diff --git a/requirements.txt b/requirements.txt
index 4b6f62a..061f6cc 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -38,7 +38,7 @@ flask-limiter>=3.5,<4.0    # per-user rate limits on AI + key routes (in-memory
 # Cloud: PDF storage + delivery via Cloudflare R2 (Stage 8). OPTIONAL at
 # runtime — when the R2_* env vars are unset the editor streams PDFs directly
 # (graceful fallback). boto3 talks to R2's S3-compatible API for upload + signed URLs.
-boto3>=1.34,<2.0
+boto3>=1.43.56,<2.0
 
 # Dev / tests
 pytest>=9.1.1,<10.0