---
id: "bug-1718"
status: "fixed"
status_updated: "2026-09-24"
status_note: ""
component: "controller"
severity: "unknown"
timestamp: "2026-08-26T16:23:00Z"
last_seen: "2026-09-19T09:00:00Z"
occurrences: 1
files: ["src/controller/testsuite/test_rcfile_integration.sh"]
tags: ["bash", "python", "pty", "heredoc", "stdin", "xce-test-rc-file", "task-3.1"]
related: []
legacy: true
---

# bug-1718: A python3 pty-driver embedded via a heredoc on a command that ALSO receives piped stdin silently…

## Description
A python3 pty-driver embedded via a heredoc on a command that ALSO receives piped stdin silently discards the piped input

## Environment
_Not recorded (migrated from buglog.json)._

## Reproduction
_Not recorded (migrated from buglog.json)._

## Root cause
First draft of run_interactive_pty() did: printf '%s\n' "$script" | python3 - "$XCE_TEST" ... <<PYEOF ... PYEOF. python3 - reads its ENTIRE program from stdin until EOF; a <<HEREDOC redirect on the same command line takes precedence over the pipe for that command's stdin (the pipe's implicit fd0 assignment is overridden by the explicit redirect), so the heredoc (the Python source) became the process's only stdin content. Once python3 finished reading its own program from that stream, stdin was already at EOF -- the script's own sys.stdin.read() (meant to receive the piped xce_test command script) returned empty every time, silently. No error was raised; it just produced an empty commands list, which would have made every interactive-scenario assertion trivially fail once real command sending began (caught before ever running the script standalone, via careful re-reading of the draft rather than via a failing run).

## Fix
Write the Python driver ONCE to its own temp file via mktemp + cat >"$PTY_DRIVER" <<PYEOF ... PYEOF at script startup (cleaned up by an EXIT trap), then invoke it as printf ... | python3 "$PTY_DRIVER" args... -- this leaves the pipe as the sole, unambiguous stdin source for the running Python process, since python3 <file> does not consume stdin to obtain its own source.

## Verification
_Not recorded (migrated from buglog.json)._

## References
_Not recorded (migrated from buglog.json)._