diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index c791aebf97..1528f789ec 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -230,6 +230,17 @@ function normalizeMessages(
       const parts = msg.content
       const first = parts.findIndex((part) => part.type === "tool-call")
       if (first === -1) return [msg]
+      if (
+        parts
+          .slice(first)
+          .some(
+            (part) =>
+              part.type === "reasoning" &&
+              (part.providerOptions?.anthropic?.signature != null ||
+                part.providerOptions?.anthropic?.redactedData != null),
+          )
+      )
+        return [msg]
       if (!parts.slice(first).some((part) => part.type !== "tool-call")) return [msg]
       return [
         { ...msg, content: parts.filter((part) => part.type !== "tool-call") },
diff --git a/packages/opencode/src/session/message-v2.ts b/packages/opencode/src/session/message-v2.ts
index c7d8594553..2884c4cf86 100644
--- a/packages/opencode/src/session/message-v2.ts
+++ b/packages/opencode/src/session/message-v2.ts
@@ -285,13 +285,7 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
         if (part.type !== "reasoning") return false
         return part.metadata?.anthropic?.signature != null
       })
-      const splitAnthropicSteps = ["@ai-sdk/anthropic", "@ai-sdk/google-vertex/anthropic"].includes(model.api.npm)
-      let hasClientToolCall = false
       for (const part of msg.parts) {
-        if (splitAnthropicSteps && hasClientToolCall && (part.type === "text" || part.type === "reasoning")) {
-          assistantMessage.parts.push({ type: "step-start" })
-          hasClientToolCall = false
-        }
         if (part.type === "text") {
           const text = part.text === "" && hasSignedReasoning ? " " : part.text
           assistantMessage.parts.push({
@@ -300,14 +294,11 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
             ...(differentModel ? {} : { providerMetadata: part.metadata }),
           })
         }
-        if (part.type === "step-start") {
+        if (part.type === "step-start")
           assistantMessage.parts.push({
             type: "step-start",
           })
-          hasClientToolCall = false
-        }
         if (part.type === "tool") {
-          if (part.metadata?.providerExecuted !== true) hasClientToolCall = true
           toolNames.add(part.tool)
           if (part.state.status === "completed") {
             const outputText = part.state.time.compacted
diff --git a/packages/opencode/test/provider/transform.test.ts b/packages/opencode/test/provider/transform.test.ts
index 7fb22ddf57..e456d1075a 100644
--- a/packages/opencode/test/provider/transform.test.ts
+++ b/packages/opencode/test/provider/transform.test.ts
@@ -1680,6 +1680,25 @@ describe("ProviderTransform.message - anthropic empty content filtering", () =>
     ])
   })
 
+  test("leaves signed anthropic reasoning after tool calls unchanged", () => {
+    const msgs = [
+      {
+        role: "assistant",
+        content: [
+          { type: "reasoning", text: "First thought", providerOptions: { anthropic: { signature: "sig-1" } } },
+          { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+          { type: "reasoning", text: "Second thought", providerOptions: { anthropic: { signature: "sig-2" } } },
+          { type: "tool-call", toolCallId: "toolu_2", toolName: "glob", input: { pattern: "**/*.pdf" } },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, anthropicModel, {}) as any[]
+
+    expect(result).toHaveLength(1)
+    expect(result[0].content).toMatchObject(msgs[0].content)
+  })
+
   test("splits vertex anthropic assistant messages when text trails tool calls", () => {
     const model = {
       ...anthropicModel,
diff --git a/packages/opencode/test/session/message-v2.test.ts b/packages/opencode/test/session/message-v2.test.ts
index 6556dfe8a6..75850e59fb 100644
--- a/packages/opencode/test/session/message-v2.test.ts
+++ b/packages/opencode/test/session/message-v2.test.ts
@@ -1150,113 +1150,6 @@ describe("session.message-v2.toModelMessage", () => {
     ])
   })
 
-  test("splits anthropic replay when text follows a completed tool call", async () => {
-    const anthropicModel: Provider.Model = {
-      ...model,
-      id: ProviderV2.ModelID.make("claude-opus-4-8"),
-      providerID: ProviderV2.ID.make("anthropic"),
-      api: { id: "claude-opus-4-8", url: "https://api.anthropic.com", npm: "@ai-sdk/anthropic" },
-    }
-    const assistantID = "m-assistant"
-
-    const result = await MessageV2.toModelMessages(
-      [
-        {
-          info: assistantInfo(assistantID, "m-parent", undefined, {
-            providerID: anthropicModel.providerID,
-            modelID: anthropicModel.id,
-          }),
-          parts: [
-            { ...basePart(assistantID, "p1"), type: "step-start" },
-            {
-              ...basePart(assistantID, "p2"),
-              type: "tool",
-              callID: "toolu_1",
-              tool: "read",
-              state: {
-                status: "completed",
-                input: { filePath: "/root" },
-                output: "ok",
-                title: "Read",
-                metadata: {},
-                time: { start: 0, end: 1 },
-              },
-            },
-            { ...basePart(assistantID, "p3"), type: "text", text: "done" },
-          ] as SessionLegacy.Part[],
-        },
-      ],
-      anthropicModel,
-    )
-
-    expect(result.map((message) => message.role)).toEqual(["assistant", "tool", "assistant"])
-    expect(result[0].content).toMatchObject([{ type: "tool-call", toolCallId: "toolu_1" }])
-    expect(result[2].content).toMatchObject([{ type: "text", text: "done" }])
-  })
-
-  test("splits anthropic replay without moving signed reasoning", async () => {
-    const anthropicModel: Provider.Model = {
-      ...model,
-      id: ProviderV2.ModelID.make("claude-opus-4-8"),
-      providerID: ProviderV2.ID.make("anthropic"),
-      api: { id: "claude-opus-4-8", url: "https://api.anthropic.com", npm: "@ai-sdk/anthropic" },
-    }
-    const assistantID = "m-assistant"
-    const tool = (id: string, callID: string) => ({
-      ...basePart(assistantID, id),
-      type: "tool" as const,
-      callID,
-      tool: "bash",
-      state: {
-        status: "completed" as const,
-        input: { command: "pwd" },
-        output: "ok",
-        title: "Bash",
-        metadata: {},
-        time: { start: 0, end: 1 },
-      },
-    })
-
-    const result = await MessageV2.toModelMessages(
-      [
-        {
-          info: assistantInfo(assistantID, "m-parent", undefined, {
-            providerID: anthropicModel.providerID,
-            modelID: anthropicModel.id,
-          }),
-          parts: [
-            { ...basePart(assistantID, "p1"), type: "step-start" },
-            {
-              ...basePart(assistantID, "p2"),
-              type: "reasoning",
-              text: "one",
-              metadata: { anthropic: { signature: "sig-1" } },
-            },
-            tool("p3", "toolu_1"),
-            {
-              ...basePart(assistantID, "p4"),
-              type: "reasoning",
-              text: "two",
-              metadata: { anthropic: { signature: "sig-2" } },
-            },
-            tool("p5", "toolu_2"),
-          ] as SessionLegacy.Part[],
-        },
-      ],
-      anthropicModel,
-    )
-
-    expect(result.map((message) => message.role)).toEqual(["assistant", "tool", "assistant", "tool"])
-    expect(result[0].content).toMatchObject([
-      { type: "reasoning", text: "one", providerOptions: { anthropic: { signature: "sig-1" } } },
-      { type: "tool-call", toolCallId: "toolu_1" },
-    ])
-    expect(result[2].content).toMatchObject([
-      { type: "reasoning", text: "two", providerOptions: { anthropic: { signature: "sig-2" } } },
-      { type: "tool-call", toolCallId: "toolu_2" },
-    ])
-  })
-
   test("drops messages that only contain step-start parts", async () => {
     const assistantID = "m-assistant"