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<@ULVA73B9P> hi, does pip_install_requirements even work? I've checked the code, it installs requirements AFTER the process that will run the flow function was started, so it will not see any new dependencies, right?

hi i will fix marvin but yes it should because run_steps executes before the flow entrypoint is imported

if you're seeing something unexpected, please share a repro and `prefect version` output

<@ULVA73B9P> please concisely explain, link relevant code

&gt; does pip_install_requirements even work? I've checked the code, it installs requirements AFTER the process that will run the flow function was started, so it will not see any new dependencies, right?

:white_check_mark: thought for 108.8 seconds

Concise answer: *yes, a process has already started — but not the one that runs your flow function.*

`pip_install_requirements` runs in the *workspace resolver* subprocess, which prepares the run environment *before* Prefect starts the engine process that imports and executes the flow. So the flow process *does* see those installed dependencies.

Relevant code:

- Workspace starter spawns the resolver process first: <https://github.com/PrefectHQ/prefect/blob/main/src/prefect/runner/_workspace_starter.py#L348-L365>
- The resolver prepares the workspace and runs pull steps: <https://github.com/PrefectHQ/prefect/blob/main/src/prefect/runner/_workspace_resolver.py#L290-L393>
- `deployment.pull_steps` are executed here: <https://github.com/PrefectHQ/prefect/blob/main/src/prefect/runner/_workspace_resolver.py#L362-L368>
- `pip_install_requirements` itself does `python -m pip install -r ...`: <https://github.com/PrefectHQ/prefect/blob/main/src/prefect/deployments/steps/utility.py#L278-L338>
- Only after that does Prefect start the engine process that runs the flow: <https://github.com/PrefectHQ/prefect/blob/main/src/prefect/runner/_starter_engine.py#L27-L150>

So the accurate explanation is:

&gt; `pip_install_requirements` runs after Prefect has started a *prep/resolver* subprocess, but before it starts the *engine/flow* subprocess. So newly installed dependencies are available to the flow run process.