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Merged
mdeyell-valid-mind merged 1 commit into from
Jun 12, 2026
Merged

Add MCP debug logging #69

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5 changes: 5 additions & 0 deletions internal/api/handlers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3338,22 +3338,27 @@ func (h *Handler) writeRPCResult(w http.ResponseWriter, id json.RawMessage, resu

func (h *Handler) forwardProxyEnvelope(ctx context.Context, server string, envelope mcp.Envelope, protocolVersion string) (mcp.ForwardResult, bool) {
if h.forwarder == nil {
h.debugf("forward proxy skipped server=%s method=%s reason=no_forwarder", server, envelope.Method)
return mcp.ForwardResult{}, false
}
resolver, ok := h.svc.(interface {
ResolveContext(context.Context, string) (mcp.Upstream, error)
})
if !ok {
h.debugf("forward proxy skipped server=%s method=%s reason=no_resolver", server, envelope.Method)
return mcp.ForwardResult{}, false
}
upstream, err := resolver.ResolveContext(ctx, server)
if err != nil {
h.debugf("forward proxy resolve failed server=%s method=%s err=%v", server, envelope.Method, err)
return mcp.ForwardResult{}, false
}
result, err := h.forwarder.ForwardEnvelope(ctx, upstream, envelope, protocolVersion)
if err != nil {
h.debugf("forward proxy upstream failed server=%s method=%s protocol=%s err=%v", server, envelope.Method, protocolVersion, err)
return mcp.ForwardResult{}, false
}
h.debugf("forward proxy upstream response server=%s method=%s status=%d content_type=%q protocol=%q session_expired=%t", server, envelope.Method, result.StatusCode, result.ContentType, result.ProtocolVersion, result.SessionExpired)
return result, true
}

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14 changes: 14 additions & 0 deletions internal/mcp/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -539,20 +539,25 @@ func (c *Client) invokeHTTP(ctx context.Context, upstream Upstream, tool string,
}
if len(rpcResp.Error) > 0 && string(rpcResp.Error) != "null" {
if isMissingSessionRPCError(rpcResp.Error) {
c.debugf("upstream http tools.call missing session server=%s session=%q status=%d error=%s", upstream.Name, result.SessionID, result.StatusCode, truncateForLog(rpcResp.Error, 600))
if retryErr := c.reinitializeRequiredHTTPSession(ctx, upstream, result.SessionID); retryErr != nil {
c.debugf("upstream http tools.call session retry init failed server=%s session=%q err=%v", upstream.Name, result.SessionID, retryErr)
return InvokeResult{}, retryErr
}
result, err = c.doHTTPEnvelopeWithSessionRetry(ctx, upstream, body, DefaultMCPProtocolVersion)
if err != nil {
c.debugf("upstream http tools.call session retry transport failed server=%s err=%v", upstream.Name, err)
return InvokeResult{}, err
}
rpcResp, err = decodeRPCResponse(result, json.RawMessage([]byte("1")))
if err != nil {
c.debugf("upstream http tools.call session retry decode failed server=%s status=%d err=%v", upstream.Name, result.StatusCode, err)
return InvokeResult{}, err
}
}
}
if len(rpcResp.Error) > 0 && string(rpcResp.Error) != "null" {
c.debugf("upstream http tools.call rpc error server=%s status=%d error=%s", upstream.Name, result.StatusCode, truncateForLog(rpcResp.Error, 600))
return InvokeResult{StatusCode: result.StatusCode, Body: rpcResp.Error, Failed: true}, nil
}
bodyBytes := rpcResp.Result
Expand Down Expand Up @@ -755,14 +760,18 @@ func (c *Client) reinitializeRequiredHTTPSession(ctx context.Context, upstream U

currentSessionID := c.getSession(upstream.Name)
if failedSessionID != "" && currentSessionID != "" && currentSessionID != failedSessionID {
c.debugf("upstream session reinit skipped server=%s failed_session=%q current_session=%q reason=session_already_replaced", upstream.Name, failedSessionID, currentSessionID)
return nil
}
if failedSessionID == "" && currentSessionID != "" {
c.debugf("upstream session reinit skipped server=%s current_session=%q reason=session_already_exists", upstream.Name, currentSessionID)
return nil
}
if failedSessionID != "" {
c.debugf("upstream session reinit clearing server=%s session=%q", upstream.Name, failedSessionID)
c.clearSessionIfCurrent(upstream.Name, failedSessionID)
} else {
c.debugf("upstream session reinit clearing server=%s session=(none)", upstream.Name)
c.clearSession(upstream.Name)
}
return c.initializeHTTPSessionCandidates(ctx, upstream, true)
Expand All @@ -782,18 +791,23 @@ func (c *Client) ensureHTTPSessionMode(ctx context.Context, upstream Upstream, r
func (c *Client) initializeHTTPSessionCandidates(ctx context.Context, upstream Upstream, requireSession bool) error {
var lastErr error
for _, protocolVersion := range httpProtocolCandidates() {
c.debugf("upstream session initialize attempt server=%s protocol=%s require_session=%t", upstream.Name, protocolVersion, requireSession)
hadSession, err := c.initializeHTTPSession(ctx, upstream, protocolVersion)
if err != nil {
lastErr = err
c.debugf("upstream session initialize failed server=%s protocol=%s err=%v", upstream.Name, protocolVersion, err)
if isProtocolNegotiationError(err) {
c.debugf("upstream session initialize trying fallback server=%s rejected_protocol=%s", upstream.Name, protocolVersion)
continue
}
return err
}
if !requireSession || hadSession {
c.debugf("upstream session initialize accepted server=%s protocol=%s had_session=%t", upstream.Name, protocolVersion, hadSession)
return nil
}
lastErr = fmt.Errorf("upstream initialize using MCP %s did not return Mcp-Session-Id", protocolVersion)
c.debugf("upstream session initialize rejected server=%s protocol=%s reason=missing_session_id", upstream.Name, protocolVersion)
}
if lastErr != nil {
return lastErr
Expand Down
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