Add Claude Fable 5.2 support on OpenCode 1, OpenCode 2 and Pi

CHANGELOG.md

@@ -4,6 +4,7 @@ This repo is a CortexKit-maintained Anthropic auth monorepo for OpenCode and Pi.
 
 ## Unreleased
 
+- Adds Claude Fable 5.2 (`claude-fable-5-2`) on OpenCode 1, OpenCode 2 and Pi, sent the way Claude Code sends it: adaptive thinking, medium default effort, per-message effort and Anthropic's safety fallback. Fast mode stays off for Fable 5.2 until Anthropic enables it for subscription accounts.
 - Claude subscription requests no longer carry a `service_tier` field a host adds, keeping them in the shape Claude Code sends; API-key requests keep it.
 ## 2.7.3
 

packages/core/src/mid-conversation-output-config.ts

@@ -54,7 +54,7 @@ export function usesPerTurnControl(model: unknown): boolean {
 
 /**
  * Models whose OAuth requests carry `PER_TURN_CONTROL_BETA`: those whose
- * Claude Code main beta list includes it (Opus 5.5, Sonnet 5.5, Fable 5.1 and
+ * Claude Code main beta list includes it (Opus 5.5, Sonnet 5.5, Fable 5.1/5.2 and
  * Haiku 5.5 in Claude Code 2.1.302). Sending the beta does not by itself make
  * a model eligible for effort markers; `supportsPerMessageEffort` decides that.
  */
@@ -69,7 +69,7 @@ export function sendsPerTurnControlBeta(model: unknown): boolean {
 /**
  * Whether a request may move effort changes into empty system messages.
  *
- * Models with `effortMarkers: "always"` (Fable 5.1) are always eligible,
+ * Models with `effortMarkers: "always"` (Fable 5.1/5.2) are always eligible,
  * whatever the thinking field says. Models with `"with-adaptive-thinking"`
  * (Opus 5.5, Sonnet 5.5) qualify only with adaptive thinking: Anthropic
  * rejects a differing per-message effort with HTTP 400 on Sonnet 5.5
@@ -135,7 +135,7 @@ export function applyMidConversationOutputConfig(
   }
 
   const compacted = compactTransitions(transitions)
-  // Models with `effortMarkers: "always"` (Fable 5.1) always pin top-level
+  // Models with `effortMarkers: "always"` (Fable 5.1/5.2) always pin top-level
   // effort. The other models leave a request without an effort change exactly
   // as the host built it.
   const pinsEveryRequest = pinsEffortOnEveryRequest(body.model)

packages/core/src/model-capabilities.ts

@@ -153,6 +153,7 @@ export type ClaudeModelCatalogue = {
 export type ClaudeRefusalRecoveryFamily =
   | 'fable-5'
   | 'fable-5-1'
+  | 'fable-5-2'
   | 'opus-5'
   | 'opus-5-5'
 
@@ -246,6 +247,20 @@ const FABLE_MYTHOS_5_1_CATALOGUE: ClaudeModelCatalogue = {
   },
 }
 
+const FABLE_5_2_CATALOGUE: ClaudeModelCatalogue = {
+  releaseDate: '2026-11-09',
+  contextWindow: 1_000_000,
+  maxOutputTokens: 128_000,
+  pricing: {
+    input: 8,
+    output: 40,
+    // Anthropic's Claude Fable 5.2 model page lists cache reads at $0.20/M.
+    cacheRead: 0.2,
+    cacheWrite5m: 10,
+    cacheWrite1h: 16,
+  },
+}
+
 export const CLAUDE_MODEL_CAPABILITIES: readonly ClaudeModelCapabilities[] = [
   {
     id: 'claude-fable-5',
@@ -319,6 +334,26 @@ export const CLAUDE_MODEL_CAPABILITIES: readonly ClaudeModelCapabilities[] = [
     scopedQuota: 'mythos',
     fastMode: false,
   },
+  {
+    id: 'claude-fable-5-2',
+    name: 'Claude Fable 5.2',
+    family: 'fable',
+    idSuffixes: 'any',
+    catalogue: FABLE_5_2_CATALOGUE,
+    thinkingModes: ['adaptive'],
+    rejectsForcedToolChoice: true,
+    efforts: { variants: ALL_ADAPTIVE_EFFORTS, default: 'medium' },
+    effortMarkers: 'always',
+    turnEndNote: true,
+    thinkingBindingControls: true,
+    claudeCodeBetas: claudeCodeBetaLists({ perTurnControl: true }),
+    serverSideFallback: true,
+    refusalRecoveryFamily: 'fable-5-2',
+    scopedQuota: 'fable',
+    // Claude Code's runtime capability list for 5.2 lacks fast_mode today, so
+    // we don't send speed: fast until a real request proves subscription accounts accept it.
+    fastMode: false,
+  },
   {
     id: 'claude-opus-5',
     name: 'Claude Opus 5',

packages/core/src/models.ts

@@ -14,6 +14,7 @@ export { normalizeAnthropicModelId }
 export const CLAUDE_FABLE_5_MODEL_ID = 'claude-fable-5'
 export const CLAUDE_MYTHOS_5_MODEL_ID = 'claude-mythos-5'
 export const CLAUDE_FABLE_5_1_MODEL_ID = 'claude-fable-5-1'
+export const CLAUDE_FABLE_5_2_MODEL_ID = 'claude-fable-5-2'
 export const CLAUDE_MYTHOS_5_1_MODEL_ID = 'claude-mythos-5-1'
 
 /**
@@ -43,6 +44,7 @@ export const CLAUDE_FABLE_MYTHOS_5_MODEL_IDS = [
   CLAUDE_FABLE_5_MODEL_ID,
   CLAUDE_MYTHOS_5_MODEL_ID,
   ...CLAUDE_FABLE_MYTHOS_5_1_MODEL_IDS,
+  CLAUDE_FABLE_5_2_MODEL_ID,
 ] as const
 
 export type ClaudeFableMythos5ModelId =
@@ -55,9 +57,12 @@ export const CLAUDE_FABLE_MYTHOS_5_SUMMARIZED_THINKING = {
 
 const FABLE_5_CATALOGUE = getClaudeModelCatalogue(CLAUDE_FABLE_5_MODEL_ID)
 const FABLE_5_1_CATALOGUE = getClaudeModelCatalogue(CLAUDE_FABLE_5_1_MODEL_ID)
+const FABLE_5_2_CATALOGUE = getClaudeModelCatalogue(CLAUDE_FABLE_5_2_MODEL_ID)
 
 export const CLAUDE_FABLE_MYTHOS_5_PRICING = FABLE_5_CATALOGUE.pricing
 export const CLAUDE_FABLE_MYTHOS_5_1_PRICING = FABLE_5_1_CATALOGUE.pricing
+export const CLAUDE_FABLE_5_2_PRICING = FABLE_5_2_CATALOGUE.pricing
+export const CLAUDE_FABLE_5_2_RELEASE_DATE = FABLE_5_2_CATALOGUE.releaseDate
 
 export const CLAUDE_FABLE_MYTHOS_5_CONTEXT_WINDOW =
   FABLE_5_CATALOGUE.contextWindow
@@ -118,9 +123,11 @@ export function isClaudeFable51Model(model: unknown) {
 }
 
 export function getClaudeFableMythos5ReleaseDate(model: unknown) {
-  return isClaudeFableOrMythos51Model(model)
-    ? CLAUDE_FABLE_MYTHOS_5_1_RELEASE_DATE
-    : CLAUDE_FABLE_MYTHOS_5_RELEASE_DATE
+  const row = resolveClaudeModelCapabilities(model)
+  return (
+    (isFableOrMythosRow(row) && row?.catalogue?.releaseDate) ||
+    CLAUDE_FABLE_MYTHOS_5_RELEASE_DATE
+  )
 }
 
 export const CLAUDE_SONNET_5_MODEL_ID = 'claude-sonnet-5'