diff --git a/src/hooks/anthropic-effort/hook.ts b/src/hooks/anthropic-effort/hook.ts
index ef6c98529..47c4d7c87 100644
--- a/src/hooks/anthropic-effort/hook.ts
+++ b/src/hooks/anthropic-effort/hook.ts
@@ -1,6 +1,6 @@
 import { log, normalizeModelID } from "../../shared"
 
-const OPUS_4_6_PATTERN = /claude-opus-4[-.]6/i
+const OPUS_PATTERN = /claude-opus/i
 
 function isClaudeProvider(providerID: string, modelID: string): boolean {
   if (["anthropic", "google-vertex-anthropic", "opencode"].includes(providerID)) return true
@@ -8,9 +8,9 @@ function isClaudeProvider(providerID: string, modelID: string): boolean {
   return false
 }
 
-function isOpus46(modelID: string): boolean {
+function isOpusModel(modelID: string): boolean {
   const normalized = normalizeModelID(modelID)
-  return OPUS_4_6_PATTERN.test(normalized)
+  return OPUS_PATTERN.test(normalized)
 }
 
 interface ChatParamsInput {
@@ -54,7 +54,7 @@ export function createAnthropicEffortHook() {
       if (!isClaudeProvider(model.providerID, model.modelID)) return
       if (output.options.effort !== undefined) return
 
-      const opus = isOpus46(model.modelID)
+      const opus = isOpusModel(model.modelID)
       const clamped = clampVariant(message.variant, opus)
       output.options.effort = clamped
 
diff --git a/src/hooks/anthropic-effort/index.test.ts b/src/hooks/anthropic-effort/index.test.ts
index 666a5c2ac..a82665cdc 100644
--- a/src/hooks/anthropic-effort/index.test.ts
+++ b/src/hooks/anthropic-effort/index.test.ts
@@ -116,6 +116,21 @@ describe("createAnthropicEffortHook", () => {
       //#then should normalize and inject effort
       expect(output.options.effort).toBe("max")
     })
+
+    it("should preserve max for other opus model IDs such as opus-4-5", async () => {
+      //#given another opus model id that is not 4.6
+      const hook = createAnthropicEffortHook()
+      const { input, output } = createMockParams({
+        modelID: "claude-opus-4-5",
+      })
+
+      //#when chat.params hook is called
+      await hook["chat.params"](input, output)
+
+      //#then max should still be treated as valid for opus family
+      expect(output.options.effort).toBe("max")
+      expect(input.message.variant).toBe("max")
+    })
   })
 
   describe("conditions NOT met - should skip", () => {
diff --git a/src/plugin/chat-params.test.ts b/src/plugin/chat-params.test.ts
index 91d194b9e..4abcfbe93 100644
--- a/src/plugin/chat-params.test.ts
+++ b/src/plugin/chat-params.test.ts
@@ -35,4 +35,37 @@ describe("createChatParamsHandler", () => {
     //#then
     expect(called).toBe(true)
   })
+
+  test("passes the original mutable message object to chat.params hooks", async () => {
+    //#given
+    const handler = createChatParamsHandler({
+      anthropicEffort: {
+        "chat.params": async (input) => {
+          input.message.variant = "high"
+        },
+      },
+    })
+
+    const message = { variant: "max" }
+    const input = {
+      sessionID: "ses_chat_params",
+      agent: { name: "sisyphus" },
+      model: { providerID: "opencode", modelID: "claude-sonnet-4-6" },
+      provider: { id: "opencode" },
+      message,
+    }
+
+    const output = {
+      temperature: 0.1,
+      topP: 1,
+      topK: 1,
+      options: {},
+    }
+
+    //#when
+    await handler(input, output)
+
+    //#then
+    expect(message.variant).toBe("high")
+  })
 })
diff --git a/src/plugin/chat-params.ts b/src/plugin/chat-params.ts
index 14ff4ed8e..c4bd5e626 100644
--- a/src/plugin/chat-params.ts
+++ b/src/plugin/chat-params.ts
@@ -6,6 +6,10 @@ export type ChatParamsInput = {
   message: { variant?: string }
 }
 
+type ChatParamsHookInput = ChatParamsInput & {
+  rawMessage?: Record<string, unknown>
+}
+
 export type ChatParamsOutput = {
   temperature?: number
   topP?: number
@@ -17,7 +21,7 @@ function isRecord(value: unknown): value is Record<string, unknown> {
   return typeof value === "object" && value !== null
 }
 
-function buildChatParamsInput(raw: unknown): ChatParamsInput | null {
+function buildChatParamsInput(raw: unknown): ChatParamsHookInput | null {
   if (!isRecord(raw)) return null
 
   const sessionID = raw.sessionID
@@ -56,7 +60,9 @@ function buildChatParamsInput(raw: unknown): ChatParamsInput | null {
     agent: { name: agentName },
     model: { providerID, modelID },
     provider: { id: providerId },
-    message: typeof variant === "string" ? { variant } : {},
+    message,
+    rawMessage: message,
+    ...(typeof variant === "string" ? {} : {}),
   }
 }
 
@@ -69,7 +75,7 @@ function isChatParamsOutput(raw: unknown): raw is ChatParamsOutput {
 }
 
 export function createChatParamsHandler(args: {
-  anthropicEffort: { "chat.params"?: (input: ChatParamsInput, output: ChatParamsOutput) => Promise<void> } | null
+  anthropicEffort: { "chat.params"?: (input: ChatParamsHookInput, output: ChatParamsOutput) => Promise<void> } | null
 }): (input: unknown, output: unknown) => Promise<void> {
   return async (input, output): Promise<void> => {
     const normalizedInput = buildChatParamsInput(input)