Prompt compression for RAG

Reduce retrieved context without hiding the trade-off.

Protect the facts and structures your application depends on, compress low-value context, inspect the redline, and evaluate answers on representative retrieval workloads.

Protected citations and identifiers
Original-input fallback
Inspectable before and after
Workload-specific evaluation

Protect

Define what must survive.

RAG quality depends on more than semantic similarity. Mark the details that must remain exact.

  • Numbers, units, dates, and identifiers
  • Citations, source labels, and tenant terms
  • Instructions, negations, and output constraints

Compress

Remove low-value context selectively.

Use compression when dynamic retrieval context is long enough to justify the added work.

  • Skip prompts that are already efficient
  • Preserve structure and critical spans
  • Return the original when savings are not worthwhile

Verify

Measure the downstream task.

A smaller prompt is not a win if the answer becomes less grounded, complete, or useful.

  • Compare original and compressed outputs
  • Score grounding and information preservation separately
  • Review failures on a frozen representative sample

Good fit

Dynamic context with visible input cost and a measurable task.

Document QA, research synthesis, support knowledge, compliance review, and other retrieval-heavy workflows are strongest candidates when prompt size is material and the team can define a correct downstream result.

Test compression on the RAG workload you actually run.

Start with representative prompts, explicit must-keep information, and the exact model configuration used in production.