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Add: --install-hook for auto-reapply after CC updates #654

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44cfb05
Add --install-hook for auto-reapply after CC updates
LeonFedotov Apr 1, 2026
0534878
fix: harden hook mode — validate settings shape, reject conflicting f…
LeonFedotov Apr 1, 2026
b50cca8
fix: validate JSON shape and use exact hook match
LeonFedotov Apr 1, 2026
9ebb8d8
fix: distinguish ENOENT from EACCES in settings read
LeonFedotov Apr 2, 2026
5b11d41
fix: flatten settings.json error handling into single try/catch
LeonFedotov Apr 2, 2026
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212 changes: 191 additions & 21 deletions src/index.tsx
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Original file line number Diff line number Diff line change
@@ -1,4 +1,7 @@
#!/usr/bin/env node
import * as os from 'node:os';
import * as fsSync from 'node:fs';
import * as path from 'node:path';
import { render } from 'ink';
import { Command } from 'commander';
import chalk from 'chalk';
Expand Down Expand Up @@ -181,6 +184,12 @@ const main = async () => {
'--config-url <url>',
'fetch configuration from a URL instead of local config.json'
)
.option(
'--install-hook',
'install a SessionStart hook so patches auto-reapply after CC updates'
)
.option('--remove-hook', 'remove the auto-reapply SessionStart hook')
.option('-q, --quiet', 'suppress output (for use with --apply in hooks)')
.action(async () => {
// This action handles the default case (no subcommand).
// All the --flag handling lives here so that Commander's subcommand
Expand Down Expand Up @@ -224,6 +233,20 @@ const main = async () => {
return;
}

// Handle --install-hook / --remove-hook flags
if (options.installHook && options.removeHook) {
console.error(
chalk.red(
'Error: Cannot use --install-hook and --remove-hook together.'
)
);
process.exit(1);
}
if (options.installHook || options.removeHook) {
await handleHookMode(!!options.installHook);
return;
Comment on lines +236 to +247
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@coderabbitai coderabbitai Bot Apr 2, 2026

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⚠️ Potential issue | 🟠 Major

Reject mixed command modes instead of silently picking one.

This branch short-circuits the rest of the default action, so --remove-hook --apply / --install-hook --patches ... return success after only managing the hook, while --install-hook --list-patches never reaches this block because list mode returned earlier. Please make hook management mutually exclusive with the other top-level modes instead of ignoring part of the CLI input.

💡 Proposed guard 
       if (options.installHook && options.removeHook) {
         console.error(
           chalk.red(
             'Error: Cannot use --install-hook and --remove-hook together.'
           )
         );
         process.exit(1);
       }
+      if (
+        (options.installHook || options.removeHook) &&
+        (options.apply ||
+          options.restore ||
+          options.revert ||
+          options.listPatches ||
+          options.listSystemPrompts !== undefined ||
+          options.configUrl ||
+          options.patches)
+      ) {
+        console.error(
+          chalk.red(
+            'Error: --install-hook/--remove-hook cannot be combined with other command modes.'
+          )
+        );
+        process.exit(1);
+      }
       if (options.installHook || options.removeHook) {
         await handleHookMode(!!options.installHook);
         return;
       }
🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@src/index.tsx` around lines 236 - 247, Reject combined hook and other
top-level modes: instead of short-circuiting, check that when
options.installHook or options.removeHook is set no other top-level action flags
(e.g. options.apply, options.patches, options.listPatches or any other mutually
exclusive CLI mode flags used elsewhere) are also present; if they are, print an
error (similar to the existing message) and exit non‑zero. Only call await
handleHookMode(!!options.installHook) and return when install/removeHook is the
sole top-level mode; otherwise fail fast. Use the existing symbols
options.installHook, options.removeHook and handleHookMode to locate and
implement the guard.

}
Comment thread
coderabbitai[bot] marked this conversation as resolved.

// Handle --apply flag for non-interactive mode
if (options.apply) {
// Parse patch filter if provided
Expand All @@ -232,7 +255,7 @@ const main = async () => {
.split(',')
.map((id: string) => id.trim())
: null;
await handleApplyMode(patchFilter, options.configUrl);
await handleApplyMode(patchFilter, options.configUrl, !!options.quiet);
return;
}

Expand Down Expand Up @@ -334,6 +357,148 @@ const main = async () => {
program.parse();
};

/**
* Handles --install-hook / --remove-hook flags.
* Installs or removes a Claude Code SessionStart hook that runs
* `tweakcc --apply --quiet` after CC auto-updates.
*/
async function handleHookMode(install: boolean): Promise<void> {
const home = os.homedir();
const settingsPath = path.join(home, '.claude', 'settings.json');

// Read existing settings
let settings: Record<string, unknown> = {};
try {
const raw = fsSync.readFileSync(settingsPath, 'utf8');
const parsed: unknown = JSON.parse(raw);
if (parsed == null || Array.isArray(parsed) || typeof parsed !== 'object') {
console.error(
chalk.red(`Error: ${settingsPath} must contain a JSON object.`)
);
process.exit(1);
}
settings = parsed as Record<string, unknown>;
} catch (error) {
const err = error as NodeJS.ErrnoException;
if (err.code === 'ENOENT') {
// File doesn't exist — start fresh
} else if (error instanceof SyntaxError) {
console.error(
chalk.red(
`Error: ${settingsPath} contains invalid JSON. Please fix it manually.`
)
);
process.exit(1);
} else {
console.error(
chalk.red(
`Error reading ${settingsPath}: ${error instanceof Error ? error.message : String(error)}`
)
);
process.exit(1);
}
}
Comment on lines +371 to +400
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@coderabbitai coderabbitai Bot Apr 1, 2026

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⚠️ Potential issue | 🟠 Major

Do not overwrite Claude settings when JSON parsing fails.

At Line 366-Line 368, invalid JSON is treated the same as a missing file. In install mode, this can replace an existing settings.json with a new minimal object and drop unrelated user settings.

Suggested fix 
-  } catch {
-    // File doesn't exist or isn't valid JSON — start fresh
+  } catch (error) {
+    const err = error as NodeJS.ErrnoException;
+    if (err.code !== 'ENOENT') {
+      console.error(chalk.red(`Error reading ${settingsPath}: ${err.message}`));
+      process.exit(1);
+    }
   }

Also applies to: 405-410

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@src/index.tsx` around lines 363 - 368, The try/catch around reading/parsing
settings (fsSync.readFileSync(settingsPath) and JSON.parse) currently treats
parse errors the same as a missing file and can overwrite user settings; change
the catch to distinguish a missing file (ENOENT) from a JSON parse error: if the
file is missing, initialize settings to an empty object; if JSON.parse throws,
log the parse error and leave the existing settings variable untouched (do not
replace it with a new minimal object or write out a new settings.json). Apply
the same fix to the other read/parse block mentioned (the block around lines
405-410) so parse failures never overwrite existing settings.


const hooks =
settings.hooks != null &&
typeof settings.hooks === 'object' &&
!Array.isArray(settings.hooks)
? (settings.hooks as Record<string, unknown>)
: {};
Comment thread
coderabbitai[bot] marked this conversation as resolved.
const rawSessionStart = hooks.SessionStart;
const sessionStart = Array.isArray(rawSessionStart)
? (rawSessionStart as Array<{
matcher?: string;
hooks?: Array<{ type?: string; command?: string; timeout?: number }>;
}>)
: [];

const hookCommand = 'tweakcc --apply --quiet';

const existingIdx = sessionStart.findIndex(entry =>
entry.hooks?.some(h => h.command === hookCommand)
);

if (install) {
if (existingIdx !== -1) {
console.log(chalk.green('Auto-reapply hook is already installed.'));
console.log(chalk.dim(`Location: ${settingsPath}`));
process.exit(0);
}

sessionStart.push({
matcher: '',
hooks: [
{
type: 'command',
command: hookCommand,
timeout: 30,
},
],
});

hooks.SessionStart = sessionStart;
settings.hooks = hooks;

fsSync.mkdirSync(path.dirname(settingsPath), { recursive: true });
fsSync.writeFileSync(
settingsPath,
JSON.stringify(settings, null, 2) + '\n',
'utf8'
);
Comment on lines +443 to +448
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⚠️ Potential issue | 🟠 Major

Handle write-side failures before exiting.

mkdirSync / writeFileSync can still fail on EACCES, EPERM, disk-full, or a read-only file. Right now that turns --install-hook / --remove-hook into an uncaught exception path. Please funnel both write sites through one guarded helper so the CLI prints a clear write error instead of a stack trace.

💡 Proposed helper 
+function writeClaudeSettings(
+  settingsPath: string,
+  settings: Record<string, unknown>
+): void {
+  try {
+    fsSync.mkdirSync(path.dirname(settingsPath), { recursive: true });
+    fsSync.writeFileSync(
+      settingsPath,
+      JSON.stringify(settings, null, 2) + '\n',
+      'utf8'
+    );
+  } catch (error) {
+    console.error(
+      chalk.red(
+        `Error writing ${settingsPath}: ${error instanceof Error ? error.message : String(error)}`
+      )
+    );
+    process.exit(1);
+  }
+}
+
 ...
-    fsSync.mkdirSync(path.dirname(settingsPath), { recursive: true });
-    fsSync.writeFileSync(
-      settingsPath,
-      JSON.stringify(settings, null, 2) + '\n',
-      'utf8'
-    );
+    writeClaudeSettings(settingsPath, settings);
 ...
-    fsSync.writeFileSync(
-      settingsPath,
-      JSON.stringify(settings, null, 2) + '\n',
-      'utf8'
-    );
+    writeClaudeSettings(settingsPath, settings);

Also applies to: 489-492

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@src/index.tsx` around lines 443 - 448, Wrap the synchronous directory
creation and file write operations into a single guarded helper (e.g.,
ensureDirAndWriteSync or safeWriteSettings) that takes settingsPath and
contents, calls fsSync.mkdirSync(path.dirname(settingsPath), { recursive: true
}) and fsSync.writeFileSync(settingsPath, ...), and catches any exceptions
(EACCES/EPERM/ENOSPC/etc.); on error, call the CLI logger/console.error with a
clear message including the path and error.message and exit with non-zero status
instead of letting the exception bubble. Replace the two existing write sites
that use fsSync.mkdirSync/fsSync.writeFileSync (the block around settingsPath
and the similar block at the other location) to call this helper so both
--install-hook / --remove-hook paths use the guarded writer.


console.log(
chalk.green('Auto-reapply hook installed in Claude Code settings.')
);
console.log(
chalk.dim(
'After CC updates, patches will be reapplied automatically on next session start.'
)
);
console.log(chalk.dim(`Location: ${settingsPath}`));
console.log(chalk.dim('To remove: tweakcc --remove-hook'));
} else {
if (existingIdx === -1) {
console.log(chalk.yellow('No auto-reapply hook found to remove.'));
process.exit(0);
}

const entry = sessionStart[existingIdx];
const hookIdx =
entry.hooks?.findIndex(h => h.command === hookCommand) ?? -1;
if (hookIdx !== -1 && entry.hooks) {
entry.hooks.splice(hookIdx, 1);
if (entry.hooks.length === 0) {
sessionStart.splice(existingIdx, 1);
}
} else {
sessionStart.splice(existingIdx, 1);
}

if (sessionStart.length === 0) {
delete hooks.SessionStart;
} else {
hooks.SessionStart = sessionStart;
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}
if (Object.keys(hooks).length === 0) {
delete settings.hooks;
} else {
settings.hooks = hooks;
}

fsSync.writeFileSync(
settingsPath,
JSON.stringify(settings, null, 2) + '\n',
'utf8'
);

console.log(chalk.green('Auto-reapply hook removed.'));
console.log(chalk.dim(`Location: ${settingsPath}`));
}

process.exit(0);
}

/**
* Handles the --apply flag for non-interactive mode.
* All errors in detection will throw with detailed messages.
Expand All @@ -342,24 +507,27 @@ const main = async () => {
*/
async function handleApplyMode(
patchFilter: string[] | null,
configUrl?: string
configUrl?: string,
quiet: boolean = false
): Promise<void> {
console.log('Applying saved customizations to Claude Code...');
const log = quiet ? () => {} : console.log.bind(console);

log('Applying saved customizations to Claude Code...');

// Read the configuration (from URL or local file)
let config;
if (configUrl) {
console.log(`Fetching configuration from: ${configUrl}`);
log(`Fetching configuration from: ${configUrl}`);
try {
config = await fetchConfigFromUrl(configUrl);
console.log('Configuration fetched successfully.');
log('Configuration fetched successfully.');
} catch (error) {
const message = error instanceof Error ? error.message : String(error);
console.error(chalk.red(`Error: ${message}`));
process.exit(1);
}
} else {
console.log(`Configuration saved at: ${CONFIG_FILE}`);
log(`Configuration saved at: ${CONFIG_FILE}`);
config = await readConfigFile();
}

Expand All @@ -383,37 +551,39 @@ async function handleApplyMode(
const { ccInstInfo } = result.startupCheckInfo;

if (ccInstInfo.nativeInstallationPath) {
console.log(
log(
`Found Claude Code (native installation): ${ccInstInfo.nativeInstallationPath}`
);
} else {
console.log(`Found Claude Code at: ${ccInstInfo.cliPath}`);
log(`Found Claude Code at: ${ccInstInfo.cliPath}`);
}
console.log(`Version: ${ccInstInfo.version}`);
log(`Version: ${ccInstInfo.version}`);

// Preload strings file for system prompts
console.log('Loading system prompts...');
log('Loading system prompts...');
const preloadResult = await preloadStringsFile(ccInstInfo.version);
if (!preloadResult.success) {
console.log(chalk.red('\n✖ Error downloading system prompts:'));
console.log(chalk.red(` ${preloadResult.errorMessage}`));
console.log(
log(chalk.red('\n✖ Error downloading system prompts:'));
log(chalk.red(` ${preloadResult.errorMessage}`));
log(
chalk.yellow(
'\n⚠ System prompts not available - skipping system prompt customizations'
)
);
}

// Apply the customizations
console.log('Applying customizations...');
log('Applying customizations...');
const { results } = await applyCustomization(
config,
ccInstInfo,
patchFilter
);

// Print patch results
printPatchResults(results, patchFilter);
if (!quiet) {
printPatchResults(results, patchFilter);
}

// Check if any patches failed
const hasFailures = results.some(r => r.failed);
Expand All @@ -422,28 +592,28 @@ async function handleApplyMode(
);

if (hasFailures) {
console.log(chalk.yellow('Customizations applied with some failures.'));
console.log(
log(chalk.yellow('Customizations applied with some failures.'));
log(
chalk.dim(
'These patching errors do not affect your system prompt patches.'
)
);
if (hasSystemPromptChanges) {
console.log(
log(
chalk.dim(
'Your system prompt customizations were still applied successfully.'
)
);
}
console.log(
log(
chalk.dim(
'Please open an issue on https://github.com/Piebald-AI/tweakcc/issues/new reporting these patching errors.'
)
);
} else {
console.log(chalk.green('Customizations applied successfully!'));
log(chalk.green('Customizations applied successfully!'));
}
console.log(
log(
chalk.dim(
'Run with --restore/--revert to revert Claude Code to its original state.'
)
Expand Down