feat(client): declare ?kinds=agent-skill, and treat a 422 as "no skills yet"

[XieX]

Stacks on #94 -> #93 -> #87. Spec: ai-sdks-monorepo#23. TypeScript counterpart: js-ai-sdk#87. Server side: streamer#4730.

This is the SDK half of the release blocker: other SDKs retry forever when they see a skill payload. Flag Delivery's answer is ?kinds=, which narrows a connection to the payload kinds it declares, defaulting to {flagging} (so we need to opt-in to see skills).

The declaration

Every request now carries kinds=agent-skill — both endpoints, and on the first request as well as the ones after it, since it selects what the connection is served rather than describing what the store already holds. Without it the store receives the environment's flag payload and no skills at all, so this is a functional requirement, not for correctness/optimization.

It also fixes something that was already wrong. A skill-enabled environment assigns two payloads, so _ProtocolReader has been warning about the second on every connection, reading only the first intent, and never adopting a basis for the flag payload — re-downloading and discarding it on every reconnect. Declaring one kind makes the connection single-payload, which is the shape the reader is built for. (That is also why declaring flagging,agent-skill is not the safe-looking option it appears to be.)

No mv, still — but for a corrected reason. It selects the flag data model, and objectQueryForCommand overrides whatever a request asks for with the payload's own default for any non-flagging payload, so sending it would state a preference that is ignored. The old comment said the connection would be refused over it.

The 422

Delivery answers 422 no_accepted_payloads when the credential's assignment holds no payload of the declared kind. That is every project in which no skill has ever been created: gonfalon's payloadIDsForEnvironment appends the agent-skill payload ID only "if one already exists" and never lazily creates it.

Both obvious classifications are wrong. Reverting just the 422 case and rerunning the new tests prints exactly what the recoverable reading gives you:

Skill delivery has stopped and will not retry: gave up after 2 consecutive
failures; last error: LaunchDarkly returned HTTP 422.

...for an environment whose only problem is that nobody has made a skill yet. Fatal is no better: the skill created a minute later never arrives until the process restarts.

So _NoSkillPayloadError, caught ahead of _RecoverableTransportError (which it subclasses, so nothing else has to change):

• counted under the new StoreDiagnostics.payload_unavailable;
• logged once per store, with a message that names the state rather than the status;
• retried at max_backoff indefinitely — at the cap because _failures deliberately never moves, so the exponential schedule would otherwise sit at the initial delay forever;
• kept off connection_failures, last_error and failed.

It commits no payload, so is_initialized() stays false and write_skills("*") still withholds the prune. That is the right answer: "LaunchDarkly has no skill payload for this environment" and "this environment's every skill was revoked" are the two readings of an empty answer, and only the second may delete a customer's files.

Tests

Nine, each of which fails with the source reverted:

• the declaration on /sdk/poll (first request and the one carrying a basis) and on /sdk/stream, and on the from-scratch 400 retry — where the two existing query == {} assertions became {"kinds": ...}, which is a better assertion: the declaration is not client state;
• FDV2_PAYLOAD_KIND and FDV2_OBJECT_KIND held apart;
• the 422's classification, and that its message explains the state;
• that a 422 repeated well past max_consecutive_failures=1 neither stops delivery nor counts, and is said exactly once;
• that it waits the cap and not the initial delay (recording _stop so the assertion is on the interval asked for, not on wall-clock timing);
• that a skill payload arriving after two 422s is picked up, with both diagnostics reading as what happened;
• that it leaves the store uninitialised, so a wildcard reconcile leaves a stale file on disk.

The fake endpoint gained default_poll_status, since "every request is answered 422" is not something a queue can express.

Gate

From python/: make test (1888 passed, 11 skipped), make typecheck (clean, 51 source files), make lint, make format-check — all clean.

🤖 Generated with Claude Code, edited by @XieX

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Note

Overview
FDv2 skill delivery now opts into the agent-skill payload on every poll/stream request via ?kinds=agent-skill, replacing the previous default flag payload. That makes connections single-payload (matching _ProtocolReader) and is required for skills to arrive at all; basis retries still send kinds because it is not client state.

HTTP 422 (“no payload of this kind”) is treated as an idle waiting state, not a transport failure: new _NoSkillPayloadError is handled before the recoverable path, increments StoreDiagnostics.payload_unavailable, logs once, retries at max_backoff without touching failed/connection_failures/last_error, and leaves is_initialized() false so write_skills("*") does not prune. Docs and tests cover declaration on poll/stream, 422 classification, backoff cap, pickup after first skill is created, and prune safety.

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