diff --git a/CLAUDE.md b/CLAUDE.md
index 93cc8cd..3c06fdc 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -196,3 +196,8 @@ pytest -q
 - LinkedIn rate-limits aggressively; keep batches small while testing.
 - Standard pip struggles with pydantic dependency resolution in this stack; always use uv pip install instead.
 - The system Python is protected by PEP 668 (externally-managed-environment). Always use explicit virtual environment paths (e.g., .venv/bin/python, .venv/bin/pytest) for all terminal commands instead of relying on global commands.
+- **browser-use 0.8.0 `executable_path` required on Linux (confirmed 2026-06-17)**: `LocalBrowserWatchdog._find_installed_browser_path()` globs `chrome-linux/chrome` but playwright ≥1.40 installs to `chrome-linux64/chrome`. The watchdog silently falls through to `uvx playwright install chrome --with-deps`, which fails if `uvx` is not on PATH (`FileNotFoundError: 'uvx'`). Fix: pass `executable_path=_find_chromium_executable()` to `Browser()` in `_agent_session` — this makes the watchdog skip the auto-install entirely. `_find_chromium_executable()` in `agent_fallback.py` includes the `chrome-linux64` pattern.
+- **browser-use 0.8.0 "Result failed" JSON errors are non-fatal step-level retries** (observed 2026-06-17): lines like `❌ Result failed 1/4 times: 1 validation error for AgentOutput Invalid JSON: trailing characters` mean the model's tool-call response had trailing characters and browser-use retried (up to 4 times per step). These do not abort the agent run; they appear in `history.errors()` but `is_done()` can still be `True`. Expect a handful per run.
+- **Browser-agent run times: 2–4 minutes per company** (Infosys 21 steps/149s, TCS 24 steps/195s, tested 2026-06-17). This tier is a true last resort — only fires when all static tiers miss. The agent often uses a search engine (DuckDuckGo/Bing) when direct navigation fails, adding several extra steps. Google is rate-limited (CAPTCHA) and the agent falls back to Bing automatically.
+- **Browser-agent partial result pattern (TCS, 2026-06-17)**: `is_successful()=False` with `careers_url` populated but `position_url=None`. TCS uses a custom ATS (iBegin) that requires login/registration before individual job listings are accessible; the agent found the portal but could not navigate to a specific posting. Such records land in `needs_review` as expected. Login-gated ATSes are a known hard limit of the static-HTML tiers and the browser agent alike.
+- **Browser-agent live results (2026-06-17)**: Infosys → `careers_url=https://career.infosys.com/joblist` + `position_url=https://career.infosys.com/jobdesc?jobReferenceCode=INFSYS-EXTERNAL-247232` (both HTTP 200). TCS → `careers_url=https://ibegin.tcsapps.com/candidate/` (HTTP 200) + `position_url=None`. Both sites had failed all heuristic tiers (403 homepage / custom subdomain blocking httpx).
diff --git a/jobsource/agent_fallback.py b/jobsource/agent_fallback.py
index e7f06e9..e6d1c53 100644
--- a/jobsource/agent_fallback.py
+++ b/jobsource/agent_fallback.py
@@ -1,11 +1,301 @@
 """Browser Use fused fallback: find careers page AND extract one job URL in one session.
 
-Scaffold stub -- not implemented yet.
+This is the LAST tier of the cascade (Stage 2, Tier 6 / Stage 3, Tier 5). It fires only
+when all cheaper tiers in cascade.py and extract.py have missed. A single Browser Use
+agent session does both:
+  1. Navigate to the company website and locate the careers/jobs page.
+  2. From that page, open one specific open-position URL.
+
+Both URLs are returned in one call — never two browser sessions for the same company.
+A module-level memo keyed by normalized host ensures a same-domain second call (e.g.
+cascade passes the root website, extract passes the careers URL on the same host) is a
+cache hit with no new browser launch.
+
+Graceful degradation:
+  - ENABLE_BROWSER_AGENT=false       → log INFO, return None
+  - Placeholder AGENT_MODEL/LLM key  → log INFO, return None
+  - browser_use import error         → log WARNING, return None
+  - Chromium/navigation/agent error  → log WARNING, return None
+In all cases the batch still completes; those records land in needs_review.
 """
-# TODO (Stage 2/3 last resort): implement per CLAUDE.md "Stage 2 — tier 6" and "Stage 3 — tier 5".
-# This is the LAST tier of the cascade. Fires only when all cheaper tiers in cascade.py
-# and extract.py have failed. One Browser Use agent session does both:
-#   1. Navigate to the company website and locate the careers/jobs page.
-#   2. From the careers page, return the URL of one open position.
-# Graceful degradation: if Browser Use / Playwright / LLM key are unavailable, log clearly
-# and return (careers_url=None, position_url=None) so the pipeline records needs_review.
+from __future__ import annotations
+
+import asyncio
+import glob
+import logging
+import os
+import pathlib
+import platform
+from concurrent.futures import ThreadPoolExecutor
+from urllib.parse import urlsplit
+
+from pydantic import BaseModel
+
+from .config import get_settings
+
+logger = logging.getLogger(__name__)
+
+# ---------------------------------------------------------------------------
+# Result models
+# ---------------------------------------------------------------------------
+
+
+class AgentFallbackResult(BaseModel):
+    """Public result of find_and_extract()."""
+
+    careers_url: str | None = None
+    position_url: str | None = None
+
+
+class _AgentOutput(BaseModel):
+    """Structured-output schema handed to the Browser Use Agent."""
+
+    careers_url: str | None = None
+    position_url: str | None = None
+
+
+# ---------------------------------------------------------------------------
+# Module-level memo — one entry per normalized host
+# ---------------------------------------------------------------------------
+
+_MEMO: dict[str, AgentFallbackResult | None] = {}
+
+# Max browser-agent steps before timing out.
+_MAX_STEPS = 30
+
+# Task prompt for the fused Stage-2 + Stage-3 session.
+_TASK_TEMPLATE = (
+    "You are helping a job-sourcing pipeline. Given a company website URL, do the following "
+    "in a single browsing session:\n"
+    "1. Navigate to {website}\n"
+    "2. Find the company's official careers or jobs page (the page that lists open positions). "
+    "   Explore navigation menus, footer links, or search for '/careers', '/jobs', etc.\n"
+    "3. Once on the careers page, open one specific open-position detail page "
+    "   (a page for exactly one role — not a listing index, filter, or category page).\n"
+    "4. Return both URLs in the structured output fields:\n"
+    "   - careers_url: the URL of the careers/jobs listing page\n"
+    "   - position_url: the URL of one specific open-position detail page\n"
+    "If you cannot find a careers page or any open positions, set the corresponding field to null."
+)
+
+
+# ---------------------------------------------------------------------------
+# Availability gate
+# ---------------------------------------------------------------------------
+
+
+def _agent_unavailable() -> bool:
+    """Return True when the browser agent is not configured (placeholder values)."""
+    s = get_settings()
+    return (
+        s.agent_model.startswith("PLACEHOLDER")
+        or s.llm_api_key.startswith("PLACEHOLDER")
+    )
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _site_key(url: str) -> str:
+    """Normalized netloc for memo keying — strips 'www.', lowercased."""
+    host = urlsplit(url).netloc.lower()
+    return host.removeprefix("www.")
+
+
+def _find_chromium_executable() -> str | None:
+    """Return the Playwright-installed Chromium binary path, or None if not found.
+
+    browser-use 0.8.0's LocalBrowserWatchdog only globs `chrome-linux/chrome` but
+    playwright ≥1.40 installs to `chrome-linux64/chrome`. Passing executable_path
+    explicitly bypasses the watchdog's uvx-based auto-install fallback.
+    """
+    pw_base = os.environ.get("PLAYWRIGHT_BROWSERS_PATH")
+    if not pw_base:
+        system = platform.system()
+        if system == "Darwin":
+            pw_base = str(pathlib.Path.home() / "Library" / "Caches" / "ms-playwright")
+        elif system == "Windows":
+            pw_base = str(pathlib.Path.home() / "AppData" / "Local" / "ms-playwright")
+        else:
+            pw_base = str(pathlib.Path.home() / ".cache" / "ms-playwright")
+
+    system = platform.system()
+    if system == "Darwin":
+        patterns = [
+            f"{pw_base}/chromium-*/chrome-mac/Chromium.app/Contents/MacOS/Chromium",
+            f"{pw_base}/chromium-*/chrome-mac-arm64/Chromium.app/Contents/MacOS/Chromium",
+        ]
+    elif system == "Windows":
+        patterns = [
+            f"{pw_base}\\chromium-*\\chrome-win\\chrome.exe",
+            f"{pw_base}\\chromium-*\\chrome-win64\\chrome.exe",
+        ]
+    else:
+        patterns = [
+            f"{pw_base}/chromium-*/chrome-linux64/chrome",
+            f"{pw_base}/chromium-*/chrome-linux/chrome",
+        ]
+
+    for pattern in patterns:
+        matches = sorted(glob.glob(pattern))
+        if matches:
+            return matches[-1]  # newest version last alphabetically
+
+    return None
+
+
+def _build_chat_model():  # type: ignore[return]
+    """Construct the chat-model instance for the Browser Use agent.
+
+    Test seam — monkeypatch this to inject a fake without touching Browser Use.
+    Lazy-imports browser_use so a missing package never crashes module import.
+
+    agent_model format: "provider:model_id" (e.g. "anthropic:claude-sonnet-4-6").
+    Unknown/absent provider prefix defaults to ChatOpenAI.
+    """
+    from browser_use import ChatAnthropic, ChatOpenAI  # lazy import
+
+    s = get_settings()
+    model_str: str = s.agent_model
+    api_key: str | None = None if s.llm_api_key.startswith("PLACEHOLDER") else s.llm_api_key
+
+    if ":" in model_str:
+        provider, model_id = model_str.split(":", 1)
+    else:
+        provider, model_id = "openai", model_str
+
+    if provider == "anthropic":
+        kwargs = {"model": model_id}
+        if api_key:
+            kwargs["api_key"] = api_key
+        return ChatAnthropic(**kwargs)
+    else:
+        kwargs = {"model": model_id}
+        if api_key:
+            kwargs["openai_api_key"] = api_key
+        return ChatOpenAI(**kwargs)
+
+
+async def _agent_session(website: str, chat) -> _AgentOutput | None:  # type: ignore[return]
+    """Run a single Browser Use session; return structured output or None."""
+    from browser_use import Agent, Browser  # lazy import
+
+    s = get_settings()
+    # Pass executable_path explicitly so browser-use skips its uvx-based auto-installer.
+    # browser-use 0.8.0's LocalBrowserWatchdog globs chrome-linux/chrome but playwright
+    # ≥1.40 installs to chrome-linux64/chrome — the two paths diverge and the watchdog
+    # falls through to `uvx playwright install` even when chromium is present.
+    chromium_exe = _find_chromium_executable()
+    browser = Browser(headless=s.browser_headless, executable_path=chromium_exe)
+    task = _TASK_TEMPLATE.format(website=website)
+    agent = Agent(
+        task=task,
+        llm=chat,
+        browser=browser,
+        output_model_schema=_AgentOutput,
+    )
+    try:
+        history = await agent.run(max_steps=_MAX_STEPS)
+        out = history.structured_output
+        if isinstance(out, _AgentOutput):
+            return out
+        return None
+    finally:
+        try:
+            await browser.close()
+        except Exception:
+            pass
+
+
+def _run_blocking(coro_factory) -> _AgentOutput | None:  # type: ignore[return]
+    """Run an async coroutine from synchronous code.
+
+    Uses asyncio.run() when no event loop is running (the normal CLI path).
+    Falls back to a one-shot ThreadPoolExecutor when called from inside an
+    already-running loop (e.g. an async Prefect flow).
+    """
+    try:
+        asyncio.get_running_loop()
+        # Already inside a running loop — offload to a thread.
+        with ThreadPoolExecutor(max_workers=1) as pool:
+            future = pool.submit(asyncio.run, coro_factory())
+            return future.result()
+    except RuntimeError:
+        # No running loop — safe to call asyncio.run() directly.
+        return asyncio.run(coro_factory())
+
+
+def _valid_url(val: str | None) -> str | None:
+    """Return val if it's an http(s) URL, else None."""
+    if val and isinstance(val, str) and val.startswith(("http://", "https://")):
+        return val
+    return None
+
+
+# ---------------------------------------------------------------------------
+# Public entry point
+# ---------------------------------------------------------------------------
+
+
+def find_and_extract(website: str) -> AgentFallbackResult | None:
+    """Fused Stage-2 + Stage-3 fallback: browser agent finds careers page AND one job URL.
+
+    Returns an AgentFallbackResult on success, or None on any graceful failure.
+    Never raises — all errors are logged and swallowed so the pipeline continues.
+    Results are memoized per normalized host so a same-domain second call is free.
+    """
+    s = get_settings()
+
+    if not s.enable_browser_agent:
+        logger.info("agent_fallback(%s): ENABLE_BROWSER_AGENT=false, skipping", website)
+        return None
+
+    if _agent_unavailable():
+        logger.info(
+            "agent_fallback(%s): agent_model or llm_api_key not configured, skipping", website
+        )
+        return None
+
+    key = _site_key(website)
+    if key in _MEMO:
+        logger.info("agent_fallback(%s): memo hit, returning cached result", website)
+        return _MEMO[key]
+
+    # Build the chat model (lazy import — handles missing browser_use gracefully).
+    try:
+        chat = _build_chat_model()
+    except Exception as exc:
+        logger.warning("agent_fallback(%s): failed to build chat model: %s", website, exc)
+        _MEMO[key] = None
+        return None
+
+    # Run the fused browser session.
+    try:
+        raw: _AgentOutput | None = _run_blocking(lambda: _agent_session(website, chat))
+    except Exception as exc:
+        logger.warning("agent_fallback(%s): agent session error: %s", website, exc)
+        _MEMO[key] = None
+        return None
+
+    if raw is None:
+        logger.info("agent_fallback(%s): agent returned no structured output", website)
+        _MEMO[key] = None
+        return None
+
+    result = AgentFallbackResult(
+        careers_url=_valid_url(raw.careers_url),
+        position_url=_valid_url(raw.position_url),
+    )
+
+    if result.careers_url or result.position_url:
+        logger.info(
+            "agent_fallback(%s): careers_url=%s position_url=%s",
+            website, result.careers_url, result.position_url,
+        )
+    else:
+        logger.info("agent_fallback(%s): agent found no usable URLs", website)
+
+    _MEMO[key] = result
+    return result
diff --git a/jobsource/careers/cascade.py b/jobsource/careers/cascade.py
index c9e0601..77f096a 100644
--- a/jobsource/careers/cascade.py
+++ b/jobsource/careers/cascade.py
@@ -7,10 +7,11 @@ Cascade order (return early on first success):
   3.  Homepage scan  → heuristics.scan_homepage_links()    confidence 0.60
   4.  Sitemap        → heuristics.parse_sitemap()          confidence 0.50
   5.  Cheap-LLM      → classify_llm.classify_careers_link()  confidence 0.55
-  6.  Browser agent  → agent_fallback (not implemented in this phase)
+  6.  Browser agent  → agent_fallback.find_and_extract()   confidence 0.50
 
 Returns a CareersResult with the URL, confidence, method string, and — when
-the ATS tier resolves — the first open-position URL for free (Stage-3 shortcut).
+the ATS tier or browser-agent tier resolves — the first open-position URL for
+free (Stage-3 shortcut).
 
 The optional *client* parameter follows the managed-client pattern from
 resolve.py: supply an existing httpx.Client to reuse connections; otherwise a
@@ -23,7 +24,9 @@ import logging
 import httpx
 from pydantic import BaseModel
 
+from ..config import get_settings
 from ..http import build_client, request_with_retries
+from .. import agent_fallback as _agent_fallback
 from . import ats as _ats
 from . import classify_llm as _classify_llm
 from . import heuristics as _heuristics
@@ -41,7 +44,7 @@ class CareersResult(BaseModel):
 
     careers_url: str | None = None
     confidence: float = 0.0
-    # method values: "ats:{name}" | "url_pattern" | "homepage_scan" | "sitemap" | "llm_classify" | "none"
+    # method values: "ats:{name}" | "url_pattern" | "homepage_scan" | "sitemap" | "llm_classify" | "browser_agent" | "none"
     method: str = "none"
     ats_name: str | None = None
     # Free Stage-3 shortcut: populated when ATS tier resolves (first open job URL).
@@ -163,6 +166,26 @@ def find_careers_page(
         except Exception as exc:
             logger.warning("cascade(%s): llm_classify tier error: %s", website, exc)
 
+        # ------------------------------------------------------------------
+        # Tier 6 — Browser agent (fused Stage-2 + Stage-3 fallback)
+        # ------------------------------------------------------------------
+        if get_settings().enable_browser_agent:
+            try:
+                ag = _agent_fallback.find_and_extract(website)
+                if ag and ag.careers_url:
+                    logger.info(
+                        "cascade(%s): resolved via browser_agent careers_url=%s",
+                        website, ag.careers_url,
+                    )
+                    return CareersResult(
+                        careers_url=ag.careers_url,
+                        confidence=0.50,
+                        method="browser_agent",
+                        position_url=ag.position_url,
+                    )
+            except Exception as exc:
+                logger.warning("cascade(%s): browser_agent tier error: %s", website, exc)
+
         logger.info("cascade(%s): all tiers missed", website)
         return CareersResult()
 
diff --git a/jobsource/extract.py b/jobsource/extract.py
index a6f7c84..977a13f 100644
--- a/jobsource/extract.py
+++ b/jobsource/extract.py
@@ -10,11 +10,13 @@ Cascade order (return early on first hit):
   3.  Job-like anchors — first <a> whose href matches /job|/position|/opening|/vacanc.
   4.  Cheap-LLM        — classify_job_link() from classify_llm; no-ops gracefully
                         when the LLM is not configured.
-  5.  Miss            — return (None, "none").
+  5.  Browser agent   — agent_fallback.find_and_extract(); fused with Stage-2 so
+                        the same memoized session covers both stages.
+  6.  Miss            — return (None, "none").
 
 Returns (url: str | None, method: str). Never raises — any tier failure logs
 and falls through. method is one of:
-  "ats:{name}" | "json_ld" | "anchor" | "llm_classify" | "none"
+  "ats:{name}" | "json_ld" | "anchor" | "llm_classify" | "browser_agent" | "none"
 """
 from __future__ import annotations
 
@@ -26,8 +28,10 @@ from urllib.parse import urlsplit
 import httpx
 from bs4 import BeautifulSoup
 
+from . import agent_fallback as _agent_fallback
 from .careers import ats as _ats
 from .careers.classify_llm import classify_job_link, extract_anchors
+from .config import get_settings
 from .http import build_client, request_with_retries
 
 logger = logging.getLogger(__name__)
@@ -206,6 +210,20 @@ def extract_open_position(
         except Exception as exc:
             logger.warning("extract(%s): llm_classify tier error: %s", careers_url, exc)
 
+        # ------------------------------------------------------------------
+        # Tier 5 — Browser agent (fused; memo-shared with cascade Tier 6)
+        # ------------------------------------------------------------------
+        if get_settings().enable_browser_agent:
+            try:
+                ag = _agent_fallback.find_and_extract(careers_url)
+                if ag and ag.position_url:
+                    logger.info(
+                        "extract(%s): browser_agent pos=%s", careers_url, ag.position_url
+                    )
+                    return ag.position_url, "browser_agent"
+            except Exception as exc:
+                logger.warning("extract(%s): browser_agent tier error: %s", careers_url, exc)
+
         logger.info("extract(%s): all tiers missed", careers_url)
         return None, "none"
 
diff --git a/tests/test_agent_fallback.py b/tests/test_agent_fallback.py
new file mode 100644
index 0000000..b8f0696
--- /dev/null
+++ b/tests/test_agent_fallback.py
@@ -0,0 +1,386 @@
+"""Tests for jobsource/agent_fallback.py — all network-free via monkeypatching."""
+from __future__ import annotations
+
+import pytest
+
+import jobsource.agent_fallback as _mod
+from jobsource.agent_fallback import (
+    AgentFallbackResult,
+    _AgentOutput,
+    _site_key,
+    _valid_url,
+    find_and_extract,
+)
+
+
+# ---------------------------------------------------------------------------
+# Helpers and fakes
+# ---------------------------------------------------------------------------
+
+
+def _placeholder_settings(**overrides):
+    """Return a fake settings object with placeholder values (agent unavailable)."""
+    defaults = {
+        "enable_browser_agent": True,
+        "agent_model": "PLACEHOLDER_AGENT_MODEL",
+        "llm_api_key": "PLACEHOLDER_LLM_API_KEY",
+        "browser_headless": True,
+    }
+    defaults.update(overrides)
+    return type("S", (), defaults)()
+
+
+def _real_settings(**overrides):
+    """Return a fake settings object with non-placeholder values."""
+    defaults = {
+        "enable_browser_agent": True,
+        "agent_model": "anthropic:claude-sonnet-4-6",
+        "llm_api_key": "sk-ant-real",
+        "browser_headless": True,
+    }
+    defaults.update(overrides)
+    return type("S", (), defaults)()
+
+
+def _patch_settings(monkeypatch, settings_obj):
+    monkeypatch.setattr(_mod, "get_settings", lambda: settings_obj)
+
+
+def _patch_chat(monkeypatch, chat_obj=None):
+    """Monkeypatch _build_chat_model to return chat_obj (default sentinel)."""
+    chat_obj = chat_obj or object()
+    monkeypatch.setattr(_mod, "_build_chat_model", lambda: chat_obj)
+    return chat_obj
+
+
+def _patch_session(monkeypatch, output: _AgentOutput | None):
+    """Monkeypatch _agent_session so no real browser launches."""
+    async def _fake_session(website, chat):
+        return output
+    monkeypatch.setattr(_mod, "_agent_session", _fake_session)
+
+
+# ---------------------------------------------------------------------------
+# _site_key
+# ---------------------------------------------------------------------------
+
+class TestSiteKey:
+    def test_strips_www(self):
+        assert _site_key("https://www.acme.com/foo") == "acme.com"
+
+    def test_lowercases(self):
+        assert _site_key("https://ACME.COM") == "acme.com"
+
+    def test_no_www(self):
+        assert _site_key("https://acme.com/careers") == "acme.com"
+
+    def test_subdomain_preserved(self):
+        assert _site_key("https://jobs.acme.com") == "jobs.acme.com"
+
+
+# ---------------------------------------------------------------------------
+# _valid_url
+# ---------------------------------------------------------------------------
+
+class TestValidUrl:
+    def test_https_url_passes(self):
+        assert _valid_url("https://acme.com/jobs/1") == "https://acme.com/jobs/1"
+
+    def test_http_url_passes(self):
+        assert _valid_url("http://acme.com/jobs/1") == "http://acme.com/jobs/1"
+
+    def test_none_returns_none(self):
+        assert _valid_url(None) is None
+
+    def test_junk_string_returns_none(self):
+        assert _valid_url("null") is None
+
+    def test_relative_url_returns_none(self):
+        assert _valid_url("/jobs/1") is None
+
+
+# ---------------------------------------------------------------------------
+# Gate: enable_browser_agent=False
+# ---------------------------------------------------------------------------
+
+class TestFeatureFlagGate:
+    def test_returns_none_when_flag_off(self, monkeypatch):
+        _patch_settings(monkeypatch, _placeholder_settings(enable_browser_agent=False))
+        # Clear memo so there's no cached entry from another test.
+        _mod._MEMO.clear()
+        result = find_and_extract("https://acme.com")
+        assert result is None
+
+    def test_does_not_cache_when_flag_off(self, monkeypatch):
+        _patch_settings(monkeypatch, _placeholder_settings(enable_browser_agent=False))
+        _mod._MEMO.clear()
+        find_and_extract("https://flagoff.com")
+        assert "flagoff.com" not in _mod._MEMO
+
+
+# ---------------------------------------------------------------------------
+# Gate: placeholder LLM config
+# ---------------------------------------------------------------------------
+
+class TestPlaceholderGate:
+    def test_returns_none_for_placeholder_model(self, monkeypatch):
+        _patch_settings(monkeypatch, _placeholder_settings())
+        _mod._MEMO.clear()
+        result = find_and_extract("https://acme.com")
+        assert result is None
+
+    def test_returns_none_for_placeholder_key_only(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings(llm_api_key="PLACEHOLDER_LLM_API_KEY"))
+        _mod._MEMO.clear()
+        result = find_and_extract("https://acme.com")
+        assert result is None
+
+    def test_returns_none_for_placeholder_model_only(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings(agent_model="PLACEHOLDER_AGENT_MODEL"))
+        _mod._MEMO.clear()
+        result = find_and_extract("https://acme.com")
+        assert result is None
+
+
+# ---------------------------------------------------------------------------
+# Gate: _build_chat_model raises (missing package / bad config)
+# ---------------------------------------------------------------------------
+
+class TestChatModelBuildFailure:
+    def test_returns_none_and_memos_none_on_import_error(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+
+        def _raise():
+            raise ImportError("browser_use not installed")
+
+        monkeypatch.setattr(_mod, "_build_chat_model", _raise)
+        result = find_and_extract("https://chatfail.com")
+        assert result is None
+        assert _mod._MEMO.get("chatfail.com") is None
+
+
+# ---------------------------------------------------------------------------
+# Gate: _agent_session raises / returns None
+# ---------------------------------------------------------------------------
+
+class TestAgentSessionFailure:
+    def test_returns_none_on_session_exception(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+        _patch_chat(monkeypatch)
+
+        async def _raise_session(website, chat):
+            raise RuntimeError("Chromium unavailable")
+
+        monkeypatch.setattr(_mod, "_agent_session", _raise_session)
+        result = find_and_extract("https://chromiumfail.com")
+        assert result is None
+
+    def test_returns_none_when_session_returns_none(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+        _patch_chat(monkeypatch)
+        _patch_session(monkeypatch, None)
+        result = find_and_extract("https://nonefail.com")
+        assert result is None
+
+
+# ---------------------------------------------------------------------------
+# Success path: structured output parsed into AgentFallbackResult
+# ---------------------------------------------------------------------------
+
+class TestSuccessPath:
+    def test_both_urls_returned(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+        _patch_chat(monkeypatch)
+        _patch_session(
+            monkeypatch,
+            _AgentOutput(
+                careers_url="https://acme.com/careers",
+                position_url="https://acme.com/careers/jobs/42-swe",
+            ),
+        )
+        result = find_and_extract("https://acme.com")
+        assert result is not None
+        assert result.careers_url == "https://acme.com/careers"
+        assert result.position_url == "https://acme.com/careers/jobs/42-swe"
+
+    def test_junk_careers_url_filtered(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+        _patch_chat(monkeypatch)
+        _patch_session(
+            monkeypatch,
+            _AgentOutput(careers_url="null", position_url="https://acme.com/jobs/1"),
+        )
+        result = find_and_extract("https://acme.com")
+        assert result is not None
+        assert result.careers_url is None
+        assert result.position_url == "https://acme.com/jobs/1"
+
+    def test_result_stored_in_memo(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+        _patch_chat(monkeypatch)
+        _patch_session(
+            monkeypatch,
+            _AgentOutput(
+                careers_url="https://memo-test.com/careers",
+                position_url="https://memo-test.com/jobs/1",
+            ),
+        )
+        find_and_extract("https://memo-test.com")
+        cached = _mod._MEMO.get("memo-test.com")
+        assert cached is not None
+        assert cached.careers_url == "https://memo-test.com/careers"
+
+
+# ---------------------------------------------------------------------------
+# Memo: same-domain second call uses cache, not a second session
+# ---------------------------------------------------------------------------
+
+class TestMemo:
+    def test_second_call_uses_cache(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+        _patch_chat(monkeypatch)
+
+        call_count = 0
+
+        async def _counting_session(website, chat):
+            nonlocal call_count
+            call_count += 1
+            return _AgentOutput(
+                careers_url="https://sharetest.com/careers",
+                position_url="https://sharetest.com/jobs/1",
+            )
+
+        monkeypatch.setattr(_mod, "_agent_session", _counting_session)
+
+        r1 = find_and_extract("https://sharetest.com")
+        r2 = find_and_extract("https://sharetest.com/careers")  # same host, careers path
+
+        assert call_count == 1, "Expected exactly one browser session for the same host"
+        assert r1 == r2
+
+    def test_memo_none_prevents_retry(self, monkeypatch):
+        _patch_settings(monkeypatch, _real_settings())
+        _mod._MEMO.clear()
+        _patch_chat(monkeypatch)
+
+        call_count = 0
+
+        async def _failing_session(website, chat):
+            nonlocal call_count
+            call_count += 1
+            raise RuntimeError("broken")
+
+        monkeypatch.setattr(_mod, "_agent_session", _failing_session)
+
+        find_and_extract("https://memonil.com")
+        find_and_extract("https://memonil.com")  # should use cached None
+
+        assert call_count == 1
+
+
+# ---------------------------------------------------------------------------
+# Cascade/extract wiring integration (lightweight, no real browser)
+# ---------------------------------------------------------------------------
+
+class TestCascadeWiring:
+    """Verify find_and_extract is reachable from cascade.find_careers_page."""
+
+    def test_cascade_tier6_returns_browser_agent_method(self, monkeypatch):
+        from jobsource.careers.cascade import find_careers_page, CareersResult
+
+        # Patch all cheaper tiers to miss.
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._ats.detect_and_fetch", lambda *a, **kw: None
+        )
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._ats.recover_via_slug_guess", lambda *a, **kw: None
+        )
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._heuristics.probe_url_patterns", lambda *a, **kw: None
+        )
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._heuristics.scan_homepage_links", lambda *a, **kw: None
+        )
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._heuristics.parse_sitemap", lambda *a, **kw: None
+        )
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._classify_llm.extract_anchors", lambda *a, **kw: []
+        )
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._classify_llm.classify_careers_link",
+            lambda *a, **kw: None,
+        )
+        # Patch the safe homepage fetch.
+        from jobsource.careers import cascade as _cascade
+        monkeypatch.setattr(_cascade, "_safe_get_html", lambda *a, **kw: None)
+
+        # Patch agent_fallback.
+        _mod._MEMO.clear()
+        monkeypatch.setattr(
+            "jobsource.careers.cascade._agent_fallback.find_and_extract",
+            lambda *a, **kw: AgentFallbackResult(
+                careers_url="https://wired.com/careers",
+                position_url="https://wired.com/jobs/1",
+            ),
+        )
+
+        result = find_careers_page("https://wired.com")
+        assert result.method == "browser_agent"
+        assert result.careers_url == "https://wired.com/careers"
+        assert result.position_url == "https://wired.com/jobs/1"
+        assert result.confidence == 0.50
+
+
+class TestExtractWiring:
+    """Verify find_and_extract is reachable from extract.extract_open_position."""
+
+    def test_extract_tier5_returns_browser_agent_method(self, monkeypatch):
+        from jobsource.extract import extract_open_position
+
+        # Patch cheaper tiers to miss (ATS, JSON-LD, anchors, LLM).
+        monkeypatch.setattr(
+            "jobsource.extract._ats.detect_ats_in_url", lambda *a, **kw: None
+        )
+        monkeypatch.setattr(
+            "jobsource.extract._ats.detect_ats_in_html", lambda *a, **kw: None
+        )
+
+        import httpx
+        fake_response = type(
+            "R",
+            (),
+            {"status_code": 200, "text": "<html><body></body></html>"},
+        )()
+
+        monkeypatch.setattr(
+            "jobsource.extract.request_with_retries",
+            lambda *a, **kw: fake_response,
+        )
+        monkeypatch.setattr(
+            "jobsource.extract.extract_anchors", lambda *a, **kw: []
+        )
+        monkeypatch.setattr(
+            "jobsource.extract.classify_job_link", lambda *a, **kw: None
+        )
+
+        # Patch agent_fallback.
+        _mod._MEMO.clear()
+        monkeypatch.setattr(
+            "jobsource.extract._agent_fallback.find_and_extract",
+            lambda *a, **kw: AgentFallbackResult(
+                careers_url="https://extract-wired.com/careers",
+                position_url="https://extract-wired.com/jobs/99",
+            ),
+        )
+
+        url, method = extract_open_position("https://extract-wired.com/careers")
+        assert method == "browser_agent"
+        assert url == "https://extract-wired.com/jobs/99"