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Chat sessions

Send one agent Playground message

Send one message to a project's MCP servers and get the model's reply plus the telemetry a participant in the conversation could not see: which tools ran, with what arguments, what each returned, per-call latency, and token usage.

Spends model credits per call. idempotencyKey is required and must be STABLE for the triggering intent — a fresh key per HTTP attempt deduplicates nothing, so a timeout-and-retry would run and bill the turn twice. With a stable key, a retry replays the completed turn.

Omit sessionId to start a session; pass the one this returns to continue it. Configuration (modelId, target, systemPrompt, toolMode) pins on the FIRST turn — a continuation that resends any of it is refused with details.reason: "CONFIG_ON_CONTINUATION".

Only sessions created through this endpoint may be continued through it (CONTINUATION_NOT_ALLOWED): appending to a human's live Playground session would interleave two writers on one transcript.

toolMode defaults to read_only, which advertises only tools the server annotated readOnlyHint: true. That hint is server-asserted, so read_only is a policy this host applies, not a guarantee it can verify. auto advertises everything and may cause real external side effects through arbitrary third-party tools.

post/chat-sessions/messages

Request body

idempotencyKeystring required

STABLE identity for this turn's intent — reuse it when retrying. A fresh key per attempt deduplicates nothing and will bill the turn twice. Printable ASCII only.

messagestring required

The message to send, as the user.

projectIdstring

Required to START a session; ignored when continuing one.

sessionIdstring

Continue this session. Omit to start a new one.

modelIdstring

Provider-prefixed model id, e.g. anthropic/claude-sonnet-5. Required on a first turn. A BARE id is rejected with details.reason: "MODEL_AMBIGUOUS" rather than guessed — an unprefixed id is indistinguishable from a local Ollama model, and guessing would spend on the wrong rail.

environmentIdstring

Target this environment's servers. Mutually exclusive with serverIds. First turn only.

serverIdsstring[]

Target these project servers. Mutually exclusive with environmentId. First turn only. Server CONFIGS are never accepted — only ids the project already holds.

systemPromptstring

First turn only.

temperaturenumber

First turn only — pinned to the session and reused on every continuation.

maxStepsinteger
toolMode'read_only' | 'auto'

read_only advertises only tools annotated readOnlyHint: true. auto advertises everything and MAY CAUSE REAL EXTERNAL SIDE EFFECTS. First turn only.

allowedServerIdsstring[]

Narrow THIS TURN to a subset of the target's servers. An empty array narrows to none and is rejected — omit the field to use the whole target. Per-turn, not pinned.

allowedToolsstring[]

Advertise only these tool names, for THIS TURN. An empty array advertises no tools at all — the same request as maxToolCalls: 0. Per-turn, not pinned.

maxToolCallsinteger

Cap the tool calls this turn may make, enforced at DISPATCH rather than by bounding steps (one step can emit several parallel calls). 0 advertises no tools at all.

Response

The turn ran. persisted.outcome reports whether the transcript landed — a turn that ran but failed to persist still spent, so this is a 200 with an honest persisted block rather than an error.

sessionIdstring nullable required

The one public session id. Pass it back to continue, and to the trace/detail reads. NULL only when the turn ran but its transcript did not persist — which persisted.outcome reports, and which must not be read as "nothing happened": the turn already spent.

turnIdstring required

Minted by the turn lease and used by the ingest dedupe, so it names the same turn in both.

projectIdstring required

The project this turn ran in. On a continuation the caller never sent it — it comes off the session row — so this is the only place the response names the session's project.

replystring
finishReasonstring nullable
toolMode'read_only' | 'auto'
advertisedToolCountinteger

Tools the model could see this turn.

excludedToolCountinteger

Tools the tool policy withheld.

origin'api' required
replayboolean

Set when this idempotencyKey replayed an already-completed turn. Nothing was spent.

messagestring

Changes