diff --git a/src/lib/boss-data.ts b/src/lib/boss-data.ts
index 3ac3a83..76554bd 100644
--- a/src/lib/boss-data.ts
+++ b/src/lib/boss-data.ts
@@ -1548,6 +1548,46 @@ function sameStringSet(a: string[] | undefined, b: string[] | undefined) {
   return left.length === right.length && left.every((value, index) => value === right[index]);
 }
 
+function dispatchPlanTargetSignature(target: DispatchPlanTarget) {
+  return [
+    target.projectId,
+    target.deviceId,
+    target.threadId,
+    target.threadDisplayName,
+    target.folderName,
+    target.codexFolderRef ?? "",
+    target.codexThreadRef ?? "",
+    target.reason,
+  ].join("\u001f");
+}
+
+function sameDispatchPlanTargets(a: DispatchPlanTarget[], b: DispatchPlanTarget[]) {
+  return sameStringSet(
+    a.map((target) => dispatchPlanTargetSignature(target)),
+    b.map((target) => dispatchPlanTargetSignature(target)),
+  );
+}
+
+function normalizeDispatchPlanTargetsForCreate(
+  state: BossState,
+  targets: DispatchPlanTarget[],
+) {
+  if (targets.length === 0) {
+    throw new Error("DISPATCH_PLAN_TARGETS_REQUIRED");
+  }
+
+  const validatedTargets = targets.map((target) =>
+    validateDispatchTargetAgainstState(state, normalizedDispatchPlanTarget(target, undefined, { allowInvalid: false }) as DispatchPlanTarget),
+  );
+
+  const uniqueProjectIds = normalizeStringSet(validatedTargets.map((target) => target.projectId));
+  if (uniqueProjectIds.length !== validatedTargets.length) {
+    throw new Error("DISPATCH_PLAN_TARGET_DUPLICATE");
+  }
+
+  return validatedTargets;
+}
+
 function normalizedDispatchPlanTarget(
   raw: Partial<DispatchPlanTarget>,
   fallback?: DispatchPlanTarget,
@@ -3774,26 +3814,29 @@ export async function createDispatchPlan(input: {
     const groupProjectId = input.groupProjectId.trim();
     const requestMessageId = input.requestMessageId.trim();
     const requestedBy = input.requestedBy.trim();
+    const summary = input.summary?.trim() ?? "";
 
     if (!groupProjectId) throw new Error("DISPATCH_PLAN_GROUP_PROJECT_REQUIRED");
     if (!requestMessageId) throw new Error("DISPATCH_PLAN_REQUEST_MESSAGE_REQUIRED");
+    if (!requestedBy) throw new Error("DISPATCH_PLAN_REQUESTED_BY_REQUIRED");
 
+    const validatedTargets = normalizeDispatchPlanTargetsForCreate(state, input.targets);
     const existing = state.dispatchPlans.find(
       (plan) =>
         plan.groupProjectId === groupProjectId &&
         plan.requestMessageId === requestMessageId,
     );
     if (existing) {
+      const payloadMatches =
+        existing.requestedBy === requestedBy &&
+        existing.summary === summary &&
+        sameDispatchPlanTargets(existing.targets, validatedTargets);
+      if (!payloadMatches) {
+        throw new Error("DISPATCH_PLAN_RETRY_MISMATCH");
+      }
       return existing;
     }
 
-    if (!requestedBy) throw new Error("DISPATCH_PLAN_REQUESTED_BY_REQUIRED");
-    const targets = input.targets.map((target) =>
-      normalizedDispatchPlanTarget(target, undefined, { allowInvalid: false }),
-    ) as DispatchPlanTarget[];
-    if (targets.length === 0) throw new Error("DISPATCH_PLAN_TARGETS_REQUIRED");
-    const validatedTargets = targets.map((target) => validateDispatchTargetAgainstState(state, target));
-
     const plan: DispatchPlan = {
       planId: randomToken("dispatch-plan"),
       groupProjectId,
@@ -3801,7 +3844,7 @@ export async function createDispatchPlan(input: {
       requestedBy,
       status: "pending_user_confirmation",
       targets: validatedTargets,
-      summary: input.summary?.trim() ?? "",
+      summary,
       createdAt: nowIso(),
     };
     state.dispatchPlans.unshift(plan);