[Temasar1]

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Summary

This PR is for majorly for feedback and how it relates to existing or work in progress, though in as much as i think this is needed for Mesh in assisting fast development without needing the full cardano node(in most cases) or any external provider before testing a transaction which could easily be built against a fast local TS chain

Adds @meshsdk/devnet: a single-process Cardano node with a slot ticker, mempool, and HTTP API. DevnetProvider is a drop-in IFetcher + ISubmitter + IListener for MeshTxBuilder / MeshWallet (no Blockfrost, no cardano-node). CLI: mesh-devnet. Ledger: HarmonicLabs Conway UTXO / UTXOW / UTXOS (ADA, native assets, Plutus V1–V3). No certificates, withdrawals, or governance yet.

How this relates to #858 (@meshsdk/tx-emulator)

Same goal (Mesh against a local chain). Different layer. Please review whether we want both.

	this PR @meshsdk/devnet	#858 @meshsdk/tx-emulator
Shape	Process + HTTP + CLI	In-process library
Engine	HarmonicLabs + CEK	Scalus
Time	Blocks produced on a slot tick	Caller setSlot / tick
Use	App / e2e against a running node	Unit tests, forks, dry-run simulate

Review: keep both (node vs emulator), or fold this into Scalus like #858?

Also #862: a builder with only fetcher: DevnetProvider would evaluate with Scalus, then this node would re-validate with HarmonicLabs. Confirm we pass this package’s evaluator, or evaluator: null.

@lisicky @twwu123

Test plan

• npm run build:mesh --workspace @meshsdk/devnet
• npm test --workspace @meshsdk/devnet
• npm run dev then npx mesh-devnet selftest --from 0 --to 1 --ada 5
• MeshTxBuilder + DevnetProvider submit lands in a block
• No remaining cardano-devnet bin or import path

Please provide a brief, concise summary of the changes in your pull request. Explain the problem you are trying to solve and the solution you have implemented.

Affect components

Please indicate which part of the Mesh Repo

• @meshsdk/common
• @meshsdk/contract
• @meshsdk/core
• @meshsdk/core-csl
• @meshsdk/core-cst
• @meshsdk/hydra
• @meshsdk/provider
• @meshsdk/react
• @meshsdk/svelte
• @meshsdk/transaction
• @meshsdk/wallet
• Mesh playground (i.e. https://meshjs.dev/)
• Mesh CLI

Type of Change

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• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Bug fix (non-breaking change which fixes an issue)
• Code refactoring (improving code quality without changing its behavior)
• Documentation update (adding or updating documentation related to the project)

Related Issues

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Checklist

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• My code is appropriately commented and includes relevant documentation, if necessary
• I have added tests to cover my changes, if necessary
• I have updated the documentation, if necessary
• All new and existing tests pass (i.e. npm run test)
• The build is pass (i.e. npm run build)

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