fix(aibridge): handle sonnet 5 adaptive thinking in bedrock (#27339)

Adds sonnet 5 to the list of models that require adaptive thinking for
Bedrock InvokeModel.

Smoke-tested locally.

> Obligatory disclosure: a Coder agent helped with this.

aibridge/intercept/messages/base.go

@@ -424,7 +424,7 @@ func (i *interceptionBase) withBedrockMantleOptions(ctx context.Context) ([]opti
 // augmentRequestForBedrockInvokeModel changes the model used for the request since AWS Bedrock doesn't support
 // Anthropics' model names. It also converts adaptive thinking to enabled with a budget for models that
 // don't support adaptive thinking natively, or enabled thinking to adaptive for models that only support
-// adaptive (Opus 4.7+).
+// adaptive.
 func (i *interceptionBase) augmentRequestForBedrockInvokeModel() {
 	if i.bedrock == nil {
 		return
@@ -440,7 +440,7 @@ func (i *interceptionBase) augmentRequestForBedrockInvokeModel() {
 
 	switch {
 	case bedrockModelRequiresAdaptiveThinking(model):
-		// Symmetric conversion for adaptive-only models (Opus 4.7+): rewrite
+		// Symmetric conversion for adaptive-only models: rewrite
 		// thinking.type "enabled" with budget_tokens to the "adaptive" shape,
 		// since Bedrock returns 400 for these models when the legacy shape is
 		// used. Claude Code falls back to the legacy shape when it cannot
@@ -468,7 +468,7 @@ func (i *interceptionBase) augmentRequestForBedrockInvokeModel() {
 	}
 
 	// Strip body fields that Bedrock does not accept. Adaptive-only models
-	// (Opus 4.7+) support output_config natively without a beta flag, so
+	// support output_config natively without a beta flag, so
 	// keep it for those models even when the effort-2025-11-24 flag is
 	// absent from the request.
 	var exemptFields []string
@@ -496,8 +496,8 @@ func (i *interceptionBase) augmentRequestForBedrockInvokeModel() {
 }
 
 // bedrockModelSupportsAdaptiveThinking returns true if the given Bedrock model ID
-// supports the "adaptive" thinking type natively (i.e. Claude 4.6 models, and
-// adaptive-only models such as Opus 4.7+).
+// supports the "adaptive" thinking type natively (i.e. Claude 4.6 models and
+// adaptive-only models).
 // See https://docs.aws.amazon.com/bedrock/latest/userguide/claude-messages-adaptive-thinking.html
 func bedrockModelSupportsAdaptiveThinking(model string) bool {
 	return strings.Contains(model, "anthropic.claude-opus-4-6") ||
@@ -507,13 +507,13 @@ func bedrockModelSupportsAdaptiveThinking(model string) bool {
 
 // bedrockModelRequiresAdaptiveThinking returns true if the given Bedrock model
 // ID only supports the "adaptive" thinking type and rejects the legacy
-// "enabled" + budget_tokens shape with a 400. Claude Opus 4.7 was the first
-// model in this category.
+// "enabled" + budget_tokens shape with a 400.
 //
 // See https://docs.aws.amazon.com/bedrock/latest/userguide/model-card-anthropic-claude-opus-4-7.html
 func bedrockModelRequiresAdaptiveThinking(model string) bool {
 	return strings.Contains(model, "anthropic.claude-opus-4-7") ||
-		strings.Contains(model, "anthropic.claude-opus-4-8")
+		strings.Contains(model, "anthropic.claude-opus-4-8") ||
+		strings.Contains(model, "anthropic.claude-sonnet-5")
 }
 
 // filterBedrockBetaFlags removes unsupported beta flags from the Anthropic-Beta

aibridge/intercept/messages/base_internal_test.go

@@ -716,7 +716,7 @@ func TestAugmentRequestForBedrock_AdaptiveThinking(t *testing.T) {
 			expectRemovedFields: []string{"output_config", "metadata", "service_tier", "container", "inference_geo", "context_management"},
 		},
 
-		// Adaptive-only models (Opus 4.7+), see coder/aibridge#280. The
+		// Adaptive-only models, see coder/aibridge#280. The
 		// conversion drops budget_tokens and flips the type; an explicit
 		// output_config.effort from the caller is preserved, but none is
 		// fabricated when absent.
@@ -765,6 +765,21 @@ func TestAugmentRequestForBedrock_AdaptiveThinking(t *testing.T) {
 			requestBody:        `{"max_tokens":10000,"thinking":{"type":"enabled","budget_tokens":5000}}`,
 			expectThinkingType: "adaptive",
 		},
+		{
+			name:               "sonnet_5_model_with_enabled_thinking_is_converted_to_adaptive_and_drops_budget",
+			bedrockModel:       "anthropic.claude-sonnet-5",
+			requestBody:        `{"max_tokens":10000,"thinking":{"type":"enabled","budget_tokens":5000}}`,
+			expectThinkingType: "adaptive",
+		},
+		{
+			name:                "regional_sonnet_5_model_keeps_adaptive_thinking_and_effort_and_strips_output_config_format",
+			bedrockModel:        "us.anthropic.claude-sonnet-5",
+			requestBody:         `{"max_tokens":10000,"thinking":{"type":"adaptive"},"output_config":{"effort":"medium","format":{"type":"json_schema","schema":{"type":"object"}}}}`,
+			expectThinkingType:  "adaptive",
+			expectEffort:        "medium",
+			expectKeptFields:    []string{"output_config", "output_config.effort"},
+			expectRemovedFields: []string{"output_config.format"},
+		},
 		{
 			// Opus 4.7 on Bedrock rejects output_config.format (structured
 			// outputs) with a 400 even though it accepts output_config.effort.

aibridge/intercept/messages/reqpayload.go

@@ -76,7 +76,7 @@ var (
 	// If the beta flag is present in the (already-filtered) Anthropic-Beta header,
 	// the field is kept; otherwise it is stripped. Model-specific beta flags must
 	// be removed from the header before this check (see filterBedrockBetaFlags).
-	// Adaptive-only models (Opus 4.7+) are exempt for output_config since they
+	// Adaptive-only models are exempt for output_config since they
 	// support it natively without a beta flag, see
 	// bedrockModelRequiresAdaptiveThinking.
 	bedrockBetaGatedFields = map[string]string{
@@ -342,8 +342,9 @@ func (RequestPayload) resultToRawMessage(items []gjson.Result) []json.RawMessage
 // The two Bedrock thinking-type conversions below are a temporary shim.
 // AI Gateway relays the Anthropic Messages API shape to Bedrock, whose Claude
 // models accept a disjoint subset on each generation (older models reject
-// "adaptive"; Opus 4.7+ rejects "enabled"). A planned native Bedrock provider
-// removes the impedance mismatch and lets us delete this whole block. Hopefully.
+// "adaptive"; adaptive-only models reject "enabled"). A planned native
+// Bedrock provider removes the impedance mismatch and lets us delete this
+// whole block. Hopefully.
 
 // bedrockThinkingEffortRatios maps an output_config.effort hint to the fraction
 // of max_tokens to allocate as thinking budget. The mapping is a heuristic
@@ -402,7 +403,7 @@ func (p RequestPayload) convertAdaptiveThinkingForBedrock() (RequestPayload, err
 
 // convertEnabledThinkingForBedrock rewrites thinking.type "enabled" to plain
 // "adaptive", dropping budget_tokens. Needed for Bedrock models that only
-// support adaptive thinking (Opus 4.7+).
+// support adaptive thinking.
 //
 // We deliberately do not derive output_config.effort from the budget. Any
 // such mapping would be invented (no canonical budget-to-effort relationship
@@ -421,7 +422,7 @@ func (p RequestPayload) convertEnabledThinkingForBedrock() (RequestPayload, erro
 
 // removeBedrockUnsupportedOutputConfigSubFields drops sub-fields of
 // output_config that Bedrock rejects even on models where the parent
-// output_config object is accepted. Adaptive-only models (Opus 4.7+) accept
+// output_config object is accepted. Adaptive-only models accept
 // output_config.effort but reject output_config.format (structured outputs)
 // with a 400 "Extra inputs are not permitted." The generic field-strip pass
 // (removeUnsupportedBedrockFields) operates at top-level granularity only, so
@@ -444,7 +445,7 @@ func (p RequestPayload) removeBedrockUnsupportedOutputConfigSubFields() (Request
 // calling this method (see filterBedrockBetaFlags).
 //
 // Fields exempted by exemptFields are always kept regardless of beta flag
-// state. Adaptive-only Bedrock models (Opus 4.7+) require output_config
+// state. Adaptive-only Bedrock models require output_config
 // without a beta flag, so callers pass the field through this set to bypass
 // the effort-2025-11-24 gate.
 func (p RequestPayload) removeUnsupportedBedrockFields(headers http.Header, exemptFields ...string) (RequestPayload, error) {

aibridge/internal/integrationtest/bridge_internal_test.go

@@ -460,13 +460,15 @@ func TestAWSBedrockIntegration(t *testing.T) {
 		}
 
 		cases := []struct {
-			name               string
-			model              string
-			smallFastModel     string
-			expectThinkingType string
-			expectBudgetTokens int64    // 0 means budget_tokens should not be present
-			expectKeptFields   []string // fields from strippableFields expected to survive
-			expectedBetaFlags  []string // values expected in the anthropic_beta array in the forwarded body
+			name                string
+			model               string
+			smallFastModel      string
+			expectThinkingType  string
+			expectEffort        string
+			expectBudgetTokens  int64    // 0 means budget_tokens should not be present
+			sendThinkingEnabled bool     // send enabled thinking with budget_tokens instead of the fixture's adaptive thinking
+			expectKeptFields    []string // fields from strippableFields expected to survive
+			expectedBetaFlags   []string // values expected in the anthropic_beta array in the forwarded body
 		}{
 			// "beddel" matches no model prefix, so adaptive thinking is converted
 			// to enabled with budget, and all model-gated beta flags are stripped.
@@ -474,6 +476,7 @@ func TestAWSBedrockIntegration(t *testing.T) {
 				name:               "beddel",
 				model:              "beddel",
 				smallFastModel:     "modrock",
+				expectEffort:       "",
 				expectThinkingType: "enabled",
 				expectBudgetTokens: 16000, // 32000 * 0.5 (medium effort)
 				expectedBetaFlags:  []string{"interleaved-thinking-2025-05-14"},
@@ -483,6 +486,7 @@ func TestAWSBedrockIntegration(t *testing.T) {
 				name:               "opus-4.5",
 				model:              "anthropic.claude-opus-4-5-20250514-v1:0",
 				smallFastModel:     "anthropic.claude-haiku-4-5-20241022-v1:0",
+				expectEffort:       "medium",
 				expectThinkingType: "enabled",
 				expectBudgetTokens: 16000,
 				expectKeptFields:   []string{"output_config"},
@@ -493,6 +497,7 @@ func TestAWSBedrockIntegration(t *testing.T) {
 				name:               "sonnet-4.5",
 				model:              "anthropic.claude-sonnet-4-5-20241022-v2:0",
 				smallFastModel:     "anthropic.claude-haiku-4-5-20241022-v1:0",
+				expectEffort:       "",
 				expectThinkingType: "enabled",
 				expectBudgetTokens: 16000,
 				expectKeptFields:   []string{"context_management"},
@@ -503,10 +508,23 @@ func TestAWSBedrockIntegration(t *testing.T) {
 			{
 				name:               "opus-4.6",
 				model:              "anthropic.claude-opus-4-6-20260619-v1:0",
+				expectEffort:       "",
 				smallFastModel:     "anthropic.claude-haiku-4-5-20241022-v1:0",
 				expectThinkingType: "adaptive",
 				expectedBetaFlags:  []string{"interleaved-thinking-2025-05-14"},
 			},
+			// Sonnet 5 requires adaptive thinking, so legacy enabled thinking is
+			// converted and output_config.effort is preserved.
+			{
+				name:                "sonnet-5",
+				model:               "us.anthropic.claude-sonnet-5",
+				smallFastModel:      "anthropic.claude-haiku-4-5-20241022-v1:0",
+				expectEffort:        "medium",
+				expectThinkingType:  "adaptive",
+				sendThinkingEnabled: true,
+				expectKeptFields:    []string{"output_config"},
+				expectedBetaFlags:   []string{"interleaved-thinking-2025-05-14"},
+			},
 		}
 
 		for _, tc := range cases {
@@ -535,6 +553,13 @@ func TestAWSBedrockIntegration(t *testing.T) {
 
 					reqBody, err := sjson.SetBytes(fix.Request(), "stream", streaming)
 					require.NoError(t, err)
+					if tc.sendThinkingEnabled {
+						reqBody, err = sjson.SetBytes(reqBody, "thinking", map[string]any{
+							"type":          "enabled",
+							"budget_tokens": 16000,
+						})
+						require.NoError(t, err)
+					}
 
 					// Send with Anthropic-Beta header containing flags that should be filtered.
 					resp, err := bridgeServer.makeRequest(t, http.MethodPost, pathAnthropicMessages, reqBody, http.Header{
@@ -562,6 +587,7 @@ func TestAWSBedrockIntegration(t *testing.T) {
 					} else {
 						assert.False(t, gjson.GetBytes(body, "thinking.budget_tokens").Exists(), "budget_tokens should not be present")
 					}
+					assert.Equal(t, tc.expectEffort, gjson.GetBytes(body, "output_config.effort").String(), "effort mismatch")
 
 					// The Bedrock SDK middleware moves Anthropic-Beta from the header
 					// into the body as "anthropic_beta".