diff --git a/packages/opencode/src/session/index.ts b/packages/opencode/src/session/index.ts
index f8a2ba91..90eee24e 100644
--- a/packages/opencode/src/session/index.ts
+++ b/packages/opencode/src/session/index.ts
@@ -44,6 +44,7 @@ export namespace Session {
         .object({
           additions: z.number(),
           deletions: z.number(),
+          files: z.number(),
           diffs: Snapshot.FileDiff.array().optional(),
         })
         .optional(),
diff --git a/packages/opencode/src/session/summary.ts b/packages/opencode/src/session/summary.ts
index 9795a306..f7ab0fb5 100644
--- a/packages/opencode/src/session/summary.ts
+++ b/packages/opencode/src/session/summary.ts
@@ -47,6 +47,7 @@ export namespace SessionSummary {
       draft.summary = {
         additions: diffs.reduce((sum, x) => sum + x.additions, 0),
         deletions: diffs.reduce((sum, x) => sum + x.deletions, 0),
+        files: diffs.length,
       }
     })
     await Storage.write(["session_diff", input.sessionID], diffs)