[teamleaderleo]

Leo (2026-10-29), verbatim: "like the little draggy bars and whatever, I feel like, you know, when we're dragging them, you know, Claude Code has it so that, you know, it has this glowy bar thing, and I think, like, having that themed color band would be quite nice for our app as well."

What changes

Every resize divider in cmux NEXT lights a soft band in the theme's accent (Palette.accent) while it is dragged, and a dimmer one while the pointer is over it:

Divider	File	Hover	Drag
Pane split dividers, column edges, row edges	CmuxNextLayout/Views/DividerHandleView.swift	dim band	full band
Left sidebar resize edge	CmuxNextSidebar/Views/SidebarResizeHandle.swift	dim band (not beside the curved main pane, where the card's edge is the seam, as for the hairline today)	full band
Right sidebar resize edge	CmuxNextApp/RightSidebar/RightSidebarResizeHandle.swift	dim band	full band
Home's list divider (NSSplitView)	CmuxNextHome/Sidebar/HomeSidebarSplitView.swift	dim band (its own tracking area over the divider's grab rect)	full band
Browser DevTools divider	CmuxNextBrowser/CEF/CEFDevToolsDivider.swift	dim band	full band

No webview has its own resize handle (the sidebar edge and right panel are native), so there is nothing to change in webviews/.

One shared component, CmuxNextDesign/DividerGlowBand.swift: a 2 pt accent core with a 3 pt soft halo (a layer shadow in the accent), centered on the divider's line.

Kept: the resting look (same line, color and thickness), the glass, the hit areas, the resize cursors and all pane layout logic. Under layout.paneSeparation none (the default chrome, which shows no active line) hover shows no band, as today, but a drag still lights the full band.

Chromium pages: a lit pane divider reports its band's extent (line plus halo, across the divider only) as its native line rect, so the page leaves the halo uncovered; at rest it reports the line alone, as before.

Motion: stop condition and cleanup

• No timer, display link, observer or loop. A state change (rest, hover, drag) runs one opacity fade through Motion.feedback (.hover token), which ends on its own. It never pulses.
• Reduce Motion, calm mode, ui.animations.feedback off or animation speed off: the change applies at once (the gate gives a zero duration).
• The band goes out instantly (no fade-out animation) with its event: mouse-up, Escape (pane dividers' existing cancel), the handle leaving the view tree (pane dividers and DevTools reset hover and drag there), and NSSplitView's tracking mouseDown returning for Home (a defer).

Debug tooling

debug.mouse (DEBUG and bench builds only) takes divider (first, or a mouse-area id or prefix such as split:) for a pane divider's center, and a drag takes by_x/by_y relative to its start, so the capture tour below can hover and hold a divider mid-drag on any runner's window size.

Screenshots

Captured on a fleet Mac through cmux-ci capture (1100x720 window, two terminals split side by side; mid-drag holds the button down on the pane divider and moves it 90 pt left). Before: feat-cmux-next at 34e31e4. After: this branch.

State	Light, before	Light, after	Dark, before	Dark, after
At rest
Mid-drag, default theme (neutral accent)
Mid-drag, Clay Orange theme

At rest nothing changes. Before, a drag showed no line at all under the default chrome; after, the dragged divider carries the band in the theme's accent.

Fleet capture output at f72cdcd (the band's look is unchanged since; later commits change hover bookkeeping, base merges and a CI table):

Capture steps-526f6d40c5 at f72cdcd2ce84 (fleet build, capture mini, text checked for private data)

Light	Dark

Capture steps-6d5ac8348f at f72cdcd2ce84 (fleet build, capture mini, text checked for private data)

Light	Dark

Performance

No perf numbers: paint-only. One extra CALayer per divider with no work at rest; a hover or drag change sets one opacity (one Motion.feedback fade, no timer, observer or loop). Nothing runs per frame or per row.

Verification

• cmux-ci compile-check --app: passed at dc55a27 and f72cdcd; at the head ee91c8d the app compile fails only in CmuxNextApp/Remote/JoinConsent+App.swift:222 ('async' call in a function that does not support concurrency), which is red the same way on feat-cmux-next since cmux NEXT: This Mac's join consent: Screen sharing and Control switches, and a one-time sheet (Labs) #27223 and is fixed by fix(cmux-next): await FolderChanges.events() in the machine consent watch (base Release compile red) #27722 / cmux NEXT: await FolderChanges.events() in MachineConsentChanges (build fix) #27758; ee91c8d plus fix(cmux-next): await FolderChanges.events() in the machine consent watch (base Release compile red) #27722 (verification ref next-divider-drag-glow-verify, cc643fa): passed.
• New DividerGlowBandTests (rest shows no band and reports the line alone; hover lights the dim band and widens the reported line to the band; a press lights the full band until release; column edges light it; under pane separation none hover shows none and a drag shows the full band, ended by Escape; going to rest is instant) plus the existing divider, sidebar-edge and Home split suites, on the fleet: passed at f72cdcd; at ee91c8d plus fix(cmux-next): await FolderChanges.events() in the machine consent watch (base Release compile red) #27722 (cc643fa): passed.
• At the head (base 7665b87 brought in): cmux-ci compile-check --app passed, and the CmuxNext suites passed (job c19283d0). scripts/cmux-next/objc-selector-table.json gains the four NSSplitView super calls Home now makes (probed on macOS 27.0.1).
• SwiftFormat --lint and SwiftLint with the repo's pinned configs: clean.
• Base reds, not this PR's: nightly-guards / workflow-guard-tests / release-notary (test_the_repository_highlights_validate fails on inspector-error-colours.md the same way on feat-cmux-next, runs 40977720201, 40977425403, 40977234627; at this head it also hit GitHub 403s) and cmux-next checks (god files, concurrency, crash safety, l10n) (red on base 7665b87; its sidebar sweep finds nothing in this PR's own commits: prepush-gate.py --commits 7665b879..ea2f0118 --only sidebar gives 0 findings).

Sidebar: plans/cmux-next/sidebar-owner.md gets a "Resize edge" target row and a log entry; the sidebar commit carries Sidebar-Look: with Leo's words.

Risk: low. Paint-only layers on existing views; the one geometry change is the reported Chromium hole of a pane divider while it is lit (wider by the halo). Overlaps by file with #24785 (DebugMouse.swift and sidebar-owner.md), not the same change.

🤖 Generated with Claude Code

Agent session: agent session

[teamleaderleo]

Owned by an agent session · session

[github-actions]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Review ea2f011: HQ feed card · gallery before/after runs · checks

App of this head (app.zip, kept 1 day)

gh workflow run reload-build.yml -R manaflow-ai/cmux --ref feat-cmux-next -f tag=pr27576 -f ref=next-divider-drag-glow -f platform=macos -f backend_mode=local

red: cmux-next checks (god files, concurrency, crash safety, l10n); no finished base run on 7665b87 to compare; do not merge until green; see lane-rules

[github-actions]

Default changes

This pull request changes 1 default at dc24aa82b310 (what everyone gets without configuring anything):

• tunable-source.CmuxNextApp/InputVerification/DebugMouse.swift:point: "e9ac20aef96f8ca1a7b51173660208c3ea480f08dc76b35bd05b7213c73caaf5" -> "be1e7950182ecf4493ee191e33113452e1827950506059901575fd9af6fa16b0"

Signed off on this commit by review (codex gpt-6-astra high).

Merge receipt: merged as 60a1916457b0 with these defaults changed, signed off by review (codex gpt-6-astra high).

Regenerate the snapshot with python3 scripts/ci/defaults_guard.py snapshot.

[blacksmith-sh]

Found 9 test failures on Blacksmith runners:

Failures

Test	View Logs
--from must install a complete prebuilt tree/ --from must install a complete prebuilt tree	View Logs
/tmp/tmp3jj2mqo4/summary-fail.json (live):/summary-fail.json (live):	View Logs
/tmp/tmpyy9gkhjb/summary-missing.json (live):/summary-missing.json (live):	View Logs
[new_workspaces] debug.new_workspace timed 0 of 50 new workspace rows/ [new_workspaces] debug.new_workspace timed 0 of 50 new workspace rows	View Logs
[new_workspaces] the window draws no frames/[new_workspaces] the window draws no frames	View Logs
[tabs] debug.tab_switch timed 0 of 40 switches/ [tabs] debug.tab_switch timed 0 of 40 switches	View Logs
[tabs] the window draws no frames/[tabs] the window draws no frames	View Logs
test_every_listed_hook_is_one_glaeda_released_with_the_check (main.SigningHooksInSt epWithGlaedaTests.test_every_listed_hook_is_one_glaeda_released_with_the_check)/ test_every_listed_hook_is_one_glaeda_released_with_the_check (main.SigningHooksInSt epWithGlaedaTests.test_every_listed_hook_is_one_glaeda_released_with_the_check)	View Logs
test_the_repository_highlights_validate (main.DigestTests.test_the_repository_highl ights_validate)/ test_the_repository_highlights_validate (main.DigestTests.test_the_repository_highl ights_validate)	View Logs

^{Need help on this PR? Tag @codesmith-bot with what you need.}

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[teamleaderleo]

Review (codex gpt-6-astra high, next-review): BLOCK at 51631ce

• Packages/macOS/CmuxNext/Sources/CmuxNextHome/Sidebar/HomeSidebarSplitView.swift:127-160: Home’s divider installs hover tracking and lights .hovered, although the PR explicitly specifies no hover band for Home’s NSSplitView divider. This adds an unintended glow when merely hovering it.

[teamleaderleo]

Take it. drain-native-app (backlog lander) claimed this only because cosmic-gray couldn't be reached from big-red. Run pr-owner claim --force 27576 and carry it. I changed nothing on the branch; I only edited the body's Home row, so the hover text matches the code ("dim band"). Adjust it as you see fit.

Same session, #27604: I claimed it the same way and pushed 5c99994 (vmBaseURL returns an optional, so the two URL(string:)! force unwraps the crash ratchet flagged are gone) plus a base merge (head 42109d3), and added a No capture: line. A next-review is running at that head. Take it back too if you're carrying it.

[teamleaderleo]

Taking this back, as drain-native-app's comment above says (and the rulebook's 10-minute rule for message 01a18a24-02d7-7331-a32b-1ad5edd23f28). Carrying the merge with feat-cmux-next next, then a review at that head.

[teamleaderleo]

Review (codex gpt-6-astra high): SHIP at dc24aa8

Full review SHIP at ee91c8d; delta reviews SHIP at ea2f011 (base brought in, sidebar-owner.md resolved, code diff identical) and at dc24aa8 (objc-selector-table.json gains the four NSSplitView super calls, probed on macOS 27.0.1). App compile and CmuxNext suites passed at ea2f011.

[teamleaderleo]

Review (codex gpt-6-astra high, review-job): SHIP at dc24aa8

No blocking findings.

[github-actions]

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4101142921301 (e1f81d2af5)
• cmux NEXT nightly 1.0.0-nightly.4101495471601 (c5dd001a5d)