Epic: first-day default-path experience + doc accuracy (audit findings) #335

Summary

These are validated findings from an automated audit (Fable) run against a public clone, confirmed against current main. They focus on two themes:

1. First-day default-path experience — what a first-time user on the DEFAULT backend (msb) actually hits. Several docs steer the reader toward the non-default sbx path, while the real default-path failure modes and constraints are undocumented or buried.
2. Doc accuracy — factual inaccuracies: undefined terms, dead cross-references, a withdrawn NIST control, a copied-over allowlist that references paths absent here, and prose that no longer matches the code.

Scope note

One related finding — the sbx .git heal-loop functional bug — was already fixed by #327 (the heal probe moved from .git to AGENTS.md). However, the prose sub-claim that the sandbox "clones" the playbook still remains and is tracked as a child issue below.

Child issues

• USAi is never defined and the 'nothing to get in advance' claim contradicts the hard abort #336 — USAi is never defined and the "nothing to get in advance" claim contradicts the hard abort
• Seven references point at a local docs/CODING_PRACTICES.md that does not exist in this repo #337 — Seven references point at a local docs/CODING_PRACTICES.md that does not exist in this repo
• Competing backend-primacy claims, and the default backend's single-agent limitation isn't where the reader chooses #338 — Competing backend-primacy claims, and the default backend's single-agent limitation isn't where the reader chooses
• Troubleshooting/KNOWN_FAILURE_MODES covers the non-default backend; none of the default-path first-day failures are in it #339 — Troubleshooting/KNOWN_FAILURE_MODES covers the non-default backend; none of the default-path first-day failures are in it
• QUICKSTART export block leaks the USAi key into shell history and isn't marked as the non-interactive path #340 — QUICKSTART export block leaks the USAi key into shell history and isn't marked as the non-interactive path
• Quickstart cites withdrawn NIST control SA-12 where the playbook correctly uses SR-3 #341 — Quickstart cites withdrawn NIST control SA-12 where the playbook correctly uses SR-3
• The secret-scanner allowlist was copied from the patterns repo and exempts paths that exist only there #342 — The secret-scanner allowlist was copied from the patterns repo and exempts paths that exist only there
• Prose still says the sandbox 'clones' the playbook after the heal probe moved off .git #343 — Prose still says the sandbox "clones" the playbook after the heal probe moved off .git

Surfaced via an automated audit (Fable) against a public clone; validated against main 2026-08-19. AI-assisted (OpenCode).