[teamleaderleo]

The session-tree Pinned and Earlier rows discarded AcpmuxChat.harness and rendered only a title plus age. That made old Claude/Codex chats indistinguishable after they left a workspace, despite the current sidebar contract requiring a harness mark with a stable fallback on every agent/session row.

This draft carries the harness family through the metadata-only history model and feed, resolves registered harness ids through AgentBrandCatalog, and gives unknown harnesses a person mark tinted with GroupColor.unset(id:). The row uses the shared leading icon column, clears the mark on reuse, and keeps the type only in accessibility text. Existing click, pin menu, age layout, row height, and sidebar.sessionTree default are unchanged.

Evidence and prior art

• SidebarChatHistoryRow.swift previously documented “No kind icon” and owned only title/meta labels.
• SidebarChatHistory.swift dropped the harness, while SidebarChatHistoryFeed.historyChat had it at the source.
• cmux NEXT sidebar: chat history (Earlier) and pinning under the session tree #22323 established the title-only history row before the sidebar icon rule; cmux NEXT sidebar: harness icons with stable colours on agent rows, no routine status words #27586 covers live workspace/Priority/Chief/remote rows, not history rows; Chats: acpmux owns the chat list; the sidebar history holds only its window (P0 stall) #28055 owns the history feed performance path.
• The implementation follows leo-workspace/design/sidebar.md and cmux-design-references/apps/claude/live/sidebar-linked-session-nesting.png's compact, icon-led nested session treatment.

Tests

• SidebarChatHistoryTests verifies the feed preserves Codex/Claude harnesses.
• A row-reuse regression verifies known Codex uses the catalog mark, unknown acme-agent gets a stable fallback colour, and the previous mark identity is not retained.
• git diff --check and scripts/cmux-next/prepush-gate.py pass.
• cmux-ci test -- swift test --package-path Packages/macOS/CmuxNext --filter SidebarChatHistoryTests -j 4 dispatched run 41151216458 for head 5e2ee40f9407f05ba3ffdd21178039ec4d23f4fb; the lane stopped its wrapper after 30s, and the saved receipt remains available for the fleet wait. No green claim is made yet.

Capture

Draft capture is still required before marking ready: add a DEBUG history fixture with Claude, Codex and an unknown harness in Pinned/Earlier, then attach 2x light and dark before/after images.

risk: normal

Agent session: agent session

[teamleaderleo]

Review (codex gpt-6-astra high, router-review): BLOCK at 5e2ee40

BLOCK at 5e2ee40

Visual verdict: BLOCK — required after screenshots are absent.

1. [P1] [blocking] The changed sidebar UI cannot be visually reviewed. The PR explicitly says capture is still required ([review/pr.body:21]), while the image manifest reports no GitHub-hosted images ([review/images/README.txt:2]). This prevents verification of the new row icons, colors, and layout.

Follow-ups: none

[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)}

Not verified: macOS jobs did not run: compile and app tests were skipped on c95e454173; ci-status is green without them.

CI passes on c95e454173 (run 41262511374 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.

Default changes

This pull request changes 1 default at c95e4541730b (what everyone gets without configuring anything):

• tunable-source.CmuxNextAgentLanes/SidebarChatHistoryFeed.swift:historyChat: "26981e7628d24125f0b16298e8437ffb488ddb39e5697507948848821f091f26" -> "22b1ce3eb88be73456abad0f6f81fcfa43a91406ace1db0079ad268f97e9c3bb"

Signed off on this commit by review (subagent claude-opus-5-5 medium).

Merge receipt: merged as 9175c1bb4384 with these defaults changed, signed off by review (subagent claude-opus-5-5 medium).

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

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4130052256501 (28aa638015)

[teamleaderleo]

Review (subagent claude-opus-5-5 medium): SHIP at c95e454

Compile: no problems found. Every API the diff calls exists at the head (SidebarStyle.titleTextX/iconBox/kindGlyphSize, AgentBrandCatalog.brand(for:), templateImage(brand:size:), GroupColor.unset(id:)), and the new harness: parameters default to nil, so the other callers compile unchanged. Row reuse resets harness, colour, image and visibility on every configure. Layout: with no icon the title x is unchanged; with one it follows the shared icon column. The merge resolution keeps base's anti-clipping meta frame. Row height is unchanged. The earlier BLOCK at 5e2ee40 was only about missing screenshots, which never block.

Follow-ups:

• [follow-up] The accessibility label uses the raw harness id ("claude-code"). It should use a display name.
• [follow-up] The fallback person.crop.circle symbol should take SymbolConfiguration(pointSize: SidebarStyle.kindGlyphSize) so it matches the brand marks.
• [follow-up] A catalog harness with no mark draws the person symbol in the plain secondary tint, not the per-harness fallback colour.