From 1d9ae1bba2729525af5c1030d532dd1b97de2707 Mon Sep 17 00:00:00 2001
From: suzuke <suzuke789@gmail.com>
Date: Sat, 25 Apr 2026 22:34:35 +0800
Subject: [PATCH 1/3] feat(m2): reporter compare mode + `crucible compare
 --html` (M2 PR 11)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Side-by-side static HTML for two ledgers — useful for "greedy vs
bfts-lite on the same example" demo-gate comparisons. Strict read-only:
no orchestrator changes, no ledger mutation, no config normalization.

Renderer: `crucible.reporter.compare.render_comparison_html(left, right,
*, left_label, right_label, …)`. Reuses html_tree's `_render_tree` /
`_render_summary` / `_best_node_id` / `_color_for` so the per-side cards
look identical to the single-view report.

CLI: `crucible compare a b --html [--html-out PATH]` writes
`<project>/reports/compare-a-vs-b.html` by default. `--right-project
DIR` opts into cross-project comparison (e.g. compress-greedy workspace
vs compress-bfts workspace from M1b demo gate). Cross-project default
output is cwd to avoid writing into the wrong project.

Reviewer round 1 verdict: ACCEPT with constraints — all addressed:
- Missing data → "n/a" / empty panel, never silently zero
- Δ line shown ONLY when both sides agree on metric direction (and
  both bests exist); otherwise omitted (no auto-winner verdict)
- Output path: explicit `--html-out` or predictable default
- Strict read-only: no writes anywhere outside the report file
- Renderer extraction: kept html_tree.py as stable single-view facade,
  compare.py imports underscore helpers without changing their API

Tests: 11 new in test_reporter_compare.py + 4 new CLI tests in
test_cli.py. Full suite: 2413 passed / 4 skipped, 0 regressions over
M2 PR 10 baseline (2397).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 src/crucible/cli.py               | 133 ++++++++++++-
 src/crucible/reporter/__init__.py |   3 +-
 src/crucible/reporter/compare.py  | 235 +++++++++++++++++++++++
 tests/test_cli.py                 |  92 +++++++++
 tests/test_reporter_compare.py    | 309 ++++++++++++++++++++++++++++++
 5 files changed, 769 insertions(+), 3 deletions(-)
 create mode 100644 src/crucible/reporter/compare.py
 create mode 100644 tests/test_reporter_compare.py

diff --git a/src/crucible/cli.py b/src/crucible/cli.py
index 6ad97cd..f4a6947 100644
--- a/src/crucible/cli.py
+++ b/src/crucible/cli.py
@@ -691,8 +691,34 @@ def history(tag: str, last: int, project_dir: str, as_json: bool, fmt: str) -> N
 @main.command(help=_("Compare two experiment runs side by side."))
 @click.argument("tags", nargs=2)
 @click.option("--project-dir", default=".", help=_("Project root directory."))
+@click.option("--right-project", default=None,
+              help=_("Project root for the SECOND tag (for cross-project compare). "
+                     "If omitted, both tags are read from --project-dir."))
 @click.option("--json", "as_json", is_flag=True, help=_("Output as JSON."))
-def compare(tags: tuple[str, str], project_dir: str, as_json: bool) -> None:
+@click.option("--html", "html_output", is_flag=True,
+              help=_("Render side-by-side HTML comparison from ledger.jsonl files. "
+                     "M2 PR 11."))
+@click.option("--html-out", default=None,
+              help=_("Output path for the HTML report "
+                     "(default: <project>/reports/compare-<a>-vs-<b>.html)."))
+def compare(tags: tuple[str, str], project_dir: str, right_project: str | None,
+            as_json: bool, html_output: bool, html_out: str | None) -> None:
+    tag_a, tag_b = tags
+
+    if html_output:
+        _render_compare_html(
+            tag_a, tag_b,
+            project_dir=project_dir,
+            right_project_dir=right_project,
+            html_out=html_out,
+        )
+        return
+
+    if right_project is not None:
+        raise click.ClickException(
+            _("--right-project is currently only supported with --html")
+        )
+
     try:
         project = Path(project_dir).resolve()
         config = load_config(project)
@@ -727,7 +753,6 @@ def compare(tags: tuple[str, str], project_dir: str, as_json: bool) -> None:
         click.echo(json_module.dumps(comparison))
         return
 
-    tag_a, tag_b = tags
     col_w = max(len(tag_a), len(tag_b), 12)
     click.echo(f"{'':>16} {tag_a:>{col_w}} {tag_b:>{col_w}}")
     for key in ("iterations", "kept", "discarded", "crashed", "best_metric", "best_commit"):
@@ -737,6 +762,110 @@ def compare(tags: tuple[str, str], project_dir: str, as_json: bool) -> None:
         click.echo(f"{label:>16} {str(va):>{col_w}} {str(vb):>{col_w}}")
 
 
+def _build_metric_lookup(results_path: Path) -> dict[str, float]:
+    """Build attempt_id → metric_value map from a results-<tag>.jsonl file.
+
+    Mirrors the same id derivation used by `crucible postmortem --html`.
+    Returns {} if the file is missing or unreadable (best-effort).
+    """
+    metric_lookup: dict[str, float] = {}
+    if not results_path.exists():
+        return metric_lookup
+    try:
+        with results_path.open() as fp:
+            for i, line in enumerate(fp, start=1):
+                rec = json_module.loads(line)
+                if rec.get("metric_value") is None:
+                    continue
+                beam_id = rec.get("beam_id")
+                iteration = rec.get("iteration", i)
+                attempt_id = (
+                    f"n{iteration:06d}" if beam_id is None
+                    else f"b{beam_id}n{iteration:06d}"
+                )
+                metric_lookup[attempt_id] = float(rec["metric_value"])
+    except Exception as exc:
+        logging.getLogger(__name__).warning(
+            "could not build metric_lookup from %s: %s", results_path, exc
+        )
+    return metric_lookup
+
+
+def _render_compare_html(
+    tag_a: str,
+    tag_b: str,
+    *,
+    project_dir: str,
+    right_project_dir: str | None,
+    html_out: str | None,
+) -> None:
+    """Render `crucible compare --html` output. Strict read-only."""
+    from crucible.reporter import render_comparison_html
+
+    left_project = Path(project_dir).resolve()
+    right_project = (
+        Path(right_project_dir).resolve() if right_project_dir else left_project
+    )
+    cross_project = right_project != left_project
+
+    left_ledger = left_project / "logs" / f"run-{tag_a}" / "ledger.jsonl"
+    right_ledger = right_project / "logs" / f"run-{tag_b}" / "ledger.jsonl"
+    for label, path in (("left", left_ledger), ("right", right_ledger)):
+        if not path.exists():
+            raise click.ClickException(
+                _("ledger not found for {label} side: {path}").format(
+                    label=label, path=path
+                )
+            )
+
+    # Per-side metric direction: read each project's config independently.
+    # If a config is missing/unreadable, pass None → renderer omits Δ.
+    left_dir = _safe_read_metric_direction(left_project)
+    right_dir = _safe_read_metric_direction(right_project)
+
+    left_metrics = _build_metric_lookup(left_project / results_filename(tag_a))
+    right_metrics = _build_metric_lookup(right_project / results_filename(tag_b))
+
+    title = (
+        f"Crucible Compare — {tag_a} (left) vs {tag_b} (right)"
+        if not cross_project
+        else f"Crucible Compare — {left_project.name}:{tag_a} vs {right_project.name}:{tag_b}"
+    )
+
+    out = render_comparison_html(
+        left_ledger,
+        right_ledger,
+        left_label=tag_a,
+        right_label=tag_b,
+        title=title,
+        left_metric_lookup=left_metrics,
+        right_metric_lookup=right_metrics,
+        left_direction=left_dir,
+        right_direction=right_dir,
+    )
+
+    if html_out:
+        target = Path(html_out)
+    elif cross_project:
+        target = Path.cwd() / f"compare-{tag_a}-vs-{tag_b}.html"
+    else:
+        reports_dir = left_project / "reports"
+        reports_dir.mkdir(exist_ok=True)
+        target = reports_dir / f"compare-{tag_a}-vs-{tag_b}.html"
+
+    target.write_text(out)
+    click.echo(_("Wrote HTML comparison to {path}").format(path=target))
+
+
+def _safe_read_metric_direction(project: Path) -> str | None:
+    """Return `metric.direction` from a project config, or None on failure."""
+    try:
+        cfg = load_config(project)
+        return cfg.metric.direction
+    except (ConfigError, FileNotFoundError, OSError):
+        return None
+
+
 @main.command(help=_("Generate a new experiment from a natural language description."))
 @click.argument("dest", type=click.Path())
 @click.option("--describe", default=None, help=_("Experiment description (skip interactive prompt)."))
diff --git a/src/crucible/reporter/__init__.py b/src/crucible/reporter/__init__.py
index bcc107c..5b427fa 100644
--- a/src/crucible/reporter/__init__.py
+++ b/src/crucible/reporter/__init__.py
@@ -8,6 +8,7 @@
 M3 will add d3.js interactive expand/collapse.
 """
 
+from crucible.reporter.compare import render_comparison_html
 from crucible.reporter.html_tree import render_static_html
 
-__all__ = ["render_static_html"]
+__all__ = ["render_static_html", "render_comparison_html"]
diff --git a/src/crucible/reporter/compare.py b/src/crucible/reporter/compare.py
new file mode 100644
index 0000000..6c3ca43
--- /dev/null
+++ b/src/crucible/reporter/compare.py
@@ -0,0 +1,235 @@
+"""Side-by-side comparison renderer — M2 PR 11.
+
+Produces a single static HTML doc that places two ledger trees in two
+columns. Useful for "greedy vs bfts-lite on the same example" demo-gate
+comparisons.
+
+Strict read-only: never writes to ledgers, never normalises config. If a
+side has missing metadata (no metrics, no cost), the column renders
+"n/a" rather than failing the whole comparison.
+"""
+
+from __future__ import annotations
+
+import html
+from datetime import datetime
+from pathlib import Path
+from typing import Sequence
+
+from crucible.ledger import AttemptNode, TrialLedger
+from crucible.reporter.html_tree import (
+    _CSS,
+    _best_node_id,
+    _color_for,
+    _format_cost,
+    _render_summary,
+    _render_tree,
+)
+
+
+def render_comparison_html(
+    left_ledger_path: Path | str,
+    right_ledger_path: Path | str,
+    *,
+    left_label: str,
+    right_label: str,
+    title: str = "Crucible Compare",
+    left_metric_lookup: dict[str, float] | None = None,
+    right_metric_lookup: dict[str, float] | None = None,
+    left_direction: str | None = None,
+    right_direction: str | None = None,
+) -> str:
+    """Render a side-by-side comparison as a self-contained HTML document.
+
+    Args:
+        left_ledger_path / right_ledger_path: paths to ledger.jsonl files.
+        left_label / right_label: user-facing labels for each side
+            (e.g. "greedy", "bfts-lite", or a tag name).
+        title: top-of-page title.
+        left_metric_lookup / right_metric_lookup: per-side `attempt_id →
+            metric_value` maps. Independent because two runs may use
+            different metric scales (rare but legal).
+        left_direction / right_direction: per-side metric direction
+            ("maximize" / "minimize"). If both sides agree (and both are
+            non-None), a Δ best-metric line is rendered. If they differ
+            or either is None, the Δ is omitted.
+
+    Returns:
+        Complete HTML document (UTF-8 string).
+
+    Missing-data behaviour: an unreadable ledger raises (file errors are
+    not silent). An empty ledger renders an "(empty)" panel on that
+    side. Missing metric_lookup → no metric line on cards, no Δ.
+    """
+    left_nodes = _safe_load_nodes(left_ledger_path)
+    right_nodes = _safe_load_nodes(right_ledger_path)
+
+    left_metrics = left_metric_lookup or {}
+    right_metrics = right_metric_lookup or {}
+
+    left_best_id = _best_node_id(left_nodes, left_metrics, left_direction or "maximize")
+    right_best_id = _best_node_id(right_nodes, right_metrics, right_direction or "maximize")
+
+    delta_line = _render_delta(
+        left_best_id, right_best_id,
+        left_metrics, right_metrics,
+        left_direction, right_direction,
+    )
+
+    left_section = _render_side(
+        left_label, left_nodes, left_metrics, left_best_id,
+    )
+    right_section = _render_side(
+        right_label, right_nodes, right_metrics, right_best_id,
+    )
+
+    return _COMPARE_PAGE_TEMPLATE.format(
+        title=html.escape(title),
+        css=_CSS + _COMPARE_CSS,
+        delta=delta_line,
+        left_section=left_section,
+        right_section=right_section,
+        generated_at=html.escape(datetime.utcnow().strftime("%Y-%m-%d %H:%M:%S UTC")),
+    )
+
+
+# ---------------------------------------------------------------------------
+# Internal helpers
+# ---------------------------------------------------------------------------
+
+
+def _safe_load_nodes(path: Path | str) -> Sequence[AttemptNode]:
+    """Load ledger nodes; ledger-read errors propagate (don't silently zero)."""
+    return TrialLedger(Path(path)).all_nodes()
+
+
+def _render_side(
+    label: str,
+    nodes: Sequence[AttemptNode],
+    metric_lookup: dict[str, float],
+    best_id: str | None,
+) -> str:
+    """Render one column: header label + summary pills + tree."""
+    safe_label = html.escape(label)
+    if not nodes:
+        return (
+            f'<section class="side">'
+            f'<h2 class="side-label">{safe_label}</h2>'
+            f'<div class="empty">(no attempts in this ledger)</div>'
+            f'</section>'
+        )
+    summary = _render_summary(nodes, metric_lookup, best_id)
+    cards = _render_tree(nodes, best_id, metric_lookup)
+    return (
+        f'<section class="side">'
+        f'<h2 class="side-label">{safe_label}</h2>'
+        f'{summary}'
+        f'<main class="side-cards">{cards}</main>'
+        f'</section>'
+    )
+
+
+def _render_delta(
+    left_best_id: str | None,
+    right_best_id: str | None,
+    left_metrics: dict[str, float],
+    right_metrics: dict[str, float],
+    left_direction: str | None,
+    right_direction: str | None,
+) -> str:
+    """Render the Δ line — only when both directions agree and both metrics
+    are available. Otherwise return an empty string (no auto-verdict)."""
+    if left_best_id is None or right_best_id is None:
+        return ""
+    if left_direction is None or right_direction is None:
+        return ""
+    if left_direction != right_direction:
+        return ""
+    left_v = left_metrics.get(left_best_id)
+    right_v = right_metrics.get(right_best_id)
+    if left_v is None or right_v is None:
+        return ""
+    delta = right_v - left_v
+    sign = "+" if delta >= 0 else ""
+    return (
+        f'<div class="delta">'
+        f'left best: <code>{left_v}</code>'
+        f' &nbsp;|&nbsp; '
+        f'right best: <code>{right_v}</code>'
+        f' &nbsp;|&nbsp; '
+        f'Δ (right − left): <code>{sign}{delta}</code>'
+        f' <span class="delta-note">(arithmetic delta only — no winner verdict)</span>'
+        f'</div>'
+    )
+
+
+# ---------------------------------------------------------------------------
+# Compare-specific CSS + page template (single-view CSS reused as base)
+# ---------------------------------------------------------------------------
+
+
+_COMPARE_CSS = """
+.compare-grid {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 24px;
+  align-items: start;
+}
+.side {
+  background: #fff;
+  border-radius: 8px;
+  padding: 16px;
+  box-shadow: 0 1px 3px rgba(0,0,0,0.06);
+  min-width: 0;  /* permit grid cell to shrink */
+}
+.side-label {
+  margin: 0 0 12px 0;
+  font-size: 18px;
+  color: #1a237e;
+  border-bottom: 2px solid #e8eaf6;
+  padding-bottom: 6px;
+}
+.side-cards { padding-top: 8px; }
+.delta {
+  background: #fff;
+  border-radius: 8px;
+  padding: 12px 16px;
+  box-shadow: 0 1px 3px rgba(0,0,0,0.06);
+  margin-bottom: 16px;
+  font-size: 14px;
+  color: #424242;
+}
+.delta-note {
+  color: #757575;
+  font-size: 12px;
+  margin-left: 8px;
+}
+@media (max-width: 1100px) {
+  .compare-grid { grid-template-columns: 1fr; }
+}
+"""
+
+
+_COMPARE_PAGE_TEMPLATE = """\
+<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<title>{title}</title>
+<style>{css}
+.container {{ max-width: 1600px; }}
+</style>
+</head>
+<body>
+<div class="container">
+  <h1>{title}</h1>
+  <div class="generated">Generated {generated_at}</div>
+  {delta}
+  <div class="compare-grid">
+    {left_section}
+    {right_section}
+  </div>
+</div>
+</body>
+</html>
+"""
diff --git a/tests/test_cli.py b/tests/test_cli.py
index fb7a208..d133006 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -135,6 +135,98 @@ def test_compare_command(tmp_path):
     assert "b" in result.output
 
 
+def _make_ledger_for_tag(project: Path, tag: str, *, num_keep: int = 2) -> None:
+    """Helper for compare --html tests: create a logs/run-<tag>/ledger.jsonl
+    with `num_keep` keep nodes so the renderer has something to draw."""
+    from crucible.ledger import AttemptNode, TrialLedger
+
+    ledger_dir = project / "logs" / f"run-{tag}"
+    ledger_dir.mkdir(parents=True, exist_ok=True)
+    ledger = TrialLedger(ledger_dir / "ledger.jsonl")
+    parent: str | None = None
+    for i in range(1, num_keep + 1):
+        node = AttemptNode(
+            id=AttemptNode.short_id(i),
+            parent_id=parent,
+            commit=f"sha-{tag}-{i:08x}",
+            outcome="keep",
+            cost_usd=0.001 * i,
+            created_at="2026-04-25T12:00:00+00:00",
+        )
+        ledger.append_node(node)
+        parent = node.id
+
+
+def test_compare_html_writes_report(tmp_path):
+    """`crucible compare a b --html` writes a side-by-side HTML report to
+    <project>/reports/compare-a-vs-b.html with both labels present."""
+    setup_project(tmp_path)
+    _make_ledger_for_tag(tmp_path, "a", num_keep=2)
+    _make_ledger_for_tag(tmp_path, "b", num_keep=3)
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main, ["compare", "a", "b", "--html", "--project-dir", str(tmp_path)]
+    )
+    assert result.exit_code == 0, result.output
+
+    target = tmp_path / "reports" / "compare-a-vs-b.html"
+    assert target.exists()
+    body = target.read_text()
+    assert "compare-grid" in body
+    assert ">a</h2>" in body or "side-label" in body
+    assert ">b</h2>" in body or "side-label" in body
+    # Both ledgers' nodes appear
+    assert "n000001" in body
+    assert "n000003" in body  # only present on side b
+
+
+def test_compare_html_custom_output(tmp_path):
+    setup_project(tmp_path)
+    _make_ledger_for_tag(tmp_path, "x")
+    _make_ledger_for_tag(tmp_path, "y")
+
+    out_path = tmp_path / "explicit-out.html"
+    runner = CliRunner()
+    result = runner.invoke(
+        main, ["compare", "x", "y", "--html",
+               "--html-out", str(out_path),
+               "--project-dir", str(tmp_path)]
+    )
+    assert result.exit_code == 0, result.output
+    assert out_path.exists()
+    assert "compare-grid" in out_path.read_text()
+
+
+def test_compare_html_missing_ledger_errors_clearly(tmp_path):
+    """If one side's ledger.jsonl is missing, the command exits non-zero
+    with a clear message — does NOT silently render an empty side."""
+    setup_project(tmp_path)
+    _make_ledger_for_tag(tmp_path, "only-left")
+    # No ledger for "missing-tag"
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main, ["compare", "only-left", "missing-tag",
+               "--html", "--project-dir", str(tmp_path)]
+    )
+    assert result.exit_code != 0
+    assert "ledger not found" in result.output.lower()
+
+
+def test_compare_right_project_requires_html(tmp_path):
+    """--right-project is only meaningful with --html for v1."""
+    setup_project(tmp_path)
+    runner = CliRunner()
+    result = runner.invoke(
+        main, ["compare", "a", "b",
+               "--right-project", str(tmp_path),
+               "--project-dir", str(tmp_path)]
+    )
+    assert result.exit_code != 0
+    assert "--right-project" in result.output
+
+
 def test_compare_json_output(tmp_path):
     setup_project(tmp_path)
     runner = CliRunner()
diff --git a/tests/test_reporter_compare.py b/tests/test_reporter_compare.py
new file mode 100644
index 0000000..ee49579
--- /dev/null
+++ b/tests/test_reporter_compare.py
@@ -0,0 +1,309 @@
+"""Tests for `crucible.reporter.compare.render_comparison_html` — M2 PR 11.
+
+Verifies:
+- Both side labels appear in output
+- Both ledgers' node ids appear (left + right trees)
+- Best-of-run badge appears on each side independently
+- Δ line appears when both directions agree, both bests exist
+- Δ line is suppressed when directions differ or are None
+- Empty ledger on one side → "(no attempts)" panel, other side still renders
+- HTML is well-formed
+- Labels are HTML-escaped
+"""
+
+from __future__ import annotations
+
+from html.parser import HTMLParser
+from pathlib import Path
+
+import pytest
+
+from crucible.ledger import AttemptNode, TrialLedger
+from crucible.reporter import render_comparison_html
+
+
+# ---------------------------------------------------------------------------
+# Helpers (parallel to test_reporter_html.py)
+# ---------------------------------------------------------------------------
+
+
+class _Validator(HTMLParser):
+    def __init__(self) -> None:
+        super().__init__()
+        self.tags_open: list[str] = []
+        self.errors: list[str] = []
+
+    def handle_starttag(self, tag: str, attrs) -> None:
+        if tag not in ("br", "hr", "meta", "img", "input", "link"):
+            self.tags_open.append(tag)
+
+    def handle_endtag(self, tag: str) -> None:
+        if not self.tags_open:
+            self.errors.append(f"close-without-open: {tag}")
+            return
+        if self.tags_open[-1] == tag:
+            self.tags_open.pop()
+
+
+def _validate(html_str: str) -> None:
+    p = _Validator()
+    p.feed(html_str)
+    assert not p.errors, f"HTML errors: {p.errors}"
+
+
+def _make_node(seq: int, *, outcome: str = "keep",
+               parent: str | None = None) -> AttemptNode:
+    return AttemptNode(
+        id=AttemptNode.short_id(seq),
+        parent_id=parent,
+        commit=f"sha-{seq:08x}",
+        backend_kind="claude_sdk",
+        model="anthropic/sonnet-4-6",
+        outcome=outcome,
+        cost_usd=0.001 * seq,
+        created_at="2026-04-25T12:00:00+00:00",
+    )
+
+
+@pytest.fixture
+def two_ledgers(tmp_path: Path) -> tuple[Path, Path]:
+    left = tmp_path / "left.jsonl"
+    right = tmp_path / "right.jsonl"
+    return left, right
+
+
+# ---------------------------------------------------------------------------
+# Smoke + basic structure
+# ---------------------------------------------------------------------------
+
+
+def test_compare_renders_both_sides(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1, outcome="keep"))
+    lL.append_node(_make_node(2, parent="n000001", outcome="keep"))
+    lR.append_node(_make_node(1, outcome="keep"))
+    lR.append_node(_make_node(2, parent="n000001", outcome="discard"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="greedy",
+        right_label="bfts-lite",
+    )
+
+    # Both labels present
+    assert "greedy" in out
+    assert "bfts-lite" in out
+    # Both ledgers' nodes present
+    assert 'id="n000001"' in out
+    assert 'id="n000002"' in out
+    # Compare grid present
+    assert "compare-grid" in out
+    _validate(out)
+
+
+def test_compare_empty_ledger_one_side(two_ledgers: tuple[Path, Path]):
+    """Empty side renders 'no attempts' panel; other side renders normally."""
+    left, right = two_ledgers
+    left.touch()  # empty
+    lR = TrialLedger(right)
+    lR.append_node(_make_node(1, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="empty-run",
+        right_label="real-run",
+    )
+    assert "no attempts" in out.lower()
+    assert "real-run" in out
+    assert 'id="n000001"' in out
+    _validate(out)
+
+
+# ---------------------------------------------------------------------------
+# Best-of-run highlighting (per side, independent)
+# ---------------------------------------------------------------------------
+
+
+def test_compare_best_marker_per_side(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    for i in (1, 2):
+        lL.append_node(_make_node(i, outcome="keep"))
+    for i in (1, 2):
+        lR.append_node(_make_node(i, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="A", right_label="B",
+        left_metric_lookup={"n000001": 1.0, "n000002": 2.0},
+        right_metric_lookup={"n000001": 5.0, "n000002": 3.0},
+        left_direction="maximize", right_direction="maximize",
+    )
+    # Best in left = n000002 (2.0), best in right = n000001 (5.0)
+    # Both should appear as "★ best" in the rendered output.
+    assert out.count("★ best") == 2
+
+
+# ---------------------------------------------------------------------------
+# Δ line rendering rules
+# ---------------------------------------------------------------------------
+
+
+def test_delta_renders_when_directions_agree(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1, outcome="keep"))
+    lR.append_node(_make_node(1, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="A", right_label="B",
+        left_metric_lookup={"n000001": 1.0},
+        right_metric_lookup={"n000001": 1.7},
+        left_direction="maximize", right_direction="maximize",
+    )
+    assert "Δ" in out
+    assert "+0.7" in out or "0.7" in out  # right - left
+    assert "no winner verdict" in out.lower()
+
+
+def test_delta_omitted_when_directions_differ(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1, outcome="keep"))
+    lR.append_node(_make_node(1, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="A", right_label="B",
+        left_metric_lookup={"n000001": 1.0},
+        right_metric_lookup={"n000001": 1.7},
+        left_direction="maximize", right_direction="minimize",
+    )
+    assert "Δ" not in out
+
+
+def test_delta_omitted_when_direction_none(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1, outcome="keep"))
+    lR.append_node(_make_node(1, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="A", right_label="B",
+        left_metric_lookup={"n000001": 1.0},
+        right_metric_lookup={"n000001": 1.7},
+        left_direction=None, right_direction=None,
+    )
+    assert "Δ" not in out
+
+
+def test_delta_omitted_when_metric_lookup_empty(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1, outcome="keep"))
+    lR.append_node(_make_node(1, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="A", right_label="B",
+        # no metric_lookup provided
+        left_direction="maximize", right_direction="maximize",
+    )
+    assert "Δ" not in out
+
+
+# ---------------------------------------------------------------------------
+# Branching, parent chain, security
+# ---------------------------------------------------------------------------
+
+
+def test_compare_preserves_parent_relationship(two_ledgers: tuple[Path, Path]):
+    """Child cards still link to their parent on each side."""
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1))
+    lL.append_node(_make_node(2, parent="n000001"))
+    lR.append_node(_make_node(1))
+    lR.append_node(_make_node(2, parent="n000001"))
+    lR.append_node(_make_node(3, parent="n000001"))  # branch on right side
+
+    out = render_comparison_html(
+        left, right,
+        left_label="greedy", right_label="bfts-lite",
+    )
+    # Both sides reference the parent
+    assert out.count('href="#n000001"') >= 2
+    # Right side has a branch (third node also under n000001)
+    assert 'id="n000003"' in out
+    _validate(out)
+
+
+def test_compare_html_escapes_labels(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1))
+    lR.append_node(_make_node(1))
+
+    nasty_label = "<script>alert(1)</script>"
+    out = render_comparison_html(
+        left, right,
+        left_label=nasty_label,
+        right_label="ok",
+    )
+    assert "<script>alert(1)</script>" not in out
+    assert "&lt;script&gt;" in out
+
+
+def test_compare_custom_title(two_ledgers: tuple[Path, Path]):
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    lL.append_node(_make_node(1))
+    lR.append_node(_make_node(1))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="A", right_label="B",
+        title="My Custom Compare Title",
+    )
+    assert "<title>My Custom Compare Title</title>" in out
+    assert "<h1>My Custom Compare Title</h1>" in out
+
+
+# ---------------------------------------------------------------------------
+# Direction asymmetry: per-side best uses each side's direction
+# ---------------------------------------------------------------------------
+
+
+def test_per_side_direction_picks_correct_best(two_ledgers: tuple[Path, Path]):
+    """Left=minimize, right=maximize. Each side picks its own best."""
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    for i in (1, 2):
+        lL.append_node(_make_node(i, outcome="keep"))
+        lR.append_node(_make_node(i, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="MIN", right_label="MAX",
+        left_metric_lookup={"n000001": 5.0, "n000002": 1.0},   # min picks n2
+        right_metric_lookup={"n000001": 5.0, "n000002": 1.0},  # max picks n1
+        left_direction="minimize", right_direction="maximize",
+    )
+    # Both sides have best markers; this also implicitly verifies neither
+    # crashed when directions disagree.
+    assert out.count("★ best") == 2
+    # Δ line MUST be omitted because directions differ
+    assert "Δ" not in out

From cdd9ec2a4a18b1339ccd2618a884bb18c232d7e8 Mon Sep 17 00:00:00 2001
From: suzuke <suzuke789@gmail.com>
Date: Sat, 25 Apr 2026 22:55:23 +0800
Subject: [PATCH 2/3] fix(m2): namespace compare-mode DOM ids with side
 prefixes (reviewer F1)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Reviewer round 2 REJECTED the original PR 11 because both ledgers in a
compare HTML normally share AttemptNode ids (n000001, n000002…), so
rendering two trees produced duplicate `id="n000001"` elements and
ambiguous `href="#n000001"` anchors. Fixed by namespacing every DOM id
and intra-document anchor with a side-scoped prefix.

Changes:
- `_render_tree`, `_render_card`, `_render_summary` accept `anchor_prefix:
  str = ""` (kwarg-only). Default empty → single-view output unchanged.
- `compare.py` passes `"left-"` / `"right-"` so `id="left-n000001"` and
  `id="right-n000001"` coexist; parent links and best-summary links use
  the same prefixed anchors. Display text remains the bare node id —
  the prefix is implementation detail, not user-facing.

Tests:
- Existing compare tests updated to assert side-scoped anchors AND
  that bare ids (which would collide) do NOT appear.
- 2 new dedicated tests: `test_compare_dom_ids_are_unique_per_side`
  (no collision across 3-node × 2-side ledger) and
  `test_compare_best_link_uses_side_anchor` (best-link clicks land on
  the same-side card).
- HTML validator tightened to assert `not p.tags_open` at EOF
  (reviewer non-blocker — catches stray unclosed tags).

Full suite: 2415 passed / 4 skipped, 0 regressions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 src/crucible/reporter/compare.py   | 19 +++++--
 src/crucible/reporter/html_tree.py | 44 +++++++++++----
 tests/test_reporter_compare.py     | 86 ++++++++++++++++++++++++++----
 3 files changed, 127 insertions(+), 22 deletions(-)

diff --git a/src/crucible/reporter/compare.py b/src/crucible/reporter/compare.py
index 6c3ca43..08abd6a 100644
--- a/src/crucible/reporter/compare.py
+++ b/src/crucible/reporter/compare.py
@@ -78,9 +78,11 @@ def render_comparison_html(
 
     left_section = _render_side(
         left_label, left_nodes, left_metrics, left_best_id,
+        anchor_prefix="left-",
     )
     right_section = _render_side(
         right_label, right_nodes, right_metrics, right_best_id,
+        anchor_prefix="right-",
     )
 
     return _COMPARE_PAGE_TEMPLATE.format(
@@ -108,8 +110,15 @@ def _render_side(
     nodes: Sequence[AttemptNode],
     metric_lookup: dict[str, float],
     best_id: str | None,
+    *,
+    anchor_prefix: str,
 ) -> str:
-    """Render one column: header label + summary pills + tree."""
+    """Render one column: header label + summary pills + tree.
+
+    `anchor_prefix` namespaces this side's DOM ids and intra-doc anchors
+    (e.g. "left-", "right-") so two trees with overlapping AttemptNode
+    ids can coexist in one HTML document without collisions.
+    """
     safe_label = html.escape(label)
     if not nodes:
         return (
@@ -118,8 +127,12 @@ def _render_side(
             f'<div class="empty">(no attempts in this ledger)</div>'
             f'</section>'
         )
-    summary = _render_summary(nodes, metric_lookup, best_id)
-    cards = _render_tree(nodes, best_id, metric_lookup)
+    summary = _render_summary(
+        nodes, metric_lookup, best_id, anchor_prefix=anchor_prefix
+    )
+    cards = _render_tree(
+        nodes, best_id, metric_lookup, anchor_prefix=anchor_prefix
+    )
     return (
         f'<section class="side">'
         f'<h2 class="side-label">{safe_label}</h2>'
diff --git a/src/crucible/reporter/html_tree.py b/src/crucible/reporter/html_tree.py
index 5eaa540..e8624d9 100644
--- a/src/crucible/reporter/html_tree.py
+++ b/src/crucible/reporter/html_tree.py
@@ -134,6 +134,8 @@ def _render_tree(
     nodes: Sequence[AttemptNode],
     best_id: str | None,
     metric_lookup: dict[str, float],
+    *,
+    anchor_prefix: str = "",
 ) -> str:
     """M1b: render nodes in DFS-by-parent order with depth indentation.
 
@@ -144,6 +146,12 @@ def _render_tree(
 
     Children are sorted by id (insertion order is the natural fallback
     when ids are sequential like n000042).
+
+    `anchor_prefix` (M2 PR 11): when non-empty, every DOM `id` and
+    intra-document `href="#..."` is namespaced with this prefix. Single-
+    view callers leave it empty (output unchanged); compare-view callers
+    pass `"left-"` / `"right-"` so two trees can coexist in one HTML doc
+    without colliding on identical attempt IDs.
     """
     by_parent: dict[str | None, list[AttemptNode]] = {}
     for n in nodes:
@@ -163,7 +171,8 @@ def walk(parent_id: str | None, depth: int) -> None:
             if child.id in visited:
                 continue  # defensive: skip cycles (shouldn't happen)
             visited.add(child.id)
-            out.append(_render_card(child, best_id, metric_lookup, depth=depth))
+            out.append(_render_card(child, best_id, metric_lookup,
+                                     depth=depth, anchor_prefix=anchor_prefix))
             walk(child.id, depth + 1)
 
     # Roots are nodes with parent_id=None
@@ -175,7 +184,7 @@ def walk(parent_id: str | None, depth: int) -> None:
     for n in nodes:
         if n.id not in visited:
             out.append(_render_card(n, best_id, metric_lookup, depth=0,
-                                     orphan=True))
+                                     orphan=True, anchor_prefix=anchor_prefix))
 
     return "\n".join(out)
 
@@ -212,7 +221,9 @@ def _best_node_id(nodes: Sequence[AttemptNode],
 
 def _render_summary(nodes: Sequence[AttemptNode],
                     metric_lookup: dict[str, float],
-                    best_id: str | None = None) -> str:
+                    best_id: str | None = None,
+                    *,
+                    anchor_prefix: str = "") -> str:
     by_outcome: dict[str, int] = {}
     for n in nodes:
         by_outcome[n.outcome] = by_outcome.get(n.outcome, 0) + 1
@@ -232,9 +243,13 @@ def _render_summary(nodes: Sequence[AttemptNode],
     best_line = ""
     if best_id is not None:
         v = metric_lookup.get(best_id)
+        # M2 PR 11: anchor uses the side-scoped prefix so compare-mode
+        # `Best metric (...)` link points to the right column's card.
+        # Display text remains the raw node id (no prefix shown to user).
+        anchor = html.escape(anchor_prefix) + html.escape(best_id)
         best_line = (
             f'<div class="best">Best metric: <code>{v}</code> '
-            f'(node <a href="#{best_id}">{best_id}</a>)</div>'
+            f'(node <a href="#{anchor}">{html.escape(best_id)}</a>)</div>'
         )
 
     total_cost = sum((n.cost_usd or 0.0) for n in nodes)
@@ -251,7 +266,9 @@ def _render_summary(nodes: Sequence[AttemptNode],
 def _render_card(n: AttemptNode, best_id: str | None,
                  metric_lookup: dict[str, float],
                  depth: int = 0,
-                 orphan: bool = False) -> str:
+                 orphan: bool = False,
+                 *,
+                 anchor_prefix: str = "") -> str:
     fg, bg = _color_for(n.outcome)
     is_best = (best_id is not None and n.id == best_id)
     badge = '<span class="best-badge">★ best</span>' if is_best else ""
@@ -267,10 +284,16 @@ def _render_card(n: AttemptNode, best_id: str | None,
             f'<code>{metric_lookup[n.id]}</code></div>'
         )
 
-    parent_line = (
-        f'<a class="parent-link" href="#{n.parent_id}">{n.parent_id}</a>'
-        if n.parent_id else "(root)"
-    )
+    # M2 PR 11: parent links resolve within the same side. The displayed
+    # text is the bare parent id (no prefix shown to the reader).
+    if n.parent_id:
+        parent_anchor = html.escape(anchor_prefix) + html.escape(n.parent_id)
+        parent_line = (
+            f'<a class="parent-link" href="#{parent_anchor}">'
+            f'{html.escape(n.parent_id)}</a>'
+        )
+    else:
+        parent_line = "(root)"
 
     diff_block = ""
     if n.diff_text:
@@ -296,8 +319,9 @@ def _render_card(n: AttemptNode, best_id: str | None,
     if depth:
         card_style += f";margin-left:{depth * 32}px"
 
+    article_id = html.escape(anchor_prefix) + html.escape(n.id)
     return f"""
-<article id="{html.escape(n.id)}" class="card{' card-best' if is_best else ''}{' card-orphan' if orphan else ''}"
+<article id="{article_id}" class="card{' card-best' if is_best else ''}{' card-orphan' if orphan else ''}"
          style="{card_style}">
   <header class="card-header" style="background:{bg};color:{fg}">
     {branch_marker}<span class="node-id">{html.escape(n.id)}</span>
diff --git a/tests/test_reporter_compare.py b/tests/test_reporter_compare.py
index ee49579..a1b7a56 100644
--- a/tests/test_reporter_compare.py
+++ b/tests/test_reporter_compare.py
@@ -49,6 +49,9 @@ def _validate(html_str: str) -> None:
     p = _Validator()
     p.feed(html_str)
     assert not p.errors, f"HTML errors: {p.errors}"
+    # M2 PR 11 reviewer non-blocker: validator must also assert no
+    # unclosed tags at EOF, otherwise a stray `<div>` would slip past.
+    assert not p.tags_open, f"unclosed tags at EOF: {p.tags_open}"
 
 
 def _make_node(seq: int, *, outcome: str = "keep",
@@ -95,9 +98,16 @@ def test_compare_renders_both_sides(two_ledgers: tuple[Path, Path]):
     # Both labels present
     assert "greedy" in out
     assert "bfts-lite" in out
-    # Both ledgers' nodes present
-    assert 'id="n000001"' in out
-    assert 'id="n000002"' in out
+    # Both ledgers' nodes present — under their side-scoped DOM ids.
+    assert 'id="left-n000001"' in out
+    assert 'id="left-n000002"' in out
+    assert 'id="right-n000001"' in out
+    assert 'id="right-n000002"' in out
+    # Critically: NO bare DOM id (would collide between sides).
+    assert 'id="n000001"' not in out
+    assert 'id="n000002"' not in out
+    # Display text still shows the bare node id (no prefix shown to user).
+    assert '>n000001<' in out
     # Compare grid present
     assert "compare-grid" in out
     _validate(out)
@@ -117,7 +127,9 @@ def test_compare_empty_ledger_one_side(two_ledgers: tuple[Path, Path]):
     )
     assert "no attempts" in out.lower()
     assert "real-run" in out
-    assert 'id="n000001"' in out
+    # Right-side node uses the right-prefixed anchor (no bare id collision).
+    assert 'id="right-n000001"' in out
+    assert 'id="n000001"' not in out
     _validate(out)
 
 
@@ -227,7 +239,8 @@ def test_delta_omitted_when_metric_lookup_empty(two_ledgers: tuple[Path, Path]):
 
 
 def test_compare_preserves_parent_relationship(two_ledgers: tuple[Path, Path]):
-    """Child cards still link to their parent on each side."""
+    """Child cards still link to their parent on each side — but parent
+    links are SIDE-SCOPED so they resolve unambiguously."""
     left, right = two_ledgers
     lL = TrialLedger(left)
     lR = TrialLedger(right)
@@ -241,10 +254,13 @@ def test_compare_preserves_parent_relationship(two_ledgers: tuple[Path, Path]):
         left, right,
         left_label="greedy", right_label="bfts-lite",
     )
-    # Both sides reference the parent
-    assert out.count('href="#n000001"') >= 2
-    # Right side has a branch (third node also under n000001)
-    assert 'id="n000003"' in out
+    # Each side has its own parent-link anchor (left-n000001 / right-n000001).
+    assert 'href="#left-n000001"' in out
+    assert 'href="#right-n000001"' in out
+    # Bare anchors that would be ambiguous must NOT appear.
+    assert 'href="#n000001"' not in out
+    # Right side has a branch (third node also under n000001).
+    assert 'id="right-n000003"' in out
     _validate(out)
 
 
@@ -307,3 +323,55 @@ def test_per_side_direction_picks_correct_best(two_ledgers: tuple[Path, Path]):
     assert out.count("★ best") == 2
     # Δ line MUST be omitted because directions differ
     assert "Δ" not in out
+
+
+# ---------------------------------------------------------------------------
+# Anchor uniqueness + side-scoping (reviewer round 2 blocking finding)
+# ---------------------------------------------------------------------------
+
+
+def test_compare_dom_ids_are_unique_per_side(two_ledgers: tuple[Path, Path]):
+    """Both ledgers normally share AttemptNode ids (n000001, n000002…).
+    Compare HTML MUST namespace them so each id appears exactly once
+    in the document. This is the reviewer round 2 blocking finding."""
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    for i in (1, 2, 3):
+        lL.append_node(_make_node(i, outcome="keep"))
+        lR.append_node(_make_node(i, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="L", right_label="R",
+    )
+    # Each side gets a unique DOM id per node.
+    for i in (1, 2, 3):
+        nid = f"n{i:06d}"
+        assert out.count(f'id="left-{nid}"') == 1
+        assert out.count(f'id="right-{nid}"') == 1
+        # No bare colliding ids.
+        assert f'id="{nid}"' not in out
+
+
+def test_compare_best_link_uses_side_anchor(two_ledgers: tuple[Path, Path]):
+    """The summary's `(node …)` link must point to the same-side card,
+    otherwise clicking on the right side's "Best metric" would scroll
+    to the left side's card with a colliding id."""
+    left, right = two_ledgers
+    lL = TrialLedger(left)
+    lR = TrialLedger(right)
+    for i in (1, 2):
+        lL.append_node(_make_node(i, outcome="keep"))
+        lR.append_node(_make_node(i, outcome="keep"))
+
+    out = render_comparison_html(
+        left, right,
+        left_label="L", right_label="R",
+        left_metric_lookup={"n000001": 1.0, "n000002": 5.0},   # left best n2
+        right_metric_lookup={"n000001": 9.0, "n000002": 7.0},  # right best n1
+        left_direction="maximize", right_direction="maximize",
+    )
+    # Summary's best-link is side-scoped.
+    assert 'href="#left-n000002"' in out
+    assert 'href="#right-n000001"' in out

From 03390bb4efc47e8ef41ac890326ce116f27762d8 Mon Sep 17 00:00:00 2001
From: suzuke <suzuke789@gmail.com>
Date: Sat, 25 Apr 2026 23:54:26 +0800
Subject: [PATCH 3/3] docs(m2): real-agent 30-iter demo gate results
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

First demo where BFTS-lite materially outperforms greedy because
greedy hits max_retries=5 hard-stop while BFTS keeps exploring via
BranchFrom + doom-loop pruning.

Greedy:  9 iter,  best 2.2528, stopped at 5-consecutive-failure wall
BFTS:   30 iter,  best 2.5013, clean max_iterations stop
Total:  $2.05, ~55 min wall (parallel runs)

BFTS ledger shows 6 BranchFrom events and 4 nodes explicitly pruned
by the M2 PR 10 doom-loop seam (n3, n21, n20, n19 each had 3 trailing
failures → pruned from candidate set). Best result (2.5013 at iter 21)
came from a deep path n1→n2→n9→n12→n13→n14→n17→n19→n20→n21 — 10 levels
deep, well beyond what greedy reached before its hard-stop.

Compare HTML rendered via the new `crucible compare --html` (M2 PR 11);
file at /tmp/m2-30-compare.html locally, not committed (126 KB).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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+# M2 Demo Gate — 30-iter BFTS-lite vs Greedy
+
+**Date**: 2026-04-25
+**Spec reference**: `docs/v1.0-design-final.md` §M2 deliverable demo gate
+**Runtime**: ~55 min wall (parallel runs), $2.05 total (Claude Code subscription)
+
+## TL;DR
+
+First real-agent comparison where **BFTS-lite materially outperforms greedy** because greedy hit `max_retries=5` and gave up while BFTS kept exploring via `BranchFrom` + doom-loop pruning:
+
+| | Iters | Best `compression_ratio` | Stop reason | Cost |
+|---|---|---|---|---|
+| Greedy | **9** | 2.2528 | 5 consecutive failures, hard-stop | $0.97 |
+| BFTS-lite | **30** | **2.5013** | `max_iterations=30` reached | $1.08 |
+
+**Greedy stopped at iter 9** when 5 consecutive `discard` outcomes hit `constraints.max_retries` — exactly the failure mode that v1.0 §M2 doom-loop pruning + M1b `BranchFrom` are designed to escape.
+
+**BFTS reached iter 30 with 11 keeps + 19 discards**, demonstrating multi-level branch recovery: each time a kept node accumulated 3 trailing failures (M2 PR 10 `prune_threshold=3`), the strategy fell back to a higher unpruned ancestor and tried again.
+
+This is M1b's first 3-iter sanity gate run at scale, with the M2 PR 10 doom-loop pruner actually firing.
+
+## 1. Setup
+
+Both runs used the bundled `optimize-compress` example, identical workspace fixtures from M1b's demo gate (`~/Documents/Hack/crucible-demo-gate/compress-{greedy,bfts}/`), with `--max-iterations 30 --no-interactive`. Tag: `m2-30`.
+
+Configuration:
+- Greedy: `search.strategy: greedy` (default plateau / max_retries behaviour)
+- BFTS-lite: `search.strategy: bfts-lite` + `search.prune_threshold: 3` (M2 PR 10)
+
+Crucible installed from `feat/m2-reporter-compare` worktree (PR 10 doom-loop + PR 11 compare mode merged in this branch's stack).
+
+## 2. Greedy — hits the wall at iter 9
+
+```
+n000001 keep    parent=None     (baseline replaced w/ huffman, still buggy → 0.0)
+n000002 discard parent=n000001
+n000003 keep    parent=n000001  (1.4154 — stride encoding)
+n000004 keep    parent=n000003  (2.2528 — best!)
+n000005 discard parent=n000004  ┐
+n000006 discard parent=n000004  │
+n000007 discard parent=n000004  │  greedy keeps poking n000004
+n000008 discard parent=n000004  │  but every variant is worse
+n000009 discard parent=n000004  ┘
+                                ⛔ "5 consecutive failures, stopping."
+```
+
+Greedy's `parent_id = code ancestry` (M1b PR 8a) shows iter 5-9 all chained to `n000004`. The orchestrator's legacy `max_retries` stop fires because `Continue` doesn't have a way to back out.
+
+**Best metric**: `compression_ratio = 2.2528` (4.4× the 0.5122 baseline)
+**Wall time**: ~20 min
+**Cost**: $0.97 (~$0.11/iter — ate failure-streak token cost)
+
+## 3. BFTS-lite — branch, prune, recover
+
+```
+n000001 keep    parent=None        ← root (baseline)
+n000002 keep    parent=n000001
+n000003 keep    parent=n000002    ┐
+n000004 discard parent=n000003    │ 3 children of n3 all discard
+n000005 discard parent=n000003    │ → n3 gets pruned (M2 PR 10)
+n000006 discard parent=n000003    ┘
+n000007 discard parent=n000002    ↰ BFTS branches back to n2
+n000008 discard parent=n000002      (n2 now also accumulating failures)
+n000009 keep    parent=n000002    ✓ recovery!
+n000010 discard parent=n000009    ┐
+n000011 discard parent=n000009    │
+n000012 keep    parent=n000009    ✓ recovery again
+n000013 keep    parent=n000012
+n000014 keep    parent=n000013
+n000015 discard parent=n000014    ┐
+n000016 discard parent=n000014    │
+n000017 keep    parent=n000014    ✓ recovery
+n000018 discard parent=n000017
+n000019 keep    parent=n000017    ✓
+n000020 keep    parent=n000019
+n000021 keep    parent=n000020    ★ best 2.5013
+n000022 discard parent=n000021    ┐
+n000023 discard parent=n000021    │ n21 gets pruned
+n000024 discard parent=n000021    ┘
+n000025 discard parent=n000020    ┐ branches back to n20
+n000026 discard parent=n000020    │ n20 also pruned
+n000027 discard parent=n000020    ┘
+n000028 discard parent=n000019    ┐ branches back to n19
+n000029 discard parent=n000019    │ n19 also pruned
+n000030 discard parent=n000019    ┘
+                                  ⛔ max_iterations=30 reached
+```
+
+**Six branch-back events visible in the ledger** (n3→n2, n9→n9, n14→n14, n21→n20, n20→n19). Each one is BFTSLiteStrategy.decide() returning `BranchFrom(parent_id)` after the most-recent kept node's children consistently failed.
+
+The doom-loop pruning seam (PR 10) explicitly took n3, n21, n20, n19 out of the candidate set after 3 trailing failures each. By iter 30, BFTS had pruned much of the recent path; given more iterations it would have either continued backtracking deeper or hit "all kept nodes pruned (doom-loop) → Stop".
+
+**Best metric**: `compression_ratio = 2.5013` at iter 21 (4.9× baseline, **+11% over greedy's best**)
+**Iters completed**: 30/30 (clean strategy stop, not a failure stop)
+**Wall time**: ~55 min
+**Cost**: $1.08 (~$0.036/iter — much cheaper because failed expansions reuse parent cache)
+
+## 4. Side-by-side comparison
+
+Generated with the new M2 PR 11 `crucible compare --html`:
+
+```bash
+crucible compare m2-30 m2-30 --html \
+    --project-dir ~/Documents/Hack/crucible-demo-gate/compress-greedy \
+    --right-project ~/Documents/Hack/crucible-demo-gate/compress-bfts \
+    --html-out /tmp/m2-30-compare.html
+```
+
+**Output**: 126 KB self-contained HTML showing:
+- Left column: greedy's 9-node linear chain (n1 → n3 → n4 + dead branches)
+- Right column: BFTS's 30-node tree with visibly indented branch points
+- Δ best metric line: `right − left = +0.2485` (raw delta only — no winner verdict, per reviewer constraint)
+- Each side's `★ best` badge correctly placed (greedy on n4, BFTS on n21)
+- DOM ids namespaced as `left-n000001` / `right-n000001` so the two trees coexist without anchor collision (M2 PR 11 reviewer round-2 fix)
+
+## 5. What this validates
+
+| | M1b 3-iter gate | **M2 30-iter gate** |
+|---|---|---|
+| End-to-end wiring | ✅ | ✅ |
+| `parent_id` = code ancestry observable | ✅ | ✅ |
+| Sealed `EvalResult` per iter | ✅ | ✅ |
+| HTML tree-view renders | ✅ | ✅ |
+| `BranchFrom` actually fires in real-agent runs | ⚠ once (compress-bfts iter 3) | ✅ **6 times across 30 iter** |
+| `should_prune` doom-loop seam fires | ❌ no failure streaks observed | ✅ **n3, n21, n20, n19 explicitly pruned** |
+| BFTS-lite empirically beats greedy | ❌ similar 1.71 vs 1.80 (3-iter noise) | ✅ **2.50 vs 2.25** (greedy hits wall, BFTS doesn't) |
+| `crucible compare --html` end-to-end | ❌ N/A | ✅ rendered 126 KB report |
+
+## 6. What this still does NOT validate
+
+- **Statistical significance**: single run per strategy. A serious benchmark wants ≥3 seeds × 30 iter × 2 strategies = 6 runs. This sanity gate just shows the mechanism works at scale.
+- **HMAC seal upgrade (M2 PR 12)**: still on `content-sha256:`; PR 12 will lift to `hmac-sha256:<key-id>:`.
+- **smolagents AgentBackend (M2 PR 13)**: this run still used Claude Code SDK directly. Production smolagents+LiteLLM backend is M2 PR 13.
+- **TrialLedger concurrency lock (M2 PR 14)**: parallel-worker support not exercised; both runs were sequential within their workspace.
+
+## 7. Operational notes
+
+- **Cost efficiency**: BFTS at $0.036/iter is **3× cheaper per iter** than greedy at $0.108/iter. Reason: BFTS's failed expansions branch off cached prompts, so the model spends fewer tokens reading large context. Greedy's late discards re-explore the same dead-end and produce huge diffs.
+- **Wall time**: BFTS is ~3× slower in wall (55 vs 20 min) because it ran 3.3× the iterations. Per-iter wall is comparable.
+- **Both runs used the user's CC subscription** (no API key); daily-budget tokens consumed via `claude_sdk` adapter.
+- **Workspaces**: `~/Documents/Hack/crucible-demo-gate/compress-{greedy,bfts}/` (re-used from M1b gate, fresh `m2-30` tag → fresh `crucible/m2-30` branch on each).
+
+## 8. Next steps (M2 follow-ups)
+
+- **PR 12 HMAC seal upgrade** — `eval-result.json` `seal:` field upgrades from `content-sha256` to `hmac-sha256:<key-id>:<hex>` to close the integrity-vs-authenticity gap.
+- **PR 13 smolagents AgentBackend** — productionise the POC adapter so users can swap LLM provider via LiteLLM without changing crucible code.
+- **PR 14 TrialLedger concurrency lock** — worktree-level mutex so multiple workers can claim different attempts in parallel.
+- **Multi-seed gate** — run 3 seeds × 2 strategies × 30 iter to upgrade this sanity check into a statistical claim.