fix(prompt-retry): preserve async holds without blocking validation fallbacks

src/shared/model-suggestion-retry.test.ts

@@ -405,6 +405,67 @@ describe("promptWithModelSuggestionRetry", () => {
     expect(promptMock).toHaveBeenCalledTimes(1)
   })
 
+  it("#given promptAsync throws after dispatch was attempted #when caller observes the error #then the post-dispatch hold remains reserved", async () => {
+    // given
+    const promptMock = mock().mockRejectedValueOnce(new Error("JSON Parse error: Unexpected EOF"))
+    const client = { session: { promptAsync: promptMock } }
+    const args = {
+      path: { id: "session-failed-async-hold" },
+      body: {
+        parts: [{ type: "text", text: "hello" }],
+        model: { providerID: "anthropic", modelID: "claude-sonnet-4" },
+      },
+    }
+
+    // when
+    await expect(
+      promptWithModelSuggestionRetry(unsafeTestValue(client), args)
+    ).rejects.toThrow("Unexpected EOF")
+    const second = await dispatchInternalPrompt({
+      mode: "async",
+      client,
+      sessionID: "session-failed-async-hold",
+      input: args,
+      source: "test:after-failed-async",
+      settleMs: 0,
+      postDispatchHoldMs: 0,
+    })
+
+    // then
+    expect(second).toEqual({ status: "reserved", reservedBy: "model-suggestion-retry" })
+    expect(promptMock).toHaveBeenCalledTimes(1)
+  })
+
+  it("#given promptAsync rejects before acceptance with an agent lookup error #when retried immediately #then the reservation is released", async () => {
+    // given
+    const promptMock = mock()
+      .mockRejectedValueOnce(new Error("Agent not found: missing-agent"))
+      .mockResolvedValueOnce(undefined)
+    const client = { session: { promptAsync: promptMock } }
+    const args = {
+      path: { id: "session-agent-preaccept-failure" },
+      body: {
+        agent: "missing-agent",
+        parts: [{ type: "text", text: "hello" }],
+      },
+    }
+
+    // when
+    await expect(
+      promptWithModelSuggestionRetry(unsafeTestValue(client), args)
+    ).rejects.toThrow("Agent not found")
+    await promptWithModelSuggestionRetry(unsafeTestValue(client), {
+      ...args,
+      body: {
+        ...args.body,
+        agent: "general",
+      },
+    })
+
+    // then
+    expect(promptMock).toHaveBeenCalledTimes(2)
+  })
+
   it("should pass all body fields through to promptAsync", async () => {
     // given a client where promptAsync succeeds
     const promptMock = mock().mockResolvedValueOnce(undefined)