# Code organization & structural quality — Phase Q framing

The **why** behind a dedicated code-reorganization / structural-refactor pillar. This is
the framing and settled-decision record for **Phase Q (Quality)** — bringing the ReaSampler
`src/` tree into a healthier structure (more encapsulation, granular namespaces, `src/`
subdirectories) **without sacrificing runtime performance**, against a stated quality bar:

> "**mtytel Vital is my code reference for quality.**" — Daniel
>
> Bring the codebase "**into the realm of something I can stand to look at.**"

Its build roadmap's landed history lives in **`docs/ARCHIVE.md`** ("Phase Q — Quality:
the decision record") and its authoritative spec now lives in root **`CLAUDE.md`**
(§Directory and namespace layout, §Performance guardrails, §Structural heuristics)
plus the per-directory `src/**/CLAUDE.md` files. This doc holds the *why* — the quality bar, the evidence base
(a grep-verified SOLID audit), the target directory/namespace shape grounded in the Vital
reference, and the numbered fork decisions.

**Status:** framed by product-designer (2026-07-26); gate reconciled + naming dimension added
(2026-07-27); **pre-restructure functional + DSP audit wave (Q-W0) added 2026-07-27** (Daniel's ask —
§2c, forks Q-10/Q-11). Forks Q-1 … Q-11 below are the decision record; **Q-1 (namespace letter),
Q-10 (audit-report home), and Q-11 (pitch-remediation depth) are SETTLED (Daniel, 2026-07-27)**; the
remaining forks (Q-2…Q-9) carry a leading recommendation and are Daniel's to call.
Three audits ground the phase: the two structural, grep-verified ones — a **SOLID audit** (§2) and a
**naming/symbol-consistency audit** (§2b) — plus the **functional + DSP audit** defined as Q-W0 (§2c),
which runs *first* and is *executed* in-phase (this doc scopes it, staff-engineer performs it).

---

## 0. TL;DR

- **Phase Q opens with a pre-restructure audit (Q-W0), then does the structural reorg.** Before a
  single file moves, a **functional + DSP quality audit** (§2c) runs first — a close-eyed pass over
  the DSP paths (**pitch especially**), duplicate code / reinvented wheels, and env-coupled-constant
  domain-modeling smells — producing a triaged findings report. **Q-W1 (the first structural wave)
  is gated on that triage being complete and Daniel signing off on each finding's disposition.**
  Fixes classified fix-now are eliminated in Q-W0 (or folded into the wave that opens the file), not
  carried untouched into the reorg. Everything below §2c is the structural reorg that follows.
- **This is not a feature phase — it is a quality phase.** The code works. The pure-core /
  shell split is real and healthy (30 pure static libs, each with its own CTest executable,
  the discipline CMake-enforces). What Phase Q fixes is that the *shape* of the code doesn't
  yet read the way the architecture actually is: `src/` is one flat 45-file directory, all
  37 headers sit in one flat `reasampler` namespace, four modules have grown into
  god-modules, one utility (JSON parsing) is copy-pasted across four models, and a set of
  symbols are named inconsistently or collision-prone (§2b). Phase Q addresses four dimensions:
  **structure** (directories), **encapsulation** (namespaces + JSON dedupe), **factoring**
  (god-module splits), and **naming** (a consistent component-naming scheme, §2b + Q-7…Q-9).
- **The quality bar is Vital** (§1). Vital groups its ~1,000-file synth by *subsystem*
  (`common/` `synthesis/` `interface/` `plugin/`) with nested functional sub-dirs. That is
  the aspirational shape: the directory tree *is* the architecture diagram. ReaSampler's
  subsystem groupings already exist — latent in the CMake link graph — but are invisible in
  the code's shape. Phase Q makes them visible.
- **Performance is a hard constraint, not a nicety.** The reorg is directory + namespace +
  file-split — it must cost **zero runtime**. The two hot paths (`peaks` envelope compute;
  audition/preview; the realtime-capture tick) must keep their exact call/inline shape: **no
  added virtual dispatch, no header→TU indirection on a hot path.** This is an explicit
  acceptance criterion on every point, not a footnote (§3).
- **This phase is GATED on the tree being otherwise quiescent** (§4). A structural reorg that
  lands while Phase S (on the phase-s worktree) is mid-flight would create catastrophic merge
  conflicts — the reorg touches nearly every file, and every in-flight branch is diffed against
  the *old* layout. As of 2026-07-27 the outstanding work is **Phase S** (merged to dev) and
  **Phase L L3** (the VST restyle, itself gated on Phase S) — Daniel's plain target: *"when
  Phase S and L3 are finished."* (L1/L2/L4–L7 have already landed; D2 is functionally complete;
  M9 is abandoned.) Stated prominently because getting the gate wrong is the one way this phase
  does real damage.
- **Beyond SOLID, Phase Q also fixes naming.** The reorg gives every symbol a *directory +
  namespace home* (Q-3/Q-4); §2b's grep-verified naming audit adds the orthogonal dimension of
  giving poorly/inconsistently-named symbols a *consistent name*, measured against the same
  Vital "something I can stand to look at" bar. Renames ride the waves that already relocate the
  file (a rename is nearly free when a file is already moving); the scheme + new forks (Q-7…Q-9)
  are in §6.
- **Every point is independently landable and CTest-green at every step** (§5). The CMake
  targets already draw the module seams; a file move + namespace change keeps
  `ctest --test-dir build` green at each point. Green-CTest-at-every-point is an acceptance
  criterion, not an aspiration — it is *how* a reorg this broad stays safe.

---

## 1. The quality bar — Vital, read from its actual structure

Daniel named **Vital** (`github.com/mtytel/vital`, the spectral-warping wavetable synth) as
his code-quality reference. Read from the actual repository, not from reputation, here is
what makes Vital's structure the aspirational shape — and what maps cleanly onto ReaSampler.

### 1.1 Vital groups by subsystem; the directory tree *is* the architecture

Vital's `src/` is organized top-level by **subsystem concern**:

| Vital `src/` dir | Contains | ReaSampler analogue |
|---|---|---|
| `common/` | shared utilities, data types used everywhere | the pure data/util core (`bank_model`, `app_version`, a new `json`) |
| `synthesis/` | the audio engine — nested further by concern | the capture/audio core (`capture`, `peaks`, `render_settings`, `wav_trim`) |
| `interface/` | all UI / editor code | the UI core + shells (`theme`, `component_geometry`, `bank_panel`, `draw_kit`) |
| `plugin/` | the plugin-wrapper / host-boundary layer | the REAPER-facing shells + `main.cpp` |
| `headless/` `standalone/` | build-shape entry points | (n/a in one extension binary; the Phase S VST3 is the second artifact) |

And critically, `synthesis/` is **itself** subdivided by function —
`synth_engine/ modulators/ filters/ effects/ producers/ framework/ lookups/ utilities/`.
The grouping principle is **layered functional architecture**: core generation → processing
→ infrastructure → support, each a directory. You can read the subsystem map off the folder
tree without opening a file. *That* is "code you can stand to look at": the structure
teaches you the architecture.

### 1.2 What ReaSampler has vs. what Vital has

ReaSampler's architecture is **already** subsystem-layered — it is just invisible:

- **The pure/shell split is real and CMake-enforced** — 30 pure static libraries, each with
  its own test executable, none linking a REAPER SDK. This is the *load-bearing* discipline
  and it is genuinely healthy (the SOLID audit confirms: "NO genuine core→REAPER leaks
  found — the split is intact and CMake-enforced").
- **But the *shape* hides it.** All 45 files sit in **one flat `src/` directory**; all 37
  headers sit in **one flat `reasampler` namespace**. The subsystem groupings —
  model / view / capture / audio / ui / reclaim / version — exist only in the link graph
  (`target_link_libraries` edges), never in the code you *read*.
- **Vital's lesson, applied:** ReaSampler doesn't need to *invent* an architecture — it needs
  to make its existing one **legible**. The reorg is a change of *shape*, not of *substance*.
  That is exactly why it can be zero-runtime-cost and CTest-green throughout: the seams
  already exist; Phase Q draws them where a reader can see them.

*(Note on the reference: Daniel wrote "mtytell"; the canonical repo is `mtytel/vital`. The
structural facts above are read from that repository's `src/` tree. Vital is GPLv3 — we
borrow its **structural pattern**, not its code.)*

---

## 2. The evidence base — grep-verified SOLID audit (Single-Responsibility lens)

The reorg is not driven by taste alone; it is grounded in a **grep-verified** staff-engineer
SOLID analysis of the actual `src/` tree (45 files / ~19,800 LOC). Reproduced here as the
decision-grade evidence; the PLAN points and CONTEXT spec cite back to it.

### 2.1 The three structural problems that dominate

1. **Four god-modules** — each carrying 4–8 distinct responsibilities:
   - `bank_panel.cpp` (**2,424 LOC**) — 8+ responsibilities: rendering, thumbnail
     compute+cache, audio audition engine, bank CRUD (*duplicates `actions.cpp`'s verbs*),
     context menus, input handling, new-content detection, OS drag-out + drop-target, window
     lifecycle + a ~20-function public API.
   - `main.cpp` (**1,762 LOC**) — owns-the-API-pointers is only ~120 lines of it. Also
     carries: full capture orchestration (`RunCapture` / `captureAndIndexOne` /
     `renderOffline` / batch/recapture/realtime `Run*`), `FxBypassGuard` (100+ LOC,
     precision-invariant-critical, buried), scope/source resolution, provenance assembly,
     the realtime-capture lifecycle state machine + globals, two RAII selection guards, and
     ~350 lines of hand-written registration boilerplate.
   - `actions.cpp` (**981 LOC**) — two unrelated command-id families in one TU (Design View
     family + multi-bank/prune family, the latter holding `doBankPruneFolder`, **the only
     file-deletion authority**), plus its own `promptText`/`mintBankId` *duplicating*
     `bank_panel`.
   - `persist.cpp` (**766 LOC**) — 5 responsibilities: session lifecycle+poll, ext-state
     serialization bridge, folder relocation, GUID minting, and prune scanning + filesystem
     deletion (`deleteOrphanFile` via `SHFileOperationW`).

2. **JSON serialization duplicated across four model modules.** `bank_model`, `bank_book`,
   `view_mode_model`, and `owned_manifest` **each hand-roll their own `Parser`**
   (parseString / parseInt / parseKey / skipValue + escape). This is the single largest
   DRY + SRP violation and the **highest-leverage single fix** in the phase.

3. **Zero namespace granularity.** All 37 headers live in one flat `reasampler` namespace;
   `src/` is one flat directory. Subsystem groupings are latent in the CMake link graph but
   invisible in code shape — the exact gap §1 identifies against Vital.

### 2.2 Per-module Single-Responsibility verdicts (the audit's own words)

- **Pure core is mostly clean.** `peaks`, `provenance`, `prune_reconcile`, and every geometry
  mirror (`mode_switch` / `bank_grid` / `tab_strip` / `action_buttons` /
  `component_geometry` / `prune_button`) are **single-responsibility exemplars** — leave them
  alone, just relocate + namespace them.
- **Mixed (model + JSON):** `bank_model`, `bank_book`, `view_mode_model` (1,040 LOC — 4
  indices + planner + JSON), `owned_manifest`. The JSON extraction (Q-W1) resolves the mixed
  half of each.
- **Shells split cleanly:** `capture` / `capture_realtime` (two backends behind one header);
  `view` (derive-visibility + apply-to-REAPER).

### 2.3 Other SOLID letters (secondary, in-scope where cheap)

- **O (Open/Closed):** the capture-action *table* is good OCP; the ~350-line hand-written
  **non-table** registration blocks in `main.cpp` are the opposite — every new action edits
  4 parallel places. A registration-table closes this (a candidate Q point, Q-6 dependent).
- **I (Interface Segregation):** `capture.h` / `persist.h` / `bank_panel.h` are **fat
  headers** — split them alongside their TU splits.
- **L / D:** `ICaptureBackend`/`Offline`/`Realtime` is a clean Liskov story (no violation);
  `main`/`bank_panel` depending on concrete backends is a low-priority D concern, explicitly
  **out of scope** for Phase Q (it is a design change, not a reorg).

### 2.4 Encapsulation gaps (beyond the four god-modules)

- **JSON parser duplicated 4× → extract a pure `json` core** (the highest-leverage change).
- **Bank-CRUD verbs duplicated** in `bank_panel.cpp` *and* `actions.cpp` — dedupe to one
  owner.
- `peaks` forces whole-file `std::vector<float>` materialization on the thumbnail path (clean
  API, but a data-ownership boundary forces a copy) — **noted, not scoped**: touching it
  risks the hot path (§3), so it is a deliberate non-goal for Phase Q.

---

## 2b. The naming audit — grep-verified symbol/module-naming inconsistencies

The SOLID audit (§2) grounds *where responsibilities live*; this section grounds *what things are
called*. Same rigor: **every claim below cites a symbol or file verified by grep/read of the
actual `src/` tree (2026-07-27), not taste asserted in the abstract.** The reorg is the moment to
fix naming because a rename is nearly free when the file is already being relocated or split
(Q-W1–Q-W6). Measured against the same bar: *"something I can stand to look at"* means a newcomer
can predict a symbol's name from its role and never meets two unrelated things sharing one name.

### 2b.1 The good news — what is already consistent (leave alone)

Two families are already named on a legible principle; the audit's job there is only to *protect*
them through the reorg, not to change them:

- **The geometry-mirror *verb* vocabulary is consistent.** Every pure layout/hit-test module uses
  the same two verbs: `compute<Thing>Rects` / `compute<Thing>` for layout and `hitTest<Thing>` for
  hit-testing — verified across `bank_grid` (`computeCellRects`/`hitTestCell`), `mode_switch`
  (`computeSegmentRects`/`hitTestSegment`), `action_buttons` (`computeButtonRects`/`hitTestButton`),
  `action_bar` (`computeBarSlots`/`hitTestActionBar`), `tab_strip`
  (`computeTabRects`/`hitTestTabStrip`), `prune_button` (`computePruneButton`/`hitTestPruneButton`),
  `overflow_menu` (`computeMenuButton`/`hitTestMenuButton`), `footer_bar`
  (`computeFooterBar`/`hitTestFooterBar`), `card_drag` (`computeSlotRects`/`hitTestSlot`),
  `component_geometry` (`computeButtonBox`/`hitTestBox`). This is a real, followed convention —
  preserve it verbatim.
- **The `_tests` suffix is uniform.** Every pure module's CTest executable is `<module>_tests`
  (30 targets in CLAUDE.md's table, no exceptions). No action.

### 2b.2 Ambiguous / collision-prone symbols (the highest-priority fixes)

These are the naming equivalent of the JSON-`Parser` DRY violation — concrete hazards, not taste:

1. **Four hand-rolled `Parser` classes, one name.** `class Parser` is defined **four times** —
   `bank_model.cpp:306`, `bank_book.cpp:663`, `owned_manifest.cpp:107`, `view_mode_model.cpp:654`.
   Q-W1 already deletes three of them by extracting `core/json`; the naming rule is that the
   survivor is **`json::Parser`** (or a more specific `json::Reader`/`json::Writer` pair — see
   Q-8), never a bare `Parser` in flat scope.
2. **`FooterRect` and `ButtonRect` are shared across pure UI modules — and the codebase already
   *knows* it.** `struct FooterRect` and `struct ButtonRect` are defined in `prune_button.h`
   (lines 32, 46) and **reused** by `footer_bar.h`, which carries an explicit in-file "NAME NOTE"
   (`footer_bar.h:27–34`) documenting that `ButtonRect / FooterRect / SegmentRect / ActionBarRect /
   KitBox / KitButtonBox` are "already owned in this namespace" and that new types must carry a
   `FooterBar*` prefix to avoid collision. That comment is a smell made visible: the flat
   `reasampler::` namespace forces every pure-UI author to hand-check for name collisions before
   minting a type. This is the single strongest in-codebase argument for the Q-4 sub-namespaces —
   under `reasampler::ui` these shared rect types get one clear owner and the hand-checking stops.
3. **`Sample` (`bank_model.h:69`, the bank metadata struct) vs `AudioSample` (the `peaks` float
   alias).** Already flagged in §2.4/Q-4; verified — `Sample` is the model record, `AudioSample`
   is a raw PCM float. Under `model::Sample` vs `audio::AudioSample` the collision risk is gone,
   but the *names* still read oddly side by side (a `Sample` that is metadata, an `AudioSample`
   that is one float). Noted; the namespace split is the required fix, a rename is optional (Q-8).
4. **`Selection` (`bank_grid.h:112`) and `CellRect` (`bank_grid.h:23`) are generic names in a
   flat namespace.** `Selection` in particular is the kind of name a newcomer cannot place without
   opening the file. `ui::Selection` / `ui::CellRect` resolve it structurally; no rename needed
   beyond the namespace.

### 2b.3 Inconsistent module/type *naming families* (the taste-but-grounded tier)

Here the names are legal and non-colliding but do not read on one principle — the "stand to look
at" gap:

1. **The model-family suffixes disagree: `_model` vs `_book` vs `Index`.** Verified: the pure model
   modules are `bank_model.{h,cpp}` (owning `class BankIndex`, `bank_model.h:132`), `bank_book.{h,cpp}`
   (owning `class BankBook`, `bank_book.h:208`), `view_mode_model.{h,cpp}` (owning `class ViewModeModel`,
   `view_mode_model.h:376`), `owned_manifest.{h,cpp}` (owning `class OwnedFileManifest`,
   `owned_manifest.h:52`). Four modules, four different file↔class naming relationships:
   `bank_model`→`BankIndex` (file says "model," class says "index"), `bank_book`→`BankBook`
   (file = class), `view_mode_model`→`ViewModeModel` (file = class), `owned_manifest`→`OwnedFileManifest`
   (file ≈ class, but the class adds "File"). The `bank_model`/`BankIndex` mismatch is the worst:
   the file name and its primary class name share no word. This is a genuine legibility wart — the
   fix is a *rename decision* (Q-8), not something the directory move alone resolves.
2. **The `bank_book` "wraps `bank_model`" relationship is invisible in the names.** `BankBook`
   (`bank_book.h:208`) is a registry of `Bank` (`bank_book.h:147`), each wrapping a `BankIndex`
   (`bank_model.h:132`). The names `Book` → `Bank` → `Index` do not read as a containment hierarchy;
   a reader has to learn it. (Not necessarily worth a rename — "book of banks" is evocative — but
   it is the kind of call Q-8 should make deliberately, not by accident.)
3. **`realtime_record.h` (pure) vs `capture_realtime.cpp` (shell) — the word order flips.** Verified:
   the pure realtime module is `realtime_record.{h}` (owning `RecordModePlan`/`RecordPhase`/
   `RecordTickInputs`, `realtime_record.h:57–173`) while its shell is `capture_realtime.cpp`. So the
   pure core is `realtime_record` but the shell is `capture_realtime` — the two halves of one feature
   are named on inverted word order (`realtime_record` vs `capture_realtime`). Compare the *clean*
   shell-pair convention elsewhere: `drag_out` (pure) ↔ `drag_out_win` (shell) — same stem, suffix
   marks the platform shell. The realtime pair breaks that pattern. This is the clearest shell↔core
   naming-drift instance in the tree (Q-9).
4. **`capture.{h,cpp}` is the *offline* backend shell, but the name claims all of capture.**
   Verified: `capture.h` declares `ICaptureBackend`, `OfflineRenderBackend`, **and**
   `RealtimeRecordBackend` (`capture.h:112,124,201`), while the realtime *implementation* lives in
   `capture_realtime.cpp` and its pure planner in `realtime_record.h`. So `capture` is really
   "capture interface + offline backend," a fat header (the §2.3 Interface-Segregation concern) whose
   name oversells its scope. Its Q-W3 hoist (`capture_orchestrator`/`scope_resolve`) is the moment
   to right-size the name.

### 2b.4 Abbreviations / opacity (low-severity, opportunistic)

Swept for names a newcomer couldn't decode; the tree is mostly clean here (a credit to it). Two
minor notes:

- **`guid_diff` / `GuidBaseline` (`guid_diff.h:40`)** — "GUID diff" is decodable in context (it
  diffs the live track/item GUID set between polls) but `GuidBaseline` reads more clearly as "the
  previous-poll snapshot" than the module name suggests. Low priority; leave unless its `core/view`
  relocation invites it.
- **`MinMax` (`peaks.h:30`), `KitBox` (`component_geometry.h:28`)** — terse but correct and local;
  no change. Named here only to record they were swept and cleared.

### 2b.5 What the naming audit does NOT touch (hard boundary)

The FOREVER-STABLE on-the-wire/on-disk contracts are **not** C++ symbol names and are **out of
scope for every rename**: `command_id` strings (`CEREBELLUM_REASAMPLER_*` / `_BETA_`), action
display names (`"ReaSampler: …"`), ext-state namespace (`"reasampler"` / `"reasampler_beta"`) and
its keys (`"banks"`, `"view_state"`, `"tail_setting"`, `"owned_files"`, `"version"`), the
`reasampler:` lane-name prefix, and the Phase S VST3 class UID. Renaming a C++ class is orthogonal
to these strings; the audit's renames touch symbols only, never a shipped contract literal. This
is the same guardrail §7 states for the reorg, restated for the naming dimension because a careless
"tidy the names" pass is exactly how a shipped id gets broken.

---

## 2c. The pre-restructure functional + DSP quality audit (Q-W0 — runs FIRST)

The §2 SOLID audit and §2b naming audit are **structural** analyses — they ground *where
responsibilities live* and *what things are called*. Daniel asked (2026-07-27) for a **third audit
that runs before the reorg begins**, on a different axis: *does the code do the right thing, and does
it do it well.* That is **Q-W0** — a thorough functional + DSP static analysis producing a written,
triaged findings report, complementary to (not a repeat of) §2/§2b. Its rationale: the structural
reorg is the wrong moment to discover a bad algorithm. A reinvented wheel or a numerically-fragile
DSP path should be eliminated — or consciously documented — **before** it is relocated,
re-namespaced, and split, not carried forward untouched into a tidier tree. "Something I can stand to
look at" is partly shape (§2/§2b) and partly *functional soundness* (§2c).

Q-W0 is **not executed by product-designer** — this doc *defines the wave and its scope*; the audit
itself is staff-engineer/DSP work. The wave's landed history lives in **`docs/ARCHIVE.md`**
("Q-W0 fix-now remediations" and "Phase Q — Quality: the decision record"), and its findings live in
**`docs/product/code-quality-audit.md`**; this section is the evidence-doc framing (the *why* and
the smell taxonomy), matching how §2/§2b frame the structural audits.

### 2c.1 Audit surfaces (the named targets)

1. **DSP / audio — a close eye on pitch** (Daniel's verbatim emphasis). Assess *algorithm quality* —
   correctness, artifacts, numerical robustness, interpolation quality, reinvented-wheel vs.
   established DSP technique — across:
   - **`src/vst/pitch_shift`** — the **hand-rolled OLA pitch-preserve** engine. Highest priority.
     Look at window function + overlap factor choice, phase coherence between frames, transient
     smearing and formant behavior, and buffer-edge handling. A hand-rolled OLA shifter is exactly
     the class of "reinvented wheel / poor-quality algorithm" Daniel wants scrutinized: is the
     technique sound, are the artifacts acceptable, is a better-established method (e.g. a
     phase-vocoder or WSOLA variant) warranted — and if the current approach is kept, is that a
     *documented* decision?
   - **`sampler_core`** — repitch ratio math, interpolation order/quality (linear vs. higher-order),
     loop-point-aware sustain crossfade behavior, and voice-stealing correctness (clicks or
     discontinuities on steal).
   - **`peaks`** — envelope min/max binning correctness.
   - **`wav_trim`** — the realtime-tail decay-scan threshold + truncate plan (numerical edge cases).
   - **capture / tail paths** — DSP-adjacent arithmetic in range/tail handling.
2. **Architecture smells (functional lens).** Duplicate code, reinvented wheels, poor abstractions,
   and leaky pure/shell boundaries — overlapping §2/§2b's territory but reporting the *functional*
   smell those audits did not target (a duplicated *algorithm*, not merely a duplicated
   *responsibility*; a `core/` module reaching a host type; algorithm math stranded untestable in a
   shell).
3. **Env-coupled-constant domain-modeling smells — a first-class category.** ANY value stored in a
   **frame / rate / DPI / tick-coupled** domain that should instead be stored **rate-free and
   resolved at the point of use** is a domain-modeling smell. The correct framing is *store rate-free,
   resolve at use* — **not** "rescale by the rate at the boundary." This is grounded in the
   load-bearing invariant that wall-clock times are stored as **rate-free SECONDS** resolved against
   the live project rate (`sample_map`), with **NO hardcoded sample rates in `src/`** (Daniel's
   standing ruling). **There was a prior incident on exactly this** — envelope times stored in the
   frame domain — which is why it is called out as its own smell category and not folded into
   "architecture smells." Sweep at least: envelope times, loop points, fade lengths, tail lengths,
   and any UI geometry constant that silently bakes in a DPI or a rate.

### 2c.2 Deliverable, triage, and the sub-gate

- **Deliverable:** a **written findings report** over the surfaces above — a committed doc,
  `docs/product/code-quality-audit.md` (Q-10, settled §2c.3), beside this framing.
- **Triage:** every finding is classified **eliminate-before-restructure** (fix-now) or
  **document-and-defer** (with a one-line rationale, so a deferral is a recorded decision, never a
  silent omission).
- **Where fixes land:** fix-now findings are remediated **in Q-W0**, or folded into the downstream
  wave that already opens the file (recorded per finding). They are **not** silently deferred into the
  structural waves — eliminations happen here or as folded-in remediation, so Q-W1+ inherits a
  functionally-sound tree.
- **Reshaping downstream:** Q-W0's findings may **add or reshape** Q-W1..Q-W6 points (an algorithm
  rewrite that changes a module's shape; a domain-modeling fix that changes a payload). Those reshapes
  are folded in before Q-W1 begins.
- **The sub-gate:** Q-W1 does not begin until Q-W0's **triage is complete and Daniel has signed off**
  on every finding's disposition. This is the entry gate to the whole structural reorg.

### 2c.3 Q-10 — where the findings report lives. SETTLED (Daniel, 2026-07-27): a committed doc.

The Q-W0 findings report is a **committed doc under `docs/product/`** — `code-quality-audit.md`,
beside the SOLID/naming audit this doc already holds. It travels with the tree, each finding's
disposition is reviewable in one place, and it matches the precedent set by §2/§2b living as
committed framing. The Q-W0 "Triage + report" step writes *this* file — the report's home is
explicit, not a placeholder.

- **Considered and set aside:** a tracked **issue list** (one issue per finding). Would fit if each
  finding needed independent lifecycle state (assignee, open/closed) driving work item by item. Set
  aside because the audit is a one-shot pre-reorg sweep, not an ongoing backlog, and a single
  reviewable doc reads better against the "stand to look at" bar.

### 2c.4 Q-11 — how deep pitch remediation goes. SETTLED (Daniel, 2026-07-27): defer to findings.

The remediation depth is **not pre-committed** — it is decided by what the Q-W0 audit actually
finds in the OLA pitch-preserve engine (`src/vst/pitch_shift`). The settled rule:

- **Default: document-and-defer.** Absent findings that matter, record the artifacts/limits as a
  known, documented trade-off and change nothing now — this keeps Phase Q a reorg.
- **Escalation, in order, only if the audit surfaces artifacts that matter for the tool's use:**
  weigh a **bounded fix** (tune window/overlap/edge handling within the existing OLA approach — no
  new dependency, no new module shape) **before** a **technique replacement**.
- **Technique replacement is a Daniel decision at triage time, not an automatic Q-W0 action.**
  Swapping in a stronger method (phase-vocoder / WSOLA) is a real DSP change that reshapes
  `pitch_shift` and would **spill a downstream Q-wave point** — so if the audit's findings point that
  way, Q-W0 surfaces the recommendation and Daniel makes the call; Q-W0 does not perform a technique
  replacement on its own authority.

---

## 3. Performance is a hard constraint (the guardrail, carried verbatim-in-spirit)

Daniel's stated non-negotiable: reorganize **without sacrificing actual performance.** The
reorg is directory / namespace / file-split — it is **zero runtime cost IF** the following
hold. These are acceptance criteria on every relevant point, not advice:

1. **Hot path — `peaks`** (`computeEnvelope` / `lastFrameAboveThreshold` over full PCM):
   **NO virtual dispatch, NO `peaks` interface, NO added header→TU indirection.** Keep
   `computeEnvelope` a **free function on `const std::vector<float>&`** so it inlines exactly
   as today. Relocating the file + namespacing it is fine; wrapping it in an abstraction is
   forbidden.
2. **Hot path — audition / preview:** splitting `panel_audition` into its own TU is fine —
   but the call must stay a **direct call-through, not virtual**.
3. **Hot path — realtime-capture tick:** keep the idle fast-path a **single pointer test.**
   The realtime lifecycle may move to its own TU (`realtime_lifecycle`) but the tick's
   branch shape must not change.
4. **JSON extraction is OFF all hot paths** — serialization runs at save/load, never per
   frame. Safe to abstract freely (this is *why* Q-W1 is the safe opener).
5. **`FxBypassGuard` runs per-capture, not per-frame** — keep it a **stack RAII** object when
   it moves out of `main.cpp`; do not heap-allocate or virtualize it.

**Net (the audit's own conclusion):** every recommended split falls on a **cold path** or
**preserves call/inline shape** on the two hot ones. The acceptance bar for the phase:
*if a split would add an indirection on a path in the list above, it is out of scope —
rework the split to avoid it, or drop it.*

---

## 4. The GATE — Phase Q starts only when the tree is quiescent (load-bearing)

**Phase Q is gated on the completion of ALL other scheduled and in-flight work.** State this
prominently; it is the single most important sequencing fact in the phase.

**Why the gate exists — merge-conflict blast radius.** Phase Q's whole nature is that it
touches **nearly every file in `src/`** (relocating into subdirectories, changing the
namespace of every header, splitting the four largest TUs). Meanwhile:

- **Phase S** lives on the **phase-s worktree**, is **not on dev**, and is a large body of
  work (a whole second VST3 build artifact + pure sampler core). Its branch is diffed against
  the *current* flat layout.
- **Phase L** has **L3** (VST editor + embed-strip restyle, gated on Phase S landing on dev)
  still to land — it touches the Phase S draw shells (`reasampler_editor` / `reasampler_embed`),
  which arrive on dev with Phase S. (L1/L2/L4/L5/L6/L7 have **already landed** — see
  `docs/ARCHIVE.md`; the once-listed "L2 pending" is stale and has been corrected here.)
- **D2** is **functionally complete** (D2-W1..W3-B landed; the only open item — a per-track
  lane-split panel indicator — is *explicitly deferred*, not a blocking residual). **M9** (slots)
  is **abandoned** (Daniel, 2026-07-27) — will not be built. D2 is named in the gate only so a
  future reactivation of its deferred panel indicator re-arms the "tree must be quiescent"
  condition; M9 is out and cannot re-arm it.

A structural reorg landing while any of these is mid-flight would force every in-flight
branch through a **rename-and-relocate-everything** merge — the worst possible conflict
class (every hunk moved, every namespace-qualified reference changed). The cost is not linear;
it is a combinatorial re-resolution of every open branch against a moved tree.

**The gate, stated as a rule (reconciled to reality, product-designer 2026-07-27):** Phase Q
does not begin until the tree is **quiescent**, with no large branch outstanding. As of
2026-07-27 the outstanding work is precisely:

1. **Phase S** — merged to dev (currently on the phase-s worktree; the large second-artifact
   branch, the dominant gate item).
2. **Phase L L3** — merged to dev (the VST restyle; itself gated on Phase S, so it lands after
   Phase S reaches dev). **L2 is already landed** — the earlier "L2 + L3" wording was stale.
3. **D2** — confirmed complete or its deferred indicator explicitly re-deferred. It is
   functionally complete today; this line stays only so that if the deferred panel indicator is
   picked up as active work, it re-arms the quiescence condition.
4. **M9** — **abandoned** (Daniel, 2026-07-27). This gate condition is permanently satisfied;
   M9 will not be reactivated.

Restated as the plain readiness target Daniel named: **"when Phase S and L3 are finished."**
Phase Q is the *last* structural pillar precisely because it reshapes the ground every other
pillar stands on. Landing it early would tax every subsequent phase; landing it last taxes
nothing.

*(Sequencing corollary: because the gate is "everything else first," Phase Q's own internal
sequencing —§5— is about risk-ordering the reorg, not about racing other phases.)*

---

## 5. Sequencing shape — big-bang vs. incremental (feeds the waves)

**Settled shape: incremental, risk-ordered waves, each independently landable and
CTest-green.** A big-bang "rename everything in one commit" is rejected — it defeats the one
safety property the CMake seams give us (green CTest at every step) and produces an
un-reviewable diff. Instead, the reorg is decomposed so each wave is a safe, reviewable,
individually-revertible step:

- **W1 — the safe, high-leverage opener (zero-god-module-risk):** extract the pure `json`
  core and delete the four duplicate `Parser`s, *plus* impose the `core/ shell/ app/`
  directory layout and sub-namespaces on the modules that **don't** need splitting (the 30
  clean pure libs + the clean shells). This is pure relocation + one genuine
  encapsulation win, no god-module surgery. Lowest risk, highest legibility payoff, done
  first.
- **W2–W5 — the four god-module splits, one per wave**, ordered by risk (the audit's own
  S-leverage ranking): `bank_panel` (W2, biggest), `main.cpp` (W3), `actions.cpp` (W4,
  includes deduping bank verbs against `bank_panel`), `persist.cpp` (W5, isolates the
  single file-deletion authority). Each god-module split is its own wave because each is a
  large, independently-reviewable change with its own verification surface.
- **W6 — the OCP registration-table** (close the ~350-line hand-written registration blocks)
  and any fat-header (I) splits not already resolved. Sequenced last because it depends on
  the `main.cpp` split (W3) having already isolated the registration code.

**Where the naming work (§2b) rides — renames follow relocations, no dedicated wave (Q-7).**
A rename is cheapest when the file is already moving or splitting, so naming does **not** get its
own wave; each fix rides the wave that already touches its file:

- **W1 absorbs** the collision fixes (§2b.2): the survivor `Parser` becomes `json::Parser` (or the
  Q-8 `Reader`/`Writer` pair) as the four copies collapse; and every clean pure-UI type
  (`FooterRect`/`ButtonRect`/`Selection`/`CellRect`) gets its `ui::` (etc.) home as the modules
  relocate — retiring the `footer_bar.h` hand-collision "NAME NOTE." W1 already re-namespaces the
  clean modules, so the sub-namespace half of every §2b fix lands here for free.
- **W1 also carries** any *pure-model* class rename Q-8 settles (e.g. `BankIndex`→a name matching
  `bank_model`), because those modules relocate in W1 and a class rename is a mechanical
  find-replace verified by the module's own test executable.
- **W2 absorbs** the `bank_panel`-side names as the god-module splits into `panel_*`.
- **W3 absorbs** the `capture`/`realtime` shell↔core word-order fix (Q-9) — the realtime lifecycle
  is *already* being hoisted in W3, so aligning `capture_realtime`/`realtime_record` naming is a
  rider on a move that is happening regardless.

The rule (Q-7): **no rename lands on a file that is not otherwise being touched by its wave.** A
rename that would force a file to move *only* to be renamed is deferred — the churn/legibility
trade isn't worth a standalone edit. This keeps the naming dimension inside the same
"green-CTest-at-every-point, minimal-diff-per-wave" discipline as the rest of Phase Q.

**Why incremental beats big-bang here, concretely:** the CMake per-module static-lib + per-
module test-executable structure means a file move + namespace change is *mechanically*
verifiable — `ctest` is green or it isn't, at every point. That property only pays off if the
reorg is *in points*. One giant commit throws the property away. Incremental is not just
safer; it is the only shape that uses the seams the architecture already gives us.

---

## 6. Forks — the decision record

**Fork Q-1 — namespace letter. SETTLED (this doc): `Q` (Quality).**

- **Settled:** the phase is namespaced **`Q` (Quality)**. M / D / B / R / V / S / L are all
  taken (Milestone / Design / Bank / Reclaim / Version / Sampler / Look-and-feel).
- **Considered and set aside:** `O` (Organization) — rejected on two grounds: (1) the glyph
  `O` reads ambiguously against zero in point ids (`O1`, `O10`), a real legibility cost in a
  phase *about* legibility; (2) "Organization" undersells the charter — this phase is
  measured against a **quality bar** Daniel set (Vital), and the reorg is the *means*, not
  the end. `Q` names the end.
- **Reasoning:** `Q` is unambiguous, unused, and reads sensibly ("Phase Q — Quality"). The
  point-id family is `Q1 … Qn` with wave prefixes `Q-W1 … Q-W6` matching the house
  wave-naming (cf. `D2-W1`, `ps-w6`, `pL-w2`).

**Fork Q-2 — JSON extraction in scope? RECOMMEND: yes, and it is the W1 opener.**

- **Recommendation:** **in scope, and first.** The 4× duplicated `Parser` is the single
  largest DRY+SRP violation (§2.1), it is entirely **off the hot paths** (§3.4, safe to
  abstract freely), and it is the highest-leverage single change in the audit. Extracting a
  pure `core/json` module and deleting the four copies is the ideal low-risk opener — it
  proves the wave discipline (relocate + encapsulate, CTest-green) before any god-module
  surgery.
- **Alternative considered:** defer JSON to a later, separate cleanup. Rejected — it is the
  cheapest, safest, highest-payoff move; deferring it wastes the opener slot on pure
  relocation with no encapsulation win.
- **Watch (the audit flags it):** guard the `Parser` name-unification against cross-lib
  collisions when the four copies merge into one; and mind `Sample` vs `AudioSample` when
  sub-namespacing (§Q-5 collision note).

**Fork Q-3 — directory naming: `core/ shell/ app/` vs a Vital-style subsystem-first tree.
RECOMMEND: `core/ shell/ app/` as the top split, subsystem dirs beneath `core/`.**

- **Recommendation:** top-level by the **load-bearing discipline** (`core/` = pure/testable,
  `shell/` = REAPER-facing, `app/` = the entry TU), then **subsystem dirs beneath** — the
  audit's proposed map: `core/model/ core/view/ core/capture/ core/audio/ core/ui/
  core/reclaim/ core/version/ core/json/`, and `shell/capture/ shell/panel/ shell/view/
  shell/persist/ shell/actions/`, with `app/main.cpp`.
- **Why this over pure-Vital (subsystem-first, e.g. `model/ capture/ ui/` at top):** the
  **pure/shell split is ReaSampler's most load-bearing invariant** — it is CMake-enforced and
  it is the thing that keeps the core unit-testable outside the DAW. Making it the *top* level
  of the directory tree makes the invariant **structurally visible and hard to violate** (a
  file's directory tells you instantly whether it may touch a REAPER type). Vital has no
  equivalent pure/host split to protect, so its subsystem-first tree is right *for Vital*;
  `core/ shell/` is the ReaSampler-native reading of the same "directory = architecture"
  lesson. Subsystem grouping still happens — one level down — so we get both readings.
- **Alternative:** flat subsystem-first (`model/ view/ capture/ audio/ ui/ …`) with the
  pure/shell distinction living only in namespaces. Rejected: it demotes the most important
  invariant from *structure* to *convention*, which is exactly the drift Phase Q exists to
  reverse.

**Fork Q-4 — sub-namespace, or sub-directory only? RECOMMEND: both — sub-namespace to match
the sub-directory.**

- **Recommendation:** granular sub-namespaces mirroring the directories:
  `reasampler::model`, `reasampler::view`, `reasampler::capture`, `reasampler::audio`,
  `reasampler::ui`, `reasampler::reclaim`, `reasampler::version`, `reasampler::json`. Directory
  and namespace agree, so a symbol's home is unambiguous from either.
- **Why:** namespaces are the *code-visible* half of the "make the architecture legible" goal
  (directories are the filesystem half). Sub-dirs without sub-namespaces leaves every symbol
  still in one flat `reasampler::` soup — half the win. Vital's own headers group by concern;
  matching namespace-to-directory is the standard C++ reading of that.
- **Cost (name it):** sub-namespacing is the change with the **widest edit surface** — every
  qualified reference across TUs updates. This is precisely why the GATE (§4) matters and why
  W1 does the namespace move on the *clean* modules first (mechanical, no logic change), with
  the god-module splits (W2–W5) namespacing their own new TUs as they land.
- **Collision watch (audit):** `Sample` (bank_model) vs `AudioSample` (peaks alias) and the
  unified `Parser` must not collide once sub-namespaced — resolve by their new
  `model::` / `audio::` / `json::` homes.

**Fork Q-5 — how aggressive the god-module split? RECOMMEND: split to the audit's named seams,
no finer.**

- **Recommendation:** split each god-module along the **exact seams the audit names** and
  stop there:
  - `bank_panel` → `panel_render` / `panel_thumbnails` / `panel_audition` / `panel_input` /
    `panel_bank_ops` / `panel_window`.
  - `main.cpp` → hoist `capture_orchestrator` / `scope_resolve` / `realtime_lifecycle`,
    leaving `main` = API pointers + entry + dispatch.
  - `actions.cpp` → `design_view_actions` / `bank_actions` / `prune_action`, deduping the
    bank verbs against `bank_panel`'s `panel_bank_ops`.
  - `persist.cpp` → `session` / `ext_state_io` / `prune_fs` (**isolating the single
    file-deletion authority** into `prune_fs`).
- **Why stop there:** the seams are already validated by the audit and correspond to real
  responsibilities. Splitting *finer* (one file per function) would trade a god-module for a
  fragmentation problem — the opposite failure. "Something Daniel can stand to look at" is
  well-factored, not atomized.
- **Alternative (lighter):** split only the two worst (`bank_panel`, `main.cpp`), leave
  `actions`/`persist` as-is. Rejected: `persist`'s buried file-deletion authority and
  `actions`'s duplicated bank verbs are real hazards worth resolving while the tree is open;
  doing them now (behind the gate) is cheaper than a second reorg later.

**Fork Q-6 — the OCP registration-table (W6): in scope or deferred? RECOMMEND: in scope, last.**

- **Recommendation:** **in scope as the final wave.** The ~350-line hand-written registration
  blocks are a genuine OCP wart (every new action edits 4 parallel places); a registration
  table closes it. Sequenced **last** because it depends on the `main.cpp` split (W3) having
  isolated the registration code — you can't table-ify code you haven't first extracted.
- **Alternative:** drop it — it's OCP, not the SRP focus of the phase. A reasonable trim if
  Daniel wants Phase Q strictly scoped to the reorg. Kept in with a leading recommendation
  because, once W3 has hoisted the registration code, tabling it is a small, high-legibility
  finish — but it is the most droppable point if the phase needs narrowing.

**Fork Q-7 — is naming its own wave, or does it ride the relocation waves? RECOMMEND: rides the
waves; no dedicated naming wave.** SETTLED-by-structure once Q-3/Q-4 are settled.

- **Recommendation:** naming fixes ride the wave that already relocates or splits the file (§5),
  under the rule *no rename lands on a file the wave isn't otherwise touching.* A rename is nearly
  free during a relocation (the file is open, the diff is already large, the module's own test
  executable verifies it) and near-pure-churn as a standalone edit. Because Q-3 (directories) and
  Q-4 (sub-namespaces) already move and re-namespace every file, the *collision* half of the
  naming audit (§2b.2) is resolved by the namespace split with zero extra renames — the sub-
  namespace *is* the fix. Only the genuine *class/module renames* (Q-8/Q-9) add symbol churn, and
  those are scoped to files already in motion.
- **Alternative considered:** a dedicated final "naming pass" wave (Q-W7). Rejected: it would
  re-open files W1–W6 just closed, producing exactly the churn-without-relocation the rule forbids,
  and a diff that touches everything again defeats the per-wave reviewability property.
- **This makes Q-7 not really a judgment call once Q-3/Q-4 are settled** — it is the forced
  consequence of "renames are cheapest during relocation." Recorded as a fork only because Daniel
  might still want naming called out as a first-class deliverable rather than folded silently into
  the reorg waves; if so, the plan *names* the riders per wave (it does, §5) without adding a wave.

**Fork Q-8 — how far to push *class/module* renames (beyond the free namespace fix)? RECOMMEND:
fix the two that actively mislead; leave the merely-quirky.** Daniel's to call.

- **Recommendation (leading):** rename only where a name *actively misleads* a reader, and stop:
  - **`BankIndex` → a name matching `bank_model`** (§2b.3.1) — the file/class word-mismatch is the
    worst offender (`bank_model.h` owns `class BankIndex`; the two share no word). Two shapes:
    (a) rename the class to `BankModel` (file = class, matches `ViewModeModel`/`BankBook`); or
    (b) rename the *file* to `bank_index.{h,cpp}` (class stays `BankIndex`). **Prefer (a)** — it
    makes the model family read on one principle (`BankModel`/`BankBook`/`ViewModeModel`, all
    `<noun>Model`/`<noun>Book`), and it is a class rename W1 verifies via `bank_model_tests`.
  - **The unified JSON `Parser`** (§2b.2.1) — make it a `json::Reader` + `json::Writer` pair (or
    keep `json::Parser` if extraction stays parse-only). This is a *new* module's naming, decided
    at W1 mint time, so it costs nothing to get right.
- **Leave quirky-but-harmless:** `Book`→`Bank`→`Index` containment (§2b.3.2 — evocative, learnable),
  `Sample`/`AudioSample` (§2b.2.3 — the namespace split already de-collides them; renaming
  `AudioSample`→`Pcm`/`PcmSample` is optional polish), `guid_diff`/`GuidBaseline`, `MinMax`,
  `KitBox`. Renaming these is pure taste with no misleading-a-reader payoff — the "stand to look
  at" bar is met by the namespace homes alone.
- **Alternative (more aggressive):** normalize the *entire* model family to one suffix
  (`BankModel`/`BankBookModel`/`ViewModeModel`/`OwnedManifestModel`) and rename `AudioSample`→
  `PcmSample`. Rejected as the lead because it renames things that already read fine, adding symbol
  churn (every call site, every test) for marginal legibility — but it is a coherent option if
  Daniel wants the model family *rigidly* uniform. Kept on the table as Daniel's call.
- **Alternative (minimal):** do zero class renames; let the sub-namespaces (Q-4) carry the whole
  naming win. Defensible — it is the lowest-churn, lowest-risk reading, and the namespace split
  genuinely resolves every *collision*. Rejected as the lead only because `bank_model`/`BankIndex`
  is a standing "what is this file" cost the reorg is uniquely cheap to fix.

**Fork Q-9 — align the `capture_realtime` / `realtime_record` shell↔core word order? RECOMMEND:
yes, during W3.** Daniel's to call.

- **Recommendation:** align the pair to the house shell↔core convention (`drag_out` ↔
  `drag_out_win`: shared stem, suffix marks the shell). The pure planner `realtime_record` and its
  shell `capture_realtime` invert word order for one feature — the tree's clearest shell/core drift
  (§2b.3.3). W3 is *already* hoisting the realtime lifecycle, so aligning the names is a rider on a
  move that happens anyway. Two shapes: (a) core `capture_realtime` / shell `capture_realtime_shell`
  (stem = `capture_realtime`, matches the `capture` offline pair); (b) core `realtime_record` /
  shell `realtime_record_shell`. **Prefer (a)** — it nests the realtime naming under `capture_*`
  alongside the offline path, so the whole capture subsystem reads on one stem.
- **Alternative:** leave it — the inversion is cosmetic and both names are individually clear.
  Reasonable if Daniel wants W3 kept strictly to the god-module split with no adjacent renames. The
  fix is cheap enough (W3 touches these files regardless) that the lead is to take it, but it is
  the most droppable of the three naming forks.

---

## 7. What Phase Q does NOT change (guardrails)

- **The pure-core / shell split is strengthened, never dissolved.** The whole point is to
  make it *more* legible (top-level `core/` vs `shell/`). No file moves across the boundary;
  no core file gains a REAPER type; the CMake per-module test executables stay green.
- **Every precision invariant holds.** Null-test, bit-identical repeats, non-destructive
  capture, exact bounds, relative-paths-only — none is code Phase Q rewrites. `FxBypassGuard`
  (the precision-critical guard) *moves* out of `main.cpp` but stays a stack RAII object with
  identical behavior (§3.5).
- **Capture ≠ placement.** No `Run*` / capture-orchestrator path may gain an `InsertMedia`
  call during the split. The load-bearing rule is invariant under reorganization.
- **The single file-deletion authority stays one obvious module.** `persist`'s `prune_fs`
  split *concentrates* the deletion authority (`SHFileOperationW`) into one named module —
  it must not spread it. This is a safety property the reorg improves, never dilutes.
- **Relative-paths-only in the persisted index** — untouched (a data invariant, not a
  structural one).
- **Performance** — §3 is a hard acceptance bar: no hot-path indirection, ever.
- **No behavior change.** Phase Q is a pure structural refactor. If a point changes observable
  behavior, it has exceeded its charter and must be reworked. The test suite passing
  unchanged **is** the proof of correctness (green CTest at every point).

---

## 8. Sources

- Vital source structure — `github.com/mtytel/vital`, `src/` subsystem tree
  (`common/ synthesis/ interface/ plugin/ headless/ standalone/`) and the nested
  `synthesis/` functional sub-dirs (`synth_engine/ modulators/ filters/ effects/ producers/
  framework/ lookups/ utilities/`). Read from the repository tree, 2026-07-26. Vital is
  GPLv3 — the borrowed artifact is the **structural pattern**, not code.
- The SOLID-compliance audit (§2) — grep-verified staff-engineer analysis of the actual
  ReaSampler `src/` tree (45 files / ~19,800 LOC), 2026-07-26. The evidence base for every
  reorg move and the performance guardrails (§3).
