diff --git a/src/resources/extensions/gsd/git-service.ts b/src/resources/extensions/gsd/git-service.ts
index 2791dce49..edf11fdd0 100644
--- a/src/resources/extensions/gsd/git-service.ts
+++ b/src/resources/extensions/gsd/git-service.ts
@@ -28,6 +28,8 @@ export interface GitPreferences {
   commit_type?: string;
 }
 
+export const VALID_BRANCH_NAME = /^[a-zA-Z0-9_\-\/.]+$/;
+
 export interface CommitOptions {
   message: string;
   allowEmpty?: boolean;
@@ -123,9 +125,11 @@ export class GitServiceImpl {
   /**
    * Smart staging: `git add -A` excluding GSD runtime paths via pathspec.
    * Falls back to plain `git add -A` if the exclusion pathspec fails.
+   * @param extraExclusions Additional pathspec exclusions beyond RUNTIME_EXCLUSION_PATHS.
    */
-  private smartStage(): void {
-    const excludes = RUNTIME_EXCLUSION_PATHS.map(p => `':(exclude)${p}'`);
+  private smartStage(extraExclusions: readonly string[] = []): void {
+    const allExclusions = [...RUNTIME_EXCLUSION_PATHS, ...extraExclusions];
+    const excludes = allExclusions.map(p => `':(exclude)${p}'`);
     const args = ["add", "-A", "--", ".", ...excludes];
     try {
       this.git(args);
@@ -157,13 +161,14 @@ export class GitServiceImpl {
   /**
    * Auto-commit dirty working tree with a conventional chore message.
    * Returns the commit message on success, or null if nothing to commit.
+   * @param extraExclusions Additional paths to exclude from staging (e.g. [".gsd/"] for pre-switch commits).
    */
-  autoCommit(unitType: string, unitId: string): string | null {
+  autoCommit(unitType: string, unitId: string, extraExclusions: readonly string[] = []): string | null {
     // Quick check: is there anything dirty at all?
     const status = this.git(["status", "--short"], { allowFailure: true });
     if (!status) return null;
 
-    this.smartStage();
+    this.smartStage(extraExclusions);
 
     // After smart staging, check if anything was actually staged
     // (all changes might have been runtime files that got excluded)
@@ -297,8 +302,9 @@ export class GitServiceImpl {
       }
     }
 
-    // Auto-commit dirty state via smart staging before checkout
-    this.autoCommit("pre-switch", current);
+    // Auto-commit dirty state via smart staging before checkout.
+    // Exclude .gsd/ to prevent merge conflicts when both branches modify planning artifacts.
+    this.autoCommit("pre-switch", current, [".gsd/"]);
 
     this.git(["checkout", branch]);
     return created;
@@ -312,7 +318,8 @@ export class GitServiceImpl {
     const current = this.getCurrentBranch();
     if (current === mainBranch) return;
 
-    this.autoCommit("pre-switch", current);
+    // Exclude .gsd/ to prevent merge conflicts when both branches modify planning artifacts.
+    this.autoCommit("pre-switch", current, [".gsd/"]);
 
     this.git(["checkout", mainBranch]);
   }
diff --git a/src/resources/extensions/gsd/tests/git-service.test.ts b/src/resources/extensions/gsd/tests/git-service.test.ts
index d5e70d9fe..f0096084f 100644
--- a/src/resources/extensions/gsd/tests/git-service.test.ts
+++ b/src/resources/extensions/gsd/tests/git-service.test.ts
@@ -453,6 +453,49 @@ async function main(): Promise<void> {
     rmSync(repo, { recursive: true, force: true });
   }
 
+  // ─── GitServiceImpl: autoCommit with extraExclusions ───────────────────
+
+  console.log("\n=== GitServiceImpl: autoCommit with extraExclusions ===");
+
+  {
+    const repo = initTempRepo();
+    const svc = new GitServiceImpl(repo);
+
+    // Create both a .gsd/ planning file and a regular source file
+    createFile(repo, ".gsd/milestones/M001/M001-ROADMAP.md", "- [x] S01");
+    createFile(repo, "src/feature.ts", "export const y = 2;");
+
+    // Auto-commit with .gsd/ excluded (simulates pre-switch)
+    const msg = svc.autoCommit("pre-switch", "main", [".gsd/"]);
+    assertEq(msg, "chore(main): auto-commit after pre-switch", "pre-switch autoCommit with .gsd/ exclusion commits");
+
+    // Verify .gsd/ file was NOT committed
+    const show = run("git show --stat HEAD", repo);
+    assert(!show.includes("ROADMAP"), ".gsd/ files excluded from pre-switch auto-commit");
+    assert(show.includes("feature.ts"), "non-.gsd/ files included in pre-switch auto-commit");
+
+    rmSync(repo, { recursive: true, force: true });
+  }
+
+  // ─── GitServiceImpl: autoCommit extraExclusions — only .gsd/ dirty ────
+
+  console.log("\n=== GitServiceImpl: autoCommit extraExclusions — only .gsd/ dirty ===");
+
+  {
+    const repo = initTempRepo();
+    const svc = new GitServiceImpl(repo);
+
+    // Create only .gsd/ planning files
+    createFile(repo, ".gsd/milestones/M001/M001-ROADMAP.md", "- [x] S01");
+    createFile(repo, ".gsd/STATE.md", "state content");
+
+    // Auto-commit with .gsd/ excluded — nothing else to commit
+    const result = svc.autoCommit("pre-switch", "main", [".gsd/"]);
+    assertEq(result, null, "autoCommit returns null when only .gsd/ files are dirty and excluded");
+
+    rmSync(repo, { recursive: true, force: true });
+  }
+
   // ─── GitServiceImpl: commit returns null when nothing staged ───────────
 
   console.log("\n=== GitServiceImpl: commit empty ===");