Expressions

SuperPlane uses Expr for expressions. Expressions let you reference data from upstream nodes, transform values, and control workflow logic.

The message chain (`$`)

As a run executes, each node’s output is added to the message chain. Access it through $, referencing nodes by display name:

{{$['Node Name'].data.field}}
{{$['Node Name'].data.nested.field}}
{{$['Node Name'].data.array[0].value}}

Every entry also includes a .config property — the node’s resolved configuration at run time:

{{$['HTTP Request'].config.url}}
{{$['HTTP Request'].config.method}}

`root()` and `previous()`

Function	Returns
`root()`	The payload that started the run (the trigger event).
`previous()`	The immediate upstream node’s payload.
`previous(n)`	Walk n levels upstream.

{{root().data.ref}}
{{previous().data.status}}

previous() is not available when a node has multiple inputs (e.g. after a Merge). Use $['Node Name'] instead.

Syntax: text fields vs conditions

Expressions appear in two contexts with slightly different syntax:

Text fields (URLs, message bodies, labels) — wrap each expression in {{ }}:

Deployment of {{$['Release'].data.name}} failed. See: {{$['Deploy'].data.workflow_run.html_url}}

Condition fields (If, Filter) — the entire field is one bare expression that must return true or false:

$['Get cat fact'].data.body.length <= 160 && $['Health Check'].data.body.healthy

Type $ in a condition field or {{ in a text field to trigger autocomplete.

Operators

Beyond standard arithmetic (+, -, *, /, %, **) and comparison (==, !=, <, >, <=, >=):

Operator	What it does	Example
`&&` `\|\|` `!`	Logical (aliases: `and`, `or`, `not`)	`{{$['a'].data.ok && !$['b'].data.failed}}`
`contains`	String contains substring	`{{$['node'].data.body contains "error"}}`
`startsWith`	String prefix check	`{{$['node'].data.ref startsWith "refs/heads/"}}`
`endsWith`	String suffix check	`{{$['node'].data.branch endsWith "-hotfix"}}`
`matches`	Regex match (RE2)	`{{$['node'].data.msg matches "^fix\$.*\$"}}`
`in` / `not in`	Membership test	`{{$['node'].data.env in ["staging", "prod"]}}`
`??`	Nil coalescing (fallback)	`{{$['node'].data.label ?? "default"}}`
`? :`	Ternary	`{{$['node'].data.ok ? "pass" : "fail"}}`
`?.`	Optional chaining	`{{$['node'].data?.user?.name}}`

Closures (`#`)

Array functions accept a closure where # is the current element:

{{filter($['node'].data.items, # > 10)}}
{{map($['node'].data.users, #.name)}}
{{any($['node'].data.tags, # == "critical")}}
{{sortBy($['node'].data.alerts, #.severity, "desc")}}

reduce() adds #acc for the accumulator:

{{reduce($['node'].data.items, #acc + #.price, 0)}}

Common patterns

Fallback for missing fields:

{{$['Webhook'].data.user.name ?? "unknown"}}

Ternary in a text field:

Status: {{$['Deploy'].data.success ? "Deployed" : "Failed"}}

Check array membership:

{{"production" in $['node'].data.environments}}

Filter and join:

{{join(filter($['node'].data.tags, # startsWith "env:"), ", ")}}

Date comparison (event in the last hour):

{{now().Sub(date($['node'].data.timestamp)).Hours() < 1}}

Build a JSON string:

{{toJSON({status: $['Deploy'].data.result, ref: root().data.ref})}}

Function reference

SuperPlane expressions have access to the full set of Expr built-in functions for strings, arrays, dates, math, and type conversion. See the Expression Functions Reference for the complete list with signatures and examples.

For the Expr language specification, see the Expr documentation.