diff --git a/src/lib/inference/local.test.ts b/src/lib/inference/local.test.ts
index 5c6d2fdcd36..3dac656c7b7 100644
--- a/src/lib/inference/local.test.ts
+++ b/src/lib/inference/local.test.ts
@@ -619,21 +619,127 @@ describe("local inference helpers", () => {
   });
 
   it("fails ollama model validation when Ollama returns an error payload", () => {
-    const result = validateOllamaModel("gabegoodhart/minimax-m2.1:latest", () =>
-      JSON.stringify({ error: "model requires more system memory" }),
-    );
+    const payload = JSON.stringify({ error: "model requires more system memory" });
+    const captureEx = () => ({ stdout: payload, exitCode: 0, timedOut: false });
+    const result = validateOllamaModel("gabegoodhart/minimax-m2.1:latest", () => payload, undefined, captureEx);
     expect(result.ok).toBe(false);
     expect(result.message).toMatch(/requires more system memory/);
   });
 
   it("passes ollama model validation when the probe returns a normal payload", () => {
-    const result = validateOllamaModel("nemotron-3-nano:30b", () =>
-      JSON.stringify({ model: "nemotron-3-nano:30b", response: "hello", done: true }),
-    );
+    const payload = JSON.stringify({ model: "nemotron-3-nano:30b", response: "hello", done: true });
+    const captureEx = () => ({ stdout: payload, exitCode: 0, timedOut: false });
+    const result = validateOllamaModel("nemotron-3-nano:30b", () => payload, undefined, captureEx);
     expect(result).toEqual({ ok: true });
   });
 
   it("treats non-JSON probe output as success once the model responds", () => {
-    expect(validateOllamaModel("nemotron-3-nano:30b", () => "ok")).toEqual({ ok: true });
+    const captureEx = () => ({ stdout: "ok", exitCode: 0, timedOut: false });
+    expect(validateOllamaModel("nemotron-3-nano:30b", () => "ok", undefined, captureEx)).toEqual({ ok: true });
+  });
+
+  it("passes ollama memory validation when total RAM covers the model on unified-memory hosts", () => {
+    // Simulate Spark: Ollama returns available-RAM OOM error, but total RAM is 128 GB.
+    const freeOutput = "               total        used        free\nMem:          131072       120000       1000";
+    const oomPayload = JSON.stringify({ error: "model requires more system memory (21.2 GiB) than is available (5.6 GiB)" });
+    const captureEx = () => ({ stdout: oomPayload, exitCode: 0, timedOut: false });
+    const capture = (cmd: string | string[]) => {
+      const c = Array.isArray(cmd) ? cmd.join(" ") : cmd;
+      if (c.includes("free")) return freeOutput;
+      return oomPayload;
+    };
+    const result = validateOllamaModel("nemotron-3-nano:30b", capture, () => true, captureEx);
+    expect(result.ok).toBe(true);
+  });
+
+  it("fails ollama memory validation when total RAM is also insufficient", () => {
+    const freeOutput = "               total        used        free\nMem:           16384        15000        100";
+    const oomPayload = JSON.stringify({ error: "model requires more system memory (21.2 GiB) than is available (5.6 GiB)" });
+    const captureEx = () => ({ stdout: oomPayload, exitCode: 0, timedOut: false });
+    const capture = (cmd: string | string[]) => {
+      const c = Array.isArray(cmd) ? cmd.join(" ") : cmd;
+      if (c.includes("free")) return freeOutput;
+      return oomPayload;
+    };
+    const result = validateOllamaModel("nemotron-3-nano:30b", capture, () => true, captureEx);
+    expect(result.ok).toBe(false);
+    expect(result.message).toMatch(/failed the local probe/);
   });
+
+  it("does not bypass OOM error on non-Spark hosts even with large total RAM", () => {
+    const freeOutput = "               total        used        free\nMem:          262144       250000       1000";
+    const oomPayload = JSON.stringify({ error: "model requires more system memory (21.2 GiB) than is available (5.6 GiB)" });
+    const captureEx = () => ({ stdout: oomPayload, exitCode: 0, timedOut: false });
+    const capture = (cmd: string | string[]) => {
+      const c = Array.isArray(cmd) ? cmd.join(" ") : cmd;
+      if (c.includes("free")) return freeOutput;
+      return oomPayload;
+    };
+    const result = validateOllamaModel("nemotron-3-nano:30b", capture, () => false, captureEx);
+    expect(result.ok).toBe(false);
+    expect(result.message).toMatch(/failed the local probe/);
+  });
+
+  it("retries with extended timeout when first probe returns empty (slow model load on unified-memory host)", () => {
+    // Simulate Spark: first probe times out (curl exit 28), retry with 300s timeout succeeds.
+    const commands: string[] = [];
+    let captureExCallCount = 0;
+    const captureEx = (cmd: string[]) => {
+      captureExCallCount++;
+      commands.push(cmd.join(" "));
+      // First call: initial probe times out; second call: 300s retry succeeds.
+      if (captureExCallCount === 1) return { stdout: "", exitCode: 28, timedOut: true };
+      return { stdout: JSON.stringify({ response: "Hi" }), exitCode: 0, timedOut: false };
+    };
+    const result = validateOllamaModel("nemotron-3-nano:30b", () => "", () => true, captureEx);
+    expect(result.ok).toBe(true);
+    expect(captureExCallCount).toBe(2);
+    expect(commands[1]).toMatch(/--max-time.*300|300.*--max-time/);
+  });
+
+  it("does not retry on non-Spark hosts when first probe returns empty", () => {
+    let callCount = 0;
+    const captureEx = () => { callCount++; return { stdout: "", exitCode: 7, timedOut: false }; };
+    const result = validateOllamaModel("nemotron-3-nano:30b", () => "", () => false, captureEx);
+    expect(result.ok).toBe(false);
+    expect(callCount).toBe(1);
+  });
+
+  it("does not retry on Spark when probe fails fast (connection refused, not a timeout)", () => {
+    // exit code 7 = curl connection refused — should surface immediately, not stall 300s.
+    let callCount = 0;
+    const captureEx = () => { callCount++; return { stdout: "", exitCode: 7, timedOut: false }; };
+    const result = validateOllamaModel("nemotron-3-nano:30b", () => "", () => true, captureEx);
+    expect(result.ok).toBe(false);
+    expect(callCount).toBe(1);
+    expect(result.message).toMatch(/did not answer the local probe in time/);
+  });
+
+  it("fails when both probe attempts return empty (model truly unhealthy or too slow)", () => {
+    const captureEx = () => ({ stdout: "", exitCode: 28, timedOut: true });
+    const result = validateOllamaModel("nemotron-3-nano:30b", () => "", () => true, captureEx);
+    expect(result.ok).toBe(false);
+    expect(result.message).toMatch(/did not answer the local probe in time/);
+  });
+
+  it("passes when first probe times out then retry returns OOM error but total RAM is sufficient", () => {
+    // Composite: mode 2 (first probe timeout) + mode 1 (retry returns OOM error).
+    const freeOutput = "               total        used        free\nMem:          131072       120000       1000";
+    const oomPayload = JSON.stringify({ error: "model requires more system memory (21.2 GiB) than is available (5.6 GiB)" });
+    let captureExCallCount = 0;
+    const captureEx = (cmd: string[]) => {
+      captureExCallCount++;
+      // First call: initial probe times out; second call: 300s retry returns OOM error.
+      if (captureExCallCount === 1) return { stdout: "", exitCode: 28, timedOut: true };
+      return { stdout: oomPayload, exitCode: 0, timedOut: false };
+    };
+    const capture = (cmd: string | string[]) => {
+      const c = Array.isArray(cmd) ? cmd.join(" ") : cmd;
+      if (c.includes("free")) return freeOutput;
+      return "";
+    };
+    const result = validateOllamaModel("nemotron-3-nano:30b", capture, () => true, captureEx);
+    expect(result.ok).toBe(true);
+  });
+
 });
diff --git a/src/lib/inference/local.ts b/src/lib/inference/local.ts
index 2f05080832a..d4dbd136524 100644
--- a/src/lib/inference/local.ts
+++ b/src/lib/inference/local.ts
@@ -11,14 +11,16 @@ import os from "node:os";
 import nodePath from "node:path";
 import type { CurlProbeResult } from "../adapters/http/probe";
 import { runCurlProbe } from "../adapters/http/probe";
+import type { CaptureResult } from "../runner";
 import { buildSubprocessEnv } from "../subprocess-env";
 
-const { shellQuote, runCapture } = require("../runner");
+const { shellQuote, runCapture, runCaptureEx } = require("../runner");
 
 import { OLLAMA_PORT, OLLAMA_PROXY_PORT, VLLM_PORT } from "../core/ports";
 import { sleepSeconds } from "../core/wait";
 
 const { isWsl } = require("../platform");
+const { detectNvidiaPlatform } = require("./nim");
 
 /** Port containers use to reach Ollama — proxy on non-WSL, direct on WSL2. */
 export const OLLAMA_CONTAINER_PORT = isWsl() ? OLLAMA_PORT : OLLAMA_PROXY_PORT;
@@ -33,6 +35,8 @@ export const LARGE_OLLAMA_MIN_MEMORY_MB = 32768;
 
 export type RunCaptureFn = (cmd: string | string[], opts?: { ignoreError?: boolean }) => string;
 
+export type RunCaptureExFn = (cmd: string[]) => CaptureResult;
+
 // Hosts that the WSL-side onboard CLI tries when probing Ollama. Native Linux
 // and macOS only ever reach Ollama on the local loopback. WSL with Docker
 // Desktop can also reach a Windows-host Ollama through the docker-desktop
@@ -720,10 +724,22 @@ export function getOllamaProbeCommand(
 export function validateOllamaModel(
   model: string,
   runCaptureImpl?: RunCaptureFn,
+  isSparkImpl?: () => boolean,
+  runCaptureExImpl?: RunCaptureExFn,
 ): ValidationResult {
   const capture = runCaptureImpl ?? runCapture;
+  const captureEx = runCaptureExImpl ?? runCaptureEx;
+  const isSpark = isSparkImpl ?? (() => detectNvidiaPlatform() === "spark");
   const probeCmd = getOllamaProbeCommand(model);
-  const output = capture(probeCmd, { ignoreError: true });
+  const probeResult = captureEx(probeCmd);
+  let output = probeResult.stdout;
+  // On DGX Spark (128 GB unified memory), loading a large model from disk can take >2 min.
+  // Only retry with a 300 s timeout when the initial probe genuinely timed out — fast
+  // failures (connection refused, Ollama not running) surface immediately. (#3251)
+  if (isSpark() && probeResult.timedOut) {
+    const retryResult = captureEx(getOllamaProbeCommand(model, 300));
+    output = retryResult.stdout;
+  }
   if (!output) {
     return {
       ok: false,
@@ -746,6 +762,25 @@ export function validateOllamaModel(
             `model's capabilities and pick one whose list includes 'tools'.`,
         };
       }
+      // Ollama checks available RAM instead of total; false positive on DGX Spark
+      // unified-memory hosts where GPU and CPU share the same 128 GB pool. (#3251)
+      const memMatch = errText.match(
+        /model requires more system memory \(([0-9.]+)\s*GiB\) than is available \([0-9.]+\s*GiB\)/i,
+      );
+      if (memMatch && isSpark()) {
+        const requiresGiB = parseFloat(memMatch[1]);
+        const freeOut = capture(["free", "-m"], { ignoreError: true });
+        if (freeOut) {
+          const memLine = freeOut.split("\n").find((l: string) => l.includes("Mem:"));
+          if (memLine) {
+            const totalMB = parseInt(memLine.trim().split(/\s+/)[1], 10) || 0;
+            const totalGiB = totalMB / 1024;
+            if (totalGiB >= requiresGiB) {
+              return { ok: true };
+            }
+          }
+        }
+      }
       return {
         ok: false,
         message: `Selected Ollama model '${model}' failed the local probe: ${errText}`,
diff --git a/src/lib/runner.ts b/src/lib/runner.ts
index 0bedf4777d7..1a0674b2118 100644
--- a/src/lib/runner.ts
+++ b/src/lib/runner.ts
@@ -259,6 +259,49 @@ function runCapture(cmd: readonly string[], opts: CaptureOptions = {}): string {
 // Unified redaction — see redact.ts (#2381).
 const { redact, redactError, writeRedactedResult } = require("./security/redact");
 
+/** Structured result returned by runCaptureEx. */
+export interface CaptureResult {
+  stdout: string;
+  exitCode: number | null;
+  /** True when spawnSync sets result.error due to a timeout (ETIMEDOUT). */
+  timedOut: boolean;
+}
+
+/**
+ * Like runCapture but returns a structured result instead of throwing or
+ * collapsing errors to an empty string.  Use this when the caller needs to
+ * distinguish a real timeout (curl exit 28 / spawn ETIMEDOUT) from other
+ * failures such as connection-refused.
+ */
+function runCaptureEx(cmd: readonly string[], opts: Omit<CaptureOptions, "ignoreError"> = {}): CaptureResult {
+  if (!Array.isArray(cmd) || cmd.length === 0) {
+    throw new Error("runCaptureEx: cmd must be a non-empty argv array");
+  }
+  const exe = cmd[0];
+  const args = cmd.slice(1);
+  const { env: extraEnv, stdio: _stdio, ...spawnOpts } = opts as CaptureOptions;
+  try {
+    const result = spawnSync(exe, args, {
+      ...spawnOpts,
+      cwd: ROOT,
+      env: { ...process.env, ...extraEnv },
+      stdio: ["pipe", "pipe", "pipe"],
+      encoding: "utf-8",
+    });
+    const timedOut =
+      (result.error != null && (result.error as NodeJS.ErrnoException).code === "ETIMEDOUT") ||
+      result.status === 28;
+    const stdout = result.stdout || "";
+    return {
+      stdout: (typeof stdout === "string" ? stdout : stdout.toString("utf-8")).trim(),
+      exitCode: result.status,
+      timedOut,
+    };
+  } catch (err) {
+    throw redactError(err);
+  }
+}
+
 /**
  * Shell-quote a value for safe interpolation into bash -c strings.
  * Wraps in single quotes and escapes embedded single quotes.
@@ -295,6 +338,7 @@ export {
   run,
   runShell,
   runCapture,
+  runCaptureEx,
   runFile,
   runInteractive,
   runInteractiveShell,
diff --git a/test/ollama-tools-capability.test.ts b/test/ollama-tools-capability.test.ts
index a8d7cdfdad0..6a9fe91faf3 100644
--- a/test/ollama-tools-capability.test.ts
+++ b/test/ollama-tools-capability.test.ts
@@ -29,6 +29,8 @@ interface LocalInferenceModule {
   validateOllamaModel: (
     model: string,
     capture?: CaptureFn,
+    isSparkImpl?: () => boolean,
+    captureExImpl?: (cmd: string[]) => { stdout: string; exitCode: number | null; timedOut: boolean },
   ) => { ok: boolean; message?: string };
   setResolvedOllamaHost: (host: string) => void;
   resetOllamaHostCache: () => void;
@@ -176,7 +178,9 @@ describe("validateOllamaModel — tools-capable error mapping", () => {
         }),
       },
     ]);
-    const result = localInference.validateOllamaModel("phi4", capture);
+    const payload = JSON.stringify({ error: "registry.ollama.ai/library/phi4 does not support tools" });
+    const captureEx = () => ({ stdout: payload, exitCode: 0, timedOut: false });
+    const result = localInference.validateOllamaModel("phi4", capture, () => false, captureEx);
     expect(result.ok).toBe(false);
     expect(result.message).toBeTruthy();
     expect(result.message!).toContain("phi4");