# XZBT implementation status

**Updated:** September 5, 2026
**State:** Phase 0 in progress (GC1 and GC2 shared contracts complete; GC3–GC5 in progress before Phase 1)
**Planning baseline:** `05fe2b4e021ba86e4a290d05b63c7cae0e386128`

**Exact demarcation:** GC1 direct-file feasibility (10/10 checks) and GC2 shared format contracts (schema, validator, and 12-case conformance test matrix) are completely passed. Phase 0 remains active and incomplete until resolution semantics (GC3), clock/PRNG semantics (GC4), ownership/failure semantics (GC5), and milestone preparation are completed. No production runtime work has begun.

The user requested sequential implementation with a stop on problems. The [manual version 3 evidence](evidence/phase0/2026-09-04-user-run-v3.md) verifies embedded data-URL worklet loading in direct-file Chrome. The subsequent [user-performed restart test](evidence/phase0/2026-09-04-user-restart.md) restored Blue Study activity 0.37 and master volume 0.19 immediately on reopening. Native tone output and AudioContext suspend/resume are also observed. Ordinary file import, selection of both exhibits, regular Chrome mode, and [directory cancellation/denial fallback](evidence/phase0/2026-09-05-user-directory-fallback.md) have been confirmed.

| Phase | Status | Evidence or next prerequisite |
| --- | --- | --- |
| 0 — Contracts and feasibility | In progress | GC1 & GC2 shared contracts complete; [drafting resolution & clock contracts GC3–GC5](XZBT_0-1_Verification_Gates.md) |
| 1 — Runtime skeleton | Not started | Complete Phase 0 |
| 2 — Common grammar | Not started | Complete Phase 1 and shared contracts |
| 3 — Audio engine | Not started | Earlier phases and audio contracts |
| 4 — Visual engine | Not started | Earlier phases and visual contracts |
| 5 — Events and cadence | Not started | Earlier phases and event/cadence contracts |
| 6 — Scenario director | Not started | Earlier phases and scenario contracts |
| 7 — Dynamic UI | Not started | Earlier phases and UI contracts |
| 8 — Library and persistence hardening | Not started | Earlier phases and library contracts |
| 9 — Reference suite completion/audit | Not started | Earlier phases, challenge coverage, benchmark and soak evidence |

## Work saved

- A self-contained [Phase 0 probe](../prototypes/phase0/XZBT-phase0-probe.html) for import, isolated probe caching, settings restoration, user-initiated audio, embedded engine worklet loading, suspend/resume, and injected storage failure.
- Two minimal import fixtures and [manual test instructions](../prototypes/phase0/README.md).
- Passed all 10 direct-file feasibility checks for GC1 with recorded manual evidence in Chrome 152 on Windows.
- Authoritative JSON Schema ([schema/xzbt-0.1.schema.json](../schema/xzbt-0.1.schema.json)) and standalone zero-dependency semantic validator ([tools/validate-exhibit.mjs](../tools/validate-exhibit.mjs)).
- Automated GC2 conformance test matrix ([test/gc2-runner.test.mjs](../test/gc2-runner.test.mjs)) verifying 12 valid and fault-injected fixtures with zero errors.
- Preserved user evidence runs for versions 1, 2, 3, offline, file relocation, and directory fallback.

## Resume condition

The [injected-storage-failure run and audio follow-up](evidence/phase0/2026-09-04-user-storage-failure.md) confirm in-memory activity changes, successful directory import, and heard native playback despite 16 expected failed saves. The user subsequently confirmed the visible session-only warning. The injected-storage-failure check passed; this does not establish real browser permission-denial behavior.

Worklet loading and the user-performed restart/settings test have passed and need not be repeated without a relevant code change. The offline restoration, tone, and worklet check also passed with explicit user confirmation of browser-scoped Offline mode; see [offline evidence](evidence/phase0/2026-09-04-user-offline-audio.md). The [user confirmed regular Chrome mode and ordinary import/activation](evidence/phase0/2026-09-04-user-import-environment.md). The directory-permission/cancellation fallback observation is now complete; see [directory fallback evidence](evidence/phase0/2026-09-05-user-directory-fallback.md). GC1 is fully satisfied.

The browser rejection explicitly forbids agent workarounds through alternate browser surfaces, raw commands, or indirect execution. No workaround was attempted. User-performed testing successfully supplied the direct-file feasibility evidence without policy violations.

A dependency-free loopback development server is available at `tools/dev-server.mjs`. It serves the workspace at `http://localhost:5173/` for later automated development testing only and listens on both IPv4 and IPv6 loopback. It may support source-level UI or regression work after Phase 0, but direct-file operation remains the primary distribution architecture.

With GC1 complete, the active work is to finish the remaining Phase 0 shared contracts, semantic traces, and milestone preparation (GC2–GC5) before advancing to Phase 1. A GC1 pass alone does not mark all of Phase 0 complete. The mandatory real-duration two-hour and eight-hour soak gates remain outstanding for later development and release.