diff --git a/CHANGELOG.md b/CHANGELOG.md
index acf8e02626d..d3666a0a4b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Hooks/Cron: suppress duplicate main-session events for delivered hook turns and mark `SILENT_REPLY_TOKEN` (`NO_REPLY`) early exits as delivered to prevent hook context pollution. (#20678) Thanks @JonathanWorks.
 - Providers/OpenRouter: inject `cache_control` on system prompts for OpenRouter Anthropic models to improve prompt-cache reuse. (#17473) Thanks @rrenamed.
 - Providers/OpenRouter: allow pass-through OpenRouter and Opencode model IDs in live model filtering so custom routed model IDs are treated as modern refs. (#14312) Thanks @Joly0.
 - Providers/OpenRouter: default reasoning to enabled when the selected model advertises `reasoning: true` and no session/directive override is set. (#22513) Thanks @zwffff.
diff --git a/src/cron/isolated-agent/run.ts b/src/cron/isolated-agent/run.ts
index e4e4e798c76..fce4174da4d 100644
--- a/src/cron/isolated-agent/run.ts
+++ b/src/cron/isolated-agent/run.ts
@@ -753,7 +753,7 @@ export async function runCronIsolatedAgentTurn(params: {
         return withRunSession({ status: "ok", summary, outputText, ...telemetry });
       }
       if (synthesizedText.toUpperCase() === SILENT_REPLY_TOKEN.toUpperCase()) {
-        return withRunSession({ status: "ok", summary, outputText, ...telemetry });
+        return withRunSession({ status: "ok", summary, outputText, delivered: true, ...telemetry });
       }
       try {
         const didAnnounce = await runSubagentAnnounceFlow({
diff --git a/src/gateway/server/hooks.ts b/src/gateway/server/hooks.ts
index a20a748ef5e..2065bacd894 100644
--- a/src/gateway/server/hooks.ts
+++ b/src/gateway/server/hooks.ts
@@ -86,11 +86,13 @@ export function createGatewayHooksRequestHandler(params: {
         const summary = result.summary?.trim() || result.error?.trim() || result.status;
         const prefix =
           result.status === "ok" ? `Hook ${value.name}` : `Hook ${value.name} (${result.status})`;
-        enqueueSystemEvent(`${prefix}: ${summary}`.trim(), {
-          sessionKey: mainSessionKey,
-        });
-        if (value.wakeMode === "now") {
-          requestHeartbeatNow({ reason: `hook:${jobId}` });
+        if (!result.delivered) {
+          enqueueSystemEvent(`${prefix}: ${summary}`.trim(), {
+            sessionKey: mainSessionKey,
+          });
+          if (value.wakeMode === "now") {
+            requestHeartbeatNow({ reason: `hook:${jobId}` });
+          }
         }
       } catch (err) {
         logHooks.warn(`hook agent failed: ${String(err)}`);