From ff6f1d0d52e087e82b662637de139b89eda50e45 Mon Sep 17 00:00:00 2001
From: bluelovers <codelovers@users.sourceforge.net>
Date: Mon, 26 Oct 2026 06:21:34 +0800
Subject: [PATCH] feat(core): add pcre2 option to grep tool

ripgrep's default regex engine rejects look-around and backreferences, so
patterns such as `(?<![\w.])log(?![\w])` fail with a regex parse error.

Expose an opt-in `pcre2` flag that appends `--pcre2` and no other engine
switches, so callers can use those constructs without gaining a general
escape hatch for arbitrary ripgrep arguments.

Authored with the assistance of an AI agent (model: opencode/mimo-v2.6-flash-free).
---
 packages/core/src/filesystem.ts       | 1 +
 packages/core/src/ripgrep.ts          | 4 ++++
 packages/core/src/tool/plugin/grep.ts | 8 +++++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/packages/core/src/filesystem.ts b/packages/core/src/filesystem.ts
index ab421a7737a6..e77b1513a4f7 100644
--- a/packages/core/src/filesystem.ts
+++ b/packages/core/src/filesystem.ts
@@ -79,6 +79,7 @@ export class GrepInput extends Schema.Class<GrepInput>("FileSystem.GrepInput")({
   include: Schema.optionalKey(Schema.String),
   literal: Schema.optionalKey(Schema.Boolean),
   caseSensitive: Schema.optionalKey(Schema.Boolean),
+  pcre2: Schema.optionalKey(Schema.Boolean),
   limit: Schema.optionalKey(PositiveInt),
 }) {}
 
diff --git a/packages/core/src/ripgrep.ts b/packages/core/src/ripgrep.ts
index aa3b06f827dc..0cc3748d06e9 100644
--- a/packages/core/src/ripgrep.ts
+++ b/packages/core/src/ripgrep.ts
@@ -76,6 +76,8 @@ export interface GrepInput {
   readonly include?: string
   readonly literal?: boolean
   readonly caseSensitive?: boolean
+  /** Enable ripgrep's PCRE2 engine so patterns may use look-around and backreferences. */
+  readonly pcre2?: boolean
   readonly limit: number
   readonly signal?: AbortSignal
 }
@@ -228,6 +230,8 @@ const layer = Layer.effect(
             ...(input.caseSensitive === false ? ["--ignore-case"] : []),
             ...(input.include ? [`--glob=${input.include}`] : []),
             "--glob=!**/.git/**",
+            // PCRE2 is opt-in; it is the only engine switch exposed because it enables look-around/backreferences.
+            ...(input.pcre2 ? ["--pcre2"] : []),
             "--",
             input.pattern,
             input.file ?? ".",
diff --git a/packages/core/src/tool/plugin/grep.ts b/packages/core/src/tool/plugin/grep.ts
index 0062e33b8289..c447f98ab9ef 100644
--- a/packages/core/src/tool/plugin/grep.ts
+++ b/packages/core/src/tool/plugin/grep.ts
@@ -32,6 +32,10 @@ export const Input = Schema.Struct({
   caseSensitive: FileSystem.GrepInput.fields.caseSensitive.annotate({
     description: "Use case-sensitive matching (default: true).",
   }),
+  pcre2: FileSystem.GrepInput.fields.pcre2.annotate({
+    description:
+      "Search with ripgrep's PCRE2 engine (default: false). Required when `pattern` uses look-around or backreferences.",
+  }),
   limit: FileSystem.GrepInput.fields.limit.annotate({
     description: `Maximum number of matching lines to return (default: ${FileSystem.DEFAULT_SEARCH_LIMIT})`,
   }),
@@ -76,7 +80,7 @@ export const Plugin = {
           name,
           options: { codemode: false },
           description:
-            "Search file contents using ripgrep's regular expression syntax or literal text matching. Use it to locate specific code, symbols, or text patterns, and narrow searches with `path` or `include`. Returns matching file paths, line numbers, and line previews.",
+            "Search file contents using ripgrep's regular expression syntax or literal text matching. Use it to locate specific code, symbols, or text patterns, and narrow searches with `path` or `include`. Patterns with look-around or backreferences need `pcre2: true`. Returns matching file paths, line numbers, and line previews.",
           input: Input,
           output: Output,
           execute: (input, context) =>
@@ -94,6 +98,7 @@ export const Plugin = {
                   include: input.include,
                   literal: input.literal,
                   caseSensitive: input.caseSensitive,
+                  pcre2: input.pcre2,
                   limit: input.limit,
                 },
                 sessionID: context.sessionID,
@@ -116,6 +121,7 @@ export const Plugin = {
                   include: input.include,
                   literal: input.literal,
                   caseSensitive: input.caseSensitive,
+                  pcre2: input.pcre2,
                   limit: limit + 1,
                 })
                 .pipe(