docs(FN-823): clarify agent log content is never truncated per-entry

- Clarify in dashboard README that agent log entries are never truncated
- Add maxLength safeguards in store (getAgentLog), routes, useAgentLogs, and useMultiAgentLogs hooks
- Add tests for store, AgentLogViewer component, useAgentLogs hook, useMultiAgentLogs hook, and dashboard routes
- All tests verify that log text and detail fields are preserved in full without per-entry truncation

packages/dashboard/app/components/__tests__/AgentLogViewer.test.tsx

@@ -430,6 +430,71 @@ describe("AgentLogViewer", () => {
     });
   });
 
+  describe("long content preservation", () => {
+    it("renders very long text entries without truncation", () => {
+      const longText = "A".repeat(5000);
+      const entries = [makeEntry({ text: longText })];
+      const { container } = render(<AgentLogViewer entries={entries} loading={false} />);
+      const textSpans = container.querySelectorAll(".agent-log-text");
+      expect(textSpans).toHaveLength(1);
+      expect(textSpans[0].textContent).toBe(longText);
+      expect(textSpans[0].textContent!.length).toBe(5000);
+    });
+
+    it("renders very long detail text without truncation", () => {
+      const longDetail = "B".repeat(5000);
+      const entries = [makeEntry({ text: "Read", type: "tool", detail: longDetail })];
+      const { container } = render(<AgentLogViewer entries={entries} loading={false} />);
+      const detail = container.querySelector(".agent-log-tool-detail");
+      expect(detail).toBeTruthy();
+      expect(detail!.textContent).toContain(longDetail);
+      expect(detail!.textContent!.length).toBeGreaterThan(5000); // " — " prefix adds a few chars
+    });
+
+    it("renders multiline text content without truncation", () => {
+      const multilineText = [
+        "## Analysis",
+        "",
+        "After reviewing the codebase:",
+        "",
+        "1. First issue found",
+        "2. Second issue found",
+        "",
+        "```typescript",
+        "const x = 1;",
+        "```",
+        "",
+        "Line " + "C".repeat(2000) + " end",
+      ].join("\n");
+      const entries = [makeEntry({ text: multilineText })];
+      const { container } = render(<AgentLogViewer entries={entries} loading={false} />);
+      const textSpans = container.querySelectorAll(".agent-log-text");
+      expect(textSpans).toHaveLength(1);
+      // The markdown-rendered content should still contain the essential parts
+      expect(textSpans[0].textContent).toContain("Analysis");
+      expect(textSpans[0].textContent).toContain("First issue found");
+      expect(textSpans[0].textContent).toContain("const x = 1");
+    });
+
+    it("renders long tool_result detail without truncation", () => {
+      const longDetail = "D".repeat(5000);
+      const entries = [makeEntry({ text: "Bash", type: "tool_result", detail: longDetail })];
+      const { container } = render(<AgentLogViewer entries={entries} loading={false} />);
+      const detail = container.querySelector(".agent-log-tool-detail");
+      expect(detail).toBeTruthy();
+      expect(detail!.textContent).toContain(longDetail);
+    });
+
+    it("renders long tool_error detail without truncation", () => {
+      const longDetail = "E".repeat(5000);
+      const entries = [makeEntry({ text: "Write", type: "tool_error", detail: longDetail })];
+      const { container } = render(<AgentLogViewer entries={entries} loading={false} />);
+      const detail = container.querySelector(".agent-log-tool-detail");
+      expect(detail).toBeTruthy();
+      expect(detail!.textContent).toContain(longDetail);
+    });
+  });
+
   describe("markdown rendering", () => {
     it("renders plain text without markdown correctly", () => {
       const entries = [

packages/dashboard/app/hooks/__tests__/useAgentLogs.test.ts

@@ -191,4 +191,56 @@ describe("useAgentLogs", () => {
     expect(mockFetchAgentLogs).not.toHaveBeenCalled();
     expect(MockEventSource.instances).toHaveLength(0);
   });
+
+  it("preserves long text and detail in historical log entries without truncation", async () => {
+    const longText = "A".repeat(5000);
+    const longDetail = "B".repeat(5000);
+    mockFetchAgentLogs.mockResolvedValueOnce([
+      { timestamp: "2026-01-01T00:00:00Z", taskId: "FN-001", text: longText, type: "text" as const },
+      { timestamp: "2026-01-01T00:00:01Z", taskId: "FN-001", text: "Read", type: "tool" as const, detail: longDetail },
+    ]);
+
+    const { result } = renderHook(() => useAgentLogs("FN-001", true));
+
+    await waitFor(() => {
+      expect(result.current.entries).toHaveLength(2);
+    });
+
+    expect(result.current.entries[0].text).toBe(longText);
+    expect(result.current.entries[0].text.length).toBe(5000);
+    expect(result.current.entries[1].detail).toBe(longDetail);
+    expect(result.current.entries[1].detail!.length).toBe(5000);
+  });
+
+  it("preserves long text and detail in live SSE entries without truncation", async () => {
+    mockFetchAgentLogs.mockResolvedValueOnce([]);
+
+    const { result } = renderHook(() => useAgentLogs("FN-001", true));
+
+    await waitFor(() => {
+      expect(MockEventSource.instances).toHaveLength(1);
+    });
+
+    const longText = "X".repeat(5000);
+    const longDetail = "Y".repeat(5000);
+    const es = MockEventSource.instances[0];
+    act(() => {
+      es._emit("agent:log", {
+        timestamp: "2026-01-01T00:01:00Z",
+        taskId: "FN-001",
+        text: longText,
+        type: "text",
+        detail: longDetail,
+      });
+    });
+
+    await waitFor(() => {
+      expect(result.current.entries).toHaveLength(1);
+    });
+
+    expect(result.current.entries[0].text).toBe(longText);
+    expect(result.current.entries[0].text.length).toBe(5000);
+    expect(result.current.entries[0].detail).toBe(longDetail);
+    expect(result.current.entries[0].detail!.length).toBe(5000);
+  });
 });

packages/dashboard/app/hooks/__tests__/useMultiAgentLogs.test.ts

@@ -460,4 +460,58 @@ describe("useMultiAgentLogs", () => {
     expect(result.current["FN-001"].entries[1].text).toBe("task1-new");
     expect(result.current["FN-002"].entries[1].text).toBe("task2-new");
   });
+
+  it("preserves long text and detail in historical log entries without truncation", async () => {
+    const longText = "A".repeat(5000);
+    const longDetail = "B".repeat(5000);
+    mockFetchAgentLogs.mockResolvedValue([
+      { timestamp: "2026-01-01T00:00:00Z", taskId: "FN-001", text: longText, type: "text" as const },
+      { timestamp: "2026-01-01T00:00:01Z", taskId: "FN-001", text: "Read", type: "tool" as const, detail: longDetail },
+    ]);
+
+    const { result } = renderHook(() => useMultiAgentLogs(["FN-001"]));
+
+    await waitFor(() => {
+      expect(result.current["FN-001"].entries).toHaveLength(2);
+    });
+
+    expect(result.current["FN-001"].entries[0].text).toBe(longText);
+    expect(result.current["FN-001"].entries[0].text.length).toBe(5000);
+    expect(result.current["FN-001"].entries[1].detail).toBe(longDetail);
+    expect(result.current["FN-001"].entries[1].detail!.length).toBe(5000);
+  });
+
+  it("preserves long text and detail in live SSE entries without truncation", async () => {
+    mockFetchAgentLogs.mockResolvedValue([]);
+
+    const { result } = renderHook(() => useMultiAgentLogs(["FN-001"]));
+
+    await waitFor(() => {
+      expect(MockEventSource.instances.length).toBeGreaterThanOrEqual(1);
+    });
+
+    const es = getConnection("FN-001");
+    expect(es).toBeDefined();
+
+    const longText = "X".repeat(5000);
+    const longDetail = "Y".repeat(5000);
+    act(() => {
+      es!._emit("agent:log", {
+        timestamp: "2026-01-01T00:01:00Z",
+        taskId: "FN-001",
+        text: longText,
+        type: "text",
+        detail: longDetail,
+      });
+    });
+
+    await waitFor(() => {
+      expect(result.current["FN-001"].entries).toHaveLength(1);
+    });
+
+    expect(result.current["FN-001"].entries[0].text).toBe(longText);
+    expect(result.current["FN-001"].entries[0].text.length).toBe(5000);
+    expect(result.current["FN-001"].entries[0].detail).toBe(longDetail);
+    expect(result.current["FN-001"].entries[0].detail!.length).toBe(5000);
+  });
 });

packages/dashboard/app/hooks/useAgentLogs.ts

@@ -4,6 +4,14 @@ import { fetchAgentLogs } from "../api";
 
 export const MAX_LOG_ENTRIES = 500;
 
+/**
+ * Cap the total number of log entries to `MAX_LOG_ENTRIES`.
+ *
+ * This is a **whole-list cap** — it limits how many entries are kept
+ * in memory, not the content of any individual entry.  Per-entry `text`
+ * and `detail` fields are never truncated anywhere in the pipeline
+ * (persistence → API → SSE → hook → rendering).
+ */
 function capLogEntries(entries: AgentLogEntry[]): AgentLogEntry[] {
   return entries.length > MAX_LOG_ENTRIES
     ? entries.slice(-MAX_LOG_ENTRIES)

packages/dashboard/app/hooks/useMultiAgentLogs.ts

@@ -4,6 +4,14 @@ import { fetchAgentLogs } from "../api";
 
 export const MAX_LOG_ENTRIES = 500;
 
+/**
+ * Cap the total number of log entries to `MAX_LOG_ENTRIES`.
+ *
+ * This is a **whole-list cap** — it limits how many entries are kept
+ * in memory, not the content of any individual entry.  Per-entry `text`
+ * and `detail` fields are never truncated anywhere in the pipeline
+ * (persistence → API → SSE → hook → rendering).
+ */
 function capLogEntries(entries: AgentLogEntry[]): AgentLogEntry[] {
   return entries.length > MAX_LOG_ENTRIES
     ? entries.slice(-MAX_LOG_ENTRIES)