Fix: small model dispatch fails for custom OpenAI-compatible providers (#2134) (#2135)

* fix: add support for custom provider base URLs from config

* feat: read custom provider apiKey from config and use it as primary credential when it exists

* doc: update small-model documentation

packages/web/server/lib/small-model/call.js

@@ -1,4 +1,5 @@
 import { readAuthFile, writeAuthFile } from '../opencode/auth.js';
+import { readConfig } from '../opencode/shared.js';
 import { getCatalogProvider } from './catalog.js';
 import { getAuthEntryForProvider } from './resolve.js';
 
@@ -279,13 +280,41 @@ const callCodexResponses = async ({ accessToken, accountId, modelID, prompt, sys
   return result;
 };
 
+// ---------------------------------------------------------------------------
+// Custom provider configuration support
+// ---------------------------------------------------------------------------
+
+const readProviderConfig = (workingDirectory, providerID) => {
+  try {
+    const config = readConfig(workingDirectory);
+    const providerCfg = config?.provider?.[providerID];
+    if (!providerCfg || typeof providerCfg !== 'object') return null;
+    const baseURL = typeof providerCfg?.options?.baseURL === 'string' ? providerCfg.options.baseURL.trim() : null;
+    const apiKey = typeof providerCfg?.options?.apiKey === 'string' ? providerCfg.options.apiKey.trim() : null;
+    return {
+      baseURL,
+      // Shape the config-supplied key as a regular api-key auth entry so it
+      // can win the precedence check below and flow through the dispatch's
+      // `entry.type === 'api' ? entry.key : ...` branch unchanged.
+      auth: apiKey ? { type: 'api', key: apiKey } : null,
+    };
+  } catch {
+    // Provider config is non-essential — continue with catalog-only resolution.
+    return null;
+  }
+}
+
 // ---------------------------------------------------------------------------
 // Dispatch
 // ---------------------------------------------------------------------------
 
-export async function callSmallModel({ auth, catalog, providerID, modelID, prompt, system, maxOutputTokens }) {
+export async function callSmallModel({ auth, catalog, workingDirectory, providerID, modelID, prompt, system, maxOutputTokens }) {
   const tokens = Number(maxOutputTokens) > 0 ? Number(maxOutputTokens) : DEFAULT_MAX_OUTPUT_TOKENS;
-  const entry = getAuthEntryForProvider(auth, providerID);
+  const providerConfig = readProviderConfig(workingDirectory, providerID);
+  // Match OpenCode's resolveSDK precedence:
+  // config provider.<id>.options.apiKey (providerConfig.auth) wins; the
+  // auth.json entry is only a fallback.
+  const entry = providerConfig?.auth || getAuthEntryForProvider(auth, providerID);
   if (!entry) {
     throw new Error(`No OpenCode login found for provider "${providerID}"`);
   }
@@ -343,13 +372,21 @@ export async function callSmallModel({ auth, catalog, providerID, modelID, promp
   }
 
   // Everything else: OpenAI-compatible chat completions against the catalog's
-  // base URL for that provider (openai itself included).
+  // base URL for that provider (openai itself included). When a custom provider
+  // is not in the catalog (e.g. a user-configured OpenAI-compatible proxy),
+  // fall back to its baseURL from the OpenCode provider config. The openai
+  // provider also respects provider.openai.options.baseURL — OpenCode itself
+  // uses the same config for all providers including openai.
   const provider = getCatalogProvider(catalog, providerID);
-  const baseURL = providerID === 'openai'
-    ? 'https://api.openai.com/v1'
-    : typeof provider?.api === 'string' && provider.api
-      ? provider.api
-      : null;
+  const providerConfigUrl = providerConfig?.baseURL;
+  const defaultOpenaiUrl = 'https://api.openai.com/v1';
+  const baseURL = typeof providerConfigUrl === 'string' && providerConfigUrl
+    ? providerConfigUrl
+    : providerID === 'openai'
+      ? defaultOpenaiUrl
+      : typeof provider?.api === 'string' && provider.api
+        ? provider.api
+        : null;
   if (!baseURL) {
     throw new Error(`Provider "${providerID}" has no known API base URL`);
   }