Tempo advances its protocol layer with the T4 hardfork definition landing in the chain specification and a new consensus metadata encoding scheme embedded directly into block construction.

> impact

**What shipped.** Two foundational protocol changes landed for Tempo this week. First, PR #3427 introduces `TempoHardfork::T4` to the chain specification, formally defining the next hardfork milestone in the Tempo network's upgrade path. Second, PR #3092 by Hamdi Allam adds consensus metadata encoding directly into Tempo blocks, changing how block-level data is structured and surfaced to validators and downstream consumers. **Why it matters.** The T4 hardfork entry in the chain spec is the first concrete on-chain signal that a network upgrade is being staged. Node operators, indexers, and anyone running infrastructure against Tempo should treat this as an early warning to begin reviewing their upgrade readiness. Meanwhile, embedding consensus metadata into blocks is a meaningful architectural shift — it moves information that may have previously lived outside the block structure (or required separate lookups) into the block itself, tightening the coupling between consensus state and execution state. This likely supports TIP-related features and simplifies the trust model for light clients and bridges that need to verify consensus properties from block data alone. **Impact on builders.** If you parse Tempo blocks — whether you're running a custom indexer, a bridge relayer, or block explorer infrastructure — both of these changes will affect you. The T4 hardfork may introduce breaking changes to block validation rules or state transition logic once activated, so pinning your node software version and monitoring the Tempo release channel is critical. The consensus metadata encoding change alters the block envelope schema now, meaning any deserialization logic that assumes the current block format will need to be updated. Downstream tooling authors should audit their block decoding paths and test against the latest devnet or testnet blocks as soon as T4 is available on a test network.

> Try this now

try this

# --- Tempo T4 Hardfork & Consensus Metadata: Developer Walkthrough ---

# 1. Check your node's chain spec for T4 support.
#    If you're running a Tempo node, pull the latest source and verify
#    that your chain spec includes the T4 hardfork definition.
#    This ensures your node will recognize T4 activation when it lands.

# $ git pull origin main
# $ grep -r 'T4' chain/spec.go   # or the relevant chain spec file
# You should see something like:
#   TempoHardfork::T4 => { activation_block: ... }

# 2. Inspect the new block structure with consensus metadata.
#    After syncing to a T4-enabled testnet (when available), fetch a
#    recent block and examine the new consensus metadata field.

# import tempo_sdk
# client = tempo_sdk.Client("https://testnet-rpc.tempo.network")
# block = client.get_block("latest")
#
# # The block envelope now includes embedded consensus metadata
# print(block.consensus_metadata)
# # Expected: a structured object with validator set info, TIP references,
# #           or other consensus-layer attestations

# 3. Update your block deserialization logic.
#    If you have a custom indexer or parser, the block schema has changed.
#    Make sure your decoder handles the new field gracefully.

# import json
# raw_block = client.get_raw_block("latest")
# decoded = json.loads(raw_block)
#
# # Old path (may break):
# # header = decoded["header"]
# # tx_root = header["transactions_root"]
#
# # New path — account for consensus_metadata:
# header = decoded["header"]
# consensus_meta = header.get("consensus_metadata", None)
# if consensus_meta is None:
#     print("WARNING: Running against a pre-T4 block or outdated node")
# else:
#     print(f"Consensus metadata version: {consensus_meta['version']}")
#     print(f"Validator set hash: {consensus_meta['validator_set_hash']}")

# 4. Pin your node version and set up upgrade monitoring.
#    T4 activation will require a coordinated node upgrade.
#    Set an alert for the activation block height once announced.

# $ tempo version
# # Ensure this returns a version that includes T4 chain spec support
# # If not, upgrade before the activation block height