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/providers/[id]/models/route.js

@@ -1,6 +1,6 @@
 import { NextResponse } from "next/server";
 import { getProviderConnectionById } from "@/models";
-import { isOpenAICompatibleProvider } from "@/shared/constants/providers";
+import { isOpenAICompatibleProvider, isAnthropicCompatibleProvider } from "@/shared/constants/providers";
 
 // Provider models endpoints configuration
 const PROVIDER_MODELS_CONFIG = {
@@ -119,6 +119,47 @@ export async function GET(request, { params }) {
       });
     }
 
+    if (isAnthropicCompatibleProvider(connection.provider)) {
+      let baseUrl = connection.providerSpecificData?.baseUrl;
+      if (!baseUrl) {
+        return NextResponse.json({ error: "No base URL configured for Anthropic compatible provider" }, { status: 400 });
+      }
+      
+      baseUrl = baseUrl.replace(/\/$/, "");
+      if (baseUrl.endsWith("/messages")) {
+        baseUrl = baseUrl.slice(0, -9);
+      }
+      
+      const url = `${baseUrl}/models`;
+      const response = await fetch(url, {
+        method: "GET",
+        headers: {
+          "Content-Type": "application/json",
+          "x-api-key": connection.apiKey,
+          "anthropic-version": "2023-06-01",
+          "Authorization": `Bearer ${connection.apiKey}`
+        },
+      });
+
+      if (!response.ok) {
+        const errorText = await response.text();
+        console.log(`Error fetching models from ${connection.provider}:`, errorText);
+        return NextResponse.json(
+          { error: `Failed to fetch models: ${response.status}` },
+          { status: response.status }
+        );
+      }
+
+      const data = await response.json();
+      const models = data.data || data.models || [];
+
+      return NextResponse.json({
+        provider: connection.provider,
+        connectionId: connection.id,
+        models
+      });
+    }
+
     const config = PROVIDER_MODELS_CONFIG[connection.provider];
     if (!config) {
       return NextResponse.json(

src/app/api/providers/[id]/test/route.js

@@ -2,7 +2,7 @@ import { NextResponse } from "next/server";
 import { getProviderConnectionById, updateProviderConnection, isCloudEnabled } from "@/lib/localDb";
 import { getConsistentMachineId } from "@/shared/utils/machineId";
 import { syncToCloud } from "@/app/api/sync/cloud/route";
-import { isOpenAICompatibleProvider } from "@/shared/constants/providers";
+import { isOpenAICompatibleProvider, isAnthropicCompatibleProvider } from "@/shared/constants/providers";
 import {
   GEMINI_CONFIG,
   ANTIGRAVITY_CONFIG,
@@ -322,6 +322,32 @@ async function testApiKeyConnection(connection) {
     }
   }
 
+  // Anthropic Compatible providers - test via /models endpoint
+  if (isAnthropicCompatibleProvider(connection.provider)) {
+    let modelsBase = connection.providerSpecificData?.baseUrl;
+    if (!modelsBase) {
+      return { valid: false, error: "Missing base URL" };
+    }
+    try {
+      modelsBase = modelsBase.replace(/\/$/, "");
+      if (modelsBase.endsWith("/messages")) {
+        modelsBase = modelsBase.slice(0, -9);
+      }
+      
+      const modelsUrl = `${modelsBase}/models`;
+      const res = await fetch(modelsUrl, {
+        headers: { 
+          "x-api-key": connection.apiKey,
+          "anthropic-version": "2023-06-01",
+          "Authorization": `Bearer ${connection.apiKey}`
+        },
+      });
+      return { valid: res.ok, error: res.ok ? null : "Invalid API key or base URL" };
+    } catch (err) {
+      return { valid: false, error: err.message };
+    }
+  }
+
   try {
     switch (connection.provider) {
       case "openai": {

src/app/api/providers/route.js

@@ -1,7 +1,7 @@
 import { NextResponse } from "next/server";
 import { getProviderConnections, createProviderConnection, getProviderNodeById, isCloudEnabled } from "@/models";
 import { APIKEY_PROVIDERS } from "@/shared/constants/config";
-import { isOpenAICompatibleProvider } from "@/shared/constants/providers";
+import { isOpenAICompatibleProvider, isAnthropicCompatibleProvider } from "@/shared/constants/providers";
 import { getConsistentMachineId } from "@/shared/utils/machineId";
 import { syncToCloud } from "@/app/api/sync/cloud/route";
 
@@ -33,7 +33,11 @@ export async function POST(request) {
     const { provider, apiKey, name, priority, globalPriority, defaultModel, testStatus } = body;
 
     // Validation
-    if (!provider || (!APIKEY_PROVIDERS[provider] && !isOpenAICompatibleProvider(provider))) {
+    const isValidProvider = APIKEY_PROVIDERS[provider] || 
+                          isOpenAICompatibleProvider(provider) || 
+                          isAnthropicCompatibleProvider(provider);
+
+    if (!provider || !isValidProvider) {
       return NextResponse.json({ error: "Invalid provider" }, { status: 400 });
     }
     if (!apiKey) {
@@ -62,6 +66,22 @@ export async function POST(request) {
         baseUrl: node.baseUrl,
         nodeName: node.name,
       };
+    } else if (isAnthropicCompatibleProvider(provider)) {
+      const node = await getProviderNodeById(provider);
+      if (!node) {
+        return NextResponse.json({ error: "Anthropic Compatible node not found" }, { status: 404 });
+      }
+
+      const existingConnections = await getProviderConnections({ provider });
+      if (existingConnections.length > 0) {
+        return NextResponse.json({ error: "Only one connection is allowed for this Anthropic Compatible node" }, { status: 400 });
+      }
+
+      providerSpecificData = {
+        prefix: node.prefix,
+        baseUrl: node.baseUrl,
+        nodeName: node.name,
+      };
     }
 
     const newConnection = await createProviderConnection({

src/app/api/providers/validate/route.js

@@ -1,6 +1,6 @@
 import { NextResponse } from "next/server";
 import { getProviderNodeById } from "@/models";
-import { isOpenAICompatibleProvider } from "@/shared/constants/providers";
+import { isOpenAICompatibleProvider, isAnthropicCompatibleProvider } from "@/shared/constants/providers";
 
 // POST /api/providers/validate - Validate API key with provider
 export async function POST(request) {
@@ -33,6 +33,34 @@ export async function POST(request) {
         });
       }
 
+      if (isAnthropicCompatibleProvider(provider)) {
+        const node = await getProviderNodeById(provider);
+        if (!node) {
+          return NextResponse.json({ error: "Anthropic Compatible node not found" }, { status: 404 });
+        }
+        
+        let normalizedBase = node.baseUrl?.trim().replace(/\/$/, "") || "";
+        if (normalizedBase.endsWith("/messages")) {
+          normalizedBase = normalizedBase.slice(0, -9); // remove /messages
+        }
+        
+        const modelsUrl = `${normalizedBase}/models`;
+        
+        const res = await fetch(modelsUrl, {
+          headers: { 
+            "x-api-key": apiKey,
+            "anthropic-version": "2023-06-01",
+            "Authorization": `Bearer ${apiKey}` 
+          },
+        });
+        
+        isValid = res.ok;
+        return NextResponse.json({
+          valid: isValid,
+          error: isValid ? null : "Invalid API key",
+        });
+      }
+
       switch (provider) {
         case "openai":
           const openaiRes = await fetch("https://api.openai.com/v1/models", {