diff --git a/CHANGELOG.md b/CHANGELOG.md
index 36e86fe801..10518c4765 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,7 @@
 - **fix(routing):** the `auto` model keyword now works on the Codex `/v1/responses` path — `resolveResponsesApiModel` rewrote the bare `auto` keyword to `codex/auto`, which ChatGPT rejects (`The 'auto' model is not supported when using Codex with a ChatGPT account`). `auto` (OmniRoute's zero-config auto-routing keyword) now passes through untouched so combo routing handles it. ([#3509](https://github.com/diegosouzapw/OmniRoute/issues/3509))
 - **fix(cli-tools):** saving the OpenCode/CLI tool config no longer 400s in cloud mode — every CLI tool card posts `apiKey: null` (the real key is resolved server-side from `keyId`), but `guideSettingsSaveSchema` used `z.string().optional()`, which rejects `null`. The schema now normalizes `null` → `undefined`, so the save succeeds and the `keyId`/default path is used. ([#3552](https://github.com/diegosouzapw/OmniRoute/issues/3552))
 - **fix(catalog):** PublicAI is no longer miscatalogued as keyless/free — it requires an API key (registry `authType:"apikey"`; signup grants a one-time credit, then it bills). The three PublicAI models moved from `freeType:"keyless"` (which could pick them into the no-auth pool and dispatch with no `Authorization` header) to `"one-time-initial"`, and the provider's `hasFree` flag is now `false` — matching `freeTierCatalog.ts`, which already excluded publicai. ([#3558](https://github.com/diegosouzapw/OmniRoute/issues/3558))
+- **fix(gemini-web):** a missing Playwright Chromium browser no longer loops and trips the provider breaker — when the browser binary is not installed, `chromium.launch()` threw an error surfaced as a retryable **500**, so accountFallback marked the account unavailable and retry-looped. It is now classified as a host/config problem and returns **503** with an actionable message (`npx playwright install chromium`) and the `X-Omni-Fallback-Hint: connection_cooldown` header, which skips the provider circuit breaker and applies a short non-exponential cooldown. ([#3516](https://github.com/diegosouzapw/OmniRoute/issues/3516))
 
 ---
 
diff --git a/open-sse/executors/gemini-web.ts b/open-sse/executors/gemini-web.ts
index 0d21f99437..4c06e2a9f0 100644
--- a/open-sse/executors/gemini-web.ts
+++ b/open-sse/executors/gemini-web.ts
@@ -19,6 +19,19 @@ import { sanitizeErrorMessage } from "../utils/error.ts";
 // ─── Constants ──────────────────────────────────────────────────────────────
 
 const GEMINI_URL = "https://gemini.google.com/app";
+
+/**
+ * Whether an error came from Playwright failing to launch because the browser binary is not
+ * installed (`chromium.launch: Executable doesn't exist at ...`). This is a host/config
+ * problem, not a transient upstream fault, so the executor must NOT surface it as a retryable
+ * 500 (which marks the account unavailable and loops / trips the provider breaker). See #3516.
+ */
+export function isMissingBrowserExecutable(message: string): boolean {
+  if (!message) return false;
+  return /executable doesn't exist|executablenotfound|playwright install|chromium.*download/i.test(
+    message
+  );
+}
 const GEMINI_USER_AGENT =
   "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/147.0.0.0 Safari/537.36";
 
@@ -292,10 +305,36 @@ export class GeminiWebExecutor extends BaseExecutor {
         transformedBody: body,
       };
     } catch (error) {
+      const rawMessage = error instanceof Error ? error.message : "Unknown error";
+      // #3516: a missing Playwright browser is a host/config problem, not a transient upstream
+      // fault. Surface an actionable error and tag it with the connection-cooldown hint so
+      // accountFallback skips the provider circuit breaker and applies a short, non-exponential
+      // cooldown instead of looping on a retryable 500.
+      if (isMissingBrowserExecutable(rawMessage)) {
+        return {
+          response: new Response(
+            JSON.stringify({
+              error:
+                "Gemini Web requires the Playwright Chromium browser, which is not installed. " +
+                "Run `npx playwright install chromium` on the host (or rebuild the Docker image with browsers).",
+            }),
+            {
+              status: 503,
+              headers: {
+                "Content-Type": "application/json",
+                "X-Omni-Fallback-Hint": "connection_cooldown",
+              },
+            }
+          ),
+          url: GEMINI_URL,
+          headers: {},
+          transformedBody: body,
+        };
+      }
       return {
         response: new Response(
           JSON.stringify({
-            error: sanitizeErrorMessage(error instanceof Error ? error.message : "Unknown error"),
+            error: sanitizeErrorMessage(rawMessage),
           }),
           { status: 500, headers: { "Content-Type": "application/json" } }
         ),
diff --git a/tests/unit/gemini-web-missing-browser-3516.test.ts b/tests/unit/gemini-web-missing-browser-3516.test.ts
new file mode 100644
index 0000000000..b52da4fe2e
--- /dev/null
+++ b/tests/unit/gemini-web-missing-browser-3516.test.ts
@@ -0,0 +1,29 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { isMissingBrowserExecutable } from "../../open-sse/executors/gemini-web.ts";
+
+// Regression for #3516: when the Playwright Chromium binary isn't installed, chromium.launch()
+// throws "browserType.launch: Executable doesn't exist at ...". gemini-web returned that as a
+// generic 500, which accountFallback treats as a retryable upstream error → the account is
+// marked unavailable and the request loops/trips the provider breaker. A missing browser is a
+// host/config problem, not a transient upstream fault — it must be classified so the executor
+// can surface an actionable error and use the connection-cooldown hint instead of the 500 loop.
+
+test("#3516 detects the Playwright missing-executable launch error", () => {
+  const msg =
+    "browserType.launch: Executable doesn't exist at /home/node/.cache/ms-playwright/" +
+    "chromium_headless_shell-1223/chrome-linux/headless_shell\n" +
+    "╔════════════════════════════════════════════════════════════╗\n" +
+    "║ Looks like Playwright Test or Playwright was just installed  ║";
+  assert.equal(isMissingBrowserExecutable(msg), true);
+});
+
+test("#3516 detects the 'npx playwright install' guidance variant", () => {
+  assert.equal(isMissingBrowserExecutable("Please run the following command: npx playwright install"), true);
+});
+
+test("#3516 does NOT classify a normal upstream/network error as missing-executable", () => {
+  assert.equal(isMissingBrowserExecutable("No response from Gemini"), false);
+  assert.equal(isMissingBrowserExecutable("fetch failed: ECONNRESET"), false);
+  assert.equal(isMissingBrowserExecutable(""), false);
+});
diff --git a/tests/unit/gemini-web.test.ts b/tests/unit/gemini-web.test.ts
index 492aba830e..b4f837c80b 100644
--- a/tests/unit/gemini-web.test.ts
+++ b/tests/unit/gemini-web.test.ts
@@ -75,18 +75,22 @@ test("Provider: gemini-web has correct models", async () => {
   assert.ok(modelIds.includes("gemini-2.0-flash"));
 });
 
-// ─── Regression: #2832 — Playwright missing in Docker (runner-base) ──────────
+// ─── Regression: #2832 / #3516 — Playwright missing in Docker (runner-base) ──
 //
 // When the `runner-base` Docker image is used (no Playwright browsers installed),
 // `import("playwright")` succeeds but `chromium.launch()` throws the well-known
-// "Executable doesn't exist" error. The executor MUST surface this as a sanitized
-// 500 — never an unhandled rejection — so users get a clear error message rather
-// than a silent stream abort.
+// "Executable doesn't exist" error. The executor MUST surface this as a structured,
+// sanitized response — never an unhandled rejection / silent stream abort.
 //
-// Hard rule #12: error must go through sanitizeErrorMessage (no raw err.message
-// or stack trace in the response body).
+// #3516 superseded the original 500: a missing browser is a host/config problem,
+// not a transient upstream fault, so it now returns 503 with the
+// `X-Omni-Fallback-Hint: connection_cooldown` header (skips the provider circuit
+// breaker, short non-exponential cooldown) and an actionable message — instead of a
+// retryable 500 that marked the account unavailable and looped.
+//
+// Hard rule #12: the body carries no raw err.message stack trace.
 
-test("#2832: Playwright launch failure returns sanitized 500, not unhandled rejection", async () => {
+test("#2832/#3516: missing Playwright browser returns an actionable 503 with cooldown hint, not a retryable 500", async () => {
   const playwrightError = new Error(
     "browserType.launch: Executable doesn't exist at /home/node/.cache/ms-playwright/chromium_headless_shell-1161/chrome-linux/headless_shell\n" +
       "    at /app/node_modules/playwright-core/lib/server/browserType.js:123:19"
@@ -110,10 +114,17 @@ test("#2832: Playwright launch failure returns sanitized 500, not unhandled reje
       log: null,
     });
 
-    assert.equal(result.response.status, 500, "should return HTTP 500");
+    // #3516: missing browser → 503 + connection-cooldown hint (not a retryable 500 loop).
+    assert.equal(result.response.status, 503, "missing browser should return HTTP 503");
+    assert.equal(
+      result.response.headers.get("X-Omni-Fallback-Hint"),
+      "connection_cooldown",
+      "must signal connection cooldown so the provider breaker is skipped"
+    );
     const json = (await result.response.json()) as any;
     assert.ok(typeof json.error === "string", "error field must be a string");
-    // Hard rule #12: sanitizeErrorMessage must strip the stack trace tail.
+    assert.match(json.error, /playwright install|not installed/i, "message must be actionable");
+    // No raw stack trace / source path leaks into the body.
     assert.ok(!json.error.includes("\n    at "), "must not contain multi-line stack trace");
     assert.ok(!json.error.includes("node_modules/playwright-core"), "must not contain node_modules source path");
   } finally {