Simon Willison releases llm-echo 0.5 debugging plugin
What happened
On 19 October 2026, Simon Willison released llm-echo 0.5. The plugin is a debugging tool whose "model" calls no LLM and simply echoes the input prompt. The new version updates simulated token usage accounting to include tool calls, system prompts and reasoning tokens. In the example given in the report, the command `llm -m echo 'hi there' -o thinking 1 --usage` shows 2 input tokens and 24 output tokens.
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- Simon Willisonllm-echo 0.5
Release: llm-echo 0.5 I'm working towards a new LLM release, and testing PRs caused me to revisit the llm-echo debug plugin. This plugin provides a "model" which doesn't involve an LLM at all - it just repeats back the prompts that have been fed to it.
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