ci(cache-impact): watch desktop session prompt swap and environment probes#6079
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SivanCola merged 1 commit intoJul 6, 2026
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…robes The cache-impact gate watched only internal/ prompt surfaces, but two cache-sensitive surfaces lived outside it: - desktop/session_prompt.go rewrites the persisted leading system message with the freshly composed prompt on every tab resume/rebind; any byte difference there invalidates the whole conversation's prefix cache and persists the rewrite. - internal/environment/* composes the environment section embedded in the cached system prefix; probe output changes shift the prefix bytes for every session. Add both to the cache-sensitive list and to the system-prompt-sensitive list so changes require Cache-impact/Cache-guard lines and an explicit System-prompt-review note.
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Summary
The cache-impact gate watched only
internal/prompt surfaces, leaving two cache-sensitive surfaces unguarded:desktop/session_prompt.go— rewrites the persisted leading system message with the freshly composed prompt on every tab resume/rebind (sessionWithFreshSystemPrompt). Any byte difference there invalidates the whole conversation's prefix cache and persists the rewrite; it is exactly the class of change this gate exists for, and today a PR touching it sails through with no Cache-impact note.internal/environment/*— composes the environment probe section embedded in the cached system prefix (boot.goprompt assembly). Probe output changes shift prefix bytes for every session on upgrade.Both are added to the cache-sensitive list (requires
Cache-impact:/Cache-guard:lines) and to the system-prompt-sensitive list (requires an explicitSystem-prompt-review:note), since both shape the provider-visible system prompt.Verification
bash -n scripts/check-cache-impact.shdesktop/session_prompt.gowithout the lines → fails listing the file; with lines butSystem-prompt-review: N/A→ fails demanding a named review; with a named review → passes listing both files;desktop/tabs.goalone → "No cache-sensitive prompt/tool files changed" (no new noise for general desktop PRs).Cache impact
Cache-impact: none - CI gate configuration only; no runtime behavior change.
Cache-guard: scenario runs above exercise the new watchlist entries in both pass and fail directions.
System-prompt-review: N/A
Context: follow-up from the desktop-vs-CLI cost triage (#2945) — the desktop resume prompt-swap path was identified as an unguarded prefix-cache invalidation surface.