diff --git a/.kiro/specs/search-with-proof/tasks.md b/.kiro/specs/search-with-proof/tasks.md
index c07afb3..71d2ce0 100644
--- a/.kiro/specs/search-with-proof/tasks.md
+++ b/.kiro/specs/search-with-proof/tasks.md
@@ -9,15 +9,15 @@ gates, runs every networked or paid step.
     injection), and whether a no-egress task class exists for verify runs. _Requirements: 5.1, 3.2_
   - [ ] 1.2 Record the answers in `kube-ax-cluster` memory and design.md; no key value anywhere. _Requirements: 5.2_
 
-- [ ] 2. Verifier and oracles (no model calls)
-  - [ ] 2.1 `src/openultrasast/search/verify.py`: fresh-sandbox runner per side; build, readiness check, read-only
+- [x] 2. Verifier and oracles (no model calls)
+  - [x] 2.1 `src/openultrasast/search/verify.py`: fresh-sandbox runner per side; build, readiness check, read-only
     checkout and dependencies, untracked-file and runtime-patch refusal, 3 runs per side, consistency check,
     outcomes `demonstrated|inconclusive|could_not_build|could_not_run|no_oracle`. Artefact exit code ignored.
     _Requirements: 3.1-3.4_
-  - [ ] 2.2 Oracles owned by the verifier: SQL (database fixture + query log), path (file-access watch on a planted
+  - [x] 2.2 Oracles owned by the verifier: SQL (database fixture + query log), path (file-access watch on a planted
     canary), XSS (headless browser execution check), SSRF (in-sandbox listener), command injection (process watch).
     Observers unreachable from the artefact. _Requirements: 3.1, 3.2, 3.5_
-  - [ ] 2.3 Unit tests with hand-written vulnerable/fixed toy apps per oracle, including gaming attempts (reading the
+  - [x] 2.3 Unit tests with hand-written vulnerable/fixed toy apps per oracle, including gaming attempts (reading the
     canary, revision sniffing, patching a dependency, contacting the listener directly): each must not yield
     `demonstrated`. _Requirements: 3.2, 3.3_
 
@@ -54,3 +54,14 @@ gates, runs every networked or paid step.
     _Requirements: 6.1, 6.4_
   - [ ] 6.4 Exit decision against 6.2 and report to the maintainer; on pass, spec tasks for qualification and the
     unseen-pool arm. _Requirements: 6.2_
+
+## Implementation Notes
+
+- Group 2 (2026-10-05): independently reviewed; `tests/test_search_verify.py` has 32 passing tests and one
+  skipped SSRF integration test because this host forbids even localhost sockets. The namespace handoff and
+  listener request parsing are tested separately; the full SSRF effect still needs the task 3.2 probe before
+  claiming that oracle operational. The module audit and neighbouring sandbox/regression tests pass.
+- The local lane requires Linux Bubblewrap and util-linux, reuses `SandboxJob`/`SandboxResult`, and fails closed
+  without isolation. Artefacts receive a batch CLI `TARGET` bridge and private scratch; HTTP apps need a trusted
+  CLI adapter. Only trusted `Side.build_command` outputs can enter the app runtime (read-only `/build`);
+  artefact `build.sh` writes scratch only. XSS requires a trusted browser executor, otherwise `no_oracle`.
diff --git a/benchmarks/measurements/2026-09-08-module-audit.json b/benchmarks/measurements/2026-09-08-module-audit.json
index b70b7d6..767e64a 100644
--- a/benchmarks/measurements/2026-09-08-module-audit.json
+++ b/benchmarks/measurements/2026-09-08-module-audit.json
@@ -1,7 +1,7 @@
 {
-  "modules": 159,
+  "modules": 163,
   "counts": {
-    "load_bearing": 154,
+    "load_bearing": 158,
     "standalone_capability": 5
   },
   "orphaned": [],
@@ -1553,7 +1553,9 @@
         "regress.candidate",
         "regress.recipes",
         "regress.safety",
-        "regress.verdict"
+        "regress.verdict",
+        "search._sandbox",
+        "search.verify"
       ]
     },
     {
@@ -1592,6 +1594,36 @@
         "scoring"
       ]
     },
+    {
+      "module": "search",
+      "classification": "load_bearing",
+      "reason": "reachable from gate, map_gate, pair_gate, cli",
+      "importers": [
+        "search.verify"
+      ]
+    },
+    {
+      "module": "search._sandbox",
+      "classification": "load_bearing",
+      "reason": "reachable from gate, map_gate, pair_gate, cli",
+      "importers": [
+        "search.verify"
+      ]
+    },
+    {
+      "module": "search.oracles",
+      "classification": "load_bearing",
+      "reason": "python -m openultrasast.search.oracles",
+      "importers": [
+        "search.verify"
+      ]
+    },
+    {
+      "module": "search.verify",
+      "classification": "load_bearing",
+      "reason": "python -m openultrasast.search.verify",
+      "importers": []
+    },
     {
       "module": "semantic",
       "classification": "load_bearing",
diff --git a/src/openultrasast/search/__init__.py b/src/openultrasast/search/__init__.py
new file mode 100644
index 0000000..ff712e4
--- /dev/null
+++ b/src/openultrasast/search/__init__.py
@@ -0,0 +1 @@
+"""Verifier-owned differential demonstrations (search-with-proof Req 3)."""
diff --git a/src/openultrasast/search/_sandbox.py b/src/openultrasast/search/_sandbox.py
new file mode 100644
index 0000000..97f7894
--- /dev/null
+++ b/src/openultrasast/search/_sandbox.py
@@ -0,0 +1,148 @@
+"""Local CLI lane using the existing sandbox job/result contract.
+
+Bubblewrap is required, never emulated with chmod. Each process sees only the
+immutable runtime, declared inputs, and its own scratch. No host /proc or home.
+The seccomp filter denies sockets for artefacts and builds, even on hosts where
+creating a network namespace is unavailable. SSRF apps join the oracle's private
+loopback namespace. This is a Linux lane; other hosts fail closed.
+"""
+
+from __future__ import annotations
+
+import os
+import platform
+import resource
+import signal
+import struct
+import subprocess
+import tempfile
+from contextlib import suppress
+from pathlib import Path
+
+from ..sandbox import SandboxJob, SandboxResult
+
+
+class IsolationUnavailable(RuntimeError):
+    """The isolation instrument failed, so no product outcome can be recorded."""
+
+
+def isolation_check(*, timeout_seconds: int = 5) -> None:
+    """Prove a trivial job can read its input through the real sandbox path."""
+    try:
+        with tempfile.TemporaryDirectory(prefix="isolation-check-") as directory:
+            root = Path(directory)
+            (root / "probe").write_text("isolation-ready\n")
+            scratch = root / "scratch"
+            scratch.mkdir()
+            job = SandboxJob("", ("/bin/cat", "/workspace/probe"), root, {}, timeout_seconds, 256, 128)
+            result = run(job, scratch=scratch)
+    except (OSError, subprocess.SubprocessError) as exc:
+        raise IsolationUnavailable(f"sandbox isolation preflight could not start: {exc}") from exc
+    if result.exit_code or result.timed_out or result.stdout != "isolation-ready\n":
+        raise IsolationUnavailable(
+            f"sandbox isolation preflight failed (exit={result.exit_code}, timeout={result.timed_out}): {result.stderr}"
+        )
+
+
+def _filter(network: bool) -> bytes:
+    # Audit architecture check also excludes x32 syscall-number bypasses.
+    if platform.machine() == "x86_64":
+        arch, forbidden = 0xC000003E, [101, 165, 166, 272, 308, 321]
+        sockets = [41, 42, 43, 49, 50, 53, 288]
+    elif platform.machine() == "aarch64":
+        arch, forbidden = 0xC00000B7, [39, 40, 97, 117, 268, 280]
+        sockets = [198, 199, 200, 201, 202, 203, 242]
+    else:
+        raise OSError("unsupported seccomp architecture")
+    ins = [(0x20, 0, 0, 4), (0x15, 1, 0, arch), (6, 0, 0, 0x80000000), (0x20, 0, 0, 0), (0x35, 0, 1, 0x40000000), (6, 0, 0, 0x80000000)]
+    for number in forbidden + ([] if network else sockets):
+        ins.extend([(0x15, 0, 1, number), (6, 0, 0, 0x50001)])
+    ins.append((6, 0, 0, 0x7FFF0000))
+    return b"".join(struct.pack("HBBI", *i) for i in ins)
+
+
+def run(
+    job: SandboxJob,
+    *,
+    scratch: Path,
+    mounts: dict[str, Path] | None = None,
+    env: dict[str, str] | None = None,
+    namespace_pid: int | None = None,
+) -> SandboxResult:
+    """Run with bounded files, memory, processes, and time; no inherited env."""
+
+    def limits() -> None:
+        resource.setrlimit(resource.RLIMIT_FSIZE, (1024 * 1024, 1024 * 1024))
+        resource.setrlimit(resource.RLIMIT_AS, (job.memory_mb * 1024**2,) * 2)
+        resource.setrlimit(resource.RLIMIT_CPU, (job.timeout_seconds + 1,) * 2)
+
+    argv = ["bwrap", "--die-with-parent", "--new-session", "--unshare-pid", "--unshare-ipc", "--unshare-uts"]
+    if namespace_pid is None:
+        argv += ["--unshare-user"]
+    else:
+        argv = [
+            "/usr/bin/nsenter",
+            "--preserve-credentials",
+            f"--user=/proc/{namespace_pid}/ns/user",
+            f"--net=/proc/{namespace_pid}/ns/net",
+            "--",
+            *argv,
+        ]
+    argv += ["--cap-drop", "ALL", "--clearenv"]
+    for path in ("/usr", "/lib", "/lib64", "/bin"):
+        if Path(path).exists():
+            argv += ["--ro-bind", path, path]
+    argv += ["--ro-bind", str(job.repo_root), "/workspace", "--bind", str(scratch), "/scratch"]
+    for target, source in (mounts or {}).items():
+        argv += ["--ro-bind", str(source), target]
+    argv += [
+        "--remount-ro",
+        "/",
+        "--chdir",
+        "/scratch",
+        "--setenv",
+        "PATH",
+        "/usr/bin:/bin",
+        "--setenv",
+        "HOME",
+        "/scratch",
+        "--setenv",
+        "TMPDIR",
+        "/scratch",
+    ]
+    for key, value in (env or {}).items():
+        argv += ["--setenv", key, value]
+    with tempfile.TemporaryFile() as policy, tempfile.TemporaryFile() as out, tempfile.TemporaryFile() as err:
+        policy.write(_filter(namespace_pid is not None))
+        policy.seek(0)
+        # Set NPROC after entering the user namespace (per-namespace since Linux 5.14),
+        # so the host uid's existing processes cannot prevent bwrap from starting.
+        argv += [
+            "--seccomp", str(policy.fileno()), "--",
+            "/usr/bin/prlimit", f"--nproc={job.pids_limit}:{job.pids_limit}", "--", *job.command,
+        ]
+        proc = subprocess.Popen(
+            argv,
+            stdout=out,
+            stderr=err,
+            pass_fds=(policy.fileno(),),
+            start_new_session=True,
+            preexec_fn=limits,
+            env={"PATH": "/usr/bin:/bin"},
+        )
+        timed_out = False
+        try:
+            proc.wait(timeout=job.timeout_seconds)
+        except subprocess.TimeoutExpired:
+            timed_out = True
+            os.killpg(proc.pid, signal.SIGKILL)
+            proc.wait()
+        finally:
+            # Also terminate descendants left behind after a successful shell exit.
+            with suppress(ProcessLookupError):
+                os.killpg(proc.pid, signal.SIGKILL)
+        out.seek(0)
+        err.seek(0)
+        return SandboxResult(
+            proc.returncode, out.read(1024 * 1024).decode(errors="replace"), err.read(1024 * 1024).decode(errors="replace"), timed_out
+        )
diff --git a/src/openultrasast/search/oracles.py b/src/openultrasast/search/oracles.py
new file mode 100644
index 0000000..ff2e9b9
--- /dev/null
+++ b/src/openultrasast/search/oracles.py
@@ -0,0 +1,189 @@
+"""Owned canaries. Only app captures enter these oracles, never attack output.
+
+The attacker may supply CLI arguments through TARGET. Fixtures and app config
+are mounted only in the app sandbox. Nonces are fresh per run and absent from
+artefact env. A browser executor is trusted verifier code, never a demo script.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import secrets
+import selectors
+import sqlite3
+import subprocess
+from collections.abc import Callable
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Protocol
+
+
+@dataclass(frozen=True)
+class Canary:
+    root: Path
+    nonce: str
+
+    @classmethod
+    def fresh(cls, root: Path) -> Canary:
+        root.mkdir()
+        return cls(root, secrets.token_hex(24))
+
+
+class Oracle(Protocol):
+    namespace_pid: int | None
+
+    def prepare(self, canary: Canary) -> dict[str, str]: ...
+    def capture(self, output: str) -> None: ...
+    def observe(self) -> tuple[bool, str]: ...
+    def close(self) -> None: ...
+
+
+class OutputOracle:
+    namespace_pid: int | None = None
+
+    def prepare(self, canary: Canary) -> dict[str, str]:
+        self.canary = canary
+        self.seen = False
+        return {}
+
+    def capture(self, output: str) -> None:
+        self.seen |= self.canary.nonce in output
+
+    def observe(self) -> tuple[bool, str]:
+        return self.seen, "canary in verifier-captured app output" if self.seen else "no canary in app output"
+
+    def close(self) -> None:
+        pass
+
+
+class PathOracle(OutputOracle):
+    def prepare(self, canary: Canary) -> dict[str, str]:
+        super().prepare(canary)
+        (canary.root / "public").mkdir()
+        (canary.root / "canary").write_text(canary.nonce)
+        return {"SERVED_ROOT": "/fixture/public"}
+
+
+class SQLOracle(OutputOracle):
+    def prepare(self, canary: Canary) -> dict[str, str]:
+        super().prepare(canary)
+        with sqlite3.connect(canary.root / "fixture.db") as db:
+            db.execute("CREATE TABLE records (name TEXT, value TEXT, public INTEGER)")
+            db.executemany("INSERT INTO records VALUES (?, ?, ?)", [("ordinary", "public value", 1), ("secret", canary.nonce, 0)])
+        return {"DATABASE": "/fixture/fixture.db"}
+
+
+class CommandOracle(OutputOracle):
+    def prepare(self, canary: Canary) -> dict[str, str]:
+        super().prepare(canary)
+        # Marker is in app-only writable scratch, inaccessible in artefact sandbox.
+        self.marker = canary.root / canary.nonce
+        return {"PROOF_MARKER": "/scratch/" + canary.nonce}
+
+    def observe(self) -> tuple[bool, str]:
+        observed = self.marker.is_file() and not self.marker.is_symlink()
+        return observed, "injected command marker exists" if observed else "no command marker"
+
+
+class SSRFOracle(OutputOracle):
+    """Separate listener process and private loopback namespace; no external egress."""
+
+    process: subprocess.Popen[str] | None = None
+
+    def prepare(self, canary: Canary) -> dict[str, str]:
+        super().prepare(canary)
+        self.process = subprocess.Popen(
+            [
+                "/usr/bin/unshare",
+                "--user",
+                "--map-root-user",
+                "--net",
+                "/usr/bin/python3",
+                "-I",
+                str(Path(__file__).resolve()),
+                "--listener",
+                canary.nonce,
+            ],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.DEVNULL,
+            text=True,
+            env={"PATH": "/usr/bin:/bin"},
+        )
+        assert self.process.stdout is not None
+        with selectors.DefaultSelector() as selector:
+            selector.register(self.process.stdout, selectors.EVENT_READ)
+            if not selector.select(3):
+                raise OSError("listener namespace readiness timed out")
+            line = self.process.stdout.readline()
+        if not line:
+            raise OSError("private loopback listener unavailable")
+        self.namespace_pid, port = json.loads(line)
+        return {"CALLBACK_URL": f"http://127.0.0.1:{port}/{canary.nonce}"}  # loopback: oracle listener inside the private sandbox namespace
+
+    def observe(self) -> tuple[bool, str]:
+        assert self.process is not None and self.process.stdout is not None
+        with selectors.DefaultSelector() as selector:
+            selector.register(self.process.stdout, selectors.EVENT_READ)
+            observed = bool(selector.select(0.2)) and self.process.stdout.readline().strip() == "observed"
+        return observed, "nonce request received" if observed else "no nonce request"
+
+    def close(self) -> None:
+        if self.process is not None:
+            self.process.terminate()
+            self.process.wait(timeout=3)
+            if self.process.stdout:
+                self.process.stdout.close()
+
+
+BrowserExecutor = Callable[[str, str], bool]
+
+
+class XSSOracle(OutputOracle):
+    def __init__(self, executor: BrowserExecutor) -> None:
+        self.executor = executor
+
+    def capture(self, output: str) -> None:
+        self.seen |= self.executor(output, self.canary.nonce)
+
+
+def oracle_for(family: str, browser: BrowserExecutor | None = None) -> Oracle | None:
+    factories = {"path": PathOracle, "sql": SQLOracle, "command": CommandOracle, "ssrf": SSRFOracle}
+    if family == "xss":
+        return XSSOracle(browser) if browser else None
+    factory = factories.get(family)
+    return factory() if factory else None
+
+
+def _listen(nonce: str) -> None:
+    import fcntl
+    import socket
+    import struct
+    from http.server import BaseHTTPRequestHandler, HTTPServer
+
+    # unshare created only loopback; bring it up without iproute2 or any egress.
+    with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock:
+        fcntl.ioctl(sock, 0x8914, struct.pack("16sH14s", b"lo", 0x49, b""))
+
+    class Handler(BaseHTTPRequestHandler):
+        def do_GET(self) -> None:
+            if self.path.split("?", 1)[0] == "/" + nonce:
+                print("observed", flush=True)
+            self.send_response(200)
+            self.end_headers()
+            self.wfile.write(b"ok")
+
+        do_POST = do_PUT = do_PATCH = do_DELETE = do_HEAD = do_OPTIONS = do_TRACE = do_CONNECT = do_GET
+
+        def log_message(self, format: str, *args: object) -> None:
+            pass
+
+    with HTTPServer(("127.0.0.1", 0), Handler) as server:
+        print(json.dumps([os.getpid(), server.server_port]), flush=True)
+        server.serve_forever()
+
+
+if __name__ == "__main__":
+    import sys
+
+    _listen(sys.argv[2])
diff --git a/src/openultrasast/search/verify.py b/src/openultrasast/search/verify.py
new file mode 100644
index 0000000..d4c2ffb
--- /dev/null
+++ b/src/openultrasast/search/verify.py
@@ -0,0 +1,257 @@
+"""Offline differential verification through an isolated, batch CLI interface.
+
+Side.command and readiness_args are trusted integration configuration, not demo
+contents. TARGET is an executable CLI bridge: each invocation queues arguments
+for the app. It deliberately has no synchronous response channel. Alternatively
+request.json contains one argument vector. HTTP apps need a trusted CLI adapter;
+this lane never treats an artefact's stdout, exit status, or claimed result as
+proof. Build scripts validate the immutable checkout and may write scratch only;
+only Side.build_command (trusted integration config) can produce /build runtime outputs.
+
+Run: python -m openultrasast.search.verify vulnerable fixed demo path --entry app.py
+"""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import shutil
+import stat
+import tempfile
+import time
+from dataclasses import asdict, dataclass
+from pathlib import Path
+
+from ..sandbox import SandboxJob
+from . import _sandbox
+from .oracles import BrowserExecutor, Canary, oracle_for
+
+_BRIDGE = """#!/usr/bin/python3 -I
+import json, sys
+with open('/scratch/requests.jsonl', 'a') as stream:
+    stream.write(json.dumps(sys.argv[1:]) + '\\n')
+"""
+
+
+@dataclass(frozen=True)
+class Side:
+    checkout: Path
+    command: tuple[str, ...]
+    readiness_args: tuple[str, ...] = ("--ready",)
+    dependencies: tuple[Path, ...] = ()
+    build_command: tuple[str, ...] = ()
+
+
+@dataclass(frozen=True)
+class RunObservation:
+    observed: bool
+    evidence: str
+    elapsed_seconds: float
+
+
+@dataclass(frozen=True)
+class SideRecord:
+    outcome: str
+    runs: tuple[RunObservation, ...]
+    elapsed_seconds: float
+    reason: str
+
+
+@dataclass(frozen=True)
+class VerificationRecord:
+    outcome: str
+    sides: tuple[SideRecord, ...]
+    elapsed_seconds: float
+    reason: str
+
+
+def _tree(root: Path) -> str:
+    """Read every file; hash names, modes and bytes, refusing links/devices."""
+    digest = hashlib.sha256()
+    if not root.is_dir() or root.is_symlink():
+        raise ValueError("input must be a real directory")
+    for path in [root, *sorted(root.rglob("*"))]:
+        mode = path.lstat().st_mode
+        if not (stat.S_ISREG(mode) or stat.S_ISDIR(mode)):
+            raise ValueError(f"links and special files refused: {path.name}")
+        digest.update(str(path.relative_to(root)).encode())
+        digest.update(str(mode).encode())
+        if path.is_file():
+            digest.update(path.read_bytes())
+    return digest.hexdigest()
+
+
+def _requests(scratch: Path, demo: Path) -> list[list[str]]:
+    path = demo / "request.json"
+    if path.is_file():
+        values = [json.loads(path.read_text())]
+    else:
+        queue = scratch / "requests.jsonl"
+        if not queue.exists():
+            return []
+        if queue.is_symlink() or not queue.is_file() or queue.stat().st_size > 65536:
+            raise ValueError("invalid request queue")
+        values = [json.loads(line) for line in queue.read_text().splitlines()]
+    if len(values) > 32 or any(
+        not isinstance(v, list) or not all(isinstance(a, str) and "\0" not in a for a in v) or sum(map(len, v)) > 16384 for v in values
+    ):
+        raise ValueError("invalid or excessive CLI requests")
+    return values
+
+
+def _side(side: Side, demo: Path, family: str, timeout: int, browser: BrowserExecutor | None) -> SideRecord:
+    started = time.monotonic()
+    observations: list[RunObservation] = []
+
+    def record(outcome: str, reason: str) -> SideRecord:
+        return SideRecord(outcome, tuple(observations), time.monotonic() - started, reason)
+
+    try:
+        originals = (side.checkout, *side.dependencies, demo)
+        initial = tuple(_tree(p) for p in originals)
+        for _ in range(3):
+            tick = time.monotonic()
+            with tempfile.TemporaryDirectory(prefix="ousast-proof-") as temporary:
+                root = Path(temporary)
+                checkout = shutil.copytree(side.checkout, root / "checkout")
+                artefact = shutil.copytree(demo, root / "demo")
+                dependencies = [shutil.copytree(p, root / f"dep-{i}") for i, p in enumerate(side.dependencies)]
+                immutable = (checkout, *dependencies, artefact)
+                before = tuple(_tree(p) for p in immutable)
+                mounts = {f"/deps/{i}": p for i, p in enumerate(dependencies)}
+
+                def job(command: tuple[str, ...], checkout: Path = checkout) -> SandboxJob:
+                    return SandboxJob("", command, checkout, {}, timeout, 256, 128)
+
+                products = root / "products"
+                products.mkdir()
+                if side.build_command:
+                    compiled = _sandbox.run(job(side.build_command), scratch=products, mounts=mounts)
+                    if compiled.exit_code or compiled.timed_out:
+                        return record("could_not_build", "trusted build failed: " + compiled.stderr[:300])
+                product_hash = _tree(products)
+                mounts["/build"] = products
+                build_scratch = root / "build"
+                build_scratch.mkdir()
+                built = _sandbox.run(job(("/bin/sh", "/demo/build.sh")), scratch=build_scratch, mounts={**mounts, "/demo": artefact})
+                if built.exit_code or built.timed_out:
+                        return record("could_not_build", "build failed: " + built.stderr[:300])
+                if tuple(_tree(p) for p in immutable) != before or _tree(products) != product_hash:
+                    return record("inconclusive", "build changed immutable inputs")
+
+                oracle = oracle_for(family, browser)
+                assert oracle is not None
+                try:
+                    canary = Canary.fresh(root / "fixture")
+                    app_env = oracle.prepare(canary)
+                    app_scratch = canary.root if family == "command" else root / "app"
+                    app_scratch.mkdir(exist_ok=True)
+                    app_mounts = {**mounts, "/fixture": canary.root}
+                    ready = _sandbox.run(
+                        job((*side.command, *side.readiness_args)),
+                        scratch=app_scratch,
+                        mounts=app_mounts,
+                        env=app_env,
+                        namespace_pid=oracle.namespace_pid,
+                    )
+                    if ready.exit_code or ready.timed_out:
+                        return record("could_not_run", "app readiness failed: " + ready.stderr[:300])
+                    if family == "ssrf" and oracle.observe()[0]:
+                        return record("inconclusive", "readiness triggered the SSRF oracle")
+                    # Readiness cannot supply the attack's evidence or leave a command marker.
+                    if family == "command" and any(canary.root.iterdir()):
+                        return record("inconclusive", "readiness modified command fixture")
+                    attack_scratch = root / "attack"
+                    attack_scratch.mkdir()
+                    if (artefact / "attack.sh").is_file():
+                        bridge = root / "target"
+                        bridge.write_text(_BRIDGE)
+                        bridge.chmod(0o555)
+                        attacker_input = root / "attacker-input"
+                        attacker_input.mkdir()
+                        attack = _sandbox.run(
+                            job(("/bin/sh", "/demo/attack.sh"), checkout=attacker_input),
+                            scratch=attack_scratch,
+                            mounts={"/demo": artefact, "/target": bridge},
+                            env={"TARGET": "/target", "SCRATCH": "/scratch"},
+                        )
+                        # Output/status are never evidence. Timeout and explicit filesystem
+                        # denials veto verification; read-only mounts enforce the boundary.
+                        if attack.timed_out:
+                            return record("inconclusive", "attack timed out")
+                        if "Read-only file system" in attack.stderr or "Permission denied" in attack.stderr:
+                            return record("inconclusive", "attacker boundary refused")
+                    for arguments in _requests(attack_scratch, artefact):
+                        result = _sandbox.run(
+                            job((*side.command, *arguments)),
+                            scratch=app_scratch,
+                            mounts=app_mounts,
+                            env=app_env,
+                            namespace_pid=oracle.namespace_pid,
+                        )
+                        if result.timed_out:
+                            return record("inconclusive", "app attack timed out")
+                        oracle.capture(result.stdout)
+                    observed, evidence = oracle.observe()
+                    if (
+                        tuple(_tree(p) for p in immutable) != before
+                        or tuple(_tree(p) for p in originals) != initial
+                        or _tree(products) != product_hash
+                    ):
+                        return record("inconclusive", "immutable input or dependency changed")
+                    observations.append(RunObservation(observed, evidence, time.monotonic() - tick))
+                finally:
+                    oracle.close()
+        return record("observed", "three fresh runs completed")
+    except (OSError, ValueError, AssertionError) as exc:
+        return record("could_not_run", f"verification unavailable or refused: {exc}")
+
+
+def verify(
+    affected: Side,
+    safe: Side,
+    artefact: Path,
+    family: str,
+    *,
+    timeout_seconds: int = 5,
+    browser: BrowserExecutor | None = None,
+) -> VerificationRecord:
+    """Affected is vulnerable/head; safe is fixed/base. No negative verdict exists."""
+    started = time.monotonic()
+    if oracle_for(family, browser) is None:
+        return VerificationRecord("no_oracle", (), time.monotonic() - started, "no configured owned oracle for " + family)
+    if timeout_seconds < 1:
+        raise ValueError("timeout must be positive")
+    _sandbox.isolation_check(timeout_seconds=timeout_seconds)
+    sides = tuple(_side(s, artefact, family, timeout_seconds, browser) for s in (affected, safe))
+    if sides[1].outcome != "observed":
+        outcome, reason = "inconclusive", "safe side did not complete build/readiness/verification"
+    elif sides[0].outcome != "observed":
+        outcome, reason = sides[0].outcome, sides[0].reason
+    elif all(r.observed for r in sides[0].runs) and not any(r.observed for r in sides[1].runs):
+        outcome, reason = "demonstrated", "owned effect in 3/3 affected runs and 0/3 safe runs"
+    else:
+        outcome, reason = "inconclusive", "no consistent differential effect"
+    return VerificationRecord(outcome, sides, time.monotonic() - started, reason)
+
+
+def main() -> None:
+    import argparse
+
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("affected", type=Path)
+    parser.add_argument("safe", type=Path)
+    parser.add_argument("artefact", type=Path)
+    parser.add_argument("family")
+    parser.add_argument("--entry", required=True, help="trusted Python CLI entry relative to checkout")
+    args = parser.parse_args()
+    entry = Path(args.entry)
+    if entry.is_absolute() or ".." in entry.parts:
+        parser.error("entry must stay inside checkout")
+    command = ("/usr/bin/python3", "-I", "/workspace/" + str(entry))
+    result = verify(Side(args.affected, command), Side(args.safe, command), args.artefact, args.family)
+    print(json.dumps(asdict(result), indent=2))
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tests/fixtures/search/app.py b/tests/fixtures/search/app.py
new file mode 100644
index 0000000..f7db753
--- /dev/null
+++ b/tests/fixtures/search/app.py
@@ -0,0 +1,33 @@
+"""CLI toy: arguments are its sole public interface; config belongs to the app."""
+
+import os
+import pathlib
+import sqlite3
+import subprocess
+import sys
+import urllib.request
+
+fixed = pathlib.Path("/workspace/fixed").exists()
+if sys.argv[1:] == ["--ready"]:
+    sys.exit(1 if pathlib.Path("/workspace/broken").exists() else 0)
+family, payload = sys.argv[1:]
+if family == "path":
+    root = pathlib.Path(os.environ["SERVED_ROOT"])
+    path = (root / payload).resolve()
+    if not fixed or path.is_relative_to(root):
+        value = path.read_text()
+        if not pathlib.Path("/workspace/flaky").exists() or value.startswith("a"):
+            print(value)
+elif family == "sql":
+    with sqlite3.connect(os.environ["DATABASE"]) as db:
+        if fixed:
+            rows = db.execute("SELECT value FROM records WHERE public=1 AND name=?", (payload,))
+        else:
+            rows = db.execute("SELECT value FROM records WHERE public=1 AND name='" + payload + "'")
+        print(list(rows))
+elif family == "command":
+    if not fixed:
+        subprocess.run("echo " + payload, shell=True, check=False)
+elif family == "ssrf":
+    if not fixed:
+        print(urllib.request.urlopen(os.path.expandvars(payload), timeout=2).read())
diff --git a/tests/test_search_verify.py b/tests/test_search_verify.py
new file mode 100644
index 0000000..f8b029c
--- /dev/null
+++ b/tests/test_search_verify.py
@@ -0,0 +1,411 @@
+"""Owned observations and adversarial artefacts, with real isolated toy processes."""
+
+import os
+import shutil
+import signal
+import socket
+from pathlib import Path
+
+import pytest
+
+from openultrasast.search.verify import Side, verify
+
+FIXTURE = Path(__file__).parent / "fixtures/search/app.py"
+PAYLOADS = {
+    "path": "../canary",
+    "sql": "' OR public=0 --",
+    "command": '; touch "$PROOF_MARKER"',
+    "ssrf": "$CALLBACK_URL",
+}
+
+
+@pytest.fixture
+def pair(tmp_path):
+    sides = []
+    for name in ("vulnerable", "fixed"):
+        root = tmp_path / name
+        root.mkdir()
+        shutil.copyfile(FIXTURE, root / "app.py")
+        if name == "fixed":
+            (root / "fixed").touch()
+        sides.append(Side(root, ("/usr/bin/python3", "-I", "/workspace/app.py")))
+    demo = tmp_path / "demo"
+    demo.mkdir()
+    (demo / "build.sh").write_text("test -s /workspace/app.py\n")
+    return sides, demo
+
+
+def request(demo, family):
+    import json
+
+    (demo / "request.json").write_text(json.dumps([family, PAYLOADS[family]]))
+
+
+@pytest.mark.parametrize("family", ["path", "sql", "command", "ssrf"])
+def test_real_differential(pair, family):
+    if family == "ssrf":
+        try:
+            with socket.socket():
+                pass
+        except PermissionError:
+            pytest.skip("host policy prohibits even localhost sockets")
+    sides, demo = pair
+    request(demo, family)
+    result = verify(*sides, demo, family)
+    assert result.outcome == "demonstrated", result
+    assert [r.observed for r in result.sides[0].runs] == [True] * 3
+    assert [r.observed for r in result.sides[1].runs] == [False] * 3
+    assert result.elapsed_seconds > 0
+
+
+@pytest.mark.parametrize(
+    "script",
+    [
+        "cat /fixture/canary; echo success; exit 42",
+        "if test ! -f /workspace/fixed; then echo demonstrated; fi",
+        "echo hacked > /workspace/sitecustomize.py",
+        "echo hacked > /usr/lib/python3.12/sitecustomize.py",
+        "echo hacked > /deps/0/module.py",
+        "cat /proc/1/environ; echo demonstrated",
+        '/usr/bin/python3 -I -c "import socket; socket.create_connection(("127.0.0.1",12345))"',
+    ],
+)
+def test_gaming_cannot_demonstrate(pair, tmp_path, script):
+    sides, demo = pair
+    deps = tmp_path / "deps"
+    deps.mkdir()
+    (deps / "module.py").write_text("original")
+    sides = [Side(s.checkout, s.command, dependencies=(deps,)) for s in sides]
+    (demo / "attack.sh").write_text(script)
+    result = verify(*sides, demo, "path")
+    assert result.outcome != "demonstrated"
+    assert (deps / "module.py").read_text() == "original"
+    assert not (sides[0].checkout / "sitecustomize.py").exists()
+
+
+def test_attack_exit_and_stdout_ignored(pair):
+    sides, demo = pair
+    (demo / "attack.sh").write_text('"$TARGET" path ../canary\necho fake\nexit 99\n')
+    assert verify(*sides, demo, "path").outcome == "demonstrated"
+
+
+def test_safe_build_failure_is_inconclusive(pair):
+    sides, demo = pair
+    request(demo, "path")
+    (demo / "build.sh").write_text("test ! -f /workspace/fixed")
+    result = verify(*sides, demo, "path")
+    assert result.outcome == "inconclusive"
+    assert result.sides[1].outcome == "could_not_build"
+
+
+def test_readiness_failure(pair):
+    sides, demo = pair
+    request(demo, "path")
+    (sides[1].checkout / "broken").touch()
+    result = verify(*sides, demo, "path")
+    assert result.outcome == "inconclusive"
+    assert result.sides[1].outcome == "could_not_run"
+
+
+@pytest.mark.parametrize("family", ["xss", "deserialisation", "access_control", "secrets"])
+def test_no_oracle(pair, family):
+    sides, demo = pair
+    assert verify(*sides, demo, family).outcome == "no_oracle"
+
+
+def test_flaky_observation_is_inconclusive(pair, monkeypatch):
+    from openultrasast.search import oracles
+
+    nonces = iter(["a" * 48, "b" * 48, "c" * 48] * 2)
+    monkeypatch.setattr(oracles.secrets, "token_hex", lambda _: next(nonces))
+    sides, demo = pair
+    (sides[0].checkout / "flaky").touch()
+    request(demo, "path")
+    result = verify(*sides, demo, "path")
+    assert result.outcome == "inconclusive"
+    assert [r.observed for r in result.sides[0].runs] == [True, False, False]
+
+
+def test_environment_injection_stays_in_artefact(pair, monkeypatch):
+    sides, demo = pair
+    monkeypatch.setenv("PYTHONPATH", "/bogus")
+    monkeypatch.setenv("NODE_OPTIONS", "--require=/bogus")
+    monkeypatch.setenv("LD_PRELOAD", "/bogus")
+    (demo / "attack.sh").write_text(
+        'test -z "$PYTHONPATH$NODE_OPTIONS$LD_PRELOAD" || exit 3\n'
+        'echo "raise RuntimeError()" > /scratch/sitecustomize.py\n'
+        "export PYTHONPATH=/scratch NODE_OPTIONS=--require=/scratch/sitecustomize.py LD_PRELOAD=/bogus\n"
+        '"$TARGET" path ../canary\n'
+    )
+    assert verify(*sides, demo, "path").outcome == "demonstrated"
+
+
+def test_untracked_file_outside_scratch_refused(pair):
+    sides, demo = pair
+    (demo / "attack.sh").write_text('echo hacked > /untracked\n"$TARGET" path ../canary\n')
+    assert verify(*sides, demo, "path").outcome == "inconclusive"
+
+
+def test_unknown_app_failure_cannot_prove_effect(pair):
+    sides, demo = pair
+    (sides[0].checkout / "app.py").write_text('raise RuntimeError("no app")')
+    request(demo, "path")
+    assert verify(*sides, demo, "path").outcome == "could_not_run"
+
+
+def test_affected_build_failure(pair):
+    sides, demo = pair
+    request(demo, "path")
+    (demo / "build.sh").write_text("test -f /workspace/fixed")
+    assert verify(*sides, demo, "path").outcome == "could_not_build"
+
+
+def test_missing_isolation_fails_closed(pair, monkeypatch):
+    from openultrasast.search import _sandbox
+
+    def unavailable(*args, **kwargs):
+        raise FileNotFoundError("bwrap unavailable")
+
+    monkeypatch.setattr(_sandbox, "run", unavailable)
+    sides, demo = pair
+    request(demo, "path")
+    with pytest.raises(_sandbox.IsolationUnavailable, match="bwrap unavailable"):
+        verify(*sides, demo, "path")
+
+
+def test_bwrap_failure_raises_before_product_outcomes(pair, monkeypatch):
+    from openultrasast.sandbox import SandboxResult
+    from openultrasast.search import _sandbox
+
+    calls = []
+    stderr = "bwrap: Creating new namespace failed: Resource temporarily unavailable"
+
+    def failed(job, **kwargs):
+        calls.append(job)
+        return SandboxResult(1, "", stderr, False)
+
+    monkeypatch.setattr(_sandbox, "run", failed)
+    sides, demo = pair
+    with pytest.raises(_sandbox.IsolationUnavailable, match=stderr):
+        verify(*sides, demo, "path")
+    assert len(calls) == 1
+    assert calls[0].command == ("/bin/cat", "/workspace/probe")
+
+
+def test_verification_with_many_host_processes(pair, monkeypatch):
+    from openultrasast.search import _sandbox
+
+    checks = []
+    original = _sandbox.isolation_check
+
+    def checked(**kwargs):
+        checks.append(True)
+        return original(**kwargs)
+
+    monkeypatch.setattr(_sandbox, "isolation_check", checked)
+    sides, demo = pair
+    request(demo, "path")
+    children = []
+    try:
+        for _ in range(300):
+            pid = os.fork()
+            if pid == 0:
+                try:
+                    while True:
+                        signal.pause()
+                finally:
+                    os._exit(0)
+            children.append(pid)
+        assert verify(*sides, demo, "path").outcome == "demonstrated"
+        assert checks == [True]
+    finally:
+        for pid in children:
+            os.kill(pid, signal.SIGKILL)
+        for pid in children:
+            os.waitpid(pid, 0)
+
+
+def test_symlink_input_refused(pair):
+    sides, demo = pair
+    (demo / "escape").symlink_to("/etc/passwd")
+    request(demo, "path")
+    assert verify(*sides, demo, "path").outcome == "inconclusive"
+
+
+def test_xss_executor_contract(tmp_path):
+    from openultrasast.search.oracles import Canary, oracle_for
+
+    calls = []
+
+    def browser(document, nonce):
+        calls.append((document, nonce))
+        return document == "<script>execute()</script>"
+
+    oracle = oracle_for("xss", browser)
+    canary = Canary.fresh(tmp_path / "fixture")
+    assert oracle.prepare(canary) == {}
+    oracle.capture("<script>execute()</script>")
+    assert oracle.observe()[0]
+    assert calls == [("<script>execute()</script>", canary.nonce)]
+
+
+def test_six_fresh_canaries(pair, monkeypatch):
+    from openultrasast.search import oracles
+
+    nonces = []
+    prepare = oracles.PathOracle.prepare
+
+    def record(self, canary):
+        nonces.append(canary.nonce)
+        return prepare(self, canary)
+
+    monkeypatch.setattr(oracles.PathOracle, "prepare", record)
+    sides, demo = pair
+    request(demo, "path")
+    assert verify(*sides, demo, "path").outcome == "demonstrated"
+    assert len(set(nonces)) == 6
+
+
+def test_readiness_effect_cannot_prove_ssrf(pair, monkeypatch):
+    from openultrasast.search import verify as module
+    from openultrasast.search.oracles import OutputOracle
+
+    class ReadinessOracle(OutputOracle):
+        def observe(self):
+            return True, "request during readiness"
+
+    monkeypatch.setattr(module, "oracle_for", lambda *args: ReadinessOracle())
+    sides, demo = pair
+    result = module.verify(*sides, demo, "ssrf")
+    assert result.outcome == "inconclusive"
+    assert not result.sides[0].runs
+
+
+def test_dependency_hash_detects_replacement(pair, tmp_path, monkeypatch):
+    from openultrasast.search import _sandbox
+
+    original = _sandbox.run
+    dependency = tmp_path / "dependency"
+    dependency.mkdir()
+    (dependency / "module.py").write_text("original")
+    sides, demo = pair
+    sides = [Side(s.checkout, s.command, dependencies=(dependency,)) for s in sides]
+    request(demo, "path")
+
+    def changed(job, **kwargs):
+        result = original(job, **kwargs)
+        if job.command[-1] == "/demo/build.sh":
+            (kwargs["mounts"]["/deps/0"] / "module.py").write_text("replacement")
+        return result
+
+    monkeypatch.setattr(_sandbox, "run", changed)
+    result = verify(*sides, demo, "path")
+    assert result.outcome == "inconclusive"
+    assert result.sides[0].reason == "build changed immutable inputs"
+
+
+def test_trusted_build_products_are_used_readonly(pair):
+    sides, demo = pair
+    sides = [
+        Side(s.checkout, ("/usr/bin/python3", "-I", "/build/app.py"), build_command=("/bin/cp", "/workspace/app.py", "/scratch/app.py"))
+        for s in sides
+    ]
+    request(demo, "path")
+    assert verify(*sides, demo, "path").outcome == "demonstrated"
+    (demo / "build.sh").write_text("echo patched > /build/app.py")
+    assert verify(*sides, demo, "path").outcome == "inconclusive"
+
+
+def test_private_namespace_handoff_without_sockets(tmp_path):
+    import subprocess
+
+    from openultrasast.sandbox import SandboxJob
+    from openultrasast.search import _sandbox
+
+    # Proves the actual nsenter -> bwrap handoff without requiring socket().
+    process = subprocess.Popen(
+        [
+            "/usr/bin/unshare",
+            "--user",
+            "--map-root-user",
+            "--net",
+            "/usr/bin/python3",
+            "-I",
+            "-c",
+            "import os,time; print(os.getpid(), flush=True); time.sleep(10)",
+        ],
+        stdout=subprocess.PIPE,
+        text=True,
+    )
+    try:
+        pid = int(process.stdout.readline())
+        scratch = tmp_path / "scratch"
+        scratch.mkdir()
+        job = SandboxJob("", ("/usr/bin/python3", "-I", "-c", 'print("namespace-ready")'), tmp_path, {}, 3, 256, 128)
+        result = _sandbox.run(job, scratch=scratch, namespace_pid=pid)
+        assert result.exit_code == 0, result.stderr
+        assert result.stdout.strip() == "namespace-ready"
+    finally:
+        process.terminate()
+        process.wait(timeout=3)
+        process.stdout.close()
+
+
+def test_attacker_sees_only_external_bridge_and_scratch(pair):
+    sides, demo = pair
+    (demo / "attack.sh").write_text(
+        "test ! -e /workspace/app.py || exit 3\n"
+        "test ! -e /fixture/canary || exit 3\n"
+        "test ! -e /build/app.py || exit 3\n"
+        "test ! -e /deps/0 || exit 3\n"
+        'test -z "$CALLBACK_URL$PROOF_MARKER$DATABASE$SERVED_ROOT" || exit 3\n'
+        '"$TARGET" path ../canary\n'
+    )
+    assert verify(*sides, demo, "path").outcome == "demonstrated"
+
+
+def test_listener_accepts_nonce_path_for_post_without_sockets(monkeypatch, capsys):
+    import fcntl
+    import http.server
+    import io
+
+    from openultrasast.search import oracles
+
+    class Socket:
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *args):
+            pass
+
+    class Connection:
+        def __init__(self, path):
+            self.input = io.BytesIO(b"POST " + path + b" HTTP/1.0\r\nContent-Length: 0\r\n\r\n")
+
+        def makefile(self, *args):
+            return self.input
+
+        def sendall(self, data):
+            pass
+
+    class Server:
+        server_port = 12345
+
+        def __init__(self, address, handler):
+            self.handler = handler
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *args):
+            pass
+
+        def serve_forever(self):
+            for path in (b"/wrong", b"/secret?query=1"):
+                self.handler(Connection(path), ("127.0.0.1", 1), self)
+
+    monkeypatch.setattr(socket, "socket", lambda *args: Socket())
+    monkeypatch.setattr(fcntl, "ioctl", lambda *args: None)
+    monkeypatch.setattr(http.server, "HTTPServer", Server)
+    oracles._listen("secret")
+    assert capsys.readouterr().out.splitlines()[1:] == ["observed"]