diff --git a/src/security_scanner/runtime/scan_worker.py b/src/security_scanner/runtime/scan_worker.py
index 979bcd4..527b94b 100644
--- a/src/security_scanner/runtime/scan_worker.py
+++ b/src/security_scanner/runtime/scan_worker.py
@@ -19,6 +19,7 @@
 from security_scanner.scanners.gitleaks.scanner import GitleaksScanner
 from security_scanner.storage.base import (
     IncrementalScanStore,
+    JOB_TYPE_BASELINE,
     ScanJob,
     ScanLedgerEntry,
 )
@@ -121,16 +122,13 @@ def run_scan_worker_once(request: ScanWorkerRequest) -> ScanWorkerSummary:
             findings = request.scanner.scan(
                 repo_full_name=job.repo_id,
                 root=repo_path,
-                scan_options=ScanOptions(
-                    include_history=True,
-                    git_log_opts=f"{job.commit_sha}^!",
-                ),
+                scan_options=_scan_options_for_job(job),
                 scan_run_id=scan_run_id,
                 rule_pack_version=job.rule_pack_version,
             )
-            branch = branch_from_ref(job.ref_name)
+            commit, branch = _finding_context_for_job(job)
             findings = [
-                finding_with_context(finding, commit=job.commit_sha, branch=branch)
+                finding_with_context(finding, commit=commit, branch=branch)
                 for finding in findings
             ]
             scanned_at = _now(request)
@@ -234,6 +232,23 @@ def make_default_scanner() -> GitleaksScanner:
     return GitleaksScanner()
 
 
+def _scan_options_for_job(job: ScanJob) -> ScanOptions:
+    """Return gitleaks scan options for one queued job."""
+    if job.job_type == JOB_TYPE_BASELINE:
+        return ScanOptions(include_history=True)
+    return ScanOptions(
+        include_history=True,
+        git_log_opts=f"{job.commit_sha}^!",
+    )
+
+
+def _finding_context_for_job(job: ScanJob) -> tuple[str | None, str | None]:
+    """Return occurrence context to stamp onto scanner findings."""
+    if job.job_type == JOB_TYPE_BASELINE:
+        return None, None
+    return job.commit_sha, branch_from_ref(job.ref_name)
+
+
 def _advance_repo_health(
     request: ScanWorkerRequest, job: ScanJob, *, completed_at: dt.datetime
 ) -> None:
diff --git a/tests/test_scan_worker.py b/tests/test_scan_worker.py
index 0677c84..6ed66e1 100644
--- a/tests/test_scan_worker.py
+++ b/tests/test_scan_worker.py
@@ -12,7 +12,12 @@
     run_scan_worker,
     run_scan_worker_once,
 )
-from security_scanner.storage.base import ScanJob, ScanLedgerEntry, ScanLedgerKey
+from security_scanner.storage.base import (
+    JOB_TYPE_BASELINE,
+    ScanJob,
+    ScanLedgerEntry,
+    ScanLedgerKey,
+)
 
 NOW = dt.datetime(2026, 6, 12, 12, 0, tzinfo=dt.UTC)
 REPO_ID = "repo_synthetic000000000001"
@@ -472,7 +477,16 @@ def test_worker_threads_leased_job_fence_into_retryable_failure():
 
 def _baseline_job() -> ScanJob:
     job = _job()
-    return ScanJob(**{**job.__dict__, "job_type": "baseline"})
+    return ScanJob(
+        **{
+            **job.__dict__,
+            "job_type": JOB_TYPE_BASELINE,
+            "commit_sha": "baseline",
+            "new_sha": "baseline",
+            "commit_range": None,
+            "ref_name": "refs/remotes/origin/HEAD",
+        }
+    )
 
 
 def test_completed_incremental_job_advances_incremental_repo_health():
@@ -492,7 +506,21 @@ def test_completed_baseline_job_advances_baseline_repo_health():
 
     run_scan_worker_once(_request(store, scanner))
 
-    assert store.health_advances == [(REPO_ID, "baseline", NOW)]
+    assert store.health_advances == [(REPO_ID, JOB_TYPE_BASELINE, NOW)]
+
+
+def test_baseline_job_runs_full_history_without_sentinel_context():
+    store = FakeWorkerStore([_baseline_job()])
+    scanner = FakeScanner(findings=[_finding(commit=None)])
+
+    run_scan_worker_once(_request(store, scanner))
+
+    call = scanner.calls[0]
+    assert call["scan_options"] == ScanOptions(include_history=True, git_log_opts=None)
+    _, findings, ledger = store.completed[0]
+    assert findings[0].repo.commit is None
+    assert findings[0].repo.branch is None
+    assert ledger.commit_sha == "baseline"
 
 
 def test_ledger_already_present_completion_still_advances_repo_health():