1 files changed, 81 insertions, 19 deletions

diff --git a/agent/tools/edit.lua b/agent/tools/edit.lua
index 7ad39c2..ec96aa6 100644
--- a/agent/tools/edit.lua
+++ b/agent/tools/edit.lua
@@ -10,6 +10,82 @@
 -- All matches are evaluated against the original file, not
 -- progressively against the result of earlier entries.
 
+local uv = require("luv")
+
+-- ---------------------------------------------------------------------------
+-- Coroutine-synchronous libuv wrappers. panto runs each tool handler in
+-- its own coroutine and drives a single `uv.run()` to completion; a
+-- handler may only block by yielding on a pending libuv op whose
+-- callback resumes it exactly once. `await` encapsulates that: arm one
+-- op, yield, return the callback's `(err, value)` results.
+-- ---------------------------------------------------------------------------
+local function await(arm)
+    local co = assert(coroutine.running(),
+        "edit: await must run inside a tool handler coroutine")
+    local res, fired = nil, false
+    arm(function(...)
+        assert(not fired, "edit: libuv callback fired twice")
+        fired = true
+        res = table.pack(...)
+        local ok, err = coroutine.resume(co)
+        if not ok then error(err, 0) end
+    end)
+    coroutine.yield()
+    return table.unpack(res, 1, res.n)
+end
+
+local function fs_open(path, flags, mode)
+    return await(function(resolve) uv.fs_open(path, flags, mode, resolve) end)
+end
+local function fs_fstat(fd)
+    return await(function(resolve) uv.fs_fstat(fd, resolve) end)
+end
+local function fs_read(fd, size, offset)
+    return await(function(resolve) uv.fs_read(fd, size, offset, resolve) end)
+end
+local function fs_write(fd, data, offset)
+    return await(function(resolve) uv.fs_write(fd, data, offset, resolve) end)
+end
+local function fs_close(fd)
+    return await(function(resolve) uv.fs_close(fd, resolve) end)
+end
+
+-- Read an entire file into a string. Returns (content, nil) or
+-- (nil, err). EOF on `fs_read` is the empty string, not nil.
+local function read_all(path)
+    local err, fd = fs_open(path, "r", 0)
+    if not fd then return nil, err end
+    local serr, st = fs_fstat(fd)
+    if not st then fs_close(fd); return nil, serr end
+    local parts, offset = {}, 0
+    while true do
+        local rerr, data = fs_read(fd, 64 * 1024, offset)
+        if rerr then fs_close(fd); return nil, rerr end
+        if data == nil or #data == 0 then break end
+        parts[#parts + 1] = data
+        offset = offset + #data
+    end
+    fs_close(fd)
+    return table.concat(parts), nil
+end
+
+-- Overwrite a file with `content` (O_WRONLY|O_CREAT|O_TRUNC, 0644).
+-- Returns (true, nil) or (nil, err).
+local function write_all(path, content)
+    local err, fd = fs_open(path, "w", tonumber("644", 8))
+    if not fd then return nil, err end
+    -- A single `fs_write` may short-write; loop until all bytes land.
+    local offset = 0
+    while offset < #content do
+        local werr, n = fs_write(fd, content:sub(offset + 1), offset)
+        if not n then fs_close(fd); return nil, werr end
+        offset = offset + n
+    end
+    -- Empty content still needs the truncate that O_TRUNC gave us.
+    fs_close(fd)
+    return true, nil
+end
+
 return {
     name = "std.edit",
     description = "Apply exact-text replacements to a file. Each entry's `old` must match exactly once in the original file (not progressively). Edits whose ranges overlap, match zero times, or match multiple times reject the entire call — no partial edits, file untouched. Keep `old` minimal but unique; widen with surrounding context if needed.",
@@ -45,14 +121,9 @@ return {
         end
 
         -- Load the file.
-        local f, open_err = io.open(path, "rb")
-        if not f then
-            return "Error: " .. (open_err or ("could not open " .. path))
-        end
-        local original = f:read("a")
-        f:close()
+        local original, read_err = read_all(path)
         if not original then
-            return "Error: failed to read " .. path
+            return "Error: " .. (read_err or ("could not read " .. path))
         end
 
         -- Validate every entry first, collecting the byte-range each
@@ -170,19 +241,10 @@ return {
         local new_content = table.concat(out)
 
         -- Write back.
-        local wf, werr = io.open(path, "wb")
-        if not wf then
-            return "Error: file read OK but failed to reopen for write: " ..
-                (werr or "?")
-        end
-        local ok, write_err = wf:write(new_content)
+        local ok, write_err = write_all(path, new_content)
         if not ok then
-            wf:close()
-            return "Error: write failed: " .. tostring(write_err)
-        end
-        local close_ok, close_err = wf:close()
-        if not close_ok then
-            return "Error: close failed: " .. tostring(close_err)
+            return "Error: file read OK but write failed: " ..
+                tostring(write_err)
         end
 
         return string.format(