Consensus

Head slot tracking, justification, finalization, and fork choice analysis for PQ Devnet clients.

This notebook examines:

  • Head slot vs current slot (how far behind each client is)
  • Justified and finalized slot progression
  • Head-to-justified, justified-to-finalized, and head-to-finalized distances
  • Fork choice reorgs
Show code
import json
from pathlib import Path

import pandas as pd
import plotly.graph_objects as go
from plotly.subplots import make_subplots
from IPython.display import display

# Set default renderer for static HTML output
import plotly.io as pio
pio.renderers.default = "notebook"
Show code
# Resolve devnet_id
DATA_DIR = Path("../data")

if devnet_id is None:
    devnets_path = DATA_DIR / "devnets.json"
    if devnets_path.exists():
        with open(devnets_path) as f:
            devnets = json.load(f).get("devnets", [])
        if devnets:
            devnet_id = devnets[-1]["id"]
            print(f"Using latest devnet: {devnet_id}")
    else:
        raise ValueError("No devnets.json found. Run 'just detect-devnets' first.")

DEVNET_DIR = DATA_DIR / devnet_id
print(f"Loading data from: {DEVNET_DIR}")
Loading data from: ../data/pqdevnet-20260507T2011Z
Show code
# Load devnet metadata
with open(DATA_DIR / "devnets.json") as f:
    devnets_data = json.load(f)
    devnet_info = next((d for d in devnets_data["devnets"] if d["id"] == devnet_id), None)

if devnet_info:
    print(f"Devnet: {devnet_info['id']}")
    print(f"Duration: {devnet_info['duration_hours']:.1f} hours")
    print(f"Time: {devnet_info['start_time']} to {devnet_info['end_time']}")
    print(f"Slots: {devnet_info['start_slot']} \u2192 {devnet_info['end_slot']}")
    print(f"Clients: {', '.join(devnet_info['clients'])}")
Devnet: pqdevnet-20260507T2011Z
Duration: 4.3 hours
Time: 2026-05-07T20:11:31+00:00 to 2026-05-08T00:27:40+00:00
Slots: 0 β†’ 3876
Clients: ethlambda_0, ethlambda_1, gean_0, gean_1, grandine_0, grandine_1, lantern_0, lantern_1, nlean_0, nlean_1, qlean_0, qlean_1, ream_0, ream_1, zeam_0, zeam_1

Load DataΒΆ

Show code
# Unified client list from devnet metadata (includes all containers via cAdvisor)
all_clients = sorted(devnet_info["clients"])
n_cols = min(len(all_clients), 2)
n_rows = -(-len(all_clients) // n_cols)

# Load head slot data
head_df = pd.read_parquet(DEVNET_DIR / "head_slot.parquet")
head_df = head_df.groupby(["client", "metric", "timestamp"], as_index=False)["value"].max()
print(f"Head slot: {len(head_df)} records, clients: {sorted(head_df['client'].unique())}")

# Load finality data
finality_df = pd.read_parquet(DEVNET_DIR / "finality_metrics.parquet")
finality_df = finality_df.groupby(["client", "metric", "timestamp"], as_index=False)["value"].max()
print(f"Finality: {len(finality_df)} records, clients: {sorted(finality_df['client'].unique())}")
print(f"Finality metrics: {sorted(finality_df['metric'].unique())}")

# Load fork choice reorgs
reorgs_df = pd.read_parquet(DEVNET_DIR / "fork_choice_reorgs.parquet")
reorgs_df = reorgs_df.groupby(["client", "timestamp"], as_index=False)["value"].max()
print(f"Reorgs: {len(reorgs_df)} records, clients: {sorted(reorgs_df['client'].unique())}")

print(f"\nAll clients ({len(all_clients)}): {all_clients}")
Head slot: 7174 records, clients: ['ethlambda_0', 'ethlambda_1', 'gean_0', 'gean_1', 'grandine_0', 'grandine_1', 'lantern_0', 'lantern_1', 'nlean_0', 'nlean_1', 'qlean_0', 'qlean_1', 'ream_0', 'ream_1', 'zeam_0', 'zeam_1']
Finality: 9370 records, clients: ['ethlambda_0', 'ethlambda_1', 'gean_0', 'gean_1', 'grandine_0', 'grandine_1', 'lantern_0', 'lantern_1', 'nlean_0', 'nlean_1', 'qlean_0', 'qlean_1', 'ream_0', 'ream_1', 'zeam_0', 'zeam_1']
Finality metrics: ['lean_finalized_slot', 'lean_justified_slot', 'lean_latest_finalized_slot', 'lean_latest_justified_slot']
Reorgs: 3294 records, clients: ['ethlambda_0', 'ethlambda_1', 'gean_0', 'gean_1', 'grandine_0', 'grandine_1', 'lantern_0', 'lantern_1', 'nlean_0', 'nlean_1', 'qlean_0', 'qlean_1', 'zeam_0', 'zeam_1']

All clients (16): ['ethlambda_0', 'ethlambda_1', 'gean_0', 'gean_1', 'grandine_0', 'grandine_1', 'lantern_0', 'lantern_1', 'nlean_0', 'nlean_1', 'qlean_0', 'qlean_1', 'ream_0', 'ream_1', 'zeam_0', 'zeam_1']

Head Slot vs Current SlotΒΆ

Comparing each client's head slot (lean_head_slot) against the expected current slot (lean_current_slot). A gap indicates the client is falling behind.

Show code
fig = make_subplots(
    rows=n_rows, cols=n_cols,
    subplot_titles=all_clients,
    vertical_spacing=0.12 / max(n_rows - 1, 1) * 2,
    horizontal_spacing=0.08,
)

colors = {"lean_head_slot": "#636EFA", "lean_current_slot": "#EF553B"}
labels = {"lean_head_slot": "head_slot", "lean_current_slot": "current_slot"}
legend_added = set()

for i, client in enumerate(all_clients):
    row = i // n_cols + 1
    col = i % n_cols + 1
    cdf = head_df[head_df["client"] == client]
    has_data = False
    for metric in ["lean_current_slot", "lean_head_slot"]:
        mdf = cdf[cdf["metric"] == metric].sort_values("timestamp")
        if mdf.empty:
            continue
        has_data = True
        label = labels[metric]
        show_legend = metric not in legend_added
        legend_added.add(metric)
        fig.add_trace(
            go.Scatter(
                x=mdf["timestamp"], y=mdf["value"],
                name=label, legendgroup=metric,
                showlegend=show_legend,
                line=dict(color=colors[metric]),
            ),
            row=row, col=col,
        )
    if not has_data:
        fig.add_trace(
            go.Scatter(x=[None], y=[None], showlegend=False, hoverinfo='skip'),
            row=row, col=col,
        )
        _n = (row - 1) * n_cols + col
        _s = "" if _n == 1 else str(_n)
        fig.add_annotation(
            text="No data available",
            xref=f"x{_s} domain", yref=f"y{_s} domain",
            x=0.5, y=0.5,
            showarrow=False,
            font=dict(size=12, color="#999"),
        )
    fig.update_yaxes(title_text="Slot", row=row, col=col)

fig.update_layout(
    title="Head Slot vs Current Slot by Client",
    height=270 * n_rows,
)
fig.show()

Head, Justified & Finalized SlotsΒΆ

Progression of justified and finalized slots over time. With 3SF, both should track closely behind the head slot.

Show code
jf_metrics = ["lean_latest_justified_slot", "lean_latest_finalized_slot"]
jf_df = finality_df[finality_df["metric"].isin(jf_metrics)].copy()

head_only_all = head_df[head_df["metric"] == "lean_head_slot"].copy()
head_only_all["metric"] = "lean_head_slot"

combined = pd.concat([jf_df, head_only_all], ignore_index=True)

fig = make_subplots(
    rows=n_rows, cols=n_cols,
    subplot_titles=all_clients,
    vertical_spacing=0.12 / max(n_rows - 1, 1) * 2,
    horizontal_spacing=0.08,
)

colors = {
    "lean_head_slot": "#636EFA",
    "lean_latest_justified_slot": "#00CC96",
    "lean_latest_finalized_slot": "#EF553B",
}
labels = {
    "lean_head_slot": "head",
    "lean_latest_justified_slot": "justified",
    "lean_latest_finalized_slot": "finalized",
}
legend_added = set()

for i, client in enumerate(all_clients):
    row = i // n_cols + 1
    col = i % n_cols + 1
    cdf = combined[combined["client"] == client]
    has_data = False
    for metric in ["lean_head_slot", "lean_latest_justified_slot", "lean_latest_finalized_slot"]:
        mdf = cdf[cdf["metric"] == metric].sort_values("timestamp")
        if mdf.empty:
            continue
        has_data = True
        show_legend = metric not in legend_added
        legend_added.add(metric)
        fig.add_trace(
            go.Scatter(
                x=mdf["timestamp"], y=mdf["value"],
                name=labels[metric], legendgroup=metric,
                showlegend=show_legend,
                line=dict(color=colors[metric]),
            ),
            row=row, col=col,
        )
    if not has_data:
        fig.add_trace(
            go.Scatter(x=[None], y=[None], showlegend=False, hoverinfo='skip'),
            row=row, col=col,
        )
        _n = (row - 1) * n_cols + col
        _s = "" if _n == 1 else str(_n)
        fig.add_annotation(
            text="No data available",
            xref=f"x{_s} domain", yref=f"y{_s} domain",
            x=0.5, y=0.5,
            showarrow=False,
            font=dict(size=12, color="#999"),
        )
    fig.update_yaxes(title_text="Slot", row=row, col=col)

fig.update_layout(
    title="Head, Justified & Finalized Slot by Client",
    height=270 * n_rows,
)
fig.show()

Head-to-Finalized DistanceΒΆ

Total distance between head slot and finalized slot. This is the combined gap across justification and finalization, showing the overall finality lag.

finalized
justified
head
current
Show code
head_ts_hf = head_df[head_df["metric"] == "lean_head_slot"][["client", "timestamp", "value"]].rename(columns={"value": "head_slot"})
fin_ts_hf = finality_df[finality_df["metric"] == "lean_latest_finalized_slot"][["client", "timestamp", "value"]].rename(columns={"value": "finalized_slot"})
head_fin_lag = head_ts_hf.merge(fin_ts_hf, on=["client", "timestamp"], how="inner")
head_fin_lag["lag"] = head_fin_lag["head_slot"] - head_fin_lag["finalized_slot"]

fig = make_subplots(
    rows=n_rows, cols=n_cols,
    subplot_titles=all_clients,
    vertical_spacing=0.12 / max(n_rows - 1, 1) * 2,
    horizontal_spacing=0.08,
)

for i, client in enumerate(all_clients):
    row = i // n_cols + 1
    col = i % n_cols + 1
    cdf = head_fin_lag[head_fin_lag["client"] == client].sort_values("timestamp")
    if not cdf.empty:
        fig.add_trace(
            go.Scatter(
                x=cdf["timestamp"], y=cdf["lag"],
                name=client, showlegend=False,
                line=dict(color="#636EFA"),
            ),
            row=row, col=col,
        )
    else:
        fig.add_trace(
            go.Scatter(x=[None], y=[None], showlegend=False, hoverinfo='skip'),
            row=row, col=col,
        )
        _n = (row - 1) * n_cols + col
        _s = "" if _n == 1 else str(_n)
        fig.add_annotation(
            text="No data available",
            xref=f"x{_s} domain", yref=f"y{_s} domain",
            x=0.5, y=0.5,
            showarrow=False,
            font=dict(size=12, color="#999"),
        )
    fig.update_yaxes(title_text="Slots", row=row, col=col)

fig.update_layout(
    title="Head-to-Finalized Distance (head_slot - finalized_slot)",
    height=270 * n_rows,
)
fig.show()

Current-to-Head DistanceΒΆ

Difference between current slot and head slot. A value of 0 means the client is fully synced; higher values indicate falling behind.

finalized
justified
head
current
Show code
current_df = head_df[head_df["metric"] == "lean_current_slot"][["client", "timestamp", "value"]].rename(columns={"value": "current_slot"})
head_only = head_df[head_df["metric"] == "lean_head_slot"][["client", "timestamp", "value"]].rename(columns={"value": "head_slot"})
lag_df = current_df.merge(head_only, on=["client", "timestamp"], how="inner")
lag_df["lag"] = lag_df["current_slot"] - lag_df["head_slot"]

fig = make_subplots(
    rows=n_rows, cols=n_cols,
    subplot_titles=all_clients,
    vertical_spacing=0.12 / max(n_rows - 1, 1) * 2,
    horizontal_spacing=0.08,
)

for i, client in enumerate(all_clients):
    row = i // n_cols + 1
    col = i % n_cols + 1
    cdf = lag_df[lag_df["client"] == client].sort_values("timestamp")
    if not cdf.empty:
        fig.add_trace(
            go.Scatter(
                x=cdf["timestamp"], y=cdf["lag"],
                name=client, showlegend=False,
                line=dict(color="#636EFA"),
            ),
            row=row, col=col,
        )
    else:
        fig.add_trace(
            go.Scatter(x=[None], y=[None], showlegend=False, hoverinfo='skip'),
            row=row, col=col,
        )
        _n = (row - 1) * n_cols + col
        _s = "" if _n == 1 else str(_n)
        fig.add_annotation(
            text="No data available",
            xref=f"x{_s} domain", yref=f"y{_s} domain",
            x=0.5, y=0.5,
            showarrow=False,
            font=dict(size=12, color="#999"),
        )
    fig.update_yaxes(title_text="Slots behind", row=row, col=col)

fig.update_layout(
    title="Current-to-Head Distance (current_slot - head_slot)",
    height=270 * n_rows,
)
fig.show()

Head-to-Justified DistanceΒΆ

Gap between head slot and justified slot. A growing gap means the client's head is advancing but justification is not keeping up.

finalized
justified
head
current
Show code
head_ts = head_df[head_df["metric"] == "lean_head_slot"][["client", "timestamp", "value"]].rename(columns={"value": "head_slot"})
just_ts = finality_df[finality_df["metric"] == "lean_latest_justified_slot"][["client", "timestamp", "value"]].rename(columns={"value": "justified_slot"})
justification_lag = head_ts.merge(just_ts, on=["client", "timestamp"], how="inner")
justification_lag["lag"] = justification_lag["head_slot"] - justification_lag["justified_slot"]

fig = make_subplots(
    rows=n_rows, cols=n_cols,
    subplot_titles=all_clients,
    vertical_spacing=0.12 / max(n_rows - 1, 1) * 2,
    horizontal_spacing=0.08,
)

for i, client in enumerate(all_clients):
    row = i // n_cols + 1
    col = i % n_cols + 1
    cdf = justification_lag[justification_lag["client"] == client].sort_values("timestamp")
    if not cdf.empty:
        fig.add_trace(
            go.Scatter(
                x=cdf["timestamp"], y=cdf["lag"],
                name=client, showlegend=False,
                line=dict(color="#636EFA"),
            ),
            row=row, col=col,
        )
    else:
        fig.add_trace(
            go.Scatter(x=[None], y=[None], showlegend=False, hoverinfo='skip'),
            row=row, col=col,
        )
        _n = (row - 1) * n_cols + col
        _s = "" if _n == 1 else str(_n)
        fig.add_annotation(
            text="No data available",
            xref=f"x{_s} domain", yref=f"y{_s} domain",
            x=0.5, y=0.5,
            showarrow=False,
            font=dict(size=12, color="#999"),
        )
    fig.update_yaxes(title_text="Slots", row=row, col=col)

fig.update_layout(
    title="Head-to-Justified Distance (head_slot - justified_slot)",
    height=270 * n_rows,
)
fig.show()

Justified-to-Finalized DistanceΒΆ

Gap between justified slot and finalized slot. A growing gap means justification is advancing but finalization is stalling.

finalized
justified
head
current
Show code
fin_ts = finality_df[finality_df["metric"] == "lean_latest_finalized_slot"][["client", "timestamp", "value"]].rename(columns={"value": "finalized_slot"})
finality_lag = just_ts.merge(fin_ts, on=["client", "timestamp"], how="inner")
finality_lag["lag"] = finality_lag["justified_slot"] - finality_lag["finalized_slot"]

fig = make_subplots(
    rows=n_rows, cols=n_cols,
    subplot_titles=all_clients,
    vertical_spacing=0.12 / max(n_rows - 1, 1) * 2,
    horizontal_spacing=0.08,
)

for i, client in enumerate(all_clients):
    row = i // n_cols + 1
    col = i % n_cols + 1
    cdf = finality_lag[finality_lag["client"] == client].sort_values("timestamp")
    if not cdf.empty:
        fig.add_trace(
            go.Scatter(
                x=cdf["timestamp"], y=cdf["lag"],
                name=client, showlegend=False,
                line=dict(color="#636EFA"),
            ),
            row=row, col=col,
        )
    else:
        fig.add_trace(
            go.Scatter(x=[None], y=[None], showlegend=False, hoverinfo='skip'),
            row=row, col=col,
        )
        _n = (row - 1) * n_cols + col
        _s = "" if _n == 1 else str(_n)
        fig.add_annotation(
            text="No data available",
            xref=f"x{_s} domain", yref=f"y{_s} domain",
            x=0.5, y=0.5,
            showarrow=False,
            font=dict(size=12, color="#999"),
        )
    fig.update_yaxes(title_text="Slots", row=row, col=col)

fig.update_layout(
    title="Justified-to-Finalized Distance (justified_slot - finalized_slot)",
    height=270 * n_rows,
)
fig.show()

Fork Choice ReorgsΒΆ

Cumulative chain reorgs per client. Reorgs occur when the fork choice rule switches to a different chain head, often caused by late-arriving blocks or attestations.

Show code
fig = make_subplots(
    rows=n_rows, cols=n_cols,
    subplot_titles=all_clients,
    vertical_spacing=0.12 / max(n_rows - 1, 1) * 2,
    horizontal_spacing=0.08,
)

for i, client in enumerate(all_clients):
    row = i // n_cols + 1
    col = i % n_cols + 1
    cdf = reorgs_df[reorgs_df["client"] == client].sort_values("timestamp")
    if not cdf.empty:
        fig.add_trace(
            go.Scatter(
                x=cdf["timestamp"], y=cdf["value"],
                name=client, showlegend=False,
                line=dict(color="#636EFA"),
            ),
            row=row, col=col,
        )
    else:
        fig.add_trace(
            go.Scatter(x=[None], y=[None], showlegend=False, hoverinfo='skip'),
            row=row, col=col,
        )
        _n = (row - 1) * n_cols + col
        _s = "" if _n == 1 else str(_n)
        fig.add_annotation(
            text="No data available",
            xref=f"x{_s} domain", yref=f"y{_s} domain",
            x=0.5, y=0.5,
            showarrow=False,
            font=dict(size=12, color="#999"),
        )
    fig.update_yaxes(title_text="Cumulative reorgs", row=row, col=col)

fig.update_layout(
    title="Fork Choice Reorgs by Client",
    height=270 * n_rows,
)
fig.show()

SummaryΒΆ

Show code
summary_rows = []

for client in all_clients:
    row = {"Client": client}

    # Current-to-head distance
    client_lag = lag_df[lag_df["client"] == client]["lag"]
    if not client_lag.empty:
        row["Avg C-H Dist."] = f"{client_lag.mean():.1f}"
        row["Max C-H Dist."] = f"{client_lag.max():.0f}"

    # Head-to-justified distance
    client_just = justification_lag[justification_lag["client"] == client]["lag"]
    if not client_just.empty:
        row["Avg H-J Dist."] = f"{client_just.mean():.1f}"
        row["Max H-J Dist."] = f"{client_just.max():.0f}"

    # Justified-to-finalized distance
    client_fin = finality_lag[finality_lag["client"] == client]["lag"]
    if not client_fin.empty:
        row["Avg J-F Dist."] = f"{client_fin.mean():.1f}"
        row["Max J-F Dist."] = f"{client_fin.max():.0f}"

    # Head-to-finalized distance
    client_hf = head_fin_lag[head_fin_lag["client"] == client]["lag"]
    if not client_hf.empty:
        row["Avg H-F Dist."] = f"{client_hf.mean():.1f}"
        row["Max H-F Dist."] = f"{client_hf.max():.0f}"

    # Reorgs
    client_reorgs = reorgs_df[reorgs_df["client"] == client]["value"]
    if not client_reorgs.empty:
        row["Reorgs"] = f"{client_reorgs.max():.0f}"

    # Final head slot
    client_head = head_df[(head_df["client"] == client) & (head_df["metric"] == "lean_head_slot")]
    if not client_head.empty:
        row["Final Head Slot"] = f"{client_head['value'].max():.0f}"

    # Final finalized slot
    client_finalized = finality_df[(finality_df["client"] == client) & (finality_df["metric"] == "lean_latest_finalized_slot")]
    if not client_finalized.empty:
        row["Final Finalized Slot"] = f"{client_finalized['value'].max():.0f}"

    summary_rows.append(row)

if summary_rows:
    summary_df = pd.DataFrame(summary_rows).set_index("Client").fillna("-")
    display(summary_df)

print(f"\nDevnet: {devnet_id}")
if devnet_info:
    print(f"Duration: {devnet_info['duration_hours']:.1f} hours")
Avg C-H Dist. Max C-H Dist. Avg H-J Dist. Max H-J Dist. Avg J-F Dist. Max J-F Dist. Avg H-F Dist. Max H-F Dist. Reorgs Final Head Slot Final Finalized Slot
Client
ethlambda_0 2.7 11 557.0 2048 15.0 225 572.0 2052 9 3903 1851
ethlambda_1 1.9 10 558.2 2048 14.6 225 572.8 2052 11 3903 1851
gean_0 1.8 10 558.2 2048 14.6 225 572.8 2052 9 3903 1851
gean_1 1.8 10 557.6 2048 14.9 225 572.5 2052 11 3903 1851
grandine_0 23.4 2708 1081.3 3722 25.7 182 1107.0 3771 12 3881 1851
grandine_1 11.3 2053 1110.1 3722 28.2 225 1138.3 3771 15 3881 1851
lantern_0 406.1 1758 154.6 295 14.6 225 169.2 299 106 2150 1851
lantern_1 1649.8 3472 189.9 201 48.0 72 237.9 250 1 1851 1835
nlean_0 2.0 11 560.1 2048 13.7 225 573.7 2052 6 3903 1851
nlean_1 2.2 19 559.4 2048 14.3 225 573.7 2052 5 3903 1851
qlean_0 37.0 1983 46.6 2025 26.7 225 73.3 2025 29 3876 1851
qlean_1 1.7 18 16.2 87 27.9 225 44.1 257 31 1747 1723
ream_0 -11.5 0 168.1 478 30.5 225 198.6 482 - 2334 1851
ream_1 -0.9 0 23.9 144 25.1 225 49.0 255 - 1999 1851
zeam_0 4.8 67 551.2 2049 9.1 182 560.2 2053 10 3904 1851
zeam_1 4.3 68 552.5 2050 14.6 225 567.1 2054 8 3905 1851
Devnet: pqdevnet-20260507T2011Z
Duration: 4.3 hours