[wan9chi]

Motivation

A task that reads a file and writes it back is never cached today ("not cached because it modified its inputs"). That covers tsc --incremental rewriting tsconfig.tsbuildinfo, tools updating their cache files, formatters, and most build tools on a built tree, which read their previous outputs.

Inputs are fingerprinted after the run, so such a file can simply be compared with how the task left it. And because the task wrote it, it may also be missing, as on a clean checkout, where a hit restores it.

Changes

• Each inferred input records may_be_missing, true for a path the task wrote. Validation accepts a missing path when it's set; a path that's there must still match.
• What the task wrote comes from every write fspy recorded, before output exclusions and Vite's ignoreOutput are applied. Those still decide only what is archived.
• The refusal is removed with its summary notice, its --last-details text and the suggested exclusions, along with the input_read_write_not_cached fixture and the docs section about it. The cache schema version is bumped.
• node_compile_cache_outside_workspace caught a misplaced compile cache only through the refusal, so it now lists the workspace root after its runs.

E2E cases: rewrite_own_file (synthetic, vtt fs read/write) and typescript_incremental (TypeScript 7 tsc --incremental --noEmit). The first commit records today's refusals; the second shows hits, including after tsconfig.tsbuildinfo is removed.

Part of a stack that lets automatic tracking cache tasks which read their own outputs and list the folders holding them, so they also hit on a clean checkout.

🤖 Generated with Claude Code

[github-actions]

fspy benchmark

linux

dynamic/launch             change  -0.21%  [ -2.86% ..  +3.54%]  overhead   +53.34%
dynamic/access             change  +0.87%  [ -2.00% ..  +3.82%]  overhead   +22.52%
dynamic/access-relative    change  +0.00%  [ -4.78% ..  +8.97%]  overhead   +70.31%
dynamic/access-contended   change  +2.32%  [ -6.54% .. +12.11%]  overhead   +34.08%
static/launch              change  +0.09%  [-10.44% .. +12.24%]  overhead  +186.34%
static/access              change  -0.16%  [ -1.02% ..  +0.91%]  overhead +1446.72%
static/access-relative     change  +0.18%  [ -0.58% ..  +1.04%]  overhead +1976.34%
static/access-contended    change  +0.04%  [ -1.04% ..  +1.45%]  overhead +1441.58%

macos

dynamic/launch             change  +0.01%  [ -5.16% ..  +6.58%]  overhead  +231.96%
dynamic/access             change  -0.34%  [ -8.17% ..  +8.74%]  overhead    +3.97%
dynamic/access-relative    change  +0.55%  [ -8.00% ..  +7.28%]  overhead  +245.43%
dynamic/access-contended   change  +1.47%  [ -3.64% .. +18.37%]  overhead    +1.46%

windows

dynamic/launch             change  +0.48%  [ -3.96% ..  +3.48%]  overhead   +26.89%
dynamic/access             change  +0.19%  [ -0.56% ..  +0.75%]  overhead    +1.14%
dynamic/access-relative    change  +0.00%  [ -0.73% ..  +0.54%]  overhead    +0.94%
dynamic/access-contended   change  +0.00%  [ -0.70% ..  +0.36%]  overhead    +1.45%