fix(#801): diff non-git-dir error envelope now includes error_kind, hint, and message fields

ROADMAP.md

@@ -7766,3 +7766,5 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 799. **`claw --output-format json ""` and `claw "   "` returned `empty_prompt` + `hint:null`** — dogfooded 2026-05-27 on `bff37000`. The empty-prompt guard at the fallthrough path emitted `"empty prompt: provide a subcommand..."` with no `\n` delimiter. Fix: added `\n` + usage hint. Integration test `empty_prompt_has_non_null_hint_798`. Committed as `efb1542a`. 61 CLI contract tests pass. [SCOPE: claw-code]
 
 800. **`classify_error_kind` unit test coverage gap: `invalid_history_count` and `unknown_option` arms had zero assertions** — found 2026-05-27 on `efb1542a`. Audit of 39 distinct classifier return values vs 37 unit test assertions revealed 2 untested arms. Fix: added 3 `assert_eq!` covering both arms (invalid_history_count prefix + contains paths, unknown_option prefix). Committed as `6ee67d6c`. All 39 return values now have unit test coverage. [SCOPE: claw-code]
+
+801. **`claw --output-format json diff` in a non-git directory was missing `error_kind`, `hint`, and `message` fields** — dogfooded 2026-05-27 on `1201dc60`. The diff handler's no-git-repo JSON branch constructed a custom object with only `status:"error"` + `result:"no_git_repo"` + `detail`, violating the error envelope contract that every error has `error_kind` + `hint`. Fix: added `error_kind: "no_git_repo"`, `hint: "Run git init..."`, and `message` fields. Integration test `diff_non_git_dir_has_error_kind_and_hint_801`. 62 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori non-git-dir probe on `1201dc60`, 2026-05-27.

rust/crates/rusty-claude-cli/src/main.rs

@@ -8331,11 +8331,15 @@ fn render_diff_json_for(cwd: &Path) -> Result<serde_json::Value, Box<dyn std::er
         .map(|o| o.status.success())
         .unwrap_or(false);
     if !in_git_repo {
+        // #801: add error_kind, hint, message fields for envelope parity with other error paths
         return Ok(serde_json::json!({
             "kind": "diff",
             "action": "diff",
             "status": "error",
+            "error_kind": "no_git_repo",
             "result": "no_git_repo",
+            "message": format!("{} is not inside a git project", cwd.display()),
+            "hint": "Run `git init` to create a repository, or change to a directory that is inside a git project.",
             "working_directory": cwd.display().to_string(),
             "detail": format!("{} is not inside a git project", cwd.display()),
         }));

rust/crates/rusty-claude-cli/tests/output_format_contract.rs

@@ -3451,3 +3451,38 @@ fn empty_prompt_has_non_null_hint_798() {
         "hint should reference usage, got: {h:?}"
     );
 }
+
+#[test]
+fn diff_non_git_dir_has_error_kind_and_hint_801() {
+    // #801: `claw --output-format json diff` in a non-git directory returned
+    // status:"error" + result:"no_git_repo" but had no error_kind, hint, or
+    // message fields — violating the error envelope contract. Fix: added all
+    // three fields to the no_git_repo JSON branch.
+    let root = unique_temp_dir("diff-nongit-801");
+    fs::create_dir_all(&root).expect("temp dir");
+    // Intentionally NOT running git init
+
+    let output = run_claw(&root, &["--output-format", "json", "diff"], &[]);
+    // diff non-git may exit 0 (custom JSON handler) — check envelope content
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value =
+        serde_json::from_str(stdout.trim()).expect("diff non-git should emit valid JSON");
+    assert_eq!(j["status"], "error");
+    assert_eq!(j["result"], "no_git_repo");
+    assert_eq!(
+        j["error_kind"], "no_git_repo",
+        "diff non-git must have error_kind (#801), got {:?}",
+        j["error_kind"]
+    );
+    let h = j["hint"]
+        .as_str()
+        .expect("diff non-git must have non-null hint (#801)");
+    assert!(
+        h.contains("git init") || h.contains("git"),
+        "hint should suggest git init, got: {h:?}"
+    );
+    assert!(
+        j["message"].as_str().is_some(),
+        "diff non-git must have message field (#801)"
+    );
+}