Hide file content

Overview

Per-project settings page that marks specific lines or character ranges of a source file as hidden from the agent file tools. When the model calls read_file the hidden lines or characters come back as [hidden], and search_files silently skips any match that lands inside a hidden range or character span. The on-disk file is never modified, so the redaction stays purely on the model-facing side.

Usage

Open Settings → This project → More settings → Hide file content, or navigate directly to #/settings/project/hide.

1. Tap + Add file, or tap a saved file row to edit it.

2. The file opens in the real CodeMirror text editor (Select hidden content, dark theme, line numbers, syntax highlighting) with the original content. It is read-only — the text cannot be edited, only marked.

3. Whole-line hiding — tap a line number in the toggle gutter (the column left of the text) to hide that line; tap it again to show it. Hidden lines get a highlighted background and a ✓ in the gutter. Each gutter cell is exactly as tall as the line it belongs to and 2rem wide, so a tap always lands on the line you aimed at.

4. Character-range hiding — drag to select text inside the editor. The status bar updates with the column range, and Hide selected text in the sticky footer becomes enabled. Tap it to mark that span; tap it again with the same selection to clear it. A span on a single line hides the exact columns; a span that crosses line breaks hides the full middle lines plus the boundary columns.

5. For larger whole-line selections, expand Enter line ranges manually and enter inclusive From / To numbers. Invalid values are explained rather than silently changed. Adjacent and overlapping ranges are merged on save; the same is done for character spans.

6. Tap Save. Every action (hide selection, cancel, save) lives in the sticky footer, so it stays reachable and tappable no matter how far the editor or the manual ranges scroll. The editor returns to the file list only after saving succeeds. A failed save keeps the selection available for retry, and controls are disabled while a save is in progress.

Removing a hiding

Every file row on the list carries its own Remove action, so a file can be un-hidden without opening the editor:

• Remove writes the whole rule set back without that file's entry; the row disappears and a status line reports `<path>` is no longer hidden. Nothing is written until the confirmation is accepted, and a declined confirmation leaves the list untouched.

• A failed write keeps every row, re-enables the controls, and says so: "Nothing changed; the file is still hidden." The action can be retried immediately.

• One write at a time: while a removal is in flight the row shows Removing… and all remove controls are disabled, so a double tap cannot queue a second write.

• Removal is available to whoever can open project settings; it is the same endpoint the editor uses. The on-disk file is never touched, so un-hidden content is visible to the agent file tools on the very next call.

• Keyboard focus moves to the next row's Remove (or + Add file when the list empties) after a successful removal, so the tapped control disappearing never drops focus on the page body.

Button layout

The footer is the only interactive band: it is position: sticky; bottom: 0 and owns every control of this view. The editor and its help line scroll underneath it, and the footer — not the content — wins taps in that band.

┌─────────────────────────────┐
│ editor (read-only, scrolls) │
│ …help line (non-interactive)│
├─────────────────────────────┤  ← sticky footer starts here
│ [Hide selected text]  Cancel Save │
└─────────────────────────────┘

Do not move an action back into the editor body: a control rendered outside the footer can overlap the footer band and swallow taps meant for Cancel/Save.
The preview uses the existing 1 MiB file-editor read limit; if a file cannot be previewed, manual ranges remain available.

Back retains an unsaved selection in memory for a return visit to the same file and project. Cancel asks before discarding changes. Drafts contain only paths and ranges, not file content; they do not survive a reload, which warns while an editor has unsaved changes. To stop hiding a file, remove its ranges and save; removing all saved ranges and characters requires confirmation.

Protection limits

This is not a security boundary. Only read_file and search_files are filtered. Shell, MCP, and other access can still read the original content. These limits are visible on the list and editor, not hidden in a help popup. Rules track line numbers and column positions, not text, so review them after editing or moving file content.

# Settings → Project → More settings → Hide file content
src/secrets.js  →  Lines 3 · Text on line 1, cols 18–25

After saving, a read_file call on that file returns the hidden content replaced by a marker:

# File: src/secrets.js
# Lines: 1-4
const apiKey = "[hidden]";
const normal = 1;
[hidden]

And a search_files call for text that falls only inside a hidden range or character span returns no match for that line, even when the rest of the line is visible.

Labels

Every summary label comes from one helper, describeHidden({ ranges, chars }), so the list and the editor can never disagree about what is hidden:

• A rule that hides only characters is labelled as text, never as lines, so no row ever reads "No lines selected".

• Overlapping spans on the same line are merged before they are labelled, and several spans are separated with ;.

• The editor footer repeats the label under the count line (1 line, 1 text span) and keeps showing Fix the range values to continue. while a manual range is invalid.

Behavior

• Rules are stored per project under hideFileContent in .mouaif.json (or the DB-backed project row). Shape:

{
  "hideFileContent": [
    {
      "path": "src/secrets.js",
      "ranges": [ { "start": 3, "end": 3 } ],
      "chars":  [ { "startLine": 1, "endLine": 1, "startCol": 18, "endCol": 25 } ]
    }
  ]
}

• ranges is the existing 1-indexed inclusive whole-line set. chars is the new 1-indexed inclusive character-span set; it is optional and only present when at least one character span is stored. Older saved data without chars keeps working unchanged.

• A malformed range (start below 1, or end below start) is dropped on save; a malformed span (start below 1, end before start on a single line, non-integers) is dropped on save. An entry with no valid ranges and no valid spans is dropped entirely.

• Only read_file and search_files are redacted. list_files returns paths (no content), and write_file / edit_file modify the on-disk file rather than expose it, so they are unchanged.

• The redaction applies to whole-file reads and to startLine / endLine slices. Slices retain their original line offset when checking rules, so a hidden range cannot be recovered by requesting a sub-window. In-process regression coverage: node scripts/test-hide-file-slices.js.

• search_files skips a match when its column range overlaps any hidden character span on that line (or when the whole line is hidden by a range). In-process regression coverage: node scripts/test-hide-file-char-spans.js.

• The replacement keeps the newline structure intact, so line numbers and the total line count are identical to the real file. Character spans are replaced in place; the marker does not extend the line.

• The on-disk file is untouched; removing a rule restores full visibility immediately.

Related

• Native file tools: docs/features/file-tools.md.

• Tool authorization: docs/features/tool-authorization.md.

• Project settings storage: docs/features/project-settings-storage.md.