Merge remote-tracking branch 'origin/master' into simpl-d-fs-write-only

# Conflicts:
#	docs/rfc/implemented/simplification/2026-07-04-prune-write-only-fs-surface.md
#	packages/fs/fs-local/src/fsio.ts

packages/fs/tool-fs/src/index.ts

@@ -23,11 +23,14 @@
  */
 
 import type { Context } from 'cordis'
-import { applyReadTool } from './read.ts'
+import z from 'schemastery'
+import { applyReadTool, READ_LIMIT, STREAM_MIN_SIZE } from './read.ts'
 import { applyWriteTool } from './write.ts'
 import { applyEditTool } from './edit.ts'
+import { READ_MAX_BYTES, READ_MAX_LINE_LENGTH } from './read-render.ts'
 
 export { READ_LIMIT, STREAM_MIN_SIZE, applyReadTool, parseReadArgs } from './read.ts'
+export type { ReadToolCaps } from './read.ts'
 export { applyWriteTool, formatWriteOutput, parseWriteArgs } from './write.ts'
 export { applyEditTool, formatEditOutput, parseEditArgs } from './edit.ts'
 export { READ_MAX_BYTES, READ_MAX_LINE_LENGTH, buildWindow, formatReadOutput } from './read-render.ts'
@@ -41,9 +44,49 @@ export const name = 'tool-fs'
 /** Services required by the filesystem tool suite. */
 export const inject = ['tools', 'fs', 'systemPrompt']
 
+/** Plugin config (all optional — `Config` supplies the defaults). */
+export interface Config {
+  /** Default and maximum number of lines returned by one `read` call. */
+  readLimit?: number
+  /** Maximum characters returned for a single line before truncation. */
+  readMaxLineLength?: number
+  /** Maximum bytes returned for the selected lines of one `read` call. */
+  readMaxBytes?: number
+  /** Files at or above this size stream instead of loading whole into memory. */
+  readStreamMinSize?: number
+}
+
+export const Config: z<Config> = z.object({
+  readLimit: z.number().default(READ_LIMIT),
+  readMaxLineLength: z.number().default(READ_MAX_LINE_LENGTH),
+  readMaxBytes: z.number().default(READ_MAX_BYTES),
+  readStreamMinSize: z.number().default(STREAM_MIN_SIZE),
+})
+
+/** The shape after schemastery applied the defaults. */
+type ResolvedConfig = Required<Config>
+
+/** Every read cap counts lines/chars/bytes — a positive integer, or windowing arithmetic misbehaves silently. */
+function assertPositiveInteger(name: string, value: number): void {
+  if (!Number.isInteger(value) || value < 1) {
+    throw new Error(`tool-fs: ${name} must be a positive integer`)
+  }
+}
+
 /** Register the full `read`/`write`/`edit` filesystem tool suite. */
-export function apply(ctx: Context): void {
-  applyReadTool(ctx)
+export function apply(ctx: Context, config: Config): void {
+  // schemastery (Config) has already filled every defaulted field.
+  const resolved = config as ResolvedConfig
+  assertPositiveInteger('readLimit', resolved.readLimit)
+  assertPositiveInteger('readMaxLineLength', resolved.readMaxLineLength)
+  assertPositiveInteger('readMaxBytes', resolved.readMaxBytes)
+  assertPositiveInteger('readStreamMinSize', resolved.readStreamMinSize)
+  applyReadTool(ctx, {
+    limit: resolved.readLimit,
+    maxLineLength: resolved.readMaxLineLength,
+    maxBytes: resolved.readMaxBytes,
+    streamMinSize: resolved.readStreamMinSize,
+  })
   applyWriteTool(ctx)
   applyEditTool(ctx)
 }

packages/fs/tool-fs/src/read-render.ts

@@ -18,21 +18,22 @@
 
 import { FsError } from '@deepseek-ai/dsh-fs'
 
-/** Maximum characters returned for a single line. */
+/** Default maximum characters returned for a single line (the `readMaxLineLength` config). */
 export const READ_MAX_LINE_LENGTH = 2000
 
-/** Maximum bytes returned for selected file lines. */
+/** Default maximum bytes returned for selected file lines (the `readMaxBytes` config). */
 export const READ_MAX_BYTES = 50 * 1024
 
-const READ_MAX_LINE_SUFFIX = `... (line truncated to ${READ_MAX_LINE_LENGTH} chars)`
-const LINE_BUFFER_CAP = READ_MAX_LINE_LENGTH + 1
-
 /** Resolved read window. The consumer applies its defaults/caps before calling. */
 export interface ReadWindow {
   /** 1-based first line to return. */
   offset: number
   /** Maximum number of lines to return. */
   limit: number
+  /** Maximum characters returned for a single line; overflow is truncated with a suffix. */
+  maxLineLength: number
+  /** Maximum bytes of selected output; overflow stops the scan and marks `truncatedByBytes`. */
+  maxBytes: number
 }
 
 /** One line returned from a text file. */
@@ -77,8 +78,8 @@ function newAccumulator(): WindowAccumulator {
   return { lines: [], totalLines: 0, outputBytes: 0, truncatedByBytes: false, done: false }
 }
 
-function truncateLine(line: string): string {
-  return line.length > READ_MAX_LINE_LENGTH ? `${line.substring(0, READ_MAX_LINE_LENGTH)}${READ_MAX_LINE_SUFFIX}` : line
+function truncateLine(line: string, maxLineLength: number): string {
+  return line.length > maxLineLength ? `${line.substring(0, maxLineLength)}... (line truncated to ${maxLineLength} chars)` : line
 }
 
 function lineByteSize(line: string, currentLineCount: number): number {
@@ -89,9 +90,9 @@ function consumeLine(acc: WindowAccumulator, rawLine: string, request: ReadWindo
   acc.totalLines += 1
   if (acc.totalLines < request.offset || acc.lines.length >= request.limit) return
 
-  const text = truncateLine(rawLine)
+  const text = truncateLine(rawLine, request.maxLineLength)
   const bytes = lineByteSize(text, acc.lines.length)
-  if (acc.outputBytes + bytes > READ_MAX_BYTES) {
+  if (acc.outputBytes + bytes > request.maxBytes) {
     acc.truncatedByBytes = true
     acc.done = true
     return
@@ -116,7 +117,7 @@ function finish(acc: WindowAccumulator, request: ReadWindow, displayPath: string
  * Accepts an `AsyncIterable<string>` (a chunked `streamText`) or an
  * `Iterable<string>` (a whole-file `readText` wrapped as `[text]`), so one code
  * path serves both. Scans for newlines with a capped line buffer (a newline-free
- * giant line is truncated, never buffered past {@link READ_MAX_LINE_LENGTH}),
+ * giant line is truncated, never buffered past `request.maxLineLength`),
  * enforces the byte cap, and throws `FS_NOT_FOUND` for an offset past EOF.
  */
 export async function buildWindow(
@@ -125,12 +126,14 @@ export async function buildWindow(
   displayPath: string,
 ): Promise<WindowResult> {
   const acc = newAccumulator()
+  // One char past the truncation point is enough to prove a line overflows.
+  const lineBufferCap = request.maxLineLength + 1
   let lineBuffer = ''
 
   function appendToLineBuffer(segment: string): void {
-    if (lineBuffer.length >= LINE_BUFFER_CAP) return
+    if (lineBuffer.length >= lineBufferCap) return
     lineBuffer += segment
-    if (lineBuffer.length > LINE_BUFFER_CAP) lineBuffer = lineBuffer.slice(0, LINE_BUFFER_CAP)
+    if (lineBuffer.length > lineBufferCap) lineBuffer = lineBuffer.slice(0, lineBufferCap)
   }
 
   function flushLine(): void {

packages/fs/tool-fs/src/read.ts

@@ -23,12 +23,27 @@ import { buildWindow, formatReadOutput } from './read-render.ts'
 import type { FileReadOutcome } from './read-render.ts'
 import { sessionCwd } from './session-cwd.ts'
 
-/** Default and maximum number of lines returned by one `read` call. */
+/** Default and maximum number of lines returned by one `read` call (the `readLimit` config). */
 export const READ_LIMIT = 2000
 
-/** Files at or above this size stream; smaller files read whole into memory. */
+/**
+ * Default streaming threshold (the `readStreamMinSize` config): files at or
+ * above this size stream; smaller files read whole into memory.
+ */
 export const STREAM_MIN_SIZE = 10 * 1024 * 1024
 
+/** Resolved read-tool caps — plugin config after defaulting (see `Config` in index.ts). */
+export interface ReadToolCaps {
+  /** Default and maximum number of lines returned by one call. */
+  limit: number
+  /** Maximum characters returned for a single line. */
+  maxLineLength: number
+  /** Maximum bytes returned for selected file lines. */
+  maxBytes: number
+  /** Files at or above this size stream; smaller files read whole into memory. */
+  streamMinSize: number
+}
+
 /** Validated `read` arguments after defaulting. */
 interface ReadInput {
   filePath: string
@@ -43,17 +58,17 @@ function parsePositiveInteger(value: number, name: string): number {
   return value
 }
 
-/** Validate value constraints the schema DSL can't express. */
-export function parseReadArgs(args: { file_path: string; offset?: number; limit?: number }): ReadInput {
+/** Validate value constraints the schema DSL can't express. `maxLimit` is the deployment's line cap. */
+export function parseReadArgs(args: { file_path: string; offset?: number; limit?: number }, maxLimit: number): ReadInput {
   if (args.file_path.trim().length === 0) throw new Error('file_path must be a non-empty string')
   const offset = args.offset === undefined ? 1 : parsePositiveInteger(args.offset, 'offset')
-  const limit = args.limit === undefined ? READ_LIMIT : parsePositiveInteger(args.limit, 'limit')
-  if (limit > READ_LIMIT) throw new Error(`limit must be less than or equal to ${READ_LIMIT}`)
+  const limit = args.limit === undefined ? maxLimit : parsePositiveInteger(args.limit, 'limit')
+  if (limit > maxLimit) throw new Error(`limit must be less than or equal to ${maxLimit}`)
   return { filePath: args.file_path, offset, limit }
 }
 
 /** Register the `read` tool and its system-prompt guidance. */
-export function applyReadTool(ctx: Context): void {
+export function applyReadTool(ctx: Context, caps: ReadToolCaps): void {
   ctx.systemPrompt.section({
     name: 'tool:read',
     order: 100,
@@ -66,10 +81,10 @@ export function applyReadTool(ctx: Context): void {
     parameters: {
       file_path: { type: 'string', required: true, description: 'Path to read, resolved by the filesystem backend.' },
       offset: { type: 'number', description: '1-based first line to return. Defaults to 1.' },
-      limit: { type: 'number', description: `Maximum number of lines to return. Defaults to ${READ_LIMIT}.` },
+      limit: { type: 'number', description: `Maximum number of lines to return. Defaults to ${caps.limit}.` },
     },
     async execute(args, exec): Promise<ContentBlock[]> {
-      const input = parseReadArgs(args)
+      const input = parseReadArgs(args, caps.limit)
       const cwd = sessionCwd(exec)
       const target = await ctx.fs.resolve(input.filePath, cwd !== undefined ? { cwd } : undefined)
 
@@ -83,10 +98,14 @@ export function applyReadTool(ctx: Context): void {
 
       // Stream when the file is large OR size is unknown, so a size-less backend
       // never buffers an arbitrarily large file.
-      const chunks = info.size === undefined || info.size >= STREAM_MIN_SIZE
+      const chunks = info.size === undefined || info.size >= caps.streamMinSize
         ? await ctx.fs.streamText(target, exec.signal)
         : [await ctx.fs.readText(target, exec.signal)]
-      const window = await buildWindow(chunks, { offset: input.offset, limit: input.limit }, target.displayPath)
+      const window = await buildWindow(
+        chunks,
+        { offset: input.offset, limit: input.limit, maxLineLength: caps.maxLineLength, maxBytes: caps.maxBytes },
+        target.displayPath,
+      )
 
       const outcome: FileReadOutcome = {
         offset: input.offset,
@@ -104,7 +123,8 @@ export function applyReadTool(ctx: Context): void {
     // appended (`Read foo.txt (5 - 8)`), `read` kind (icon), and a follow-along
     // location whose line is the read's offset (defaulting to 1). The window is
     // derived from the RAW args (offset/limit as the model passed them), NOT the
-    // tool's defaulted 1/READ_LIMIT, so an unbounded read shows a bare title.
+    // tool's defaulted 1/configured limit, so an unbounded read shows a bare
+    // title (and the presenter stays a pure function of args, config-free).
     presentCall(args): GenericCallView {
       const { offset, limit } = args
       const window = limit !== undefined && limit > 0