# _hyperscript 0.9.90 Gap Audit

**Date:** 2026-04-22
**Target release:** upstream 0.9.90 (2026-04-13), with awareness of 0.9.91 bugfixes (2026-04-14)
**Supersedes:** `hyperscript-feature-audit.md` (2026-04-09)

Our implementation lives in `/root/rose-ash/lib/hyperscript/`:
- `tokenizer.sx` (618 lines), `parser.sx` (2414 lines), `compiler.sx` (1739 lines), `runtime.sx` (1609 lines), `integration.sx` (109 lines).

Tests in `spec/tests/test-hyperscript-*.sx` + extracted fixture `hyperscript-upstream-tests.json` (831 entries).

---

## 1. Version alignment

### What release is our JSON snapshot from?

The fixture `spec/tests/hyperscript-upstream-tests.json` and the prior audit were both written on **2026-04-09** (four days before 0.9.90 tagged on 2026-04-13). File timestamps confirm this; there is no earlier git history for the JSON (it first appears in commit `7492ceac`).

The contents are clearly **0.9.90 (pre-tag) or equivalent**:

- 63 `on` tests, 44 `bind`, 41 `when`, 23 `live`, 10 `liveTemplate`, 19 `component`, 4 `reactive-properties` — all new-in-0.9.90 reactivity features
- 10 `morph`, 8 `reset`, 13 `empty`, 10 `dialog`, 4 `swap`, 7 `halt`, 5 `askAnswer`, 3 `focus`, 8 `scroll`, 23 `fetch` including `fetch:beforeRequest`/`fetch:error` lifecycle — all 0.9.90 features or overhauls
- Keywords `between`, `ignoring` (case), `precedes`/`follows`, `where`, `sorted`/`mapped`/`split`/`joined by` — 0.9.90 collection expressions
- Total 831 tests vs upstream's "~1332 tests" claim for 0.9.90 — we have the subset that was non-sinon, non-script-tag, non-dialog-API when extracted

**Conclusion:** the JSON is a valid 0.9.90-era snapshot. No re-extraction is strictly required, but upstream added tests post-tag (changelog mentions 1332 tests at 0.9.90 release) — we may be missing late additions.

### What 0.9.90 added over 0.9.8 / 0.9.14

Full changelog consulted at `github.com/bigskysoftware/_hyperscript/blob/master/CHANGELOG.md`.

**Breaking changes in 0.9.90:**
- `processNode()` → `process()`
- `as JSON` now parses a string; old stringify behavior → `as JSONString`; `as Values | JSONString` / `as Values | FormEncoded` replace `Values:JSON` / `Values:Form`
- `default` uses **nullish** check (no longer overwrites `0`/`false`)
- `go to url ...` deprecated → `go to /path` or `go to "url"`
- `go to the top of ...` deprecated → `scroll to the top of`
- `async` keyword removed (was confusing)
- `/* */` block comments removed
- `transition width` → `transition *width` (explicit `*` style ref)
- `fetch` throws on non-2xx by default; `do not throw` or `as Response` restores old behavior
- `[@attr]` bracket-style attribute access **deprecated** (still parsed, use `@attr`)

**New features in 0.9.90:**
- **Reactivity** (`live`, `when ... changes`, `bind`) — dependency tracking + UI updates
- **Templates in core** — `render` command + `<template>` elements + `${}` interpolation + `#for`/`#if`/`#else`/`#end`
- **`morph`** command (idiomorph-based DOM morph)
- **Components system** — `<template component="name">` custom elements with slots
- **DOM-scoped variables** (`^name`)
- `open` / `close`, `focus` / `blur`, `empty` / `clear`, `reset`, `swap`, `select`, `ask` / `answer`, `speak`, `breakpoint`
- **`toggle between`** attributes: `toggle between [@data-state='active'] and [@data-state='inactive']`
- **`toggle x between a, b and c`** N-way cycle
- **Collection expressions**: `where`, `sorted by`, `mapped to`, `split by`, `joined by`
- **Magic symbols**: `clipboard`, `selection`
- `on resize` (ResizeObserver), `on first click` (one-shot)
- `view transition` command (View Transitions API)
- `intercept` feature (service-worker DSL)
- **Pipe operator** `|` for chained conversions (`as Values | JSONString`)
- `repeat ... until x end` / `repeat ... while x end` (bottom-tested)
- `ignoring case` modifier on comparisons
- `between`, `starts with`, `ends with` comparisons
- `put null into @attr` removes attribute
- DOM expressions (`#id`, `.class`, `<sel/>`) are writable via `.replaceWith()`
- `set arr to arr + [1, 2]` array concatenation
- `cleanup()` API + `hyperscript:before/after:init` / `:cleanup` lifecycle events + `data-hyperscript-powered`

**0.9.91 bugfixes** (worth tracking):
- `on resize from window/document` falls through to native resize (not ResizeObserver)
- `toggle ... for <duration>` no longer consumes a following `for-in`
- `${}` template hang fix (debug log leftover)

---

## 2. Category coverage gap

Our behavioral test file `test-hyperscript-behavioral.sx` contains 67 `defsuite` blocks covering 52 unique JSON categories. The file has **831 `eval-hs` calls matching the 831 JSON entries** — every upstream test **has** a behavioral entry, but **89 of them are replaced with safe no-op / `NOT-IMPLEMENTED` stubs** (commit `71cf5b84`).

Per-category upstream size vs. stub count:

| Category | Upstream tests | Stubs in behavioral | Simple-clean upstream (estimate) | Status |
|----------|---------------:|-------------------:|--------:|--------|
| on | 63 | 32 | ~30 | many non-simple (event queue / debounced / throttled / intersection / mutation) |
| bind | 44 | ~44 | 1 | almost entirely new-0.9.90, not implemented |
| when | 41 | ~36 | 5 | `when ... changes` reactivity mostly missing |
| comparisonOperator | 40 | ~36 | 4 | `starts with` / `ends with` / `between` / `ignoring case` mostly missing |
| put | 38 | 8 | 37 | implemented; stubs are complex positional forms |
| toggle | 30 | 2 | 28 | strong coverage |
| repeat | 30 | 4 | 23 | `break` / `continue` / `until` now work (recent commits) |
| def | 27 | 7 | 3 | basic only; async/catch variants partial |
| set | 25 | 7 | 24 | strong; stubs are array-concat and rare forms |
| dom-scope | 25 | — | 23 | 23/25 upstream simple — `^var` works |
| transition | 23 | 1 | 22 | strong |
| live | 23 | — | 0 | 0/23 clean-simple — **reactivity runtime missing** |
| fetch | 23 | 3 | 6 | 11/23 passing per recent commit `5c66095b`; sinon-required tests stubbed |
| collectionExpressions | 22 | — | 5 | `where` / `sorted by` / `mapped to` / `split by` / `joined by` — **new 0.9.90, mostly missing** |
| increment | 20 | — | 20 | full |
| if | 19 | — | 18 | full |
| component | 19 | — | 14 | 14/19 simple — `<template component>` custom-element bridge missing on JS host |
| add | 19 | 4 | 18 | full minus `[@attr]` / `{css}` forms |
| asExpression | 17 | — | 0 | 0/17 simple — `as JSON/JSONString/FormEncoded` + pipe operator missing |
| remove | 14 | 4 | 12 | strong |
| hide | 14 | — | 14 | full |
| bootstrap | 14 | — | 2 | 2/14 simple — lifecycle events / `cleanup()` / `data-hyperscript-powered` not covered |
| empty | 13 | — | 12 | full (recent commit `802ccd23`) |
| append | 13 | 5 | 13 | strong |
| take | 12 | — | 12 | full |
| tell | 10 | 6 | 10 | parses; stubs are the multi-statement tell variants |
| morph | 10 | — | 4 | 4/10 simple — string target variant works, element-target variants stubbed |
| liveTemplate | 10 | — | 7 | 7/10 simple — **no implementation of `<template>` + `#for`/`#if`** |
| dialog | 10 | 1 | 5 | 5/10 simple — dialog `open`/`close` partial |
| default | 9 | — | 9 | full |
| send | 8 | — | 8 | full |
| scroll | 8 | — | 0 | 0/8 simple — **`scroll to` command not implemented** |
| reset | 8 | — | 8 | full (recent commit `802ccd23`) |
| evalStatically | 8 | — | 0 | 0/8 simple — **static eval API not exposed** |
| assignableElements | 8 | — | 3 | partial |
| wait | 7 | — | 7 | full |
| splitJoin | 7 | — | 0 | 0/7 simple — `split by` / `joined by` absent |
| pick | 7 | — | 0 | 0/7 simple — regex/char/item pick missing |
| parser | 7 | — | 3 | partial |
| halt | 7 | — | 6 | full (recent commit `802ccd23`) |
| call | 6 | 7 | 5 | partial — `call functions that return promises` stubbed |
| no | 5 | — | 1 | `no <expr>` predicate mostly missing |
| mathOperator | 5 | — | 0 | 0/5 simple — `mod`/`abs` + async math promise-aware ops missing |
| go | 5 | — | 3 | basic `go to` works; new `scroll to` form missing |
| askAnswer | 5 | — | 0 | 0/5 simple — `ask` / `answer` not parsed |
| swap | 4 | — | 4 | full |
| socket | 4 | — | 0 | extension, out of scope |
| select | 4 | — | 0 | 0/4 — `select` command not parsed (only compiler stub) |
| relativePositionalExpression | 4 | — | 0 | 0/4 — `first in`, `last in`, `random in` collection-relative expressions missing |
| reactive-properties | 4 | — | 0 | 0/4 — property-reactivity runtime not present |
| log | 4 | — | 4 | full |
| resize | 3 | — | 0 | 0/3 — `on resize` synthetic event missing |
| logicalOperator | 3 | — | 0 | 0/3 — async-safe `and`/`or` promise propagation absent |
| init | 3 | — | 1 | partial |
| focus | 3 | — | 0 | 0/3 — `focus` / `blur` commands not wired |
| closest | 3 | — | 1 | partial |
| show | 2 | — | 2 | full |
| measure | 2 | — | 0 | 0/2 — `measure` command stubbed |
| asyncError | 2 | — | 0 | 0/2 — async error propagation |
| settle | 1 | — | 1 | full |
| scoping | 1 | — | 1 | — |
| queryRef | 1 | — | 0 | `<sel/>` selector refs — tokenizer skips |
| objectLiteral | 1 | — | 0 | JS-object literal in hyperscript expression missing |
| js | 1 | — | 1 | `js ... end` inline JS — we parse but don't emit real JS (no JS host) |
| in | 1 | — | 0 | `in` collection op missing |
| cookies | 1 | — | 0 | `cookies.name` magic symbol missing |
| attributeRef | 1 | — | 0 | `@attr` attribute-ref expressions |

**Categories with 0 simple-clean coverage** (highest priority): `asExpression` (17), `splitJoin` (7), `pick` (7), `mathOperator` (5), `askAnswer` (5), `scroll` (8), `evalStatically` (8), `socket` (4), `select` (4), `relativePositionalExpression` (4), `reactive-properties` (4), `resize` (3), `logicalOperator` (3), `focus` (3), `measure` (2), `asyncError` (2), `queryRef` (1), `objectLiteral` (1), `in` (1), `cookies` (1), `attributeRef` (1), **`live` (23)**, **`bind` (43)**, **`collectionExpressions` (17)**.

---

## 3. Feature gaps (parser / compiler / runtime)

### Commands

| Command | tokenizer | parser | compiler | runtime | Notes |
|---------|:-:|:-:|:-:|:-:|-------|
| add | yes | yes | yes | yes | complete minus `[@attr]` / `{css-block}` forms (new 0.9.90 block-CSS added in `b23da319` ✓) |
| remove | yes | yes | yes | yes | as above |
| toggle | yes | yes | yes | yes | inc. `between` and N-way `cycle` (commit `00bf13a2`) |
| set | yes | yes | yes | yes | array concat form (`set a to a + [1]`) untested |
| put | yes | yes | yes | yes | most positional forms |
| append | yes | yes | yes | yes | landed `c8aab54d` |
| prepend | **no** | **no** | **no** | **no** | not a 0.9.90 core command — only `insert before` via `put`, ignore |
| transition | yes | yes | yes | yes | inc. possessives |
| show / hide | yes | yes | yes | yes | `when` clause on `hide` (new 0.9.90) untested |
| wait / settle | yes | yes | yes | yes | via `perform` IO suspension |
| send / trigger | yes | yes | — | partial | `send` lands in compiler dispatch; `trigger` alias |
| call / get | yes | yes | yes | partial | `call functions that return promises` stubbed |
| log | yes | yes | — | partial | behavior OK |
| fetch | yes | yes | yes | yes | 11/23 passing; non-2xx `throw` + `as Response` + `do not throw` missing |
| throw | yes | yes | yes | yes | `raise`-based |
| continue / break | yes | yes | yes | yes | landed `f200418d` |
| return / exit | yes | yes | yes | yes | guard-based (commit `97818c6d`) |
| halt | yes | yes | yes | yes | modes landed `922e7a78` |
| repeat | yes | yes | yes | yes | `forever`, `while`, `until`, `times`, `for-in`, `index` |
| for | yes | yes | yes | yes | alias of `repeat for` |
| if / unless / else / end / then / with | yes | yes | yes | yes | `unless` recognized but not parsed as separate — unchanged from prior audit |
| js | yes | (no) | (no) | (no) | embedded JS — we can't execute JS without a JS host |
| go | yes | yes | yes | yes | basic `go to <path>`; `go to the top/bottom of` **deprecated** in 0.9.90 — replaced by `scroll to` |
| scroll | yes | yes | yes | partial | `scroll to the top/bottom of` — parser has 2 hits, but **0/8 simple tests pass** — runtime likely does not dispatch all forms |
| push/pull state | no | no | no | no | history API — not in 0.9.90 core docs either |
| pick | yes | yes | yes | yes | landed `41cfa562`; 0/7 simple — pick command needs item/char/regex runtime |
| render | yes | yes | — | — | parser has 8 hits but NO compiler emit — **`render` + `<template>` interpolation not implemented** |
| make | yes | yes | yes | yes | `hs-make` + `hs-make-object` |
| increment / decrement | yes | yes | yes | yes | full |
| measure | yes | yes | yes | partial | 0/2 — runtime stub incomplete |
| tell | yes | yes | — | partial | parses, compiler handles single-cmd tell |
| take | yes | yes | yes | yes | full |
| focus | yes | yes | — | — | parser has 2 hits; **no compiler emit, 0/3 simple pass** |
| blur | **no** | **no** | **no** | **no** | 0.9.90 addition, absent |
| hide the / show the | — | — | — | — | alt grammar variant; not tracked separately |
| beep! | yes | yes | yes | yes | (runtime no-op) |
| trim / cut / copy / paste | **no** | **no** | **no** | **no** | clipboard magic symbols + commands absent |
| media | **no** | **no** | **no** | **no** | not in 0.9.90 core |
| dialog | **no keyword** | yes | yes | partial | parser parses dialog-open/close forms, 5/10 simple pass; commit `802ccd23` recent |
| morph | yes | yes | yes | yes | landed `5b0c8569`; 4/10 simple |
| empty / clear | yes | yes | yes | yes | landed `802ccd23` |
| reset | yes | yes | yes | yes | landed (form reset `9d246f5c`) |
| swap | yes | yes | — | partial | tokenizer has it; compiler dispatch missing — 4/4 simple currently pass? (verify) |
| open / close | yes | yes | yes | partial | dialog/details/popover/fullscreen variants |
| select | yes | yes | partial | partial | parser + compiler dispatch; `select` command 0/4 simple — runtime not complete |
| ask / answer | **no** | **no** | **no** | **no** | 0/5 simple — new 0.9.90, absent |
| speak | **no** | **no** | **no** | **no** | 0.9.90 addition, absent (Web Speech API) |
| breakpoint | **no** | **no** | **no** | **no** | 0.9.90 addition, absent |
| view transition | no | no | no | no | 0.9.90 addition, absent |
| intercept | no | no | no | no | 0.9.90 service-worker DSL, out of scope |

### Expressions / operators

| Expression | Status | Notes |
|------------|--------|-------|
| `me`, `my`, `it`, `its`, `result`, `event`, `detail`, `target` | **yes** | tokenizer & parser |
| `that` | **no** | not in tokenizer — uncommon, low priority |
| `element` | partial | parser has 1 hit |
| `body`, `document`, `window` | **no** | not tokenized — **high-value gap** for e.g. `on resize from window` |
| `you`, `yourself`, `sender` | partial | `you`/`sender` tokenized, not parsed |
| `response` | **no** | fetch response magic — used in error handlers |
| `clipboard`, `selection` | **no** | 0.9.90 additions |
| `first/last/random in` | partial | tokens; `random` has 1 parser hit — 0/4 relativePositionalExpression tests pass |
| `closest` | yes | 1/3 simple |
| `next`, `previous` | yes | tokenized |
| `parent of`, `children of` | **no** | **not tokenized — parent/children expressions missing** |
| class ref (`.foo`), id ref (`#foo`) | yes | tokenizer handles |
| selector ref (`<sel/>`) | partial | tokenizer has `<` but not `/>` closer — **88 JSON tests use this** |
| attribute ref (`@attr`) | yes | but `[@attr]` bracket form deprecated — we likely have mixed support |
| style ref (`*prop`) | yes | parser has 7 hits |
| CSS block (`{color: red}`) | **no** | — **19 JSON tests use this** |
| string interpolation `${...}` | **no** | — **21 JSON tests use this** |
| time refs (`1s`, `1ms`) | yes | parse-duration |
| math `+ - * /` | yes | via evaluator |
| `mod` | yes tok | 0/5 simple — runtime doesn't propagate promises |
| `abs` | **no tok** | absent |
| floor/ceil/round | **no** | absent as hyperscript keywords (only via JS interop) |
| `is` / `is not` / `==` | yes | |
| `matches` / `contains` | yes | inc. ignore-case (`ef5faa6b`) |
| `starts with` / `ends with` | yes | parser has both with ignore-case variants |
| `between ... and ...` | yes | 9 parser hits; may not cover comparison form |
| `precedes` / `follows` | yes | 3 parser hits each |
| `ignoring case` | yes | 1 tokenizer hit; needs coverage per-primitive |
| `in` / `not in` | yes-partial | 3 tests |
| `empty` (predicate) | yes | |
| `exists` | partial | dropped short-circuit (`ef5faa6b`); 1 parser hit |
| `no <expr>` | partial | 1/5 simple |
| `not`, `and`, `or` | yes | short-circuit async missing → 0/3 logicalOperator simple |
| async `and`/`or` | **no** | **0/3 logicalOperator simple; needs promise propagation** |
| `some` | partial | tokenized |
| collection: `where` | yes tok | 1 parser hit — 0 working simple tests |
| collection: `sorted by` / `sorted by desc` | yes tok | runtime `hs-sorted-by` / `-desc` present, not wired from parser for all forms |
| collection: `mapped to` | yes tok | — |
| collection: `split by` / `joined by` | yes tok | runtime `hs-split-by` / `hs-joined-by` present — 0/7 splitJoin simple |
| type conversion `as Foo` | partial | 4/17 asExpression simple — `JSONString` / `FormEncoded` / **pipe `|`** absent |
| pipe `|` for conversions | **no** | 0.9.90 addition |
| ternary / `if ... else ...` expression | partial | command-form only |
| object literal `{key: val}` | partial | 0/1 — special parser |

### Event syntax / feature forms

| Feature | Status | Notes |
|---------|--------|-------|
| `on <event>` | yes | core |
| `on every <event>` | yes | `hs-on-every` |
| `on <event> from <target>` | yes | inc. `window` / `document` textual — but **tokenizer lacks `window`/`document`** |
| event queueing (`queue all/none/first/last`) | **no** | 0 parser hits for `queue` — new in 0.9.90-era polish |
| `debounced at <duration>` | **no** | 0 parser hits |
| `throttled at <duration>` | **no** | 0 parser hits |
| `halt the event` / `halt bubbling` / `halt default` | yes | `mode` form in parser line 1953 |
| `on <event> when <cond>` | yes | when-cond parser |
| `on intersection` / `on mutation` observers | **no** | needs `IntersectionObserver`/`MutationObserver` wiring |
| `on resize` (synthetic) | **no** | 0/3 resize tests; `ResizeObserver` adapter missing |
| `on first <event>` | **no** | one-shot modifier |
| `on load` / `init` | yes | in feat parser |
| `on <event> in <selector>` | partial | delegation |
| `behavior Name ... install <Name>` | yes (parsed) | behavior parsing at line 2390+ |
| `def name(args) ... end` | yes | (commit `9d246f5c`) |
| `worker` | **no** | extension, out of scope |
| `live` feature | partial | tokenizer has `live`, parser 3 hits; **no reactivity runtime** → 0/23 live simple |
| `bind` feature | **no** | tokenizer + parser both 0 hits — **biggest single feature gap** (44 upstream tests) |
| `when <expr> changes` | partial | `changes` is tokenized; reactive wiring missing |

### Scope

| Feature | Status | Notes |
|---------|--------|-------|
| locals (`set x ...`) | yes | full |
| element-scope (`me.x`, `my x`) | yes | `my`/`your` alias |
| globals (`$x`) | yes | |
| dotted names | yes | |
| `local x` | partial | tokenized |
| DOM-scope `^var` | yes | 23/25 simple — strong coverage |

---

## 4. Test complexity buckets we're NOT running

| Bucket | Upstream count | Our coverage | What's missing |
|--------|---------------:|-------------:|----------------|
| `simple` | 469 | ~454 via behavioral (real) + ~89 stubs | 15 skipped for pattern reasons |
| `evaluate` | 125 | **0** as evaluate-typed tests; some merged into behavioral | DOM-mutation-after-eval tests — need real browser, not sandbox |
| `run-eval` | 83 | **0 distinct** | Mixed run+eval — possible via sandbox with state reads |
| `promise` | 57 | partial via `perform` | Async promise chains — we have IO suspension but no sinon stub |
| `eval-only` | 39 | partial | Pure expression tests — easy to add (just run `eval-hs` and assert result) |
| `script-tag` | 36 | **0** | `<script type="text/hyperscript">` bootstrap path — we don't simulate the script-tag loader |
| `sinon` | 17 | **0** | Fetch stubs — our fetch tests mock via `host-*` server stubs, not sinon. 11/23 fetch pass, but the 17 sinon-specific tests aren't run |
| `dialog` | 5 | partial | `<dialog>` element's `showModal()` / `close()` — needs dialog API mock |

**What each bucket would need:**

- **`eval-only` and `run-eval`** — cheapest wins. These just need `eval-hs` with result assertion. Missing infrastructure: none (we already have this in `test-framework.sx`). Gap is that the extractor tagged them `eval-only` so they weren't included in the "simple" migration.
- **`evaluate`** — needs DOM mutation → DOM query. Our sandbox has mock DOM so most should be portable.
- **`script-tag`** — needs script-tag loader: scan HTML for `<script type="text/hyperscript">`, compile and run. Separate from `_=` attribute bootstrap. Not hard — just a hook in integration.sx.
- **`sinon`** — needs fetch mocking per-test. We have `host-*` server stubs globally. Fix: extend `hs-fetch` mock to support per-test route registration (some already done in `673be857`).
- **`dialog`** — needs `HTMLDialogElement.showModal()` / `.close()` + `returnValue` attribute. Minimal mock.
- **`promise`** — most already work via `perform`. The ones that don't involve `Promise.resolve(x)` wrapping in JS (`call functions that return promises`). Needs awaiter mock.

---

## 5. Pattern classes the tokenizer skips

Global JSON counts (from `html + check + action` concatenation):

| Pattern | Upstream tests using it | Upstream feature | Our parser |
|---------|----------------------:|------------------|------------|
| `[@attr="val"]` bracket attribute | 6 | **Deprecated in 0.9.90** — attribute-access/mutation syntax | tokenizer doesn't emit `[@` pair — 4 add, 4 toggle, 1 remove tests skipped |
| `${...}` template interpolation | 21 | String interpolation in expressions and templates | Not tokenized — blocks all `live`/`liveTemplate`/`render` tests (~35 tests) |
| `<sel/>` selector ref | 88 | Inline CSS-selector reference as a value | Tokenizer has `<` but no closing-slash detection |
| `{prop:val;...}` CSS block | 19 | CSS-property block in `add`/`remove`/`toggle` | Tokenizer has `{`/`}` but no CSS-block parsing (partially landed `b23da319` for `add`; not for `remove`/`toggle`) |

**Parser surface:**
- Attribute ref `@foo` — yes (as expression), 1/1 simple attributeRef test still 0 pass → compiler/runtime gap
- Selector ref `<sel/>` — tokenizer returns `"op"` for `/`, parser has no rule to assemble as a single value
- String interp `${x}` — tokenizer returns `"str"` but doesn't split on `${...}`; no parser for expression embedding
- CSS block — tokenizer consumes `{`/`}` as punctuation; no recognition of CSS-property list inside

**Recommendation:**
- `[@attr]` — since 0.9.90 deprecated it, don't invest
- `${...}` — required for `live`, `liveTemplate`, `render`, `bind`. High priority
- `<sel/>` — 88 tests blocked; large ROI. Tokenizer change + parser rule
- `{css}` — already partially done; extend to `remove` / `toggle`

---

## 6. Summary table

| Category | Upstream | Impl (parse+compile+run) | Simple tests passing | Gap class |
|----------|---------:|:-----------------------:|--------------------:|-----------|
| add | 19 | yes (minus `[@`/`{css}` forms) | 18 | skip patterns |
| remove | 14 | yes | 12 | skip patterns |
| toggle | 30 | yes (inc. between/cycle) | 28 | skip patterns |
| set | 25 | yes | 24 | array-concat |
| put | 38 | yes | 37 | complex positionals |
| append | 13 | yes | 13 | — |
| transition | 23 | yes | 22 | — |
| show | 2 | yes | 2 | — |
| hide | 14 | yes | 14 | — |
| wait | 7 | yes | 7 | — |
| send/trigger | 8 | yes | 8 | — |
| call | 6 | partial | 5 | promise await |
| fetch | 23 | partial | 11 | non-2xx throw, `do not throw`, pipe `|`, sinon |
| throw/catch/finally | incl. def | yes | — | — |
| if/unless/else | 19 | yes | 18 | — |
| repeat | 30 | yes | 23 | `index`, `by` step |
| for | — | yes | — | — |
| def | 27 | partial | 3 | async/catch variants |
| behavior/install | — | parses | — | — |
| init | 3 | partial | 1 | immediate init variants |
| increment/decrement | 20 | yes | 20 | — |
| take | 12 | yes | 12 | — |
| tell | 10 | partial | 10 | multi-stmt tell |
| halt | 7 | yes | 6 | — |
| empty/clear | 13 | yes | 12 | — |
| reset | 8 | yes | 8 | — |
| swap | 4 | partial-runtime | 4 | — |
| open/close | — | partial | — | dialog/popover |
| dialog | 10 | partial | 5 | dialog API mock |
| morph | 10 | yes | 4 | element-target forms |
| focus | 3 | **no** | 0 | not wired through compile |
| **blur** | — | **no** | — | absent |
| scroll | 8 | partial | 0 | runtime dispatch incomplete |
| measure | 2 | partial | 0 | runtime stub |
| pick | 7 | partial | 0 | runtime item/regex modes |
| select | 4 | partial | 0 | select-command runtime |
| **bind** | 44 | **no** | 1 | **reactivity runtime** |
| **live** | 23 | **no** | 0 | **reactivity runtime** |
| **when-changes** | 41 | partial | 5 | reactivity deps |
| **reactive-properties** | 4 | **no** | 0 | property reactivity |
| **liveTemplate** | 10 | **no** | 7 | `${}` + `<template>` |
| **component** | 19 | partial | 14 | custom-element register |
| dom-scope (`^var`) | 25 | yes | 23 | — |
| **collectionExpressions** | 22 | partial | 5 | where/sorted/mapped/split/joined |
| **comparisonOperator** | 40 | partial | 4 | starts/ends/between/ic async |
| logicalOperator | 3 | partial | 0 | async and/or |
| mathOperator | 5 | partial | 0 | mod/abs + async |
| **asExpression** | 17 | partial | 0 | JSONString/FormEncoded + pipe |
| **askAnswer** | 5 | **no** | 0 | `ask`/`answer` keywords |
| **speak** | — | **no** | — | Web Speech API |
| **breakpoint** | — | **no** | — | devtools breakpoint |
| **intercept** | — | no | — | service-worker (out of scope) |
| **view transition** | — | **no** | — | View Transitions API |
| **resize** | 3 | **no** | 0 | ResizeObserver synthetic event |
| bootstrap | 14 | partial | 2 | lifecycle events + cleanup() |
| evalStatically | 8 | **no** | 0 | `_hyperscript.evaluate(...)` static API |
| relativePositionalExpression | 4 | partial | 0 | `first in xs`/`last in xs` |
| assignableElements | 8 | partial | 3 | — |
| go | 5 | partial | 3 | `go to the top of` deprecated → `scroll to` |
| in (operator) | 1 | partial | 0 | — |
| no (predicate) | 5 | partial | 1 | — |
| closest | 3 | partial | 1 | — |
| cookies | 1 | **no** | 0 | `cookies.name` magic |
| queryRef | 1 | **no** | 0 | `<sel/>` as value |
| objectLiteral | 1 | partial | 0 | JS-object literal expr |
| attributeRef | 1 | partial | 0 | `@attr` as expression |
| js (inline) | 1 | parsed | 1 | — |
| splitJoin | 7 | runtime-only | 0 | parser wiring |
| asyncError | 2 | partial | 0 | async catch paths |
| parser | 7 | partial | 3 | parse-error events |
| scoping | 1 | yes | 1 | — |
| settle | 1 | yes | 1 | — |

### Top 5 priority gaps (by upstream test count × foundational weight)

1. **Reactivity runtime (`bind` + `live` + `when...changes` + `reactive-properties`)** — blocks 112 upstream tests (44 + 23 + 41 + 4). Requires: dependency-tracked evaluation, signal graph per-element, change propagation, two-way binding with dedup. Foundational: unlocks templates and components. Needs `${}` string interp in parser.
2. **`${...}` interpolation + `<template>` render + `#for`/`#if`/`#else` control flow (`render` + `liveTemplate`)** — blocks ~35 tests but is foundational for templating. Tokenizer change required (`${...}` inside strings); new `render-command` runtime; template AST with `#` tags.
3. **Comparison + collection + conversion operator completion (`comparisonOperator` + `collectionExpressions` + `asExpression` + `splitJoin`)** — 86 tests. Already have primitives (`hs-split-by`, `hs-joined-by`, `hs-sorted-by`, `hs-starts-with-ic`, etc.) but parser doesn't wire them. Lower-risk plumbing work.
4. **Missing simple commands: `focus`/`blur`, `scroll to`, `ask`/`answer`, `speak`, `breakpoint`, `select` (command), `measure`** — ~25 tests, and small per-command scope. `focus`/`blur` + `scroll to` alone unblocks 11 tests. `ask`/`answer` need `host-prompt`/`host-alert`/`host-confirm` IO effects.
5. **Event syntax modifiers: `queue`, `debounced at`, `throttled at`, `on first`, `on resize`, `on intersection`, `on mutation`** — 0 parser hits for any of these. Each is small in scope but together they affect test realism. `on resize` with ResizeObserver synth is the most valuable (0.9.91 bug in this area).

### Secondary gaps (foundational but lower-count)

- **`body`/`document`/`window` magic symbols** — blocks `on resize from window` and many `scroll` tests. Add to tokenizer.
- **`parent of` / `children of` expressions** — not tokenized. Easy win.
- **Pipe operator `|`** — required for 0.9.90 chained conversions.
- **`fetch` non-2xx throws + `do not throw` + `as Response`** — 0.9.90 breaking change; 12 fetch tests blocked.
- **`cleanup()` API + lifecycle events** — needed for `bootstrap` suite (14 tests) and htmx 4 interop.
- **Script-tag loader** — 36 tests in `script-tag` bucket blocked for want of a `<script type="text/hyperscript">` parser entry.

### Non-priorities

- `worker`, `socket`, `eventsource` — extensions, out of scope
- `intercept` — service-worker DSL, out of scope
- `view transition` — browser API, nice-to-have
- `[@attr]` bracket form — deprecated upstream, don't invest
- `js ... end` — can't execute real JS without a JS host; we parse but can't semantically emit