diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9571c9b..a90892a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,8 @@ Follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) · versioned wi
 - **Server-side Provider Credentials.** Provider keys are now masked even for same-origin Settings responses, are
   preserved when masked/empty fields are saved, and model/health probes resolve configured keys inside the server.
   Browser localStorage is no longer used as a credential store.
+- **Image Job Deduplication.** Consistent portrait/reference generation accepts an `Idempotency-Key` and returns the
+  existing job for repeated submissions; completed job mappings are evicted with the job cache.
 - **Security Regression Coverage.** Added a Python test gate for character metadata validation, private-download URL
   rejection and oversized JSON request rejection.
 - **Navigation Reliability.** Rehearser phase requests now survive the feature-module initialization boundary.
diff --git a/TODO.md b/TODO.md
index 824e3e8..bb36175 100644
--- a/TODO.md
+++ b/TODO.md
@@ -51,8 +51,8 @@ the first block before investing in architecture or polish.
 - [ ] **M — Make profile portraits and character sheets use one canonical identity.**
   Share age, hair, eyes, face, build, skin tone, marks and era; version the prompt and
   detect stale or inconsistent images.
-- [ ] **M — Add bounded duplicate-generation protection.** Ensure double-clicks and
-  retried requests cannot create duplicate voice, image or casting jobs.
+- [ ] **M — Add bounded duplicate-generation protection.** Consistent portrait/reference jobs now deduplicate
+  repeated requests with `Idempotency-Key`; extend the same bounded contract to voice and casting jobs.
 - [ ] **M — Improve large-table performance.** Virtualize/paginate character and voice
   tables, update only affected rows, and disable preloading on low-memory devices.
 - [ ] **M — Add explicit cache invalidation and eviction.** Cache `/api/voices` safely
diff --git a/routes/conversation.py b/routes/conversation.py
index d3b254c..31ab866 100644
--- a/routes/conversation.py
+++ b/routes/conversation.py
@@ -60,6 +60,7 @@ _attribution_llm_lock = threading.Lock()
 # entries are pruned an hour after completion so this can't grow unbounded.
 _consistent_image_jobs: dict[str, dict] = {}
 _consistent_image_jobs_lock = threading.Lock()
+_consistent_image_idempotency: dict[str, str] = {}
 
 
 def _cij_new(job_id: str, name: str) -> None:
@@ -72,6 +73,9 @@ def _cij_new(job_id: str, name: str) -> None:
         cutoff = now - 3600
         for stale_id in [j for j, v in _consistent_image_jobs.items() if v.get("done") and v.get("updated", 0) < cutoff]:
             _consistent_image_jobs.pop(stale_id, None)
+            for key, mapped_id in list(_consistent_image_idempotency.items()):
+                if mapped_id == stale_id:
+                    _consistent_image_idempotency.pop(key, None)
 
 
 def _cij_set(job_id: str, **fields) -> None:
@@ -3014,6 +3018,14 @@ async def character_generate_consistent_images(request: Request):
     the face consistent across both deliverables.
     """
     data = await request.json()
+    idempotency_key = str(request.headers.get("idempotency-key") or "").strip()
+    if len(idempotency_key) > 200:
+        raise HTTPException(400, "Idempotency-Key is too long")
+    if idempotency_key:
+        with _consistent_image_jobs_lock:
+            previous_job_id = _consistent_image_idempotency.get(idempotency_key)
+            if previous_job_id and previous_job_id in _consistent_image_jobs:
+                return {"job_id": previous_job_id, "deduplicated": True}
     name = str(data.get("name") or "").strip()
     book = str(data.get("book") or "").strip()
     sheet: dict = data.get("sheet") or {}
@@ -3068,6 +3080,9 @@ async def character_generate_consistent_images(request: Request):
     # fetch that a page reload would then throw away mid-render.
     job_id = uuid.uuid4().hex
     _cij_new(job_id, name or "Character")
+    if idempotency_key:
+        with _consistent_image_jobs_lock:
+            _consistent_image_idempotency[idempotency_key] = job_id
 
     def _worker() -> None:
         try: