openclaw - 💡(How to fix) Fix [Feature]: Forward session_id to OpenRouter for sticky routing & prompt caching

Summary

Add a config option to automatically forward OpenClaw's internal session ID as session_id to the OpenRouter API, enabling sticky routing and prompt cache optimization.

Problem to solve

OpenRouter supports session_id for sticky routing (routing all requests in a session to the same provider, maximizing prompt cache hits). OpenClaw already tracks session IDs internally but has no mechanism to forward them. The extra_body config only supports static values. This means every request misses prompt caching benefits.

Proposed solution

With a ~10-line change in resolveExtraParams() to read the active session ID and merge it into extra_body. Follows existing params precedence (global → provider → agent).

Alternatives considered

Static extra_body (defeats purpose), plugin hooks (no existing hook), custom proxy (over-engineered).

Impact

Affected: All OpenClaw operators using OpenRouter Severity: Blocks workflow optimization — missed prompt caches mean higher latency, higher cost, inconsistent provider behavior Frequency: Always — every request affected, 6-8 missed cache opportunities per typical conversation Consequence: 2-5x more input tokens than necessary; compounds across sub-agent pipelines

Evidence/examples

No response

Additional information

No response