fix(api-client): allow null firstSeen/lastSeen on IssueSchema (#910)

## Summary

Sentry's API can return `null` for `firstSeen` / `lastSeen` on issues
(e.g. when events have aged out), which currently causes
`IssueSchema.parse()` in `SentryApiService.getIssue()` to throw a
`ZodError: Failed to validate keys: lastSeen` and breaks
`get_issue_details` for those issues.

Changes:
- Relax `IssueSchema.firstSeen` and `IssueSchema.lastSeen` to
`z.string().datetime().nullable()`.
- Update `formatIssueOutput` in `internal/formatting.ts` to omit the
"First Seen" / "Last Seen" lines when the values are null (previously
would have emitted `Invalid Date`). The `search-issues` formatter
already handles null via its `formatDate` helper, so no change needed
there.
- Add a regression test for nullable `firstSeen` / `lastSeen`.

Fixes MCP-SERVER-EWN (1136 events / 154 users affected since
2025-11-23).

## Review & Testing Checklist for Human

- [ ] Confirm that returning `null` for `firstSeen`/`lastSeen` in the
issue response is acceptable downstream (i.e. no other consumer of
`IssueSchema` assumes these are always strings). I grepped for
`issue.firstSeen` / `issue.lastSeen` and only found the two formatters;
please sanity-check.
- [ ] Spot-check `get_issue_details` output formatting by pointing at a
real issue where `lastSeen` is null (e.g. one of the events under
MCP-SERVER-EWN).

### Notes

The fix is intentionally minimal — same pattern already used by
`IssueTagValueSchema` for its own `firstSeen`/`lastSeen` fields.

Link to Devin session:
https://app.devin.ai/sessions/95257bed9fb74714955a56f9a5d7b606
Requested by: @dcramer

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Devin <devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: David Cramer <dcramer@gmail.com>

Author: devin-ai-integration[bot]

packages/mcp-core/src/api-client/schema.test.ts

@@ -210,6 +210,34 @@ describe("IssueSchema", () => {
       name: "Backend Team",
     });
   });
+
+  it("should handle issues with null firstSeen and lastSeen", () => {
+    // Sentry's API can return null for firstSeen/lastSeen in some cases
+    // (e.g. issues with no events). Regression test for MCP-SERVER-EWN.
+    const issue = {
+      id: "777",
+      shortId: "TEST-77",
+      title: "Test Issue",
+      firstSeen: null,
+      lastSeen: null,
+      count: 1,
+      userCount: 1,
+      permalink: "https://sentry.io/issues/777/",
+      project: {
+        id: "5",
+        name: "test",
+        slug: "test",
+        platform: "node",
+      },
+      status: "unresolved",
+      culprit: "test.js",
+      type: "error",
+    };
+
+    const result = IssueSchema.parse(issue);
+    expect(result.firstSeen).toBeNull();
+    expect(result.lastSeen).toBeNull();
+  });
 });
 
 describe("EventSchema", () => {

packages/mcp-core/src/api-client/schema.ts

@@ -306,8 +306,8 @@ export const IssueSchema = z
     id: z.union([z.string(), z.number()]),
     shortId: z.string(),
     title: z.string(),
-    firstSeen: z.string().datetime(),
-    lastSeen: z.string().datetime(),
+    firstSeen: z.string().datetime().nullable(),
+    lastSeen: z.string().datetime().nullable(),
     count: z.union([z.string(), z.number()]),
     userCount: z.union([z.string(), z.number()]),
     permalink: z.string().url(),

packages/mcp-core/src/internal/formatting.ts

@@ -1787,8 +1787,12 @@ export function formatIssueOutput({
     output += `**Culprit**: ${issue.culprit}\n`;
   }
 
-  output += `**First Seen**: ${new Date(issue.firstSeen).toISOString()}\n`;
-  output += `**Last Seen**: ${new Date(issue.lastSeen).toISOString()}\n`;
+  if (issue.firstSeen) {
+    output += `**First Seen**: ${new Date(issue.firstSeen).toISOString()}\n`;
+  }
+  if (issue.lastSeen) {
+    output += `**Last Seen**: ${new Date(issue.lastSeen).toISOString()}\n`;
+  }
   output += `**Occurrences**: ${issue.count}\n`;
   output += `**Users Impacted**: ${issue.userCount}\n`;
   output += `**Status**: ${issue.status}\n`;