`variables` not being used in playwright commands

[rynonl]

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• Check the documentation for relevant information
• Search existing issues to avoid duplicates

Environment Information

Please provide the following information to help us reproduce and resolve your issue:

Stagehand:

• Language/SDK: Python
• Stagehand version: 0.5.4

AI Provider:

• Provider: Anthropic
• Model: claude-haiku-4-5-20251001

Issue Description

The code indicates that I can pass a variables argument to both act and observe so that I can keep sensitive data out of the LLM, just like with the Typescript SDK (docs).

When I pass a variables dict:

page.act(Enter %employer_legal_name% in the 'Contract name' field, variables={"employer_legal_name": "foo"})

The prompt correctly tells the LLM that the variables are available, and the observe result comes back like:

"{""selector"": ""xpath=/html/body[1]/table[2]/tbody[1]/tr[1]/td[3]/table[1]/tbody[1]/tr[6]/td[3]/table[1]/tbody[1]/tr[2]/td[2]/p[1]/input[1]"", ""description"": ""The 'Contract name' textbox field where the employer legal name should be entered"", ""backend_node_id"": null, ""method"": ""fill"", ""arguments"": [""%employer_legal_name%""]}"

where "employer_legal_name" was the name of my variable.

However, when the playwright portion runs, it uses the string literal "employer_legal_name" rather than resolving the value of that key in my variables dict.

Steps to Reproduce

1. Pass variables to act or observe
2. Observe that the variable key is used in the resulting playwright command, rather than the variable value

[afanslau]

I'm also facing this issue. Variables work great when calling page.act("Fill in the username field with %username%", variables={"username": "my_username"}). But when I try to use a cached action,

{
    "selector": "xpath=/html/body[1]/main[1]/section[1]/div[1]/div[1]/div[1]/div[1]/div[1]/form[1]/div[1]/div[1]/div[1]/div[1]/input[1]",
    "description": "Username input textbox for logging into the account",
    "backend_node_id": null,
    "method": "fill",
    "arguments": [
      "%username%"
    ]
  }

page.act(action, variables={"username": "my_username"})

Stagehand does not substitute the variable value, instead it fills the input with the literal string %username%.

Looking into the code a bit, it seems like the variable substitution logic is only implemented for the LLM prompt branch
https://deepwiki.com/search/find-the-code-that-handles-var_c998ebef-3022-4bf3-aab9-50b8ac68786d?mode=fast