fix+test(#753): claw -p (no arg) parity with #750: error_kind:missing_prompt with non-null hint

ROADMAP.md

@@ -7671,3 +7671,5 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 751. **ROADMAP #750 has no regression test: `claw prompt --output-format json` no-arg `error_kind` and `hint` could silently regress** — confirmed by gaebal-gajae on `ac925ed4`. Fix: add `prompt_no_arg_json_error_kind_750` test asserting nonzero exit, `error_kind:"missing_prompt"`, non-empty `hint` mentioning `claw prompt` or `echo`. Source: gaebal-gajae dogfood on `ac925ed4`, 2026-05-26.
 
 752. **`claw <subcommand> --output-format json <bogus-arg>` returned `hint: null` for all `cli_parse` errors when an unrecognized positional arg was supplied** — dogfooded 2026-05-26 on `ddc71b56`. Generic `unrecognized argument` format string had no `\n` so `split_error_hint` emitted null hint (only the `--json` special-case added a hint). Fix: add else-branch appending `\nRun `claw <verb> --help` for usage.` to the generic arm. Affected surfaces: `sandbox`, `doctor`, `version`, and any other subcommand routing through the same unrecognized-arg path. Source: Jobdori dogfood on `ddc71b56`, 2026-05-26.
+
+753. **`claw --output-format json -p` (no prompt arg) returned `error_kind:"unknown"` and `hint: null`** — parity gap with #750/#751 which fixed the explicit `prompt` verb. Identified by gaebal-gajae on `ddc71b56`. Fix: same `missing_prompt:` prefix + newline usage hint as #750. Regression guard: `short_p_flag_no_arg_json_error_kind_753` asserting nonzero exit, `error_kind:"missing_prompt"`, non-empty hint mentioning `claw -p` or `claw prompt`. Source: gaebal-gajae dogfood on `ddc71b56`, 2026-05-26.

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

@@ -861,7 +861,8 @@ fn parse_args(args: &[String]) -> Result<CliAction, String> {
                 // Claw Code compat: -p "prompt" = one-shot prompt
                 let prompt = args[index + 1..].join(" ");
                 if prompt.trim().is_empty() {
-                    return Err("-p requires a prompt string".to_string());
+                    // #753: same missing_prompt shape as claw prompt (no arg) fix in #750
+                    return Err("missing_prompt: -p requires a prompt string.\nUsage: claw -p <text>  or  claw prompt <text>".to_string());
                 }
                 return Ok(CliAction::Prompt {
                     prompt,

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

@@ -1504,6 +1504,53 @@ fn prompt_no_arg_json_error_kind_750() {
     );
 }
 
+#[test]
+fn short_p_flag_no_arg_json_error_kind_753() {
+    // #753: `claw --output-format json -p` (no prompt) must emit error_kind:"missing_prompt"
+    // and non-empty hint. Before #753 it returned error_kind:"unknown" + hint:null.
+    // Parity with #750 which fixed the explicit `prompt` verb.
+    use std::process::Command;
+    let root = unique_temp_dir("short-p-no-arg");
+    fs::create_dir_all(&root).expect("temp dir");
+    let bin = env!("CARGO_BIN_EXE_claw");
+
+    let output = Command::new(bin)
+        .current_dir(&root)
+        .args(["--output-format", "json", "-p"])
+        .output()
+        .expect("claw -p should run");
+    assert!(
+        !output.status.success(),
+        "claw -p with no arg must exit non-zero"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let raw = if stdout.trim().starts_with('{') {
+        stdout.trim().to_string()
+    } else {
+        String::from_utf8_lossy(&output.stderr)
+            .lines()
+            .filter(|l| l.starts_with('{'))
+            .collect::<Vec<_>>()
+            .join("")
+    };
+    let parsed: serde_json::Value = serde_json::from_str(&raw).unwrap_or_else(|_| {
+        panic!("claw -p (no arg) --output-format json must emit valid JSON; got: {raw}")
+    });
+    assert_eq!(
+        parsed["error_kind"], "missing_prompt",
+        "claw -p no-arg must have error_kind:missing_prompt (#753); got: {parsed}"
+    );
+    let hint = parsed["hint"].as_str().unwrap_or("");
+    assert!(
+        !hint.is_empty(),
+        "claw -p no-arg hint must be non-empty (#753)"
+    );
+    assert!(
+        hint.contains("claw -p") || hint.contains("claw prompt"),
+        "hint should mention 'claw -p' or 'claw prompt': {hint}"
+    );
+}
+
 #[test]
 fn bare_slash_command_hint_745() {
     // #747/#745: claw <slash-cmd> --output-format json must return non-null hint.