diff --git a/apps/x/packages/core/docs/turn-runtime-design.md b/apps/x/packages/core/docs/turn-runtime-design.md
index 9a0ca542..88290b7e 100644
--- a/apps/x/packages/core/docs/turn-runtime-design.md
+++ b/apps/x/packages/core/docs/turn-runtime-design.md
@@ -479,11 +479,12 @@ Every AI SDK `streamText` invocation performs exactly one model step. Tool
 execution is controlled manually by the turn loop.
 
 ```ts
-type ModelRequestMessageRef =
-  | { kind: "context" }                          // the inline context block
-  | { kind: "input" }                            // the turn's user message
-  | { kind: "assistant"; modelCallIndex: number } // → model_call_completed
-  | { kind: "toolResult"; toolCallId: string };   // → tool_result
+// Compact string refs, so raw JSONL reads naturally:
+//   "context"                  the inline context block
+//   "input"                    the turn's user message
+//   "assistant:<index>"        → that model_call_completed's message
+//   "toolResult:<toolCallId>"  → that tool_result
+type ModelRequestMessageRef = string;
 
 interface ModelRequest {
   contextRef?: { previousTurnId: string };  // call 0 only (cross-turn prefix)
@@ -503,10 +504,11 @@ agent model call in the turn.
 
 `request` is a list of references into the turn's own events: every
 referenced byte exists exactly once in the file. A request records only what
-is new since the previous model call — call 0 is `[{context}?, {input}]`
+is new since the previous model call — call 0 is `["context"?, "input"]`
 (context only when inline and nonempty; cross-turn prefixes ride
-`contextRef`); call N is `[{assistant: N-1}, …that batch's toolResults in
-source order]`; a re-issued call after an interruption is `[]`. The system
+`contextRef`); call N is `["assistant:N-1", …that batch's
+"toolResult:<id>" refs in source order]`; a re-issued call after an
+interruption is `[]`. The system
 prompt and tool set are not repeated: they are byte-identical to
 `turn_created.agent.resolved` by construction.
 
diff --git a/apps/x/packages/core/package.json b/apps/x/packages/core/package.json
index 08c2644d..8ba46048 100644
--- a/apps/x/packages/core/package.json
+++ b/apps/x/packages/core/package.json
@@ -8,7 +8,8 @@
     "build": "rm -rf dist && tsc -p tsconfig.build.json",
     "dev": "tsc -w -p tsconfig.build.json",
     "test": "vitest run",
-    "test:watch": "vitest"
+    "test:watch": "vitest",
+    "inspect-turn": "node dist/turns/inspect-cli.js"
   },
   "dependencies": {
     "@agentclientprotocol/claude-agent-acp": "^0.39.0",
diff --git a/apps/x/packages/core/src/sessions/sessions.test.ts b/apps/x/packages/core/src/sessions/sessions.test.ts
index fccdb948..6ff498d8 100644
--- a/apps/x/packages/core/src/sessions/sessions.test.ts
+++ b/apps/x/packages/core/src/sessions/sessions.test.ts
@@ -86,7 +86,7 @@ function turnLog(
         turnId,
         ts: TS,
         modelCallIndex: 0,
-        request: { messages: [{ kind: 'input' as const }], parameters: {} },
+        request: { messages: ['input'], parameters: {} },
     };
     switch (status) {
         case "idle":
diff --git a/apps/x/packages/core/src/turns/context-resolver.test.ts b/apps/x/packages/core/src/turns/context-resolver.test.ts
index 78cb34bd..6ccfe671 100644
--- a/apps/x/packages/core/src/turns/context-resolver.test.ts
+++ b/apps/x/packages/core/src/turns/context-resolver.test.ts
@@ -60,8 +60,8 @@ function completedTurnLog(
                 ...(Array.isArray(context) ? {} : { contextRef: context }),
                 messages:
                     Array.isArray(context) && context.length > 0
-                        ? [{ kind: "context" as const }, { kind: "input" as const }]
-                        : [{ kind: "input" as const }],
+                        ? ["context", "input"]
+                        : ["input"],
                 parameters: {},
             },
         },
@@ -138,7 +138,7 @@ function limitFailedTurnLog(turnId: string): TEvent[] {
             ts,
             modelCallIndex: 0,
             request: {
-                messages: [{ kind: "input" as const }],
+                messages: ["input"],
                 parameters: {},
             },
         },
diff --git a/apps/x/packages/core/src/turns/fs-repo.test.ts b/apps/x/packages/core/src/turns/fs-repo.test.ts
index b4afe769..583ea330 100644
--- a/apps/x/packages/core/src/turns/fs-repo.test.ts
+++ b/apps/x/packages/core/src/turns/fs-repo.test.ts
@@ -41,7 +41,7 @@ function requested(turnId = TURN_ID): z.infer<typeof TurnEvent> {
         ts: "2026-07-02T10:00:01Z",
         modelCallIndex: 0,
         request: {
-            messages: [{ kind: "input" }],
+            messages: ["input"],
             parameters: {},
         },
     };
diff --git a/apps/x/packages/core/src/turns/inspect-cli.ts b/apps/x/packages/core/src/turns/inspect-cli.ts
new file mode 100644
index 00000000..3329d99d
--- /dev/null
+++ b/apps/x/packages/core/src/turns/inspect-cli.ts
@@ -0,0 +1,105 @@
+// Turn inspector: prints, per model call, the EXACT provider payload the
+// loop sent — rebuilt from the durable file by the same composer the loop
+// transmits through (compose-model-request.ts). This is where the woven
+// wire-form messages (user-message context, attachments, tool-result
+// envelopes) are visible; the file itself stores only structural facts and
+// references.
+//
+// Usage:
+//   npm run inspect-turn -- <turnId | path/to/turn.jsonl> [modelCallIndex] [--full]
+//
+// --full prints the entire system prompt and untruncated message contents.
+import fs from "node:fs";
+import path from "node:path";
+import {
+    reduceTurn,
+    type JsonValue,
+    type TurnEvent,
+} from "@x/shared/dist/turns.js";
+import type { z } from "zod";
+import { convertFromMessages } from "../agents/runtime.js";
+import { WorkDir } from "../config/config.js";
+import { composeModelRequest } from "./compose-model-request.js";
+import { TurnRepoContextResolver } from "./context-resolver.js";
+import { FSTurnRepo } from "./fs-repo.js";
+
+function usage(): never {
+    console.error(
+        "usage: inspect-turn <turnId | path/to/turn.jsonl> [modelCallIndex] [--full]",
+    );
+    process.exit(1);
+}
+
+function clip(text: string, full: boolean, limit = 400): string {
+    if (full || text.length <= limit) return text;
+    return `${text.slice(0, limit)}… [${text.length} chars total; pass --full]`;
+}
+
+async function main(): Promise<void> {
+    const args = process.argv.slice(2).filter((a) => a !== "--full");
+    const full = process.argv.includes("--full");
+    const target = args[0];
+    if (!target) usage();
+    const onlyIndex = args[1] !== undefined ? Number(args[1]) : undefined;
+
+    const turnsRootDir = path.join(WorkDir, "storage", "turns");
+    const repo = new FSTurnRepo({ turnsRootDir });
+    const turnId = target.endsWith(".jsonl")
+        ? path.basename(target, ".jsonl")
+        : target;
+
+    let events: Array<z.infer<typeof TurnEvent>>;
+    if (target.endsWith(".jsonl") && fs.existsSync(target)) {
+        // Direct path: parse in place (still strict via the reducer below).
+        events = fs
+            .readFileSync(target, "utf8")
+            .trim()
+            .split("\n")
+            .map((line) => JSON.parse(line) as z.infer<typeof TurnEvent>);
+    } else {
+        events = await repo.read(turnId);
+    }
+    const state = reduceTurn(events);
+    const resolver = new TurnRepoContextResolver({ turnRepo: repo });
+    const prefix = await resolver.resolve(state.definition.context);
+    const encode = (messages: Parameters<typeof convertFromMessages>[0]) =>
+        convertFromMessages(messages) as unknown as JsonValue[];
+
+    console.log(`turn ${turnId}`);
+    console.log(
+        `agent ${state.definition.agent.resolved.agentId}  model ${state.definition.agent.resolved.model.provider}/${state.definition.agent.resolved.model.model}  calls ${state.modelCalls.length}`,
+    );
+
+    for (const call of state.modelCalls) {
+        if (onlyIndex !== undefined && call.index !== onlyIndex) continue;
+        const composed = composeModelRequest(state, call.index, prefix, encode);
+        console.log(`\n━━ model call ${call.index} ━━ (as sent to the provider)`);
+        console.log(`system (${composed.systemPrompt.length} chars): ${clip(composed.systemPrompt, full)}`);
+        console.log(
+            `tools (${composed.tools.length}): ${composed.tools.map((t) => t.name).join(", ")}`,
+        );
+        console.log(`messages (${composed.messages.length}):`);
+        for (const message of composed.messages) {
+            const m = message as { role?: string; content?: unknown };
+            const content =
+                typeof m.content === "string"
+                    ? m.content
+                    : JSON.stringify(m.content);
+            console.log(`  [${m.role}] ${clip(content, full)}`);
+        }
+        if (call.error !== undefined) {
+            console.log(`  → failed: ${call.error}`);
+        } else if (call.response !== undefined) {
+            const response =
+                typeof call.response.content === "string"
+                    ? call.response.content
+                    : JSON.stringify(call.response.content);
+            console.log(`  → response (${call.finishReason}): ${clip(response, full)}`);
+        }
+    }
+}
+
+main().catch((error: unknown) => {
+    console.error(error instanceof Error ? error.message : error);
+    process.exit(1);
+});
diff --git a/apps/x/packages/core/src/turns/runtime.test.ts b/apps/x/packages/core/src/turns/runtime.test.ts
index 3fad9d4b..1d2671ed 100644
--- a/apps/x/packages/core/src/turns/runtime.test.ts
+++ b/apps/x/packages/core/src/turns/runtime.test.ts
@@ -3,7 +3,6 @@ import type { z } from "zod";
 import {
     MODEL_CALL_LIMIT_ERROR_CODE,
     type JsonValue,
-    type ModelRequestMessageRef,
     type ResolvedAgent,
     type ToolDescriptor,
     type TurnEvent,
@@ -422,7 +421,7 @@ describe("plain model response (26.1)", () => {
         const request = log[1];
         expect(request).toMatchObject({
             modelCallIndex: 0,
-            request: { messages: [{ kind: "input" }] },
+            request: { messages: ["input"] },
         });
         // The model received the composed payload: resolved system prompt,
         // snapshot tools, encoded messages.
@@ -525,11 +524,11 @@ describe("mixed sync and async tools (26.2)", () => {
                 ? secondRequest.request.messages
                 : [],
         ).toEqual([
-            { kind: "assistant", modelCallIndex: 0 },
-            { kind: "toolResult", toolCallId: "A" },
-            { kind: "toolResult", toolCallId: "B" },
-            { kind: "toolResult", toolCallId: "C" },
-            { kind: "toolResult", toolCallId: "D" },
+            "assistant:0",
+            "toolResult:A",
+            "toolResult:B",
+            "toolResult:C",
+            "toolResult:D",
         ]);
         // The live model call saw the results in source order.
         expect(
@@ -1166,7 +1165,7 @@ describe("crash recovery (26.7)", () => {
 
     function seedRequested(
         index: number,
-        refs: z.infer<typeof ModelRequestMessageRef>[] = [{ kind: "input" }],
+        refs: string[] = ["input"],
     ): z.infer<typeof TurnEvent> {
         return {
             type: "model_call_requested",
diff --git a/apps/x/packages/core/src/turns/runtime.ts b/apps/x/packages/core/src/turns/runtime.ts
index fd7caaf4..d82e575a 100644
--- a/apps/x/packages/core/src/turns/runtime.ts
+++ b/apps/x/packages/core/src/turns/runtime.ts
@@ -6,7 +6,8 @@ import {
     type JsonValue,
     type ModelCallFailed,
     type ModelRequest,
-    type ModelRequestMessageRef,
+    assistantRef,
+    toolResultRef,
     type ToolCallState,
     type ToolDescriptor,
     type ToolInvocationRequested,
@@ -856,25 +857,22 @@ class TurnAdvance {
         const index = this.state.modelCalls.length;
         const context = this.definition.context;
         const isRef = !Array.isArray(context);
-        let refs: Array<z.infer<typeof ModelRequestMessageRef>>;
+        let refs: string[];
         if (index === 0) {
             refs =
                 !isRef && context.length > 0
-                    ? [{ kind: "context" }, { kind: "input" }]
-                    : [{ kind: "input" }];
+                    ? ["context", "input"]
+                    : ["input"];
         } else {
             const previous = this.state.modelCalls[index - 1];
             refs =
                 previous.response !== undefined
                     ? [
-                          { kind: "assistant", modelCallIndex: previous.index },
+                          assistantRef(previous.index),
                           ...this.state.toolCalls
                               .filter((tc) => tc.modelCallIndex === previous.index)
                               .sort((a, b) => a.order - b.order)
-                              .map((tc) => ({
-                                  kind: "toolResult" as const,
-                                  toolCallId: tc.toolCallId,
-                              })),
+                              .map((tc) => toolResultRef(tc.toolCallId)),
                       ]
                     : []; // re-issue after an interrupted call adds nothing new
         }
diff --git a/apps/x/packages/shared/src/turns.test.ts b/apps/x/packages/shared/src/turns.test.ts
index 4f5f4d11..844d76b2 100644
--- a/apps/x/packages/shared/src/turns.test.ts
+++ b/apps/x/packages/shared/src/turns.test.ts
@@ -346,13 +346,13 @@ function syncToolSequence(): TEvent[] {
     const call0 = assistantCalls(toolCallPart("tc1", "echo"));
     return [
         created(),
-        requested(0, [{ kind: "input" }]),
+        requested(0, ["input"]),
         completed(0, call0),
         permRequired("tc1", "echo"),
         permResolved("tc1", "allow"),
         invocation("tc1"),
         result("tc1", "echo"),
-        requested(1, [{ kind: "assistant", modelCallIndex: 0 }, { kind: "toolResult", toolCallId: "tc1" }]),
+        requested(1, ["assistant:0", "toolResult:tc1"]),
         completed(1, assistantText("done")),
         turnCompletedEv(),
     ];
@@ -393,7 +393,7 @@ describe("plain completion", () => {
     it("reduces a plain model response to a completed turn", () => {
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             stepEvent(0),
             completed(0, assistantText("done")),
             turnCompletedEv(),
@@ -418,7 +418,7 @@ describe("plain completion", () => {
     it("leaves usage fields undefined when never reported", () => {
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, assistantText("a"), { inputTokens: 5 }),
         ]);
         expect(state.usage).toEqual({ inputTokens: 5 });
@@ -434,7 +434,7 @@ describe("tool execution", () => {
         );
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
         ]);
         expect(state.toolCalls).toHaveLength(2);
@@ -457,7 +457,7 @@ describe("tool execution", () => {
     it("leaves identity undefined for tools missing from the agent snapshot", () => {
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, assistantCalls(toolCallPart("x1", "unknown-tool"))),
             result("x1", "unknown-tool", "runtime", "No such tool", true),
         ]);
@@ -480,7 +480,7 @@ describe("tool execution", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         const state = reduceTurn([
             created({ config: { autoPermission: true, humanAvailable: true, maxModelCalls: 20 } }),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             permRequired("tc1", "echo"),
             permClassified("tc1", "allow"),
@@ -497,7 +497,7 @@ describe("tool execution", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             permRequired("tc1", "echo"),
             permClassificationFailed(["tc1"]),
@@ -512,7 +512,7 @@ describe("tool execution", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             invocation("tc1"),
             progress("tc1"),
@@ -526,7 +526,7 @@ describe("tool execution", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             permRequired("tc1", "echo"),
             permResolved("tc1", "deny"),
@@ -541,7 +541,7 @@ describe("context references", () => {
     it("accepts a referenced context with matching contextRef on requests", () => {
         const state = reduceTurn([
             created({ context: { previousTurnId: PREV_TURN_ID } }),
-            requested(0, [{ kind: "input" }], {
+            requested(0, ["input"], {
                 contextRef: { previousTurnId: PREV_TURN_ID },
             }),
             completed(0, assistantText("done")),
@@ -554,7 +554,7 @@ describe("context references", () => {
         expectCorruption(
             [
                 created({ context: { previousTurnId: PREV_TURN_ID } }),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
             ],
             /contextRef inconsistent/,
         );
@@ -564,7 +564,7 @@ describe("context references", () => {
         expectCorruption(
             [
                 created({ context: { previousTurnId: PREV_TURN_ID } }),
-                requested(0, [{ kind: "input" }], {
+                requested(0, ["input"], {
                     contextRef: { previousTurnId: "some-other-turn" },
                 }),
             ],
@@ -576,7 +576,7 @@ describe("context references", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }], {
+                requested(0, ["input"], {
                     contextRef: { previousTurnId: PREV_TURN_ID },
                 }),
             ],
@@ -592,13 +592,13 @@ describe("context references", () => {
         ];
         const state = reduceTurn([
             created({ context }),
-            requested(0, [{ kind: "context" }, { kind: "input" }]),
+            requested(0, ["context", "input"]),
             completed(0, assistantText("done")),
             turnCompletedEv(),
         ]);
         expect(deriveTurnStatus(state)).toBe("completed");
         expectCorruption(
-            [created({ context }), requested(0, [{ kind: "input" }])],
+            [created({ context }), requested(0, ["input"])],
             /references do not match/,
         );
     });
@@ -607,7 +607,7 @@ describe("context references", () => {
         expectCorruption(
             [
                 created({ context: { previousTurnId: PREV_TURN_ID } }),
-                requested(0, [{ kind: "input" }], {
+                requested(0, ["input"], {
                     contextRef: { previousTurnId: PREV_TURN_ID },
                 }),
                 completed(0, assistantCalls(toolCallPart("tc1", "echo"))),
@@ -616,8 +616,8 @@ describe("context references", () => {
                 requested(
                     1,
                     [
-                        { kind: "assistant", modelCallIndex: 0 },
-                        { kind: "toolResult", toolCallId: "tc1" },
+                        "assistant:0",
+                        "toolResult:tc1",
                     ],
                     { contextRef: { previousTurnId: PREV_TURN_ID } },
                 ),
@@ -635,7 +635,7 @@ describe("suspension", () => {
         );
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             permRequired("tc1", "echo"),
             invocation("a1", fetchTool),
@@ -653,7 +653,7 @@ describe("suspension", () => {
         );
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             permRequired("tc1", "echo"),
             invocation("a1", fetchTool),
@@ -673,7 +673,7 @@ describe("suspension", () => {
         );
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             invocation("a1", fetchTool),
             invocation("a2", fetchTool),
@@ -682,9 +682,9 @@ describe("suspension", () => {
             suspendedEv([], [{ id: "a1", tool: fetchTool }]),
             result("a1", "fetch", "async", "first"),
             requested(1, [
-                { kind: "assistant", modelCallIndex: 0 },
-                { kind: "toolResult", toolCallId: "a1" },
-                { kind: "toolResult", toolCallId: "a2" },
+                "assistant:0",
+                "toolResult:a1",
+                "toolResult:a2",
             ]),
             completed(1, assistantText("done")),
             turnCompletedEv(),
@@ -697,7 +697,7 @@ describe("suspension", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permRequired("tc1", "echo"),
                 permResolved("tc1", "allow"),
@@ -717,7 +717,7 @@ describe("suspension", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permRequired("tc1", "echo"),
                 invocation("a1", fetchTool),
@@ -731,7 +731,7 @@ describe("suspension", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 suspendedEv([{ id: "tc1", name: "echo" }], []),
             ],
             /suspension while a model call is unsettled/,
@@ -743,7 +743,7 @@ describe("recovery-shaped histories", () => {
     it("accepts an interrupted model call closed and re-issued (§23 fix)", () => {
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             callFailed(0, "interrupted by process restart"),
             requested(1, []),
             completed(1, assistantText("done")),
@@ -760,7 +760,7 @@ describe("recovery-shaped histories", () => {
                 created({
                     config: { autoPermission: false, humanAvailable: true, maxModelCalls: 1 },
                 }),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 callFailed(0, "interrupted"),
                 requested(1, []),
             ],
@@ -772,7 +772,7 @@ describe("recovery-shaped histories", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             invocation("tc1"),
             result(
@@ -782,7 +782,7 @@ describe("recovery-shaped histories", () => {
                 "Tool execution was interrupted; its outcome is unknown and it was not retried.",
                 true,
             ),
-            requested(1, [{ kind: "assistant", modelCallIndex: 0 }, { kind: "toolResult", toolCallId: "tc1" }]),
+            requested(1, ["assistant:0", "toolResult:tc1"]),
             completed(1, assistantText("done")),
             turnCompletedEv(),
         ]);
@@ -794,7 +794,7 @@ describe("recovery-shaped histories", () => {
         const call0 = assistantCalls(toolCallPart("a1", "fetch"));
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             invocation("a1", fetchTool),
             suspendedEv([], [{ id: "a1", tool: fetchTool }]),
@@ -808,7 +808,7 @@ describe("recovery-shaped histories", () => {
     it("accepts a live model failure closing the turn", () => {
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             callFailed(0),
             turnFailedEv("provider exploded"),
         ]);
@@ -821,7 +821,7 @@ describe("recovery-shaped histories", () => {
             created({
                 config: { autoPermission: false, humanAvailable: true, maxModelCalls: 1 },
             }),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             invocation("tc1"),
             result("tc1", "echo"),
@@ -840,7 +840,7 @@ describe("invariants", () => {
     });
 
     it("rejects a log not starting with turn_created", () => {
-        expectCorruption([requested(0, [{ kind: "input" }])], /first event must be turn_created/);
+        expectCorruption([requested(0, ["input"])], /first event must be turn_created/);
     });
 
     it("rejects duplicate turn_created", () => {
@@ -849,7 +849,7 @@ describe("invariants", () => {
 
     it("rejects mismatched turn ids", () => {
         expectCorruption(
-            [created(), { ...requested(0, [{ kind: "input" }]), turnId: "other" }],
+            [created(), { ...requested(0, ["input"]), turnId: "other" }],
             /does not match turn/,
         );
     });
@@ -882,9 +882,9 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, assistantText("a")),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
             ],
             /out of order/,
         );
@@ -892,7 +892,7 @@ describe("invariants", () => {
 
     it("rejects concurrent unresolved model requests", () => {
         expectCorruption(
-            [created(), requested(0, [{ kind: "input" }]), requested(1, [])],
+            [created(), requested(0, ["input"]), requested(1, [])],
             /concurrent unresolved model call requests/,
         );
     });
@@ -912,7 +912,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, assistantText("a")),
                 completed(0, assistantText("b")),
             ],
@@ -924,7 +924,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 callFailed(0),
                 completed(0, assistantText("a")),
             ],
@@ -937,9 +937,9 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
-                requested(1, [{ kind: "assistant", modelCallIndex: 0 }]),
+                requested(1, ["assistant:0"]),
             ],
             /while tool calls are unresolved/,
         );
@@ -952,11 +952,11 @@ describe("invariants", () => {
                 created({
                     config: { autoPermission: false, humanAvailable: true, maxModelCalls: 1 },
                 }),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 result("tc1", "echo"),
-                requested(1, [{ kind: "assistant", modelCallIndex: 0 }, { kind: "toolResult", toolCallId: "tc1" }]),
+                requested(1, ["assistant:0", "toolResult:tc1"]),
             ],
             /exceeds maxModelCalls/,
         );
@@ -966,7 +966,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(
                     0,
                     assistantCalls(toolCallPart("tc1", "echo"), toolCallPart("tc1", "echo")),
@@ -981,11 +981,11 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 result("tc1", "echo"),
-                requested(1, [{ kind: "assistant", modelCallIndex: 0 }, { kind: "toolResult", toolCallId: "tc1" }]),
+                requested(1, ["assistant:0", "toolResult:tc1"]),
                 completed(1, assistantCalls(toolCallPart("tc1", "echo"))),
             ],
             /duplicate tool call id/,
@@ -1000,16 +1000,16 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 result("tc1", "echo"),
                 invocation("tc2"),
                 result("tc2", "echo"),
                 requested(1, [
-                    { kind: "assistant", modelCallIndex: 0 },
-                    { kind: "toolResult", toolCallId: "tc2" },
-                    { kind: "toolResult", toolCallId: "tc1" },
+                    "assistant:0",
+                    "toolResult:tc2",
+                    "toolResult:tc1",
                 ]),
             ],
             /references do not match/,
@@ -1018,7 +1018,7 @@ describe("invariants", () => {
 
     it("rejects permission records targeting unknown tool calls", () => {
         expectCorruption(
-            [created(), requested(0, [{ kind: "input" }]), completed(0, assistantText("a")), permRequired("ghost", "echo")],
+            [created(), requested(0, ["input"]), completed(0, assistantText("a")), permRequired("ghost", "echo")],
             /unknown tool call/,
         );
     });
@@ -1028,7 +1028,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permRequired("tc1", "echo"),
                 permRequired("tc1", "echo"),
@@ -1042,7 +1042,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permClassified("tc1", "allow"),
             ],
@@ -1055,7 +1055,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permResolved("tc1", "allow"),
             ],
@@ -1068,7 +1068,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permRequired("tc1", "echo"),
                 permResolved("tc1", "allow"),
@@ -1083,7 +1083,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permRequired("tc1", "echo"),
                 invocation("tc1"),
@@ -1097,7 +1097,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 permRequired("tc1", "echo"),
                 permResolved("tc1", "deny"),
@@ -1112,7 +1112,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 invocation("tc1"),
@@ -1126,7 +1126,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1", echoTool, { execution: "async" }),
             ],
@@ -1137,7 +1137,7 @@ describe("invariants", () => {
     it("rejects progress without invocation", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         expectCorruption(
-            [created(), requested(0, [{ kind: "input" }]), completed(0, call0), progress("tc1")],
+            [created(), requested(0, ["input"]), completed(0, call0), progress("tc1")],
             /progress without invocation/,
         );
     });
@@ -1147,7 +1147,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 result("tc1", "echo"),
@@ -1162,7 +1162,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 result("tc1", "echo"),
@@ -1175,7 +1175,7 @@ describe("invariants", () => {
     it("rejects sync-sourced results without invocation", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         expectCorruption(
-            [created(), requested(0, [{ kind: "input" }]), completed(0, call0), result("tc1", "echo", "sync")],
+            [created(), requested(0, ["input"]), completed(0, call0), result("tc1", "echo", "sync")],
             /sync tool result without invocation/,
         );
     });
@@ -1185,7 +1185,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 result("tc1", "echo", "async"),
@@ -1199,7 +1199,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, assistantText("a")),
                 stepEvent(0),
             ],
@@ -1210,7 +1210,7 @@ describe("invariants", () => {
     it("rejects completion while tool calls remain unresolved", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         expectCorruption(
-            [created(), requested(0, [{ kind: "input" }]), completed(0, call0), turnCompletedEv()],
+            [created(), requested(0, ["input"]), completed(0, call0), turnCompletedEv()],
             /completion while tool calls lack terminal results/,
         );
     });
@@ -1220,7 +1220,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, call0),
                 invocation("tc1"),
                 result("tc1", "echo"),
@@ -1237,14 +1237,14 @@ describe("invariants", () => {
     it("rejects terminal failure while tool calls remain unresolved", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         expectCorruption(
-            [created(), requested(0, [{ kind: "input" }]), completed(0, call0), turnFailedEv()],
+            [created(), requested(0, ["input"]), completed(0, call0), turnFailedEv()],
             /failure while tool calls lack terminal results/,
         );
     });
 
     it("rejects terminal events while a model call is unsettled", () => {
         expectCorruption(
-            [created(), requested(0, [{ kind: "input" }]), turnCancelledEv()],
+            [created(), requested(0, ["input"]), turnCancelledEv()],
             /cancellation while a model call is unsettled/,
         );
     });
@@ -1252,7 +1252,7 @@ describe("invariants", () => {
     it("rejects any event after a terminal event", () => {
         const base = [
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, assistantText("a")),
         ];
         for (const terminal of [turnCompletedEv(), turnFailedEv(), turnCancelledEv()]) {
@@ -1267,7 +1267,7 @@ describe("invariants", () => {
         expectCorruption(
             [
                 created(),
-                requested(0, [{ kind: "input" }]),
+                requested(0, ["input"]),
                 completed(0, assistantText("a")),
                 turnCompletedEv(),
                 turnFailedEv(),
@@ -1282,14 +1282,14 @@ describe("derivations", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         const pending = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             permRequired("tc1", "echo"),
             suspendedEv([{ id: "tc1", name: "echo" }], []),
         ]);
         expect(deriveTurnStatus(pending)).toBe("suspended");
 
-        const idle = reduceTurn([created(), requested(0, [{ kind: "input" }]), completed(0, call0)]);
+        const idle = reduceTurn([created(), requested(0, ["input"]), completed(0, call0)]);
         expect(deriveTurnStatus(idle)).toBe("idle");
     });
 
@@ -1300,16 +1300,16 @@ describe("derivations", () => {
         );
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
             invocation("tc1"),
             invocation("tc2"),
             result("tc2", "echo", "sync", { n: 2 }),
             result("tc1", "echo", "sync", "plain text"),
             requested(1, [
-                { kind: "assistant", modelCallIndex: 0 },
-                { kind: "toolResult", toolCallId: "tc1" },
-                { kind: "toolResult", toolCallId: "tc2" },
+                "assistant:0",
+                "toolResult:tc1",
+                "toolResult:tc2",
             ]),
             completed(1, assistantText("done")),
             turnCompletedEv(),
@@ -1326,7 +1326,7 @@ describe("derivations", () => {
     it("omits failed model calls from the transcript", () => {
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             callFailed(0, "interrupted"),
             requested(1, []),
             completed(1, assistantText("done")),
@@ -1338,7 +1338,7 @@ describe("derivations", () => {
     it("transcript excludes the context prefix", () => {
         const state = reduceTurn([
             created({ context: { previousTurnId: PREV_TURN_ID } }),
-            requested(0, [{ kind: "input" }], {
+            requested(0, ["input"], {
                 contextRef: { previousTurnId: PREV_TURN_ID },
             }),
             completed(0, assistantText("done")),
@@ -1352,7 +1352,7 @@ describe("derivations", () => {
         const call0 = assistantCalls(toolCallPart("tc1", "echo"));
         const state = reduceTurn([
             created(),
-            requested(0, [{ kind: "input" }]),
+            requested(0, ["input"]),
             completed(0, call0),
         ]);
         expect(() => turnTranscript(state)).toThrowError(/unresolved/);
diff --git a/apps/x/packages/shared/src/turns.ts b/apps/x/packages/shared/src/turns.ts
index 3b71b0d3..6d28e035 100644
--- a/apps/x/packages/shared/src/turns.ts
+++ b/apps/x/packages/shared/src/turns.ts
@@ -130,15 +130,39 @@ export const TurnCreated = z.object({
 // identical to turn_created.agent.resolved by construction. The exact
 // provider payload is rebuilt deterministically by the request composer
 // (core), which is the same code path the loop sends through.
-export const ModelRequestMessageRef = z.discriminatedUnion("kind", [
-    z.object({ kind: z.literal("context") }),
-    z.object({ kind: z.literal("input") }),
-    z.object({
-        kind: z.literal("assistant"),
-        modelCallIndex: z.number().int().nonnegative(),
-    }),
-    z.object({ kind: z.literal("toolResult"), toolCallId: z.string() }),
-]);
+// Compact string refs so raw JSONL reads naturally:
+//   "context" | "input" | "assistant:<modelCallIndex>" | "toolResult:<toolCallId>"
+export const ModelRequestMessageRef = z
+    .string()
+    .regex(/^(context|input|assistant:\d+|toolResult:.+)$/);
+
+export type ParsedRequestRef =
+    | { kind: "context" }
+    | { kind: "input" }
+    | { kind: "assistant"; modelCallIndex: number }
+    | { kind: "toolResult"; toolCallId: string };
+
+export const assistantRef = (modelCallIndex: number): string =>
+    `assistant:${modelCallIndex}`;
+export const toolResultRef = (toolCallId: string): string =>
+    `toolResult:${toolCallId}`;
+
+export function parseRequestRef(ref: string): ParsedRequestRef {
+    if (ref === "context" || ref === "input") {
+        return { kind: ref };
+    }
+    if (ref.startsWith("assistant:")) {
+        const modelCallIndex = Number(ref.slice("assistant:".length));
+        if (!Number.isInteger(modelCallIndex) || modelCallIndex < 0) {
+            throw new Error(`malformed request ref: ${ref}`);
+        }
+        return { kind: "assistant", modelCallIndex };
+    }
+    if (ref.startsWith("toolResult:")) {
+        return { kind: "toolResult", toolCallId: ref.slice("toolResult:".length) };
+    }
+    throw new Error(`malformed request ref: ${ref}`);
+}
 
 export const ModelRequest = z.object({
     contextRef: TurnContextRef.optional(),
@@ -505,21 +529,18 @@ function applyModelCallRequested(
     }
 
     const context = state.definition.context;
-    let expectedRefs: Array<z.infer<typeof ModelRequestMessageRef>>;
+    let expectedRefs: string[];
     if (event.modelCallIndex === 0) {
         if (isContextRef(context)) {
             if (event.request.contextRef?.previousTurnId !== context.previousTurnId) {
                 fail("model request contextRef inconsistent with turn context");
             }
-            expectedRefs = [{ kind: "input" }];
+            expectedRefs = ["input"];
         } else {
             if (event.request.contextRef !== undefined) {
                 fail("model request has contextRef but turn context is inline");
             }
-            expectedRefs =
-                context.length > 0
-                    ? [{ kind: "context" }, { kind: "input" }]
-                    : [{ kind: "input" }];
+            expectedRefs = context.length > 0 ? ["context", "input"] : ["input"];
         }
     } else {
         if (event.request.contextRef !== undefined) {
@@ -529,11 +550,10 @@ function applyModelCallRequested(
         expectedRefs =
             previous.response !== undefined
                 ? [
-                      { kind: "assistant", modelCallIndex: previous.index },
-                      ...batchToolCalls(state, previous.index).map((tc) => ({
-                          kind: "toolResult" as const,
-                          toolCallId: tc.toolCallId,
-                      })),
+                      assistantRef(previous.index),
+                      ...batchToolCalls(state, previous.index).map((tc) =>
+                          toolResultRef(tc.toolCallId),
+                      ),
                   ]
                 : []; // re-issue after an interrupted call adds nothing new
     }
@@ -988,7 +1008,8 @@ export function requestMessagesFor(
     if (!call) {
         throw new Error(`no model call at index ${modelCallIndex}`);
     }
-    return call.request.messages.flatMap((ref) => {
+    return call.request.messages.flatMap((raw) => {
+        const ref = parseRequestRef(raw);
         switch (ref.kind) {
             case "context": {
                 const context = state.definition.context;