core/tools: add get_truncated tool for chained resume

src/plyngent/agent/directive_checkpoint.py

@@ -21,6 +21,7 @@ Tool playbook still applies (see system). Hard constraints:
 use `run_argv_batch` for ordered pipelines.
 - `edit_replace`: fix match / `max_replaces`; `edit_lineno` edits only lines read via \
 `read_file(with_lineno=true)`, and line numbers reset after any file write.
+- Truncated results carry a `TRUNCATE_TOKEN`; continue with `get_truncated`.
 - Prefer `fetch` for HTTP(S); private/LAN hosts need human policy allow (not YOLO).
 - PTY secrets only via `ask_into_pty`; denylists and confirms still apply.
 - `wait` pauses; pressing Enter disturbs early (optional reason).

src/plyngent/config/models.py

@@ -32,6 +32,8 @@ raise `max_replaces` or narrow `old_string`.
 - `edit_lineno` edits only lines you read via `read_file(path, with_lineno=true)`; \
 re-read with line numbers after any `edit_*` / `write_file` / copy/move/delete, \
 since line numbers go stale.
+- Truncated `read_file` / `fetch` results carry a `TRUNCATE_TOKEN`; use \
+`get_truncated` with it to keep reading (chains through truncations).
 
 ### Commands
 - Prefer `run_argv` / `run_argv_batch` (argv lists, no shell) over `bash -c` or similar.

src/plyngent/tools/file/__init__.py

@@ -5,6 +5,7 @@ from .edit_replace import edit_replace as edit_replace
 from .fs_ops import copy_path as copy_path
 from .fs_ops import delete_path as delete_path
 from .fs_ops import move_path as move_path
+from .get_truncated import get_truncated as get_truncated
 from .glob_paths import glob_paths as glob_paths
 from .grep_files import grep_files as grep_files
 from .listdir import listdir as listdir
@@ -25,4 +26,5 @@ FILE_TOOLS = [
     move_path,
     delete_path,
     new_temporary_workspace,
+    get_truncated,
 ]

src/plyngent/tools/file/get_truncated.py

@@ -0,0 +1,40 @@
+"""``get_truncated`` tool: resume truncated tool results via a truncate token."""
+
+from __future__ import annotations
+
+from plyngent.agent import ToolTag, tool
+from plyngent.agent.budget import DEFAULT_TOOL_RESULT_MAX_CHARS
+from plyngent.tools.file.read import read_file
+from plyngent.tools.net.fetch import fetch
+from plyngent.tools.truncate_token import decode_truncate_token, truncate_with_token
+
+
+@tool(tags=ToolTag.LOCAL | ToolTag.INSTANCE_STATE)
+async def get_truncated(token: str, *, max_chars: int = DEFAULT_TOOL_RESULT_MAX_CHARS) -> str:
+    """Fetch the next chunk of a truncated result using its ``TRUNCATE_TOKEN``.
+
+    Pass the token shown at the end of a truncated ``read_file``, ``fetch``, or
+    earlier ``get_truncated`` result to keep reading without re-requesting the
+    whole source or raising limits. Truncated output carries a fresh token, so
+    chunks chain indefinitely.
+    """
+    parsed = decode_truncate_token(token)
+    if parsed is None:
+        return "error: invalid truncate token"
+    if parsed.kind == "http":
+        return await fetch.handler(parsed.location, offset=parsed.offset, max_chars=parsed.limit)
+    text = await read_file.handler(parsed.location)
+    if text.startswith("error:"):
+        return text
+    start = parsed.offset
+    segment = text[start : start + max_chars]
+    chunk, _ = truncate_with_token(
+        segment,
+        max_chars,
+        kind="file",
+        location=parsed.location,
+        offset=start,
+        limit=max_chars,
+        total_len=len(text),
+    )
+    return chunk