feat(mcp): add branch cost confirmation elicitation

[barryroodt]

Stacked on #391. Review that first. This is part of AI-1091.

What kind of change does this PR introduce?

Feature: add form-mode cost confirmation to create_branch.

What is the current behavior?

#391 provides the shared confirmation codec/verifier, ServerContext, result passthrough, and project flow. Branch creation still uses the existing hash validation.

What is the new behavior?

Modern form clients can call create_branch without confirm_cost_id. They receive an action-only, property-less prompt for $0.01344/hr (about $9.68 over 30 days).

Acceptance creates the branch from signed arguments. Missing responses and changed costs re-prompt. A wrong-tool state or changed arguments fail. Decline and cancel create no branch.

Capability-free and URL-only clients keep hash validation. A supplied legacy ID cannot bypass the capable-client flow. Project-scoped injection works, and existing output fields such as with_data remain.

How to Review

1. Server and shared state

   • packages/mcp-server-supabase/src/server.ts
   • packages/mcp-server-supabase/src/tools/cost-confirmation.ts

2. Branch handler and pricing

   • packages/mcp-server-supabase/src/tools/branching-tools.ts
   • packages/mcp-server-supabase/src/pricing.ts

3. Behavioral coverage

   • packages/mcp-server-supabase/src/server.test.ts
   • Inspect the capable, legacy, argument-binding, and project-scoped paths.

• Is create_branch enabled only through the intended server path?
• Does the discriminated state bind project ID, branch name, and BranchCost?
• Do capable clients always use elicitation, even with a legacy ID?
• Do accept, decline, cancellation, wrong-tool, and argument-change outcomes look correct?

Verification

• pnpm --filter @supabase/mcp-server-supabase test src/server.test.ts -t "create_(project|branch) cost confirmation via elicitation" (17 passed)
• pnpm --filter @supabase/mcp-server-supabase build (typecheck + build passed)
• pnpm test:packed-platform-consumer (3 assertions passed)
• pnpm exec biome ci . (passed)

Additional context

Commit 24535f1 chore: refresh management API types adds two generated lines to packages/mcp-server-supabase/src/management-api/types.ts because the CI generation gate detected upstream schema drift. Feature behavior and verification remain unchanged.

This does not change create_project, mcp-utils, platform adapters, stdio, pricing values, manifests, or docs.

Known limits: confirmations are not single-use, legacy IDs remain precomputable, and the branch rate remains the existing package constant.

AI-assisted; human review required.

[pkg-pr-new]

Open in StackBlitz

pnpm add https://pkg.pr.new/@supabase/mcp-server-postgrest@4382f06

pnpm add https://pkg.pr.new/@supabase/mcp-server-supabase@4382f06

pnpm add https://pkg.pr.new/@supabase/mcp-utils@4382f06

commit: 4382f06

[coveralls]

Coverage Report for CI Build 33491960331

Warning

No base build found for commit de9e9bb on feat/hosted-project-cost-elicitation.
Coverage changes can't be calculated without a base build.
If a base build is processing, this comment will update automatically when it completes.

Coverage: 96.034%

Details

• Patch coverage: 13 uncovered changes across 1 file (120 of 133 lines covered, 90.23%).

Uncovered Changes

File	Changed	Covered	%
packages/mcp-server-supabase/src/tools/branching-tools.ts	116	103	88.79%
Total (3 files)	133	120	90.23%

Coverage Regressions

Requires a base build to compare against. How to fix this →

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Coverage Stats

Relevant Lines:	3333
Covered Lines:	3218
Line Coverage:	96.55%
Relevant Branches:	449
Covered Branches:	414
Branch Coverage:	92.2%
Branches in Coverage %:	Yes
Coverage Strength:	57.54 hits per line

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💛 - Coveralls