diff --git a/open-sse/utils/stream.js b/open-sse/utils/stream.js
index 33e7fb04..9573d4c3 100644
--- a/open-sse/utils/stream.js
+++ b/open-sse/utils/stream.js
@@ -75,6 +75,35 @@ export function createSSEStream(options = {}) {
   let openAIResponsesTerminalSeen = false;
   let openAIResponsesDoneSent = false;
   let streamDoneSent = false;  // track duplicate [DONE] across transform + flush
+  let finalized = false;
+
+  // Usage/logging tail, callable from transform() as well as flush(): a client that
+  // closes right after the terminal event cancels the reader, and flush() never runs.
+  const finalizeStream = () => {
+    if (finalized) return;
+    finalized = true;
+
+    const isPassthrough = mode === STREAM_MODE.PASSTHROUGH;
+    let finalUsage = isPassthrough ? usage : state?.usage;
+
+    if (!hasValidUsage(finalUsage) && totalContentLength > 0) {
+      finalUsage = estimateUsage(body, totalContentLength, isPassthrough ? FORMATS.OPENAI : sourceFormat);
+      if (isPassthrough) usage = finalUsage; else state.usage = finalUsage;
+    }
+
+    if (hasValidUsage(finalUsage)) {
+      logUsage(isPassthrough ? provider : (state?.provider || targetFormat), finalUsage, model, connectionId, apiKey);
+    } else {
+      appendRequestLog({ model, provider, connectionId, tokens: null, status: "200 OK" }).catch(() => { });
+    }
+
+    if (onStreamComplete) {
+      onStreamComplete({
+        content: accumulatedContent,
+        thinking: accumulatedThinking
+      }, finalUsage, ttftAt);
+    }
+  };
 
   return new TransformStream({
     transform(chunk, controller) {
@@ -105,6 +134,7 @@ export function createSSEStream(options = {}) {
         if (mode === STREAM_MODE.PASSTHROUGH) {
           let output;
           let injectedUsage = false;
+          let responsesTerminal = false;
 
           if (trimmed.startsWith("data:") && trimmed.slice(5).trim() !== "[DONE]") {
             try {
@@ -168,6 +198,8 @@ export function createSSEStream(options = {}) {
                 usage = mergeUsage(usage, extracted);
               }
 
+              responsesTerminal = isOpenAIResponsesTerminalEvent(currentOpenAIResponsesEvent, parsed);
+
               const isFinishChunk = parsed.choices?.[0]?.finish_reason;
               if (isFinishChunk && !hasValidUsage(parsed.usage)) {
                 const estimated = estimateUsage(body, totalContentLength, FORMATS.OPENAI);
@@ -202,6 +234,8 @@ export function createSSEStream(options = {}) {
 
           reqLogger?.appendConvertedChunk?.(output);
           controller.enqueue(sharedEncoder.encode(output));
+          // Responses clients (codex CLI) close on response.completed instead of [DONE]
+          if (responsesTerminal) finalizeStream();
           continue;
         }
 
@@ -292,6 +326,8 @@ export function createSSEStream(options = {}) {
           controller.enqueue(sharedEncoder.encode(output));
           currentOpenAIResponsesEvent = null;
           sseEmittedCount++;
+          // Responses clients (codex) close on response.completed instead of [DONE]
+          if (openAIResponsesTerminalSeen) finalizeStream();
           continue;
         }
 
@@ -355,16 +391,6 @@ export function createSSEStream(options = {}) {
             controller.enqueue(sharedEncoder.encode(output));
           }
 
-          if (!hasValidUsage(usage) && totalContentLength > 0) {
-            usage = estimateUsage(body, totalContentLength, FORMATS.OPENAI);
-          }
-
-          if (hasValidUsage(usage)) {
-            logUsage(provider, usage, model, connectionId, apiKey);
-          } else {
-            appendRequestLog({ model, provider, connectionId, tokens: null, status: "200 OK" }).catch(() => { });
-          }
-          
           // IMPORTANT: In passthrough mode we still must terminate the SSE stream.
           // Some clients (e.g. OpenClaw) expect the OpenAI-style sentinel:
           //   data: [DONE]\n\n
@@ -377,12 +403,7 @@ export function createSSEStream(options = {}) {
             controller.enqueue(sharedEncoder.encode(doneOutput));
           }
 
-          if (onStreamComplete) {
-            onStreamComplete({
-              content: accumulatedContent,
-              thinking: accumulatedThinking
-            }, usage, ttftAt);
-          }
+          finalizeStream();
           return;
         }
 
@@ -444,24 +465,10 @@ export function createSSEStream(options = {}) {
           streamDoneSent = true;
         }
 
-        if (!hasValidUsage(state?.usage) && totalContentLength > 0) {
-          state.usage = estimateUsage(body, totalContentLength, sourceFormat);
-        }
-
-        if (hasValidUsage(state?.usage)) {
-          logUsage(state.provider || targetFormat, state.usage, model, connectionId, apiKey);
-        } else {
-          appendRequestLog({ model, provider, connectionId, tokens: null, status: "200 OK" }).catch(() => { });
-        }
-        
-        if (onStreamComplete) {
-          onStreamComplete({
-            content: accumulatedContent,
-            thinking: accumulatedThinking
-          }, state?.usage, ttftAt);
-        }
+        finalizeStream();
       } catch (error) {
         console.log("Error in flush:", error);
+        finalizeStream();
       }
     }
   });