal, null);
+
+    expect(signal).toBe(tc.signal);
+    cleanup();
+  });
+
+  it("returns already-aborted signal when timeout is pre-aborted", () => {
+    const tc = new AbortController();
+    const up = new AbortController();
+    tc.abort("timeout-reason");
+
+    const { signal, cleanup } = combineAbortSignals(tc.signal, up.signal);
+
+    expect(signal.aborted).toBe(true);
+    expect(signal.reason).toBe("timeout-reason");
+    cleanup();
+  });
+
+  it("returns already-aborted signal when upstream is pre-aborted", () => {
+    const tc = new AbortController();
+    const up = new AbortController();
+    up.abort("upstream-reason");
+
+    const { signal, cleanup } = combineAbortSignals(tc.signal, up.signal);
+
+    expect(signal.aborted).toBe(true);
+    expect(signal.reason).toBe("upstream-reason");
+    cleanup();
+  });
+
+  it("aborts combined signal when timeout fires", () => {
+    const tc = new AbortController();
+    const up = new AbortController();
+    const { signal, cleanup } = combineAbortSignals(tc.signal, up.signal);
+
+    expect(signal.aborted).toBe(false);
+    tc.abort("timed-out");
+
+    expect(signal.aborted).toBe(true);
+    expect(signal.reason).toBe("timed-out");
+    cleanup();
+  });
+
+  it("aborts combined signal when upstream fires", () => {
+    const tc = new AbortController();
+    const up = new AbortController();
+    const { signal, cleanup } = combineAbortSignals(tc.signal, up.signal);
+
+    expect(signal.aborted).toBe(false);
+    up.abort("user-cancelled");
+
+    expect(signal.aborted).toBe(true);
+    expect(signal.reason).toBe("user-cancelled");
+    cleanup();
+  });
+
+  it("does not abort combined signal after cleanup removes listeners", () => {
+    const tc = new AbortController();
+    const up = new AbortController();
+    const { signal, cleanup } = combineAbortSignals(tc.signal, up.signal);
+
+    cleanup();
+    tc.abort("late");
+
+    expect(signal.aborted).toBe(false);
+  });
+
+  it("does not double-abort when both signals fire after first", () => {
+    const tc = new AbortController();
+    const up = new AbortController();
+    const { signal, cleanup } = combineAbortSignals(tc.signal, up.signal);
+
+    tc.abort("first");
+    up.abort("second");
+
+    expect(signal.aborted).toBe(true);
+    expect(signal.reason).toBe("first");
+    cleanup();
+  });
+});
diff --git a/test/responseValidation.truncation.test.ts b/test/responseValidation.truncation.test.ts
new file mode 100644
index 0000000..71634d7
--- /dev/null
+++ b/test/responseValidation.truncation.test.ts
@@ -0,0 +1,82 @@
+import * as v from "valibot";
+import { describe, expect, it } from "vitest";
+
+import { LibrusResponseValidationError } from "../src/sdk/models/errors.js";
+import { parseApiResponse } from "../src/sdk/validation/responseValidation.js";
+
+const ENDPOINT = "https://api.librus.pl/3.0/Test";
+
+const fiveFieldSchema = v.object({
+  a: v.string(),
+  b: v.string(),
+  c: v.string(),
+  d: v.string(),
+  e: v.string(),
+});
+
+const twoFieldSchema = v.object({
+  x: v.string(),
+  y: v.string(),
+});
+
+function throwingParse(
+  schema: Parameters<typeof parseApiResponse>[0],
+  payload: unknown,
+): LibrusResponseValidationError {
+  try {
+    parseApiResponse(schema, payload, ENDPOINT);
+  } catch (err) {
+    if (err instanceof LibrusResponseValidationError) {
+      return err;
+    }
+  }
+  throw new Error(
+    "expected parseApiResponse to throw LibrusResponseValidationError",
+  );
+}
+
+describe("parseApiResponse — issue truncation", () => {
+  it("truncates to 3 issues when schema produces more", () => {
+    const err = throwingParse(fiveFieldSchema, {});
+
+    expect(err.details?.issues).toHaveLength(3);
+  });
+
+  it("includes all issues when schema produces fewer than 3", () => {
+    const err = throwingParse(twoFieldSchema, {});
+
+    expect(err.details?.issues).toHaveLength(2);
+  });
+
+  it("formats field issues as 'path: message'", () => {
+    const err = throwingParse(twoFieldSchema, {});
+    const issues = err.details?.issues ?? [];
+
+    expect(issues[0]).toMatch(/^x: /);
+    expect(issues[1]).toMatch(/^y: /);
+  });
+
+  it("formats root-level issues without a path prefix", () => {
+    const err = throwingParse(v.string(), 42);
+    const issues = err.details?.issues ?? [];
+
+    expect(issues).toHaveLength(1);
+    expect(issues[0]).not.toMatch(/^\w+: /);
+  });
+
+  it("returns parsed output for a valid payload", () => {
+    const result = parseApiResponse(
+      twoFieldSchema,
+      { x: "hello", y: "world" },
+      ENDPOINT,
+    );
+
+    expect(result).toEqual({ x: "hello", y: "world" });
+  });
+
+  it("includes endpoint in error details", () => {
+    const err = throwingParse(twoFieldSchema, {});
+
+    expect(err.details?.endpoint).toBe(ENDPOINT);
+  });
+});