diff --git a/routes/radiosonde.py b/routes/radiosonde.py
index 06cab90..b9115d9 100644
--- a/routes/radiosonde.py
+++ b/routes/radiosonde.py
@@ -43,9 +43,10 @@ from utils.validation import (
     validate_longitude,
 )
 
-logger = get_logger('intercept.radiosonde')
-
-radiosonde_bp = Blueprint('radiosonde', __name__, url_prefix='/radiosonde')
+logger = get_logger('intercept.radiosonde')
+
+radiosonde_bp = Blueprint('radiosonde', __name__, url_prefix='/radiosonde')
+PROJECT_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
 # Track radiosonde state
 radiosonde_running = False
@@ -112,6 +113,17 @@ def _resolve_pip_python(pip_bin: str | None) -> str | None:
     return _resolve_shebang_interpreter(pip_bin)
 
 
+def _build_auto_rx_env(auto_rx_dir: str) -> dict[str, str]:
+    """Build environment for radiosonde_auto_rx with compatibility shims."""
+    env = os.environ.copy()
+    python_path_entries = [PROJECT_ROOT, auto_rx_dir]
+    existing_pythonpath = env.get('PYTHONPATH', '')
+    if existing_pythonpath:
+        python_path_entries.append(existing_pythonpath)
+    env['PYTHONPATH'] = os.pathsep.join(entry for entry in python_path_entries if entry)
+    return env
+
+
 def _iter_auto_rx_python_candidates(auto_rx_path: str):
     """Yield plausible Python interpreters for radiosonde_auto_rx."""
     auto_rx_abs = os.path.abspath(auto_rx_path)
@@ -158,6 +170,7 @@ def _iter_auto_rx_python_candidates(auto_rx_path: str):
 def _resolve_auto_rx_python(auto_rx_path: str) -> tuple[str | None, str, list[str]]:
     """Pick a Python interpreter that can import autorx.scan successfully."""
     auto_rx_dir = os.path.dirname(os.path.abspath(auto_rx_path))
+    auto_rx_env = _build_auto_rx_env(auto_rx_dir)
     checked: list[str] = []
     last_error = 'No usable Python interpreter found'
 
@@ -167,6 +180,7 @@ def _resolve_auto_rx_python(auto_rx_path: str) -> tuple[str | None, str, list[st
             dep_check = subprocess.run(
                 [python_bin, '-c', 'import autorx.scan'],
                 cwd=auto_rx_dir,
+                env=auto_rx_env,
                 capture_output=True,
                 timeout=10,
             )
@@ -670,16 +684,18 @@ def start_radiosonde():
 
     # Set cwd to the auto_rx directory so 'from autorx.scan import ...' works
     auto_rx_dir = os.path.dirname(os.path.abspath(auto_rx_path))
-
-    try:
-        logger.info(f"Starting radiosonde_auto_rx: {' '.join(cmd)}")
-        app_module.radiosonde_process = subprocess.Popen(
-            cmd,
+    auto_rx_env = _build_auto_rx_env(auto_rx_dir)
+
+    try:
+        logger.info(f"Starting radiosonde_auto_rx: {' '.join(cmd)}")
+        app_module.radiosonde_process = subprocess.Popen(
+            cmd,
             stdout=subprocess.DEVNULL,
-            stderr=subprocess.PIPE,
-            start_new_session=True,
-            cwd=auto_rx_dir,
-        )
+            stderr=subprocess.PIPE,
+            start_new_session=True,
+            cwd=auto_rx_dir,
+            env=auto_rx_env,
+        )
 
         # Wait briefly for process to start
         time.sleep(2.0)
diff --git a/semver.py b/semver.py
new file mode 100644
index 0000000..9f4278f
--- /dev/null
+++ b/semver.py
@@ -0,0 +1,162 @@
+"""Minimal semver compatibility shim.
+
+This project vendors a tiny subset of the ``semver`` package API so
+integrations like radiosonde_auto_rx can run even when the external
+dependency is missing from the target Python environment.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, replace
+import re
+from typing import Iterable
+
+_SEMVER_RE = re.compile(
+    r"^\s*"
+    r"(?P<major>0|[1-9]\d*)"
+    r"(?:\.(?P<minor>0|[1-9]\d*))?"
+    r"(?:\.(?P<patch>0|[1-9]\d*))?"
+    r"(?:-(?P<prerelease>[0-9A-Za-z.-]+))?"
+    r"(?:\+(?P<build>[0-9A-Za-z.-]+))?"
+    r"\s*$"
+)
+
+
+def _split_prerelease(value: str | None) -> list[int | str]:
+    if not value:
+        return []
+    parts: list[int | str] = []
+    for token in value.split("."):
+        parts.append(int(token) if token.isdigit() else token)
+    return parts
+
+
+def _compare_identifiers(left: Iterable[int | str], right: Iterable[int | str]) -> int:
+    left_parts = list(left)
+    right_parts = list(right)
+    for l_part, r_part in zip(left_parts, right_parts):
+        if l_part == r_part:
+            continue
+        if isinstance(l_part, int) and isinstance(r_part, str):
+            return -1
+        if isinstance(l_part, str) and isinstance(r_part, int):
+            return 1
+        return -1 if l_part < r_part else 1
+    if len(left_parts) == len(right_parts):
+        return 0
+    return -1 if len(left_parts) < len(right_parts) else 1
+
+
+@dataclass(frozen=True)
+class VersionInfo:
+    major: int
+    minor: int = 0
+    patch: int = 0
+    prerelease: str | None = None
+    build: str | None = None
+
+    @classmethod
+    def parse(cls, version: str) -> "VersionInfo":
+        match = _SEMVER_RE.match(str(version))
+        if not match:
+            raise ValueError(f"{version!r} is not valid SemVer")
+        groups = match.groupdict()
+        return cls(
+            major=int(groups["major"]),
+            minor=int(groups["minor"] or 0),
+            patch=int(groups["patch"] or 0),
+            prerelease=groups["prerelease"],
+            build=groups["build"],
+        )
+
+    @classmethod
+    def isvalid(cls, version: str) -> bool:
+        return _SEMVER_RE.match(str(version)) is not None
+
+    @classmethod
+    def is_valid(cls, version: str) -> bool:
+        return cls.isvalid(version)
+
+    def compare(self, other: str | "VersionInfo") -> int:
+        return compare(self, other)
+
+    def match(self, expr: str) -> bool:
+        return match(str(self), expr)
+
+    def bump_major(self) -> "VersionInfo":
+        return VersionInfo(self.major + 1, 0, 0)
+
+    def bump_minor(self) -> "VersionInfo":
+        return VersionInfo(self.major, self.minor + 1, 0)
+
+    def bump_patch(self) -> "VersionInfo":
+        return VersionInfo(self.major, self.minor, self.patch + 1)
+
+    def finalize_version(self) -> "VersionInfo":
+        return VersionInfo(self.major, self.minor, self.patch)
+
+    def replace(self, **changes) -> "VersionInfo":
+        return replace(self, **changes)
+
+    def __str__(self) -> str:
+        value = f"{self.major}.{self.minor}.{self.patch}"
+        if self.prerelease:
+            value += f"-{self.prerelease}"
+        if self.build:
+            value += f"+{self.build}"
+        return value
+
+
+def parse(version: str) -> VersionInfo:
+    return VersionInfo.parse(version)
+
+
+def compare(left: str | VersionInfo, right: str | VersionInfo) -> int:
+    left_ver = left if isinstance(left, VersionInfo) else parse(str(left))
+    right_ver = right if isinstance(right, VersionInfo) else parse(str(right))
+
+    left_core = (left_ver.major, left_ver.minor, left_ver.patch)
+    right_core = (right_ver.major, right_ver.minor, right_ver.patch)
+    if left_core != right_core:
+        return -1 if left_core < right_core else 1
+
+    if left_ver.prerelease == right_ver.prerelease:
+        return 0
+    if left_ver.prerelease is None:
+        return 1
+    if right_ver.prerelease is None:
+        return -1
+    return _compare_identifiers(
+        _split_prerelease(left_ver.prerelease),
+        _split_prerelease(right_ver.prerelease),
+    )
+
+
+def match(version: str | VersionInfo, expr: str) -> bool:
+    version_info = version if isinstance(version, VersionInfo) else parse(str(version))
+    expression = str(expr).strip()
+    for operator in ("<=", ">=", "==", "!=", "<", ">"):
+        if expression.startswith(operator):
+            other = parse(expression[len(operator):].strip())
+            result = compare(version_info, other)
+            return {
+                "<": result < 0,
+                "<=": result <= 0,
+                ">": result > 0,
+                ">=": result >= 0,
+                "==": result == 0,
+                "!=": result != 0,
+            }[operator]
+    return compare(version_info, parse(expression)) == 0
+
+
+def max_ver(left: str | VersionInfo, right: str | VersionInfo) -> VersionInfo:
+    left_ver = left if isinstance(left, VersionInfo) else parse(str(left))
+    right_ver = right if isinstance(right, VersionInfo) else parse(str(right))
+    return left_ver if compare(left_ver, right_ver) >= 0 else right_ver
+
+
+def min_ver(left: str | VersionInfo, right: str | VersionInfo) -> VersionInfo:
+    left_ver = left if isinstance(left, VersionInfo) else parse(str(left))
+    right_ver = right if isinstance(right, VersionInfo) else parse(str(right))
+    return left_ver if compare(left_ver, right_ver) <= 0 else right_ver