fix: use weak var instead of weak let for macOS 26 / Swift 6 compat

[XueyanZhang]

Closes #9652

Summary

weak let is rejected by the Swift compiler on newer toolchains (e.g. the macOS 26 SDK): a weak reference can become nil at runtime when the referenced object is deallocated, so its storage must be mutable. The compiler error is

error: 'weak' must be a mutable variable, because it may change at runtime

CI runs on macOS 15.7.4 where these still compile, so this is latent there — it only surfaces on macOS 26, where it blocks the test-target compile (e.g. cmuxTests/AppDelegateEqualizeSplitsShortcutTests.swift:4922 fails first and aborts the whole cmux-unit build).

Changes

Replaces weak let with weak var at the four remaining sites. None of the variables are reassigned, so the change is purely a compile-time correctness fix with no behavioral difference:

File	Variable
cmuxTests/AppDelegateEqualizeSplitsShortcutTests.swift	weakRemovablePanel
Packages/macOS/CmuxCommandPalette/Tests/.../CommandPaletteInteractionMonitorTests.swift	weakMonitor
Packages/macOS/CmuxSimulator/Tests/.../SimulatorWorkerClientContainmentTests.swift	weakClient
Packages/iOS/CmuxMobileShell/Tests/.../MobileMacConnectionPoolTests.swift	weakShell

The fifth site originally reported (Packages/iOS/CmuxMobileSupport/Sources/.../ComposerDictationController.swift) was already fixed on main (now weak var), so this PR covers the remainder.

Why no regression test

Compile-time fix only. On CI's macOS 15.7.4 the code already compiles, so there is no observable runtime behavior to assert; a "test" would just duplicate a compile that already passes. Per the project's test-quality policy, no fake regression test is added.

Test plan

• swift build --build-tests for CmuxCommandPalette on macOS 26 — its test target (containing one of the weak var sites) compiles clean.
• Mechanical correctness: every site is a direct weak let → weak var, the exact form the compiler error mandates; none of the variables are reassigned.
• CI (macOS 15.7.4) — confirms no regression; the change is a no-op there (macOS 15 still accepts weak let).

Summary by CodeRabbit

• Tests
  • Corrected weak-reference test declarations across iOS and macOS test suites.
  • Improved reliability of deallocation and cleanup assertions for shells, monitors, simulator clients, and panels.

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📥 Commits

Reviewing files that changed from the base of the PR and between a7fb822 and 8ef4f92.

📒 Files selected for processing (1)

• Packages/iOS/CmuxMobileShell/Tests/CmuxMobileShellTests/MobileMacConnectionPoolTests.swift

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📝 Walkthrough

Walkthrough

Four test weak-reference bindings changed from weak let to weak var. Existing deallocation and observer-cleanup assertions remain unchanged.

Changes

Weak reference binding fixes

Layer / File(s)	Summary
Update weak reference declarations Packages/iOS/CmuxMobileShell/Tests/..., Packages/macOS/CmuxCommandPalette/Tests/..., Packages/macOS/CmuxSimulator/Tests/..., cmuxTests/AppDelegateEqualizeSplitsShortcutTests.swift	Four test weak references now use mutable var bindings. Existing assertions remain unchanged.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Possibly related PRs

• manaflow-ai/cmux#8931: Adds related connection-pool behavior and tests in the same suite.
• manaflow-ai/cmux#9417: Updates weak-reference test bindings from weak let to weak var.

Suggested reviewers: austinywang, lawrencecchen

🚥 Pre-merge checks | ✅ 25

✅ Passed checks (25 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR replaces four reported weak let declarations, and the fifth linked issue location is documented as already fixed on main.
Out of Scope Changes check	✅ Passed	All four changes directly implement the linked issue and contain no unrelated code or behavior changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Cmux Swift Actor Isolation	✅ Passed	The commit changes only four Swift test files from weak let to weak var; no production Swift or actor-isolation declaration changed.
Cmux Swift Blocking Runtime	✅ Passed	The commit changes only four test files, each by replacing weak let with weak var; it adds no blocking or timing synchronization, and the production source is unchanged.
Cmux Browser Automation Off-Main	✅ Passed	HEAD^..HEAD changes only four test files, each replacing weak let with weak var; no browser automation, WebKit, socket-worker, or policy-routing code changed.
Cmux Expensive Synchronous Load	✅ Passed	HEAD-parent diff changes only four test files, each solely from weak let to weak var; no production Swift or expensive synchronous load/path change is present.
Cmux Cache Substitution Correctness	✅ Passed	The commit only changes four test declarations from weak let to weak var; no production cache, persistence, history, undo, or snapshot read changed.
Cmux No Hacky Sleeps	✅ Passed	The actual diff changes only four Swift test files from weak let to weak var; the rule covers non-Swift runtime changes, and no timing constructs were added.
Cmux Algorithmic Complexity	✅ Passed	The HEAD diff changes only four test files, each by one weak let→weak var declaration; no collection scans, sorting, filtering, joins, or runtime algorithm changes were added.
Cmux Swift Concurrency	✅ Passed	The diff only changes four existing weak let declarations to weak var; it adds no Dispatch, Combine, completion-handler, or fire-and-forget Task patterns.
Cmux Swift @Concurrent	✅ Passed	The diff only changes four weak let declarations to weak var; it adds no @concurrent/nonisolated/async or call-site changes, so the concurrency rule is not violated.
Cmux Swift Package Boundaries	✅ Passed	The commit changes only four test files from weak let to weak var; ComposerDictationController is unchanged and already uses weak var, so no production boundary violation exists.
Cmux Swiftpm Lockfiles	✅ Passed	The PR diff contains only four Swift test-file weak-reference edits; it changes no Package.swift, Package.resolved, .gitignore, workflow, or Xcode package reference covered by the rule.
Cmux Swift Logging	✅ Passed	The patch only changes four test declarations from weak let to weak var; it adds no logging and does not modify production Swift code.
Cmux User-Facing Error Privacy	✅ Passed	The HEAD diff only changes four weak let declarations to weak var in test files; it adds no user-facing errors, alerts, command output, API bodies, or recovery copy.
Cmux Full Internationalization	✅ Passed	The HEAD diff changes only four weak references in test files; it adds no user-facing text, localization keys, catalogs, web messages, or locale data.
Cmux Swiftui State Layout	✅ Passed	The commit changes only four weak let declarations to weak var; it adds no SwiftUI state, layout, lazy-row store, or render-time mutation patterns.
Cmux Architecture Rethink	✅ Passed	The diff only changes four test-local weak bindings from let to var; it adds no timing, polling, locks, observers, side channels, duplicate wiring, or lifecycle-owner changes.
Cmux Swift Auxiliary Window Close Shortcuts	✅ Passed	The diff changes only four test files and four weak declarations; it adds no NSWindow, NSPanel, WindowGroup, identifier, or close-shortcut code.
Cmux Source Artifacts	✅ Passed	All four changed paths are intentional Swift test files; the diff only changes weak let to weak var and adds no logs, caches, build output, temp folders, or other artifacts.
Cmux No Test Or Debug Seam In Production Source	✅ Passed	The PR commit changes only four test files; no production Sources path is modified, and added lines contain only weak var replacements with no debug/test seam.
Cmux No Ambient Global State	✅ Passed	The HEAD diff changes only four local weak bindings in test functions; it adds no production Swift file, top-level mutable state, namespace type, or singleton.
Title check	✅ Passed	The title clearly identifies the weak-reference declaration fix and its macOS 26 and Swift 6 compatibility purpose.
Description check	✅ Passed	The description explains the cause, affected files, testing, and rationale for omitting a regression test; non-applicable template sections are reasonably omitted.

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Note

GitHub couldn't provide a complete incremental comparison for this pull request, so CodeRabbit is performing a full review instead. This review may take a little longer.

[XueyanZhang]

Rebased onto latest main. Note: the fifth site (ComposerDictationController.swift) was already fixed upstream, so this covers the remaining four weak let sites. @lawrencecchen could you take a look?

[teamleaderleo]

Thanks for this! We checked the weak var change against current main and would like to land it. The one thing left is the CLA (CLA.md): if you're OK with it, comment exactly I have read the CLA Document v2.2 and I hereby sign the CLA and we'll take it from there.

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[XueyanZhang]

I have read the CLA Document v2.2 and I hereby sign the CLA

[XueyanZhang]

Thank! Sorry there was a delay XD

[teamleaderleo]

Review: The four weak-reference declarations are the required Swift 6 compile fix and preserve test intent. Fixed: no additional changes needed. Left: required CI is still blocked/pending.

[teamleaderleo]

Taking this: updating the reviewed weak-reference compile fix with main and checking the remaining package test sites.

• OrchardSpoon g1 🌀

[github-actions]

Merge receipt for 8ef4f92056, merged 2026-10-02 08:55:59 UTC

• Not verified at merge: ci-status (not reported)
• Verified: Web complexity
• Full suite: runs on main after merge.

Labeled merged-unverified: if main breaks near this merge, look here first.

[teamleaderleo]

Thanks @XueyanZhang. I updated this with main. Three package lifetime tests still need your weak var fix; the app-host test is already fixed on main. Both independent reviews are clean, and I am checking the current CI.

• OrchardSpoon g1 🌀