## Summary
- Fixes ENXIO error when reopening `/dev/tty` after stdin reaches EOF
- Fixes ESPIPE error when reading from reopened TTY streams
- Adds ref/unref methods to tty.ReadStream for socket-like behavior
- Enables TUI applications that read piped input then switch to
interactive TTY mode
## The Problem
TUI applications and interactive CLI tools have a pattern where they:
1. Read piped input as initial data: `echo "data" | tui-app`
2. After stdin ends, reopen `/dev/tty` for interactive session
3. Use the TTY for interactive input/output
This didn't work in Bun due to missing functionality:
- **ESPIPE error**: TTY ReadStreams incorrectly had `pos=0` causing
`pread()` syscall usage which fails on character devices
- **Missing methods**: tty.ReadStream lacked ref/unref methods that TUI
apps expect for socket-like behavior
- **Hardcoded isTTY**: tty.ReadStream always set `isTTY = true` even for
non-TTY file descriptors
## The Solution
1. **Fix ReadStream position**: For fd-based streams (like TTY), don't
default `start` to 0. This keeps `pos` undefined, ensuring `read()`
syscall is used instead of `pread()`.
2. **Add ref/unref methods**: Implement ref/unref on tty.ReadStream
prototype to match Node.js socket-like behavior, allowing TUI apps to
control event loop behavior.
3. **Dynamic isTTY check**: Use `isatty(fd)` to properly detect if the
file descriptor is actually a TTY.
## Test Results
```bash
$ bun test test/regression/issue/tty-reopen-after-stdin-eof.test.ts
✓ can reopen /dev/tty after stdin EOF for interactive session
✓ TTY ReadStream should not set position for character devices
$ bun test test/regression/issue/tty-readstream-ref-unref.test.ts
✓ tty.ReadStream should have ref/unref methods when opened on /dev/tty
✓ tty.ReadStream ref/unref should behave like Node.js
$ bun test test/regression/issue/tui-app-tty-pattern.test.ts
✓ TUI app pattern: read piped stdin then reopen /dev/tty
✓ tty.ReadStream handles non-TTY file descriptors correctly
```
## Compatibility
Tested against Node.js v24.3.0 - our behavior now matches:
- ✅ Can reopen `/dev/tty` after stdin EOF
- ✅ TTY ReadStream has `pos: undefined` and `start: undefined`
- ✅ tty.ReadStream has ref/unref methods for socket-like behavior
- ✅ `isTTY` is properly determined using `isatty(fd)`
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
