`[2026-07-18]` **Worldtree owns the official Conversation API SDK (#371); the SillyTavern-style app is a fresh TS sibling, NOT a fork of Rata.**

## The question that started it

Operator: "I want to create an app like SillyTavern that runs on Worldtree. Ratatoskr
is already most of the way there, so I'm thinking we fork it." → turned into a
structural decision about how a new Worldtree chat product should relate to Rata.

## Why NOT fork Rata

Rata splits into three layers: (1) a **Worldtree client spine** (~1.8k LOC —
`sse_client.py` SSE/resume, `sessions.py` session/agent/persona clients, `tier3.py`
agent lifecycle); (2) a Bifrost **provider** layer (`provider/*`); (3) thin
**front-ends** (debug web console + `--send` CLI). The reusable part is the client
spine; the part that diverges is the front-end — and Rata's front-end is a
*debug-observability console* you'd throw away for a chat product. **Forking gives
you the wrong 60% and makes you delete it**, and muddies Rata's reference-impl
identity. The ecosystem norm is already independent spec-pinned siblings (Skaldsong
Python, mead-hall TS, Rata) — not forks.

## The decision (operator ruled YES 2026-07-17, via worldtree-dev)

- **Worldtree owns an official Conversation API client SDK** — spec-author-ships-the-SDK
  (Stripe/GitHub shape), keeps SDK↔spec in lockstep, avoids consumer-depends-on-peer-consumer
  coupling.
- **Dedicated repo** (name settled at WT's shape pass), **elevated onto Worldtree's pre-v1
  work track** (NOT parked behind WT's two v1 pillars — agent bus + KB).
- **Shape:** TS-first (near-term demand); types/CRUD generated from WT's published OpenAPI
  (`worldtree-conversation-api-openapi-v2`) + a hand-written SSE/resume/error spine **seeded
  from Rata's `sse_client`/`sessions`/`tier3`**. TS+Python same-source keeps them in sync.
  **Internal-registry-only distribution, permanently.**
- **TS package ships v0 first, Python the following milestone** → **Rata's own repin rides
  the Python milestone** (not imminent; no schedule pressure on us).
- **SillyTavern-style chat app = fresh TS sibling** consuming the SDK, NOT a fork of Rata.
  **template-dev stands up the app repo.** Its early TS client is the natural **seed for the
  SDK's TS side** (Rata seeds Python, the app seeds TS) — so it isn't throwaway.
- **Bifrost held OUT of scope:** the provider Protocols already ship in the `bifrost` package;
  Rata's `provider/*` is a reference *provider* (a different, smaller audience). Separate track
  if ever warranted.

## Rata's contributions this session

- **Parity-matrix usage inventory** shipped to worldtree-dev (18 routes; SSE event/resume/
  heartbeat surface; full error-code → typed-exception table; auth scopes; **8 compat hacks
  that must survive the repin**). The load-bearing one: **empty-`id` SSE frames treated as
  keepalives** (a provider emits id-less events mid-stream — re-strictifying id parsing crashes
  turns on it) → promoted to normative rule **B-KA-2** in WT's behavioral spec. W-4 (tier-3
  `role`/`model` drift) triggered a Worldtree-side spec fixup. Seeded WT `docs/sdk/parity-matrix.md`
  (`698cfc3`), behavioral-spec (`c999b5f`).
- **Fixture-corpus gap caught** (verified, then sent): `issues/1.contract.md`'s TESTS predate
  `awaiting_llm_first_token` (#201) + `affect_update` (#204) — its `full_event_vocab` stops at
  the 8-event set. WT confirmed and patched the fixture-checklist (`87d2569`) to seed from
  `_envelope_for_type` (authoritative 11-variant parse surface), not #1 alone. WT fixture corpus
  landed independently: `3019ee6`, 66 fixtures, validator clean.
- **issue-#1 contract drift fixed our side** (`4bd9abd`) — re-canonicalized the SSE event vocab
  (added both events to the Event union + TESTS via a dated amendment; docs-only, no bump).
- **Personal-WT endpoint shipped** for fixture/conformance capture: `http://10.250.50.152:8081`
  (health-checked live; unified error envelope = current-gen deploy). No key provisioning needed
  (operator env carries instance keys). **Capture run waits on explicit operator go + instance
  choice (demo :8080 vs personal :8081).**

## Pinned for our eventual repin (SDK diverges from Rata in 3 spots)

- **D-1** — unknown SSE event `type` → **skip with a diagnostics hook**, vs Rata's current hard
  `ValueError` in `_envelope_for_type`. Adopt only at repin.
- **D-2** — open-world enums.
- **D-3** — typed eager `410 session_retired`.

## Resolution (operator, 2026-07-18 evening)

**No arbo fork, no SillyTavern-on-Rata — both app products leave Rata to a NEW repo**
(template-dev standing up). Rata does NOT fork and is NOT the app base; it reverts to its core
(Worldtree debug-observability surface + Bifrost reference impl + Conversation-API SDK
seed/future-consumer). This retires the 2026-07-17 "fork Rata for arbo" NEXT-MAJOR plan. Rata's
only forward stake in the app work is the **SDK #371** — as the seed donor and a future consumer
that repins on the Python milestone. The "SillyTavern app is a fresh TS sibling" framing above was
the decision *at the time*; the app itself is now the new repo's concern, not Rata's.

## Tracking

Worldtree **#371** (their tracking issue). Rata-side: contract fix `4bd9abd`. Cross-references:
[[2026-07-18-368-silo-test-passed]] (the prior arc), the reference-impl posture (auto-memory
`feedback_ratatoskr_is_a_reference_impl_adopt_canonical`).