shard-wiki/research/260614-strudel-deep-dive/findings.md

Strudel.cc — live-coding REPL — deep dive (findings)

Date: 2026-06-14 · Source: SHARD-WP-0004 T5 · Subject: Strudel.cc (the JavaScript port of TidalCycles) — a browser live-coding REPL where code is a running musical performance.

Why this dive

The closing, lowest-priority dive — and the extreme of the live↔snapshot axis. Where Processing (T4) renders visual output at view time, Strudel renders time-based audio that only exists while running and evolving. It is the limit case for "can a page be a live computation?" — the answer where static projection is least faithful. Enrichment-only; feeds UC-54/55 and hardens the snapshot-degradation rule.

1. Code as a live, evaluated performance

• Strudel ports TidalCycles' pattern language to JavaScript, running entirely in the browser (Web Audio). You write pattern expressions (e.g. note("c e g"), sound("bd sd") with transformations) and evaluate them live; the sound updates without stopping — the essence of live coding.
• The artifact is terse source text (a pattern); the "content" is the sound it produces over time. There is no document, no output cell, no file of results — output is ephemeral, temporal, and performative.
• A Strudel "page" (a shared REPL link / snippet) is source + the implicit promise of a running evaluation. The source is tiny and diffable; the experience is not capturable as text.

2. The limit of static projection

Strudel pushes past Processing on every "live" dimension:

• Temporal & generative — output unfolds over time and may be non-deterministic (randomness, evolving state). There is no single "frame"; the faithful capture is a recording (audio), itself just one performance, not the artifact.
• Performative — the value is partly the act of live editing; even a recording loses the live-coding dimension.
• So on the live↔snapshot axis (named at T6), Strudel sits at the far live end: the best static projection is (a) the source (canonical, diffable) + (b) an optional audio recording snapshot, explicitly marked as one rendering of a live/temporal artifact.

This makes Strudel the honesty test for the contract: shard-wiki must be able to attach such a source, present it truthfully (here is the source; a live render needs the runtime; a recording is one performance), and never imply a static page captures it.

3. INTENT mapping (enrichment-only — no new UC)

Reinforcements / refinements

• Live-evaluated, time-based content (UC-54/55). Strudel is the extreme executable-as- page: source canonical, presentation = a temporal live evaluation. Confirms the page model must represent content whose rendered form is time-based / generative / performative.
• live↔snapshot axis (T6) — far end. Establishes the upper bound: some content is irreducibly live; static projection degrades to source + a recording snapshot, with honesty about what's lost. Generalizes Processing's "snapshot frame" to "recording of one performance."
• Graceful degradation (INTENT). A backend that can't run the REPL still serves the source (tiny, diffable) and any recording as read/projection/backup — the limited-backend-still-usable rule, at the hardest content type.
• Union without erasure. Presenting a Strudel shard must surface "this is a live temporal artifact; what you see/hear statically is source / one recording" — never hide the liveness or imply completeness.

Boundaries

• shard-wiki is not an audio/REPL runtime; default = attach the source + offer/store a recording with provenance; live in-viewer evaluation is a gated capability (trust/ sandbox, like Processing T4). Source is canonical; everything rendered is a degrading, view-time/temporal projection.

4. UC disposition (enrichment-only)

Mechanism (findings §)	Catalog UC / thread
Pattern source = live, evaluated, time-based performance (§1)	UC-54 / UC-55 (enriched: time-based/generative executable content)
Output ephemeral/temporal/non-deterministic → no faithful static form (§2)	links live↔snapshot axis (T6), far end
Best static projection = source + audio recording snapshot, marked as one performance (§2)	links UC-83/UC-84 (degrading projection), UC-37 (recording as backup)
Limited backend still serves source + recording (§3)	links UC-37 graceful degradation
Live in-viewer evaluation = capability + trust/sandbox (§3)	links UC-35

No new UC — Strudel is design prior art marking the far live end of the projection/ liveness model; it adds no orchestration scenario, it bounds one.

5. Architecture notes for SHARD-WP-0002

• T16 (projection): anchor the far end of the live↔snapshot axis — content can be irreducibly live/temporal/generative; the contract must allow a projection to declare "no faithful static form; static = source + a marked recording." Combined with T4's materialization-timing and continuity facets, the projection model now spans: ahead-of-time materialized → view-time one-shot → view-time continuous/interactive → temporal/generative/performative (recording-only snapshot).
• T12/T15 (page model): time-based / generative executable content as a page-model edge; source canonical, render temporal.
• T11 (capabilities): "live-evaluate (audio/REPL) in viewer" capability + trust/sandbox; default off → source + recording.

6. Open questions

1. Does the contract carry an explicit "irreducibly live / no faithful static form" flag on a projection (so the union renders the honest fallback automatically)? (The far-end resolution of the live↔snapshot axis open question from T6.)
2. Is a recording modeled as a stored derivation-projection snapshot with provenance (one performance, time T, source rev R), reusing the UC-84 snapshot machinery?

7. Sources

• strudel.cc (docs, REPL); TidalCycles (tidalcycles.org) — the pattern language Strudel ports; Web Audio.
• prior: research/260614-processing-deep-dive/ (view-time render, continuity, UC-54/55); research/260614-squeak-pharo-deep-dive/ (live↔snapshot axis); research/260614-mathematica-deep-dive/ (Dynamic interactive, snapshot-only).

8. Traceability

No new UC (enrichment / design prior art; the far live end). Enriched: UC-54, UC-55; links UC-83/UC-84 (degrading projection), UC-37 (recording = backup / graceful degradation), UC-35 (live-evaluate capability + trust). Architecture cross-refs: SHARD-WP-0002 T16 (far end of live↔snapshot axis: irreducibly-live content, static = source + marked recording), T12/T15 (time-based/generative executable content), T11 (live-evaluate capability + sandbox).