# Start Gsd 3 > Learn GSD lesson 3 through its file-backed planning and build workflow. Use when the student types /start-gsd-3. - Skill: `carlvellotti/start-gsd-3` (Agent Skill) - Install (CLI): `npx skillmds@latest add carlvellotti/start-gsd-3` - Raw SKILL.md: https://api.skillmd.com/api/skills/carlvellotti/start-gsd-3/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Productivity - Author: carlvellotti (https://skillmd.com/u/carlvellotti) - Updated: 2026-09-10 - Page: https://skillmd.com/skills/carlvellotti/start-gsd-3 --- # 3.3 Plan the Build ## Setup ACTION: Read and follow `.claude/rules/teaching-rules.md` before teaching. Then run this idempotent staging action. It never replaces existing work. Echo and summarize the clickable staged path. ```bash mkdir -p "expense-splitter" printf '[expense-splitter](expense-splitter/)\\n' ``` Now we turn your roadmap into executable plans. GSD breaks each phase into small atomic tasks - 2-3 tasks per plan. Each task is designed to fit in about 50% of a fresh context window. This "aggressive atomicity" is what prevents context rot. No single task is big enough to degrade quality. STOP: Ready to plan Phase 1? USER: Yes --- ## Optional: Discuss Before Planning Quick note: there's an optional `/gsd:discuss-phase 1` you can run before planning. It lets you specify preferences - UI style, specific behaviors, error handling approach. GSD captures those and feeds them into planning. We'll skip it for now. You can explore it on your own projects. STOP: Sound good? USER: Yes --- ## What Happens During Planning When you run `/gsd:plan-phase 1`, here's what happens: 1. **Research** - GSD spawns agents to research phase-specific details 2. **Plan** - Creates atomic plans (2-3 tasks each) 3. **Verify** - Runs a verification check to make sure plans actually achieve the phase goals The planner creates plans, a checker reviews them, planner revises if needed. This loop runs until plans pass verification. **Time expectation:** This takes **5-10 minutes**. Research, planning, and verification all happen automatically. **When it finishes**, you'll see "PHASE 1 PLANNED" and be back at the normal composer. I will narrate progress and results in prose. STOP: What will you type when you're back at the normal prompt? USER: Done Right - you'll type "done" so we can look at the plans together. --- ## Run It Type `/gsd:plan-phase 1` and hit enter. GSD will run a planner, checker, and possibly a researcher. I will narrate their visible progress in prose. This takes 5-10 minutes. STOP: Run `/gsd:plan-phase 1` now. Type "done" when it finishes. USER: Done --- ## Let's See What GSD Created ACTION: Find the actual phase folder under `expense-splitter/.planning/phases/`, list its contents in prose, and link the files. You should see several PLAN.md files. ACTION: Read one of the PLAN.md files, summarize its XML task structure, and include its clickable link. --- ## Understanding the Plan Structure Notice the XML structure? This IS the prompt that subagents will execute. Each `` has: - **name** - what we're doing - **files** - what files to touch - **action** - specific instructions - **verify** - how to check it worked - **done** - what "complete" looks like This isn't a document that becomes a prompt. It **IS** the executable instruction. STOP: See how specific each task is? No ambiguity. USER: Yes --- ## Understanding Waves Look at the plan numbers: 01-01, 01-02... The first number is the phase. The second is the plan number. Plans are assigned to **"waves."** Independent tasks run in parallel. Wave 1 might have plan 01-01 running. Wave 2 waits for Wave 1 to complete, then runs. This is "wave-based parallelism." GSD maximizes efficiency by running independent work in parallel, while ensuring dependent work waits. STOP: Make sense how waves work? USER: Yes --- ## Why This Matters Here's what's powerful: Each plan is small enough for one focused subagent. Each subagent gets a fresh 200k context - no degradation. The last task executes with the same quality as the first. Your main session stays clean while agents do the heavy lifting. STOP: Ready to execute and watch subagents build your app? USER: Yes --- ## What's Next You have atomic plans ready to execute. Each plan fits in ~50% context. They've been verified to achieve phase goals. Waves let independent work happen in parallel. Next, you'll run execute-phase and actually watch GSD build your Expense Splitter. This is where it gets real. STOP: Ready to build? Type `/start-gsd-4` to continue. USER: Ready --- ## Important Notes for Claude - The exact phase folder name depends on how GSD named it during roadmapping - Number of PLAN.md files varies based on scope - If planning fails, may need to run /gsd:plan-phase 1 again - **After "done"**: Always show the plan files - read at least one PLAN.md so student sees the XML structure - Make sure student understands plans ARE the prompts, not documents that become prompts ## Success Criteria - [ ] Student ran /gsd:plan-phase 1 successfully - [ ] PLAN.md files exist in the phase folder - [ ] Student saw the XML task structure (Claude read and showed a plan file) - [ ] Student understands wave-based parallelism - [ ] Student understands why small plans prevent context rot - [ ] Student understands plans ARE the executable prompts ## Sendoff ACTION: Before wrapping up, record this lesson as complete by running this WITHOUT NARRATING the raw output: ```bash fspm progress complete gsd-3 ``` If it fails because the fspm CLI isn't installed, follow the teaching rules' missing-CLI guidance: tell the learner progress tracking needs the FSPM CLI, offer to install it, and continue the wrap-up either way. Then close out with the student's options, in natural language (never as a command list): - Mention they can leave feedback on this lesson anytime — if they have some, collect it conversationally and submit it with the CLI (see teaching rules). - Remind them, briefly and only if it fits the moment, that they can always ask for a recap, a quiz on what they just did, a saved note, or where they stand in the course. - End with the next step: when you're ready for the next lesson, use `/clear` first, then: `/start-gsd-4`