fix: cap ai snapshots for tool calls (#763) (thanks @thesash)

src/agents/tools/browser-tool.ts

@@ -44,6 +44,8 @@ const BROWSER_ACT_KINDS = [
 
 type BrowserActKind = (typeof BROWSER_ACT_KINDS)[number];
 
+const DEFAULT_AI_SNAPSHOT_MAX_CHARS = 80_000;
+
 // NOTE: Using a flattened object schema instead of Type.Union([Type.Object(...), ...])
 // because Claude API on Vertex AI rejects nested anyOf schemas as invalid JSON Schema.
 // The discriminator (kind) determines which properties are relevant; runtime validates.
@@ -326,14 +328,19 @@ export function createBrowserTool(opts?: {
               : undefined;
           const maxChars =
             typeof params.maxChars === "number" &&
-            Number.isFinite(params.maxChars)
-              ? params.maxChars
+            Number.isFinite(params.maxChars) &&
+            params.maxChars > 0
+              ? Math.floor(params.maxChars)
+              : undefined;
+          const resolvedMaxChars =
+            format === "ai"
+              ? (maxChars ?? DEFAULT_AI_SNAPSHOT_MAX_CHARS)
               : undefined;
           const snapshot = await browserSnapshot(baseUrl, {
             format,
             targetId,
             limit,
-            maxChars,
+            ...(resolvedMaxChars ? { maxChars: resolvedMaxChars } : {}),
             profile,
           });
           if (snapshot.format === "ai") {

src/browser/pw-tools-core.ts

@@ -10,8 +10,6 @@ import {
 let nextUploadArmId = 0;
 let nextDialogArmId = 0;
 
-const MAX_SNAPSHOT_CHARS = 80_000;
-
 function requireRef(value: unknown): string {
   const ref = typeof value === "string" ? value.trim() : "";
   if (!ref) throw new Error("ref is required");
@@ -44,18 +42,17 @@ export async function snapshotAiViaPlaywright(opts: {
     ),
     track: "response",
   });
+  let snapshot = String(result?.full ?? "");
   const maxChars = opts.maxChars;
   const limit =
     typeof maxChars === "number" && Number.isFinite(maxChars) && maxChars > 0
       ? Math.floor(maxChars)
-      : MAX_SNAPSHOT_CHARS;
-  let snapshot = String(result?.full ?? "");
-  let truncated = false;
-  if (snapshot.length > limit) {
+      : undefined;
+  if (limit && snapshot.length > limit) {
     snapshot = `${snapshot.slice(0, limit)}\n\n[...TRUNCATED - page too large]`;
-    truncated = true;
+    return { snapshot, truncated: true };
   }
-  return truncated ? { snapshot, truncated } : { snapshot };
+  return { snapshot };
 }
 
 export async function clickViaPlaywright(opts: {

src/browser/routes/agent.ts

@@ -567,23 +567,22 @@ export function registerBrowserAgentRoutes(
         ? Number(req.query.maxChars)
         : undefined;
     const limit = Number.isFinite(limitRaw) ? limitRaw : undefined;
-    const maxChars = Number.isFinite(maxCharsRaw) ? maxCharsRaw : undefined;
+    const maxChars =
+      typeof maxCharsRaw === "number" &&
+      Number.isFinite(maxCharsRaw) &&
+      maxCharsRaw > 0
+        ? Math.floor(maxCharsRaw)
+        : undefined;
 
     try {
       const tab = await profileCtx.ensureTabAvailable(targetId || undefined);
       if (format === "ai") {
         const pw = await requirePwAi(res, "ai snapshot");
         if (!pw) return;
-        const resolvedMaxChars =
-          typeof maxChars === "number" && maxChars > 0
-            ? maxChars
-            : typeof limit === "number" && limit > 0
-              ? limit
-              : undefined;
         const snap = await pw.snapshotAiViaPlaywright({
           cdpUrl: profileCtx.profile.cdpUrl,
           targetId: tab.targetId,
-          ...(resolvedMaxChars ? { maxChars: resolvedMaxChars } : {}),
+          ...(maxChars ? { maxChars } : {}),
         });
         return res.json({
           ok: true,