Have MsgsBetweenSeqNums populate TxHash

[rstout]

We need TxHash in order to call CCTPv2's HTTP API: https://developers.circle.com/api-reference/cctp/all/get-messages-v-2

Naively setting TxHash in message headers will cause OCR consensus issues, as seen when the Solana chain accessor populated TxHash. In order to prevent consensus issues, setting TxHash is now behind a feature flag in the OffchainConfig (stored in CCIPHome). The DefaultAccessor now populates TxHash by default, but ccipChainReader clears TxHash by default. This means initially, we'll set TxHash and then immediately clear it (maintaining the previous behavior of not having set TxHash). populateTxHashEnabled can then be set for either Commit or Exec to then switch to the mode where TxHash gets populated. This is done via an MCMS proposal to update CCIPHome config, which should be picked up by all nodes within 10s of each other and allow DONs to proceed without consensus issues.

[github-actions]

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[ogtownsend]

TxHash is left out of several of the exec codecs, will this be a problem? Example:

• EVM: https://github.com/smartcontractkit/chainlink/blob/develop/core/capabilities/ccip/ccipevm/executecodec.go#L195-L202
• Solana: https://github.com/smartcontractkit/chainlink/blob/develop/core/capabilities/ccip/ccipsolana/executecodec.go#L177-L185

[rstout]

TxHash is left out of several of the exec codecs, will this be a problem? Example:

• EVM: https://github.com/smartcontractkit/chainlink/blob/develop/core/capabilities/ccip/ccipevm/executecodec.go#L195-L202
• Solana: https://github.com/smartcontractkit/chainlink/blob/develop/core/capabilities/ccip/ccipsolana/executecodec.go#L177-L185

It shouldn't be, the codecs are for encoding/decoding reports, and TxHash doesn't need to be included in the reports. The place that needs to populate TxHash is the chain readers, and this seems to be the case, so TxHash should be populated.

[ogtownsend]

lgtm!

[Copilot]

Pull request overview

This PR adds support for populating the TxHash field in CCIP message headers, which is required for calling CCTPv2's HTTP API. The implementation includes a feature flag (PopulateTxHashEnabled) to control this behavior for backwards compatibility.

Key changes:

• Adds PopulateTxHashEnabled configuration flag to control TxHash population
• Updates MsgsBetweenSeqNums to populate TxHash from types.Sequence.TxHash field
• Introduces a ChainAccessorWrapper to conditionally clear TxHash based on the feature flag

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pluginconfig/execute.go	Adds PopulateTxHashEnabled configuration field
pkg/chainaccessor/default_accessor.go	Populates TxHash from sequence item using hexutil.Encode
pkg/chainaccessor/default_accessor_test.go	Comprehensive tests for TxHash population scenarios
execute/chainaccessor_wrapper.go	Wrapper implementation to conditionally clear TxHash
execute/chainaccessor_wrapper_test.go	Tests for wrapper's TxHash enable/disable logic
execute/factory.go	Integrates wrapper with configuration flag

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[ogtownsend]

much cleaner, thanks!

[github-actions]

Metric	add-msg-tx-hash	main
Coverage	70.4%	69.4%