# LibTmux.wait_for

- **Module:** LibTmux
- **Package:** LibTmux
- **Language:** Julia
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-julia/blob/1a68a11f071686736937d027b190b43cf946c385/src/waits.jl#L166
- **Page:** https://libtmux.org/en/julia/latest/reference/libtmux-wait_for/

```
wait_for(
    predicate,
    stream::LibTmux.ObservationStream;
    kwargs...,
)
```

## Methods

Consume raw pane output until `predicate(result::OutputWaitResult)` returns `true`. The predicate runs outside the reader lock and must return promptly. One total deadline includes baseline capture, predicate calls and every read; a synchronous predicate cannot be forcibly interrupted. Cancellation and an expired deadline are checked again before accepting its result.

```julia
wait_for(predicate, stream::ObservationStream; baseline=false, timeout=5.0,
         cancel=nothing, max_bytes=65536, invalid=:error, mode=:raw)
```



By default only output consumed by this call is considered. `baseline=true` first tests an independently captured screen, bounded by `max_bytes`, with soft-wrapped rows joined so text wider than the pane still matches; an oversized capture raises `OutputLimitExceeded`. A rejected baseline is never concatenated with subsequent raw bytes. Already queued output remains eligible; register a new stream before sending input when fresh-output evidence matters.

Predicates see a tail of at most `max_bytes` bytes, not unlimited history. UTF-8 spans chunks through `TextDecoder`; malformed input follows `invalid`. Terminal escapes remain literal data. `mode=:rendered` refuses streaming screen reconstruction before I/O; explicit captures remain available.

The stream retains incomplete UTF-8 across successive waits, including after cancellation or a predicate exception. Only one helper may consume it at a time, on its consumer task. A UTF-8 policy change requires no pending bytes. Direct raw reads during a helper are refused; raw reads between helpers make later text waits refuse lost decoder continuity. Register a new stream after a strict UTF-8 error or to change consumption modes.

The caller retains ownership of the stream and connection. Stream overflow, topology loss, cancellation, EOF and transport errors propagate without replay.

## Parameters

- `predicate` (`Any`)
- `stream` (`LibTmux.ObservationStream`)
- `kwargs`

## Guides

Pages that discuss `wait_for`.

- [Observing output](/en/julia/latest/topics/observations/)