Add read-only Yamcs mission control action

[Paul Lizer (paullizer)]

Summary

Adds a first-class, read-only yamcs action type that connects SimpleChat agents to a Yamcs mission control server using the official yamcs-client Python package.

The action gets its own configuration panel in the Add/Edit Action modal — including a Test Yamcs Connection button — rather than reusing the generic endpoint/auth form. It follows the existing Snowflake and Tableau full-stack patterns, and where those two differ it follows Tableau, since Yamcs is addressed by a real server URL rather than a synthetic endpoint constant.

Version bumped 0.250.208 → 0.250.209.

Read-only by design

Yamcs supports commanding, parameter writes, script execution, and data link control. None of that is exposed. The guarantee is enforced in three independent places:

1. Only read functions are declared in get_functions() and plugin metadata, so no write operation is ever offered to an agent.
2. additionalFields.read_only is forced to true during manifest normalization and cannot be flipped from a stored manifest.
3. The optional archive SQL function is disabled by default and, when enabled, is allowlisted to SELECT / SHOW / DESC / DESCRIBE with a forbidden-keyword guard and an automatic row limit.

list_commands returns mission database command definitions only and never issues a command. The plugin description states this explicitly so the model does not assume otherwise.

Functions

Function	Purpose
list_instances	Yamcs instances on the server
list_links	Data links with status and packet counts
list_parameters	MDB parameters, filterable by name text or type
describe_parameter	One parameter: type, units, enumerations
list_commands	Command definitions only
get_parameter_values	Latest processed values
list_parameter_history	Archived values over a time range
list_events	Archived events by severity/source/text
list_packets	Archived packet metadata
list_alarms	Archived alarms
execute_archive_sql	Guarded read-only archive SQL; off by default

Authentication

UI method	auth.type	Yamcs credential
Username and Password	username_password	Credentials(username=..., password=...)
API Key	key	APIKeyCredentials(key) → x-api-key header
Bearer Token	key	Credentials(access_token=...)
No Authentication	NoAuth	None
Reusable Identity	identity	resolved from the identity auth type

Reusable identities are accepted for api_key, bearer_token, and username_password.

Test Connection

POST /api/plugins/test-yamcs-connection verifies reachability, validates credentials, and confirms the configured instance actually exists — reporting the Yamcs version and available instance count. When editing a saved action it resolves the stored credential from Key Vault, so the secret does not need re-entering to run a test. Failures map 401/403 → 403 and 404 → 404 with credential-scrubbed messages.

Two real bugs caught during verification

1. urlparse("host:8090") misreads the hostname as a URL scheme. My first normalizer relied on urlparse().scheme to decide whether to prepend https://. Because host:port is the normal Yamcs address form, urlparse parsed yamcs.example.com as the scheme, so the check passed and no scheme was added. The Yamcs client then defaults a schemeless address to plain HTTP — a silent TLS downgrade. Fixed with an explicit ^https?:// check. (Tableau's normalizer shares this pattern but isn't exposed to it, since Tableau URLs rarely carry ports. Left alone as out of scope.)

2. APIKeyCredentials stores the key on .password, not .key. Confirmed against the real library; the test fake was corrected so it can't encode a wrong assumption about the API surface.

Verified against the real library, not just fakes

Installed yamcs-client==2.1.0 in a throwaway venv and confirmed:

• All three imports resolve (YamcsClient, Credentials, APIKeyCredentials)
• The constructor accepts a full URL plus the kwargs the plugin passes, with no network I/O
• ctx.session.request exists, so the timeout wrapper is valid
• All four credential paths produce correct auth behavior (x-api-key header, Authorization: Bearer, lazy login, None)
• Protobuf coexistence: yamcs-client vendorizes protobuf 7.35 internally, verified to work alongside the repo's pinned protobuf==6.33.5

⚠️ Licensing — needs a compliance look

yamcs-client is LGPL-3.0, the first LGPL dependency in this repository (Snowflake is Apache-2.0, tableauserverclient is MIT). It is consumed as an unmodified, dynamically linked pip dependency, which is the standard-compliant usage pattern — but flagging it explicitly so it's a conscious decision rather than something that slips through. Documented in both the feature doc and the release notes under Breaking Changes.

Testing

Suite	Result
functional_tests/test_yamcs_action_plugin.py (new)	14/14 pass
functional_tests/route_tests/ (3 files)	12/12 pass
Snowflake + Tableau regression	9/9 pass

The new test covers normalization and clamping, factory manifest handling, metadata and the absence of write functions, the full auth mapping matrix, construction-time validation failures, health-checker validation for each failure mode, the reusable identity contract, all read-only retrievals, argument validation, the archive SQL default gate and read-only guard, row/byte truncation, secret redaction, and missing-dependency handling.

The new route is covered by the existing path-prefix policy rules in route_tests, so no test-data edits were needed there. Plugin discovery was separately confirmed to surface yamcs in the action-type picker. Python compile, JS syntax, JSON, and Jinja template checks are all clean.

Files

New (7): functions_yamcs_operations.py, semantic_kernel_plugins/yamcs_plugin.py, semantic_kernel_plugins/yamcs_plugin_factory.py, two JSON schemas, docs/explanation/features/YAMCS_ACTION.md, functional_tests/test_yamcs_action_plugin.py

Modified (14): both kernel loaders, health checker, Key Vault redaction, workspace identities, governance aliases/labels, route_backend_plugins.py, _plugin_modal.html, plugin_modal_stepper.js, view-utils.js, requirements.txt, config.py, features index, release notes

Notes for reviewers

• Streaming/subscription APIs are intentionally not exposed, since agent tool calls are request/response.
• Testing a connection that uses a reusable identity requires saving the action first; the UI states this.
• No associated GitHub issue exists yet — happy to open one and link it if preferred.