From d25e32326d1cf9bee89653a33d3bb689e72a1944 Mon Sep 17 00:00:00 2001
From: Maxim Ivanov <makcimbx@users.noreply.github.com>
Date: Sat, 30 May 2026 10:24:18 +0000
Subject: [PATCH] fix: scope JSON-string cleanup to Read tool

Keep existing object-argument cleanup behavior, but avoid parsing and stripping arbitrary JSON-string arguments for unrelated tools where empty strings or arrays may be valid payloads. Add regression coverage for non-Read and non-object Read arguments.
---
 .../translator/response/openai-responses.ts   | 12 +++--
 .../translator-resp-openai-responses.test.ts  | 45 +++++++++++++++++++
 2 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/open-sse/translator/response/openai-responses.ts b/open-sse/translator/response/openai-responses.ts
index ebd417d007..0b50f80c0e 100644
--- a/open-sse/translator/response/openai-responses.ts
+++ b/open-sse/translator/response/openai-responses.ts
@@ -9,13 +9,17 @@ function normalizeToolName(value) {
   return typeof value === "string" ? value.trim() : "";
 }
 
-function stripEmptyOptionalToolArgs(value) {
+function stripEmptyOptionalToolArgs(value, toolName) {
   if (value == null) return value;
 
   if (typeof value === "string") {
+    // JSON-string cleanup is intentionally scoped to Claude Code's Read tool.
+    // For arbitrary tools, empty strings/arrays may be valid user payloads.
+    if (toolName !== "Read") return value;
     try {
       const parsed = JSON.parse(value);
-      const cleaned = stripEmptyOptionalToolArgs(parsed);
+      if (Array.isArray(parsed) || typeof parsed !== "object" || parsed === null) return value;
+      const cleaned = stripEmptyOptionalToolArgs(parsed, toolName);
       return JSON.stringify(cleaned ?? {});
     } catch {
       return value;
@@ -655,7 +659,7 @@ export function openaiResponsesToOpenAIResponse(chunk, state) {
 
       state.toolCallIndex++;
 
-      const argsToEmit = stripEmptyOptionalToolArgs(item.arguments);
+      const argsToEmit = stripEmptyOptionalToolArgs(item.arguments, toolName);
 
       const argsStr =
         argsToEmit != null
@@ -697,7 +701,7 @@ export function openaiResponsesToOpenAIResponse(chunk, state) {
 
     // Only emit if arguments exist in the done event AND they weren't already streamed via deltas
     if (item.arguments != null && !buffered) {
-      const argsToEmit = stripEmptyOptionalToolArgs(item.arguments);
+      const argsToEmit = stripEmptyOptionalToolArgs(item.arguments, toolName);
 
       const argsStr = typeof argsToEmit === "string" ? argsToEmit : JSON.stringify(argsToEmit);
       if (argsStr) {
diff --git a/tests/unit/translator-resp-openai-responses.test.ts b/tests/unit/translator-resp-openai-responses.test.ts
index 569cfa5f0d..d837baff5b 100644
--- a/tests/unit/translator-resp-openai-responses.test.ts
+++ b/tests/unit/translator-resp-openai-responses.test.ts
@@ -242,6 +242,31 @@ test("Responses -> OpenAI: empty-name tool call is deferred until output_item.do
   );
 });
 
+test("Responses -> OpenAI: preserves non-Read JSON-string tool arguments", () => {
+  const state = {};
+  openaiResponsesToOpenAIResponse(
+    {
+      type: "response.output_item.added",
+      item: { type: "function_call", call_id: "call_note", name: "save_note" },
+    },
+    state
+  );
+  const done = openaiResponsesToOpenAIResponse(
+    {
+      type: "response.output_item.done",
+      item: {
+        type: "function_call",
+        call_id: "call_note",
+        name: "save_note",
+        arguments: '{"text":"","tags":[]}',
+      },
+    },
+    state
+  );
+
+  assert.equal(done.choices[0].delta.tool_calls[0].function.arguments, '{"text":"","tags":[]}');
+});
+
 test("Responses -> OpenAI: preserves falsy JSON-string tool arguments while cleaning", () => {
   const state = {};
   openaiResponsesToOpenAIResponse(
@@ -262,6 +287,26 @@ test("Responses -> OpenAI: preserves falsy JSON-string tool arguments while clea
   assert.equal(done.choices[0].delta.tool_calls[0].function.arguments, "false");
 });
 
+test("Responses -> OpenAI: preserves non-object Read JSON-string arguments", () => {
+  const state = {};
+  openaiResponsesToOpenAIResponse(
+    {
+      type: "response.output_item.added",
+      item: { type: "function_call", call_id: "call_read", name: "Read" },
+    },
+    state
+  );
+  const done = openaiResponsesToOpenAIResponse(
+    {
+      type: "response.output_item.done",
+      item: { type: "function_call", call_id: "call_read", name: "Read", arguments: "null" },
+    },
+    state
+  );
+
+  assert.equal(done.choices[0].delta.tool_calls[0].function.arguments, "null");
+});
+
 test("Responses -> OpenAI: strips empty optional args from JSON-string output_item.done arguments", () => {
   const state = {};
   openaiResponsesToOpenAIResponse(