diff --git a/changelog.d/1616-openai-chat-tool-patterns.md b/changelog.d/1616-openai-chat-tool-patterns.md
new file mode 100644
index 000000000..225d3f4a5
--- /dev/null
+++ b/changelog.d/1616-openai-chat-tool-patterns.md
@@ -0,0 +1,4 @@
+- Typed chat on OpenAI answers again: OpenAI refused every message because
+  `resolve_area`'s area-id pattern uses Unicode classes Chat Completions does
+  not accept. Chat leaves those patterns out; area ids are still checked
+  before the tool runs (samehkhamis, #1616).
diff --git a/server/providers/openai/chat.js b/server/providers/openai/chat.js
index 413d69ba9..6ca4648d6 100644
--- a/server/providers/openai/chat.js
+++ b/server/providers/openai/chat.js
@@ -64,6 +64,30 @@ function validMessages(messages) {
   return !pending.length;
 }
 
+/**
+ * A tool schema without the `pattern`s Chat Completions refuses: it answers
+ * 400 for a whole request whose tool uses Unicode property classes (`\p{L}`),
+ * as `resolve_area`'s area ids do. Every argument is still checked against
+ * the action's own contract before the tool runs, so the model loses a hint,
+ * not a rule. Realtime voice accepts these patterns and keeps them.
+ */
+export function chatSchema(schema) {
+  if (Array.isArray(schema)) return schema.map(chatSchema);
+  if (!object(schema)) return schema;
+  return Object.fromEntries(
+    Object.entries(schema)
+      .filter(
+        ([key, value]) =>
+          !(
+            key === 'pattern' &&
+            typeof value === 'string' &&
+            /\\[pP]\{/.test(value)
+          ),
+      )
+      .map(([key, value]) => [key, chatSchema(value)]),
+  );
+}
+
 export function createOpenAiChatHandler({
   annotationGuidance,
   tools = GEV_REALTIME_TOOLS,
@@ -126,7 +150,12 @@ export function createOpenAiChatHandler({
           tools: offeredTools(tools, { overpass }).map(
             ({ name, description, parameters }) => ({
               type: 'function',
-              function: { name, description, parameters, strict: false },
+              function: {
+                name,
+                description,
+                parameters: chatSchema(parameters),
+                strict: false,
+              },
             }),
           ),
         },
diff --git a/src/textChatServer.test.mjs b/src/textChatServer.test.mjs
index 61b09e987..b7137bbdd 100644
--- a/src/textChatServer.test.mjs
+++ b/src/textChatServer.test.mjs
@@ -3,7 +3,10 @@ import assert from 'node:assert/strict';
 import http from 'node:http';
 import { once } from 'node:events';
 import { createGeminiChatHandler } from '../server/providers/gemini/chat.js';
-import { createOpenAiChatHandler } from '../server/providers/openai/chat.js';
+import {
+  chatSchema,
+  createOpenAiChatHandler,
+} from '../server/providers/openai/chat.js';
 import { GEV_REALTIME_TOOLS } from '../server/providers/openai/tools.js';
 import {
   realtimeDirectives,
@@ -534,6 +537,11 @@ for (const [name, provider] of Object.entries(providers)) {
       assert.equal(offered.includes('osm_query'), overpass);
       assert.equal(prompt.includes('osm_query'), overpass);
       assert.ok(offered.includes('resolve_area'));
+      // Chat Completions answers 400 invalid_function_parameters for a
+      // pattern with Unicode property classes, as resolve_area's area ids
+      // use; OpenAI chat leaves those patterns out.
+      if (name === 'openai')
+        assert.doesNotMatch(JSON.stringify(body.tools), /\\\\[pP]\{/);
     }
   });
   test(`${name} throttled replies say they are rate limited`, async (t) => {
@@ -697,3 +705,25 @@ test('OpenAI empty tool arrays are removed before history is returned', async (t
   const body = await (await f.send()).json();
   assert.equal(body.content.tool_calls, undefined);
 });
+
+test('OpenAI chat schemas drop only the patterns Chat Completions refuses', () => {
+  assert.match(JSON.stringify(GEV_REALTIME_TOOLS), /\\\\[pP]\{/);
+  assert.deepEqual(
+    chatSchema({
+      type: 'object',
+      properties: {
+        id: { type: 'string', pattern: '^ne:[\\p{L}]+$', maxLength: 80 },
+        code: { type: 'string', pattern: '^[A-Z]{2}$' },
+        list: { type: 'array', items: [{ pattern: '\\P{N}' }] },
+      },
+    }),
+    {
+      type: 'object',
+      properties: {
+        id: { type: 'string', maxLength: 80 },
+        code: { type: 'string', pattern: '^[A-Z]{2}$' },
+        list: { type: 'array', items: [{}] },
+      },
+    },
+  );
+});