diff --git a/src/core/openai.ts b/src/core/openai.ts
new file mode 100644
index 0000000..404afed
--- /dev/null
+++ b/src/core/openai.ts
@@ -0,0 +1,102 @@
+import type { HttpResponse, TranscribeResult } from './ports';
+
+export interface OpenAiSettings {
+  baseUrl: string;
+  model: string;
+  apiKey: string;
+  language: string;
+}
+
+export const DEFAULT_OPENAI: Readonly<OpenAiSettings> = {
+  baseUrl: 'https://api.aitunnel.ru/v1',
+  model: 'gpt-4o-transcribe',
+  apiKey: '',
+  language: '',
+};
+
+// MUST быть меньше SENT_STALE_MS (record.ts): иначе зависший sent
+// восстановится раньше, чем провайдер сдастся по таймауту.
+export const REQUEST_TIMEOUT_MS = 5 * 60_000;
+
+export const NO_API_KEY = 'не задан API-ключ';
+export const NO_BASE_URL = 'не задан адрес сервиса';
+export const EMPTY_AUDIO = 'пустая запись';
+export const CANCELLED = 'запрос отменён';
+export const TIMED_OUT = 'таймаут запроса (5 мин)';
+
+const DETAIL_LIMIT = 200;
+const REASON_LIMIT = 300;
+
+const FIELDS = ['baseUrl', 'model', 'apiKey', 'language'] as const;
+
+// Сохранённое поверх умолчаний; нестроковое поле → умолчание; всё обрезается.
+export function readSettings(saved: unknown): OpenAiSettings {
+  const src = saved !== null && typeof saved === 'object' ? (saved as Record<string, unknown>) : {};
+  const out: OpenAiSettings = { ...DEFAULT_OPENAI };
+  for (const key of FIELDS) {
+    const value = src[key];
+    if (typeof value === 'string') out[key] = value.trim();
+  }
+  return out;
+}
+
+function parseJson(text: string): unknown {
+  try {
+    return JSON.parse(text);
+  } catch {
+    return undefined;
+  }
+}
+
+function textField(body: string): string | null {
+  const json = parseJson(body);
+  if (json === null || typeof json !== 'object') return null;
+  const text = (json as { text?: unknown }).text;
+  return typeof text === 'string' ? text : null;
+}
+
+function detail(body: string): string {
+  const json = parseJson(body);
+  if (json !== null && typeof json === 'object') {
+    const error = (json as { error?: unknown }).error;
+    if (error !== null && typeof error === 'object') {
+      const message = (error as { message?: unknown }).message;
+      if (typeof message === 'string' && message.trim() !== '') return message.trim();
+    }
+  }
+  return body.trim().slice(0, DETAIL_LIMIT);
+}
+
+// Причины здесь ещё не очищены: redact применяет OpenAiTranscriber.
+export function classify(res: HttpResponse): TranscribeResult {
+  const { status, text } = res;
+  if (status >= 200 && status < 300) {
+    const value = textField(text);
+    if (value !== null) return { ok: true, text: value };
+    const snippet = text.trim().slice(0, DETAIL_LIMIT);
+    return {
+      ok: false,
+      kind: 'permanent',
+      message: `HTTP ${status}: ответ без поля text${snippet ? `: ${snippet}` : ''}`,
+    };
+  }
+  const info = detail(text);
+  const message = info ? `HTTP ${status}: ${info}` : `HTTP ${status}`;
+  // 3xx до нас доходит только при неверном baseUrl (редиректы адаптер проходит сам).
+  const permanent = status >= 300 && status < 500 && status !== 408 && status !== 429;
+  return { ok: false, kind: permanent ? 'permanent' : 'temporary', message };
+}
+
+// Причина попадает во frontmatter и в заметку: ни ключа, ни тела запроса.
+export function redact(message: string, secrets: { apiKey: string; boundary?: string }): string {
+  let out = message;
+  const lower = out.toLowerCase();
+  const cuts = [lower.indexOf('content-disposition')];
+  if (secrets.boundary) cuts.push(out.indexOf(`--${secrets.boundary}`), out.indexOf(secrets.boundary));
+  const cut = Math.min(...cuts.filter((i) => i >= 0), out.length);
+  out = out.slice(0, cut);
+  if (cut < message.length) out = out.replace(/[\s:]+$/, '');
+  if (secrets.apiKey) out = out.split(secrets.apiKey).join('***');
+  out = out.replace(/Bearer\s+\S+/g, 'Bearer ***');
+  return out.slice(0, REASON_LIMIT);
+}
diff --git a/tests/openai-classify.test.ts b/tests/openai-classify.test.ts
new file mode 100644
index 0000000..2fda343
--- /dev/null
+++ b/tests/openai-classify.test.ts
@@ -0,0 +1,75 @@
+import { describe, expect, it } from 'vitest';
+import { classify } from '../src/core/openai';
+
+const res = (status: number, text = '') => ({ status, text });
+
+describe('classify: 2xx', () => {
+  it('returns the text as is', () => {
+    expect(classify(res(200, '{"text":"привет"}'))).toEqual({ ok: true, text: 'привет' });
+  });
+
+  it('returns whitespace-only text unchanged (queue decides "no speech")', () => {
+    expect(classify(res(200, '{"text":"  "}'))).toEqual({ ok: true, text: '  ' });
+  });
+
+  it.each(['<html>oops</html>', '{"foo":1}', '{"text":5}', 'null', '[]', '"str"'])(
+    '200 with %s → permanent',
+    (body) => {
+      expect(classify(res(200, body))).toEqual({
+        ok: false,
+        kind: 'permanent',
+        message: `HTTP 200: ответ без поля text: ${body}`,
+      });
+    },
+  );
+
+  it('cuts the body to 200 chars', () => {
+    const body = `<html>${'x'.repeat(1000)}`;
+    expect(classify(res(200, body))).toEqual({
+      ok: false,
+      kind: 'permanent',
+      message: `HTTP 200: ответ без поля text: ${body.slice(0, 200)}`,
+    });
+  });
+
+  it('empty 2xx body → permanent without snippet', () => {
+    expect(classify(res(204, ''))).toEqual({ ok: false, kind: 'permanent', message: 'HTTP 204: ответ без поля text' });
+  });
+});
+
+describe('classify: errors', () => {
+  it.each([301, 302, 399, 400, 401, 403, 404, 413, 415, 422, 499])('%i → permanent', (status) => {
+    expect(classify(res(status, 'x'))).toEqual({ ok: false, kind: 'permanent', message: `HTTP ${status}: x` });
+  });
+
+  it.each([100, 101, 408, 429, 500, 502, 503, 599, 600])('%i → temporary', (status) => {
+    expect(classify(res(status, 'x'))).toEqual({ ok: false, kind: 'temporary', message: `HTTP ${status}: x` });
+  });
+
+  it('takes error.message from an OpenAI-style body', () => {
+    expect(classify(res(401, '{"error":{"message":"Invalid API key"}}'))).toEqual({
+      ok: false,
+      kind: 'permanent',
+      message: 'HTTP 401: Invalid API key',
+    });
+  });
+
+  it.each(['{"error":{"message":""}}', '{"error":"bad"}', '{"error":null}'])(
+    'falls back to the body when error.message is unusable: %s',
+    (body) => {
+      expect(classify(res(400, body))).toEqual({ ok: false, kind: 'permanent', message: `HTTP 400: ${body}` });
+    },
+  );
+
+  it('cuts a plain body to 200 chars after trim', () => {
+    expect(classify(res(500, `  ${'y'.repeat(1000)}`))).toEqual({
+      ok: false,
+      kind: 'temporary',
+      message: `HTTP 500: ${'y'.repeat(200)}`,
+    });
+  });
+
+  it.each(['', '  \n '])('empty body %j → "HTTP <code>"', (body) => {
+    expect(classify(res(503, body))).toEqual({ ok: false, kind: 'temporary', message: 'HTTP 503' });
+  });
+});
diff --git a/tests/openai-redact.test.ts b/tests/openai-redact.test.ts
new file mode 100644
index 0000000..d1a0f97
--- /dev/null
+++ b/tests/openai-redact.test.ts
@@ -0,0 +1,40 @@
+import { describe, expect, it } from 'vitest';
+import { redact } from '../src/core/openai';
+
+const KEY = 'sk-test-123';
+
+describe('redact', () => {
+  it('replaces every occurrence of the key', () => {
+    expect(redact(`a ${KEY} b ${KEY}`, { apiKey: KEY })).toBe('a *** b ***');
+  });
+
+  it('masks any Bearer token', () => {
+    expect(redact('Authorization: Bearer abc.def-1', { apiKey: KEY })).toBe('Authorization: Bearer ***');
+  });
+
+  it('leaves the message alone for an empty key', () => {
+    expect(redact('HTTP 401: nope', { apiKey: '' })).toBe('HTTP 401: nope');
+  });
+
+  it('cuts at the multipart boundary and trims trailing ": "', () => {
+    const b = '----voice-note-0000';
+    expect(redact(`HTTP 400: echo --${b}\r\nContent-Disposition: form-data`, { apiKey: KEY, boundary: b })).toBe(
+      'HTTP 400: echo',
+    );
+    expect(redact(`HTTP 400: --${b}\r\n`, { apiKey: KEY, boundary: b })).toBe('HTTP 400');
+  });
+
+  it('cuts at Content-Disposition regardless of case', () => {
+    expect(redact('HTTP 400: got content-disposition: form-data; name="file"', { apiKey: KEY })).toBe('HTTP 400: got');
+  });
+
+  it('caps the result at 300 chars', () => {
+    expect(redact('x'.repeat(500), { apiKey: KEY })).toHaveLength(300);
+  });
+
+  it('replaces the key before capping, so no key fragment survives the cut', () => {
+    const out = redact(`${'y'.repeat(295)}${KEY}`, { apiKey: KEY });
+    expect(out).toBe(`${'y'.repeat(295)}***`);
+    expect(out).not.toContain('sk-');
+  });
+});
diff --git a/tests/openai-settings.test.ts b/tests/openai-settings.test.ts
new file mode 100644
index 0000000..85d6b45
--- /dev/null
+++ b/tests/openai-settings.test.ts
@@ -0,0 +1,43 @@
+import { describe, expect, it } from 'vitest';
+import { DEFAULT_OPENAI, readSettings } from '../src/core/openai';
+
+describe('DEFAULT_OPENAI', () => {
+  it('points to AITUNNEL gpt-4o-transcribe with no key and auto language', () => {
+    expect(DEFAULT_OPENAI).toEqual({
+      baseUrl: 'https://api.aitunnel.ru/v1',
+      model: 'gpt-4o-transcribe',
+      apiKey: '',
+      language: '',
+    });
+  });
+});
+
+describe('readSettings', () => {
+  it.each([undefined, null, 'str', 42, []])('falls back to defaults for %j', (saved) => {
+    expect(readSettings(saved)).toEqual(DEFAULT_OPENAI);
+  });
+
+  it('overlays saved fields on defaults', () => {
+    expect(readSettings({ apiKey: 'sk-test-1' })).toEqual({ ...DEFAULT_OPENAI, apiKey: 'sk-test-1' });
+  });
+
+  it('trims all four fields', () => {
+    expect(
+      readSettings({ baseUrl: ' https://x/v1 ', model: ' m \n', apiKey: '  sk-test-1 \n', language: ' ru ' }),
+    ).toEqual({ baseUrl: 'https://x/v1', model: 'm', apiKey: 'sk-test-1', language: 'ru' });
+  });
+
+  it('uses the default for a non-string field', () => {
+    expect(readSettings({ model: 5, apiKey: null })).toEqual(DEFAULT_OPENAI);
+  });
+
+  it('keeps an explicitly blanked baseUrl blank (precheck reports it)', () => {
+    expect(readSettings({ baseUrl: '   ' }).baseUrl).toBe('');
+  });
+
+  it('returns a fresh object', () => {
+    const s = readSettings(undefined);
+    s.apiKey = 'changed';
+    expect(DEFAULT_OPENAI.apiKey).toBe('');
+  });
+});