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iOS: preserve workspace list geometry and scroll position - #13445

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azooz2003-bit wants to merge 21 commits into
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@azooz2003-bit

@azooz2003-bit azooz2003-bit commented Sep 21, 2026 •

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Live workspace updates could move the viewport or trigger table layout while agents streamed notifications. UIKit now owns the list’s safe-area geometry, and ordinary content updates change only existing visible cells.

  • Keep setContentScrollView(_:for:); remove manual parent-bar geometry translation and safe-area writes.
  • Compare rendered row fields, ignore detail-only relay changes, and compare timestamps at the displayed minute precision.
  • Update visible cell content without reconfigureRows, reloads, or table batches when height and native actions are unchanged. Refresh retained and prefetched cells in willDisplay so offscreen updates appear correctly.
  • Use exact delegated row heights and disable automatic self-sizing invalidation. Real height changes still invalidate geometry, including offscreen rows, while preserving a surviving visible row’s screen position.
  • Preserve displayed order across background source permutations in every sorting mode. A load run exposed Mac “Reorder on Notification” permuting the source array independently of iOS sorting. Sort/scope choices, membership, pinning, grouping and collapsing reset presentation; local drag moves use the displayed row identities.
  • Coalesce updates during dragging/deceleration and apply the latest state afterward.

This separates content, geometry and presentation-order ownership. Background notifications and remote-only order changes no longer continually rearrange an already displayed list. Dynamic row heights remain supported. Composer blur was not added.

Apple references: Lists and tables HIG, self-sizing invalidation, and native scroll edges.

Validation at ae9b5e86210457685ceb7e4ba1f65810f5015919:

  • Swift syntax and diff checks passed.
  • Matching Mac controller build 6b34146e20b5a31855d9c30d and iOS controller build 30a08a2e595ab5d4bb6592cf succeeded from this exact source. The Mac build embeds the same staging Iroh environment as the queued phone package; source code is unchanged.
  • Scroll-update, height, sorting, drag/drop, scroll-preservation and edge-effect suites passed. The broad run failed 12 tests, all of which also fail on the base revision with only its compilation-required public Foundation import. The baseline additionally reproduces the preview-refresh failure that passes with this fix. There were no final-only failures; the full suite remains red.
  • Real load: 20 GPT-5.6-Luna sessions in 20 workspaces, all observed active for 381.6 seconds, with 546 notifications. The simulator received current content throughout 42 Computer Use accessibility paging actions (including a continuous 330.4-second loop). No relative-order violations across the snapshots. All load surfaces were closed after verification.
  • Recorded 474 seconds and inspected overview plus dense frame samples. CPU samples showed the main thread waiting in 90.0% and 80.4% of observed samples in two 20-second windows. These measurements do not establish per-frame latency.
  • Acceptance remains OPEN: pointer drag injection fails with noWindowsAvailable, so normal touch tracking and deceleration were not exercised. Native accessibility paging is insufficient to claim hitch-free touch scrolling. Instruments attach hung; CPU samples and raw video are retained at artifacts/jolt-scroll-current/ in HQ.
  • The iPhone is unreachable; the signed exact-source jolt package is queued under the personal profile. The default controller recipes bake different Iroh environments. The final Mac artifact was rebuilt with the phone environment, its embedded configuration was verified, and a fresh same-account simulator connection succeeded with all 20 workspaces. Physical-device readiness is still blocked by the unreachable phone.

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📝 Walkthrough

Walkthrough

The workspace list controller no longer writes chrome safe-area insets. UIKit retains safe-area and adjusted-inset handling. Row updates now compare displayed render state and apply incremental structural changes. The shell module re-exports Foundation's public API.

Changes

Workspace List Behavior

Layer / File(s) Summary
Remove controller inset forwarding
Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListTableViewController.swift, Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListBarUnderlap.swift, Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListScrollEdgeCoordinator.swift, Packages/iOS/CmuxMobileShellUI/Tests/CmuxMobileShellUITests/ChromeInsetWriteBudgetTests.swift, Packages/iOS/CmuxMobileShellUI/Tests/CmuxMobileShellUITests/WorkspaceListScrollEdgeEffectTests.swift
The controller removes chrome inset calculations, writes, diagnostics, and write-budget state. Layout only refreshes scroll-edge registration. The write-budget tests are deleted, and documentation describes UIKit-managed safe-area, inset, and offset behavior.
Compare workspace row render state
Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListTableCoordinator.swift, Packages/iOS/CmuxMobileShellUI/Tests/CmuxMobileShellUITests/WorkspaceListScrollUpdateTests.swift
The coordinator compares fields used by workspace rows after timestamp normalization. Tests cover relay-only detail changes that result in no table update.
Apply incremental structural updates
Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListTableCoordinator.swift
Structural changes use delete and insert row batches instead of a full reload. The coordinator reloads affected rows, reconfigures remaining changed rows, tracks height changes, and restores the viewport anchor.

Foundation Module Re-export

Layer / File(s) Summary
Re-export Foundation API
Packages/iOS/CmuxMobileShell/Sources/CmuxMobileShell/MobileShellComposite+WorkspaceListRecovery.swift
The file changes import Foundation to public import Foundation, re-exporting Foundation's public API through CmuxMobileShell.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Suggested reviewers: lawrencecchen

Merge Risk: ⚪ Minimal · up to 671b5

The workspace list now uses UIKit-managed geometry and incremental updates while preserving visible content during structural changes. No concrete merge-blocking production risk remains.


Important

Pre-merge checks failed

Please resolve all errors before merging. Addressing warnings is optional.

❌ Failed checks (1 error, 1 warning)

Check name Status Explanation Resolution
Cmux Algorithmic Complexity ❌ Error WorkspaceListTableDataSource.replaceItems adds newIDs.difference(from: oldIDs) at Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListTableCoordinator.swift:1687. Swift's order… Replace difference(from:) with a linear-time ID-based update plan. Build old and new ID-to-index dictionaries or sets, derive removals and insertions in one pass, and apply those UIKit row operations from the resulting index plan. Alterna…
Docstring Coverage ⚠️ Warning Docstring coverage is 5.88% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 17 functions across 7 files. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (23 passed)
Check name Status Explanation
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 PR changes only iOS workspace-list UI, row comparison, viewport anchoring, safe-area handling, tests, and a public Foundation import. The authoritative diff contains no Cloud terminal creati…
Cmux Swift Actor Isolation ✅ Passed PASS. The production changes do not introduce a service protocol, shared mutable Sendable reference, or background access to UI state. The new WorkspaceRowRenderState is a private, UI-only value pro…
Cmux Swift Blocking Runtime ✅ Passed The production Swift diff adds no semaphore, blocking wait, sleep, delayed dispatch, polling loop, main-queue sync, timer, or manual lock. The controller removes the prior RunLoop.main.perform write…
Cmux Browser Automation Off-Main ✅ Passed The check is not applicable to this pull request. The authoritative diff changes only iOS workspace-list files and tests. Sources/TerminalController.swift and `Packages/macOS/CmuxControlSocket/Sourc…
Cmux Expensive Synchronous Load ✅ Passed No failure condition is introduced. The production diff changes workspace-row rendering, table batch updates, viewport anchoring, documentation, a public Foundation import, and removes manual safe-are…
Cmux Cache Substitution Correctness ✅ Passed PASS: The diff contains no cache substitution in a persistence, history, undo, or snapshot path. The changed WorkspaceListTableCoordinator values (appliedItems, configuredItemsByID, height cache…
Cmux No Hacky Sleeps ✅ Passed PASS. The authoritative diff changes only Swift source, Swift tests, and Swift documentation. It introduces no TypeScript, JavaScript, shell, or build/runtime-script changes, and the patch adds no fix…
Cmux Swift Concurrency ✅ Passed The diff introduces no prohibited Swift concurrency pattern. New production code performs synchronous UIKit table updates, viewport anchoring, and render-state projection. The only Task sites in `Wo…
Cmux Swift @Concurrent ✅ Passed PASS. The PR adds no @concurrent, nonisolated async, Task, or await work. The changed coordinator and data-source logic remains synchronous and @MainActor-isolated. The recovery file changes…
Cmux Swift Package Boundaries ✅ Passed PASS: The production diff changes existing iOS UI glue in the CmuxMobileShellUI SwiftPM target. The new render-state projection and viewport-anchor code are private, @MainActor, and tied to `UITab…
Cmux Swiftpm Lockfiles ✅ Passed PASS. The PR changes only Swift source and test files. It does not change any Package.swift, Package.resolved, .gitignore, Xcode project, workspace, or workflow file. The affected package manifests an…
Cmux Swift Logging ✅ Passed The reviewed Swift diff adds no print, debugPrint, dump, NSLog, file/stdout logging, Logger, or sensitive-data logging. The production changes remove the diagnostics import and geometry code…
Cmux User-Facing Error Privacy ✅ Passed PASS: The PR adds no user-facing error, alert, command output, API error body, or recovery copy. The production diff changes UIKit geometry, row rendering, viewport anchoring, documentation, and `publ…
Cmux Full Internationalization ✅ Passed The authoritative diff changes UIKit geometry, workspace-row render/update logic, a public Foundation import, comments, and tests. It adds no user-facing Swift text, localization keys, string catalogs…
Cmux Swiftui State Layout ✅ Passed PASS. The PR does not introduce a prohibited SwiftUI state or layout pattern. WorkspaceListBarUnderlap changes only documentation; its ViewModifier body is unchanged. The new `WorkspaceRowRenderSt…
Cmux Architecture Rethink ✅ Passed The PR does not introduce a prohibited architectural repair path. It removes the manual additionalSafeAreaInsets owner, the RunLoop.main.perform reset, and ChromeInsetWriteBudget. The new struct…
Cmux Swift Auxiliary Window Close Shortcuts ✅ Passed The pull-request diff changes workspace-list UIKit/SwiftUI bridge logic, recovery imports, row updates, and tests. It does not add or materially change a standalone cmux-owned NSWindow, NSPanel, NSWin…
Cmux Source Artifacts ✅ Passed All changed paths are intentional Swift source or test files under Packages/iOS. The PR deletes one obsolete test and modifies workspace-list implementation, documentation, and tests. No logs, screens…
Cmux No Test Or Debug Seam In Production Source ✅ Passed The pull request adds no test/debug seam in production Swift source. The added production declarations are a private WorkspaceRowRenderState projection and production viewport-diff methods; none has…
Title check ✅ Passed The title clearly identifies the main changes: preserving workspace-list geometry and scroll position on iOS.
Description check ✅ Passed The description provides a detailed summary of the behavior changes, implementation scope, testing results, known limitations, and acceptance status. It is relevant and mostly complete for the pull re…
Full details: Cmux Algorithmic Complexity

Explanation

WorkspaceListTableDataSource.replaceItems adds newIDs.difference(from: oldIDs) at Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListTableCoordinator.swift:1687. Swift's ordered collection diff has worst-case O(n×m) behavior. This runs for each structural workspace-list update, which can contain about 1000 workspaces. The PR provides no benchmark or profiling evidence for this slower shape. The other new indexes and lookups are linear, but they do not remove this introduced quadratic worst case.

Resolution

Replace difference(from:) with a linear-time ID-based update plan. Build old and new ID-to-index dictionaries or sets, derive removals and insertions in one pass, and apply those UIKit row operations from the resulting index plan. Alternatively, use a documented benchmark-backed threshold with a linear fallback for large workspace lists.

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Actionable comments posted: 1


  • 🪄 Fix CodeRabbit comments on this PR
🤖 Prompt to fix review comments
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Inline comments:
In
`@Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListTableCoordinator.swift`:
- Line 260: Update the per-row height comparison in the structural update flow
so it always compares each old/new item cache key, without gating the comparison
on changedRowHeightsStable. Keep setting changedRowHeightsStable to false and
inserting the item ID into changedRowHeightIDs for every mismatch, using
changedRowHeightIDs as the reload-membership source of truth.

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  • Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/WorkspaceListTableCoordinator.swift

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@greptile-apps review

@azooz2003-bit azooz2003-bit changed the title iOS: let UIKit own workspace list geometry iOS: preserve workspace list geometry and scroll position Sep 22, 2026
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cursor Bot commented Sep 23, 2026

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This was superseded by the merged #14040, which carries the workspace-list geometry and scroll behavior. I’m closing the older branch so the queue points at the current implementation. Thanks for the original fix :)

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