fix(cron): SSH dispatch validation + failure detection + broken import

1. New cron/ssh_dispatch.py — validated SSH dispatch:
   - SSHEnvironment probes remote hermes binary via test -x
   - DispatchResult returns success=False on broken paths
   - dispatch_to_hosts / format_dispatch_report for multi-host ops

2. cron/scheduler.py — 7 new failure phrases:
   - no such file or directory, command not found
   - hermes binary not found, hermes not found
   - ssh: connect to host, connection timed out, host key verification failed

3. cron/__init__.py — fix broken import (#541):
   - Removed stale ModelContextError and CRON_MIN_CONTEXT_TOKENS
   - Was blocking all from cron import ... calls

Closes #561 (Closes #350, #541)

cron/__init__.py

@@ -26,7 +26,7 @@ from cron.jobs import (
     trigger_job,
     JOBS_FILE,
 )
-from cron.scheduler import tick, ModelContextError, CRON_MIN_CONTEXT_TOKENS
+from cron.scheduler import tick
 
 __all__ = [
     "create_job",
@@ -39,6 +39,4 @@ __all__ = [
     "trigger_job",
     "tick",
     "JOBS_FILE",
-    "ModelContextError",
-    "CRON_MIN_CONTEXT_TOKENS",
 ]

cron/scheduler.py

@@ -186,7 +186,14 @@ _SCRIPT_FAILURE_PHRASES = (
     "unable to execute",
     "permission denied",
     "no such file",
+    "no such file or directory",
+    "command not found",
     "traceback",
+    "hermes binary not found",
+    "hermes not found",
+    "ssh: connect to host",
+    "connection timed out",
+    "host key verification failed",
 )
 
 

cron/ssh_dispatch.py

@@ -0,0 +1,243 @@
+"""SSH Dispatch — validated remote hermes execution for cron jobs.
+
+Provides SSH-based dispatch to VPS agents with:
+- Pre-flight validation (hermes binary exists and is executable)
+- Structured DispatchResult with success/failure reporting
+- Multi-host dispatch with formatted reports
+
+Usage:
+    from cron.ssh_dispatch import dispatch_to_host, dispatch_to_hosts, format_dispatch_report
+
+    result = dispatch_to_host("ezra", "143.198.27.163", "Check the beacon repo for open issues")
+    if not result.success:
+        print(result.error)
+
+    results = dispatch_to_hosts(["ezra", "bezalel"], "Run fleet health check")
+    print(format_dispatch_report(results))
+
+Ref: #350, #541, #561
+"""
+
+from __future__ import annotations
+
+import logging
+import subprocess
+from dataclasses import dataclass, field
+from typing import Dict, List, Optional
+
+logger = logging.getLogger(__name__)
+
+# Known VPS hosts (can be overridden via env or config)
+DEFAULT_HOSTS: Dict[str, str] = {
+    "ezra": "143.198.27.163",
+    "bezalel": "159.203.146.185",
+}
+
+# SSH options for non-interactive, fast-fail connections
+_SSH_OPTS = [
+    "-o", "ConnectTimeout=10",
+    "-o", "StrictHostKeyChecking=accept-new",
+    "-o", "BatchMode=yes",
+    "-o", "LogLevel=ERROR",
+]
+
+# Paths to check for hermes binary on remote
+_HERMES_CHECK_PATHS = [
+    "~/.local/bin/hermes",
+    "/usr/local/bin/hermes",
+    "~/.hermes/bin/hermes",
+]
+
+
+@dataclass
+class DispatchResult:
+    """Result of an SSH dispatch attempt."""
+    host: str
+    address: str
+    success: bool
+    output: str = ""
+    error: str = ""
+    hermes_found: bool = False
+    hermes_path: str = ""
+    exit_code: int = -1
+
+    @property
+    def summary(self) -> str:
+        if self.success:
+            return f"[OK] {self.host} ({self.address})"
+        return f"[FAIL] {self.host} ({self.address}): {self.error}"
+
+
+def probe_hermes(host: str, address: str) -> tuple[bool, str]:
+    """Check if hermes binary exists and is executable on remote host.
+
+    Returns (found, path).
+    """
+    check_cmds = " || ".join(f"test -x {p} && echo {p}" for p in _HERMES_CHECK_PATHS)
+    remote_cmd = f"bash -c '{check_cmds} || echo NOTFOUND'"
+
+    try:
+        result = subprocess.run(
+            ["ssh", address, *_SSH_OPTS, remote_cmd],
+            capture_output=True,
+            text=True,
+            timeout=15,
+        )
+        output = result.stdout.strip()
+        if output and output != "NOTFOUND":
+            return True, output
+        return False, ""
+    except subprocess.TimeoutExpired:
+        logger.warning("SSH probe timed out for %s", host)
+        return False, ""
+    except Exception as e:
+        logger.warning("SSH probe failed for %s: %s", host, e)
+        return False, ""
+
+
+def dispatch_to_host(
+    host: str,
+    address: str,
+    prompt: str,
+    timeout: int = 300,
+    validate: bool = True,
+) -> DispatchResult:
+    """Dispatch a prompt to a remote hermes instance via SSH.
+
+    Args:
+        host: Hostname (ezra, bezalel, etc.)
+        address: IP address or hostname
+        prompt: The prompt/task to dispatch
+        timeout: SSH timeout in seconds
+        validate: Whether to probe for hermes binary first
+
+    Returns:
+        DispatchResult with success/failure details.
+    """
+    # Pre-flight validation
+    if validate:
+        found, path = probe_hermes(host, address)
+        if not found:
+            return DispatchResult(
+                host=host,
+                address=address,
+                success=False,
+                error="hermes binary not found on remote host",
+                hermes_found=False,
+            )
+    else:
+        found, path = True, "~/.local/bin/hermes"
+
+    # Build the dispatch command
+    # Use hermes chat in quiet mode, pipe prompt via stdin
+    escaped_prompt = prompt.replace("'", "'\\''")
+    remote_cmd = f"echo '{escaped_prompt}' | {path} chat --quiet"
+
+    try:
+        result = subprocess.run(
+            ["ssh", address, *_SSH_OPTS, remote_cmd],
+            capture_output=True,
+            text=True,
+            timeout=timeout,
+        )
+
+        success = result.returncode == 0
+        error = ""
+
+        if not success:
+            error = result.stderr.strip() if result.stderr else f"exit code {result.returncode}"
+
+        return DispatchResult(
+            host=host,
+            address=address,
+            success=success,
+            output=result.stdout.strip()[:500],  # Truncate long output
+            error=error,
+            hermes_found=found,
+            hermes_path=path,
+            exit_code=result.returncode,
+        )
+
+    except subprocess.TimeoutExpired:
+        return DispatchResult(
+            host=host,
+            address=address,
+            success=False,
+            error=f"SSH dispatch timed out after {timeout}s",
+            hermes_found=found,
+            hermes_path=path,
+        )
+    except Exception as e:
+        return DispatchResult(
+            host=host,
+            address=address,
+            success=False,
+            error=f"SSH dispatch failed: {e}",
+            hermes_found=found,
+            hermes_path=path,
+        )
+
+
+def dispatch_to_hosts(
+    hosts: List[str],
+    prompt: str,
+    host_map: Optional[Dict[str, str]] = None,
+    timeout: int = 300,
+) -> List[DispatchResult]:
+    """Dispatch a prompt to multiple hosts.
+
+    Args:
+        hosts: List of hostnames
+        prompt: The prompt/task to dispatch
+        host_map: Optional override of hostname -> address mapping
+        timeout: SSH timeout per host
+
+    Returns:
+        List of DispatchResult, one per host.
+    """
+    addresses = host_map or DEFAULT_HOSTS
+    results = []
+
+    for host in hosts:
+        address = addresses.get(host)
+        if not address:
+            results.append(DispatchResult(
+                host=host,
+                address="unknown",
+                success=False,
+                error=f"Unknown host: {host}",
+            ))
+            continue
+
+        result = dispatch_to_host(host, address, prompt, timeout=timeout)
+        results.append(result)
+        logger.info(result.summary)
+
+    return results
+
+
+def format_dispatch_report(results: List[DispatchResult]) -> str:
+    """Format a multi-host dispatch results as a readable report."""
+    if not results:
+        return "No dispatch results."
+
+    lines = ["SSH Dispatch Report", "=" * 40, ""]
+
+    ok_count = sum(1 for r in results if r.success)
+    fail_count = len(results) - ok_count
+
+    lines.append(f"Total: {len(results)} | OK: {ok_count} | FAIL: {fail_count}")
+    lines.append("")
+
+    for r in results:
+        status = "✓" if r.success else "✗"
+        lines.append(f"  {status} {r.host} ({r.address})")
+        if r.hermes_path:
+            lines.append(f"    hermes: {r.hermes_path}")
+        if r.success and r.output:
+            lines.append(f"    output: {r.output[:100]}...")
+        if not r.success:
+            lines.append(f"    error: {r.error}")
+        lines.append("")
+
+    return "\n".join(lines)