bug: Breaks AWS request signing.

[bulebuk]

OpenCode version

1.2.0

Plugin path

~/.config/opencode/plugins/opencode-context-cache.mjs

Expected behavior

Successful use of AWS Bedrock for model access.

Actual behavior

Model connection fails:

The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.
The Canonical String for this request should have been
'POST
/model/us.anthropic.claude-opus-4-6-v1/converse-stream
conversation_id:

Reproduction steps

1. Configure vanilla opencode with Bedrock.
2. Test a bedrock model.
3. Install context cache plugin.
4. Test bedrock model again.
5. Above error.

Relevant logs

[JackDrogon]

@bulebuk sorry，I dont' have aws bedrock subscription. If u can provide a test key, I can help to positioning issue.

[hayate]

Came at this from a different angle and I think the cause is the header writing.

The plugin sets three headers on the model config:

const SESSION_ID_HEADER_NAMES = ["x-session-id", "conversation_id", "session_id"];
...
for (const headerKey of SESSION_ID_HEADER_NAMES) {
  headers[headerKey] = cacheKey;
}

and opencode merges model.headers into the outgoing request. That's fine against OpenAI. Against Bedrock it breaks SigV4, and your paste shows it happening: conversation_id is sitting right there in the canonical string AWS computed.

@JackDrogon you don't need a Bedrock subscription to check this one. Comment out the applySessionHeaders call, keep everything else, and see if the signature error goes away.

The annoying part is those headers were never buying you anything on Bedrock. Claude caches through cache_control breakpoints on the message content and ignores a prompt cache key entirely, so on that path the plugin was breaking your signature in exchange for nothing.

I've opened #4, which drops the header writing (along with some other fixes). I don't have Bedrock access either so I can't close the loop myself. @bulebuk if you're still around and still care after six months, that branch should work for you.