Document local PromptKit backend support

docs/internal/configuration.md

@@ -39,14 +39,20 @@ This establishes the public precedence order without giving environment input a
 second file schema. Loading and application reject malformed YAML, unsupported
 file versions, unknown fields, invalid values, and identifiers that are empty
 or collide after whitespace normalization. The file application also makes the
-effective extraction-worker default follow the effective LLM limit.
+effective extraction-worker default follow the effective LLM limit. A present
+PromptKit local-backend object requires and trims its endpoint, defaults its
+omitted concurrency limit to zero, and is copied so the parsed file model
+cannot alias the populated **Config**.
 
 **Config.Validate** checks configuration-only invariants before resolution. It
 rejects incompatible profile sources, invalid state-surface values, unsupported
 concurrency settings, malformed bindings and references, invalid retries, and
-invalid pipeline, step, or lane structure. Its errors retain the closest known
-pipeline, lane, and binding context. It deliberately does not require modules
-to be registered: that requires a catalog and belongs to resolution.
+invalid pipeline, step, or lane structure. PromptKit local-backend validation
+accepts only an absolute HTTP or HTTPS endpoint with a host and no user
+information, query, or fragment, and rejects a negative local concurrency
+limit. Its errors retain the closest known pipeline, lane, and binding context.
+It deliberately does not require modules to be registered: that requires a
+catalog and belongs to resolution.
 
 The exact user-selectable values and validation rules are defined in
 [Configuration](../config.md). Keep additions to the file model, an
@@ -71,7 +77,8 @@ options, and returns the fixed ordered pipeline shape. The resulting
 changes, a clone of the input configuration, and the resolved pipeline.
 Callers may therefore retain or modify their input slices and maps without
 changing the resolved result, and later consumers cannot mutate the original
-configuration through the effective value.
+configuration through the effective value. This ownership includes the nested
+PromptKit local-backend value.
 
 Resolution failures stop before module construction and source parsing. They
 include an error path for an unconfigured pipeline, missing module, missing
@@ -94,9 +101,12 @@ Configuration summaries must use **Redacted**, **RedactedSummaryPayload**, or
 Those methods copy every binding and nested option container, replace values
 whose key is credential-shaped with **[REDACTED]**, and omit materialized
 reference content while retaining safe binding and reference provenance. The
-payload must not alias the source configuration or resolved pipeline. This
-redaction is deliberately narrow: it protects configuration summaries and does
-not authorize recording arbitrary environment values or provider requests.
+payload must not alias the source configuration or resolved pipeline.
+PromptKit's local endpoint and concurrency limit are preserved as non-secret
+configuration metadata in the independently owned summary; the object contains
+no credential value. This redaction is deliberately narrow: it protects
+configuration summaries and does not authorize recording arbitrary environment
+values or provider requests.
 
 ## Invariants To Preserve
 

docs/internal/llm.md

@@ -56,6 +56,13 @@ distinct and deterministically ordered. Endpoint-only profiles retain an empty
 backend ID, which the published JSON omits. Successful completion responses and
 recorded profile manifests identify the adapter provider as `promptkit`.
 
+The CLI's preparation-only engine and the production adapter use the same
+conversion helper to register the optional conventional `local` backend.
+Preflight therefore resolves the same backend membership as runtime without
+performing generation. When the registration is absent, a profile selecting
+`backend: local` fails preparation instead of falling back to a built-in or
+endpoint-only target.
+
 Before execution, the adapter also contributes a non-secret checkpoint
 fingerprint for the effective PromptKit profile source. It combines the
 identity of PromptKit's compiled-in profile catalog with a deterministic digest
@@ -65,7 +72,11 @@ paths. It covers both explicit binding profiles and prompt-selected defaults,
 so changing a model or other profile setting cannot reuse checkpoints created
 under the prior profile source. This cache identity is independent of durable
 profile provenance: run manifests continue to list only profiles actually
-observed during LLM calls.
+observed during LLM calls. When the local backend is registered, a second
+fingerprint hashes its trimmed endpoint behind a stable marker. Changing that
+semantic execution target invalidates checkpoint reuse. The raw endpoint is not
+stored in checkpoint identity, and the local concurrency limit is excluded
+because it changes scheduling rather than execution semantics.
 
 ## Shared Provider-Call Limit
 
@@ -85,8 +96,10 @@ PromptKit applies a second, independent admission limit when the selected
 profile names a limited backend. It sits beneath the Notarius scheduled client,
 so it may narrow but cannot expand the application-wide limit. Built-in
 OpenRouter profiles select PromptKit's reserved backend and its upstream
-capacity policy. Endpoint-only profiles do not select a PromptKit backend and
-remain limited only by the Notarius scheduler.
+capacity policy. A positive configured local-backend limit bounds active local
+generations inside PromptKit; zero leaves that backend unlimited there.
+Endpoint-only profiles do not select a PromptKit backend and remain limited
+only by the Notarius scheduler.
 
 ## Prompt And Schema Assets