cat:monitor-subagents

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Check status of running subagents including token usage and context limits

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Monitor Subagents

Purpose

Track the status of active subagents, monitor their token consumption, detect context limit approaches, and identify compaction events. Enables the parent agent to make informed decisions about intervention or result collection.

When to Use

After spawning one or more subagents
Periodically during long-running orchestration
When deciding whether to spawn additional subagents
Before collecting results to verify completion
When suspecting a subagent has stalled or hit limits

Workflow

1. Run Monitoring Script (Recommended)

Use the optimized monitoring script for minimal context impact:

/workspace/cat/scripts/monitor-subagents.sh

Output format:

{
  "subagents": [
    {"id": "a1b2c3d4", "task": "1.2-parser", "status": "running", "tokens": 45000, "compactions": 0},
    {"id": "b2c3d4e5", "task": "1.3-formatter", "status": "warning", "tokens": 85000, "compactions": 1}
  ],
  "summary": {"total": 2, "running": 1, "complete": 0, "warning": 1}
}

Status values:

running - Active, tokens below threshold
warning - Tokens >= 80K (40% of context), consider intervention
complete - Completion marker (.completion.json) found in worktree

Token Metric Source:

The tokens field in monitor output comes from:

.completion.json if subagent has completed (preferred)
Session file parsing for running subagents (legacy method)

For accurate token metrics on completed subagents, use /cat:token-report which extracts totalTokens from Task tool completions. This metric matches the CLI "Done" display and represents actual context processed, not cumulative API response tokens.

2. Interpret Results

If status = "warning":

Subagent approaching context limits (>= 80K tokens)
For accurate current metrics, run /cat:token-report
Consider collecting partial results with collect-results
May need to decompose remaining work

If status = "complete":

Subagent finished, ready for result collection
Check .completion.json in worktree for details

If compactions > 0:

Subagent experienced context pressure
Quality may have degraded
Collect results and review carefully

Examples

Quick Status Check

# Single command returns all subagent status
/workspace/cat/scripts/monitor-subagents.sh

Check Specific Subagent

# Filter output with jq
/workspace/cat/scripts/monitor-subagents.sh | jq '.subagents[] | select(.id == "a1b2c3d4")'

Count Active Subagents

# Get summary counts only
/workspace/cat/scripts/monitor-subagents.sh | jq '.summary'

Anti-Patterns

Use single script call for all metrics

# ❌ Running jq manually each poll (accumulates tool call overhead)
jq -s '[...] | add' "${SESSION_FILE}"
jq -s '[...] | length' "${SESSION_FILE}"

# ✅ Single script call returns all data
/workspace/cat/scripts/monitor-subagents.sh

Use reasonable polling intervals (30-60 seconds)

# ❌ Checking every second
while true; do
  /workspace/cat/scripts/monitor-subagents.sh
  sleep 1
done

# ✅ Reasonable polling interval (30-60 seconds)
while true; do
  /workspace/cat/scripts/monitor-subagents.sh
  sleep 60
done

Treat compaction as intervention signal

# ❌ Ignoring compaction
if [ "${COMPACTIONS}" -gt 0 ]; then
  echo "Compaction detected, continuing anyway..."
fi

# ✅ Treat compaction as intervention signal
if [ "${COMPACTIONS}" -gt 0 ]; then
  echo "Compaction detected - initiating result collection"
  # Trigger collect-results
fi

Verify session activity (worktree presence alone is insufficient)

# ❌ Assuming worktree = active subagent
ACTIVE_COUNT=$(git worktree list | grep -c "-sub-")

# ✅ Verify session activity
for worktree in $(get_subagent_worktrees); do
  if is_session_active "${worktree}"; then
    ACTIVE_COUNT=$((ACTIVE_COUNT + 1))
  fi
done

Related Skills

cat:spawn-subagent - Launch new subagents
cat:collect-results - Gather completed subagent work
cat:token-report - Detailed token analysis
cat:parallel-execute - Orchestrate multiple subagents