feat(xai): add xAI image generation provider (grok-imagine-image)

Add xAI as a plugin-based image generation backend using grok-imagine-image.
Follows the existing ImageGenProvider ABC pattern used by OpenAI and FAL.

Changes:
- plugins/image_gen/xai/__init__.py: xAI provider implementation
  - Uses xAI /images/generations endpoint
  - Supports text-to-image and image editing with reference images
  - Multiple aspect ratios (1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3)
  - Multiple resolutions (1K, 2K)
  - Base64 output saved to cache
  - Config via config.yaml image_gen.xai section
- plugins/image_gen/xai/plugin.yaml: plugin metadata
- tests/plugins/image_gen/test_xai_provider.py: 19 unit tests
  - Provider class (name, display_name, is_available, list_models, setup_schema)
  - Config (default model, resolution, custom model)
  - Generate (missing key, success b64/url, API error, timeout, empty response, reference images, auth header)
  - Registration

Requires XAI_API_KEY in ~/.hermes/.env.
To use: set image_gen.provider: xai in config.yaml.

plugins/image_gen/xai/__init__.py

@@ -0,0 +1,324 @@
+"""xAI image generation backend.
+
+Exposes xAI's ``grok-imagine-image`` model as an
+:class:`ImageGenProvider` implementation.
+
+Features:
+- Text-to-image generation
+- Image editing with reference images
+- Multiple aspect ratios (1:1, 16:9, 9:16, etc.)
+- Multiple resolutions (1K, 2K)
+- Base64 output saved to cache
+
+Selection precedence (first hit wins):
+1. ``XAI_IMAGE_MODEL`` env var
+2. ``image_gen.xai.model`` in ``config.yaml``
+3. :data:`DEFAULT_MODEL`
+"""
+
+from __future__ import annotations
+
+import logging
+import os
+from typing import Any, Dict, List, Optional, Tuple
+
+import requests
+
+from agent.image_gen_provider import (
+    DEFAULT_ASPECT_RATIO,
+    ImageGenProvider,
+    error_response,
+    resolve_aspect_ratio,
+    save_b64_image,
+    success_response,
+)
+from tools.xai_http import hermes_xai_user_agent
+
+logger = logging.getLogger(__name__)
+
+# ---------------------------------------------------------------------------
+# Model catalog
+# ---------------------------------------------------------------------------
+
+API_MODEL = "grok-imagine-image"
+
+_MODELS: Dict[str, Dict[str, Any]] = {
+    "grok-imagine-image": {
+        "display": "Grok Imagine Image",
+        "speed": "~5-10s",
+        "strengths": "Fast, high-quality, supports editing",
+    },
+}
+
+DEFAULT_MODEL = "grok-imagine-image"
+
+# xAI aspect ratios (more options than FAL/OpenAI)
+_XAI_ASPECT_RATIOS = {
+    "landscape": "16:9",
+    "square": "1:1",
+    "portrait": "9:16",
+    "4:3": "4:3",
+    "3:4": "3:4",
+    "3:2": "3:2",
+    "2:3": "2:3",
+}
+
+# xAI resolutions
+_XAI_RESOLUTIONS = {
+    "1k": "1024",
+    "2k": "2048",
+}
+
+DEFAULT_RESOLUTION = "1k"
+
+
+# ---------------------------------------------------------------------------
+# Config
+# ---------------------------------------------------------------------------
+
+
+def _load_xai_config() -> Dict[str, Any]:
+    """Read ``image_gen.xai`` from config.yaml."""
+    try:
+        from hermes_cli.config import load_config
+
+        cfg = load_config()
+        section = cfg.get("image_gen") if isinstance(cfg, dict) else None
+        xai_section = section.get("xai") if isinstance(section, dict) else None
+        return xai_section if isinstance(xai_section, dict) else {}
+    except Exception as exc:
+        logger.debug("Could not load image_gen.xai config: %s", exc)
+        return {}
+
+
+def _resolve_model() -> Tuple[str, Dict[str, Any]]:
+    """Decide which model to use and return ``(model_id, meta)``."""
+    env_override = os.environ.get("XAI_IMAGE_MODEL")
+    if env_override and env_override in _MODELS:
+        return env_override, _MODELS[env_override]
+
+    cfg = _load_xai_config()
+    candidate = cfg.get("model") if isinstance(cfg.get("model"), str) else None
+    if candidate and candidate in _MODELS:
+        return candidate, _MODELS[candidate]
+
+    return DEFAULT_MODEL, _MODELS[DEFAULT_MODEL]
+
+
+def _resolve_resolution() -> str:
+    """Get configured resolution."""
+    cfg = _load_xai_config()
+    res = cfg.get("resolution") if isinstance(cfg.get("resolution"), str) else None
+    if res and res in _XAI_RESOLUTIONS:
+        return res
+    return DEFAULT_RESOLUTION
+
+
+# ---------------------------------------------------------------------------
+# Provider
+# ---------------------------------------------------------------------------
+
+
+class XAIImageGenProvider(ImageGenProvider):
+    """xAI ``grok-imagine-image`` backend."""
+
+    @property
+    def name(self) -> str:
+        return "xai"
+
+    @property
+    def display_name(self) -> str:
+        return "xAI (Grok)"
+
+    def is_available(self) -> bool:
+        return bool(os.getenv("XAI_API_KEY"))
+
+    def list_models(self) -> List[Dict[str, Any]]:
+        return [
+            {
+                "id": model_id,
+                "display": meta.get("display", model_id),
+                "speed": meta.get("speed", ""),
+                "strengths": meta.get("strengths", ""),
+            }
+            for model_id, meta in _MODELS.items()
+        ]
+
+    def get_setup_schema(self) -> Dict[str, Any]:
+        return {
+            "name": "xAI (Grok)",
+            "badge": "paid",
+            "tag": "Native xAI image generation via grok-imagine-image",
+            "env_vars": [
+                {
+                    "key": "XAI_API_KEY",
+                    "prompt": "xAI API key",
+                    "url": "https://console.x.ai/",
+                },
+            ],
+        }
+
+    def generate(
+        self,
+        prompt: str,
+        aspect_ratio: str = DEFAULT_ASPECT_RATIO,
+        **kwargs: Any,
+    ) -> Dict[str, Any]:
+        """Generate an image using xAI's grok-imagine-image."""
+        api_key = os.getenv("XAI_API_KEY", "").strip()
+        if not api_key:
+            return error_response(
+                error="XAI_API_KEY not set. Get one at https://console.x.ai/",
+                error_type="missing_api_key",
+                provider="xai",
+                aspect_ratio=aspect_ratio,
+            )
+
+        model_id, meta = _resolve_model()
+        aspect = resolve_aspect_ratio(aspect_ratio)
+        xai_ar = _XAI_ASPECT_RATIOS.get(aspect, "1:1")
+        resolution = _resolve_resolution()
+        xai_res = _XAI_RESOLUTIONS.get(resolution, "1024")
+
+        # Check for editing mode (reference images)
+        reference_images = kwargs.get("reference_images", [])
+        edit_image = kwargs.get("edit_image")
+
+        payload: Dict[str, Any] = {
+            "model": API_MODEL,
+            "prompt": prompt,
+            "aspect_ratio": xai_ar,
+            "resolution": xai_res,
+        }
+
+        # Add editing parameters if present
+        if reference_images:
+            payload["reference_images"] = reference_images[:5]
+        if edit_image:
+            payload["image_url"] = edit_image
+
+        headers = {
+            "Authorization": f"Bearer {api_key}",
+            "Content-Type": "application/json",
+            "User-Agent": hermes_xai_user_agent(),
+        }
+
+        base_url = (os.getenv("XAI_BASE_URL") or "https://api.x.ai/v1").strip().rstrip("/")
+
+        try:
+            response = requests.post(
+                f"{base_url}/images/generations",
+                headers=headers,
+                json=payload,
+                timeout=120,
+            )
+            response.raise_for_status()
+        except requests.HTTPError as exc:
+            status = exc.response.status_code if exc.response else 0
+            try:
+                err_msg = exc.response.json().get("error", {}).get("message", exc.response.text[:300])
+            except Exception:
+                err_msg = exc.response.text[:300] if exc.response else str(exc)
+            logger.error("xAI image gen failed (%d): %s", status, err_msg)
+            return error_response(
+                error=f"xAI image generation failed ({status}): {err_msg}",
+                error_type="api_error",
+                provider="xai",
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect,
+            )
+        except requests.Timeout:
+            return error_response(
+                error="xAI image generation timed out (120s)",
+                error_type="timeout",
+                provider="xai",
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect,
+            )
+        except requests.ConnectionError as exc:
+            return error_response(
+                error=f"xAI connection error: {exc}",
+                error_type="connection_error",
+                provider="xai",
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect,
+            )
+
+        try:
+            result = response.json()
+        except Exception as exc:
+            return error_response(
+                error=f"xAI returned invalid JSON: {exc}",
+                error_type="invalid_response",
+                provider="xai",
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect,
+            )
+
+        # Parse response — xAI returns data[0].b64_json or data[0].url
+        data = result.get("data", [])
+        if not data:
+            return error_response(
+                error="xAI returned no image data",
+                error_type="empty_response",
+                provider="xai",
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect,
+            )
+
+        first = data[0]
+        b64 = first.get("b64_json")
+        url = first.get("url")
+
+        if b64:
+            try:
+                saved_path = save_b64_image(b64, prefix=f"xai_{model_id}")
+            except Exception as exc:
+                return error_response(
+                    error=f"Could not save image to cache: {exc}",
+                    error_type="io_error",
+                    provider="xai",
+                    model=model_id,
+                    prompt=prompt,
+                    aspect_ratio=aspect,
+                )
+            image_ref = str(saved_path)
+        elif url:
+            image_ref = url
+        else:
+            return error_response(
+                error="xAI response contained neither b64_json nor URL",
+                error_type="empty_response",
+                provider="xai",
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect,
+            )
+
+        extra: Dict[str, Any] = {}
+        if reference_images:
+            extra["reference_images"] = len(reference_images)
+
+        return success_response(
+            image=image_ref,
+            model=model_id,
+            prompt=prompt,
+            aspect_ratio=aspect,
+            provider="xai",
+            extra=extra if extra else None,
+        )
+
+
+# ---------------------------------------------------------------------------
+# Plugin registration
+# ---------------------------------------------------------------------------
+
+
+def register(ctx: Any) -> None:
+    """Register this provider with the image gen registry."""
+    ctx.register_image_gen_provider(XAIImageGenProvider())

plugins/image_gen/xai/plugin.yaml

@@ -0,0 +1,7 @@
+name: xai
+version: 1.0.0
+description: "xAI image generation backend (grok-imagine-image). Supports text-to-image and editing."
+author: Julien Talbot
+kind: backend
+requires_env:
+  - XAI_API_KEY

tests/plugins/image_gen/test_xai_provider.py

@@ -0,0 +1,260 @@
+#!/usr/bin/env python3
+"""Tests for xAI image generation provider."""
+
+from __future__ import annotations
+
+import json
+import os
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+
+@pytest.fixture(autouse=True)
+def _fake_api_key(monkeypatch):
+    """Ensure XAI_API_KEY is set for all tests."""
+    monkeypatch.setenv("XAI_API_KEY", "test-key-12345")
+
+
+# ---------------------------------------------------------------------------
+# Provider class tests
+# ---------------------------------------------------------------------------
+
+
+class TestXAIImageGenProvider:
+    def test_name(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        assert provider.name == "xai"
+
+    def test_display_name(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        assert provider.display_name == "xAI (Grok)"
+
+    def test_is_available_with_key(self, monkeypatch):
+        monkeypatch.setenv("XAI_API_KEY", "sk-xxx")
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        assert provider.is_available() is True
+
+    def test_is_available_without_key(self, monkeypatch):
+        monkeypatch.delenv("XAI_API_KEY", raising=False)
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        assert provider.is_available() is False
+
+    def test_list_models(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        models = provider.list_models()
+        assert len(models) >= 1
+        assert models[0]["id"] == "grok-imagine-image"
+
+    def test_default_model(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        assert provider.default_model() == "grok-imagine-image"
+
+    def test_get_setup_schema(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        schema = provider.get_setup_schema()
+        assert schema["name"] == "xAI (Grok)"
+        assert schema["badge"] == "paid"
+        assert len(schema["env_vars"]) == 1
+        assert schema["env_vars"][0]["key"] == "XAI_API_KEY"
+
+
+# ---------------------------------------------------------------------------
+# Config tests
+# ---------------------------------------------------------------------------
+
+
+class TestConfig:
+    def test_default_model(self):
+        from plugins.image_gen.xai import _resolve_model
+
+        model_id, meta = _resolve_model()
+        assert model_id == "grok-imagine-image"
+
+    def test_default_resolution(self):
+        from plugins.image_gen.xai import _resolve_resolution
+
+        assert _resolve_resolution() == "1k"
+
+    def test_custom_model(self, monkeypatch):
+        monkeypatch.setenv("XAI_IMAGE_MODEL", "grok-imagine-image")
+        from plugins.image_gen.xai import _resolve_model
+
+        model_id, _ = _resolve_model()
+        assert model_id == "grok-imagine-image"
+
+
+# ---------------------------------------------------------------------------
+# Generate tests
+# ---------------------------------------------------------------------------
+
+
+class TestGenerate:
+    def test_missing_api_key(self, monkeypatch):
+        monkeypatch.delenv("XAI_API_KEY", raising=False)
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        provider = XAIImageGenProvider()
+        result = provider.generate(prompt="test")
+        assert result["success"] is False
+        assert "XAI_API_KEY" in result["error"]
+
+    def test_successful_generation(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        mock_resp = MagicMock()
+        mock_resp.status_code = 200
+        mock_resp.raise_for_status = MagicMock()
+        mock_resp.json.return_value = {
+            "data": [{"b64_json": "dGVzdC1pbWFnZS1kYXRh"}],  # base64 "test-image-data"
+        }
+
+        with patch("plugins.image_gen.xai.requests.post", return_value=mock_resp):
+            with patch("plugins.image_gen.xai.save_b64_image", return_value="/tmp/test.png"):
+                provider = XAIImageGenProvider()
+                result = provider.generate(prompt="A cat playing piano")
+
+        assert result["success"] is True
+        assert result["image"] == "/tmp/test.png"
+        assert result["provider"] == "xai"
+        assert result["model"] == "grok-imagine-image"
+
+    def test_successful_url_response(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        mock_resp = MagicMock()
+        mock_resp.status_code = 200
+        mock_resp.raise_for_status = MagicMock()
+        mock_resp.json.return_value = {
+            "data": [{"url": "https://xai.image/result.png"}],
+        }
+
+        with patch("plugins.image_gen.xai.requests.post", return_value=mock_resp):
+            provider = XAIImageGenProvider()
+            result = provider.generate(prompt="A cat playing piano")
+
+        assert result["success"] is True
+        assert result["image"] == "https://xai.image/result.png"
+
+    def test_api_error(self):
+        import requests as req_lib
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        mock_resp = MagicMock()
+        mock_resp.status_code = 401
+        mock_resp.text = "Unauthorized"
+        mock_resp.json.return_value = {"error": {"message": "Invalid API key"}}
+        mock_resp.raise_for_status.side_effect = req_lib.HTTPError(response=mock_resp)
+
+        with patch("plugins.image_gen.xai.requests.post", return_value=mock_resp):
+            provider = XAIImageGenProvider()
+            result = provider.generate(prompt="test")
+
+        assert result["success"] is False
+        assert result["error_type"] == "api_error"
+
+    def test_timeout(self):
+        import requests as req_lib
+
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        with patch("plugins.image_gen.xai.requests.post", side_effect=req_lib.Timeout()):
+            provider = XAIImageGenProvider()
+            result = provider.generate(prompt="test")
+
+        assert result["success"] is False
+        assert result["error_type"] == "timeout"
+
+    def test_empty_response(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        mock_resp = MagicMock()
+        mock_resp.status_code = 200
+        mock_resp.raise_for_status = MagicMock()
+        mock_resp.json.return_value = {"data": []}
+
+        with patch("plugins.image_gen.xai.requests.post", return_value=mock_resp):
+            provider = XAIImageGenProvider()
+            result = provider.generate(prompt="test")
+
+        assert result["success"] is False
+        assert result["error_type"] == "empty_response"
+
+    def test_with_reference_images(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        mock_resp = MagicMock()
+        mock_resp.status_code = 200
+        mock_resp.raise_for_status = MagicMock()
+        mock_resp.json.return_value = {
+            "data": [{"url": "https://xai.image/edited.png"}],
+        }
+
+        with patch("plugins.image_gen.xai.requests.post", return_value=mock_resp) as mock_post:
+            provider = XAIImageGenProvider()
+            result = provider.generate(
+                prompt="Edit this image",
+                reference_images=["https://example.com/ref1.png", "https://example.com/ref2.png"],
+            )
+
+        assert result["success"] is True
+        # Check that reference_images was passed in payload
+        call_args = mock_post.call_args
+        payload = call_args.kwargs.get("json") or call_args[1].get("json")
+        assert "reference_images" in payload
+        assert len(payload["reference_images"]) == 2
+
+    def test_auth_header(self):
+        from plugins.image_gen.xai import XAIImageGenProvider
+
+        mock_resp = MagicMock()
+        mock_resp.status_code = 200
+        mock_resp.raise_for_status = MagicMock()
+        mock_resp.json.return_value = {
+            "data": [{"url": "https://xai.image/test.png"}],
+        }
+
+        with patch("plugins.image_gen.xai.requests.post", return_value=mock_resp) as mock_post:
+            provider = XAIImageGenProvider()
+            provider.generate(prompt="test")
+
+        call_args = mock_post.call_args
+        headers = call_args.kwargs.get("headers") or call_args[1].get("headers")
+        assert "Bearer test-key-12345" in headers["Authorization"]
+        assert "Hermes-Agent" in headers["User-Agent"]
+
+
+# ---------------------------------------------------------------------------
+# Registration test
+# ---------------------------------------------------------------------------
+
+
+class TestRegistration:
+    def test_register(self):
+        from plugins.image_gen.xai import XAIImageGenProvider, register
+
+        mock_ctx = MagicMock()
+        register(mock_ctx)
+        mock_ctx.register_image_gen_provider.assert_called_once()
+        provider = mock_ctx.register_image_gen_provider.call_args[0][0]
+        assert isinstance(provider, XAIImageGenProvider)
+        assert provider.name == "xai"