Document prompt sessions and concurrency defaults

docs/integrations/json-output.md

@@ -98,6 +98,11 @@ summarize results without embedding lane payload bytes. A chunk-plan summary is
 provenance for the plan used by this run; cache records, debug artifacts, and
 other operational state are not published as bundle files.
 
+When present, `metadata.session_id` is the effective non-secret routing
+correlation identifier used for the run. It can be visible to providers and is
+not a substitute for a cache or checkpoint identity. Its generation and
+override behavior are defined by the [CLI reference](../cli.md#run).
+
 Each `llm_profiles` entry identifies effective, non-secret LLM execution
 provenance:
 

docs/integrations/pkg-promptkit.md

@@ -48,11 +48,13 @@ adapter boundary. It also retains responsibility for pipeline retries,
 scheduling, debug persistence, redaction, profile provenance, and conversion
 from private model responses into durable domain artifacts.
 
-Notarius sends its trimmed run session through PromptKit's direct session
+Notarius sends one stable effective session through PromptKit's direct session
 field, which is authoritative for provider session behavior. It also retains
 the same value as the `session_id` prompt variable for maintained prompt
-compatibility. Session IDs are stable, non-secret correlation identifiers and
-may be exposed to providers and provider observability.
+compatibility. The generated identifier is 76 ASCII characters, within
+PromptKit v0.5.0's 256-code-point session limit. Session IDs are non-secret
+correlation identifiers and may be exposed to providers and provider
+observability. The CLI contract owns generation and override behavior.
 
 Notarius records PromptKit's selected backend ID and effective reasoning
 setting as optional run-manifest provenance. Endpoint-only profiles have no