Rehearse connected workflows

Test actual upstream outputs at each connected input boundary.

node packages/block-cli/cli.js preview my-type.json
node packages/block-cli/cli.js preview my-type.json sample-inputs.json

sample-inputs.json is keyed by Step ID, then input name:

{ "first": { "text": "  My sample  " } }

previewProjectType(type, options) from packages/block-platform/type-preview.js rehearses the pinned workflow without changing it. Options accept inputs, scoped context, an abort signal, onResult, and a sandbox run implementation for browser workers. The CLI uses the same isolated Node runtime as Block tests. Unconnected inputs start with the Block's first fixture, then Step config and custom sample values; connected values always come from actual upstream output. Conditions use the production bypass rules. Inputs and outputs are validated at each boundary. Offline checks share a 15-second deadline and 4 MB combined sample budget. Interactive browser previews permit 64 MB of recorded data; waiting for hosted consent and execution does not consume the local deadline.

The report contains a digest and per-Step results. passed means no executed Step failed; only complete: true means all enabled Steps completed. Hosted workspaces, missing context and dependent blocked Steps produce an incomplete report. The same connected rehearsal also runs within type fixture validation and server import admission; an executed combination that fails is rejected. Incomplete host coverage is marked explicitly. This does not replace static admission checks, individual fixtures, or actual host/media testing in a project. In the builder choose Preview connected workflow to inspect per-Step inputs, outputs and failures.

Interactive hosted rehearsal

In the Project Type Builder, choose Preview connected workflow. For included hosted Blocks, complete or reuse each account-bound package review first. The preview then asks for a model, payment choice, and cost confirmation for each actual hosted invocation. A package review never substitutes its sample output for an upstream result. Cancel at any point to stop downstream execution.

Use Custom sample inputs for values keyed by Step ID. Use Sample project context for a JSON object containing the context fields requested by Blocks:

{"metadata":{"schemaVersion":1,"hasDialogue":true}}

Each Block receives only its declared context inputs and permissions. Context samples are copied; testing cannot write through to a production project. Conditions read the resolved inputs and apply the same pass-through rules used in production. Changing either sample clears the displayed prior result.

Before passing hosted output downstream, StillMade re-fetches the authenticated run and checks the package, input, model selection, quote, output and media receipts. Generated image references can feed recipe image inputs: the browser decodes the verified media without resizing it. The recipe limit remains one megapixel. Arbitrary URLs in sample JSON do not authorize image decoding. Local JavaScript Blocks retain reference-based image contracts.

The browser host opts into interactive: true, supplies verifyHostedResult, and may supply resolveInput for authorized media conversion. These are trusted host callbacks, never functions supplied by imported packages. Omitting the verifier prevents hosted execution. Keep interactive mode off in automated admission and CLI checks; enabling it does not provide provider credentials, payment authorization, or a server-certified workflow receipt.

A successful sample rehearsal proves that those enabled Steps ran with those inputs. It does not prove every possible project, workspace interaction, or conditional branch. Manual StillMade workspaces still need their working preview or a real project. Changing accounts cancels the active hosted preview.