diff --git a/packages/opencode/src/tool/edit.ts b/packages/opencode/src/tool/edit.ts
index 9505dd9eab96..3711a9234105 100644
--- a/packages/opencode/src/tool/edit.ts
+++ b/packages/opencode/src/tool/edit.ts
@@ -38,8 +38,18 @@ export const EditTool = Tool.define("edit", {
   description: DESCRIPTION,
   parameters: z.object({
     filePath: z.string().describe("The absolute path to the file to modify"),
-    oldString: z.string().describe("The text to replace"),
-    newString: z.string().describe("The text to replace it with (must be different from oldString)"),
+    oldString: z
+      .preprocess(
+        (v) => (v !== null && typeof v === "object" ? JSON.stringify(v, null, 2) : v),
+        z.string(),
+      )
+      .describe("The text to replace"),
+    newString: z
+      .preprocess(
+        (v) => (v !== null && typeof v === "object" ? JSON.stringify(v, null, 2) : v),
+        z.string(),
+      )
+      .describe("The text to replace it with (must be different from oldString)"),
     replaceAll: z.boolean().optional().describe("Replace all occurrences of oldString (default false)"),
   }),
   async execute(params, ctx) {
diff --git a/packages/opencode/src/tool/write.ts b/packages/opencode/src/tool/write.ts
index 6b134e5253de..aa331624d386 100644
--- a/packages/opencode/src/tool/write.ts
+++ b/packages/opencode/src/tool/write.ts
@@ -20,8 +20,13 @@ const MAX_PROJECT_DIAGNOSTICS_FILES = 5
 export const WriteTool = Tool.define("write", {
   description: DESCRIPTION,
   parameters: z.object({
-    content: z.string().describe("The content to write to the file"),
     filePath: z.string().describe("The absolute path to the file to write (must be absolute, not relative)"),
+    content: z
+      .preprocess(
+        (v) => (v !== null && typeof v === "object" ? JSON.stringify(v, null, 2) : v),
+        z.string(),
+      )
+      .describe("The content to write to the file"),
   }),
   async execute(params, ctx) {
     const filepath = path.isAbsolute(params.filePath) ? params.filePath : path.join(Instance.directory, params.filePath)