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Sandbox mode: troubleshooting

Common surprises in sandbox mode and how to resolve them.

"A node returned { sandbox: true, intercepted: true, ... } instead of data"

The node tried to open a network connection the sandbox has no mock for. Only HTTP, email (SMTP) and PostgreSQL or MySQL connections are mocked. Anything else is blocked, and the node returns this stub so the run can continue.

Fix: pin the node with the data downstream nodes need. See Pinning data on a node.

"My node returned placeholder values like "string" and 0"

Expected. Snapshot and execution-history mock data keep the shape of a real response but replace every value with a placeholder. See Shapes, not values.

Fix: if you need real values, pin the node or edit its output with Edit JSON.

"My node returned generic data"

No snapshot or execution-history data exists for that operation yet, so Flero used data generated from the service's schema.

Fix: pin a realistic response, or run the operation live once. After a clean successful run, later sandbox runs can learn the response shape from it. See Execution history.

"My node returned an empty object {}"

Nothing matched: no mock data exists for that node and operation, and no recent successful run had a usable output.

Check:

  • The connector node has an operation selected. Mock data is matched by node type and operation.
  • A successful live run of that operation exists in your workspace. Flero skips outputs that look like errors.

Fix: pin the node.

"A Code node made a real network call in sandbox"

Expected. Code and Terminal nodes are not sandboxed. They run as they do live, including any network calls your snippet makes.

Fix: pin the node if it must stay inert during a dry run.

"My pinned data is ignored"

Check, in order:

  1. The workflow was saved after pinning. Until you save, the pin exists only in your editor session.
  2. The pinned data is a JSON object. An array or a plain value is not a valid pin.
  3. The workflow was not imported from somewhere that stripped node settings. A pin travels with the workflow's configuration, so an import that dropped it lost the pin.

Sandbox mode is not required. Pins apply in every mode.

"A node returns the same data even in Production"

It is pinned. Pins apply on live runs too, so a pinned connector does not call its service.

Fix: open the node's Output tab and click Pin Data again to unpin it.

"I reran a sandbox execution and it ran live"

Expected. A rerun always runs live, whatever mode the original used.

Fix: to repeat a dry run, select Sandbox in the editor header and press Test Run.

"The sandbox switch does not stick when I reopen the workflow"

The mode is saved with the workflow, but switching does not save automatically.

Fix: switch to Sandbox, then save the workflow.

"My webhook or scheduled run did not use sandbox"

Expected. Only runs started from the editor with Test Run are sandboxed. Webhook, schedule and event-triggered runs always run live.

"An approval email went out during a sandbox run"

Expected. Approval request emails and run result emails come from Flero itself, not from a node, so the sandbox does not stop them. Only calls made by nodes are mocked.

"Sandbox runs fill up my executions list"

Sandbox runs are real executions that do not talk to the outside world. The list marks them with a "Sandbox" dot. There is no filter by mode. Monitoring counts them too.

"Local SQLite behaves the same in sandbox and live"

Expected. SQLite works on local files, not network connections, so the sandbox does not intercept it.

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