ADR-059: Decompose LlmServiceManager into focused collaborators 

Context 

LlmServiceManager had grown to 987 lines. It is the extension's central entry point — a SingletonInterface implementing LlmServiceManagerInterface, which ADR-028 classifies as a Category-1 public API. A responsibility scan found nine distinct groups in one class:

1. Skill-injection glue (delegates to SkillInjectionService).
2. Default-configuration resolution.
3. Loading the nr_llm extension configuration.
4. The keyed, ExtensionConfiguration-backed provider registry (register / look up / list / configure providers by string identifier).
5. Generic dispatch (chat, complete, embed, vision, streamChat, chatWithTools).
6. Configuration-backed dispatch (the *WithConfiguration methods).
7. The database-backed adapter factory facade.
8. Pipeline plumbing (runThroughPipeline, budget metadata, transient configuration synthesis).
9. Message shaping (system-prompt injection and message normalisation).

Two of these groups additionally carried duplicated code: the two embedding entry points each held an inline copy of the cache-metadata block, and six generic entry points repeated the same options / provider-key extraction preamble.

Decision 

Decompose the manager in stages. This ADR records stage 1, which extracts the self-contained groups while leaving the dispatch logic in place. The manager remains final and keeps implementing the unchanged LlmServiceManagerInterface; every former public method is retained as a thin delegation, so the Category-1 contract, the class name, registerProvider and the three non-interface public methods (getAdapterFromModel, getAdapterFromConfiguration, getAdapterRegistry) are unchanged.

Extracted collaborators (all private, autowired via the Classes/* resource block in Services.yaml):

• KeyedProviderRegistry — groups 3 + 4. Holds the mutable provider map and the loaded extension configuration, so it is itself a SingletonInterface. ProviderCompilerPass still adds its registerProvider method calls to the manager service, which forward here.
• ConfigurationResolver — group 2. readonly; resolves the backend-managed default configuration through the repository.
• MessageShaper — group 9. readonly, stateless message normalisation and system-prompt injection.
• EmbedCacheKeyBuilder — deduplicates the two inline embed cache-metadata blocks. The blocks are not identical: the ad-hoc embed() path keys by provider identifier with the payload {input, options} and a nrllm_provider_<id> tag, while embedForConfiguration() keys by configuration identifier plus the effective model (options override or the configuration's model id) with a nrllm_configuration_<id> tag, so two configurations pointing at different models never share entries. The builder therefore shares only the structure (the positive-ttl guard and the {cacheKey, cacheTtl, cacheTags} shape with the common nrllm_embeddings tag); each caller supplies its own namespace, key payload and scope tag. This difference is intentional, not a defect.

The repeated options / provider-key preamble becomes a private splitProviderKey() on the manager (the six callers all remain on the manager in stage 1).

The manager's constructor changes accordingly — it drops ExtensionConfiguration, LoggerInterface, CacheManagerInterface and the LlmConfigurationRepository (now owned by the collaborators) and gains the four collaborators. The constructor is not part of the interface contract; production wiring is autowired.

Consequences 

• Behaviour is unchanged. The interface signatures, the provider-resolution error messages and their exception codes, and the two embed cache-keying strategies are all preserved. The existing manager / integration / e2e tests continue to exercise the behaviour through the facade; they construct the manager through a test factory (LlmServiceManagerTestFactory) that accepts the previous leaf-dependency shape and wires the new collaborators, so the call sites did not each have to change shape. The extracted classes additionally get their own unit tests.
• New private services keep the documented public-service set stable (ADR-028); the PublicServicesPolicyTest count is unchanged.
• The manager drops from 987 to roughly 790 lines.