Description

The curly template formatter ({{var}} syntax) raises a TemplateFormatError reporting unreplaced variables when a substituted input value happens to contain {{...}} patterns — even if all template variables were successfully replaced.

Steps to reproduce

from agenta.sdk.types import PromptTemplate

prompt = PromptTemplate(
    user_prompt="Hello {{name}}",
    template_format="curly",
)

# This raises TemplateFormatError: "Unreplaced variables in curly template: ['name']"
result = prompt.format(name="I am {{name}}")

Expected behavior

The template should substitute {{name}} with the literal string "I am {{name}}", producing "Hello I am {{name}}". The {{name}} in the output is user data, not an unresolved template variable.

Actual behavior

TemplateFormatError is raised because the post-substitution validation (compute_truly_unreplaced) re-scans the rendered output for {{...}} patterns and finds {{name}} in the substituted value, falsely treating it as an unreplaced placeholder.

Root cause

The validation logic in _format_with_template (in both sdk/agenta/sdk/types.py and sdk/agenta/sdk/workflows/handlers.py) works in two phases:

1. Replace all {{expr}} placeholders with resolved values via apply_replacements
2. Re-scan the output for any remaining {{...}} patterns and intersect with the original placeholder set (compute_truly_unreplaced)

Step 2 is the problem: it cannot distinguish between {{...}} patterns that were in the original template (genuinely unreplaced) and {{...}} patterns that were injected by substituted values.

Affected code paths

• PromptTemplate._format_with_template in sdk/agenta/sdk/types.py
• _format_with_template in sdk/agenta/sdk/workflows/handlers.py

Impact

Any user whose input data contains {{...}} patterns (e.g., template examples, documentation text, code snippets) will get spurious errors when using the curly template format.