diff --git a/packages/ui/src/components/chat/work-status/DOCUMENTATION.md b/packages/ui/src/components/chat/work-status/DOCUMENTATION.md
index 0c310f50..f23be5cc 100644
--- a/packages/ui/src/components/chat/work-status/DOCUMENTATION.md
+++ b/packages/ui/src/components/chat/work-status/DOCUMENTATION.md
@@ -95,11 +95,11 @@ which requests only providers enabled for this panel.
 
 | Block | Source | Notes |
 |---|---|---|
-| Context + cost | `contextUsage.ts` over `useSessionMessages`, `Session.cost` | see below — the store getters cannot serve this |
+| Context + cost | `contextUsage.ts` over `useSessionMessages`; cost via `useSubagentCostRollup` (own cost + every descendant subagent, recursively) | see below — the store getters cannot serve this |
 | Branch, ahead/behind, attention | `useGitStore` directory state | warmed via `runBackgroundNetworkTask(ensureStatus)` and refreshed from Git mutation hints |
 | Changed files | `useGitStore` status `files` + `diffStats` | working tree, not session-authored edits |
 | PR + checks | `useFreshestPrVisualSummaryForBranch` | **read-only**; follows the freshest remote-keyed entry for the branch |
-| Subagents | child sessions from `useAllLiveSessions` (`parentID`) + `useAllSessionStatuses` | |
+| Subagents | child sessions from `useAllLiveSessions` (`parentID`) + `useAllSessionStatuses`; per-row cost from `useSubagentCostRollup`'s `perChildCost` (each child's own subtree total, so nested subagent-of-subagent cost rolls up under its immediate parent row) | |
 | Subagent blockers | directory `permission` / `question` maps | one subscription covers every child |
 | Usage | `components/usage/usageGroups.ts` over `useQuotaStore` | grouping shared with the mobile popover; presentation is not |
 | Linked threads | `lib/linkedIssues.ts` over session metadata | written by the flows that attach an issue or PR |