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Cap tool results at 20KB; restore full vault text on disk with grep-first steering #27

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teddy-paris merged 1 commit into from
Jul 13, 2026
Merged

Cap tool results at 20KB; restore full vault text on disk with grep-first steering #27

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8 changes: 7 additions & 1 deletion packages/coding-agent/src/core/tools/truncate.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,13 @@
*/

export const DEFAULT_MAX_LINES = 2000;
export const DEFAULT_MAX_BYTES = 50 * 1024; // 50KB
// 20KB per tool result: bounds how much any single read/find/grep can drag
// into billed model context (each result rides along with every subsequent
// call in the session). Offset/limit pagination remains available for more —
// the truncation notices tell the model how to continue. Lowered from the
// upstream 50KB after a production session accumulated ~450KB of context via
// nine max-size reads of a legal document (CD-1284 follow-up).
export const DEFAULT_MAX_BYTES = 20 * 1024; // 20KB
export const GREP_MAX_LINE_LENGTH = 500; // Max chars per grep match line

export interface TruncationResult {
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31 changes: 14 additions & 17 deletions packages/coding-agent/src/linc/casedev-vault-api.ts
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Expand Up @@ -48,10 +48,6 @@ export interface CaseDevVaultReadTextParams {
filename?: string;
}

export const CASEDEV_VAULT_TEXT_MAX_CHARS = 10_000;
export const CASEDEV_VAULT_TEXT_TRUNCATION_WARNING =
"this document is too long to view in full. Use targeted vault searches to retrieve more context";

export interface CaseDevVaultSearchParams {
query: string;
method?: "hybrid" | "global" | "entity" | "fast" | "vector" | "graph" | "local";
Expand Down Expand Up @@ -287,24 +283,25 @@ export async function readCaseDevVaultObjectText(
const filename = baseName.endsWith(".txt") ? baseName : `${baseName}.txt`;
await mkdir(params.outDir, { recursive: true });
const outputPath = safeOutputPath(params.outDir, filename);
const truncated = text.length > CASEDEV_VAULT_TEXT_MAX_CHARS;
const visibleTextLimit = truncated
? CASEDEV_VAULT_TEXT_MAX_CHARS - CASEDEV_VAULT_TEXT_TRUNCATION_WARNING.length - 2
: CASEDEV_VAULT_TEXT_MAX_CHARS;
const visibleText = text.slice(0, visibleTextLimit);
const output = truncated ? `${CASEDEV_VAULT_TEXT_TRUNCATION_WARNING}\n\n${visibleText}` : visibleText;
await writeFile(outputPath, output, "utf8");
const pageMarkers = (visibleText.match(/^--- Page \d+ ---$/gm) ?? []).length;
// The full text is written to disk deliberately: files on disk are outside
// model context and cost nothing, and grep over the complete text is what
// makes comprehensive large-document analysis possible. Context safety is
// enforced where the cost is — per-result output caps on read/grep/bash —
// not by truncating the file (which silently breaks any search past the
// cut and does nothing for other large files in the workspace).
await writeFile(outputPath, text, "utf8");
const pageMarkers = (text.match(/^--- Page \d+ ---$/gm) ?? []).length;
const usage =
'Locate content with `grep -n "pattern" <path>` and read only narrow line ranges around matches. Never page through the full text — it is too large for the conversation.';
return {
objectId: params.objectId,
path: outputPath,
chars: text.length,
pageMarkers,
note: truncated
? CASEDEV_VAULT_TEXT_TRUNCATION_WARNING
: pageMarkers > 0
? "Text contains --- Page N --- markers; cite findings by those page numbers."
: "This document has no page markers; cite findings by section or heading.",
note:
(pageMarkers > 0
? "Text contains --- Page N --- markers; cite findings by those page numbers. "
: "This document has no page markers; cite findings by section or heading. ") + usage,
};
}

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4 changes: 2 additions & 2 deletions packages/coding-agent/src/linc/casedev-vault-tools.ts
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Expand Up @@ -351,7 +351,7 @@ export function createCaseDevVaultTools(): ToolDefinition[] {
name: "casedev_vault_read_text",
label: "case.dev vault read text",
description:
"Write up to the first 10,000 characters of an ingested Case.dev vault object's extracted text into the workspace as a .txt file. Use targeted vault searches for additional context.",
"Write the full extracted text of an ingested Case.dev vault object into the workspace as a .txt file, page-numbered when the source is paginated. Locate content with grep -n and read only narrow line ranges around matches; never page the full text into the conversation.",
promptSnippet: "Read a bounded excerpt of a Case.dev vault object's extracted text into the workspace.",
parameters: vaultReadTextSchema,
async execute(_toolCallId, params: VaultReadTextInput, signal, _onUpdate, ctx) {
Expand Down Expand Up @@ -439,7 +439,7 @@ export function createCaseDevVaultTools(): ToolDefinition[] {
name: "vault_read_text",
label: "vault_read_text",
description:
"Write up to the first 10,000 characters of an ingested matter document's extracted text into the workspace as a .txt file. Use targeted vault searches for additional context.",
"Write the full extracted text of an ingested matter document into the workspace as a .txt file, page-numbered when the source is paginated. The right tool for comprehensively analyzing document content at any size: locate content with grep -n and read only narrow line ranges around matches; never page the full text into the conversation.",

@vercel vercel Bot Jul 13, 2026

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Stale promptSnippet/promptGuidelines strings for the vault read-text tools contradict the updated full-text/grep-first tool descriptions, injecting conflicting guidance into the system prompt.

Fix on Vercel

promptSnippet: "Read a bounded excerpt of a matter document's extracted text into the workspace",
promptGuidelines: [
"Originals from vault_download are raw bytes and often scanned images; use vault_read_text for a bounded excerpt and targeted vault searches for additional context.",
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18 changes: 7 additions & 11 deletions packages/coding-agent/test/casedev-vault-api.test.ts
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Expand Up @@ -4,8 +4,6 @@ import { join } from "node:path";
import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
import type { ExtensionContext } from "../src/core/extensions/types.ts";
import {
CASEDEV_VAULT_TEXT_MAX_CHARS,
CASEDEV_VAULT_TEXT_TRUNCATION_WARNING,
downloadCaseDevVaultObject,
listCaseDevVaults,
readCaseDevVaultObjectText,
Expand Down Expand Up @@ -232,8 +230,8 @@ describe("Case.dev vault REST API helper", () => {
});
});

it("limits extracted object text and prepends targeted-search guidance", async () => {
const text = "x".repeat(CASEDEV_VAULT_TEXT_MAX_CHARS + 1);
it("writes large extracted text to disk in full with grep-first guidance", async () => {
const text = "x".repeat(50_000);
vi.stubGlobal(
"fetch",
vi.fn(async () => jsonResponse({ text, metadata: { filename: "long.pdf" } })),
Expand All @@ -248,15 +246,13 @@ describe("Case.dev vault REST API helper", () => {
expect(result).toMatchObject({
objectId: "obj-long",
chars: text.length,
note: CASEDEV_VAULT_TEXT_TRUNCATION_WARNING,
});
expect(result.note).toContain("grep -n");
expect(result.note).toContain("Never page through the full text");
// The on-disk file is complete: disk is outside model context and free,
// and grep over the whole text is what enables large-document analysis.
const written = await readFile(join(cwd, "long.pdf.txt"), "utf-8");
expect(written).toHaveLength(CASEDEV_VAULT_TEXT_MAX_CHARS);
expect(written).toBe(
`${CASEDEV_VAULT_TEXT_TRUNCATION_WARNING}\n\n${"x".repeat(
CASEDEV_VAULT_TEXT_MAX_CHARS - CASEDEV_VAULT_TEXT_TRUNCATION_WARNING.length - 2,
)}`,
);
expect(written).toBe(text);
});

it("rejects text reads for objects with no extracted text", async () => {
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2 changes: 1 addition & 1 deletion packages/coding-agent/test/tools.test.ts
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Expand Up @@ -84,7 +84,7 @@ describe("Coding Agent Tools", () => {

it("should truncate when byte limit exceeded", async () => {
const testFile = join(testDir, "large-bytes.txt");
// Create file that exceeds 50KB byte limit but has fewer than 2000 lines
// Create file that exceeds the byte limit but has fewer than 2000 lines
const lines = Array.from({ length: 500 }, (_, i) => `Line ${i + 1}: ${"x".repeat(200)}`);
writeFileSync(testFile, lines.join("\n"));

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