diff --git a/open-sse/services/compression/adaptiveCompression/ladder.ts b/open-sse/services/compression/adaptiveCompression/ladder.ts
index 2302b2c64b..24a08c9920 100644
--- a/open-sse/services/compression/adaptiveCompression/ladder.ts
+++ b/open-sse/services/compression/adaptiveCompression/ladder.ts
@@ -36,6 +36,7 @@ const AGGRESSIVENESS: Record<string, number> = {
   "session-dedup": 10, // stackPriority 3 — lossless cross-turn dedup
   ccr: 15, // stackPriority 4 — reversible retrieval marker, only if it shrinks
   rtk: 20, // stackPriority 10 — command-output filtering
+  "codex-responses": 22, // stackPriority 12 — conservative Responses tool-output compaction (single-mode)
   ionizer: 25, // stackPriority 13 — tabular row sampling (lighter than headroom)
   headroom: 30, // stackPriority 15 — tabular JSON compaction
   lite: 40, // pri 5, but cheap prose pass (pre-existing reorder, kept as-is)
@@ -64,6 +65,7 @@ const REDUCTION_FACTOR: Record<string, number> = {
   "session-dedup": 0.95,
   ccr: 0.9, // conservative: only replaces a block when the marker is shorter than it
   rtk: 0.85,
+  "codex-responses": 0.85, // conservative, lossless-first tool-output compaction (Responses API)
   ionizer: 0.83, // row sampling, lighter than headroom's full tabular compaction
   headroom: 0.8,
   lite: 0.92,