chore: import upstream snapshot with attribution

2026-07-13 11:56:03 +08:00
commit b4fbd6fe9f
6241 changed files with 2261833 additions and 0 deletions
@@ -0,0 +1,316 @@
+---
+sidebar_position: 11
+title: "Image Generation Provider Plugins"
+description: "How to build an image-generation backend plugin for Hermes Agent"
+---
+
+# Building an Image Generation Provider Plugin
+
+Image-gen provider plugins register a backend that services every `image_generate` tool call — DALL·E, gpt-image, Grok, Flux, Imagen, Stable Diffusion, fal, Replicate, a local ComfyUI rig, anything. Built-in providers (OpenAI, OpenAI-Codex, xAI) all ship as plugins. You can add a new one, or override a bundled one, by dropping a directory into `plugins/image_gen/<name>/`.
+
+:::tip
+Image-gen is one of several **backend plugins** Hermes supports. The others (with more specialized ABCs) are [Memory Provider Plugins](/developer-guide/memory-provider-plugin), [Context Engine Plugins](/developer-guide/context-engine-plugin), and [Model Provider Plugins](/developer-guide/model-provider-plugin). General tool/hook/CLI plugins live in [Build a Hermes Plugin](/developer-guide/plugins).
+:::
+
+## How discovery works
+
+Hermes scans for image-gen backends in three places:
+
+1. **Bundled** — `<repo>/plugins/image_gen/<name>/` (auto-loaded with `kind: backend`, always available)
+2. **User** — `~/.hermes/plugins/image_gen/<name>/` (opt-in via `plugins.enabled`)
+3. **Pip** — packages declaring a `hermes_agent.plugins` entry point
+
+Each plugin's `register(ctx)` function calls `ctx.register_image_gen_provider(...)` — that puts it into the registry in `agent/image_gen_registry.py`. The active provider is picked by `image_gen.provider` in `config.yaml`; `hermes tools` walks users through selection.
+
+The `image_generate` tool wrapper asks the registry for the active provider and dispatches there. If no provider is registered, the tool surfaces a helpful error pointing at `hermes tools`.
+
+## Directory structure
+
+```
+plugins/image_gen/my-backend/
+├── __init__.py      # ImageGenProvider subclass + register()
+└── plugin.yaml      # Manifest with kind: backend
+```
+
+A bundled plugin is complete at this point. User plugins at `~/.hermes/plugins/image_gen/<name>/` need to be added to `plugins.enabled` in `config.yaml` (or run `hermes plugins enable <name>`).
+
+## The ImageGenProvider ABC
+
+Subclass `agent.image_gen_provider.ImageGenProvider`. The only required members are the `name` property and the `generate()` method — everything else has sane defaults:
+
+```python
+# plugins/image_gen/my-backend/__init__.py
+from typing import Any, Dict, List, Optional
+import os
+
+from agent.image_gen_provider import (
+    DEFAULT_ASPECT_RATIO,
+    ImageGenProvider,
+    error_response,
+    normalize_reference_images,
+    resolve_aspect_ratio,
+    save_b64_image,
+    success_response,
+)
+
+
+class MyBackendImageGenProvider(ImageGenProvider):
+    @property
+    def name(self) -> str:
+        # Stable id used in image_gen.provider config. Lowercase, no spaces.
+        return "my-backend"
+
+    @property
+    def display_name(self) -> str:
+        # Human label shown in `hermes tools`. Defaults to name.title() if omitted.
+        return "My Backend"
+
+    def is_available(self) -> bool:
+        # Return False if credentials or deps are missing.
+        # The tool's availability gate calls this before dispatch.
+        if not os.environ.get("MY_BACKEND_API_KEY"):
+            return False
+        try:
+            import my_backend_sdk  # noqa: F401
+        except ImportError:
+            return False
+        return True
+
+    def list_models(self) -> List[Dict[str, Any]]:
+        # Catalog shown in `hermes tools` model picker.
+        return [
+            {
+                "id": "my-model-fast",
+                "display": "My Model (Fast)",
+                "speed": "~5s",
+                "strengths": "Quick iteration",
+                "price": "$0.01/image",
+            },
+            {
+                "id": "my-model-hq",
+                "display": "My Model (HQ)",
+                "speed": "~30s",
+                "strengths": "Highest fidelity",
+                "price": "$0.04/image",
+            },
+        ]
+
+    def default_model(self) -> Optional[str]:
+        return "my-model-fast"
+
+    def get_setup_schema(self) -> Dict[str, Any]:
+        # Metadata for the `hermes tools` picker — keys to prompt for at setup.
+        return {
+            "name": "My Backend",
+            "badge": "paid",        # optional; shown as a short tag in the picker
+            "tag": "One-line description shown under the name",
+            "env_vars": [
+                {
+                    "key": "MY_BACKEND_API_KEY",
+                    "prompt": "My Backend API key",
+                    "url": "https://my-backend.example.com/api-keys",
+                },
+            ],
+        }
+
+    def capabilities(self) -> Dict[str, Any]:
+        # Declare whether this backend supports image-to-image / editing.
+        # The tool layer surfaces this in the dynamic schema so the model
+        # knows when `image_url` is honored. Default (if you omit this) is
+        # text-only: {"modalities": ["text"], "max_reference_images": 0}.
+        return {"modalities": ["text", "image"], "max_reference_images": 4}
+
+    def generate(
+        self,
+        prompt: str,
+        aspect_ratio: str = DEFAULT_ASPECT_RATIO,
+        *,
+        image_url: Optional[str] = None,
+        reference_image_urls: Optional[List[str]] = None,
+        **kwargs: Any,
+    ) -> Dict[str, Any]:
+        prompt = (prompt or "").strip()
+        aspect_ratio = resolve_aspect_ratio(aspect_ratio)
+
+        if not prompt:
+            return error_response(
+                error="Prompt is required",
+                error_type="invalid_input",
+                provider=self.name,
+                prompt="",
+                aspect_ratio=aspect_ratio,
+            )
+
+        # Routing: if image_url (or reference_image_urls) is set, the call is
+        # an image-to-image / edit request; otherwise text-to-image. Report
+        # which path you took via the `modality` field of success_response.
+        sources = []
+        if image_url:
+            sources.append(image_url)
+        sources.extend(normalize_reference_images(reference_image_urls) or [])
+        modality = "image" if sources else "text"
+
+        # Model selection precedence: env var → config → default. The helper
+        # _resolve_model() in the built-in openai plugin is a good reference.
+        model_id = kwargs.get("model") or self.default_model() or "my-model-fast"
+
+        try:
+            import my_backend_sdk
+            client = my_backend_sdk.Client(api_key=os.environ["MY_BACKEND_API_KEY"])
+            if modality == "image":
+                result = client.edit(
+                    prompt=prompt,
+                    model=model_id,
+                    image_urls=sources,
+                )
+            else:
+                result = client.generate(
+                    prompt=prompt,
+                    model=model_id,
+                    aspect_ratio=aspect_ratio,
+                )
+
+            # Two shapes supported:
+            #   - URL string: return it as `image`
+            #   - base64 data: save under $HERMES_HOME/cache/images/ via save_b64_image()
+            if result.get("image_b64"):
+                path = save_b64_image(
+                    result["image_b64"],
+                    prefix=self.name,
+                    extension="png",
+                )
+                image = str(path)
+            else:
+                image = result["image_url"]
+
+            return success_response(
+                image=image,
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect_ratio,
+                provider=self.name,
+                modality=modality,
+            )
+        except Exception as exc:
+            return error_response(
+                error=str(exc),
+                error_type=type(exc).__name__,
+                provider=self.name,
+                model=model_id,
+                prompt=prompt,
+                aspect_ratio=aspect_ratio,
+            )
+
+
+def register(ctx) -> None:
+    """Plugin entry point — called once at load time."""
+    ctx.register_image_gen_provider(MyBackendImageGenProvider())
+```
+
+## plugin.yaml
+
+```yaml
+name: my-backend
+version: 1.0.0
+description: My image backend — text-to-image via My Backend SDK
+author: Your Name
+kind: backend
+requires_env:
+  - MY_BACKEND_API_KEY
+```
+
+`kind: backend` is what routes the plugin to the image-gen registration path. `requires_env` is prompted during `hermes plugins install`.
+
+## ABC reference
+
+Full contract in `agent/image_gen_provider.py`. The methods you'll typically override:
+
+| Member | Required | Default | Purpose |
+|---|---|---|---|
+| `name` | ✅ | — | Stable id used in `image_gen.provider` config |
+| `display_name` | — | `name.title()` | Label shown in `hermes tools` |
+| `is_available()` | — | `True` | Gate for missing creds/deps |
+| `list_models()` | — | `[]` | Catalog for `hermes tools` model picker |
+| `default_model()` | — | first from `list_models()` | Fallback when no model is configured |
+| `get_setup_schema()` | — | minimal | Picker metadata + env-var prompts |
+| `generate(prompt, aspect_ratio, **kwargs)` | ✅ | — | The call |
+
+## Response format
+
+`generate()` must return a dict built via `success_response()` or `error_response()`. Both live in `agent/image_gen_provider.py`.
+
+**Success:**
+```python
+success_response(
+    image=<url-or-absolute-path>,
+    model=<model-id>,
+    prompt=<echoed-prompt>,
+    aspect_ratio="landscape" | "square" | "portrait",
+    provider=<your-provider-name>,
+    extra={...},  # optional backend-specific fields
+)
+```
+
+**Error:**
+```python
+error_response(
+    error="human-readable message",
+    error_type="provider_error" | "invalid_input" | "<exception class name>",
+    provider=<your-provider-name>,
+    model=<model-id>,
+    prompt=<prompt>,
+    aspect_ratio=<resolved aspect>,
+)
+```
+
+The tool wrapper JSON-serializes the dict and hands it to the LLM. Errors are surfaced as the tool result; the LLM decides how to explain them to the user.
+
+## Handling base64 vs URL output
+
+Some backends return image URLs (fal, Replicate); others return base64 payloads (OpenAI gpt-image-2). For the base64 case, use `save_b64_image()` — it writes to `$HERMES_HOME/cache/images/<prefix>_<timestamp>_<uuid>.<ext>` and returns the absolute `Path`. Pass that path (as `str`) as `image=` in `success_response()`. Gateway delivery (Telegram photo bubble, Discord attachment) recognizes both URLs and absolute paths.
+
+## User overrides
+
+Drop a user plugin at `~/.hermes/plugins/image_gen/<name>/` with the same `name` property as a bundled one and enable it via `hermes plugins enable <name>` — the registry is last-writer-wins, so your version replaces the built-in. Useful for pointing an `openai` plugin at a private proxy, or swapping in a custom model catalog.
+
+## Testing
+
+```bash
+export HERMES_HOME=/tmp/hermes-imggen-test
+mkdir -p $HERMES_HOME/plugins/image_gen/my-backend
+# …copy __init__.py + plugin.yaml into that dir…
+
+export MY_BACKEND_API_KEY=your-test-key
+hermes plugins enable my-backend
+
+# Pick it as the active provider
+echo "image_gen:" >> $HERMES_HOME/config.yaml
+echo "  provider: my-backend" >> $HERMES_HOME/config.yaml
+
+# Exercise it
+hermes -z "Generate an image of a corgi in a spacesuit"
+```
+
+Or interactively: `hermes tools` → "Image Generation" → select `my-backend` → enter API key if prompted.
+
+## Reference implementations
+
+- **`plugins/image_gen/openai/__init__.py`** — gpt-image-2 at low/medium/high tiers as three virtual model IDs sharing one API model with different `quality` params. Good example of tiered models under a single backend + config.yaml precedence chain.
+- **`plugins/image_gen/xai/__init__.py`** — Grok Imagine via xAI. Different shape (URL output, simpler catalog).
+- **`plugins/image_gen/openai-codex/__init__.py`** — Codex-style Responses API variant reusing the OpenAI SDK with a different routing base URL.
+
+## Distribute via pip
+
+```toml
+# pyproject.toml
+[project.entry-points."hermes_agent.plugins"]
+my-backend-imggen = "my_backend_imggen_package"
+```
+
+`my_backend_imggen_package` must expose a top-level `register` function. See [Distribute via pip](/developer-guide/plugins#distribute-via-pip) in the general plugin guide for the full setup.
+
+## Related pages
+
+- [Image Generation](/user-guide/features/image-generation) — user-facing feature documentation
+- [Plugins overview](/user-guide/features/plugins) — all plugin types at a glance
+- [Build a Hermes Plugin](/developer-guide/plugins) — general tools/hooks/slash commands guide