[turinglambdaai]

Closes #339.

Failure mode

On GitHub Actions windows-latest runners, raco rivet build for a WinUI 3 app intermittently fails with

    0 Error(s)
error writing to stream port
  system error: Invalid access to memory location.; win_err=998
##[error]Process completed with exit code 1.

even though the child MSBuild exited 0 and the executable was produced (the link steps and 0 Error(s) summary are right there in the log). Three occurrences in one day on the shuttle private repo; every immediate rerun was green.

Root cause

The CLI runs tools with inherited stdout/stderr. On Actions, that ambient stdout is the hosted log pipe. When the runner-side log processing drops the pipe, the next printf/eprintf from rivet itself raises error writing to stream port — and because the whole command runs on those ports, a log-transport failure is conflated with a build failure.

Fix

rivet-cli/main.rkt wraps the command dispatch in call-with-tolerant-logging (rivet-cli/tolerant-log.rkt): both ambient ports become delegating ports whose failed write (or failed close) is treated as a completed write — the bytes are dropped, the command keeps running. The child's exit code remains the only success signal; healthy transports pass output through byte-for-byte, byte order preserved.

Deliberately minimal: no child-process redirection, no buffering, no behavior change other than not dying when the sink dies.

Tests

rivet/tests/tolerant-log.rkt:

• passthrough fidelity to a healthy port,
• thousands of interleaved stdout/stderr writes into transports that raise on every write (the issue's signature),
• a raising close handler (covers exit-path cleanup).

Local: suite green (raco test rivet/tests/); CLI smoke (raco rivet --help, doctor) unchanged.

CHANGELOG

### Fixed entry under Unreleased.

[turinglambdaai]

Follow-up review fix added at cf714a142a250a5b02d2888c518c44a1716bf4b6: the tolerant CLI output wrapper borrows current-output-port/current-error-port; its close callback must not close the original ambient port. Previously close-output-port proxy closed the caller-owned terminal/log stream, which could poison later output. The wrapper now drops its own close without affecting the underlying sink. Added regression coverage for both ordinary borrowed string sink and a base port with a failing/observable close handler. CI must be assessed again on the new head; prior greens on 0d3d126 do not validate these new commits.