diff --git a/apps/backend/lambdas/projects/handler.ts b/apps/backend/lambdas/projects/handler.ts
index f82ef6ae..32da8e11 100644
--- a/apps/backend/lambdas/projects/handler.ts
+++ b/apps/backend/lambdas/projects/handler.ts
@@ -208,12 +208,26 @@ export const handler = async (event: any): Promise<APIGatewayProxyResult> => {
     if (rawPath.startsWith('/') && rawPath.split('/').length === 2 && method === 'PUT') {
       const id = rawPath.split('/')[1];
       if (!id) return json(400, { message: 'id is required' });
-      const body = event.body ? JSON.parse(event.body) as Record<string, { name: string, total_budget: number }> : {};
+      let body: Record<string, unknown>;
+      try {
+        body = event.body ? JSON.parse(event.body) as Record<string, unknown> : {};
+      } catch (e) {
+        return json(400, { message: 'Invalid JSON in request body' });
+      }
+
+      const result = ProjectValidationUtils.buildUpdateValues(body);
+      if (!result.isValid) return json(400, { message: result.error });
+      const updateValues = result.values!;
+
+      if (Object.keys(updateValues).length === 0) {
+        return json(400, { message: 'No valid fields provided' });
+      }
+
       const updatedProject = await db
         .updateTable("branch.projects")
-        .set(body)
+        .set(updateValues)
         .where("project_id", "=", Number(id))
-        .returning(["project_id", "name", "description", "total_budget"]) // control returned fields
+        .returning(["project_id", "name", "description", "total_budget"])
         .executeTakeFirst();
       if (!updatedProject) return json(404, { message: `Project not found for id: ${id}` });
       return json(200, updatedProject);
diff --git a/apps/backend/lambdas/projects/test/crud.test.ts b/apps/backend/lambdas/projects/test/crud.test.ts
index 961869ec..478140bb 100644
--- a/apps/backend/lambdas/projects/test/crud.test.ts
+++ b/apps/backend/lambdas/projects/test/crud.test.ts
@@ -97,3 +97,29 @@ test("project get 400 test 🌞", async () => {
   let body = await res.json();
   expect(body.message).toBe("Project not found for id: 1000");
 });
+
+test("update project ignores protected fields 🌞", async () => {
+  const beforeRes = await fetch("http://localhost:3000/projects/1");
+  expect(beforeRes.status).toBe(200);
+  const before = await beforeRes.json();
+
+  const res = await fetch("http://localhost:3000/projects/1", {
+    method: "PUT",
+    body: JSON.stringify({
+      name: "Project 1 Sanitized",
+      project_id: 9999,
+      created_at: "2000-01-01T00:00:00.000Z",
+    }),
+  });
+
+  expect(res.status).toBe(200);
+  const body = await res.json();
+  expect(body.project_id).toBe(1);
+  expect(body.name).toBe("Project 1 Sanitized");
+
+  const afterRes = await fetch("http://localhost:3000/projects/1");
+  expect(afterRes.status).toBe(200);
+  const after = await afterRes.json();
+  expect(after.project_id).toBe(1);
+  expect(after.created_at).toBe(before.created_at);
+});
\ No newline at end of file
diff --git a/apps/backend/lambdas/projects/validation-utils.ts b/apps/backend/lambdas/projects/validation-utils.ts
index 16cb9b87..f9f3fc44 100644
--- a/apps/backend/lambdas/projects/validation-utils.ts
+++ b/apps/backend/lambdas/projects/validation-utils.ts
@@ -87,4 +87,67 @@ export class ProjectValidationUtils {
     }
     return { isValid: true, value: d.length === 0 ? '' : d };
   }
+  static buildUpdateValues(body: Record<string, unknown>): { isValid: boolean; error?: string; values?: Record<string, unknown> } {
+  const updateValues: Record<string, unknown> = {};
+
+  if ('name' in body) {
+    const nameResult = ProjectValidationUtils.validateName(body.name);
+    if (!nameResult.isValid) return { isValid: false, error: nameResult.error };
+    updateValues.name = nameResult.value;
+  }
+
+  if ('description' in body) {
+    if (body.description === undefined || body.description === null) {
+      updateValues.description = '';
+    } else if (typeof body.description !== 'string') {
+      return { isValid: false, error: "'description' must be a string" };
+    } else {
+      const description = body.description.trim();
+      if (description.length > 1000) {
+        return { isValid: false, error: "'description' must be <= 1000 chars" };
+      }
+      updateValues.description = description;
+    }
+  }
+
+  if ('total_budget' in body) {
+    const parsedBudget = ProjectValidationUtils.parseNumericToFixed(body.total_budget);
+    if (parsedBudget === 'INVALID') return { isValid: false, error: "'total_budget' must be a number" };
+    updateValues.total_budget = parsedBudget;
+  }
+
+  if ('currency' in body) {
+    if (body.currency === undefined || body.currency === null) {
+      updateValues.currency = null;
+    } else if (typeof body.currency !== 'string') {
+      return { isValid: false, error: "'currency' must be 1-10 chars" };
+    } else {
+      const currencyResult = ProjectValidationUtils.validateCurrency(body.currency);
+      if (!currencyResult.isValid) return { isValid: false, error: currencyResult.error };
+      updateValues.currency = currencyResult.value;
+    }
+  }
+
+  if ('start_date' in body) {
+    if (body.start_date === undefined || body.start_date === null || body.start_date === '') {
+      updateValues.start_date = null;
+    } else if (typeof body.start_date !== 'string' || !ProjectValidationUtils.isValidDate(body.start_date)) {
+      return { isValid: false, error: "'start_date' must be YYYY-MM-DD" };
+    } else {
+      updateValues.start_date = body.start_date;
+    }
+  }
+
+  if ('end_date' in body) {
+    if (body.end_date === undefined || body.end_date === null || body.end_date === '') {
+      updateValues.end_date = null;
+    } else if (typeof body.end_date !== 'string' || !ProjectValidationUtils.isValidDate(body.end_date)) {
+      return { isValid: false, error: "'end_date' must be YYYY-MM-DD" };
+    } else {
+      updateValues.end_date = body.end_date;
+    }
+  }
+
+  return { isValid: true, values: updateValues };
+}
 }