fix(setup): write MCP grants in Antigravity's own syntax

[rlorenzo]

Problem

setup re-asked to add auto-approve MCP permissions for Antigravity CLI on every run, even after answering yes:

── Antigravity CLI MCP Servers ──
  MCP servers already configured

  Auto-approve permissions to add:

  • mcp__playwright__*

Antigravity parses grants as command(...) / mcp(<server>/*), not Claude Code's mcp__<server>__*. Its log shows the rejection:

permission_grant_store.go:367] ignoring invalid allow entry
"mcp__playwright__*": invalid grant string: "mcp__playwright__*"

It then dropped the entry when rewriting settings.json on the next launch, so the check in is_mcp_permitted never found it again.

Fix

mcp_permission_for() translates the MCP_SERVERS pattern into the tool's own grant syntax; configure_mcp translates once and uses the result for both the check and the write.

Verification

Ran agy with mcp(playwright/*) in the allow list:

CLI settings initialized: permissions=&{Allow:[... mcp(playwright/*)] Deny:[] Ask:[]}

Parsed, retained, no invalid allow entry warning. bash -n setup passes.

[greptile-apps]

Greptile Summary

The PR translates MCP permission patterns into Antigravity’s native grant syntax and adds regression coverage for translation, detection, writes, preservation of existing settings, and idempotence.

• Antigravity now receives mcp(<server>/*) grants instead of Claude-style patterns.
• The translated value is consistently used for permission checks and writes.
• The new Bats suite directly addresses the prior request for automated regression coverage.

Confidence Score: 5/5

The PR appears safe to merge; the Antigravity grant fix is internally consistent and now has targeted regression coverage.

No actionable new defects or outstanding findings remain. The previous regression-test suggestion was addressed by the added Bats suite and its thread was manually resolved without explanation.

Important Files Changed

Filename	Overview
setup	Adds tool-specific MCP permission translation and consistently applies the translated grant during detection and writing.
test/setup-mcp.bats	Adds comprehensive regression tests for Antigravity translation, permission detection, settings preservation, refusal behavior, valid JSON, and repeated-run idempotence.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    A[MCP server definition] --> B[Parse server and permission]
    B --> C[mcp_permission_for]
    C -->|Antigravity| D["mcp(server/*)"]
    C -->|Other tools| E[Original permission]
    D --> F[Check existing grant]
    E --> F
    F -->|Missing| G[Write permission]
    F -->|Present| H[Skip prompt and write]

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[rlorenzo]

@greptileai review