runs: filter chips + compare selection up to 8

- /compare accepts ?stem=…&stem=… (repeated) for 2-8 runs; legacy ?a=&b=
  still works. compare.js parses multi-stem; template drops stem_a/_b
  data attrs that were unused.
- compare-select.js: MAX bumped to 8, button enables at 2-8 selected.
  URL emitted as ?stem=… per selection.
- runs list gets a dataset/algorithm chip filter bar above #runs-slot
  (pattern ported from metrics.js). Chips reflect the union of values in
  the current list; selection state persists across htmx swaps. Non-
  matching rows get .filtered-out (display:none).
- _runs.html li now carries data-embedder/data-generator so the filter
  can key on them.

app/web/main.py

@@ -1020,14 +1020,23 @@ async def run_frames(stem: str) -> Response:
 
 
 @app.get("/compare", response_class=HTMLResponse)
-async def compare_page(request: Request, a: str = "", b: str = "") -> HTMLResponse:
-    for label, stem in (("a", a), ("b", b)):
-        if not stem or not _STEM_RE.match(stem):
-            raise HTTPException(400, f"missing or malformed stem for {label!r}")
-        if not (FIGS_DIR / f"{stem}.html").is_file():
+async def compare_page(request: Request) -> HTMLResponse:
+    q = request.query_params
+    stems = [s for s in q.getlist("stem") if s]
+    if not stems:
+        # Legacy two-stem form: ?a=&b=
+        stems = [s for s in (q.get("a", ""), q.get("b", "")) if s]
+    if not (2 <= len(stems) <= 8):
+        raise HTTPException(400, f"need 2..8 stems, got {len(stems)}")
+    for stem in stems:
+        if not _STEM_RE.match(stem):
+            raise HTTPException(400, f"malformed stem: {stem!r}")
+        has_sidecar = (FIGS_DIR / f"{stem}.frames.json").is_file()
+        has_html = (FIGS_DIR / f"{stem}.html").is_file()
+        if not (has_sidecar or has_html):
             raise HTTPException(404, f"no such run: {stem}")
     return templates.TemplateResponse(
-        request, "compare.html", {"stem_a": a, "stem_b": b}
+        request, "compare.html", {"stems": stems}
     )
 
 

app/web/static/compare-select.js

@@ -3,7 +3,8 @@
 // the polled region and re-apply checked state on every afterSwap.
 
 (function () {
-  const MAX = 2;
+  const MIN = 2;
+  const MAX = 8;
   const selected = new Set();
 
   const btn = document.getElementById('compare-btn');
@@ -14,7 +15,7 @@
   function refreshButton() {
     const n = selected.size;
     countEl.textContent = `(${n}/${MAX})`;
-    btn.disabled = n !== MAX;
+    btn.disabled = n < MIN || n > MAX;
   }
 
   function applyToDOM() {
@@ -54,10 +55,10 @@
   });
 
   btn.addEventListener('click', () => {
-    if (selected.size !== MAX) return;
-    const [a, b] = [...selected];
-    const url = `/compare?a=${encodeURIComponent(a)}&b=${encodeURIComponent(b)}`;
-    window.open(url, '_blank', 'noopener');
+    const n = selected.size;
+    if (n < MIN || n > MAX) return;
+    const qs = [...selected].map((s) => `stem=${encodeURIComponent(s)}`).join('&');
+    window.open(`/compare?${qs}`, '_blank', 'noopener');
   });
 
   applyToDOM();

app/web/static/compare.js

@@ -1,9 +1,13 @@
-// compare.js — thin shim that parses ?a=&b= and hands off to panel-grid.js.
+// compare.js — thin shim that parses ?stem=…&stem=… (legacy ?a=&b=) and
+// hands off to panel-grid.js.
 
 import { mountPanels } from './panel-grid.js?v=1';
 
 const params = new URLSearchParams(window.location.search);
-const stems = [params.get('a') || '', params.get('b') || ''].filter(Boolean);
+let stems = params.getAll('stem').filter(Boolean);
+if (stems.length === 0) {
+  stems = [params.get('a') || '', params.get('b') || ''].filter(Boolean);
+}
 
 const host = document.getElementById('panel-host');
 const controls = document.getElementById('compare-controls');

app/web/static/runs-filter.js

@@ -0,0 +1,114 @@
+// Filter the recent-runs list by dataset + algorithm chips.
+// State lives outside #runs-slot so it survives the 3s htmx poll. After
+// each swap we repopulate chip options from whatever runs came back, then
+// re-apply the current selection to hide non-matching rows.
+
+(function () {
+  const slot = document.getElementById('runs-slot');
+  const dsEl = document.getElementById('runs-flt-dataset');
+  const algEl = document.getElementById('runs-flt-algo');
+  if (!slot || !dsEl || !algEl) return;
+
+  // null = "all selected" (no filtering on this axis). Populated Sets
+  // override that. Sticky across htmx swaps.
+  let datasets = null;
+  let algorithms = null;
+
+  function scanValues() {
+    const ds = new Set();
+    const alg = new Set();
+    slot.querySelectorAll('li.run').forEach((li) => {
+      const d = li.dataset.generator; if (d) ds.add(d);
+      const a = li.dataset.embedder;  if (a) alg.add(a);
+    });
+    return {
+      datasets: [...ds].sort(),
+      algorithms: [...alg].sort(),
+    };
+  }
+
+  function paint(container, values, selected) {
+    container.innerHTML = '';
+    for (const v of values) {
+      const b = document.createElement('button');
+      b.type = 'button';
+      const on = selected == null || selected.has(v);
+      b.className = 'chip' + (on ? ' is-on' : '');
+      b.dataset.value = v;
+      b.dataset.role = 'value';
+      b.setAttribute('aria-pressed', on ? 'true' : 'false');
+      b.textContent = v;
+      container.appendChild(b);
+    }
+    for (const [role, label] of [['all', 'all'], ['none', 'none']]) {
+      const b = document.createElement('button');
+      b.type = 'button';
+      b.className = 'chip chip-meta';
+      b.dataset.role = role;
+      b.textContent = label;
+      container.appendChild(b);
+    }
+  }
+
+  function repaint() {
+    const { datasets: allDs, algorithms: allAlg } = scanValues();
+    paint(dsEl, allDs, datasets);
+    paint(algEl, allAlg, algorithms);
+  }
+
+  function apply() {
+    slot.querySelectorAll('li.run').forEach((li) => {
+      const ds = li.dataset.generator || '';
+      const al = li.dataset.embedder || '';
+      const passDs = datasets == null || datasets.has(ds);
+      const passAl = algorithms == null || algorithms.has(al);
+      li.classList.toggle('filtered-out', !(passDs && passAl));
+    });
+  }
+
+  function bind(container, getSet, setSet, allGetter) {
+    container.addEventListener('click', (e) => {
+      const btn = e.target.closest('.chip');
+      if (!btn) return;
+      const role = btn.dataset.role;
+      const all = allGetter();
+      let cur = getSet();
+      if (cur == null) cur = new Set(all);
+      if (role === 'value') {
+        const v = btn.dataset.value;
+        if (cur.has(v)) cur.delete(v);
+        else cur.add(v);
+      } else if (role === 'all') {
+        cur = new Set(all);
+      } else if (role === 'none') {
+        cur = new Set();
+      }
+      setSet(cur);
+      repaint();
+      apply();
+    });
+  }
+
+  bind(
+    dsEl,
+    () => datasets,
+    (s) => { datasets = s; },
+    () => scanValues().datasets,
+  );
+  bind(
+    algEl,
+    () => algorithms,
+    (s) => { algorithms = s; },
+    () => scanValues().algorithms,
+  );
+
+  document.body.addEventListener('htmx:afterSwap', (e) => {
+    if (e.target && e.target.id === 'runs-slot') {
+      repaint();
+      apply();
+    }
+  });
+
+  repaint();
+  apply();
+})();

app/web/static/style.css

@@ -513,6 +513,37 @@ button.submit:disabled { background: var(--faint); border-color: var(--faint); c
   font-size: 0.76rem;
   font-style: italic;
 }
+
+.runs-filter {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.6rem 1.4rem;
+  padding: 0.25rem 0 0.7rem;
+  margin-bottom: 0.3rem;
+  border-bottom: 1px dashed var(--rule);
+}
+.runs-filter-group {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  min-width: 0;
+  flex: 1 1 auto;
+}
+.runs-filter-group .ctl-label {
+  font-family: var(--mono);
+  font-size: 0.66rem;
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+  color: var(--faint);
+}
+.runs-filter-group .chips {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.25rem 0.3rem;
+  align-items: center;
+}
+
+.runs li.run.filtered-out { display: none; }
 .runs li.run.just-submitted {
   background: linear-gradient(to right, var(--accent-tint), transparent 60%);
   padding-left: 0.55rem;

app/web/templates/_runs.html

@@ -7,7 +7,9 @@
 {% else %}
   <ul class="runs">
     {% for r in runs %}
-      <li class="run {% if just_submitted is defined and r.id == just_submitted %}just-submitted{% endif %}{% if r.stale %} stale{% endif %}">
+      <li class="run {% if just_submitted is defined and r.id == just_submitted %}just-submitted{% endif %}{% if r.stale %} stale{% endif %}"
+          data-embedder="{{ r.embedder_short or '' }}"
+          data-generator="{{ r.generator_short or '' }}">
         {% if r.emb_exists and not r.stale %}
           <input type="checkbox" class="compare-cb" data-stem="{{ r.emb_file[:-5] }}" aria-label="select run for comparison" />
         {% else %}

app/web/templates/compare.html

@@ -4,7 +4,7 @@
   <meta charset="utf-8" />
   <meta name="viewport" content="width=device-width,initial-scale=1" />
   <title>embedding notebook &middot; compare</title>
-  <link rel="stylesheet" href="/static/style.css?v=28" />
+  <link rel="stylesheet" href="/static/style.css?v=29" />
   <script type="importmap">
   {
     "imports": {
@@ -34,8 +34,7 @@
   </div>
 </header>
 
-<section class="compare-layout" id="compare-layout"
-         data-stem-a="{{ stem_a }}" data-stem-b="{{ stem_b }}">
+<section class="compare-layout" id="compare-layout">
 
   <div class="compare-controls" id="compare-controls">
     <button type="button" class="cc-play" id="cc-play" aria-label="play / pause">&#9654;</button>

app/web/templates/index.html

@@ -4,7 +4,7 @@
   <meta charset="utf-8" />
   <meta name="viewport" content="width=device-width,initial-scale=1" />
   <title>embedding notebook</title>
-  <link rel="stylesheet" href="/static/style.css?v=28" />
+  <link rel="stylesheet" href="/static/style.css?v=29" />
   <script src="https://unpkg.com/htmx.org@2.0.4"></script>
   <script type="importmap">
   {
@@ -303,9 +303,20 @@
 
     <div class="compare-bar">
       <button type="button" id="compare-btn" disabled>
-        compare selected <span id="compare-count">(0/2)</span>
+        compare selected <span id="compare-count">(0/8)</span>
       </button>
-      <span class="compare-hint muted">pick two embeddings &rarr; side-by-side animation in a new tab</span>
+      <span class="compare-hint muted">pick 2&ndash;8 embeddings &rarr; side-by-side animation in a new tab</span>
+    </div>
+
+    <div class="runs-filter" id="runs-filter">
+      <div class="runs-filter-group">
+        <span class="ctl-label">dataset</span>
+        <div class="chips" id="runs-flt-dataset" aria-label="filter by dataset"></div>
+      </div>
+      <div class="runs-filter-group">
+        <span class="ctl-label">algorithm</span>
+        <div class="chips" id="runs-flt-algo" aria-label="filter by algorithm"></div>
+      </div>
     </div>
 
     <div
@@ -471,7 +482,8 @@
 <script src="/static/theme.js?v=11"></script>
 <script type="module" src="/static/dataset-picker.js?v=11"></script>
 <script type="module" src="/static/metrics.js?v=11"></script>
-<script src="/static/compare-select.js?v=1"></script>
+<script src="/static/compare-select.js?v=2"></script>
+<script src="/static/runs-filter.js?v=1"></script>
 <script type="module" src="/static/run-modal.js?v=1"></script>
 <script>
   // Anchor-links alone don't expand <details>; force it.