cheez-write

name	cheez-write
compatibility	Requires tilth MCP server
allowed-tools	mcp__tilth__tilth_edit, mcp__tilth__tilth_read
description	Hash-anchored file editing using tilth MCP. Replace specific functions or blocks using hash anchors from tilth_read, not entire file rewrites. Use when: editing code, replacing functions, deleting blocks, or making precise surgical changes. Always read first to get hash anchors. Do NOT use for reading files — use cheez-read. Do NOT use for searching — use cheez-search. Examples: "replace the validateToken function with this new implementation", "delete lines 44-89", "update the authenticate method".

cheez-write

Hard dependency: If mcp__tilth__tilth_edit is unavailable, stop immediately and report "tilth MCP server is not loaded — cannot proceed." Do NOT fall back to Edit, Write, or any host tool.

Hash-anchored file editing via tilth MCP (tilth_edit). Never rewrite whole files. Use hash anchors from tilth_read to make precise, surgical edits.

---

Core Principle: Anchors, Not Rewrites

Traditional AI editing rewrites entire files, wasting tokens and risking data loss. tilth_edit uses hash anchors — unique identifiers for each line — to:

• Make precise, surgical changes
• Reject edits if the file changed (hash mismatch)
• Show you exactly what changed

The protocol:

1. Read the file section with tilth_read → get hash anchors
2. Note start/end anchors for the block you'll change
3. Call tilth_edit with those anchors and new content

---

Hash Anchor Format

When you read a file with tilth_read, lines have anchors:

42:a3f│  let x = compute();
43:f1b│  return x;

Format: <line>:<hash>│ <content>

The hash is a short content fingerprint. If someone else edits the file, hashes change, and your edit is safely rejected.

---

MCP Tool Reference

tilth_edit — Precise File Editing

Single line edit:

tilth_edit({
  "path": "src/auth.ts",
  "edits": [
    { "start": "42:a3f", "content": "  let x = recompute();" }
  ]
})

Multi-line range replacement:

tilth_edit({
  "path": "src/auth.ts",
  "edits": [
    {
      "start": "44:b2c",
      "end": "89:e1d",
      "content": "export function handleAuth(req, res, next) {\n  // new implementation\n  const token = extractToken(req);\n  if (!token) return res.status(401).end();\n  next();\n}"
    }
  ]
})

Delete a block:

tilth_edit({
  "path": "src/auth.ts",
  "edits": [
    { "start": "44:b2c", "end": "89:e1d", "content": "" }
  ]
})

Multiple edits in one call:

tilth_edit({
  "path": "src/auth.ts",
  "edits": [
    { "start": "12:a1b", "content": "import { newHelper } from './helpers';" },
    { "start": "44:b2c", "end": "89:e1d", "content": "// replaced function\n..." }
  ]
})

Show diff in response:

tilth_edit({
  "path": "src/auth.ts",
  "diff": true,
  "edits": [...]
})

---

The Read-Edit Protocol

Step 1: Read to Get Anchors

tilth_read(path: "src/auth.ts", section: "44-89")

Output:

44:b2c│ export function handleAuth(req, res, next) {
45:c3d│   const token = req.headers.authorization?.split(' ')[1];
...
88:d4e│   next();
89:e1d│ }

Step 2: Note Your Anchors

• Start anchor: 44:b2c (first line of function)
• End anchor: 89:e1d (closing brace)

Step 3: Edit with Anchors

tilth_edit({
  "path": "src/auth.ts",
  "edits": [{
    "start": "44:b2c",
    "end": "89:e1d",
    "content": "export function handleAuth(req, res, next) {\n  const token = extractToken(req);\n  if (!validateToken(token)) {\n    return res.status(401).json({ error: 'Invalid token' });\n  }\n  req.user = decodeToken(token);\n  next();\n}"
  }]
})

---

Replacing Entire Functions

This is the most common use case. The pattern:

1. Read the function (outline first if file is large):

   tilth_read(path: "src/auth.ts")
   # See: [44-89]  export fn handleAuth(req, res, next)
   
   tilth_read(path: "src/auth.ts", section: "44-89")
   # Get hash anchors
   

2. Note start/end anchors from the hashlined output

3. Replace the entire function body:

   tilth_edit({
     "path": "src/auth.ts",
     "edits": [{
       "start": "44:b2c",
       "end": "89:e1d",
       "content": "<your new function implementation>"
     }]
   })
   

---

Hash Mismatch Handling

If the file changed since you read it:

Error: Hash mismatch at line 44
Expected: b2c
Found: f9a

Current content:
44:f9a│ export async function handleAuth(req, res, next) {
...

Recovery:

1. Read the section again → get new anchors
2. Review the current content (someone else may have made changes)
3. Edit with new anchors

This is a safety feature, not a bug.

---

Caller Updates After Signature Changes

When you edit a function signature, tilth_edit shows callers that may need updating:

Edit applied to src/auth.ts

── callers that may need updates ──
  src/routes/api.ts:34   router.use('/api/*', handleAuth)
  src/routes/admin.ts:12 app.use(handleAuth)
  src/middleware.ts:8    const wrapped = handleAuth(...)

Check these locations and update if needed.

---

Common Patterns

Insert After a Line

Use the start anchor of the line AFTER where you want to insert:

tilth_edit({
  "path": "src/auth.ts",
  "edits": [{
    "start": "13:abc",
    "content": "import { newHelper } from './helpers';\nimport { oldImport } from './old';"
  }]
})

This replaces line 13. To truly "insert", include the original line 13 content in your new content.

Delete Multiple Functions

tilth_edit({
  "path": "src/auth.ts",
  "edits": [
    { "start": "44:b2c", "end": "89:e1d", "content": "" },
    { "start": "120:f4g", "end": "180:h5i", "content": "" }
  ]
})

Batch Edits Across Files

Make separate tilth_edit calls per file (cannot batch across files):

tilth_edit({ path: "src/auth.ts", edits: [...] })
tilth_edit({ path: "src/routes.ts", edits: [...] })

---

Large Files: Outline First

For large files, tilth_read shows an outline, not hashlined content:

# src/giant.ts (2400 lines, ~32k tokens) [outline]

[1-20]    imports
[22-89]   interface Config
[91-450]  class GiantHandler
  [100-180]  fn process
  [182-340]  fn validate

To edit, drill into the specific section:

tilth_read(path: "src/giant.ts", section: "100-180")
# Now you get hashlined content for fn process

Then edit with those anchors.

---

DO NOT

• DO NOT rewrite entire files — use hash anchors for surgical edits
• DO NOT guess hash values — always read first to get current anchors
• DO NOT ignore hash mismatches — re-read and retry
• DO NOT use host Edit tool — use tilth_edit exclusively
• DO NOT edit without reading — you need the anchors
• DO NOT use for reading — use cheez-read (tilth_read)
• DO NOT use for searching — use cheez-search (tilth_search)

---

What This Skill Doesn't Do

• Read files — use cheez-read first to get anchors
• Search code — use cheez-search to find what to edit
• Run tests after editing — use test/build skills
• Commit changes — use commit skill
• Review your edits — use age/code-review skills