fix(#746): non-TTY interactive-only error populates hint field via newline split

Author: code-yeongyu

ROADMAP.md

@@ -7657,3 +7657,5 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 744. **ROADMAP #741 has no regression test: `claw config list/show/bogus --output-format json hint` field could silently regress to null** — confirmed by gaebal-gajae on `2036f0bd`. Pattern same as #736→#737 and #740→#742: implementation fix without a pinning test. Fix: add `config_unsupported_section_json_hint_741` test iterating `[list, show, bogus, help]` and asserting `kind:config`, `status:error`, `error_kind:unsupported_config_section`, `hint` is non-empty string, `supported_sections[]` is non-empty. Source: gaebal-gajae dogfood on `2036f0bd`, 2026-05-26.
 
 745. **`claw issue --output-format json` and all other direct-CLI slash commands (pr, commit, etc.) returned `hint: null` — the `bare_slash_command_guidance` message strings had no `\n` separator between short error and remediation text, so `split_error_hint` couldn't populate the hint field** — dogfooded 2026-05-26 on `92e053a1`. The #738 fix added `\n` to the `--resume SESSION /cmd` path but missed the direct-CLI path (e.g. `claw issue`, `claw pr`). The `bare_slash_command_guidance` function formats two message variants: resume-supported and non-resume; both lacked `\n`. Fix: add `\n` before the remediation text in both format strings. Source: Jobdori dogfood on `92e053a1`, 2026-05-26.
+
+746. **`claw --output-format json` (bare, no TTY, no prompt) returned `hint: null` — the non-TTY interactive-only guard error string had no `\n` separator, so `split_error_hint` couldn't extract the remediation text into `.hint`** — dogfooded 2026-05-26 on `3c5459a3`. The single-string message `"interactive_only: claw requires an interactive terminal (stdin is not a TTY and no prompt was provided \u2014 pipe a prompt or run in a TTY)"` contained the hint inline but no newline, so callers reading `.hint` got null and had to parse the prose `error` string. Fix: split at `\n` — short error `"interactive_only: claw requires an interactive terminal."` + hint `"Stdin is not a TTY…pipe a prompt with \`echo 'task' | claw\` or run \`claw\` in an interactive terminal."`. Source: Jobdori dogfood on `3c5459a3`, 2026-05-26.

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

@@ -990,7 +990,8 @@ fn parse_args(args: &[String]) -> Result<CliAction, String> {
             // (#696: emit a typed error instead of hanging indefinitely)
             // Skip this guard in test builds (parse_args tests run in non-TTY context).
             #[cfg(not(test))]
-            return Err("interactive_only: claw requires an interactive terminal (stdin is not a TTY and no prompt was provided — pipe a prompt or run in a TTY)".into());
+            // #746: newline before remediation so split_error_hint populates hint field
+            return Err("interactive_only: claw requires an interactive terminal.\nStdin is not a TTY and no prompt was provided — pipe a prompt with `echo 'task' | claw` or run `claw` in an interactive terminal.".into());
         }
         return Ok(CliAction::Repl {
             model,