fix(tools): default Claude tool type when missing

Strict Anthropic-compatible gateways (e.g. MiniMax) reject Claude-format
requests with HTTP 400 when tools[].type is missing. Normalize each
missing/falsy tools[].type to "custom" before dispatch when the final
request format is Claude. Built-in tool types (computer_use, bash,
web_search_*) are passed through untouched.

open-sse/handlers/chatCore.js

@@ -28,6 +28,7 @@ import { compressWithPxpipe } from "../rtk/pxpipe.js";
 import { getCapabilitiesForModel } from "../providers/capabilities.js";
 import { stripUnsupportedModalities } from "../translator/concerns/modality.js";
 import { prefetchRemoteImages } from "../translator/concerns/prefetch.js";
+import { defaultClaudeToolType } from "../translator/concerns/toolCall.js";
 import { resolveSessionId } from "../utils/sessionManager.js";
 
 /**
@@ -235,6 +236,12 @@ export async function handleChatCore({ body, modelInfo, credentials, log, onCred
     delete translatedBody.tools;
   }
 
+  // Claude tool schema requires `type` to be explicitly set; strict gateways (e.g., MiniMax)
+  // reject legacy payloads that omit it with HTTP 400. Default to "custom" when missing.
+  if (finalFormat === FORMATS.CLAUDE && Array.isArray(translatedBody.tools)) {
+    translatedBody.tools = defaultClaudeToolType(translatedBody.tools);
+  }
+
   // Per-request opt-out: client can bypass all token savers via header
   const tokenSaverEnabled = clientRawRequest?.headers?.[TOKEN_SAVER_HEADER]?.toLowerCase() !== "off";