diff --git a/src/agents/base.ts b/src/agents/base.ts
index 3b923e31..d0d33da4 100644
--- a/src/agents/base.ts
+++ b/src/agents/base.ts
@@ -9,12 +9,15 @@ import { CUSTOM_MODELS } from '../config/customModels.js';
 import { getIterationTrailingMessage } from '../config/hintConfig.js';
 import { getRateLimitForModel } from '../config/rateLimits.js';
 import { getRetryConfig } from '../config/retryConfig.js';
-import { EditFile } from '../gadgets/EditFile.js';
+import { FileInsertContent } from '../gadgets/FileInsertContent.js';
+import { FileRemoveContent } from '../gadgets/FileRemoveContent.js';
+import { FileSearchAndReplace } from '../gadgets/FileSearchAndReplace.js';
 import { Finish } from '../gadgets/Finish.js';
 import { ListDirectory } from '../gadgets/ListDirectory.js';
 import { ReadFile } from '../gadgets/ReadFile.js';
 import { Sleep } from '../gadgets/Sleep.js';
 import { CreatePR } from '../gadgets/github/index.js';
+import { initSessionState } from '../gadgets/sessionState.js';
 import { Tmux } from '../gadgets/tmux.js';
 import { TodoDelete, TodoUpdateStatus, TodoUpsert } from '../gadgets/todo/index.js';
 import {
@@ -274,6 +277,9 @@ function createAgentBuilderWithGadgets(
 	llmCallLogger: import('../utils/llmLogging.js').LLMCallLogger,
 	repoDir: string,
 ): BuilderType {
+	// Initialize session state for gadgets (e.g., Finish checks PR requirement for implementation)
+	initSessionState(agentType);
+
 	// Check if AU features should be enabled (repo has .au file at root)
 	const auEnabled = existsSync(join(repoDir, '.au'));
 
@@ -285,7 +291,14 @@ function createAgentBuilderWithGadgets(
 		// Filesystem gadgets (read-only for planning)
 		new ListDirectory(),
 		new ReadFile(),
-		...(isReadOnlyAgent ? [] : [new EditFile(), new WriteFile()]),
+		...(isReadOnlyAgent
+			? []
+			: [
+					new FileSearchAndReplace(),
+					new FileInsertContent(),
+					new FileRemoveContent(),
+					new WriteFile(),
+				]),
 		// Shell commands via tmux (no timeout issues)
 		new Tmux(),
 		new Sleep(),
@@ -332,7 +345,7 @@ function createAgentBuilderWithGadgets(
 		.withGadgets(...allGadgets);
 
 	// Implementation agent uses sequential execution to ensure file operations
-	// are properly ordered (e.g., EditFile then ReadFile on same file)
+	// are properly ordered (e.g., FileSearchAndReplace then ReadFile on same file)
 	if (agentType === 'implementation') {
 		return builder.withGadgetExecutionMode('sequential');
 	}
diff --git a/src/agents/prompts/templates/partials/rules-efficiency.eta b/src/agents/prompts/templates/partials/rules-efficiency.eta
index 290c834e..e420fc76 100644
--- a/src/agents/prompts/templates/partials/rules-efficiency.eta
+++ b/src/agents/prompts/templates/partials/rules-efficiency.eta
@@ -2,97 +2,11 @@
 
 When you encounter multiple errors (type errors, test failures, lint errors):
 1. Read and analyze ALL errors before making any fixes
-2. Fix ALL errors in a SINGLE response with multiple EditFile calls
+2. Fix ALL errors in a SINGLE response with multiple gadget calls (FileSearchAndReplace, FileInsertContent, FileRemoveContent)
 3. Run verification ONCE after all fixes
-4. Repeat only if new errors appear
+4. Repeat only if errors appear again
 
 NEVER fix errors one-by-one. This wastes iterations. Batch all fixes together.
 
-### Debugging Persistent Test Failures (CRITICAL)
-
-If the SAME test fails 2-3 times after your fixes, STOP making more fixes. Instead, investigate:
-
-**When mocks aren't being called (e.g., "Number of calls: 0"):**
-1. The problem is NOT your test setup - the code path isn't executing at all
-2. Add `console.log` statements to the IMPLEMENTATION code to trace execution:
-   - At the function entry point
-   - Before conditional branches
-   - Inside the block that should call the mocked function
-3. Run the test again and read the console output to find where execution stops
-4. Fix the actual implementation issue, not the test
-
-**When assertions fail with wrong values:**
-1. Add `console.log` to print actual values at key points
-2. Check if your changes accidentally broke an existing code path
-3. Verify dependencies are wired correctly (DI, imports, function parameters)
-
-**Loop Detection - recognize when you're stuck:**
-- If you've edited the same file 3+ times for the same error: STOP
-- If you've run `verify-final-vN` where N > 3: STOP
-- Step back and ask: "Why isn't the code reaching this point?"
-- Read the implementation code, not just the test
-
-**Debug-first approach:**
-```
-1. Test fails → Add console.log to implementation
-2. Run test → Read logs to understand flow
-3. Identify root cause → Fix implementation (not test setup)
-4. Remove console.log → Verify fix
-```
-
-Remember: Tests that "should" call mocks but don't are telling you the implementation path is wrong, not the mock setup.
-
-### Handling Breaking Changes (Critical)
-
-If you modify a function signature, class constructor, or API contract,
-do not wait for the compiler/linter to report errors.
-Immediately perform a codebase-wide search for all usages of that symbol and update all call sites
-in a single batch. Avoid the 'fix-run-repeat' loop for known breaking changes.
-
-### Tooling & Verification
-
-When validating changes, always prioritize auto-fixing commands (e.g., format, lint --fix) before
-running read-only checks. If a generated artifact (like a migration or lockfile) looks incorrect,
-investigate the environment state rather than manually patching the output.
-
-### Acting on EditFile/WriteFile Results (CRITICAL)
-
-EditFile and WriteFile return structured output. You MUST read and act on it.
-
-**Status Codes:**
-- `status=success` - Edit worked, but CHECK THE DIAGNOSTICS SECTION
-- `status=failed` - Search content not found, USE THE SUGGESTIONS
-- `status=error` - Operation failed (permissions, path), read error message
-
-**On status=failed (search not found):**
-
-The output includes a SUGGESTIONS section with similar content found in the file:
-```
-SUGGESTIONS (similar content found):
-Line 42 (85% similar):
-```{what actually exists}```
-```
-
-1. READ this section - it shows what the file actually contains
-2. Adjust your search pattern to match the actual content
-3. Common issues: whitespace differences, indentation, content changed by previous edit
-4. NEVER retry the exact same search - that's a loop
-
-**On status=success (check diagnostics):**
-
-Success responses include TypeScript and Biome diagnostics:
-```
-=== TypeScript Check ===
-{any type errors from your edit}
-
-=== Biome Lint ===
-{any lint issues from your edit}
-```
-
 If diagnostics show issues, FIX THEM IMMEDIATELY before making more edits.
 Don't proceed to other files until the current file is clean.
-
-**Recovery Escalation:**
-1. First failure: Use SUGGESTIONS to adjust search pattern
-2. Second failure: Read entire file with ReadFile, understand actual structure
-3. Third failure: Use WriteFile to replace the entire file content
\ No newline at end of file
diff --git a/src/agents/prompts/templates/planning.eta b/src/agents/prompts/templates/planning.eta
index c889c598..24ae582a 100644
--- a/src/agents/prompts/templates/planning.eta
+++ b/src/agents/prompts/templates/planning.eta
@@ -127,7 +127,7 @@ Review the updated description and move to TODO when ready to implement!
 - `ReadFile` - Read file contents
 - `Tmux` - Run shell commands (for exploration: grep, find, etc.)
 
-⚠️ **You do NOT have access to:** EditFile, WriteFile, CreatePR - these are reserved for the implementation agent.
+⚠️ **You do NOT have access to:** FileSearchAndReplace, FileInsertContent, FileRemoveContent, WriteFile, CreatePR - these are reserved for the implementation agent.
 
 ## Rules
 
diff --git a/src/agents/respond-to-review.ts b/src/agents/respond-to-review.ts
index 9098c34c..aad03e14 100644
--- a/src/agents/respond-to-review.ts
+++ b/src/agents/respond-to-review.ts
@@ -8,7 +8,9 @@ import { getCompactionConfig } from '../config/compactionConfig.js';
 import { getIterationTrailingMessage } from '../config/hintConfig.js';
 import { getRateLimitForModel } from '../config/rateLimits.js';
 import { getRetryConfig } from '../config/retryConfig.js';
-import { EditFile } from '../gadgets/EditFile.js';
+import { FileInsertContent } from '../gadgets/FileInsertContent.js';
+import { FileRemoveContent } from '../gadgets/FileRemoveContent.js';
+import { FileSearchAndReplace } from '../gadgets/FileSearchAndReplace.js';
 import { ListDirectory } from '../gadgets/ListDirectory.js';
 import { ReadFile } from '../gadgets/ReadFile.js';
 import { Sleep } from '../gadgets/Sleep.js';
@@ -18,6 +20,7 @@ import {
 	GetPRDiff,
 	ReplyToReviewComment,
 } from '../gadgets/github/index.js';
+import { initSessionState } from '../gadgets/sessionState.js';
 import { Tmux } from '../gadgets/tmux.js';
 import { githubClient } from '../github/client.js';
 import type { AgentInput, AgentResult, CascadeConfig, ProjectConfig } from '../types/index.js';
@@ -251,6 +254,9 @@ function createRespondToReviewAgentBuilder(
 	llmCallLogger: import('../utils/llmLogging.js').LLMCallLogger,
 	repoDir: string,
 ): BuilderType {
+	// Initialize session state for gadgets
+	initSessionState('respond-to-review');
+
 	// Check if AU features should be enabled (repo has .au file at root)
 	const auEnabled = existsSync(join(repoDir, '.au'));
 
@@ -259,7 +265,9 @@ function createRespondToReviewAgentBuilder(
 		// Filesystem gadgets
 		new ListDirectory(),
 		new ReadFile(),
-		new EditFile(),
+		new FileSearchAndReplace(),
+		new FileInsertContent(),
+		new FileRemoveContent(),
 		new WriteFile(),
 		// Shell commands via tmux
 		new Tmux(),
diff --git a/src/gadgets/EditFile.ts b/src/gadgets/EditFile.ts
deleted file mode 100644
index 3de3aab5..00000000
--- a/src/gadgets/EditFile.ts
+++ /dev/null
@@ -1,825 +0,0 @@
-/**
- * EditFile gadget - Edit files using search/replace with layered matching.
- *
- * Uses layered matching strategies: exact → whitespace → indentation → fuzzy
- * This approach reduces edit errors by ~9x (per Aider benchmarks).
- */
-
-import { execSync } from 'node:child_process';
-import { readFileSync, realpathSync, writeFileSync } from 'node:fs';
-import { resolve, sep } from 'node:path';
-
-import { Gadget, z } from 'llmist';
-
-import { applyReplacement, findAllMatches, getMatchFailure } from './editfile/matcher.js';
-import { invalidateFileRead } from './readTracking.js';
-
-const ALLOWED_PATHS = ['/tmp'];
-
-function validatePath(inputPath: string): string {
-	const cwd = process.cwd();
-	const resolvedPath = resolve(cwd, inputPath);
-
-	let finalPath: string;
-	try {
-		finalPath = realpathSync(resolvedPath);
-	} catch (error) {
-		const nodeError = error as NodeJS.ErrnoException;
-		if (nodeError.code === 'ENOENT') {
-			finalPath = resolvedPath;
-		} else {
-			throw error;
-		}
-	}
-
-	// Check if within CWD
-	const cwdWithSep = cwd + sep;
-	if (finalPath.startsWith(cwdWithSep) || finalPath === cwd) {
-		return finalPath;
-	}
-
-	// Check if within allowed paths
-	for (const allowedPath of ALLOWED_PATHS) {
-		const allowedWithSep = allowedPath + sep;
-		if (finalPath.startsWith(allowedWithSep) || finalPath === allowedPath) {
-			return finalPath;
-		}
-	}
-
-	throw new Error(
-		`Path access denied: ${inputPath}. Path must be within working directory or allowed paths (${ALLOWED_PATHS.join(', ')})`,
-	);
-}
-
-export class EditFile extends Gadget({
-	name: 'EditFile',
-	description: `Edit a file using one of three modes:
-
-**search_replace**: Search for content and replace it.
-- Uses layered matching: exact → whitespace → indentation → fuzzy
-- Reduces edit errors by ~9x
-
-**insert_at_line**: Insert content at a specific line number.
-- Line numbers are 1-based
-- Content is inserted BEFORE the specified line
-- Use line beyond EOF to append at end
-
-**remove_lines**: Remove a range of lines from the file.
-- Line numbers are 1-based and inclusive
-
-For multiple edits, call this gadget multiple times.`,
-	timeoutMs: 30000,
-	maxConcurrent: 1, // Sequential execution to prevent race conditions on file writes
-	schema: z.discriminatedUnion('mode', [
-		// Mode 1: search_replace (current behavior)
-		z.object({
-			mode: z.literal('search_replace'),
-			comment: z.string().min(1).describe('Brief rationale for this gadget call'),
-			filePath: z.string().describe('Path to the file to edit'),
-			search: z.string().min(1).describe('The content to search for'),
-			replace: z.string().describe('The content to replace with (empty to delete)'),
-		}),
-
-		// Mode 2: insert_at_line
-		z.object({
-			mode: z.literal('insert_at_line'),
-			comment: z.string().min(1).describe('Brief rationale for this gadget call'),
-			filePath: z.string().describe('Path to the file to edit'),
-			line: z
-				.number()
-				.int()
-				.min(1)
-				.describe('Line number to insert BEFORE (1-based). Use line beyond EOF to append.'),
-			content: z.string().describe('Content to insert (can be multiline)'),
-		}),
-
-		// Mode 3: remove_lines
-		z.object({
-			mode: z.literal('remove_lines'),
-			comment: z.string().min(1).describe('Brief rationale for this gadget call'),
-			filePath: z.string().describe('Path to the file to edit'),
-			startLine: z.number().int().min(1).describe('First line to remove (1-based, inclusive)'),
-			endLine: z.number().int().min(1).describe('Last line to remove (1-based, inclusive)'),
-		}),
-	]),
-	examples: [
-		{
-			params: {
-				mode: 'search_replace' as const,
-				comment: 'Increasing timeout from 1s to 5s to fix test flakiness',
-				filePath: 'src/config.ts',
-				search: 'timeout: 1000',
-				replace: 'timeout: 5000',
-			},
-			output: `path=src/config.ts status=success matches=1 strategy=exact
-
-Replaced 1 occurrence.
-
-=== Edit 1 (lines 5-5) ===
---- BEFORE ---
-   1 | import { foo } from "bar";
-   2 |
-   3 | const CONFIG = {
-   4 |   debug: false,
-<  5 |   timeout: 1000,
-   6 |   retries: 3,
-   7 | };
-
---- AFTER ---
-   1 | import { foo } from "bar";
-   2 |
-   3 | const CONFIG = {
-   4 |   debug: false,
->  5 |   timeout: 5000,
-   6 |   retries: 3,
-   7 | };
-
-=== TypeScript Check ===
-No type errors found.
-
-=== Biome Lint ===
-No lint issues found.`,
-			comment: 'Single edit with before/after context and diagnostics',
-		},
-		{
-			params: {
-				mode: 'search_replace' as const,
-				comment: 'Updating retry constant per requirements',
-				filePath: 'src/constants.ts',
-				search: 'MAX_RETRIES = 3',
-				replace: 'MAX_RETRIES = 5',
-			},
-			output: `path=src/constants.ts status=success matches=2 strategy=exact
-
-Replaced 2 occurrences.
-
-=== Edit 1 (lines 4-4) ===
---- BEFORE ---
-   1 | // API constants
-   2 | export const API_URL = "https://api.example.com";
-   3 |
-<  4 | export const MAX_RETRIES = 3;
-   5 | export const TIMEOUT = 5000;
-
---- AFTER ---
-   1 | // API constants
-   2 | export const API_URL = "https://api.example.com";
-   3 |
->  4 | export const MAX_RETRIES = 5;
-   5 | export const TIMEOUT = 5000;
-
-=== Edit 2 (lines 12-12) ===
---- BEFORE ---
-   9 | // Client constants
-  10 | export const CLIENT_URL = "https://client.example.com";
-  11 |
-< 12 | export const MAX_RETRIES = 3;
-  13 | export const CLIENT_TIMEOUT = 3000;
-
---- AFTER ---
-   9 | // Client constants
-  10 | export const CLIENT_URL = "https://client.example.com";
-  11 |
-> 12 | export const MAX_RETRIES = 5;
-  13 | export const CLIENT_TIMEOUT = 3000;
-
-=== TypeScript Check ===
-No type errors found.
-
-=== Biome Lint ===
-No lint issues found.`,
-			comment: 'Multiple matches replaced with before/after for each',
-		},
-		{
-			params: {
-				mode: 'search_replace' as const,
-				comment: 'Enabling feature flag for new functionality',
-				filePath: 'src/data.json',
-				search: '"enabled": false',
-				replace: '"enabled": true',
-			},
-			output: `path=src/data.json status=success matches=1 strategy=exact
-
-Replaced 1 occurrence.
-
-=== Edit 1 (lines 3-3) ===
---- BEFORE ---
-   1 | {
-   2 |   "name": "example",
-<  3 |   "enabled": false,
-   4 |   "count": 0
-   5 | }
-
---- AFTER ---
-   1 | {
-   2 |   "name": "example",
->  3 |   "enabled": true,
-   4 |   "count": 0
-   5 | }`,
-			comment: 'Non-TypeScript file (no diagnostics appended)',
-		},
-		// insert_at_line examples
-		{
-			params: {
-				mode: 'insert_at_line' as const,
-				comment: 'Adding lodash import at top of file',
-				filePath: 'src/utils.ts',
-				line: 1,
-				content: "import _ from 'lodash';",
-			},
-			output: `path=src/utils.ts mode=insert_at_line status=success
-
-Inserted 1 line at line 1.
-
---- BEFORE (around line 1) ---
-<  1 | import { foo } from 'bar';
-   2 | import { baz } from 'qux';
-   3 |
-
---- AFTER ---
->  1 | import _ from 'lodash';
-   2 | import { foo } from 'bar';
-   3 | import { baz } from 'qux';
-   4 |
-
-=== TypeScript Check ===
-No type errors found.
-
-=== Biome Lint ===
-No lint issues found.`,
-			comment: 'Insert import at beginning of file',
-		},
-		{
-			params: {
-				mode: 'insert_at_line' as const,
-				comment: 'Adding helper function in middle of file',
-				filePath: 'src/helpers.ts',
-				line: 10,
-				content: 'function validate(x: number): boolean {\n  return x > 0;\n}',
-			},
-			output: `path=src/helpers.ts mode=insert_at_line status=success
-
-Inserted 3 lines at line 10.
-
---- BEFORE (around line 10) ---
-   7 | }
-   8 |
-   9 | // Utils below
-< 10 | function process(data: string) {
-  11 |   return data.trim();
-  12 | }
-
---- AFTER ---
-   7 | }
-   8 |
-   9 | // Utils below
-> 10 | function validate(x: number): boolean {
-  11 |   return x > 0;
-  12 | }
-  13 | function process(data: string) {
-  14 |   return data.trim();
-  15 | }
-
-=== TypeScript Check ===
-No type errors found.
-
-=== Biome Lint ===
-No lint issues found.`,
-			comment: 'Insert multiline block in middle of file',
-		},
-		{
-			params: {
-				mode: 'insert_at_line' as const,
-				comment: 'Appending export at end of file',
-				filePath: 'src/index.ts',
-				line: 999,
-				content: "export * from './newModule';",
-			},
-			output: `path=src/index.ts mode=insert_at_line status=success
-
-Appended 1 line at end of file.
-
---- BEFORE (end of file) ---
-   3 | export * from './utils';
-   4 | export * from './helpers';
-   5 |
-
---- AFTER ---
-   3 | export * from './utils';
-   4 | export * from './helpers';
-   5 |
->  6 | export * from './newModule';
-
-=== TypeScript Check ===
-No type errors found.
-
-=== Biome Lint ===
-No lint issues found.`,
-			comment: 'Append at end of file (line beyond EOF)',
-		},
-		// remove_lines examples
-		{
-			params: {
-				mode: 'remove_lines' as const,
-				comment: 'Removing unused import',
-				filePath: 'src/app.ts',
-				startLine: 3,
-				endLine: 3,
-			},
-			output: `path=src/app.ts mode=remove_lines status=success
-
-Removed 1 line (line 3).
-
---- BEFORE ---
-   1 | import { foo } from 'foo';
-   2 | import { bar } from 'bar';
-<  3 | import { unused } from 'unused';
-   4 | import { baz } from 'baz';
-   5 |
-
---- AFTER ---
-   1 | import { foo } from 'foo';
-   2 | import { bar } from 'bar';
-   3 | import { baz } from 'baz';
-   4 |
-
-=== TypeScript Check ===
-No type errors found.
-
-=== Biome Lint ===
-No lint issues found.`,
-			comment: 'Remove single line',
-		},
-		{
-			params: {
-				mode: 'remove_lines' as const,
-				comment: 'Removing deprecated function',
-				filePath: 'src/legacy.ts',
-				startLine: 5,
-				endLine: 10,
-			},
-			output: `path=src/legacy.ts mode=remove_lines status=success
-
-Removed 6 lines (lines 5-10).
-
---- BEFORE ---
-   2 |
-   3 | export function keepThis() {}
-   4 |
-<  5 | /** @deprecated */
-<  6 | function oldFunc(x: number) {
-<  7 |   console.log('deprecated');
-<  8 |   return x * 2;
-<  9 | }
-< 10 |
-  11 | export function keepThisToo() {}
-
---- AFTER ---
-   2 |
-   3 | export function keepThis() {}
-   4 |
-   5 | export function keepThisToo() {}
-
-=== TypeScript Check ===
-No type errors found.
-
-=== Biome Lint ===
-No lint issues found.`,
-			comment: 'Remove block of lines',
-		},
-		{
-			params: {
-				mode: 'remove_lines' as const,
-				comment: 'Removing comment block from config',
-				filePath: 'config/settings.json',
-				startLine: 2,
-				endLine: 4,
-			},
-			output: `path=config/settings.json mode=remove_lines status=success
-
-Removed 3 lines (lines 2-4).
-
---- BEFORE ---
-   1 | {
-<  2 |   "// NOTE": "Remove this later",
-<  3 |   "// TODO": "Clean up config",
-<  4 |   "// FIXME": "Legacy value",
-   5 |   "enabled": true,
-   6 |   "timeout": 5000
-   7 | }
-
---- AFTER ---
-   1 | {
-   2 |   "enabled": true,
-   3 |   "timeout": 5000
-   4 | }`,
-			comment: 'Remove from non-TS file (no diagnostics)',
-		},
-	],
-}) {
-	override execute(params: this['params']): string {
-		// Validate and resolve path (shared across all modes)
-		const validatedPath = validatePath(params.filePath);
-
-		// Dispatch to mode handler
-		switch (params.mode) {
-			case 'search_replace':
-				return this.handleSearchReplace(
-					params as Extract<this['params'], { mode: 'search_replace' }>,
-					validatedPath,
-				);
-			case 'insert_at_line':
-				return this.handleInsertAtLine(
-					params as Extract<this['params'], { mode: 'insert_at_line' }>,
-					validatedPath,
-				);
-			case 'remove_lines':
-				return this.handleRemoveLines(
-					params as Extract<this['params'], { mode: 'remove_lines' }>,
-					validatedPath,
-				);
-		}
-	}
-
-	private handleSearchReplace(
-		params: Extract<this['params'], { mode: 'search_replace' }>,
-		validatedPath: string,
-	): string {
-		const { filePath, search, replace } = params;
-
-		// Read file content
-		let content: string;
-		try {
-			content = readFileSync(validatedPath, 'utf-8');
-		} catch (error) {
-			const nodeError = error as NodeJS.ErrnoException;
-			if (nodeError.code === 'ENOENT') {
-				throw new Error(`File not found: ${filePath}`);
-			}
-			throw error;
-		}
-
-		// Find ALL matches using layered strategies
-		const matches = findAllMatches(content, search);
-
-		if (matches.length === 0) {
-			// No match found - throw with helpful suggestions
-			const failure = getMatchFailure(content, search);
-			throw new Error(this.formatFailure(filePath, search, failure));
-		}
-
-		// Store original content for before/after display
-		const originalLines = content.split('\n');
-
-		// Collect before contexts BEFORE applying any replacements
-		const beforeContexts: Array<{
-			startLine: number;
-			endLine: number;
-			context: string;
-		}> = [];
-		for (const match of matches) {
-			beforeContexts.push({
-				startLine: match.startLine,
-				endLine: match.endLine,
-				context: this.formatContext(originalLines, match.startLine, match.endLine, 5, '<'),
-			});
-		}
-
-		// Apply replacements in reverse order (to preserve indices)
-		let newContent = content;
-		const sortedMatches = [...matches].sort((a, b) => b.startIndex - a.startIndex);
-		for (const match of sortedMatches) {
-			newContent = applyReplacement(newContent, match, replace);
-		}
-
-		// Write file
-		writeFileSync(validatedPath, newContent, 'utf-8');
-		invalidateFileRead(validatedPath);
-
-		// Build and return success output
-		return this.buildSearchReplaceOutput(
-			filePath,
-			validatedPath,
-			matches,
-			beforeContexts,
-			replace,
-			newContent,
-		);
-	}
-
-	private handleInsertAtLine(
-		params: Extract<this['params'], { mode: 'insert_at_line' }>,
-		validatedPath: string,
-	): string {
-		const { filePath, line, content: insertContent } = params;
-
-		// Read file content
-		let content: string;
-		try {
-			content = readFileSync(validatedPath, 'utf-8');
-		} catch (error) {
-			const nodeError = error as NodeJS.ErrnoException;
-			if (nodeError.code === 'ENOENT') {
-				// For insert, create empty file
-				content = '';
-			} else {
-				throw error;
-			}
-		}
-
-		const lines = content.split('\n');
-		const insertLines = insertContent.split('\n');
-		const insertAtEnd = line > lines.length;
-		const effectiveLine = Math.min(line, lines.length + 1);
-
-		// Store before context
-		const beforeContext = this.formatContext(lines, effectiveLine, effectiveLine, 3, '<');
-
-		// Insert lines
-		const newLines = [
-			...lines.slice(0, effectiveLine - 1),
-			...insertLines,
-			...lines.slice(effectiveLine - 1),
-		];
-
-		const newContent = newLines.join('\n');
-		writeFileSync(validatedPath, newContent, 'utf-8');
-		invalidateFileRead(validatedPath);
-
-		// Build output
-		const output: string[] = [`path=${filePath} mode=insert_at_line status=success`, ''];
-
-		if (insertAtEnd) {
-			output.push(
-				`Appended ${insertLines.length} line${insertLines.length > 1 ? 's' : ''} at end of file.`,
-			);
-		} else {
-			output.push(
-				`Inserted ${insertLines.length} line${insertLines.length > 1 ? 's' : ''} at line ${effectiveLine}.`,
-			);
-		}
-
-		output.push(
-			'',
-			insertAtEnd
-				? '--- BEFORE (end of file) ---'
-				: `--- BEFORE (around line ${effectiveLine}) ---`,
-			beforeContext || '(empty file)',
-			'',
-			'--- AFTER ---',
-			this.formatContext(newLines, effectiveLine, effectiveLine + insertLines.length - 1, 3),
-		);
-
-		if (filePath.endsWith('.ts') || filePath.endsWith('.tsx')) {
-			output.push('', this.runDiagnostics(validatedPath));
-		}
-
-		return output.join('\n');
-	}
-
-	private handleRemoveLines(
-		params: Extract<this['params'], { mode: 'remove_lines' }>,
-		validatedPath: string,
-	): string {
-		const { filePath, startLine, endLine } = params;
-
-		// Validate line range
-		if (startLine > endLine) {
-			throw new Error(`Invalid line range: startLine (${startLine}) > endLine (${endLine})`);
-		}
-
-		// Read file content
-		let content: string;
-		try {
-			content = readFileSync(validatedPath, 'utf-8');
-		} catch (error) {
-			const nodeError = error as NodeJS.ErrnoException;
-			if (nodeError.code === 'ENOENT') {
-				throw new Error(`File not found: ${filePath}`);
-			}
-			throw error;
-		}
-
-		const lines = content.split('\n');
-
-		// Validate startLine
-		if (startLine > lines.length) {
-			throw new Error(`startLine (${startLine}) is beyond end of file (${lines.length} lines)`);
-		}
-
-		const effectiveEndLine = Math.min(endLine, lines.length);
-		const removedCount = effectiveEndLine - startLine + 1;
-
-		// Store before context with highlight on lines to remove
-		const beforeContext = this.formatContext(lines, startLine, effectiveEndLine, 3, '<');
-
-		// Remove lines
-		const newLines = [...lines.slice(0, startLine - 1), ...lines.slice(effectiveEndLine)];
-
-		const newContent = newLines.join('\n');
-		writeFileSync(validatedPath, newContent, 'utf-8');
-		invalidateFileRead(validatedPath);
-
-		// Build output
-		const lineDesc =
-			removedCount === 1 ? `line ${startLine}` : `lines ${startLine}-${effectiveEndLine}`;
-
-		const output: string[] = [
-			`path=${filePath} mode=remove_lines status=success`,
-			'',
-			`Removed ${removedCount} line${removedCount > 1 ? 's' : ''} (${lineDesc}).`,
-			'',
-			'--- BEFORE ---',
-			beforeContext,
-			'',
-			'--- AFTER ---',
-			this.formatContext(
-				newLines,
-				Math.max(1, startLine - 1),
-				Math.min(newLines.length, startLine),
-				3,
-			) || '(empty file)',
-		];
-
-		if (filePath.endsWith('.ts') || filePath.endsWith('.tsx')) {
-			output.push('', this.runDiagnostics(validatedPath));
-		}
-
-		return output.join('\n');
-	}
-
-	private buildSearchReplaceOutput(
-		filePath: string,
-		validatedPath: string,
-		matches: Array<{
-			startLine: number;
-			endLine: number;
-			strategy: string;
-		}>,
-		beforeContexts: Array<{
-			startLine: number;
-			endLine: number;
-			context: string;
-		}>,
-		replace: string,
-		newContent: string,
-	): string {
-		const newLines = newContent.split('\n');
-		const output: string[] = [
-			`path=${filePath} status=success matches=${matches.length} strategy=${matches[0].strategy}`,
-			'',
-			`Replaced ${matches.length} occurrence${matches.length > 1 ? 's' : ''}.`,
-		];
-
-		const replacementLineCount = replace.split('\n').length;
-		let cumulativeLineDelta = 0;
-
-		for (let i = 0; i < matches.length; i++) {
-			const match = matches[i];
-			const matchedLineCount = match.endLine - match.startLine + 1;
-			const lineDelta = replacementLineCount - matchedLineCount;
-			const afterStartLine = match.startLine + cumulativeLineDelta;
-			const afterEndLine = afterStartLine + replacementLineCount - 1;
-
-			output.push(
-				'',
-				`=== Edit ${i + 1} (lines ${match.startLine}-${match.endLine}) ===`,
-				'--- BEFORE ---',
-				beforeContexts[i].context,
-				'',
-				'--- AFTER ---',
-				this.formatContext(newLines, afterStartLine, afterEndLine, 5),
-			);
-
-			cumulativeLineDelta += lineDelta;
-		}
-
-		if (filePath.endsWith('.ts') || filePath.endsWith('.tsx')) {
-			output.push('', this.runDiagnostics(validatedPath));
-		}
-
-		return output.join('\n');
-	}
-
-	private formatFailure(
-		filePath: string,
-		search: string,
-		failure: {
-			reason: string;
-			suggestions: Array<{
-				content: string;
-				lineNumber: number;
-				similarity: number;
-			}>;
-			nearbyContext: string;
-		},
-	): string {
-		const lines: string[] = [
-			`ERROR: Search content NOT FOUND in file ${filePath}`,
-			'',
-			'SEARCH CONTENT:',
-			'```',
-			search,
-			'```',
-		];
-
-		if (failure.suggestions.length > 0) {
-			lines.push('', 'SUGGESTIONS (similar content found):');
-			for (const suggestion of failure.suggestions) {
-				const percent = Math.round(suggestion.similarity * 100);
-				lines.push(
-					'',
-					`Line ${suggestion.lineNumber} (${percent}% similar):`,
-					'```',
-					suggestion.content,
-					'```',
-				);
-			}
-
-			if (failure.nearbyContext) {
-				lines.push('', 'CONTEXT:', failure.nearbyContext);
-			}
-		}
-
-		return lines.join('\n');
-	}
-
-	private formatContext(
-		lines: string[],
-		startLine: number,
-		endLine: number,
-		contextLines = 5,
-		editMarker = '>',
-	): string {
-		const rangeStart = Math.max(0, startLine - 1 - contextLines);
-		const rangeEnd = Math.min(lines.length, endLine + contextLines);
-
-		const result: string[] = [];
-		for (let i = rangeStart; i < rangeEnd; i++) {
-			const lineNum = i + 1;
-			const isEdited = lineNum >= startLine && lineNum <= endLine;
-			const marker = isEdited ? editMarker : ' ';
-			const paddedNum = String(lineNum).padStart(4);
-			result.push(`${marker}${paddedNum} | ${lines[i]}`);
-		}
-
-		return result.join('\n');
-	}
-
-	private runDiagnostics(filePath: string): string {
-		const sections: string[] = [];
-
-		// TypeScript check
-		try {
-			execSync('npx tsc --noEmit --pretty false', {
-				encoding: 'utf-8',
-				cwd: process.cwd(),
-				timeout: 20000,
-				stdio: 'pipe',
-			});
-			sections.push('=== TypeScript Check ===');
-			sections.push('No type errors found.');
-		} catch (error) {
-			const execError = error as { stdout?: string; stderr?: string };
-			const output = [execError.stdout, execError.stderr].filter(Boolean).join('\n');
-			// Filter to errors in the edited file, but keep full error messages
-			const lines = output.split('\n');
-			const fileErrors: string[] = [];
-			let includeNext = false;
-			for (const line of lines) {
-				if (line.includes(filePath)) {
-					fileErrors.push(line);
-					includeNext = true;
-				} else if (includeNext && (line.startsWith(' ') || line === '')) {
-					fileErrors.push(line);
-				} else {
-					includeNext = false;
-				}
-			}
-			sections.push('=== TypeScript Check ===');
-			sections.push(fileErrors.join('\n') || 'No type errors found.');
-		}
-
-		// Biome lint check
-		try {
-			execSync(`npx biome check "${filePath}"`, {
-				encoding: 'utf-8',
-				cwd: process.cwd(),
-				timeout: 10000,
-				stdio: 'pipe',
-			});
-			sections.push('');
-			sections.push('=== Biome Lint ===');
-			sections.push('No lint issues found.');
-		} catch (error) {
-			const execError = error as { stdout?: string; stderr?: string };
-			// Biome outputs diagnostics to stdout, summary to stderr - capture both
-			const output = [execError.stdout, execError.stderr].filter(Boolean).join('\n');
-			sections.push('');
-			sections.push('=== Biome Lint ===');
-			sections.push(output.trim() || 'No lint issues found.');
-		}
-
-		return sections.join('\n');
-	}
-}
diff --git a/src/gadgets/FileInsertContent.ts b/src/gadgets/FileInsertContent.ts
new file mode 100644
index 00000000..2a7b387a
--- /dev/null
+++ b/src/gadgets/FileInsertContent.ts
@@ -0,0 +1,341 @@
+/**
+ * FileInsertContent gadget - Insert content at a specific line number.
+ *
+ * Line numbers are 1-based. Content is inserted BEFORE the specified line.
+ * Use a line beyond EOF to append at end.
+ */
+
+import { readFileSync, writeFileSync } from 'node:fs';
+
+import { Gadget, z } from 'llmist';
+
+import { invalidateFileRead } from './readTracking.js';
+import {
+	formatContext,
+	runDiagnostics,
+	shouldRunDiagnostics,
+	validatePath,
+} from './shared/index.js';
+
+export class FileInsertContent extends Gadget({
+	name: 'FileInsertContent',
+	description: `Insert content at a specific line number in a file.
+
+- Line numbers are 1-based
+- Content is inserted BEFORE the specified line
+- Use line beyond EOF to append at end`,
+	timeoutMs: 30000,
+	maxConcurrent: 1, // Sequential execution to prevent race conditions on file writes
+	schema: z.object({
+		comment: z.string().min(1).describe('Brief rationale for this gadget call'),
+		filePath: z.string().describe('Path to the file to edit'),
+		line: z
+			.number()
+			.int()
+			.min(1)
+			.describe('Line number to insert BEFORE (1-based). Use line beyond EOF to append.'),
+		content: z.string().describe('Content to insert (can be multiline)'),
+	}),
+	examples: [
+		// Example 1: Single-line import at top
+		{
+			params: {
+				comment: 'Adding lodash import at top of file',
+				filePath: 'src/utils.ts',
+				line: 1,
+				content: "import _ from 'lodash';",
+			},
+			output: `path=src/utils.ts status=success
+
+Inserted 1 line at line 1.
+
+--- BEFORE (around line 1) ---
+<  1 | import { foo } from 'bar';
+   2 | import { baz } from 'qux';
+   3 |
+
+--- AFTER ---
+>  1 | import _ from 'lodash';
+   2 | import { foo } from 'bar';
+   3 | import { baz } from 'qux';
+   4 |
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Insert import at beginning of file',
+		},
+		// Example 2: Multi-line function insertion
+		{
+			params: {
+				comment: 'Adding helper function in middle of file',
+				filePath: 'src/helpers.ts',
+				line: 10,
+				content: `function validate(x: number): boolean {
+  return x > 0;
+}`,
+			},
+			output: `path=src/helpers.ts status=success
+
+Inserted 3 lines at line 10.
+
+--- BEFORE (around line 10) ---
+   7 | }
+   8 |
+   9 | // Utils below
+< 10 | function process(data: string) {
+  11 |   return data.trim();
+  12 | }
+
+--- AFTER ---
+   7 | }
+   8 |
+   9 | // Utils below
+> 10 | function validate(x: number): boolean {
+  11 |   return x > 0;
+  12 | }
+  13 | function process(data: string) {
+  14 |   return data.trim();
+  15 | }
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Insert multiline block in middle of file',
+		},
+		// Example 3: Inserting a full interface definition
+		{
+			params: {
+				comment: 'Adding User interface after imports',
+				filePath: 'src/types/user.ts',
+				line: 5,
+				content: `export interface User {
+  id: string;
+  email: string;
+  name: string;
+  createdAt: Date;
+  updatedAt: Date;
+  role: 'admin' | 'user' | 'guest';
+  preferences: {
+    theme: 'light' | 'dark';
+    notifications: boolean;
+  };
+}`,
+			},
+			output: `path=src/types/user.ts status=success
+
+Inserted 12 lines at line 5.
+
+--- BEFORE (around line 5) ---
+   2 | import type { BaseEntity } from './base';
+   3 | import type { Preferences } from './preferences';
+   4 |
+<  5 | // User types will be defined here
+   6 |
+
+--- AFTER ---
+   2 | import type { BaseEntity } from './base';
+   3 | import type { Preferences } from './preferences';
+   4 |
+>  5 | export interface User {
+>  6 |   id: string;
+>  7 |   email: string;
+>  8 |   name: string;
+>  9 |   createdAt: Date;
+> 10 |   updatedAt: Date;
+> 11 |   role: 'admin' | 'user' | 'guest';
+> 12 |   preferences: {
+> 13 |     theme: 'light' | 'dark';
+> 14 |     notifications: boolean;
+> 15 |   };
+> 16 | }
+  17 | // User types will be defined here
+  18 |
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Insert complete interface definition',
+		},
+		// Example 4: Append at end of file
+		{
+			params: {
+				comment: 'Appending export at end of file',
+				filePath: 'src/index.ts',
+				line: 999,
+				content: "export * from './newModule';",
+			},
+			output: `path=src/index.ts status=success
+
+Appended 1 line at end of file.
+
+--- BEFORE (end of file) ---
+   3 | export * from './utils';
+   4 | export * from './helpers';
+   5 |
+
+--- AFTER ---
+   3 | export * from './utils';
+   4 | export * from './helpers';
+   5 |
+>  6 | export * from './newModule';
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Append at end of file (line beyond EOF)',
+		},
+		// Example 5: Inserting a complete class
+		{
+			params: {
+				comment: 'Adding Logger class implementation',
+				filePath: 'src/utils/logger.ts',
+				line: 8,
+				content: `export class Logger {
+  private readonly prefix: string;
+  private readonly level: LogLevel;
+
+  constructor(prefix: string, level: LogLevel = 'info') {
+    this.prefix = prefix;
+    this.level = level;
+  }
+
+  info(message: string, context?: Record<string, unknown>): void {
+    this.log('info', message, context);
+  }
+
+  error(message: string, context?: Record<string, unknown>): void {
+    this.log('error', message, context);
+  }
+
+  private log(level: LogLevel, message: string, context?: Record<string, unknown>): void {
+    const timestamp = new Date().toISOString();
+    console.log(JSON.stringify({ timestamp, level, prefix: this.prefix, message, ...context }));
+  }
+}`,
+			},
+			output: `path=src/utils/logger.ts status=success
+
+Inserted 22 lines at line 8.
+
+--- BEFORE (around line 8) ---
+   5 | type LogLevel = 'debug' | 'info' | 'warn' | 'error';
+   6 |
+   7 | // Logger implementation
+<  8 | export function createLogger(prefix: string) {
+
+--- AFTER ---
+   5 | type LogLevel = 'debug' | 'info' | 'warn' | 'error';
+   6 |
+   7 | // Logger implementation
+>  8 | export class Logger {
+>  9 |   private readonly prefix: string;
+> 10 |   private readonly level: LogLevel;
+> 11 |
+> 12 |   constructor(prefix: string, level: LogLevel = 'info') {
+> 13 |     this.prefix = prefix;
+> 14 |     this.level = level;
+> 15 |   }
+> 16 |
+> 17 |   info(message: string, context?: Record<string, unknown>): void {
+> 18 |     this.log('info', message, context);
+> 19 |   }
+> 20 |
+> 21 |   error(message: string, context?: Record<string, unknown>): void {
+> 22 |     this.log('error', message, context);
+> 23 |   }
+> 24 |
+> 25 |   private log(level: LogLevel, message: string, context?: Record<string, unknown>): void {
+> 26 |     const timestamp = new Date().toISOString();
+> 27 |     console.log(JSON.stringify({ timestamp, level, prefix: this.prefix, message, ...context }));
+> 28 |   }
+> 29 | }
+  30 | export function createLogger(prefix: string) {
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Insert complete class definition',
+		},
+	],
+}) {
+	override execute(params: this['params']): string {
+		const { filePath, line, content: insertContent } = params;
+
+		// Validate and resolve path
+		const validatedPath = validatePath(filePath);
+
+		// Read file content
+		let content: string;
+		try {
+			content = readFileSync(validatedPath, 'utf-8');
+		} catch (error) {
+			const nodeError = error as NodeJS.ErrnoException;
+			if (nodeError.code === 'ENOENT') {
+				// For insert, create empty file
+				content = '';
+			} else {
+				throw error;
+			}
+		}
+
+		const lines = content.split('\n');
+		const insertLines = insertContent.split('\n');
+		const insertAtEnd = line > lines.length;
+		const effectiveLine = Math.min(line, lines.length + 1);
+
+		// Store before context
+		const beforeContext = formatContext(lines, effectiveLine, effectiveLine, 3, '<');
+
+		// Insert lines
+		const newLines = [
+			...lines.slice(0, effectiveLine - 1),
+			...insertLines,
+			...lines.slice(effectiveLine - 1),
+		];
+
+		const newContent = newLines.join('\n');
+		writeFileSync(validatedPath, newContent, 'utf-8');
+		invalidateFileRead(validatedPath);
+
+		// Build output
+		const output: string[] = [`path=${filePath} status=success`, ''];
+
+		if (insertAtEnd) {
+			output.push(
+				`Appended ${insertLines.length} line${insertLines.length > 1 ? 's' : ''} at end of file.`,
+			);
+		} else {
+			output.push(
+				`Inserted ${insertLines.length} line${insertLines.length > 1 ? 's' : ''} at line ${effectiveLine}.`,
+			);
+		}
+
+		output.push(
+			'',
+			insertAtEnd
+				? '--- BEFORE (end of file) ---'
+				: `--- BEFORE (around line ${effectiveLine}) ---`,
+			beforeContext || '(empty file)',
+			'',
+			'--- AFTER ---',
+			formatContext(newLines, effectiveLine, effectiveLine + insertLines.length - 1, 3),
+		);
+
+		if (shouldRunDiagnostics(filePath)) {
+			output.push('', runDiagnostics(validatedPath));
+		}
+
+		return output.join('\n');
+	}
+}
diff --git a/src/gadgets/FileRemoveContent.ts b/src/gadgets/FileRemoveContent.ts
new file mode 100644
index 00000000..217c8e1f
--- /dev/null
+++ b/src/gadgets/FileRemoveContent.ts
@@ -0,0 +1,203 @@
+/**
+ * FileRemoveContent gadget - Remove a range of lines from a file.
+ *
+ * Line numbers are 1-based and inclusive.
+ */
+
+import { readFileSync, writeFileSync } from 'node:fs';
+
+import { Gadget, z } from 'llmist';
+
+import { invalidateFileRead } from './readTracking.js';
+import {
+	formatContext,
+	runDiagnostics,
+	shouldRunDiagnostics,
+	validatePath,
+} from './shared/index.js';
+
+export class FileRemoveContent extends Gadget({
+	name: 'FileRemoveContent',
+	description: `Remove a range of lines from a file.
+
+- Line numbers are 1-based and inclusive
+- startLine and endLine define the range to remove`,
+	timeoutMs: 30000,
+	maxConcurrent: 1, // Sequential execution to prevent race conditions on file writes
+	schema: z.object({
+		comment: z.string().min(1).describe('Brief rationale for this gadget call'),
+		filePath: z.string().describe('Path to the file to edit'),
+		startLine: z.number().int().min(1).describe('First line to remove (1-based, inclusive)'),
+		endLine: z.number().int().min(1).describe('Last line to remove (1-based, inclusive)'),
+	}),
+	examples: [
+		// Example 1: Remove single line
+		{
+			params: {
+				comment: 'Removing unused import',
+				filePath: 'src/app.ts',
+				startLine: 3,
+				endLine: 3,
+			},
+			output: `path=src/app.ts status=success
+
+Removed 1 line (line 3).
+
+--- BEFORE ---
+   1 | import { foo } from 'foo';
+   2 | import { bar } from 'bar';
+<  3 | import { unused } from 'unused';
+   4 | import { baz } from 'baz';
+   5 |
+
+--- AFTER ---
+   1 | import { foo } from 'foo';
+   2 | import { bar } from 'bar';
+   3 | import { baz } from 'baz';
+   4 |
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Remove single line',
+		},
+		// Example 2: Remove block of lines (deprecated function)
+		{
+			params: {
+				comment: 'Removing deprecated function',
+				filePath: 'src/legacy.ts',
+				startLine: 5,
+				endLine: 10,
+			},
+			output: `path=src/legacy.ts status=success
+
+Removed 6 lines (lines 5-10).
+
+--- BEFORE ---
+   2 |
+   3 | export function keepThis() {}
+   4 |
+<  5 | /** @deprecated */
+<  6 | function oldFunc(x: number) {
+<  7 |   console.log('deprecated');
+<  8 |   return x * 2;
+<  9 | }
+< 10 |
+  11 | export function keepThisToo() {}
+
+--- AFTER ---
+   2 |
+   3 | export function keepThis() {}
+   4 |
+   5 | export function keepThisToo() {}
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Remove block of lines',
+		},
+		// Example 3: Remove from non-TS file
+		{
+			params: {
+				comment: 'Removing comment block from config',
+				filePath: 'config/settings.json',
+				startLine: 2,
+				endLine: 4,
+			},
+			output: `path=config/settings.json status=success
+
+Removed 3 lines (lines 2-4).
+
+--- BEFORE ---
+   1 | {
+<  2 |   "// NOTE": "Remove this later",
+<  3 |   "// TODO": "Clean up config",
+<  4 |   "// FIXME": "Legacy value",
+   5 |   "enabled": true,
+   6 |   "timeout": 5000
+   7 | }
+
+--- AFTER ---
+   1 | {
+   2 |   "enabled": true,
+   3 |   "timeout": 5000
+   4 | }`,
+			comment: 'Remove from non-TS file (no diagnostics)',
+		},
+	],
+}) {
+	override execute(params: this['params']): string {
+		const { filePath, startLine, endLine } = params;
+
+		// Validate line range
+		if (startLine > endLine) {
+			throw new Error(`Invalid line range: startLine (${startLine}) > endLine (${endLine})`);
+		}
+
+		// Validate and resolve path
+		const validatedPath = validatePath(filePath);
+
+		// Read file content
+		let content: string;
+		try {
+			content = readFileSync(validatedPath, 'utf-8');
+		} catch (error) {
+			const nodeError = error as NodeJS.ErrnoException;
+			if (nodeError.code === 'ENOENT') {
+				throw new Error(`File not found: ${filePath}`);
+			}
+			throw error;
+		}
+
+		const lines = content.split('\n');
+
+		// Validate startLine
+		if (startLine > lines.length) {
+			throw new Error(`startLine (${startLine}) is beyond end of file (${lines.length} lines)`);
+		}
+
+		const effectiveEndLine = Math.min(endLine, lines.length);
+		const removedCount = effectiveEndLine - startLine + 1;
+
+		// Store before context with highlight on lines to remove
+		const beforeContext = formatContext(lines, startLine, effectiveEndLine, 3, '<');
+
+		// Remove lines
+		const newLines = [...lines.slice(0, startLine - 1), ...lines.slice(effectiveEndLine)];
+
+		const newContent = newLines.join('\n');
+		writeFileSync(validatedPath, newContent, 'utf-8');
+		invalidateFileRead(validatedPath);
+
+		// Build output
+		const lineDesc =
+			removedCount === 1 ? `line ${startLine}` : `lines ${startLine}-${effectiveEndLine}`;
+
+		const output: string[] = [
+			`path=${filePath} status=success`,
+			'',
+			`Removed ${removedCount} line${removedCount > 1 ? 's' : ''} (${lineDesc}).`,
+			'',
+			'--- BEFORE ---',
+			beforeContext,
+			'',
+			'--- AFTER ---',
+			formatContext(
+				newLines,
+				Math.max(1, startLine - 1),
+				Math.min(newLines.length, startLine),
+				3,
+			) || '(empty file)',
+		];
+
+		if (shouldRunDiagnostics(filePath)) {
+			output.push('', runDiagnostics(validatedPath));
+		}
+
+		return output.join('\n');
+	}
+}
diff --git a/src/gadgets/FileSearchAndReplace.ts b/src/gadgets/FileSearchAndReplace.ts
new file mode 100644
index 00000000..4cd312b2
--- /dev/null
+++ b/src/gadgets/FileSearchAndReplace.ts
@@ -0,0 +1,439 @@
+/**
+ * FileSearchAndReplace gadget - Search for content and replace it.
+ *
+ * Uses layered matching strategies: exact → whitespace → indentation → fuzzy
+ * This approach reduces edit errors by ~9x (per Aider benchmarks).
+ */
+
+import { readFileSync, writeFileSync } from 'node:fs';
+
+import { Gadget, z } from 'llmist';
+
+import { invalidateFileRead } from './readTracking.js';
+import {
+	applyReplacement,
+	findAllMatches,
+	formatContext,
+	getMatchFailure,
+	runDiagnostics,
+	shouldRunDiagnostics,
+	validatePath,
+} from './shared/index.js';
+
+export class FileSearchAndReplace extends Gadget({
+	name: 'FileSearchAndReplace',
+	description: `Search for content in a file and replace it.
+
+Uses layered matching: exact → whitespace → indentation → fuzzy
+This reduces edit errors by ~9x.
+
+All occurrences of the search content are replaced.`,
+	timeoutMs: 30000,
+	maxConcurrent: 1, // Sequential execution to prevent race conditions on file writes
+	schema: z.object({
+		comment: z.string().min(1).describe('Brief rationale for this gadget call'),
+		filePath: z.string().describe('Path to the file to edit'),
+		search: z.string().min(1).describe('The content to search for'),
+		replace: z.string().describe('The content to replace with (empty to delete)'),
+	}),
+	examples: [
+		// Example 1: Single-line replacement
+		{
+			params: {
+				comment: 'Increasing timeout from 1s to 5s to fix test flakiness',
+				filePath: 'src/config.ts',
+				search: 'timeout: 1000',
+				replace: 'timeout: 5000',
+			},
+			output: `path=src/config.ts status=success matches=1 strategy=exact
+
+Replaced 1 occurrence.
+
+=== Edit 1 (lines 5-5) ===
+--- BEFORE ---
+   1 | import { foo } from "bar";
+   2 |
+   3 | const CONFIG = {
+   4 |   debug: false,
+<  5 |   timeout: 1000,
+   6 |   retries: 3,
+   7 | };
+
+--- AFTER ---
+   1 | import { foo } from "bar";
+   2 |
+   3 | const CONFIG = {
+   4 |   debug: false,
+>  5 |   timeout: 5000,
+   6 |   retries: 3,
+   7 | };
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Single edit with before/after context and diagnostics',
+		},
+		// Example 2: Multi-line function replacement
+		{
+			params: {
+				comment: 'Replacing sync function with async implementation',
+				filePath: 'src/api/users.ts',
+				search: `function getUser(id: string): User | null {
+  const user = userCache.get(id);
+  return user || null;
+}`,
+				replace: `async function getUser(id: string): Promise<User | null> {
+  // Check cache first
+  const cached = userCache.get(id);
+  if (cached) return cached;
+
+  // Fetch from database
+  const user = await db.users.findById(id);
+  if (user) {
+    userCache.set(id, user);
+  }
+  return user;
+}`,
+			},
+			output: `path=src/api/users.ts status=success matches=1 strategy=exact
+
+Replaced 1 occurrence.
+
+=== Edit 1 (lines 12-15) ===
+--- BEFORE ---
+   9 | import { db } from '../db';
+  10 | import { userCache } from '../cache';
+  11 |
+< 12 | function getUser(id: string): User | null {
+< 13 |   const user = userCache.get(id);
+< 14 |   return user || null;
+< 15 | }
+  16 |
+  17 | function updateUser(id: string, data: Partial<User>): void {
+
+--- AFTER ---
+   9 | import { db } from '../db';
+  10 | import { userCache } from '../cache';
+  11 |
+> 12 | async function getUser(id: string): Promise<User | null> {
+> 13 |   // Check cache first
+> 14 |   const cached = userCache.get(id);
+> 15 |   if (cached) return cached;
+> 16 |
+> 17 |   // Fetch from database
+> 18 |   const user = await db.users.findById(id);
+> 19 |   if (user) {
+> 20 |     userCache.set(id, user);
+> 21 |   }
+> 22 |   return user;
+> 23 | }
+  24 |
+  25 | function updateUser(id: string, data: Partial<User>): void {
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Replace entire function with new async implementation',
+		},
+		// Example 3: Adding error handling to existing code
+		{
+			params: {
+				comment: 'Adding try-catch error handling to API call',
+				filePath: 'src/services/payment.ts',
+				search: `const result = await stripe.charges.create({
+  amount: order.total,
+  currency: 'usd',
+  source: token,
+});
+return result;`,
+				replace: `try {
+  const result = await stripe.charges.create({
+    amount: order.total,
+    currency: 'usd',
+    source: token,
+  });
+  return result;
+} catch (error) {
+  logger.error('Payment failed', { orderId: order.id, error });
+  throw new PaymentError('Failed to process payment', { cause: error });
+}`,
+			},
+			output: `path=src/services/payment.ts status=success matches=1 strategy=exact
+
+Replaced 1 occurrence.
+
+=== Edit 1 (lines 24-29) ===
+--- BEFORE ---
+  21 | async function processPayment(order: Order, token: string) {
+  22 |   validateOrder(order);
+  23 |
+< 24 |   const result = await stripe.charges.create({
+< 25 |     amount: order.total,
+< 26 |     currency: 'usd',
+< 27 |     source: token,
+< 28 |   });
+< 29 |   return result;
+  30 | }
+
+--- AFTER ---
+  21 | async function processPayment(order: Order, token: string) {
+  22 |   validateOrder(order);
+  23 |
+> 24 |   try {
+> 25 |     const result = await stripe.charges.create({
+> 26 |       amount: order.total,
+> 27 |       currency: 'usd',
+> 28 |       source: token,
+> 29 |     });
+> 30 |     return result;
+> 31 |   } catch (error) {
+> 32 |     logger.error('Payment failed', { orderId: order.id, error });
+> 33 |     throw new PaymentError('Failed to process payment', { cause: error });
+> 34 |   }
+  35 | }
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Wrap existing code with try-catch error handling',
+		},
+		// Example 4: Multiple occurrences
+		{
+			params: {
+				comment: 'Updating retry constant per requirements',
+				filePath: 'src/constants.ts',
+				search: 'MAX_RETRIES = 3',
+				replace: 'MAX_RETRIES = 5',
+			},
+			output: `path=src/constants.ts status=success matches=2 strategy=exact
+
+Replaced 2 occurrences.
+
+=== Edit 1 (lines 4-4) ===
+--- BEFORE ---
+   1 | // API constants
+   2 | export const API_URL = "https://api.example.com";
+   3 |
+<  4 | export const MAX_RETRIES = 3;
+   5 | export const TIMEOUT = 5000;
+
+--- AFTER ---
+   1 | // API constants
+   2 | export const API_URL = "https://api.example.com";
+   3 |
+>  4 | export const MAX_RETRIES = 5;
+   5 | export const TIMEOUT = 5000;
+
+=== Edit 2 (lines 12-12) ===
+--- BEFORE ---
+   9 | // Client constants
+  10 | export const CLIENT_URL = "https://client.example.com";
+  11 |
+< 12 | export const MAX_RETRIES = 3;
+  13 | export const CLIENT_TIMEOUT = 3000;
+
+--- AFTER ---
+   9 | // Client constants
+  10 | export const CLIENT_URL = "https://client.example.com";
+  11 |
+> 12 | export const MAX_RETRIES = 5;
+  13 | export const CLIENT_TIMEOUT = 3000;
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Multiple matches replaced with before/after for each',
+		},
+		// Example 5: Non-TypeScript file (no diagnostics)
+		{
+			params: {
+				comment: 'Enabling feature flag for new functionality',
+				filePath: 'src/data.json',
+				search: '"enabled": false',
+				replace: '"enabled": true',
+			},
+			output: `path=src/data.json status=success matches=1 strategy=exact
+
+Replaced 1 occurrence.
+
+=== Edit 1 (lines 3-3) ===
+--- BEFORE ---
+   1 | {
+   2 |   "name": "example",
+<  3 |   "enabled": false,
+   4 |   "count": 0
+   5 | }
+
+--- AFTER ---
+   1 | {
+   2 |   "name": "example",
+>  3 |   "enabled": true,
+   4 |   "count": 0
+   5 | }`,
+			comment: 'Non-TypeScript file (no diagnostics appended)',
+		},
+	],
+}) {
+	override execute(params: this['params']): string {
+		const { filePath, search, replace } = params;
+
+		// Validate and resolve path
+		const validatedPath = validatePath(filePath);
+
+		// Read file content
+		let content: string;
+		try {
+			content = readFileSync(validatedPath, 'utf-8');
+		} catch (error) {
+			const nodeError = error as NodeJS.ErrnoException;
+			if (nodeError.code === 'ENOENT') {
+				throw new Error(`File not found: ${filePath}`);
+			}
+			throw error;
+		}
+
+		// Find ALL matches using layered strategies
+		const matches = findAllMatches(content, search);
+
+		if (matches.length === 0) {
+			// No match found - throw with helpful suggestions
+			const failure = getMatchFailure(content, search);
+			throw new Error(this.formatFailure(filePath, search, failure));
+		}
+
+		// Store original content for before/after display
+		const originalLines = content.split('\n');
+
+		// Collect before contexts BEFORE applying any replacements
+		const beforeContexts: Array<{
+			startLine: number;
+			endLine: number;
+			context: string;
+		}> = [];
+		for (const match of matches) {
+			beforeContexts.push({
+				startLine: match.startLine,
+				endLine: match.endLine,
+				context: formatContext(originalLines, match.startLine, match.endLine, 5, '<'),
+			});
+		}
+
+		// Apply replacements in reverse order (to preserve indices)
+		let newContent = content;
+		const sortedMatches = [...matches].sort((a, b) => b.startIndex - a.startIndex);
+		for (const match of sortedMatches) {
+			newContent = applyReplacement(newContent, match, replace);
+		}
+
+		// Write file
+		writeFileSync(validatedPath, newContent, 'utf-8');
+		invalidateFileRead(validatedPath);
+
+		// Build and return success output
+		return this.buildOutput(filePath, validatedPath, matches, beforeContexts, replace, newContent);
+	}
+
+	private buildOutput(
+		filePath: string,
+		validatedPath: string,
+		matches: Array<{
+			startLine: number;
+			endLine: number;
+			strategy: string;
+		}>,
+		beforeContexts: Array<{
+			startLine: number;
+			endLine: number;
+			context: string;
+		}>,
+		replace: string,
+		newContent: string,
+	): string {
+		const newLines = newContent.split('\n');
+		const output: string[] = [
+			`path=${filePath} status=success matches=${matches.length} strategy=${matches[0].strategy}`,
+			'',
+			`Replaced ${matches.length} occurrence${matches.length > 1 ? 's' : ''}.`,
+		];
+
+		const replacementLineCount = replace.split('\n').length;
+		let cumulativeLineDelta = 0;
+
+		for (let i = 0; i < matches.length; i++) {
+			const match = matches[i];
+			const matchedLineCount = match.endLine - match.startLine + 1;
+			const lineDelta = replacementLineCount - matchedLineCount;
+			const afterStartLine = match.startLine + cumulativeLineDelta;
+			const afterEndLine = afterStartLine + replacementLineCount - 1;
+
+			output.push(
+				'',
+				`=== Edit ${i + 1} (lines ${match.startLine}-${match.endLine}) ===`,
+				'--- BEFORE ---',
+				beforeContexts[i].context,
+				'',
+				'--- AFTER ---',
+				formatContext(newLines, afterStartLine, afterEndLine, 5),
+			);
+
+			cumulativeLineDelta += lineDelta;
+		}
+
+		if (shouldRunDiagnostics(filePath)) {
+			output.push('', runDiagnostics(validatedPath));
+		}
+
+		return output.join('\n');
+	}
+
+	private formatFailure(
+		filePath: string,
+		search: string,
+		failure: {
+			reason: string;
+			suggestions: Array<{
+				content: string;
+				lineNumber: number;
+				similarity: number;
+			}>;
+			nearbyContext: string;
+		},
+	): string {
+		const lines: string[] = [
+			`ERROR: Search content NOT FOUND in file ${filePath}`,
+			'',
+			'SEARCH CONTENT:',
+			'```',
+			search,
+			'```',
+		];
+
+		if (failure.suggestions.length > 0) {
+			lines.push('', 'SUGGESTIONS (similar content found):');
+			for (const suggestion of failure.suggestions) {
+				const percent = Math.round(suggestion.similarity * 100);
+				lines.push(
+					'',
+					`Line ${suggestion.lineNumber} (${percent}% similar):`,
+					'```',
+					suggestion.content,
+					'```',
+				);
+			}
+
+			if (failure.nearbyContext) {
+				lines.push('', 'CONTEXT:', failure.nearbyContext);
+			}
+		}
+
+		return lines.join('\n');
+	}
+}
diff --git a/src/gadgets/Finish.ts b/src/gadgets/Finish.ts
index b32a6bca..ce1398e0 100644
--- a/src/gadgets/Finish.ts
+++ b/src/gadgets/Finish.ts
@@ -1,4 +1,5 @@
 import { Gadget, TaskCompletionSignal, z } from 'llmist';
+import { getSessionState } from './sessionState.js';
 
 export class Finish extends Gadget({
 	name: 'Finish',
@@ -16,6 +17,16 @@ export class Finish extends Gadget({
 	],
 }) {
 	override execute(params: this['params']): never {
+		const state = getSessionState();
+
+		// For implementation agent, require PR creation
+		if (state.agentType === 'implementation' && !state.prCreated) {
+			throw new Error(
+				'Cannot finish implementation session without creating a PR. ' +
+					'You must call CreatePR to submit your changes before calling Finish.',
+			);
+		}
+
 		throw new TaskCompletionSignal(params.comment);
 	}
 }
diff --git a/src/gadgets/WriteFile.ts b/src/gadgets/WriteFile.ts
index 5c8c412e..9a870510 100644
--- a/src/gadgets/WriteFile.ts
+++ b/src/gadgets/WriteFile.ts
@@ -92,6 +92,46 @@ No type errors found.
 No lint issues found.`,
 			comment: 'Write a TypeScript file with diagnostics output',
 		},
+		{
+			params: {
+				comment: 'Creating user service class',
+				filePath: 'src/services/userService.ts',
+				content: `import { db } from '../db';
+import type { User } from '../types';
+
+export class UserService {
+  async getUser(id: string): Promise<User | null> {
+    return db.users.findById(id);
+  }
+
+  async createUser(data: Partial<User>): Promise<User> {
+    return db.users.create(data);
+  }
+
+  async updateUser(id: string, data: Partial<User>): Promise<User> {
+    const user = await this.getUser(id);
+    if (!user) {
+      throw new Error(\`User not found: \${id}\`);
+    }
+    return db.users.update(id, data);
+  }
+
+  async deleteUser(id: string): Promise<void> {
+    await db.users.delete(id);
+  }
+}`,
+			},
+			output: `path=src/services/userService.ts
+
+Wrote 542 bytes
+
+=== TypeScript Check ===
+No type errors found.
+
+=== Biome Lint ===
+No lint issues found.`,
+			comment: 'Write a complete TypeScript file with multi-line content',
+		},
 	],
 }) {
 	override execute(params: this['params']): string {
diff --git a/src/gadgets/github/CreatePR.ts b/src/gadgets/github/CreatePR.ts
index cc474b3d..968af225 100644
--- a/src/gadgets/github/CreatePR.ts
+++ b/src/gadgets/github/CreatePR.ts
@@ -1,6 +1,7 @@
 import { Gadget, z } from 'llmist';
 import { githubClient } from '../../github/client.js';
 import { runCommand } from '../../utils/repo.js';
+import { recordPRCreation } from '../sessionState.js';
 
 export class CreatePR extends Gadget({
 	name: 'CreatePR',
@@ -150,6 +151,10 @@ If hooks fail or timeout, the full output will be shown.`,
 			draft: params.draft,
 		});
 		const draftLabel = params.draft ? ' (draft)' : '';
+
+		// Record PR creation for session state (Finish gadget uses this to verify implementation completed)
+		recordPRCreation(pr.htmlUrl);
+
 		return `PR #${pr.number} created successfully${draftLabel}: ${pr.htmlUrl}`;
 	}
 }
diff --git a/src/gadgets/index.ts b/src/gadgets/index.ts
index fb2b9f34..49edfe5d 100644
--- a/src/gadgets/index.ts
+++ b/src/gadgets/index.ts
@@ -1,3 +1,9 @@
+// File editing gadgets
+export { FileSearchAndReplace } from './FileSearchAndReplace.js';
+export { FileInsertContent } from './FileInsertContent.js';
+export { FileRemoveContent } from './FileRemoveContent.js';
+export { WriteFile } from './WriteFile.js';
+
 // Trello gadgets
 export {
 	ReadTrelloCard,
diff --git a/src/gadgets/readTracking.ts b/src/gadgets/readTracking.ts
index 622cd9ea..b047711a 100644
--- a/src/gadgets/readTracking.ts
+++ b/src/gadgets/readTracking.ts
@@ -39,7 +39,7 @@ export function markDirectoryListed(key: string): void {
 
 /**
  * Invalidate read tracking for a specific file.
- * Called after EditFile or WriteFile modifies a file.
+ * Called after file editing gadgets or WriteFile modifies a file.
  */
 export function invalidateFileRead(path: string): void {
 	readFiles.delete(path);
diff --git a/src/gadgets/sessionState.ts b/src/gadgets/sessionState.ts
new file mode 100644
index 00000000..c8d72c0a
--- /dev/null
+++ b/src/gadgets/sessionState.ts
@@ -0,0 +1,19 @@
+// Session-level state accessible to all gadgets
+let sessionState = {
+	agentType: null as string | null,
+	prCreated: false,
+	prUrl: null as string | null,
+};
+
+export function initSessionState(agentType: string): void {
+	sessionState = { agentType, prCreated: false, prUrl: null };
+}
+
+export function recordPRCreation(prUrl: string): void {
+	sessionState.prCreated = true;
+	sessionState.prUrl = prUrl;
+}
+
+export function getSessionState() {
+	return { ...sessionState };
+}
diff --git a/src/gadgets/shared/diagnostics.ts b/src/gadgets/shared/diagnostics.ts
new file mode 100644
index 00000000..6a6fd621
--- /dev/null
+++ b/src/gadgets/shared/diagnostics.ts
@@ -0,0 +1,80 @@
+/**
+ * Diagnostics runner for file editing gadgets.
+ *
+ * Runs TypeScript type checking and Biome linting after file modifications.
+ */
+
+import { execSync } from 'node:child_process';
+
+/**
+ * Run TypeScript and Biome diagnostics on a file.
+ *
+ * @param filePath The file path being checked (for filtering errors)
+ * @returns Formatted diagnostics output string
+ */
+export function runDiagnostics(filePath: string): string {
+	const sections: string[] = [];
+
+	// TypeScript check
+	try {
+		execSync('npx tsc --noEmit --pretty false', {
+			encoding: 'utf-8',
+			cwd: process.cwd(),
+			timeout: 20000,
+			stdio: 'pipe',
+		});
+		sections.push('=== TypeScript Check ===');
+		sections.push('No type errors found.');
+	} catch (error) {
+		const execError = error as { stdout?: string; stderr?: string };
+		const output = [execError.stdout, execError.stderr].filter(Boolean).join('\n');
+		// Filter to errors in the edited file, but keep full error messages
+		const lines = output.split('\n');
+		const fileErrors: string[] = [];
+		let includeNext = false;
+		for (const line of lines) {
+			if (line.includes(filePath)) {
+				fileErrors.push(line);
+				includeNext = true;
+			} else if (includeNext && (line.startsWith(' ') || line === '')) {
+				fileErrors.push(line);
+			} else {
+				includeNext = false;
+			}
+		}
+		sections.push('=== TypeScript Check ===');
+		sections.push(fileErrors.join('\n') || 'No type errors found.');
+	}
+
+	// Biome lint check
+	try {
+		execSync(`npx biome check "${filePath}"`, {
+			encoding: 'utf-8',
+			cwd: process.cwd(),
+			timeout: 10000,
+			stdio: 'pipe',
+		});
+		sections.push('');
+		sections.push('=== Biome Lint ===');
+		sections.push('No lint issues found.');
+	} catch (error) {
+		const execError = error as { stdout?: string; stderr?: string };
+		// Biome outputs diagnostics to stdout, summary to stderr - capture both
+		const output = [execError.stdout, execError.stderr].filter(Boolean).join('\n');
+		sections.push('');
+		sections.push('=== Biome Lint ===');
+		sections.push(output.trim() || 'No lint issues found.');
+	}
+
+	return sections.join('\n');
+}
+
+/**
+ * Check if a file should have diagnostics run.
+ *
+ * @param filePath The file path to check
+ * @returns True if the file is a TypeScript file
+ */
+export function shouldRunDiagnostics(filePath: string): boolean {
+	return filePath.endsWith('.ts') || filePath.endsWith('.tsx');
+}
diff --git a/src/gadgets/shared/index.ts b/src/gadgets/shared/index.ts
new file mode 100644
index 00000000..17248b94
--- /dev/null
+++ b/src/gadgets/shared/index.ts
@@ -0,0 +1,8 @@
+/**
+ * Shared utilities for file editing gadgets.
+ */
+
+export * from './types.js';
+export * from './matcher.js';
+export * from './pathValidation.js';
+export * from './diagnostics.js';
diff --git a/src/gadgets/editfile/matcher.ts b/src/gadgets/shared/matcher.ts
similarity index 94%
rename from src/gadgets/editfile/matcher.ts
rename to src/gadgets/shared/matcher.ts
index 7ed2a179..3f59d716 100644
--- a/src/gadgets/editfile/matcher.ts
+++ b/src/gadgets/shared/matcher.ts
@@ -1,5 +1,5 @@
 /**
- * Layered matching algorithm for EditFile gadget.
+ * Layered matching algorithm for file editing gadgets.
  *
  * Tries strategies in order: exact → whitespace → indentation → fuzzy
  * This approach reduces edit errors by ~9x (per Aider benchmarks).
@@ -478,3 +478,28 @@ function getContext(content: string, lineNumber: number, contextLines: number):
 
 	return contextWithNumbers.join('\n');
 }
+
+/**
+ * Format context lines around an edited range for output display.
+ */
+export function formatContext(
+	lines: string[],
+	startLine: number,
+	endLine: number,
+	contextLines = 5,
+	editMarker = '>',
+): string {
+	const rangeStart = Math.max(0, startLine - 1 - contextLines);
+	const rangeEnd = Math.min(lines.length, endLine + contextLines);
+
+	const result: string[] = [];
+	for (let i = rangeStart; i < rangeEnd; i++) {
+		const lineNum = i + 1;
+		const isEdited = lineNum >= startLine && lineNum <= endLine;
+		const marker = isEdited ? editMarker : ' ';
+		const paddedNum = String(lineNum).padStart(4);
+		result.push(`${marker}${paddedNum} | ${lines[i]}`);
+	}
+
+	return result.join('\n');
+}
diff --git a/src/gadgets/shared/pathValidation.ts b/src/gadgets/shared/pathValidation.ts
new file mode 100644
index 00000000..7fae100c
--- /dev/null
+++ b/src/gadgets/shared/pathValidation.ts
@@ -0,0 +1,53 @@
+/**
+ * Path validation for file editing gadgets.
+ *
+ * Validates that file paths are within the current working directory
+ * or allowed directories (e.g., /tmp).
+ */
+
+import { realpathSync } from 'node:fs';
+import { resolve, sep } from 'node:path';
+
+const ALLOWED_PATHS = ['/tmp'];
+
+/**
+ * Validate and resolve a file path.
+ *
+ * @param inputPath The input path (relative or absolute)
+ * @returns The validated absolute path
+ * @throws Error if the path is outside allowed directories
+ */
+export function validatePath(inputPath: string): string {
+	const cwd = process.cwd();
+	const resolvedPath = resolve(cwd, inputPath);
+
+	let finalPath: string;
+	try {
+		finalPath = realpathSync(resolvedPath);
+	} catch (error) {
+		const nodeError = error as NodeJS.ErrnoException;
+		if (nodeError.code === 'ENOENT') {
+			finalPath = resolvedPath;
+		} else {
+			throw error;
+		}
+	}
+
+	// Check if within CWD
+	const cwdWithSep = cwd + sep;
+	if (finalPath.startsWith(cwdWithSep) || finalPath === cwd) {
+		return finalPath;
+	}
+
+	// Check if within allowed paths
+	for (const allowedPath of ALLOWED_PATHS) {
+		const allowedWithSep = allowedPath + sep;
+		if (finalPath.startsWith(allowedWithSep) || finalPath === allowedPath) {
+			return finalPath;
+		}
+	}
+
+	throw new Error(
+		`Path access denied: ${inputPath}. Path must be within working directory or allowed paths (${ALLOWED_PATHS.join(', ')})`,
+	);
+}
diff --git a/src/gadgets/editfile/types.ts b/src/gadgets/shared/types.ts
similarity index 96%
rename from src/gadgets/editfile/types.ts
rename to src/gadgets/shared/types.ts
index a04c3f92..1356da06 100644
--- a/src/gadgets/editfile/types.ts
+++ b/src/gadgets/shared/types.ts
@@ -1,5 +1,5 @@
 /**
- * Types for the EditFile gadget's layered matching algorithm.
+ * Types for the file editing gadgets' layered matching algorithm.
  */
 
 /**
diff --git a/src/triggers/index.ts b/src/triggers/index.ts
index c4209b2e..4d497792 100644
--- a/src/triggers/index.ts
+++ b/src/triggers/index.ts
@@ -37,7 +37,7 @@ export function registerBuiltInTriggers(registry: TriggerRegistry): void {
 	registry.register(new AttachmentAddedTrigger());
 
 	// GitHub: PR opened trigger (initial review on new PRs)
-	// DISABLED: Triggers respond-to-review which has EditFile - needs review
+	// DISABLED: Triggers respond-to-review which has file editing gadgets - needs review
 	// registry.register(new PROpenedTrigger());
 
 	// GitHub: PR review comment trigger
diff --git a/src/utils/interactive.ts b/src/utils/interactive.ts
index f6d4898c..1624c30a 100644
--- a/src/utils/interactive.ts
+++ b/src/utils/interactive.ts
@@ -9,36 +9,57 @@ function horizontalLine(): string {
 }
 
 /**
- * Display EditFile params with mode-specific formatting.
+ * Display FileSearchAndReplace params.
  */
-function displayEditFileParams(params: Record<string, unknown>): void {
+function displayFileSearchAndReplaceParams(params: Record<string, unknown>): void {
 	// Comment (rationale for the edit)
 	if (params.comment) {
 		console.log(chalk.dim('Comment: ') + chalk.white(String(params.comment)));
 	}
 
-	// File path and mode
+	// File path
 	if (params.filePath) {
-		const modeStr = params.mode ? chalk.yellow(`[${params.mode}]`) : '';
-		console.log(`${chalk.dim('File: ')}${chalk.cyan(String(params.filePath))} ${modeStr}`);
+		console.log(`${chalk.dim('File: ')}${chalk.cyan(String(params.filePath))}`);
 		console.log(horizontalLine());
 	}
 
-	// Mode-specific display
-	switch (params.mode) {
-		case 'search_replace':
-			displaySearchReplaceMode(params);
-			break;
-		case 'insert_at_line':
-			displayInsertAtLineMode(params);
-			break;
-		case 'remove_lines':
-			displayRemoveLinesMode(params);
-			break;
-		default:
-			// Fallback for unknown mode - show as search_replace for backwards compat
-			displaySearchReplaceMode(params);
+	displaySearchReplaceMode(params);
+}
+
+/**
+ * Display FileInsertContent params.
+ */
+function displayFileInsertContentParams(params: Record<string, unknown>): void {
+	// Comment (rationale for the edit)
+	if (params.comment) {
+		console.log(chalk.dim('Comment: ') + chalk.white(String(params.comment)));
+	}
+
+	// File path
+	if (params.filePath) {
+		console.log(`${chalk.dim('File: ')}${chalk.cyan(String(params.filePath))}`);
+		console.log(horizontalLine());
+	}
+
+	displayInsertAtLineMode(params);
+}
+
+/**
+ * Display FileRemoveContent params.
+ */
+function displayFileRemoveContentParams(params: Record<string, unknown>): void {
+	// Comment (rationale for the edit)
+	if (params.comment) {
+		console.log(chalk.dim('Comment: ') + chalk.white(String(params.comment)));
 	}
+
+	// File path
+	if (params.filePath) {
+		console.log(`${chalk.dim('File: ')}${chalk.cyan(String(params.filePath))}`);
+		console.log(horizontalLine());
+	}
+
+	displayRemoveLinesMode(params);
 }
 
 /**
@@ -119,11 +140,19 @@ export function displayGadgetCall(
 
 	console.log(horizontalLine());
 
-	// Special formatting for EditFile
-	if (name === 'EditFile') {
-		displayEditFileParams(params);
-	} else {
-		displayDefaultParams(params);
+	// Special formatting for file editing gadgets
+	switch (name) {
+		case 'FileSearchAndReplace':
+			displayFileSearchAndReplaceParams(params);
+			break;
+		case 'FileInsertContent':
+			displayFileInsertContentParams(params);
+			break;
+		case 'FileRemoveContent':
+			displayFileRemoveContentParams(params);
+			break;
+		default:
+			displayDefaultParams(params);
 	}
 
 	console.log(horizontalLine());
diff --git a/tests/unit/gadgets/editfile/matcher.test.ts b/tests/unit/gadgets/shared/matcher.test.ts
similarity index 99%
rename from tests/unit/gadgets/editfile/matcher.test.ts
rename to tests/unit/gadgets/shared/matcher.test.ts
index c17cf19c..0c3ec3b0 100644
--- a/tests/unit/gadgets/editfile/matcher.test.ts
+++ b/tests/unit/gadgets/shared/matcher.test.ts
@@ -3,7 +3,7 @@ import {
 	applyReplacement,
 	findMatch,
 	getMatchFailure,
-} from '../../../../src/gadgets/editfile/matcher.js';
+} from '../../../../src/gadgets/shared/matcher.js';
 
 describe('Matcher', () => {
 	describe('findMatch', () => {