fix: remove serde(flatten) annotation for TurnError

[owenlin0]

The problem with using serde(flatten) on Turn status is that it conditionally serializes the error field, which is not the pattern we want in API v2 where all fields on an object should always be returned.

#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
#[serde(rename_all = "camelCase")]
#[ts(export_to = "v2/")]
pub struct Turn {
    pub id: String,
    /// Only populated on a `thread/resume` response.
    /// For all other responses and notifications returning a Turn,
    /// the items field will be an empty list.
    pub items: Vec<ThreadItem>,
    #[serde(flatten)]
    pub status: TurnStatus,
}

#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
#[serde(tag = "status", rename_all = "camelCase")]
#[ts(tag = "status", export_to = "v2/")]
pub enum TurnStatus {
    Completed,
    Interrupted,
    Failed { error: TurnError },
    InProgress,
}

serializes to:

{
  "id": "turn-123",
  "items": [],
  "status": "completed"
}

{
  "id": "turn-123",
  "items": [],
  "status": "failed",
  "error": {
    "message": "Tool timeout",
    "codexErrorInfo": null
  }
}

Instead we want:

{
  "id": "turn-123",
  "items": [],
  "status": "completed",
  "error": null
}

{
  "id": "turn-123",
  "items": [],
  "status": "failed",
  "error": {
    "message": "Tool timeout",
    "codexErrorInfo": null
  }
}

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep Turn.status flat when serializing

The Turn struct now stores status as a normal field while TurnStatus is still internally tagged with status; without the previous #[serde(flatten)], any v2 Turn serialization will nest a second status key (e.g., { "status": { "status": "completed" }, "error": null }) instead of the expected top-level string shown in the commit description. That breaks the v2 API schema for every Turn response/notification, changing status from a string to an object and likely invalidating clients deserializing existing payloads.

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[celia-oai]

I think codex' review is valid. you want to remove the tag in this line & below.

[owenlin0]

codex the implementer has failed me

[bolinfest]

the pattern we want in API v2 where all fields on an object should always be returned

Hmm, is this a good choice for error, though? In a JSON-RPC style response, result and error are generally mutually exclusive:

https://www.jsonrpc.org/specification#response_object

[owenlin0]

Hmm, is this a good choice for error, though? In a JSON-RPC style response, result and error are generally mutually exclusive:

@bolinfest This is a fine contract for RPC calls, but this Turn object gets serialized out in notifications (and RPC calls like thread/resume), and the client has to have nasty code like const errorObj = "error" in turn ? turn.error : null; so it's a bit of a different scenario