docs: describe the same-file write ordering of a batch

AGENTS.md

@@ -80,7 +80,7 @@ Async SQLAlchemy + aiosqlite. `MemoryStore`: schema init (+ lightweight SQLite `
 - **`responses_bridge` / `responses_dispatch`**: chat ↔ OpenAI Responses; stream text/reasoning deltas (`response.reasoning_text.done` repeats what its fragments spelled out, so the loop streams each part once and still keeps the whole text in the round's message); tool calls + usage on `response.completed`; a request carrying `tools` returns every round's reasoning as a `reasoning` item of `reasoning_text` parts — "必须完整回传 `reasoning_content` … 即使该轮模型未实际进行工具调用" (a missing item and an empty part are both a 400, so a round that kept none sends a blank line) — and a round's `function_call` items stay contiguous ahead of their outputs (`call, output, call, output` was a 400: the second call reads as a round of its own without reasoning); reasoning is read back from the item's `content` parts.
 - **`messages_bridge` / `messages_dispatch`**: chat ↔ Anthropic Messages; system fold; tool_use/tool_result; stream text + tool argument fragments; `thinking` from the request's `reasoning_effort` (level → token budget, floor 1024, `max_tokens` grown when the budget would leave no room) plus the client's configured `thinking_budget_tokens`; a server tool (`server_tool_use` + its `web_search_tool_result`) is the surface's own business — it streams `input_json_delta` fragments like a call but nothing local asked for it, so only a `tool_use` block becomes a tool call and nothing is executed; `thinking` and the two search blocks are kept as `AssistantChatMessage.provider_blocks` (the thinking text also lands in `reasoning_content`, so it streams as reasoning) and go back with the round, which is also why a round that kept only those blocks is not an empty completion; a chat-completions request drops the field (`compat.coerce_chat_messages`).
 - **Provider-side tools**: `provider_tools` on the OpenAI **and** DeepSeek presets (list of dicts; `[{type="web_search"}]` when omitted; `[]` disables) threaded via `ChatAgent`/`run_chat_loop` into Responses and Messages; never executed by `ToolRegistry`. The Messages surface declares its own server tool instead — a bare `web_search` becomes `{type="web_search_20250305", name="web_search"}` (the search then runs inside the response, and its `encrypted_content` results go back verbatim with the round — `AssistantChatMessage.provider_blocks`) — and a DeepSeek provider on a surface that ignores hosted tools (`config.routing.local_web_search`) gets the local `web_search` tool from `tools/net/search.py` instead.
-- **`@tool` / `ToolRegistry`**: decorator infers JSON Schema from type hints; execute tools by name. Before running, `execute` answers a call that omits a required argument with the accepted names (`_missing_required_error`) — the handler's bare `TypeError` never reaches the model, and no confirm prompt fires for a call that cannot run. Shape mistakes inside a *present* argument are the tool's own job (see the `chat` bullet).
+- **`@tool` / `ToolRegistry`**: decorator infers JSON Schema from type hints; execute tools by name. Before running, `execute` answers a call that omits a required argument with the accepted names (`_missing_required_error`) — the handler's bare `TypeError` never reaches the model, and no confirm prompt fires for a call that cannot run. Shape mistakes inside a *present* argument are the tool's own job (see the `chat` bullet). `@tool(writes=("path",))` names a handler's file arguments: one batch applies calls that name the same file one at a time, in call order — the lock is taken before the confirm prompt, so a pending prompt cannot be overtaken — while different files keep running in parallel.
 - **`run_chat_loop`**: multi-round tool loop; default **streaming** text deltas + stream tool-call merge; parallel tools; tool-result char budget; soft context compact on request (**API-calibrated** after first usage when available); cooperative cancel points; optional `on_limit`; resolved `reasoning_effort` on every request (see Config).
 - **`ChatAgent`**: optional `MemoryStore` (user message persisted immediately; **completed tool batches checkpointed** mid-turn; unfinished assistant suffix rolled back on failure); `stream`; system prompt; `provider_tools`; `retry()` continues incomplete turns (user-only **or** after committed tools — does not re-run those tools).
 - **`/compact`**: soft-compact tool dumps → model summary (no tools) via the same kind dispatch → **new** session seeded with summary message. Soft-compact keeps the last **12** tool results full-size by default (`DEFAULT_RECENT_TOOL_RESULTS`); older tool payloads shrink first.

README.md

@@ -306,7 +306,7 @@ Type `/help` in the REPL for the live list. Common ones:
 | `/config` | Edit `plyngent.toml` ($VISUAL/$EDITOR or system open); reload after blocking editor |
 | `/quit` | Leave the REPL |
 
-User messages are saved immediately. On API error or Ctrl+C, unfinished assistant text is discarded — tool calls that already produced a result stay, so `/retry` does not run them again — but the user message stays so `/retry` works after resume. Interactive auto-retry waits 5s, 10s, 15s, 20s, then +10s each step (10 attempts); an attempt that gets a full model round back **resets that budget**, so a connection that recovers and drops again starts over from 5s.
+User messages are saved immediately. On API error or Ctrl+C, unfinished assistant text is discarded — tool calls that already produced a result stay, so `/retry` does not run them again — but the user message stays so `/retry` works after resume. Interactive auto-retry waits 5s, 10s, 15s, 20s, then +10s each step (10 attempts); an attempt that gets a full model round back **resets that budget**, so a connection that recovers and drops again starts over from 5s. Tool calls of one round run in parallel, but writes to the same file apply one at a time, in call order — a later edit sees the earlier one's result instead of stale text.
 
 Ctrl+C cancels the in-flight turn, and during the auto-retry countdown it cancels the retry. Model-initiated prompts run off the event loop: a `wait` prompt is cancelled by Ctrl+C (the tool reports `cancelled by user` and the turn continues), while `ask_user_*` and confirm prompts ignore it with a one-line hint — answer them to continue. Ctrl+C never exits the REPL (use Ctrl+D or `/quit`), and MCP servers run in their own process group, so it never kills them either.