refactor(rulebased): remove the client-wide lastSelectedID

pkg/model/provider/rulebased/client.go

@@ -13,15 +13,13 @@ import (
 	"fmt"
 	"log/slog"
 	"slices"
-	"sync/atomic"
 
 	"github.com/docker/docker-agent/pkg/chat"
 	"github.com/docker/docker-agent/pkg/config/latest"
 	"github.com/docker/docker-agent/pkg/environment"
 	"github.com/docker/docker-agent/pkg/model/provider/base"
 	"github.com/docker/docker-agent/pkg/model/provider/contracts"
 	"github.com/docker/docker-agent/pkg/model/provider/options"
-	"github.com/docker/docker-agent/pkg/modelsdev"
 	"github.com/docker/docker-agent/pkg/tools"
 )
 
@@ -39,10 +37,6 @@ type Client struct {
 	routes   []Provider
 	fallback Provider
 	matcher  *matcher
-	// lastSelectedID holds the ID of the provider selected by the most recent
-	// call. A plain atomic pointer suffices because it is the only mutable
-	// field; everything else is set once at construction and read-only after.
-	lastSelectedID atomic.Pointer[modelsdev.ID]
 }
 
 // NewClient creates a new rule-based routing client.
@@ -120,8 +114,9 @@ func filterOutMaxTokens(opts []options.Opt) []options.Opt {
 	return filtered
 }
 
-// CreateChatCompletionStream selects a provider based on input and delegates the call.
-// The selected provider's ID is recorded in LastSelectedModelID.
+// CreateChatCompletionStream selects a provider based on input and delegates
+// the call. The returned stream reports the selected provider as its
+// ServingModel.
 func (c *Client) CreateChatCompletionStream(
 	ctx context.Context,
 	messages []chat.Message,
@@ -133,7 +128,6 @@ func (c *Client) CreateChatCompletionStream(
 	}
 
 	selectedID := provider.ID()
-	c.lastSelectedID.Store(&selectedID)
 	slog.DebugContext(ctx, "Rule-based router selected model",
 		"router", c.ID().String(),
 		"selected_model", selectedID.String(),
@@ -162,17 +156,6 @@ func (c *Client) CreateChatCompletionStream(
 	return &routedStream{MessageStream: stream, serving: serving}, nil
 }
 
-// LastSelectedModelID returns the ID of the provider selected by the most
-// recent CreateChatCompletionStream call. This allows callers to display
-// the YAML-configured sub-model name for rule-based routing. Accounting uses
-// the request-bound ServingModel on the returned stream instead.
-func (c *Client) LastSelectedModelID() modelsdev.ID {
-	if id := c.lastSelectedID.Load(); id != nil {
-		return *id
-	}
-	return modelsdev.ID{}
-}
-
 // selectProvider finds the best matching provider for the messages.
 func (c *Client) selectProvider(messages []chat.Message) (Provider, bool) {
 	userMessage := getLastUserMessage(messages)

pkg/model/provider/rulebased/client_race_test.go

@@ -15,7 +15,9 @@ import (
 	"github.com/docker/docker-agent/pkg/model/provider/options"
 )
 
-func TestLastSelectedModelID_Concurrent(t *testing.T) {
+// One router serves every conversation of a team load: each stream must report
+// its own route, never another request's.
+func TestServingModel_ConcurrentRoutes(t *testing.T) {
 	t.Parallel()
 
 	cfg := &latest.ModelConfig{
@@ -51,9 +53,6 @@ func TestLastSelectedModelID_Concurrent(t *testing.T) {
 				require.Equal(t, want, stream.(contracts.ServingStream).ServingModel().ID)
 			}
 		})
-		wg.Go(func() {
-			_ = client.LastSelectedModelID()
-		})
 	}
 	wg.Wait()
 }

pkg/runtime/routing_pricing_test.go

@@ -259,7 +259,6 @@ func TestRoutedPricing(t *testing.T) {
 			}
 			switch {
 			case tc.fallback:
-				assert.Equal(t, leafID, router.LastSelectedModelID(), "failed route selection must not price the successful outer fallback")
 				assert.Equal(t, 1, leaf.callCount, "cooldown stays keyed to the failed outer router")
 				assert.Equal(t, 2, fallback.callCount)
 			case tc.noMatch: