fix(rpc): accept exact-boundary v2 chunks

packages/coding-agent/src/modes/rpc/rpc-frame.ts

@@ -147,7 +147,7 @@ export class RpcFrameDecoder {
 			count < 2 ||
 			count > Math.ceil(MAX_RPC_REASSEMBLED_BYTES / RPC_CHUNK_PAYLOAD_BYTES) ||
 			index >= count ||
-			byteLength <= MAX_RPC_FRAME_BYTES ||
+			byteLength < MAX_RPC_FRAME_BYTES ||
 			byteLength > MAX_RPC_REASSEMBLED_BYTES
 		)
 			throw new Error("invalid rpc chunk metadata");

packages/coding-agent/test/rpc-frame.test.ts

@@ -208,6 +208,27 @@ describe("RPC frame encoding", () => {
 		expect(decoded).toEqual(frame);
 	});
 
+	it("accepts a chunked logical frame at the exact physical-frame boundary", () => {
+		const frame = {
+			id: "request-boundary",
+			type: "response",
+			command: "get_state",
+			success: true,
+			data: { payload: "" },
+		};
+		const emptyBytes = Buffer.byteLength(JSON.stringify(frame), "utf8");
+		frame.data.payload = "x".repeat(MAX_RPC_FRAME_BYTES - emptyBytes);
+		expect(Buffer.byteLength(JSON.stringify(frame), "utf8")).toBe(MAX_RPC_FRAME_BYTES);
+
+		const encoder = new RpcFrameEncoder();
+		encoder.setProtocolVersion(2);
+		const decoder = new RpcFrameDecoder();
+		let decoded: object | undefined;
+		for (const line of encoder.encode(frame).trimEnd().split("\n")) decoded = decoder.push(JSON.parse(line));
+
+		expect(decoded).toEqual(frame);
+	});
+
 	it("preserves terminal message counts above the protocol v2 ceiling", () => {
 		const encoder = new RpcFrameEncoder();
 		encoder.setProtocolVersion(2);