diff --git a/apps/x/packages/core/src/application/assistant/instructions.ts b/apps/x/packages/core/src/application/assistant/instructions.ts
index 64d97c1d..629a7673 100644
--- a/apps/x/packages/core/src/application/assistant/instructions.ts
+++ b/apps/x/packages/core/src/application/assistant/instructions.ts
@@ -88,12 +88,12 @@ When a user asks for ANY task that might require external capabilities (web sear
 ## Workspace Access & Scope
 - You have full read/write access inside \`\${BASE_DIR}\` (this resolves to the user's \`~/.rowboat\` directory). Create folders, files, and agents there using builtin tools or allowed shell commands—don't wait for the user to do it manually.
 - If a user mentions a different root (e.g., \`~/.rowboatx\` or another path), clarify whether they meant the Rowboat workspace and propose the equivalent path you can act on. Only refuse if they explicitly insist on an inaccessible location.
-- Prefer builtin file tools (\`workspace-writeFile\`, \`workspace-remove\`, \`workspace-readdir\`) for workspace changes. Reserve refusal or "you do it" responses for cases that are truly outside the Rowboat sandbox.
+- Prefer builtin file tools (\`workspace-edit\` for modifications, \`workspace-writeFile\` for new files, \`workspace-remove\`, \`workspace-readdir\`) for workspace changes. Reserve refusal or "you do it" responses for cases that are truly outside the Rowboat sandbox.
 
 ## Builtin Tools vs Shell Commands
 
 **IMPORTANT**: Rowboat provides builtin tools that are internal and do NOT require security allowlist entries:
-- \`workspace-readFile\`, \`workspace-writeFile\`, \`workspace-remove\` - File operations
+- \`workspace-readFile\`, \`workspace-writeFile\`, \`workspace-edit\`, \`workspace-remove\` - File operations
 - \`workspace-readdir\`, \`workspace-exists\`, \`workspace-stat\` - Directory exploration
 - \`workspace-mkdir\`, \`workspace-rename\`, \`workspace-copy\` - File/directory management
 - \`analyzeAgent\` - Agent analysis
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 ceb2f940..40a61960 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
@@ -168,6 +168,7 @@ The Rowboat copilot has access to special builtin tools that regular agents don'
 - \`workspace-readdir\` - List directory contents (supports recursive exploration)
 - \`workspace-readFile\` - Read file contents
 - \`workspace-writeFile\` - Create or update file contents
+- \`workspace-edit\` - Make precise edits by replacing specific text (safer than full rewrites)
 - \`workspace-remove\` - Remove files or directories
 - \`workspace-exists\` - Check if a file or directory exists
 - \`workspace-stat\` - Get file/directory statistics
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 eff523a0..dcd763de 100644
--- a/apps/x/packages/core/src/application/lib/builtin-tools.ts
+++ b/apps/x/packages/core/src/application/lib/builtin-tools.ts
@@ -156,14 +156,14 @@ export const BuiltinTools: z.infer<typeof BuiltinToolsSchema> = {
             mkdirp: z.boolean().optional().describe('Create parent directories if needed (default: true)'),
             expectedEtag: z.string().optional().describe('ETag to check for concurrent modifications (conflict detection)'),
         }),
-        execute: async ({ 
-            path: relPath, 
-            data, 
-            encoding, 
-            atomic, 
-            mkdirp, 
-            expectedEtag 
-        }: { 
+        execute: async ({
+            path: relPath,
+            data,
+            encoding,
+            atomic,
+            mkdirp,
+            expectedEtag
+        }: {
             path: string;
             data: string;
             encoding?: 'utf8' | 'base64' | 'binary';
@@ -186,6 +186,57 @@ export const BuiltinTools: z.infer<typeof BuiltinToolsSchema> = {
         },
     },
 
+    'workspace-edit': {
+        description: 'Make precise edits to a file by replacing specific text. Safer than rewriting entire files - produces smaller diffs and reduces risk of data loss.',
+        inputSchema: z.object({
+            path: z.string().min(1).describe('Workspace-relative file path'),
+            oldString: z.string().describe('Exact text to find and replace'),
+            newString: z.string().describe('Replacement text'),
+            replaceAll: z.boolean().optional().describe('Replace all occurrences (default: false, fails if not unique)'),
+        }),
+        execute: async ({
+            path: relPath,
+            oldString,
+            newString,
+            replaceAll = false
+        }: {
+            path: string;
+            oldString: string;
+            newString: string;
+            replaceAll?: boolean;
+        }) => {
+            try {
+                const result = await workspace.readFile(relPath, 'utf8');
+                const content = result.data;
+
+                const occurrences = content.split(oldString).length - 1;
+
+                if (occurrences === 0) {
+                    return { error: 'oldString not found in file' };
+                }
+
+                if (occurrences > 1 && !replaceAll) {
+                    return {
+                        error: `oldString found ${occurrences} times. Use replaceAll: true or provide more context to make it unique.`
+                    };
+                }
+
+                const newContent = replaceAll
+                    ? content.replaceAll(oldString, newString)
+                    : content.replace(oldString, newString);
+
+                await workspace.writeFile(relPath, newContent, { encoding: 'utf8' });
+
+                return {
+                    success: true,
+                    replacements: replaceAll ? occurrences : 1
+                };
+            } catch (error) {
+                return { error: error instanceof Error ? error.message : 'Unknown error' };
+            }
+        },
+    },
+
     'workspace-mkdir': {
         description: 'Create a directory in the workspace',
         inputSchema: z.object({