[remote-controlled-man]

What does this PR do?

Precompiled prompt values can contain braces, such as Use {name} or {{question}}. get_langchain_prompt(context=...) currently turns those values into LangChain variables, causing missing-key errors or changing the supplied text during formatting.

Keep supplied braces opaque while converting the template, then escape them for LangChain. Preserve the existing JSON conversion order and evaluate only referenced values. Apply this to text prompts, chat prompts and resolved message history. Unfilled variables still belong to LangChain; ordinary compile() behavior is unchanged.

Type of change

• Bug fix

Verification

uv sync --locked --python /opt/homebrew/opt/python@3.12/bin/python3.12
.venv/bin/python -m pytest tests/unit/test_prompt_compilation.py -q
.venv/bin/ruff check .
.venv/bin/ruff format --check langfuse/model.py tests/unit/test_prompt_compilation.py
.venv/bin/mypy langfuse --no-error-summary

59 prompt-compilation tests pass, including literal-brace regressions through real LangChain templates. The initial regression run failed 8 cases on unchanged source. Backend e2e and live-provider tests were not run: this conversion is covered locally without a server or model requests.

Checklist

• I self-reviewed the diff using code_review.md.
• I added regression tests for the changed behavior.
• Existing examples and environment settings remain accurate.
• No generated files were edited.
• No credentials were committed.

AI disclosure: OpenAI Codex found this during a source audit and prepared the patch, tests and description.

Confidence Score: 5/5

The PR appears safe to merge; no actionable issues were found.

Summary

The PR keeps braces in supplied values literal when converting text and chat prompts for LangChain.

• Text and chat prompts keep supplied braces literal in LangChain.

No actionable issues were found.

_{Reviews (1) · Last reviewed commit: "fix(prompts): avoid evaluating unused co..." · Reviewed by Greptile}

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