diff --git a/apps/api/src/tests/job.test.js b/apps/api/src/tests/job.test.js
new file mode 100644
index 0000000000..8be7c43291
--- /dev/null
+++ b/apps/api/src/tests/job.test.js
@@ -0,0 +1,172 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { createJobSchema, updateJobSchema } from "../validators/job.js";
+
+// ─── createJobSchema ───
+
+test("createJobSchema accepts valid budget range", () => {
+  const result = createJobSchema.safeParse({
+    title: "Build a website",
+    description: "Need a modern landing page with responsive design",
+    budgetMin: 100,
+    budgetMax: 500,
+    categoryId: "web-development",
+    skills: ["react", "css"],
+  });
+  assert.equal(result.success, true);
+  assert.equal(result.data.budgetMin, 100);
+  assert.equal(result.data.budgetMax, 500);
+});
+
+test("createJobSchema accepts equal budget min and max", () => {
+  const result = createJobSchema.safeParse({
+    title: "Fixed price job",
+    description: "This is a fixed price job posting example",
+    budgetMin: 200,
+    budgetMax: 200,
+    categoryId: "design",
+  });
+  assert.equal(result.success, true);
+});
+
+test("createJobSchema rejects inverted budget range", () => {
+  const result = createJobSchema.safeParse({
+    title: "Bad job",
+    description: "This job has inverted budget range values",
+    budgetMin: 500,
+    budgetMax: 100,
+    categoryId: "dev",
+  });
+  assert.equal(result.success, false);
+  assert.ok(result.error.issues.some((i) => i.path.includes("budgetMax")));
+});
+
+test("createJobSchema rejects negative budgetMin", () => {
+  const result = createJobSchema.safeParse({
+    title: "Negative min",
+    description: "Testing negative budget minimum value here",
+    budgetMin: -10,
+    budgetMax: 100,
+    categoryId: "dev",
+  });
+  assert.equal(result.success, false);
+});
+
+test("createJobSchema rejects NaN budgetMax", () => {
+  const result = createJobSchema.safeParse({
+    title: "NaN test",
+    description: "Testing NaN budget maximum value in this test",
+    budgetMin: 100,
+    budgetMax: NaN,
+    categoryId: "dev",
+  });
+  assert.equal(result.success, false);
+});
+
+test("createJobSchema rejects Infinity budgetMin", () => {
+  const result = createJobSchema.safeParse({
+    title: "Infinity test",
+    description: "Testing infinity budget minimum value here",
+    budgetMin: Infinity,
+    budgetMax: 500,
+    categoryId: "dev",
+  });
+  assert.equal(result.success, false);
+});
+
+test("createJobSchema rejects missing title", () => {
+  const result = createJobSchema.safeParse({
+    description: "No title provided for this job posting",
+    budgetMin: 100,
+    budgetMax: 500,
+    categoryId: "dev",
+  });
+  assert.equal(result.success, false);
+});
+
+test("createJobSchema rejects title too short", () => {
+  const result = createJobSchema.safeParse({
+    title: "Hi",
+    description: "This description is long enough to pass validation",
+    budgetMin: 100,
+    budgetMax: 500,
+    categoryId: "dev",
+  });
+  assert.equal(result.success, false);
+});
+
+test("createJobSchema defaults skills to empty array", () => {
+  const result = createJobSchema.safeParse({
+    title: "No skills job",
+    description: "This job posting has no skills specified at all here",
+    budgetMin: 100,
+    budgetMax: 500,
+    categoryId: "dev",
+  });
+  assert.equal(result.success, true);
+  assert.deepEqual(result.data.skills, []);
+});
+
+test("createJobSchema rejects empty skill string", () => {
+  const result = createJobSchema.safeParse({
+    title: "Empty skill",
+    description: "This job has an empty string in skills array field",
+    budgetMin: 100,
+    budgetMax: 500,
+    categoryId: "dev",
+    skills: ["react", ""],
+  });
+  assert.equal(result.success, false);
+});
+
+// ─── updateJobSchema ───
+
+test("updateJobSchema accepts partial update with only title", () => {
+  const result = updateJobSchema.safeParse({ title: "New Title" });
+  assert.equal(result.success, true);
+});
+
+test("updateJobSchema accepts partial update with valid budget range", () => {
+  const result = updateJobSchema.safeParse({
+    budgetMin: 200,
+    budgetMax: 800,
+  });
+  assert.equal(result.success, true);
+});
+
+test("updateJobSchema rejects inverted budget range when both present", () => {
+  const result = updateJobSchema.safeParse({
+    budgetMin: 500,
+    budgetMax: 100,
+  });
+  assert.equal(result.success, false);
+  assert.ok(result.error.issues.some((i) => i.path.includes("budgetMax")));
+});
+
+test("updateJobSchema accepts update with only budgetMin", () => {
+  const result = updateJobSchema.safeParse({ budgetMin: 300 });
+  assert.equal(result.success, true);
+});
+
+test("updateJobSchema accepts update with only budgetMax", () => {
+  const result = updateJobSchema.safeParse({ budgetMax: 900 });
+  assert.equal(result.success, true);
+});
+
+test("updateJobSchema accepts empty object (no-op update)", () => {
+  const result = updateJobSchema.safeParse({});
+  assert.equal(result.success, true);
+});
+
+test("updateJobSchema accepts equal budget values", () => {
+  const result = updateJobSchema.safeParse({
+    budgetMin: 250,
+    budgetMax: 250,
+  });
+  assert.equal(result.success, true);
+});
+
+test("updateJobSchema rejects negative budgetMin in partial update", () => {
+  const result = updateJobSchema.safeParse({ budgetMin: -50 });
+  assert.equal(result.success, false);
+});
diff --git a/apps/api/src/validators/job.js b/apps/api/src/validators/job.js
index 5593a844af..508bb966a9 100644
--- a/apps/api/src/validators/job.js
+++ b/apps/api/src/validators/job.js
@@ -1,12 +1,94 @@
 import { z } from "zod";
 
-export const createJobSchema = z.object({
-  title: z.string().min(4),
-  description: z.string().min(10),
-  budgetMin: z.number().nonnegative(),
-  budgetMax: z.number().nonnegative(),
-  categoryId: z.string().min(1),
-  skills: z.array(z.string().min(1)).default([])
+/**
+ * Base job schema without refinements.
+ * Separated so that `.partial()` can be called on the raw object
+ * (Zod v4 forbids `.partial()` on refined schemas).
+ */
+const baseJobFields = z.object({
+  title: z.string()
+    .min(4, "Title must be at least 4 characters")
+    .max(200, "Title must be at most 200 characters"),
+  description: z.string()
+    .min(10, "Description must be at least 10 characters")
+    .max(5000, "Description must be at most 5000 characters"),
+  budgetMin: z.number()
+    .nonnegative("budgetMin must be non-negative")
+    .finite("budgetMin must be a finite number"),
+  budgetMax: z.number()
+    .nonnegative("budgetMax must be non-negative")
+    .finite("budgetMax must be a finite number"),
+  categoryId: z.string()
+    .min(1, "categoryId is required")
+    .max(100, "categoryId must be at most 100 characters"),
+  skills: z.array(
+    z.string()
+      .min(1, "Skill must be a non-empty string")
+      .max(50, "Skill must be at most 50 characters")
+  ).max(20, "Maximum 20 skills allowed").default([])
 });
 
-export const updateJobSchema = createJobSchema.partial();
+/**
+ * Schema for creating a new job posting.
+ *
+ * Validates:
+ * - title: 4-200 characters
+ * - description: 10-5000 characters
+ * - budgetMin: non-negative finite number
+ * - budgetMax: non-negative finite number, must be >= budgetMin
+ * - categoryId: non-empty string
+ * - skills: array of strings (defaults to empty)
+ *
+ * @example
+ * ```js
+ * const result = createJobSchema.safeParse({
+ *   title: "Build a website",
+ *   description: "Need a modern landing page with responsive design",
+ *   budgetMin: 100,
+ *   budgetMax: 500,
+ *   categoryId: "web-development",
+ *   skills: ["react", "css"]
+ * });
+ * ```
+ */
+export const createJobSchema = baseJobFields.refine(
+  (data) => data.budgetMax >= data.budgetMin,
+  {
+    message: "budgetMax must be greater than or equal to budgetMin",
+    path: ["budgetMax"],
+  }
+);
+
+/**
+ * Schema for updating an existing job posting.
+ *
+ * All fields are optional (partial update).
+ * When both budgetMin and budgetMax are provided,
+ * budgetMax must be >= budgetMin.
+ *
+ * @example
+ * ```js
+ * // Valid: update only title
+ * updateJobSchema.parse({ title: "New Title" });
+ *
+ * // Valid: update both budgets with valid range
+ * updateJobSchema.parse({ budgetMin: 200, budgetMax: 800 });
+ *
+ * // Invalid: inverted budget range
+ * updateJobSchema.parse({ budgetMin: 500, budgetMax: 100 });
+ * // => throws ZodError
+ * ```
+ */
+export const updateJobSchema = baseJobFields.partial().refine(
+  (data) => {
+    // Only validate when both fields are present
+    if (data.budgetMin !== undefined && data.budgetMax !== undefined) {
+      return data.budgetMax >= data.budgetMin;
+    }
+    return true;
+  },
+  {
+    message: "budgetMax must be greater than or equal to budgetMin when both are provided",
+    path: ["budgetMax"],
+  }
+);