diff --git a/src/components/AssigneeInput.svelte b/src/components/AssigneeInput.svelte
index bb2573c30..2e8a44b45 100644
--- a/src/components/AssigneeInput.svelte
+++ b/src/components/AssigneeInput.svelte
@@ -1,12 +1,9 @@
 <script lang="ts">
   import type { Author } from "@bindings/cob/Author";
 
+  import { parseAssignee } from "@app/lib/inputValidation";
   import { invoke } from "@app/lib/invoke";
-  import {
-    authorForNodeId,
-    parseNodeId,
-    publicKeyFromDid,
-  } from "@app/lib/utils";
+  import { authorForNodeId, publicKeyFromDid } from "@app/lib/utils";
 
   import Button from "@app/components/Button.svelte";
   import Icon from "@app/components/Icon.svelte";
@@ -32,9 +29,9 @@
   let updatedAssignees: Author[] = $state([]);
   let showInput: boolean = $state(false);
   let inputValue = $state("");
-  let validationMessage: string | undefined = $state(undefined);
-  let valid: boolean = $state(false);
-  let assignee: string | undefined = undefined;
+  const parsed = $derived(parseAssignee(inputValue, updatedAssignees));
+  const validationMessage = $derived(parsed.error);
+  const valid = $derived(parsed.error === undefined);
 
   let removeToggles: Record<string, boolean> = $state({});
 
@@ -45,35 +42,12 @@
     updatedAssignees = assignees;
 
     showInput = false;
-    validationMessage = undefined;
-    valid = true;
     removeToggles = {};
   });
 
-  $effect(() => {
-    if (inputValue === "") {
-      validationMessage = "";
-      valid = true;
-    } else {
-      const parsedNodeId = parseNodeId(inputValue);
-      if (parsedNodeId) {
-        assignee = `${parsedNodeId.prefix}${parsedNodeId.pubkey}`;
-        if (updatedAssignees.find(({ did }) => did === assignee)) {
-          validationMessage = "This assignee is already added";
-          valid = false;
-        } else {
-          validationMessage = undefined;
-          valid = true;
-        }
-      } else {
-        validationMessage = "This is not a valid DID";
-        valid = false;
-      }
-    }
-  });
-
   async function addAssignee() {
-    if (valid && assignee) {
+    const assignee = parsed.did;
+    if (assignee) {
       const alias = await invoke<string | null>("alias", {
         nid: publicKeyFromDid(assignee),
       });
diff --git a/src/components/LabelInput.svelte b/src/components/LabelInput.svelte
index 8da8d0a7e..94da1228b 100644
--- a/src/components/LabelInput.svelte
+++ b/src/components/LabelInput.svelte
@@ -1,4 +1,6 @@
 <script lang="ts">
+  import { labelError } from "@app/lib/inputValidation";
+
   import Button from "@app/components/Button.svelte";
   import Icon from "@app/components/Icon.svelte";
   import Label from "@app/components/Label.svelte";
@@ -23,10 +25,9 @@
   let updatedLabels: string[] = $state([]);
   let showInput: boolean = $state(false);
   let inputValue = $state("");
-  let validationMessage: string | undefined = $state();
-  let valid: boolean = $state(false);
-
   const sanitizedValue = $derived(inputValue.trim());
+  const validationMessage = $derived(labelError(inputValue, updatedLabels));
+  const valid = $derived(validationMessage === undefined);
 
   let removeToggles: Record<string, boolean> = $state({});
 
@@ -37,28 +38,9 @@
     updatedLabels = labels;
 
     showInput = false;
-    validationMessage = undefined;
-    valid = true;
     removeToggles = {};
   });
 
-  $effect(() => {
-    if (inputValue !== "") {
-      if (sanitizedValue.length > 0) {
-        if (updatedLabels.includes(sanitizedValue)) {
-          valid = false;
-          validationMessage = "This label is already assigned";
-        } else {
-          valid = true;
-          validationMessage = undefined;
-        }
-      }
-    } else {
-      valid = true;
-      validationMessage = "";
-    }
-  });
-
   function addLabel() {
     if (valid && sanitizedValue) {
       updatedLabels = [...updatedLabels, sanitizedValue].sort();
diff --git a/src/lib/inputValidation.ts b/src/lib/inputValidation.ts
new file mode 100644
index 000000000..ef3625056
--- /dev/null
+++ b/src/lib/inputValidation.ts
@@ -0,0 +1,37 @@
+import { parseNodeId } from "@app/lib/utils";
+
+export type AliasError =
+  | "AliasError.EmptyAlias"
+  | "AliasError.TooLongAlias"
+  | "AliasError.InvalidAlias";
+
+export function aliasErrors(alias: string): AliasError[] {
+  const errors: AliasError[] = [];
+  if (alias.length === 0) errors.push("AliasError.EmptyAlias");
+  if (alias.length > 32) errors.push("AliasError.TooLongAlias");
+  if (alias.includes(" ")) errors.push("AliasError.InvalidAlias");
+  return errors;
+}
+
+export function labelError(
+  label: string,
+  labels: string[],
+): string | undefined {
+  if (labels.includes(label.trim())) {
+    return "This label is already assigned";
+  }
+}
+
+export function parseAssignee(
+  input: string,
+  assignees: { did: string }[],
+): { did?: string; error?: string } {
+  if (input === "") return {};
+  const nodeId = parseNodeId(input);
+  if (!nodeId) return { error: "This is not a valid DID" };
+  const did = `${nodeId.prefix}${nodeId.pubkey}`;
+  if (assignees.some(assignee => assignee.did === did)) {
+    return { error: "This assignee is already added" };
+  }
+  return { did };
+}
diff --git a/src/views/auth/CreateIdentity.svelte b/src/views/auth/CreateIdentity.svelte
index ef4c8e1ce..ccd7526cf 100644
--- a/src/views/auth/CreateIdentity.svelte
+++ b/src/views/auth/CreateIdentity.svelte
@@ -3,6 +3,7 @@
 
   import debounce from "lodash/debounce";
 
+  import { aliasErrors } from "@app/lib/inputValidation";
   import { invoke } from "@app/lib/invoke";
   import * as router from "@app/lib/router";
   import { createEventEmittersOnce } from "@app/lib/startup.svelte";
@@ -28,23 +29,15 @@
   }, 400);
 
   function validateInput(field: "alias" | "passphrase") {
-    if (field === "alias" && alias.length === 0) {
-      errors.alias.push({ code: "AliasError.EmptyAlias" });
-    }
-    if (field === "alias" && alias.length > 32) {
-      errors.alias.push({ code: "AliasError.TooLongAlias" });
-    }
-    if (field === "alias" && alias.includes(" ")) {
-      errors.alias.push({ code: "AliasError.InvalidAlias" });
+    if (field === "alias") {
+      errors.alias = aliasErrors(alias).map(code => ({ code }));
     }
     if (field === "passphrase" && passphrase.length === 0) {
       errors.passphrase.push({ code: "PassphraseError.InvalidPassphrase" });
     }
   }
 
-  const validAlias = $derived(
-    alias.length > 0 && alias.length <= 32 && !alias.includes(" "),
-  );
+  const validAlias = $derived(aliasErrors(alias).length === 0);
   const validPassphrase = $derived(
     passphrase.length > 0 && passphrase === passphraseRepeat,
   );
diff --git a/tests/unit/inputValidation.test.ts b/tests/unit/inputValidation.test.ts
new file mode 100644
index 000000000..f0e1e797f
--- /dev/null
+++ b/tests/unit/inputValidation.test.ts
@@ -0,0 +1,51 @@
+import { describe, expect, test } from "vitest";
+
+import {
+  aliasErrors,
+  labelError,
+  parseAssignee,
+} from "@app/lib/inputValidation";
+
+const nid = "z6MkqGC3nWZhYieEVTVDKW5v588CiGfsDSmRVG9ZwwWTvLSK";
+
+test.each([
+  ["alice", []],
+  ["", ["AliasError.EmptyAlias"]],
+  ["a".repeat(32), []],
+  ["a".repeat(33), ["AliasError.TooLongAlias"]],
+  ["a b", ["AliasError.InvalidAlias"]],
+  [
+    `${"a ".repeat(17)}`,
+    ["AliasError.TooLongAlias", "AliasError.InvalidAlias"],
+  ],
+])("aliasErrors(%j) is %j", (alias, expected) => {
+  expect(aliasErrors(alias)).toEqual(expected);
+});
+
+test("labelError flags a label that is already assigned", () => {
+  expect(labelError(" bug ", ["bug"])).toBe("This label is already assigned");
+  expect(labelError("feature", ["bug"])).toBeUndefined();
+  expect(labelError("  ", ["bug"])).toBeUndefined();
+});
+
+describe("parseAssignee", () => {
+  test("accepts a NID or a DID", () => {
+    expect(parseAssignee(nid, [])).toEqual({ did: `did:key:${nid}` });
+    expect(parseAssignee(`did:key:${nid}`, [])).toEqual({
+      did: `did:key:${nid}`,
+    });
+  });
+
+  test("rejects an assignee that is already added", () => {
+    expect(parseAssignee(nid, [{ did: `did:key:${nid}` }])).toEqual({
+      error: "This assignee is already added",
+    });
+  });
+
+  test("rejects anything else, but not an empty input", () => {
+    expect(parseAssignee("alice", [])).toEqual({
+      error: "This is not a valid DID",
+    });
+    expect(parseAssignee("", [])).toEqual({});
+  });
+});