fix(viem-adapter): getChainId returns 0 without a static chain config

[gomesalexandre]

Does what it says on the box.

ViemAdapter.getChainId() reads this._publicClient.chain?.id ?? 0 - a static property that is undefined whenever the PublicClient is built without a chain (a valid, common setup: createPublicClient({ transport: http(url) }) for a custom/unlisted RPC endpoint), silently returning chain id 0 instead of the real network id.

Both EthersV5Adapter.getChainId() and EthersV6Adapter.getChainId() instead derive the chain id from a live network call (provider.getNetwork()). Viem itself exposes the matching live action for exactly this - publicClient.getChainId(), which calls eth_chainId on the RPC - and it's already available on the PublicClient type this adapter holds, just wasn't being used.

Fix

Swap this._publicClient.chain?.id ?? 0 for this._publicClient.getChainId(), matching the ethers adapters' live-query semantics and viem's own idiomatic API.

Test

Added packages/contracts-ts/tests/viemAdapterGetChainId.test.ts: constructs a ViemAdapter over a PublicClient with no chain passed (only transport), and asserts getChainId() still returns the real chain id via the live RPC call.

• Fails on old code: Expected: 11155111, Received: 0
• Passes on the fix

Ran the full contracts-ts suite locally after the change - 75/75 passing, no regressions. tsc --noEmit and eslint both clean on sdk-viem-adapter.

Risk

Low - one-line swap to an existing, already-typed viem action; only touches a path where the caller omitted chain from their PublicClient, which previously produced a silently wrong (0) value.

Summary by CodeRabbit

• Bug Fixes
  • Corrected chain ID detection for Viem-based connections without a predefined chain configuration.
  • Chain IDs are now retrieved from the connected network, preventing an incorrect value of 0.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: 8fd7bc57-a321-4193-925b-92318fb6cd36

📥 Commits

Reviewing files that changed from the base of the PR and between 9057b6d and 92bc42a.

📒 Files selected for processing (2)

• packages/contracts-ts/tests/viemAdapterGetChainId.test.ts
• packages/providers/viem-adapter/src/ViemAdapter.ts

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

---

📝 Walkthrough

Walkthrough

ViemAdapter.getChainId() now queries the live RPC through viem. A test verifies the actual chain ID when the client has no static chain configuration.

Changes

Viem chain ID resolution

Layer / File(s)	Summary
Live chain ID lookup and validation packages/providers/viem-adapter/src/ViemAdapter.ts, packages/contracts-ts/tests/viemAdapterGetChainId.test.ts	getChainId() now calls viem’s RPC-backed getChainId(). The test covers a client without a configured chain and checks the live chain ID.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 92bc4

Viem clients without static chain configuration now return the RPC’s actual chain ID rather than zero. The affected behavior is covered by an RPC-only regression test, with no remaining merge-blocking risk identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the Viem adapter bug: getChainId returns 0 when no static chain configuration exists. It directly matches the main code change and regression test.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

Some tools did not complete. Review the errors below.

🔧 ESLint

If the error stems from missing dependencies, add them to the package.json file. For unrecoverable errors (e.g., due to private dependencies), disable the tool in the CodeRabbit configuration.

packages/contracts-ts/tests/viemAdapterGetChainId.test.ts

Parsing error: Unable to parse the specified 'tsconfig' file. Ensure it's correct and has valid syntax.

packages/app-data/tsconfig.json(2,14): error TS6053: File '@cow-sdk/typescript-config/base.json' not found.

packages/providers/viem-adapter/src/ViemAdapter.ts

Parsing error: Unable to parse the specified 'tsconfig' file. Ensure it's correct and has valid syntax.

packages/app-data/tsconfig.json(2,14): error TS6053: File '@cow-sdk/typescript-config/base.json' not found.

---

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.}