diff --git a/internal/dev-entrypoint/opencode-provider-proxy.mjs b/internal/dev-entrypoint/opencode-provider-proxy.mjs
index 1fd6b598..a0106f20 100644
--- a/internal/dev-entrypoint/opencode-provider-proxy.mjs
+++ b/internal/dev-entrypoint/opencode-provider-proxy.mjs
@@ -2,6 +2,7 @@
 import { randomBytes } from "node:crypto";
 import { createServer, request as httpRequest } from "node:http";
 import { request as httpsRequest } from "node:https";
+import { Transform } from "node:stream";
 
 const serviceId = process.env.OTEL_SERVICE_NAME || process.env.HWLAB_SERVICE_ID || "opencode-provider-proxy";
 const port = parsePositiveInteger(process.env.PORT || process.env.HWLAB_OPENCODE_PROVIDER_PROXY_PORT, 4097);
@@ -110,12 +111,14 @@ async function proxyProviderRequest(clientReq, clientRes, url) {
       headers: providerRequestHeaders(clientReq.headers, target, trace, startSpanId)
     }, (upstreamRes) => {
       statusCode = upstreamRes.statusCode || 502;
+      const filterReasoning = shouldFilterOpenAIReasoning(route, upstreamRes.headers);
       clientRes.writeHead(statusCode, {
         ...providerResponseHeaders(upstreamRes.headers),
         traceparent: traceparent(trace.traceId, startSpanId),
         "x-hwlab-otel-trace-id": trace.traceId
       });
-      upstreamRes.pipe(clientRes);
+      const responseStream = filterReasoning ? upstreamRes.pipe(openAIReasoningFilterStream()) : upstreamRes;
+      responseStream.pipe(clientRes);
       upstreamRes.on("end", settle);
       upstreamRes.on("close", settle);
       upstreamRes.on("error", (error) => {
@@ -183,6 +186,76 @@ function providerRoute(pathname) {
   return `${publicBasePath}${stripped.startsWith("/") ? stripped : `/${stripped}`}`;
 }
 
+function shouldFilterOpenAIReasoning(route, headers) {
+  return route === `${publicBasePath}/chat/completions` && /^text\/event-stream(?:\s*;|$)/iu.test(firstHeaderValue(headers?.["content-type"]));
+}
+
+function openAIReasoningFilterStream() {
+  let pending = "";
+  return new Transform({
+    transform(chunk, _encoding, callback) {
+      pending += chunk.toString("utf8");
+      let newlineIndex = pending.indexOf("\n");
+      while (newlineIndex >= 0) {
+        const line = pending.slice(0, newlineIndex + 1);
+        pending = pending.slice(newlineIndex + 1);
+        const next = filterOpenAISseLine(line);
+        if (next) this.push(next);
+        newlineIndex = pending.indexOf("\n");
+      }
+      callback();
+    },
+    flush(callback) {
+      if (pending) {
+        const next = filterOpenAISseLine(pending);
+        if (next) this.push(next);
+      }
+      callback();
+    }
+  });
+}
+
+function filterOpenAISseLine(line) {
+  const match = line.match(/^(data:\s*)(.*?)(\r?\n)?$/u);
+  if (!match) return line;
+  const [, prefix, payload, lineEnding = ""] = match;
+  const text = payload.trim();
+  if (!text || text === "[DONE]") return line;
+  try {
+    const parsed = JSON.parse(text);
+    const choices = Array.isArray(parsed.choices) ? parsed.choices.map(filterOpenAIChoiceReasoning).filter(Boolean) : parsed.choices;
+    if (Array.isArray(parsed.choices)) {
+      if (choices.length === 0 && parsed.usage === null) return "";
+      parsed.choices = choices;
+    }
+    return `${prefix}${JSON.stringify(parsed)}${lineEnding}`;
+  } catch {
+    return line;
+  }
+}
+
+function filterOpenAIChoiceReasoning(choice) {
+  if (!choice || typeof choice !== "object") return choice;
+  const next = { ...choice };
+  if (next.delta && typeof next.delta === "object") {
+    const delta = { ...next.delta };
+    delete delta.reasoning_content;
+    delete delta.reasoning;
+    delete delta.reasoning_details;
+    if (delta.content === null) delete delta.content;
+    next.delta = delta;
+  }
+  if (next.message && typeof next.message === "object") {
+    next.message = { ...next.message };
+    delete next.message.reasoning_content;
+    delete next.message.reasoning;
+    delete next.message.reasoning_details;
+  }
+  const deltaEmpty = next.delta && typeof next.delta === "object" && Object.keys(next.delta).length === 0;
+  if (deltaEmpty && next.finish_reason == null && next.logprobs == null) return null;
+  return next;
+}
+
 function providerRequestHeaders(headers, target, trace, parentSpanId) {
   const result = {};
   for (const [name, value] of Object.entries(headers)) {