Headless Claude Code: drive claude -p and the Agent SDK from your scripts

Take Claude Code out of the terminal and into your scripts. Print mode and structured JSON, the Claude Agent SDK in TypeScript and Python, chaining sessions, and the permission-and-cost discipline that keeps an unattended run from deleting your repo or running up an API bill once the June 15 billing change lands. Episode page & show notes Try a walking desk - stay healthy & sharp while you learn & code The Act II pivot from driving one Claude Code session by hand to calling it from a script: same agent, same loop, but you pre-decide what's allowed in code before the run ever starts. The tutorial. Print mode (claude -p) as a Unix citizen — piping stdin (and the 10MB cap), the --bare flag for deterministic CI runs, and structured output via --output-format json (the result, session_id, total_cost_usd, and subtype fields), stream-json with the init and api_retry events, and --json-schema for typed data instead of prose. The run-bounding flags — --max-turns, --max-budget-usd, --model/--fallback-model, --allowedTools/--permission-mode — and chaining turns with --resume/--session-id/--fork-session. Why a model refusal can't be caught from the exit code. Copyable patterns: a commit-message generator (and the space-before-* permission footgun), a stdin-fed typo linter that needs no Bash permission, and a locked-down CI run. Then the Claude Agent SDK (renamed from the Claude Code SDK in September 2025): query() and the options that mirror the CLI flags, custom in-process tools, the Python ClaudeSDKClient, hooks and subagents in code, and the can_use_tool permission callback. Full reference in the headless docs and the migration guide. The pitfalls. --dangerously-skip-permissions in an unattended run — how to recognize the silent-success failure, and the least-privilege allowlist that replaces it — and the June 15, 2026 billing change that moves Agent SDK and claude -p usage to a separate metered credit pool, plus how to watch total_cost_usd and bound it. News. Claude Code 2.1.166 (June 6): a fallbackModel setting (up to three), thinking-off controls, a "*" deny-all glob, and a cross-session permission-escalation fix; latest is 2.1.167 (changelog). 2.1.163 added additionalContext from Stop hooks, /plugin list, and version-pinning settings. And Claude Opus 4.1 is deprecated, retiring on the API August 5, 2026 (release notes). Earlier episodes referenced: CLAUDE.md and --resume, permissions and plan mode, custom slash commands and hooks, skills, subagents and the orchestrator pattern, MCP servers, cost and rate-limit engineering and evals, ultraplan/ultrareview, and parallel sessions with git worktrees.