> ## Documentation Index > Fetch the complete documentation index at: https://gomodel.enterpilot.io/docs/llms.txt > Use this file to discover all available pages before exploring further. # Prompt Compression > Reduce repeated and structural context in inference requests before they reach the provider, without changing the request's structure. Usage Analytics showing $268.63 estimated cost and $45.17 Pro saved, 14.4% less ## Proven in production Prompt compression has been exercised on billions of production tokens across agentic coding, chat, and tool-heavy workloads. * **Lossless.** Compression only replaces content the model has already seen in the same request with a reference to it, or re-encodes structured data reversibly. The model receives the same information; nothing is summarized or dropped. The single lossy option, tool-result pruning, is a separate policy that is off by default. * **No prompt-cache degradation.** Because the previously sent prefix of a session is replayed byte-for-byte and only new messages are rewritten, provider prompt caches keep hitting across turns. Testers actually noticed about a 2% *increase* in prompt-cache hits, since shorter, more stable requests fit the cache better — which adds savings on top of the compression itself. * **Real savings of 5%–15%** for our testers, depending on the use case. Agents that re-read files, replay tool output, or carry long histories sit at the top of that range; short, non-repetitive chat sits at the bottom, where the compressor simply forwards requests unchanged. * **Full control.** Choose the level per gateway or per request, exclude models by glob, protect pre-existing history with `new_messages_only`, keep source code verbatim, and inspect every rewrite through response headers, audit revisions, and metrics. ## Overview Prompt compression rewrites supported inference requests before they reach the provider. It reduces repeated or structural context while preserving the request's non-text structure. It supports `POST /v1/chat/completions`, `POST /v1/messages`, and `POST /v1/responses`. Tool-call arguments, non-text parts, and unknown JSON fields are left intact. Responses reasoning items are always replayed unchanged, because the Responses API can require them alongside function calls. The default `high` policy combines line-run deduplication with normalization: * file-read line-number gutters become a compact range header * replayed chat-completions reasoning is removed when it is safe to do so * known tool-result envelopes, search results, logs, JSON, and unified diffs use content-aware normalization * profitable homogeneous JSON arrays and structured logs use reversible, self-describing encodings The compressor is deterministic and fails open. It forwards a request unchanged when a rewrite is below the saving threshold or would exceed its work budget. Source code is preserved by default; enable code deduplication only when the extra saving is worth replacing exact repeated source with references. For a detected session, the gateway retains the exact body it previously sent upstream and replays that prefix byte-for-byte on later turns. This protects a provider prompt-cache prefix while allowing new messages to reference repeated history. Use `new_messages_only` when the gateway may join a conversation whose prefix it did not observe. ## Configure compression | Environment variable | Default | Purpose | | ----------------------------------------- | -------------- | --------------------------------------------------------------------------------------------------- | | `PRO_COMPRESSION_LEVEL` | `high` | Select `none`, `low`, `medium`, or `high`. An explicit value makes the Dashboard setting read-only. | | `PRO_COMPRESSION_SCOPE` | `full_history` | Use `new_messages_only` to protect pre-existing conversation history. | | `PRO_COMPRESSION_EXCLUDE_MODELS` | — | Comma-separated requested-model globs to skip, such as `ollama/*`. | | `PRO_COMPRESSION_MIN_BLOCK_CHARS` | `128` | Minimum repeated line-run size under the high preset. | | `PRO_COMPRESSION_MIN_SAVINGS_TOKENS` | `32` | Minimum estimated net saving under the high preset. | | `PRO_COMPRESSION_DEDUPLICATE_CODE` | `false` | Permit repeated source-code runs to be replaced with references. | | `PRO_COMPRESSION_NORMALIZE` | `true` | Enable content normalization and tool-schema stabilization. | | `PRO_COMPRESSION_COMPRESS_JSON_STRUCTURE` | high preset | Enable reversible JSON-table encoding. | | `PRO_COMPRESSION_COMPRESS_LOG_STRUCTURE` | high preset | Enable reversible structured-log encoding. | Set `PRO_COMPRESSION_LEVEL=none` to disable compression for the whole gateway. For one request, send: ```http theme={null} X-GoModel-Compression: off ``` The per-request opt-out and the `none` level bypass request-body parsing, so the request is forwarded unchanged. ## Inspect compression Compressed responses include estimated savings and the number of replaced duplicate blocks: ```http theme={null} X-GoModel-Pro-Tokens-Saved: 1843 X-GoModel-Pro-Compression-Blocks: 12 ``` Audit logs retain the original request and a revision for each rewriter. The revision records its byte sizes and compression detail; the rewritten body is also retained when `LOGGING_LOG_BODIES=true`. Prometheus metrics use the `gomodel_pro_compression_` prefix, and the Dashboard Usage page reports Pro savings in tokens or cost.