diff --git a/src/agents/pi-embedded-runner/run/attempt.test.ts b/src/agents/pi-embedded-runner/run/attempt.test.ts
index 33a4f9654..020372122 100644
--- a/src/agents/pi-embedded-runner/run/attempt.test.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.test.ts
@@ -560,6 +560,51 @@ describe("wrapStreamFnRepairMalformedToolCallArguments", () => {
     expect(partialToolCall.arguments).toEqual({});
     expect(streamedToolCall.arguments).toEqual({});
   });
+
+  it("clears a cached repair when later deltas make the trailing suffix invalid", async () => {
+    const partialToolCall = { type: "toolCall", name: "read", arguments: {} };
+    const streamedToolCall = { type: "toolCall", name: "read", arguments: {} };
+    const partialMessage = { role: "assistant", content: [partialToolCall] };
+    const baseFn = vi.fn(() =>
+      createFakeStream({
+        events: [
+          {
+            type: "toolcall_delta",
+            contentIndex: 0,
+            delta: '{"path":"/tmp/report.txt"}',
+            partial: partialMessage,
+          },
+          {
+            type: "toolcall_delta",
+            contentIndex: 0,
+            delta: "x",
+            partial: partialMessage,
+          },
+          {
+            type: "toolcall_delta",
+            contentIndex: 0,
+            delta: "yzq",
+            partial: partialMessage,
+          },
+          {
+            type: "toolcall_end",
+            contentIndex: 0,
+            toolCall: streamedToolCall,
+            partial: partialMessage,
+          },
+        ],
+        resultMessage: { role: "assistant", content: [partialToolCall] },
+      }),
+    );
+
+    const stream = await invokeWrappedStream(baseFn);
+    for await (const _item of stream) {
+      // drain
+    }
+
+    expect(partialToolCall.arguments).toEqual({});
+    expect(streamedToolCall.arguments).toEqual({});
+  });
 });
 
 describe("isOllamaCompatProvider", () => {
diff --git a/src/agents/pi-embedded-runner/run/attempt.ts b/src/agents/pi-embedded-runner/run/attempt.ts
index 790323b82..2f77b46af 100644
--- a/src/agents/pi-embedded-runner/run/attempt.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.ts
@@ -557,6 +557,25 @@ function repairToolCallArgumentsInMessage(
   typedBlock.arguments = repairedArgs;
 }
 
+function clearToolCallArgumentsInMessage(message: unknown, contentIndex: number): void {
+  if (!message || typeof message !== "object") {
+    return;
+  }
+  const content = (message as { content?: unknown }).content;
+  if (!Array.isArray(content)) {
+    return;
+  }
+  const block = content[contentIndex];
+  if (!block || typeof block !== "object") {
+    return;
+  }
+  const typedBlock = block as { type?: unknown; arguments?: unknown };
+  if (!isToolCallBlockType(typedBlock.type)) {
+    return;
+  }
+  typedBlock.arguments = {};
+}
+
 function repairMalformedToolCallArgumentsInMessage(
   message: unknown,
   repairedArgsByIndex: Map<number, Record<string, unknown>>,
@@ -637,6 +656,10 @@ function wrapStreamRepairMalformedToolCallArguments(
                       `repairing kimi-coding tool call arguments after ${repair.trailingSuffix.length} trailing chars`,
                     );
                   }
+                } else {
+                  repairedArgsByIndex.delete(event.contentIndex);
+                  clearToolCallArgumentsInMessage(event.partial, event.contentIndex);
+                  clearToolCallArgumentsInMessage(event.message, event.contentIndex);
                 }
               }
             }