chore: sync OpenAPI contract

[JasonLovesDoggo]

Automated sync of `contract/openapi.yaml` from the monorepo.

Source commit: trylitmus/litmus@25274156c014dca5bee2a4dd236a2b947dbe6fa2

Review the diff, then merge. If the SDK has codegen (e.g. `pnpm generate`),
run it after merging to update generated types.

[greptile-apps]

Greptile Summary

This PR syncs the OpenAPI contract from the monorepo, adding the $sessionend event type (with clear documentation distinguishing it from $abandon) and seven new generation-metadata fields — model, provider, input_tokens, output_tokens, total_tokens, duration_ms, ttft_ms, and cost — to the Event schema. The changes are well-documented and structurally sound; the only suggestion is adding minimum: 0 to the numeric fields to prevent semantically invalid negative values from being accepted.

Confidence Score: 5/5

Safe to merge; the only finding is a P2 suggestion to add minimum: 0 constraints on numeric fields.

All changes are additive (new fields and a new event type), backward-compatible, and well-documented. The single finding is a style/best-practice suggestion that doesn't block correctness or break existing consumers.

No files require special attention beyond the optional minimum: 0 suggestion in contract/openapi.yaml.

Important Files Changed

Filename	Overview
contract/openapi.yaml	Adds $sessionend event type with clarifying docs, and seven new generation-metadata fields (model, provider, input_tokens, output_tokens, total_tokens, duration_ms, ttft_ms, cost) to the Event schema; numeric fields are missing minimum: 0 constraints.

Entity Relationship Diagram

%%{init: {'theme': 'neutral'}}%%
erDiagram
    Event {
        string id PK
        string session_id
        string type
        string project_id
        string prompt_id
        string prompt_version
        string generation_id
        string user_id
        string model "NEW"
        string provider "NEW"
        integer input_tokens "NEW"
        integer output_tokens "NEW"
        integer total_tokens "NEW"
        integer duration_ms "NEW"
        integer ttft_ms "NEW"
        number cost "NEW"
        object metadata
        string timestamp
    }

    IngestRequest {
        array events
    }

    IngestResponse {
        integer accepted
    }

    IngestRequest ||--o{ Event : "contains (1-1000)"

Loading

Prompt To Fix All With AI

This is a comment left during a code review.
Path: contract/openapi.yaml
Line: 144-162

Comment:
**Missing `minimum: 0` on numeric fields**

All seven new numeric properties (`input_tokens`, `output_tokens`, `total_tokens`, `duration_ms`, `ttft_ms`, `cost`) accept negative values as written. Negative token counts, latencies, or costs are semantically invalid and would silently poison any aggregations or dashboards built on these fields.

Adding `minimum: 0` to each property enforces the invariant at the schema level and lets SDK codegen produce typed helpers with correct bounds.

```suggestion
        input_tokens:
          type: integer
          minimum: 0
          description: Number of input tokens consumed.
        output_tokens:
          type: integer
          minimum: 0
          description: Number of output tokens produced.
        total_tokens:
          type: integer
          minimum: 0
          description: Total tokens (input + output).
        duration_ms:
          type: integer
          minimum: 0
          description: End-to-end generation latency in milliseconds.
        ttft_ms:
          type: integer
          minimum: 0
          description: Time to first token in milliseconds.
        cost:
          type: number
          format: double
          minimum: 0
          description: Generation cost in USD.
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (1): Last reviewed commit: "chore: sync OpenAPI contract from monore..." | Re-trigger Greptile}

[greptile-apps]

Missing minimum: 0 on numeric fields

All seven new numeric properties (input_tokens, output_tokens, total_tokens, duration_ms, ttft_ms, cost) accept negative values as written. Negative token counts, latencies, or costs are semantically invalid and would silently poison any aggregations or dashboards built on these fields.

Adding minimum: 0 to each property enforces the invariant at the schema level and lets SDK codegen produce typed helpers with correct bounds.

Suggested change

	input_tokens:
	type: integer
	description: Number of input tokens consumed.
	output_tokens:
	type: integer
	description: Number of output tokens produced.
	total_tokens:
	type: integer
	description: Total tokens (input + output).
	duration_ms:
	type: integer
	description: End-to-end generation latency in milliseconds.
	ttft_ms:
	type: integer
	description: Time to first token in milliseconds.
	cost:
	type: number
	format: double
	description: Generation cost in USD.
	input_tokens:
	type: integer
	minimum: 0
	description: Number of input tokens consumed.
	output_tokens:
	type: integer
	minimum: 0
	description: Number of output tokens produced.
	total_tokens:
	type: integer
	minimum: 0
	description: Total tokens (input + output).
	duration_ms:
	type: integer
	minimum: 0
	description: End-to-end generation latency in milliseconds.
	ttft_ms:
	type: integer
	minimum: 0
	description: Time to first token in milliseconds.
	cost:
	type: number
	format: double
	minimum: 0
	description: Generation cost in USD.

Prompt To Fix With AI

This is a comment left during a code review.
Path: contract/openapi.yaml
Line: 144-162

Comment:
**Missing `minimum: 0` on numeric fields**

All seven new numeric properties (`input_tokens`, `output_tokens`, `total_tokens`, `duration_ms`, `ttft_ms`, `cost`) accept negative values as written. Negative token counts, latencies, or costs are semantically invalid and would silently poison any aggregations or dashboards built on these fields.

Adding `minimum: 0` to each property enforces the invariant at the schema level and lets SDK codegen produce typed helpers with correct bounds.

```suggestion
        input_tokens:
          type: integer
          minimum: 0
          description: Number of input tokens consumed.
        output_tokens:
          type: integer
          minimum: 0
          description: Number of output tokens produced.
        total_tokens:
          type: integer
          minimum: 0
          description: Total tokens (input + output).
        duration_ms:
          type: integer
          minimum: 0
          description: End-to-end generation latency in milliseconds.
        ttft_ms:
          type: integer
          minimum: 0
          description: Time to first token in milliseconds.
        cost:
          type: number
          format: double
          minimum: 0
          description: Generation cost in USD.
```

How can I resolve this? If you propose a fix, please make it concise.