fix(sse): skip empty-name tool calls in Responses API translator

Prevents infinite retry loops when models generate tool calls with
empty function names. The normalizeToolName function converted these
to "placeholder_tool" which does not exist in any client's tool
registry, causing repeated error-retry cycles.

open-sse/translator/request/openai-responses.ts

@@ -120,6 +120,12 @@ export function openaiResponsesToOpenAIRequest(
     }
 
     if (itemType === "function_call") {
+      // Skip tool calls with empty names to avoid infinite placeholder_tool loops
+      const fnName = toString(item.name);
+      if (!fnName || !fnName.trim()) {
+        continue;
+      }
+
       // Start or append assistant message with tool_calls
       if (!currentAssistantMsg) {
         currentAssistantMsg = {
@@ -136,7 +142,7 @@ export function openaiResponsesToOpenAIRequest(
         id: toString(item.call_id),
         type: "function",
         function: {
-          name: toString(item.name),
+          name: fnName,
           arguments: item.arguments,
         },
       });
@@ -319,10 +325,15 @@ export function openaiToOpenAIResponsesRequest(
         for (const toolCallValue of msg.tool_calls) {
           const toolCall = toRecord(toolCallValue);
           const fn = toRecord(toolCall.function);
+          // Skip tool calls with empty names to avoid infinite placeholder_tool loops
+          const fnName = toString(fn.name).trim();
+          if (!fnName) {
+            continue;
+          }
           input.push({
             type: "function_call",
             call_id: toString(toolCall.id),
-            name: toString(fn.name),
+            name: fnName,
             arguments: toString(fn.arguments, "{}"),
           });
         }

tests/unit/empty-tool-name-loop.test.mjs

@@ -0,0 +1,180 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+const { openaiResponsesToOpenAIRequest, openaiToOpenAIResponsesRequest } =
+  await import("../../open-sse/translator/request/openai-responses.ts");
+
+// ──────────────────────────────────────────────────────────────────────────────
+// Responses API -> Chat Completions direction
+// ──────────────────────────────────────────────────────────────────────────────
+
+test("openaiResponsesToOpenAIRequest: skips function_call items with empty name", () => {
+  const body = {
+    model: "gpt-4",
+    input: [
+      { type: "message", role: "user", content: "hello" },
+      { type: "function_call", call_id: "call_1", name: "", arguments: "{}" },
+    ],
+  };
+
+  const result = openaiResponsesToOpenAIRequest("gpt-4", body, true, {});
+  const messages = result.messages;
+
+  // Should have only the user message, no assistant message with empty tool call
+  const assistantMsgs = messages.filter((m) => m.role === "assistant");
+  assert.equal(assistantMsgs.length, 0, "empty-name function_call should be skipped entirely");
+});
+
+test("openaiResponsesToOpenAIRequest: skips function_call items with whitespace-only name", () => {
+  const body = {
+    model: "gpt-4",
+    input: [
+      { type: "message", role: "user", content: "hello" },
+      { type: "function_call", call_id: "call_1", name: "   ", arguments: "{}" },
+    ],
+  };
+
+  const result = openaiResponsesToOpenAIRequest("gpt-4", body, true, {});
+  const messages = result.messages;
+
+  const assistantMsgs = messages.filter((m) => m.role === "assistant");
+  assert.equal(assistantMsgs.length, 0, "whitespace-only name function_call should be skipped");
+});
+
+test("openaiResponsesToOpenAIRequest: keeps function_call items with valid name", () => {
+  const body = {
+    model: "gpt-4",
+    input: [
+      { type: "message", role: "user", content: "hello" },
+      {
+        type: "function_call",
+        call_id: "call_1",
+        name: "get_weather",
+        arguments: '{"city":"NYC"}',
+      },
+    ],
+  };
+
+  const result = openaiResponsesToOpenAIRequest("gpt-4", body, true, {});
+  const messages = result.messages;
+
+  const assistantMsgs = messages.filter((m) => m.role === "assistant");
+  assert.equal(assistantMsgs.length, 1, "valid function_call should produce assistant message");
+  assert.equal(assistantMsgs[0].tool_calls.length, 1);
+  assert.equal(assistantMsgs[0].tool_calls[0].function.name, "get_weather");
+});
+
+test("openaiResponsesToOpenAIRequest: mixed valid and empty names keeps only valid", () => {
+  const body = {
+    model: "gpt-4",
+    input: [
+      { type: "message", role: "user", content: "hello" },
+      { type: "function_call", call_id: "call_1", name: "", arguments: "{}" },
+      {
+        type: "function_call",
+        call_id: "call_2",
+        name: "get_weather",
+        arguments: '{"city":"NYC"}',
+      },
+      { type: "function_call", call_id: "call_3", name: "  ", arguments: "{}" },
+    ],
+  };
+
+  const result = openaiResponsesToOpenAIRequest("gpt-4", body, true, {});
+  const messages = result.messages;
+
+  const assistantMsgs = messages.filter((m) => m.role === "assistant");
+  assert.equal(assistantMsgs.length, 1);
+  assert.equal(assistantMsgs[0].tool_calls.length, 1, "only valid tool call should remain");
+  assert.equal(assistantMsgs[0].tool_calls[0].function.name, "get_weather");
+});
+
+// ──────────────────────────────────────────────────────────────────────────────
+// Chat Completions -> Responses API direction
+// ──────────────────────────────────────────────────────────────────────────────
+
+test("openaiToOpenAIResponsesRequest: skips tool_calls with empty function name", () => {
+  const body = {
+    messages: [
+      { role: "user", content: "hello" },
+      {
+        role: "assistant",
+        content: null,
+        tool_calls: [{ id: "call_1", type: "function", function: { name: "", arguments: "{}" } }],
+      },
+    ],
+  };
+
+  const result = openaiToOpenAIResponsesRequest("gpt-4", body, true, {});
+  const fnCalls = result.input.filter((i) => i.type === "function_call");
+  assert.equal(fnCalls.length, 0, "empty-name tool_call should be skipped");
+});
+
+test("openaiToOpenAIResponsesRequest: skips tool_calls with whitespace-only function name", () => {
+  const body = {
+    messages: [
+      { role: "user", content: "hello" },
+      {
+        role: "assistant",
+        content: null,
+        tool_calls: [
+          { id: "call_1", type: "function", function: { name: "   ", arguments: "{}" } },
+        ],
+      },
+    ],
+  };
+
+  const result = openaiToOpenAIResponsesRequest("gpt-4", body, true, {});
+  const fnCalls = result.input.filter((i) => i.type === "function_call");
+  assert.equal(fnCalls.length, 0, "whitespace-only name tool_call should be skipped");
+});
+
+test("openaiToOpenAIResponsesRequest: keeps tool_calls with valid function name", () => {
+  const body = {
+    messages: [
+      { role: "user", content: "hello" },
+      {
+        role: "assistant",
+        content: null,
+        tool_calls: [
+          {
+            id: "call_1",
+            type: "function",
+            function: { name: "get_weather", arguments: '{"city":"NYC"}' },
+          },
+        ],
+      },
+    ],
+  };
+
+  const result = openaiToOpenAIResponsesRequest("gpt-4", body, true, {});
+  const fnCalls = result.input.filter((i) => i.type === "function_call");
+  assert.equal(fnCalls.length, 1);
+  assert.equal(fnCalls[0].name, "get_weather");
+});
+
+test("openaiToOpenAIResponsesRequest: mixed valid and empty names keeps only valid", () => {
+  const body = {
+    messages: [
+      { role: "user", content: "hello" },
+      {
+        role: "assistant",
+        content: null,
+        tool_calls: [
+          { id: "call_1", type: "function", function: { name: "", arguments: "{}" } },
+          {
+            id: "call_2",
+            type: "function",
+            function: { name: "get_weather", arguments: '{"city":"NYC"}' },
+          },
+          { id: "call_3", type: "function", function: { name: "  \t  ", arguments: "{}" } },
+        ],
+      },
+    ],
+  };
+
+  const result = openaiToOpenAIResponsesRequest("gpt-4", body, true, {});
+  const fnCalls = result.input.filter((i) => i.type === "function_call");
+  assert.equal(fnCalls.length, 1, "only valid tool call should remain");
+  assert.equal(fnCalls[0].name, "get_weather");
+});