* fix(file-context): preserve targeted reads + invalidate on mtime (#1719)
The PreToolUse:Read hook unconditionally rewrote tool input to
{file_path, limit:1}, which interacted with two failure modes:
1. Subagent edits a file → parent's next Read still gets truncated
because the observation snapshot predates the change.
2. Claude requests a different section with offset/limit → the hook
strips them, so the Claude Code harness's read-dedup cache returns
"File unchanged" against the prior 1-line read. The file becomes
unreadable for the rest of the conversation, even though the hook's
own recovery hint says "Read again with offset/limit for the
section you need."
Two complementary fixes:
- **mtime invalidation**: stat the file (we already stat for the size
gate) and compare mtimeMs to the newest observation's created_at_epoch.
If the file is newer, pass the read through unchanged so fresh content
reaches Claude.
- **Targeted-read pass-through**: when toolInput already specifies
offset and/or limit, preserve them in updatedInput instead of
collapsing to {limit:1}. The harness's dedup cache then sees a
distinct input and lets the read proceed.
The unconstrained-read path (no offset, no limit) is unchanged: still
truncated to 1 line plus the observation timeline, so token economics
are preserved for the common case.
Tests cover all three branches: existing truncation, targeted-read
pass-through (offset+limit, limit-only), and mtime-driven bypass.
Fixes#1719
* refactor(file-context): address review findings on #1719 fix
- Add offset-only test case for full targeted-read branch coverage
- Use >= for mtime comparison to handle same-millisecond edge case
- Add Number.isFinite() + bounds guards on offset/limit pass-through
- Trim over-verbose comments to concise single-line summaries
- Remove redundant `as number` casts after typeof narrowing
- Add comment explaining fileMtimeMs=0 sentinel invariant
Tran Quang