diff --git a/open-sse/utils/stream.ts b/open-sse/utils/stream.ts
index b9eda7e997..230e5b4f29 100644
--- a/open-sse/utils/stream.ts
+++ b/open-sse/utils/stream.ts
@@ -246,12 +246,34 @@ function containsMalformedTextualToolCall(text: unknown): boolean {
   return text.replace(/[\u200B-\u200D\uFEFF]/g, "").includes("[Tool call:");
 }
 
+function extractAllowedToolNames(body: unknown): Set<string> | null {
+  const record = asRecord(body);
+  const tools = record.tools;
+  if (!Array.isArray(tools)) return null;
+  const names = new Set<string>();
+  for (const tool of tools) {
+    if (!tool || typeof tool !== "object" || Array.isArray(tool)) continue;
+    const item = tool as JsonRecord;
+    const directName = typeof item.name === "string" ? item.name.trim() : "";
+    const fn =
+      item.function && typeof item.function === "object" && !Array.isArray(item.function)
+        ? (item.function as JsonRecord)
+        : null;
+    const functionName = typeof fn?.name === "string" ? fn.name.trim() : "";
+    const name = functionName || directName;
+    if (name) names.add(name);
+  }
+  return names.size > 0 ? names : null;
+}
+
 function collectPassthroughTextualToolCall(
   text: string,
-  toolCalls: Map<string, ToolCall>
+  toolCalls: Map<string, ToolCall>,
+  allowedToolNames?: Set<string> | null
 ): ToolCall | null {
   const parsed = parseTextualToolCallFromContent(text);
   if (!parsed) return null;
+  if (allowedToolNames?.size && !allowedToolNames.has(parsed.name)) return null;
   const key = `textual:${toolCalls.size}`;
   const toolCall: ToolCall = {
     id: `call_${Date.now()}_${toolCalls.size}`,
@@ -669,6 +691,7 @@ export function createSSEStream(options: StreamOptions = {}) {
   /** Passthrough: accumulate tool_calls deltas for call log responseBody */
   const passthroughToolCalls = new Map<string, ToolCall>();
   let passthroughToolCallSeq = 0;
+  const allowedToolNames = extractAllowedToolNames(body);
   let skipPassthroughEvent = false;
 
   // State for translate mode (accumulatedContent for call log response body)
@@ -1399,12 +1422,13 @@ export function createSSEStream(options: StreamOptions = {}) {
                       if (parsedCandidate?.kind === "complete") {
                         const collectedToolCall = collectPassthroughTextualToolCall(
                           bufferedCandidate,
-                          passthroughToolCalls
+                          passthroughToolCalls,
+                          allowedToolNames
                         );
                         if (collectedToolCall) {
                           delta.tool_calls = [toStreamingToolCallDelta(collectedToolCall)];
+                          passthroughHasToolCalls = true;
                         }
-                        passthroughHasToolCalls = true;
                         textualToolCallConverted = true;
                         passthroughBufferedTextualToolCallContent = "";
                         delete delta.content;
@@ -1760,14 +1784,18 @@ export function createSSEStream(options: StreamOptions = {}) {
                   if (
                     collectPassthroughTextualToolCall(
                       finalBufferedTextualToolCall,
-                      passthroughToolCalls
+                      passthroughToolCalls,
+                      allowedToolNames
                     )
                   ) {
                     passthroughHasToolCalls = true;
                   }
                   passthroughBufferedTextualToolCallContent = "";
                 }
-                if (content && collectPassthroughTextualToolCall(content, passthroughToolCalls)) {
+                if (
+                  content &&
+                  collectPassthroughTextualToolCall(content, passthroughToolCalls, allowedToolNames)
+                ) {
                   passthroughHasToolCalls = true;
                   content = "";
                 } else if (containsMalformedTextualToolCall(content)) {
diff --git a/tests/unit/stream-utils.test.ts b/tests/unit/stream-utils.test.ts
index 1a35f19975..66fc476d92 100644
--- a/tests/unit/stream-utils.test.ts
+++ b/tests/unit/stream-utils.test.ts
@@ -232,6 +232,53 @@ test("createSSEStream passthrough converts split textual tool-call content at co
   assert.doesNotMatch(text, /\[Tool call: terminal\]/);
 });
 
+test("createSSEStream passthrough suppresses textual tool calls for unknown tools", async () => {
+  let onCompletePayload = null;
+  const toolText = `[Tool call: search_files_ide]
+Arguments: {"path":"/opt/OmniRoute/src","target":"files"}`;
+
+  const text = await readTransformed(
+    [
+      `data: ${JSON.stringify({
+        id: "chatcmpl_unknown_textual_tool",
+        object: "chat.completion.chunk",
+        created: 1,
+        model: "antigravity/gemini-3.5-flash-low",
+        choices: [{ index: 0, delta: { role: "assistant", content: toolText } }],
+      })}\n\n`,
+      `data: ${JSON.stringify({
+        id: "chatcmpl_unknown_textual_tool",
+        object: "chat.completion.chunk",
+        created: 1,
+        model: "antigravity/gemini-3.5-flash-low",
+        choices: [{ index: 0, delta: {}, finish_reason: "stop" }],
+      })}\n\n`,
+    ],
+    {
+      mode: "passthrough",
+      sourceFormat: FORMATS.OPENAI,
+      provider: "antigravity",
+      model: "antigravity/gemini-3.5-flash-low",
+      body: {
+        messages: [{ role: "user", content: "inspect files" }],
+        tools: [
+          { type: "function", function: { name: "search_files", parameters: { type: "object" } } },
+        ],
+      },
+      onComplete(payload) {
+        onCompletePayload = payload;
+      },
+    }
+  );
+
+  const choice = onCompletePayload.responseBody.choices[0];
+  assert.equal(choice.finish_reason, "stop");
+  assert.equal(choice.message.content, null);
+  assert.equal(choice.message.tool_calls, undefined);
+  assert.doesNotMatch(text, /search_files_ide/);
+  assert.doesNotMatch(JSON.stringify(onCompletePayload.responseBody), /search_files_ide/);
+});
+
 test("createSSEStream passthrough suppresses malformed textual tool-call content", async () => {
   let onCompletePayload = null;
   const malformedToolText = `(empty)[Tool call: terminal]\nArguments: {"command":"sqlite3 /opt/O\u200dmniRoute/data/o\u200dmniroute.`;