`showcase/integrations/mastra/shared-tools` was a real committed directory
where a symlink into the single source of truth belongs, violating the
single-source symlink mechanism documented in showcase/AGENTS.md.
Root cause: commit 534cd1efa7 ("fix(showcase): D5 integration fixes across
12 frameworks") deleted the symlink and committed 14 real files in its place
— the classic clobber the guard in showcase/scripts/validate-shared-symlinks.ts
was written to catch. The symlink was originally added by 93d5815cdb and
pointed at `../../shared/typescript/tools`.
Divergence inventory: NONE. All 14 files were byte-identical to
showcase/shared/typescript/tools (identical git blob hashes and sha256s), so
nothing mastra-specific, stale, or additive was carried in the copy. Restoring
the symlink is therefore a pure structural fix with zero content change — the
restored link blob is the same object (ddc634b6) the pre-erosion symlink had.
Also removes the healed `mastra/shared-tools` key from
validate-shared-symlinks.baseline.json, per the shrink-only ratchet (the
validator reports stale entries specifically so this is mechanical).
langgraph-typescript/shared-tools and claude-sdk-typescript/shared-tools are
eroded the same way by the same commit and are also byte-identical to the
shared source; they stay baselined here and are left for follow-up so each
conversion carries its own behavior proof.
Restore the 12 Python integration tools/ dirs to symlinks into
shared/python/tools. They had eroded to real, drifting copies via an
accidental stage_shared() leak (commit 534cd1efa7) — the structural root
cause of showcase divergence bugs. Symlinking re-establishes the single
source of truth; content is identical to shared (only render_a2ui naming
and the shared roll_dice/sanitize additions are adopted).
Add showcase/AGENTS.md documenting the 4 iron rules and the single-source
symlink mechanism, plus a validate-shared-symlinks CI guard (shrink-only
baseline) that fails on any NEW erosion.
Jordan Ritter