fix(rpc): handle eth_config when no timestamp fork is active yet

[panos-xyz]

Summary

• eth_config returned error "no active timestamp fork found" when the chain is at block 0 (Bernoulli/Curie block-based fork era)
• This caused morphnode to fail its startup readiness check and retry indefinitely, blocking sync from genesis
• Fixed by falling back to latest_ts when no timestamp fork is active, so the response correctly reflects the current chain state (useZktrie: true, jadeForkTime set, next pointing to Morph203)

Root Cause

eth_config collects all timestamp-based fork activation timestamps and finds the latest one <= latest block timestamp. At genesis (block 0, timestamp ~0 or early), all timestamp forks (Morph203 @ 1747029600, Viridian, Emerald, Jade) are in the future, so rfind returns None → error.

Test Plan

• cargo check -p morph-rpc passes
• cargo build --release passes
• Started mainnet node from genesis: morphnode no longer loops on "Waiting for geth to be ready" and begins syncing immediately
• eth_config response at block 0 correctly returns useZktrie: true and jadeForkTime

Summary by CodeRabbit

• Bug Fixes
  • Enhanced fork timestamp selection to gracefully handle scenarios where no active timestamp fork exists. The system now falls back to the current block timestamp instead of failing, ensuring stable operation across all timestamp configurations.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 55c679e5-e8d0-4fd4-ad9f-553b444082b6

📥 Commits

Reviewing files that changed from the base of the PR and between 7d75856 and 12fa914.

📒 Files selected for processing (1)

• crates/rpc/src/eth_config.rs

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📝 Walkthrough

Walkthrough

The change modifies fork timestamp selection logic in eth_config.rs. When no active timestamp fork exists, the code now falls back to using the latest timestamp instead of returning an error, allowing continued processing with the current block state timestamp.

Changes

Cohort / File(s)	Summary
Fork Timestamp Fallback Logic crates/rpc/src/eth_config.rs	Modified config_impl to fall back to latest_ts when no active timestamp fork is found, replacing previous error return. Added explanatory comment on block-based fork era behavior and expected useZktrie=true result for pre-Morph203.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• feat: implement eth_config RPC with morph extension #72 — Modifies the same fork-timestamp selection logic in config_impl within crates/rpc/src/eth_config.rs.

Suggested reviewers

• chengwenxi
• anylots

Poem

🐰 When forks fade and timestamps flee,
No error thrown, just fall back free!
The latest path is always there,
Like carrots hopping everywhere! 🥕

🚥 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 accurately describes the main change: handling the eth_config RPC response when no timestamp fork is active yet, which is the core fix for the startup readiness check issue.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ 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/eth-config-no-timestamp-fork

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