diff --git a/packages/server/src/http/validate.ts b/packages/server/src/http/validate.ts
index 409e0fa..0d7a048 100644
--- a/packages/server/src/http/validate.ts
+++ b/packages/server/src/http/validate.ts
@@ -42,8 +42,13 @@ export function requireValidId(c: Context, name: string): string {
 
 /** Parse a positive-integer path parameter (e.g. Trace file index). */
 export function positiveIntParam(c: Context, name: string): number {
-  const v = Number.parseInt(pathParam(c, name), 10);
-  if (!Number.isInteger(v) || v < 1) throw badRequest(`${name} must be a positive integer.`);
+  // Match digits only: Number.parseInt would accept trailing garbage ("12abc" -> 12).
+  const raw = pathParam(c, name);
+  if (!/^\d+$/.test(raw)) throw badRequest(`${name} must be a positive integer.`);
+  const v = Number.parseInt(raw, 10);
+  // isSafeInteger (not isInteger) also rejects overlong indices like "99999999999999999999"
+  // that would otherwise parse to an imprecise float (1e20).
+  if (!Number.isSafeInteger(v) || v < 1) throw badRequest(`${name} must be a positive integer.`);
   return v;
 }
 
@@ -163,8 +168,20 @@ export function optionalNumber(
 /** Validate a yyyy-mm-dd query parameter (defaults to undefined). */
 export function optionalDateParam(value: string | undefined, label: string): string | undefined {
   if (value === undefined || value === "") return undefined;
-  if (!/^\d{4}-\d{2}-\d{2}$/.test(value)) {
-    throw badRequest(`${label} must be in YYYY-MM-DD format.`);
+  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(value);
+  // The shape check alone accepts impossible dates (2026-13-40, 2026-02-30); verify it's a real
+  // calendar day by round-tripping through UTC (which never rolls over into an adjacent month).
+  if (m) {
+    const [, y, mo, d] = m;
+    const dt = new Date(`${value}T00:00:00Z`);
+    if (
+      !Number.isNaN(dt.getTime()) &&
+      dt.getUTCFullYear() === Number(y) &&
+      dt.getUTCMonth() + 1 === Number(mo) &&
+      dt.getUTCDate() === Number(d)
+    ) {
+      return value;
+    }
   }
-  return value;
+  throw badRequest(`${label} must be a valid date in YYYY-MM-DD format.`);
 }
diff --git a/packages/server/test/validate.test.ts b/packages/server/test/validate.test.ts
new file mode 100644
index 0000000..8323a84
--- /dev/null
+++ b/packages/server/test/validate.test.ts
@@ -0,0 +1,67 @@
+/**
+ * Request-validation helper unit tests: positiveIntParam rejects trailing garbage, and
+ * optionalDateParam rejects impossible calendar dates (shape-only checks let these through).
+ */
+import { describe, expect, it } from "vitest";
+import type { Context } from "hono";
+import { optionalDateParam, positiveIntParam } from "../src/http/validate.js";
+import { HttpError } from "../src/http/errors.js";
+
+/** Minimal Context stub exposing a single path parameter. */
+function ctxWithParam(name: string, value: string | undefined): Context {
+  return { req: { param: (n: string) => (n === name ? value : undefined) } } as unknown as Context;
+}
+
+describe("positiveIntParam", () => {
+  it("parses a plain positive integer", () => {
+    expect(positiveIntParam(ctxWithParam("idx", "12"), "idx")).toBe(12);
+  });
+
+  it("rejects trailing garbage (parseInt would accept it)", () => {
+    expect(() => positiveIntParam(ctxWithParam("idx", "12abc"), "idx")).toThrow(HttpError);
+  });
+
+  it("rejects a leading sign, whitespace, and non-digits", () => {
+    for (const bad of ["+1", " 1", "1 ", "1.5", "0x10"]) {
+      expect(() => positiveIntParam(ctxWithParam("idx", bad), "idx")).toThrow(HttpError);
+    }
+  });
+
+  it("rejects zero (must be >= 1)", () => {
+    expect(() => positiveIntParam(ctxWithParam("idx", "0"), "idx")).toThrow(HttpError);
+  });
+
+  it("rejects overlong indices that would parse to an imprecise float", () => {
+    // "99999999999999999999" parses to 1e20 — isSafeInteger rejects it, isInteger would not.
+    expect(() => positiveIntParam(ctxWithParam("idx", "9".repeat(20)), "idx")).toThrow(HttpError);
+  });
+
+  it("an empty/missing path param is rejected upstream by pathParam (404), not the digits guard", () => {
+    expect(() => positiveIntParam(ctxWithParam("idx", ""), "idx")).toThrow(HttpError);
+    expect(() => positiveIntParam(ctxWithParam("idx", undefined), "idx")).toThrow(HttpError);
+  });
+});
+
+describe("optionalDateParam", () => {
+  it("returns undefined for missing or empty input", () => {
+    expect(optionalDateParam(undefined, "from")).toBeUndefined();
+    expect(optionalDateParam("", "from")).toBeUndefined();
+  });
+
+  it("accepts a real calendar date", () => {
+    expect(optionalDateParam("2026-07-20", "from")).toBe("2026-07-20");
+    expect(optionalDateParam("2024-02-29", "from")).toBe("2024-02-29"); // leap day
+  });
+
+  it("rejects malformed shapes", () => {
+    for (const bad of ["2026/07/20", "20260720", "2026-7-20", "not-a-date"]) {
+      expect(() => optionalDateParam(bad, "from")).toThrow(HttpError);
+    }
+  });
+
+  it("rejects impossible dates that pass the shape check", () => {
+    for (const bad of ["2026-13-40", "2026-02-30", "2026-00-10", "2026-01-00", "2025-02-29"]) {
+      expect(() => optionalDateParam(bad, "from")).toThrow(HttpError);
+    }
+  });
+});