fix(chainspec): use MORPH_BASE_FEE as genesis default instead of INITIAL_BASE_FEE

[panos-xyz]

Summary

• When baseFeePerGas is absent in genesis JSON, upstream reth defaults to Ethereum's INITIAL_BASE_FEE (1,000,000,000 = 1 Gwei)
• morph-geth's CalcBaseFee() returns 1,000,000 (0.001 Gwei) as the default
• This mismatch causes morph-reth and morph-geth to compute different genesis block header hashes, breaking batch submission since morphnode's GenesisBatchHeader is derived from the geth-computed hash

Fix

Override the default baseFeePerGas to MORPH_BASE_FEE (1,000,000) in both genesis header construction paths when baseFeePerGas is not explicitly set:

• make_genesis_header() — used for predefined networks (mainnet/testnet) with custom state root
• from_genesis_with_config() None branch — used for CLI-provided genesis (devnet)

The fix only applies when baseFeePerGas is absent; explicitly set values are preserved.

Root cause reference

morph/go-ethereum/consensus/misc/eip1559.go:

func CalcBaseFee(...) *big.Int {
    return big.NewInt(1000000) // 0.001 Gwei
}

morph/go-ethereum/core/genesis.go:

if g.BaseFee != nil {
    head.BaseFee = g.BaseFee
} else {
    head.BaseFee = misc.CalcBaseFee(...)  // → 1_000_000
}

Test plan

• cargo check -p morph-chainspec passes
• Devnet genesis block hash matches between morph-reth and morph-geth when baseFeePerGas is omitted from genesis JSON

Summary by CodeRabbit

• Bug Fixes
  • Improved genesis block initialization to ensure the correct base fee per gas value is applied when constructing genesis headers and recomputing the corresponding hash to reflect accurate configuration.

[coderabbitai]

📝 Walkthrough

Walkthrough

Modified genesis header construction in the chainspec to apply MORPH_BASE_FEE when base fee per gas is absent from genesis configuration. Updated two code paths to properly handle base fee assignment and recompute genesis hash accordingly.

Changes

Cohort / File(s)	Summary
Genesis base fee handling crates/chainspec/src/spec.rs	Added Sealable import and updated make_genesis_header and from_genesis_with_config to use MORPH_BASE_FEE as fallback when genesis lacks base fee per gas. Modified hash computation to use hash_slow() instead of cached genesis hash when base fee is corrected.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Suggested reviewers

• panos-xyz
• anylots

Poem

🐰 A base fee now stands firm and true,
When genesis lacked what it should do,
MORPH steps in with steadfast grace,
Hashing slowly finds its place! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(chainspec): use MORPH_BASE_FEE as genesis default instead of INITIAL_BASE_FEE' accurately describes the main change in the pull request.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/genesis-base-fee-default

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[chengwenxi]

LGTM

[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

crates/chainspec/src/spec.rs (1)

41-46: Extract the base-fee defaulting rule into one helper.

The same Morph-specific fallback is implemented twice (Lines 41-46 and Lines 269-275). Centralizing this logic would reduce drift risk in consensus-critical paths.

Also applies to: 269-275

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@crates/chainspec/src/spec.rs` around lines 41 - 46, The duplicated
Morph-specific fallback for base fee (checking genesis.base_fee_per_gas and
setting inner.base_fee_per_gas to MORPH_BASE_FEE) should be extracted into a
single helper to avoid drift: add a helper like apply_morph_base_fee(header:
&mut Header) or default_base_fee_if_missing(header: &mut Header) that sets
header.base_fee_per_gas = Some(MORPH_BASE_FEE) when it is None, then replace
both occurrences (the blocks that inspect genesis.base_fee_per_gas /
inner.base_fee_per_gas and the similar block later) with calls to that helper;
keep the MORPH_BASE_FEE symbol and use the existing Header type and field names
(base_fee_per_gas) to maintain consensus semantics.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@crates/chainspec/src/spec.rs`:
- Around line 269-279: Add two unit tests in this module covering genesis
baseFeePerGas: one that builds a spec where genesis.base_fee_per_gas is None and
asserts the resulting header (via base_spec.genesis_header.header().clone(),
then MorphHeader::from(...) and SealedHeader::new(...)) has
header.base_fee_per_gas == Some(MORPH_BASE_FEE) and computes the expected hash,
and another where genesis.base_fee_per_gas is set explicitly and assert that the
explicit value is preserved in the header and that the resulting hash differs
from the omitted case; use the existing helper construction (base_spec, genesis,
MorphHeader::from, header.hash_slow, SealedHeader::new) to create the headers
and compare expected values.

---

Nitpick comments:
In `@crates/chainspec/src/spec.rs`:
- Around line 41-46: The duplicated Morph-specific fallback for base fee
(checking genesis.base_fee_per_gas and setting inner.base_fee_per_gas to
MORPH_BASE_FEE) should be extracted into a single helper to avoid drift: add a
helper like apply_morph_base_fee(header: &mut Header) or
default_base_fee_if_missing(header: &mut Header) that sets
header.base_fee_per_gas = Some(MORPH_BASE_FEE) when it is None, then replace
both occurrences (the blocks that inspect genesis.base_fee_per_gas /
inner.base_fee_per_gas and the similar block later) with calls to that helper;
keep the MORPH_BASE_FEE symbol and use the existing Header type and field names
(base_fee_per_gas) to maintain consensus semantics.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: be01b4d6-5042-4bb8-bd89-395427117618

📥 Commits

Reviewing files that changed from the base of the PR and between ab638b1 and 34e82d4.

📒 Files selected for processing (1)

• crates/chainspec/src/spec.rs

[coderabbitai]

⚠️ Potential issue | 🟠 Major

Add regression tests for omitted vs explicit baseFeePerGas in genesis.

This branch changes consensus-critical genesis header/hash behavior, but there’s no accompanying test in this module asserting: (1) omitted baseFeePerGas becomes MORPH_BASE_FEE, and (2) explicit baseFeePerGas is preserved. Please add both cases to prevent future hash regressions.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@crates/chainspec/src/spec.rs` around lines 269 - 279, Add two unit tests in
this module covering genesis baseFeePerGas: one that builds a spec where
genesis.base_fee_per_gas is None and asserts the resulting header (via
base_spec.genesis_header.header().clone(), then MorphHeader::from(...) and
SealedHeader::new(...)) has header.base_fee_per_gas == Some(MORPH_BASE_FEE) and
computes the expected hash, and another where genesis.base_fee_per_gas is set
explicitly and assert that the explicit value is preserved in the header and
that the resulting hash differs from the omitted case; use the existing helper
construction (base_spec, genesis, MorphHeader::from, header.hash_slow,
SealedHeader::new) to create the headers and compare expected values.