**Description**
This consolidates all the copy-pasted processors that existed per
endpoint we support into one generic processor. This was made possible
thanks to the series of refactoring that we landed in the past few weeks
primarily for dynamic module work #90.

Notably, now in order to add an endpoint, majority of the new code will
be in translator (where also have shared generic interface) as well as
the type definition. No longer it requires the huge copy paste of
processors.

**Related Issues/PRs (if applicable)**

Resolves #1083 
Blocker for #1429 #1584 #1592 #1594

---------

Signed-off-by: Takeshi Yoneda <t.y.mathetake@gmail.com>
Co-authored-by: Ignasi Barrera <ignasi@tetrate.io>

…ranslation (#1812)

**Description**

Discovered a bug when sending `streaming` request to AWS Bedrock with
body mutation set with `serviceTier:default` at route level. The request
translation for AWS Bedrock request is incorrect due to the bug and
resulting in an error from AWS Bedrock

Malformed message structure for AWS Bedrock
```
{
  ...
  "messages" : [ 
    {
      "role" : "user",
      "content" : "Explain what AWS Bedrock is in one sentence."
    } 
  ],
  "serviceTier" : {
    "type" : "default"
  }
  ....
}
```

AWS Bedrock expects message content structure [1]
```
{
 ...
  "messages" : [ {
    "role" : "user",
    "content" : [ {
      "text" : "Explain what AWS Bedrock is in one sentence."
    } ],
  } ],
  "serviceTier" : {
    "type" : "default"
  }
}
```

Error response due to malformed request body for AWS Bedrock
```
'Response code: 400\n'
{'Date': 'Sat, 24 Jan 2026 20:59:22 GMT', 'Content-Type': 'application/json', 'Content-Length': '35', 'x-amzn-RequestId': '1140c7eb-bedd-42f7-aeed-657bd6fdfc46', 'x-amzn-ErrorType': 'SerializationException:http://internal.amazon.com/coral/com.amazon.coral.service/', 'Cache-Control': 'proxy-revalidate', 'Connection': 'keep-alive'}

{"Message":"Unexpected field type"}
```

** Root Cause **
After OpenAI request format -> Bedrock request format translation is
done, current logic informs BodyMutator to use original request instead
of translated request to mutate with forceBodyMutation flag set to true
for initial request, this causes the undesired behavior.

**My Debugging and Analysis**:

in `endpointspec.go`'s ParseBody method return non-nil mutatedBody when
it's streaming request and cost is configured which result in non-nil
`mutatedBody` at [2]

in processor_impl.go's ProcessRequestBody method, `forceBodyMutation` is
set to true for initial request at [3] later cause problem in
```
if onRetry && b.originalBody != nil {
	// On retry, restore the original body first
	requestBody = b.originalBody
}
```
that resets translated body(supposed to Bedrock format) back to original
OpenAI format.

**My proposed solution**:
Remove request body restoration in body mutation.

**Disclaimer**:
Debug analysis and code change in processor_impl.go were done myself and
test cases were added with Claude Code and tweaked manually.

**Related Issues/PRs (if applicable)**
Related PR: #1600

1:
https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ConverseStream.html
2:
https://github.com/envoyproxy/ai-gateway/blob/main/internal/endpointspec/endpointspec.go#L90
3:
https://github.com/envoyproxy/ai-gateway/blob/main/internal/extproc/processor_impl.go#L174-L176

---------

Signed-off-by: Xiaolin Lin <xlin158@bloomberg.net>
Signed-off-by: achoo30 <achoo30@bloomberg.net>
Co-authored-by: Aaron Choo <achoo30@bloomberg.net>
Co-authored-by: Dan Sun <dsun20@bloomberg.net>