Lindy Common Errors

Overview

Troubleshooting guide for Lindy AI agent errors. Lindy agents fail at specific points in the workflow: trigger reception, action execution, condition evaluation, or exit condition evaluation. This guide covers each failure class.

Prerequisites

Access to Lindy dashboard (https://app.lindy.ai)
Ability to view agent Tasks tab for error details
For webhook debugging: curl installed

Instructions

Capture the failing run identifier, trigger payload shape, and first failing step without copying sensitive fields into the incident record.
Reproduce the behavior in a test agent or disabled workflow using a bounded input.
Apply the smallest trace-supported remediation, then rerun both the failure fixture and a normal-success fixture before restoring schedules.

Trigger Errors

Webhook Not Firing

Symptoms: No task created when webhook is sent Causes & Solutions:

Cause	Diagnostic	Fix
Wrong URL	Check webhook URL in agent config	Copy exact URL from trigger settings
Missing auth	`curl -v` shows 401	Add `Authorization: Bearer <secret>` header
Agent inactive	Dashboard shows agent paused	Activate the agent
Filter blocking	Trigger filter too restrictive	Review filter conditions, test with broader filter
Wrong HTTP method	Using GET instead of POST	Lindy webhooks require POST

# Diagnostic: Test webhook connectivity
curl -v -X POST "https://public.lindy.ai/api/v1/webhooks/YOUR_ID" \
  -H "Authorization: Bearer YOUR_SECRET" \
  -H "Content-Type: application/json" \
  -d '{"test": true}'
# Expect: 200 OK

Email Trigger Not Activating

Symptoms: Emails arrive but agent does not wake up Solutions:

Verify Gmail/Outlook authorization is current (re-authorize if expired)
Check label filter — Lindy Email Received trigger can filter by label
Confirm email matches trigger filter conditions (sender, subject, etc.)
Check that agent is active, not paused

Schedule Trigger Missed

Symptoms: Agent did not run at scheduled time Solutions:

Verify timezone settings match your expectation
Check credit balance — agents stop if credits exhausted
Review schedule configuration (daily vs weekday vs custom)

Action Errors

Slack Send Failed

Error	Cause	Fix
Channel not found	Channel name wrong or private	Use exact channel name; ensure bot is invited
Not authorized	Slack token expired	Re-authorize Slack in Lindy integrations
Rate limited	Too many messages	Reduce trigger frequency or batch messages

Gmail Send Failed

Error	Cause	Fix
Authentication expired	OAuth token expired	Re-authorize Gmail in Settings
Recipient rejected	Invalid email address	Validate email format in prior step
Draft not found	Thread ID mismatch	Verify thread context in action config

HTTP Request Action Failed

Error	Cause	Fix
Connection refused	Target API down	Verify target URL is reachable
401 Unauthorized	Auth header misconfigured	Check Authorization header value
Timeout	Target API slow	Increase timeout or optimize target endpoint
SSL error	Invalid certificate	Ensure target uses valid HTTPS cert

# Diagnostic: Test target API independently
curl -v -X POST "https://api.yourapp.com/endpoint" \
  -H "Content-Type: application/json" \
  -d '{"test": true}'

Run Code Action Failed

Error	Cause	Fix
Import error	Library not available	Use only pre-installed libraries (pandas, numpy, etc.)
Type error	Input variable is string	Cast explicitly: `int(var)`, `json.loads(var)`
Timeout	Long-running computation	Optimize code; avoid infinite loops
Return value empty	No `return` statement	Add explicit `return` with result data

Knowledge Base Returns No Results

Cause	Fix
Fuzziness at 0 (keyword only)	Increase to 100 for semantic search
Content not indexed	Trigger Resync Knowledge Base action
Query too vague	Switch field to AI Prompt mode with specific instructions
File too large (>20MB)	Split into smaller files

Agent Step Errors

Agent Loops Indefinitely

Cause: Exit conditions never satisfied Fix: Add measurable, achievable exit conditions:

Primary: "Found at least 3 relevant results"
Fallback: "Made 5 search attempts without finding results"

Agent Picks Wrong Condition Branch

Cause: Ambiguous condition prompt Fix: Make conditions mutually exclusive with clear criteria:

Branch A: "Go down this path if the email mentions billing, payment, or invoice"
Branch B: "Go down this path if the email mentions a technical issue, bug, or error"
Branch C: "Go down this path for all other topics"

Credit Overrun Warning

Symptom: "Task using more resources than expected" pause Cause: Agent step consuming too many credits (complex reasoning) Fix: Simplify prompt, reduce available skills (2-4 max), use smaller model

Debugging Checklist

Open agent Tasks tab — find the failed task
Click into the task — review each step's input/output
Identify the failing step (red indicator)
Check the step's error message and stack trace
Verify integration authorizations are current
Test the trigger independently (curl for webhooks)
Test the action independently (manual run)
Check credit balance — insufficient credits halt execution

Error Handling

Error Category	HTTP Status	Retry?	Notes
Auth failure	401	No	Re-authorize integration
Rate limited	429	Yes	Wait for credit reset
Agent not found	404	No	Verify agent exists and is active
Action timeout	504	Yes	Simplify step or increase timeout
Run Code error	500	Maybe	Fix code, then retry
Credit exhausted	402	No	Upgrade plan or wait for monthly reset

Output

Return a compact incident record: observed error, failing trigger or action, correlation ID, reproduction input, remediation applied, and the verification result. Separate platform failures from errors in the connected service.

Examples

When an agent step times out, replay the same bounded input in a test agent, inspect the step trace, reduce the action payload or timeout only where the trace identifies the bottleneck, then rerun the original fixture before re-enabling the production schedule.

Resources

Next Steps

Proceed to lindy-debug-bundle for comprehensive diagnostics.

lindy-common-errors