chat: piped stdin is truncated to the first line (cat file | qwisp chat silently answers on line 1)

[penta2himajin]

Symptom

cat file | qwisp chat (and qwisp chat < file) silently answers using only the first line of the input. No error, no warning, exit 0.

Both the help text and the usage line advertise this path:

• chat [opts] <prompt> one-shot chat; reads stdin if no prompt is given
• usage: qwisp chat [--max-tokens N] [--lossless] <prompt> (or pipe text via stdin)

Cause

swift/Sources/qwisp/main.swift:126:

let prompt = promptText.isEmpty ? (readLine(strippingNewline: true) ?? "") : promptText

readLine() returns one line. Everything after the first newline is discarded. There is no TTY check — the same call serves the interactive case (where one line is right) and the piped case (where it is not).

Why it matters

Silent truncation, the same class as #151: the user gets a plausible, successful answer to a question the model was never given the context for. Piping a file is the natural way to ask about a document, and the help text points straight at it.

Found while setting up #162's A/B harness: qwisp chat < prompt.txt on a 126KB (~35K-token) file ingested 52 tokens and reported prompt 52 tok (94 tok/s) · gen 32 tok (96.4 tok/s) — a completely healthy-looking run that measured nothing. It was caught only because that harness asserts on prompt length; nothing in qwisp itself flagged it.

Fix

Read stdin to EOF when stdin is not a TTY; keep readLine() for the interactive case.

Refs

swift/Sources/qwisp/main.swift:124-128 · #151 (same silent-failure class)