Grok Build CLI: support soft-warn hook feedback (non-blocking context inject)

[phpmac]

Summary

Please add a non-blocking soft-warn path for Grok Build CLI hooks so agents can see policy reminders without denying the tool call.

Today, PreToolUse only documents:

{"decision": "allow"}
{"decision": "deny", "reason": "..."}

• deny + reason reaches the agent (Hook denied: ...) and works for hard blocks.
• Soft signals (systemMessage, Claude-style hookSpecificOutput.additionalContext, or decision: allow + reason) do not reliably enter the model context on Grok Build, so plugins like hookify cannot implement action: warn (educate the agent, do not block the write).

This forces a bad tradeoff:

Approach	Agent sees message?	Tool continues?
decision: deny	Yes	No (stalls agent turns / freezes editing)
decision: allow + reason / additionalContext	No (current behavior)	Yes

Why it matters

Claude Code documents soft inject via hookSpecificOutput.additionalContext (and has its own issues when only systemMessage is used — see anthropics/claude-code#20747, #25987). Grok Build already loads Claude-compatible plugins and hooks/hooks.json, but without soft inject, warn-style rules cannot educate the agent on Grok.

Use case example: a warn rule for full-width Chinese punctuation / emoji in file content — we want the model to correct style without blocking every write (blocking makes the agent appear stuck).

Requested behavior

For PreToolUse (and ideally PostToolUse, which currently ignores stdout as passive):

1. When the hook returns allow (or omits deny) and includes a message field, inject that text into the next model turn context (same class of mechanism as Claude additionalContext / a system-reminder block).
2. Suggested accepted fields (any one is fine if documented):
   • reason on allow
   • systemMessage
   • hookSpecificOutput.additionalContext
3. Optionally surface soft messages in TUI hook_annotation (today annotations appear for blocked tools; soft allow often produces no agent-visible annotation).
4. Keep deny semantics unchanged for hard blocks.

Environment

• Grok Build CLI 0.2.93 (local)
• Docs: bundled 10-hooks.md (allow/deny only; PostToolUse stdout ignored)
• Plugin: hookify (Claude Code + Grok dual use)

Notes

• There is no public GitHub for the Grok Build CLI binary itself; filing here because this is the official Grok Build plugin/hooks surface and issue Plugin hooks: honor a per-hook name/description and show it in /hooks + trust UI (currently opaque 'Hook N') #71 already discusses hooks UX in /hooks.
• If CLI harness issues should go elsewhere (e.g. in-app /feedback only), please point maintainers/users to the right channel.

Thanks.