diff --git a/culprit_finder/src/culprit_finder/culprit_finder.py b/culprit_finder/src/culprit_finder/culprit_finder.py
index 2115b307..47219004 100644
--- a/culprit_finder/src/culprit_finder/culprit_finder.py
+++ b/culprit_finder/src/culprit_finder/culprit_finder.py
@@ -18,6 +18,28 @@
 
 CULPRIT_FINDER_WORKFLOW_NAME = "culprit_finder.yml"
 
+# Configuration for projects that require special handling for external dependencies.
+# Some projects (e.g., JAX) depend on the HEAD of another repository (e.g., XLA).
+# When bisecting historical commits, running them against the *current* HEAD of the dependency
+# often causes build failures unrelated to the regression being investigated.
+#
+# This map defines how to "time-travel" for these dependencies:
+# - dependency_repo: The external repository to look up.
+# - input_name: The workflow input variable to set with the pinned commit hash.
+# - workflows: The specific workflows where this logic should apply.
+PROJECT_CONFIG = {
+    "jax-ml/jax": {
+        "dependency_repo": "openxla/xla",
+        "input_name": "xla-commit",
+        "workflows": ["wheel_tests_continuous.yml", "build_artifacts.yml"],
+    },
+    "google-ml-infra/jax-fork": {
+        "dependency_repo": "openxla/xla",
+        "input_name": "xla-commit",
+        "workflows": ["wheel_tests_continuous.yml", "build_artifacts.yml"],
+    },
+}
+
 
 class CulpritFinder:
   """Culprit finder class to find the culprit commit for a GitHub workflow."""
@@ -196,6 +218,28 @@ def _test_commit(
       )
       previous_run_id = previous_run.id if previous_run else None
 
+      if self._repo in PROJECT_CONFIG and self._workflow_file in PROJECT_CONFIG[self._repo]["workflows"]:
+          config = PROJECT_CONFIG[self._repo]
+          logging.info("Project %s matched special case config", self._repo)
+
+          # Get date of the commit we are testing
+          commit_details = self._gh_client.get_commit(commit_sha)
+          # PyGithub returns naive datetime objects in UTC.
+          # get_last_commit_before's `until` parameter natively handles this datetime object.
+          commit_date = commit_details.commit.committer.date
+
+          # Find dependency commit at that time
+          dep_repo = config["dependency_repo"]
+          logging.info("Looking up dependency commit for %s at %s", dep_repo, commit_date)
+          dep_commit = self._gh_client.get_last_commit_before(dep_repo, commit_date)
+
+          if dep_commit:
+              input_name = config["input_name"]
+              logging.info("Pinning %s to %s", input_name, dep_commit.sha)
+              inputs[input_name] = dep_commit.sha
+          else:
+              logging.warning("Could not find matching commit for %s at %s", dep_repo, commit_date)
+
       self._gh_client.trigger_workflow(
         workflow_to_trigger,
         branch_name,
diff --git a/culprit_finder/src/culprit_finder/github_client.py b/culprit_finder/src/culprit_finder/github_client.py
index a72477cb..502552ba 100644
--- a/culprit_finder/src/culprit_finder/github_client.py
+++ b/culprit_finder/src/culprit_finder/github_client.py
@@ -2,12 +2,13 @@
 Module for interacting with the GitHub API via PyGithub.
 """
 
-import logging
 import os
 import re
-import time
-from typing import Optional
 import subprocess
+import logging
+import datetime
+from typing import Optional
+import time
 
 import github
 from github.Commit import Commit
@@ -29,7 +30,8 @@ def __init__(self, repo: str, token: str):
         repo: The GitHub repository in 'owner/repo' format.
         token: The GitHub access token for authentication.
     """
-    self._repo = github.Github(auth=github.Auth.Token(token)).get_repo(repo, lazy=True)
+    self._gh = github.Github(auth=github.Auth.Token(token))
+    self._repo = self._gh.get_repo(repo, lazy=True)
 
   def compare_commits(self, base_sha: str, head_sha: str) -> list[Commit]:
     """
@@ -341,6 +343,42 @@ def get_run_jobs(self, run_id: str | int) -> list[WorkflowJob]:
     run = self.get_run(str(run_id))
     return list(run.jobs())
 
+  def get_commit(self, sha: str) -> Commit:
+    """
+    Gets details of a specific commit.
+
+    Args:
+        sha: The SHA of the commit to retrieve.
+
+    Returns:
+        A Commit object.
+    """
+    return self._repo.get_commit(sha)
+
+  def get_last_commit_before(
+    self, repo_name: str, date: str | datetime.datetime, branch: str = "main"
+  ) -> Commit | None:
+    """
+    Finds the latest commit in a repository that is older than or equal to a given date.
+
+    Args:
+        repo_name: The GitHub repository to search in 'owner/repo' format.
+        date: The ISO 8601 date string or datetime object to search before (inclusive).
+        branch: The branch to search on.
+
+    Returns:
+        The matching Commit object, or None if not found.
+    """
+    target_repo = self._gh.get_repo(repo_name, lazy=True)
+    # PyGithub's get_commits returns a PaginatedList in reverse chronological order.
+    # We use `until` to filter commits before the date.
+    commits = target_repo.get_commits(sha=branch, until=date)
+
+    # Calling `totalCount` on a PaginatedList forces PyGithub to fetch the entire 
+    # pagination graph just to get the count. This is a massive API overhead.
+    # Instead, we just take the first item from the iterator, which only fetches the first page.
+    return next(iter(commits), None)
+
 
 def get_github_token() -> str | None:
   """Retrieves the GitHub access token from the environment or from the the GitHub CLI if not present.
diff --git a/culprit_finder/tests/test_culprit_finder.py b/culprit_finder/tests/test_culprit_finder.py
index c0b00983..a333bb59 100644
--- a/culprit_finder/tests/test_culprit_finder.py
+++ b/culprit_finder/tests/test_culprit_finder.py
@@ -170,6 +170,79 @@ def test_test_commit_outcomes(
   )
 
 
+@pytest.mark.parametrize("has_culprit_workflow", [True, False])
+def test_test_commit_with_project_config(
+  mocker, mock_gh_client, has_culprit_workflow, mock_state, mock_state_persister
+):
+  """Tests that _test_commit injects the pinned dependency if the repo matches PROJECT_CONFIG."""
+  repo_name = "jax-ml/jax"
+  workflow_file = "wheel_tests_continuous.yml"
+  branch = "test-branch"
+  commit_sha = "sha1"
+  dep_commit_sha = "xla_sha_123"
+
+  # Create finder with specific repo and workflow
+  finder = culprit_finder.CulpritFinder(
+    repo=repo_name,
+    start_sha="start_sha",
+    end_sha="end_sha",
+    workflow_file=workflow_file,
+    has_culprit_finder_workflow=has_culprit_workflow,
+    gh_client=mock_gh_client,
+    state=mock_state,
+    state_persister=mock_state_persister,
+  )
+
+  # Mock completion
+  mock_wait = mocker.patch.object(finder, "_wait_for_workflow_completion")
+  mock_wait.return_value = factories.create_run(
+    mocker, head_sha=commit_sha, conclusion="success", status="completed"
+  )
+  mock_gh_client.get_latest_run.return_value = None
+
+  # Mock dependency lookup
+  mock_commit = mocker.Mock()
+  mock_commit.commit.committer.date = "2023-01-01T00:00:00Z"
+  mock_gh_client.get_commit.return_value = mock_commit
+  
+  mock_dep_commit = mocker.Mock()
+  mock_dep_commit.sha = dep_commit_sha
+  mock_gh_client.get_last_commit_before.return_value = mock_dep_commit
+  
+  is_good = finder._test_commit(commit_sha, branch)
+
+  assert is_good is True
+  mock_gh_client.get_commit.assert_called_once_with(commit_sha)
+  mock_gh_client.get_last_commit_before.assert_called_once_with(
+    "openxla/xla", "2023-01-01T00:00:00Z"
+  )
+
+  # Determine expected arguments based on configuration
+  if has_culprit_workflow:
+    expected_workflow = CULPRIT_WORKFLOW
+    expected_inputs = {"workflow-to-debug": workflow_file, "xla-commit": dep_commit_sha}
+  else:
+    expected_workflow = workflow_file
+    expected_inputs = {"xla-commit": dep_commit_sha}
+
+  mock_gh_client.trigger_workflow.assert_called_once_with(
+    expected_workflow,
+    branch,
+    expected_inputs,
+  )
+
+
+def test_test_commit_failure(mocker, finder, mock_gh_client):
+  """Tests that _test_commit returns False if the workflow fails."""
+  mock_wait = mocker.patch.object(finder, "_wait_for_workflow_completion")
+  mock_wait.return_value = factories.create_run(mocker, "sha", "completed", "failure")
+
+  # Mock get_latest_run to return None for the "previous run" check
+  mock_gh_client.get_latest_run.return_value = None
+
+  assert finder._test_commit("sha", "branch") is False
+
+
 @pytest.mark.parametrize("has_culprit_workflow", [True, False])
 def test_test_commit_with_specific_job(
   mocker, finder_factory, mock_gh_client, has_culprit_workflow
diff --git a/culprit_finder/tests/test_github_client.py b/culprit_finder/tests/test_github_client.py
index 1dab1c9e..a53928fc 100644
--- a/culprit_finder/tests/test_github_client.py
+++ b/culprit_finder/tests/test_github_client.py
@@ -295,3 +295,46 @@ def test_find_previous_successful_job_run_not_found(mocker):
 
   with pytest.raises(ValueError, match="No previous successful run found for job"):
     client.find_previous_successful_job_run(failed_run, "my_job")
+
+
+def test_get_commit(mocker):
+  """Tests getting a specific commit."""
+  client = github_client.GithubClient("owner/repo", token="test-token")
+  mock_repo = client._repo
+  expected_commit = mocker.Mock()
+  mock_repo.get_commit.return_value = expected_commit
+  
+  result = client.get_commit("mock_sha")
+  assert result == expected_commit
+  mock_repo.get_commit.assert_called_once_with("mock_sha")
+
+
+def test_get_last_commit_before_found(mocker):
+  """Tests finding the last commit before a date when commits exist."""
+  client = github_client.GithubClient("owner/repo", token="test-token")
+  mock_gh = client._gh
+  mock_target_repo = mocker.Mock()
+  mock_gh.get_repo.return_value = mock_target_repo
+  
+  expected_commit = mocker.Mock()
+  mock_commits = [expected_commit, mocker.Mock()]
+  mock_target_repo.get_commits.return_value = mock_commits
+  
+  result = client.get_last_commit_before("other/repo", "2023-01-01T00:00:00Z")
+  
+  assert result == expected_commit
+  mock_target_repo.get_commits.assert_called_once_with(sha="main", until="2023-01-01T00:00:00Z")
+
+
+def test_get_last_commit_before_not_found(mocker):
+  """Tests getting last commit before a date when no commits exist."""
+  client = github_client.GithubClient("owner/repo", token="test-token")
+  mock_gh = client._gh
+  mock_target_repo = mocker.Mock()
+  mock_gh.get_repo.return_value = mock_target_repo
+  
+  mock_target_repo.get_commits.return_value = []
+  
+  result = client.get_last_commit_before("other/repo", "2023-01-01T00:00:00Z")
+  
+  assert result is None