**Agent: Claude (Opus 4.6)**

## 1. Does the recipe work as advertised?

**Partially.** The pre-flight validation and offset-resolution logic work exactly as documented: a 4-hunk, 3-file scenario (rename logger keys in UserService + OrderService, bump MAX_RETRIES, increase TIMEOUT_MS) resolved cleanly with correct offsets. The descending-offset grouping produced the right order for multi-hunk-per-file edits, and the string replacements via the resolved offsets were verified correct against file contents.

**However, the `WriteCommandAction.writeCommandAction(project).run<Exception>` call deadlocks** in the MCP Steroid test harness. Root cause: the EDT is blocked in a `runBlocking` call (`CliIntegrationTestBase`) waiting for the agent process to finish — so any `invokeLater`, `writeAction`, or `WriteCommandAction.run` that needs EDT dispatch hangs indefinitely. This is an environment issue (the test runner occupies the EDT), not a recipe logic bug, but it means **the recipe as-written cannot execute end-to-end in at least one supported MCP Steroid execution context.** I verified edits by applying the resolved hunks via `java.io.File` I/O — all 4 hunks landed correctly, confirming the algorithm is sound even though the IDE write path is blocked.

## 2. Are the defaults sensible?

**Pre-flight validation** is well-calibrated. The uniqueness check (`indexOf` + second `indexOf`) correctly rejects ambiguous matches while allowing legitimate single-occurrence edits. The error messages include hunk index, file path, and offset positions — actionable without extra debugging.

**Descending-offset ordering** is correct and essential. In my UserService test (hunks at offsets 120 and 190), applying offset-190 first preserved offset-120's validity. This is the right default.

**Success message** reports hunk count and per-file breakdown — adequate but could include byte-ranges or line numbers for easier verification.

## 3. Ergonomics in practice

The recipe requires **~27 lines / ~1,500 bytes** of Kotlin (excluding the `patches` list itself). An equivalent `VfsUtil.saveText` approach for the same 4-hunk, 3-file scenario takes **~15 lines / ~700 bytes**. The recipe is ~2× heavier in token cost.

The overhead buys: (a) atomicity via `WriteCommandAction`, (b) pre-flight validation with clear errors, (c) automatic descending-offset handling. For 2+ hunks these are genuine wins. For a single hunk in one file, the recipe is overkill — the recipe's own docs correctly note this.

The main ergonomic cost is that the caller must copy ~20 lines of boilerplate (`ResolvedHunk` data class, `readAction` validation loop, `groupBy`/`sortedByDescending`, `WriteCommandAction` block, `commitAllDocuments`). This is a recipe (copy-paste template), not a library function, so the boilerplate is inherent.

## 4. Failure modes

**old_string absent:** Pre-flight throws `IllegalArgumentException("Hunk #2: old_string not found in .../Config.java — verify with Grep first")`. No edits are applied — files remain untouched. Error message is actionable. **Clean fail.** ✓

**old_string non-unique:** Pre-flight throws with both offsets: `"first at offset 87, next at 167"`. Again, no edits applied. The suggestion to "expand old_string with surrounding context" is helpful. **Clean fail.** ✓

**Atomicity on pre-flight failure:** When hunk #2 of 3 fails validation, hunks #0 and #1 (which would have been valid) are also not applied. The `mapIndexed` in `readAction` short-circuits on the first `require` failure. **All-or-nothing guarantee holds at the validation layer.** ✓

**EDT blocked (environment failure):** The recipe hangs silently with no timeout or error. This is the most dangerous failure mode — the caller gets no feedback, just a timeout from MCP Steroid's execution wrapper.

## 5. Concrete improvement suggestions

1. **Add an EDT-availability check before the write phase.** Change: insert `require(!ApplicationManager.getApplication().isDispatchThread || /* can acquire write lock */) { "EDT appears blocked; apply-patch requires EDT access for WriteCommandAction" }` before the `WriteCommandAction` block. Symptom: recipe hangs indefinitely when EDT is occupied (as in test harness contexts). Effect: fail-fast with an actionable message instead of silent deadlock.

2. **Add a timeout wrapper around `WriteCommandAction.run`.** Change: wrap the write phase in `withTimeout(30_000) { ... }` (or document that callers should). Symptom: in my run, the write phase hung forever with no signal. Effect: bounded failure with a clear "write timed out" error.

3. **Include a line-number mapping in the success output.** Change: after applying, compute `document.getLineNumber(h.offset)` for each hunk and print `"line N: old → new"`. Symptom: current output says `"Config.java: 1 hunk(s)"` but doesn't help the caller verify *which* line changed. Effect: easier post-edit verification without re-reading the file.