fix: extend empty-text gate to Bedrock and Vertex signature namespaces

The hasSignedReasoning gate introduced in this PR only matches Anthropic's

direct-API signature path (metadata.anthropic.signature). When Claude is

hosted on AWS Bedrock or GCP Vertex AI, the reasoning part metadata stores

the signature under metadata.bedrock.signature / metadata.vertex.signature

respectively. The gate never fires for those providers, so empty text parts

between signed reasoning blocks are not substituted with a space, and

Anthropic/Bedrock/Vertex still reject the compacted message with:

  messages.N.content.M: 'thinking' or 'redacted_thinking' blocks in the

  latest assistant message cannot be modified

Extend the check to match signatures under any of the three provider

namespaces. Adds two tests covering the Bedrock and Vertex paths.

Author: omer-koren

packages/opencode/src/session/message-v2.ts

@@ -854,11 +854,17 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
         role: "assistant",
         parts: [],
       }
-      // Substitute a space for empty text between signed Anthropic reasoning
+      // Substitute a space for empty text between signed reasoning
       // blocks to keep thinking block positions (and signatures) valid without
       // triggering Anthropic's empty-content rejection or the AI SDK's filter.
+      // Signatures live under the provider-namespaced metadata key: anthropic
+      // (direct API), bedrock (AWS Bedrock), or vertex (GCP Vertex AI).
       const hasSignedReasoning = msg.parts.some(
-        (p) => p.type === "reasoning" && (p.metadata as any)?.anthropic?.signature != null,
+        (p) =>
+          p.type === "reasoning" &&
+          ((p.metadata as any)?.anthropic?.signature != null ||
+            (p.metadata as any)?.bedrock?.signature != null ||
+            (p.metadata as any)?.vertex?.signature != null),
       )
       for (const part of msg.parts) {
         if (part.type === "text") {

packages/opencode/test/session/message-v2.test.ts

@@ -1126,6 +1126,58 @@ describe("session.message-v2.toModelMessage", () => {
     expect((result[1].content as any[]).find((p) => p.type === "text").text).toBe("the answer")
   })
 
+  test("substitutes space for empty text when reasoning signature is under 'bedrock' namespace", async () => {
+    // AWS Bedrock hosts Anthropic Claude but stores signatures under metadata.bedrock
+    const assistantID = "m-assistant-bedrock"
+    const input: MessageV2.WithParts[] = [
+      {
+        info: assistantInfo(assistantID, "m-parent"),
+        parts: [
+          {
+            ...basePart(assistantID, "p1"),
+            type: "reasoning",
+            text: "thinking-bedrock",
+            metadata: { bedrock: { signature: "bedrock-sig" } },
+          },
+          { ...basePart(assistantID, "p2"), type: "text", text: "" },
+          { ...basePart(assistantID, "p3"), type: "text", text: "answer" },
+        ] as MessageV2.Part[],
+      },
+    ]
+
+    const result = await MessageV2.toModelMessages(input, model)
+
+    expect(result).toHaveLength(1)
+    const texts = (result[0].content as any[]).filter((p) => p.type === "text")
+    expect(texts.map((t) => t.text)).toStrictEqual([" ", "answer"])
+  })
+
+  test("substitutes space for empty text when reasoning signature is under 'vertex' namespace", async () => {
+    // GCP Vertex AI hosts Anthropic Claude but stores signatures under metadata.vertex
+    const assistantID = "m-assistant-vertex"
+    const input: MessageV2.WithParts[] = [
+      {
+        info: assistantInfo(assistantID, "m-parent"),
+        parts: [
+          {
+            ...basePart(assistantID, "p1"),
+            type: "reasoning",
+            text: "thinking-vertex",
+            metadata: { vertex: { signature: "vertex-sig" } },
+          },
+          { ...basePart(assistantID, "p2"), type: "text", text: "" },
+          { ...basePart(assistantID, "p3"), type: "text", text: "answer" },
+        ] as MessageV2.Part[],
+      },
+    ]
+
+    const result = await MessageV2.toModelMessages(input, model)
+
+    expect(result).toHaveLength(1)
+    const texts = (result[0].content as any[]).filter((p) => p.type === "text")
+    expect(texts.map((t) => t.text)).toStrictEqual([" ", "answer"])
+  })
+
   test("leaves empty text alone when reasoning has no Anthropic signature", async () => {
     // Non-Anthropic providers' reasoning doesn't position-validate, so empty text
     // should be filtered normally rather than substituted.