FABRIC-4.md: new forward-looking design-notes scratchpad

Not a successor to FABRIC-3.md (still the living document) -- a
separate, lower-discipline space for theory-stage ideas caught before
they have real scope. First entry: the Stadium-level "wheel" idea from
conversation with Captain Bob -- a second, Q48.16 phase-accumulator
clock fed by RWOT + the inference engine, meant to schedule when a
future sieve-stack slips in, rate starting fixed and graduating to
adaptive later, mirroring L8's own hardcoded-to-inferred history.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QgooKd5hJNtTYqB6CyK5f9

FABRIC-4.md

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+# FABRIC-4.md — forward-looking design notes
+
+**Status:** Not a successor to `FABRIC-3.md` and not a punch-list document. `FABRIC-3.md` is
+still the living document — nothing here supersedes it, and this file doesn't follow the
+close-and-carry-forward discipline `FABRIC.md` → `FABRIC-2.md` → `FABRIC-3.md` used (that
+chain triggers on *closing* a document; `FABRIC-3.md` isn't closed). This is a separate,
+lower-discipline scratchpad for design ideas caught early — theory-stage, pre-punch-list,
+often missing a stated "why" on purpose (captured as raised, not fully justified yet). An idea
+graduates out of here into `FABRIC-3.md` §I (or wherever `FABRIC-3.md` is by then) once it has
+a real scope, not before.
+
+---
+
+## 1. Stadium-level "wheel" — a second clock alongside the heartbeat (2026-09-03)
+
+Raised in conversation with Captain Bob, theory stage — no code, no scope, deliberately not
+punch-listed yet.
+
+**The mechanism.** A second clock, independent of but derived from the true heartbeat
+(`HeartbeatState`, Loop #7), advanced by a fixed-point (Q48.16, this project's standard)
+phase accumulator: each master heartbeat tick adds a `rate` scalar to the wheel's own
+`phase`; whenever `phase` crosses `1.0` the wheel fires (advances its own state) and the
+crossing remainder carries forward. This is a continuous scalar, not an integer tick-divisor
+— `rate` can sit anywhere, including above `1.0`. A wheel with `rate > 1` fires more than
+once per master tick (multiple threshold-crossings per tick, remainder still carried); one
+with `rate < 1` accumulates across several master ticks before firing once. Nothing about the
+mechanism privileges either side of `1.0` — "runs ahead of baseline" and "runs stretched
+behind baseline" are the same math with a different scalar.
+
+**What feeds it.** Not a new signal source — this wheel listens to two already-real, already-
+built mechanisms: `rolling_window_of_truth.c` (Loop #2's circular-buffer execution history —
+`rolling_window_measure_diversity()`, `rolling_window_find_hottest_word()`,
+`rolling_window_count_transition()`, `rolling_window_pattern_capture_rate()`,
+`rolling_window_is_warm()`) and `inference_engine.c` (Loops #5/#6 — `InferenceOutputs`:
+decay-slope, variance-inflection point, fit quality). Both exist today at the **per-VM**
+level (each patron/word-owning VM has its own rolling window and runs its own inference
+pass) — the wheel itself is meant to live at the **Stadium** level, one layer up. This is a
+genuinely new axis: nothing today aggregates RWOT/inference-engine output across the whole
+Stadium floor into one fleet-wide signal. **Open, not decided:** what the aggregation actually
+is (sum across patrons? mean? the hottest patron's own values only? something else) — flagged
+in conversation, not resolved.
+
+**What it's for.** Not a sieve itself. The wheel is a *scheduler/gate*: it decides *when* to
+slip an appropriate sieve into a stack of sieves that doesn't exist yet (see §2 below) —
+running its own clock, potentially ahead of the true heartbeat, is what buys it lead time to
+notice a transition worth reacting to before the baseline heartbeat would get there on its
+own. It is not itself the thing doing the sieving.
+
+**Build sequencing, decided in conversation.** `rate` starts as a fixed build parameter (same
+shape as `ACL-BASE-TTL`/`Q.SLOT` — a plain constant or Kconfig symbol, not adaptive from day
+one). Reasoning, Captain Bob's own: a fixed rate is the only version that can go through this
+project's existing DoE apparatus and produce a clean, attributable measurement (rate held
+constant, everything else varies) — if the rate self-tunes from day one there's no fixed
+baseline to compare "does the wheel actually help" against. Only *after* a real, measured
+baseline exists does `rate` itself graduate to adaptive/self-tuning — reusing the same
+inference-engine machinery the wheel already listens to, not new plumbing. This mirrors the
+L8 Jacquard selector's own real history: hardcoded compudynamics constant first, later
+replaced by the VM Fleet Attractor's dynamically-inferred rate
+(`docs/working/architecture/VM-FLEET-ATTRACTOR-DESIGN-20260705.md`). Same graduation, one
+level up the stack.
+
+**Explicitly not decided yet, per Captain Bob ("we'll talk about why later"):**
+- The actual *purpose* — why this wheel, what real problem it solves. Deferred on purpose.
+- The sieve stack itself — what a "sieve" is concretely, what gets sieved, how many. A larger,
+  separate vision (128–256 wheels, each fed by an "appropriate" — possibly learned/neural,
+  vocabulary not yet resolved against anything this codebase currently has — source, forming
+  a coincidence-pattern sieve) was raised earlier in the same conversation as a *distinct*,
+  further-out idea; this single-wheel scheduler is deliberately scoped smaller and doesn't
+  presuppose that larger picture is right.
+- Whether "trivial to add a wheel" (an earlier framing) still matters once there's only one —
+  a generic `{rate, phase, state}` table is a premature abstraction for a single instance;
+  build the one wheel concretely first, generalize only if/when a second one is actually
+  needed (this project's own standing convention — three similar lines beat a premature
+  abstraction).