diff --git a/Makefile b/Makefile
index 8251587d6..7b3fcd506 100644
--- a/Makefile
+++ b/Makefile
@@ -58,6 +58,7 @@ help:
 	@echo "  make check-star-map    Assert star_map_data.json is up to date (part of pre-pr-client)"
 	@echo "  make economy-db        Import economics data into systems.db (TOML/JSON → SQLite)"
 	@echo "  make atlas-generate    Generate atlas city/road/rail markers for all inhabited bodies"
+	@echo "  make test-atlas-determinism  Determinism smoke test for generate_atlas.py (#847)"
 	@echo "  make fixtures-client    Generate GDScript->Rust cross-encoder fixtures (#475)"
 	@echo "  make golden-diff        Show diff if golden file output has changed"
 	@echo "  make golden-update      Regenerate golden file and stage for commit"
@@ -223,6 +224,9 @@ test-ipc-integration:
 test-ipc-benchmark:
 	tests/run-ipc-benchmark
 
+test-atlas-determinism:  ## Determinism smoke test for generate_atlas.py (#847)
+	tests/run-atlas-determinism
+
 # --- Clean ---
 
 clean-imports:
diff --git a/tests/run-all b/tests/run-all
index 6d7706667..9c4b80842 100755
--- a/tests/run-all
+++ b/tests/run-all
@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 # tests/run-all: Run all test suites in order (D-030)
-# Invokes run-rust, run-godot, run-ipc-fixtures, run-ipc-protocol, run-ipc-integration.
+# Invokes run-rust, run-godot, run-ipc-fixtures, run-ipc-protocol,
+# run-ipc-integration, run-visual, run-atlas-determinism.
 # Exit: 0 = all suites pass, non-zero = any suite failed
 # Stdout: {"suite":"all","total":N,"passed":N,"failed":N,"duration_ms":N,"suites":[...]}
 set -euo pipefail
@@ -26,6 +27,7 @@ SUITES=(
     run-ipc-protocol
     run-ipc-integration
     run-visual
+    run-atlas-determinism
 )
 
 START_MS=$(date +%s%3N)
diff --git a/tests/run-atlas-determinism b/tests/run-atlas-determinism
new file mode 100755
index 000000000..14353c35f
--- /dev/null
+++ b/tests/run-atlas-determinism
@@ -0,0 +1,136 @@
+#!/usr/bin/env bash
+# tests/run-atlas-determinism: Determinism smoke test for generate_atlas.py (#847)
+#
+# Imports generate_atlas as a Python module, calls process_body() twice with
+# seed=42 and dry_run=True, compares the returned markers dicts as JSON.
+# No wiki files are written or modified.
+#
+# Purpose: cheap guardrail against determinism regressions in terrain analysis,
+# city placement, A* road routing, infrastructure MST, and gate terminal
+# placement. GJ892f is a domed body (population=300, 1 city) — the smallest
+# well-exercised case in the atlas pipeline.
+#
+# Spec ref: #847
+# Exit: 0 = deterministic (pass), non-zero = failure
+# Stdout: {"suite":"atlas-determinism","total":1,"passed":N,"failed":N,"duration_ms":N}
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+START_MS=$(date +%s%3N)
+
+# Write the comparison script to a real file so that the generate_atlas venv
+# bootstrap (os.execv) can re-exec it from the venv Python when needed.
+# A heredoc (python3 - <<'EOF') does not work after os.execv because stdin
+# has already been consumed.
+HELPER=$(mktemp /tmp/atlas_det_helper.XXXXXX.py)
+trap "rm -f '$HELPER'" EXIT
+
+cat > "$HELPER" << 'PYEOF'
+"""Atlas determinism helper — called by tests/run-atlas-determinism (#847).
+
+Imports generate_atlas as a module and calls process_body() twice with
+dry_run=True. Compares the returned markers dicts as JSON. Exits 0 if
+identical, 1 if they differ, 2 on setup/import failure.
+"""
+import json
+import os
+import sqlite3
+import sys
+from pathlib import Path
+
+REPO_ROOT = Path(os.environ["SR_REPO_ROOT"])
+sys.path.insert(0, str(REPO_ROOT / "tooling" / "planet-gen"))
+
+try:
+    import generate_atlas
+except ImportError as e:
+    print(f"SKIP: generate_atlas import failed (missing deps?): {e}", file=sys.stderr)
+    sys.exit(2)
+
+DB_PATH = REPO_ROOT / "server" / "data" / "systems.db"
+BODY_ID = "GJ892f"   # domed, pop=300 → exactly 1 city; minimal and fast
+SEED = 42
+
+if not DB_PATH.exists():
+    print(f"SKIP: systems.db not found: {DB_PATH}", file=sys.stderr)
+    sys.exit(2)
+
+conn = sqlite3.connect(str(DB_PATH))
+conn.execute("PRAGMA foreign_keys=ON")
+row = conn.execute("""
+    SELECT b.body_id, b.system_id, b.terrain_reference, b.population,
+           b.settlement_pattern, b.planet_class, b.economic_role,
+           COALESCE(b.cultural_corridor, s.cultural_corridor)
+    FROM bodies b JOIN star_systems s ON b.system_id = s.system_id
+    WHERE b.body_id = ?
+""", (BODY_ID,)).fetchone()
+conn.close()
+
+if not row:
+    print(f"SKIP: {BODY_ID} not found in systems.db", file=sys.stderr)
+    sys.exit(2)
+
+body_info = dict(zip(
+    ("body_id", "system_id", "terrain_reference", "population",
+     "settlement_pattern", "planet_class", "economic_role", "cultural_corridor"),
+    row,
+))
+body_info["population"] = body_info["population"] or 0
+
+kwargs = dict(
+    body_info=body_info,
+    seed=SEED,
+    noise_factor=0.25,
+    dry_run=True,   # no files written
+    force=True,     # skip the already-populated check
+    verbose=False,
+)
+
+a = generate_atlas.process_body(**kwargs)
+b = generate_atlas.process_body(**kwargs)
+
+if a["status"] != "generated":
+    print(f"FAIL: run 1 status={a['status']} — {a.get('message', '')}", file=sys.stderr)
+    sys.exit(1)
+if b["status"] != "generated":
+    print(f"FAIL: run 2 status={b['status']} — {b.get('message', '')}", file=sys.stderr)
+    sys.exit(1)
+
+json_a = json.dumps(a["markers"], indent=2)
+json_b = json.dumps(b["markers"], indent=2)
+
+if json_a == json_b:
+    print(f"PASS: {BODY_ID} markers identical on two runs (seed={SEED})", file=sys.stderr)
+    sys.exit(0)
+else:
+    import difflib
+    diff = "\n".join(list(difflib.unified_diff(
+        json_a.splitlines(), json_b.splitlines(), lineterm="",
+        fromfile="run1", tofile="run2",
+    ))[:40])
+    print(f"FAIL: {BODY_ID} markers differ between run 1 and run 2 (seed={SEED})", file=sys.stderr)
+    print(diff, file=sys.stderr)
+    sys.exit(1)
+PYEOF
+
+set +e
+SR_REPO_ROOT="$REPO_ROOT" python3 "$HELPER" 2>&1 >&2
+EXIT_CODE=$?
+set -e
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+# Exit code 2 = setup failure / missing deps → count as 0 tests (skip, not fail)
+if [[ $EXIT_CODE -eq 0 ]]; then
+    PASSED=1; FAILED=0; TOTAL=1
+elif [[ $EXIT_CODE -eq 2 ]]; then
+    PASSED=0; FAILED=0; TOTAL=0
+    echo "  [atlas-determinism] SKIPPED (import failure or missing DB)" >&2
+else
+    PASSED=0; FAILED=1; TOTAL=1
+fi
+
+printf '{"suite":"atlas-determinism","total":%d,"passed":%d,"failed":%d,"duration_ms":%d}\n' \
+    "$TOTAL" "$PASSED" "$FAILED" "$DURATION_MS"
+exit $EXIT_CODE