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feat-cma-scale — Cloud Managed Agents at scale

Branch: session/feat-cma-scale. Scope: packages/plugins/claude-managed-agent only (plus the root pnpm-lock.yaml for the SDK dependency move).

Goal: run Claude Managed Agents (CMA) efficiently at scale — a persistent control plane instead of create-and-delete per run, a bounded-concurrency fan-out service, per-session budget caps, and token/cost figures that actually reach the platform's usage rollups.

What shipped​

1. SDK dependency​

@anthropic-ai/sdk moved from devDependencies 0.91.1 to dependencies ^0.117.1. It was already the transport on develop (AnthropicManagedAgentsClient wraps client.beta.*), but as a dev dependency the published/bundled plugin declared no runtime dependency on it — tsup keeps it external, so the import would have been unresolved for any consumer installing the package. 0.117.x is also the first version with the typed limited networking policy, budget, initial_events and agent_with_overrides shapes this branch relies on.

There are no left-behind non-SDK call sites — every CMA request goes through AnthropicManagedAgentsClient, and utils/cma-sdk.ts is the single construction seam (API key + base URL resolution) used by the pipeline, the control plane and the fan-out.

Deviation from the brief: the brief assumed managed-agents-client.ts was a hand-rolled REST client to be left alone while new code went through a new SDK wrapper. It was already SDK-based, so the wrapper stayed in place and was extended instead of duplicated.

2. Persistent control plane — utils/control-plane.ts​

New user-scope, x-hidden, plugin-written settings: managedAgentId, managedAgentConfigHash, managedEnvironmentId, managedEnvironmentConfigHash (persisted through context.updateSettings('user', …)).

  • ensureManagedAgent — no stored id → create; stored id + matching hash → reuse; hash drift → agents.update (new immutable version upstream); stored id missing/archived → recreate. The config hash deliberately excludes the model: sessions pin the model per run via agent_with_overrides, so a model change must not churn agent versions.
  • ensureManagedEnvironment — same matrix against the resolved networking policy. The policy comes from the optional serializable execContext.runtimeEnvironment object when the platform provides one (Environments feature, parallel branch — read defensively, the entity is not imported), else the existing CLAUDE_MANAGED_AGENT_EGRESS_HOSTS env-var fallback.
  • Persisting state is best-effort: a failed write logs and the run continues with the resolved ids.

New setting reuseControlPlane (boolean, default true). When false the plugin falls back to today's ephemeral behavior: work-scoped agent + environment created per run and torn down at cleanup. In reuse mode the run's session is archived (not deleted) and the agent/environment are never touched.

3. Fan-out — utils/fan-out.ts + ClaudeManagedAgentPlugin.runSessions()​

runManagedSessions(client, {prompts, agentId, environmentId, concurrency = 5, perSessionBudgetUsd?, timeoutMs?, resources?, agentOverrides?, signal?, archiveSessions?}) → per-prompt {id, status, output?, sessionId?, tokens?, costUsd?, error?}, in prompt order. Simple index-cursor worker pool (no dependencies); a failing session never aborts its siblings; every created session is archived best-effort; timeoutMs is converted into a poll-attempt bound over the existing waitForSessionIdle polling (the events stream has no replay, so poll-to-idle stays the mechanism).

Two entry points:

  • Pipeline step run-variant-sessions (optional, steps.ts): active only when the generation form's variant_sessions > 1. Each variant gets a single combined prompt (buildVariantSessionPrompt — bootstrap / generate / collect phases in one message), results are parsed independently and merged with de-duplication (mergeVariantOutputs: item key = lowercased name::source_url, first variant wins). A failed variant becomes a warning; only an all-failed batch fails the run. With variant_sessions at its default of 1 the step is skipped and the single-session path is unchanged.
  • plugin.runSessions({prompts, userId, workId?, concurrency?, perSessionBudgetUsd?, timeoutMs?, resources?, signal?}) for API-side / Trigger.dev callers. Resolves settings (work-scoped when workId is given, else user-scoped), ensures the control plane, runs the batch, and tears down an ephemeral control plane afterwards.

Registration: onLoad publishes the service on the platform's custom-capability registry under CMA_FAN_OUT_CAPABILITY ('claude-managed-agent.fan-out'), so callers can reach it via CustomCapabilityRegistryService.getImplementation(CMA_FAN_OUT_CAPABILITY) without holding the plugin instance. Registration is guarded (partial contexts, duplicate-name throw on re-load) and never fatal to loading the plugin; the lifecycle manager already unregisters by provider on unload.

4. Budget caps​

New form field per_session_budget_usd (1..500). budget is create-only upstream, so it is passed to sessions.create as {type:'limit', max_list_cost:{amount:'<cents>', currency:'USD'}} — integer minor units, never floats.

The ceiling is enforced by a single helper, clampPerSessionBudgetUsd (form-schema.ts), applied on all three paths that can reach sessions.create: form validation, a raw GenerationRequest reaching execute() directly, and the programmatic runSessions(). variant_sessions (1..8) and target_items (1..250) are clamped the same way.

5. Usage accounting — utils/usage-metrics.ts​

buildManagedAgentMetrics() writes tokenUsage.total.totalTokens and totalCost at the metrics root, plus a per-session breakdown under custom for logs.

This was the branch's one real defect. The interrupted session put those keys inside the custom bag (via the plugin-runtime buildMetrics() helper, which nests whatever it is given under metrics.custom), while the platform's consumer, extractPipelineUsageMetrics in packages/agent/src/utils/metrics.util.ts, only reads metrics.tokenUsage.total.totalTokens, metrics.totalCost and per-step steps[*].custom.totalTokens|totalCost. Every token and dollar the plugin reported was therefore dropped from the rollup — wired but dead, and pinned that way by a test. The shape now matches the agent-pipeline plugin's convention, and the contract is asserted with a faithful replica of the consumer in the plugin spec (plugin packages cannot import @ever-works/agent).

Per-session cost comes from usage.list_cost (integer minor units, USD-only; non-USD or malformed amounts yield undefined rather than a wrong number).

Token counting goes through one seam, toManagedSessionTokenUsage(), shared by the fan-out and single-session paths. totalTokens counts every billed token class: input_tokens + output_tokens + cache_creation_input_tokens + cache_read_input_tokens. The two cache counters are reported by the sessions API outside input_tokens, and managed-agent sessions re-read a large cached prefix on every turn, so omitting them under-reported the rollup by orders of magnitude (see review findings below).

No plugin_usage_events ledger row is emitted. That was checked, not assumed: PluginUsageService is an API/agent-side Nest provider reached only through the *.facade.ts seams (ai / search / screenshot / extractor / email / notification / metrics). PluginContext exposes no usage seam and PluginEventName has no usage event, so a pipeline plugin cannot reach the ledger. Per the brief this falls back to reporting figures in the pipeline metrics — see follow-ups.

Data model / endpoints / UI​

None. No entities, no migration, no controllers, no web routes, no i18n keys. The two new form fields and reuseControlPlane render from the plugin's existing JSON-schema/form provider surfaces.

Test commands​

cd packages/plugins/claude-managed-agent
pnpm type-check          # tsc --noEmit
pnpm test                # vitest run — 6 files, 55 tests
npx vitest run src/utils/usage-metrics.spec.ts
npx vitest run src/utils/control-plane.spec.ts
npx vitest run src/utils/fan-out.spec.ts
npx vitest run src/claude-managed-agent.plugin.spec.ts

# from repo root
npx turbo build --filter=@ever-works/claude-managed-agent-plugin...
npx prettier --check "packages/plugins/claude-managed-agent/src/**/*.ts"

Coverage added on this branch: ensure-agent create/reuse/version-bump/recreate matrix; ensure-environment with and without the runtimeEnvironment context object; fan-out pool concurrency ceiling, budget pass-through, failure isolation, archive behavior, timeout derivation and cancellation; ephemeral-mode fallback end to end; capability registration (including double-load); budget clamping on the programmatic path; and the usage-metrics shape against a replica of the platform consumer.

Pre-merge review findings (fixed on this branch)​

  1. Cached input tokens were dropped from the usage rollup. mapSession() mapped cache_creation_input_tokens / cache_read_input_tokens onto ManagedAgentsUsage, but nothing read them: both the fan-out toTokenUsage() and the single-session metrics block computed totalTokens = input_tokens + output_tokens. Anthropic reports both cache counters outside input_tokens, so a session using {input 1200, output 800, cache_creation 24000, cache_read 640000} reported total_tokens_used: 2000 instead of 666,000. The custom.usage bag was also a regression against develop, which at least carried the raw usage object. Fixed by a single shared mapper (toManagedSessionTokenUsage) used by both paths, with the cache counters summed into totalTokens and broken out in custom.usage.
  2. Ephemeral runs ignored the runtime environment's networking policy. The reuseControlPlane === false branch of execute() built its environment inline with createEnvironment({ name }) and never consulted execContext.runtimeEnvironment, so resolveNetworking() never ran on that path — an explicit limited egress allow-list was silently downgraded to the env-var default (unrestricted). The reuse path and ensureControlPlane's own ephemeral branch both honored it; only this duplicated inline copy did not. Networking is a security control, so both modes now resolve it.
  3. The fan-out concurrency test asserted nothing. expect(peakActive) .toBeLessThanOrEqual(2) also passes for a fully serial pool, so a regression to one-session-at-a-time would have stayed green. Tightened to toBe(2).

Regression coverage added for all three, plus the previously unasserted per-session budget cap on the single-session path.

Known follow-ups​

  1. Ledger rows. To get real plugin_usage_events rows for pipeline runs, the seam has to be added platform-side: a PluginUsageCapability.PIPELINE enum value (additive, the column is varchar — no migration) and a PluginUsageService.record() call from DataGeneratorService.convertPipelineMetrics(), which already has the work/user scope and the extracted totals. Deliberately out of scope here: it is a cross-cutting change affecting every pipeline plugin, not just this one.
  2. Session runtime cost. usage.list_cost covers model tokens; the $0.08/hour session runtime charge is not broken out by the API response the plugin sees, so totalCost under-reports wall-clock-heavy runs.
  3. runtimeEnvironment producer. The plugin reads the object defensively; nothing sets it yet. When the Environments branch lands, verify the field name and shape against resolveNetworking() and add an integration-level assertion.
  4. Fan-out concurrency is not exposed on the generation form. Variant runs use the default of 5; only the programmatic runSessions() caller can tune it.
  5. No SSE consumption. Sessions are still polled to idle. If the events stream gains replay, waitForSessionIdle is the single place to swap.