reasampler/docs/product/removal-and-prune.md

# Removal & prune — product notes

Framing, rationale, and open forks behind the two missing removal capabilities:
**sample-remove** (a sample-level index verb) and **prune** (the file-lifecycle
path CONTEXT.md keeps forward-referencing but never scoped). The tickable spec
lives in `PLAN.md` (Phase B point B5 for remove; **Phase R** for prune) and the
authoritative technical detail in `CONTEXT.md` (§Sample removal, §Prune — file
lifecycle). This doc holds the *why* — the workflow, the guardrails, the
index-vs-file boundary, and the forks that need a Daniel decision.

Status: framed by product-designer (2026-07-23); **all five forks settled by Daniel
(2026-07-24)** — R-A this-bank-primary, R-B batched REAPER undo points
(Phase-B-wide), R-C trash-preferred-with-unlink-fallback, R-D owned-file manifest
(seam lands early in Phase B / capture), R-E manual action + panel button. The
decisions are folded into the fork sections below and into the B5 / Phase R spec
prose in CONTEXT.md and the tickable points in PLAN.md.

---

## The one boundary that governs everything: index vs. file

ReaSampler already draws a hard line, stated repeatedly in CONTEXT.md: **a bank
operation touches the *index*, never the *file*.** Move, copy, evacuate, and
delete-bank are all index-only; files persist on disk "until prune." Every
removal capability below sits on exactly one side of that line, and keeping the
two verbs on opposite sides is the whole design.

- **Sample-remove drops an index entry.** It is the sample-level sibling of the
  bank verbs — move/copy/evacuate all keep the sample *somewhere*; remove is
  "drop this entry outright." It is **index-only, non-destructive to the file**,
  and — exactly like a plain delete-bank of a non-empty bank — it can *create*
  an orphan when it removes the last index reference to a file. It sits on the
  **same side of the line as every existing Phase B op.**

- **Prune deletes files off disk.** It is the *only* operation in the entire
  system that removes bytes. It reconciles the physical bank folder against the
  union of all bank indices and reclaims files referenced by no bank. It sits on
  the **file side of the line, alone.**

So the crisp statement, worth putting in the spec verbatim:

> **Remove creates orphans; prune reclaims them.** Sample-remove and delete-bank
> drop index entries and may leave a file referenced by nothing. Prune is the
> single path that turns such an orphan back into free disk space. No other
> operation deletes a file; prune deletes *only* files no index references.

This is why they are two different scope objects (Phase B vs. Phase R), even
though a naive reading ("both are 'delete' verbs") would lump them together.

---

## Sample-remove — the missing sample-level verb

### What the user is doing

The user has a sample they no longer want in a bank (or in the pool): a bad take,
a duplicate they don't want collapsed, a sample they filed into "Drums" by
mistake. Today they can *relocate* it (move/copy/evacuate) but they cannot drop
it. Remove is the "get this out of here" verb. Two intents hide inside it, and
the distinction is a fork (R-A below):

1. **Remove from *this* bank** — drop the entry from the bank the user is looking
   at, leaving any copies in other banks untouched. (If the sample was copied
   into "Drums" and also lives in the pool, remove-from-Drums leaves the pool copy
   alone.)
2. **Remove from *everywhere*** — drop every index entry for this sample across
   all banks in one act ("purge this sample from the library").

### Reconciling with existing invariants

- **Collapse-by-hash:** unaffected. Remove operates on a specific `Sample` entry
  in a specific `BankIndex` (the `remove` primitive `bank_model` already has, per
  CLAUDE.md — B5 exposes it, it does not add it). Because dedup is per-bank and
  cross-bank dedup is deliberately *not* enforced, "remove from this bank" and
  "the same hash still lives in another bank" coexist cleanly — that is the same
  coexistence copy already relies on.
- **Files-are-never-deleted-by-a-bank-op:** upheld. Remove is index-only, exactly
  like move/copy/evacuate/delete-bank. When remove drops the *last* reference to a
  file, it produces the **same orphaned-until-prune state** a non-empty
  delete-bank already produces — a designed state, not a new hazard class. The
  file is reclaimed later by prune, never by remove.
- **Pool privileges:** the pool cannot be *deleted, renamed, or evacuated*, but
  individual samples **can** be removed from the pool — otherwise the pool would
  become a roach-motel (samples check in, never leave except by moving to a named
  bank). Remove-from-pool is allowed; it is the pool's own "drop this sample"
  verb. (The pool-as-container privilege is untouched; only its *contents* are
  removable.)
- **Non-destructive:** remove mutates only index + ext-state, touches no file and
  no timeline item — the Phase B non-destructive guarantee extends to it verbatim.

### Guardrails

Remove is *less* dangerous than it first looks, because it never deletes a file —
the bytes survive on disk until an explicit prune. So the recovery story is: an
accidental remove loses the *index entry*, not the audio. But there are two
sharpnesses to guard:

- **Last-reference remove is the orphan-maker.** Removing a sample that exists in
  only one bank orphans its file (until prune). This is the same footgun as
  non-empty delete-bank, and it deserves the same treatment: **confirm when the
  remove drops the last index reference** ("Remove 'kick_03'? It is in no other
  bank — its file will remain on disk until pruned."). A remove of a sample that
  still lives in another bank is cheap and reversible-in-spirit (re-copy it back)
  and need not confirm. This makes the confirmation *earned* by actual risk rather
  than fired on every remove.
- **Undo.** REAPER's own undo stack does not natively cover ext-state index
  mutations, so this is a Phase-B-wide decision (fork R-B, **settled**): bank/index
  mutations integrate into REAPER's undo system as **batched undo points**
  (`Undo_BeginBlock` / `Undo_EndBlock`), so one bank operation is one Ctrl-Z. Remove
  is where the gap first bites — it is the first verb whose *only* effect is
  destruction of an index entry with no relocation — but the fix is shared by every
  Phase B verb.

### Where it lives

Remove is a `bank_book`/`BankIndex` verb (pure), a bindable `actions` entry, and a
`bank_panel` affordance on the current selection — the exact three-layer shape
every Phase B verb already takes. That is why it belongs **in Phase B as B5**, not
in a phase of its own: same modules, same pattern, same side of the index/file
line. It is the verb Phase B forgot, not a new pillar.

---

## Prune — the file-lifecycle path CONTEXT.md kept promising

### What the user is doing

The user has been working for a while: capturing, re-capturing (M10), deleting
banks, removing samples. Each of those left files on disk that no index references
any more — the "orphaned-until-prune" state the multi-bank spec designs in on
purpose. Over a long project the bank folder accumulates dead `.wav` files that
cost disk and clutter. **Prune is the reclaim pass**: "sweep the bank folder,
delete the files nothing references, tell me what you reclaimed."

This is the path CONTEXT.md forward-references in at least four places ("files
persist on disk until prune," "the capture/prune path reclaims it") but never
scopes. It is a real, promised capability with **no phase, no module, no point**
— a dangling reference the plan has to make good on.

### The load-bearing precedent: prune-on-reconcile already exists for modes

ReaSampler already shipped this exact shape once. Design View's `view_mode_model`
has **`ViewModeModel::reconcile(liveGuids)`** — a pure function fed the live set
(the tracks that still exist), returning the residual membership entries to drop
(CONTEXT.md §Design View: "prunes orphaned snapshots on every toggle/load;
tolerates unknown/stale GUIDs (prune on reconcile)"). Prune is the **file-pool
mirror of that pure pattern**:

> `reconcile(liveGuids)` reconciles *membership entries* against *live tracks*.
> Prune reconciles *files on disk* against *referenced files* (the union of every
> bank's index). Same shape — feed the pure core the live set, get back the
> residuals — one level down (files instead of GUIDs).

This is the "mirror the existing pure pattern" move the whole codebase is built
on (`bank_model`, `view_mode_model`, `bank_book` are all the same pure-registry
shape). The **pure part of prune** — "given the set of files on disk and the set
of files referenced by the book, compute the orphan set" — is a REAPER-free,
unit-testable function that belongs with the pure cores. Only the two ends are
shell work: *enumerating* the bank folder (filesystem I/O) and *deleting* the
orphans (filesystem I/O). Keep the decision (which files are orphans) pure and
tested; keep the I/O thin. This is the same pure/shell split as everything else.

### Reconciling with existing invariants

- **This is the one place the "files are never deleted" rule is *intentionally*
  broken — and it must be the *only* one.** Every other invariant says "no bank op
  deletes a file." Prune is explicitly not a bank op; it is the file-lifecycle op,
  and its entire job is deletion. The spec must state this asymmetry loudly so a
  reviewer never reads prune as violating the bank-op rule: **prune is the sole
  file-deletion authority; a bank op that deletes a file is still a bug.**
- **Referenced-set is the union across *all* banks, pool included.** A file is an
  orphan iff **no** bank in the book references it. Because copy means one file can
  be referenced by several banks, prune must union references across the whole
  book before deciding — deleting a file still referenced by "Drums" because it
  left the pool would be catastrophic. The referenced-set computation is the
  safety-critical core and the thing to test hardest (the null test of prune:
  *prune never deletes a file that any index references*).
- **Relative-paths-only / project-relative resolution:** prune enumerates and
  deletes within the project bank folder using the same M4 project-relative path
  resolution the index uses. It must resolve the *same* way the index does, or it
  could mis-identify orphans across a Save-As relocation. Prune runs against the
  *resolved current* bank folder, never a stale absolute path.
- **Collapse-by-hash:** irrelevant to prune's decision (prune works on files and
  references, not hashes) but worth noting: two index entries that collapsed onto
  one file mean one file, multiple references — prune's union handles this for
  free (the file is referenced, so it survives).
- **Determinism / bit-identical / null-test (capture):** untouched — prune sits
  below the capture path entirely, same as multi-bank.

### Guardrails — this is the genuinely destructive act

Prune deletes real bytes irreversibly (a deleted `.wav` is gone unless it went to
an OS trash — see fork R-C). It earns the strongest guardrails in the product:

- **Dry-run first, always.** Prune should *report before it deletes*: "12 files
  (34 MB) are referenced by no bank. Delete them?" A prune that silently sweeps is
  unacceptable for an irreversible file-delete. The dry-run (compute-and-report,
  the pure core with no deletion) is arguably the *primary* surface, and the
  actual deletion is the confirmed second step. This mirrors how every safe
  garbage-collector / disk-cleaner works (npm prune --dry-run, git gc reporting,
  Lightroom's "delete rejected photos" confirmation).
- **Confirm with a manifest.** The confirmation names the count and the reclaimed
  size and — for a small set — the files. The user approves a *specific* deletion,
  not an abstract "clean up."
- **Never touch a referenced file, and never touch a non-bank file.** Prune's
  scope is *files in the bank folder that the book once owned and no longer
  references*. A file that was never a bank file (a user dropped something into the
  folder by hand) is out of scope — prune should only reclaim files it can
  attribute to the bank system's own leavings, not act as a general folder cleaner.
  (This is a fork — R-D — because "how does prune know a file was ever ours"
  depends on whether we track a manifest of owned files.)
- **Recoverability via the OS trash (fork R-C, settled: trash-preferred).** Prune
  routes deletions to the platform recycle bin / trash where a portable move-to-trash
  is available, so an accidental prune is recoverable outside the app; it falls back
  to unlink (behind the dry-run + confirm guardrail) only where the platform affords
  no portable trash. Whether SWELL / the platform layer gives us that portable "move
  to trash" is a to-verify per platform — but the *default* is the safest deletion
  the platform affords, and "delete where possible" means recoverable-trash-preferred,
  never plain unlink-by-default.

### Where it lives — and why it is its own phase, not a Phase B point

Prune is **not** a Phase B point. Three reasons it earns its own lettered phase
(proposed **Phase R — Reclaim / file lifecycle**):

1. **It is a different pillar.** Phase B is the *bank container* pillar
   (index-only, non-destructive, above the file). Prune is the *file lifecycle*
   pillar (the one path that deletes files). CONTEXT.md already names it as a
   separate concern every time it says "the capture/**prune** path" — file
   lifecycle is spoken of as its own thing, owned by neither the capture nor the
   bank layer. Giving it its own phase matches how the spec already talks about it.
2. **It serves more than Phase B.** Orphans are produced by delete-bank *and*
   sample-remove (B5) *and*, arguably, by M10 re-capture superseding an old file,
   *and* by Design View's deleted-track residual files if any exist. Prune is the
   downstream reclaim for *all* file-orphaning paths, not a Phase-B-internal
   cleanup. A capability multiple pillars forward-reference should not be nested
   inside one of them.
3. **It carries a new risk class and new invariants.** Every phase so far has been
   non-destructive-to-files by construction. Prune is the first phase that deletes
   files, so it needs its own invariant section (the prune null test, the
   referenced-set union, the dry-run guarantee, trash-routing). Burying that under
   a Phase B checkbox would hide the one genuinely destructive capability in the
   product inside a phase whose headline invariant is "non-destructive." The
   dissonance alone argues for separation.

Lettered, per the established convention (`M` = capture pillar, `D` = Design View,
`B` = Banks): **`R` = Reclaim.** It reads correctly — Phase R is "the file
lifecycle pillar," not "a bank sub-step."

**Sequencing:** Phase R depends on B1/B2 (it needs the multi-bank book to compute
the referenced-set union across all banks) and on B5 conceptually (sample-remove
is a primary orphan-producer, so prune is most useful once remove exists), but it
does not depend on the B3/B4 *UI*. It can land any time after the book exists;
practically it should follow B5 so the two removal verbs ship as a coherent pair
(remove-then-prune is the workflow, mirroring evacuate-then-delete).

---

## Settled forks (Daniel, 2026-07-24)

### Sample-remove

**Fork R-A — remove scope. SETTLED: THIS BANK (this-bank-primary).**
Remove drops the entry from the bank in view only, leaving copies in other banks
untouched. This is the core (and shipped) verb.
- *from-this-bank* is the composable primitive (it is literally the
  `BankIndex::remove` the model already has); "from everywhere" is then "remove
  from each bank that holds it," which the user can also achieve by removing per
  bank. It matches the partition mental model (fork 3): a sample is in one bank, so
  remove-from-this-bank usually *is* remove-from-everywhere.
- **Decision:** ship **from-this-bank** as B5's core verb and the only surfaced
  affordance. Keep the `scope: this-bank | all-banks` seam in the action signature
  as designed, but **this-bank is the settled default and the only shipped verb**;
  all-banks stays a *latent parameter*, not a surfaced convenience — it can be
  promoted later behind that seam without a rewrite if the copy workflow proves to
  scatter samples in practice. (Settled 2026-07-24, confirming the product-designer
  lean; from-everywhere is explicitly *not* elevated to a co-equal verb now.)

**Fork R-B — undo model for index mutations (Phase-B-wide, surfaced by remove).
SETTLED: BATCH UNDO POINTS (option (iii) — REAPER-integrated, batched).**
REAPER's undo stack does not natively cover `"reasampler"` ext-state index
mutations, so move/copy/evacuate/delete-bank/remove needed an undo story. Daniel
chose to integrate bank/index mutations into **REAPER's own undo system as batched
undo points** — the `Undo_BeginBlock` / `Undo_EndBlock` direction — batching the
related index mutations of one bank operation into a single undo point, so a bank
operation is one Ctrl-Z. The considered alternatives:
- *(i)* Accept no undo (rely on confirmations + files surviving) — **rejected**, too
  weak once remove destroys an index entry with no relocation.
- *(ii)* A ReaSampler-internal single-snapshot "undo last bank change" — **rejected**
  in favour of the more integrated (iii); the earlier product-designer lean toward
  (ii) was overridden.
- *(iii)* **CHOSEN** — hook REAPER's undo system properly, batching related index
  mutations into single undo points.
- **Scope — Phase-B-wide.** This is decided for **all of Phase B at once**, and it
  **retro-touches B1–B4**, not just B5: every index verb (create/rename/reorder/
  delete-bank, move, copy, evacuate, remove) wraps its mutation in an undo block.
  Surfaced with B1's open questions, not only at B5.
- **Must-verify-before-build (carry-forward).** The whole approach depends on
  `"reasampler"` ext-state mutations participating correctly in
  `Undo_BeginBlock`/`Undo_EndBlock` undo blocks. **Confirm against
  `vendor/reaper-sdk` that ext-state changes are captured/restored by REAPER undo
  blocks before building** — if they are not, the batched-undo-point approach does
  not hold and the decision must be revisited. Flagged as a hard prerequisite.
  (Settled 2026-07-24.)

### Prune

**Fork R-C — deletion mechanism: unlink vs. OS trash. SETTLED: TRASH-PREFERRED,
UNLINK FALLBACK.** Prune routes deletions to the platform recycle bin / trash
(recoverable outside the app) **wherever the platform affords a portable
move-to-trash**, and falls back to unlink — behind the dry-run + confirm guardrail —
only where it does not. Trash is the settled default; "delete where possible" reads
as *recoverable-trash-preferred*, never plain unlink-by-default.
- **To-verify (carried, per platform):** whether a portable move-to-trash exists via
  SWELL, or must be hand-rolled per platform — Win `SHFileOperation`/`IFileOperation`,
  macOS `NSFileManager trashItemAtURL:`, Linux XDG trash spec. The move-to-trash
  surface is an explicit to-verify before use, not an assumed capability. (Settled
  2026-07-24.)

**Fork R-D — orphan attribution: manifest-tracked vs. index-diff vs.
folder-sweep. SETTLED: OWNED-FILE MANIFEST — and the seam lands EARLY (Phase B /
capture).** The book tracks the set of files it has created; prune reclaims
`(owned ∩ on-disk) − referenced`. The considered alternatives:
- *(i) folder-sweep* — reclaim every unreferenced file in the folder. **Rejected** —
  it would delete a user's hand-placed file, violating "only reclaim our own
  leavings."
- *(ii) index-diff only* — record a file's identity when its *last* index reference
  drops and prune only that set. Safe but partial (misses files orphaned outside a
  tracked drop path). Not chosen.
- *(iii) owned-file manifest* — **CHOSEN.** Safest and most general: distinguishes
  "our orphan" from "user's file" and from "already-gone."
- **Seam lands early (accepted design-the-seam-now call).** The manifest is cheap to
  maintain from capture onward but a **backfill cliff** to reconstruct later — you
  cannot tell, after the fact, which folder files were ever ours. Daniel accepted the
  recommendation to **start the owned-file manifest at capture time NOW, in Phase B,
  even though prune (which consumes it) ships in Phase R.** So: **capture writes each
  file it creates into an owned-file manifest persisted in the `"reasampler"`
  ext-state**, and Phase R's R1/R2 *consume* that manifest. The exact persistence
  shape — a sibling ext-state key vs. folded into the `banks` blob — is a small
  residual to settle at build; the **manifest-now decision is firm**. (Settled
  2026-07-24; the up-front point is added to Phase B / the capture path in PLAN.md.)

**Fork R-E — prune trigger: manual-only vs. offer-on-orphaning vs. periodic.
SETTLED: MANUAL ACTION + PANEL BUTTON.** Prune runs via a bindable manual action
(dry-run-first, confirm-to-delete) **and** a button in the `bank_panel` that fires
that same action. No background sweep. The earlier optional "…and prune now at the
delete-bank confirmation" convenience was **not** selected — it is dropped from the
settled spec (explicitly out of scope). A periodic/background sweep remains rejected
(silent irreversible file-deletion violates the guardrails). So R3 gains a
`bank_panel` button affordance alongside the action registration. (Settled
2026-07-24.)

---

## Summary of the boundary (for the spec)

| | Sample-remove (B5) | Delete-bank (B1/B3, shipped-spec) | Prune (Phase R) |
|---|---|---|---|
| Object | one `Sample` entry | one bank + its member entries | files on disk |
| Side of the line | index | index | **file** |
| Deletes bytes? | no | no | **yes (only op that does)** |
| Produces orphans? | yes (last-ref) | yes (non-empty) | — (it *reclaims* them) |
| Reversible? | Ctrl-Z (batched undo, R-B) / re-capture | Ctrl-Z (batched undo, R-B) / re-create | **no in-app** (recoverable via OS trash, R-C) |
| Guardrail | confirm on last-ref | confirm on non-empty | dry-run + manifest confirm |