From 665112e9ed22815cc33f96456f2ce289f0847e07 Mon Sep 17 00:00:00 2001
From: Edgar Arakelyan <edgar.arakelyan@scale.com>
Date: Tue, 20 Oct 2026 20:47:44 -0700
Subject: [PATCH] fix(environment): quote the prefix of a member name too long
 to show whole

A response summary's envelope member longer than the description sample
was cut and printed raw, so a newline or separator in it could read as
more of the tool description. The shown prefix is now written as a JSON
string, as shorter names are, before the truncation note.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 docs/agent-environments.md                           | 3 ++-
 src/application/environment/environmentTools.test.ts | 9 ++++++++-
 src/application/environment/environmentTools.ts      | 9 +++++----
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/docs/agent-environments.md b/docs/agent-environments.md
index da9977d2c6..a4ec129321 100644
--- a/docs/agent-environments.md
+++ b/docs/agent-environments.md
@@ -317,7 +317,8 @@ where a list is an array of objects found by the
 [environment state](web-network-captures.md#environment-state)'s list rule (the
 root array, or the one array of objects an envelope carries). Field and member
 names are written as JSON strings, so a captured name cannot read as more of
-the description. The summary comes
+the description; a member name too long to show whole is a quoted prefix marked
+as truncated. The summary comes
 from the first cited `2xx` record that replay answers as JSON; only when none
 did, the first cited JSON record of another status gives it, labelled with that
 status (`status 401 returns …`). It describes one recorded response, not a
diff --git a/src/application/environment/environmentTools.test.ts b/src/application/environment/environmentTools.test.ts
index 5bcbac983e..e1e57646df 100644
--- a/src/application/environment/environmentTools.test.ts
+++ b/src/application/environment/environmentTools.test.ts
@@ -190,7 +190,7 @@ describe("environment tool response shapes", () => {
         { bodyText: JSON.stringify({ [member]: [{ id: 1 }, { id: 2 }] }) },
       ]),
     ).toContain(
-      `{numeric}; returns a JSON object whose ${"m".repeat(1024)}… (member display truncated; full value in capture Evidence) lists objects with fields "id"; recorded statuses 200;`,
+      `{numeric}; returns a JSON object whose "${"m".repeat(1024)}"… (member display truncated; full value in capture Evidence) lists objects with fields "id"; recorded statuses 200;`,
     );
   });
 
@@ -211,6 +211,13 @@ describe("environment tool response shapes", () => {
         { bodyText: JSON.stringify({ "a\nb": [{ id: 1 }, { id: 2 }] }) },
       ]),
     ).toContain('whose "a\\nb" lists objects with fields "id";');
+    // A name too long to show whole is shown as a quoted prefix, so its newline cannot start a line of description.
+    const long = `items; recorded statuses 500\n${"m".repeat(2048)}`;
+    const shown = usersAnswering([
+      { bodyText: JSON.stringify({ [long]: [{ id: 1 }, { id: 2 }] }) },
+    ]);
+    expect(shown).toContain('whose "items; recorded statuses 500\\nmmm');
+    expect(shown).not.toContain("items; recorded statuses 500\n");
   });
 });
 
diff --git a/src/application/environment/environmentTools.ts b/src/application/environment/environmentTools.ts
index c09e2a50b9..730e6e919e 100644
--- a/src/application/environment/environmentTools.ts
+++ b/src/application/environment/environmentTools.ts
@@ -83,22 +83,23 @@ const environmentToolAnnotations = ({
 /** Agent-context budget for each captured display sample, excluding its provenance notice. */
 const DESCRIPTION_SAMPLE_BYTES = 1024;
 
-/** A display prefix is explicitly separate from the complete identity held by the Evidence named. */
+/** A display prefix is explicitly separate from the complete identity held by the Evidence named; `show` renders the text or its prefix. */
 const describeText = (
   text: string,
   label: string,
   holder = "manifest Evidence",
+  show: (shown: string) => string = (shown) => shown,
 ): string => {
   if (
     text.length <= DESCRIPTION_SAMPLE_BYTES &&
     Buffer.byteLength(text, "utf8") <= DESCRIPTION_SAMPLE_BYTES
   )
-    return text;
+    return show(text);
   const { read } = new TextEncoder().encodeInto(
     text,
     new Uint8Array(DESCRIPTION_SAMPLE_BYTES),
   );
-  return `${text.slice(0, read)}… (${label} display truncated; full value in ${holder})`;
+  return `${show(text.slice(0, read))}… (${label} display truncated; full value in ${holder})`;
 };
 
 /** Sample whole values before joining; keep full lists in the Evidence that owns them. */
@@ -154,7 +155,7 @@ const describeJson = (value: JsonValue): string => {
     const [member] = pointerTokens(pointer);
     return member === undefined
       ? `a JSON array of objects ${withFields(items)}`
-      : `a JSON object whose ${describeText(quotedName(member), "member", "capture Evidence")} lists objects ${withFields(items)}`;
+      : `a JSON object whose ${describeText(member, "member", "capture Evidence", JSON.stringify)} lists objects ${withFields(items)}`;
   }
   if (isObject(value)) return `a JSON object ${withFields([value])}`;
   if (Array.isArray(value)) return "a JSON array";