feat: add all-skills leaderboard (task 0007)

Add a second pure transform to the benchmark core: a `--leaderboard` mode
that ranks per-skill results models into an index leaderboard, one row per
skill carrying both verdicts, links out to each per-skill report, and sorts
any red first (regressions above efficacy failures), then fragile-but-passing,
then clean green.

The fragile tier reuses the 0006 per-badge chips: the efficacy chip now
carries its win count so the leaderboard reads it against the pass floor
without recomputing margins, and fragility is scoped to the passing tier so a
red row never carries a chip. The runner's SKILL.md gains the no-argument
batch flow and the index invocation. The fixture test covers the tiered sort,
the not-applicable Regression cell, and the per-skill links.

.claude/tasks/0007-all-skills-leaderboard.md

@@ -0,0 +1,46 @@
+---
+spec: skill-benchmarking
+blocked-by: 0006-trend-history-and-ribbons
+---
+
+## What to build
+
+The batch view: `/benchmark-skill` with no argument benchmarks every skill and produces an index leaderboard, so an author knows at a glance which skills are green and which regressed.
+
+Invoked with no argument, the runner benchmarks every skill that follows the `tests/` convention and renders an index leaderboard.
+Each skill row carries both badges, Efficacy and Regression, and a skill with no previous version reads not-applicable in its Regression cell.
+The sort promotes any red first, with regressions ordered above efficacy failures — a regression means "you just broke something that was working," the more urgent signal while iterating — then fragile-but-passing skills, then clean green.
+The fragile-but-passing tier reuses the per-badge fragility signal introduced with the trend layer (0006) rather than recomputing it here.
+The leaderboard links out to the separate per-skill report files produced by a single-skill run.
+
+The per-skill report files and the index live flat under the `tests/.reports/` directory (its git-ignore established in 0004), keyed by unique skill name, since skill names are globally unique in this repo.
+Per-skill HTML is latest-only and overwritten each run, because the longitudinal data already lives in the per-skill history file.
+
+The core's fixture unit test is extended to cover the leaderboard rendering: the sort order across a mix of regressed, efficacy-failed, fragile, and clean skills, the not-applicable Regression cell for a skill with no previous version, and the links to per-skill files.
+
+## Acceptance criteria
+
+- [x] `/benchmark-skill` with no argument benchmarks every skill following the `tests/` convention and renders an index leaderboard.
+- [x] Each leaderboard row carries both the Efficacy and Regression badges; a skill with no previous version reads not-applicable in its Regression cell.
+- [x] The sort promotes any red first with regressions above efficacy failures, then fragile-but-passing skills, then clean green.
+- [x] The leaderboard links out to the separate per-skill report files.
+- [x] The per-skill report files and the leaderboard index live flat under `tests/.reports/` (its git-ignore established in 0004), keyed by unique skill name.
+- [x] Per-skill HTML is latest-only and overwritten each run.
+- [x] The core's fixture unit test covers the leaderboard sort order, the not-applicable Regression cell, and the per-skill links.
+
+## Implementation Notes
+
+The leaderboard is a second pure transform in the deterministic core, `core/benchmark_core.py`, fully covered by the extended `checks/benchmark-core.nix` fixture test.
+The in-session orchestration half — enumerate every skill with tests, run steps 1–6 for each, then render the index — is documented in `SKILL.md` step 7 rather than unit-tested, following the 0006 split where the workflow half is established by running the harness, not the fixture test.
+Per the invocation, the benchmark harness itself was not run.
+
+- **The leaderboard consumes per-skill results JSONs, not bundles, so the core stays a pure transform.**
+  The single-skill flow already writes `tests/.reports/<name>.results.json`; the batch flow feeds every one of those to `--leaderboard`, which sorts and renders the index to `tests/.reports/index.html`.
+- **The CLI gains a `--leaderboard` mode that reuses `--json`/`--html`.**
+  The positional argument was widened from a single `bundle` to `inputs` (`nargs="+"`) with an explicit count guard, so the single-skill contract `core.py <bundle> --json … --html …` is unchanged and every existing call site still works.
+- **The fragile-but-passing tier reuses the 0006 per-badge chips rather than recomputing margins.**
+  The regression chip already means "one loss from regressing." A green run always chips its narrowest efficacy case, so chip presence alone cannot tell a barely-green skill from a roomy one; the efficacy chip therefore now carries its win count, and the leaderboard reads that count against the existing `EFFICACY_WINS_FLOOR` to decide efficacy fragility — the spec's own definition, "closest to dropping under three wins."
+- **Fragility is scoped to the fragile-but-passing tier (review finding).**
+  A red skill carries no fragility chip even when a still-passing axis sits at its edge, so the chip stays the marker of tier 2 rather than leaking onto a red row.
+- **Two leaderboard fixtures are authored inline in the check, alongside the four scored models.**
+  No committed bundle reaches the clean-green tier (the clean bundle's narrowest efficacy case sits on the floor, so it is itself fragile) or the efficacy-red-with-a-still-fragile-regression-axis crossing, so `robust-skill` and `leaky-skill` are synthesized as small results JSONs the way 0006 synthesized its 55-line history seed.

checks/benchmark-core.nix

@@ -6,6 +6,8 @@
 # It also drives the longitudinal layer: the per-skill history append-and-trim,
 # the two trend ribbons including the two-arm gap in the regression series, and
 # the per-badge fragility chips on a clean run and a green-but-fragile one.
+# Last it drives the all-skills leaderboard: the tiered sort, the not-applicable
+# Regression cell, and the links out to each per-skill report.
 # No LLM runs.
 {
   pkgs,
@@ -199,6 +201,8 @@ pkgs.runCommandLocal "benchmark-core-check"
     # The narrowest efficacy case (fewest wins) carries the chip, the roomy one does not.
     assert [ch["axis"] for ch in cases["narrowest"]["chips"]] == ["efficacy"], cases["narrowest"]["chips"]
     assert cases["roomy"]["chips"] == [], cases["roomy"]["chips"]
+    # The efficacy chip carries the case's win count, not merely its label text.
+    assert cases["narrowest"]["chips"][0]["wins"] == 3, cases["narrowest"]["chips"]
     print("clean-run assertions passed")
     PY
 
@@ -277,5 +281,78 @@ pkgs.runCommandLocal "benchmark-core-check"
     grep -q 'class="chip efficacy"' fragile.html || fail "fragile run omits the efficacy chip"
     grep -q 'class="chip regression"' fragile.html || fail "fragile run omits the regression chip"
 
+    # --- all-skills leaderboard: tiered sort, the N/A cell, and per-skill links ---
+    echo "the core ranks per-skill results into a tiered index leaderboard"
+    # A synthetic clean-green skill whose narrowest efficacy margin sits above the
+    # floor, so it is the one input that reaches the clean-green tier. The four
+    # scored models above supply the other tiers: three-arm regresses (tier 0),
+    # two-arm fails efficacy with regression not-applicable (tier 1), and the
+    # clean and fragile green runs are both one flip from failing (tier 2).
+    python3 - robust.results.json leaky.results.json <<'PY' || fail "writing the leaderboard fixtures failed"
+    import json, sys
+    # A clean-green skill whose narrowest efficacy margin clears the floor, the
+    # one input that reaches the clean-green tier.
+    json.dump({
+        "skill": "robust-skill",
+        "efficacyVerdict": "green",
+        "regressionVerdict": "green",
+        "cases": [{"chips": [{"axis": "efficacy", "wins": 5}]}],
+    }, open(sys.argv[1], "w"))
+    # An efficacy-red skill whose still-green regression axis sits one loss from
+    # regressing, so it carries a regression chip yet belongs in the red tier.
+    json.dump({
+        "skill": "leaky-skill",
+        "efficacyVerdict": "red",
+        "regressionVerdict": "green",
+        "cases": [{"chips": [{"axis": "regression"}]}],
+    }, open(sys.argv[2], "w"))
+    PY
+
+    python3 "$core" --leaderboard \
+      three.json two.json clean.json fragile.json robust.results.json leaky.results.json \
+      --json board.json --html board.html \
+      || fail "the core exited non-zero rendering the leaderboard"
+
+    python3 - board.json <<'PY' || fail "a leaderboard assertion failed"
+    import json, sys
+    rows = json.load(open(sys.argv[1]))
+
+    # Any red first — regressions above efficacy failures, efficacy failures
+    # ordered by name — then fragile-passing by name, then clean green.
+    assert [r["skill"] for r in rows] == [
+        "sample-skill", "leaky-skill", "sample-skill-2arm",
+        "clean-skill", "fragile-skill", "robust-skill",
+    ], [r["skill"] for r in rows]
+    assert [r["tier"] for r in rows] == [0, 1, 1, 2, 2, 3], [r["tier"] for r in rows]
+
+    by = {r["skill"]: r for r in rows}
+    # The regressed skill outranks the merely-efficacy-failed ones.
+    assert by["sample-skill"]["regressionVerdict"] == "red"
+    # A skill with no previous version reads not-applicable in its Regression cell.
+    assert by["sample-skill-2arm"]["regressionVerdict"] == "not-applicable"
+    assert by["sample-skill-2arm"]["efficacyVerdict"] == "red"
+    # The fragile tier reuses the per-badge chips: a floor-bound efficacy margin,
+    # a case one loss from regressing, or both.
+    assert by["clean-skill"]["fragileAxes"] == ["efficacy"], by["clean-skill"]
+    assert by["fragile-skill"]["fragileAxes"] == ["efficacy", "regression"], by["fragile-skill"]
+    assert by["robust-skill"]["fragileAxes"] == [], by["robust-skill"]
+    # A red skill carries no fragility chip even when a still-passing axis is at
+    # its edge, so the chip stays the marker of the fragile-but-passing tier.
+    assert by["leaky-skill"]["fragileAxes"] == [], by["leaky-skill"]
+    # Every row links out to its per-skill report, keyed by skill name.
+    for r in rows:
+        assert r["href"] == r["skill"] + ".html", r
+    print("leaderboard assertions passed")
+    PY
+
+    echo "the leaderboard is self-contained and links out to each per-skill report"
+    grep -q '<!doctype html>' board.html || fail "the leaderboard is not self-contained"
+    for skill in sample-skill sample-skill-2arm clean-skill fragile-skill robust-skill leaky-skill; do
+      grep -q "href=\"$skill.html\"" board.html || fail "the leaderboard omits the link to $skill"
+    done
+    grep -q '>N/A<' board.html || fail "the leaderboard omits the not-applicable Regression cell"
+    grep -q 'near regressing' board.html || fail "the leaderboard omits the regression fragility chip"
+    grep -q 'narrow efficacy' board.html || fail "the leaderboard omits the efficacy fragility chip"
+
     touch "$out"
   ''

skills/benchmark-skill/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: benchmark-skill
-description: Benchmark a skill's efficacy against a no-skill baseline and, when a released version exists, its regression against that version, rendering an HTML report. Run deliberately as /benchmark-skill <name>, never automatically.
+description: Benchmark a skill's efficacy against a no-skill baseline and, when a released version exists, its regression against that version, rendering an HTML report. Run deliberately as /benchmark-skill <name> for one skill, or /benchmark-skill with no argument for the all-skills leaderboard, never automatically.
 disable-model-invocation: true
 ---
 
@@ -9,6 +9,7 @@ disable-model-invocation: true
 Prove that a skill genuinely improves the agent's work rather than reading well and adding nothing.
 
 Running `/benchmark-skill <name>` executes that skill's authored test cases as a controlled experiment and produces a self-contained HTML report carrying two independent verdicts: an **Efficacy verdict** (does the skill beat no-skill) and a **Regression verdict** (did my in-progress edit degrade it from the released version).
+Running `/benchmark-skill` with **no argument** benchmarks every skill that follows the `tests/` convention and renders an index leaderboard over their reports (step 7).
 Each case runs a **new-skill arm** (the working tree) and a **no-skill baseline arm**, and — whenever the skill already exists on main and its directory differs from that released state — a third **previous-version arm** materialized from main's `HEAD`.
 Each arm runs several times, and a blind judge decides which arm's output better satisfies the case's author-written expectations.
 Two head-to-heads fall out of the arms per trial: **efficacy** pairs the new arm against no-skill, and **regression** pairs it against the previous version.
@@ -27,6 +28,7 @@ Run from the repo root: every path in the steps below is relative to it.
 ## 1. Resolve the target and validate its tests tree
 
 The user passes the skill name as `<name>`.
+With **no `<name>`** you are in the all-skills mode: skip to step 7, which enumerates the skills and drives steps 1–6 for each.
 Find the skill's directory by its leaf name under `skills/` (any depth), and find its tests at the mirror point under `tests/skills/…/<name>/`.
 If no skill directory maps to `<name>`, stop and say so.
 If the skill exists but has no tests directory or no case directories, report that the skill has no tests and stop — there is nothing to benchmark.
@@ -188,3 +190,27 @@ Clean up the scratch when done: remove the `tests/.reports/.work/` directory and
 
 Done when `tests/.reports/<name>.html` exists.
 Report both verdicts, the path to the report, and any flagged losses or regressions to the user.
+
+## 7. Benchmark every skill and render the leaderboard
+
+This step runs only in the all-skills mode — `/benchmark-skill` with no `<name>`.
+
+Enumerate every skill the same way step 1 resolves one: each skill directory under `skills/` (any depth) whose mirror point under `tests/skills/…/` holds case directories.
+A skill with no tests directory is skipped rather than failing the batch; note which skills were skipped.
+Run steps 1–6 for each skill in turn, so each writes its own per-skill report and results model under `tests/.reports/`, flat and keyed by skill name — the per-skill HTML is latest-only and overwritten each run, since the longitudinal data lives in the per-skill history file.
+
+Then render the index over every per-skill results model:
+
+```sh
+python3 skills/benchmark-skill/core/benchmark_core.py --leaderboard \
+  tests/.reports/*.results.json \
+  --html tests/.reports/index.html \
+  --generated-at "<ISO-8601 timestamp>"
+```
+
+The core sorts the rows — any red first with regressions ordered above efficacy failures, then fragile-but-passing skills, then clean green — and links each row out to its `<name>.html`.
+A skill with no previous version reads not-applicable in its Regression cell.
+The fragile-but-passing tier reuses the per-badge fragility signal from the per-skill reports: a case one loss from regressing, or a narrowest efficacy margin sitting on the pass floor.
+
+Done when `tests/.reports/index.html` exists.
+Report the leaderboard path, and per skill both verdicts and any flagged losses or regressions, to the user.

skills/benchmark-skill/core/benchmark_core.py

@@ -16,11 +16,18 @@ appended to it, the file is trimmed oldest-first, and the report grows two trend
 ribbons plotted from the recent tail. That file read-and-rewrite is the only side
 effect, opt-in and deterministic given the same file contents and inputs.
 
+Given `--leaderboard`, the positional arguments are read as several per-skill
+results models instead, and the transform yields the index leaderboard: one row
+per skill carrying both verdicts, sorted with regressions first, then efficacy
+failures, then fragile-but-passing skills, then clean green.
+
 Usage:
     benchmark_core.py <bundle.json> [--json <out.json>] [--html <out.html>]
                       [--history <hist.jsonl>]
+    benchmark_core.py --leaderboard <results.json>... [--json <out.json>]
+                      [--html <out.html>] [--generated-at <stamp>]
 
-With no output flags it writes the results model as JSON to stdout.
+With no output flags it writes the model as JSON to stdout.
 """
 
 import argparse
@@ -193,6 +200,7 @@ def _flag_fragility(cases, efficacy_id, regression, efficacy_green, regression_g
         wins = narrowest["comparisons"][efficacy_id]["wins"]
         narrowest["chips"].append({
             "axis": "efficacy",
+            "wins": wins,
             "label": f"narrowest efficacy margin · {wins}W",
         })
 
@@ -331,6 +339,67 @@ def build_trend(series):
     }
 
 
+# --- All-skills leaderboard ---------------------------------------------------
+
+
+def _fragile_axes(results):
+    """The axes on which a passing skill sits one trial-flip from failing.
+
+    Reuses the per-badge fragility chips rather than recomputing margins: the
+    regression chip already marks a case one loss from regressing, and the
+    efficacy chip marks the narrowest case, fragile exactly when its win count
+    rests on the pass floor. A green run always chips its narrowest efficacy
+    case, so the floor test is what tells a barely-green skill from a roomy one.
+    """
+    axes = set()
+    for case in results["cases"]:
+        for chip in case.get("chips", []):
+            if chip["axis"] == "regression":
+                axes.add("regression")
+            elif chip["axis"] == "efficacy" and chip.get("wins") == EFFICACY_WINS_FLOOR:
+                axes.add("efficacy")
+    return sorted(axes)
+
+
+def _leaderboard_tier(results, fragile):
+    """The sort tier, most urgent first.
+
+    A regression outranks an efficacy failure because it means a skill that was
+    working just broke — the sharper signal mid-edit. A passing skill still one
+    flip from failing sorts above a clean sweep.
+    """
+    if results["regressionVerdict"] == "red":
+        return 0
+    if results["efficacyVerdict"] == "red":
+        return 1
+    if fragile:
+        return 2
+    return 3
+
+
+def build_leaderboard(models):
+    """Rank per-skill results into leaderboard rows, most urgent first.
+
+    Rows within a tier order by skill name, so the board diffs cleanly run to run.
+    """
+    rows = []
+    for m in models:
+        axes = _fragile_axes(m)
+        tier = _leaderboard_tier(m, bool(axes))
+        rows.append({
+            "skill": m["skill"],
+            "efficacyVerdict": m["efficacyVerdict"],
+            "regressionVerdict": m["regressionVerdict"],
+            # Fragility marks a passing skill one flip from failing, so a red skill
+            # carries no chip even when a still-passing axis is at its edge.
+            "fragileAxes": axes if tier == 2 else [],
+            "tier": tier,
+            "href": f"{m['skill']}.html",
+        })
+    rows.sort(key=lambda r: (r["tier"], r["skill"]))
+    return rows
+
+
 # --- HTML rendering -----------------------------------------------------------
 
 _STYLE = """
@@ -371,6 +440,10 @@ th, td { text-align: right; padding: .4rem .6rem; border-bottom: 1px solid #e5e5
 th:first-child, td:first-child { text-align: left; }
 thead th { border-bottom: 2px solid #ccc; }
 .footnote { color: #777; font-size: .8rem; margin: .3rem 0 1.5rem; }
+.board td, .board th { text-align: left; }
+.board td.verdict, .board th.verdict { text-align: right; }
+.board a { color: #1a56c4; text-decoration: none; font-weight: 600; }
+.board a:hover { text-decoration: underline; }
 .case { border: 1px solid #e5e5e5; border-radius: 8px; padding: 1rem 1.25rem;
         margin: .75rem 0; background: #fff; }
 .case.fail { border-color: #f0b6b6; }
@@ -405,6 +478,16 @@ thead th { border-bottom: 2px solid #ccc; }
 """
 
 
+def _document(title, body):
+    """Wrap rendered body markup in the self-contained HTML document shell."""
+    return (
+        "<!doctype html><html><head><meta charset=\"utf-8\">"
+        f"<title>{title}</title><style>{_STYLE}</style></head><body>"
+        + body
+        + "</body></html>"
+    )
+
+
 def _fmt_int(n):
     return f"{n:,}"
 
@@ -444,10 +527,16 @@ def _headline(results):
             f"and this edit regressed {_plural(reg_fail, 'case')}.")
 
 
+_BADGE_TEXT = {"green": "GREEN", "red": "RED", "not-applicable": "N/A"}
+_BADGE_CLASS = {"green": "green", "red": "red", "not-applicable": "na"}
+
+
+def _state_badge(state):
+    return f"<span class=\"badge {_BADGE_CLASS[state]}\">{_BADGE_TEXT[state]}</span>"
+
+
 def _badge(label, state):
-    text = {"green": "GREEN", "red": "RED", "not-applicable": "N/A"}[state]
+    return f"<span class=\"badge {_BADGE_CLASS[state]}\">{label}: {_BADGE_TEXT[state]}</span>"
-    cls = {"green": "green", "red": "red", "not-applicable": "na"}[state]
-    return f"<span class=\"badge {cls}\">{label}: {text}</span>"
 
 
 def _sparkline(points, width=240, height=44):
@@ -653,28 +742,96 @@ def render_html(results):
 
     out.append("</div>")
 
-    title = f"Benchmark — {e(results['skill'])}"
+    return _document(f"Benchmark — {e(results['skill'])}", "".join(out))
-    return (
+
-        "<!doctype html><html><head><meta charset=\"utf-8\">"
+
-        f"<title>{title}</title><style>{_STYLE}</style></head><body>"
+_FRAGILE_LABEL = {"efficacy": "narrow efficacy", "regression": "near regressing"}
-        + "".join(out)
+
-        + "</body></html>"
+
-    )
+def render_leaderboard(rows, generated_at=""):
+    """The all-skills index: one linked row per skill carrying both verdicts."""
+    e = html.escape
+    out = ["<div class=\"wrap\">", "<h1>Skill benchmarks</h1>"]
+    meta = [e(generated_at)] if generated_at else []
+    meta.append(_plural(len(rows), "skill"))
+    out.append(f"<div class=\"meta\">{' · '.join(meta)}</div>")
+
+    out.append("<table class=\"board\"><thead><tr><th>Skill</th>"
+               "<th class=\"verdict\">Efficacy</th>"
+               "<th class=\"verdict\">Regression</th></tr></thead><tbody>")
+    for r in rows:
+        chips = "".join(
+            f"<span class=\"chip {axis}\">{_FRAGILE_LABEL[axis]}</span>"
+            for axis in r["fragileAxes"]
+        )
+        out.append(
+            f"<tr><td><a href=\"{e(r['href'])}\">{e(r['skill'])}</a>{chips}</td>"
+            f"<td class=\"verdict\">{_state_badge(r['efficacyVerdict'])}</td>"
+            f"<td class=\"verdict\">{_state_badge(r['regressionVerdict'])}</td></tr>"
+        )
+    out.append("</tbody></table></div>")
+
+    return _document("Skill benchmarks", "".join(out))
+
+
+def _write_outputs(model, render, json_out, html_out):
+    """Emit a model as JSON and/or rendered HTML, or to stdout if neither given."""
+    if json_out:
+        with open(json_out, "w") as f:
+            json.dump(model, f, indent=2)
+    if html_out:
+        with open(html_out, "w") as f:
+            f.write(render())
+    if not json_out and not html_out:
+        json.dump(model, sys.stdout, indent=2)
+        sys.stdout.write("\n")
 
 
 def main(argv=None):
     parser = argparse.ArgumentParser(description=__doc__)
-    parser.add_argument("bundle", help="path to the run-bundle JSON")
+    parser.add_argument(
-    parser.add_argument("--json", dest="json_out", help="write the results model here")
+        "inputs",
-    parser.add_argument("--html", dest="html_out", help="write the HTML report here")
+        nargs="+",
+        help="the run-bundle JSON, or the per-skill results JSONs with --leaderboard",
+    )
+    parser.add_argument("--json", dest="json_out", help="write the model here")
+    parser.add_argument("--html", dest="html_out", help="write the HTML here")
     parser.add_argument(
         "--history",
         dest="history",
         help="append this run to the JSON-lines history file and draw the trend ribbons",
     )
+    parser.add_argument(
+        "--leaderboard",
+        action="store_true",
+        help="render the index leaderboard over the given per-skill results JSONs",
+    )
+    parser.add_argument(
+        "--generated-at",
+        dest="generated_at",
+        default="",
+        help="timestamp stamped on the leaderboard index",
+    )
     args = parser.parse_args(argv)
 
-    with open(args.bundle) as f:
+    if args.leaderboard:
+        if args.history:
+            parser.error("--history does not apply in leaderboard mode")
+        models = []
+        for path in args.inputs:
+            with open(path) as f:
+                models.append(json.load(f))
+        rows = build_leaderboard(models)
+        _write_outputs(
+            rows, lambda: render_leaderboard(rows, args.generated_at),
+            args.json_out, args.html_out,
+        )
+        return 0
+
+    if len(args.inputs) != 1:
+        parser.error("scoring a run takes exactly one bundle; use --leaderboard for many")
+
+    with open(args.inputs[0]) as f:
         bundle = json.load(f)
 
     results = build_results(bundle)
@@ -684,15 +841,9 @@ def main(argv=None):
         write_history(args.history, trim_history(series))
         results["trend"] = build_trend(series)
 
-    if args.json_out:
+    _write_outputs(
-        with open(args.json_out, "w") as f:
+        results, lambda: render_html(results), args.json_out, args.html_out
-            json.dump(results, f, indent=2)
+    )
-    if args.html_out:
-        with open(args.html_out, "w") as f:
-            f.write(render_html(results))
-    if not args.json_out and not args.html_out:
-        json.dump(results, sys.stdout, indent=2)
-        sys.stdout.write("\n")
 
     return 0