diff --git a/package.json b/package.json
index 3f8e729fe9..04283a3a73 100644
--- a/package.json
+++ b/package.json
@@ -170,7 +170,8 @@
       "@sinclair/typebox": "0.34.47"
     },
     "patchedDependencies": {
-      "@mariozechner/pi-agent-core": "patches/@mariozechner__pi-agent-core.patch"
+      "@mariozechner/pi-agent-core": "patches/@mariozechner__pi-agent-core.patch",
+      "@mariozechner/pi-coding-agent": "patches/@mariozechner__pi-coding-agent.patch"
     }
   },
   "vitest": {
diff --git a/patches/@mariozechner__pi-coding-agent.patch b/patches/@mariozechner__pi-coding-agent.patch
index 08270770eb..ba46e77fa3 100644
--- a/patches/@mariozechner__pi-coding-agent.patch
+++ b/patches/@mariozechner__pi-coding-agent.patch
@@ -26,3 +26,23 @@ index 0000000..1111111 100644
  }
  /** Result from createAgentSession */
  export interface CreateAgentSessionResult {
+diff --git a/dist/core/session-manager.js b/dist/core/session-manager.js
+index b2aba5280d002253b0938b75aedbb9e6e6c4dcf8..67464efff535dbd7a8e6ed825aab2b305ca2aee2 100644
+--- a/dist/core/session-manager.js
++++ b/dist/core/session-manager.js
+@@ -161,6 +161,15 @@ export function buildSessionContext(entries, leafId, byId) {
+     const messages = [];
+     const appendMessage = (entry) => {
+         if (entry.type === "message") {
++            // PATCH: Filter out empty error assistant messages to prevent session corruption
++            // When 429/500 errors occur during tool execution, empty error messages get persisted
++            // to the session file. These break the tool_use -> tool_result chain for Claude/Gemini.
++            const msg = entry.message;
++            if (msg.role === "assistant" &&
++                msg.stopReason === "error" &&
++                (!msg.content || msg.content.length === 0)) {
++                return; // Skip empty error messages
++            }
+             messages.push(entry.message);
+         }
+         else if (entry.type === "custom_message") {
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index c8ac64885b..e6852d6284 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -11,6 +11,9 @@ patchedDependencies:
   '@mariozechner/pi-agent-core':
     hash: 01312ceb1f6be7e42822c24c9a7a4f7db56b24ae114a364855bd3819779d1cf4
     path: patches/@mariozechner__pi-agent-core.patch
+  '@mariozechner/pi-coding-agent':
+    hash: 58af7c712ebe270527c2ad9d3351fac39d6cd4b81cc475a258d87840b446b90e
+    path: patches/@mariozechner__pi-coding-agent.patch
 
 importers:
 
@@ -39,7 +42,7 @@ importers:
         version: 0.41.0(ws@8.19.0)(zod@4.3.5)
       '@mariozechner/pi-coding-agent':
         specifier: ^0.41.0
-        version: 0.41.0(ws@8.19.0)(zod@4.3.5)
+        version: 0.41.0(patch_hash=58af7c712ebe270527c2ad9d3351fac39d6cd4b81cc475a258d87840b446b90e)(ws@8.19.0)(zod@4.3.5)
       '@mariozechner/pi-tui':
         specifier: ^0.41.0
         version: 0.41.0
@@ -3807,7 +3810,7 @@ snapshots:
       - ws
       - zod
 
-  '@mariozechner/pi-coding-agent@0.41.0(ws@8.19.0)(zod@4.3.5)':
+  '@mariozechner/pi-coding-agent@0.41.0(patch_hash=58af7c712ebe270527c2ad9d3351fac39d6cd4b81cc475a258d87840b446b90e)(ws@8.19.0)(zod@4.3.5)':
     dependencies:
       '@mariozechner/clipboard': 0.3.0
       '@mariozechner/pi-agent-core': 0.41.0(patch_hash=01312ceb1f6be7e42822c24c9a7a4f7db56b24ae114a364855bd3819779d1cf4)(ws@8.19.0)(zod@4.3.5)