fix(shared): port checks no longer fail on hosts with IPv6 disabled

[mr-joom]

Hosts booted without IPv6 support return EAFNOSUPPORT when a port probe opens an IPv6 socket. The shared network helper treated that as an occupied port, so desktop startup could reject every otherwise free port.

The helper now treats EAFNOSUPPORT like the existing EADDRNOTAVAIL case. IPv4 is still checked, and an occupied IPv4 port remains unavailable. Contributor commits from @mr-joom's #15044 are preserved; main was merged to resolve the conflict.

Verification:

• Fresh test reduction kept six behavioral cases while removing 48 lines of global mocking. The EAFNOSUPPORT regression fails on main (1 failed, 5 passed) and passes with the fix (6 passed). Focused lint, formatting and shared typecheck passed; the separate implementation pass retained the minimal errno check and shortened the comment. One full-diff review round by Claude Opus 5.5 and Codex GPT-6 Sol found no code issues; both independently reran the six focused cases.
• Linux process-local seccomp filter returned real kernel EAFNOSUPPORT from socket(AF_INET6, ...). Main reported a free IPv4 port unavailable and discarded the preferred port; the fix reported it available and kept the preferred port. Both versions rejected an occupied IPv4 port. Syscall tracing confirmed the errno.
• An isolated network namespace with IPv6 addresses disabled exercised the existing EADDRNOTAVAIL path; free and occupied IPv4 behavior stayed correct.

Before/after syscall and port-selection output.

These process-local checks do not change host networking. They reproduce the errno without rebooting into an IPv6-disabled kernel. A machine actually booted with ipv6.disable=1, macOS, Windows, iOS, Android, and Electron desktop were not tested. This is nonvisual port-selection behavior; syscall output and focused tests are the evidence.

Implementation: GPT-6.1 Sol through the Codex harness in T3 Code; tests: GPT-6 Astra; adversarial review: Claude Opus 5.5 and GPT-6 Sol.

[macroscopeapp]

Approvability

Verdict: Approved at 86394f1

Macroscope's review found this PR approvable — This is a narrowly scoped shared-network bug fix that handles IPv6-disabled hosts without changing occupied-port detection or APIs. Focused regression coverage is included for both relevant error codes.

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Dismissing prior approval to re-evaluate 935a294

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between c5a929e and 935a294.

📒 Files selected for processing (2)

• packages/shared/src/Net.test.ts
• packages/shared/src/Net.ts

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📝 Walkthrough

canListenOnHost now treats EAFNOSUPPORT as available, alongside EADDRNOTAVAIL. Tests verify the result for EAFNOSUPPORT and confirm that EACCES still indicates an unavailable host.

Changes: Host availability error handling

Layer / File(s)	Summary
Handle unsupported address families packages/shared/src/Net.ts, packages/shared/src/Net.test.ts	canListenOnHost treats EAFNOSUPPORT like EADDRNOTAVAIL. Tests use a mocked listener to verify that EAFNOSUPPORT returns true and EACCES returns false.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 935a2

This fix lets port checks pass on hosts with IPv6 disabled, so the desktop app no longer exits with a port-unavailable error. Other bind failures are still reported as unavailable. No merge-blocking risk was identified.

Pre-merge checks: 5

Check name	Status	Explanation
Linked Issues check		Issue [#15038] requires port checks to allow desktop startup when IPv6 is disabled. canListenOnHost now treats EAFNOSUPPORT like EADDRNOTAVAIL, and tests cover the IPv6-disabled case plus reject…
Out of Scope Changes check		The source change and tests directly address issue [#15038]. No unrelated changes appear in the pull request diff.
Docstring Coverage		No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Title check		The title clearly and concisely describes the fix for port checks on hosts without IPv6 support. It uses a conventional commit format and matches the main change.
Description check		The description explains the problem, the implementation, verification results, tested environments, limitations, and agent usage. It provides focused evidence for the behavioral change. The scope sec…

Full details: Linked Issues check

Explanation

Issue [#15038] requires port checks to allow desktop startup when IPv6 is disabled. canListenOnHost now treats EAFNOSUPPORT like EADDRNOTAVAIL, and tests cover the IPv6-disabled case plus rejection of EACCES.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2 files.

Full details: Description check

Explanation

The description explains the problem, the implementation, verification results, tested environments, limitations, and agent usage. It provides focused evidence for the behavioral change. The scope section does not explicitly link the underlying issue or maintainer approval, but the provided PR objectives identify issue #15038 and the description is otherwise complete.

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[juliusmarminge]

Taking over this one. I'll merge main into the branch, trim the tests to the minimum, keep the fix, run adversarial reviews, and push here. Thanks @mr-joom for the root cause.

Dismissing prior approval to re-evaluate 86394f1