diff --git a/src/cli/commands/repo_init.ts b/src/cli/commands/repo_init.ts
index 263a69d..10ba3c2 100644
--- a/src/cli/commands/repo_init.ts
+++ b/src/cli/commands/repo_init.ts
@@ -105,6 +105,7 @@ export const repoUpgradeCommand = new Command()
       upgradedAt: result.upgradedAt,
       skillsUpdated: result.skillsUpdated,
       settingsUpdated: result.settingsUpdated,
+      gitignoreCreated: result.gitignoreCreated,
       tool: result.tool,
     };
 
diff --git a/src/domain/repo/repo_service.ts b/src/domain/repo/repo_service.ts
index e72afea..5682e1a 100644
--- a/src/domain/repo/repo_service.ts
+++ b/src/domain/repo/repo_service.ts
@@ -83,6 +83,7 @@ export interface RepoUpgradeResult {
   upgradedAt: string;
   skillsUpdated: string[];
   settingsUpdated: boolean;
+  gitignoreCreated: boolean;
   tool: AiTool;
 }
 
@@ -231,6 +232,12 @@ export class RepoService {
       settingsUpdated = await this.updateClaudeSettings(repoPath);
     }
 
+    // Create .gitignore if it doesn't exist
+    const gitignoreCreated = await this.createGitignoreIfNotExists(
+      repoPath,
+      tool,
+    );
+
     // createUpgradeMarker always sets upgradedAt, but TypeScript doesn't know this
     if (!updatedMarker.upgradedAt) {
       throw new Error(
@@ -245,6 +252,7 @@ export class RepoService {
       upgradedAt: updatedMarker.upgradedAt,
       skillsUpdated,
       settingsUpdated,
+      gitignoreCreated,
       tool,
     };
   }
diff --git a/src/domain/repo/repo_service_test.ts b/src/domain/repo/repo_service_test.ts
index 7a61339..7698236 100644
--- a/src/domain/repo/repo_service_test.ts
+++ b/src/domain/repo/repo_service_test.ts
@@ -722,6 +722,45 @@ Deno.test("RepoService.upgrade skips settings for non-claude tools", async () =>
   });
 });
 
+Deno.test("RepoService.upgrade creates .gitignore if missing", async () => {
+  await withTempDir(async (tempDir) => {
+    const service = new RepoService("0.1.0");
+    const repoPath = RepoPath.create(tempDir);
+
+    // Init (creates .gitignore), then delete it
+    await service.init(repoPath);
+    const gitignorePath = join(tempDir, ".gitignore");
+    await Deno.remove(gitignorePath);
+
+    // Upgrade should recreate .gitignore
+    const upgradeService = new RepoService("0.2.0");
+    const result = await upgradeService.upgrade(repoPath);
+
+    assertEquals(result.gitignoreCreated, true);
+
+    const content = await Deno.readTextFile(gitignorePath);
+    assertStringIncludes(content, ".swamp/telemetry/");
+    assertStringIncludes(content, ".swamp/secrets/keyfile");
+    assertStringIncludes(content, ".claude/");
+  });
+});
+
+Deno.test("RepoService.upgrade does not overwrite existing .gitignore", async () => {
+  await withTempDir(async (tempDir) => {
+    const service = new RepoService("0.1.0");
+    const repoPath = RepoPath.create(tempDir);
+
+    // Init creates .gitignore
+    await service.init(repoPath);
+
+    // Upgrade should leave .gitignore unchanged
+    const upgradeService = new RepoService("0.2.0");
+    const result = await upgradeService.upgrade(repoPath);
+
+    assertEquals(result.gitignoreCreated, false);
+  });
+});
+
 Deno.test("RepoService.init cursor instructions have MDC frontmatter", async () => {
   await withTempDir(async (tempDir) => {
     const service = new RepoService("0.1.0");
diff --git a/src/presentation/output/repo_output.ts b/src/presentation/output/repo_output.ts
index eff67e0..c2f0879 100644
--- a/src/presentation/output/repo_output.ts
+++ b/src/presentation/output/repo_output.ts
@@ -46,6 +46,7 @@ export interface RepoUpgradeData {
   upgradedAt: string;
   skillsUpdated: string[];
   settingsUpdated: boolean;
+  gitignoreCreated: boolean;
   tool: string;
 }