Add per-parent-task delegation tree (cross-process linkage)#54
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Link each delegated sub-call back to the top-level task that spawned it,
across the orchestrator→MCP-child process boundary. The CLI mints a
task_id per routed task; the orchestrator CLI adapter injects it as
TANGLEBRAIN_TASK_ID into the orchestrator subprocess (only when the
delegate tool is injected); the orchestrator forwards env to the MCP
delegate child; run_delegate reads it back and stamps each delegate
record's parent_task_id. The rollup groups delegates by_parent
("Linked to: N parent task(s)"); sub-calls run outside a propagated
task group as "unlinked".
New fields are written only when present, so existing usage records and
readers are unaffected. Manually verified live end-to-end through the
real claude→MCP-delegate boundary (parent + delegate records shared the
same id). The orchestrator-forwards-env hop is a load-bearing assumption,
not a TangleBrain guarantee — a delegate that loses the env degrades
safely to "unlinked", never an error.
Closes the deferred entry-criterion spike for the scatter-gather epic.
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This was referenced Jun 19, 2026
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What
Link each delegated sub-call back to the specific top-level task that spawned it, across the
orchestrator → MCP-delegate-child process boundary — the deferred stretch item of the scatter-gather
epic (#39), whose entry criterion was a live-verification spike.
Mechanism:
run_oncemints atask_idper routed task → the orchestrator CLI adapter injects itas
TANGLEBRAIN_TASK_IDinto the orchestrator subprocess env (gated oninject_delegate) → theorchestrator forwards env to the MCP delegate child →
run_delegatereads it back and stamps eachdelegate record's
parent_task_id. The rollup gains aby_parentgrouping("Linked to: N parent task(s)"); sub-calls run outside a propagated task group as
unlinked.New record fields (
task_id,parent_task_id) are written only when present, so existing usagerecords and readers are unaffected.
Why
#39was core-complete with this one stretch item deferred precisely because it can't be testedhermetically — it depends on a real orchestrator CLI forwarding env to the MCP child it spawns.
Test plan
make teston 3.10/3.11/3.12). New unit coverage: env-injectiongating, env read-back, record write/omit,
by_parentgrouping +unlinkedsentinel, router-pathtask_idthreading, all-unlinked format.tanglebrainthrough the real router → claude →delegate_local; theparent task record (
model: claude,task_id: X) and the delegate record (model: gpt-oss-120b,parent_task_id: X) shared the same id. The--statstree rendered "Linked to: 1 parent task(s)".delegate MCP isn't registered. The env-forwarding hop is identical across CLIs, so claude proves
the mechanism. Documented as a load-bearing assumption in
delegate.py(degrades safely tounlinked, never errors).Independent Critic reviewed (diff-only): SHIP; both SHOULD-FIXes addressed (router-path opts test +
load-bearing comment) plus NITs (all-unlinked format, CHANGELOG wording).
Closes #52.