> ## Documentation Index
> Fetch the complete documentation index at: https://praison.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Durable Outbound Delivery
> Retry-with-backoff and dead-letter queue for all bot channels so transient errors never drop agent replies
```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
from praisonaiagents import Agent
agent = Agent(name="support", instructions="Reply helpfully on Slack or Telegram.")
agent.start("Tell the user their ticket was updated.")
```
Every bot reply now survives transient channel errors — 5xx responses, 429 rate limits, and network blips are automatically retried with bounded exponential backoff before parking in a Dead Letter Queue on permanent failure.
The user sends a bot reply; transient channel errors retry with backoff before a permanent failure lands in the dead-letter queue.
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
graph LR
subgraph "Durable Outbound Delivery"
Reply[🤖 Agent Reply] --> Retry{🔄 Retry\nw/ backoff}
Retry -->|success| Sent[✅ Delivered]
Retry -->|transient error| Wait[⏳ Wait\nRetry-After]
Wait --> Retry
Retry -->|permanent fail| DLQ[📦 Dead Letter\nQueue]
end
classDef agent fill:#8B0000,stroke:#7C90A0,color:#fff
classDef process fill:#189AB4,stroke:#7C90A0,color:#fff
classDef success fill:#10B981,stroke:#7C90A0,color:#fff
classDef warning fill:#F59E0B,stroke:#7C90A0,color:#fff
classDef config fill:#6366F1,stroke:#7C90A0,color:#fff
class Reply agent
class Retry,Wait process
class Sent success
class DLQ warning
```
## Quick Start
All six adapters now retry on transient failures by default — no config needed:
```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
from praisonaiagents import Agent
from praisonai.bots import TelegramBot
agent = Agent(
name="Support Agent",
instructions="Answer user questions helpfully.",
)
bot = TelegramBot(token="YOUR_TOKEN", agent=agent)
await bot.start()
```
Slack, Discord, WhatsApp, Email, Linear, and AgentMail behave identically — transient 5xx and 429 errors are retried automatically.
Add a `dlq_path` so permanently-failed replies are parked for later replay:
```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
from praisonaiagents import Agent
from praisonai.bots import SlackBot, BotConfig, OutboundResilienceConfig
config = BotConfig(
outbound_resilience=OutboundResilienceConfig(
dlq_path="~/.praisonai/state/outbound_dlq.db",
max_attempts=5,
initial_ms=1000,
max_ms=30000,
)
)
agent = Agent(name="Slack Agent", instructions="Help the team.")
bot = SlackBot(token="YOUR_TOKEN", agent=agent, config=config)
await bot.start()
```
Fine-tune retry behaviour per channel:
```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
from praisonai.bots import BotConfig, OutboundResilienceConfig
config = BotConfig(
outbound_resilience=OutboundResilienceConfig(
initial_ms=500, # first retry after 500ms
max_ms=15000, # cap at 15s
factor=2.0, # double each attempt
max_attempts=4, # give up after 4 tries
jitter=0.3, # add 30% random jitter
dlq_path="~/.praisonai/state/dlq.db",
)
)
```
***
## How It Works
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
sequenceDiagram
participant Agent
participant Adapter
participant Channel
participant DLQ
Agent->>Adapter: reply text
Adapter->>Channel: send (attempt 1)
Channel-->>Adapter: 429 Too Many Requests (Retry-After: 5s)
Note over Adapter: wait 5s (honours Retry-After)
Adapter->>Channel: send (attempt 2)
Channel-->>Adapter: 503 Service Unavailable
Note over Adapter: exponential backoff
Adapter->>Channel: send (attempt 3)
Channel-->>Adapter: ✅ 200 OK
Adapter-->>Agent: success
```
The mixin (`OutboundResilienceMixin`) wraps each adapter's raw send with `deliver_outbound()`. State is initialised lazily from `self.config.outbound_resilience` — existing adapter constructors need no changes.
***
## Channel Support
All six channels now share the same durable delivery path:
| Channel | Retry + backoff | DLQ support | Notes |
| --------- | --------------- | ----------- | ------------------------------------------------ |
| Telegram | ✅ | ✅ | Had this previously; unchanged |
| Slack | ✅ | ✅ | New in PR #2484 |
| Discord | ✅ | ✅ | New in PR #2484 |
| WhatsApp | ✅ | ✅ | Previously swallowed errors silently — now fixed |
| Email | ✅ | ✅ | New in PR #2484 |
| Linear | ✅ | ✅ | New in PR #2484 |
| AgentMail | ✅ | ✅ | New in PR #2484 |
WhatsApp previously swallowed permanent send errors silently. This was fixed: permanent failures now propagate, matching every other channel.
***
## What Gets Retried
| Error type | Retried? | Notes |
| ------------------------------------ | -------- | ------------------------------------ |
| HTTP 5xx | ✅ | Full backoff sequence |
| HTTP 429 | ✅ | Waits for `Retry-After` header first |
| Network blips / timeout | ✅ | Transient |
| HTTP 401 Unauthorized | ❌ → DLQ | Token/account issue, not per-message |
| HTTP 403 Forbidden | ❌ → DLQ | Permanent — bot kicked or blocked |
| HTTP 404 Not Found | ❌ → DLQ | Chat deleted or not found |
| HTTP 410 Gone | ❌ → DLQ | Permanently removed |
| Platform patterns ("bot was kicked") | ❌ → DLQ | Platform-specific classification |
***
## Configuration Options
| Option | Type | Default | Description |
| -------------- | ------- | ------- | ---------------------------------------------------- |
| `initial_ms` | `int` | `1000` | First retry delay in milliseconds |
| `max_ms` | `int` | `10000` | Maximum retry delay cap |
| `factor` | `float` | `1.5` | Backoff multiplier per attempt |
| `max_attempts` | `int` | `3` | Total attempts before parking in DLQ |
| `jitter` | `float` | `0.25` | Random jitter fraction (0–1) |
| `dlq_path` | `str` | `None` | Path to SQLite DLQ file; no DLQ when omitted |
| `enabled` | `bool` | `True` | Set `False` to opt a channel out of durable delivery |
***
## Best Practices
Without `dlq_path`, failed replies after max attempts are re-raised and logged but not recoverable. A DLQ lets you replay them after fixing an outage.
The mixin reads the `Retry-After` response header and waits exactly that long before the next attempt, so your bot stays within platform rate limits without sleeping longer than necessary.
Set `outbound_resilience.enabled = False` in a channel's config to disable durable delivery for that channel only — useful for fire-and-forget channels where retries would send duplicates.
Parked entries are permanent failures. Set up alerts on DLQ growth to detect channels that are consistently unreachable (e.g. bots kicked from a workspace).
***
## Related
Short-circuit known-dead channels before sending
Overview of all supported messaging channels
Full delivery configuration reference
Dead-letter queue for inbound messages