diff --git a/changelog.d/fixes/12180-embedding-lazy-probe.md b/changelog.d/fixes/12180-embedding-lazy-probe.md
new file mode 100644
index 0000000000..18a3752be1
--- /dev/null
+++ b/changelog.d/fixes/12180-embedding-lazy-probe.md
@@ -0,0 +1,5 @@
+- **fix(memory):** self-hosted embedding endpoints now vectorize — the vector width is
+  measured from the first embedding that comes back instead of being read from a registry
+  that cannot describe them, so `vec_memories` is created and memories stop piling up
+  unvectorized behind a green health check
+  ([#12180](https://github.com/diegosouzapw/OmniRoute/pull/12180)) — thanks @kanade-hoshino
diff --git a/src/lib/memory/embedding/index.ts b/src/lib/memory/embedding/index.ts
index 8205b75524..805a8a5905 100644
--- a/src/lib/memory/embedding/index.ts
+++ b/src/lib/memory/embedding/index.ts
@@ -52,6 +52,39 @@ function resolveRemoteDimensions(model: string): number | null {
   return typeof dim === "number" ? dim : null;
 }
 
+/**
+ * Fill in the vector width the lazy probe was waiting for.
+ *
+ * `dimensions` is null for every source the hard-coded registry does not
+ * describe — a self-hosted endpoint by definition — and the only thing that can
+ * answer it is an embedding that has actually come back. Callers that hold one
+ * pass its length here; the signature is rebuilt the same way the resolution
+ * built it, so reindex detection still sees a model change as a change. (#12154)
+ */
+export function withMeasuredDimensions(
+  resolution: EmbeddingResolution,
+  dimensions: number
+): EmbeddingResolution {
+  if (
+    resolution.dimensions !== null ||
+    !resolution.source ||
+    !Number.isInteger(dimensions) ||
+    dimensions <= 0
+  ) {
+    return resolution;
+  }
+  return {
+    ...resolution,
+    dimensions,
+    signature: makeSignature(
+      resolution.source,
+      resolution.identity ?? resolution.model,
+      dimensions
+    ),
+    reason: `${resolution.reason} [dim=${dimensions} measured]`,
+  };
+}
+
 /** Build the remote EmbeddingResolution used by both explicit + auto paths. */
 function remoteResolution(model: string, reasonPrefix: string): EmbeddingResolution {
   const dimensions = resolveRemoteDimensions(model);
diff --git a/src/lib/memory/reindex.ts b/src/lib/memory/reindex.ts
index 8d459edaa7..0f7e8b7b42 100644
--- a/src/lib/memory/reindex.ts
+++ b/src/lib/memory/reindex.ts
@@ -8,7 +8,8 @@ import {
   countMemoryReindexPending,
   markMemoryNeedsReindex,
 } from "@/lib/db/memoryVec";
-import { resolveEmbeddingSource, embed } from "./embedding";
+import { resolveEmbeddingSource, embed, withMeasuredDimensions } from "./embedding";
+import type { EmbeddingResolution } from "./embedding/types";
 import { getVectorStore } from "./vectorStore";
 import { getMemorySettings } from "./settings";
 import { logger } from "../../../open-sse/utils/logger.ts";
@@ -16,6 +17,97 @@ import { sanitizeErrorMessage } from "../../../open-sse/utils/error.ts";
 
 const log = logger("MEMORY_REINDEX");
 
+type ReindexItem = { id: string; content: string; key: string };
+type MemorySettings = Awaited<ReturnType<typeof getMemorySettings>>;
+type VectorStore = NonNullable<ReturnType<typeof getVectorStore>>;
+
+function errMsg(err: unknown): string {
+  return sanitizeErrorMessage(err instanceof Error ? err.message : String(err));
+}
+
+/**
+ * Nothing but a returned embedding can supply the vector width for a source the
+ * registry does not describe. Spend one embed to measure it and reuse that
+ * vector rather than paying for it twice (#12154).
+ */
+async function measureUnknownWidth(
+  resolution: EmbeddingResolution,
+  probeItem: ReindexItem | undefined,
+  settings: MemorySettings
+): Promise<{ effective: EmbeddingResolution; probed: Map<string, Float32Array> }> {
+  const probed = new Map<string, Float32Array>();
+  if (!probeItem) {
+    return { effective: resolution, probed };
+  }
+  const probe = await embed(probeItem.content, settings);
+  if (!("vector" in probe)) {
+    return { effective: resolution, probed };
+  }
+  probed.set(probeItem.id, probe.vector);
+  return {
+    effective: withMeasuredDimensions(resolution, probe.vector.length),
+    probed,
+  };
+}
+
+/**
+ * ensureReady() returns `{ ready: false }` (without throwing) when dimensions
+ * are still unknown — abort so we don't burn embed credits upserting into a
+ * missing `vec_memories` table (#8074).
+ */
+async function ensureReindexStoreReady(
+  vec: VectorStore,
+  effective: EmbeddingResolution,
+  resolution: EmbeddingResolution,
+  pending: number
+): Promise<boolean> {
+  try {
+    const ready = await vec.ensureReady(effective);
+    if (ready.ready) return true;
+    log.warn("memory.reindex.ensure_ready.skipped", {
+      reason: ready.reason,
+      pending,
+      model: resolution.model,
+      dimensions: resolution.dimensions,
+    });
+    return false;
+  } catch (err: unknown) {
+    log.warn("memory.reindex.ensure_ready.fail", { error: errMsg(err) });
+    return false;
+  }
+}
+
+async function reindexOneItem(
+  item: ReindexItem,
+  settings: MemorySettings,
+  vec: VectorStore,
+  probed: Map<string, Float32Array>
+): Promise<"processed" | "error"> {
+  try {
+    const reusable = probed.get(item.id);
+    const embeddingResult = reusable ? { vector: reusable } : await embed(item.content, settings);
+
+    if (!("vector" in embeddingResult)) {
+      log.warn("memory.reindex.embed.fail", {
+        id: item.id,
+        reason: embeddingResult.reason,
+        message: sanitizeErrorMessage(embeddingResult.message),
+      });
+      return "error";
+    }
+
+    await vec.upsertVector(item.id, embeddingResult.vector);
+    markMemoryNeedsReindex(item.id, false);
+    return "processed";
+  } catch (err: unknown) {
+    log.warn("memory.reindex.item.fail", {
+      id: item.id,
+      error: errMsg(err),
+    });
+    return "error";
+  }
+}
+
 /**
  * Process up to `limit` memories that are marked needs_reindex=1.
  * Generates embedding + upserts into sqlite-vec for each.
@@ -30,7 +122,6 @@ export async function runReindexBatch(limit = 100): Promise<{ processed: number;
     return { processed: 0, errors: 0 };
   }
 
-  // Resolve embedding source and vector store once for the whole batch
   const settings = await getMemorySettings();
   const resolution = resolveEmbeddingSource(settings);
 
@@ -48,25 +139,11 @@ export async function runReindexBatch(limit = 100): Promise<{ processed: number;
     return { processed: 0, errors: 0 };
   }
 
-  // Ensure the vector table is ready before processing. ensureReady() returns
-  // `{ ready: false }` (without throwing) when dimensions are still unknown —
-  // abort the batch in that case so we don't burn embed credits upserting into
-  // a missing `vec_memories` table (#8074).
-  try {
-    const ready = await vec.ensureReady(resolution);
-    if (!ready.ready) {
-      log.warn("memory.reindex.ensure_ready.skipped", {
-        reason: ready.reason,
-        pending: queue.length,
-        model: resolution.model,
-        dimensions: resolution.dimensions,
-      });
-      return { processed: 0, errors: 0 };
-    }
-  } catch (err: unknown) {
-    log.warn("memory.reindex.ensure_ready.fail", {
-      error: sanitizeErrorMessage(err instanceof Error ? err.message : String(err)),
-    });
+  const probeItem = resolution.dimensions === null ? queue[0] : undefined;
+  const { effective, probed } = await measureUnknownWidth(resolution, probeItem, settings);
+
+  const ready = await ensureReindexStoreReady(vec, effective, resolution, queue.length);
+  if (!ready) {
     return { processed: 0, errors: 0 };
   }
 
@@ -74,29 +151,9 @@ export async function runReindexBatch(limit = 100): Promise<{ processed: number;
   let errors = 0;
 
   for (const item of queue) {
-    try {
-      const embeddingResult = await embed(item.content, settings);
-
-      if (!("vector" in embeddingResult)) {
-        log.warn("memory.reindex.embed.fail", {
-          id: item.id,
-          reason: embeddingResult.reason,
-          message: sanitizeErrorMessage(embeddingResult.message),
-        });
-        errors++;
-        continue;
-      }
-
-      await vec.upsertVector(item.id, embeddingResult.vector);
-      markMemoryNeedsReindex(item.id, false);
-      processed++;
-    } catch (err: unknown) {
-      log.warn("memory.reindex.item.fail", {
-        id: item.id,
-        error: sanitizeErrorMessage(err instanceof Error ? err.message : String(err)),
-      });
-      errors++;
-    }
+    const outcome = await reindexOneItem(item, settings, vec, probed);
+    if (outcome === "processed") processed++;
+    else errors++;
   }
 
   log.info("memory.reindex.batch.complete", { processed, errors, batchSize: queue.length });
diff --git a/src/lib/memory/store.ts b/src/lib/memory/store.ts
index 2ddb457d45..a186f8ec47 100644
--- a/src/lib/memory/store.ts
+++ b/src/lib/memory/store.ts
@@ -7,7 +7,7 @@ import { upsertSemanticMemoryPoint, deleteSemanticMemoryPoint } from "./qdrant";
 import { Memory, MemoryType } from "./types";
 import { logger } from "../../../open-sse/utils/logger.ts";
 import { sanitizeErrorMessage } from "../../../open-sse/utils/error.ts";
-import { resolveEmbeddingSource, embed } from "./embedding";
+import { resolveEmbeddingSource, embed, withMeasuredDimensions } from "./embedding";
 import { getVectorStore } from "./vectorStore";
 import { getMemorySettings } from "./settings";
 import { markMemoryNeedsReindex } from "@/lib/db/memoryVec";
@@ -154,7 +154,18 @@ function scheduleVectorUpsert(id: string, content: string): void {
         return;
       }
 
-      await vec.ensureReady(resolution);
+      // The vector in hand is the lazy probe the resolution is waiting for: the
+      // registry has no width for a self-hosted endpoint, so without this
+      // ensureReady() never creates vec_memories and every upsert below fails
+      // into the catch, leaving the memory stored but never vectorized (#12154).
+      const ready = await vec.ensureReady(
+        withMeasuredDimensions(resolution, embeddingResult.vector.length)
+      );
+      if (!ready.ready) {
+        log.warn("memory.vec.ensure_ready.skipped", { id, reason: ready.reason });
+        safeMarkNeedsReindex(id, true);
+        return;
+      }
       await vec.upsertVector(id, embeddingResult.vector);
       safeMarkNeedsReindex(id, false);
     } catch (err: unknown) {
diff --git a/tests/unit/memory-vec-lazy-probe-12154.test.ts b/tests/unit/memory-vec-lazy-probe-12154.test.ts
new file mode 100644
index 0000000000..5f74ad20fc
--- /dev/null
+++ b/tests/unit/memory-vec-lazy-probe-12154.test.ts
@@ -0,0 +1,77 @@
+/**
+ * #12154 — a self-hosted embedding endpoint never got `vec_memories` created,
+ * so memories were stored but never vectorized while health stayed green.
+ *
+ * `resolveEmbeddingSource` returns `dimensions: null` for any source the
+ * hard-coded registry does not describe, and a self-hosted endpoint is by
+ * definition absent from it. Both write paths then deadlocked: the vector store
+ * refuses to create the table without a width, and the width can only come from
+ * an embedding that has actually come back.
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+
+const { withMeasuredDimensions } = await import("../../src/lib/memory/embedding/index.ts");
+
+function resolution(overrides = {}) {
+  return {
+    source: "remote",
+    model: "memory-custom/Qwen3-Embedding-0.6B",
+    dimensions: null,
+    identity: "http://tei.internal:8080|Qwen3-Embedding-0.6B",
+    signature: "remote:http://tei.internal:8080|Qwen3-Embedding-0.6B:null",
+    reason: "custom remote provider configured (dim=unknown, will probe at embed time)",
+    ...overrides,
+  };
+}
+
+test("a measured width fills in the pending lazy probe", () => {
+  const filled = withMeasuredDimensions(resolution(), 1024);
+  assert.equal(filled.dimensions, 1024);
+  assert.match(filled.reason, /dim=1024 measured/);
+});
+
+test("the signature keeps its identity and gains the width", () => {
+  const filled = withMeasuredDimensions(resolution(), 1024);
+  // Identity, not model: the same model id can exist at several custom endpoints,
+  // and the resolution built its signature that way too.
+  assert.equal(filled.signature, "remote:http://tei.internal:8080|Qwen3-Embedding-0.6B:1024");
+});
+
+test("a resolution with no identity signs by model", () => {
+  const filled = withMeasuredDimensions(
+    resolution({
+      identity: undefined,
+      model: "openai/text-embedding-3-small",
+      signature: "remote:openai/text-embedding-3-small:null",
+    }),
+    1536
+  );
+  assert.equal(filled.signature, "remote:openai/text-embedding-3-small:1536");
+});
+
+test("a width the registry already knows is never overwritten", () => {
+  const known = resolution({ dimensions: 1536, signature: "remote:openai/x:1536" });
+  assert.equal(withMeasuredDimensions(known, 1024), known);
+});
+
+test("a nonsense measurement is ignored rather than written into the signature", () => {
+  const pending = resolution();
+  for (const bad of [0, -1, 1.5, Number.NaN]) {
+    assert.equal(withMeasuredDimensions(pending, bad), pending, `width ${bad}`);
+  }
+});
+
+test("a resolution with no source stays unusable", () => {
+  const none = resolution({ source: null, model: null, signature: "null:null:null" });
+  assert.equal(withMeasuredDimensions(none, 1024), none);
+});
+
+test("two endpoints serving the same model id do not share a signature", () => {
+  const a = withMeasuredDimensions(resolution(), 1024);
+  const b = withMeasuredDimensions(
+    resolution({ identity: "http://other.internal:8080|Qwen3-Embedding-0.6B" }),
+    1024
+  );
+  assert.notEqual(a.signature, b.signature);
+});