[rigor789]

What is the current behavior?

Without a console, an app's stdio is /dev/null. print() output is lost, and so is NSLog on devices, where it only goes to stderr on iPadOS 26.7. A CLI can't attach to it after launch, because stdio is fixed when the process starts.

What is the new behavior?

In debug builds whose CLI sets forwardStdio in the app's package.json, with stdout still /dev/null, the runtime pipes stdout and stderr into os_log under the org.nativescript.stdio subsystem, with stdout and stderr as categories.

• Older CLIs never set the key, and release builds and attached consoles fail the checks, so nothing changes for them.
• stdout becomes line buffered, or print() would wait for a full buffer.
• Long lines are split the same way as console messages.
• Devices forward both streams. The simulator forwards stdout only, because NSLog there also reaches the unified log and would print twice. That means fputs(..., stderr) isn't forwarded on the simulator.

Known limits: output buffered at the moment of a crash is lost, so the last lines before an abort() may not appear. An unterminated final line isn't forwarded until a newline arrives or it reaches 64 KB.

Testing

Demo app with Swift code calling print() (short, 5,000 characters, background thread), NSLog and fputs(stderr), on both launches of each run:

Setup	Result
New CLI, default, simulator and iPad	Hidden, and all 11 console messages intact
New CLI, --log debug, simulator	print() shown, 5,000-character line intact, NSLog once (from Foundation)
New CLI, --log debug, iPad (iPadOS 26.7)	print(), NSLog and stderr all shown once
Published CLI 9.1.1, simulator	No forwarding
simctl launch --console-pty	print() goes to the console directly

Older iOS versions weren't tested, and NSLog may behave differently there. A launch from Xcode itself wasn't tested either.

Part of a stack

Base: #530. The CLI side is NativeScript/nativescript-cli#6181.

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Reviewing files that changed from the base of the PR and between db9cadd and 8715264.

Files selected for processing: 6

• NativeScript/NativeScript.mm
• NativeScript/runtime/Helpers.h
• NativeScript/runtime/Helpers.mm
• NativeScript/runtime/StdioForwarder.h
• NativeScript/runtime/StdioForwarder.mm
• v8ios.xcodeproj/project.pbxproj

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