Add notes about OpenClaw settings to massively improve Cache Hits with DS4 to README

[srinathh]

Added usage notes for OpenClaw regarding turning off the message envelope to improve DS4 cache-hit performance massively.

[osolmaz]

OpenClaw's default configuration causes a
Message Envelope to be sent with every
message that injects a timestamp whose location moves with every request. This
can cause heavy cache misses.

Seems like something that should be fixed on openclaw side, taking this over there

[osolmaz]

I followed this up on the OpenClaw side and could not reproduce the claim that OpenClaw's default timestamping busts DS4 prompt caching.

In the normal embedded OpenClaw path, prior messages are stamped from each message's stored timestamp. That means the same earlier user message should serialize to the same bytes when it is replayed as history. The OpenClaw provider-payload tests I added checked that the reusable request prefix stays byte-stable with timestamping left on.

I did land a related OpenClaw change, but it is narrower than the original claim here: agents.defaults.envelopeTimestamp: "off" now consistently removes OpenClaw-owned timestamp text from both message envelopes and model-input timestamp prefixes. That is useful for users who explicitly want bare user-turn bytes, but it is not a reproduced fix for default OpenClaw timestamping breaking DS4 caching.

OpenClaw PR: openclaw/openclaw#93238
Merged commit: openclaw/openclaw@8c108c2

[srinathh]

Thanks so much! I will check this PR out & try to rebuild my OpenClaw image and & see . Yesterday I deep dived using the trace functionality in DS4 and in OpenClaw to isloate that the problem was being caused by injectTimestamp pathway in Openclaw. I saw yesterday that pull openclaw/openclaw#90811 is also influencing that - so probably fixed upstream between the two. If these work, we should be good & i'll close the PR