feat: Add Anthropic Compatible provider support

- Added support for 'anthropic-compatible' provider nodes in backend.
- Implemented isAnthropicCompatible logic in open-sse for /messages URL construction and headers.
- Added UI for creating and managing Anthropic Compatible providers in the dashboard.
- Updated validation logic for Anthropic-compatible endpoints.
- Sanitize base URL input (strip trailing /messages) to prevent 404s and improve UX.
- Improve validation: use GET /models (2xx success), and support x-api-key / Authorization Bearer hybrid proxies.
- Enable model import via /models for Anthropic Compatible providers.
- Ensure Authorization is omitted when x-api-key is present to avoid strict proxy conflicts.
- Resolve Anthropic-compatible credentials by prefix during model resolution (e.g., acx/model).
- Update default executor to match provider header/url behavior for Anthropic-compatible providers.

src/app/api/provider-nodes/route.js

@@ -1,11 +1,15 @@
 import { NextResponse } from "next/server";
 import { createProviderNode, getProviderNodes } from "@/models";
-import { OPENAI_COMPATIBLE_PREFIX } from "@/shared/constants/providers";
+import { OPENAI_COMPATIBLE_PREFIX, ANTHROPIC_COMPATIBLE_PREFIX } from "@/shared/constants/providers";
 
 const OPENAI_COMPATIBLE_DEFAULTS = {
   baseUrl: "https://api.openai.com/v1",
 };
 
+const ANTHROPIC_COMPATIBLE_DEFAULTS = {
+  baseUrl: "https://api.anthropic.com/v1",
+};
+
 // GET /api/provider-nodes - List all provider nodes
 export async function GET() {
   try {
@@ -21,7 +25,7 @@ export async function GET() {
 export async function POST(request) {
   try {
     const body = await request.json();
-    const { name, prefix, apiType, baseUrl } = body;
+    const { name, prefix, apiType, baseUrl, type } = body;
 
     if (!name?.trim()) {
       return NextResponse.json({ error: "Name is required" }, { status: 400 });
@@ -31,20 +35,44 @@ export async function POST(request) {
       return NextResponse.json({ error: "Prefix is required" }, { status: 400 });
     }
 
-    if (!apiType || !["chat", "responses"].includes(apiType)) {
-      return NextResponse.json({ error: "Invalid OpenAI compatible API type" }, { status: 400 });
+    // Determine type
+    const nodeType = type || "openai-compatible";
+
+    if (nodeType === "openai-compatible") {
+      if (!apiType || !["chat", "responses"].includes(apiType)) {
+        return NextResponse.json({ error: "Invalid OpenAI compatible API type" }, { status: 400 });
+      }
+
+      const node = await createProviderNode({
+        id: `${OPENAI_COMPATIBLE_PREFIX}${apiType}-${crypto.randomUUID()}`,
+        type: "openai-compatible",
+        prefix: prefix.trim(),
+        apiType,
+        baseUrl: (baseUrl || OPENAI_COMPATIBLE_DEFAULTS.baseUrl).trim(),
+        name: name.trim(),
+      });
+      return NextResponse.json({ node }, { status: 201 });
     }
 
-    const node = await createProviderNode({
-      id: `${OPENAI_COMPATIBLE_PREFIX}${apiType}-${crypto.randomUUID()}`,
-      type: "openai-compatible",
-      prefix: prefix.trim(),
-      apiType,
-      baseUrl: (baseUrl || OPENAI_COMPATIBLE_DEFAULTS.baseUrl).trim(),
-      name: name.trim(),
-    });
+    if (nodeType === "anthropic-compatible") {
+      // Sanitize Base URL: remove trailing slash, and remove trailing /messages if user added it
+      // This prevents double-appending /messages at runtime
+      let sanitizedBaseUrl = (baseUrl || ANTHROPIC_COMPATIBLE_DEFAULTS.baseUrl).trim().replace(/\/$/, "");
+      if (sanitizedBaseUrl.endsWith("/messages")) {
+        sanitizedBaseUrl = sanitizedBaseUrl.slice(0, -9); // remove /messages
+      }
 
-    return NextResponse.json({ node }, { status: 201 });
+      const node = await createProviderNode({
+        id: `${ANTHROPIC_COMPATIBLE_PREFIX}${crypto.randomUUID()}`,
+        type: "anthropic-compatible",
+        prefix: prefix.trim(),
+        baseUrl: sanitizedBaseUrl,
+        name: name.trim(),
+      });
+      return NextResponse.json({ node }, { status: 201 });
+    }
+
+    return NextResponse.json({ error: "Invalid provider node type" }, { status: 400 });
   } catch (error) {
     console.log("Error creating provider node:", error);
     return NextResponse.json({ error: "Failed to create provider node" }, { status: 500 });