Fable
The reply room that writes the next line while reading the draft
The post station had a reply room specifically for writing replies on behalf of merchant guilds from various places. With every sentence the old clerk wrote, he pressed the previously written content close at hand before deciding how the next sentence should continue.
At first the letters were short, and the clerk could finish them from experience. Later the replies had to include quotes, risk notices, attachment descriptions and the customer's tone, and any wrong sentence would affect later commitments.
The stationmaster first gave the clerk a handbook of stock phrases. The letters looked more complete, but often contradicted themselves: the beginning promised delivery in three days, while the end said two weeks of review were needed.
Someone again demanded that the clerk check everything after writing. Checking can catch some errors, but the generation process itself is still like a one-way road, where early choices affect the later text all the way through.
Later the reply room changed its rules: for every character written, it could only view the draft already written and the permitted materials, then predict the most suitable next character.
This approach is well suited to continuous generation and makes costs clearly visible. The longer the letter, the more steps; the larger the context, the more information each step examines. Later the stationmaster also discovered that the further the clerk wrote, the more easily he was led astray by what came before. If a polite tone was chosen early, it would continue to be polite later; if a constraint was missed earlier, later commitments might drift further and further.
The stationmaster discovered that the reply room fears unbounded free writing most. It must be given clear tasks, available materials, format constraints, and stopping conditions; otherwise it will mistake fluency for correctness. Later the manager wrote this lesson into the daily rules: first look at the scenario, then the boundaries, and finally who can take over when it fails. Only when all of these are clear will a beautiful demo become deliverable work.
Finally, the post station understood: writing is not spitting out an answer all at once, but continuing step by step within a limited context. Each step is like a small decision, and their accumulation becomes the whole letter. So the reply room added stopping rules: when writing reaches price, date or responsibility points, re-check the materials; when the end marker is reached, wrap up and stop adding flourishes for the sake of flow. Only when continuation ability is placed within boundaries is it suitable for formal replies.