fix(tools): scope Claude tool type defaulting to gateways that need it (#3905)

defaultClaudeToolType() stamped tools[].type = "custom" onto every
Claude-format request carrying tools since e08ac6da. That satisfied
MiniMax (error 2013) but broke Anthropic-compatible endpoints that only
accept the legacy typeless tool shape. DeepSeek's endpoint
(api.deepseek.com/anthropic/v1/messages) whitelists its tool `type` enum
to the web_search_* variants and answers HTTP 400 "unknown variant
`custom`", so every Claude Code request routed to a DeepSeek connection
failed and surfaced as a persistent 503.

Run the defaulting only when the target provider declares the new
requireClaudeToolType quirk (MiniMax, MiniMax-CN). Add
shouldDefaultClaudeToolType(provider, finalFormat, tools, PROVIDERS) in
translator/concerns/toolCall.js so the gate is unit-testable, and cover
MiniMax keeping the explicit type, DeepSeek/Anthropic staying typeless,
non-Claude formats and tool-less requests never defaulting.

Effectively a no-op for MiniMax and a restore of the pre-e08ac6da
behaviour everywhere else. Another strict gateway now only needs the same
one-line quirk instead of a global behavioural change.

open-sse/handlers/chatCore.js

@@ -28,7 +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 { defaultClaudeToolType, shouldDefaultClaudeToolType } from "../translator/concerns/toolCall.js";
 import { resolveSessionId } from "../utils/sessionManager.js";
 
 /**
@@ -243,7 +243,11 @@ export async function handleChatCore({ body, modelInfo, credentials, log, onCred
 
   // 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)) {
+  // Provider-scoped via quirks (shouldDefaultClaudeToolType): only gateways that declare
+  // requireClaudeToolType get the explicit type. Applying it unconditionally breaks
+  // Claude-format endpoints that only accept the legacy typeless tool shape — DeepSeek's
+  // Anthropic-compatible endpoint 400s with "unknown variant `custom`" (#3905).
+  if (shouldDefaultClaudeToolType(provider, finalFormat, translatedBody.tools, PROVIDERS)) {
     translatedBody.tools = defaultClaudeToolType(translatedBody.tools);
   }
 

open-sse/providers/registry/minimax-cn.js

@@ -22,6 +22,7 @@ export default {
     headers: { ...CLAUDE_API_HEADERS },
     quirks: {
       dropOutputConfig: true,
+      requireClaudeToolType: true,
     },
     reasoningInject: {
       scope: "all",

open-sse/providers/registry/minimax.js

@@ -22,6 +22,7 @@ export default {
     headers: { ...CLAUDE_API_HEADERS },
     quirks: {
       dropOutputConfig: true,
+      requireClaudeToolType: true,
     },
     reasoningInject: {
       scope: "all",

open-sse/translator/concerns/toolCall.js

@@ -1,5 +1,7 @@
 // Tool call helper functions for translator
 
+import { FORMATS } from "../formats.js";
+
 // Anthropic tool_use.id must match: ^[a-zA-Z0-9_-]+$
 const TOOL_ID_PATTERN = /^[a-zA-Z0-9_-]+$/;
 
@@ -165,3 +167,16 @@ export function defaultClaudeToolType(tools) {
   return tools.map(tool => tool?.type ? tool : { ...tool, type: "custom" });
 }
 
+// Whether Claude-format tools need explicit `type` defaulting before dispatch.
+// Only gateways that declare the `requireClaudeToolType` quirk (MiniMax) reject typeless
+// tools. Applying the default globally breaks Claude-format endpoints that only accept the
+// legacy typeless tool shape — DeepSeek's Anthropic-compatible endpoint answers HTTP 400
+// "unknown variant `custom`" and every Claude Code request routed there fails (#3905).
+export function shouldDefaultClaudeToolType(provider, finalFormat, tools, PROVIDERS) {
+  return (
+    finalFormat === FORMATS.CLAUDE
+    && Array.isArray(tools)
+    && PROVIDERS?.[provider]?.quirks?.requireClaudeToolType === true
+  );
+}
+

tests/translator/bugs-3905-deepseek-tool-type.test.js

@@ -0,0 +1,33 @@
+// Regression for #3905: defaultClaudeToolType() (type:"custom") must only run for
+// gateways that declare the requireClaudeToolType quirk (MiniMax). Claude-format
+// endpoints that only accept the legacy typeless tool shape — e.g. DeepSeek's
+// Anthropic-compatible endpoint, which answers HTTP 400 "unknown variant `custom`" —
+// must never receive tools[].type = "custom".
+import { describe, it, expect } from "vitest";
+import { PROVIDERS } from "../../open-sse/providers/index.js";
+import { FORMATS } from "../../open-sse/translator/formats.js";
+import { shouldDefaultClaudeToolType } from "../../open-sse/translator/concerns/toolCall.js";
+
+const tools = [{ name: "get_weather", description: "weather", input_schema: { type: "object" } }];
+
+describe("Claude tool `type` defaulting is provider-scoped (#3905)", () => {
+  it("runs only for providers declaring requireClaudeToolType", () => {
+    expect(shouldDefaultClaudeToolType("minimax", FORMATS.CLAUDE, tools, PROVIDERS)).toBe(true);
+    expect(shouldDefaultClaudeToolType("minimax-cn", FORMATS.CLAUDE, tools, PROVIDERS)).toBe(true);
+    // Endpoints accepting only the legacy typeless shape must NOT get type:"custom".
+    expect(shouldDefaultClaudeToolType("deepseek", FORMATS.CLAUDE, tools, PROVIDERS)).toBe(false);
+    expect(shouldDefaultClaudeToolType("claude", FORMATS.CLAUDE, tools, PROVIDERS)).toBe(false);
+  });
+
+  it("never applies outside Claude-format requests or without tools", () => {
+    expect(shouldDefaultClaudeToolType("minimax", FORMATS.OPENAI, tools, PROVIDERS)).toBe(false);
+    expect(shouldDefaultClaudeToolType("minimax", FORMATS.CLAUDE, undefined, PROVIDERS)).toBe(false);
+    expect(shouldDefaultClaudeToolType("minimax", FORMATS.CLAUDE, null, PROVIDERS)).toBe(false);
+  });
+
+  it("declares the quirk only on the MiniMax providers (registry tripwire)", () => {
+    expect(PROVIDERS.minimax?.quirks?.requireClaudeToolType).toBe(true);
+    expect(PROVIDERS["minimax-cn"]?.quirks?.requireClaudeToolType).toBe(true);
+    expect(PROVIDERS.deepseek?.quirks?.requireClaudeToolType).toBeUndefined();
+  });
+});