fix(merge): refuse unresolved conflicts in merge's own name

src/commands/merge.rs

@@ -167,10 +167,16 @@ pub fn handle_merge(opts: MergeOptions<'_>) -> anyhow::Result<()> {
     let env = CommandEnv::for_action(config)?;
     let repo = &env.repo;
     let config = &env.config;
+    // Cache current worktree for multiple queries
+    let current_wt = repo.current_worktree();
     // Ahead of the branch check: mid-rebase and mid-bisect both detach HEAD, so
     // an unguarded merge blames the detached HEAD and points at `git switch`,
     // which abandons the operation instead of finishing it.
     repo.ensure_no_operation_in_progress("merge")?;
+    // Merge stages on the user's behalf through the commit and squash steps, so
+    // it takes their index gate here: in its own name, and ahead of the
+    // approval prompts rather than partway through the flow.
+    current_wt.ensure_no_unmerged_paths("merge")?;
     // Merge requires being on a branch (can't merge from detached HEAD)
     let current_branch = env.require_branch("merge")?.to_string();
 
@@ -187,9 +193,6 @@ pub fn handle_merge(opts: MergeOptions<'_>) -> anyhow::Result<()> {
     } = flags.resolve(&resolved.merge);
     let stage_mode = stage.unwrap_or(resolved.commit.stage());
 
-    // Cache current worktree for multiple queries
-    let current_wt = repo.current_worktree();
-
     // Validate --no-commit: requires clean working tree
     if !commit {
         let dirty_files = current_wt.dirty_files()?;

src/git/repository/working_tree.rs

@@ -512,12 +512,15 @@ impl<'a> WorkingTree<'a> {
     /// Fail when the index still holds unresolved conflicts.
     ///
     /// A precondition for the commands that stage on the user's behalf
-    /// (`wt step commit`, `wt step squash`). `git add -A` collapses an
-    /// unmerged path's three stages into one entry, so it resolves the
+    /// (`wt step commit`, `wt step squash`, `wt merge`). `git add -A` collapses
+    /// an unmerged path's three stages into one entry, so it resolves the
     /// conflict as far as the index is concerned while the file on disk still
     /// holds `<<<<<<<` markers — and it takes git's own refusal to commit
     /// with it. Asking before staging is what keeps the markers out of a
     /// commit.
+    ///
+    /// `action` names the command the user typed, so each entry point gates in
+    /// its own name rather than in the name of a step it delegates to.
     pub fn ensure_no_unmerged_paths(&self, action: &str) -> anyhow::Result<()> {
         let files = self.unmerged_paths()?;
         if files.is_empty() {

tests/integration_tests/merge.rs

@@ -3589,6 +3589,25 @@ fn test_step_commit_refuses_unmerged_paths(mut repo: TestRepo) {
     );
 }
 
+/// `wt merge` stages through the commit and squash steps, so it needs the same
+/// index gate — under its own name. Delegating the refusal to the step would
+/// answer `wt merge` with "Cannot squash".
+#[rstest]
+fn test_merge_refuses_unmerged_paths(mut repo: TestRepo) {
+    let feature_wt = stop_feature_on_conflicted_stash_pop(&mut repo);
+    let head_before = repo.head_sha_in(&feature_wt);
+
+    assert_cmd_snapshot!(
+        "merge_refuses_unmerged_paths",
+        make_snapshot_cmd(&repo, "merge", &["--yes"], Some(&feature_wt))
+    );
+    assert_eq!(
+        repo.head_sha_in(&feature_wt),
+        head_before,
+        "the refusal must leave HEAD alone; merging here would commit the conflict markers"
+    );
+}
+
 // =============================================================================
 // JSON output tests
 // =============================================================================

tests/snapshots/integration__integration_tests__merge__merge_refuses_unmerged_paths.snap

@@ -0,0 +1,52 @@
+---
+source: tests/integration_tests/merge.rs
+info:
+  program: wt
+  args:
+    - merge
+    - "--yes"
+  env:
+    APPDATA: "[TEST_CONFIG_HOME]"
+    CLAUDE_CONFIG_DIR: "[TEST_CLAUDE_CONFIG]"
+    CLICOLOR_FORCE: "1"
+    COLUMNS: "500"
+    GIT_AUTHOR_DATE: "2025-01-01T00:00:00Z"
+    GIT_COMMITTER_DATE: "2025-01-01T00:00:00Z"
+    GIT_CONFIG_GLOBAL: "[TEST_GIT_CONFIG]"
+    GIT_CONFIG_SYSTEM: /dev/null
+    GIT_TERMINAL_PROMPT: "0"
+    HOME: "[TEST_HOME]"
+    LANG: C
+    LC_ALL: C
+    LLVM_PROFILE_FILE: "[LLVM_PROFILE_FILE]"
+    MOCK_CONFIG_DIR: "[MOCK_CONFIG_DIR]"
+    OPENCODE_CONFIG_DIR: "[TEST_OPENCODE_CONFIG]"
+    PATH: "[PATH]"
+    TERM: alacritty
+    USERPROFILE: "[TEST_HOME]"
+    WORKTRUNK_APPROVALS_PATH: "[TEST_APPROVALS]"
+    WORKTRUNK_CONFIG_PATH: "[TEST_CONFIG]"
+    WORKTRUNK_SYSTEM_CONFIG_PATH: "[TEST_SYSTEM_CONFIG]"
+    WORKTRUNK_TEST_BASH_INSTALLED: "0"
+    WORKTRUNK_TEST_CLAUDE_INSTALLED: "0"
+    WORKTRUNK_TEST_CODEX_INSTALLED: "0"
+    WORKTRUNK_TEST_DELAYED_STREAM_MS: "-1"
+    WORKTRUNK_TEST_EPOCH: "1735776000"
+    WORKTRUNK_TEST_FISH_INSTALLED: "0"
+    WORKTRUNK_TEST_GEMINI_INSTALLED: "0"
+    WORKTRUNK_TEST_NUSHELL_ENV: "0"
+    WORKTRUNK_TEST_OPENCODE_INSTALLED: "0"
+    WORKTRUNK_TEST_PARENT_SHELL: ""
+    WORKTRUNK_TEST_POWERSHELL_ENV: "0"
+    WORKTRUNK_TEST_POWERSHELL_INSTALLED: "0"
+    WORKTRUNK_TEST_SKIP_URL_HEALTH_CHECK: "1"
+    WORKTRUNK_TEST_ZSH_INSTALLED: "0"
+    XDG_CONFIG_HOME: "[TEST_CONFIG_HOME]"
+---
+success: false
+exit_code: 1
+----- stdout -----
+
+----- stderr -----
+✗ Cannot merge: 1 path with unresolved conflicts
+  conflict.txt