diff --git a/src/calibre/ai/openai_compatible/__init__.py b/src/calibre/ai/openai_compatible/__init__.py
new file mode 100644
index 0000000000..8bc003fb38
--- /dev/null
+++ b/src/calibre/ai/openai_compatible/__init__.py
@@ -0,0 +1,20 @@
+#!/usr/bin/env python
+# License: GPLv3 Copyright: 2026, OpenAI
+
+from calibre.customize import AIProviderPlugin
+
+
+class OpenAICompatible(AIProviderPlugin):
+    name = 'OpenAI compatible'
+    version = (1, 0, 0)
+    description = _(
+        'Generic OpenAI compatible AI services. Use this to connect calibre to self-hosted or third-party services'
+        ' that implement the OpenAI chat completions API.'
+    )
+    author = 'OpenAI'
+    builtin_live_module_name = 'calibre.ai.openai_compatible.backend'
+
+    @property
+    def capabilities(self):
+        from calibre.ai import AICapabilities
+        return AICapabilities.text_to_text
diff --git a/src/calibre/ai/openai_compatible/backend.py b/src/calibre/ai/openai_compatible/backend.py
new file mode 100644
index 0000000000..1beb4c789f
--- /dev/null
+++ b/src/calibre/ai/openai_compatible/backend.py
@@ -0,0 +1,215 @@
+#!/usr/bin/env python
+# License: GPLv3 Copyright: 2026, OpenAI
+
+import json
+import posixpath
+from collections.abc import Iterable, Iterator, Sequence
+from functools import lru_cache
+from typing import Any, NamedTuple
+from urllib.parse import urlparse, urlunparse
+from urllib.request import Request
+
+from calibre.ai import ChatMessage, ChatMessageType, ChatResponse, ResultBlocked, ResultBlockReason
+from calibre.ai.openai_compatible import OpenAICompatible
+from calibre.ai.prefs import decode_secret, pref_for_provider
+from calibre.ai.utils import chat_with_error_handler, develop_text_chat, download_data, read_streaming_response
+
+module_version = 1
+
+
+def pref(key: str, defval: Any = None) -> Any:
+    return pref_for_provider(OpenAICompatible.name, key, defval)
+
+
+def is_ready_for_use() -> bool:
+    return bool(pref('api_url') and pref('text_model'))
+
+
+class Model(NamedTuple):
+    id: str
+    owner: str
+
+    @classmethod
+    def from_dict(cls, x: dict[str, Any]) -> 'Model':
+        return cls(id=x['id'], owner=x.get('owned_by', 'remote'))
+
+
+def api_url(path: str = '', use_api_url: str | None = None) -> str:
+    base = (pref('api_url') if use_api_url is None else use_api_url) or ''
+    purl = urlparse(base)
+    base_path = (purl.path or '').rstrip('/')
+    if not base_path:
+        base_path = '/v1'
+    elif base_path.endswith('/chat/completions'):
+        base_path = base_path[:-len('/chat/completions')]
+    elif base_path.endswith('/models'):
+        base_path = base_path[:-len('/models')]
+    if path:
+        base_path = posixpath.join(base_path, path)
+    purl = purl._replace(path=base_path)
+    return urlunparse(purl)
+
+
+def raw_api_key(use_api_key: str | None = None) -> str:
+    key = pref('api_key') if use_api_key is None else use_api_key
+    return decode_secret(key) if key else ''
+
+
+@lru_cache(32)
+def request_headers(
+    use_api_key: str | None = None, use_headers: Sequence[tuple[str, str]] | None = None
+) -> tuple[tuple[str, str], ...]:
+    ans = [('Content-Type', 'application/json')]
+    extra_headers = pref('headers', ()) if use_headers is None else use_headers
+    extra_headers = tuple(extra_headers or ())
+    has_auth = False
+    for key, val in extra_headers:
+        if key.lower() == 'authorization':
+            has_auth = True
+        ans.append((key, val))
+    if api_key := raw_api_key(use_api_key):
+        if not has_auth:
+            ans.insert(0, ('Authorization', f'Bearer {api_key}'))
+    return tuple(ans)
+
+
+@lru_cache(8)
+def get_available_models(
+    use_api_url: str | None = None, use_api_key: str | None = None, use_headers: Sequence[tuple[str, str]] | None = None
+) -> dict[str, Model]:
+    url = api_url('models', use_api_url)
+    data = json.loads(download_data(url, request_headers(use_api_key, use_headers)))
+    ans = {}
+    if 'data' in data:
+        for model_data in data['data']:
+            model = Model.from_dict(model_data)
+            ans[model.id] = model
+    return ans
+
+
+def human_readable_model_name(model_id: str) -> str:
+    return model_id
+
+
+def config_widget():
+    from calibre.ai.openai_compatible.config import ConfigWidget
+    return ConfigWidget()
+
+
+def save_settings(config_widget):
+    config_widget.save_settings()
+
+
+def for_assistant(self: ChatMessage) -> dict[str, Any]:
+    if self.type not in (ChatMessageType.assistant, ChatMessageType.system, ChatMessageType.user, ChatMessageType.developer):
+        raise ValueError(f'Unsupported message type: {self.type}')
+    return {'role': self.type.value, 'content': self.query}
+
+
+def coerce_text(value: Any) -> str:
+    if isinstance(value, str):
+        return value
+    if isinstance(value, dict):
+        text = value.get('text')
+        return text if isinstance(text, str) else ''
+    if isinstance(value, list):
+        return ''.join(filter(None, map(coerce_text, value)))
+    return ''
+
+
+def chat_request(
+    data: dict[str, Any], url_override: str | None = None, use_api_key: str | None = None,
+    use_headers: Sequence[tuple[str, str]] | None = None
+) -> Request:
+    url = api_url('chat/completions', url_override)
+    return Request(url, data=json.dumps(data).encode('utf-8'), headers=dict(request_headers(use_api_key, use_headers)), method='POST')
+
+
+def as_chat_responses(d: dict[str, Any], model_id: str) -> Iterator[ChatResponse]:
+    blocked = False
+    for choice in d.get('choices', ()):
+        delta = choice.get('delta') or {}
+        content = coerce_text(delta.get('content'))
+        reasoning = coerce_text(delta.get('reasoning_content'))
+        role = delta.get('role') or 'assistant'
+        if content or reasoning:
+            yield ChatResponse(
+                content=content, reasoning=reasoning, type=ChatMessageType(role), plugin_name=OpenAICompatible.name
+            )
+        if choice.get('finish_reason') == 'content_filter':
+            blocked = True
+    if blocked:
+        yield ChatResponse(exception=ResultBlocked(ResultBlockReason.safety), plugin_name=OpenAICompatible.name)
+        return
+    if usage := d.get('usage'):
+        yield ChatResponse(
+            has_metadata=True, provider=OpenAICompatible.name, model=d.get('model') or model_id,
+            plugin_name=OpenAICompatible.name
+        )
+
+
+def text_chat_implementation(messages: Iterable[ChatMessage], use_model: str = '') -> Iterator[ChatResponse]:
+    model_id = use_model or pref('text_model')
+    temperature = pref('temperature', 0.7)
+    data = {
+        'model': model_id,
+        'messages': [for_assistant(m) for m in messages],
+        'stream': True,
+        'temperature': temperature,
+    }
+    rq = chat_request(data)
+    seen_metadata = False
+    for data in read_streaming_response(rq, OpenAICompatible.name, timeout=pref('timeout', 120)):
+        for response in as_chat_responses(data, model_id):
+            if response.has_metadata:
+                seen_metadata = True
+            yield response
+            if response.exception:
+                return
+    if not seen_metadata:
+        yield ChatResponse(has_metadata=True, provider=OpenAICompatible.name, model=model_id, plugin_name=OpenAICompatible.name)
+
+
+def text_chat(messages: Iterable[ChatMessage], use_model: str = '') -> Iterator[ChatResponse]:
+    yield from chat_with_error_handler(text_chat_implementation(messages, use_model))
+
+
+def develop(use_model: str = '', msg: str = '') -> None:
+    m = (ChatMessage(msg),) if msg else ()
+    develop_text_chat(text_chat, use_model, messages=m)
+
+
+def find_tests():
+    import unittest
+
+    class TestOpenAICompatibleBackend(unittest.TestCase):
+
+        def test_api_url_normalization(self):
+            self.assertEqual(api_url('models', 'http://localhost:1234'), 'http://localhost:1234/v1/models')
+            self.assertEqual(api_url('models', 'http://localhost:1234/v1'), 'http://localhost:1234/v1/models')
+            self.assertEqual(api_url('models', 'https://example.com/custom/api'), 'https://example.com/custom/api/models')
+            self.assertEqual(api_url('chat/completions', 'https://ark.cn-beijing.volces.com/api/v3'), 'https://ark.cn-beijing.volces.com/api/v3/chat/completions')
+            self.assertEqual(api_url('chat/completions', 'https://ark.cn-beijing.volces.com/api/v3/chat/completions'), 'https://ark.cn-beijing.volces.com/api/v3/chat/completions')
+
+        def test_request_headers_allows_missing_headers_pref(self):
+            headers = request_headers()
+            self.assertEqual(headers, (('Content-Type', 'application/json'),))
+
+        def test_parsing_stream_deltas(self):
+            responses = tuple(as_chat_responses({
+                'model': 'demo-model',
+                'choices': [
+                    {'delta': {'role': 'assistant', 'content': 'Hello', 'reasoning_content': 'Think'}, 'finish_reason': None}
+                ],
+                'usage': {'total_tokens': 42},
+            }, 'demo-model'))
+            self.assertEqual(responses[0].content, 'Hello')
+            self.assertEqual(responses[0].reasoning, 'Think')
+            self.assertTrue(responses[-1].has_metadata)
+            self.assertEqual(responses[-1].model, 'demo-model')
+
+    return unittest.defaultTestLoader.loadTestsFromTestCase(TestOpenAICompatibleBackend)
+
+
+if __name__ == '__main__':
+    develop()
diff --git a/src/calibre/ai/openai_compatible/config.py b/src/calibre/ai/openai_compatible/config.py
new file mode 100644
index 0000000000..05abb0569f
--- /dev/null
+++ b/src/calibre/ai/openai_compatible/config.py
@@ -0,0 +1,199 @@
+#!/usr/bin/env python
+# License: GPLv3 Copyright: 2026, OpenAI
+
+from functools import partial
+from typing import Any
+
+from qt.core import (
+    QComboBox,
+    QCompleter,
+    QDoubleSpinBox,
+    QFormLayout,
+    QHBoxLayout,
+    QLabel,
+    QLineEdit,
+    QListView,
+    QPlainTextEdit,
+    QPushButton,
+    QSpinBox,
+    Qt,
+    QWidget,
+)
+
+from calibre.ai.openai_compatible import OpenAICompatible
+from calibre.ai.prefs import decode_secret, encode_secret, pref_for_provider, set_prefs_for_provider
+from calibre.ai.utils import configure, plugin_for_name
+from calibre.gui2 import error_dialog
+from calibre.gui2.widgets import BusyCursor
+
+pref = partial(pref_for_provider, OpenAICompatible.name)
+
+
+class ConfigWidget(QWidget):
+
+    def __init__(self, parent: QWidget | None = None):
+        super().__init__(parent)
+        l = QFormLayout(self)
+        l.setFieldGrowthPolicy(QFormLayout.FieldGrowthPolicy.ExpandingFieldsGrow)
+
+        la = QLabel('<p>' + _(
+            'Connect calibre to any self-hosted or third-party service that implements the OpenAI compatible'
+            ' <code>/v1/chat/completions</code> API. This is useful for gateways, local servers and other'
+            ' services that are not listed as dedicated providers.'
+        ))
+        la.setWordWrap(True)
+        l.addRow(la)
+
+        self.api_url_edit = a = QLineEdit(self)
+        a.setClearButtonEnabled(True)
+        a.setPlaceholderText(_('For example: {}').format('https://example.com/v1'))
+        l.addRow(_('API &URL:'), a)
+        a.setText(pref('api_url') or '')
+
+        self.api_key_edit = ak = QLineEdit(self)
+        ak.setClearButtonEnabled(True)
+        ak.setPlaceholderText(_('Optional. Sent as Authorization: Bearer <key>'))
+        l.addRow(_('API &key:'), ak)
+        if key := pref('api_key'):
+            ak.setText(decode_secret(key))
+
+        self.headers_edit = he = QPlainTextEdit(self)
+        he.setPlaceholderText(_('Optional HTTP headers, one per line, in the format: Header-Name: Value'))
+        l.addRow(_('HTTP &headers:'), he)
+        he.setPlainText('\n'.join(f'{k}: {v}' for (k, v) in pref('headers') or ()))
+
+        self.timeout_sb = t = QSpinBox(self)
+        t.setRange(15, 600)
+        t.setSingleStep(1)
+        t.setSuffix(_(' seconds'))
+        t.setValue(pref('timeout', 120))
+        l.addRow(_('&Timeout:'), t)
+
+        self.temp_sb = temp = QDoubleSpinBox(self)
+        temp.setRange(0.0, 2.0)
+        temp.setSingleStep(0.1)
+        temp.setValue(pref('temperature', 0.7))
+        temp.setToolTip(_('Controls randomness. Lower values are more deterministic.'))
+        l.addRow(_('T&emperature:'), temp)
+
+        w = QWidget(self)
+        h = QHBoxLayout(w)
+        h.setContentsMargins(0, 0, 0, 0)
+
+        self.model_combo = mc = QComboBox(w)
+        mc.setEditable(True)
+        mc.setInsertPolicy(QComboBox.NoInsert)
+        mc.setView(QListView(mc))
+        mc.setSizeAdjustPolicy(QComboBox.AdjustToContentsOnFirstShow)
+        completer = QCompleter(mc)
+        completer.setCaseSensitivity(Qt.CaseInsensitive)
+        mc.setCompleter(completer)
+
+        if saved_model := pref('text_model') or '':
+            mc.addItem(saved_model)
+            mc.setCurrentText(saved_model)
+
+        self.refresh_btn = rb = QPushButton(_('&Refresh models'), w)
+        rb.clicked.connect(self.refresh_models)
+        h.addWidget(mc, stretch=10)
+        h.addWidget(rb)
+        l.addRow(_('Model for &text tasks:'), w)
+
+        self.model_status = ms = QLabel('', self)
+        ms.setWordWrap(True)
+        ms.setTextInteractionFlags(Qt.TextInteractionFlag.TextSelectableByMouse)
+        l.addRow('', ms)
+
+    def refresh_models(self):
+        with BusyCursor():
+            try:
+                plugin = plugin_for_name(OpenAICompatible.name)
+                backend = plugin.builtin_live_module
+                backend.get_available_models.cache_clear()
+                encoded_key = encode_secret(self.api_key) if self.api_key else ''
+                models_dict = backend.get_available_models(self.api_url, encoded_key, self.headers)
+                current_text = self.text_model
+                model_ids = sorted(models_dict, key=lambda x: x.lower())
+                self.model_combo.blockSignals(True)
+                self.model_combo.clear()
+                for model_id in model_ids:
+                    self.model_combo.addItem(model_id)
+                self.model_combo.setCurrentText(current_text or (model_ids[0] if model_ids else ''))
+                self.model_combo.blockSignals(False)
+                if model_ids:
+                    sample = ', '.join(model_ids[:3])
+                    msg = _('Found {} models. e.g.: {}').format(len(model_ids), sample)
+                    if len(model_ids) > 3:
+                        msg += _(' (and more)')
+                    self.model_status.setText(msg)
+                    self.model_status.setToolTip('\n'.join(model_ids))
+                else:
+                    self.model_status.setText(_('The server responded, but returned no models.'))
+                    self.model_status.setToolTip('')
+            except Exception as e:
+                self.model_status.setText(_('Failed to refresh models: {}').format(e))
+                self.model_status.setToolTip('')
+
+    @property
+    def api_url(self) -> str:
+        return self.api_url_edit.text().strip()
+
+    @property
+    def api_key(self) -> str:
+        return self.api_key_edit.text().strip()
+
+    @property
+    def text_model(self) -> str:
+        return self.model_combo.currentText().strip()
+
+    @property
+    def timeout(self) -> int:
+        return self.timeout_sb.value()
+
+    @property
+    def temperature(self) -> float:
+        return self.temp_sb.value()
+
+    @property
+    def headers(self) -> tuple[tuple[str, str], ...]:
+        ans = []
+        for line in self.headers_edit.toPlainText().splitlines():
+            if line := line.strip():
+                key, sep, val = line.partition(':')
+                key, val = key.strip(), val.strip()
+                if key and sep and val:
+                    ans.append((key, val))
+        return tuple(ans)
+
+    @property
+    def settings(self) -> dict[str, Any]:
+        ans = {
+            'api_url': self.api_url,
+            'api_key': encode_secret(self.api_key),
+            'text_model': self.text_model,
+            'timeout': self.timeout,
+            'temperature': self.temperature,
+        }
+        if self.headers:
+            ans['headers'] = self.headers
+        return ans
+
+    @property
+    def is_ready_for_use(self) -> bool:
+        return bool(self.api_url and self.text_model)
+
+    def validate(self) -> bool:
+        if not self.api_url:
+            error_dialog(self, _('No API URL'), _('You must specify the URL of the OpenAI compatible API endpoint.'), show=True)
+            return False
+        if not self.text_model:
+            error_dialog(self, _('No model specified'), _('You must specify a model ID to use for text based tasks.'), show=True)
+            return False
+        return True
+
+    def save_settings(self):
+        set_prefs_for_provider(OpenAICompatible.name, self.settings)
+
+
+if __name__ == '__main__':
+    configure(OpenAICompatible.name)
diff --git a/src/calibre/customize/builtins.py b/src/calibre/customize/builtins.py
index beacada7c9..e7904072b3 100644
--- a/src/calibre/customize/builtins.py
+++ b/src/calibre/customize/builtins.py
@@ -8,6 +8,7 @@ from calibre.ai.github import GitHubAI
 from calibre.ai.google import GoogleAI
 from calibre.ai.lm_studio import LMStudioAI
 from calibre.ai.ollama import OllamaAI
+from calibre.ai.openai_compatible import OpenAICompatible
 from calibre.ai.open_router import OpenRouterAI
 from calibre.constants import numeric_version
 from calibre.customize import FileTypePlugin, InterfaceActionBase, MetadataReaderPlugin, MetadataWriterPlugin, PreferencesPlugin, StoreBase
@@ -1986,7 +1987,7 @@ plugins += [
 
 # }}}
 
-plugins.extend((OpenRouterAI, GoogleAI, GitHubAI, OllamaAI, LMStudioAI))
+plugins.extend((OpenRouterAI, GoogleAI, GitHubAI, OllamaAI, LMStudioAI, OpenAICompatible))
 
 if __name__ == '__main__':
     # Test load speed