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Learn Claude Code -- A nano Claude Code-like agent, built from 0 to 1

                    THE AGENT PATTERN
                    =================

    User --> messages[] --> LLM --> response
                                      |
                            stop_reason == "tool_use"?
                           /                          \
                         yes                           no
                          |                             |
                    execute tools                    return text
                    append results
                    loop back -----------------> messages[]

    That's the minimal loop. Every AI coding agent needs this loop.
    Production agents add policy, permissions, and lifecycle layers.

12 progressive sessions, from a simple loop to isolated autonomous execution. Each session adds one mechanism. Each mechanism has one motto.

s01   "One loop & Bash is all you need" — one tool + one loop = an agent

s02   "Adding a tool means adding one handler" — the loop stays the same; new tools register into the dispatch map

s03   "An agent without a plan drifts" — list the steps first, then execute; completion doubles

s04   "Break big tasks down; each subtask gets a clean context" — subagents use independent messages[], keeping the main conversation clean

s05   "Load knowledge when you need it, not upfront" — inject via tool_result, not the system prompt

s06   "Context will fill up; you need a way to make room" — three-layer compression strategy for infinite sessions

s07   "Break big goals into small tasks, order them, persist to disk" — a file-based task graph with dependencies, laying the foundation for multi-agent collaboration

s08   "Run slow operations in the background; the agent keeps thinking" — daemon threads run commands, inject notifications on completion

s09   "When the task is too big for one, delegate to teammates" — persistent teammates + async mailboxes

s10   "Teammates need shared communication rules" — one request-response pattern drives all negotiation

s11   "Teammates scan the board and claim tasks themselves" — no need for the lead to assign each one

s12   "Each works in its own directory, no interference" — tasks manage goals, worktrees manage directories, bound by ID

The Core Pattern

def agent_loop(messages):
    while True:
        response = client.messages.create(
            model=MODEL, system=SYSTEM,
            messages=messages, tools=TOOLS,

        messages.append({"role": "assistant",
                         "content": response.content})

        if response.stop_reason != "tool_use":
            return

        res