fix(nonce): use per-network genesis nonce seed instead of hardcoded mainnet

[wcatz]

Summary

Nonce evolution was seeded with mainnet's Shelley genesis hash for ALL networks. Preview and preprod have different genesis nonces, so every computed epoch nonce was wrong from epoch 0 onwards.

Changes

• Per-network genesis nonce constants (mainnet, preprod, preview — verified against Koios)
• genesisNonceForNetwork() and shelleyStartForNetwork() helpers
• Replace all hardcoded ShelleyGenesisHash references with network-aware lookups
• PreviewShelleyStartEpoch = 0 (preview has no Byron era)

Test plan

• All tests pass
• Deploy preview full mode, verify nonces match Koios for all epochs
• Deploy mainnet, verify nonce computation

Summary by CodeRabbit

Release Notes

• New Features

  • Added support for preview network alongside mainnet and preprod environments.
  • Enabled network-specific genesis nonce initialization for accurate epoch calculations across all supported networks.

• Bug Fixes

  • Fixed epoch-to-slot calculations for preview network.

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR introduces network-specific nonce initialization by adding genesis nonce constants for mainnet, preprod, and preview networks, creating helper functions to select network-appropriate values, and updating the initialNonce function signature to accept a networkMagic parameter for per-network nonce seeding.

Changes

Cohort / File(s)	Summary
Nonce Core Logic nonce.go	Added network-specific genesis nonce constants (MainnetGenesisNonce, PreprodGenesisNonce, PreviewGenesisNonce). Introduced genesisNonceForNetwork(networkMagic int) and shelleyStartForNetwork(networkMagic int) helpers. Changed initialNonce signature to initialNonce(fullMode bool, networkMagic int). Updated ComputeEpochNonce, BackfillNonces, and NonceIntegrityCheck to use network-aware logic. Retained ShelleyGenesisHash as backward-compatible alias for MainnetGenesisNonce.
Epoch Constants leaderlog.go	Added new exported constant PreviewShelleyStartEpoch = 0 to define the preview network's Shelley era epoch baseline.
Test Updates comprehensive_test.go	Updated initialNonce call sites in TestInitialNonceModes and TestResyncFromDB_BlockCountMismatch to pass MainnetNetworkMagic as the second argument to match the new function signature.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• fix(nonce): era-aware stability window and Babbage VRF domain separator #57: Both PRs modify nonce-related logic and epoch constants with multi-network support considerations
• fix(nonce): recompute era-aware nonce from raw VRF output #59: Directly related as both modify ComputeEpochNonce and BackfillNonces with network-aware nonce computations
• Fix/pr71 coderabbit issues #73: Connected through ComputeEpochNonce modifications and network-aware nonce evolution logic

Poem

🐰 Across the networks, nonces bloom,
Mainnet, Preprod, Preview's room,
Each network its genesis seed knows,
As magic constants gently flows! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 71.43% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: replacing hardcoded mainnet genesis nonce with per-network seeds.
Description check	✅ Passed	The description includes all required template sections: summary of the issue and fix, detailed list of changes, test plan with checkboxes, and necessary context for reviewers.

_{✏️ 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/per-network-genesis-nonce

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

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

Inline comments:
In `@comprehensive_test.go`:
- Around line 1642-1643: The prevNonce is created with MainnetNetworkMagic but
the test constructs the NonceTracker using PreprodNetworkMagic; update the call
to initialNonce to use PreprodNetworkMagic so the nonce network magic matches
the NonceTracker setup (change prevNonce := initialNonce(true,
MainnetNetworkMagic) to use PreprodNetworkMagic); ensure this change is applied
in the test where prevNonce is used alongside store.UpsertEvolvingNonce and the
NonceTracker instance so the recomputation/repair scenario remains identical.

🪄 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: f5c4c9f3-24a0-4138-8cbe-31fbdddaf3df

📥 Commits

Reviewing files that changed from the base of the PR and between 82ad6b3 and 5c46721.

📒 Files selected for processing (3)

• comprehensive_test.go
• leaderlog.go
• nonce.go

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Network magic mismatch in test setup.

The test uses PreprodNetworkMagic for the NonceTracker (line 1648) but initializes prevNonce with MainnetNetworkMagic. For consistency with the test scenario, this should use PreprodNetworkMagic:

🔧 Suggested fix

-	prevNonce := initialNonce(true, MainnetNetworkMagic)
+	prevNonce := initialNonce(true, networkMagic)

The test still validates the recomputation mechanism correctly (block count mismatch triggers repair), but using the matching network magic makes the test setup more realistic and consistent.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	prevNonce := initialNonce(true, MainnetNetworkMagic)
	if err := store.UpsertEvolvingNonce(ctx, epoch-1, prevNonce, 100); err != nil {
	prevNonce := initialNonce(true, networkMagic)
	if err := store.UpsertEvolvingNonce(ctx, epoch-1, prevNonce, 100); err != nil {

🤖 Prompt for AI Agents

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

In `@comprehensive_test.go` around lines 1642 - 1643, The prevNonce is created
with MainnetNetworkMagic but the test constructs the NonceTracker using
PreprodNetworkMagic; update the call to initialNonce to use PreprodNetworkMagic
so the nonce network magic matches the NonceTracker setup (change prevNonce :=
initialNonce(true, MainnetNetworkMagic) to use PreprodNetworkMagic); ensure this
change is applied in the test where prevNonce is used alongside
store.UpsertEvolvingNonce and the NonceTracker instance so the
recomputation/repair scenario remains identical.