Summary

Ran /setup-gbrain on Windows 11 / MSYS (MINGW64) bash with gbrain v0.18.2. PGLite-local path completed successfully but hit three quirks the SKILL.md docs don't cover. Filing so the next Windows user doesn't have to re-debug.

Environment

• OS: Windows 11 (10.0.26200), MINGW64_NT-10.0-26200
• Shell: bash via MSYS / Git for Windows
• bun: 1.1.2
• gstack: v1.17.0.0
• gbrain: 0.18.2 (pinned commit 08b3698e)
• claude-code: present on PATH

Quirk 1 — bun install postinstall script fails non-fatally

The installer (gstack-gbrain-install) aborts with exit 1 at:

bun install v1.1.2 (c8d072c2)
$ command -v gbrain >/dev/null 2>&1 && gbrain apply-migrations --yes --non-interactive || echo '[gbrain] postinstall skipped...' 1>&2
error: Failed to run script C:\Users\xhiri\gbrain\[eval] due to error expected a command or assignment but got: "Redirect"
error: postinstall script from "gbrain" exited with 1

Cause: bun-on-Windows's [eval] subprocess can't parse >/dev/null 2>&1 in package.json's postinstall. Deps actually install fine; the failing command is graceful-degradation code that probes for a not-yet-linked gbrain binary. The || fallback path is what fires on Mac/Linux when gbrain isn't on PATH yet. On Windows bun, parsing dies before the || ever evaluates.

Workaround that works: ignore the installer's exit, then manually:

( cd ~/gbrain && bun link --silent )
gbrain --version  # should print 0.18.2

Suggested upstream fix: rewrite the postinstall in package.json to a .js script (node -e '...' or a small scripts/postinstall.js) so it doesn't depend on shell-redirect parsing. Or detect the failure mode in gstack-gbrain-install and continue past it.

Quirk 2 — claude mcp list reports ✗ Failed to connect while in-session MCP works

After successful claude mcp add --scope user gbrain -- "$GBRAIN_BIN" serve, running claude mcp list shows:

gbrain: C:/Users/xhiri/.bun/bin/gbrain serve - ✗ Failed to connect

But mcp__gbrain__get_stats and other MCP tools called from the same Claude Code session work perfectly.

Cause: PGLite is single-writer. Claude Code's session has its own gbrain serve running and connected. claude mcp list spawns an independent test connection that can't acquire the lock — looks like "Failed to connect" but really means "another writer holds the lock."

Suggested fix: either soften the diagnostic (Connected (lock held by peer) for PGLite when another instance has the lock and is responsive), or note this in the SKILL.md's "Important Rules" section so users don't think the registration failed.

Quirk 3 — gbrain put v0.18.2 doesn't accept stdin; SKILL.md smoke-test syntax is broken

/setup-gbrain SKILL.md, Step 9:

echo "Set up on $(date). Smoke test for /setup-gbrain." | gbrain put "$SLUG"
gbrain search "smoke test" | grep -i "$SLUG"

gbrain put v0.18.2 does NOT read stdin. It requires the --content flag (per gbrain put --help). The echo | form fails with No such file or directory. The smoke test fires the doctor's NEEDS_CONTEXT escalation when it shouldn't.

Workaround:

gbrain put "$SLUG" --content "Set up on $(date). Smoke test for /setup-gbrain."

Or, better, use the MCP tool path which is the production route:

# in Claude Code: mcp__gbrain__put_page + mcp__gbrain__search

Suggested fix: update the SKILL.md Step 9 smoke-test command to use --content (or --content - for stdin convention if gbrain put will start accepting stdin in a future version).

Other minor Windows notes (FYI, not blockers)

• gbrain on Windows installs to C:/Users/<user>/.bun/bin/gbrain.exe, not ~/.bun/bin/gbrain. The skill's MCP-registration absolute-path fallback (GBRAIN_BIN="$HOME/.bun/bin/gbrain") won't find it without the .exe; command -v gbrain worked correctly so this didn't matter on this install, but might bite users without bun-bin on PATH.
• ~/.gbrain/config.json writes database_path (not path as the skill's prose mentions); minor discrepancy.
• MCP tools surfaced mid-session after claude mcp add — SKILL.md says "restart required." On this Claude Code version (Windows, late April 2026), MCP discovery is dynamic. Worth softening the wording.

Repro environment

• gbrain.exe at C:/Users/xhiri/.bun/bin/gbrain.exe
• PGLite brain at C:\Users\xhiri\.gbrain\brain.pglite\
• gbrain doctor: status warnings, score 70 (fresh install, expected)
• Smoke test: PASS via mcp__gbrain__put_page + mcp__gbrain__search (score 0.999), FAIL via CLI echo | gbrain put

Happy to test fixes if they ship.