pi-hashline-edit-pro

Hash-anchored read and replace tools for pi-coding-agent. Every line of a file gets a unique 3-character hash, and you edit by hash. No line numbers, no fuzzy matching, no edits landing on the wrong line.

Fork of pi-hashline-edit by RimuruW, extended with 3-character hashes and collision resolution.

What you get

• Read with anchors. Every line comes back as HASH│content. The hash is the line's address.
• Edit by hash. replace targets a range of hashes, so edits always land on the lines you meant.
• Anchors that stay put. Edit one part of a file and the hashes of the rest stay the same. Read once, keep editing.
• Fresh anchors, automatically. After every write you get the new anchors. After every replace you get the diff with the new hashes.
• Undo when you need it. The last replace on a file can be reverted, even after a restart.
• Safe writes. Permissions, line endings, BOMs, symlinks, and hard links survive every edit.

Quick start

1. Read a file:

ve7│function hello() {
szJ│  console.log("world");
kQm│}

2. Replace a line by its hash:

{
  "path": "src/main.ts",
  "hash_bounds": ["szJ", "szJ"],
  "new_content": "  console.log('hi');"
}

3. Keep editing. Anchors for lines you didn't touch stay valid, and auto-read hands you fresh anchors after each change.

Installation

pi install npm:pi-hashline-edit-pro

From a local checkout:

pi install /path/to/pi-hashline-edit-pro

The read tool

read returns a text file with every line prefixed by HASH│content. The hash is 3 characters from A-Za-z0-9 (for example aB3).

Parameter	Description
offset	Start reading from this line number (1-indexed).
limit	Maximum number of lines to return.

Paged output ends with a continuation hint, for example [Showing lines 1-50 of 120. Use offset=51 to continue.].

Lines up to 200KB are shown in full. Larger lines are replaced by a marker with a bash inspection hint (sed -n 'Np' <path> | head -c 204800), because hash anchors need full lines.

Edge cases:

• Images (JPEG, PNG, GIF, WebP) come back as visual attachments.
• Binary files and directories are rejected with a descriptive error.
• UTF-16 and UTF-32 text (detected via BOM) is rejected, since editing it would corrupt the file.
• Empty files come back as a single empty-line hash (HASH│); use replace on that hash to insert content.
• BOMs are stripped for display. Non-UTF-8 bytes are shown as U+FFFD; editing such a file rewrites it as UTF-8, with a warning.
• Files over 238,328 lines are rejected with [E_FILE_TOO_LARGE].

The replace tool

The built-in edit tool is disabled. replace is the only edit path, and it takes the hash anchors from read output.

One edit per call, with hash_bounds and new_content at the top level:

{
  "path": "src/main.ts",
  "hash_bounds": ["szJ", "kQm"],
  "new_content": "  console.log('hi');\n}"
}

Field	Description
hash_bounds	Pair of 3-char hashes from read output marking the first and last line of the range to replace (inclusive).
new_content	Replacement content as a single string with \n line separators; a trailing newline is the last line's ending, not an extra empty line. Use "" to delete the range.

Notes:

• The request is checked before any file I/O, so a bad request never touches the file.
• Common copy-paste slips are fixed automatically and reported: a leftover HASH│ prefix in new_content or hash_bounds, diff-preview rows pasted into the replacement, a reversed range, or a boundary line pasted twice. A new line that duplicates a unique line adjacent to the range is stripped automatically. file_path works as an alias for path in all three tools.
• An edit that produces identical content reports No changes made and leaves the anchors alone.
• After a successful edit you get the post-edit diff with fresh anchors, so you can keep editing without re-reading.

Undo

undo_last_replace reverts the most recent successful replace on a file, restoring the exact previous content, BOM and line endings included, plus the previous anchors.

• History is per-file and single-level: only the most recent replace can be reverted.
• History is persisted and survives session restarts. A failed write does not clear it.
• Every applied replace is undoable: the undo record is saved before the edit is written.
• A successful write clears the history for that file.
• If the file was modified or deleted since the last replace, the undo is refused rather than overwriting those changes.

Auto-read

Enabled by default. After a successful write that changes the file, the extension reads the file and appends an --- Auto-read (hashline anchors) --- block to the result, so you get fresh HASH│content anchors without a separate read call.

• After replace and undo_last_replace, the result shows the post-edit diff. The +HASH│ and HASH│ rows carry the current hashes, so follow-up edits can anchor on the diff directly. Call read when you want the full file's anchors.
• After replace and undo_last_replace, the result shows the post-edit diff. The +HASH│ and HASH│ rows carry the current hashes, so follow-up edits can anchor on the diff directly. The -HASH│ rows show removed lines with their old hashes, so you can see exactly which anchors were deleted (those hashes are stale after the edit). Call read when you want the full file's anchors.
• Auto-read keeps a 50KB display budget. Lines over 50KB are skipped with a marker instead of their content (use read for lines up to 200KB).
• Toggle at runtime with /toggle-auto-read; the setting persists across sessions.

Settings

Command	Description
/toggle-auto-read	Toggle automatic hashline anchors after write and post-edit diffs after replace and undo_last_replace operations. Persists across sessions.

Settings live in ~/.config/pi-hashline-edit-pro/config.json, created automatically when a setting is toggled. On non-Windows platforms, the config directory honors XDG_CONFIG_HOME when set (falling back to ~/.config); on Windows it always uses ~/.config:

{
  "autoRead": true
}

How anchors work

Each line is canonicalized (carriage returns stripped, trailing whitespace trimmed) and hashed with xxhash-wasm (xxHash32), then mapped to a 3-character string over A-Za-z0-9, which gives 62³ = 238,328 possible anchors. The canonicalization keeps anchors stable across editor-save cycles that add or remove trailing whitespace.

The alphabet is sized for an LLM consumer: the model tokenizes rather than squinting at glyphs, so case and digits are all included. The URL-safe specials - and _ are deliberately excluded. A hash starting with - is shape-identical to a diff-preview deletion row, and -/_ at a line start are markdown-active, inviting mis-copying and false autocorrections.

Unique anchors by construction. If a line's base hash collides with an already-assigned hash, the next free hash is allocated from a bitset by probing with a stride coprime to the hash space (O(1) amortized). The stride is 62² + 62 + 1, so consecutive collisions, runs of blank lines, repeated }, land on anchors that differ in all three characters instead of sharing a prefix. Every line in a file therefore gets a unique anchor; two byte-identical lines (repeated }, repeated import statements) never share one. The same guarantee sets the file size cap: at most 238,328 lines per file, beyond which read and replace reject with [E_FILE_TOO_LARGE] (use write for very large files).

Hashes live in a persistent per-file store (~/.config/pi-hashline-edit-pro/hash-store.sqlite) that keeps the hashes of unchanged lines across edits. When a range is replaced, the runtime maps the old content onto the new content and copies hashes for lines that survived; only genuinely new lines get fresh hashes.

Two guarantees make this safe even with duplicated content:

• An edited range never borrows a hash from a line outside it. Lines outside the replaced range keep their hashes unconditionally, even when their content is byte-identical to lines inside the range.
• Re-inserted identical text keeps its hash. If replacement content matches a line that was just removed, the removed line's hash is reused. "Replace X with X" doesn't rotate the anchor.

A no-op replace never changes the file, so anchors remain valid. On first run after upgrading from an older version, the previous hash-store.json is imported once and renamed to hash-store.json.bak.

Error codes

Code	Meaning
[E_BAD_SHAPE]	Request envelope or edit item has unknown, missing, or wrongly-typed fields (for example new_content must be a string with \n line separators).
[E_BAD_REF]	An anchor in hash_bounds is not a bare 3-char hash.
[E_STALE_ANCHOR]	An anchor does not match any line in the current file; call read for fresh anchors.
[E_AMBIGUOUS_ANCHOR]	An anchor matches multiple lines; call read for fresh anchors.
[E_INVALID_PATCH]	A new_content line is a diff-preview row (+HASH│, -HASH│, - │). The marker is stripped automatically with a warning.
[E_BARE_HASH_PREFIX]	A new_content line starts with a hash-like HASH│ prefix. The prefix is stripped automatically with a warning.
[E_BAD_OP]	Range start line is after range end line. The pair is swapped automatically with a warning.
[E_WOULD_EMPTY]	An edit would empty a non-empty file; use write instead.
[E_NOT_FOUND]	The path does not exist.
[E_ACCESS]	The file is not readable or writable.
[E_NOT_TEXT]	The path is a directory, binary file, image, or UTF-16/UTF-32 encoded text; hashline editing only supports text files.
[E_UNDO_STALE]	undo_last_replace refused: the file was modified or deleted after the last replace.
[E_UNDO_UNAVAILABLE]	Undo history could not be persisted to the hash store; the replace was refused and the file was left unchanged.
[E_FILE_TOO_LARGE]	The file exceeds the 238,328-line hashline limit.

Troubleshooting

• Stale anchors. [E_STALE_ANCHOR] or [E_AMBIGUOUS_ANCHOR] mean the file changed since the anchors were read. Call read for fresh anchors and retry.
• Reset the hash store. Anchors live in ~/.config/pi-hashline-edit-pro/hash-store.sqlite (with -wal/-shm sidecars). Quit pi, delete those three files, and the store is rebuilt on the next session. Anchor history is lost, but no project files are touched.
• Corrupt store. If the store fails its health check it is renamed to hash-store.sqlite.corrupt-<timestamp> and rebuilt automatically.
• Config directory moved. On non-Windows platforms, if XDG_CONFIG_HOME is set, the config directory (and the hash store inside it) lives at $XDG_CONFIG_HOME/pi-hashline-edit-pro instead of ~/.config/pi-hashline-edit-pro. An existing store is not migrated automatically. To keep anchor and undo history, move the old hash-store.sqlite files (plus -wal/-shm sidecars) into the new directory before the first run.

Development

Requires Node.js ≥ 22.19 and npm.

npm install
npm test
npm run lint
npm run typecheck

Set PI_HASHLINE_DEBUG=1 to show an "active" notification at session start.

Credits

• RimuruW, original pi-hashline-edit and the strict-semantics policy
• can1357, original oh-my-pi implementation and the hashline concept

License

MIT