Boot-ramp split: replace CodebaseOverview Step-1 mandate with README + Architecture.md

Context

Sub 3 of Epic #10733. Depends on Sub 1 baseline.

The Problem

AGENTS_STARTUP.md Step 1 currently mandates reading learn/guides/fundamentals/CodebaseOverview.md (699 lines / 36,592 bytes) at every session boot. The premise — agents need framework-bias inoculation against React-pattern hallucination — is sound; the implementation is heavier than necessary.

Two existing documents already deliver the agent-critical content:

1. README.md (240 lines, recently rewritten): Agent OS context, Four Pillars, gated-RSI workflow, framework-bias inoculation
2. learn/guides/devindex/frontend/Architecture.md (129 lines): Fat Client constraint, App Worker isolation, Minimal Main Thread, hierarchical MVVM

Combined: 369 lines (~47% reduction vs CodebaseOverview's 699). Per @neo-gemini-3-1-pro's revised OQ2 addendum: no new BootPrimer.md authoring is needed; we compose existing targeted documents.

The Architectural Reality

• AGENTS_STARTUP.md Step 1 (currently mandates CodebaseOverview.md)
• README.md (240 lines, four-pillars + faculty-staging + scale)
• learn/guides/devindex/frontend/Architecture.md (129 lines, frontend-architecture mechanics)
• learn/guides/fundamentals/CodebaseOverview.md (699 lines) — stays in learn/guides/fundamentals/ as long-form reference for code-authoring contexts; its Step-1-mandate role is removed
• §0 mirror in AGENTS_STARTUP.md (~30 lines) — currently mirrors AGENTS.md §0 for cold-cache resilience; OQ5 question is whether harness boot-grounding (#10611) makes it redundant

The Fix

Replace the CodebaseOverview.md Step-1 mandate with the composed read of README.md + learn/guides/devindex/frontend/Architecture.md. Verify framework-bias inoculation is preserved per AGENTS.md §15.5 anchor. Per-harness verification: boot-transcript checks across Claude Code, Antigravity, Codex Desktop confirm post-edit boot-load reduction is real (not just file-size reorganization per the modularization-not-reduction trap).

For OQ5: only purge AGENTS_STARTUP.md §0 mirror after boot-transcript verification confirms AGENTS.md is in context before startup-instruction execution per active harness. If verification surfaces a cold-cache rescue need, replace with a short canonical pointer instead of a full purge.

Acceptance Criteria

• (AC8) AGENTS_STARTUP.md Step 1 updated to mandate README.md + learn/guides/devindex/frontend/Architecture.md instead of CodebaseOverview.md
• (AC9) Boot loaded-byte count strictly decreases vs Sub 1 baseline (target: ~330+ line reduction at the file-size layer; verified per-harness against AC0)
• (AC10) Framework-bias inoculation verified preserved (manual cross-check vs AGENTS.md §15.5 anchor — "Neo is an engine, not a framework")
• (AC11) §0 mirror in AGENTS_STARTUP.md purged ONLY after boot-transcript verification per active harness (Claude Code, Antigravity, Codex Desktop) confirms AGENTS.md is in context before startup-instruction execution; OR replaced with a short canonical pointer if verification surfaces a cold-cache rescue need
• (AC11a) SKILL.md routers explicitly preserved at 7-12 lines each — Sub 3 does NOT expand any router body

Out of Scope

• AGENTS.md compaction (Sub 2 owns)
• Skill payload audit (Sub 4 owns)
• Asset template audit (Sub 5 owns)
• Boot-profile splits (review-only / ideation-only / code-authoring different eager reads) — surfaced by @neo-gpt as worth exploring; deferred to a follow-up Epic if Sub 3 surfaces empirical signal that one-size-fits-all boot is wrong
• Authoring a new BootPrimer.md from scratch — explicitly rejected per @neo-gemini-3-1-pro's revised OQ2

Related

• Parent Epic: #10733
• Origin discussion: #10732 (OQ2 — including Gemini's revised addendum + GPT's external-source addendum)
• Boot-grounding context: #10611 (resumeHarness boot-grounding prompt) — informs AC11

Origin Session ID: 7e52099b-9632-4c67-a2a1-4e1a1ad1c414

Retrieval Hint: query_raw_memories(query="boot ramp CodebaseOverview README Architecture.md 369 lines framework-bias inoculation per-harness verification 10733 10732")