diff --git a/CHANGELOG.md b/CHANGELOG.md
index ca5af232..19dfc8b3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,13 @@
 
 # Changelog
 
+## Sprint 160 Split-background promotion preflight (2026-07-10)
+
+- Added `--preflight-only` to `scripts/run_split_background_promotion_workflow.sh`.
+- Preflight validates local positive portfolio and operator manifest files, confirms required `pure_empty_negative` and `sparse_building_context` background categories, checks Python/curl availability and verifies the runtime API proxy returns the canonical envelope.
+- Documented the quick post-redeploy preflight command before starting long configured-YOLO matrix inference.
+- No model default, backend API, database migration, provider fetching, fake detection output or model download behavior changed.
+
 ## Sprint 159 Split-background promotion workflow wrapper (2026-07-10)
 
 - Added `scripts/run_split_background_promotion_workflow.sh` to run the split background matrix and split-aware promotion report from one operator command.
diff --git a/backend/tests/test_sprint159_split_promotion_workflow.py b/backend/tests/test_sprint159_split_promotion_workflow.py
index 8dc7b0bc..c47c7fd7 100644
--- a/backend/tests/test_sprint159_split_promotion_workflow.py
+++ b/backend/tests/test_sprint159_split_promotion_workflow.py
@@ -23,6 +23,18 @@ def test_split_background_promotion_workflow_runs_split_then_split_aware_report(
     assert "promote model default" not in source.lower()
 
 
+def test_split_background_promotion_workflow_has_safe_preflight_mode() -> None:
+    source = (ROOT / "scripts" / "run_split_background_promotion_workflow.sh").read_text(encoding="utf-8")
+
+    assert "--preflight-only" in source
+    assert "PREFLIGHT_ONLY" in source
+    assert "curl -fsS" in source
+    assert "OPERATOR_SAMPLE_MANIFEST_PATH is required" in source
+    assert "pure_empty_negative" in source
+    assert "sparse_building_context" in source
+    assert "Split-background promotion preflight passed" in source
+
+
 def test_readiness_checks_split_background_promotion_workflow_syntax() -> None:
     readiness = (ROOT / "scripts" / "run_readiness_check.sh").read_text(encoding="utf-8")
 
diff --git a/docs/AI_PIPELINES.md b/docs/AI_PIPELINES.md
index 6315fd00..56a99673 100644
--- a/docs/AI_PIPELINES.md
+++ b/docs/AI_PIPELINES.md
@@ -296,6 +296,17 @@ The wrapper keeps the same safety boundary: existing dataset upload, configured
 YOLO detection and report tooling only. It does not change model configuration
 or bypass the persisted QA/QC evidence requirement.
 
+For a quick post-redeploy check before the long matrix starts, use
+`--preflight-only` with the same positive portfolio and operator manifest. This
+checks local paths, required background categories and the runtime API envelope
+without running inference:
+
+```bash
+PROMOTION_POSITIVE_PORTFOLIO_PATH=artifacts/detection-quality-matrix/multi-sample/aoi1024bg512r3e50-positive/multi_sample_quality_summary.json \
+OPERATOR_SAMPLE_MANIFEST_PATH=storage/operator-data/operator_samples_manifest.json \
+bash scripts/run_split_background_promotion_workflow.sh --preflight-only http://192.168.10.150:1202
+```
+
 The underlying single-category matrix remains available:
 
 ```bash
diff --git a/docs/CODEX_EXECUTION_LOG.md b/docs/CODEX_EXECUTION_LOG.md
index 55da0686..ff110b1b 100644
--- a/docs/CODEX_EXECUTION_LOG.md
+++ b/docs/CODEX_EXECUTION_LOG.md
@@ -6350,3 +6350,43 @@ Open:
 - Run:
   - `PROMOTION_POSITIVE_PORTFOLIO_PATH=... bash scripts/run_split_background_promotion_workflow.sh http://192.168.10.150:1202`
 - Review the generated split-aware promotion report before any retraining, recalibration or default-model decision.
+
+# Sprint 160 - Split-background promotion preflight
+
+## What changed
+
+- Added `--preflight-only` to `scripts/run_split_background_promotion_workflow.sh`.
+- Preflight now checks:
+  - `PROMOTION_POSITIVE_PORTFOLIO_PATH` exists and is readable.
+  - `OPERATOR_SAMPLE_MANIFEST_PATH` exists and is readable.
+  - the manifest contains both `pure_empty_negative` and `sparse_building_context` background categories.
+  - Python and `curl` are available.
+  - the runtime frontend API proxy returns the canonical `data` envelope from `/api/v1/projects`.
+- Updated operator docs, TODO and changelog with the quick post-redeploy preflight command.
+
+## What was tested
+
+- Red step: `python -m pytest tests/test_sprint159_split_promotion_workflow.py -q` failed because `--preflight-only` was not yet present.
+- Ran `python -m pytest tests/test_sprint159_split_promotion_workflow.py -q`: 3 passed.
+- Ran `bash -n scripts/run_split_background_promotion_workflow.sh`.
+- Ran `python -m pytest tests/test_sprint159_split_promotion_workflow.py tests/test_sprint158_promotion_report_split_background.py -q`: 4 passed.
+- Ran `curl.exe -fsS http://192.168.10.150:1202/api/v1/projects`: runtime API proxy returned a canonical `data` envelope.
+- Ran `python -m compileall backend/app`.
+- Ran `python -m pytest` in `backend`: 447 passed, 17 existing Pydantic namespace warnings.
+- Ran `cd frontend && npm run typecheck`.
+- Ran `cd frontend && npm run build`.
+- Ran `cd backend && python -m alembic heads`: `202606120900 (head)`.
+- Ran `cd backend && python -m alembic upgrade head --sql`.
+- Ran `bash -n scripts/live_migration_smoke.sh`.
+- Ran `bash scripts/run_readiness_check.sh`: passed.
+
+## Known limitations
+
+- Preflight is intentionally non-mutating and does not run inference, create datasets, retrain models, activate defaults, fetch providers, fetch weights or change API/database behavior.
+- Full split-background matrix execution still requires redeploying this commit to the Tower/Unraid runtime and running the wrapper in the runtime checkout where the positive portfolio and operator manifest artifacts exist.
+
+## Next recommended pass
+
+- Redeploy/pull on Tower, then run:
+  - `PROMOTION_POSITIVE_PORTFOLIO_PATH=... OPERATOR_SAMPLE_MANIFEST_PATH=... bash scripts/run_split_background_promotion_workflow.sh --preflight-only http://192.168.10.150:1202`
+- If preflight passes, rerun without `--preflight-only` to generate the split summary and split-aware promotion report.
diff --git a/docs/TODO.md b/docs/TODO.md
index 0e94f0f7..a5ef0cbd 100644
--- a/docs/TODO.md
+++ b/docs/TODO.md
@@ -125,6 +125,7 @@ This file now starts with the current implementation status. Older preparation/b
 - [x] Add a split background-corpus matrix runner and report builder that runs pure-empty and sparse-context matrices separately.
 - [x] Teach the model promotion report to consume split background summaries so only `pure_empty_negative` blocks default promotion and `sparse_building_context` stays review-only.
 - [x] Add one-command operator workflow to run split background matrices and immediately build the split-aware promotion report.
+- [x] Add preflight-only validation for the split-background promotion workflow before long runtime matrices.
 - [ ] Rerun split background matrices on Tower after rebuild, then retrain or recalibrate against the cleaner pure-empty gate plus separate sparse-context inspection matrix.
 - [ ] Promote a V1 default building detector only after it passes seven positive AOIs, clean hard-negative/background gates and persisted QA/QC evidence without fake detections or model downloads.
 
diff --git a/scripts/README.md b/scripts/README.md
index 0735009e..bb844302 100644
--- a/scripts/README.md
+++ b/scripts/README.md
@@ -718,6 +718,18 @@ generated `background_corpus_split_summary.json` into the split-aware promotion
 report. It still uses only existing upload, detection and report paths; it does
 not fetch providers, fetch model weights or activate a default.
 
+Run the same command with `--preflight-only` first when checking a fresh
+redeploy. Preflight validates the positive portfolio path, operator manifest
+presence, required `pure_empty_negative` and `sparse_building_context`
+background categories, Python/curl availability and the frontend API proxy
+envelope without starting inference:
+
+```bash
+PROMOTION_POSITIVE_PORTFOLIO_PATH=/mnt/user/appdata/geointel/artifacts/detection-quality-matrix/multi-sample/aoi1024bg512r3e50-positive/multi_sample_quality_summary.json \
+OPERATOR_SAMPLE_MANIFEST_PATH=storage/operator-data/operator_samples_manifest.json \
+bash scripts/run_split_background_promotion_workflow.sh --preflight-only http://192.168.10.150:1202
+```
+
 If a legacy positive evidence portfolio records `model_asset_id` at portfolio
 level but does not include per-run tile size/overlap, pass explicit tile
 defaults instead of letting the report guess:
diff --git a/scripts/run_split_background_promotion_workflow.sh b/scripts/run_split_background_promotion_workflow.sh
index 8365f950..c67c60ec 100644
--- a/scripts/run_split_background_promotion_workflow.sh
+++ b/scripts/run_split_background_promotion_workflow.sh
@@ -10,7 +10,7 @@ Usage:
   QUALITY_TILE_SIZES="512" \
   QUALITY_TILE_OVERLAPS="64" \
   QUALITY_THRESHOLDS="0.35 0.15" \
-  bash scripts/run_split_background_promotion_workflow.sh [base_url]
+  bash scripts/run_split_background_promotion_workflow.sh [--preflight-only] [base_url]
 
 Optional environment:
   BACKGROUND_SPLIT_OUTPUT_DIR                 Split matrix output directory.
@@ -22,6 +22,7 @@ Optional environment:
   PROMOTION_MAX_BACKGROUND_DETECTIONS_PER_SAMPLE  Default: 0.
   PROMOTION_DEFAULT_POSITIVE_TILE_SIZE        Optional fallback for legacy positive portfolios.
   PROMOTION_DEFAULT_POSITIVE_TILE_OVERLAP     Optional fallback for legacy positive portfolios.
+  GE_INTEL_BASE_URL                           Default base URL when no argument is supplied.
 
 Runs the split background matrix, then builds a split-aware promotion report.
 The pure-empty background summary is the strict default gate. Sparse-context
@@ -35,11 +36,24 @@ EOF
 ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
 cd "$ROOT"
 
-BASE_URL="${1:-${GE_INTEL_BASE_URL:-http://localhost:1202}}"
-if [ "${BASE_URL}" = "-h" ] || [ "${BASE_URL}" = "--help" ]; then
-  usage
-  exit 0
-fi
+BASE_URL="${GE_INTEL_BASE_URL:-http://localhost:1202}"
+PREFLIGHT_ONLY=0
+
+while [ "$#" -gt 0 ]; do
+  case "$1" in
+    -h|--help)
+      usage
+      exit 0
+      ;;
+    --preflight-only)
+      PREFLIGHT_ONLY=1
+      ;;
+    *)
+      BASE_URL="$1"
+      ;;
+  esac
+  shift
+done
 
 if [ -z "${PROMOTION_POSITIVE_PORTFOLIO_PATH:-}" ]; then
   echo "PROMOTION_POSITIVE_PORTFOLIO_PATH is required" >&2
@@ -52,6 +66,17 @@ if [ ! -s "${PROMOTION_POSITIVE_PORTFOLIO_PATH}" ]; then
   exit 1
 fi
 
+if [ -z "${OPERATOR_SAMPLE_MANIFEST_PATH:-}" ]; then
+  echo "OPERATOR_SAMPLE_MANIFEST_PATH is required" >&2
+  usage
+  exit 1
+fi
+
+if [ ! -s "${OPERATOR_SAMPLE_MANIFEST_PATH}" ]; then
+  echo "Operator sample manifest is not readable: ${OPERATOR_SAMPLE_MANIFEST_PATH}" >&2
+  exit 1
+fi
+
 if [ -n "${PYTHON_BIN:-}" ]; then
   PYTHON_BIN="${PYTHON_BIN}"
 else
@@ -69,6 +94,49 @@ if [ -z "${PYTHON_BIN}" ]; then
   exit 1
 fi
 
+if ! command -v curl >/dev/null 2>&1; then
+  echo "curl is required for split-background promotion preflight" >&2
+  exit 1
+fi
+
+"${PYTHON_BIN}" - "${OPERATOR_SAMPLE_MANIFEST_PATH}" <<'PY'
+import json
+import sys
+from pathlib import Path
+
+manifest_path = Path(sys.argv[1])
+payload = json.loads(manifest_path.read_text(encoding="utf-8-sig"))
+samples = payload.get("samples") or payload.get("items") or []
+if not isinstance(samples, list) or not samples:
+    raise SystemExit(f"Operator sample manifest has no samples: {manifest_path}")
+
+background_categories = {
+    str(sample.get("background_category") or "")
+    for sample in samples
+    if str(sample.get("sample_role") or "") == "background_candidate"
+}
+missing = {"pure_empty_negative", "sparse_building_context"} - background_categories
+if missing:
+    raise SystemExit(
+        "Operator sample manifest is missing background categories "
+        f"{sorted(missing)}; found {sorted(background_categories)}"
+    )
+PY
+
+api_response="$(curl -fsS "${BASE_URL%/}/api/v1/projects" 2>/dev/null || true)"
+if ! printf '%s' "${api_response}" | grep -q '"data"'; then
+  echo "Runtime API proxy is not reachable or did not return the canonical envelope: ${BASE_URL%/}/api/v1/projects" >&2
+  exit 1
+fi
+
+if [ "${PREFLIGHT_ONLY}" = "1" ]; then
+  echo "Split-background promotion preflight passed"
+  echo "Base URL: ${BASE_URL}"
+  echo "Positive portfolio: ${PROMOTION_POSITIVE_PORTFOLIO_PATH}"
+  echo "Operator sample manifest: ${OPERATOR_SAMPLE_MANIFEST_PATH}"
+  exit 0
+fi
+
 stamp="$(date -u +%Y%m%dT%H%M%SZ)"
 BACKGROUND_SPLIT_OUTPUT_DIR="${BACKGROUND_SPLIT_OUTPUT_DIR:-artifacts/detection-hard-negatives/background-split/${stamp}}"
 PROMOTION_OUTPUT_DIR="${PROMOTION_OUTPUT_DIR:-artifacts/detection-model-promotion/split-aware/${stamp}}"