diff --git a/gittensor/constants.py b/gittensor/constants.py
index 0297ccd2..11b84505 100644
--- a/gittensor/constants.py
+++ b/gittensor/constants.py
@@ -105,6 +105,9 @@
 # while holding the GIL. 2s is well above the millisecond cost of real files.
 TREE_SITTER_PARSE_TIMEOUT_MICROS = 2_000_000
 
+# Wall-clock budget (s) for the isolated-subprocess scoring path.
+SCORING_SUBPROCESS_BUDGET_S = 5.0
+
 # comment nodes for token scoring
 COMMENT_NODE_TYPES = frozenset(
     {
diff --git a/gittensor/validator/oss_contributions/mirror/scoring.py b/gittensor/validator/oss_contributions/mirror/scoring.py
index 97c7910f..19a736b6 100644
--- a/gittensor/validator/oss_contributions/mirror/scoring.py
+++ b/gittensor/validator/oss_contributions/mirror/scoring.py
@@ -50,12 +50,12 @@
     calculate_review_quality_multiplier,
 )
 from gittensor.validator.utils.datetime_utils import calculate_time_decay
+from gittensor.validator.utils.isolated_scoring import isolated_calculate_token_score
 from gittensor.validator.utils.load_weights import (
     LanguageConfig,
     RepositoryConfig,
     TokenConfig,
 )
-from gittensor.validator.utils.tree_sitter_scoring import calculate_token_score_from_file_changes
 
 # ============================================================================
 # Entry point
@@ -277,7 +277,7 @@ def calculate_base_score_for_pr_files(
     they're populating (e.g. ``ScoredPR`` for OSS, ``Issue`` discovery
     fields for issue discovery).
     """
-    scoring_result: PrScoringResult = calculate_token_score_from_file_changes(
+    scoring_result: PrScoringResult = isolated_calculate_token_score(
         file_changes,
         file_contents,
         token_config,
diff --git a/gittensor/validator/utils/isolated_scoring.py b/gittensor/validator/utils/isolated_scoring.py
new file mode 100644
index 00000000..a48da99f
--- /dev/null
+++ b/gittensor/validator/utils/isolated_scoring.py
@@ -0,0 +1,134 @@
+# The MIT License (MIT)
+# Copyright © 2025 Entrius
+"""Subprocess-isolated wrapper around tree-sitter scoring.
+
+Uses a spawn-context pool (not fork - avoids inheriting bittensor
+threads/sockets) with an external wall-clock budget; on
+timeout/crash the child is killed and the PR zero-scored.
+"""
+
+from __future__ import annotations
+
+import atexit
+import multiprocessing
+import multiprocessing.pool
+import threading
+from multiprocessing import get_context
+from typing import TYPE_CHECKING, Dict, List, Optional
+
+import bittensor as bt
+
+from gittensor.classes import FileScoreResult, PrScoringResult
+from gittensor.constants import SCORING_SUBPROCESS_BUDGET_S
+from gittensor.utils.github_api_tools import FileContentPair
+from gittensor.validator.utils.load_weights import LanguageConfig, TokenConfig
+
+if TYPE_CHECKING:
+    from gittensor.classes import FileChange
+
+
+_pool: Optional[multiprocessing.pool.Pool] = None
+_pool_lock = threading.Lock()
+
+
+def _worker(
+    file_changes: List['FileChange'],
+    file_contents: Dict[str, FileContentPair],
+    weights: TokenConfig,
+    programming_languages: Dict[str, LanguageConfig],
+) -> PrScoringResult:
+    # Lazy import: avoids pulling tree_sitter into importers of this module.
+    from gittensor.validator.utils.tree_sitter_scoring import (
+        calculate_token_score_from_file_changes,
+    )
+
+    return calculate_token_score_from_file_changes(
+        file_changes,
+        file_contents,
+        weights,
+        programming_languages,
+    )
+
+
+def _ensure_pool() -> multiprocessing.pool.Pool:
+    global _pool
+    if _pool is None:
+        ctx = get_context('spawn')
+        _pool = ctx.Pool(processes=1)
+    return _pool
+
+
+def _reset_pool() -> None:
+    global _pool
+    if _pool is None:
+        return
+    try:
+        _pool.terminate()
+        _pool.join()
+    except Exception:
+        pass
+    _pool = None
+
+
+def _empty_pr_result(file_changes: List['FileChange']) -> PrScoringResult:
+    """Zero-scored result with one ``skipped-isolation-timeout`` entry per file"""
+    file_results = [
+        FileScoreResult(
+            filename=f.short_name,
+            score=0.0,
+            nodes_scored=0,
+            total_lines=f.changes,
+            is_test_file=False,
+            scoring_method='skipped-isolation-timeout',
+        )
+        for f in file_changes
+    ]
+    return PrScoringResult(
+        total_score=0.0,
+        total_nodes_scored=0,
+        total_lines=sum(f.changes for f in file_changes),
+        file_results=file_results,
+    )
+
+
+def shutdown() -> None:
+    """Tear down the worker pool; idempotent, registered with ``atexit``"""
+    with _pool_lock:
+        _reset_pool()
+
+
+atexit.register(shutdown)
+
+
+def isolated_calculate_token_score(
+    file_changes: List['FileChange'],
+    file_contents: Dict[str, FileContentPair],
+    weights: TokenConfig,
+    programming_languages: Dict[str, LanguageConfig],
+    timeout_s: float = SCORING_SUBPROCESS_BUDGET_S,
+) -> PrScoringResult:
+    """Score a PR's files in an isolated subprocess with a hard wall-clock.
+
+    On timeout or worker error the pool is reset and a zero-scored result is
+    returned.
+    """
+    with _pool_lock:
+        pool = _ensure_pool()
+        async_res = pool.apply_async(
+            _worker,
+            (file_changes, file_contents, weights, programming_languages),
+        )
+
+    # Lock not held during get() - a 5s wait would needlessly serialize callers.
+    try:
+        return async_res.get(timeout=timeout_s)
+    except multiprocessing.TimeoutError:
+        bt.logging.warning(
+            f'Isolated scoring exceeded {timeout_s}s wall budget for {len(file_changes)} files - killing worker'
+        )
+    except Exception as e:
+        bt.logging.warning(f'Isolated scoring worker raised {type(e).__name__}: {e!s} - resetting pool')
+
+    with _pool_lock:
+        _reset_pool()
+    return _empty_pr_result(file_changes)
diff --git a/tests/validator/utils/test_isolated_scoring.py b/tests/validator/utils/test_isolated_scoring.py
new file mode 100644
index 00000000..6a8bca0b
--- /dev/null
+++ b/tests/validator/utils/test_isolated_scoring.py
@@ -0,0 +1,100 @@
+# The MIT License (MIT)
+# Copyright © 2025 Entrius
+"""Tests for ``isolated_calculate_token_score`` timeout and exception paths"""
+
+from __future__ import annotations
+
+import multiprocessing
+
+import pytest
+
+from gittensor.classes import FileChange, PrScoringResult
+from gittensor.validator.utils import isolated_scoring
+from gittensor.validator.utils.load_weights import TokenConfig
+
+
+def _change(name: str = 'a.py', changes: int = 10) -> FileChange:
+    return FileChange(
+        pr_number=1,
+        repository_full_name='x/y',
+        filename=name,
+        changes=changes,
+        additions=changes,
+        deletions=0,
+        status='added',
+        file_extension='py',
+    )
+
+
+class _FakeAsyncResult:
+    def __init__(self, exc: BaseException) -> None:
+        self._exc = exc
+
+    def get(self, timeout: float | None = None):
+        raise self._exc
+
+
+class _FakePool:
+    def __init__(self, exc: BaseException) -> None:
+        self._exc = exc
+        self.terminated = False
+        self.joined = False
+
+    def apply_async(self, fn, args):
+        return _FakeAsyncResult(self._exc)
+
+    def terminate(self) -> None:
+        self.terminated = True
+
+    def join(self) -> None:
+        self.joined = True
+
+
+@pytest.fixture(autouse=True)
+def _reset_module_pool():
+    isolated_scoring._pool = None
+    yield
+    isolated_scoring._pool = None
+
+
+def _call_with_fake(fake: _FakePool, changes: list[FileChange], timeout_s: float = 0.01) -> PrScoringResult:
+    isolated_scoring._pool = fake
+    return isolated_scoring.isolated_calculate_token_score(
+        changes,
+        {},
+        weights=TokenConfig(),
+        programming_languages={},
+        timeout_s=timeout_s,
+    )
+
+
+def test_worker_timeout_yields_empty_result_and_resets_pool():
+    fake = _FakePool(multiprocessing.TimeoutError())
+    changes = [_change('a.py', 10), _change('b.py', 5)]
+
+    result = _call_with_fake(fake, changes)
+
+    assert isinstance(result, PrScoringResult)
+    assert result.total_score == 0.0
+    assert result.total_nodes_scored == 0
+    assert result.total_lines == 15
+    assert [f.filename for f in result.file_results] == ['a.py', 'b.py']
+    assert all(f.scoring_method == 'skipped-isolation-timeout' for f in result.file_results)
+    assert all(f.score == 0.0 and f.nodes_scored == 0 for f in result.file_results)
+    assert fake.terminated and fake.joined
+    assert isolated_scoring._pool is None
+
+
+def test_worker_exception_yields_empty_result_and_resets_pool():
+    fake = _FakePool(RuntimeError('boom'))
+    changes = [_change('a.py', 7)]
+
+    result = _call_with_fake(fake, changes, timeout_s=1.0)
+
+    assert isinstance(result, PrScoringResult)
+    assert result.total_score == 0.0
+    assert len(result.file_results) == 1
+    assert result.file_results[0].scoring_method == 'skipped-isolation-timeout'
+    assert result.file_results[0].total_lines == 7
+    assert fake.terminated and fake.joined
+    assert isolated_scoring._pool is None