If a reader wants the shortest possible answer to "what pattern looks most standardizable?", the answer today is not one framework or one product. It is a narrow execution contract centered on a tool-result loop.
That loop appears to converge on four high-confidence behaviors:
- tool calls are first-class runtime actions,
- completion is explicit and guarded,
- tool failures remain in-band and recoverable,
- runtime state is inspectable outside the raw transcript.
The strongest current interpretation of the emerging pattern is this:
- A coding agent runtime owns task lifecycle, not just prompt assembly.
- The runtime executes a repeated turn loop: model output, tool execution, result reinjection, recovery or completion.
- The model is allowed to propose completion, but the runtime decides whether completion is accepted.
- Failure handling is part of normal execution semantics, not an exceptional edge path.
- State for UI and control flow must be modeled explicitly enough to represent running, streaming, waiting, resumable, and completed modes.
- Context pressure eventually forces compaction or equivalent state reduction, so context management belongs inside the runtime contract.
- Delegation is useful, but only when subagents are bounded by tools, role, and reporting semantics.
- Product-specific rules should mostly live in policy, hooks, permissions, skills, or shell layers rather than in the runtime core.
The parts that look closest to standardization are:
- the tool-result loop,
- explicit completion attempts,
- guarded completion,
- recoverable tool failures,
- command-output streaming,
- a minimal inspectable runtime state model.
These are the parts that repeatedly appear even when products differ on UX, instructions, branding, plugin systems, or domain-specific workflows.
The parts that still look less stable are:
- stop-hook validation as a universal primitive,
- journaling format,
- resumability contract shape,
- subagent orchestration details,
- exact compaction API or event model.
See diagrams/convergent-runtime-pattern.mmd for the current high-level model.