[Soham Das (SohamDas2021)]

📖 Description

When a WSLc command exits without reading a large amount of its stdin, the WSLc SDK sometimes drops the command's output and reports its exit 30 s or more late. MXC warned only when that report took longer than its own 30 s wait, so when the SDK reported exactly 30 s late, a few milliseconds decided whether the warning appeared. On some hosts it didn't, and output was lost with no warning.

• Warning: now appears whenever the SDK reports the exit 10 s or more after the command ended. A normal exit is reported within milliseconds. This covers both the CLI and the SDK streaming path.
• Test: the flood case runs sleep 40 instead of sleep 3. A command that ends that long after its input backs up is reported exactly 30 s late, the delay the old check could miss.
• Docs: the exit is reported "30 seconds or more" late, not "about 50 seconds".

MXC cannot stop the SDK from dropping the output; it can only warn that this may have happened. No spec is needed: this is a bug fix with no change to the API or schema.

🔗 References

Fixes #1605. Follow-up to #1564. This edits the same part of wsl_container_runner.rs as #1597, so whichever merges second needs a small rebase.

🔍 Validation

Windows with WSL 3.0.4.0 (the same version as the CI hosts) and WSLc SDK 3.0.3.

Command	Result
cargo fmt --all -- --check	Passed
cargo clippy -p mxc-sdk --features wslc --all-targets -- -D warnings	Passed
cargo test -p mxc-sdk --features wslc --lib -- wslc	Passed: 426 passed, 0 failed, 3 ignored
Flood case run alone through wxc-exec, before the fix (6 runs)	2 of 6 lost output with no warning, which reproduces #1605
Same, after the fix (6 runs)	All 6 returned the output or the warning

Not run: the full run_wslc_all_tests.ps1 suite and the .NET and Node live WSLc tests.

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• For features or changes requiring a spec: linked the issue with maintainer-applied feature-accepted
• For implementation: linked the required approved and merged design/API spec, or explained why no spec is required
• Feature issue remains open unless this PR completes all agreed implementation, validation, and documentation
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)
• If this PR changes Cargo.lock, the dependency-feed-check check passes (see pull request builds)

📋 Issue Type

• Bug fix
• Feature
• Task

Microsoft Reviewers: Open in CodeFlow

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[Copilot]

🟡 Changes recommended

The callback-delay check measures time spent in wait() rather than exit-to-callback latency, so it can miss late callbacks and associated output loss when callers drain output before waiting.

1 open issue

• Measure callback delay independently of caller wait · New

What changed in this PR

This follow-up to #1564 addresses intermittent missing warnings after WSLc stdin floods, reported in #1605, without changing public APIs or schemas.

Changes:

• Uses a 10-second callback-wait threshold instead of requiring the 30-second wait to expire.
• Extends the stdin-flood regression command to exercise the minimum observed late-exit delay.
• Corrects documentation to describe exit reporting as delayed by 30 seconds or more.

File	Description
tests/​scripts/​run_wslc_all_tests.ps1	Runs the flood command for 40 seconds with a 120-second execution timeout.
src/​mxc-sdk/​src/​backends/​wslc/​common/​wsl_container_runner.rs	Adds elapsed-time detection for the potentially incomplete-output warning.
docs/​backends/​wslc/​wsl-container-getting-started.md	Corrects the documented delay caused by unread stdin.

_{Review effort: Balanced}