diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index 12f79b2208..4e4f3e9ae3 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -12697,6 +12697,7 @@ def main():
             return
         if action == "status":
             import subprocess
+            from hermes_cli.tools_config import _cua_driver_contract_status
             from tools.computer_use.cua_backend import (
                 cua_driver_update_check,
                 resolve_cua_driver_cmd,
@@ -12719,6 +12720,14 @@ def main():
                     print(f"cua-driver: installed at {path} ({version})")
                 else:
                     print(f"cua-driver: installed at {path}")
+                contract = _cua_driver_contract_status(path)
+                if not contract.get("ready"):
+                    print(
+                        "  ⚠ Repair required: "
+                        + (contract.get("reason") or "runtime contract is incomplete")
+                    )
+                    print("    Run: hermes computer-use install")
+                    return
                 try:
                     st = cua_driver_update_check()
                     if st and st.get("update_available"):
diff --git a/hermes_cli/tools_config.py b/hermes_cli/tools_config.py
index 530c8b7b37..1a65dcc1bb 100644
--- a/hermes_cli/tools_config.py
+++ b/hermes_cli/tools_config.py
@@ -793,6 +793,49 @@ def _cua_driver_env() -> dict:
         return dict(os.environ)
 
 
+_CUA_DRIVER_CONTRACT_CACHE: dict = {}
+
+
+def _cua_driver_contract_status(binary: Optional[str] = None) -> dict:
+    """Inspect whether an installed driver supports Hermes' runtime contract."""
+    import time
+
+    from tools.computer_use.cua_backend import cua_driver_runtime_contract_status
+
+    resolved = binary or _resolved_cua_driver_cmd()
+    if not resolved:
+        return cua_driver_runtime_contract_status(None)
+    try:
+        stat = os.stat(resolved)
+        fingerprint = (resolved, stat.st_mtime_ns, stat.st_size)
+    except OSError:
+        return cua_driver_runtime_contract_status(resolved)
+
+    now = time.monotonic()
+    if (
+        _CUA_DRIVER_CONTRACT_CACHE.get("fingerprint") == fingerprint
+        and now - _CUA_DRIVER_CONTRACT_CACHE.get("checked_at", 0.0) < 30.0
+    ):
+        return dict(_CUA_DRIVER_CONTRACT_CACHE["state"])
+
+    state = cua_driver_runtime_contract_status(resolved)
+    _CUA_DRIVER_CONTRACT_CACHE.update(
+        fingerprint=fingerprint,
+        checked_at=now,
+        state=dict(state),
+    )
+    return state
+
+
+def _cua_driver_install_ready() -> bool:
+    """Return whether an existing driver needs no install-time repair."""
+    if not _cua_driver_contract_status().get("ready"):
+        return False
+    if sys.platform == "win32":
+        return _cua_driver_autostart_registered_windows()
+    return True
+
+
 def _pip_install(
     args: List[str],
     *,
@@ -928,9 +971,9 @@ def install_cua_driver(
     The upstream installer always pulls the latest release tag, so re-running
     it is the canonical way to upgrade. We expose two modes:
 
-    * ``upgrade=False`` — original post-setup behaviour: skip if already
-      installed, install otherwise. Used by the toolset enable flow where
-      we don't want to surprise the user with a network fetch.
+    * ``upgrade=False`` — keep a compatible Cua Driver 0.20 installation,
+      repair an old or incomplete installation, and install when missing.
+      Used by the toolset enable flow.
     * ``upgrade=True`` — always re-run the installer (or call ``cua-driver
       update`` if the binary supports it). Used by ``hermes update`` and
       by ``hermes computer-use install --upgrade``.
@@ -998,8 +1041,14 @@ def install_cua_driver(
         # baked in by CD and errors cleanly on missing-arch assets.
         return _run_cua_driver_installer(label="Installing")
 
-    # Already installed and caller didn't ask to upgrade → just confirm.
-    if binary and not upgrade:
+    contract = _cua_driver_contract_status(binary) if binary else None
+    repair_existing = bool(
+        binary and not upgrade and contract and not contract.get("ready")
+    )
+
+    # A compatible existing installation needs no download. Finish the small
+    # host-specific setup that the upstream installer normally owns.
+    if binary and not upgrade and not repair_existing:
         try:
             version = subprocess.run(
                 [binary, "--version"],
@@ -1010,6 +1059,11 @@ def install_cua_driver(
         except Exception:
             _print_success(f"    {driver_cmd} already installed.")
         if is_windows:
+            if not _repair_cua_driver_autostart_windows(binary, verbose=False):
+                _print_warning(
+                    "    cua-driver is compatible, but Windows autostart repair failed."
+                )
+                return False
             _print_info("    cua-driver may spawn a UIAccess worker (cua-driver-uia.exe);")
             _print_info("    Windows/SmartScreen may prompt the first time it runs.")
         elif is_linux:
@@ -1020,6 +1074,21 @@ def install_cua_driver(
             _print_info("      System Settings > Privacy & Security > Screen Recording")
         return True
 
+    if repair_existing:
+        version = contract.get("version") or "unknown version"
+        reason = contract.get("reason") or "required runtime features are missing"
+        _print_warning(
+            f"    Found cua-driver {version}, but Hermes cannot use its current "
+            f"runtime contract: {reason}."
+        )
+        if os.environ.get("HERMES_CUA_DRIVER_CMD", "").strip():
+            _print_info(
+                "    Update the binary selected by HERMES_CUA_DRIVER_CMD, or unset "
+                "the override and run: hermes computer-use install --upgrade"
+            )
+            return False
+        _print_info("    Repairing it with the current upstream installer.")
+
     # upgrade=True path — refresh to the latest upstream release.
     if not _cua_install_target_writable():
         _print_info(
@@ -1048,7 +1117,7 @@ def install_cua_driver(
     # `hermes computer-use install --upgrade` falls through and re-runs the
     # installer as before.
     confirmed_version = None
-    if binary:
+    if binary and not repair_existing:
         _state = None
         try:
             from tools.computer_use.cua_backend import cua_driver_update_check
@@ -1099,11 +1168,20 @@ def install_cua_driver(
         before = ""
 
     ok = _run_cua_driver_installer(
-        label="Refreshing",
+        label="Repairing" if repair_existing else "Refreshing",
         verbose=False,
         pin_version=confirmed_version,
         show_progress=show_installer_progress,
     )
+    if ok and repair_existing:
+        repaired = _cua_driver_contract_status()
+        if not repaired.get("ready"):
+            _print_warning(
+                "    cua-driver was reinstalled, but its runtime contract is still "
+                f"unusable: {repaired.get('reason') or 'unknown error'}."
+            )
+            _print_info("    Run: hermes computer-use doctor")
+            return False
     if ok and before:
         try:
             after = subprocess.run(
@@ -1597,9 +1675,10 @@ def _run_cua_driver_installer(
                         pass
                 if result.returncode != 0:
                     logger.debug("cua-driver installer output:\n%s", result.stdout)
-        if result.returncode == 0 and shutil.which(driver_cmd):
+        installed_binary = _resolved_cua_driver_cmd()
+        if result.returncode == 0 and installed_binary:
             if is_windows and not _repair_cua_driver_autostart_windows(
-                driver_cmd, verbose=verbose
+                installed_binary, verbose=verbose
             ):
                 _print_warning(
                     "    cua-driver installed, but auto-start was not registered."
@@ -3283,9 +3362,9 @@ _POST_SETUP_INSTALLED: dict = {
     # Only entries here are gated; other post_setup hooks (kittentts,
     # piper, agent_browser, etc.) keep their existing behaviour. Add an
     # entry when (a) the post_setup is the ONLY install side-effect for
-    # a no-key provider, and (b) an installed-state check is cheap and
-    # doesn't trigger a heavy import.
-    "cua_driver": lambda: _resolved_cua_driver_cmd() is not None,
+    # a no-key provider, and (b) an installed-state check is local, bounded,
+    # and doesn't trigger a heavy import.
+    "cua_driver": lambda: _cua_driver_install_ready(),
 }
 
 
@@ -3395,7 +3474,7 @@ _POST_SETUP_READY: dict = {
     "agent_browser": lambda: _agent_browser_installed(),
     "browserbase": lambda: _cloud_agent_browser_installed(),
     "camofox": lambda: _camofox_installed(),
-    "cua_driver": lambda: _resolved_cua_driver_cmd() is not None,
+    "cua_driver": lambda: _cua_driver_install_ready(),
 }
 
 
diff --git a/scripts/install.ps1 b/scripts/install.ps1
index 07300b514a..2087df1e9c 100644
--- a/scripts/install.ps1
+++ b/scripts/install.ps1
@@ -3552,6 +3552,57 @@ function Install-BrowserUseCli {
     }
 }
 
+function Test-CuaDriverRuntimeContract {
+    param([Parameter(Mandatory = $true)][string]$DriverPath)
+
+    try {
+        $versionOutput = (& $DriverPath --version 2>$null | Out-String).Trim()
+        if ($LASTEXITCODE -ne 0) {
+            return $false
+        }
+        $versionMatch = [regex]::Match($versionOutput, '(\d+\.\d+\.\d+)')
+        if (-not $versionMatch.Success) {
+            return $false
+        }
+        if ([version]($versionMatch.Groups[1].Value) -lt [version]'0.20.0') {
+            return $false
+        }
+
+        $manifestOutput = (& $DriverPath manifest 2>$null | Out-String).Trim()
+        if ($LASTEXITCODE -ne 0 -or -not $manifestOutput) {
+            return $false
+        }
+        $manifest = $manifestOutput | ConvertFrom-Json
+        if (-not $manifest.mcp_invocation.args) {
+            return $false
+        }
+
+        $required = @{
+            mcp = @('--socket', '--grant')
+            serve = @(
+                '--socket', '--permission-mode', '--capability-manifest',
+                '--approve-capability-manifest', '--embedded'
+            )
+            stop = @('--socket')
+        }
+        foreach ($commandName in $required.Keys) {
+            $command = $manifest.subcommands | Where-Object { $_.name -eq $commandName }
+            if (-not $command) {
+                return $false
+            }
+            $argNames = @($command.args | ForEach-Object { $_.name })
+            foreach ($requiredArg in $required[$commandName]) {
+                if ($requiredArg -notin $argNames) {
+                    return $false
+                }
+            }
+        }
+        return $true
+    } catch {
+        return $false
+    }
+}
+
 # cua-driver powers the computer_use toolset (background desktop control).
 # Provision it at install time so enabling the tool later -- via `hermes
 # tools`, the dashboard, or the desktop app -- is a config flip, not a
@@ -3563,9 +3614,13 @@ function Install-CuaDriver {
         Write-Info "Skipping Computer Use (cua-driver) install (-SkipComputerUse)"
         return
     }
-    if (Get-Command cua-driver -ErrorAction SilentlyContinue) {
-        Write-Success "Computer Use driver (cua-driver) already installed"
-        return
+    $existingCuaDriver = Get-Command cua-driver -ErrorAction SilentlyContinue
+    if ($existingCuaDriver) {
+        if (Test-CuaDriverRuntimeContract -DriverPath $existingCuaDriver.Source) {
+            Write-Success "Computer Use driver (cua-driver) already installed and compatible"
+            return
+        }
+        Write-Warn "Existing cua-driver is old or incomplete; repairing it"
     }
 
     Write-Info "Installing Computer Use driver (cua-driver)..."
diff --git a/scripts/install.sh b/scripts/install.sh
index 1b00b4df97..9496397c52 100755
--- a/scripts/install.sh
+++ b/scripts/install.sh
@@ -2501,6 +2501,37 @@ install_browser_use_cli() {
     fi
 }
 
+cua_driver_runtime_compatible() {
+    local driver_path version_output manifest_output
+    local major minor
+    driver_path="$(command -v cua-driver 2>/dev/null)" || return 1
+    version_output="$("$driver_path" --version 2>/dev/null)" || return 1
+    if [[ ! "$version_output" =~ ([0-9]+)\.([0-9]+)\.([0-9]+) ]]; then
+        return 1
+    fi
+    major="${BASH_REMATCH[1]}"
+    minor="${BASH_REMATCH[2]}"
+    if (( major == 0 && minor < 20 )); then
+        return 1
+    fi
+    manifest_output="$("$driver_path" manifest 2>/dev/null)" || return 1
+    local required
+    for required in \
+        '"mcp_invocation"' \
+        '"--socket"' \
+        '"--grant"' \
+        '"--permission-mode"' \
+        '"--capability-manifest"' \
+        '"--approve-capability-manifest"' \
+        '"--embedded"'; do
+        case "$manifest_output" in
+            *"$required"*) ;;
+            *) return 1 ;;
+        esac
+    done
+    return 0
+}
+
 install_computer_use_driver() {
     # cua-driver powers the computer_use toolset (background desktop control).
     # Provision it at install time so enabling the tool later — via
@@ -2519,8 +2550,11 @@ install_computer_use_driver() {
             ;;
     esac
     if command -v cua-driver >/dev/null 2>&1; then
-        log_success "Computer Use driver (cua-driver) already installed"
-        return 0
+        if cua_driver_runtime_compatible; then
+            log_success "Computer Use driver (cua-driver) already installed and compatible"
+            return 0
+        fi
+        log_warn "Existing cua-driver is old or incomplete; repairing it"
     fi
     # Non-admin macOS accounts can't receive the CuaDriver.app bundle in
     # /Applications; skip cleanly instead of failing loudly (#47865 class).
diff --git a/tests/hermes_cli/test_install_cua_driver.py b/tests/hermes_cli/test_install_cua_driver.py
index 55d82408a4..bc9152e123 100644
--- a/tests/hermes_cli/test_install_cua_driver.py
+++ b/tests/hermes_cli/test_install_cua_driver.py
@@ -8,8 +8,8 @@ must:
   can call it unconditionally without warning unsupported-platform users.
 * Re-run the installer even when the binary is already on PATH (this is the
   fix for the "we only pulled cua-driver once on enable" complaint).
-* Preserve original ``upgrade=False`` behaviour for the toolset-enable flow:
-  skip if installed, install otherwise, warn on unsupported platforms.
+* For ``upgrade=False``, keep compatible installations, repair old or
+  incomplete installations, and install when missing.
 
 The pre-install arch probe that used to live alongside this function was
 deleted (see top-of-file comment in tools_config.py) — the upstream
@@ -21,6 +21,7 @@ cleanly on missing-arch assets, and the upgrade path uses
 
 from __future__ import annotations
 
+import json
 import sys
 from types import SimpleNamespace
 from unittest.mock import patch
@@ -28,6 +29,86 @@ from unittest.mock import patch
 import pytest
 
 
+def _runtime_manifest(version="0.20.0", *, omit=None):
+    omit = set(omit or ())
+    required = {
+        "mcp": {"--socket", "--grant"},
+        "serve": {
+            "--socket",
+            "--permission-mode",
+            "--capability-manifest",
+            "--approve-capability-manifest",
+            "--embedded",
+        },
+        "stop": {"--socket"},
+    }
+    return {
+        "binary_version": version,
+        "mcp_invocation": {"command": "/opt/cua-driver", "args": ["mcp"]},
+        "subcommands": [
+            {
+                "name": command,
+                "args": [
+                    {"name": arg}
+                    for arg in sorted(args - omit)
+                ],
+            }
+            for command, args in required.items()
+        ],
+    }
+
+
+class TestCuaDriverRuntimeContract:
+    def test_current_manifest_is_ready(self):
+        from hermes_cli import tools_config
+
+        result = SimpleNamespace(
+            returncode=0,
+            stdout=json.dumps(_runtime_manifest()),
+            stderr="",
+        )
+        with patch("subprocess.run", return_value=result):
+            state = tools_config._cua_driver_contract_status("/opt/cua-driver")
+
+        assert state == {
+            "ready": True,
+            "binary": "/opt/cua-driver",
+            "version": "0.20.0",
+            "reason": "",
+        }
+
+    @pytest.mark.parametrize("version", ["0.19.4", "bad-version"])
+    def test_old_or_unversioned_driver_needs_repair(self, version):
+        from hermes_cli import tools_config
+
+        result = SimpleNamespace(
+            returncode=0,
+            stdout=json.dumps(_runtime_manifest(version)),
+            stderr="",
+        )
+        with patch("subprocess.run", return_value=result):
+            state = tools_config._cua_driver_contract_status("/opt/cua-driver")
+
+        assert state["ready"] is False
+        assert state["reason"]
+
+    def test_incomplete_manifest_needs_repair(self):
+        from hermes_cli import tools_config
+
+        result = SimpleNamespace(
+            returncode=0,
+            stdout=json.dumps(
+                _runtime_manifest(omit={"--approve-capability-manifest"})
+            ),
+            stderr="",
+        )
+        with patch("subprocess.run", return_value=result):
+            state = tools_config._cua_driver_contract_status("/opt/cua-driver")
+
+        assert state["ready"] is False
+        assert "serve --approve-capability-manifest" in state["reason"]
+
+
 class TestInstallCuaDriverUpgrade:
     # ``install_cua_driver`` supports macOS, Windows AND Linux. For everything
     # below except the two unsupported-platform cases, the Linux host takes a
@@ -236,10 +317,77 @@ class TestInstallCuaDriverUpgrade:
                           side_effect=lambda n: "/usr/local/bin/" + n
                                                  if n in {"cua-driver", "curl"} else None), \
              patch.object(tools_config, "_run_cua_driver_installer") as runner, \
+             patch.object(
+                 tools_config,
+                 "_cua_driver_contract_status",
+                 return_value={"ready": True, "version": "0.20.0", "reason": ""},
+             ), \
+             patch.object(
+                 tools_config,
+                 "_repair_cua_driver_autostart_windows",
+                 return_value=True,
+             ), \
              patch("subprocess.run"):
             assert tools_config.install_cua_driver(upgrade=False) is True
             runner.assert_not_called()
 
+    def test_non_upgrade_repairs_incompatible_existing_driver(self):
+        from hermes_cli import tools_config
+
+        incompatible = {
+            "ready": False,
+            "version": "0.19.4",
+            "reason": "Hermes computer use requires cua-driver 0.20.0 or newer",
+        }
+        repaired = {"ready": True, "version": "0.20.0", "reason": ""}
+        with patch.object(
+                 tools_config.shutil,
+                 "which",
+                 side_effect=lambda name: f"/usr/bin/{name}",
+             ), \
+             patch.object(
+                 tools_config,
+                 "_resolved_cua_driver_cmd",
+                 return_value="/usr/bin/cua-driver",
+             ), \
+             patch.object(
+                 tools_config,
+                 "_cua_driver_contract_status",
+                 side_effect=[incompatible, repaired],
+             ), \
+             patch.object(
+                 tools_config,
+                 "_run_cua_driver_installer",
+                 return_value=True,
+             ) as runner:
+            assert tools_config.install_cua_driver(upgrade=False) is True
+
+        assert runner.call_args.kwargs["label"] == "Repairing"
+
+    def test_incompatible_explicit_override_is_not_replaced(self, monkeypatch):
+        from hermes_cli import tools_config
+
+        monkeypatch.setenv("HERMES_CUA_DRIVER_CMD", "/opt/custom/cua-driver")
+        incompatible = {
+            "ready": False,
+            "version": "0.19.4",
+            "reason": "Hermes computer use requires cua-driver 0.20.0 or newer",
+        }
+        with patch.object(
+                 tools_config,
+                 "_resolved_cua_driver_cmd",
+                 return_value="/opt/custom/cua-driver",
+             ), \
+             patch.object(
+                 tools_config,
+                 "_cua_driver_contract_status",
+                 return_value=incompatible,
+             ), \
+             patch.object(tools_config, "_run_cua_driver_installer") as runner:
+            assert tools_config.install_cua_driver(upgrade=False) is False
+
+        runner.assert_not_called()
+
     def test_non_upgrade_without_binary_runs_installer(self):
         from hermes_cli import tools_config
 
@@ -1049,7 +1197,10 @@ class TestWindowsAutostartRepair:
         assert captured["cmd"][:4] == [
             "powershell", "-NoProfile", "-ExecutionPolicy", "Bypass",
         ]
-        repair.assert_called_once_with("cua-driver", verbose=False)
+        repair.assert_called_once_with(
+            r"C:\Users\Ha Trung\AppData\Local\Programs\Cua\cua-driver\bin\cua-driver.exe",
+            verbose=False,
+        )
 
     @pytest.mark.windows_only
     def test_autostart_repair_quotes_username_space_path_via_file_path(self):
diff --git a/tests/hermes_cli/test_post_setup_gating.py b/tests/hermes_cli/test_post_setup_gating.py
index ea1a62a42b..713df383ec 100644
--- a/tests/hermes_cli/test_post_setup_gating.py
+++ b/tests/hermes_cli/test_post_setup_gating.py
@@ -27,6 +27,24 @@ class TestPostSetupGate:
             "computer_use", {}
         ) is True
 
+    def test_incompatible_cua_driver_forces_setup(self, monkeypatch):
+        from hermes_cli import tools_config
+
+        monkeypatch.setattr(tools_config, "_cua_driver_install_ready", lambda: False)
+
+        assert tools_config._toolset_needs_configuration_prompt(
+            "computer_use", {}
+        ) is True
+
+    def test_compatible_cua_driver_skips_setup(self, monkeypatch):
+        from hermes_cli import tools_config
+
+        monkeypatch.setattr(tools_config, "_cua_driver_install_ready", lambda: True)
+
+        assert tools_config._toolset_needs_configuration_prompt(
+            "computer_use", {}
+        ) is False
+
 
     def test_post_setup_predicate_exception_does_not_block(self, monkeypatch):
         """A predicate that raises must be treated as 'satisfied' so a
@@ -39,4 +57,3 @@ class TestPostSetupGate:
         monkeypatch.setitem(tools_config._POST_SETUP_INSTALLED, "cua_driver", _boom)
         assert tools_config._post_setup_already_installed("cua_driver") is True
 
-
diff --git a/tests/hermes_cli/test_web_routers_tools_install_on_enable.py b/tests/hermes_cli/test_web_routers_tools_install_on_enable.py
index 7a7b8e3b45..f4d840d6a2 100644
--- a/tests/hermes_cli/test_web_routers_tools_install_on_enable.py
+++ b/tests/hermes_cli/test_web_routers_tools_install_on_enable.py
@@ -55,6 +55,9 @@ class TestToggleToolsetInstallOnEnable:
         monkeypatch.setattr(
             tools_config, "_resolved_cua_driver_cmd", lambda: None
         )
+        monkeypatch.setattr(
+            tools_config, "_cua_driver_install_ready", lambda: False
+        )
 
         resp = self.client.put(
             "/api/tools/toolsets/computer_use", json={"enabled": True}
@@ -77,6 +80,9 @@ class TestToggleToolsetInstallOnEnable:
         monkeypatch.setattr(
             tools_config, "_resolved_cua_driver_cmd", lambda: "/usr/bin/cua-driver"
         )
+        monkeypatch.setattr(
+            tools_config, "_cua_driver_install_ready", lambda: True
+        )
 
         resp = self.client.put(
             "/api/tools/toolsets/computer_use", json={"enabled": True}
@@ -92,6 +98,9 @@ class TestToggleToolsetInstallOnEnable:
         monkeypatch.setattr(
             tools_config, "_resolved_cua_driver_cmd", lambda: None
         )
+        monkeypatch.setattr(
+            tools_config, "_cua_driver_install_ready", lambda: False
+        )
 
         resp = self.client.put(
             "/api/tools/toolsets/computer_use", json={"enabled": False}
@@ -107,6 +116,9 @@ class TestToggleToolsetInstallOnEnable:
         monkeypatch.setattr(
             tools_config, "_resolved_cua_driver_cmd", lambda: None
         )
+        monkeypatch.setattr(
+            tools_config, "_cua_driver_install_ready", lambda: False
+        )
 
         def _boom(subcommand, name, **kwargs):
             raise RuntimeError("spawn exploded")
diff --git a/tests/tools/test_computer_use.py b/tests/tools/test_computer_use.py
index 6a61c1d25b..f42efa6b56 100644
--- a/tests/tools/test_computer_use.py
+++ b/tests/tools/test_computer_use.py
@@ -768,13 +768,35 @@ class TestLazyMcpInstall:
 
     def test_start_lazy_installs_mcp(self):
         from tools.computer_use import cua_backend
-        with patch.object(cua_backend, "_maybe_nudge_update"), \
+        with patch.object(
+                 cua_backend,
+                 "cua_driver_runtime_contract_status",
+                 return_value={"ready": True},
+             ), \
+             patch.object(cua_backend, "_maybe_nudge_update"), \
              patch("tools.lazy_deps.ensure") as mock_ensure, \
              patch.object(cua_backend._CuaDriverSession, "start") as mock_sess_start:
             cua_backend.CuaDriverBackend().start()
         mock_ensure.assert_called_once_with("tool.computer_use", prompt=False)
         mock_sess_start.assert_called_once()
 
+    def test_start_reports_incompatible_existing_driver_before_mcp_setup(self):
+        from tools.computer_use import cua_backend
+
+        state = {
+            "ready": False,
+            "reason": "Hermes computer use requires cua-driver 0.20.0 or newer",
+        }
+        with patch.object(
+                 cua_backend,
+                 "cua_driver_runtime_contract_status",
+                 return_value=state,
+             ), patch("tools.lazy_deps.ensure") as mock_ensure:
+            with pytest.raises(RuntimeError, match="hermes computer-use install"):
+                cua_backend.CuaDriverBackend().start()
+
+        mock_ensure.assert_not_called()
+
     def test_start_propagates_feature_unavailable(self):
         """When mcp can't be installed (lazy installs off / network), start()
         surfaces the actionable FeatureUnavailable rather than a session that
@@ -784,7 +806,12 @@ class TestLazyMcpInstall:
         unavailable = FeatureUnavailable(
             "tool.computer_use", ("mcp==1.28.1",), "lazy installs disabled"
         )
-        with patch.object(cua_backend, "_maybe_nudge_update"), \
+        with patch.object(
+                 cua_backend,
+                 "cua_driver_runtime_contract_status",
+                 return_value={"ready": True},
+             ), \
+             patch.object(cua_backend, "_maybe_nudge_update"), \
              patch("tools.lazy_deps.ensure", side_effect=unavailable), \
              patch.object(cua_backend._CuaDriverSession, "start") as mock_sess_start:
             with pytest.raises(FeatureUnavailable):
@@ -2071,7 +2098,10 @@ class TestSessionLifecycle:
 
         # Stub the optional-dep lazy-install so start() runs end-to-end
         # without trying to pip-install anything.
-        with patch("tools.lazy_deps.ensure"):
+        with patch(
+            "tools.computer_use.cua_backend.cua_driver_runtime_contract_status",
+            return_value={"ready": True},
+        ), patch("tools.lazy_deps.ensure"):
             backend.start()
 
         # First call_tool after _session.start() must be start_session
@@ -2083,9 +2113,7 @@ class TestSessionLifecycle:
 
 
     def test_session_lifecycle_failures_are_non_fatal(self):
-        """If start_session raises (older cua-driver build, anonymous
-        path), backend.start() must still succeed — the rest of the
-        wrapper works fine in anonymous mode."""
+        """A lifecycle-label failure does not discard an otherwise valid runtime."""
         from unittest.mock import MagicMock, patch
         from tools.computer_use.cua_backend import CuaDriverBackend
 
@@ -2097,7 +2125,10 @@ class TestSessionLifecycle:
             RuntimeError("older cua-driver — start_session unknown"),
         ]
 
-        with patch("tools.lazy_deps.ensure"):
+        with patch(
+            "tools.computer_use.cua_backend.cua_driver_runtime_contract_status",
+            return_value={"ready": True},
+        ), patch("tools.lazy_deps.ensure"):
             backend.start()  # must not raise
 
 
diff --git a/tools/computer_use/cua_backend.py b/tools/computer_use/cua_backend.py
index c0a899c3c2..f866e47aeb 100644
--- a/tools/computer_use/cua_backend.py
+++ b/tools/computer_use/cua_backend.py
@@ -928,6 +928,136 @@ def cua_driver_binary_available() -> bool:
     return resolve_cua_driver_cmd() is not None
 
 
+_CUA_DRIVER_RUNTIME_CONTRACT_MIN = (0, 20, 0)
+_CUA_DRIVER_RUNTIME_CONTRACT_ARGS = {
+    "mcp": {"--socket", "--grant"},
+    "serve": {
+        "--socket",
+        "--permission-mode",
+        "--capability-manifest",
+        "--approve-capability-manifest",
+        "--embedded",
+    },
+    "stop": {"--socket"},
+}
+
+
+def cua_driver_runtime_contract_status(binary: Optional[str] = None) -> Dict[str, Any]:
+    """Report whether a local driver can host Hermes' 0.20 integration."""
+    resolved = binary or resolve_cua_driver_cmd()
+    if not resolved:
+        return {
+            "ready": False,
+            "binary": None,
+            "version": None,
+            "reason": "cua-driver is not installed",
+        }
+
+    try:
+        from tools.environments.local import _sanitize_subprocess_env
+
+        result = subprocess.run(
+            [resolved, "manifest"],
+            capture_output=True,
+            text=True,
+            encoding="utf-8",
+            errors="replace",
+            timeout=15.0 if sys.platform == "win32" else 5.0,
+            stdin=subprocess.DEVNULL,
+            env=_sanitize_subprocess_env(cua_driver_child_env()),
+            creationflags=windows_hide_flags(),
+        )
+    except (OSError, subprocess.SubprocessError) as exc:
+        return {
+            "ready": False,
+            "binary": resolved,
+            "version": None,
+            "reason": f"manifest check failed: {exc}",
+        }
+
+    if result.returncode != 0:
+        detail = (result.stderr or result.stdout or "manifest command failed").strip()
+        return {
+            "ready": False,
+            "binary": resolved,
+            "version": None,
+            "reason": detail.splitlines()[-1][:200],
+        }
+
+    try:
+        manifest = json.loads(result.stdout or "")
+    except (TypeError, ValueError):
+        manifest = None
+    if not isinstance(manifest, dict):
+        return {
+            "ready": False,
+            "binary": resolved,
+            "version": None,
+            "reason": "driver manifest is missing or invalid",
+        }
+
+    raw_version = str(manifest.get("binary_version") or "").strip()
+    match = re.fullmatch(r"v?(\d+)\.(\d+)\.(\d+)(?:[-+].*)?", raw_version)
+    if not match:
+        return {
+            "ready": False,
+            "binary": resolved,
+            "version": raw_version or None,
+            "reason": "driver manifest does not report a semantic version",
+        }
+    version = tuple(int(part) for part in match.groups())
+    if version < _CUA_DRIVER_RUNTIME_CONTRACT_MIN:
+        return {
+            "ready": False,
+            "binary": resolved,
+            "version": raw_version,
+            "reason": "Hermes computer use requires cua-driver 0.20.0 or newer",
+        }
+
+    invocation = manifest.get("mcp_invocation")
+    invocation_args = invocation.get("args") if isinstance(invocation, dict) else None
+    if not (
+        isinstance(invocation_args, list)
+        and invocation_args
+        and all(isinstance(arg, str) for arg in invocation_args)
+    ):
+        return {
+            "ready": False,
+            "binary": resolved,
+            "version": raw_version,
+            "reason": "driver manifest does not provide an MCP launch command",
+        }
+
+    advertised: Dict[str, set[str]] = {}
+    for command in manifest.get("subcommands") or []:
+        if not isinstance(command, dict) or not isinstance(command.get("name"), str):
+            continue
+        advertised[command["name"]] = {
+            arg["name"]
+            for arg in command.get("args") or []
+            if isinstance(arg, dict) and isinstance(arg.get("name"), str)
+        }
+
+    missing = []
+    for command, required_args in _CUA_DRIVER_RUNTIME_CONTRACT_ARGS.items():
+        for arg in sorted(required_args - advertised.get(command, set())):
+            missing.append(f"{command} {arg}")
+    if missing:
+        return {
+            "ready": False,
+            "binary": resolved,
+            "version": raw_version,
+            "reason": "driver manifest is missing: " + ", ".join(missing),
+        }
+
+    return {
+        "ready": True,
+        "binary": resolved,
+        "version": raw_version,
+        "reason": "",
+    }
+
+
 def cua_driver_update_check(*, timeout: Optional[float] = None) -> Optional[Dict[str, Any]]:
     """Run ``cua-driver check-update --json`` and return its parsed state.
 
@@ -2295,10 +2425,8 @@ class CuaDriverBackend(ComputerUseBackend):
         # We mint a UUID4-based id once per CuaDriverBackend instance —
         # one Hermes run = one backend = one label — and pass it as
         # `session` on every cua-driver tool call. Labels are an
-        # additive feature on the cua-driver side: when our id is
-        # unknown to the driver (older builds), the tool calls
-        # degrade to the anonymous / unsynced path documented in the
-        # MCP server instructions.
+        # part of the required Cua Driver 0.20 runtime contract checked at
+        # backend startup.
         self._session_id: str = f"hermes-{uuid.uuid4().hex[:12]}"
         self._typed_browser = CuaTypedBrowserRoute(
             session_id=self._session_id,
@@ -2328,6 +2456,17 @@ class CuaDriverBackend(ComputerUseBackend):
 
     # ── Lifecycle ──────────────────────────────────────────────────
     def start(self) -> None:
+        contract = cua_driver_runtime_contract_status()
+        if not contract.get("ready"):
+            reason = contract.get("reason") or "runtime contract is incomplete"
+            if os.environ.get(_CUA_DRIVER_CMD_ENV, "").strip():
+                repair = (
+                    "Update the binary selected by HERMES_CUA_DRIVER_CMD or "
+                    "remove that override."
+                )
+            else:
+                repair = "Run `hermes computer-use install` to repair it."
+            raise RuntimeError(f"cua-driver is not ready: {reason}. {repair}")
         _maybe_nudge_update()
         # The MCP client SDK (`mcp`) is an optional dependency (the
         # `computer-use` / `mcp` extras), not part of Hermes' minimal core.
diff --git a/website/docs/reference/cli-commands.md b/website/docs/reference/cli-commands.md
index 5a388fa62f..49cbf54615 100644
--- a/website/docs/reference/cli-commands.md
+++ b/website/docs/reference/cli-commands.md
@@ -1433,6 +1433,13 @@ Subcommands:
 to use for re-running the install if the toolset toggle didn't trigger
 it (for example, on returning-user setups).
 
+If cua-driver is already present, Hermes checks its version and runtime
+manifest. A compatible 0.20.0 or newer installation is left in place. An old or
+incomplete standard installation is repaired with the current upstream
+installer. Hermes never replaces a custom binary selected through
+`HERMES_CUA_DRIVER_CMD`; update that binary directly or remove the override.
+`hermes computer-use status` reports when repair is required.
+
 The built-in `computer_use` toolset is the recommended Hermes integration.
 Registering raw Cua MCP tools is an alternative when you need Cua's low-level
 tool vocabulary. `cua-driver skills install` detects Hermes and links Cua's
diff --git a/website/docs/user-guide/features/computer-use.md b/website/docs/user-guide/features/computer-use.md
index 11bacd6fc2..da0e2e1912 100644
--- a/website/docs/user-guide/features/computer-use.md
+++ b/website/docs/user-guide/features/computer-use.md
@@ -62,6 +62,13 @@ This fetches and runs the upstream cua-driver installer — `install.sh`
 on macOS/Linux, `install.ps1` on Windows. Use `hermes computer-use
 status` to verify the install.
 
+Already have cua-driver? Hermes reuses it when it supports the 0.20 runtime
+contract. During setup and toolset enablement, Hermes checks the local version
+and manifest. It repairs an old or incomplete standard installation through
+the upstream installer. A binary selected with `HERMES_CUA_DRIVER_CMD` stays
+under your control, so Hermes reports the incompatibility and leaves it
+unchanged.
+
 If you install Cua Driver first, `cua-driver skills install` detects Hermes
 and links Cua's skill pack into the Hermes skills directory automatically.
 You can also register raw Cua MCP tools as a custom MCP server, but that is an