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Developer Tools

The Developer Tools section of the dashboard gives technical team members a set of utilities for debugging, testing, and inspecting your Synapse integration. You'll find it in the sidebar under Developer Tools.

Note

Developer Tools are available to the Owner, Admin, and Developer roles. Other roles will not see this section in the sidebar.

Available Tools

Dead Letter Queue

The Dead Letter Queue (DLQ) inspector shows messages that failed to process after multiple retry attempts. This includes failed email sends, failed flow triggers, and other background tasks.

For each failed message, you can see:

FieldDescription
Task nameThe type of job that failed (e.g., Email Send, Flow Trigger)
Error messageWhat went wrong
GuidanceSuggested action to resolve the issue
Retry countHow many times the system attempted to process this message
StatusCurrent state: failed, retried, dismissed, or auto-retrying

From the DLQ inspector, you can:

  • Retry a failed message to re-attempt processing
  • Dismiss a message if the failure is expected or no longer relevant
  • View the payload to see the full message data for debugging

Message Visibility

Synapse separates DLQ messages into two categories:

  • Tenant-visible messages are delivery failures (hard bounces, spam complaints, template suppression) that your team should act on. These show actionable guidance.
  • Internal messages are infrastructure issues (provider timeouts, rate limits) that Synapse handles automatically with extended retries. These are visible to help you understand the full picture but typically resolve on their own.

NLT Template Tester

The NLT Template Tester lets you write and preview NLT (Natural Language Template) expressions in real time, without creating a full email template.

How it works:

  1. Enter NLT syntax in the editor (e.g., {the user's First Name, or "there"}).
  2. Use the sample contact and event data provided, or edit the test data to match your use case.
  3. See the rendered output instantly in the preview pane.

This is useful for:

  • Testing complex expressions before putting them in a real template (conditionals, loops, filters)
  • Debugging NLT errors -- the tester shows validation diagnostics inline
  • Learning NLT syntax -- experiment freely without affecting live templates
  • Converting between NLT and Jinja2 -- the tester includes a built-in converter

The tester includes a variable picker overlay with all available contact fields and event attributes, so you can insert expressions without memorizing the syntax.

HTML Converter

The HTML Converter is a testing tool for the email editor's HTML parsing engine. It converts raw HTML into Synapse's internal block format and back, letting you verify that complex email templates import correctly.

This is primarily useful when:

  • Migrating templates from another email platform that uses raw HTML
  • Debugging rendering issues where the email editor doesn't display HTML as expected
  • Verifying round-trip fidelity -- paste HTML, convert to blocks, convert back to HTML, and compare

The converter handles Jinja2 and NLT template expressions embedded in HTML, preserving them through the conversion process.

Event Schemas (Coming Soon)

A JSON schema registry for all event types in your workspace, with validation rules. This will help you verify that your events conform to the expected structure before sending them.

Flow JSON Inspector (Coming Soon)

A read-only viewer for raw flow configuration data with syntax highlighting. Useful for debugging complex flows or exporting flow definitions for version control.

API Playground (Coming Soon)

An interactive API explorer built from the OpenAPI specification. Test API calls directly from the dashboard without switching to a separate tool.

Next Steps