docs: add CLI MCP operator design and questions - #35
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- Record the operator HOW: Kubebuilder layout, CR API, and phased PRs - Capture Q1–Q16 (images, sandbox class, idle GC in Phase 4, pool in Phase 5) - Pause proxy HOW until that operator exists; align Q1 with operator ownership Signed-off-by: Alexey Kazakov <alkazako@redhat.com> Co-authored-by: Cursor <cursoragent@cursor.com>
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WalkthroughThe PR adds design proposals for a CLI MCP Operator and a deferred credential-isolating proxy. It defines CRD contracts, ownership, reconciliation, sandbox lifecycle, security controls, readiness requirements, build structure, and phased implementation decisions. ChangesCLI MCP Operator and credential proxy design
Estimated code review effort: 2 (Simple) | ~15 minutes Merge Risk: ⚪ Minimal · up to This PR adds and refines proposal documentation without introducing an actionable merge-blocking risk; it is merge-ready after normal checks and review. Suggested labels: 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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Actionable comments posted: 17
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In `@docs/proposals/cli-mcp-operator-design.md`:
- Around line 98-99: Update the documented RBAC for the MCP ServiceAccount and
operator so session-secret access is separated from administrative Secret
access, avoiding namespace-wide read permissions that expose unrelated Secret
data; alternatively, explicitly document namespace-wide Secret access as a trust
boundary and add tests proving cross-instance isolation. Apply the same
correction to the corresponding permissions described elsewhere in the proposal.
- Around line 496-498: The Phase 6 rollout guidance must not permit production
first-party MCP client wiring before the proxy and egress controls are
available. Update the Phase 6 “Other repo / GitOps” guidance to remain
test-only, or defer production wiring until after Phase 7, while preserving the
existing prerequisite sequencing.
- Line 88: Update the operator’s sandbox Pod event handling to filter out
routine last-activity patches while still enqueueing reconciles for assignment
and relevant spec changes. Use requeueAfter to schedule idle-session expiry, and
ensure each accepted activity update reschedules that expiry without causing a
full reconcile for every bash request.
- Line 359: Restrict user-controlled sandbox environment configuration so
CliMcpInstance writers cannot use env.valueFrom to expose Secret data in the
bash-capable sandbox. Prefer removing Secret references from the v1 env
contract; otherwise enforce an admission allowlist for referenced Secrets and
ensure only trusted administrators can create or update these references, while
preserving ordinary non-Secret environment values.
In `@docs/proposals/cli-mcp-operator-questions.md`:
- Around line 202-205: Update Option A so the finalizer waits for all
operator-owned children—including Deployments, Services, NetworkPolicies,
ServiceAccounts, Roles/RoleBindings, HMAC Secrets, warm-pool Pods, sandbox Pods,
and session Secrets—to be deleted before removing the finalizer; alternatively,
explicitly define UID-safe cleanup and adoption behavior before releasing the CR
name.
- Around line 202-205: Update Option A’s finalizer sequence to quiesce the MCP
first: scale the MCP Deployment to zero and wait for its Pods to terminate
before deleting session Pods and Secrets. Then retain the existing
wait-for-session-cleanup step before removing the finalizer.
- Around line 290-298: Update the Ready contract to validate required data keys
in each required Secret, not only object existence: require kubeconfig in
cli-mcp-<name>-kubeconfig, key in the operator-created HMAC Secret, and
the required TLS certificate keys on generic Kubernetes. Report missing or empty
keys through an invalid-secret condition, while leaving kubeconfig parsing out
of scope.
- Around line 221-228: The proposed `/assign` authorization must not rely solely
on Pod labels such as `cli-mcp.redhat.com/instance` and `component=server`,
because unauthenticated callers could spoof them and claim pool Pods or select
session tokens. Update the `/assign` flow to authenticate and authorize the
caller using an identity-aware mechanism, or explicitly enforce the namespace as
a trusted boundary before allowing assignment.
- Around line 312-321: Define a concrete versioned transport for SandboxConfig
shared by pool and MCP on-demand pod creation, including serialization for
EnvVar.ValueFrom, resources, imagePullPolicy, and image. Specify whether it uses
Deployment arguments or an operator-owned ConfigMap, how it is mounted or
passed, refresh and rollout behavior, and the required ConfigMap RBAC; ensure
both paths consume the same resolved overlay.
- Around line 124-131: Update the typed instance API and its reconciliation
logic for replicas, warmPoolSize, and idleTimeout to enforce the design
document’s minimums, maximums, nonnegative pool size, and positive timeout. Add
matching CEL validation and controller-side caps so invalid or excessive values
cannot cause unbounded fan-out or immediate session deletion; anchor changes to
the relevant spec fields and operator reconciliation paths.
In `@docs/proposals/credential-proxy-design.md`:
- Around line 189-203: Revise the target package layout and related flags
section to remove MCP-server startup reconciliation and operator-owned
configuration responsibilities, including fixed kubeconfig Secret naming. Align
the document with Q1 and the operator contract in cli-mcp-operator-design, or
clearly label the conflicting material as historical so ownership remains
exclusively with the operator.
- Around line 130-139: Update the NetworkPolicy discussion in
docs/proposals/credential-proxy-design.md lines 130-139 to remove the claim that
Proxy ingress stops unauthorized clients, or explicitly add a non-spoofable
authentication control. Reconsider the NetworkPolicy-only recommendation in
docs/proposals/credential-proxy-questions.md lines 62-76 for namespaces where
untrusted principals can create pods, and align it with the corrected security
boundary.
- Around line 302-307: Define the fail-closed contract across the Phase 3 design
and the readiness questions: in docs/proposals/credential-proxy-design.md lines
302-307, specify how cmd/server observes operator readiness before creating
sessions; in docs/proposals/credential-proxy-questions.md lines 265-286, specify
the handling of existing sandboxes when proxy, ConfigMap, or NetworkPolicy
readiness is lost, including drift detection and remediation.
- Around line 165-177: Define a dedicated proxy ServiceAccount for the proxy
Deployment, set the Deployment to use it, and disable service-account token
automounting. Ensure the proxy mounts only its required Secret and ConfigMap
volumes, without RoleBindings, and add a generated Deployment assertion covering
these settings.
- Around line 224-233: Update the route schema and Kubernetes injector so each
route deterministically selects exactly one kubeconfig user: either reject
duplicate normalized server entries with different users or add an explicit
context/user reference and resolve credentials through it. Ensure the route
identity cannot depend on iteration order, and add coverage using two users and
contexts targeting the same API server.
In `@docs/proposals/credential-proxy-questions.md`:
- Around line 121-137: Add pods/ephemeralcontainers to the Kubernetes L7
denylist by parsing resource and subresource path segments rather than relying
on raw suffix matching. Extend the related tests to cover encoded paths, query
strings, upgrade requests, and confirm logs and watch requests remain allowed.
- Around line 80-99: Align Option A’s proxy egress policy with validated
kubeconfig server routes: either derive allowed TCP ports from the validated
routes, or reject unsupported ports before publishing routes and the dummy
kubeconfig. Ensure route validation, published routes, and NetworkPolicy
connectivity consistently support only reachable ports.
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⚙️ CodeRabbit configuration file
-Focus on major issues impacting performance, readability, maintainability and security. Avoid nitpicks and avoid verbosity.
Files:
docs/proposals/credential-proxy-design.mddocs/proposals/credential-proxy-questions.mddocs/proposals/cli-mcp-operator-questions.mddocs/proposals/cli-mcp-operator-design.md
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docs/proposals/credential-proxy-design.md
[uncategorized] ~187-~187: The official name of this software platform is spelled with a capital “H”.
Context: ...cmd/proxy | MITM forward proxy | CD (.github/workflows/cd.yml) gains a third matrix...
(GITHUB)
docs/proposals/credential-proxy-questions.md
[grammar] ~87-~87: Ensure spelling is correct
Context: ...he internet. 0.0.0.0/0 does not cover IPv6. ### Option B: Resolve kubeconfig hostnames a...
(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)
[grammar] ~157-~157: Ensure spelling is correct
Context: ...te only - Pro: Easier to pull claw bugfixes. - Con: Dead injectors, gateway mod...
(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)
[grammar] ~179-~179: Ensure spelling is correct
Context: ...phase. - Pro: One label domain. NP podSelectors are obvious. Two CRs in one namespace c...
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docs/proposals/cli-mcp-operator-design.md
[style] ~353-~353: Three successive sentences begin with the same word. Consider rewording the sentence or use a thesaurus to find a synonym.
Context: ...onal name cli-mcp-<name>-kubeconfig). No spec.args passthrough. No `spec.proxy...
(ENGLISH_WORD_REPEAT_BEGINNING_RULE)
[style] ~353-~353: Three successive sentences begin with the same word. Consider rewording the sentence or use a thesaurus to find a synonym.
Context: ...beconfig). No spec.argspassthrough. Nospec.proxy` in this revision (Q14). No...
(ENGLISH_WORD_REPEAT_BEGINNING_RULE)
[style] ~353-~353: Three successive sentences begin with the same word. Consider rewording the sentence or use a thesaurus to find a synonym.
Context: ...No spec.proxy in this revision (Q14). No spec.sandbox.type enum and no `PodTem...
(ENGLISH_WORD_REPEAT_BEGINNING_RULE)
[grammar] ~359-~359: Ensure spelling is correct
Context: ....sandbox: image, resources, env ([]corev1.EnvVar, including valueFrom), image...
(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)
[style] ~420-~420: Consider using “impractical” to avoid wordiness.
Context: ... the better home? 3. What did I skip as not practical, and why is that acceptable? Per-phase...
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docs/proposals/credential-proxy-design.md
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🔇 Additional comments (2)
docs/proposals/cli-mcp-operator-design.md (1)
166-166: 🗄️ Data Integrity & IntegrationDefine the recovery contract for a recreated HMAC Secret.
The design recreates the HMAC key and rolls only the MCP Deployment. The supplied
pkg/sandbox/handler.gocontract validates per-session bearer tokens at/exec, but this document does not define how existing sessions behave after the key changes. Drain or delete those sessions, reissue tokens, or verify that old tokens remain valid before reportingReady.docs/proposals/cli-mcp-operator-questions.md (1)
254-265: 🔒 Security & PrivacyDefine the exact authorization pattern for
/sessions/{id}.The API path is
/sessions/{id}, but the design lists/sessionsfor--allow-pathsand for the optional KubernetesnonResourceURLsrule. If the RBAC rule is exact, it will not authorize the subpath. Kubernetes supports suffix wildcards fornonResourceURLs; define and test the exact pattern forDELETE /sessions/{id}. (kubernetes.io)Source: MCP tools
- Quiesce MCP (scale to 0) before session teardown; idle GC uses a Pod predicate and requeueAfter instead of per-bash reconciles - Restrict MCP Secret RBAC to create/delete; Ready checks required keys - Pass sandbox overlay via Deployment flags, not a ConfigMap; keep first-party catalog consume test-only until proxy isolation exists Signed-off-by: Alexey Kazakov <alkazako@redhat.com> Co-authored-by: Cursor <cursoragent@cursor.com>
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