feat: integrate Cronos (chainId 25) as second-class EVM chain

[NeOMakinG]

Description

Add support for Cronos (EVM L1, chainId 25) as a second-class citizen. Cronos is an EVM-compatible L1 blockchain with CRO as the native gas token.

This is PR 2 of 17 in a sequential chain integration series. These PRs must be reviewed and merged in order, as each builds on the previous one (stacked branches).

PR merge order:

1. Mantle (feat: integrate Mantle (chainId 5000) as second-class EVM chain #11905)
2. Cronos (feat: integrate Cronos (chainId 25) as second-class EVM chain #11910) ← this PR
3. Sonic (feat: integrate Sonic (eip155:146) as second-class EVM chain #11923)
4. Unichain (feat: integrate Unichain (eip155:130) as second-class citizen via Relay #11924)
5. BOB (feat: integrate BOB (eip155:60808) as second-class citizen #11925)
6. Mode (feat: integrate Mode (eip155:34443) as second-class citizen #11926)
7. Soneium (feat: integrate Soneium (chainId: 1868) via Relay #11930)
8. Hemi (feat: integrate Hemi (chainId: 43111) via Relay #11931)
9. World Chain (feat: integrate World Chain (480) as second-class Relay chain #11932)
10. Blast (feat: integrate Blast (81457) as second-class Relay chain #11933)
11. zkSync Era (feat: integrate zkSync Era (324) as second-class Relay chain #11934)
12. Story (feat: integrate Story (1514) as second-class Relay chain #11936)
13. Plume (feat: integrate Plume (98866) as second-class Relay chain #11937)
14. Flow EVM (feat: integrate Flow EVM (747) as second-class Relay chain #11938)
15. Celo (feat: integrate Celo (42220) as second-class Relay chain #11939)
16. Ethereal (feat: integrate Ethereal (5064014) as second-class Relay chain #11940)

Note: Linea (#11922) is already in develop.

Implements: CAIP constants, chain adapter, plugin, feature flag, Relay swapper mapping, HDWallet support flags, CSP headers, asset generation script, and all required shared-file entries.

Issue (if applicable)

Part of #11902

Risk

Low - All changes are behind the Cronos feature flag (VITE_FEATURE_CRONOS), disabled by default in production.

No new on-chain transactions or contract interactions. Standard EVM chain support using existing SecondClassEvmAdapter pattern.

Testing

Engineering

1. Set VITE_FEATURE_CRONOS=true in .env.development
2. Run yarn dev
3. Verify Cronos appears in chain selector
4. Verify native CRO balance loads on Cronos
5. Verify Relay swap routes include Cronos

Operations

• 🏁 My feature is behind a flag and doesn't require operations testing (yet)

Summary by CodeRabbit

• New Features

  • Added support for the Cronos blockchain network, enabling users to manage assets, trade, and interact with the Cronos ecosystem directly within the platform.

• Chores

  • Updated environment configuration and documentation to support new blockchain integration.

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request implements comprehensive support for the Cronos blockchain (chainId 25) across the entire ShapeShift ecosystem. The integration includes CAIP constants, EVM chain adapters, wallet capability flags, asset data generation, feature gating, plugin registration, transaction status utilities, and configuration setup.

Changes

Cohort / File(s)	Summary
Configuration & Environment .env, .env.development, src/config.ts, src/vite-env.d.ts, .gitignore	Added environment variables VITE_CRONOS_NODE_URL (with default and development values) and VITE_FEATURE_CRONOS with validators. Updated .gitignore for ephemeral Claude plans.
CAIP Constants & Types packages/caip/src/constants.ts, packages/types/src/base.ts, packages/types/src/zerion.ts	Introduced cronosAssetId, cronosChainId constants, CronosMainnet to CHAIN_REFERENCE, updated VALID_CHAIN_IDS and FEE_ASSET_IDS. Extended type unions to include CronosMainnet and updated Zerion chain mappings.
Coingecko Adapter Integration packages/caip/src/adapters/coingecko/index.ts, packages/caip/src/adapters/coingecko/utils.ts, packages/caip/src/adapters/coingecko/utils.test.ts	Added Cronos to CoingeckoAssetPlatform enum, wired bidirectional mappings between Cronos and chainId, extended asset parsing to handle Cronos platform tokens.
EVM Chain Adapters packages/chain-adapters/src/evm/EvmBaseAdapter.ts, packages/chain-adapters/src/evm/SecondClassEvmAdapter.ts, packages/chain-adapters/src/evm/cronos/CronosChainAdapter.ts, packages/chain-adapters/src/evm/cronos/index.ts, packages/chain-adapters/src/evm/index.ts	Registered CronosMainnet in EVM chain IDs, added chain capability routing, created Cronos-specific adapter extending SecondClassEvmAdapter with BIP44 parameters and asset/RPC configuration.
Type Mappings packages/chain-adapters/src/types.ts	Extended ChainSpecificAccount, ChainSpecificFeeData, ChainSignTx, ChainSpecificBuildTxData, ChainSpecificGetFeeDataInput type mappings to include CronosMainnet; added Cronos to ChainAdapterDisplayName enum.
Contract Clients packages/contracts/src/ethersProviderSingleton.ts, packages/contracts/src/viemClient.ts	Added rpcUrlByChainId case for CronosMainnet, created viemCronosClient, extended viemClientByChainId and viemNetworkIdByChainId mappings with Cronos references.
Wallet Provider Capabilities packages/hdwallet-core/src/ethereum.ts, packages/hdwallet-core/src/wallet.ts, packages/hdwallet-coinbase/src/coinbase.ts, packages/hdwallet-gridplus/src/gridplus.ts, packages/hdwallet-keepkey/src/keepkey.ts, packages/hdwallet-ledger/src/ledger.ts, packages/hdwallet-metamask-multichain/src/shapeshift-multichain.ts, packages/hdwallet-native/src/ethereum.ts, packages/hdwallet-phantom/src/phantom.ts, packages/hdwallet-trezor/src/trezor.ts, packages/hdwallet-vultisig/src/vultisig.ts, packages/hdwallet-walletconnectv2/src/walletconnectV2.ts	Added _supportsCronos capability flag to all wallet implementations (set to true for GridPlus, Ledger, MetaMask, Native, Trezor, WalletConnectV2; false for Coinbase, KeepKey, Phantom, Vultisig). Created supportsCronos type guard in wallet.ts.
Asset Data & Base Assets packages/utils/src/assetData/baseAssets.ts, packages/utils/src/assetData/getBaseAsset.ts, packages/utils/src/chainIdToFeeAssetId.ts, packages/utils/src/getAssetNamespaceFromChainId.ts, packages/utils/src/getChainShortName.ts, packages/utils/src/getNativeFeeAssetReference.ts	Exported cronos asset constant with metadata (icon, explorer, symbol CRO). Extended getBaseAsset, chainIdToFeeAssetId, asset namespace, and chain short name utilities with Cronos routing logic.
Asset Generation Scripts scripts/generateAssetData/coingecko.ts, scripts/generateAssetData/cronos/index.ts, scripts/generateAssetData/generateAssetData.ts, scripts/generateAssetData/generateRelatedAssetIndex/generateChainRelatedAssetIndex.ts	Added Cronos asset fetching via coingecko, created cronos module to fetch and unfreeze assets, integrated into asset data generation pipeline. Added manual related asset mapping linking Ethereum CRO (erc20:0xa0b73e1ff0b80914ab6fe0444e65848c4c34450b) to Cronos CRO (slip44:60).
Feature Flags & State src/state/slices/preferencesSlice/preferencesSlice.ts, src/state/slices/opportunitiesSlice/mappings.ts, src/state/migrations/index.ts, src/test/mocks/store.ts, src/constants/chains.ts	Added Cronos to FeatureFlags type and initialized from config. Gated CronosMainnet in SECOND_CLASS_CHAINS and knownChainIds behind enabledFlags.Cronos. Added empty DeFi opportunities mapping and migration entry 295.
Plugin Registration src/plugins/cronos/index.tsx, src/plugins/activePlugins.ts	Created cronos plugin that registers ChainAdapter with RPC URL and getKnownTokens resolver. Added cronos to activePlugins export array.
Utilities & Hooks src/lib/utils/cronos.ts, src/lib/coingecko/utils.ts, src/lib/account/evm.ts, src/lib/asset-service/service/AssetService.ts, src/hooks/useWalletSupportsChain/useWalletSupportsChain.ts, src/hooks/useActionCenterSubscribers/useSendActionSubscriber.tsx	Created Cronos utility module with isCronosChainAdapter type guard and getCronosTransactionStatus (JSON-RPC eth_getTransactionReceipt polling). Extended coingecko supported chains, EVM account derivation, asset service filtering, wallet chain support checks, and transaction status polling with Cronos logic.
UI Components & Pages src/components/TradeAssetSearch/hooks/useGetPopularAssetsQuery.tsx, src/pages/Markets/components/MarketsRow.tsx	Added cronosAssetId to popular assets when feature flag enabled. Extended market row filtering to gate CronosMainnet behind Cronos feature flag.
Relay & Swapper packages/swapper/src/swappers/RelaySwapper/constant.ts, packages/swapper/src/swappers/RelaySwapper/utils/relayTokenToAssetId.ts	Extended chainIdToRelayChainId mapping for Cronos. Added CronosMainnet case to relayTokenToAssetId switch statement.
CSP Headers headers/csps/chains/cronos.ts, headers/csps/index.ts	Created Cronos CSP configuration exporting connect-src directive with VITE_CRONOS_NODE_URL. Added cronos import and export to CSP index.
Developer Documentation .beads/ss-dx5.4.json, .claude/contracts/second-class-evm-chain.md, .claude/skills/chain-integration/SKILL.md, AGENTS.md, CLAUDE.md	Added task definition for Cronos integration under parent epic ss-dx5. Updated second-class EVM chain contract with feature flag and URL validation details, manual related asset index guidance. Added developer workflow documentation for issue tracking, session completion, and pre-push lint requirements.
Build Configuration package.json	Increased Node.js memory limit for type-check script to 8GB (NODE_OPTIONS=--max-old-space-size=8192).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• shapeshift/web#11918: Implements identical second-class EVM chain integration pattern for Berachain across the same modules and functions.
• shapeshift/web#11569: Adds Katana chain support using the same code paths and file modifications as this Cronos integration.
• shapeshift/web#11956: Implements the second-class EVM chain integration specification documented in .claude/contracts/second-class-evm-chain.md that governs these changes.

Suggested labels

capy

Poem

🐰 A hop across the cosmos wide,
Cronos joins the relay ride!
CRO tokens bounce with glee,
Wallets sync in harmony—
slip44:60 marks the way,
ShapeShift grows another day! 🌟

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% 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
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title clearly and concisely describes the main change: integrating Cronos as a second-class EVM chain with chainId 25, which is the primary objective of the changeset.

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

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/integrate-cronos-relay

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[gomesalexandre]

Happy camper generally but only 2 popular assets - happy on search though. Probably a similar fix as other second-class evm chains PRs.

Also same bug as cross-swap TO CRO present with relay, same wrapped-native asset issue as others

https://jam.dev/c/6109e7ac-37e9-4f43-84de-12b6868399ff

Cronos (receive) side Tx cronoscan.com/tx/0xec233afcac26adcac06b68f83df288fac37edc5e7963837e3e01df8a97ea3b1d

[gomesalexandre]

happy on all counts - cronos sends, swaps (both directions), tx history, execution price, popular assets, CRO cross-chain relation all working

https://jam.dev/c/9634e466-e766-49f8-988d-65d755a874db

[coderabbitai]

Actionable comments posted: 8

🧹 Nitpick comments (3)

src/plugins/cronos/index.tsx (1)

22-36: fromAssetId is called twice per asset — optional single-pass refactor.

fromAssetId(asset.assetId) is invoked in the .filter() predicate and again in .map() to extract assetReference. These can be merged into one pass to avoid redundant parsing.

♻️ Combine filter + map into a single reduce pass

-                return assetService.assets
-                    .filter(asset => {
-                      const { chainId, assetNamespace } = fromAssetId(asset.assetId)
-                      return chainId === cronosChainId && assetNamespace === 'erc20'
-                    })
-                    .map(asset => ({
-                      assetId: asset.assetId,
-                      contractAddress: fromAssetId(asset.assetId).assetReference,
-                      symbol: asset.symbol,
-                      name: asset.name,
-                      precision: asset.precision,
-                    }))
+                return assetService.assets.reduce<
+                  Array<{ assetId: string; contractAddress: string; symbol: string; name: string; precision: number }>
+                >((acc, asset) => {
+                  const { chainId, assetNamespace, assetReference } = fromAssetId(asset.assetId)
+                  if (chainId === cronosChainId && assetNamespace === 'erc20') {
+                    acc.push({
+                      assetId: asset.assetId,
+                      contractAddress: assetReference,
+                      symbol: asset.symbol,
+                      name: asset.name,
+                      precision: asset.precision,
+                    })
+                  }
+                  return acc
+                }, [])

🤖 Prompt for AI Agents

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

In `@src/plugins/cronos/index.tsx` around lines 22 - 36, getKnownTokens currently
calls fromAssetId(asset.assetId) twice per asset (once in the .filter predicate
and again in .map), causing redundant work; update getKnownTokens to parse each
asset's id once (e.g., use a single .reduce over assetService.assets or first
.map to include parsed = fromAssetId(asset.assetId) then filter on
parsed.chainId/assetNamespace and return the final object using
parsed.assetReference) so you only call fromAssetId once per asset; target the
getKnownTokens function and the use of fromAssetId, assetService.assets, and the
filter/map logic when making this change.

scripts/generateAssetData/generateRelatedAssetIndex/generateChainRelatedAssetIndex.ts (1)

276-285: Optional: remove now-unreachable return at Line 285.

The recovery block (Lines 277–282) handles the sole remaining case (!group), making the trailing return on Line 285 dead code. The three mutually exclusive guards now cover every possible state of group:

Condition	Handled by
group && includes	Line 264
group && !includes	Line 272
!group	Lines 277–282 (new)

♻️ Proposed cleanup

     // Group absent from index but asset has a relatedAssetKey - recover by creating the group
     if (!group) {
       console.log(
         `Recovering orphaned relatedAssetKey for ${assetId}: creating group ${existingRelatedAssetKey}`,
       )
       relatedAssetIndex[existingRelatedAssetKey] = [assetId]
       return
     }
-
-    return
   }

🤖 Prompt for AI Agents

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

In
`@scripts/generateAssetData/generateRelatedAssetIndex/generateChainRelatedAssetIndex.ts`
around lines 276 - 285, Remove the now-unreachable trailing "return" after the
orphan recovery block in generateChainRelatedAssetIndex: the code paths for
group && includes, group && !includes, and !group (the recovery that sets
relatedAssetIndex[existingRelatedAssetKey] = [assetId]) already cover all cases,
so delete the redundant return statement that follows that block (the lone
"return" after handling !group involving group, assetId,
existingRelatedAssetKey, and relatedAssetIndex).

packages/chain-adapters/src/evm/cronos/CronosChainAdapter.ts (1)

18-20: Remove the duplicate isCronosChainAdapter type guard — it's dead code.

The canonical implementation lives in src/lib/utils/cronos.ts with the necessary null/undefined defensive checks, and that's the version consumed throughout the codebase. This one is never called, and the unsafe cast (adapter as ChainAdapter).getType() would throw if adapter is null or undefined.

♻️ Proposed fix

-export const isCronosChainAdapter = (adapter: unknown): adapter is ChainAdapter => {
-  return (adapter as ChainAdapter).getType() === KnownChainIds.CronosMainnet
-}
-
 export class ChainAdapter extends SecondClassEvmAdapter<KnownChainIds.CronosMainnet> {

Based on learnings: "For second-class EVM chain adapters (those extending SecondClassEvmAdapter), the type guard function should only exist in src/lib/utils/[chain].ts with defensive null/undefined and function checks. Do not duplicate the type guard in the adapter file itself, as it is dead code and the utils version is the canonical implementation actually used throughout the codebase." (gomesalexandre, PR #11905)

🤖 Prompt for AI Agents

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

In `@packages/chain-adapters/src/evm/cronos/CronosChainAdapter.ts` around lines 18
- 20, Remove the dead duplicate type guard isCronosChainAdapter from
CronosChainAdapter.ts; instead rely on the canonical implementation in
src/lib/utils/cronos.ts which includes null/undefined and function checks.
Delete the exported isCronosChainAdapter function (the one casting to
ChainAdapter and calling getType() against KnownChainIds.CronosMainnet) so there
is only a single safe type guard used across the codebase.

🤖 Prompt for all review comments with AI agents

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

Inline comments:
In @.claude/contracts/second-class-evm-chain.md:
- Line 200: The doc currently tells contributors to add a manual mapping to
manualRelatedAssetIndex but omits which files to modify; update both
generateRelatedAssetIndex.ts and generateChainRelatedAssetIndex.ts to include
the new mapping for the chain native (use the same pattern as the stablecoin
example) by adding an entry in manualRelatedAssetIndex that links the Ethereum
ERC20 identifier (eip155:1/erc20:0x...) to the chain native slip44:60; ensure
you follow the existing stablecoin mapping format and include the exact token
IDs so the per-chain "Popular Asset" filtering works correctly.

In @.claude/plan.md:
- Around line 15-26: The current plan to create synthetic internal txs from
WBERA Withdrawal events in parseTx() (using berachainChainId, WETH_ABI,
WBERA_CONTRACT) can generate false positives; update the fallback so after
detecting this.chainId === berachainChainId && internalTxs.length === 0 you
parse Withdrawal events from the receipt but only convert an event into a
synthetic internal tx when the event.src is not the user's pubkey and either
matches a configured list of known relay/fill contract addresses or passes an
explicit allowlist check; also deduplicate or aggregate multiple Withdrawal
events per tx (e.g., ignore duplicates originating from the same src or sum wad
per src when appropriate) before pushing { from: WBERA_CONTRACT, to: pubkey,
value: wad } so parse() produces Receive transfers with fewer false positives.
- Around line 21-25: The WBERA_CONTRACT constant is incorrect in the plan which
will make the Withdrawal-event fallback in parseTx() never match logs; update
the constant WBERA_CONTRACT to the canonical Berachain mainnet address
0x6969696969696969696969696969696969696969 and in parseTx() (the
berachainChainId conditional after internalTxs Promise.all) filter receipt.logs
for Withdrawal events emitted by that WBERA_CONTRACT, parse pubkey and wad from
the event, and push synthetic internal tx objects shaped like { from:
WBERA_CONTRACT, to: pubkey, value: wad } so the fallback actually produces
internalTxs when none were fetched.

In `@AGENTS.md`:
- Line 31: The "Clean up" step text is ambiguous about pruning remote branches;
update the line that currently reads "Clean up - Clear stashes, prune remote
branches" to explicitly state you should prune stale local remote-tracking
references (e.g., use "git fetch --prune" or "git remote prune origin") and
avoid wording that could be interpreted as deleting branches on the remote (do
not suggest "git push origin --delete <branch>"). Ensure the new phrasing
clarifies the safe intended operation and replaces the existing "prune remote
branches" fragment in AGENTS.md.
- Around line 19-39: Clarify the failure path for quality gates by updating the
MANDATORY WORKFLOW and CRITICAL RULES: state that Step 2 ("Run quality gates —
Tests, linters, builds") must pass before performing Step 4 ("PUSH TO REMOTE"),
and if any gate fails the agent must stop, create an issue/ticket and attach
failure logs, run automatic retries or request human approval (do not perform
"git push"), and only proceed with the push sequence after the issue is resolved
and gates pass; update the wording in the "Step 2" and "CRITICAL RULES" sections
to explicitly prohibit pushing on failed gates and to require recording the
failure (issue, logs) and awaiting remediation or explicit human sign-off.

In `@packages/chain-adapters/src/evm/SecondClassEvmAdapter.ts`:
- Around line 480-482: The fee computation produces "NaN" when
receipt.effectiveGasPrice is undefined; update the calculation in
SecondClassEvmAdapter where `fee` is computed so both operands are wrapped with
`bnOrZero` (i.e., use
bnOrZero(receipt.gasUsed).times(bnOrZero(receipt.effectiveGasPrice)).toFixed(0))
to ensure undefined values become zero and avoid NaN propagating into
`parsedTx.fee`; adjust the `fee` declaration accordingly to use `bnOrZero` on
both `receipt.gasUsed` and `receipt.effectiveGasPrice`.

In `@src/config.ts`:
- Line 69: Update the validator for VITE_CRONOS_NODE_URL to use url() instead of
str(): locate the config schema entry named VITE_CRONOS_NODE_URL and replace its
validator call so it performs URL format validation (use the same url() helper
used by other *_NODE_URL entries) to ensure proper startup validation.

In `@src/state/slices/preferencesSlice/preferencesSlice.ts`:
- Line 43: Add a new environment validator named VITE_FEATURE_CRONOS to the
configuration export (the same config object that holds other VITE_FEATURE_*
keys) by adding VITE_FEATURE_CRONOS: bool({ default: false }) so the feature
flag used by the preferences slice (Cronos) is validated and typed correctly;
update the config export type if necessary so VITE_FEATURE_CRONOS is available
throughout the app.

---

Nitpick comments:
In `@packages/chain-adapters/src/evm/cronos/CronosChainAdapter.ts`:
- Around line 18-20: Remove the dead duplicate type guard isCronosChainAdapter
from CronosChainAdapter.ts; instead rely on the canonical implementation in
src/lib/utils/cronos.ts which includes null/undefined and function checks.
Delete the exported isCronosChainAdapter function (the one casting to
ChainAdapter and calling getType() against KnownChainIds.CronosMainnet) so there
is only a single safe type guard used across the codebase.

In
`@scripts/generateAssetData/generateRelatedAssetIndex/generateChainRelatedAssetIndex.ts`:
- Around line 276-285: Remove the now-unreachable trailing "return" after the
orphan recovery block in generateChainRelatedAssetIndex: the code paths for
group && includes, group && !includes, and !group (the recovery that sets
relatedAssetIndex[existingRelatedAssetKey] = [assetId]) already cover all cases,
so delete the redundant return statement that follows that block (the lone
"return" after handling !group involving group, assetId,
existingRelatedAssetKey, and relatedAssetIndex).

In `@src/plugins/cronos/index.tsx`:
- Around line 22-36: getKnownTokens currently calls fromAssetId(asset.assetId)
twice per asset (once in the .filter predicate and again in .map), causing
redundant work; update getKnownTokens to parse each asset's id once (e.g., use a
single .reduce over assetService.assets or first .map to include parsed =
fromAssetId(asset.assetId) then filter on parsed.chainId/assetNamespace and
return the final object using parsed.assetReference) so you only call
fromAssetId once per asset; target the getKnownTokens function and the use of
fromAssetId, assetService.assets, and the filter/map logic when making this
change.

[coderabbitai]

🤖 Prompt for all review comments with AI agents

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

Duplicate comments:
In `@packages/chain-adapters/src/evm/SecondClassEvmAdapter.ts`:
- Around line 480-482: The fee calculation in SecondClassEvmAdapter using
receipt.gasUsed and receipt.effectiveGasPrice can produce NaN for legacy Cronos
receipts where effectiveGasPrice is undefined; update the fee computation in the
block that assigns fee to wrap both operands with bnOrZero (i.e., use
bnOrZero(receipt.gasUsed.toString()) and
bnOrZero(receipt.effectiveGasPrice?.toString())) before multiplying and calling
toFixed(0) so the multiplication never yields NaN and legacy/undefined gas price
values are handled safely.