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-20260512T1356Z
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-20260512T1356Z
Duration: 3.9 hours
Time: 2026-05-12T13:56:10+00:00 to 2026-05-12T17:50:06+00:00
Slots: 83 β†’ 3566
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: 6878 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: 8814 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: 3194 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 1.7 24 361.7 1508 55.1 380 416.8 1557 37 3579 2022
ethlambda_1 2.4 26 362.1 1510 55.7 380 417.8 1559 34 3581 2022
gean_0 6.7 122 363.0 1509 53.3 380 416.3 1558 25 3580 2022
gean_1 2.0 25 363.1 1509 55.8 380 418.9 1558 34 3580 2022
grandine_0 13.7 2423 1039.5 3577 38.6 380 1078.1 3577 36 3577 2022
grandine_1 6.1 641 1020.0 3577 39.2 380 1059.2 3577 27 3577 2022
lantern_0 13.9 190 377.5 1507 49.1 380 426.6 1556 24 3578 2022
lantern_1 8.3 120 405.0 1510 49.3 380 454.3 1559 28 3581 2022
nlean_0 7.6 158 362.8 1507 54.4 380 417.2 1556 18 3578 2022
nlean_1 6.1 108 362.5 1511 54.6 380 417.0 1560 18 3582 2022
qlean_0 14.3 290 351.3 1501 55.7 380 407.0 1550 249 3572 2022
qlean_1 5.7 71 329.2 1390 55.8 380 384.9 1439 616 3461 2022
ream_0 -2.0 0 88.9 350 47.4 144 136.3 386 - 2025 1966
ream_1 -0.5 0 61.2 344 69.9 380 131.1 393 - 1775 1625
zeam_0 7.2 15 1561.5 3295 20.9 81 1582.4 3315 10 3568 253
zeam_1 7.0 15 1558.6 3296 21.5 132 1580.2 3316 12 3569 253
Devnet: pqdevnet-20260512T1356Z
Duration: 3.9 hours