diff --git a/.github/actions/bulletin/action.yml b/.github/actions/bulletin/action.yml
index 0f4d7a6..35349f4 100644
--- a/.github/actions/bulletin/action.yml
+++ b/.github/actions/bulletin/action.yml
@@ -72,6 +72,11 @@ runs:
         CI: "true"
         FORCE_COLOR: "0"
         NODE_NO_WARNINGS: "1"
+        # ubuntu-latest runners have ≥16 GiB RAM; default ~2 GiB Node heap
+        # leaves no headroom if a transient leak window opens during a WS
+        # halt teardown. Raising it is a cheap safety net independent of
+        # the in-CLI cancellation fixes.
+        NODE_OPTIONS: "--max-old-space-size=4096"
         RETRY_DELAY: ${{ inputs.retry-delay }}
 
     - name: Upload to Bulletin
@@ -124,5 +129,7 @@ runs:
         CI: "true"
         FORCE_COLOR: "0"
         NODE_NO_WARNINGS: "1"
+        # See note in the authorize step above.
+        NODE_OPTIONS: "--max-old-space-size=4096"
         RETRY_DELAY: ${{ inputs.retry-delay }}
         CACHE: ${{ inputs.cache }}
diff --git a/packages/cli/src/bulletin/store.ts b/packages/cli/src/bulletin/store.ts
index a09f652..5d7932d 100644
--- a/packages/cli/src/bulletin/store.ts
+++ b/packages/cli/src/bulletin/store.ts
@@ -43,6 +43,15 @@ const WAVE_TIMEOUT_MS = 60_000;
 const STORE_CALL_TIMEOUT_MS = 60_000;
 export const FINAL_STORE_CALL_TIMEOUT_MS = 180_000;
 const FETCH_NONCE_TIMEOUT_MS = 15_000;
+// polkadot-api ws-provider defaults to 40_000 ms, which is shorter than a
+// single Bulletin chunk's worst-case best-block inclusion latency under
+// contention (we observed >50 s outliers). Raise it well above WAVE_TIMEOUT_MS
+// so the transport layer never tears down a healthy WS while the chain is
+// still acknowledging an in-flight extrinsic.
+const WS_HEARTBEAT_TIMEOUT_MS = 300_000;
+// polkadot-api ws-provider default is 3_500 ms; give the handshake more
+// headroom on slow links (CI runners → Scaleway can spike past that).
+const WS_CONNECT_TIMEOUT_MS = 10_000;
 let rxUnhandledErrorGuardInstalled = false;
 
 export type AdaptiveWindowUpdateInput = {
@@ -468,7 +477,14 @@ export function formatTransactionWatchFailure(
 
 export function createBulletinClient(rpc: string): PolkadotClient {
   installRxUnhandledErrorGuard();
-  return createPolkadotClient(withPolkadotSdkCompat(getWsProvider(rpc)));
+  return createPolkadotClient(
+    withPolkadotSdkCompat(
+      getWsProvider(rpc, {
+        heartbeatTimeout: WS_HEARTBEAT_TIMEOUT_MS,
+        timeout: WS_CONNECT_TIMEOUT_MS,
+      }),
+    ),
+  );
 }
 
 async function storeContentOnBulletin(