diff --git a/src/utils/attachments.ts b/src/utils/attachments.ts
index 4085c42b9..7eb449474 100644
--- a/src/utils/attachments.ts
+++ b/src/utils/attachments.ts
@@ -819,6 +819,10 @@ export async function getAttachments(
         !options?.skipSkillDiscovery
           ? [
               maybe('skill_discovery', async () => {
+                if (suppressNextDiscovery) {
+                  suppressNextDiscovery = false
+                  return []
+                }
                 const result = await skillSearchModules.prefetch.getTurnZeroSkillDiscovery(
                   input,
                   messages ?? [],
@@ -2638,6 +2642,7 @@ const sentSkillNames = new Map<string, Set<string>>()
 export function resetSentSkillNames(): void {
   sentSkillNames.clear()
   suppressNext = false
+  suppressNextDiscovery = false
 }
 
 /**
@@ -2661,6 +2666,18 @@ export function suppressNextSkillListing(): void {
 }
 let suppressNext = false
 
+/**
+ * Suppress the next skill-discovery injection on resume. Same rationale as
+ * suppressNextSkillListing: skill_discovery attachments are not persisted to
+ * transcript for non-ant users, so the prior process's discovery result is
+ * already in the conversation history the model sees. Re-generating it would
+ * inject duplicate content and bust the prompt cache prefix.
+ */
+export function suppressNextSkillDiscovery(): void {
+  suppressNextDiscovery = true
+}
+let suppressNextDiscovery = false
+
 // When skill-search is enabled and the filtered (bundled + MCP) listing exceeds
 // this count, fall back to bundled-only. Protects MCP-heavy users (100+ servers)
 // from truncation while keeping the turn-0 guarantee for typical setups.
diff --git a/src/utils/conversationRecovery.ts b/src/utils/conversationRecovery.ts
index 51c36520c..3379e9dd0 100644
--- a/src/utils/conversationRecovery.ts
+++ b/src/utils/conversationRecovery.ts
@@ -18,7 +18,7 @@ import type {
   NormalizedUserMessage,
 } from '../types/message.js'
 import { PERMISSION_MODES } from '../types/permissions.js'
-import { suppressNextSkillListing } from './attachments.js'
+import { suppressNextSkillDiscovery, suppressNextSkillListing } from './attachments.js'
 import {
   copyFileHistoryForResume,
   type FileHistorySnapshot,
@@ -403,6 +403,16 @@ export function restoreSkillStateFromMessages(messages: Message[]): void {
       suppressNextSkillListing()
     }
   }
+
+  // Unconditionally suppress skill_listing and skill_discovery on resume.
+  // Attachments are not persisted to transcript for non-ant users
+  // (isLoggableMessage filters them out), so the per-type checks above may
+  // never find them even though the prior process already injected the content
+  // into the conversation via <system-reminder> blocks. Without this, every
+  // resume re-injects ~1K tokens of duplicate content and busts the Anthropic
+  // prompt cache prefix (which requires 100% byte-identical segments).
+  suppressNextSkillListing()
+  suppressNextSkillDiscovery()
 }
 
 /**