fix(agents): sanitize tool names in system context and deduplicate on merge

mitchmcalister · mitchmcalister · commit c39c5cc97332 · 2026-03-30T22:49:52.000Z
diff --git a/src/agents/command/attempt-execution.test.ts b/src/agents/command/attempt-execution.test.ts
@@ -266,4 +266,12 @@ describe("buildPartialExecutionSystemContext", () => {
     });
     expect(ctx).toBeUndefined();
   });
+
+  it("returns undefined when all tool names sanitize to empty", () => {
+    const ctx = buildPartialExecutionSystemContext({
+      toolNames: ["!!!", "<<<>>>"],
+      didSendViaMessagingTool: false,
+    });
+    expect(ctx).toBeUndefined();
+  });
 });
diff --git a/src/agents/command/attempt-execution.ts b/src/agents/command/attempt-execution.ts
@@ -343,10 +343,11 @@ export function resolveRetryImages(params: {
 export function buildPartialExecutionSystemContext(
   partialExecution: PartialExecution,
 ): string | undefined {
-  if (partialExecution.toolNames.length === 0) {
+  const safeNames = FailoverError.sanitizeToolNames(partialExecution.toolNames);
+  if (safeNames.length === 0) {
     return undefined;
   }
-  const toolList = partialExecution.toolNames.join(", ");
+  const toolList = safeNames.join(", ");
   const messagingWarning = partialExecution.didSendViaMessagingTool
     ? " At least one of these tools sent a user-visible message — do not resend it."
     : "";
diff --git a/src/agents/model-fallback.test.ts b/src/agents/model-fallback.test.ts
@@ -1631,14 +1631,15 @@ describe("runWithModelFallback", () => {
           throw new FailoverError("rate_limit", {
             reason: "rate_limit",
             partialExecution: {
-              toolNames: ["web_search"],
+              toolNames: ["bash", "web_search"],
               didSendViaMessagingTool: true,
             },
           });
         }
         return "ok";
       },
     });
+    // bash appears in both attempts; Set dedup should keep it only once
     expect(captured[2]?.previousPartialExecution).toEqual({
       toolNames: ["bash", "web_search"],
       didSendViaMessagingTool: true,
diff --git a/src/agents/model-fallback.ts b/src/agents/model-fallback.ts
@@ -819,8 +819,10 @@ export async function runWithModelFallback<T>(params: {
         mergedPartialExecution = mergedPartialExecution
           ? {
               toolNames: [
-                ...mergedPartialExecution.toolNames,
-                ...described.partialExecution.toolNames,
+                ...new Set([
+                  ...mergedPartialExecution.toolNames,
+                  ...described.partialExecution.toolNames,
+                ]),
               ],
               didSendViaMessagingTool:
                 mergedPartialExecution.didSendViaMessagingTool ||
