test: split an expression Xcode 27 cannot type-check

[teamleaderleo]

Summary

• cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift builds its replay bytes as Data(("…" + "…" + … ).utf8): six string literals concatenated inside one expression. On Xcode 27.0 / Swift 6.4 the type checker gives up on it: error: the compiler is unable to type-check this expression in reasonable time, at line 140, and build-for-testing for the cmux-unit scheme fails.
• Split it into a typed String and a typed Data. Same bytes, no behaviour change.

Testing

On a MacBook Air M5, Xcode 27.0 (27A266a), xcodebuild -scheme cmux-unit -configuration Debug build-for-testing:

• main (4c67b4d8c5): ** TEST BUILD FAILED **, the one error above (957 test files compiled before it stops).
• with this change: ** TEST BUILD SUCCEEDED **, 0 type-check errors.

CI uses Xcode 26.3, where the original expression still compiles, so this only shows up for people who have moved to Xcode 27. Not run: the test itself (the app-host test run needs the full app test environment); the change is to how a constant is spelled, not to what the test does.

Demo Video

Not applicable: test-only change.

Checklist

• I tested the change locally
• I added or updated tests for behavior changes (no behaviour change)
• I updated docs/changelog if needed (not needed)

🤖 Generated with Claude Code

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Summary by cubic

Fixes the cmux-unit test build on Xcode 27 by splitting a long string-concatenation expression that Swift 6.4 can't type-check. Replay bytes are identical, so there is no behavior change. CI still uses Xcode 26.3, so this only affects local Xcode 27 builds.

^{Written for commit c3b4fe2. Summary will update on new commits.}

Summary by CodeRabbit

• Refactor
  • Simplified internal test data construction without changing user-visible behavior.

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: manaflow-ai/cmux/.coderabbit.yaml

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 1f593dd6-7b02-4498-8832-7b61961cd192

📥 Commits

Reviewing files that changed from the base of the PR and between 02f9437 and f7b5b9b.

📒 Files selected for processing (1)

• cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift

Included review availability: Your plan provides up to 10 included reviews per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The SSH PTY regression test now constructs its replay payload through a local replayText constant before converting the text to Data. The replay string remains unchanged.

Changes

SSH PTY replay test

Layer / File(s)	Summary
Replay payload construction cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift	The test stores the terminal-query replay string in replayText and converts it with Data(replayText.utf8).

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Refactor

Suggested reviewers: austinywang

🚥 Pre-merge checks | ✅ 24 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (24 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: splitting an expression to resolve an Xcode 27 type-checking failure.
Description check	✅ Passed	The description includes a clear summary, testing details, demo-video disposition, and checklist. It omits the Review Trigger section and two review-resolution checklist items, but it remains mostly c…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Cmux Cloud Persistent Session And Early Input	✅ Passed	PASS: The pull request changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It replaces one inline Data construction with typed String and Data constants. The replay string c…
Cmux Swift Actor Isolation	✅ Passed	PASS. The pull request changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. The diff only splits a test fixture into typed String and Data values. It does not change production…
Cmux Swift Blocking Runtime	✅ Passed	PASS: The PR changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It refactors a test fixture from inline Data construction to typed String and Data values. The diff adds no …
Cmux Browser Automation Off-Main	✅ Passed	PASS. The PR changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It splits a replay string into typed String and Data values. The diff adds no browser.* command, WebKit/AppK…
Cmux Expensive Synchronous Load	✅ Passed	PASS. The reviewed range changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It replaces one inline string-to-Data expression with typed String and Data constants. The diff …
Cmux Cache Substitution Correctness	✅ Passed	PASS: The review-scoped diff changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It splits a test replay payload into a typed String and a typed Data; it does not replace an a…
Cmux No Hacky Sleeps	✅ Passed	PASS. The authoritative diff changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It only splits a test string expression into typed String and Data values. It introduces no sl…
Cmux Algorithmic Complexity	✅ Passed	PASS. The PR changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. The change splits a fixed string construction into typed String and Data values. It adds no collection scan, s…
Cmux Swift Concurrency	✅ Passed	PASS. The pull request changes only one test expression. It assigns the existing concatenated text to a typed String, then creates the same typed Data. The diff adds no Dispatch, Combine, completi…
Cmux Swift @Concurrent	✅ Passed	PASS: The PR changes only the synchronous construction of replayText and replay in a test. The authoritative diff adds no async, await, nonisolated, @concurrent, @MainActor, Task, or a…
Cmux Swift Package Boundaries	✅ Passed	PASS: The authoritative diff changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift, which belongs to the cmuxTests test target. The change only splits a test replay expression into…
Cmux Swiftpm Lockfiles	✅ Passed	PASS. The reviewed range changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. The patch splits a test string into typed String and Data values. It does not change `Package.swif…
Cmux Swift Logging	✅ Passed	PASS: The diff only refactors replay-string construction in a test. It adds no print, debugPrint, dump, NSLog, file logging, Logger declaration, or diagnostic output. The changed file is under…
Cmux User-Facing Error Privacy	✅ Passed	PASS: The PR changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It splits a test replay payload into typed String and Data values. The rule explicitly allows tests, and the d…
Cmux Full Internationalization	✅ Passed	PASS. The authoritative diff changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. The changed strings are test fixture data and terminal protocol queries, not production user-facin…
Cmux Swiftui State Layout	✅ Passed	PASS. The pull request changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. The diff only splits a local terminal replay expression into typed String and Data constants. It add…
Cmux Architecture Rethink	✅ Passed	PASS: The diff changes only a test-local replay payload construction. It replaces one inline Data expression with a typed String and Data, while preserving the same literals and call sites. It i…
Cmux Swift Auxiliary Window Close Shortcuts	✅ Passed	PASS. The PR changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift. It splits a test replay string into typed String and Data values. The diff introduces no NSWindow, NSPanel…
Cmux Source Artifacts	✅ Passed	PASS. The PR changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift, a hand-written Swift test source. The added lines define a String and convert it to Data; they do not add logs…
Cmux No Test Or Debug Seam In Production Source	✅ Passed	PASS. The review-scoped diff changes only cmuxTests/CLISSHPTYAttachProbeReplyRegressionTests.swift, which is outside the custom check's **/Sources/** production-source scope. The patch only splits…

✨ Finishing Touches

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[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge because the test-only refactor preserves the replay bytes while restoring compilation under Xcode 27.

Summary

The PR resolves an Xcode 27 / Swift 6.4 test-target compilation failure by assigning the replay payload to an explicitly typed String before converting its UTF-8 bytes to Data.

• Preserves the replay payload and test behavior.
• Reduces type-checker complexity without changing production code.
• Introduces no repository-rule or security concerns.

_{Reviews (2) · Last reviewed commit: "Merge branch 'main' into test/xcode27-ty..."}

[teamleaderleo]

Continued in #13126 (same commits, in-org branch test/xcode27-typecheck) so its macOS jobs run on the repository's configured runners. Push further changes to test/xcode27-typecheck on manaflow-ai/cmux, not to the fork.