Tag
24 posts tagged.
InvalidUpdateError: Can receive only one value per step means two parallel LangGraph nodes wrote the same state key with no reducer. Reproduce it in 15 lines and fix it the right way in Python and TypeScript (2026).
Register PreToolUse and PostToolUse hooks in the Claude Agent SDK to block dangerous tool calls, rewrite a tool's arguments, and audit every action. Copy-paste runnable Python and TypeScript, August 2026.
Define subagents in the Claude Agent SDK with the agents parameter and AgentDefinition: isolate context, run focused subtasks in parallel, restrict each one's tools, and confirm delegation. Runnable Python and TypeScript, August 2026.
A runnable Python guide to Claude structured output: the native output_config.format JSON path, Pydantic-driven schemas, strict tool use, a portable tool-use fallback, and the 400/truncation gotchas nobody covers.
A 429 is your rate limit; a 529 is Anthropic overloaded. Catch both, honor retry-after, back off with jitter, cap the retries, and never retry a 400. Full runnable Python wrapper for agent loops.
GraphRecursionError means you hit LangGraph's 25-superstep recursion limit. Raise it the right way, find the real infinite loop, and exit gracefully with RemainingSteps.
The evaluator-optimizer workflow puts a rubric-driven critic in the loop so a generator revises until it passes. A runnable Python build with real guardrails.
Run independent LLM calls at the same time in Python with asyncio.gather, cap them with a Semaphore, and survive 429 rate limits with backoff. Runnable code.
Build the orchestrator-workers agent pattern in Python with Claude: a planner that decides subtasks at runtime, parallel workers, and a synthesizer. Runnable code, July 2026.
A code-first routing tutorial: build a runnable LLM router in Python with the Claude API, add a deterministic fallback, and route by difficulty to cut cost.
Make a LangGraph agent durable with a checkpointer: attach SqliteSaver in one line, crash the graph on purpose, and resume from disk without re-running the Claude call.
A code-first prompt chaining tutorial: build a gated Python pipeline with the Claude API, add pure-Python and LLM gates, and fail fast before wasting tokens.
