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A simulation bundle runs up to five transactions in sequence against shared state: each step sees the state changes made by the step before it. Use a bundle whenever one transaction depends on another, for example an approval that enables a later transferFrom, or a deposit that a subsequent withdrawal spends. Bundles use the same builder as single simulations. A single simulation is simply a one-step bundle, so nothing changes about the editor when you add more steps.
Simulator UI showing three steps in the bundle rail and step results on the right

A three-step bundle: session strip at the top, step rail on the left, and the focused step result on the right.

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Building a bundle

Start from Simulator → New Simulation and configure the first step as usual. Then grow the bundle from the rail on the left:
  • Add a step with the + button under the step cards.
  • Import a transaction with the import button: paste an existing transaction hash or raw payload and its inputs load as a new step.
  • Reorder steps by dragging their cards. Steps execute in rail order.
Each step is independent in everything except state: it has its own Decoded/Raw toggle, its own From override, and its own set of cheatcodes (gas and value overrides, funded addresses, block and timestamp manipulation, state overrides, access lists). Cheatcodes run immediately before their step. The bundle is the unit of execution: clicking Simulate runs all steps at once, in order, on the network and block configured in the session strip.

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Reading the results

After a run, each step card in the rail shows a result badge: Click any step card to focus its individual result in the right panel: decoded output, gas used, and the Events, State, Fund Flow, and Gas Profiler tabs for that step. State flows forward only. A balance minted in step 1 is visible to steps 2 through 5, but a revert in a later step does not undo earlier steps’ results in the displayed output; each step’s view reflects the state at its position in the sequence.

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Bundles in the simulation history

Executed bundles appear in the Simulator list as a single Bundle (N txs) row showing the shared network, block, and call count. Expand the row to see each step as its own entry with its individual status and function.
Simulator list with an expanded bundle row showing individual mint, approve, and transferFrom steps, and collapsed Bundle rows with call counts

The Simulator list: an expanded bundle showing its per-step rows, with collapsed Bundle (3 txs) rows below.

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Limits

  • Five steps per bundle.
  • Cheatcodes are step-scoped. There is no bundle-level cheatcode surface.
  • Bundles are stateless between runs: re-running starts again from the configured block. For a persistent environment that accumulates state across many transactions, use Virtual Environments.

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Worked example

Simulate a Token Mint, Approve, and TransferFrom Bundle builds a complete 3-step DAI bundle, including the state override that lets the mint succeed and the step-by-step results. To run bundles programmatically instead, see Bundled Simulations in the Simulation API.