Fix false-positive duplicate userMessage warning in validateFixtures

The dedup key now includes turnIndex, hasToolResult, and sequenceIndex
alongside userMessage, so fixtures sharing a userMessage but differing
on those fields no longer trigger a spurious shadowing warning.

Author: jpr5

src/__tests__/fixture-loader.test.ts

@@ -813,6 +813,53 @@ describe("validateFixtures", () => {
     );
   });
 
+  it("no warning: same userMessage but different turnIndex", () => {
+    const fixtures = [
+      makeFixture({ match: { userMessage: "hello", turnIndex: 0 } }),
+      makeFixture({ match: { userMessage: "hello", turnIndex: 1 } }),
+    ];
+    const results = validateFixtures(fixtures);
+    const duplicateWarnings = results.filter(
+      (r) => r.severity === "warning" && r.message.includes("duplicate"),
+    );
+    expect(duplicateWarnings).toHaveLength(0);
+  });
+
+  it("no warning: same userMessage but different hasToolResult", () => {
+    const fixtures = [
+      makeFixture({ match: { userMessage: "hello", hasToolResult: false } }),
+      makeFixture({ match: { userMessage: "hello", hasToolResult: true } }),
+    ];
+    const results = validateFixtures(fixtures);
+    const duplicateWarnings = results.filter(
+      (r) => r.severity === "warning" && r.message.includes("duplicate"),
+    );
+    expect(duplicateWarnings).toHaveLength(0);
+  });
+
+  it("no warning: same userMessage but different sequenceIndex", () => {
+    const fixtures = [
+      makeFixture({ match: { userMessage: "hello", sequenceIndex: 0 } }),
+      makeFixture({ match: { userMessage: "hello", sequenceIndex: 1 } }),
+    ];
+    const results = validateFixtures(fixtures);
+    const duplicateWarnings = results.filter(
+      (r) => r.severity === "warning" && r.message.includes("duplicate"),
+    );
+    expect(duplicateWarnings).toHaveLength(0);
+  });
+
+  it("warning: same userMessage with identical turnIndex/hasToolResult/sequenceIndex", () => {
+    const fixtures = [
+      makeFixture({ match: { userMessage: "hello", turnIndex: 1, hasToolResult: true } }),
+      makeFixture({ match: { userMessage: "hello", turnIndex: 1, hasToolResult: true } }),
+    ];
+    const results = validateFixtures(fixtures);
+    expect(results.some((r) => r.severity === "warning" && r.message.includes("duplicate"))).toBe(
+      true,
+    );
+  });
+
   it("warning: catch-all not in last position", () => {
     const fixtures = [makeFixture({ match: {} }), makeFixture({ match: { userMessage: "hello" } })];
     const results = validateFixtures(fixtures);

src/fixture-loader.ts

@@ -533,18 +533,21 @@ export function validateFixtures(fixtures: Fixture[]): ValidationResult[] {
 
     // --- Warning checks ---
 
-    // Duplicate userMessage shadowing
+    // Duplicate userMessage shadowing — include turnIndex, hasToolResult, and
+    // sequenceIndex in the dedup key so that fixtures which share a userMessage
+    // but differ on those fields are NOT considered duplicates.
     const um = f.match.userMessage;
     if (typeof um === "string" && um) {
-      const prev = seenUserMessages.get(um);
+      const dedupKey = `${um}|${f.match.turnIndex}|${f.match.hasToolResult}|${f.match.sequenceIndex}`;
+      const prev = seenUserMessages.get(dedupKey);
       if (prev !== undefined) {
         results.push({
           severity: "warning",
           fixtureIndex: i,
           message: `duplicate userMessage '${um}' — shadows fixture ${prev}`,
         });
       } else {
-        seenUserMessages.set(um, i);
+        seenUserMessages.set(dedupKey, i);
       }
     }