diff --git a/open-sse/executors/commandcode.js b/open-sse/executors/commandcode.js
index 772bf4c8..6ff4b52a 100644
--- a/open-sse/executors/commandcode.js
+++ b/open-sse/executors/commandcode.js
@@ -2,6 +2,7 @@ import { randomUUID } from "crypto";
 import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
 import { convertCommandCodeToOpenAI } from "../translator/response/commandcode-to-openai.js";
+import { SSE_DONE } from "../utils/sseConstants.js";
 
 /**
  * CommandCodeExecutor — talks to https://api.commandcode.ai/alpha/generate
@@ -78,7 +79,7 @@ function wrapNdjsonAsOpenAISse(originalResponse, model) {
       if (trimmed) {
         emitChunks(convertCommandCodeToOpenAI(trimmed, state), controller);
       }
-      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+      controller.enqueue(encoder.encode(SSE_DONE));
     },
   });
 
diff --git a/open-sse/executors/cursor.js b/open-sse/executors/cursor.js
index de64870c..a14e7bfa 100644
--- a/open-sse/executors/cursor.js
+++ b/open-sse/executors/cursor.js
@@ -8,6 +8,7 @@ import {
 } from "../utils/cursorProtobuf.js";
 import { buildCursorHeaders } from "../utils/cursorChecksum.js";
 import { estimateUsage } from "../utils/usageTracking.js";
+import { SSE_DONE, SSE_HEADERS } from "../utils/sseConstants.js";
 import { FORMATS } from "../translator/formats.js";
 import { proxyAwareFetch } from "../utils/proxyFetch.js";
 import zlib from "zlib";
@@ -775,15 +776,11 @@ export class CursorExecutor extends BaseExecutor {
         usage
       })}\n\n`
     );
-    chunks.push("data: [DONE]\n\n");
+    chunks.push(SSE_DONE);
 
     return new Response(chunks.join(""), {
       status: 200,
-      headers: {
-        "Content-Type": "text/event-stream",
-        "Cache-Control": "no-cache",
-        "Connection": "keep-alive"
-      }
+      headers: { ...SSE_HEADERS }
     });
   }
 
diff --git a/open-sse/executors/github.js b/open-sse/executors/github.js
index cc26cd27..67baa969 100644
--- a/open-sse/executors/github.js
+++ b/open-sse/executors/github.js
@@ -7,6 +7,7 @@ import { openaiResponsesToOpenAIResponse } from "../translator/response/openai-r
 import { initState } from "../translator/index.js";
 import { parseSSELine, formatSSE } from "../utils/streamHelpers.js";
 import { proxyAwareFetch } from "../utils/proxyFetch.js";
+import { SSE_DONE } from "../utils/sseConstants.js";
 import crypto from "crypto";
 
 export class GithubExecutor extends BaseExecutor {
@@ -244,7 +245,7 @@ export class GithubExecutor extends BaseExecutor {
           if (!parsed) continue;
 
           if (parsed.done && stream === true) {
-            controller.enqueue(new TextEncoder().encode("data: [DONE]\n\n"));
+            controller.enqueue(new TextEncoder().encode(SSE_DONE));
             continue;
           }
 
diff --git a/open-sse/executors/grok-web.js b/open-sse/executors/grok-web.js
index 2f366f99..075927fd 100644
--- a/open-sse/executors/grok-web.js
+++ b/open-sse/executors/grok-web.js
@@ -1,5 +1,6 @@
 import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
+import { SSE_DONE, SSE_HEADERS_NO_BUFFER } from "../utils/sseConstants.js";
 
 const GROK_CHAT_API = PROVIDERS["grok-web"].baseUrl;
 const GROK_USER_AGENT = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36";
@@ -175,13 +176,13 @@ function buildStreamingResponse(eventStream, model, cid, created, isThinkingMode
           id: cid, object: "chat.completion.chunk", created, model, system_fingerprint: fp || null,
           choices: [{ index: 0, delta: {}, finish_reason: "stop", logprobs: null }],
         })));
-        controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+        controller.enqueue(encoder.encode(SSE_DONE));
       } catch (err) {
         controller.enqueue(encoder.encode(sseChunk({
           id: cid, object: "chat.completion.chunk", created, model, system_fingerprint: null,
           choices: [{ index: 0, delta: { content: `[Stream error: ${err.message || String(err)}]` }, finish_reason: "stop", logprobs: null }],
         })));
-        controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+        controller.enqueue(encoder.encode(SSE_DONE));
       } finally {
         controller.close();
       }
@@ -333,7 +334,7 @@ export class GrokWebExecutor extends BaseExecutor {
       const sseStream = buildStreamingResponse(response.body, model, cid, created, isThinking, signal);
       finalResponse = new Response(sseStream, {
         status: 200,
-        headers: { "Content-Type": "text/event-stream", "Cache-Control": "no-cache", "X-Accel-Buffering": "no" },
+        headers: { ...SSE_HEADERS_NO_BUFFER },
       });
     } else {
       finalResponse = await buildNonStreamingResponse(response.body, model, cid, created, isThinking, signal);
diff --git a/open-sse/executors/kiro.js b/open-sse/executors/kiro.js
index 47aba379..ec22b827 100644
--- a/open-sse/executors/kiro.js
+++ b/open-sse/executors/kiro.js
@@ -2,6 +2,7 @@ import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
 import { v4 as uuidv4 } from "uuid";
 import { refreshKiroToken } from "../services/tokenRefresh.js";
+import { SSE_DONE, SSE_HEADERS } from "../utils/sseConstants.js";
 
 /**
  * KiroExecutor - Executor for Kiro AI (AWS CodeWhisperer)
@@ -372,24 +373,20 @@ export class KiroExecutor extends BaseExecutor {
         }
 
         // Send final done message
-        controller.enqueue(new TextEncoder().encode("data: [DONE]\n\n"));
+        controller.enqueue(new TextEncoder().encode(SSE_DONE));
       }
     });
 
     // Pipe response body through transform stream
     if (!response.body) {
-      return new Response("data: [DONE]\n\n", { status: response.status, headers: { "Content-Type": "text/event-stream" } });
+      return new Response(SSE_DONE, { status: response.status, headers: { "Content-Type": "text/event-stream" } });
     }
     const transformedStream = response.body.pipeThrough(transformStream);
 
     return new Response(transformedStream, {
       status: response.status,
       statusText: response.statusText,
-      headers: {
-        "Content-Type": "text/event-stream",
-        "Cache-Control": "no-cache",
-        "Connection": "keep-alive"
-      }
+      headers: { ...SSE_HEADERS }
     });
   }
 
diff --git a/open-sse/executors/perplexity-web.js b/open-sse/executors/perplexity-web.js
index 2c39cf4c..931172df 100644
--- a/open-sse/executors/perplexity-web.js
+++ b/open-sse/executors/perplexity-web.js
@@ -1,5 +1,6 @@
 import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
+import { SSE_DONE, SSE_HEADERS_NO_BUFFER } from "../utils/sseConstants.js";
 
 const PPLX_SSE_ENDPOINT = PROVIDERS["perplexity-web"].baseUrl;
 const PPLX_API_VERSION = "2.18";
@@ -340,7 +341,7 @@ function buildStreamingResponse(eventStream, model, cid, created, history, curre
           id: cid, object: "chat.completion.chunk", created, model, system_fingerprint: null,
           choices: [{ index: 0, delta: {}, finish_reason: "stop", logprobs: null }],
         })));
-        controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+        controller.enqueue(encoder.encode(SSE_DONE));
 
         sessionStore(history, currentMsg, cleanResponse(fullAnswer), respBackendUuid);
       } catch (err) {
@@ -348,7 +349,7 @@ function buildStreamingResponse(eventStream, model, cid, created, history, curre
           id: cid, object: "chat.completion.chunk", created, model, system_fingerprint: null,
           choices: [{ index: 0, delta: { content: `[Stream error: ${err.message || String(err)}]` }, finish_reason: "stop", logprobs: null }],
         })));
-        controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+        controller.enqueue(encoder.encode(SSE_DONE));
       } finally {
         controller.close();
       }
@@ -493,7 +494,7 @@ export class PerplexityWebExecutor extends BaseExecutor {
       const sseStream = buildStreamingResponse(response.body, model, cid, created, parsed.history, parsed.currentMsg, signal);
       finalResponse = new Response(sseStream, {
         status: 200,
-        headers: { "Content-Type": "text/event-stream", "Cache-Control": "no-cache", "X-Accel-Buffering": "no" },
+        headers: { ...SSE_HEADERS_NO_BUFFER },
       });
     } else {
       finalResponse = await buildNonStreamingResponse(response.body, model, cid, created, parsed.history, parsed.currentMsg, signal);
diff --git a/open-sse/executors/qoder.js b/open-sse/executors/qoder.js
index fa9bcbad..2af8dda2 100644
--- a/open-sse/executors/qoder.js
+++ b/open-sse/executors/qoder.js
@@ -28,6 +28,7 @@ import { createHash } from "crypto";
 import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
 import { proxyAwareFetch } from "../utils/proxyFetch.js";
+import { SSE_DONE } from "../utils/sseConstants.js";
 import { FETCH_CONNECT_TIMEOUT_MS } from "../config/runtimeConfig.js";
 import {
   QODER_CHAT_URL_ENCODED,
@@ -241,7 +242,7 @@ function wrapQoderSSE(response, model) {
 
     const data = trimmed.slice(5).trimStart();
     if (data === "[DONE]") {
-      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+      controller.enqueue(encoder.encode(SSE_DONE));
       doneEmitted = true;
       return;
     }
@@ -260,13 +261,13 @@ function wrapQoderSSE(response, model) {
         choices: [{ index: 0, delta: { content: `\n[qoder error ${statusVal}: ${truncate(msg, 200)}]` }, finish_reason: "stop" }],
       });
       controller.enqueue(encoder.encode(`data: ${errChunk}\n\n`));
-      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+      controller.enqueue(encoder.encode(SSE_DONE));
       doneEmitted = true;
       return;
     }
     if (!inner) return;
     if (inner === "[DONE]") {
-      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+      controller.enqueue(encoder.encode(SSE_DONE));
       doneEmitted = true;
       return;
     }
@@ -301,7 +302,7 @@ function wrapQoderSSE(response, model) {
         buffer = "";
       }
       if (!doneEmitted) {
-        controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+        controller.enqueue(encoder.encode(SSE_DONE));
         doneEmitted = true;
       }
     },
diff --git a/open-sse/utils/sseConstants.js b/open-sse/utils/sseConstants.js
new file mode 100644
index 00000000..fed78dae
--- /dev/null
+++ b/open-sse/utils/sseConstants.js
@@ -0,0 +1,15 @@
+// Shared SSE primitives (no imports → safe for executors + stream.js)
+export const SSE_DONE = "data: [DONE]\n\n";
+
+export const SSE_HEADERS = {
+  "Content-Type": "text/event-stream",
+  "Cache-Control": "no-cache",
+  "Connection": "keep-alive"
+};
+
+// Variant for web-cookie executors behind nginx (disable proxy buffering)
+export const SSE_HEADERS_NO_BUFFER = {
+  "Content-Type": "text/event-stream",
+  "Cache-Control": "no-cache",
+  "X-Accel-Buffering": "no"
+};
diff --git a/open-sse/utils/stream.js b/open-sse/utils/stream.js
index 4886efe0..7f843734 100644
--- a/open-sse/utils/stream.js
+++ b/open-sse/utils/stream.js
@@ -6,7 +6,10 @@ import { parseSSELine, hasValuableContent, fixInvalidId, formatSSE } from "./str
 import { getOpenAIResponsesEventName, isOpenAIResponsesTerminalEvent, formatIncompleteOpenAIResponsesStreamFailure } from "./responsesStreamHelpers.js";
 import { dbg, isDebugEnabled } from "./debugLog.js";
 
+import { SSE_DONE, SSE_HEADERS, SSE_HEADERS_NO_BUFFER } from "./sseConstants.js";
+
 export { COLORS, formatSSE };
+export { SSE_DONE, SSE_HEADERS, SSE_HEADERS_NO_BUFFER };
 
 // sharedEncoder is stateless — safe to share across streams
 const sharedEncoder = new TextEncoder();