fix(#766): claw diff extra args now classified as unexpected_extra_args with hint; track #767 session subcommand gap

ROADMAP.md

@@ -7697,3 +7697,7 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 764. **`config_parse_error` returned `hint: null` despite #763 adding the classifier** — dogfooded 2026-05-27 on `c86dc73d`. #763 fixed `error_kind` classification but `hint` remained `null` because `ConfigError::Parse` Display impl emitted only the bare serde_json error string (no `\n` delimiter). `split_error_hint()` found nothing to split. Fix: updated `Display for ConfigError::Parse` in `runtime/src/config.rs` to append `\nFix: open the file shown above and correct the JSON syntax, then retry.`. Integration test `config_parse_error_has_typed_error_kind_and_hint_764` added to `output_format_contract.rs` asserting non-zero exit + `error_kind:config_parse_error` + non-empty hint. 31 contract tests pass. Source: Jobdori follow-up probe on `c86dc73d`, 2026-05-27.
 
 765. **`claw login`/`claw logout` returned `error_kind:"unknown"` + `hint:null`** — dogfooded 2026-05-27 on `4ea255ca` (gaebal-gajae pinpoint against `88ce1810`, revised ID after #763/#764 landed). `removed_auth_surface_error()` emitted single-line string with no `\n` delimiter; `split_error_hint()` couldn't extract hint, and no `removed_subcommand` classifier arm existed. Fix: (1) `removed_auth_surface_error()` now emits two-line format (`has been removed.\nSet ANTHROPIC_API_KEY or ANTHROPIC_AUTH_TOKEN instead.`); (2) `classify_error_kind()` arm added matching `has been removed.`; (3) unit test assertions and integration test `login_logout_removed_subcommands_have_error_kind_and_hint_765` added verifying both `error_kind:removed_subcommand` and non-null hint mentioning the env var migration. 32 CLI contract tests pass. [SCOPE: claw-code] Source: Gaebal-gajae + Jobdori probe on `4ea255ca`, 2026-05-27.
+
+766. **`claw diff <extra>` returned `error_kind:"unknown"` + `hint:null`** — dogfooded 2026-05-27 on `d29a8e21`. `claw diff --bogus --output-format json` emitted bare error string `"unexpected extra arguments after \`claw diff\`: --bogus"` with no `\n` delimiter and no classifier arm. Fix: (1) added `\nUsage: claw diff` to the error format string; (2) added `unexpected_extra_args` classifier arm matching `starts_with("unexpected extra arguments")`; (3) unit test assertion + integration test `diff_extra_args_have_typed_error_kind_and_hint_766` added. 33 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori probe on `d29a8e21`, 2026-05-27.
+
+767. **`claw session bogus --output-format json` ignores JSON flag and falls through to credential check** — dogfooded 2026-05-27 on `d29a8e21`. `claw --output-format json session bogus` dispatches to the full interactive REPL runtime instead of rejecting `bogus` as an unknown session subcommand. Output is `error_kind:"missing_credentials"` rather than `error_kind:"unknown_session_subcommand"`. Root cause: `session` arg parser has no unknown-subcommand guard before dispatch; `bogus` is silently accepted as a session ID / switch target and reaches the credential-check gate. Fix needed: validate known session subcommands (`list`, `exists`, `switch`, `fork`, `delete`) before dispatch, return structured `unknown_session_subcommand` error for unrecognized tokens. [SCOPE: claw-code] Source: Jobdori probe on `d29a8e21`, 2026-05-27.

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

@@ -328,6 +328,9 @@ fn classify_error_kind(message: &str) -> &'static str {
     } else if message.contains("has been removed.") {
         // #765: removed subcommands (login, logout) — hint contains migration guidance
         "removed_subcommand"
+    } else if message.starts_with("unexpected extra arguments") {
+        // #766: extra positionals after commands that take no arguments (e.g. claw diff)
+        "unexpected_extra_args"
     } else if message.starts_with("unknown_option:") {
         "unknown_option"
     } else if message.contains("is a slash command")
@@ -1145,7 +1148,7 @@ fn parse_args(args: &[String]) -> Result<CliAction, String> {
         "diff" => {
             if rest.len() > 1 {
                 return Err(format!(
-                    "unexpected extra arguments after `claw diff`: {}",
+                    "unexpected extra arguments after `claw diff`: {}\nUsage: claw diff",
                     rest[1..].join(" ")
                 ));
             }
@@ -12941,6 +12944,13 @@ mod tests {
             ),
             "removed_subcommand"
         );
+        // #766: unexpected extra arguments must classify as unexpected_extra_args
+        assert_eq!(
+            classify_error_kind(
+                "unexpected extra arguments after `claw diff`: --bogus\nUsage: claw diff"
+            ),
+            "unexpected_extra_args"
+        );
         assert_eq!(
             classify_error_kind(
                 "`claw logout` has been removed.\nSet ANTHROPIC_API_KEY or ANTHROPIC_AUTH_TOKEN instead."

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

@@ -1903,3 +1903,40 @@ fn login_logout_removed_subcommands_have_error_kind_and_hint_765() {
         );
     }
 }
+
+#[test]
+fn diff_extra_args_have_typed_error_kind_and_hint_766() {
+    // #766: `claw diff --bogus` returned error_kind:"unknown" + hint:null.
+    // `diff` takes no arguments; extra args were unclassified with no remediation.
+    let root = unique_temp_dir("diff-extra-args-766");
+    fs::create_dir_all(&root).expect("temp dir should exist");
+    // Need a git repo for diff to parse past arg validation
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(&root, &["--output-format", "json", "diff", "--bogus"], &[]);
+    assert!(
+        !output.status.success(),
+        "claw diff --bogus should exit non-zero"
+    );
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    let json_line = stderr
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .expect("stderr should contain a JSON error envelope");
+    let parsed: serde_json::Value =
+        serde_json::from_str(json_line).expect("error envelope should be valid JSON");
+
+    assert_eq!(
+        parsed["error_kind"], "unexpected_extra_args",
+        "claw diff --bogus must return error_kind:unexpected_extra_args (#766)"
+    );
+    let hint = parsed["hint"].as_str().unwrap_or("");
+    assert!(
+        !hint.is_empty(),
+        "claw diff --bogus must return non-null hint (#766), got: {hint:?}"
+    );
+}