adds attachment support

docs/api/rest.md

@@ -10,6 +10,12 @@ Content type:
 - Requests with bodies use `application/json`.
 - Responses are JSON unless noted otherwise.
 
+Chat upload limits:
+- Chat completion and direct message payloads support inline attachments up to a 32 MB request body.
+- Up to 8 attachments per message.
+- Image attachments: PNG or JPEG only, max 6 MB each.
+- Text attachments: up to 8 MB source size each; server accepts at most 200,000 characters of inlined text content per attachment.
+
 ## Health + Auth
 
 ### `GET /health`
@@ -74,11 +80,34 @@ Behavior notes:
   "role": "system|user|assistant|tool",
   "content": "string",
   "name": "optional",
-  "metadata": {}
+  "metadata": {},
+  "attachments": [
+    {
+      "kind": "image",
+      "id": "attachment-id",
+      "filename": "photo.jpg",
+      "mimeType": "image/jpeg",
+      "sizeBytes": 12345,
+      "dataUrl": "data:image/jpeg;base64,..."
+    },
+    {
+      "kind": "text",
+      "id": "attachment-id",
+      "filename": "notes.md",
+      "mimeType": "text/markdown",
+      "sizeBytes": 4567,
+      "text": "# Notes\\n...",
+      "truncated": false
+    }
+  ]
 }
 ```
 - Response: `{ "message": Message }`
 
+Notes:
+- `attachments` is optional and is merged into stored `message.metadata.attachments`.
+- Tool messages should not include attachments.
+
 ## Chat Completions (non-streaming)
 
 ### `POST /v1/chat-completions`
@@ -89,7 +118,30 @@ Behavior notes:
   "provider": "openai|anthropic|xai",
   "model": "string",
   "messages": [
-    { "role": "system|user|assistant|tool", "content": "string", "name": "optional" }
+    {
+      "role": "system|user|assistant|tool",
+      "content": "string",
+      "name": "optional",
+      "attachments": [
+        {
+          "kind": "image",
+          "id": "attachment-id",
+          "filename": "photo.jpg",
+          "mimeType": "image/jpeg",
+          "sizeBytes": 12345,
+          "dataUrl": "data:image/jpeg;base64,..."
+        },
+        {
+          "kind": "text",
+          "id": "attachment-id",
+          "filename": "notes.md",
+          "mimeType": "text/markdown",
+          "sizeBytes": 4567,
+          "text": "# Notes\\n...",
+          "truncated": false
+        }
+      ]
+    }
   ],
   "temperature": 0.2,
   "maxTokens": 256
@@ -112,7 +164,12 @@ Behavior notes:
 - For `chatId` calls, server stores only *new* non-assistant messages from provided history to avoid duplicates.
 - Server persists final assistant output and call metadata (`LlmCall`) in DB.
 - Server updates chat-level model metadata on each call: `lastUsedProvider`/`lastUsedModel`; first successful/failed call also initializes `initiatedProvider`/`initiatedModel` if unset.
+- Attachments are optional and currently apply to `user` messages. Persisted chat history stores them under `message.metadata.attachments`.
+- Images are forwarded inline to providers as multimodal image parts. Use PNG or JPEG for cross-provider compatibility.
+- Text files are forwarded as explicit text blocks rather than provider-managed file references. Large text attachments should already be truncated client-side before submission.
 - For `openai` and `xai`, backend enables tool use during chat completion with an internal system instruction.
+- For `openai` and `xai`, image attachments are sent as chat-completions content parts alongside text.
+- For `anthropic`, image attachments are sent as Messages API `image` blocks using base64 source data; text attachments are added as `text` blocks.
 - Available tool calls for chat: `web_search` and `fetch_url`.
 - `web_search` returns ranked results with per-result summaries/snippets. Its backend engine is selected by `CHAT_WEB_SEARCH_ENGINE` (`exa` default, or `searxng` with `SEARXNG_BASE_URL` set). SearXNG mode requires the instance to allow `format=json`.
 - `fetch_url` fetches a URL and returns plaintext page content (HTML converted to text server-side).
@@ -189,10 +246,32 @@ Search run notes:
   "role": "system|user|assistant|tool",
   "content": "...",
   "name": null,
-  "metadata": null
+  "metadata": {
+    "attachments": [
+      {
+        "kind": "image",
+        "id": "attachment-id",
+        "filename": "photo.jpg",
+        "mimeType": "image/jpeg",
+        "sizeBytes": 12345,
+        "dataUrl": "data:image/jpeg;base64,..."
+      },
+      {
+        "kind": "text",
+        "id": "attachment-id",
+        "filename": "notes.md",
+        "mimeType": "text/markdown",
+        "sizeBytes": 4567,
+        "text": "# Notes\\n...",
+        "truncated": false
+      }
+    ]
+  }
 }
 ```
 
+`metadata` remains nullable. Tool-call log messages still use `metadata.kind = "tool_call"`; regular user messages with attachments use `metadata.attachments`.
+
 `ChatDetail`
 ```json
 {