diff --git a/changelog.d/fixes/12730-vendor-route-effort-values.md b/changelog.d/fixes/12730-vendor-route-effort-values.md
new file mode 100644
index 0000000000..4866681e06
--- /dev/null
+++ b/changelog.d/fixes/12730-vendor-route-effort-values.md
@@ -0,0 +1 @@
+- **fix(providers):** OpenAI-compatible model discovery now parses per-vendor-route `effort_values` (nested under `vendors.<vendor>.capabilities.reasoning` in `/v1/models`), intersected across vendor routes so a synced level is always honored on every route the model can land on; re-syncing a connection whose catalog declares this shape no longer silently resets the synced `supportedThinkingEfforts`/`defaultThinkingEffort` data ([#12730](https://github.com/diegosouzapw/OmniRoute/pull/12730))
diff --git a/src/lib/providerModels/modelDiscovery.ts b/src/lib/providerModels/modelDiscovery.ts
index bfe9131cf4..3f79163d36 100644
--- a/src/lib/providerModels/modelDiscovery.ts
+++ b/src/lib/providerModels/modelDiscovery.ts
@@ -99,6 +99,61 @@ const effortListSchema = z.array(z.unknown());
 const supportedReasoningLevelsSchema = z.object({ supported_reasoning_levels: z.unknown() });
 const thinkingLevelsSchema = z.object({ thinking: z.object({ levels: z.unknown() }).partial() });
 
+// Vendor-route catalogs (e.g. Merge Gateway's `/v1/models`) nest per-route
+// reasoning capability under `vendors.<vendor>.capabilities.reasoning` — the
+// route's accepted effort levels live in `effort_values` (docs.merge.dev,
+// "Effort levels per route"): the SAME canonical model lists different
+// vocabularies per vendor route, and a request naming an effort level is
+// served by a route that honors it when one exists (unpinned requests
+// self-narrow). So the safe synced vocabulary is the INTERSECTION across
+// vendor routes (a synced level must be honored on every route the model can
+// land on), not the union. A route without `effort_values` (absent or empty)
+// declares "no effort control" for that vendor and is excluded from the
+// intersection. Like the other shapes in this file, detection is shape-gated,
+// not provider-gated: a record that declares this structure is declaring its
+// effort vocabulary. Validate with Zod (Hard Rule #7); a malformed ENTRY is
+// dropped individually (never the whole route — discarding a route would
+// WIDEN the intersection, fail-open).
+const vendorRouteReasoningCapabilitySchema = z.object({
+  effort_values: z.array(z.unknown()).optional(),
+});
+const vendorRoutesSchema = z.record(z.string(), z.unknown());
+
+function parseVendorRouteEffortValues(record: JsonRecord): string[][] {
+  const vendorsParsed = vendorRoutesSchema.safeParse(record.vendors);
+  if (!vendorsParsed.success) return [];
+  const perVendor: string[][] = [];
+  for (const vendorValue of Object.values(vendorsParsed.data)) {
+    const vendorRecord = asRecord(vendorValue);
+    const reasoningParsed = vendorRouteReasoningCapabilitySchema.safeParse(
+      asRecord(vendorRecord.capabilities).reasoning
+    );
+    if (!reasoningParsed.success || !reasoningParsed.data) continue;
+    const efforts = Array.from(
+      new Set(
+        (reasoningParsed.data.effort_values ?? [])
+          .filter((effort): effort is string => typeof effort === "string" && effort.length > 0)
+          .map(normalizeSupportedEffort)
+      )
+    );
+    if (efforts.length > 0) perVendor.push(efforts);
+  }
+  return perVendor;
+}
+
+/**
+ * Intersect `effort_values` across the record's vendor routes. Returns
+ * `undefined` when no vendor route declares a list (shape not present);
+ * returns an EMPTY array when routes declare disjoint vocabularies — that
+ * emptiness is authoritative (no tier works on every route) and must not
+ * fall through to lower-precedence generic shapes.
+ */
+function vendorRouteSharedEfforts(record: JsonRecord): string[] | undefined {
+  const perVendor = parseVendorRouteEffortValues(record);
+  if (perVendor.length === 0) return undefined;
+  return perVendor.reduce((acc, efforts) => acc.filter((effort) => efforts.includes(effort)));
+}
+
 // Maps common upstream synonyms onto OmniRoute's canonical effort vocabulary
 // (`src/shared/reasoning/effortStandardization.ts`). Values already in
 // `CANONICAL_EFFORT_VALUES`, and any unrecognized provider-native tier (e.g.
@@ -167,9 +222,51 @@ export function detectDefaultThinkingEffort(record: JsonRecord): string | undefi
     const raw = parsed.data.default_effort;
     if (typeof raw === "string" && raw.length > 0) return normalizeSupportedEffort(raw);
   }
+  // Vendor-route fallback — only when the `vendors` shape IS the record's
+  // winning effort-vocabulary source. If a higher-precedence declared shape
+  // (`reasoning.supported_efforts`, `metadata.reasoning.supported_efforts`)
+  // produced a usable list, the record's default must never escape that
+  // winning list. Highest shared tier wins, ranked by the canonical order
+  // (vendor arrays are not guaranteed sorted).
+  const mergeShared = vendorRouteSharedEfforts(record);
+  if (mergeShared && mergeShared.length > 0 && !hasUsableDeclaredEffortList(record)) {
+    const ranked = mergeShared
+      .map((tier) => ({ tier, rank: CANONICAL_EFFORT_VALUES.indexOf(tier as never) }))
+      .filter((x) => x.rank >= 0)
+      .sort((a, b) => b.rank - a.rank);
+    if (ranked.length > 0) return ranked[0].tier;
+  }
   return undefined;
 }
 
+/**
+ * Whether a higher-precedence declared shape (the flat import field, or either
+ * #7694 nested `supported_efforts` shape) yields a usable tier list — the
+ * exact "usable" semantics the vocabulary detection applies (non-empty after
+ * filtering + normalization). Used to decide whether the Merge vendors shape
+ * is the record's winning vocabulary source for default-effort derivation.
+ */
+function hasUsableDeclaredEffortList(record: JsonRecord): boolean {
+  if (
+    Array.isArray(record.supportedThinkingEfforts) &&
+    record.supportedThinkingEfforts.some((e) => typeof e === "string" && e.length > 0)
+  ) {
+    return true;
+  }
+  for (const holder of [record.reasoning, asRecord(record.metadata).reasoning]) {
+    const shapeParsed = reasoningSupportedEffortsSchema.safeParse(holder);
+    if (!shapeParsed.success || !shapeParsed.data) continue;
+    const rawEfforts = shapeParsed.data.supported_efforts;
+    if (
+      Array.isArray(rawEfforts) &&
+      rawEfforts.some((e) => typeof e === "string" && e.length > 0)
+    ) {
+      return true;
+    }
+  }
+  return false;
+}
+
 /**
  * #7694: read the nested `record.reasoning.supported_efforts` shape and normalize each
  * tier onto the canonical vocabulary. Returns `undefined` (never throws) when the field
@@ -214,6 +311,19 @@ export function detectSupportedThinkingEfforts(record: JsonRecord): string[] | u
     }
   }
 
+  // Vendor-route catalogs: intersect `effort_values` across vendor routes.
+  // Placed after the flat import field handling (caller) and the
+  // #7694/#9160 nested shapes so those explicit per-model declarations keep
+  // precedence; runs before the generic `capabilities.effort_tiers` fallback
+  // because per-route vocabularies are strictly more specific than a flat
+  // tier list. An empty intersection (disjoint routes) is authoritative —
+  // nothing works on every route — and must not fall through to a generic
+  // tier list.
+  const mergeShared = vendorRouteSharedEfforts(record);
+  if (mergeShared !== undefined) {
+    return mergeShared.length > 0 ? mergeShared : [];
+  }
+
   // #9160: fall back to `capabilities.effort_tiers` before the legacy fields.
   // OmniRoute's own catalog surfaces effort tiers inside `capabilities.effort_tiers`,
   // which the existing `parseEffortList` already handles (string arrays).
@@ -247,7 +357,13 @@ function hasDeclaredEffortList(record: JsonRecord): boolean {
   if (Array.isArray(asRecord(record.reasoning).supported_efforts)) return true;
   if (Array.isArray(asRecord(record.capabilities).effort_tiers)) return true;
   if (Array.isArray(record.supported_reasoning_levels)) return true;
-  return Array.isArray(asRecord(record.thinking).levels);
+  if (Array.isArray(asRecord(record.thinking).levels)) return true;
+  // `vendors.<v>.capabilities.reasoning.effort_values` counts as a declared
+  // list so the fallback chain in `normalizeDiscoveredModels` stops here
+  // instead of applying provider-specific heuristics to a record that already
+  // declares its vocabulary explicitly (mirrors the other declared shapes:
+  // detect returning undefined means "declared, nothing usable").
+  return parseVendorRouteEffortValues(record).length > 0;
 }
 
 export function isAutoFetchModelsEnabled(providerSpecificData: unknown): boolean {
diff --git a/tests/unit/model-discovery-vendor-effort-values.test.ts b/tests/unit/model-discovery-vendor-effort-values.test.ts
new file mode 100644
index 0000000000..438e63d4c1
--- /dev/null
+++ b/tests/unit/model-discovery-vendor-effort-values.test.ts
@@ -0,0 +1,169 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import {
+  detectDefaultThinkingEffort,
+  detectSupportedThinkingEfforts,
+  normalizeDiscoveredModels,
+} from "@/lib/providerModels/modelDiscovery";
+
+// Vendor-route catalogs (e.g. Merge Gateway `/v1/models`) nest per-route reasoning capability under
+// `vendors.<vendor>.capabilities.reasoning` with the route's accepted effort
+// levels in `effort_values` (docs.merge.dev, "Effort levels per route"). The
+// same canonical model declares DIFFERENT vocabularies per vendor route, and
+// unpinned requests self-narrow to a route honoring the requested level when
+// one exists — so the synced vocabulary is the INTERSECTION across routes:
+// a level outside the intersection can be silently adjusted (or 400 on pinned
+// requests) on the route a request actually lands on.
+
+function mergeRecord(vendorEfforts: Record<string, string[] | undefined>) {
+  return {
+    id: "zai/glm-5.3-flash",
+    vendors: Object.fromEntries(
+      Object.entries(vendorEfforts).map(([vendor, efforts]) => [
+        vendor,
+        { capabilities: { reasoning: { effort_values: efforts } } },
+      ])
+    ),
+  };
+}
+
+test("vendor-route effort_values from a single vendor route is parsed into supportedThinkingEfforts", () => {
+  assert.deepEqual(detectSupportedThinkingEfforts(mergeRecord({ zai: ["low", "high", "max"] })), [
+    "low",
+    "high",
+    "max",
+  ]);
+});
+
+test("vendor-route effort_values from multiple vendor routes intersects across routes", () => {
+  assert.deepEqual(
+    detectSupportedThinkingEfforts(
+      mergeRecord({
+        zai: ["low", "high", "max"],
+        baseten: ["low", "medium", "high", "xhigh"],
+        makora: ["low", "high", "max"],
+      })
+    ),
+    ["low", "high"]
+  );
+});
+
+test("vendor routes without effort_values (no effort control) are excluded from the intersection", () => {
+  // fireworks: no effort_values key at all — "no effort control" per the docs.
+  const record = {
+    id: "moonshot/kimi-k3",
+    vendors: {
+      moonshot: { capabilities: { reasoning: { effort_values: ["low", "max"] } } },
+      fireworks: { capabilities: { reasoning: {} } },
+    },
+  };
+  assert.deepEqual(detectSupportedThinkingEfforts(record), ["low", "max"]);
+});
+
+test("a malformed vendor entry is dropped individually; no throw on garbage vendors", () => {
+  const record = {
+    id: "vendor/garbage",
+    vendors: {
+      good: { capabilities: { reasoning: { effort_values: ["low", "high"] } } },
+      bad: "not-an-object",
+      worse: { capabilities: { reasoning: { effort_values: 42 } } },
+    },
+  };
+  assert.doesNotThrow(() => detectSupportedThinkingEfforts(record));
+  assert.deepEqual(detectSupportedThinkingEfforts(record), ["low", "high"]);
+});
+
+test("no vendors key degrades to undefined (legacy behavior preserved)", () => {
+  assert.equal(detectSupportedThinkingEfforts({ id: "plain/model" }), undefined);
+  assert.equal(
+    detectSupportedThinkingEfforts({ id: "plain/model", vendors: "not-a-map" }),
+    undefined
+  );
+});
+
+test("effort synonyms are normalized inside effort_values", () => {
+  assert.deepEqual(detectSupportedThinkingEfforts(mergeRecord({ zai: ["low", "extra", "max"] })), [
+    "low",
+    "xhigh",
+    "max",
+  ]);
+});
+
+test("vendor-route defaultThinkingEffort falls back to the intersected vocabulary's highest tier (rank-based)", () => {
+  // max survives both routes → default max.
+  const withMax = mergeRecord({
+    zai: ["low", "high", "max"],
+    makora: ["none", "low", "high", "max"],
+  });
+  assert.equal(detectDefaultThinkingEffort(withMax), "max");
+  // max only on one route → the intersection's highest (high) is the default.
+  const withoutSharedMax = mergeRecord({
+    zai: ["low", "high", "max"],
+    baseten: ["low", "medium", "high"],
+  });
+  assert.equal(detectDefaultThinkingEffort(withoutSharedMax), "high");
+  // Vendor arrays are not guaranteed sorted: first-route order must not
+  // decide the default — the canonical rank does.
+  const unsorted = mergeRecord({
+    zai: ["max", "low", "high"],
+    makora: ["high", "low", "max"],
+  });
+  assert.equal(detectDefaultThinkingEffort(unsorted), "max");
+});
+
+test("vendor-route default is skipped when a higher-precedence declared shape wins the list", () => {
+  // Flat import field pins the vocabulary to ["low"]; the vendors
+  // intersection must not inject a default outside it.
+  const pinnedFlat = {
+    ...mergeRecord({ zai: ["low", "high", "max"] }),
+    supportedThinkingEfforts: ["low"],
+  };
+  assert.equal(detectDefaultThinkingEffort(pinnedFlat), undefined);
+  // Same for the nested #7694 shape winning the list.
+  const pinnedNested = {
+    ...mergeRecord({ zai: ["low", "high", "max"] }),
+    reasoning: { supported_efforts: ["low"] },
+  };
+  assert.equal(detectDefaultThinkingEffort(pinnedNested), undefined);
+});
+
+test("disjoint vendor vocabularies produce an authoritative empty list (no fall-through)", () => {
+  const disjoint = mergeRecord({ a: ["low"], b: ["high"] });
+  assert.deepEqual(detectSupportedThinkingEfforts(disjoint), []);
+  // And no default can be derived from an empty intersection.
+  assert.equal(detectDefaultThinkingEffort(disjoint), undefined);
+});
+
+test("a malformed entry inside effort_values is dropped individually, not the whole route", () => {
+  const record = {
+    id: "vendor/partial",
+    vendors: {
+      a: { capabilities: { reasoning: { effort_values: ["low", 42, "high"] } } },
+      b: { capabilities: { reasoning: { effort_values: ["low", "high", "max"] } } },
+    },
+  };
+  assert.deepEqual(detectSupportedThinkingEfforts(record), ["low", "high"]);
+});
+
+test("explicit default_effort keeps precedence over the vendor-route fallback", () => {
+  const record = {
+    ...mergeRecord({ zai: ["low", "high", "max"] }),
+    reasoning: { default_effort: "high" },
+  };
+  assert.equal(detectDefaultThinkingEffort(record), "high");
+});
+
+test("normalizeDiscoveredModels threads the intersected vendor-route vocabulary into synced models", () => {
+  const models = normalizeDiscoveredModels([
+    {
+      id: "zai/glm-5.3-flash",
+      vendors: {
+        zai: { capabilities: { reasoning: { effort_values: ["low", "high", "max"] } } },
+        baseten: { capabilities: { reasoning: { effort_values: ["low", "high", "xhigh"] } } },
+      },
+    },
+  ]);
+  const synced = models.find((model) => model.id === "zai/glm-5.3-flash");
+  assert.deepEqual(synced?.supportedThinkingEfforts, ["low", "high"]);
+  assert.equal(synced?.defaultThinkingEffort, "high");
+});