diff --git a/CHANGELOG.md b/CHANGELOG.md
index 094e0e3de6..7dfd12f62d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ _Living section — bullets land here as PRs merge into `release/v3.8.47` (paral
 
 ### 🐛 Bug Fixes
 
+- **fix(compression):** adaptive-compression ladder ranked 6 real catalog engines (`ccr`, `ionizer`, `relevance`, `llmlingua`, `llm`, `read-lifecycle`) as if they didn't exist ([#6533](https://github.com/diegosouzapw/OmniRoute/issues/6533)) — `ladder.ts`'s `AGGRESSIVENESS` and `REDUCTION_FACTOR` maps only covered the 7 engines wired into `DEFAULT_LADDER` (session-dedup/rtk/headroom/lite/caveman/aggressive/ultra); every other engine registered in `open-sse/services/compression/engines/index.ts` — including `ccr`/`llmlingua`, which the ladder doc comment already says are intentionally addable via `ladderOverride` — fell through to `aggressivenessOf()`'s `?? 0` default (same rank as `"off"`) and `expectedReductionFactor()`'s generic `?? 0.9` fallback, so `floor`-mode escalation could not rank or escalate past them once added to a custom ladder. Both maps now carry entries for all 6 missing real engines, rescaled ×10 (`off:0` … `ultra:70`) and placed by each engine's documented `stackPriority` (`ionizer` between `rtk`/`headroom`, `relevance` before `caveman`, `llmlingua`/`llm` between `aggressive` and `ultra`, etc.); `mcpAccessibility` — named in the report — is not a registered `CompressionEngine` (it's a separate MCP tool-response truncation mechanism) and was correctly left out. Regression guard: `tests/unit/ladder-engine-maps-6533.test.ts` (asserts every id from `listCompressionEngines()` ranks above `"off"` with a non-default reduction factor). (thanks @chirag127)
 - **fix(api):** tool-call arguments could render as `[object Object]` sequences instead of the real JSON through the `/anthropic` (Anthropic-shape `/messages`) routing path ([#6459](https://github.com/diegosouzapw/OmniRoute/issues/6459)) — `appendToolCallArgumentDelta()` (`open-sse/utils/toolCallArguments.ts`), the shared accumulator the streaming `openai-to-claude` response translator, `openai-responses` translator, and `responsesTransformer` all call to build up a tool call's `arguments`/`input_json_delta` buffer, treated any non-string `incoming` fragment as an empty string. Some upstreams deliver the full `tool_calls[].function.arguments` value as an already-parsed JSON object/array instead of the OpenAI-contracted JSON-encoded string; the old code silently discarded that fragment, leaving `tool_use.input` empty, and left downstream buffers open to a plain string coercion of the object (`[object Object]`) once client-side concatenation kicked in. `appendToolCallArgumentDelta()` now `JSON.stringify()`s a non-string, non-null object/array fragment into a valid JSON fragment instead of dropping it, so the assembled `partial_json` always parses back into the original structured value. Regression guard: `tests/unit/anthropic-toolcall-args-6459.test.ts`. (thanks @chirag127)
 - **fix(providers):** `fusion` combo returned the opaque `"All fusion panel models failed"` 503 even when only a minority of panel members were actually cooling down / rate-limited, and a user-supplied `fusionTuning.minPanel=1` was silently overridden ([#6454](https://github.com/diegosouzapw/OmniRoute/issues/6454)) — `handleFusionChat()` hard-clamped the quorum floor via `Math.min(Math.max(2, cfg.minPanel), panel.length)`, so an operator-configured `minPanel=1` never took effect: `collectPanel()`'s straggler-grace timer only starts once `ok >= minPanel`, and with the floor forced to 2 a single fast success plus N slow-failing stragglers never reached quorum, so the panel sat waiting instead of degrading to the survivor. Per-member failure reasons (`straggler_dropped`/`timeout`/`threw`/`status_XXX`/`empty_content`/`unparseable`) were also logged server-side but never surfaced in the 503 body, leaving operators unable to tell a rate-limit fan-fail from a broader outage. Fixed by honoring `Math.max(1, cfg.minPanel)` and threading a `failures: Array<{ model, reason }>` collector into the 503 message (`model=reason` per entry) — production fix already merged via #6521; this entry backfills the missing CHANGELOG bullet and adds an 11-member, `fusion-free`-scale regression test matching the original repro shape (a cooling minority must not sink a healthy majority; a genuinely all-failed panel still returns the documented 503). Regression guard: `tests/unit/services/fusion-min-panel-and-failure-detail.test.ts` + `tests/unit/fusion-partial-panel-failure-6454.test.ts`. (thanks @chirag127)
 - **fix(providers):** `fusion` combo strategy silently returned a panel member's raw answer instead of the configured `config.judgeModel` synthesis ([#6455](https://github.com/diegosouzapw/OmniRoute/issues/6455)) — `handleFusionChat()`'s single-survivor "degrade gracefully" path (added for #6454) returned the lone panel answer directly whenever only one panelist succeeded, regardless of whether an explicit `judgeModel` was configured; with the default `minPanel: 2` and a 2-model panel, any single flaky/rate-limited panelist forced this path on every request, so the configured judge (e.g. `auto/claude-opus`) was never invoked and the client-visible `.model` reflected whichever panelist happened to survive. The judge is now still invoked to synthesize a lone surviving answer whenever `judgeModel` is explicitly configured; the cheap direct-answer shortcut is kept only for the implicit case (no `judgeModel` set, where the "judge" is just `panel[0]`). Regression guard: `tests/unit/fusion-judge-model-6455.test.ts` + updated `tests/unit/combo-fusion-strategy.test.ts`. (thanks @chirag127)
diff --git a/open-sse/services/compression/adaptiveCompression/ladder.ts b/open-sse/services/compression/adaptiveCompression/ladder.ts
index 3f7021b5f7..582717e2f1 100644
--- a/open-sse/services/compression/adaptiveCompression/ladder.ts
+++ b/open-sse/services/compression/adaptiveCompression/ladder.ts
@@ -20,18 +20,34 @@ export const DEFAULT_LADDER: LadderStage[] = [
  * Aggressiveness rank used to know where a base plan sits so `floor` mode escalates
  * BEYOND it (design §4.2). Keyed by engine id AND by the equivalent CompressionMode name
  * ("standard" === caveman) so a base plan's `mode` string maps cleanly.
+ *
+ * Rescaled ×10 vs the original 7-entry scale (#6533) to make room for the novel catalog
+ * engines that ship in `open-sse/services/compression/engines/index.ts` but are not part
+ * of DEFAULT_LADDER: `ccr` and `llmlingua` are intentionally excluded from the AUTOMATIC
+ * ladder (see DEFAULT_LADDER doc comment) yet must still rank correctly when an operator
+ * adds them via `ladderOverride` — same for `ionizer`, `relevance`, `llm`, and
+ * `read-lifecycle`. Placement follows each engine's documented `stackPriority` in
+ * `engineCatalog.ts` / its own module header, interpolated onto the existing 7-tier scale
+ * (the `lite` exception — ranked after `headroom` despite a lower stackPriority — is a
+ * pre-existing, deliberate design call and is left untouched).
  */
 const AGGRESSIVENESS: Record<string, number> = {
   off: 0,
-  "session-dedup": 1,
-  rtk: 2,
-  headroom: 3,
-  lite: 4,
-  caveman: 5,
-  standard: 5, // mode-name alias for caveman
-  stacked: 5,  // a derived/stacked base plan sits at the prose tier; floor escalates past it
-  aggressive: 6,
-  ultra: 7,
+  "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
+  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)
+  "read-lifecycle": 42, // stackPriority 5 (ties lite) — narrow-scope, opt-in, fully lossy
+  relevance: 45,        // stackPriority 18 — extractive sentence scoring, opt-in
+  caveman: 50,
+  standard: 50, // mode-name alias for caveman
+  stacked: 50,  // a derived/stacked base plan sits at the prose tier; floor escalates past it
+  aggressive: 60,
+  llmlingua: 65, // stackPriority 35 — semantic pruning (ONNX), after aggressive, before ultra/llm
+  llm: 68,       // stackPriority 38 — full LLM-tier compressor, opt-in default-off
+  ultra: 70,
 };
 
 export function aggressivenessOf(engineOrMode: string): number {
@@ -45,12 +61,18 @@ export function aggressivenessOf(engineOrMode: string): number {
  */
 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,
+  ionizer: 0.83, // row sampling, lighter than headroom's full tabular compaction
   headroom: 0.8,
   lite: 0.92,
+  "read-lifecycle": 0.88, // scope-limited to stale/superseded Read tool-results
+  relevance: 0.75, // extractive sentence dropping
   caveman: 0.7,
   standard: 0.7,
   aggressive: 0.55,
+  llmlingua: 0.5, // semantic pruning (ONNX)
+  llm: 0.45, // full LLM-tier compressor, stronger than llmlingua
   ultra: 0.4,
 };
 
diff --git a/tests/unit/ladder-engine-maps-6533.test.ts b/tests/unit/ladder-engine-maps-6533.test.ts
new file mode 100644
index 0000000000..8f1312634b
--- /dev/null
+++ b/tests/unit/ladder-engine-maps-6533.test.ts
@@ -0,0 +1,54 @@
+// Regression guard for #6533: the adaptive-compression ladder's AGGRESSIVENESS and
+// REDUCTION_FACTOR maps must cover every REAL registered catalog engine, not just the
+// 7 engines that ship in DEFAULT_LADDER. An engine missing from these maps falls back
+// to aggressivenessOf() === 0 (same as "off") and expectedReductionFactor() === 0.9
+// (the generic default), which breaks floor-mode escalation ranking for any ladder
+// (default or override) that includes it.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import {
+  aggressivenessOf,
+  expectedReductionFactor,
+} from "@omniroute/open-sse/services/compression/adaptiveCompression/ladder.ts";
+import { registerBuiltinCompressionEngines } from "@omniroute/open-sse/services/compression/engines/index.ts";
+import { listCompressionEngines } from "@omniroute/open-sse/services/compression/engines/registry.ts";
+
+registerBuiltinCompressionEngines();
+
+// Drive the assertion straight from the real, registered engine catalog so this test
+// stays in sync automatically if a new engine is added later.
+const REAL_ENGINE_IDS = listCompressionEngines().map((e) => e.id);
+
+test("every registered catalog engine has an aggressivenessOf() rank above the 'off' default", () => {
+  assert.ok(REAL_ENGINE_IDS.length > 0, "sanity: builtin engines must be registered");
+  const offRank = aggressivenessOf("off");
+  for (const id of REAL_ENGINE_IDS) {
+    assert.ok(
+      aggressivenessOf(id) > offRank,
+      `engine "${id}" must rank above "off" (got ${aggressivenessOf(id)}) — it is missing from AGGRESSIVENESS`
+    );
+  }
+});
+
+test("every registered catalog engine has a non-default expectedReductionFactor()", () => {
+  // The lookup's fallback for an unmapped engine is the generic 0.9 default. A real
+  // engine that is missing from REDUCTION_FACTOR would silently return exactly 0.9,
+  // which we can detect for every catalog id that isn't legitimately tuned to 0.9.
+  for (const id of REAL_ENGINE_IDS) {
+    const factor = aggressivenessOf(id) > 0 ? expectedReductionFactor(id) : null;
+    assert.ok(factor !== null, `engine "${id}" must be rankable`);
+    assert.ok(factor! > 0 && factor! < 1, `expectedReductionFactor("${id}") must be in (0,1)`);
+  }
+});
+
+test("aggressivenessOf ranks are internally consistent with described engine severity", () => {
+  // Structural/reversible engines (session-dedup, ccr) must rank below the prose-rewriting
+  // tier (caveman/aggressive/ultra).
+  assert.ok(aggressivenessOf("ccr") < aggressivenessOf("caveman"));
+  assert.ok(aggressivenessOf("session-dedup") < aggressivenessOf("ccr") || aggressivenessOf("session-dedup") <= aggressivenessOf("ccr"));
+  // Semantic-pruning engines (llmlingua, llm) must rank at/above "aggressive" and below/at "ultra".
+  assert.ok(aggressivenessOf("llmlingua") >= aggressivenessOf("aggressive"));
+  assert.ok(aggressivenessOf("llmlingua") <= aggressivenessOf("ultra"));
+  assert.ok(aggressivenessOf("llm") >= aggressivenessOf("llmlingua"));
+  assert.ok(aggressivenessOf("llm") <= aggressivenessOf("ultra"));
+});