fix(compression): unknown engine names surface validationErrors instead of silently falling back (#6485) (#6506)

Surface validationErrors for unknown stacked compression engines. Integrated into release/v3.8.46 with a TDD regression.

CHANGELOG.md

@@ -31,6 +31,7 @@
 
 ### 🐛 Bug Fixes
 
+- **fix(compression):** a stacked-pipeline step naming an unregistered engine now surfaces a `validationErrors` entry instead of silently no-op'ing, so misconfigured pipelines are visible in the preview API (#6506 — thanks @chirag127).
 - **feat(usage):** add a **Codex reset-credit redemption** flow to the Provider Limits UI — a `useCodexResetCreditRedemption` hook + `/api/usage/codex-reset-credit` route + `codexResetCredits` lib let you redeem banked Codex reset credits from the quota card. Regression guard: `tests/unit/codex-reset-credits.test.ts`. (thanks @JxnLexn)
 - **feat(glm):** add **team-plan quota settings** for `glm-cn` connections — a dedicated `GlmTeamQuotaFields` form section (team quota id / limits) threaded through the Add/Edit connection modals, persisted via `providerSpecificData`, with the GLM usage service reading the team quota. Regression guards: `tests/unit/glm-team-quota.test.ts`, `provider-specific-data-schema.test.ts`. (thanks @hao3039032)
 - **feat(providers):** add **TinyFish** web-fetch/search support — a `tinyfish-fetch` executor + `/v1/web/fetch` route + MCP web-fetch tool, registered as a specialty-media provider with request-validation and a search-provider catalog entry. Regression guards: `tests/unit/executor-tinyfish-fetch.test.ts`, `web-fetch-handler.test.ts`, `mcp-web-fetch-tool.test.ts`, `provider-validation-tinyfish.test.ts`. (thanks @dtybnrj)

open-sse/services/compression/strategySelector.ts

@@ -839,7 +839,10 @@ function runStackedCompression(
 
   for (const step of steps) {
     const engine = getCompressionEngine(step.engine);
-    if (!engine) continue;
+    if (!engine) {
+      acc.validationErrors.add(`Unknown compression engine: "${step.engine}"`);
+      continue;
+    }
     // Respect the registry enabled flag: a step naming a disabled engine is skipped, so an
     // operator can turn an engine off (setEngineEnabled) without editing every pipeline.
     if (getEngineEntry(step.engine)?.enabled === false) continue;
@@ -939,7 +942,10 @@ async function runStackedCompressionAsync(
 
   for (const step of steps) {
     const engine = getCompressionEngine(step.engine);
-    if (!engine) continue;
+    if (!engine) {
+      acc.validationErrors.add(`Unknown compression engine: "${step.engine}"`);
+      continue;
+    }
     // Respect the registry enabled flag (same as the sync loop) — keep both in lockstep.
     if (getEngineEntry(step.engine)?.enabled === false) continue;
     // T02: skip an engine whose breaker is OPEN (verbatim body kept — fail-open). Lockstep w/ sync.

tests/unit/compression-unknown-engine-validation-6485.test.ts

@@ -0,0 +1,45 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { applyStackedCompression } from "@omniroute/open-sse/services/compression/strategySelector";
+
+// #6485 — a stacked pipeline step naming an engine which is not registered used to
+// silently `continue`, so the caller had no signal that a configured step was a no-op.
+// The fix records a `validationErrors` entry for each unknown engine while still
+// fail-open (the request is not aborted). These tests pin that contract.
+//
+// Note: the unknown-engine path is only reachable via OBJECT steps ({ engine: "…" }).
+// Bare-string steps are coerced to the "caveman" fallback by normalizePipelineStep,
+// so they can never name an unknown engine.
+
+const body = {
+  messages: [
+    { role: "user", content: "hello ".repeat(200) },
+    { role: "assistant", content: "world ".repeat(200) },
+  ],
+};
+
+test("unknown compression engine surfaces a validationErrors entry (sync)", () => {
+  const result = applyStackedCompression(body, [{ engine: "definitely-not-a-real-engine" }]);
+  const errors = result.stats?.validationErrors ?? [];
+  assert.ok(
+    errors.some((e) => e.includes("definitely-not-a-real-engine")),
+    `expected a validationErrors entry naming the unknown engine, got: ${JSON.stringify(errors)}`
+  );
+});
+
+test("known + unknown mixed pipeline reports only the unknown engine (sync)", () => {
+  const result = applyStackedCompression(body, [
+    { engine: "session-dedup" },
+    { engine: "ghost-engine" },
+  ]);
+  const errors = result.stats?.validationErrors ?? [];
+  assert.ok(
+    errors.some((e) => e.includes("ghost-engine")),
+    `expected the unknown engine to be reported, got: ${JSON.stringify(errors)}`
+  );
+  assert.ok(
+    !errors.some((e) => e.includes("session-dedup")),
+    "a real engine must not be reported as unknown"
+  );
+});