[fix]: harden act variables prompt

[seanmcguire12]

why

• models would sometimes respond with the variable name without wrapping it in percentage signs.
• when this happens, the regex would fail to replace the variable name with the actual variable value

what changed

• adjusted the prompting for the condition when variables are provided by the user
  • the updated prompting is more specific around what the variables are used for, and the required return shape.

test plan

• existing act evals

---

Summary by cubic

Hardened the act variables prompt so models always return argument placeholders as %variableName%, preventing failed variable substitution. Also clarified the element ID format with concrete examples.

• Bug Fixes

  • Added explicit, repeated guidance to use %variableName% in the arguments array when variables are provided.
  • Improved element ID schema description with examples like '0-76' and '16-21'.

• Refactors

  • Introduced buildActVariablesPrompt() and reused it in both act and step-two prompts to keep messaging consistent and avoid duplication.

^{Written for commit 8b592f2. Summary will update on new commits. Review in cubic}

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[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

Architecture diagram

sequenceDiagram
    participant App as User Application
    participant Inf as Inference Service (act/stepTwo)
    participant PB as Prompt Builder
    participant LLM as AI Model (External)
    participant RP as Regex Processor

    Note over App,RP: Execution flow for actions involving dynamic variables

    App->>Inf: act(instruction, variables)
    
    rect rgb(240, 240, 240)
        Note over Inf,PB: Prompt Construction Phase
        Inf->>PB: buildActPrompt / buildStepTwoPrompt
        PB->>PB: NEW: buildActVariablesPrompt(variables)
        Note right of PB: Maps keys to %key% format<br/>Injects strict usage instructions
    end
    
    PB-->>Inf: Combined Prompt String

    Inf->>LLM: Send Prompt + Zod Schema
    Note over LLM: Schema CHANGED: Element ID<br/>now includes '0-76' examples

    LLM-->>Inf: Structured JSON Response (elementId, arguments)
    
    rect rgb(230, 245, 230)
        Note over Inf,RP: Variable Substitution Phase
        Inf->>RP: processArguments(arguments, variables)
        
        alt Model followed instructions (%variable%)
            RP->>RP: Regex matches %variableName%
            RP->>RP: Replace placeholder with actual value
        else Model returned raw variable name
            Note right of RP: Regex fails to match.<br/>Action executed with raw string.
        end
        RP-->>Inf: Final Action Arguments
    end

    Inf->>App: Return Action Result

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