diff --git a/backend/tests/e2e/test_replay_analytics.py b/backend/tests/e2e/test_replay_analytics.py
index 26d7724..82a6c9f 100644
--- a/backend/tests/e2e/test_replay_analytics.py
+++ b/backend/tests/e2e/test_replay_analytics.py
@@ -47,7 +47,13 @@ class ReplayPool(FakePool):
             if "COUNT" in query and "conversations" in query:
                 return FakeCursor([(len(self._convos),)])
             if "conversations" in query and "SELECT" in query:
-                return FakeCursor(self._convos)
+                # Respect LIMIT/OFFSET from params if provided
+                rows = self._convos
+                if params:
+                    offset = params.get("offset", 0)
+                    limit = params.get("limit", len(rows))
+                    rows = rows[offset : offset + limit]
+                return FakeCursor(rows)
             if "checkpoints" in query:
                 return FakeCursor(self._checkpoints)
             # Analytics queries
@@ -122,6 +128,11 @@ class TestFlow6ReplayConversation:
             assert resp.status_code == 200
             body = resp.json()
             assert body["success"] is True
+            data = body["data"]
+            assert data["total"] == 5
+            assert data["page"] == 1
+            assert data["per_page"] == 2
+            assert len(data["conversations"]) == 2
 
     def test_replay_thread_not_found(self) -> None:
         pool = ReplayPool(checkpoints=[])
diff --git a/backend/tests/unit/analytics/test_queries.py b/backend/tests/unit/analytics/test_queries.py
index 3bd9868..5a74272 100644
--- a/backend/tests/unit/analytics/test_queries.py
+++ b/backend/tests/unit/analytics/test_queries.py
@@ -158,6 +158,42 @@ class TestInterruptStatsQuery:
         assert result.expired == 0
 
 
+class TestTotalConversations:
+    @pytest.mark.asyncio
+    async def test_returns_count(self) -> None:
+        from app.analytics.queries import _total_conversations
+
+        pool = _make_pool_with_fetchone({"total": 42})
+        result = await _total_conversations(pool, range_days=7)
+        assert result == 42
+
+    @pytest.mark.asyncio
+    async def test_zero_state_returns_zero(self) -> None:
+        from app.analytics.queries import _total_conversations
+
+        pool = _make_pool_with_fetchone(None)
+        result = await _total_conversations(pool, range_days=7)
+        assert result == 0
+
+
+class TestAvgTurns:
+    @pytest.mark.asyncio
+    async def test_returns_float(self) -> None:
+        from app.analytics.queries import _avg_turns
+
+        pool = _make_pool_with_fetchone({"avg_turns": 3.5})
+        result = await _avg_turns(pool, range_days=7)
+        assert result == 3.5
+
+    @pytest.mark.asyncio
+    async def test_zero_state_returns_zero(self) -> None:
+        from app.analytics.queries import _avg_turns
+
+        pool = _make_pool_with_fetchone(None)
+        result = await _avg_turns(pool, range_days=7)
+        assert result == 0.0
+
+
 class TestGetAnalytics:
     @pytest.mark.asyncio
     async def test_returns_analytics_result(self) -> None:
diff --git a/backend/tests/unit/replay/test_api.py b/backend/tests/unit/replay/test_api.py
index c2e179b..1acf55e 100644
--- a/backend/tests/unit/replay/test_api.py
+++ b/backend/tests/unit/replay/test_api.py
@@ -119,8 +119,8 @@ class TestListConversations:
 
         with TestClient(app) as client:
             resp = client.get("/api/conversations?per_page=200")
-        # FastAPI validation rejects values > 100
-        assert resp.status_code in (200, 422)
+        # FastAPI Query(le=100) rejects values > 100
+        assert resp.status_code == 422
 
 
 class TestGetReplay:
diff --git a/backend/tests/unit/replay/test_transformer.py b/backend/tests/unit/replay/test_transformer.py
index 319c413..82af0b1 100644
--- a/backend/tests/unit/replay/test_transformer.py
+++ b/backend/tests/unit/replay/test_transformer.py
@@ -153,3 +153,105 @@ class TestTransformCheckpoints:
         rows = [_make_row([{"type": "human", "content": "Hi"}])]
         steps = transform_checkpoints(rows)
         assert isinstance(steps[0].timestamp, str)
+
+    def test_list_content_joined_to_string(self) -> None:
+        from app.replay.transformer import transform_checkpoints
+
+        rows = [
+            _make_row(
+                [
+                    {
+                        "type": "human",
+                        "content": [
+                            {"text": "Hello"},
+                            {"text": " world"},
+                        ],
+                    }
+                ]
+            )
+        ]
+        steps = transform_checkpoints(rows)
+        assert len(steps) == 1
+        assert steps[0].content == "Hello  world"
+
+    def test_checkpoint_as_string_skipped(self) -> None:
+        from app.replay.transformer import transform_checkpoints
+
+        rows = [
+            {
+                "thread_id": "t1",
+                "checkpoint_id": "cp1",
+                "checkpoint": "not-a-dict",
+                "metadata": {},
+            }
+        ]
+        steps = transform_checkpoints(rows)
+        assert steps == []
+
+    def test_channel_values_not_dict_skipped(self) -> None:
+        from app.replay.transformer import transform_checkpoints
+
+        rows = [
+            {
+                "thread_id": "t1",
+                "checkpoint_id": "cp1",
+                "checkpoint": {"channel_values": "bad"},
+                "metadata": {},
+            }
+        ]
+        steps = transform_checkpoints(rows)
+        assert steps == []
+
+    def test_tool_result_valid_json_parsed(self) -> None:
+        from app.replay.transformer import transform_checkpoints
+
+        rows = [
+            _make_row(
+                [
+                    {
+                        "type": "tool",
+                        "content": '{"order_id": "123", "status": "shipped"}',
+                        "name": "get_order_status",
+                    }
+                ]
+            )
+        ]
+        steps = transform_checkpoints(rows)
+        assert len(steps) == 1
+        assert steps[0].result == {"order_id": "123", "status": "shipped"}
+
+    def test_tool_result_invalid_json_wrapped(self) -> None:
+        from app.replay.transformer import transform_checkpoints
+
+        rows = [
+            _make_row(
+                [
+                    {
+                        "type": "tool",
+                        "content": "not valid json",
+                        "name": "some_tool",
+                    }
+                ]
+            )
+        ]
+        steps = transform_checkpoints(rows)
+        assert len(steps) == 1
+        assert steps[0].result == {"raw": "not valid json"}
+
+    def test_malformed_message_skipped_gracefully(self) -> None:
+        from app.replay.transformer import transform_checkpoints
+
+        rows = [
+            _make_row(
+                [
+                    {"type": "human", "content": "Good message"},
+                    42,  # not a dict -- will raise in _step_from_message
+                    {"type": "ai", "content": "Response", "tool_calls": []},
+                ]
+            )
+        ]
+        steps = transform_checkpoints(rows)
+        # The malformed message is skipped; the other two produce steps.
+        assert len(steps) == 2
+        assert steps[0].step == 1
+        assert steps[1].step == 2
diff --git a/backend/tests/unit/test_config.py b/backend/tests/unit/test_config.py
index 85d6959..8dd19d8 100644
--- a/backend/tests/unit/test_config.py
+++ b/backend/tests/unit/test_config.py
@@ -89,3 +89,21 @@ class TestSettings:
                 anthropic_api_key="key",
                 openai_api_key="",
             )
+
+    def test_azure_openai_missing_endpoint_rejected(self) -> None:
+        with pytest.raises(ValueError, match="AZURE_OPENAI_ENDPOINT"):
+            _isolated_settings(
+                database_url="postgresql://x:x@localhost/db",
+                llm_provider="azure_openai",
+                azure_openai_api_key="key",
+                azure_openai_deployment="my-deploy",
+            )
+
+    def test_azure_openai_missing_deployment_rejected(self) -> None:
+        with pytest.raises(ValueError, match="AZURE_OPENAI_DEPLOYMENT"):
+            _isolated_settings(
+                database_url="postgresql://x:x@localhost/db",
+                llm_provider="azure_openai",
+                azure_openai_api_key="key",
+                azure_openai_endpoint="https://example.openai.azure.com",
+            )
diff --git a/backend/tests/unit/test_safety.py b/backend/tests/unit/test_safety.py
index 861a616..6d101be 100644
--- a/backend/tests/unit/test_safety.py
+++ b/backend/tests/unit/test_safety.py
@@ -67,6 +67,17 @@ class TestClassifyMcpError:
     def test_unknown_message(self) -> None:
         assert classify_mcp_error(error_message="Something happened") == "unknown"
 
+    def test_status_code_takes_precedence_over_message(self) -> None:
+        # 429 is transient by code; message would classify as validation
+        assert classify_mcp_error(status_code=429, error_message="invalid param") == "transient"
+
+    def test_non_classified_status_falls_through_to_message(self) -> None:
+        # 200 is not in any status set, so message classification takes over
+        assert classify_mcp_error(status_code=200, error_message="timed out") == "transient"
+
+    def test_no_args_returns_unknown(self) -> None:
+        assert classify_mcp_error() == "unknown"
+
 
 class TestRetryPolicy:
     def test_transient_is_retryable(self) -> None:
diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index 982d5f4..4be2440 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -14,13 +14,24 @@
         "react-router-dom": "^7.13.2"
       },
       "devDependencies": {
+        "@testing-library/jest-dom": "^6.9.1",
+        "@testing-library/react": "^16.3.2",
         "@types/react": "^19.0.0",
         "@types/react-dom": "^19.0.0",
         "@vitejs/plugin-react": "^4.3.0",
+        "happy-dom": "^20.8.9",
         "typescript": "~5.7.0",
-        "vite": "^6.2.0"
+        "vite": "^6.2.0",
+        "vitest": "^4.1.2"
       }
     },
+    "node_modules/@adobe/css-tools": {
+      "version": "4.4.4",
+      "resolved": "https://registry.npmjs.org/@adobe/css-tools/-/css-tools-4.4.4.tgz",
+      "integrity": "sha512-Elp+iwUx5rN5+Y8xLt5/GRoG20WGoDCQ/1Fb+1LiGtvwbDavuSk0jhD/eZdckHAuzcDzccnkv+rEjyWfRx18gg==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@babel/code-frame": {
       "version": "7.29.0",
       "resolved": "https://registry.npmjs.org/@babel/code-frame/-/code-frame-7.29.0.tgz",
@@ -255,6 +266,16 @@
         "@babel/core": "^7.0.0-0"
       }
     },
+    "node_modules/@babel/runtime": {
+      "version": "7.29.2",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.29.2.tgz",
+      "integrity": "sha512-JiDShH45zKHWyGe4ZNVRrCjBz8Nh9TMmZG1kh4QTK8hCBTWBi8Da+i7s1fJw7/lYpM4ccepSNfqzZ/QvABBi5g==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=6.9.0"
+      }
+    },
     "node_modules/@babel/template": {
       "version": "7.28.6",
       "resolved": "https://registry.npmjs.org/@babel/template/-/template-7.28.6.tgz",
@@ -1152,6 +1173,97 @@
         "win32"
       ]
     },
+    "node_modules/@standard-schema/spec": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/@standard-schema/spec/-/spec-1.1.0.tgz",
+      "integrity": "sha512-l2aFy5jALhniG5HgqrD6jXLi/rUWrKvqN/qJx6yoJsgKhblVd+iqqU4RCXavm/jPityDo5TCvKMnpjKnOriy0w==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/@testing-library/dom": {
+      "version": "10.4.1",
+      "resolved": "https://registry.npmjs.org/@testing-library/dom/-/dom-10.4.1.tgz",
+      "integrity": "sha512-o4PXJQidqJl82ckFaXUeoAW+XysPLauYI43Abki5hABd853iMhitooc6znOnczgbTYmEP6U6/y1ZyKAIsvMKGg==",
+      "dev": true,
+      "license": "MIT",
+      "peer": true,
+      "dependencies": {
+        "@babel/code-frame": "^7.10.4",
+        "@babel/runtime": "^7.12.5",
+        "@types/aria-query": "^5.0.1",
+        "aria-query": "5.3.0",
+        "dom-accessibility-api": "^0.5.9",
+        "lz-string": "^1.5.0",
+        "picocolors": "1.1.1",
+        "pretty-format": "^27.0.2"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
+    "node_modules/@testing-library/jest-dom": {
+      "version": "6.9.1",
+      "resolved": "https://registry.npmjs.org/@testing-library/jest-dom/-/jest-dom-6.9.1.tgz",
+      "integrity": "sha512-zIcONa+hVtVSSep9UT3jZ5rizo2BsxgyDYU7WFD5eICBE7no3881HGeb/QkGfsJs6JTkY1aQhT7rIPC7e+0nnA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@adobe/css-tools": "^4.4.0",
+        "aria-query": "^5.0.0",
+        "css.escape": "^1.5.1",
+        "dom-accessibility-api": "^0.6.3",
+        "picocolors": "^1.1.1",
+        "redent": "^3.0.0"
+      },
+      "engines": {
+        "node": ">=14",
+        "npm": ">=6",
+        "yarn": ">=1"
+      }
+    },
+    "node_modules/@testing-library/jest-dom/node_modules/dom-accessibility-api": {
+      "version": "0.6.3",
+      "resolved": "https://registry.npmjs.org/dom-accessibility-api/-/dom-accessibility-api-0.6.3.tgz",
+      "integrity": "sha512-7ZgogeTnjuHbo+ct10G9Ffp0mif17idi0IyWNVA/wcwcm7NPOD/WEHVP3n7n3MhXqxoIYm8d6MuZohYWIZ4T3w==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/@testing-library/react": {
+      "version": "16.3.2",
+      "resolved": "https://registry.npmjs.org/@testing-library/react/-/react-16.3.2.tgz",
+      "integrity": "sha512-XU5/SytQM+ykqMnAnvB2umaJNIOsLF3PVv//1Ew4CTcpz0/BRyy/af40qqrt7SjKpDdT1saBMc42CUok5gaw+g==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.12.5"
+      },
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "@testing-library/dom": "^10.0.0",
+        "@types/react": "^18.0.0 || ^19.0.0",
+        "@types/react-dom": "^18.0.0 || ^19.0.0",
+        "react": "^18.0.0 || ^19.0.0",
+        "react-dom": "^18.0.0 || ^19.0.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        },
+        "@types/react-dom": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/@types/aria-query": {
+      "version": "5.0.4",
+      "resolved": "https://registry.npmjs.org/@types/aria-query/-/aria-query-5.0.4.tgz",
+      "integrity": "sha512-rfT93uj5s0PRL7EzccGMs3brplhcrghnDoV26NqKhCAS1hVo+WdNsPvE/yb6ilfr5hi2MEk6d5EWJTKdxg8jVw==",
+      "dev": true,
+      "license": "MIT",
+      "peer": true
+    },
     "node_modules/@types/babel__core": {
       "version": "7.20.5",
       "resolved": "https://registry.npmjs.org/@types/babel__core/-/babel__core-7.20.5.tgz",
@@ -1197,6 +1309,17 @@
         "@babel/types": "^7.28.2"
       }
     },
+    "node_modules/@types/chai": {
+      "version": "5.2.3",
+      "resolved": "https://registry.npmjs.org/@types/chai/-/chai-5.2.3.tgz",
+      "integrity": "sha512-Mw558oeA9fFbv65/y4mHtXDs9bPnFMZAL/jxdPFUpOHHIXX91mcgEHbS5Lahr+pwZFR8A7GQleRWeI6cGFC2UA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/deep-eql": "*",
+        "assertion-error": "^2.0.1"
+      }
+    },
     "node_modules/@types/debug": {
       "version": "4.1.13",
       "resolved": "https://registry.npmjs.org/@types/debug/-/debug-4.1.13.tgz",
@@ -1206,6 +1329,13 @@
         "@types/ms": "*"
       }
     },
+    "node_modules/@types/deep-eql": {
+      "version": "4.0.2",
+      "resolved": "https://registry.npmjs.org/@types/deep-eql/-/deep-eql-4.0.2.tgz",
+      "integrity": "sha512-c9h9dVVMigMPc4bwTvC5dxqtqJZwQPePsWjPlpSOnojbor6pGqdk541lfA7AqFQr5pB1BRdq0juY9db81BwyFw==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/estree": {
       "version": "1.0.8",
       "resolved": "https://registry.npmjs.org/@types/estree/-/estree-1.0.8.tgz",
@@ -1245,6 +1375,16 @@
       "integrity": "sha512-GsCCIZDE/p3i96vtEqx+7dBUGXrc7zeSK3wwPHIaRThS+9OhWIXRqzs4d6k1SVU8g91DrNRWxWUGhp5KXQb2VA==",
       "license": "MIT"
     },
+    "node_modules/@types/node": {
+      "version": "25.5.2",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-25.5.2.tgz",
+      "integrity": "sha512-tO4ZIRKNC+MDWV4qKVZe3Ql/woTnmHDr5JD8UI5hn2pwBrHEwOEMZK7WlNb5RKB6EoJ02gwmQS9OrjuFnZYdpg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "undici-types": "~7.18.0"
+      }
+    },
     "node_modules/@types/react": {
       "version": "19.2.14",
       "resolved": "https://registry.npmjs.org/@types/react/-/react-19.2.14.tgz",
@@ -1270,6 +1410,23 @@
       "integrity": "sha512-ko/gIFJRv177XgZsZcBwnqJN5x/Gien8qNOn0D5bQU/zAzVf9Zt3BlcUiLqhV9y4ARk0GbT3tnUiPNgnTXzc/Q==",
       "license": "MIT"
     },
+    "node_modules/@types/whatwg-mimetype": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/@types/whatwg-mimetype/-/whatwg-mimetype-3.0.2.tgz",
+      "integrity": "sha512-c2AKvDT8ToxLIOUlN51gTiHXflsfIFisS4pO7pDPoKouJCESkhZnEy623gwP9laCy5lnLDAw1vAzu2vM2YLOrA==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/@types/ws": {
+      "version": "8.18.1",
+      "resolved": "https://registry.npmjs.org/@types/ws/-/ws-8.18.1.tgz",
+      "integrity": "sha512-ThVF6DCVhA8kUGy+aazFQ4kXQ7E1Ty7A3ypFOe0IcJV8O/M511G99AW24irKrW56Wt44yG9+ij8FaqoBGkuBXg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/node": "*"
+      }
+    },
     "node_modules/@ungap/structured-clone": {
       "version": "1.3.0",
       "resolved": "https://registry.npmjs.org/@ungap/structured-clone/-/structured-clone-1.3.0.tgz",
@@ -1297,6 +1454,164 @@
         "vite": "^4.2.0 || ^5.0.0 || ^6.0.0 || ^7.0.0"
       }
     },
+    "node_modules/@vitest/expect": {
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/@vitest/expect/-/expect-4.1.2.tgz",
+      "integrity": "sha512-gbu+7B0YgUJ2nkdsRJrFFW6X7NTP44WlhiclHniUhxADQJH5Szt9mZ9hWnJPJ8YwOK5zUOSSlSvyzRf0u1DSBQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@standard-schema/spec": "^1.1.0",
+        "@types/chai": "^5.2.2",
+        "@vitest/spy": "4.1.2",
+        "@vitest/utils": "4.1.2",
+        "chai": "^6.2.2",
+        "tinyrainbow": "^3.1.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/vitest"
+      }
+    },
+    "node_modules/@vitest/mocker": {
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/@vitest/mocker/-/mocker-4.1.2.tgz",
+      "integrity": "sha512-Ize4iQtEALHDttPRCmN+FKqOl2vxTiNUhzobQFFt/BM1lRUTG7zRCLOykG/6Vo4E4hnUdfVLo5/eqKPukcWW7Q==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@vitest/spy": "4.1.2",
+        "estree-walker": "^3.0.3",
+        "magic-string": "^0.30.21"
+      },
+      "funding": {
+        "url": "https://opencollective.com/vitest"
+      },
+      "peerDependencies": {
+        "msw": "^2.4.9",
+        "vite": "^6.0.0 || ^7.0.0 || ^8.0.0"
+      },
+      "peerDependenciesMeta": {
+        "msw": {
+          "optional": true
+        },
+        "vite": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/@vitest/pretty-format": {
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/@vitest/pretty-format/-/pretty-format-4.1.2.tgz",
+      "integrity": "sha512-dwQga8aejqeuB+TvXCMzSQemvV9hNEtDDpgUKDzOmNQayl2OG241PSWeJwKRH3CiC+sESrmoFd49rfnq7T4RnA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "tinyrainbow": "^3.1.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/vitest"
+      }
+    },
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     "node_modules/tinyglobby": {
       "version": "0.2.15",
       "resolved": "https://registry.npmjs.org/tinyglobby/-/tinyglobby-0.2.15.tgz",
@@ -2772,6 +3318,16 @@
         "url": "https://github.com/sponsors/SuperchupuDev"
       }
     },
+    "node_modules/tinyrainbow": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/tinyrainbow/-/tinyrainbow-3.1.0.tgz",
+      "integrity": "sha512-Bf+ILmBgretUrdJxzXM0SgXLZ3XfiaUuOj/IKQHuTXip+05Xn+uyEYdVg0kYDipTBcLrCVyUzAPz7QmArb0mmw==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=14.0.0"
+      }
+    },
     "node_modules/trim-lines": {
       "version": "3.0.1",
       "resolved": "https://registry.npmjs.org/trim-lines/-/trim-lines-3.0.1.tgz",
@@ -2806,6 +3362,13 @@
         "node": ">=14.17"
       }
     },
+    "node_modules/undici-types": {
+      "version": "7.18.2",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.18.2.tgz",
+      "integrity": "sha512-AsuCzffGHJybSaRrmr5eHr81mwJU3kjw6M+uprWvCXiNeN9SOGwQ3Jn8jb8m3Z6izVgknn1R0FTCEAP2QrLY/w==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/unified": {
       "version": "11.0.5",
       "resolved": "https://registry.npmjs.org/unified/-/unified-11.0.5.tgz",
@@ -3027,6 +3590,137 @@
         }
       }
     },
+    "node_modules/vitest": {
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/vitest/-/vitest-4.1.2.tgz",
+      "integrity": "sha512-xjR1dMTVHlFLh98JE3i/f/WePqJsah4A0FK9cc8Ehp9Udk0AZk6ccpIZhh1qJ/yxVWRZ+Q54ocnD8TXmkhspGg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@vitest/expect": "4.1.2",
+        "@vitest/mocker": "4.1.2",
+        "@vitest/pretty-format": "4.1.2",
+        "@vitest/runner": "4.1.2",
+        "@vitest/snapshot": "4.1.2",
+        "@vitest/spy": "4.1.2",
+        "@vitest/utils": "4.1.2",
+        "es-module-lexer": "^2.0.0",
+        "expect-type": "^1.3.0",
+        "magic-string": "^0.30.21",
+        "obug": "^2.1.1",
+        "pathe": "^2.0.3",
+        "picomatch": "^4.0.3",
+        "std-env": "^4.0.0-rc.1",
+        "tinybench": "^2.9.0",
+        "tinyexec": "^1.0.2",
+        "tinyglobby": "^0.2.15",
+        "tinyrainbow": "^3.1.0",
+        "vite": "^6.0.0 || ^7.0.0 || ^8.0.0",
+        "why-is-node-running": "^2.3.0"
+      },
+      "bin": {
+        "vitest": "vitest.mjs"
+      },
+      "engines": {
+        "node": "^20.0.0 || ^22.0.0 || >=24.0.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/vitest"
+      },
+      "peerDependencies": {
+        "@edge-runtime/vm": "*",
+        "@opentelemetry/api": "^1.9.0",
+        "@types/node": "^20.0.0 || ^22.0.0 || >=24.0.0",
+        "@vitest/browser-playwright": "4.1.2",
+        "@vitest/browser-preview": "4.1.2",
+        "@vitest/browser-webdriverio": "4.1.2",
+        "@vitest/ui": "4.1.2",
+        "happy-dom": "*",
+        "jsdom": "*",
+        "vite": "^6.0.0 || ^7.0.0 || ^8.0.0"
+      },
+      "peerDependenciesMeta": {
+        "@edge-runtime/vm": {
+          "optional": true
+        },
+        "@opentelemetry/api": {
+          "optional": true
+        },
+        "@types/node": {
+          "optional": true
+        },
+        "@vitest/browser-playwright": {
+          "optional": true
+        },
+        "@vitest/browser-preview": {
+          "optional": true
+        },
+        "@vitest/browser-webdriverio": {
+          "optional": true
+        },
+        "@vitest/ui": {
+          "optional": true
+        },
+        "happy-dom": {
+          "optional": true
+        },
+        "jsdom": {
+          "optional": true
+        },
+        "vite": {
+          "optional": false
+        }
+      }
+    },
+    "node_modules/whatwg-mimetype": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/whatwg-mimetype/-/whatwg-mimetype-3.0.0.tgz",
+      "integrity": "sha512-nt+N2dzIutVRxARx1nghPKGv1xHikU7HKdfafKkLNLindmPU/ch3U31NOCGGA/dmPcmb1VlofO0vnKAcsm0o/Q==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/why-is-node-running": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/why-is-node-running/-/why-is-node-running-2.3.0.tgz",
+      "integrity": "sha512-hUrmaWBdVDcxvYqnyh09zunKzROWjbZTiNy8dBEjkS7ehEDQibXJ7XvlmtbwuTclUiIyN+CyXQD4Vmko8fNm8w==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "siginfo": "^2.0.0",
+        "stackback": "0.0.2"
+      },
+      "bin": {
+        "why-is-node-running": "cli.js"
+      },
+      "engines": {
+        "node": ">=8"
+      }
+    },
+    "node_modules/ws": {
+      "version": "8.20.0",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-8.20.0.tgz",
+      "integrity": "sha512-sAt8BhgNbzCtgGbt2OxmpuryO63ZoDk/sqaB/znQm94T4fCEsy/yV+7CdC1kJhOU9lboAEU7R3kquuycDoibVA==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=10.0.0"
+      },
+      "peerDependencies": {
+        "bufferutil": "^4.0.1",
+        "utf-8-validate": ">=5.0.2"
+      },
+      "peerDependenciesMeta": {
+        "bufferutil": {
+          "optional": true
+        },
+        "utf-8-validate": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/yallist": {
       "version": "3.1.1",
       "resolved": "https://registry.npmjs.org/yallist/-/yallist-3.1.1.tgz",
diff --git a/frontend/package.json b/frontend/package.json
index 7b52305..9300d43 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -6,7 +6,9 @@
   "scripts": {
     "dev": "vite",
     "build": "tsc -b && vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "dependencies": {
     "react": "^19.0.0",
@@ -15,10 +17,14 @@
     "react-router-dom": "^7.13.2"
   },
   "devDependencies": {
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
     "@types/react": "^19.0.0",
     "@types/react-dom": "^19.0.0",
     "@vitejs/plugin-react": "^4.3.0",
+    "happy-dom": "^20.8.9",
     "typescript": "~5.7.0",
-    "vite": "^6.2.0"
+    "vite": "^6.2.0",
+    "vitest": "^4.1.2"
   }
 }
diff --git a/frontend/src/api.test.ts b/frontend/src/api.test.ts
new file mode 100644
index 0000000..da6859f
--- /dev/null
+++ b/frontend/src/api.test.ts
@@ -0,0 +1,117 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { fetchConversations, fetchReplay, fetchAnalytics } from "./api";
+
+// Mock global fetch
+const mockFetch = vi.fn();
+vi.stubGlobal("fetch", mockFetch);
+
+beforeEach(() => {
+  mockFetch.mockReset();
+});
+
+function jsonResponse(body: unknown, status = 200): Response {
+  return {
+    ok: status >= 200 && status < 300,
+    status,
+    statusText: status === 200 ? "OK" : "Error",
+    json: () => Promise.resolve(body),
+  } as Response;
+}
+
+describe("fetchConversations", () => {
+  it("returns conversations page on success", async () => {
+    const data = {
+      conversations: [{ thread_id: "t1", created_at: "", last_activity: "", status: "active", total_tokens: 0, total_cost_usd: 0 }],
+      total: 1,
+      page: 1,
+      per_page: 20,
+    };
+    mockFetch.mockResolvedValue(jsonResponse({ success: true, data, error: null }));
+
+    const result = await fetchConversations();
+    expect(result.conversations).toHaveLength(1);
+    expect(result.total).toBe(1);
+    expect(mockFetch).toHaveBeenCalledWith("/api/conversations?page=1&per_page=20");
+  });
+
+  it("passes custom page and perPage", async () => {
+    mockFetch.mockResolvedValue(jsonResponse({ success: true, data: { conversations: [], total: 0, page: 2, per_page: 10 }, error: null }));
+
+    await fetchConversations(2, 10);
+    expect(mockFetch).toHaveBeenCalledWith("/api/conversations?page=2&per_page=10");
+  });
+
+  it("throws on HTTP error", async () => {
+    mockFetch.mockResolvedValue(jsonResponse({}, 500));
+
+    await expect(fetchConversations()).rejects.toThrow("API error 500");
+  });
+
+  it("throws on success=false with error message", async () => {
+    mockFetch.mockResolvedValue(jsonResponse({ success: false, data: null, error: "Database unavailable" }));
+
+    await expect(fetchConversations()).rejects.toThrow("Database unavailable");
+  });
+
+  it("throws unknown error when success=false with no message", async () => {
+    mockFetch.mockResolvedValue(jsonResponse({ success: false, data: null, error: null }));
+
+    await expect(fetchConversations()).rejects.toThrow("Unknown API error");
+  });
+});
+
+describe("fetchReplay", () => {
+  it("returns replay page on success", async () => {
+    const data = {
+      thread_id: "t1",
+      total_steps: 3,
+      page: 1,
+      per_page: 20,
+      steps: [{ step: 1, type: "message", content: "Hello", agent: null, tool: null, params: null, result: null, timestamp: "" }],
+    };
+    mockFetch.mockResolvedValue(jsonResponse({ success: true, data, error: null }));
+
+    const result = await fetchReplay("t1");
+    expect(result.total_steps).toBe(3);
+    expect(result.steps).toHaveLength(1);
+  });
+
+  it("encodes thread_id in URL", async () => {
+    mockFetch.mockResolvedValue(jsonResponse({ success: true, data: { thread_id: "a/b", total_steps: 0, page: 1, per_page: 20, steps: [] }, error: null }));
+
+    await fetchReplay("a/b");
+    expect(mockFetch).toHaveBeenCalledWith("/api/replay/a%2Fb?page=1&per_page=20");
+  });
+
+  it("throws on HTTP error", async () => {
+    mockFetch.mockResolvedValue(jsonResponse({}, 404));
+    await expect(fetchReplay("missing")).rejects.toThrow("API error 404");
+  });
+});
+
+describe("fetchAnalytics", () => {
+  it("returns analytics data on success", async () => {
+    const data = {
+      range: "7d",
+      total_conversations: 100,
+      resolution_rate: 0.75,
+      escalation_rate: 0.25,
+      avg_turns_per_conversation: 3.5,
+      avg_cost_per_conversation_usd: 0.03,
+      agent_usage: [],
+      interrupt_stats: { total: 0, approved: 0, rejected: 0, expired: 0 },
+    };
+    mockFetch.mockResolvedValue(jsonResponse({ success: true, data, error: null }));
+
+    const result = await fetchAnalytics("7d");
+    expect(result.total_conversations).toBe(100);
+    expect(result.range).toBe("7d");
+  });
+
+  it("uses default range", async () => {
+    mockFetch.mockResolvedValue(jsonResponse({ success: true, data: { range: "7d" }, error: null }));
+
+    await fetchAnalytics();
+    expect(mockFetch).toHaveBeenCalledWith("/api/analytics?range=7d");
+  });
+});
diff --git a/frontend/src/pages/DashboardPage.test.tsx b/frontend/src/pages/DashboardPage.test.tsx
new file mode 100644
index 0000000..141f7e3
--- /dev/null
+++ b/frontend/src/pages/DashboardPage.test.tsx
@@ -0,0 +1,70 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, waitFor } from "@testing-library/react";
+import { DashboardPage } from "./DashboardPage";
+
+vi.mock("../api", () => ({
+  fetchAnalytics: vi.fn(),
+}));
+
+import { fetchAnalytics } from "../api";
+const mockFetchAnalytics = vi.mocked(fetchAnalytics);
+
+beforeEach(() => {
+  mockFetchAnalytics.mockReset();
+});
+
+const MOCK_DATA = {
+  range: "30d",
+  total_conversations: 100,
+  resolution_rate: 0.75,
+  escalation_rate: 0.25,
+  avg_turns_per_conversation: 3.5,
+  avg_cost_per_conversation_usd: 0.03,
+  agent_usage: [{ agent: "order_agent", count: 50, percentage: 0.5 }],
+  interrupt_stats: { total: 10, approved: 8, rejected: 2, expired: 0 },
+};
+
+describe("DashboardPage", () => {
+  it("renders loading state initially", () => {
+    mockFetchAnalytics.mockReturnValue(new Promise(() => {})); // never resolves
+    render(<DashboardPage />);
+    expect(document.querySelector(".skeleton-box")).toBeTruthy();
+  });
+
+  it("renders data after successful fetch", async () => {
+    mockFetchAnalytics.mockResolvedValue(MOCK_DATA);
+    render(<DashboardPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText("100")).toBeInTheDocument();
+    });
+    expect(screen.getByText("75.0%")).toBeInTheDocument();
+    expect(screen.getByText("$0.03")).toBeInTheDocument();
+  });
+
+  it("renders error state on fetch failure", async () => {
+    mockFetchAnalytics.mockRejectedValue(new Error("Network error"));
+    render(<DashboardPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText("Failed to load analytics")).toBeInTheDocument();
+    });
+    expect(screen.getByText("Network error")).toBeInTheDocument();
+  });
+
+  it("renders empty state when data has zero conversations", async () => {
+    mockFetchAnalytics.mockResolvedValue({
+      ...MOCK_DATA,
+      total_conversations: 0,
+      agent_usage: [],
+      interrupt_stats: { total: 0, approved: 0, rejected: 0, expired: 0 },
+    });
+    render(<DashboardPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText("0")).toBeInTheDocument();
+    });
+    expect(screen.getByText("No agent activity recorded yet.")).toBeInTheDocument();
+    expect(screen.getByText("No interrupt events recorded yet.")).toBeInTheDocument();
+  });
+});
diff --git a/frontend/src/pages/ReplayListPage.test.tsx b/frontend/src/pages/ReplayListPage.test.tsx
new file mode 100644
index 0000000..f8ecb5b
--- /dev/null
+++ b/frontend/src/pages/ReplayListPage.test.tsx
@@ -0,0 +1,106 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, waitFor } from "@testing-library/react";
+import { MemoryRouter } from "react-router-dom";
+import { ReplayListPage } from "./ReplayListPage";
+
+vi.mock("../api", () => ({
+  fetchConversations: vi.fn(),
+}));
+
+import { fetchConversations } from "../api";
+const mockFetchConversations = vi.mocked(fetchConversations);
+
+beforeEach(() => {
+  mockFetchConversations.mockReset();
+});
+
+function renderWithRouter() {
+  return render(
+    <MemoryRouter>
+      <ReplayListPage />
+    </MemoryRouter>
+  );
+}
+
+describe("ReplayListPage", () => {
+  it("renders loading state initially", () => {
+    mockFetchConversations.mockReturnValue(new Promise(() => {}));
+    renderWithRouter();
+    expect(document.querySelector(".skeleton-box")).toBeTruthy();
+  });
+
+  it("renders empty state when no conversations", async () => {
+    mockFetchConversations.mockResolvedValue({
+      conversations: [],
+      total: 0,
+      page: 1,
+      per_page: 20,
+    });
+    renderWithRouter();
+
+    await waitFor(() => {
+      expect(screen.getByText("No conversations yet")).toBeInTheDocument();
+    });
+  });
+
+  it("renders conversation list on success", async () => {
+    mockFetchConversations.mockResolvedValue({
+      conversations: [
+        {
+          thread_id: "t1",
+          created_at: "2026-04-01T00:00:00Z",
+          last_activity: "2026-04-01T00:01:00Z",
+          status: "resolved",
+          total_tokens: 100,
+          total_cost_usd: 0.01,
+        },
+      ],
+      total: 1,
+      page: 1,
+      per_page: 20,
+    });
+    renderWithRouter();
+
+    await waitFor(() => {
+      expect(screen.getByText("t1")).toBeInTheDocument();
+    });
+    expect(screen.getByText("resolved")).toBeInTheDocument();
+  });
+
+  it("renders error state on fetch failure", async () => {
+    mockFetchConversations.mockRejectedValue(new Error("Server down"));
+    renderWithRouter();
+
+    await waitFor(() => {
+      expect(screen.getByText("Failed to load conversations")).toBeInTheDocument();
+    });
+    expect(screen.getByText("Server down")).toBeInTheDocument();
+  });
+
+  it("applies correct status badge classes", async () => {
+    mockFetchConversations.mockResolvedValue({
+      conversations: [
+        { thread_id: "t1", created_at: "", last_activity: "", status: "resolved", total_tokens: 0, total_cost_usd: 0 },
+        { thread_id: "t2", created_at: "", last_activity: "", status: "escalated", total_tokens: 0, total_cost_usd: 0 },
+        { thread_id: "t3", created_at: "", last_activity: "", status: null, total_tokens: 0, total_cost_usd: 0 },
+      ],
+      total: 3,
+      page: 1,
+      per_page: 20,
+    });
+    renderWithRouter();
+
+    await waitFor(() => {
+      expect(screen.getByText("resolved")).toBeInTheDocument();
+    });
+
+    const resolvedBadge = screen.getByText("resolved");
+    expect(resolvedBadge.className).toContain("status-badge--resolved");
+
+    const escalatedBadge = screen.getByText("escalated");
+    expect(escalatedBadge.className).toContain("status-badge--escalated");
+
+    const activeBadge = screen.getByText("active");
+    expect(activeBadge.className).toContain("status-badge--active");
+  });
+});
diff --git a/frontend/src/pages/ReplayPage.test.tsx b/frontend/src/pages/ReplayPage.test.tsx
new file mode 100644
index 0000000..5345daa
--- /dev/null
+++ b/frontend/src/pages/ReplayPage.test.tsx
@@ -0,0 +1,85 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, waitFor } from "@testing-library/react";
+import { MemoryRouter, Route, Routes } from "react-router-dom";
+import { ReplayPage } from "./ReplayPage";
+
+vi.mock("../api", () => ({
+  fetchReplay: vi.fn(),
+}));
+
+vi.mock("../components/ReplayTimeline", () => ({
+  ReplayTimeline: ({ steps }: { steps: unknown[] }) => (
+    <div data-testid="replay-timeline">{steps.length} steps</div>
+  ),
+}));
+
+import { fetchReplay } from "../api";
+const mockFetchReplay = vi.mocked(fetchReplay);
+
+beforeEach(() => {
+  mockFetchReplay.mockReset();
+});
+
+function renderWithRoute(threadId: string) {
+  return render(
+    <MemoryRouter initialEntries={[`/replay/${threadId}`]}>
+      <Routes>
+        <Route path="/replay/:threadId" element={<ReplayPage />} />
+      </Routes>
+    </MemoryRouter>
+  );
+}
+
+describe("ReplayPage", () => {
+  it("renders loading state initially", () => {
+    mockFetchReplay.mockReturnValue(new Promise(() => {}));
+    renderWithRoute("t1");
+    expect(document.querySelector(".skeleton-box")).toBeTruthy();
+  });
+
+  it("renders replay steps on success", async () => {
+    mockFetchReplay.mockResolvedValue({
+      thread_id: "t1",
+      total_steps: 2,
+      page: 1,
+      per_page: 100,
+      steps: [
+        { step: 1, type: "message", content: "Hello", agent: null, tool: null, params: null, result: null, timestamp: "2026-04-01T00:00:00Z" },
+        { step: 2, type: "response", content: "Hi!", agent: "bot", tool: null, params: null, result: null, timestamp: "2026-04-01T00:00:01Z" },
+      ],
+    });
+    renderWithRoute("t1");
+
+    await waitFor(() => {
+      expect(screen.getByTestId("replay-timeline")).toBeInTheDocument();
+    });
+    expect(screen.getByText("2 steps")).toBeInTheDocument();
+    // Thread ID appears in multiple places (header + sidebar)
+    expect(screen.getAllByText("t1").length).toBeGreaterThan(0);
+  });
+
+  it("renders empty state when no steps", async () => {
+    mockFetchReplay.mockResolvedValue({
+      thread_id: "t1",
+      total_steps: 0,
+      page: 1,
+      per_page: 100,
+      steps: [],
+    });
+    renderWithRoute("t1");
+
+    await waitFor(() => {
+      expect(screen.getByText("No replay steps found")).toBeInTheDocument();
+    });
+  });
+
+  it("renders error state on fetch failure", async () => {
+    mockFetchReplay.mockRejectedValue(new Error("Not found"));
+    renderWithRoute("t1");
+
+    await waitFor(() => {
+      expect(screen.getByText("Failed to load replay")).toBeInTheDocument();
+    });
+    expect(screen.getByText("Not found")).toBeInTheDocument();
+  });
+});
diff --git a/frontend/src/test-setup.ts b/frontend/src/test-setup.ts
new file mode 100644
index 0000000..f149f27
--- /dev/null
+++ b/frontend/src/test-setup.ts
@@ -0,0 +1 @@
+import "@testing-library/jest-dom/vitest";
diff --git a/frontend/tsconfig.tsbuildinfo b/frontend/tsconfig.tsbuildinfo
index b2985de..d0632af 100644
--- a/frontend/tsconfig.tsbuildinfo
+++ b/frontend/tsconfig.tsbuildinfo
@@ -1 +1 @@
-{"root":["./src/app.tsx","./src/api.ts","./src/main.tsx","./src/types.ts","./src/vite-env.d.ts","./src/components/agentaction.tsx","./src/components/chatinput.tsx","./src/components/chatmessages.tsx","./src/components/errorbanner.tsx","./src/components/interruptprompt.tsx","./src/components/layout.tsx","./src/components/metriccard.tsx","./src/components/navbar.tsx","./src/components/replaytimeline.tsx","./src/hooks/usewebsocket.ts","./src/pages/chatpage.tsx","./src/pages/dashboardpage.tsx","./src/pages/replaylistpage.tsx","./src/pages/replaypage.tsx","./src/pages/reviewpage.tsx"],"version":"5.7.3"}
\ No newline at end of file
+{"root":["./src/app.tsx","./src/api.test.ts","./src/api.ts","./src/main.tsx","./src/test-setup.ts","./src/types.ts","./src/vite-env.d.ts","./src/components/agentaction.tsx","./src/components/chatinput.tsx","./src/components/chatmessages.tsx","./src/components/errorbanner.tsx","./src/components/interruptprompt.tsx","./src/components/layout.tsx","./src/components/metriccard.tsx","./src/components/navbar.tsx","./src/components/replaytimeline.tsx","./src/hooks/usewebsocket.ts","./src/pages/chatpage.tsx","./src/pages/dashboardpage.test.tsx","./src/pages/dashboardpage.tsx","./src/pages/replaylistpage.test.tsx","./src/pages/replaylistpage.tsx","./src/pages/replaypage.test.tsx","./src/pages/replaypage.tsx","./src/pages/reviewpage.tsx"],"version":"5.7.3"}
\ No newline at end of file
diff --git a/frontend/vite.config.ts b/frontend/vite.config.ts
index 7f1ee01..e94eefa 100644
--- a/frontend/vite.config.ts
+++ b/frontend/vite.config.ts
@@ -1,8 +1,14 @@
+/// <reference types="vitest" />
 import react from "@vitejs/plugin-react";
 import { defineConfig } from "vite";
 
 export default defineConfig({
   plugins: [react()],
+  test: {
+    environment: "happy-dom",
+    globals: true,
+    setupFiles: ["./src/test-setup.ts"],
+  },
   server: {
     port: 5173,
     proxy: {