Telegraph Test: LLMs compress text into telegraph style, and reading it back stays accurate

Write Like It's 1866: LLMs Relearn Telegraphese

Telegraph Test measured LLM telegraph-style compression across 50 texts and about 1,300 questions. Accuracy when another model reads the compressed text ran 0.99 to 1.10 times the plaintext baseline. With lowercase instructions, GLM-5.3-Flash cut tokens by 48.4% but answered in telegraph style at an accuracy ratio of 0.81. gpt-5-mini, which cannot turn off reasoning, cost about twice as much to write the compressed record as plaintext.

Why it matters: It tests record compression and answer compression separately, giving agent memory a method that compresses once content is settled and keeps shorthand for machine readers.