diff --git a/src/agents/clawdis-tools.ts b/src/agents/clawdis-tools.ts
index 8ff19fcb4..c3fcc5f02 100644
--- a/src/agents/clawdis-tools.ts
+++ b/src/agents/clawdis-tools.ts
@@ -77,6 +77,16 @@ type StringParamOptions = {
   label?: string;
 };
 
+function readStringParam(
+  params: Record<string, unknown>,
+  key: string,
+  options: StringParamOptions & { required: true },
+): string;
+function readStringParam(
+  params: Record<string, unknown>,
+  key: string,
+  options?: StringParamOptions,
+): string | undefined;
 function readStringParam(
   params: Record<string, unknown>,
   key: string,
@@ -783,7 +793,12 @@ function createCanvasTool(): AnyAgentTool {
             payload?: { result?: string };
           };
           const result = raw?.payload?.result;
-          if (result) return { content: [{ type: "text", text: result }] };
+          if (result) {
+            return {
+              content: [{ type: "text", text: result }],
+              details: { result },
+            };
+          }
           return jsonResult({ ok: true });
         }
         case "snapshot": {
diff --git a/src/agents/models-config.ts b/src/agents/models-config.ts
index 63c1ebcbe..1a0995d26 100644
--- a/src/agents/models-config.ts
+++ b/src/agents/models-config.ts
@@ -15,7 +15,7 @@ function isRecord(value: unknown): value is Record<string, unknown> {
   return Boolean(value && typeof value === "object" && !Array.isArray(value));
 }
 
-async function readJson(pathname: string): Promise<unknown | null> {
+async function readJson(pathname: string): Promise<unknown> {
   try {
     const raw = await fs.readFile(pathname, "utf8");
     return JSON.parse(raw) as unknown;
diff --git a/src/browser/routes/agent.ts b/src/browser/routes/agent.ts
index 66a1ff883..c88775067 100644
--- a/src/browser/routes/agent.ts
+++ b/src/browser/routes/agent.ts
@@ -251,9 +251,11 @@ export function registerBrowserAgentRoutes(
                 typeof rec.value === "boolean"
                   ? rec.value
                   : undefined;
-              return { ref, type, value };
+              const parsed: BrowserFormField =
+                value === undefined ? { ref, type } : { ref, type, value };
+              return parsed;
             })
-            .filter((field): field is BrowserFormField => Boolean(field));
+            .filter((field): field is BrowserFormField => field !== null);
           if (!fields.length) return jsonError(res, 400, "fields are required");
           await pw.fillFormViaPlaywright({
             cdpPort,
diff --git a/src/cli/browser-cli-actions-input.ts b/src/cli/browser-cli-actions-input.ts
index 59fc57479..fedd73b2e 100644
--- a/src/cli/browser-cli-actions-input.ts
+++ b/src/cli/browser-cli-actions-input.ts
@@ -6,6 +6,7 @@ import {
   browserArmFileChooser,
   browserNavigate,
 } from "../browser/client-actions.js";
+import type { BrowserFormField } from "../browser/client-actions-core.js";
 import { danger } from "../globals.js";
 import { defaultRuntime } from "../runtime.js";
 import type { BrowserParentOpts } from "./browser-cli-shared.js";
@@ -18,14 +19,37 @@ async function readFile(path: string): Promise<string> {
 async function readFields(opts: {
   fields?: string;
   fieldsFile?: string;
-}): Promise<Array<Record<string, unknown>>> {
+}): Promise<BrowserFormField[]> {
   const payload = opts.fieldsFile
     ? await readFile(opts.fieldsFile)
     : (opts.fields ?? "");
   if (!payload.trim()) throw new Error("fields are required");
   const parsed = JSON.parse(payload) as unknown;
   if (!Array.isArray(parsed)) throw new Error("fields must be an array");
-  return parsed as Array<Record<string, unknown>>;
+  return parsed.map((entry, index) => {
+    if (!entry || typeof entry !== "object") {
+      throw new Error(`fields[${index}] must be an object`);
+    }
+    const rec = entry as Record<string, unknown>;
+    const ref = typeof rec.ref === "string" ? rec.ref.trim() : "";
+    const type = typeof rec.type === "string" ? rec.type.trim() : "";
+    if (!ref || !type) {
+      throw new Error(`fields[${index}] must include ref and type`);
+    }
+    if (
+      typeof rec.value === "string" ||
+      typeof rec.value === "number" ||
+      typeof rec.value === "boolean"
+    ) {
+      return { ref, type, value: rec.value };
+    }
+    if (rec.value === undefined || rec.value === null) {
+      return { ref, type };
+    }
+    throw new Error(
+      `fields[${index}].value must be string, number, boolean, or null`,
+    );
+  });
 }
 
 export function registerBrowserActionInputCommands(
diff --git a/src/infra/ws.ts b/src/infra/ws.ts
index a5986c269..99d753780 100644
--- a/src/infra/ws.ts
+++ b/src/infra/ws.ts
@@ -9,5 +9,8 @@ export function rawDataToString(
   if (typeof data === "string") return data;
   if (Buffer.isBuffer(data)) return data.toString(encoding);
   if (Array.isArray(data)) return Buffer.concat(data).toString(encoding);
-  return Buffer.from(data as ArrayBuffer | ArrayBufferView).toString(encoding);
+  if (data instanceof ArrayBuffer) {
+    return Buffer.from(data).toString(encoding);
+  }
+  return Buffer.from(String(data)).toString(encoding);
 }