Optional: color Lineage subagent dots by provider accent instead of status

[jshaust]

Problem

I run several accounts of the same provider (two Codex subscriptions, three Claude subscriptions) and delegate a lot of work to subagents. In the Lineage panel, every subagent row shows the provider glyph with a small dot, and that dot only shows run status (blue running, green done, red failed). Every Codex row looks the same, so I can't tell at a glance which account a subagent is running on. I have to hover each row for the details card.

T3 already lets me give each provider instance an accent color in Settings → Providers, and the sidebar card, the subagent hover card, and the composer's provider badge all use it. The Lineage dot is the one place that doesn't.

It gets worse when your accent colors are red and green, as mine are. Then the status dot actively misleads you about the account.

Proposal

Add an Appearance toggle, Lineage provider colors, off by default:

• Off (default): no change from today.
• On: a subagent row whose provider instance has an accent color uses that color for the dot. Rows with no accent color, and parent, fork and transfer rows, keep the status dot.
• Status stays visible in each row's label ("Running", "Done", "Failed"), in the "N failed" header, and in the hover card. Only the dot changes.

Because it's opt-in, nothing changes for anyone who doesn't turn it on.

Before / after

Demo data: four subagents on three accounts. Codex Work is amber, Codex Personal is violet, and Claude Personal is pink.

Before (status dots)	After (setting on, provider accent dots)

Setting row (Settings → Appearance):

Implementation (prototyped)

I have a working branch. It's small and web-only:

• packages/contracts/src/settings.ts: a lineageAccentColorsEnabled client setting (default false) plus its patch key.
• ThreadRelationshipIcon.tsx: an optional accentColor prop. When set, it replaces the status class on the badge dot; the status color logic is extracted unchanged.
• ThreadRelationshipsControl.tsx: when the setting is on, resolves the row's instance through deriveProviderInstanceEntries, as SubagentTooltipContent already does, and passes its accent color for subagent rows only.
• Settings → Appearance row, a settings search entry, and a test in ThreadRelationshipsControl.agents.test.tsx.

Mobile has no Lineage panel (it uses the agents sheet), so this is scoped to web and desktop. Happy to follow up on mobile if you want parity.

Would you accept a PR for this? I'm also happy to change the shape. For example, it could be on by default when the instance has an accent color, or failed rows could keep red.