fix(proxy): move SSE cap after line draining + coalesced-chunk test

wangmiao0668000666 · wangmiao0668000666 · commit 501c07a4a6f9 · 2026-06-26T17:02:02.000+08:00
diff --git a/src/agents/runtime/proxy.test.ts b/src/agents/runtime/proxy.test.ts
@@ -216,4 +216,33 @@ describe("streamProxy", () => {
     expect(result.stopReason).toBe("error");
     expect(result.errorMessage).toContain("exceeded max buffer size");
   });
+
+  it("handles a large transport chunk containing many valid newline-delimited proxy SSE lines", async () => {
+    // Regression: one TCP read can deliver >64 KiB of already-delimited lines;
+    // the cap must apply only to the unterminated tail, not the full chunk.
+    const encoder = new TextEncoder();
+    const line = `data: ${JSON.stringify({ type: "done", reason: "stop", usage })}\n`;
+    const manyLines = line.repeat(2000);
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async () => ({
+        ok: true,
+        status: 200,
+        body: new ReadableStream({
+          start(controller) {
+            controller.enqueue(encoder.encode(manyLines));
+            controller.close();
+          },
+        }),
+      })),
+    );
+
+    const stream = streamProxy(model, context, {
+      authToken: "token",
+      proxyUrl: "https://proxy.example",
+    });
+    const result = await stream.result();
+
+    expect(result.stopReason).toBe("stop");
+  });
 });
diff --git a/src/agents/runtime/proxy.ts b/src/agents/runtime/proxy.ts
@@ -229,13 +229,13 @@ export function streamProxy(
         }
 
         buffer += decoder.decode(value, { stream: true });
+        const lines = buffer.split("\n");
+        buffer = lines.pop() || "";
         if (buffer.length > PROXY_SSE_BUFFER_MAX_BYTES) {
           throw new Error(
             `Proxy SSE response exceeded max buffer size (${PROXY_SSE_BUFFER_MAX_BYTES} bytes) without line boundary`,
           );
         }
-        const lines = buffer.split("\n");
-        buffer = lines.pop() || "";
 
         for (const line of lines) {
           processSseLine(line);

Original file line number	Diff line number	Diff line change
`@@ -229,13 +229,13 @@ export function streamProxy(`
`229`	`229`	`}`
`230`	`230`
`231`	`231`	`buffer += decoder.decode(value, { stream: true });`
	`232`	`+ const lines = buffer.split("\n");`
	`233`	`+ buffer = lines.pop() \|\| "";`
`232`	`234`	`if (buffer.length > PROXY_SSE_BUFFER_MAX_BYTES) {`
`233`	`235`	`throw new Error(`
`234`	`236`	`Proxy SSE response exceeded max buffer size (${PROXY_SSE_BUFFER_MAX_BYTES} bytes) without line boundary`,
`235`	`237`	`);`
`236`	`238`	`}`
`237`		`- const lines = buffer.split("\n");`
`238`		`- buffer = lines.pop() \|\| "";`
`239`	`239`
`240`	`240`	`for (const line of lines) {`
`241`	`241`	`processSseLine(line);`