# Session 0026.0 — Transcript

> App: human-experience-filter-art
> Start: 2026-06-27T15-26 (PST)
> Type: planning-and-executing
> Posture: yolo
> Claude-Session: c6b9bebd-f94a-4fc0-982d-0a9dc00b3148
> Checkout: /Users/benstull/git/benstull.org/benstull/human-experience-filter-art
> End: 2026-06-27T18-48 (PST)
> Status: **FINALIZED** — merged to main (PR #28) and published at session end.

## Launch prompt

Build scrub-driven altitude transitions in the simulator, per the approved design at
`docs/superpowers/specs/2026-06-27-scrub-driven-altitude-transitions-design.md`. Write the
implementation plan from that spec, review it, then execute it. Make the Altitude knob
position continuously drive the transition: dragging the dial scrubs the morph video's
currentTime and crossfades the two adjacent scale soundtracks by knob angle; hold-partway
(no auto-complete), fully reversible, re-roll the destination clip on each fresh approach,
scroll-wheel auto-scrubs one altitude then locks, lock-per-altitude preserved. Phase 1:
build against current morphs. Phase 2: re-bake all 154 morphs all-intra for smooth seeking,
re-push via git-LFS. Unit tests for pure scrub logic + extend Playwright E2E.

## Plan

> Anchor: design docs/superpowers/specs/2026-06-27-scrub-driven-altitude-transitions-design.md (R2a — ELIGIBLE)
> Session type: planning-and-executing (fused) — write the plan, then execute it, ship via §9.

Scrub-driven altitude transitions. Continuous `pos` (float) drives morph `currentTime` +
two-soundtrack audio crossfade by `frac(pos)`; integer crossing commits + locks + re-rolls.
Phase 1 = interaction against current morphs; Phase 2 = all-intra re-bake (154 morphs, LFS).
Pure scrub logic kept separable + unit-tested; Playwright E2E extended to assert currentTime
+ audio gains track the dial and reverse on turn-back.

### Progress (checkpoint @ Phase-1 done)

- Plan: `docs/superpowers/plans/2026-06-27-scrub-driven-altitude-transitions.md` (approved "execute as-is").
- **Phase 1 DONE** (branch `session-0026`, 5 commits):
  - T1 `simulator/static/scrub.js` (pure UMD math) + `simulator/unit/scrub.test.js` (9 `node --test`).
  - T2 two-element audio crossfade (`<audio id=aud-b>`, `blendAudio`/`restAudio`/`ensurePlaying`/`assignElements`).
  - T3 scrub engine: drag live-drives `pos`; `setPos` seeks morph currentTime (1 seek/rAF), crossfades audio,
    commits+locks+re-rolls on integer crossings; release holds (no auto-complete); client-side `pickPoolClip`.
  - T4 wheel + label-tap → `autoScrub` (animate `pos`, land exact, lock); removed dead `advance()`/`playTransition()`.
  - T5 E2E scrub tier (6 tests green): drag tracks currentTime+gains, turn-back reverses same file + re-locks start,
    detent-crossing commits+locks (via `window.__hefState` seam), wheel auto-scrubs+locks.
- **Verification:** `node --test` 9 green · `pytest` 302 passed / 2 skipped · Playwright 6 green.
- **Phase 2 DONE** (T7–T8): `transition_cmd`/`reverse_cmd` builders + `ALL_INTRA` (`-g 1 -keyint_min 1
  -sc_threshold 0`), unit-tested; re-baked all 154 morphs all-intra (verified 93/93 I-frames on a sample),
  173M→504M, largest clip ~5.8M; committed via git-LFS and pushed (154 LFS objects, 453MB).
- **All 8 plan tasks complete. Branch `session-0026` pushed.** Final verification: `node --test` 9 green ·
  Playwright 6 green · `pytest` 302 passed/2 skipped.
- **Remaining:** merge to main + §9. Operator by-eye "feel/smoothness liked?" review is the one acceptance
  criterion automated tests can't cover (simulator-first directive) — flagged for operator before/at merge.
- **DECISION (operator): HOLD for eyeball first.** Branch `session-0026` stays UNMERGED; session NOT finalized.
  Operator pulls + runs the sim locally to judge the scrub feel/smoothness, then says merge (or requests tweaks).

### Eyeball round 1 — operator found 2 issues, both FIXED (2 more commits)

- **Fix 1 — landing jitter (frontend).** Landing jump-cut the loop back to frame 0. Each morph reproduces the
  dst clip's first 3s (`trim=0:3`), ending dst@~3s, so steady-state loop now starts at `LOOP_TAIL_S=3.0` and
  loops `[3.0, duration]` (`ensureClipMedia` custom loop; disarmed during morph scrub). Morph's last frame hands
  straight off to the loop. E2E asserts a landed clip loops from ~3s, not 0. No re-bake. (8th E2E test added.)
- **Fix 2 — red-snapper text card (content).** `reef_snapper` opened with a black NOAA title card (~0.9–2.9s).
  Re-trimmed `reef_snapper/base.mp4` to drop the first 3.0s (23s→20s, footage clean from 3.0s) and re-baked the
  7 reef_snapper morph pairs (+reverses, all-intra) from the clean base; verified snapper morph frames text-free.
- **Verification:** Playwright 7 green · all-intra re-confirmed (93/93 I-frames). Pushed to `session-0026`.
- **D2 (deferred) — reef_snapper tracked test-label.** The trim shifts the footage, so reef_snapper's one
  loop-normalized tracked label (`appear 0.0`/`disappear 0.7` + 3-keyframe track) is now slightly misaligned to
  the subject. It's demo/test material gated behind both knobs up; left as-is — re-author via `/author.html` if
  the operator wants it pixel-accurate.
### Eyeball round 2 — 2 more items, both FIXED (2 commits)

- **Fix 3 — morph→loop load jolt (double-buffer).** A pause/jolt when the morph ended and the next altitude's
  loop loaded: swapping `vid.src` to the base + seeking the tail reloaded the ON-SCREEN element (decode+seek
  stall). Added a dedicated `#vid-loop` element for the steady-state base loop; during a scrub it is PRELOADED to
  the clip we're heading toward (`loadLoop`, paused at the tail frame). The paint shader reads the active source
  (`displayVid() = busy ? vid : loopVid`), so landing is an instant source swap — no reload, no seek. E2E asserts
  the loop element is armed + playing from ~3s after landing.
- **Fix 4 — audio on/off → 0–10 level dial.** Replaced the Audio checkbox with a 0–10 range slider = master gain
  (`audioVol = level/10`), scaling rest volume + the two-track scrub crossfade. First Video-on lifts audio to
  **3/10** (was full). E2E: range 0–10 default 0; first video-on → 3.
- **Verification:** Playwright **9 green** · node unit 9 · screenshot-confirmed the dial layout.
- **D3 residual still applies:** double-buffer kills the LOAD pause both directions; the reverse/turn-back FRAME
  asymmetry (morph src-start@0 vs loop tail@3s) and the ~loop-wrap seek remain (per-clip loop files would fully
  resolve if wanted).
### Eyeball round 3 — audio-off bug (systematic-debugging), FIXED (1 commit)

- **Bug:** audio turned off *sometimes* after landing on a new altitude. **Root cause (code-traced, not guessed):**
  `fadeVolume` started a `setInterval` ramp that was **never cancelled**. `restAudio` fades the idle element to 0;
  if within FADE_MS (500ms) that same element becomes the newly-landed ACTIVE scale (`assignElements` reuses one
  element per soundtrack url), the stale fade-to-0 kept running and dragged the now-active element to silence —
  hence "only sometimes." **Fix:** `cancelFade(el)` supersedes any in-flight fade when a new fade starts
  (`fadeVolume`) or a direct volume is set (`ensurePlaying`). Added `window.__hefFade` seam + a deterministic E2E
  that PROVES it (fails with the fix disabled, passes with it). Playwright **10 green**.
### Eyeball round 4 — transition speed (1 commit)

- **Request:** slow click/auto transitions ~2x and make them the SAME speed between any two altitudes (2 away =
  2× as long as 1). `autoScrub` was a fixed 600ms total regardless of distance. Now duration is PROPORTIONAL:
  `PER_ALTITUDE_MS=1200` (≈2× the old 600) × |distance|, so a label-click/wheel jump of N altitudes takes
  N×1200ms — constant per-step speed. Manual drag unaffected. E2E asserts a 2-step jump ≈ 2× a 1-step. 11 green.
- **Resume:** merge + `wgl-session-finalize` on operator go, OR next eyeball round of tweaks.

## Deferred decisions

_Autonomous-mode low-confidence calls the driver made and would have
liked operator input on. Appended as the session runs; surfaced at
finalize. Empty if none._

- **D1 (plan) — canonical segment morph file.** The spec's component 2 says resolve the
  directed morph via `morphByPair["<fromClip>→<toClip>"]`, but its turn-back decision says
  "scrubs the SAME morph in reverse" with full reversibility. These are only mutually
  consistent if a segment uses ONE file scrubbed bidirectionally. I locked the plan to:
  per segment `[lo, lo+1]`, always use the **descend/forward** morph
  `morphByPair["<clip@lo>→<clip@lo+1>"]` and drive `currentTime = frac × duration` in both
  travel directions; the `.rev` files become unused by the scrub interaction (kept baked
  for back-compat). This means the old E2E "zoom-out plays a `.rev`" assertion is replaced
  by a "turn-back seeks the same file backward" assertion. Low-confidence on whether the
  operator specifically wanted `.rev` retained in the drag path.
- **D2 — reef_snapper tracked test-label misalignment after the text-card trim.** Trimming the snapper base by
  3.0s (to remove the title card) shifts the footage, so reef_snapper's one loop-normalized tracked label
  (`appear 0.0`/`disappear 0.7` + a 3-keyframe track) no longer follows the same subject. Left as-is: it's
  demo/test authoring gated behind both knobs up; re-author via `/author.html` if pixel-accuracy is wanted.
- **D3 — landing-jitter fix approach.** Chose a frontend loop-from-tail (`LOOP_TAIL_S=3.0`, custom
  `[3.0, duration]` loop) over re-baking morphs or baking dedicated loop clips — cheap, no media churn,
  eye-tweakable. Residual: a one-seek hitch at each loop wrap (~every 17–20s) and scrub-START (vs landing) is
  not made seamless (a looping clip is at arbitrary phase when a drag begins). If the wrap hitch bothers the
  operator, bake per-clip loop files (`base[3:end]`) for native seamless looping.

## Closeout

**Shipped.** Branch `session-0026` (14 commits) → **PR #28 merged to `main`** (Gitea
merge commit `108e620`, branch deleted). Working tree clean on `main`.

**Arc of the session:** brainstorming was pre-done (approved design existed) → claimed
0026 (planning-and-executing, yolo) → wrote the implementation plan (reviewed: operator
chose "execute as-is") → executed all 8 plan tasks (Phase 1 scrub interaction + Phase 2
all-intra re-bake) → operator held for by-eye review → **4 eyeball rounds** of fixes
(landing frame, reef_snapper text card, video double-buffer, audio dial + fade-race +
transition speed; one bug solved via systematic-debugging with a fails-without-the-fix
regression test) → operator said merge → merged + finalized.

**§9 pipeline status:** localhost + E2E green (11 Playwright + 9 node unit + 302 pytest).
This app is **simulator-first with no PPE/prod deploy infra** (runs locally; hardware/Pi
deferred per the standing directive) — no deploy stage to run; the merge is the ship for
a locally-run simulator. (Plan archive skipped: app has **no content repo** in `app.json`;
the plan stays in-repo at `docs/superpowers/plans/2026-06-27-scrub-driven-altitude-transitions.md`.)

**Deferred decisions** (also in the section above): D1 canonical-forward-morph-per-segment
(scrub same file bidirectionally); D2 reef_snapper tracked test-label misaligned by the trim;
D3 reverse/turn-back frame asymmetry + loop-wrap seek (per-clip loop files would fully fix).

**Next-session prompt (operator's call — nothing outstanding blocks):**
```
/wgl-planning-and-executing Next HEF polish: pick one of —
  (a) bake per-clip loop files base[3:end] for native seamless looping (fixes the D3
      reverse-landing frame jump + the ~17–20s loop-wrap seek), OR
  (b) continue by-eye scrub/audio feel tweaks, OR
  (c) re-author the reef_snapper tracked label for the trimmed footage (/author.html), OR
  (d) register a content repo in app.json so plans/specs archive at finalize.
```
