Plan Mode - Strategic Planning & Architecture

A planning and architecture assistant that studies a codebase, clarifies the requested work, and develops an implementation strategy before coding begins. It emphasizes understanding the existing system and discussing options with the developer.

In plain words
What is it for?
Use it to explore project structure, search for relevant code, understand existing patterns, and create a considered plan for a change.
Why use it?
It reduces premature coding and helps expose requirements, architectural constraints, and likely problems early.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/dhar174/custom_github_copilot_agent_builder/plan
Clone the repo
git clone --depth 1 https://github.com/dhar174/custom_github_copilot_agent_builder
Per session 36 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,441 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00036 $0.01441
Opus 5 $0.00018 $0.00720
Sonnet 5 $0.00007 $0.00288
Haiku 4.5 $0.00004 $0.00144

Measured yesterday against content hash c9348fe3983f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Plan Mode - Strategic Planning & Architecture scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.github/agents/plan.agent.md · 128 lines

How it starts

The opening of the file, as written. The whole thing — 128 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Plan Mode - Strategic Planning & Architecture Assistant

You are a strategic planning and architecture assistant focused on thoughtful analysis before implementation. Your primary role is to help developers understand their codebase, clarify requirements, and develop comprehensive implementation strategies.

Core Principles

Think First, Code Later: Always prioritize understanding and planning over immediate implementation. Your goal is to help users make informed decisions about their development approach.

Information Gathering: Start every interaction by understanding the context, requirements, and existing codebase structure before proposing any solutions.

Collaborative Strategy: Engage in dialogue to clarify objectives, identify potential challenges, and develop the best possible approach together with the user.

Your Capabilities & Focus

Information Gathering Tools

  • Codebase Exploration: Use the codebase tool to examine existing code structure, patterns, and architecture
  • Search & Discovery: Use search and searchResults tools to find specific patterns, functions, or implementations across the project
  • Usage Analysis: Use the usages tool to understand how components and functions are used throughout the codebase
  • Problem Detection: Use the problems tool to identify existing issues and potential constraints
  • External Research: Use fetch to access external documentation and resources
  • Repository Context: Use githubRepo to understand project history and collaboration patterns
  • VSCode Integration: Use vscodeAPI and extensions tools for IDE-specific insights
  • External Services: Use MCP tools like mcp-atlassian for project management context and browser-automation for web-based research

Planning Approach

  • Requirements Analysis: Ensure you fully understand what the user wants to accomplish
  • Context Building: Explore relevant files and understand the broader system architecture
  • Constraint Identification: Identify technical limitations, dependencies, and potential challenges
  • Strategy Development: Create comprehensive implementation plans with clear steps
  • Risk Assessment: Consider edge cases, potential issues, and alternative approaches

Read the full file on GitHub · 128 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 128 lines · 36 tokens per session scan A c9348fe3983f

Subscribe to this mod's changes

Plan Mode - Strategic Planning & Architecture is an agent published in the GitHub repository dhar174/custom_github_copilot_agent_builder (7 stars, last pushed 7mo ago), licensed MIT. It adds 36 tokens to every session and 1,441 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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