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-20260324T1507Z
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-20260324T1507Z
Duration: 4.6 hours
Time: 2026-03-24T15:07:42+00:00 to 2026-03-24T19:42:41+00:00
Slots: 0 β†’ 4084
Clients: ethlambda_0, ethlambda_1, ethlambda_2, ethlambda_3, ethlambda_4, gean_0, grandine_0, lantern_0, nlean_0, qlean_0, qlean_1, ream_0, zeam_0

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: 4661 records, clients: ['ethlambda_0', 'ethlambda_1', 'ethlambda_2', 'ethlambda_3', 'ethlambda_4', 'gean_0', 'grandine_0', 'lantern_0', 'nlean_0', 'qlean_0', 'qlean_1', 'ream_0', 'zeam_0']
Finality: 4784 records, clients: ['ethlambda_0', 'ethlambda_1', 'ethlambda_2', 'ethlambda_3', 'ethlambda_4', 'gean_0', 'grandine_0', 'lantern_0', 'nlean_0', 'qlean_0', 'qlean_1', 'ream_0', 'zeam_0']
Finality metrics: ['lean_finalized_slot', 'lean_justified_slot', 'lean_latest_finalized_slot', 'lean_latest_justified_slot']
Reorgs: 1024 records, clients: ['ethlambda_1', 'ethlambda_2', 'ethlambda_3', 'gean_0', 'grandine_0', 'lantern_0', 'nlean_0', 'qlean_0', 'qlean_1', 'zeam_0']

All clients (13): ['ethlambda_0', 'ethlambda_1', 'ethlambda_2', 'ethlambda_3', 'ethlambda_4', 'gean_0', 'grandine_0', 'lantern_0', 'nlean_0', 'qlean_0', 'qlean_1', 'ream_0', 'zeam_0']

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. Final Head Slot Final Finalized Slot Reorgs
Client
ethlambda_0 1.1 8 635.5 1014 469.0 676 1104.5 1690 2296 606 -
ethlambda_1 1.1 5 663.3 3478 490.0 676 1153.4 3478 4084 606 1
ethlambda_2 1.3 5 671.6 3478 460.5 676 1132.1 3478 4084 606 1
ethlambda_3 1.0 5 670.4 3478 460.5 676 1130.9 3478 4084 606 1
ethlambda_4 0.9 5 635.2 1014 470.4 676 1105.5 1690 2296 606 -
gean_0 69.5 754 930.4 2719 31.6 676 962.0 2745 4027 1282 133
grandine_0 118.4 1683 1490.4 3242 396.2 622 1886.5 3864 3864 54 1
lantern_0 39.3 161 2564.2 2645 676.0 676 3240.2 3321 3927 606 4
nlean_0 122.5 752 900.5 2525 466.9 676 1367.4 3201 3807 606 193
qlean_0 53.0 1506 1319.2 3478 406.2 676 1725.4 3478 4084 606 11
qlean_1 1819.0 3040 1050.1 2774 484.0 676 1534.1 3450 4056 606 17
ream_0 - - 482.9 696 577.7 676 1060.6 1372 1978 606 -
zeam_0 1.0 3 42.5 144 66.7 306 109.2 330 440 426 0
Devnet: pqdevnet-20260324T1507Z
Duration: 4.6 hours