CLIProxyAPI/internal/runtime/executor/claude_executor_request.go

package executor

import (
	"bufio"
	"bytes"
	"compress/flate"
	"compress/gzip"
	"compress/zlib"
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"sort"
	"strings"

	"github.com/andybalholm/brotli"
	"github.com/google/uuid"
	"github.com/klauspost/compress/zstd"
	claudeauth "github.com/router-for-me/CLIProxyAPI/v7/internal/auth/claude"
	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
	"github.com/router-for-me/CLIProxyAPI/v7/internal/misc"
	"github.com/router-for-me/CLIProxyAPI/v7/internal/runtime/executor/helps"
	"github.com/router-for-me/CLIProxyAPI/v7/internal/util"
	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/auth"
	"github.com/tidwall/gjson"
	"github.com/tidwall/sjson"

	"github.com/gin-gonic/gin"
)

const (
	claudeTokenCountingBeta      = "token-counting-2024-11-01"
	claudeFastModeBeta           = "fast-mode-2026-02-01"
	claudeOAuthBeta              = "oauth-2025-04-20"
	claudeCodeBeta               = "claude-code-20250219"
	claudeContext1MBeta          = "context-1m-2025-08-07"
	claudeMidConvSystemBeta      = "mid-conversation-system-2026-04-07"
	claudeAdvancedToolUseBeta    = "advanced-tool-use-2025-11-20"
	claudeEffortBeta             = "effort-2025-11-24"
	claudeServerSideFallbackBeta = "server-side-fallback-2026-06-01"
	claudeFallbackCreditBeta     = "fallback-credit-2026-06-01"
	claudeStructuredOutputsBeta  = "structured-outputs-2025-12-15"
	claudeExtendedCacheTTLBeta   = "extended-cache-ttl-2025-04-11"
	claudeCacheDiagnosisBeta     = "cache-diagnosis-2026-04-07"
)

// claudeCodeCLIConstantBetas are the betas Claude Code 2.1.220 sends on every
// /v1/messages request from the "cli" entrypoint, in wire order, excluding the
// leading claude-code-20250219.
//
// redact-thinking-2026-02-12 belongs here because cloaked requests always claim
// cc_entrypoint=cli; the "sdk-cli" entrypoint omits it.
var claudeCodeCLIConstantBetas = []string{
	"interleaved-thinking-2025-05-14",
	"redact-thinking-2026-02-12",
	"thinking-token-count-2026-05-13",
	"context-management-2025-06-27",
	"prompt-caching-scope-2026-01-05",
}

// claudeCodeTrailingBetas are caller-supplied betas that real Claude Code emits
// after effort-2025-11-24, in that relative order. They are forwarded when the
// caller asks for them and dropped otherwise.
var claudeCodeTrailingBetas = []string{
	claudeServerSideFallbackBeta,
	claudeFallbackCreditBeta,
	claudeStructuredOutputsBeta,
}

// claudeCodeCLIBetas assembles the Anthropic-Beta baseline the way Claude Code
// 2.1.220 does: the list is per-request, not a fixed string. requested holds the
// betas the caller asked for, which decide the capability flags below.
//
// Verified against api.anthropic.com with isolated 2.1.220 profiles on both
// API-key and OAuth paths. A 2026-08-03 A/B capture with two distinct OAuth
// accounts confirmed the current tool beta and OAuth trailer below.
// The full observed order is:
//
//	 1 claude-code-20250219
//	 2 oauth-2025-04-20                  OAuth credentials only
//	 3 context-1m-2025-08-07             [1m] model variants only
//	 4 interleaved-thinking-2025-05-14
//	 5 redact-thinking-2026-02-12        cli entrypoint only
//	 6 thinking-token-count-2026-05-13
//	 7 context-management-2025-06-27
//	 8 prompt-caching-scope-2026-01-05
//	 9 mid-conversation-system-2026-04-07  models accepting a role=system turn
//	10 advanced-tool-use-2025-11-20       requests with tools
//	11 effort-2025-11-24
//	12 server-side-fallback-2026-06-01
//	13 fallback-credit-2026-06-01
//	14 fast-mode-2026-02-01               speed:fast requests only
//	15 extended-cache-ttl-2025-04-11      OAuth credentials only
//	16 cache-diagnosis-2026-04-07         requests with diagnostics only
//
// An empty body keeps the optimistic role=system default, matching the cloaking
// policy for unknown and future model IDs.
func claudeCodeCLIBetas(body []byte, requested map[string]bool, oauthToken bool) string {
	betas := make([]string, 0, len(claudeCodeCLIConstantBetas)+len(claudeCodeTrailingBetas)+7)
	betas = append(betas, claudeCodeBeta)
	if oauthToken {
		betas = append(betas, claudeOAuthBeta)
	}
	if requested[claudeContext1MBeta] {
		betas = append(betas, claudeContext1MBeta)
	}
	betas = append(betas, claudeCodeCLIConstantBetas...)
	if !claudeUsesLegacySystemReminder(body) {
		betas = append(betas, claudeMidConvSystemBeta)
	}
	if tools := gjson.GetBytes(body, "tools"); tools.IsArray() && len(tools.Array()) > 0 {
		betas = append(betas, claudeAdvancedToolUseBeta)
	}
	betas = append(betas, claudeEffortBeta)
	if oauthToken && !requested[claudeFallbackCreditBeta] {
		betas = append(betas, claudeFallbackCreditBeta)
	}
	for _, beta := range claudeCodeTrailingBetas {
		if requested[beta] {
			betas = append(betas, beta)
		}
	}
	if claudeRequestUsesFastMode(body, requested) {
		betas = append(betas, claudeFastModeBeta)
	}
	if oauthToken {
		betas = append(betas, claudeExtendedCacheTTLBeta)
	}
	if diagnostics := gjson.GetBytes(body, "diagnostics"); diagnostics.IsObject() {
		betas = append(betas, claudeCacheDiagnosisBeta)
	}
	return strings.Join(betas, ",")
}

// claudeRequestUsesFastMode reports whether the request selects the fast service
// tier. Anthropic rejects the body's speed field with "Extra inputs are not
// permitted" unless fast-mode-2026-02-01 is declared, so the beta has to follow
// the body. Deriving it here rather than at the call sites is deliberate: the
// streaming and non-streaming paths previously disagreed and streaming silently
// dropped the beta, turning every fast request into a 400.
func claudeRequestUsesFastMode(body []byte, requested map[string]bool) bool {
	if requested[claudeFastModeBeta] {
		return true
	}
	speed := gjson.GetBytes(body, "speed")
	return speed.Type == gjson.String && strings.EqualFold(strings.TrimSpace(speed.String()), "fast")
}

// claudeCountTokensBetas is the fixed profile Claude Code 2.1.220 sends to
// /v1/messages/count_tokens. It is far smaller than the inference baseline:
// redact-thinking, thinking-token-count, prompt-caching-scope, effort and every
// conditional beta are absent. Verified identical across 37 captured calls.
var claudeCountTokensBetas = []string{
	claudeCodeBeta,
	"interleaved-thinking-2025-05-14",
	"context-management-2025-06-27",
	claudeTokenCountingBeta,
}

func claudeCountTokensBetasForCredential(oauthToken bool) string {
	betas := make([]string, 0, len(claudeCountTokensBetas)+1)
	betas = append(betas, claudeCodeBeta)
	if oauthToken {
		betas = append(betas, claudeOAuthBeta)
	}
	betas = append(betas, claudeCountTokensBetas[1:]...)
	return strings.Join(betas, ",")
}

func withClaudeCountTokensOAuthBeta(betas string) string {
	parts := make([]string, 0, len(claudeCountTokensBetas)+1)
	seen := make(map[string]bool)
	for _, beta := range strings.Split(betas, ",") {
		if beta = strings.TrimSpace(beta); beta != "" && !seen[beta] {
			parts = append(parts, beta)
			seen[beta] = true
		}
	}
	if seen[claudeOAuthBeta] {
		return strings.Join(parts, ",")
	}
	insertAt := 0
	if len(parts) > 0 && parts[0] == claudeCodeBeta {
		insertAt = 1
	}
	parts = append(parts, "")
	copy(parts[insertAt+1:], parts[insertAt:])
	parts[insertAt] = claudeOAuthBeta
	return strings.Join(parts, ",")
}

// withClaudeOAuthCredentialBetas restores the credential-scoped betas that
// describe the selected upstream OAuth account rather than caller capability.
//
// A confirmed native client authenticates to CPA with whatever key the user
// configured and cannot know that CPA will select an OAuth credential upstream,
// so its header never carries the OAuth betas. Passing it through verbatim ships
// a Bearer request that declares neither oauth-2025-04-20 nor
// extended-cache-ttl-2025-04-11, which no real OAuth client ever does. Passthrough
// governs what the caller expressed; the credential is CPA's own choice and has to
// be described accurately.
//
// Betas already present are left exactly where the caller put them.
func withClaudeOAuthCredentialBetas(betas string) string {
	parts := make([]string, 0, 16)
	seen := make(map[string]bool)
	for _, beta := range strings.Split(betas, ",") {
		if beta = strings.TrimSpace(beta); beta != "" && !seen[beta] {
			parts = append(parts, beta)
			seen[beta] = true
		}
	}
	if !seen[claudeOAuthBeta] {
		// Captured position 2, directly after claude-code-20250219.
		insertAt := 0
		if len(parts) > 0 && parts[0] == claudeCodeBeta {
			insertAt = 1
		}
		parts = append(parts, "")
		copy(parts[insertAt+1:], parts[insertAt:])
		parts[insertAt] = claudeOAuthBeta
	}
	if !seen[claudeExtendedCacheTTLBeta] {
		parts = append(parts, claudeExtendedCacheTTLBeta)
	}
	return strings.Join(parts, ",")
}

// claudeEntitlementError marks an upstream refusal that is a property of the
// request shape combined with the account's entitlements, not of the credential's
// health. The auth manager must neither rotate nor cool down on these.
type claudeEntitlementError struct {
	statusErr
}

func (claudeEntitlementError) IsRequestScoped() bool {
	return true
}

// classifyClaudeUpstreamError promotes upstream refusals that no other credential
// can satisfy into request-scoped errors.
//
// Anthropic answers a fast-mode request from an account without the matching
// usage credits with 429 rate_limit_error "Usage credits are required for fast
// mode". The generic pipeline reads 429 as quota exhaustion: it marks the
// credential Quota.Exceeded, applies an exponential cooldown and rotates to the
// next one, which returns the same 429. A single speed:"fast" request would walk
// the whole Claude pool and cool down every credential, all of which remain
// perfectly healthy for ordinary traffic. The refusal belongs to the request.
func classifyClaudeUpstreamError(statusCode int, body []byte) error {
	err := statusErr{code: statusCode, msg: string(body)}
	if statusCode == http.StatusTooManyRequests && claudeBodyIndicatesFastModeCredits(body) {
		return claudeEntitlementError{err}
	}
	return err
}

// claudeBodyIndicatesFastModeCredits matches Anthropic's fast-mode entitlement
// refusal without matching a genuine rate limit, which never mentions fast mode.
func claudeBodyIndicatesFastModeCredits(body []byte) bool {
	message := strings.ToLower(gjson.GetBytes(body, "error.message").String())
	if message == "" {
		message = strings.ToLower(string(body))
	}
	return strings.Contains(message, "fast mode") &&
		(strings.Contains(message, "usage credits") || strings.Contains(message, "credits are required"))
}

// claudeRequestedBetas collects every beta the caller asked for, from the
// Anthropic-Beta header and from betas lifted out of the request body.
func claudeRequestedBetas(incomingBetas string, extraBetas []string) map[string]bool {
	requested := make(map[string]bool)
	for _, beta := range strings.Split(incomingBetas, ",") {
		if beta = strings.TrimSpace(beta); beta != "" {
			requested[beta] = true
		}
	}
	for _, beta := range extraBetas {
		if beta = strings.TrimSpace(beta); beta != "" {
			requested[beta] = true
		}
	}
	return requested
}

// isAnthropicUpstreamURL reports whether a resolved request targets Anthropic's
// first-party API.
//
// Every rule that reconstructs Claude Code's identity must key on this rather
// than on the cloaked flag. Kimi rewrites base_url to api.kimi.com and custom
// gateways set their own host, yet both delegate to ClaudeExecutor and are
// therefore cloaked; a cloak-keyed rule silently rewrites their traffic too.
func isAnthropicUpstreamURL(u *url.URL) bool {
	return helps.IsAnthropicUpstreamURL(u)
}

// isAnthropicUpstreamBase reports whether a configured base URL targets Anthropic's
// first-party API. Used before the outgoing request exists.
func isAnthropicUpstreamBase(baseURL string) bool {
	parsed, err := url.Parse(strings.TrimSpace(baseURL))
	if err != nil {
		return false
	}
	return isAnthropicUpstreamURL(parsed)
}

// extractAndRemoveBetas extracts the "betas" array from the body and removes it.
// Returns the extracted betas as a string slice and the modified body.
func extractAndRemoveBetas(body []byte) ([]string, []byte) {
	betasResult := gjson.GetBytes(body, "betas")
	if !betasResult.Exists() {
		return nil, body
	}
	var betas []string
	if betasResult.IsArray() {
		for _, item := range betasResult.Array() {
			if s := strings.TrimSpace(item.String()); s != "" {
				betas = append(betas, s)
			}
		}
	} else if s := strings.TrimSpace(betasResult.String()); s != "" {
		betas = append(betas, s)
	}
	body, _ = sjson.DeleteBytes(body, "betas")
	return betas, body
}

// disableThinkingIfToolChoiceForced checks if tool_choice forces tool use and disables thinking.
// Anthropic API does not allow thinking when tool_choice is set to "any" or a specific tool.
// See: https://docs.anthropic.com/en/docs/build-with-claude/extended-thinking#important-considerations
func disableThinkingIfToolChoiceForced(body []byte) []byte {
	toolChoiceType := gjson.GetBytes(body, "tool_choice.type").String()
	// "auto" is allowed with thinking, but "any" or "tool" (specific tool) are not
	if toolChoiceType == "any" || toolChoiceType == "tool" {
		// Remove thinking configuration entirely to avoid API error
		body, _ = sjson.DeleteBytes(body, "thinking")
		// Adaptive thinking may also set output_config.effort; remove it to avoid
		// leaking thinking controls when tool_choice forces tool use.
		body, _ = sjson.DeleteBytes(body, "output_config.effort")
		if oc := gjson.GetBytes(body, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
			body, _ = sjson.DeleteBytes(body, "output_config")
		}
	}
	return body
}

// normalizeClaudeSamplingForUpstream keeps Anthropic message requests valid.
func normalizeClaudeSamplingForUpstream(body []byte) []byte {
	body, _ = sjson.DeleteBytes(body, "temperature")
	body, _ = sjson.DeleteBytes(body, "top_p")

	thinkingType := strings.ToLower(strings.TrimSpace(gjson.GetBytes(body, "thinking.type").String()))
	switch thinkingType {
	case "enabled", "adaptive", "auto":
		body, _ = sjson.DeleteBytes(body, "top_p")
		body, _ = sjson.DeleteBytes(body, "top_k")
	}
	return body
}

type compositeReadCloser struct {
	io.Reader
	closers []func() error
}

func (c *compositeReadCloser) Close() error {
	var firstErr error
	for i := range c.closers {
		if c.closers[i] == nil {
			continue
		}
		if err := c.closers[i](); err != nil && firstErr == nil {
			firstErr = err
		}
	}
	return firstErr
}

// peekableBody wraps a bufio.Reader around the original ReadCloser so that
// magic bytes can be inspected without consuming them from the stream.
type peekableBody struct {
	*bufio.Reader
	closer io.Closer
}

func (p *peekableBody) Close() error {
	return p.closer.Close()
}

func claudeResponseContentEncoding(header http.Header) string {
	return strings.Join(header.Values("Content-Encoding"), ",")
}

func decodeResponseBody(body io.ReadCloser, contentEncoding string) (io.ReadCloser, error) {
	if body == nil {
		return nil, fmt.Errorf("response body is nil")
	}
	if contentEncoding == "" {
		// No Content-Encoding header.  Attempt best-effort magic-byte detection to
		// handle misbehaving upstreams that compress without setting the header.
		// Only gzip (1f 8b) and zstd (28 b5 2f fd) have reliable magic sequences;
		// br and deflate have none and are left as-is.
		// The bufio wrapper preserves unread bytes so callers always see the full
		// stream regardless of whether decompression was applied.
		pb := &peekableBody{Reader: bufio.NewReader(body), closer: body}
		magic, peekErr := pb.Peek(4)
		if peekErr == nil || (peekErr == io.EOF && len(magic) >= 2) {
			switch {
			case len(magic) >= 2 && magic[0] == 0x1f && magic[1] == 0x8b:
				gzipReader, gzErr := gzip.NewReader(pb)
				if gzErr != nil {
					_ = pb.Close()
					return nil, fmt.Errorf("magic-byte gzip: failed to create reader: %w", gzErr)
				}
				return &compositeReadCloser{
					Reader: gzipReader,
					closers: []func() error{
						gzipReader.Close,
						pb.Close,
					},
				}, nil
			case len(magic) >= 4 && magic[0] == 0x28 && magic[1] == 0xb5 && magic[2] == 0x2f && magic[3] == 0xfd:
				decoder, zdErr := zstd.NewReader(pb)
				if zdErr != nil {
					_ = pb.Close()
					return nil, fmt.Errorf("magic-byte zstd: failed to create reader: %w", zdErr)
				}
				return &compositeReadCloser{
					Reader: decoder,
					closers: []func() error{
						func() error { decoder.Close(); return nil },
						pb.Close,
					},
				}, nil
			}
		}
		return pb, nil
	}
	encodings := strings.Split(contentEncoding, ",")
	reader := io.Reader(body)
	decoderClosers := make([]func() error, 0, len(encodings))
	cleanup := func() {
		for i := len(decoderClosers) - 1; i >= 0; i-- {
			_ = decoderClosers[i]()
		}
		_ = body.Close()
	}
	for index := len(encodings) - 1; index >= 0; index-- {
		encoding := strings.TrimSpace(strings.ToLower(encodings[index]))
		switch encoding {
		case "", "identity":
			continue
		case "gzip":
			gzipReader, errGzip := gzip.NewReader(reader)
			if errGzip != nil {
				cleanup()
				return nil, fmt.Errorf("failed to create gzip reader: %w", errGzip)
			}
			reader = gzipReader
			decoderClosers = append(decoderClosers, gzipReader.Close)
		case "deflate":
			deflateReader, errDeflate := newClaudeDeflateReader(reader)
			if errDeflate != nil {
				cleanup()
				return nil, errDeflate
			}
			reader = deflateReader
			decoderClosers = append(decoderClosers, deflateReader.Close)
		case "br":
			reader = brotli.NewReader(reader)
		case "zstd":
			decoder, errZstd := zstd.NewReader(reader)
			if errZstd != nil {
				cleanup()
				return nil, fmt.Errorf("failed to create zstd reader: %w", errZstd)
			}
			reader = decoder
			decoderClosers = append(decoderClosers, func() error {
				decoder.Close()
				return nil
			})
		default:
			cleanup()
			return nil, fmt.Errorf("unsupported content encoding %q", encoding)
		}
	}
	if len(decoderClosers) == 0 && reader == body {
		return body, nil
	}
	closers := make([]func() error, 0, len(decoderClosers)+1)
	for index := len(decoderClosers) - 1; index >= 0; index-- {
		closers = append(closers, decoderClosers[index])
	}
	closers = append(closers, body.Close)
	return &compositeReadCloser{Reader: reader, closers: closers}, nil
}

func newClaudeDeflateReader(reader io.Reader) (io.ReadCloser, error) {
	buffered := bufio.NewReader(reader)
	header, errPeek := buffered.Peek(2)
	if errPeek == nil && isZlibHeader(header) {
		zlibReader, errZlib := zlib.NewReader(buffered)
		if errZlib != nil {
			return nil, fmt.Errorf("failed to create zlib deflate reader: %w", errZlib)
		}
		return zlibReader, nil
	}
	return flate.NewReader(buffered), nil
}

func isZlibHeader(header []byte) bool {
	if len(header) < 2 {
		return false
	}
	cmf, flg := header[0], header[1]
	return cmf&0x0f == 8 && cmf>>4 <= 7 && (uint16(cmf)<<8|uint16(flg))%31 == 0
}

func applyClaudeHeaders(r *http.Request, auth *cliproxyauth.Auth, apiKey string, stream bool, extraBetas []string, body []byte, cfg *config.Config, incomingHeaders http.Header, confirmedClaudeCode bool, sessionIDs ...string) error {
	if r == nil {
		return nil
	}
	hdrDefault := func(cfgVal, fallback string) string {
		if cfgVal != "" {
			return cfgVal
		}
		return fallback
	}

	var hd config.ClaudeHeaderDefaults
	if cfg != nil {
		hd = cfg.ClaudeHeaderDefaults
	}

	hasAPIKeyAttr := auth != nil && auth.Attributes != nil && strings.TrimSpace(auth.Attributes["api_key"]) != ""
	oauthToken := isClaudeOAuthToken(apiKey) || !hasAPIKeyAttr
	useAPIKey := !oauthToken
	isAnthropicBase := isAnthropicUpstreamURL(r.URL)
	if isAnthropicBase && useAPIKey {
		r.Header.Del("Authorization")
		r.Header.Set("x-api-key", apiKey)
	} else {
		r.Header.Set("Authorization", "Bearer "+apiKey)
	}
	r.Header.Set("Content-Type", "application/json")

	if incomingHeaders == nil {
		if ginCtx, ok := r.Context().Value("gin").(*gin.Context); ok && ginCtx != nil && ginCtx.Request != nil {
			incomingHeaders = ginCtx.Request.Header
		}
	}
	stabilizeDeviceProfile := helps.ClaudeDeviceProfileStabilizationEnabled(cfg)
	var deviceProfile helps.ClaudeDeviceProfile
	if stabilizeDeviceProfile && confirmedClaudeCode {
		var errDeviceProfile error
		deviceProfile, errDeviceProfile = helps.ResolveClaudeDeviceProfileRequired(r.Context(), auth, apiKey, incomingHeaders, cfg)
		if errDeviceProfile != nil {
			return errDeviceProfile
		}
	}

	incomingBetas := strings.TrimSpace(strings.Join(incomingHeaders.Values("Anthropic-Beta"), ","))
	countTokens := r.URL != nil && strings.HasSuffix(r.URL.Path, "/count_tokens")
	baseBetas := claudeCodeCLIBetas(body, claudeRequestedBetas(incomingBetas, extraBetas), oauthToken)
	if countTokens {
		baseBetas = claudeCountTokensBetasForCredential(oauthToken)
	}
	if confirmedClaudeCode && incomingBetas != "" {
		baseBetas = incomingBetas
		if oauthToken {
			if countTokens {
				baseBetas = withClaudeCountTokensOAuthBeta(baseBetas)
			} else {
				baseBetas = withClaudeOAuthCredentialBetas(baseBetas)
			}
		}
	}
	existingSet := make(map[string]bool)
	for _, beta := range strings.Split(baseBetas, ",") {
		if beta = strings.TrimSpace(beta); beta != "" {
			existingSet[beta] = true
		}
	}
	appendBeta := func(beta string) {
		beta = strings.TrimSpace(beta)
		if beta == "" || existingSet[beta] {
			return
		}
		baseBetas += "," + beta
		existingSet[beta] = true
	}
	// On direct Anthropic an unconfirmed caller's own betas are dropped: appending
	// them to the official baseline produces a combination real Claude Code never
	// sends, which defeats the identity the rest of this path reconstructs. Other
	// Anthropic-compatible upstreams (Kimi, custom gateways) run no such check, so
	// caller betas stay functional there. This matches the CCH signing gate, which
	// is likewise limited to api.anthropic.com.
	if !confirmedClaudeCode && incomingBetas != "" && !isAnthropicBase {
		for _, beta := range strings.Split(incomingBetas, ",") {
			appendBeta(beta)
		}
	}
	// Betas lifted out of the body follow the same policy as header-supplied ones.
	// Known betas already reached the assembled baseline through the requested map,
	// which places them at their captured positions; anything left over is unknown
	// to Claude Code and Anthropic rejects it outright. Forwarding those verbatim
	// here was letting the body bypass the gate the header path enforces.
	if !isAnthropicBase {
		for _, beta := range extraBetas {
			appendBeta(beta)
		}
	}
	r.Header.Set("Anthropic-Beta", baseBetas)

	identityHeader := func(name, fallback string) {
		if confirmedClaudeCode {
			misc.EnsureHeader(r.Header, incomingHeaders, name, fallback)
			return
		}
		r.Header.Set(name, fallback)
	}
	identityHeader("Anthropic-Version", "2023-06-01")
	identityHeader("Anthropic-Dangerous-Direct-Browser-Access", "true")
	identityHeader("X-App", "cli")
	// Values below match Claude Code 2.1.220 / @anthropic-ai/sdk 0.94.0.
	identityHeader("X-Stainless-Retry-Count", "0")
	identityHeader("X-Stainless-Runtime", "node")
	identityHeader("X-Stainless-Lang", "js")
	// Claude Code omits X-Stainless-Timeout on count_tokens; only a confirmed
	// native client that sent one of its own keeps it there.
	if !countTokens {
		identityHeader("X-Stainless-Timeout", hdrDefault(hd.Timeout, "600"))
	} else if confirmedClaudeCode {
		if incomingTimeout := incomingHeaders.Get("X-Stainless-Timeout"); incomingTimeout != "" {
			r.Header.Set("X-Stainless-Timeout", incomingTimeout)
		}
	}
	// Selected-credential OAuth identity is an explicit native passthrough
	// exception. Callers pass the same agent-conversation UUID written to
	// metadata.user_id; legacy paths retain their previous cached fallback.
	sessionID := ""
	for _, candidate := range sessionIDs {
		if candidate = strings.TrimSpace(candidate); candidate != "" {
			sessionID = candidate
			break
		}
	}
	if sessionID != "" {
		r.Header.Set("X-Claude-Code-Session-Id", sessionID)
	} else {
		var errSessionID error
		sessionID, errSessionID = helps.CachedSessionIDRequired(r.Context(), apiKey)
		if errSessionID != nil {
			return errSessionID
		}
		identityHeader("X-Claude-Code-Session-Id", sessionID)
	}
	// Per-request UUID, matches Claude Code's x-client-request-id for first-party API.
	if isAnthropicBase {
		identityHeader("x-client-request-id", uuid.New().String())
	}
	r.Header.Set("Connection", "keep-alive")
	// Claude Code negotiates transport identically for streaming and non-streaming
	// requests: Accept stays application/json and full compression is offered even
	// when the body sets stream:true, because Anthropic selects SSE from the body
	// rather than from Accept. Verified across every captured 2.1.220 stream.
	// Forcing text/event-stream plus identity here would otherwise mark every
	// streaming request, which is nearly all traffic. decodeResponseBody already
	// wraps the success path, so a compressed SSE body is decoded transparently.
	applyTransportNegotiation := func() {
		if stream && !isAnthropicBase {
			// Other Anthropic-compatible upstreams (Kimi, custom gateways) may select
			// SSE from Accept and need not compress predictably, so they keep the
			// conservative contract.
			r.Header.Set("Accept", "text/event-stream")
			r.Header.Set("Accept-Encoding", "identity")
			return
		}
		r.Header.Set("Accept", "application/json")
		r.Header.Set("Accept-Encoding", "gzip, deflate, br, zstd")
	}
	applyTransportNegotiation()
	// Confirmed Claude Code requests may contribute their real software profile.
	// Unconfirmed clients always receive the CLI baseline instead of being
	// allowed to populate or reuse another client's software profile.
	if stabilizeDeviceProfile {
		if confirmedClaudeCode {
			helps.ApplyClaudeDeviceProfileHeaders(r, deviceProfile)
		} else {
			helps.ApplyClaudeDefaultDeviceProfileHeaders(r, cfg)
		}
	} else {
		helps.ApplyClaudeLegacyDeviceHeaders(r, incomingHeaders, cfg, confirmedClaudeCode)
	}
	var attrs map[string]string
	if auth != nil {
		attrs = auth.Attributes
	}
	util.ApplyCustomHeadersFromAttrs(r, attrs)
	// Custom credential headers are a configuration escape hatch for third-party
	// gateways, so they keep the last word there. On api.anthropic.com they must
	// not rewrite the reconstructed identity: an overridden Anthropic-Beta yields a
	// combination real Claude Code never sends and the API rejects, and an
	// overridden Accept-Encoding contradicts the negotiated transport. Both were
	// reachable because this ran after the whole header set was assembled.
	if isAnthropicBase {
		r.Header.Set("Anthropic-Beta", baseBetas)
		applyTransportNegotiation()
	} else if stream {
		// Elsewhere only streaming is protected, so an Accept override cannot
		// silently disable event negotiation.
		applyTransportNegotiation()
	}
	return nil
}

// doClaudeUpstreamRequest is the single send boundary for every Claude upstream
// call. Folding the wire-casing pass in here makes it structurally impossible
// for one of the three request paths to drift away from the others, which is
// exactly how the streaming and non-streaming beta sets diverged before.
func doClaudeUpstreamRequest(client *http.Client, req *http.Request) (*http.Response, error) {
	applyClaudeWireHeaderCasing(req)
	return client.Do(req)
}

// claudeWireHeaderCasing maps Go's canonical header name to the exact casing
// Claude Code 2.1.220 puts on the wire. Only the names that differ are listed;
// the other twelve already survive canonicalisation unchanged.
var claudeWireHeaderCasing = map[string]string{
	"X-Stainless-Os":      "X-Stainless-OS",
	"Anthropic-Beta":      "anthropic-beta",
	"Anthropic-Version":   "anthropic-version",
	"X-App":               "x-app",
	"X-Client-Request-Id": "x-client-request-id",

	"Anthropic-Dangerous-Direct-Browser-Access": "anthropic-dangerous-direct-browser-access",
}

// applyClaudeWireHeaderCasing restores the header name casing of the real client.
//
// CPA negotiates ALPN http/1.1 with Anthropic, so header names reach the server
// verbatim rather than lowercased by HPACK, which makes casing observable. Go
// canonicalises every name passed through Header.Set, turning the client's
// anthropic-beta and x-app into Anthropic-Beta and X-App. Writing the map keys
// directly is the only way to keep the original casing.
//
// This also fixes ordering for free: Go sorts header names bytewise when it
// serialises them, and the real client's order is exactly that same bytewise
// sort, so correct casing reproduces the correct order. Host, User-Agent and
// Content-Length remain misplaced because Go writes them ahead of the sorted
// block; that needs transport-level surgery and is out of scope here.
//
// Call this immediately before handing the request to the client and nowhere
// else. The rewritten keys are unreachable through Header.Get, which
// canonicalises its argument, so running it any earlier would silently hide
// these headers from the rest of the pipeline.
func applyClaudeWireHeaderCasing(r *http.Request) {
	if r == nil || r.Header == nil || !isAnthropicUpstreamURL(r.URL) {
		return
	}
	for canonical, wire := range claudeWireHeaderCasing {
		values, ok := r.Header[canonical]
		if !ok {
			continue
		}
		delete(r.Header, canonical)
		r.Header[wire] = values
	}
}

func claudeCreds(a *cliproxyauth.Auth) (apiKey, baseURL string) {
	if a == nil {
		return "", ""
	}
	if a.Attributes != nil {
		apiKey = a.Attributes["api_key"]
		baseURL = a.Attributes["base_url"]
	}
	if apiKey == "" {
		apiKey = claudeauth.ReadMetadataString(&a.Metadata, "access_token")
	}
	return
}

func rebuildMidSystemMessagesToTopLevel(payload []byte) []byte {
	messages := gjson.GetBytes(payload, "messages")
	if !messages.IsArray() {
		return payload
	}

	var movedSystemParts []string
	keptMessages := make([]string, 0, int(messages.Get("#").Int()))
	messages.ForEach(func(_, message gjson.Result) bool {
		if strings.EqualFold(strings.TrimSpace(message.Get("role").String()), "system") {
			movedSystemParts = append(movedSystemParts, claudeSystemTextParts(message.Get("content"))...)
			return true
		}
		keptMessages = append(keptMessages, message.Raw)
		return true
	})
	if len(movedSystemParts) == 0 {
		return payload
	}

	systemParts := claudeSystemTextParts(gjson.GetBytes(payload, "system"))
	systemParts = append(systemParts, movedSystemParts...)
	if len(systemParts) > 0 {
		if updated, errSetSystem := sjson.SetRawBytes(payload, "system", rawJSONArray(systemParts)); errSetSystem == nil {
			payload = updated
		}
	}
	if updated, errSetMessages := sjson.SetRawBytes(payload, "messages", rawJSONArray(keptMessages)); errSetMessages == nil {
		payload = updated
	}
	return payload
}

func claudeSystemTextParts(content gjson.Result) []string {
	if !content.Exists() {
		return nil
	}
	if content.Type == gjson.String {
		text := content.String()
		if strings.TrimSpace(text) == "" {
			return nil
		}
		block := []byte(`{"type":"text","text":""}`)
		block, _ = sjson.SetBytes(block, "text", text)
		return []string{string(block)}
	}
	if !content.IsArray() {
		return nil
	}

	var parts []string
	content.ForEach(func(_, item gjson.Result) bool {
		if item.Type == gjson.String {
			text := item.String()
			if strings.TrimSpace(text) != "" {
				block := []byte(`{"type":"text","text":""}`)
				block, _ = sjson.SetBytes(block, "text", text)
				parts = append(parts, string(block))
			}
			return true
		}
		if item.IsObject() && item.Get("type").String() == "text" && strings.TrimSpace(item.Get("text").String()) != "" {
			parts = append(parts, item.Raw)
		}
		return true
	})
	return parts
}

func rawJSONArray(items []string) []byte {
	if len(items) == 0 {
		return []byte("[]")
	}
	var builder strings.Builder
	builder.WriteByte('[')
	for i, item := range items {
		if i > 0 {
			builder.WriteByte(',')
		}
		builder.WriteString(item)
	}
	builder.WriteByte(']')
	return []byte(builder.String())
}

func isClaudeOAuthToken(apiKey string) bool {
	return strings.Contains(apiKey, "sk-ant-oat")
}

type claudeMCPAliasOptions struct {
	secret string
}

func resolveClaudeMCPAliasOptions(ctx context.Context) claudeMCPAliasOptions {
	// Alias identity belongs to the downstream caller, not to the selected
	// upstream credential. This keeps names stable across OAuth refresh and auth
	// failover while giving one caller a shared virtual MCP server component.
	secret := strings.TrimSpace(helps.APIKeyFromContext(ctx))
	if secret == "" {
		secret = "cpa-claude-mcp-default-caller"
	}
	return claudeMCPAliasOptions{secret: secret}
}

// prepareClaudeOAuthToolNamesForUpstream applies one request-local MCP symbol
// table across every Claude OAuth request path.
func prepareClaudeOAuthToolNamesForUpstream(body []byte, mcpAliases claudeMCPAliasOptions) ([]byte, map[string]string) {
	return remapOAuthToolNamesWithOptions(body, mcpAliases)
}

func restoreClaudeOAuthToolNamesFromResponse(body []byte, reverseMap map[string]string) []byte {
	return reverseRemapOAuthToolNames(body, reverseMap)
}

func restoreClaudeOAuthToolNamesFromStreamLine(line []byte, reverseMap map[string]string) []byte {
	return reverseRemapOAuthToolNamesFromStreamLine(line, reverseMap)
}

// remapOAuthToolNames represents every declared third-party client tool as a
// semantic Claude Code MCP extension. Existing valid MCP names and explicit
// typed Anthropic tools remain unchanged.
//
// It operates on tools[].name, tool_choice.name, and all declared
// tool_use/tool_reference references in messages.
//
// The returned map is keyed on the upstream name and maps to the client-supplied
// original name. Callers MUST pass this map to the reverse
// functions so only aliases allocated for this request are restored on the
// response. A global reverse map would mix symbols from unrelated callers.
func remapOAuthToolNames(body []byte) ([]byte, map[string]string) {
	return remapOAuthToolNamesWithOptions(body, claudeMCPAliasOptions{secret: "cpa-claude-mcp-default-caller"})
}

type claudeRawJSONEdit struct {
	start       int
	end         int
	replacement string
}

func remapOAuthToolNamesWithOptions(body []byte, mcpAliases claudeMCPAliasOptions) ([]byte, map[string]string) {
	remapped, reverseMap, ok := remapOAuthToolNamesWithBatchedEdits(body, mcpAliases)
	if ok {
		return remapped, reverseMap
	}
	return remapOAuthToolNamesWithOptionsLegacy(body, mcpAliases)
}

// remapOAuthToolNamesWithBatchedEdits records offsets from the original JSON
// and applies every rename in one copy. Repeated sjson.SetBytes calls copy most
// of the request for every historical tool reference, turning this path into
// O(body size * reference count) allocation growth.
func remapOAuthToolNamesWithBatchedEdits(body []byte, mcpAliases claudeMCPAliasOptions) ([]byte, map[string]string, bool) {
	if !gjson.ValidBytes(body) {
		return nil, nil, false
	}

	reverseMap := make(map[string]string)
	recordRename := func(original, renamed string) {
		// Preserve the first-seen original name if the same upstream name is
		// produced from multiple call sites; they all map back identically.
		if _, exists := reverseMap[renamed]; !exists {
			reverseMap[renamed] = original
		}
	}

	// Build one request-specific forward map from declarations. Every client
	// tool, including typed custom declarations and names resembling Claude
	// built-ins, gets an MCP alias. Historical references use this same map.
	tools := gjson.GetBytes(body, "tools")
	forwardMap := make(map[string]string)
	protectedNames := make(map[string]bool)
	reservedNames := helps.AugmentClaudeBuiltinToolRegistry(body, nil)
	if tools.Exists() && tools.IsArray() {
		tools.ForEach(func(_, tool gjson.Result) bool {
			name := tool.Get("name").String()
			if name != "" {
				reservedNames[name] = true
			}
			if helps.IsClaudeServerToolType(tool.Get("type").String()) {
				protectedNames[name] = true
			}
			return true
		})
		tools.ForEach(func(_, tool gjson.Result) bool {
			if helps.IsClaudeServerToolType(tool.Get("type").String()) {
				return true
			}
			name := tool.Get("name").String()
			if name == "" || helps.IsClaudeMCPToolName(name) {
				return true
			}
			if _, exists := forwardMap[name]; exists {
				return true
			}
			for attempt := uint32(0); ; attempt++ {
				alias := helps.ClaudeMCPToolAlias(mcpAliases.secret, name, attempt)
				if reservedNames[alias] {
					continue
				}
				forwardMap[name] = alias
				reservedNames[alias] = true
				break
			}
			return true
		})
	}

	rewriteName := func(name string) (string, bool) {
		if name == "" || protectedNames[name] || helps.IsClaudeMCPToolName(name) {
			return name, false
		}
		if newName, ok := forwardMap[name]; ok && newName != name {
			return newName, true
		}
		return name, false
	}

	edits := make([]claudeRawJSONEdit, 0, len(forwardMap)+1)
	appendRawEdit := func(result gjson.Result, replacement string) bool {
		start := result.Index
		end := start + len(result.Raw)
		if result.Raw == "" || start < 0 || end < start || end > len(body) || !bytes.Equal(body[start:end], []byte(result.Raw)) {
			return false
		}
		edits = append(edits, claudeRawJSONEdit{start: start, end: end, replacement: replacement})
		return true
	}
	appendStringEdit := func(result gjson.Result, replacement string) bool {
		// ClaudeMCPToolAlias only emits [A-Za-z0-9_-], so adding quotes is
		// byte-identical to sjson's encoding without another allocation.
		return appendRawEdit(result, `"`+replacement+`"`)
	}

	// 1. Rebuild typed custom tools exactly as before, but replace the original
	// tools array only after all offsets have been collected.
	toolsNeedRewrite := false
	if tools.Exists() && tools.IsArray() {
		tools.ForEach(func(_, tool gjson.Result) bool {
			toolType := tool.Get("type").String()
			if helps.IsClaudeServerToolType(toolType) {
				return true
			}
			if strings.TrimSpace(toolType) != "" {
				toolsNeedRewrite = true
				return false
			}
			name := tool.Get("name").String()
			_, toolsNeedRewrite = rewriteName(name)
			return !toolsNeedRewrite
		})
	}
	if toolsNeedRewrite {
		var toolsJSON strings.Builder
		toolsJSON.WriteByte('[')
		toolCount := 0
		tools.ForEach(func(_, tool gjson.Result) bool {
			if helps.IsClaudeServerToolType(tool.Get("type").String()) {
				if toolCount > 0 {
					toolsJSON.WriteByte(',')
				}
				toolsJSON.WriteString(tool.Raw)
				toolCount++
				return true
			}

			name := tool.Get("name").String()
			toolJSON := tool.Raw
			if strings.TrimSpace(tool.Get("type").String()) != "" {
				if updatedTool, errDelete := sjson.Delete(toolJSON, "type"); errDelete == nil {
					toolJSON = updatedTool
				}
			}
			if newName, renamed := rewriteName(name); renamed {
				updatedTool, err := sjson.Set(toolJSON, "name", newName)
				if err == nil {
					toolJSON = updatedTool
					recordRename(name, newName)
				}
			}

			if toolCount > 0 {
				toolsJSON.WriteByte(',')
			}
			toolsJSON.WriteString(toolJSON)
			toolCount++
			return true
		})
		toolsJSON.WriteByte(']')
		if !appendRawEdit(tools, toolsJSON.String()) {
			return nil, nil, false
		}
	}

	// 2. Rename tool_choice if it references a declared client tool.
	toolChoice := gjson.GetBytes(body, "tool_choice")
	if toolChoice.Get("type").String() == "tool" {
		nameResult := toolChoice.Get("name")
		tcName := nameResult.String()
		if newName, renamed := rewriteName(tcName); renamed {
			if !appendStringEdit(nameResult, newName) {
				return nil, nil, false
			}
			recordRename(tcName, newName)
		}
	}

	// 3. Rename tool references in messages while every Result.Index still
	// points into the original request bytes.
	messages := gjson.GetBytes(body, "messages")
	validOffsets := true
	if messages.Exists() && messages.IsArray() {
		messages.ForEach(func(_, msg gjson.Result) bool {
			content := msg.Get("content")
			if !content.Exists() || !content.IsArray() {
				return true
			}
			content.ForEach(func(_, part gjson.Result) bool {
				switch part.Get("type").String() {
				case "tool_use":
					nameResult := part.Get("name")
					name := nameResult.String()
					if newName, renamed := rewriteName(name); renamed {
						if !appendStringEdit(nameResult, newName) {
							validOffsets = false
							return false
						}
						recordRename(name, newName)
					}
				case "tool_reference":
					nameResult := part.Get("tool_name")
					toolName := nameResult.String()
					if newName, renamed := rewriteName(toolName); renamed {
						if !appendStringEdit(nameResult, newName) {
							validOffsets = false
							return false
						}
						recordRename(toolName, newName)
					}
				case "tool_result":
					nestedContent := part.Get("content")
					if nestedContent.Exists() && nestedContent.IsArray() {
						nestedContent.ForEach(func(_, nestedPart gjson.Result) bool {
							if nestedPart.Get("type").String() != "tool_reference" {
								return true
							}
							nameResult := nestedPart.Get("tool_name")
							nestedToolName := nameResult.String()
							if newName, renamed := rewriteName(nestedToolName); renamed {
								if !appendStringEdit(nameResult, newName) {
									validOffsets = false
									return false
								}
								recordRename(nestedToolName, newName)
							}
							return true
						})
					}
				}
				return validOffsets
			})
			return validOffsets
		})
	}
	if !validOffsets {
		return nil, nil, false
	}

	remapped, ok := applyClaudeRawJSONEdits(body, edits)
	if !ok {
		return nil, nil, false
	}
	return remapped, reverseMap, true
}

func applyClaudeRawJSONEdits(body []byte, edits []claudeRawJSONEdit) ([]byte, bool) {
	if len(edits) == 0 {
		return body, true
	}
	sort.Slice(edits, func(i, j int) bool {
		return edits[i].start < edits[j].start
	})

	finalSize := len(body)
	cursor := 0
	for _, edit := range edits {
		if edit.start < cursor || edit.start < 0 || edit.end < edit.start || edit.end > len(body) {
			return nil, false
		}
		finalSize += len(edit.replacement) - (edit.end - edit.start)
		if finalSize < 0 {
			return nil, false
		}
		cursor = edit.end
	}

	out := make([]byte, 0, finalSize)
	cursor = 0
	for _, edit := range edits {
		out = append(out, body[cursor:edit.start]...)
		out = append(out, edit.replacement...)
		cursor = edit.end
	}
	out = append(out, body[cursor:]...)
	return out, true
}

// remapOAuthToolNamesWithOptionsLegacy is the byte-for-byte compatibility
// fallback for malformed JSON or an unexpected GJSON offset. Keep it available
// as a differential-test oracle for the batched implementation.
func remapOAuthToolNamesWithOptionsLegacy(body []byte, mcpAliases claudeMCPAliasOptions) ([]byte, map[string]string) {
	reverseMap := make(map[string]string)
	recordRename := func(original, renamed string) {
		// Preserve the first-seen original name if the same upstream name is
		// produced from multiple call sites; they all map back identically.
		if _, exists := reverseMap[renamed]; !exists {
			reverseMap[renamed] = original
		}
	}

	// Build one request-specific forward map from declarations. Every client
	// tool, including typed custom declarations and names resembling Claude
	// built-ins, gets an MCP alias. Historical references use this same map.
	tools := gjson.GetBytes(body, "tools")
	forwardMap := make(map[string]string)
	protectedNames := make(map[string]bool)
	reservedNames := helps.AugmentClaudeBuiltinToolRegistry(body, nil)
	if tools.Exists() && tools.IsArray() {
		tools.ForEach(func(_, tool gjson.Result) bool {
			name := tool.Get("name").String()
			if name != "" {
				reservedNames[name] = true
			}
			if helps.IsClaudeServerToolType(tool.Get("type").String()) {
				protectedNames[name] = true
			}
			return true
		})
		tools.ForEach(func(_, tool gjson.Result) bool {
			if helps.IsClaudeServerToolType(tool.Get("type").String()) {
				return true
			}
			name := tool.Get("name").String()
			if name == "" || helps.IsClaudeMCPToolName(name) {
				return true
			}
			if _, exists := forwardMap[name]; exists {
				return true
			}
			for attempt := uint32(0); ; attempt++ {
				alias := helps.ClaudeMCPToolAlias(mcpAliases.secret, name, attempt)
				if reservedNames[alias] {
					continue
				}
				forwardMap[name] = alias
				reservedNames[alias] = true
				break
			}
			return true
		})
	}

	rewriteName := func(name string) (string, bool) {
		if name == "" || protectedNames[name] || helps.IsClaudeMCPToolName(name) {
			return name, false
		}
		if newName, ok := forwardMap[name]; ok && newName != name {
			return newName, true
		}
		return name, false
	}

	// 1. Rewrite the tools array without rebuilding from a stale gjson snapshot.
	toolsNeedRewrite := false
	if tools.Exists() && tools.IsArray() {
		tools.ForEach(func(_, tool gjson.Result) bool {
			toolType := tool.Get("type").String()
			if helps.IsClaudeServerToolType(toolType) {
				return true
			}
			if strings.TrimSpace(toolType) != "" {
				toolsNeedRewrite = true
				return false
			}
			name := tool.Get("name").String()
			_, toolsNeedRewrite = rewriteName(name)
			return !toolsNeedRewrite
		})
	}
	if toolsNeedRewrite {
		var toolsJSON strings.Builder
		toolsJSON.WriteByte('[')
		toolCount := 0
		tools.ForEach(func(_, tool gjson.Result) bool {
			if helps.IsClaudeServerToolType(tool.Get("type").String()) {
				if toolCount > 0 {
					toolsJSON.WriteByte(',')
				}
				toolsJSON.WriteString(tool.Raw)
				toolCount++
				return true
			}

			name := tool.Get("name").String()
			toolJSON := tool.Raw
			if strings.TrimSpace(tool.Get("type").String()) != "" {
				if updatedTool, errDelete := sjson.Delete(toolJSON, "type"); errDelete == nil {
					toolJSON = updatedTool
				}
			}
			if newName, renamed := rewriteName(name); renamed {
				updatedTool, err := sjson.Set(toolJSON, "name", newName)
				if err == nil {
					toolJSON = updatedTool
					recordRename(name, newName)
				}
			}

			if toolCount > 0 {
				toolsJSON.WriteByte(',')
			}
			toolsJSON.WriteString(toolJSON)
			toolCount++
			return true
		})
		toolsJSON.WriteByte(']')
		body, _ = sjson.SetRawBytes(body, "tools", []byte(toolsJSON.String()))
	}

	// 2. Rename tool_choice if it references a declared client tool.
	toolChoiceType := gjson.GetBytes(body, "tool_choice.type").String()
	if toolChoiceType == "tool" {
		tcName := gjson.GetBytes(body, "tool_choice.name").String()
		if newName, renamed := rewriteName(tcName); renamed {
			body, _ = sjson.SetBytes(body, "tool_choice.name", newName)
			recordRename(tcName, newName)
		}
	}

	// 3. Rename tool references in messages
	messages := gjson.GetBytes(body, "messages")
	if messages.Exists() && messages.IsArray() {
		messages.ForEach(func(msgIndex, msg gjson.Result) bool {
			content := msg.Get("content")
			if !content.Exists() || !content.IsArray() {
				return true
			}
			content.ForEach(func(contentIndex, part gjson.Result) bool {
				partType := part.Get("type").String()
				switch partType {
				case "tool_use":
					name := part.Get("name").String()
					if newName, renamed := rewriteName(name); renamed {
						path := fmt.Sprintf("messages.%d.content.%d.name", msgIndex.Int(), contentIndex.Int())
						body, _ = sjson.SetBytes(body, path, newName)
						recordRename(name, newName)
					}
				case "tool_reference":
					toolName := part.Get("tool_name").String()
					if newName, renamed := rewriteName(toolName); renamed {
						path := fmt.Sprintf("messages.%d.content.%d.tool_name", msgIndex.Int(), contentIndex.Int())
						body, _ = sjson.SetBytes(body, path, newName)
						recordRename(toolName, newName)
					}
				case "tool_result":
					// Handle nested tool_reference blocks inside tool_result.content[]
					toolID := part.Get("tool_use_id").String()
					_ = toolID // tool_use_id stays as-is
					nestedContent := part.Get("content")
					if nestedContent.Exists() && nestedContent.IsArray() {
						nestedContent.ForEach(func(nestedIndex, nestedPart gjson.Result) bool {
							if nestedPart.Get("type").String() == "tool_reference" {
								nestedToolName := nestedPart.Get("tool_name").String()
								if newName, renamed := rewriteName(nestedToolName); renamed {
									nestedPath := fmt.Sprintf("messages.%d.content.%d.content.%d.tool_name", msgIndex.Int(), contentIndex.Int(), nestedIndex.Int())
									body, _ = sjson.SetBytes(body, nestedPath, newName)
									recordRename(nestedToolName, newName)
								}
							}
							return true
						})
					}
				}
				return true
			})
			return true
		})
	}

	return body, reverseMap
}

// reverseRemapOAuthToolNames reverses the tool name mapping for non-stream responses
// using the per-request map produced by remapOAuthToolNames. Names the client sent
// that were NOT forward-renamed are passed through unchanged.
func reverseRemapOAuthToolNames(body []byte, reverseMap map[string]string) []byte {
	if len(reverseMap) == 0 {
		return body
	}
	content := gjson.GetBytes(body, "content")
	if !content.Exists() || !content.IsArray() {
		return body
	}
	content.ForEach(func(index, part gjson.Result) bool {
		partType := part.Get("type").String()
		switch partType {
		case "tool_use":
			name := part.Get("name").String()
			if origName, ok := reverseMap[name]; ok {
				path := fmt.Sprintf("content.%d.name", index.Int())
				body, _ = sjson.SetBytes(body, path, origName)
			}
		case "tool_reference":
			toolName := part.Get("tool_name").String()
			if origName, ok := reverseMap[toolName]; ok {
				path := fmt.Sprintf("content.%d.tool_name", index.Int())
				body, _ = sjson.SetBytes(body, path, origName)
			}
		case "tool_result":
			nestedContent := part.Get("content")
			if nestedContent.Exists() && nestedContent.IsArray() {
				nestedContent.ForEach(func(nestedIndex, nestedPart gjson.Result) bool {
					if nestedPart.Get("type").String() != "tool_reference" {
						return true
					}
					toolName := nestedPart.Get("tool_name").String()
					if origName, ok := reverseMap[toolName]; ok {
						path := fmt.Sprintf("content.%d.content.%d.tool_name", index.Int(), nestedIndex.Int())
						body, _ = sjson.SetBytes(body, path, origName)
					}
					return true
				})
			}
		}
		return true
	})
	return body
}

// reverseRemapOAuthToolNamesFromStreamLine reverses the tool name mapping for SSE
// stream lines, using the per-request reverseMap produced by remapOAuthToolNames.
func reverseRemapOAuthToolNamesFromStreamLine(line []byte, reverseMap map[string]string) []byte {
	if len(reverseMap) == 0 {
		return line
	}
	payload := helps.JSONPayload(line)
	if len(payload) == 0 || !gjson.ValidBytes(payload) {
		return line
	}

	contentBlock := gjson.GetBytes(payload, "content_block")
	if !contentBlock.Exists() {
		return line
	}

	blockType := contentBlock.Get("type").String()
	var updated []byte
	var err error

	switch blockType {
	case "tool_use":
		name := contentBlock.Get("name").String()
		if origName, ok := reverseMap[name]; ok {
			updated, err = sjson.SetBytes(payload, "content_block.name", origName)
			if err != nil {
				return line
			}
		} else {
			return line
		}
	case "tool_reference":
		toolName := contentBlock.Get("tool_name").String()
		if origName, ok := reverseMap[toolName]; ok {
			updated, err = sjson.SetBytes(payload, "content_block.tool_name", origName)
			if err != nil {
				return line
			}
		} else {
			return line
		}
	default:
		return line
	}

	trimmed := bytes.TrimSpace(line)
	if bytes.HasPrefix(trimmed, []byte("data:")) {
		return append([]byte("data: "), updated...)
	}
	return updated
}

func applyClaudeToolPrefix(body []byte, prefix string) []byte {
	if prefix == "" {
		return body
	}

	// Collect built-in tool names from the authoritative fallback seed list and
	// augment it with any typed built-ins present in the current request body.
	builtinTools := helps.AugmentClaudeBuiltinToolRegistry(body, nil)

	if tools := gjson.GetBytes(body, "tools"); tools.Exists() && tools.IsArray() {
		tools.ForEach(func(index, tool gjson.Result) bool {
			// Skip built-in tools (web_search, code_execution, etc.) which have
			// a "type" field and require their name to remain unchanged.
			if tool.Get("type").Exists() && tool.Get("type").String() != "" {
				if n := tool.Get("name").String(); n != "" {
					builtinTools[n] = true
				}
				return true
			}
			name := tool.Get("name").String()
			if name == "" || strings.HasPrefix(name, prefix) || helps.IsClaudeMCPToolName(name) {
				return true
			}
			path := fmt.Sprintf("tools.%d.name", index.Int())
			body, _ = sjson.SetBytes(body, path, prefix+name)
			return true
		})
	}

	if gjson.GetBytes(body, "tool_choice.type").String() == "tool" {
		name := gjson.GetBytes(body, "tool_choice.name").String()
		if name != "" && !strings.HasPrefix(name, prefix) && !builtinTools[name] && !helps.IsClaudeMCPToolName(name) {
			body, _ = sjson.SetBytes(body, "tool_choice.name", prefix+name)
		}
	}

	if messages := gjson.GetBytes(body, "messages"); messages.Exists() && messages.IsArray() {
		messages.ForEach(func(msgIndex, msg gjson.Result) bool {
			content := msg.Get("content")
			if !content.Exists() || !content.IsArray() {
				return true
			}
			content.ForEach(func(contentIndex, part gjson.Result) bool {
				partType := part.Get("type").String()
				switch partType {
				case "tool_use":
					name := part.Get("name").String()
					if name == "" || strings.HasPrefix(name, prefix) || builtinTools[name] || helps.IsClaudeMCPToolName(name) {
						return true
					}
					path := fmt.Sprintf("messages.%d.content.%d.name", msgIndex.Int(), contentIndex.Int())
					body, _ = sjson.SetBytes(body, path, prefix+name)
				case "tool_reference":
					toolName := part.Get("tool_name").String()
					if toolName == "" || strings.HasPrefix(toolName, prefix) || builtinTools[toolName] || helps.IsClaudeMCPToolName(toolName) {
						return true
					}
					path := fmt.Sprintf("messages.%d.content.%d.tool_name", msgIndex.Int(), contentIndex.Int())
					body, _ = sjson.SetBytes(body, path, prefix+toolName)
				case "tool_result":
					// Handle nested tool_reference blocks inside tool_result.content[]
					nestedContent := part.Get("content")
					if nestedContent.Exists() && nestedContent.IsArray() {
						nestedContent.ForEach(func(nestedIndex, nestedPart gjson.Result) bool {
							if nestedPart.Get("type").String() == "tool_reference" {
								nestedToolName := nestedPart.Get("tool_name").String()
								if nestedToolName != "" && !strings.HasPrefix(nestedToolName, prefix) && !builtinTools[nestedToolName] && !helps.IsClaudeMCPToolName(nestedToolName) {
									nestedPath := fmt.Sprintf("messages.%d.content.%d.content.%d.tool_name", msgIndex.Int(), contentIndex.Int(), nestedIndex.Int())
									body, _ = sjson.SetBytes(body, nestedPath, prefix+nestedToolName)
								}
							}
							return true
						})
					}
				}
				return true
			})
			return true
		})
	}

	return body
}

func stripClaudeToolPrefixFromResponse(body []byte, prefix string) []byte {
	if prefix == "" {
		return body
	}
	content := gjson.GetBytes(body, "content")
	if !content.Exists() || !content.IsArray() {
		return body
	}
	content.ForEach(func(index, part gjson.Result) bool {
		partType := part.Get("type").String()
		switch partType {
		case "tool_use":
			name := part.Get("name").String()
			if !strings.HasPrefix(name, prefix) {
				return true
			}
			path := fmt.Sprintf("content.%d.name", index.Int())
			body, _ = sjson.SetBytes(body, path, strings.TrimPrefix(name, prefix))
		case "tool_reference":
			toolName := part.Get("tool_name").String()
			if !strings.HasPrefix(toolName, prefix) {
				return true
			}
			path := fmt.Sprintf("content.%d.tool_name", index.Int())
			body, _ = sjson.SetBytes(body, path, strings.TrimPrefix(toolName, prefix))
		case "tool_result":
			// Handle nested tool_reference blocks inside tool_result.content[]
			nestedContent := part.Get("content")
			if nestedContent.Exists() && nestedContent.IsArray() {
				nestedContent.ForEach(func(nestedIndex, nestedPart gjson.Result) bool {
					if nestedPart.Get("type").String() == "tool_reference" {
						nestedToolName := nestedPart.Get("tool_name").String()
						if strings.HasPrefix(nestedToolName, prefix) {
							nestedPath := fmt.Sprintf("content.%d.content.%d.tool_name", index.Int(), nestedIndex.Int())
							body, _ = sjson.SetBytes(body, nestedPath, strings.TrimPrefix(nestedToolName, prefix))
						}
					}
					return true
				})
			}
		}
		return true
	})
	return body
}

func stripClaudeToolPrefixFromStreamLine(line []byte, prefix string) []byte {
	if prefix == "" {
		return line
	}
	payload := helps.JSONPayload(line)
	if len(payload) == 0 || !gjson.ValidBytes(payload) {
		return line
	}
	contentBlock := gjson.GetBytes(payload, "content_block")
	if !contentBlock.Exists() {
		return line
	}

	blockType := contentBlock.Get("type").String()
	var updated []byte
	var err error

	switch blockType {
	case "tool_use":
		name := contentBlock.Get("name").String()
		if !strings.HasPrefix(name, prefix) {
			return line
		}
		updated, err = sjson.SetBytes(payload, "content_block.name", strings.TrimPrefix(name, prefix))
		if err != nil {
			return line
		}
	case "tool_reference":
		toolName := contentBlock.Get("tool_name").String()
		if !strings.HasPrefix(toolName, prefix) {
			return line
		}
		updated, err = sjson.SetBytes(payload, "content_block.tool_name", strings.TrimPrefix(toolName, prefix))
		if err != nil {
			return line
		}
	default:
		return line
	}

	trimmed := bytes.TrimSpace(line)
	if bytes.HasPrefix(trimmed, []byte("data:")) {
		return append([]byte("data: "), updated...)
	}
	return updated
}