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Update 47 MDX doc pages, OpenAPI spec, SVG diagram, language grammar, frontend demo data, marketing page, skills, and README to use .fabro extension. Add "fabro" to fileTypes in language grammars. Document stack.child_workflow alongside stack.child_dotfile. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
76 lines
2.4 KiB
Text
76 lines
2.4 KiB
Text
---
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title: "Variables"
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description: "Using variables in workflows"
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---
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Fabro supports `$variable` placeholders that let you parameterize workflows without editing the DOT file.
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## Run config variables
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Define variables in the `[vars]` section of a run config TOML file:
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```toml title="run.toml"
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version = 1
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goal = "Run tests for $repo_name"
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graph = "check.fabro"
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[vars]
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repo_name = "fabro"
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repo_url = "https://github.com/fabro-sh/fabro"
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language = "rust"
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```
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These variables are expanded into the DOT source **before** the graph is parsed. You can use `$variable` anywhere in the DOT file — goals, prompts, labels, scripts, or any other attribute:
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```dot title="check.fabro"
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digraph Check {
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graph [goal="Run tests for $repo_name"]
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start [shape=Mdiamond, label="Start"]
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exit [shape=Msquare, label="Exit"]
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clone [label="Clone", shape=parallelogram, script="git clone $repo_url repo"]
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test [label="Test", prompt="Run the $language test suite in the repo/ directory."]
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start -> clone -> test -> exit
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}
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```
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When launched with `fabro run run.toml`, Fabro replaces `$repo_name`, `$repo_url`, and `$language` with their values before parsing the graph.
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### Undefined variables
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If a `$variable` in the DOT file has no matching entry in `[vars]`, Fabro raises an error. This catches typos early — a misspelled `$langauge` fails immediately rather than passing a literal `$langauge` to the LLM.
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### Escaping `$`
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To include a literal `$` in the output, write `$$`:
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```dot
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test [prompt="The env var is $$HOME"]
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```
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This produces `The env var is $HOME` without treating `$HOME` as a variable reference. A bare `$` not followed by an identifier character (e.g. `costs $5`) does not need escaping.
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## The `$goal` variable
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Inside agent and prompt node prompts, Fabro automatically expands `$goal` to the workflow's `goal` attribute. This happens at runtime, after graph parsing:
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```dot title="example.fabro"
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digraph Example {
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graph [goal="Implement the login feature"]
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plan [label="Plan", prompt="Create a plan for: $goal"]
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}
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```
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The plan node's prompt becomes `"Create a plan for: Implement the login feature"`.
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## Variable merging
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When using server-level run defaults alongside a run config TOML, variables are merged. Task config vars override default vars when keys collide:
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| Source | Priority |
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|---|---|
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| Run config TOML `[vars]` | Highest — wins on collision |
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| Server defaults `[vars]` | Lowest — provides fallback values |
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