fix(stream): drop leaked chat bootstrap chunk for responses clients (#3035)

Integrated into release/v3.8.8. Drops the leaked empty chat.completion.chunk bootstrap frame before response.* SSE events so strict /v1/responses clients (OpenCode) don't fail on the first frame. Thanks @CitrusIce!

CHANGELOG.md

@@ -236,6 +236,14 @@
 
 - **mcp:** move `enforceScopes` guard before `MCP_TOOL_MAP` lookup, add inline `scopes` parameter to `withScopeEnforcement()`, and declare scopes on all 24 dynamic tool definitions (memory, skills, plugins, gamification, compression) to fix scope enforcement for dynamic MCP tool groups (#2958)
 
+### ✨ New Features
+
+- **notion:** add Notion as an MCP context source — 6 tools (`notion_search`, `notion_list_databases`, `notion_get_database`, `notion_query_database`, `notion_read`, `notion_append_blocks`) scoped under `read:notion` / `write:notion`, with dashboard "Context Sources" tab, settings API, and token persistence in `key_value` table (#2959)
+
+### 🔧 Bug Fixes
+
+- **mcp:** move `enforceScopes` guard before `MCP_TOOL_MAP` lookup, add inline `scopes` parameter to `withScopeEnforcement()`, and declare scopes on all 24 dynamic tool definitions (memory, skills, plugins, gamification, compression) to fix scope enforcement for dynamic MCP tool groups (#2958)
+
 ---
 
 ## [3.8.7] — 2026-05-29

open-sse/utils/stream.ts

@@ -1255,6 +1255,45 @@ export function createSSEStream(options: StreamOptions = {}) {
               try {
                 let parsed = JSON.parse(trimmed.slice(5).trim());
 
+                // Some upstream Responses-compatible providers leak an initial Chat Completions
+                // bootstrap chunk (assistant role + empty content) before emitting proper
+                // `response.*` events. That chunk is invalid on /v1/responses and breaks strict
+                // clients like OpenCode, so drop it only for Responses-native consumers.
+                const hasActiveDeltaValue = (value: unknown): boolean => {
+                  if (typeof value === "string") return value.length > 0;
+                  if (Array.isArray(value)) return value.some((entry) => hasActiveDeltaValue(entry));
+                  if (value && typeof value === "object") {
+                    return Object.values(value).some((entry) => hasActiveDeltaValue(entry));
+                  }
+                  return value !== null && value !== undefined;
+                };
+
+                const isEmptyAssistantBootstrapChunkForResponsesClient =
+                  clientExpectsResponsesStream &&
+                  parsed?.object === "chat.completion.chunk" &&
+                  Array.isArray(parsed?.choices) &&
+                  parsed.choices.length > 0 &&
+                  parsed.choices.every((choice) => {
+                    const candidate = choice && typeof choice === "object" ? choice : {};
+                    const delta =
+                      candidate.delta && typeof candidate.delta === "object"
+                        ? candidate.delta
+                        : null;
+
+                    if (!delta || delta.role !== "assistant") return false;
+                    if (hasActiveDeltaValue(delta.content)) return false;
+                    if (candidate.finish_reason !== null && candidate.finish_reason !== undefined) {
+                      return false;
+                    }
+
+                    const { role: _role, content: _content, ...restDelta } = delta;
+                    return !hasActiveDeltaValue(restDelta);
+                  });
+
+                if (isEmptyAssistantBootstrapChunkForResponsesClient) {
+                  continue;
+                }
+
                 // Detect Responses SSE payloads (have a `type` field like "response.created",
                 // "response.output_item.added", etc.) and skip Chat Completions-specific
                 // sanitization to avoid corrupting the stream for Responses-native clients.

tests/unit/stream-utils.test.ts

@@ -652,6 +652,71 @@ test("createSSEStream passthrough preserves Responses API events and completion
   assert.equal(onCompletePayload.providerPayload.summary.object, "response");
 });
 
+test("createSSEStream passthrough drops leaked empty chat bootstrap chunks for Responses clients", async () => {
+  const text = await readTransformed(
+    [
+      `data: ${JSON.stringify({
+        id: "chatcmpl-dummy",
+        object: "chat.completion.chunk",
+        created: 1,
+        model: "gpt-5.4",
+        choices: [
+          { index: 0, delta: { role: "assistant", content: null, refusal: null }, finish_reason: null },
+        ],
+      })}\n\n`,
+      `event: response.created\ndata: ${JSON.stringify({
+        type: "response.created",
+        response: {
+          id: "resp_1",
+          object: "response",
+          model: "gpt-5.4",
+          status: "in_progress",
+          output: [],
+        },
+      })}\n\n`,
+      `event: response.in_progress\ndata: ${JSON.stringify({
+        type: "response.in_progress",
+        response: {
+          id: "resp_1",
+          object: "response",
+          model: "gpt-5.4",
+          status: "in_progress",
+          output: [],
+        },
+      })}\n\n`,
+      `data: ${JSON.stringify({
+        type: "response.output_text.delta",
+        delta: "OK",
+      })}\n\n`,
+      `data: ${JSON.stringify({
+        type: "response.completed",
+        response: {
+          id: "resp_1",
+          object: "response",
+          model: "gpt-5.4",
+          status: "completed",
+          output: [],
+          usage: { input_tokens: 2, output_tokens: 1, total_tokens: 3 },
+        },
+      })}\n\n`,
+      `data: [DONE]\n\n`,
+    ],
+    {
+      mode: "passthrough",
+      sourceFormat: FORMATS.OPENAI_RESPONSES,
+      clientResponseFormat: FORMATS.OPENAI_RESPONSES,
+      provider: "openai",
+      model: "gpt-5.4",
+      body: { input: "hello" },
+    }
+  );
+
+  assert.doesNotMatch(text, /chatcmpl-dummy/);
+  assert.match(text, /response\.created/);
+  assert.match(text, /response\.output_text\.delta/);
+  assert.match(text, /"delta":"OK"/);
+});
+
 test("buildStreamSummaryFromEvents falls back to response.output_text.delta when completed output is empty", () => {
   const summary = buildStreamSummaryFromEvents(
     [