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Extension contracts. ExtensionKind is the enum of tool-extension kinds (Wrapper / Transformer / Backend). Each kind carries its distinguishing rules as explicit properties — multiple (cardinality), preserves_schema and declares_schema (the input-schema rule), preserves_output_shape (whether a minted branch may inherit the base tool’s output schema), and relocates_execution (whether the kind moves the tool body to another process) — so generic machinery keys off a property, never off kind is WRAPPER. The per-kind extension shape is in tai42_contract.extensions.kinds.

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ExtensionKind

tai42_contract.extensions.ExtensionKind
The three tool-extension kinds and their per-kind properties. Every kind branches by rename: an extension mints a NEW-named variant tool bound alongside the original, and a stacked combo ([a, b]) binds one variant per prefix (tool, tool_a, tool_a_b). No kind replaces a tool in place.
  • WRAPPER — presents the wrapped tool’s input schema unchanged (minus its own declared reserved_params); stackable.
  • TRANSFORMER — presents its OWN composed input schema (a concrete makefun-presented signature, never bare *args/**kwargs); stackable.
  • BACKEND — one execution-backend strategy per tool (multiple=False); no input-schema rule; relocates the tool body’s execution to a worker process (relocates_execution).
Attributes

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Members

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multiple

tai42_contract.extensions.ExtensionKind.multiple
Whether a single tool may carry more than one extension of this kind.

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preserves_schema

tai42_contract.extensions.ExtensionKind.preserves_schema
Whether an extension of this kind must present the extended tool’s input schema unchanged (parameter names/types identical; the tool NAME always changes — every extension branches to a new-named tool).

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declares_schema

tai42_contract.extensions.ExtensionKind.declares_schema
Whether an extension of this kind must present its OWN concrete input schema (a real makefun-presented signature, never bare *args/**kwargs).

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relocates_execution

tai42_contract.extensions.ExtensionKind.relocates_execution
Whether an extension of this kind moves the tool body’s execution to another process. A BACKEND swaps the execution strategy for a worker (the wrapped callable is submitted and runs there, not in the process that received the call); a WRAPPER and a TRANSFORMER execute the body in-process, inside their own frame. This drives the stacking-order rule the apply site enforces: an extension that requires_body_locality (its wrapper only works in the process running the tool body, e.g. a proxy layer routing egress through a task-scoped contextvar) must bind INSIDE any relocating extension, so its wrapper travels with the body to the worker. Bound outside, the relocating layer ships only the inner callable and the locality-requiring wrapper stays behind in the submitting process, silently not applying.

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preserves_output_shape

tai42_contract.extensions.ExtensionKind.preserves_output_shape
Whether an extension of this kind returns the extended tool’s result shape unchanged, so a branch it mints may inherit the base tool’s OUTPUT schema. This is an OUTPUT-schema concern, distinct from preserves_schema (which is about the INPUT schema): a WRAPPER returns the wrapped tool’s result unchanged and a BACKEND swaps the execution strategy but returns the same output shape (both preserve), while a TRANSFORMER reshapes the result (does not preserve).