[Mongoose] Add shared Loop Runtime for capability execution

[Nickel85]

Goal

Add a shared Loop Runtime that lets Mongoose capabilities reuse execution infrastructure without turning the product into a generic loop engine.

Capabilities remain first-class concepts. A capability still owns its domain goal, prompts, tools, state needs, output contract, safety rules, and user-facing behavior. The Loop Runtime provides the common execution scaffolding those capabilities can opt into when their workflow fits a reusable pattern.

Roadmap Position

This is a roadmap evolution and architecture refinement for the existing local-first capability platform vision. It does not replace Njord, Overwatch, Mimir, Commerce, Tyr, or future specialized capabilities. It reduces duplicated implementation effort as those capabilities grow more loop-shaped.

This belongs after the early shared memory, prompt context, stable runtime, and provider-interface foundations. Earlier milestones may reserve metadata hooks or trace references, but they should not be required to ship the full Loop Runtime.

Near-term priorities remain conservative:

• stable REPL experience
• capability loading
• local-first model support
• tool integration
• example capabilities

The loop-runtime work should land as incremental enhancements:

• shared loop runtime
• loop definition files
• trace logging integration
• future Loop Tuner capability

Shared Loop Runtime

The runtime should provide reusable execution infrastructure for capability workflows:

• loading a capability definition
• loading or resolving a loop definition
• binding tool access through Mongoose providers
• supplying runtime state and context
• recording trace events
• checking exit criteria
• returning the capability output contract

Capabilities may define their own loop definition or reference reusable loop patterns. Reusable patterns should be treated as implementation support, not as product-level replacements for capability identity.

Capability Architecture Shape

Capability concepts should continue to be expressed explicitly:

Capability
├── Goal
├── Loop Definition
├── Tools
├── State
├── Prompts
└── Output Contract

This shape extends current capability metadata and Njord loop-contract work. It should remain compatible with deterministic capabilities, LLM-assisted capabilities, guarded-write capabilities, commerce workflows, monitoring workflows, and future UI-hosted workflows.

Acceptance Criteria

• Defines the shared Loop Runtime contract as an optional execution layer for capabilities.
• Documents that capabilities remain first-class and specialized.
• Defines the initial loop definition file shape, including steps, tool access, state inputs/updates, prompts, validation, exit criteria, and output contract references.
• Supports capabilities defining a custom loop or referencing a reusable loop pattern.
• Integrates with existing manifest/runtime provider concepts instead of creating a separate product surface.
• Integrates with shared Execution Traces when trace support is available.
• Includes at least one Njord example and one non-finance example.
• Keeps deterministic, direct-entrypoint capabilities working during migration.
• Avoids requiring every capability to use the Loop Runtime immediately.

Non-goals

• Do not reposition Mongoose as a standalone loop engine.
• Do not replace capability-specific implementations where specialization is required.
• Do not make v0.9 shared memory responsible for delivering the full Loop Runtime.
• Do not remove existing roadmap items for Njord, Overwatch, Mimir, Commerce, Tyr, memory, scheduling, providers, or UI host work.
• Do not grant loops autonomous write authority without the existing approval, policy, and audit roadmap gates.

Depends On

• [Mongoose] Define reference-agent boundary so Njord does not drive core runtime architecture alone #81 reference-agent boundary
• [Mongoose] Define shared agent memory provider contract #164 shared agent memory provider contract
• [Mongoose] Add shared Execution Traces for capability runs #168 shared Execution Traces

Related

• [Njord] Define AI capability loop contract and execution envelope #150 Njord AI capability loop contract
• [Njord] Add finance loop audit log and replay model before guarded execution #153 Njord finance loop audit/replay model
• [Mongoose] Add Loop Tuner meta-capability recommendations #169 Loop Tuner meta-capability