ToolSuture: Recovering Agent Capability When APIs Change

Description and use

ToolSuture restores an agent’s capability after an API change without redeploying the agent, using Gemini for semantic reasoning and independent verification.

Problem

Agents break when underlying API contracts change, even if the agent logic remains correct.

Outcome

ToolSuture restored the original shipment agent’s capability after a provider contract upgrade without modifying the agent code, achieving 0 bytes changed and 0 execution attempts in dangerous scenarios.

Workflow

• Freeze deployed agent and capture original mission
• Detect API change and obtain new tool contract
• Observe mission, old and new contracts, and runtime evidence
• Diagnose semantic equivalence using Gemini 3.6 Flash
• Apply policy to decide repair or refusal
• Plan bounded compatibility repair
• Validate repair against new contract
• Replay original mission with repaired environment
• Verify success through independent evidence checks

Evidence

MISSION COMPLETED AND VERIFIED CAPABILITY_LOST → CAPABILITY_RESTORED 0 BYTES CHANGED

Source

REFUSE CRITICAL BLOCKED SAFE_HOLD 0 EXECUTION ATTEMPTS

Source