System prompt assembly needs holistic refactor

Problem

The system prompt is the primary interface between Continue and every model it communicates with. It is currently assembled ad-hoc from hardcoded string literals spread across multiple files, accumulated through incremental changes by 400+ contributors over two years of growth. There is no template system, no per-model awareness, and no separation between base instructions, tool syntax, mode-specific behavior, and rules.

Current state

The system prompt is constructed by concatenating pieces from:

• core/llm/defaultSystemMessages.ts — mode-specific base messages (agent/chat/plan), hardcoded string literals
• gui/src/redux/util/getBaseSystemMessage.ts — mode selection and a hardcoded all-caps NO_TOOL_WARNING appended when no tools are active
• core/tools/systemMessageTools/toolCodeblocks/index.ts — tool syntax framework with hardcoded prefix, suffix, and example templates
• core/tools/systemMessageTools/buildToolsSystemMessage.ts — concatenates tool definitions (two incompatible formats: example-based for built-ins, schema-based for MCP)
• core/llm/rules/getSystemMessageWithRules.ts — appends workspace rules without budget awareness

There is no central template. No model-size or capability awareness. The only override is model.baseAgentSystemMessage, which replaces the entire base message or nothing.

What the model receives

With tools enabled (agent mode): A brief mode declaration ("You are in agent mode"), codeblock formatting instructions, then tool-use syntax rules and per-tool examples. The actual behavioral guidance is approximately 50 tokens. Everything else is tool syntax documentation.

With no tools enabled (agent mode): The same tool-use rules for tools that don't exist, followed by an all-caps message: "THE USER HAS NOT PROVIDED ANY TOOLS, DO NOT ATTEMPT TO USE ANY TOOLS." The model receives contradictory instructions in a single system message.

For local models with small context windows: No adaptation. The same prompt is sent to a 4-bit quantized 9B model as to GPT-4 or Claude. No output format guidance, no structural constraints, no awareness of context budget.

Documented downstream effects

The following open issues trace back to or are compounded by the system prompt:

• #11072 — TOOL_NAME keyword repeated in every built-in tool example; smaller models echo it as conversational text
• #11070 — Parser intercepts quoted tool syntax as real tool calls
• #11074 — Parser assumes tool calls are positionally terminal in model output
• #10783 — Reasoning content leaks into applied edits (no output structure guidance in prompt)
• #10785 — Reasoning content leaks into terminal output display
• #11069 — Vercel stream converter misroutes reasoning-delta to content
• #10781 — System prompt not sent to local LM Studio models in some configurations

An InfoWorld article (https://www.infoworld.com/article/4144487/i-ran-qwen3-5-locally-instead-of-claude-code-heres-what-happened.html) documents end-user failures with local models through Continue that are consistent with these issues: crashes mid-apply, infinite loops, mangled indentation, and erasing entire files.

Files involved

• core/llm/defaultSystemMessages.ts — base system messages
• gui/src/redux/util/getBaseSystemMessage.ts — message selection and no-tools warning
• core/tools/systemMessageTools/toolCodeblocks/index.ts — tool syntax framework
• core/tools/systemMessageTools/buildToolsSystemMessage.ts — tool message generation
• core/llm/rules/getSystemMessageWithRules.ts — rules injection
• gui/src/redux/util/constructMessages.ts — final assembly