diff --git a/apps/x/packages/core/src/application/assistant/instructions.ts b/apps/x/packages/core/src/application/assistant/instructions.ts
index 7a080785..ceb65be0 100644
--- a/apps/x/packages/core/src/application/assistant/instructions.ts
+++ b/apps/x/packages/core/src/application/assistant/instructions.ts
@@ -94,7 +94,7 @@ When a user asks for ANY task that might require external capabilities (web sear
 
 **IMPORTANT**: Rowboat provides builtin tools that are internal and do NOT require security allowlist entries:
 - \`workspace-readFile\`, \`workspace-writeFile\`, \`workspace-edit\`, \`workspace-remove\` - File operations
-- \`workspace-readdir\`, \`workspace-exists\`, \`workspace-stat\`, \`workspace-glob\` - Directory exploration and file search
+- \`workspace-readdir\`, \`workspace-exists\`, \`workspace-stat\`, \`workspace-glob\`, \`workspace-grep\` - Directory exploration and file search
 - \`workspace-mkdir\`, \`workspace-rename\`, \`workspace-copy\` - File/directory management
 - \`analyzeAgent\` - Agent analysis
 - \`addMcpServer\`, \`listMcpServers\`, \`listMcpTools\`, \`executeMcpTool\` - MCP server management and execution
diff --git a/apps/x/packages/core/src/application/assistant/skills/builtin-tools/skill.ts b/apps/x/packages/core/src/application/assistant/skills/builtin-tools/skill.ts
index 6206d35b..0113a726 100644
--- a/apps/x/packages/core/src/application/assistant/skills/builtin-tools/skill.ts
+++ b/apps/x/packages/core/src/application/assistant/skills/builtin-tools/skill.ts
@@ -177,6 +177,7 @@ The Rowboat copilot has access to special builtin tools that regular agents don'
 - \`workspace-copy\` - Copy files
 - \`workspace-getRoot\` - Get workspace root directory path
 - \`workspace-glob\` - Find files matching a glob pattern (e.g., "**/*.ts", "agents/*.md")
+- \`workspace-grep\` - Search file contents using regex, returns matching files and lines
 
 #### Agent Operations
 - \`analyzeAgent\` - Read and analyze an agent file structure
diff --git a/apps/x/packages/core/src/application/lib/builtin-tools.ts b/apps/x/packages/core/src/application/lib/builtin-tools.ts
index 8036c8de..d0bd634e 100644
--- a/apps/x/packages/core/src/application/lib/builtin-tools.ts
+++ b/apps/x/packages/core/src/application/lib/builtin-tools.ts
@@ -1,5 +1,6 @@
 import { z, ZodType } from "zod";
 import * as path from "path";
+import { execSync } from "child_process";
 import { glob } from "glob";
 import { executeCommand } from "./command-executor.js";
 import { resolveSkill, availableSkills } from "../assistant/skills/index.js";
@@ -346,6 +347,119 @@ export const BuiltinTools: z.infer<typeof BuiltinToolsSchema> = {
         },
     },
 
+    'workspace-grep': {
+        description: 'Search file contents using regex. Returns matching files and lines. Uses ripgrep if available, falls back to grep.',
+        inputSchema: z.object({
+            pattern: z.string().describe('Regex pattern to search for'),
+            searchPath: z.string().optional().describe('Directory or file to search, relative to workspace root (default: workspace root)'),
+            fileGlob: z.string().optional().describe('File pattern filter (e.g., "*.ts", "*.md")'),
+            contextLines: z.number().optional().describe('Lines of context around matches (default: 0)'),
+            maxResults: z.number().optional().describe('Maximum results to return (default: 100)'),
+        }),
+        execute: async ({
+            pattern,
+            searchPath,
+            fileGlob,
+            contextLines = 0,
+            maxResults = 100
+        }: {
+            pattern: string;
+            searchPath?: string;
+            fileGlob?: string;
+            contextLines?: number;
+            maxResults?: number;
+        }) => {
+            try {
+                const targetPath = searchPath ? path.join(WorkDir, searchPath) : WorkDir;
+
+                // Ensure target path is within workspace
+                const resolvedTargetPath = path.resolve(targetPath);
+                if (!resolvedTargetPath.startsWith(WorkDir)) {
+                    return { error: 'Search path must be within workspace' };
+                }
+
+                // Try ripgrep first
+                try {
+                    const rgArgs = [
+                        '--json',
+                        '-e', JSON.stringify(pattern),
+                        contextLines > 0 ? `-C ${contextLines}` : '',
+                        fileGlob ? `--glob ${JSON.stringify(fileGlob)}` : '',
+                        `--max-count ${maxResults}`,
+                        '--ignore-case',
+                        JSON.stringify(resolvedTargetPath),
+                    ].filter(Boolean).join(' ');
+
+                    const output = execSync(`rg ${rgArgs}`, {
+                        encoding: 'utf8',
+                        maxBuffer: 10 * 1024 * 1024,
+                        cwd: WorkDir,
+                    });
+
+                    const matches = output.trim().split('\n')
+                        .filter(Boolean)
+                        .map(line => {
+                            try {
+                                return JSON.parse(line);
+                            } catch {
+                                return null;
+                            }
+                        })
+                        .filter(m => m && m.type === 'match');
+
+                    return {
+                        matches: matches.map(m => ({
+                            file: path.relative(WorkDir, m.data.path.text),
+                            line: m.data.line_number,
+                            content: m.data.lines.text.trim(),
+                        })),
+                        count: matches.length,
+                        tool: 'ripgrep',
+                    };
+                } catch (rgError) {
+                    // Fallback to basic grep if ripgrep not available or failed
+                    const grepArgs = [
+                        '-rn',
+                        fileGlob ? `--include=${JSON.stringify(fileGlob)}` : '',
+                        JSON.stringify(pattern),
+                        JSON.stringify(resolvedTargetPath),
+                        `| head -${maxResults}`,
+                    ].filter(Boolean).join(' ');
+
+                    try {
+                        const output = execSync(`grep ${grepArgs}`, {
+                            encoding: 'utf8',
+                            maxBuffer: 10 * 1024 * 1024,
+                            shell: '/bin/sh',
+                        });
+
+                        const lines = output.trim().split('\n').filter(Boolean);
+                        return {
+                            matches: lines.map(line => {
+                                const match = line.match(/^(.+?):(\d+):(.*)$/);
+                                if (match) {
+                                    return {
+                                        file: path.relative(WorkDir, match[1]),
+                                        line: parseInt(match[2], 10),
+                                        content: match[3].trim(),
+                                    };
+                                }
+                                return { file: '', line: 0, content: line };
+                            }),
+                            count: lines.length,
+                            tool: 'grep',
+                        };
+                    } catch {
+                        // No matches found (grep returns non-zero on no matches)
+                        return { matches: [], count: 0, tool: 'grep' };
+                    }
+                }
+            } catch (error) {
+                return { error: error instanceof Error ? error.message : 'Unknown error' };
+            }
+        },
+    },
+
     analyzeAgent: {
         description: 'Read and analyze an agent file to understand its structure, tools, and configuration',
         inputSchema: z.object({