Rework child attribution to resolve each subagent to the PR its launching
turn was working on, using the parent's UNFILTERED turn data, and enforce
that every dollar is counted exactly once.
- Mutual exclusion: a child that referenced its own PR attributes
standalone and is never folded; a child with no links is folded only.
Fixes a double-charge where a self-linking child was both folded and
self-attributed.
- Recursion: a fold aggregates a child plus its non-self-linking
descendants (depth-first, cycle-guarded), so grandchildren spawned by
subagents reach the PR report.
- Global linkage: the subagent index keys by parentSessionId alone
(UUIDs are globally unique), so a child whose worktree resolves to a
different project still links.
- Date-range correctness: spawn-to-PR sets are built at assembly from the
full turn list, so a spawn in a pre-range turn attributes to the right
PR; a PR-linked parent whose own turns fall out of range is kept as a
0-cost fold anchor so its in-range child is not lost.
- Timestamp fallback compares epoch ms (mixed UTC offsets order right) and
is end-bounded: a child active after the parent's last turn is unlinked
(contributes nothing), matching orphan semantics.
- Cache adoption tries the newest prior versioned file (v6 then v5) so the
preceding build's expired-PR history survives the v7 bump; an invariant
note requires the list to cover every version that can exist on disk.
- Spawn-result pairing matches the tool_result block that carries the
agentId, not the first block, when a record batches several results.
- resolveSubagentAttribution is computed once and shared by aggregateByPr
and prLinkedTotals.
subagentSessions now counts folded subtrees (children plus descendants).
Verified on real data: attributed + unattributed reconciles to cost, and
parent-only cost plus folded-children cost equals the folded total to the
cent (no double-count).
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