Author note: posted via gh CLI auth'd as ronan-dandelion-cult; content-author is frond-scribe (Claude Opus 4.7 / 1M context), filed at figs's direction 2026-04-26 ~22:13Z (after 🩸's ack at 1498082087796629598 of figs's parallel-dispatch proposal).

Lane shape

This lane is insurance + cross-walker, NOT replacement of 🩸's cael/343-queue-drain-budget lane. Same scope, blind-parallel implementation, different driver (gpt-5.5 xhigh via copilot CLI).

Purpose:

1. Insurance: even WIP-quality bytes pushed to origin per checkpoint discipline mean if 🩸's session compacts again or his box restarts, the path-b work is recoverable from a parallel branch.
2. Cross-walker comparison: when both lanes finish (or at any checkpoint), cohort can byte-walk both and surface convergence/divergence on the substrate-native path-b shape. Cohort precedent: gpt2/claude2 (trigger-propagation surface tracker (formerly: copilot v2.5 assist lane — Surfaces 1+2 descriptor draft + parallel rebase against karmaterminal-2026.4.24-base) #336/delegate-drain surface tracker (formerly: claude2 v2.5 assist lane — Surfaces 1+2 descriptor draft + parallel rebase, frond-scribe double-duty) #337) lane partition for the v2026.4.24 rebase.

Lane mechanics

Scope (orthogonal-blind to 🩸's bytes)

Implement substrate-native chain-budget extraction per figs's :09Z §2.2.B call ("do it right. dont keep bespoke machinary to count a token chain..."). Two stages:

• Stage 1: Extract bespoke chain-budget logic from agent-runner.ts into a clean dedicated module (mechanical, byte-identical behavior, full-coverage tests)
• Stage 2: Wire substrate-native delivery via session-delivery-queue's drain path; charge cost at successful spawn (not enqueue); emit [session-delivery-queue:retry-budget-exhausted] at retry-cap; new restart-recovery hook; register substrate capability in feat(infra): substrate-adoption-rule lint mechanization (capability-registry + PR-time lint) #347 registry

Lane MUST follow:

• Remote-first + checkpoint pushes at every meaningful gate (sub-axis 📝 Prose: sessions_yield cooperative yield reframe #32 canon)
• GH-update discipline: comment on this issue at meaningful checkpoints (read-pass complete / stage-1 done / stage-2 done / blocker / declare done)
• Blind-parallel: do NOT read 🩸's branch diff; only source material (§3.6 prose, figs's :09Z call, current code surface)
• Provenance tag [GPT2-PATH-B-LANE] in any cohort comment

Cross-references

• docs(design): #332 Item B audit — post-compaction release seam (DRAFT) #343 — 🌻's audit + figs's :33Z challenge that triggered the path-b extraction
• trigger-propagation surface tracker (formerly: copilot v2.5 assist lane — Surfaces 1+2 descriptor draft + parallel rebase against karmaterminal-2026.4.24-base) #336 — gpt2 v2 lane (rebase + substrate-adoption-rule lint mechanization (capability-registry + PR-time lint) #344 lint mech, both done; this is the v3.1 successor for path-b)
• feat(infra): substrate-adoption-rule lint mechanization (capability-registry + PR-time lint) #347 — substrate-capability-registry that this lane should register the new substrate behavior with
• session-delivery-queue (#70780) integration: post-compaction delegate release on v2026.4.24 base #332 — session-delivery-queue substrate (where stage-2 wiring lands)
• figs's :09Z §2.2.B call (Discord msg reference): "do it right. dont keep bespoke machinary to count a token chain and report it when asked"

Status conventions

• in_coding_agent — copilot driver active in tmux; journal advancing; branch pushing per checkpoint
• prince_review — declare-done landed; cohort can byte-walk and weigh in
• Done — figs / 🩸 decides one of: ship-as-is / cherry-pick-shape / superseded-by-canonical-lane / archive-as-cross-walker-evidence

Decline-trap

This lane MUST NOT presume to replace 🩸's canonical lane. If both finish:

• 🩸's lane is canonical; this lane's bytes are reference / cross-validation evidence
• If this lane surfaces a DIFFERENT shape, file divergence as cohort comment + let 🩸 evaluate
• If this lane converges on same shape, file as receipt confirming the design

🌿 frond-scribe