fix: minimal system prompt sanitization

AGENTS.md

@@ -0,0 +1,43 @@
+# opencode-anthropic-auth
+
+OpenCode plugin for Anthropic OAuth authentication (Claude Pro/Max).
+
+## Testing the Plugin
+
+### 1. Add plugin to opencode.json
+
+Add the plugin path to the `plugins` field in your `opencode.json` (usually at `~/.config/opencode/opencode.json`):
+
+```json
+{
+  "plugins": [
+    "/Users/morse/Documents/GitHub/opencode-anthropic-auth/index.mjs"
+  ]
+}
+```
+
+### 2. Install dependencies
+
+```bash
+bun install
+```
+
+### 3. Test the plugin
+
+Run with default plugins disabled to isolate this plugin:
+
+```bash
+OPENCODE_DISABLE_DEFAULT_PLUGINS=true opencode run --model anthropic/claude-opus-4-5 hi
+```
+
+### Expected Results
+
+- **Success**: If the plugin works correctly, you should get a response from the model.
+- **Failure**: If you see a credentials error, the plugin is not working properly.
+
+## Features
+
+- OAuth authentication for Claude Pro/Max subscriptions
+- API key creation via Anthropic Console
+- Manual API key entry
+- Zero-cost tracking for Max plan users

index.mjs

@@ -195,15 +195,17 @@ export async function AnthropicAuthPlugin({ client }) {
                 try {
                   const parsed = JSON.parse(body);
 
-                  // Sanitize system prompt - server blocks "OpenCode" string
+                  // Sanitize system prompt - server blocks "You are OpenCode" string
+                  // Only replace this specific string, not all OpenCode references
                   if (parsed.system && Array.isArray(parsed.system)) {
                     parsed.system = parsed.system.map((item) => {
                       if (item.type === "text" && item.text) {
                         return {
                           ...item,
-                          text: item.text
-                            .replace(/OpenCode/g, "Claude Code")
-                            .replace(/opencode/gi, "Claude"),
+                          text: item.text.replace(
+                            "You are OpenCode, the best coding agent on the planet.",
+                            "You are Claude Code, Anthropic's official CLI for Claude.",
+                          ),
                         };
                       }
                       return item;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "opencode-anthropic-auth",
-  "version": "0.0.13",
+  "version": "0.0.14",
   "main": "./index.mjs",
   "devDependencies": {
     "@opencode-ai/plugin": "^0.4.45"