agent-prompt-design

name

agent-prompt-design

description

Apple's complete prompt stack for Xcode 27's coding agent, as shipped. Consult when designing or reviewing agent prompts, tool descriptions, planner/executor splits, edit-application strategies, or context-window assembly — this is a production system's actual wording, not advice about prompting. Covers: planner and executor system prompts (including a GPT-5-specific variant and a no-classify variant), reasoning vs non-reasoning variants, tool-assisted variants, an A/B test pair, three edit integrators (standard, new-code, fast-apply), retrieval query expansion, and the fourteen fragments used to frame current file, selection, snippets, issues and search results.

Everything Xcode 27 sends to a model, extracted from the shipping app. Useful as evidence rather than opinion: when deciding how to word a tool description or split planning from execution, read what a team with real usage data actually shipped.

Nothing here should be installed as an agent's own system prompt. It is reference material for writing prompts, not a prompt to adopt.

References

Agent architecture

• references/PlannerExecutorStylePlannerSystemPrompt.md: the planner half of a planner/executor split — the largest and most instructive file here.
• references/PlannerExecutorStylePlannerSystemPrompt-gpt_5.md: the same planner retargeted at GPT-5. Diff the two to see what a team changes per model.
• references/PlannerExecutorStyleNoClassify.md: the variant that skips the classification step.
• references/AgentSystemPromptAddition.md: what is appended when running in agent mode rather than chat.
• references/AgentAdditionalContext.md: extra context supplied to the agent.
• references/AgentVersions.plist: the agent backends Xcode bundles — Claude Code and Codex, pinned by version, URL and checksum.

System prompt variants

• references/BasicSystemPrompt.md and references/ToolAssistedBasicSystemPrompt.md: the baseline, with and without tools.
• references/ReasoningSystemPrompt.md and references/ToolAssistedReasoningSystemPrompt.md: the reasoning-model versions.
• references/VariantASystemPrompt.md and references/VariantBSystemPrompt.md: an A/B pair. The differences are the interesting part.
• references/TextEditorToolSystemPrompt.md: the prompt for the text-editor tool.

Applying edits

Three strategies for turning a model's output into a file change:

• references/IntegratorSystemPrompt.md, references/IntegratorUserPrompt.md
• references/NewCodeIntegratorSystemPrompt.md, references/NewCodeIntegratorUserPrompt.md
• references/FastApplyIntegratorSystemPrompt.md, references/FastApplyIntegratorUserPrompt.md

Response guidelines

• references/InQueryShortGuidelines.md, references/InQueryDetailedGuidelines.md
• references/ToolAssistedInQueryShortGuidelines.md, references/ToolAssistedInQueryDetailedGuidelines.md

Retrieval and chrome

• references/InstructionEmbeddingsQueryExpansion.md, references/LocalInfillEmbeddingsQueryExpansion.md: query expansion before embedding search.
• references/ChatTitleResolver.md: naming a conversation.
• references/PromptSuggestionGenerator.md: generating follow-up suggestions.

Context assembly

Small fragments that frame each piece of context. Read together, they show how one team budgets a context window:

AdditionalFiles, ContextItems, CurrentFile, CurrentFileAbbreviated, CurrentFileName, CurrentSelection, Interfaces, Issues, NewKnowledge, NoSelection, OriginalFile, Query, SearchResults, Snippets — each references/<name>.md.

Single-purpose tools

Short task prompts, useful mainly as examples of how terse a working tool prompt can be:

• references/CodingToolTemplateDocument.md, references/GenerateDocumentation.md
• references/CodingToolTemplateExplain.md
• references/CodingToolTemplateGeneratePreview.md, references/GeneratePreview.md
• references/CodingToolTemplateGeneratePlayground.md, references/GeneratePlayground.md