feat: add model tracking to CSV exports

- Add ModelInfo type for tracking provider/model information
- Extract model from AssistantMessage events via message.updated hook
- Add model field to SessionData and CsvEntryData
- Add setModel method to SessionManager
- Extend CSV header with model column
- Format model as providerID/modelID (e.g., anthropic/claude-opus-4)

This enables per-model token cost calculation in timesheet reports.

BREAKING CHANGE: CSV format now includes 'model' as the 16th column.
Existing CSV files need migration (add model column to header and data rows).

Author: wagnert

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@techdivision/opencode-time-tracking",
-  "version": "0.1.9",
+  "version": "0.2.0",
   "description": "Automatic time tracking plugin for OpenCode - tracks session duration and tool usage to CSV",
   "main": "src/Plugin.ts",
   "types": "src/Plugin.ts",

src/hooks/EventHook.ts

@@ -2,7 +2,7 @@
  * @fileoverview Event hook for session lifecycle and token tracking.
  */
 
-import type { Event } from "@opencode-ai/sdk"
+import type { AssistantMessage, Event, Message } from "@opencode-ai/sdk"
 
 import type { CsvWriter } from "../services/CsvWriter"
 import type { SessionManager } from "../services/SessionManager"
@@ -12,6 +12,13 @@ import type { OpencodeClient } from "../types/OpencodeClient"
 
 import { DescriptionGenerator } from "../utils/DescriptionGenerator"
 
+/**
+ * Properties for message.updated events.
+ */
+interface MessageUpdatedProperties {
+  info: Message
+}
+
 /**
  * Extracts the summary title from the last user message.
  *
@@ -60,10 +67,11 @@ async function extractSummaryTitle(
  * @returns The event hook function
  *
  * @remarks
- * Handles two types of events:
+ * Handles three types of events:
  *
- * 1. **message.part.updated** - Tracks token usage from step-finish parts
- * 2. **session.idle** - Finalizes and exports the session
+ * 1. **message.updated** - Tracks model from assistant messages
+ * 2. **message.part.updated** - Tracks token usage from step-finish parts
+ * 3. **session.idle** - Finalizes and exports the session
  *
  * @example
  * ```typescript
@@ -78,6 +86,25 @@ export function createEventHook(
   client: OpencodeClient
 ) {
   return async ({ event }: { event: Event }): Promise<void> => {
+    // Track model from assistant messages
+    if (event.type === "message.updated") {
+      const props = event.properties as MessageUpdatedProperties
+      const message = props.info
+
+      if (message.role === "assistant") {
+        const assistantMsg = message as AssistantMessage
+
+        if (assistantMsg.modelID && assistantMsg.providerID) {
+          sessionManager.setModel(assistantMsg.sessionID, {
+            modelID: assistantMsg.modelID,
+            providerID: assistantMsg.providerID,
+          })
+        }
+      }
+
+      return
+    }
+
     // Track token usage from step-finish events
     if (event.type === "message.part.updated") {
       const props = event.properties as MessagePartUpdatedProperties
@@ -129,6 +156,11 @@ export function createEventHook(
         session.tokenUsage.output +
         session.tokenUsage.reasoning
 
+      // Format model as providerID/modelID
+      const modelString = session.model
+        ? `${session.model.providerID}/${session.model.modelID}`
+        : null
+
       try {
         await csvWriter.write({
           ticket: session.ticket,
@@ -138,6 +170,7 @@ export function createEventHook(
           description,
           notes: `Auto-tracked: ${toolSummary}`,
           tokenUsage: session.tokenUsage,
+          model: modelString,
         })
 
         const minutes = Math.round(durationSeconds / 60)

src/services/CsvWriter.ts

@@ -18,7 +18,7 @@ import "../types/Bun"
  * Compatible with Jira/Tempo time tracking import.
  */
 const CSV_HEADER =
-  "id,start_date,end_date,user,ticket_name,issue_key,account_key,start_time,end_time,duration_seconds,tokens_used,tokens_remaining,story_points,description,notes"
+  "id,start_date,end_date,user,ticket_name,issue_key,account_key,start_time,end_time,duration_seconds,tokens_used,tokens_remaining,story_points,description,notes,model"
 
 /**
  * Writes time tracking entries to a CSV file.
@@ -122,6 +122,7 @@ export class CsvWriter {
       "",
       CsvFormatter.escape(data.description),
       CsvFormatter.escape(data.notes),
+      data.model ?? "",
     ]
 
     const csvLine = fields.map((f) => `"${f}"`).join(",")

src/services/SessionManager.ts

@@ -3,6 +3,7 @@
  */
 
 import type { ActivityData } from "../types/ActivityData"
+import type { ModelInfo } from "../types/ModelInfo"
 import type { SessionData } from "../types/SessionData"
 import type { TokenUsage } from "../types/TokenUsage"
 
@@ -61,6 +62,7 @@ export class SessionManager {
         cacheRead: 0,
         cacheWrite: 0,
       },
+      model: null,
     }
 
     this.sessions.set(sessionID, session)
@@ -126,4 +128,22 @@ export class SessionManager {
       session.ticket = ticket
     }
   }
+
+  /**
+   * Sets the model for a session.
+   *
+   * @param sessionID - The OpenCode session identifier
+   * @param model - The model information
+   *
+   * @remarks
+   * Only sets the model if it hasn't been set yet.
+   * The first model detected in a session is used.
+   */
+  setModel(sessionID: string, model: ModelInfo): void {
+    const session = this.sessions.get(sessionID)
+
+    if (session && !session.model) {
+      session.model = model
+    }
+  }
 }

src/types/CsvEntryData.ts

@@ -28,4 +28,12 @@ export interface CsvEntryData {
 
   /** Token consumption statistics */
   tokenUsage: TokenUsage
+
+  /**
+   * Model identifier in format `providerID/modelID`.
+   *
+   * @remarks
+   * Examples: `anthropic/claude-opus-4`, `openai/gpt-5`
+   */
+  model: string | null
 }

src/types/ModelInfo.ts

@@ -0,0 +1,28 @@
+/**
+ * @fileoverview Model information type for tracking which LLM was used.
+ */
+
+/**
+ * Information about the model used in a session.
+ *
+ * @remarks
+ * Extracted from AssistantMessage events in the OpenCode SDK.
+ * Used to calculate token costs per model.
+ */
+export interface ModelInfo {
+  /**
+   * Model identifier (e.g., "claude-opus-4", "gpt-5").
+   *
+   * @remarks
+   * This is the model name as reported by the provider.
+   */
+  modelID: string
+
+  /**
+   * Provider identifier (e.g., "anthropic", "openai").
+   *
+   * @remarks
+   * Combined with modelID to form the full model reference: `providerID/modelID`
+   */
+  providerID: string
+}

src/types/SessionData.ts

@@ -3,6 +3,7 @@
  */
 
 import type { ActivityData } from "./ActivityData"
+import type { ModelInfo } from "./ModelInfo"
 import type { TokenUsage } from "./TokenUsage"
 
 /**
@@ -20,4 +21,7 @@ export interface SessionData {
 
   /** Cumulative token usage for the session */
   tokenUsage: TokenUsage
+
+  /** Model used in this session, or `null` if not detected */
+  model: ModelInfo | null
 }