unicode-safe-file-writing

Unicode-Safe File Writing

Problem

The write_file tool may fail with 'unknown error' when the file content contains multi-byte Unicode characters such as:

• Emoji (e.g. ?, ✅, ❌)
• Special typographic symbols (e.g. →, •, —, ©)
• Non-ASCII characters outside the Latin-1 range

This is a known encoding limitation of write_file.

Solution

Fall back to run_shell and write the file using a shell heredoc (cat > file << 'EOF' ... EOF). The single-quoted delimiter 'EOF' prevents the shell from interpreting any special characters inside the block.

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Step-by-Step Recovery

Step 1 — Detect the failure

If write_file returns an error such as:

Error: unknown error

and the content contains non-ASCII characters, assume a Unicode encoding issue and proceed to the heredoc fallback.

Step 2 — Strip or replace problematic characters (if needed)

Before embedding content in the heredoc, decide whether to:

• Keep the characters as-is (works if the shell/terminal is UTF-8 aware)
• Replace emoji/symbols with ASCII equivalents (safest, most portable)
• Remove them entirely

Common replacements:

Original	Replacement
✅	[OK]
❌	[ERROR]
?	[START]
→	->
•	-
—	--

Step 3 — Write the file via heredoc

Use run_shell with the following pattern:

cat > path/to/file.ext << 'EOF'
...file content here (with Unicode stripped/replaced if needed)...
EOF

Key details:

• Use 'EOF' (single-quoted) as the heredoc delimiter — this disables all shell variable expansion and special character interpretation inside the block.
• Do not indent the closing EOF (it must start at column 0).
• For deeply nested content, choose a delimiter that cannot appear in the content itself (e.g. 'HEREDOC_END', 'FILEEND').

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Example

Failing call

write_file(
    path="src/components/StatusPanel.ts",
    content="// Status icons\nconst icons = { ok: '✅', err: '❌', run: '?' };\n"
)
# → Error: unknown error

Recovery via heredoc

cat > src/components/StatusPanel.ts << 'EOF'
// Status icons
const icons = { ok: '[OK]', err: '[ERROR]', run: '[START]' };
EOF

Or, if UTF-8 output is acceptable in the environment:

cat > src/components/StatusPanel.ts << 'EOF'
// Status icons
const icons = { ok: '✅', err: '❌', run: '?' };
EOF

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Multi-File Scenario

When writing several files and one fails, write the others with write_file as normal and apply the heredoc fallback only to the failing file(s):

# Write multiple files that contain Unicode
cat > src/utils/icons.ts << 'EOF'
export const ICONS = {
  success: '[OK]',
  failure: '[FAIL]',
  pending: '[...]',
};
EOF

cat > src/utils/labels.ts << 'EOF'
export const LABELS = {
  title: 'Dashboard',
  subtitle: 'Real-time status',
};
EOF

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Important Notes

1. Always prefer write_file first — only fall back to the heredoc approach when write_file fails.
2. Verify after writing — use run_shell with cat path/to/file or head -5 path/to/file to confirm the content was written correctly.
3. Directory creation — write_file auto-creates parent directories; the heredoc approach does not. Pre-create directories with mkdir -p path/to/dir if needed.
4. Large files — heredocs work well for files of any practical size; there is no meaningful shell limit.
5. Escaping backslashes — inside a single-quoted heredoc, backslashes are treated literally (no escaping needed), which is usually desirable.