fix: clarify Claude Code credential auth error

packages/opencode/src/provider/error.ts

@@ -27,6 +27,8 @@ export namespace ProviderError {
     /too large for model with \d+ maximum context length/i, // Mistral
     /model_context_window_exceeded/i, // z.ai non-standard finish_reason surfaced as error text
   ]
+  const CLAUDE_CODE_CREDENTIAL_PATTERN =
+    /This credential is only authorized for use with Claude Code and cannot be used for other API requests\./i
 
   function isOpenAiErrorRetryable(e: APICallError) {
     const status = e.statusCode
@@ -46,6 +48,13 @@ export namespace ProviderError {
     return /^4(00|13)\s*(status code)?\s*\(no body\)/i.test(message)
   }
 
+  function isClaudeCodeCredential(providerID: ProviderID, message: string, responseBody?: string) {
+    if (providerID !== "anthropic") return false
+    if (CLAUDE_CODE_CREDENTIAL_PATTERN.test(message)) return true
+    if (!responseBody) return false
+    return CLAUDE_CODE_CREDENTIAL_PATTERN.test(responseBody)
+  }
+
   function message(providerID: ProviderID, e: APICallError) {
     return iife(() => {
       const msg = e.message
@@ -67,10 +76,23 @@ export namespace ProviderError {
         // try to extract common error message fields
         const errMsg = body.message || body.error || body.error?.message
         if (errMsg && typeof errMsg === "string") {
+          if (isClaudeCodeCredential(providerID, errMsg, e.responseBody)) {
+            return [
+              "This Anthropic credential is restricted to Claude Code and cannot be used with OpenCode.",
+              "Use a standard Anthropic API key instead, then run `opencode auth login anthropic` to update your credentials.",
+            ].join(" ")
+          }
           return `${msg}: ${errMsg}`
         }
       } catch {}
 
+      if (isClaudeCodeCredential(providerID, msg, e.responseBody)) {
+        return [
+          "This Anthropic credential is restricted to Claude Code and cannot be used with OpenCode.",
+          "Use a standard Anthropic API key instead, then run `opencode auth login anthropic` to update your credentials.",
+        ].join(" ")
+      }
+
       // If responseBody is HTML (e.g. from a gateway or proxy error page),
       // provide a human-readable message instead of dumping raw markup
       if (/^\s*<!doctype|^\s*<html/i.test(e.responseBody)) {

packages/opencode/test/provider/error.test.ts

@@ -0,0 +1,59 @@
+import { describe, expect, test } from "bun:test"
+import { APICallError } from "ai"
+import { ProviderError } from "../../src/provider/error"
+import { ProviderID } from "../../src/provider/schema"
+
+describe("provider.error", () => {
+  test("clarifies Claude Code-only Anthropic credentials", () => {
+    const result = ProviderError.parseAPICallError({
+      providerID: ProviderID.make("anthropic"),
+      error: new APICallError({
+        message: "Unauthorized",
+        url: "https://api.anthropic.com/v1/messages",
+        requestBodyValues: {},
+        statusCode: 401,
+        responseHeaders: { "content-type": "application/json" },
+        responseBody: JSON.stringify({
+          type: "error",
+          error: {
+            type: "authentication_error",
+            message: "This credential is only authorized for use with Claude Code and cannot be used for other API requests.",
+          },
+        }),
+        isRetryable: false,
+      }),
+    })
+
+    expect(result.type).toBe("api_error")
+    if (result.type !== "api_error") return
+    expect(result.message).toContain("restricted to Claude Code")
+    expect(result.message).toContain("standard Anthropic API key")
+    expect(result.message).toContain("opencode auth login anthropic")
+  })
+
+  test("keeps generic Anthropic auth errors unchanged", () => {
+    const result = ProviderError.parseAPICallError({
+      providerID: ProviderID.make("anthropic"),
+      error: new APICallError({
+        message: "Unauthorized",
+        url: "https://api.anthropic.com/v1/messages",
+        requestBodyValues: {},
+        statusCode: 401,
+        responseHeaders: { "content-type": "application/json" },
+        responseBody: JSON.stringify({
+          type: "error",
+          error: {
+            type: "authentication_error",
+            message: "Invalid API key",
+          },
+        }),
+        isRetryable: false,
+      }),
+    })
+
+    expect(result.type).toBe("api_error")
+    if (result.type !== "api_error") return
+    expect(result.message).not.toContain("restricted to Claude Code")
+    expect(result.message).not.toContain("standard Anthropic API key")
+  })
+})