[teamleaderleo]

Summary

Labs (hq#1980): new looks and behaviors ship behind a flag that a person turns on, not in the defaults. This builds on the existing labs.previewFeatures and keeps it as the only mechanism. Its users (#20429's Now Playing card) keep reading snapshot.previewFeatures.

• Registry: each row of schemas/settings/source/labs.json is a LabsFlag with owner, created, expires (about 14 days), cohort (off / nightly-next / default) and a one-line intent (its help). gen-settings-sources.py checks the fields and generates the Swift LabsFlag enum and webviews/src/experiments/labs.generated.ts. It prints warning: labs.<name> ... expired for any flag past its expiry, including under --check; the warning never fails the run.
• Defaults: every flag defaults off. nightly-next flags are on in nightly and dev builds only. Promoting a flag to default is a one-line PR, and that PR is the design call.
• Where flags show up: Settings > Experimental > Labs (a toggle with the intent line), the palette's settings scope, Help > Feature Flags (now bound, opens that list), cmux.json, MDM, and the agent policy.
• New Tab page, team builds only: one quiet line, "Labs" (or "Labs (N on)"), on the page's column edges and type scale, collapsed by default and remembered per viewer. Open, it lists each flag as a 28px row: name, one-line intent (truncated before the badge), a "New" or "Expires soon" hint, and a switch; recently toggled first, else newest. Right-click a row for Turn On/Off and All Labs…. "All Labs…" opens Settings > Labs. A toggle is newTab.setLab, saved through the schema. Release and RC builds show nothing. Variant A of three, picked by cg-design-judge (feat(cmux-next): Labs flags, one registry for opt-in looks and behaviors (hq#1980, no bead) #20452 (comment)).
• Palette: "Labs…" (Help > Feature Flags is now Help > Labs…; "feature flags" stays a search keyword) opens Settings > Labs.
• One helper per side:
  • Swift: snapshot.lab(.name).
  • Web: useLabsFlag("name") / labsFlag("name"), which read data-labs on <html>. Every PageWebView page gets that attribute, kept current. labsTeamBuild() reads data-labs-team.
• Docs: skills/cmux-architecture/references/labs-flags.md explains how to put a change behind Labs.

Testing

• Swift

  • LabsFlagTests: the cohort and file decide a flag, a bad value is off with a diagnostic, and every flag is a toggle with its fields.
  • NewTabLabsTests: a page toggle is saved in cmux.json, and a name that is not a flag writes nothing; All Labs… runs help.featureFlags.
  • Red: the fleet run-swift-testing-suites.sh at the red commits fails (no member 'lab'; the New Tab red is a compile red, since its API did not exist yet).
  • Green: fleet run-swift-testing-suites.sh on the merged head 18a0888: 288 suites passed, 0 failed (the step exits 1 only because AcpmuxBundleReplacedTests skips without a published same-tree cmux-tui for that SHA).
  • Settings export on the merged head: no diff (exportIsFresh passes).

• Web: bun test test/new-tab-labs.test.tsx was red at e59433f (no section) and is green now. src/experiments/labs.test.ts passes.

• Checks:

  • gen-settings-sources.py --check, gen-strings.mjs --check agentPane, ui-rules, and scoped vp check pass.
  • In bun run check, every step before the final whole-repo vp check passes. That last lint was killed on big-red (143); CI react-apps-check covers it.
  • crash ratchet, concurrency, system-blue and the scoped god-file check pass. App size is at the cap (113801).

• Review (subagent): the agent pane's own web view (agent.pageHost off, the default) never got data-labs; fixed with AgentPaneLabs. The generator now rejects a key that is not labs.<name>. Known limit: a page's first moments can carry the flag list from when its web view was made; useLabsFlag follows the live value.

• Localization: the two new New Tab strings are in all 21 locales. Flag intents show in English on the New Tab page (team builds only); Settings shows them localized.

• Redesign (variant A): test/new-tab-labs.test.tsx was red first (3a5f675, 3a48dc6) and is green: collapsed by default as "Labs" / "Labs (N on)", rows with intent and switch, New / Expires soon hints, recently toggled first with a storage fallback, remembered open state, row menu. agent-pane-no-capsules, theme-colors, subtle-elevation and ui-rules pass locally. Release compile BUILD SUCCEEDED on d69557f.

Changelog

Added: Labs: opt-in flags for new looks and behaviors, listed in Settings > Experimental > Labs, the palette ("Labs…") and, in nightly and dev builds, a quick-toggle line on the New Tab page

Proof

Real cmux NEXT DEV builds from the fleet (--builder mac), on capture slots; host chip masked. Base: the New Tab page and palette before this PR. Head: this branch. The switch knob in these stills is white; since then it takes the page's theme color (theme-colors/subtle-elevation rules), otherwise unchanged.

	Light	Dark
Before: New Tab
After: Labs collapsed
After: Labs open
After: row right-click menu
Before: palette "Labs"
After: palette "Labs…"

Open, close, reopen, then turn the flag on and off (head, light):

Full quality: labs-real-toggle-after.mp4

🤖 Generated with Claude Code

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[teamleaderleo]

Bead cx-eyccd created for this PR by the cmux coordinator.

[github-actions]

all web/size checks green

[github-actions]

Not verified: macOS jobs did not run: compile and app tests were skipped on b9b8a8897d; ci-status is green without them.

CI passes on b9b8a8897d (run 38663518174 attempt 1).
macOS jobs did not run: compile and app tests were skipped: Fast static checks skipped (the macos job needs both to succeed). Re-run CI once they pass, before merging.

Written by scripts/ci/classify_failures.py (ci-failure-attribution.yml); signatures are its SIGNATURES table. A machine verdict is the runner's fault, not this PR's; yours means the failing file is one this PR changes, also red on main that main's latest full suite fails the same way, seen on other PRs that it failed on another pull request's run lately.

[github-actions]

CI fast guards passes on b9b8a8897d (https://github.com/manaflow-ai/cmux/actions/runs/38663518174). This covers only the fast guards, not CI: CI's result is the ci-status check, and the CI failure attribution comment names any failing test.

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Gallery

Review in feed

203 states changed: gallery.visual-media-board/all-previews, agent-pane.artifact-panel/markdown, agent-pane.transcript/long-code, agent-pane.edited-files/fourteen-files, pages.settings/appearance-group-9, ... · 9 new states · 51 broken states · 107 play checks failed

Diff page and renders (the run's gallery-pr artifact)

State	Before · after
gallery.visual-media-board/all-previews (Apple System Colors, chromium)
agent-pane.artifact-panel/markdown (Apple System Colors, webkit)
agent-pane.transcript/long-code (Apple System Colors Light, webkit)
agent-pane.edited-files/fourteen-files (Apple System Colors, webkit)
pages.settings/appearance-group-9 (Apple System Colors, chromium)
pages.settings/invalid-search-template (Apple System Colors Light, webkit)

197 more on the diff page.

Live preview (follows this branch; start it with scripts/gallery-live.sh up <branch> from an hq checkout):

• gallery.visual-media-board/all-previews: /wt/op-next-call-keys-labs/?entry=gallery.visual-media-board#/gallery.visual-media-board/all-previews
• agent-pane.artifact-panel/markdown: /wt/op-next-call-keys-labs/?entry=agent-pane.artifact-panel#/agent-pane.artifact-panel/markdown
• agent-pane.transcript/long-code: /wt/op-next-call-keys-labs/?entry=agent-pane.transcript#/agent-pane.transcript/long-code
• agent-pane.edited-files/fourteen-files: /wt/op-next-call-keys-labs/?entry=agent-pane.edited-files#/agent-pane.edited-files/fourteen-files
• pages.settings/appearance-group-9: /wt/op-next-call-keys-labs/?entry=pages.settings#/pages.settings/appearance-group-9
• pages.settings/invalid-search-template: /wt/op-next-call-keys-labs/?entry=pages.settings#/pages.settings/invalid-search-template
• 125 more on the diff page

Play checks failed (0 px anchor movement, 0 layout shift, no frame over 33 ms unless the entry gives a reason):

• gallery.visual-media-board/all-previews (Apple System Colors, chromium): step 1 click button "Pause previews": layout shift 0.0002 (limit 0) · step 2 click button "Play previews": layout shift 0.0002 (limit 0) · play: waitFor did not hold within 5000 ms
• agent-pane.artifact-panel/markdown (Apple System Colors, webkit): play: no element for button "Open preview"
• agent-pane.artifact-panel/html (Apple System Colors Light, chromium): play: no element for button "Open preview"
• agent-pane.artifact-panel/html (Apple System Colors Light, chromium): play: no element for button "Open preview"
• agent-pane.dictation/hide (Apple System Colors, webkit): play: no element for menuitem "Hide Dictation Button"
• agent-pane.dictation/hide (Apple System Colors, chromium): play: no element for menuitem "Hide Dictation Button"
• 596 more on the diff page

707 nondeterministic states differed from a second render of the same head (a clock or fixture leak) and are not counted as changes.

_{6554 unchanged · base 31d2b02 · head 60bdd67}

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[teamleaderleo]

Superseded: opt-ins live in Debug settings, per Lawrence.