diff --git a/docs/plans/state.json b/docs/plans/state.json
index 4046535..b3bd7e0 100644
--- a/docs/plans/state.json
+++ b/docs/plans/state.json
@@ -581,6 +581,18 @@
       ],
       "test_status": "pnpm test:run src/audit/phase0BaselineScriptWiring.test.ts + pnpm typecheck passing"
     },
+    "phase0-live-baseline-backend-list-dedup-in-cli": {
+      "status": "completed",
+      "date": "2026-02-27",
+      "updated": "2026-02-27",
+      "summary": "Deduplicated repeated backend names in phase-0 capture/drift CLI parsing so repeated `--backend` values do not duplicate drift evaluation rows or alter backend-scoped artifact suffix selection.",
+      "files_modified": [
+        "scripts/capture-phase0-live-baseline.ts",
+        "scripts/check-phase0-baseline-backend-drift.ts",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm typecheck + node --import tsx/esm scripts/check-phase0-baseline-backend-drift.ts --artifacts-dir docs/plans/artifacts --backend native,native --format json + synthetic-audit capture smoke check passing"
+    },
     "phase0-instrumentation-ticket-checklist": {
       "status": "completed",
       "date": "2026-02-25",
diff --git a/scripts/capture-phase0-live-baseline.ts b/scripts/capture-phase0-live-baseline.ts
index c3075cc..74a701e 100644
--- a/scripts/capture-phase0-live-baseline.ts
+++ b/scripts/capture-phase0-live-baseline.ts
@@ -146,9 +146,14 @@ function parseBackendTargets(raw: string | undefined): Phase0BackendTarget[] | u
     return undefined;
   }
   const parsed: Phase0BackendTarget[] = [];
+  const seen = new Set<Phase0BackendTarget>();
   for (const value of values) {
     if (BACKEND_TARGETS.includes(value as Phase0BackendTarget)) {
-      parsed.push(value as Phase0BackendTarget);
+      const backend = value as Phase0BackendTarget;
+      if (!seen.has(backend)) {
+        parsed.push(backend);
+        seen.add(backend);
+      }
       continue;
     }
     throw new Error(`Invalid backend "${value}".`);
diff --git a/scripts/check-phase0-baseline-backend-drift.ts b/scripts/check-phase0-baseline-backend-drift.ts
index 7a1481b..6204cda 100644
--- a/scripts/check-phase0-baseline-backend-drift.ts
+++ b/scripts/check-phase0-baseline-backend-drift.ts
@@ -126,9 +126,14 @@ function parseOptionalInteger(raw: string | undefined, flag: string): number | u
 function parseBackends(raw: string | undefined): Phase0BackendTarget[] {
   const values = parseCsv(raw) ?? ['pi_embedded', 'native'];
   const parsed: Phase0BackendTarget[] = [];
+  const seen = new Set<Phase0BackendTarget>();
   for (const value of values) {
     if (BACKEND_TARGETS.includes(value as Phase0BackendTarget)) {
-      parsed.push(value as Phase0BackendTarget);
+      const backend = value as Phase0BackendTarget;
+      if (!seen.has(backend)) {
+        parsed.push(backend);
+        seen.add(backend);
+      }
       continue;
     }
     throw new Error(`Invalid backend "${value}".`);