docs(grid): L0 E2E persona cognition plan — careful sequencing per Joel

[joelteply]

Joel 2026-05-29: 'would take careful planning to migrate. I would get e2e persona cognition first, within RUST alone.'

This doc is the careful planning. Implementation slices land in subsequent PRs against this plan.

What the plan covers

• Concrete definition of 'e2e persona cognition in Rust alone' — what must be Rust, what may stay transitional TS (ingress/egress at the airc boundary)
• Audit of what's already in Rust (PersonaCognition, full_evaluate, respond, service_cycle, L0-1 module)
• Audit of what's still in TS driving the loop today (PersonaAutonomousLoop, PersonaMessageEvaluator, etc.)
• Five sub-slices, each with no silent-drop window:
  • L0-2-prep — PersonaSlot extension + open enroll (no dispatch yet)
  • L0-2-dispatch — service_once_for wired, tests-only (not in production tick)
  • L0-2-cutover — atomic TS-loop deletion + Rust-loop activation
  • L0-3 — genome paging moves to Rust
  • L0-4 — inbox routing moves to Rust
  • L0-5 — final PersonaUser.ts cull

Key non-obvious findings

• Not blocked by airc#1075. L0-2-cutover uses the universal CommandExecutor's existing TS-route branch for response posting. The Rust ServiceModule dispatches Commands.execute('chat/send', ...) which currently routes through TS; that's the form-specific egress boundary that's fine to stay TS for now.
• Not blocked by e51ab14e. That blocks the chat-flow migration (PR docs(migration): chat-message-flow migration scope — gated on airc e51ab14e #1462 scope). E2E persona cognition does not require machine-singular daemon.
• Blocked by knowing the rag_engine source. Open question: how Arc is shared today. Investigation before L0-2-prep code.

Pre-implementation investigation (4 items)

Before opening L0-2-prep PR I'll resolve:

1. How Arc is sourced (runtime singleton? per-persona?)
2. How channel_registry items get populated today
3. Whether Commands.execute is reachable from inside a Rust ServiceModule
4. Existing test fixtures for PersonaCognition

🤖 Generated with Claude Code

[joelteply]

Superseded by #1464 — the L0 plan doc + L0-2-prep code landed together to canary in one merge. Plan content lives at docs/grid/L0-PERSONA-COGNITION-E2E-PLAN.md on canary.