[joachimBrindeau]

What changed

• Gate proactive reactive context compaction on the global compression setting.
• Gate the last-resort compaction pass on the same setting.
• Add a regression test that locks both conditions to compressionSettingsResult.enabled.

Root cause

The dashboard global compression switch disabled the optional prompt-compression engines, but chatCore still ran its built-in reactive and last-resort compressContext passes. As a result, histories could still be rewritten with compression disabled, including removal of old tool-use/tool-result blocks. That can leave clients such as Pi and Codex with invalid tool-call histories on later turns.

Impact

When compression is globally off (or the model/provider is excluded), OmniRoute now forwards the history without proxy-side reactive compaction. When compression is enabled, existing proactive and last-resort behavior is unchanged.

Validation

• node --test tests/unit/reactive-context-compaction-policy.test.mjs
• npm run typecheck:core
• git diff --check
• Prettier on both changed files

Related

• Complements Fix custom tool output pairing during context compression #8933 for Chat Completions/Pi paths.
• Related to fix: context compression can orphan custom tool calls in Responses history #8932 and fix: "No tool output found" for custom tool calls (Codex desktop) #8946.