docs(ios): document Xcode 27 development setup - #8400

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: cf3224635e

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 5b2b3393ed

:bot: Jude’s code review agent

Verdict: REQUEST CHANGES
Reviewed: c8ea4fb4ebdf124a273321287568407258f51a70..5b2b3393edd7b5ef6a73c8eb211d8907e8bec7f4 (exact live head 5b2b3393edd7b5ef6a73c8eb211d8907e8bec7f4)
Risk: low — documentation-only toolchain guidance, but it establishes the default developer setup path.

Blocking finding

[P2] State Xcode 27's hard host requirements beside the recommendation

mobile/README.md:26-28 tells contributors to use Xcode 27.0 by default and identifies Xcode 26 only as a compatibility path, but omits that Xcode 27 requires Apple silicon and macOS Tahoe 26.6 or later. Apple documents both constraints in the Xcode 27 release notes. Intel contributors and Apple-silicon contributors on older macOS are therefore directed toward a toolchain they cannot install or run, despite the supported Xcode 26 path.

Consequence: the primary setup guide can send a supported contributor into an impossible upgrade without telling them that Xcode 26 is the correct branch for their host.

Author action: state the Apple-silicon and macOS Tahoe 26.6+ requirements next to the Xcode 27 recommendation, link the Apple source, and explicitly direct incompatible hosts to supported Xcode 26.

Verification owner: author for the documentation change; reviewer for exact-head link, anchor, and wording validation.

Validation and residual risk

• PASS — exact base/head pinning and full two-file diff review; git diff --check passed in a clean detached exact-head lane.
• PASS — CONTRIBUTING.md points to the unique mobile/README.md#ios-toolchain anchor.
• PASS — the revised matching-default warning covers both Xcode 26 and Xcode 27; DEVELOPER_DIR selection was exercised on Xcode 27.0 (27A266a).
• PASS — repository source supports the native C/no-plugin claim and the separation between GitHub CI and internal release ownership.
• Exact-head mobile checks, all three Dart shards, Android, iOS release, security review, Semgrep, zizmor, and DCO were green when refreshed. Mobile Swift Native was still running; that external gate is a confidence gap, not the reason for this verdict.
• Xcode 26 and an intentionally mismatched global/default Xcode were not independently exercised in this review. Author action for this gap: none. Verification owner: reviewer/tooling or CI/release gate.

The rest of the documentation change is internally consistent. Re-review can approve after the host gate is made explicit at a fresh head.

:bot: Jude’s code review agent

Verdict: APPROVE
Reviewed: c8ea4fb4ebdf124a273321287568407258f51a70..f6174413ebe41914c49717efa3e6714e33581630 (exact live head f6174413ebe41914c49717efa3e6714e33581630)
Risk: low — documentation-only developer toolchain guidance.

The prior P2 is resolved. mobile/README.md:26-32 now states that Xcode 27 requires Apple silicon and macOS Tahoe 26.6+, links Apple’s Xcode 27 release notes, and explicitly routes incompatible hosts to the supported Xcode 26 path. That exactly repairs the previously impossible default journey without changing the supported-toolchain contract.

Findings: no unresolved author-actionable defect.
Author action: none.
Verification owner: reviewer/tooling and CI/release gate for residual platform execution only.

Validation

• PASS — exact one-commit delta 5b2b3393…f6174413 independently compared with the prior requested remedy.
• PASS — Apple’s current Xcode 27 release-note source contains both claims: macOS Tahoe 26.6+ and Apple-silicon-only.
• PASS — Xcode 26 is presented as supported for incompatible hosts; the existing DEVELOPER_DIR and matching-default-Xcode warning remains internally consistent.
• PASS — full PR scope remains two documentation files; Markdown target mobile/README.md#ios-toolchain, native C/no-plugin claim, and CI/release ownership were source-traced in the prior exact-head review and are unchanged by this repair.
• PASS — exact source files contain no trailing whitespace; current Mobile checks, all three Dart shards, Android, aggregate Mobile, security review, Semgrep, zizmor, and DCO are green.

Confidence gaps / residual risk

• Mobile Swift Native and Release were still running when refreshed. These external gates do not establish an author defect in this docs-only delta.
• This reviewer did not independently execute Xcode 26 on Intel/older macOS or an intentionally mismatched default Xcode. The guidance now states the relevant branch honestly; author action: none, verification owner: reviewer/tooling or CI/release gate.

No material finding remains at this exact head.