refactor(kernel): rename tabId → conversationId across contracts + consumers (218 tests)

Step 4 of the post-MVP backlog: resolve the last vocab drift. The canonical
term for a thread of turns is `conversationId` (GLOSSARY), but `AgentEvent`
variants and `RunTurnInput` still used the legacy `tabId` from the old frontend
"tab" concept, with session-orchestrator bridging `conversationId → tabId`.

Atomic, type-driven rename across the full 10-file consumer set:
- contracts/events.ts: all 11 AgentEvent variants tabId → conversationId
- contracts/runtime.ts: RunTurnInput.tabId → conversationId
- runtime/{events,run-turn,dispatch}.ts: factory params, ctx field, locals
- session-orchestrator: drop the redundant `tabId: conversationId` bridge line
- transport-http: emit wiring; external /chat field + X-Conversation-Id header
  unchanged (already canonical) — only the emitted NDJSON event field flips
- tests (run-turn, app, logic): inputs + assertions now use conversationId

Pure rename, zero behavior change: typecheck clean, 218 tests pass (unchanged
count), biome clean, `grep tabId packages/` → zero matches. Verified live:
multi-turn curl emits conversationId-keyed NDJSON and threads history correctly.
GLOSSARY drift note removed. Closes the post-MVP backlog (Steps 1–4).

4 files changed, 77 insertions, 49 deletions

diff --git a/packages/kernel/src/runtime/dispatch.ts b/packages/kernel/src/runtime/dispatch.ts
index c6c5f8e..626b333 100644
--- a/packages/kernel/src/runtime/dispatch.ts
+++ b/packages/kernel/src/runtime/dispatch.ts
@@ -13,7 +13,7 @@ export async function executeToolCall(
 	tool: ToolContract | undefined,
 	signal: AbortSignal,
 	emit: EventEmitter,
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 ): Promise<ToolResult> {
 	if (tool === undefined) {
@@ -26,7 +26,7 @@ export async function executeToolCall(
 		toolCallId: call.id,
 		signal,
 		onOutput: (data, stream) => {
-			emit(toolOutputEvent(tabId, turnId, call.id, data, stream));
+			emit(toolOutputEvent(conversationId, turnId, call.id, data, stream));
 		},
 	};
 	try {
@@ -48,7 +48,7 @@ export function createStepDispatcher(
 	policy: ToolDispatchPolicy,
 	signal: AbortSignal,
 	emit: EventEmitter,
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 ): StepDispatcher {
 	let activeCount = 0;
@@ -78,7 +78,14 @@ export function createStepDispatcher(
 	}
 
 	async function runAndResolve(entry: QueueEntry): Promise<void> {
-		const result = await executeToolCall(entry.call, entry.tool, signal, emit, tabId, turnId);
+		const result = await executeToolCall(
+			entry.call,
+			entry.tool,
+			signal,
+			emit,
+			conversationId,
+			turnId,
+		);
 		activeCount--;
 		if (entry.tool?.concurrencySafe === false) unsafeRunning = false;
 		entry.resolve(result);
diff --git a/packages/kernel/src/runtime/events.ts b/packages/kernel/src/runtime/events.ts
index 62218be..2a92008 100644
--- a/packages/kernel/src/runtime/events.ts
+++ b/packages/kernel/src/runtime/events.ts
@@ -1,57 +1,61 @@
 import type { AgentEvent } from "../contracts/events.js";
 import type { Usage } from "../contracts/provider.js";
 
-export function textDeltaEvent(tabId: string, turnId: string, delta: string): AgentEvent {
-	return { type: "text-delta", tabId, turnId, delta };
+export function textDeltaEvent(conversationId: string, turnId: string, delta: string): AgentEvent {
+	return { type: "text-delta", conversationId, turnId, delta };
 }
 
-export function reasoningDeltaEvent(tabId: string, turnId: string, delta: string): AgentEvent {
-	return { type: "reasoning-delta", tabId, turnId, delta };
+export function reasoningDeltaEvent(
+	conversationId: string,
+	turnId: string,
+	delta: string,
+): AgentEvent {
+	return { type: "reasoning-delta", conversationId, turnId, delta };
 }
 
 export function toolCallEvent(
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 	toolCallId: string,
 	toolName: string,
 	input: unknown,
 ): AgentEvent {
-	return { type: "tool-call", tabId, turnId, toolCallId, toolName, input };
+	return { type: "tool-call", conversationId, turnId, toolCallId, toolName, input };
 }
 
 export function toolResultEvent(
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 	toolCallId: string,
 	toolName: string,
 	content: string,
 	isError: boolean,
 ): AgentEvent {
-	return { type: "tool-result", tabId, turnId, toolCallId, toolName, content, isError };
+	return { type: "tool-result", conversationId, turnId, toolCallId, toolName, content, isError };
 }
 
 export function toolOutputEvent(
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 	toolCallId: string,
 	data: string,
 	stream: "stdout" | "stderr",
 ): AgentEvent {
-	return { type: "tool-output", tabId, turnId, toolCallId, data, stream };
+	return { type: "tool-output", conversationId, turnId, toolCallId, data, stream };
 }
 
-export function usageEvent(tabId: string, turnId: string, usage: Usage): AgentEvent {
-	return { type: "usage", tabId, turnId, usage };
+export function usageEvent(conversationId: string, turnId: string, usage: Usage): AgentEvent {
+	return { type: "usage", conversationId, turnId, usage };
 }
 
 export function errorEvent(
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 	message: string,
 	code?: string,
 ): AgentEvent {
 	if (code !== undefined) {
-		return { type: "error", tabId, turnId, message, code };
+		return { type: "error", conversationId, turnId, message, code };
 	}
-	return { type: "error", tabId, turnId, message };
+	return { type: "error", conversationId, turnId, message };
 }
diff --git a/packages/kernel/src/runtime/run-turn.test.ts b/packages/kernel/src/runtime/run-turn.test.ts
index 1ea6406..696a385 100644
--- a/packages/kernel/src/runtime/run-turn.test.ts
+++ b/packages/kernel/src/runtime/run-turn.test.ts
@@ -52,7 +52,7 @@ const userMessage: ChatMessage = {
 };
 
 describe("runTurn", () => {
-	it("emits events with the tabId and turnId from input", async () => {
+	it("emits events with the conversationId and turnId from input", async () => {
 		const provider = createFakeProvider([
 			[
 				{ type: "text-delta", delta: "hi" },
@@ -68,14 +68,14 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "conv-42",
+			conversationId: "conv-42",
 			turnId: "turn-99",
 			emit,
 		});
 
 		expect(events.length).toBeGreaterThan(0);
 		for (const event of events) {
-			expect(event.tabId).toBe("conv-42");
+			expect(event.conversationId).toBe("conv-42");
 			if (event.type !== "status") {
 				expect(event.turnId).toBe("turn-99");
 			}
@@ -100,7 +100,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit,
 		});
@@ -143,7 +143,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit,
 		});
@@ -201,7 +201,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -250,7 +250,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [toolA, toolB],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -294,7 +294,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [toolA, toolB],
 			dispatch: { maxConcurrent: 2, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -352,7 +352,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [toolA, toolB, toolC],
 			dispatch: { maxConcurrent: 0, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -413,7 +413,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: true },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -464,7 +464,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -513,7 +513,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit,
 			signal: ac.signal,
@@ -545,7 +545,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 			signal: ac.signal,
@@ -583,7 +583,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit,
 		});
@@ -657,7 +657,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [unsafeTool, safeTool],
 			dispatch: { maxConcurrent: 5, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -691,7 +691,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit,
 		});
@@ -724,7 +724,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit,
 		});
@@ -759,7 +759,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit: () => {},
 		});
@@ -797,7 +797,7 @@ describe("runTurn", () => {
 			messages: [userMessage],
 			tools: [tool],
 			dispatch: { maxConcurrent: 1, eager: false },
-			tabId: "tab-test",
+			conversationId: "tab-test",
 			turnId: "turn-test",
 			emit,
 		});
diff --git a/packages/kernel/src/runtime/run-turn.ts b/packages/kernel/src/runtime/run-turn.ts
index 919491a..9421d86 100644
--- a/packages/kernel/src/runtime/run-turn.ts
+++ b/packages/kernel/src/runtime/run-turn.ts
@@ -74,7 +74,7 @@ interface StepContext {
 	readonly dispatch: RunTurnInput["dispatch"];
 	readonly emit: EventEmitter;
 	readonly signal: AbortSignal;
-	readonly tabId: string;
+	readonly conversationId: string;
 	readonly turnId: string;
 }
 
@@ -96,11 +96,11 @@ function processEvent(
 	switch (event.type) {
 		case "text-delta":
 			appendTextDelta(chunks, event.delta);
-			ctx.emit(textDeltaEvent(ctx.tabId, ctx.turnId, event.delta));
+			ctx.emit(textDeltaEvent(ctx.conversationId, ctx.turnId, event.delta));
 			break;
 		case "reasoning-delta":
 			appendThinkingDelta(chunks, event.delta);
-			ctx.emit(reasoningDeltaEvent(ctx.tabId, ctx.turnId, event.delta));
+			ctx.emit(reasoningDeltaEvent(ctx.conversationId, ctx.turnId, event.delta));
 			break;
 		case "tool-call": {
 			const call: ToolCall = {
@@ -115,14 +115,22 @@ function processEvent(
 				toolName: event.toolName,
 				input: event.input,
 			});
-			ctx.emit(toolCallEvent(ctx.tabId, ctx.turnId, event.toolCallId, event.toolName, event.input));
+			ctx.emit(
+				toolCallEvent(
+					ctx.conversationId,
+					ctx.turnId,
+					event.toolCallId,
+					event.toolName,
+					event.input,
+				),
+			);
 			if (ctx.dispatch.eager) {
 				dispatcher.submit(call);
 			}
 			break;
 		}
 		case "usage":
-			ctx.emit(usageEvent(ctx.tabId, ctx.turnId, event.usage));
+			ctx.emit(usageEvent(ctx.conversationId, ctx.turnId, event.usage));
 			break;
 		case "finish":
 			break;
@@ -132,7 +140,7 @@ function processEvent(
 			} else {
 				chunks.push({ type: "error", message: event.message });
 			}
-			ctx.emit(errorEvent(ctx.tabId, ctx.turnId, event.message, event.code));
+			ctx.emit(errorEvent(ctx.conversationId, ctx.turnId, event.message, event.code));
 			break;
 	}
 }
@@ -148,7 +156,7 @@ async function executeStep(ctx: StepContext): Promise<StepResult> {
 		ctx.dispatch,
 		ctx.signal,
 		ctx.emit,
-		ctx.tabId,
+		ctx.conversationId,
 		ctx.turnId,
 	);
 
@@ -167,7 +175,7 @@ async function executeStep(ctx: StepContext): Promise<StepResult> {
 	} catch (err) {
 		const message = err instanceof Error ? err.message : String(err);
 		chunks.push({ type: "error", message });
-		ctx.emit(errorEvent(ctx.tabId, ctx.turnId, message));
+		ctx.emit(errorEvent(ctx.conversationId, ctx.turnId, message));
 		finishReason = "error";
 	}
 
@@ -184,7 +192,16 @@ async function executeStep(ctx: StepContext): Promise<StepResult> {
 		const result = results.get(call.id);
 		if (result !== undefined) {
 			const isError = result.isError ?? false;
-			ctx.emit(toolResultEvent(ctx.tabId, ctx.turnId, call.id, call.name, result.content, isError));
+			ctx.emit(
+				toolResultEvent(
+					ctx.conversationId,
+					ctx.turnId,
+					call.id,
+					call.name,
+					result.content,
+					isError,
+				),
+			);
 			toolMessages.push({
 				role: "tool",
 				chunks: [
@@ -217,7 +234,7 @@ export async function runTurn(input: RunTurnInput): Promise<RunTurnResult> {
 		toolMap.set(tool.name, tool);
 	}
 
-	const tabId = input.tabId;
+	const conversationId = input.conversationId;
 	const turnId = input.turnId;
 	const signal = input.signal ?? new AbortController().signal;
 
@@ -235,7 +252,7 @@ export async function runTurn(input: RunTurnInput): Promise<RunTurnResult> {
 			dispatch: input.dispatch,
 			emit: input.emit,
 			signal,
-			tabId,
+			conversationId,
 			turnId,
 		});