diff --git a/.config/forest.dic b/.config/forest.dic
index 2dd350500ddd..2d1dfcb9a930 100644
--- a/.config/forest.dic
+++ b/.config/forest.dic
@@ -1,4 +1,4 @@
-73
+75
 Algorand/M
 API/M
 APIs
@@ -58,6 +58,7 @@ F3
 FFI
 FIL
 Filecoin/M
+Filfox
 Filops
 FIP
 FVM
@@ -147,4 +148,5 @@ VRF
 WebAssembly
 WebSocket
 WPoStProvingPeriodDeadlines
+YAML
 zstd
diff --git a/src/dev/subcommands/mod.rs b/src/dev/subcommands/mod.rs
index d32a1199e633..477198dc5f3e 100644
--- a/src/dev/subcommands/mod.rs
+++ b/src/dev/subcommands/mod.rs
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0, MIT
 
 mod state_cmd;
+mod update_checkpoints_cmd;
 
 use crate::cli_shared::cli::HELP_MESSAGE;
 use crate::networks::generate_actor_bundle;
@@ -42,6 +43,9 @@ pub enum Subcommand {
     },
     #[command(subcommand)]
     State(state_cmd::StateCommand),
+    /// Update known blocks (checkpoints), normally in `build/known_blocks.yaml`, by querying RPC
+    /// endpoints
+    UpdateCheckpoints(update_checkpoints_cmd::UpdateCheckpointsCommand),
 }
 
 impl Subcommand {
@@ -49,6 +53,7 @@ impl Subcommand {
         match self {
             Self::FetchTestSnapshots { actor_bundle } => fetch_test_snapshots(actor_bundle).await,
             Self::State(cmd) => cmd.run().await,
+            Self::UpdateCheckpoints(cmd) => cmd.run().await,
         }
     }
 }
diff --git a/src/dev/subcommands/update_checkpoints_cmd.rs b/src/dev/subcommands/update_checkpoints_cmd.rs
new file mode 100644
index 000000000000..803ccb7cbbf6
--- /dev/null
+++ b/src/dev/subcommands/update_checkpoints_cmd.rs
@@ -0,0 +1,277 @@
+// Copyright 2019-2026 ChainSafe Systems
+// SPDX-License-Identifier: Apache-2.0, MIT
+
+use anyhow::Context as _;
+use cid::Cid;
+use clap::Parser;
+use indexmap::IndexMap;
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+use url::Url;
+
+use crate::rpc::Client;
+use crate::rpc::prelude::*;
+use crate::rpc::types::ApiTipsetKey;
+use crate::shim::clock::ChainEpoch;
+
+/// The interval between checkpoints (86400 epochs = 30 days)
+const CHECKPOINT_INTERVAL: ChainEpoch = 86400;
+
+/// YAML structure for `known_blocks.yaml`
+/// Using `IndexMap` to preserve insertion order
+#[derive(Debug, Clone, Serialize, Deserialize)]
+struct KnownBlocks {
+    #[serde(with = "cid_string_map")]
+    calibnet: IndexMap<ChainEpoch, Cid>,
+    #[serde(with = "cid_string_map")]
+    mainnet: IndexMap<ChainEpoch, Cid>,
+}
+
+/// Network selection for checkpoint updates
+#[derive(Debug, Clone, clap::ValueEnum)]
+pub enum Network {
+    /// Update both calibnet and mainnet
+    All,
+    /// Update calibnet only
+    Calibnet,
+    /// Update mainnet only
+    Mainnet,
+}
+
+/// Update known blocks in `build/known_blocks.yaml` by querying RPC endpoints
+///
+/// This command finds and adds missing checkpoint entries at constant intervals
+/// by querying Filfox or other full-archive RPC nodes that support historical queries.
+#[derive(Debug, Parser)]
+pub struct UpdateCheckpointsCommand {
+    /// Path to `known_blocks.yaml` file
+    #[arg(long, default_value = "build/known_blocks.yaml")]
+    known_blocks_file: PathBuf,
+
+    /// Mainnet RPC endpoint (Filfox recommended for full historical data)
+    #[arg(long, default_value = "https://filfox.info")]
+    mainnet_rpc: Url,
+
+    /// Calibnet RPC endpoint (Filfox recommended for full historical data)
+    #[arg(long, default_value = "https://calibration.filfox.info")]
+    calibnet_rpc: Url,
+
+    /// Which network(s) to update
+    #[arg(long, default_value = "all")]
+    network: Network,
+
+    /// Dry run - don't write changes to file
+    #[arg(long)]
+    dry_run: bool,
+}
+
+impl UpdateCheckpointsCommand {
+    pub async fn run(self) -> anyhow::Result<()> {
+        let Self {
+            known_blocks_file,
+            mainnet_rpc,
+            calibnet_rpc,
+            network,
+            dry_run,
+        } = self;
+
+        println!("Reading known blocks from: {}", known_blocks_file.display());
+        let yaml_content = std::fs::read_to_string(&known_blocks_file)
+            .context("Failed to read known_blocks.yaml")?;
+        let mut known_blocks: KnownBlocks =
+            serde_yaml::from_str(&yaml_content).context("Failed to parse known_blocks.yaml")?;
+
+        if matches!(network, Network::All | Network::Calibnet) {
+            println!("\n=== Updating Calibnet Checkpoints ===");
+            let calibnet_client = Client::from_url(calibnet_rpc);
+            update_chain_checkpoints(&calibnet_client, &mut known_blocks.calibnet, "calibnet")
+                .await?;
+        }
+
+        if matches!(network, Network::All | Network::Mainnet) {
+            println!("\n=== Updating Mainnet Checkpoints ===");
+            let mainnet_client = Client::from_url(mainnet_rpc);
+            update_chain_checkpoints(&mainnet_client, &mut known_blocks.mainnet, "mainnet").await?;
+        }
+
+        if dry_run {
+            println!("\n=== Dry Run - Changes Not Written ===");
+            println!("Would write to: {}", known_blocks_file.display());
+        } else {
+            println!("\n=== Writing Updated Checkpoints ===");
+            write_known_blocks(&known_blocks_file, &known_blocks)?;
+            println!("Successfully updated: {}", known_blocks_file.display());
+        }
+
+        Ok(())
+    }
+}
+
+async fn update_chain_checkpoints(
+    client: &Client,
+    checkpoints: &mut IndexMap<ChainEpoch, Cid>,
+    chain_name: &str,
+) -> anyhow::Result<()> {
+    println!("Fetching chain head for {chain_name}...");
+    let head = ChainHead::call(client, ())
+        .await
+        .context("Failed to get chain head")?;
+
+    let current_epoch = head.epoch();
+    println!("Current epoch: {}", current_epoch);
+
+    let latest_checkpoint_epoch = (current_epoch / CHECKPOINT_INTERVAL) * CHECKPOINT_INTERVAL;
+
+    let existing_max_epoch = checkpoints.keys().max().copied().unwrap_or(0);
+    println!("Existing max checkpoint epoch: {existing_max_epoch}");
+    println!("Latest checkpoint epoch should be: {latest_checkpoint_epoch}");
+
+    if latest_checkpoint_epoch <= existing_max_epoch {
+        println!("No new checkpoints needed (already up to date)");
+        return Ok(());
+    }
+
+    let mut needed_epochs = Vec::new();
+    let mut epoch = existing_max_epoch + CHECKPOINT_INTERVAL;
+    while epoch <= latest_checkpoint_epoch {
+        if !checkpoints.contains_key(&epoch) {
+            needed_epochs.push(epoch);
+        }
+        epoch += CHECKPOINT_INTERVAL;
+    }
+
+    if needed_epochs.is_empty() {
+        println!("No missing checkpoints to add");
+        return Ok(());
+    }
+
+    println!("Need to add {} checkpoint(s)", needed_epochs.len());
+
+    println!("Fetching checkpoints via RPC...");
+    let mut found_checkpoints: IndexMap<ChainEpoch, Cid> = IndexMap::new();
+
+    for &requested_epoch in &needed_epochs {
+        match fetch_checkpoint_at_height(client, requested_epoch).await {
+            Ok((actual_epoch, cid)) => {
+                found_checkpoints.insert(actual_epoch, cid);
+
+                if actual_epoch != requested_epoch {
+                    println!(
+                        "  ✓ Epoch {actual_epoch} (requested {requested_epoch}, no blocks at exact height): {cid}"
+                    );
+                } else {
+                    println!("  ✓ Epoch {}: {}", actual_epoch, cid);
+                }
+
+                // Map chain name for Beryx URL (calibnet -> calibration)
+                let beryx_network = if chain_name == "calibnet" {
+                    "calibration"
+                } else {
+                    chain_name
+                };
+                println!("    Verify at: https://beryx.io/fil/{beryx_network}/block-cid/{cid}",);
+            }
+            Err(e) => {
+                println!("  ✗ Epoch {requested_epoch}: {e}");
+            }
+        }
+    }
+
+    let num_found = found_checkpoints.len();
+    println!("\nAdding {num_found} new checkpoint(s) to the file...");
+
+    let mut sorted_checkpoints: Vec<_> = found_checkpoints.into_iter().collect();
+    sorted_checkpoints.sort_by_key(|(epoch, _)| std::cmp::Reverse(*epoch));
+
+    let mut new_map = IndexMap::new();
+    for (epoch, cid) in sorted_checkpoints {
+        new_map.insert(epoch, cid);
+    }
+    new_map.extend(checkpoints.drain(..));
+    *checkpoints = new_map;
+
+    if num_found < needed_epochs.len() {
+        anyhow::bail!(
+            "Only found {num_found} out of {} needed checkpoints. Consider using an RPC provider with full historical data (e.g., Filfox).",
+            needed_epochs.len()
+        );
+    }
+
+    Ok(())
+}
+
+/// Fetch a checkpoint at a specific height via RPC.
+///
+/// Returns `(actual_epoch, cid)` where `actual_epoch` might be slightly earlier than requested
+/// if there were no blocks at the exact requested height.
+async fn fetch_checkpoint_at_height(
+    client: &Client,
+    epoch: ChainEpoch,
+) -> anyhow::Result<(ChainEpoch, Cid)> {
+    let tipset = ChainGetTipSetByHeight::call(client, (epoch, ApiTipsetKey(None)))
+        .await
+        .context("ChainGetTipSetByHeight RPC call failed")?;
+
+    let actual_epoch = tipset.epoch();
+    let first_block_cid = tipset.block_headers().first().cid();
+    Ok((actual_epoch, *first_block_cid))
+}
+
+fn write_known_blocks(path: &PathBuf, known_blocks: &KnownBlocks) -> anyhow::Result<()> {
+    let mut output = String::new();
+
+    output.push_str("# This file is auto-generated by `forest-dev update-checkpoints` command.\n");
+    output.push_str("# Do not edit manually. Run the command to update checkpoints.\n\n");
+
+    output.push_str("calibnet:\n");
+    for (epoch, cid) in &known_blocks.calibnet {
+        output.push_str(&format!("  {epoch}: {cid}\n"));
+    }
+
+    output.push_str("mainnet:\n");
+    for (epoch, cid) in &known_blocks.mainnet {
+        output.push_str(&format!("  {epoch}: {cid}\n"));
+    }
+
+    std::fs::write(path, output).context(format!(
+        "Failed to write updated known blocks to {}",
+        path.display()
+    ))?;
+
+    Ok(())
+}
+
+// Custom serde module for serializing/deserializing IndexMap<ChainEpoch, Cid> as strings
+mod cid_string_map {
+    use super::*;
+    use serde::de::{Deserialize, Deserializer};
+    use serde::ser::Serializer;
+    use std::str::FromStr;
+
+    pub fn serialize<S>(map: &IndexMap<ChainEpoch, Cid>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        use serde::ser::SerializeMap;
+        let mut ser_map = serializer.serialize_map(Some(map.len()))?;
+        for (k, v) in map {
+            ser_map.serialize_entry(k, &v.to_string())?;
+        }
+        ser_map.end()
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<IndexMap<ChainEpoch, Cid>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let string_map: IndexMap<ChainEpoch, String> = IndexMap::deserialize(deserializer)?;
+        string_map
+            .into_iter()
+            .map(|(k, v)| {
+                Cid::from_str(&v)
+                    .map(|cid| (k, cid))
+                    .map_err(serde::de::Error::custom)
+            })
+            .collect()
+    }
+}