Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Make a TCP key-value server follow its wire protocol (pipelining, split reads, binary payloads, expiry, close rules)

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  "result": "I rewrote `server.py` to follow `PROTOCOL.md`, and all 12 groups of tests in my local script pass against it. The command line is unchanged: `python3 server.py [port]`, `F03_PORT`, default 18601, bound to 127.0.0.1. It uses only the standard library.\n\n**How it works**\n- **Concurrent clients:** each client gets its own thread, and they all share one store behind a single lock.\n- **Pipelining and split/merged reads:** each connection keeps its own input buffer and handles every complete command in it, so commands can arrive one byte at a time or many in one packet. Replies to a batch go out together, in order.\n- **SET:** the server reads exactly `<len>` raw bytes, so a payload containing `\\r\\n` is stored correctly. If the two bytes after the payload aren't `\\r\\n`, it replies `-ERR bad payload`, stores nothing and closes. A bad SET line gets its error as soon as the line arrives, without reading a payload.\n- **Expiry:** expired keys are removed when they're looked up, and a background sweep clears the rest every second. Every command treats expired keys as missing, and SET clears any expiry.\n- **Long lines:** a line of exactly 1024 bytes is accepted even if its `\\r` and `\\n` arrive separately. Anything longer, including 5000 bytes with no line ending, gets `-ERR line too long` and the connection closes.\n- **Closing:** after QUIT or a fatal error, anything else the client pipelined is ignored. The server finishes sending its reply before closing, so a client that has sent more data still receives the error or `+BYE`. Otherwise the reply can be lost.\n- **Isolation:** errors in one connection only close that connection. A client stalled halfway through a command doesn't block anyone else, and the accept loop keeps running if a connection can't be accepted.\n\n**Choices where the spec doesn't say**\n- **Spaces:** extra spaces between words are tolerated rather than rejected.\n- **Empty line:** gets `-ERR unknown command`.\n- **Arguments:** `PING` or `QUIT` with arguments, and `DEL` with no keys, get `-ERR wrong args`.\n- **EXPIRE:** a seconds value that isn't a finite number gets `-ERR wrong args`. Zero or a negative value makes the key expire immediately, and the reply is still `:1`.\n- **INCR:** it keeps a key's existing expiry, since the spec only says SET clears it.\n\n**What I tested**\n- Byte-at-a-time pipelining and binary payloads containing `\\r\\n`.\n- Every error reply, and which errors close the connection.\n- The 1024-byte line and 1 MiB payload limits.\n- Expiry across GET, DEL, INCR and EXPIRE.\n- 20 clients sending 10,000 INCRs in total, with the final count correct, while another client sat stalled mid-command.\n\nThe test script is at `/tmp/f03test/t.py`, outside the work directory.",
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