Subagent-Driven Development — Building a Data Model in Parallel
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Agentic Coding with Claude Code

A series on software development with Claude Code — from raw PDF sources to a deployable web application.

We are building a complete software project with Claude Code — from raw PDF sources to a finished web application. The demo project is a visualization of the Bavarian state budget 2026/27. Each article shows which tool is in play: CLAUDE.md, Plan Mode, Skills, Slash Commands, Subagents, Worktrees, MCP, Hooks, and a full deploy. Code lives openly on Codeberg, with a tag per article to follow along. Ten articles plus the prologue.

  1. 0

    What Agentic Coding Actually Means

    Prologue · Series: Agentic Coding with Claude Code. Anyone reading tech newsletters, conference keynotes, and tool landing pages this year runs into two terms sold with identical promises: Vibe Coding and Agentic Coding. The future of programming, they say.
    9. May 2026
  2. 1

    CLAUDE.md as a Briefing

    Article 1 of the series — we install Claude Code, set up the byhaushalt repo, write the first memory file, and pin down what the agent has to follow in every session. Plus: permissions, source data, the first day.
    10. May 2026
  3. 2

    Explore Before You Build — Plan Mode with Subagents

    Article 2 of the series — before byhaushalt sees its first parser code, Claude Code maps the PDF structure of the Bavarian budget plans. Plan Mode, Explore subagent, and Architecture Decision Records as tools for exploring before implementing.
    10. May 2026
  4. 3

    Writing Custom Skills — PDF Parser Skill with pytest TDD

    Article 3 of the series — the first parser code for byhaushalt takes shape via TDD: a custom skill with trigger description, uv setup, six tests before implementation, and how the sum consistency test catches hallucinations in PDF parsing.
    11. May 2026
  5. 4

    Slash Commands — Automating Repetition Away

    Article 4 of the series — three slash commands make the parser repeatable: /parse-epl for any Einzelplan, /check-totals with built-in pytest, /diff-vs-gesamt for comparison against the full budget. Plus: what xfail reveals about parser gaps.
    12. May 2026
  6. 5

    Subagent-Driven Development — Building a Data Model in Parallel

    Article 5 of the series — v0.4 delivers three JSON files, not a data model. A plan file with three tasks and parallel subagents builds schema, normalization, and property-based tests. Plus: what format inconsistency teaches about parallelization.
    13. May 2026