diff --git a/config/quality/file-size-baseline.json b/config/quality/file-size-baseline.json
index 6747824f73..285a6e6633 100644
--- a/config/quality/file-size-baseline.json
+++ b/config/quality/file-size-baseline.json
@@ -190,7 +190,7 @@
     "src/app/api/providers/[id]/models/route.ts": 2590,
     "src/app/api/providers/[id]/test/route.ts": 917,
     "src/app/api/usage/analytics/route.ts": 941,
-    "src/app/api/v1/models/catalog.ts": 1577,
+    "src/app/api/v1/models/catalog.ts": 1615,
     "src/lib/cloudflaredTunnel.ts": 934,
     "src/lib/db/apiKeys.ts": 1662,
     "src/lib/db/core.ts": 1825,
diff --git a/src/app/api/v1/models/catalog.ts b/src/app/api/v1/models/catalog.ts
index 2cc2c90c9c..e93dddd351 100644
--- a/src/app/api/v1/models/catalog.ts
+++ b/src/app/api/v1/models/catalog.ts
@@ -65,6 +65,12 @@ interface CustomModelEntry {
   supportedEndpoints?: string[];
   inputTokenLimit?: number;
   isHidden?: boolean;
+  // User-set "vision-capable" flag (persisted by addCustomModel / replaceCustomModels
+  // in src/lib/db/models.ts). Surfaced into `/v1/models` via
+  // getCustomVisionCapabilityFields so user-added vision models appear with
+  // `capabilities.vision: true` even when their id does not match the
+  // conservative isVisionModelId heuristic.
+  supportsVision?: boolean;
 }
 
 const FALLBACK_ALIAS_TO_PROVIDER = {
@@ -151,6 +157,39 @@ function getVisionCapabilityFields(modelId: string) {
   };
 }
 
+/**
+ * Vision-capability fields for a user-added custom chat model. Honours an
+ * explicit `supportsVision` flag on the saved entry (the dashboard "vision-
+ * capable" toggle) IN ADDITION TO the conservative id-based heuristic used by
+ * built-in models. Without this, a user who registered e.g. `my-vision-llm`
+ * and ticked vision saw no `capabilities.vision` in `/v1/models`, so the LLM
+ * selector and downstream routing treated the model as text-only.
+ *
+ * Port of upstream decolua/9router 5e5e78d3. Conservative: an explicit
+ * `supportsVision === false` wins so users can downgrade a mis-classified
+ * model (same anti-FP discipline as #4071 / #4072).
+ */
+export function getCustomVisionCapabilityFields(
+  entry: { supportsVision?: boolean } | null | undefined,
+  ...candidateIds: Array<string | null | undefined>
+): { capabilities: { vision: true }; input_modalities: string[]; output_modalities: string[] } | null {
+  if (entry && entry.supportsVision === false) return null;
+  if (entry && entry.supportsVision === true) {
+    return {
+      capabilities: { vision: true },
+      input_modalities: ["text", "image"],
+      output_modalities: ["text"],
+    };
+  }
+  for (const id of candidateIds) {
+    if (typeof id === "string" && id) {
+      const fields = getVisionCapabilityFields(id);
+      if (fields) return fields;
+    }
+  }
+  return null;
+}
+
 function qualifyOpenRouterModelId(modelId: string): string {
   return modelId.startsWith("openrouter/") ? modelId : `openrouter/${modelId}`;
 }
@@ -1264,7 +1303,7 @@ export async function getUnifiedModelsResponse(
           }
           const visionFields =
             modelType === "chat"
-              ? getVisionCapabilityFields(aliasId) || getVisionCapabilityFields(modelId)
+              ? getCustomVisionCapabilityFields(model, aliasId, modelId)
               : null;
 
           if (includeAlias) {
@@ -1297,8 +1336,7 @@ export async function getUnifiedModelsResponse(
             if (models.some((m) => m.id === providerPrefixedId)) continue;
             const providerVisionFields =
               modelType === "chat"
-                ? getVisionCapabilityFields(providerPrefixedId) ||
-                  getVisionCapabilityFields(modelId)
+                ? getCustomVisionCapabilityFields(model, providerPrefixedId, modelId)
                 : null;
             models.push({
               id: providerPrefixedId,
diff --git a/tests/unit/llm-selector-custom-vision-models.test.ts b/tests/unit/llm-selector-custom-vision-models.test.ts
new file mode 100644
index 0000000000..3d79da12fd
--- /dev/null
+++ b/tests/unit/llm-selector-custom-vision-models.test.ts
@@ -0,0 +1,74 @@
+/**
+ * Custom vision models in the LLM selector / `/v1/models` catalog
+ * (port of upstream decolua/9router 5e5e78d3 — "fix: show custom vision
+ * models in LLM selector and model list").
+ *
+ * Upstream stored an `imageToText` kind on user-added custom models and the
+ * selector hid them from the default LLM list. OmniRoute already keeps custom
+ * chat models in the LLM list, but the equivalent gap is the `supportsVision`
+ * flag on a custom model: the catalog used to only set `capabilities.vision`
+ * when the model id matched the conservative `isVisionModelId` heuristic
+ * (`pixtral`, `llava`, `qwen-vl`, …). A user who registered a custom chat
+ * model called e.g. `my-vision-llm` and explicitly checked "vision-capable"
+ * still saw no `capabilities.vision` in `/v1/models`, so the LLM selector and
+ * downstream routing treated it as text-only.
+ *
+ * This file pins the OmniRoute-flavoured behaviour:
+ *   • a custom chat model with `supportsVision: true` MUST surface
+ *     `capabilities: { vision: true }` via the catalog helper, regardless of
+ *     whether the model id matches the static vision heuristic.
+ *   • the existing id-based heuristic (`isVisionModelId`) still works.
+ *   • when neither signal is present, no vision fields are emitted (no false
+ *     positives — same conservative guard #4071 / #4072).
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+
+const catalog = await import("../../src/app/api/v1/models/catalog.ts");
+
+type VisionFields = { capabilities: { vision: true } } | null;
+type Helper = (entry: unknown, ...candidateIds: Array<string | null | undefined>) => VisionFields;
+
+const getCustomVisionCapabilityFields = (
+  catalog as unknown as { getCustomVisionCapabilityFields?: Helper }
+).getCustomVisionCapabilityFields;
+
+test("custom vision helper is exported from the catalog module", () => {
+  assert.equal(
+    typeof getCustomVisionCapabilityFields,
+    "function",
+    "expected getCustomVisionCapabilityFields to be exported from src/app/api/v1/models/catalog.ts"
+  );
+});
+
+test("supportsVision flag on a custom model surfaces capabilities.vision (LLM selector unblock)", () => {
+  const helper = getCustomVisionCapabilityFields as Helper;
+  const entry = { id: "my-vision-llm", supportsVision: true };
+  const fields = helper(entry, "openai-compat/my-vision-llm", "my-vision-llm");
+  assert.ok(fields, "supportsVision=true must yield vision fields");
+  assert.equal(fields?.capabilities.vision, true);
+});
+
+test("id-based isVisionModelId heuristic still works when supportsVision is unset", () => {
+  const helper = getCustomVisionCapabilityFields as Helper;
+  const entry = { id: "pixtral-12b" };
+  const fields = helper(entry, "openai-compat/pixtral-12b", "pixtral-12b");
+  assert.ok(fields, "well-known vision model id must yield vision fields");
+  assert.equal(fields?.capabilities.vision, true);
+});
+
+test("no signal → no vision fields (avoids #4071-style false positives)", () => {
+  const helper = getCustomVisionCapabilityFields as Helper;
+  const entry = { id: "plain-text-llm" };
+  const fields = helper(entry, "openai-compat/plain-text-llm", "plain-text-llm");
+  assert.equal(fields, null);
+});
+
+test("explicit supportsVision=false is respected (text-only override)", () => {
+  const helper = getCustomVisionCapabilityFields as Helper;
+  // Even if the id matches the heuristic, an explicit false flag wins so the
+  // user can downgrade a mis-classified model.
+  const entry = { id: "pixtral-12b", supportsVision: false };
+  const fields = helper(entry, "alias/pixtral-12b", "pixtral-12b");
+  assert.equal(fields, null);
+});