Code mode prompt assembly fails when a tool description contains a literal {{...}}

[mbj733]

Summary

An agent preset with mode: code (or both) renders every visible tool into the generated tools:sdk prompt section. If any tool's description (or a schema property description) contains a literal {{...}} — for example an MCP server that documents template placeholders — prompt assembly throws and the whole turn fails:

malformed prompt variable reference "{{...}}" in section "tools:sdk" (variable names match /^[a-z][a-z0-9_]*$/)

Reproduction

1. Register an MCP tool whose description contains {{...}} (for example the officecli MCP server, whose tool description includes ...scan for leftover placeholders (xxxx, lorem/ipsum, <TODO>, {{...}}, $VAR$...)).
2. Use an agent preset with mode: code.
3. Send any message — the turn fails before any tool call with the error above.

Root cause

The SDK section text is produced by renderToolsSdk (packages/core/tools/src/ts-types.ts) and renderToolsSdkPy (packages/core/tools/src/py-types.ts). Tool and property descriptions are embedded into that text (JSDoc comments / docstrings) through docLines / describe, which escape */ (and quotes/backslashes on the Python side) but do not escape adjacent {{.

The system-prompt strict interpolation (interpolate in packages/core/system-prompt/src/index.ts) then scans every section for complete {{name}} groups and rejects {{...}} as a malformed variable reference. So any third-party tool description containing a {{…}} placeholder breaks assembly.

Suggested fix

Escape adjacent {{ while collapsing descriptions so no complete {{…}} group can form, e.g. .replace(/{(?={)/g, '{ ') in both docLines (ts-types.ts) and describe (py-types.ts). I've applied exactly this on a local checkout and it resolves the failure; I also added regression tests to packages/core/tools/tests/ts-types.spec.ts and py-types.spec.ts.

[ytianxia6]

I have the same question.

[ytianxia6]

This question may be fixed!