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/debugging-signals-pipeline

Debug the signals pipeline locally end-to-end. Covers emitting test signals from fixtures, monitoring Temporal workflows via the REST API, reading sandbox agent logs from object storage, inspecting Docker sandbox containers, and diagnosing common failures (stale ClickHouse

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$ npx -y skills add posthog/posthog --skill debugging-signals-pipeline --agent claude-code

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How this skill gets triggered: by you, by Claude, or both.

  • Fires itselfAuto-invocation. Claude auto-loads it when your prompt matches the work.Auto-invocation is when the right skill fires by itself at the right moment, driven by a FLOW.md router and a hook, instead of you invoking it by name. It is the difference between a skill being installed and a skill actually getting used.Read the full definition →
  • You can call itInvoke it directly when you want it.
  • Slash command/debugging-signals-pipeline

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Debug the signals pipeline locally end-to-end. Covers emitting test signals from fixtures, monitoring Temporal workflows via the REST API, reading sandbox agent logs from object storage, inspecting Docker sandbox containers, and diagnosing common failures (stale ClickHouse

SKILL.md

debugging-signals-pipeline.SKILL.md
name: debugging-signals-pipeline
description: >
  Debug the signals pipeline locally end-to-end. Covers emitting test signals
  from fixtures, monitoring Temporal workflows via the REST API, reading sandbox
  agent logs from object storage, inspecting Docker sandbox containers, and
  diagnosing common failures (stale ClickHouse embeddings, agentsh network
  denials, inactivity timeouts). Use when a signal isn't reaching the inbox,
  a signal-report-summary workflow fails, or a sandbox task run times out.

Debugging the signals pipeline

Pipeline flow

emit_signals_from_fixture
  → signal-emitter (Temporal workflow)
    → buffer-signals (batches signals, 5s flush timer)
      → safety_filter_activity
      → flush_signals_to_s3_activity
      → signal_with_start_grouping_v2_activity
        → team-signal-grouping-v2 (30s batch collect window)
          → read_signals_from_s3_activity
          → get_embedding_activity + generate_search_queries_activity
          → run_signal_semantic_search_activity
          → match_signal_to_report_activity
          → assign_and_emit_signal_activity
          → wait_for_signal_in_clickhouse_activity
          → (if new report) signal-report-summary
            → fetch_signals_for_report_activity
            → report_safety_judge_activity
            → select_repository_activity (spawns Docker sandbox)

Emitting test signals

# Emit a single signal from the Zendesk fixture at offset 26
DEBUG=1 python manage.py emit_signals_from_fixture --type zendesk --team-id 1 --offset 26 --limit 1

# Clean up all signal data before re-emitting (avoids stale matches)
DEBUG=1 python manage.py cleanup_signals --team-id 1 --yes

# Check pipeline status
python manage.py signal_pipeline_status --team-id 1 --wait --expected-signals 1 --poll-interval 10

Always clean up before re-emitting to avoid stale embeddings causing phantom report matches.

Monitoring Temporal workflows

The Temporal UI runs at `http://localhost:8081`. The REST API is useful for scripted inspection.

List recent workflows

curl -s 'http://localhost:8081/api/v1/namespaces/default/workflows?query=ORDER+BY+StartTime+DESC&maximumPageSize=15' \
  | python3 -c "
import sys, json
for wf in json.load(sys.stdin).get('executions', []):
    info = wf['execution']
    status = wf['status'].replace('WORKFLOW_EXECUTION_STATUS_', '')
    print(f'{wf[\"startTime\"][:19]}  {status:20s} {wf[\"type\"][\"name\"]:35s} {info[\"workflowId\"][:90]}')
"

Inspect workflow history

WF_ID="buffer-signals-1"  # or team-signal-grouping-v2-1, signals-report:1:<uuid>
curl -s "http://localhost:8081/api/v1/namespaces/default/workflows/$WF_ID/history?maximumPageSize=200" \
  | python3 -c "
import sys, json
for event in json.load(sys.stdin).get('history', {}).get('events', []):
    etype = event['eventType'].replace('EVENT_TYPE_', '')
    etime = event['eventTime'][:19]
    details = ''
    for key, attrs in event.items():
        if key.endswith('Attributes') and isinstance(attrs, dict):
            if 'activityType' in attrs: details = attrs['activityType'].get('name', '')
            elif 'signalName' in attrs: details = f'signal: {attrs[\"signalName\"]}'
            elif 'startToFireTimeout' in attrs: details = f'timer: {attrs[\"startToFireTimeout\"]}'
            elif 'failure' in attrs: details = f'FAILED: {attrs[\"failure\"].get(\"message\", \"\")[:200]}'
    if details: print(f'  {etime}  {etype:50s} {details}')
"

Inspect a previous run (continued-as-new)

When a workflow has continued-as-new, use the `execution.runId` query param:

curl -s "http://localhost:8081/api/v1/namespaces/default/workflows/$WF_ID/history?execution.runId=<run-id>&maximumPageSize=200"

Reading sandbox agent logs

Agent logs are stored in object storage (MinIO locally) as JSONL files. The log URL is on the `TaskRun` model.

# In Django shell (python manage.py shell)
from products.tasks.backend.models import TaskRun
from posthog.storage import object_storage

# Find the most recent task run
run = TaskRun.objects.order_by("-created_at").first()
print(f"status: {run.status}, error: {run.error_message}")
print(f"log_url: {run.log_url}")

# Read the log
content = object_storage.read(run.log_url, missing_ok=True)

# Print last 3000 chars (most useful — shows what happened before failure)
print(content[-3000:])

The log is JSONL with entries like:

{
  "type": "notification",
  "timestamp": "...",
  "notification": { "jsonrpc": "2.0", "method": "_posthog/console", "params": { "level": "debug", "message": "..." } }
}

Key things to look for in the log tail:

  • **agentsh network events** — `DENY` entries show blocked network calls
  • **`_posthog/progress`** events — show which setup step the sandbox reached
  • **`_posthog/console`** debug messages — show sandbox provisioning, cloning, agent startup

Inspecting Docker sandbox containers

# List running sandbox containers
docker ps --filter "name=task-sandbox" --format "table {{.Names}}\t{{.Status}}\t{{.Image}}"

# See processes inside a running sandbox
docker exec <container-name> ps aux

# Read the agent-server log inside the container (while it's still running)
docker exec <container-name> cat /tmp/agent-server.log

The container is named `task-sandbox-<task-id>-<random>` and uses the `posthog-sandbox-base` image. Containers are ephemeral — they're removed after the task run completes, so inspect while running.

Common failures

`SignalReport matching query does not exist`

The `assign_and_emit_signal_activity` tried to assign a signal to a report that doesn't exist. Usually caused by stale embeddings in ClickHouse after a `cleanup_signals` that failed to delete them.

**Root cause:** `CLICKHOUSE_DATABASE` not set in `.env`. The cleanup command uses `sync_execute` which connects to the `CLICKHOUSE_DATABASE` (defaults to `default`), but the embedding tables live in the `posthog

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