diff --git a/src/resources/extensions/search-the-web/index.ts b/src/resources/extensions/search-the-web/index.ts
index da809375f..793c1ea15 100644
--- a/src/resources/extensions/search-the-web/index.ts
+++ b/src/resources/extensions/search-the-web/index.ts
@@ -10,15 +10,21 @@ import { registerSearchProviderCommand } from "./command-search-provider.js";
 import { registerNativeSearchHooks } from "./native-search.js";
 
 let toolsPromise: Promise<void> | null = null;
+let resetSearchLoopGuardStateRef: (() => void) | null = null;
 
 async function registerSearchTools(pi: ExtensionAPI): Promise<void> {
   if (!toolsPromise) {
     toolsPromise = (async () => {
-      const [{ registerSearchTool }, { registerFetchPageTool }, { registerLLMContextTool }] = await Promise.all([
+      const [
+        { registerSearchTool, resetSearchLoopGuardState },
+        { registerFetchPageTool },
+        { registerLLMContextTool },
+      ] = await Promise.all([
         importExtensionModule<typeof import("./tool-search.js")>(import.meta.url, "./tool-search.js"),
         importExtensionModule<typeof import("./tool-fetch-page.js")>(import.meta.url, "./tool-fetch-page.js"),
         importExtensionModule<typeof import("./tool-llm-context.js")>(import.meta.url, "./tool-llm-context.js"),
       ]);
+      resetSearchLoopGuardStateRef = resetSearchLoopGuardState;
       registerSearchTool(pi);
       registerFetchPageTool(pi);
       registerLLMContextTool(pi);
@@ -36,13 +42,23 @@ export default function (pi: ExtensionAPI) {
   registerNativeSearchHooks(pi);
 
   pi.on("session_start", async (_event, ctx) => {
+    const resetLoopGuardState = () => {
+      resetSearchLoopGuardStateRef?.();
+    };
+
     if (ctx.hasUI) {
-      void registerSearchTools(pi).catch((error) => {
-        ctx.ui.notify(`search-the-web failed to load: ${error instanceof Error ? error.message : String(error)}`, "warning");
-      });
+      resetLoopGuardState();
+      void registerSearchTools(pi)
+        .then(() => {
+          resetLoopGuardState();
+        })
+        .catch((error) => {
+          ctx.ui.notify(`search-the-web failed to load: ${error instanceof Error ? error.message : String(error)}`, "warning");
+        });
       return;
     }
 
     await registerSearchTools(pi);
+    resetLoopGuardState();
   });
 }
diff --git a/src/resources/extensions/search-the-web/tool-search.ts b/src/resources/extensions/search-the-web/tool-search.ts
index ba39b1332..54dab89b0 100644
--- a/src/resources/extensions/search-the-web/tool-search.ts
+++ b/src/resources/extensions/search-the-web/tool-search.ts
@@ -110,6 +110,12 @@ const MAX_CONSECUTIVE_DUPES = 3;
 let lastSearchKey = "";
 let consecutiveDupeCount = 0;
 
+/** Reset session-scoped duplicate-search guard state. */
+export function resetSearchLoopGuardState(): void {
+  lastSearchKey = "";
+  consecutiveDupeCount = 0;
+}
+
 // Summarizer responses: max 50 entries, 15-minute TTL
 const summarizerCache = new LRUTTLCache<string>({ max: 50, ttlMs: 900_000 });
 
@@ -383,16 +389,18 @@ export function registerSearchTool(pi: ExtensionAPI) {
       // ------------------------------------------------------------------
       const cacheKey = normalizeQuery(effectiveQuery) + `|f:${freshness || ""}|s:${wantSummary}|p:${provider}`;
 
-      // ── Consecutive duplicate search guard (#949) ──────────────────────
+      // ── Consecutive duplicate search guard (#949, #1671) ─────────────────
       // If the LLM keeps calling the same search query, break the loop
       // with an explicit warning instead of returning the same results.
+      // After the threshold is hit, do NOT reset the state — this keeps the
+      // guard armed so every subsequent duplicate immediately re-triggers it,
+      // preventing the "sawtooth" pattern where resetting allowed infinite loops
+      // with brief interruptions every MAX_CONSECUTIVE_DUPES+1 calls.
       if (cacheKey === lastSearchKey) {
         consecutiveDupeCount++;
         if (consecutiveDupeCount >= MAX_CONSECUTIVE_DUPES) {
-          consecutiveDupeCount = 0;
-          lastSearchKey = "";
           return {
-            content: [{ type: "text" as const, text: `⚠️ Search loop detected: the query "${params.query}" has been searched ${MAX_CONSECUTIVE_DUPES + 1} times consecutively with identical results. The information you need is already in the previous search results above. Stop searching and use those results to proceed with your task.` }],
+            content: [{ type: "text" as const, text: `⚠️ Search loop detected: the query "${params.query}" has been searched ${consecutiveDupeCount + 1} times consecutively with identical results. The information you need is already in the previous search results above. Stop searching and use those results to proceed with your task.` }],
             isError: true,
             details: { errorKind: "search_loop", error: "Consecutive duplicate search detected" } satisfies Partial<SearchDetails>,
           };
diff --git a/src/tests/search-loop-guard.test.ts b/src/tests/search-loop-guard.test.ts
new file mode 100644
index 000000000..266b5155a
--- /dev/null
+++ b/src/tests/search-loop-guard.test.ts
@@ -0,0 +1,244 @@
+/**
+ * Regression tests for the consecutive duplicate search loop guard.
+ *
+ * Covers:
+ * - Guard fires after MAX_CONSECUTIVE_DUPES identical calls (#949)
+ * - Guard stays armed after firing — subsequent duplicates immediately
+ *   re-trigger the error (#1671: the original fix reset state on trigger,
+ *   allowing the loop to restart)
+ * - Guard resets cleanly when a different query is issued
+ */
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import { registerSearchTool } from "../resources/extensions/search-the-web/tool-search.ts";
+import searchExtension from "../resources/extensions/search-the-web/index.ts";
+
+// =============================================================================
+// Mock helpers
+// =============================================================================
+
+/** Minimal Brave search API response fixture. */
+function makeBraveResponse() {
+  return {
+    query: { original: "test query", more_results_available: false },
+    web: {
+      results: [
+        {
+          title: "Result One",
+          url: "https://example.com/one",
+          description: "First result description.",
+        },
+      ],
+    },
+  };
+}
+
+/** Install a mock global fetch that always returns the given body. */
+function mockFetch(body: unknown, status = 200) {
+  const original = global.fetch;
+  (global as any).fetch = async () => ({
+    ok: status === 200,
+    status,
+    headers: { get: () => null },
+    json: async () => body,
+    text: async () => JSON.stringify(body),
+  });
+  return () => {
+    global.fetch = original;
+  };
+}
+
+/** Create a minimal mock PI that captures the registered search tool. */
+function createMockPI() {
+  const handlers: Array<{ event: string; handler: (...args: any[]) => unknown }> = [];
+  const toolsByName = new Map<string, any>();
+  let registeredTool: any = null;
+
+  const pi = {
+    on(event: string, handler: (...args: any[]) => unknown) {
+      handlers.push({ event, handler });
+    },
+    registerCommand(_name: string, _command: unknown) {},
+    registerTool(tool: any) {
+      if (typeof tool?.name === "string") {
+        toolsByName.set(tool.name, tool);
+      }
+      registeredTool = tool;
+    },
+    async fire(event: string, eventData: unknown, ctx: unknown) {
+      for (const h of handlers) {
+        if (h.event === event) await h.handler(eventData, ctx);
+      }
+    },
+    getRegisteredTool(name = "search-the-web") {
+      return toolsByName.get(name) ?? registeredTool;
+    },
+    writeTempFile: async (_content: string, _opts?: unknown) => "/tmp/search-out.txt",
+  };
+
+  return pi;
+}
+
+/** Call the search tool execute function with the given query. */
+async function callSearch(
+  execute: (...args: any[]) => Promise<any>,
+  query: string,
+  callId = "call-1"
+) {
+  const mockCtx = { ui: { notify() {} } };
+  return execute(callId, { query }, new AbortController().signal, () => {}, mockCtx);
+}
+
+// =============================================================================
+// Tests
+// =============================================================================
+
+/**
+ * Each test file gets its own module registry, so the module-level loop guard
+ * state (lastSearchKey, consecutiveDupeCount) starts fresh here.
+ */
+
+test("search loop guard fires after MAX_CONSECUTIVE_DUPES duplicates", async () => {
+  process.env.BRAVE_API_KEY = "test-key-loop-guard";
+  const restoreFetch = mockFetch(makeBraveResponse());
+
+  try {
+    const pi = createMockPI();
+    registerSearchTool(pi as any);
+    const tool = pi.getRegisteredTool();
+    assert.ok(tool, "search tool should be registered");
+
+    const execute = tool.execute.bind(tool);
+
+    // Calls 1–3: below threshold, should return search results (not an error)
+    for (let i = 1; i <= 3; i++) {
+      const result = await callSearch(execute, "loop test query", `call-${i}`);
+      assert.notEqual(result.isError, true, `call ${i} should not trigger loop guard`);
+    }
+
+    // Call 4: hits the threshold — guard fires
+    const result4 = await callSearch(execute, "loop test query", "call-4");
+    assert.equal(result4.isError, true, "call 4 should trigger the loop guard");
+    assert.equal(result4.details?.errorKind, "search_loop");
+    assert.ok(
+      result4.content[0].text.includes("Search loop detected"),
+      "error message should mention search loop"
+    );
+  } finally {
+    restoreFetch();
+    delete process.env.BRAVE_API_KEY;
+  }
+});
+
+test("search loop guard resets at session_start boundary", async () => {
+  process.env.BRAVE_API_KEY = "test-key-loop-guard-session";
+  const restoreFetch = mockFetch(makeBraveResponse());
+  const query = "session boundary query";
+
+  try {
+    const pi = createMockPI();
+    const mockCtx = {
+      hasUI: false,
+      ui: { notify() {} },
+    };
+    searchExtension(pi as any);
+    await pi.fire("session_start", {}, mockCtx);
+
+    const tool = pi.getRegisteredTool();
+    assert.ok(tool, "search tool should be registered");
+    const execute = tool.execute.bind(tool);
+
+    // Trigger guard in session 1
+    for (let i = 1; i <= 4; i++) {
+      await callSearch(execute, query, `s1-call-${i}`);
+    }
+    const guardResult = await callSearch(execute, query, "s1-call-5");
+    assert.equal(guardResult.isError, true, "session 1 should be guarded");
+    assert.equal(guardResult.details?.errorKind, "search_loop");
+
+    // New session should clear guard state
+    await pi.fire("session_start", {}, mockCtx);
+    const firstCallSession2 = await callSearch(execute, query, "s2-call-1");
+    assert.notEqual(
+      firstCallSession2.isError,
+      true,
+      "first identical query in a new session should not be blocked by prior session state",
+    );
+  } finally {
+    restoreFetch();
+    delete process.env.BRAVE_API_KEY;
+  }
+});
+
+test("search loop guard stays armed after firing — subsequent duplicates immediately re-trigger (#1671)", async () => {
+  process.env.BRAVE_API_KEY = "test-key-loop-guard-2";
+  const restoreFetch = mockFetch(makeBraveResponse());
+
+  // Use a unique query so module-level state from previous test doesn't interfere
+  const query = "persistent loop query";
+
+  try {
+    const pi = createMockPI();
+    registerSearchTool(pi as any);
+    const tool = pi.getRegisteredTool();
+    const execute = tool.execute.bind(tool);
+
+    // Exhaust the initial window (calls 1–3 succeed, call 4 fires guard)
+    for (let i = 1; i <= 3; i++) {
+      await callSearch(execute, query, `call-${i}`);
+    }
+    const guardFirst = await callSearch(execute, query, "call-4");
+    assert.equal(guardFirst.isError, true, "call 4 should trigger the loop guard");
+
+    // Key regression test: call 5 (and beyond) must ALSO trigger the guard.
+    // The original bug reset state on trigger, so call 5 was treated as a fresh
+    // first search and the loop restarted.
+    const guardSecond = await callSearch(execute, query, "call-5");
+    assert.equal(
+      guardSecond.isError, true,
+      "call 5 should STILL trigger the loop guard (guard must stay armed after firing)"
+    );
+    assert.equal(guardSecond.details?.errorKind, "search_loop");
+
+    // Call 6 as well — guard should keep firing
+    const guardThird = await callSearch(execute, query, "call-6");
+    assert.equal(
+      guardThird.isError, true,
+      "call 6 should STILL trigger the loop guard"
+    );
+  } finally {
+    restoreFetch();
+    delete process.env.BRAVE_API_KEY;
+  }
+});
+
+test("search loop guard resets cleanly when a different query is issued", async () => {
+  process.env.BRAVE_API_KEY = "test-key-loop-guard-3";
+  const restoreFetch = mockFetch(makeBraveResponse());
+
+  const queryA = "query alpha reset test";
+  const queryB = "query beta reset test";
+
+  try {
+    const pi = createMockPI();
+    registerSearchTool(pi as any);
+    const tool = pi.getRegisteredTool();
+    const execute = tool.execute.bind(tool);
+
+    // Trigger guard for queryA
+    for (let i = 1; i <= 4; i++) {
+      await callSearch(execute, queryA, `call-a-${i}`);
+    }
+
+    // Issue a different query — should succeed (resets the duplicate counter)
+    const resultB = await callSearch(execute, queryB, "call-b-1");
+    assert.notEqual(
+      resultB.isError, true,
+      "a different query after guard should not be treated as a loop"
+    );
+  } finally {
+    restoreFetch();
+    delete process.env.BRAVE_API_KEY;
+  }
+});