dsh-cache-safe-tool-result

DSH's prompt cache is a prefix cache: the provider reuses it only while the request's leading tokens are byte-identical to what it saw before. Yet the built-in tool-result pruner truncates oversized results in place, rewriting nodes that a provider request has already delivered. A single such rewrite invalidates everything after that node, re-billing the entire tail as uncached input. Production logs measured on the two sessions behind this plugin show single jumps of 50,000 to 311,788 uncached tokens, adding up to a staggering cost in long sessions.

dsh-cache-safe-tool-result enforces one invariant: a tool result may be compressed before it first enters the session surface, but once a provider request has carried it, its bytes never change again. The FIRST-PASS half mounts on the tools/post-execute waterfall and truncates over-budget results before they are appended, so a surface node is born in its final form. The GUARD half replaces the toolResultPruner service, refusing to rewrite any already-delivered node while still pruning undelivered ones normally. Both halves use only public DSH and Cordis extension points; no node_modules file is touched.

It is aimed at DSH users who run long sessions heavy with tool calls (code generation, file I/O, API queries) and want to maximise cache hit rates. Regression tests over two real production sessions confirm a 99.7% hit rate inside warm windows, refuse every recorded in-place rewrite, and keep session logs byte-stable across repeated passes, all without contacting a provider.