refactor(reasoning): use replay policy for K3

open-sse/services/reasoningCache.ts

@@ -64,6 +64,8 @@ const REASONING_REPLAY_MODEL_PATTERNS = [
 ];
 
 const DEEPSEEK_V4_MODEL_PATTERN = /deepseek[-/]v4[-.](flash|pro)/i;
+const K3_REASONING_REPLAY_MODEL_PATTERN = /(?:^|\/)(?:kimi-)?k3(?:$|-)/i;
+const NATIVE_K27_REASONING_REPLAY_MODEL_PATTERN = /(?:^|\/)kimi-k2\.7-code(?:$|-)/i;
 
 export function isDeepSeekReasoningModel(params: {
   provider: string;
@@ -94,6 +96,14 @@ export function requiresReasoningReplay(params: {
   if (normalizedInterleavedField === "reasoning_content") return true;
   if (normalizedInterleavedField === "reasoning_details") return false;
 
+  if (K3_REASONING_REPLAY_MODEL_PATTERN.test(normalizedModel)) return true;
+  if (
+    (normalizedProvider === "moonshot" || normalizedProvider === "kimi") &&
+    NATIVE_K27_REASONING_REPLAY_MODEL_PATTERN.test(normalizedModel)
+  ) {
+    return true;
+  }
+
   // DeepSeek legacy reasoner family has an inverse contract: do not replay.
   if (/deepseek-reasoner/i.test(normalizedModel) || /deepseek-r1/i.test(normalizedModel)) {
     return false;

open-sse/translator/helpers/responsesApiHelper.ts

@@ -2,7 +2,7 @@
  * Convert OpenAI Responses API format to standard chat completions format.
  * Delegates to the canonical translator to avoid logic duplication.
  */
-import { requiresAuthenticReasoningContent } from "../../utils/reasoningContentInjector.ts";
+import { requiresReasoningReplay } from "../../services/reasoningCache.ts";
 import { openaiResponsesToOpenAIRequest } from "../request/openai-responses.ts";
 import { toRecord } from "../request/openai-responses/helpers.ts";
 
@@ -23,7 +23,11 @@ export function convertResponsesApiFormat(
     credentials && typeof credentials === "object" && !Array.isArray(credentials)
       ? (credentials as Record<string, unknown>)
       : {};
-  const translationCredentials = requiresAuthenticReasoningContent(provider, model)
+  const translationCredentials = requiresReasoningReplay({
+    provider: String(provider ?? ""),
+    model: String(model ?? ""),
+    allowLegacyFallback: false,
+  })
     ? { ...credentialRecord, _preserveReasoningContent: true }
     : credentials;
   const converted = openaiResponsesToOpenAIRequest(

open-sse/translator/index.ts

@@ -13,7 +13,6 @@ import {
   providerHonorsOpenAIFormatCacheControl,
   resolveConnectionCacheOverride,
 } from "../utils/cacheControlPolicy.ts";
-import { requiresAuthenticReasoningContent } from "../utils/reasoningContentInjector.ts";
 import { isInternalReasoningPlaceholder } from "../utils/reasoningPlaceholder.ts";
 import {
   coerceToolSchemas,
@@ -162,7 +161,11 @@ function isReasoningOnlyReplayTarget(provider: unknown, model: unknown): boolean
     /(^|\/)deepseek/i.test(normalizedModel) ||
     normalizedProvider === "xiaomi-mimo" ||
     /(^|\/)mimo/i.test(normalizedModel) ||
-    requiresAuthenticReasoningContent(normalizedProvider, normalizedModel)
+    requiresReasoningReplay({
+      provider: normalizedProvider,
+      model: normalizedModel,
+      allowLegacyFallback: false,
+    })
   );
 }
 
@@ -237,12 +240,13 @@ export function translateRequest(
   const normalizedModel = String(model ?? "");
   const isKimiCoding =
     normalizedProvider === "kimi-coding" || normalizedProvider === "kimi-coding-apikey";
-  const requiresAuthenticReasoning = requiresAuthenticReasoningContent(
-    normalizedProvider,
-    normalizedModel
-  );
+  const requiresExplicitReasoningReplay = requiresReasoningReplay({
+    provider: normalizedProvider,
+    model: normalizedModel,
+    allowLegacyFallback: false,
+  });
   const preserveResponsesReasoning =
-    sourceFormat === FORMATS.OPENAI_RESPONSES && requiresAuthenticReasoning;
+    sourceFormat === FORMATS.OPENAI_RESPONSES && requiresExplicitReasoningReplay;
 
   // Phase 2: Apply thinking budget control before normalization
   result = applyThinkingBudget(result);
@@ -399,18 +403,16 @@ export function translateRequest(
     provider: normalizedProvider,
     model: normalizedModel,
   });
-  const isReasoner =
-    requiresAuthenticReasoning ||
-    requiresReasoningReplay({
+  const isReasoner = requiresReasoningReplay({
+    provider: normalizedProvider,
+    model: normalizedModel,
+    thinkingEnabled: hasThinkingConfig(result),
+    supportsReasoning: supportsReasoning({
       provider: normalizedProvider,
       model: normalizedModel,
-      thinkingEnabled: hasThinkingConfig(result),
-      supportsReasoning: supportsReasoning({
-        provider: normalizedProvider,
-        model: normalizedModel,
-      }),
-      interleavedField: resolvedCapabilities?.interleavedField ?? null,
-    });
+    }),
+    interleavedField: resolvedCapabilities?.interleavedField ?? null,
+  });
 
   // Always normalize to clean OpenAI format when target is OpenAI
   // This handles hybrid requests (e.g., OpenAI messages + Claude tools)
@@ -481,7 +483,7 @@ export function translateRequest(
 
   if (
     targetFormat === FORMATS.OPENAI &&
-    !requiresAuthenticReasoning &&
+    !requiresExplicitReasoningReplay &&
     result.messages &&
     Array.isArray(result.messages)
   ) {
@@ -599,7 +601,7 @@ export function translateRequest(
           }
           continue;
         }
-        if (requiresAuthenticReasoning) continue;
+        if (requiresExplicitReasoningReplay) continue;
         msg.content.splice(firstToolUseIdx, 0, {
           type: "thinking",
           thinking: NON_ANTHROPIC_THINKING_PLACEHOLDER,
@@ -636,7 +638,7 @@ export function translateRequest(
       // Native Moonshot K3/K2.7 accepts only the real prior reasoning. If it
       // was not supplied and the cache missed, leave it absent so upstream can
       // enforce its contract instead of corrupting history with a placeholder.
-      if (requiresAuthenticReasoning) {
+      if (requiresExplicitReasoningReplay) {
         if (msg.reasoning_content === "") delete msg.reasoning_content;
         continue;
       }
@@ -649,7 +651,7 @@ export function translateRequest(
       // deepseek-v4-flash accepts an ABSENT reasoning_content field (the 400 is
       // specific to empty-string, and even that is endpoint-dependent). Omit
       // the field instead; providers that genuinely enforce the contract
-      // (kimi-coding, moonshot authentic-reasoning) have their own paths above.
+      // (kimi-coding, moonshot reasoning replay) have their own paths above.
       if ((hasToolCalls || shouldReplayReasoningOnly) && !msg.reasoning_content) {
         if (requiresReasoningContentPresence(normalizedProvider, normalizedModel)) {
           msg.reasoning_content = NON_ANTHROPIC_THINKING_PLACEHOLDER;

open-sse/utils/reasoningContentInjector.ts

@@ -13,6 +13,8 @@
  * that proxy to thinking-mode models.
  */
 
+import { requiresReasoningReplay } from "../services/reasoningCache.ts";
+
 const PLACEHOLDER = " ";
 
 type JsonRecord = Record<string, unknown>;
@@ -30,27 +32,6 @@ const THINKING_MODEL_PATTERNS: RegExp[] = [
   /\bmimo\b/i, // xiaomi-tokenplan mimo family (e.g. xiaomi-tokenplan/mimo-v2.5-pro)
 ];
 
-const K3_AUTHENTIC_REASONING_PATTERN = /(?:^|\/)(?:kimi-)?k3(?:$|-)/i;
-const NATIVE_K27_AUTHENTIC_REASONING_PATTERN = /(?:^|\/)kimi-k2\.7-code(?:$|-)/i;
-
-/**
- * K3 requires authentic reasoning regardless of which provider serves it.
- * Native Moonshot K2.7 retains the same preserved-thinking contract. Empty
- * protocol markers remain valid only after client content and replay miss.
- */
-export function requiresAuthenticReasoningContent(provider: unknown, model: unknown): boolean {
-  const normalizedModel = String(model ?? "").trim();
-  if (K3_AUTHENTIC_REASONING_PATTERN.test(normalizedModel)) return true;
-
-  const normalizedProvider = String(provider ?? "")
-    .trim()
-    .toLowerCase();
-  return (
-    (normalizedProvider === "moonshot" || normalizedProvider === "kimi") &&
-    NATIVE_K27_AUTHENTIC_REASONING_PATTERN.test(normalizedModel)
-  );
-}
-
 export function isThinkingMessageModel(model: string | undefined | null): boolean {
   if (!model || typeof model !== "string") return false;
   return THINKING_MODEL_PATTERNS.some((re) => re.test(model));
@@ -65,7 +46,11 @@ export function shouldInjectReasoningContentPlaceholder(
     .toLowerCase();
   return (
     (normalizedProvider === "moonshot" || normalizedProvider === "kimi") &&
-    !requiresAuthenticReasoningContent(normalizedProvider, model) &&
+    !requiresReasoningReplay({
+      provider: normalizedProvider,
+      model: String(model ?? ""),
+      allowLegacyFallback: false,
+    }) &&
     isThinkingMessageModel(model)
   );
 }

tests/unit/service-reasoning-cache.test.ts

@@ -66,8 +66,8 @@ describe("reasoningCache helpers", () => {
     it("returns false for reasoning_details interleaved field", () => {
       assert.equal(
         mod.requiresReasoningReplay({
-          provider: "any",
-          model: "any",
+          provider: "moonshot",
+          model: "k3",
           interleavedField: "reasoning_details",
         }),
         false
@@ -116,6 +116,9 @@ describe("reasoningCache helpers", () => {
 
     it("detects native Kimi thinking model IDs without matching unrelated aliases", () => {
       for (const model of [
+        "k3",
+        "k3-256k",
+        "kimi-k3",
         "kimi-k2",
         "kimi-k2.6",
         "kimi-k2.6-thinking",
@@ -126,11 +129,25 @@ describe("reasoningCache helpers", () => {
         assert.equal(mod.requiresReasoningReplay({ provider: "some-other", model }), true, model);
       }
 
-      for (const model of ["k3", "moonshot-v1-8k", "kimi-latest"]) {
+      for (const model of ["moonshot-v1-8k", "kimi-latest"]) {
         assert.equal(mod.requiresReasoningReplay({ provider: "some-other", model }), false, model);
       }
     });
 
+    it("keeps K3 and native Moonshot K2.7 replay explicit", () => {
+      for (const model of ["k3", "k3-256k", "kimi-k3", "kimi-k2.7-code"]) {
+        assert.equal(
+          mod.requiresReasoningReplay({
+            provider: "moonshot",
+            model,
+            allowLegacyFallback: false,
+          }),
+          true,
+          model
+        );
+      }
+    });
+
     it("returns false when allowLegacyFallback is false and no explicit signal", () => {
       assert.equal(
         mod.requiresReasoningReplay({