@@ -74,7 +74,7 @@ export const resolve = Effect.fn("SessionTools.resolve")(function* (input: {
             metadata: val.metadata,
             status: "running",
             input: args,
-            time: { start: Date.now() },
+            time: match.state.status === "running" ? match.state.time : { start: Date.now() },
           },
         }
       }),
 
@@ -0,0 +1,163 @@
+import { expect } from "bun:test"
+import { ModelV2 } from "@opencode-ai/core/model"
+import { ProviderV2 } from "@opencode-ai/core/provider"
+import { SessionV1 } from "@opencode-ai/core/v1/session"
+import { Agent } from "@/agent/agent"
+import { MCP } from "@/mcp"
+import { Permission } from "@/permission"
+import { Provider } from "@/provider/provider"
+import { Session } from "@/session/session"
+import { MessageID, PartID, SessionID } from "@/session/schema"
+import { SessionProcessor } from "@/session/processor"
+import { SessionTools } from "@/session/tools"
+import { Tool } from "@/tool/tool"
+import { ToolRegistry } from "@/tool/registry"
+import { Truncate } from "@/tool/truncate"
+import { Plugin } from "@/plugin"
+import { Effect, Layer, Schema } from "effect"
+import { testEffect } from "../lib/effect"
+
+const callID = "call-test"
+const sessionID = SessionID.make("ses_test")
+const messageID = MessageID.ascending()
+const partID = PartID.ascending()
+
+const agent: Agent.Info = {
+  name: "build",
+  mode: "primary",
+  options: {},
+  permission: [{ permission: "*", pattern: "*", action: "allow" }],
+}
+
+const model = {
+  providerID: ProviderV2.ID.make("test"),
+  api: { id: "test-model" },
+} as Provider.Model
+
+function fakeMcp() {
+  return MCP.Service.of({
+    tools: () => Effect.succeed({}),
+  } as Partial<MCP.Interface> as MCP.Interface)
+}
+
+const fakePlugin = Plugin.Service.of({
+  init: () => Effect.void,
+  list: () => Effect.succeed([]),
+  trigger: (_name, _input, output) => Effect.succeed(output),
+} satisfies Plugin.Interface)
+
+const fakePermission = Permission.Service.of({
+  ask: () => Effect.void,
+  reply: () => Effect.void,
+  list: () => Effect.succeed([]),
+} satisfies Permission.Interface)
+
+const fakeTruncate = Truncate.Service.of({
+  cleanup: () => Effect.void,
+  write: () => Effect.succeed("output.txt"),
+  output: (text: string) => Effect.succeed({ content: text, truncated: false }),
+  limits: () => Effect.succeed({ maxLines: 2000, maxBytes: 50 * 1024 }),
+} satisfies Truncate.Interface)
+
+const layer = Layer.mergeAll(
+  Layer.succeed(Plugin.Service, fakePlugin),
+  Layer.succeed(Permission.Service, fakePermission),
+  Layer.succeed(MCP.Service, fakeMcp()),
+  Layer.succeed(Truncate.Service, fakeTruncate),
+  Layer.succeed(
+    ToolRegistry.Service,
+    ToolRegistry.Service.of({
+      ids: () => Effect.succeed(["timing"]),
+      all: () => Effect.succeed([]),
+      named: () => Effect.die("unused"),
+      tools: () =>
+        Effect.succeed([
+          {
+            id: "timing",
+            description: "updates metadata more than once",
+            parameters: Schema.Struct({}),
+            jsonSchema: { type: "object", properties: {} },
+            execute: (_args, ctx) =>
+              Effect.gen(function* () {
+                yield* ctx.metadata({ metadata: { output: "first" } })
+                yield* ctx.metadata({ metadata: { output: "second" } })
+                return { title: "timing", metadata: {}, output: "done" }
+              }),
+          } satisfies Tool.Def,
+        ]),
+    }),
+  ),
+)
+
+const it = testEffect(layer)
+
+it.effect("preserves running tool start time across metadata updates", () =>
+  Effect.gen(function* () {
+    const state: SessionV1.ToolPart = {
+      id: partID,
+      sessionID,
+      messageID,
+      type: "tool",
+      tool: "timing",
+      callID,
+      state: {
+        status: "running",
+        input: {},
+        time: { start: 100 },
+      },
+    }
+    const updates: number[] = []
+    const processor = {
+      message: {
+        id: messageID,
+        sessionID,
+        role: "assistant",
+        parentID: MessageID.ascending(),
+        agent: "build",
+        mode: "build",
+        path: { cwd: "/tmp", root: "/tmp" },
+        cost: 0,
+        tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
+        modelID: ModelV2.ID.make("test-model"),
+        providerID: ProviderV2.ID.make("test"),
+        time: { created: 1 },
+      } satisfies SessionV1.Assistant,
+      updateToolCall: (_toolCallID, update) =>
+        Effect.sync(() => {
+          const next = update(state)
+          state.state = next.state
+          if (state.state.status === "running") updates.push(state.state.time.start)
+          return state
+        }),
+      completeToolCall: () => Effect.void,
+    } satisfies Pick<SessionProcessor.Handle, "message" | "updateToolCall" | "completeToolCall">
+
+    const tools = yield* SessionTools.resolve({
+      agent,
+      model,
+      session: { id: sessionID, permission: [] } as Session.Info,
+      processor,
+      bypassAgentCheck: false,
+      messages: [],
+      promptOps: {} as never,
+    })
+    const execute = tools.timing.execute
+    if (!execute) throw new Error("timing tool is missing execute")
+
+    yield* Effect.promise(() =>
+      execute(
+        {},
+        {
+          toolCallId: callID,
+          abortSignal: new AbortController().signal,
+        },
+      ),
+    )
+
+    expect(updates).toEqual([100, 100])
+    expect(state.state.status).toBe("running")
+    if (state.state.status === "running") {
+      expect(state.state.time.start).toBe(100)
+    }
+  }),
+)
Original file line number	Diff line number	Diff line change
`@@ -74,7 +74,7 @@ export const resolve = Effect.fn("SessionTools.resolve")(function* (input: {`
`74`	`74`	`metadata: val.metadata,`
`75`	`75`	`status: "running",`
`76`	`76`	`input: args,`
`77`		`- time: { start: Date.now() },`
	`77`	`+ time: match.state.status === "running" ? match.state.time : { start: Date.now() },`
`78`	`78`	`},`
`79`	`79`	`}`
`80`	`80`	`}),`