Bug Description

After upgrading from 2026.2.26 to 2026.3.1, messages sent to different channel-bound agents on Discord are processed sequentially instead of in parallel. When sending a message to Agent A (channel #a) and then Agent B (channel #b), Agent B does not begin processing until Agent A finishes its response. Previously on 2026.2.26, both agents would process and respond independently.

Reproduction

1. Configure multiple agents with separate Discord channel bindings:

{
  "bindings": [
    {"agentId": "agent-a", "match": {"channel": "discord", "peer": {"kind": "channel", "id": "CHANNEL_A"}}},
    {"agentId": "agent-b", "match": {"channel": "discord", "peer": {"kind": "channel", "id": "CHANNEL_B"}}}
  ]
}

2. On 2026.2.26: send a message in Channel A, then immediately send a message in Channel B. Both agents respond independently and in parallel.

3. Upgrade to 2026.3.1 (no config changes).

4. Repeat the same test. Agent B now waits for Agent A to finish before it begins processing.

5. Downgrade back to 2026.2.26. Parallel behavior is immediately restored.

Expected Behavior

Messages to different channel-bound agents should be dispatched and processed in parallel, as they were on 2026.2.26.

Observed Behavior

• Agent B queues behind Agent A even though they are on separate channels with separate sessions
• This affects all channel-bound agents, not just a specific pair
• The behavior is consistent and reproducible on every message
• No config changes were made between versions

Environment

• OpenClaw 2026.3.1 (regression), working correctly on 2026.2.26
• Oracle Cloud ARM64, Linux 6.17
• Discord plugin, single bot account
• Guild config: requireMention: false, multiple channels allowed
• 8+ agents with individual channel bindings
• maxConcurrent: 25 in agents.defaults
• anthropic-messages API provider (not affected by the OpenAI WebSocket transport changes)

Workaround

Downgrade to 2026.2.26 restores parallel processing immediately.

Potentially Related Changes in 2026.3.1

• Discord/EventQueue timeout config changes
• Discord/Thread bindings lifecycle changes
• Agents/Subagents runtime events refactor