Best possible solution:

Merge the deletion after ordinary protected-label review, retaining sidebar-session-new as the sole new-session styling path.

Do we have a high-confidence way to reproduce the issue?

Not applicable: this PR removes unreachable CSS rather than addressing a runtime defect with a failing reproduction path.

Is this the best way to solve the issue?

Yes. Repository-wide source inspection shows the selector family has no consumer, so direct deletion is the narrowest maintainable solution without adding another compatibility path.

AGENTS.md: found and applied where relevant.

Codex review notes: model internal, reasoning high; reviewed against f9ebefba29a0.

Label changes:

• add P3: This is a low-risk, deletion-only stylesheet cleanup with no intended user-visible behavior change.
• add rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🌊 off-meta tidepool and patch quality is 🐚 platinum hermit.
• add status: 👀 ready for maintainer look: ClawSweeper has no concrete contributor-facing blocker left for this PR. Not applicable: The protected maintainer cleanup changes no rendered behavior, so the external-contributor real-setup proof gate is not applicable.

Label justifications:

• P3: This is a low-risk, deletion-only stylesheet cleanup with no intended user-visible behavior change.
• rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🌊 off-meta tidepool and patch quality is 🐚 platinum hermit.
• status: 👀 ready for maintainer look: ClawSweeper has no concrete contributor-facing blocker left for this PR. Not applicable: The protected maintainer cleanup changes no rendered behavior, so the external-contributor real-setup proof gate is not applicable.

PR surface:

Source -54. Total -54 across 1 file.

What I checked:

• Current-main usage: The old class appears only in its CSS definitions, while the live sidebar button uses the replacement sidebar-session-new class. (ui/src/styles/layout.css:944, f9ebefba29a0)
• Active caller: The current sidebar renders the new-session button with sidebar-session-new, not any removed selector. (ui/src/components/app-sidebar.ts:1832, f9ebefba29a0)
• Patch scope: The live PR diff deletes only the obsolete CSS rule family and the final extra blank line; it does not alter active markup or styles. (ui/src/styles/layout.css:944, cc73a8af9925)
• Protected review state: The live PR carries the protected maintainer label, so ClawSweeper policy requires explicit maintainer handling and forbids automatic close cleanup. (cc73a8af9925)

Likely related people:

• steipete: Peter Steinberger authored the merged sessions-sidebar redesign and recent work touching both the active sidebar component and shared layout stylesheet. (role: recent area contributor; confidence: high; commits: fd2a2411b96a, ae2c6117d3d3; files: ui/src/components/app-sidebar.ts, ui/src/styles/layout.css)

• 🦀 challenger crab: rare, exceptional readiness with strong proof, clean implementation, and convincing validation.
• 🦞 diamond lobster: very strong readiness with only minor maintainer review expected.
• 🐚 platinum hermit: good normal PR, likely mergeable with ordinary maintainer review.
• 🦐 gold shrimp: useful signal, but proof or patch confidence is still limited.
• 🦪 silver shellfish: thin signal; proof, validation, or implementation needs work.
• 🧂 unranked krab: not merge-ready because proof is missing/unusable or there are serious correctness or safety concerns.
• 🌊 off-meta tidepool: rating does not apply to this item.

Shiny media proof means a screenshot, video, or linked artifact directly shows the changed behavior. Runtime, network, CSP, and security claims still need visible diagnostics.

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