diff --git a/memory-bank/change-log.md b/memory-bank/change-log.md
index 4ccccdb5..9808613a 100644
--- a/memory-bank/change-log.md
+++ b/memory-bank/change-log.md
@@ -2602,3 +2602,40 @@ Validation:
 Follow-ups:
 
 - Optional next widened slice: add a focused phase22 behavioral suite for `caseDirectService` and normalize any remaining specialized encoding usage behind explicit helper options where appropriate.
+
+---
+
+### CL-073: TASK22260 essential condensed slice — case phase22 behavioural coverage + encoding contract lock
+
+date: 2026-03-25
+author: Cline
+scope: `tests/phase22/{case-service-behaviour,index}.test.cjs`
+type: change
+rationale: Condense remaining core work into one essential slice by adding explicit phase22 behavioural coverage for `caseDirectService` route composition and encoding-sensitive contracts.
+impact: Improves regression confidence for case service route-building behavior (BASE_URL composition, case-reference encoding/escaping, error-return contracts) without runtime behavior changes.
+status: completed
+
+Summary:
+
+- Added new suite `tests/phase22/case-service-behaviour.test.cjs` with focused behavioural assertions for:
+    - `getPortalModuleDetails` BASE_URL + encoded case reference composition
+    - `getPortalModuleDetailsProxy` apostrophe escape behavior in case reference
+    - `getAppealID` query composition and non-underscore value extraction
+    - `getAppealPDFDocument` failure-path logging + `error.response` passthrough
+- Updated `tests/phase22/index.test.cjs` aggregate runner to include `case-service-behaviour` suite.
+
+Validation:
+
+- `node tests/phase22/index.test.cjs` -> pass
+    - core-token: 2/2
+    - client-utils: 6/6
+    - file-client: 4/4
+    - case-service: 4/4
+    - phase22 combined: pass
+- `node tests/phase6/service-behaviour.test.cjs` -> pass (9/9)
+- `node tests/phase7/service-behaviour.test.cjs` -> pass (13/13)
+- `npm run lint` -> warnings only (pre-existing `react-hooks/exhaustive-deps`; no new lint errors)
+
+Follow-ups:
+
+- Optional closure slice: add a dedicated phase22 portal-service behavioural suite and finish harmonization of remaining direct query string composition in `portalDirectService` write helpers.
diff --git a/tests/phase22/case-service-behaviour.test.cjs b/tests/phase22/case-service-behaviour.test.cjs
new file mode 100644
index 00000000..5c37e232
--- /dev/null
+++ b/tests/phase22/case-service-behaviour.test.cjs
@@ -0,0 +1,130 @@
+const assert = require("assert");
+const {
+    createAxiosMock,
+    createLoggerMock,
+    createAxiosError,
+    loadServiceModule,
+    normalize
+} = require("../serviceHarness.cjs");
+
+const tests = [];
+const test = (name, fn) => tests.push({ name, fn });
+
+test("case/getPortalModuleDetails uses BASE_URL route and encoded case reference", async () => {
+    const axios = createAxiosMock();
+    const logger = createLoggerMock();
+
+    axios.getHandler = async () => ({ data: { value: [] } });
+
+    const caseService = loadServiceModule("caseDirectService.js", {
+        axios,
+        BASE_URL: "http://example.local",
+        consoleLogger: logger.consoleLogger
+    });
+
+    const result = await caseService.getPortalModuleDetails(
+        "appeal",
+        "REF A/B"
+    );
+
+    assert.deepStrictEqual(normalize(result), { value: [] });
+    assert.strictEqual(
+        axios.calls[0].url,
+        "http://example.local/api/endpoint/getportalmoduledetails_api?appealType=appeal&caseReference=REF%20A/B"
+    );
+});
+
+test("case/getPortalModuleDetailsProxy escapes apostrophes in case reference", async () => {
+    const axios = createAxiosMock();
+    const logger = createLoggerMock();
+
+    axios.getHandler = async () => ({ data: { value: [] } });
+
+    const caseService = loadServiceModule("caseDirectService.js", {
+        axios,
+        BASE_URL: "",
+        consoleLogger: logger.consoleLogger
+    });
+
+    const result = await caseService.getPortalModuleDetailsProxy(
+        "appeal",
+        "REF'O"
+    );
+
+    assert.deepStrictEqual(normalize(result), { value: [] });
+    assert.strictEqual(
+        axios.calls[0].url,
+        "/api/endpoint/getportalmoduledetailsproxy_api?appealType=appeal&caseReference=REF''O"
+    );
+});
+
+test("case/getAppealID composes lookup route and extracts first non-underscore value", async () => {
+    const axios = createAxiosMock();
+    const logger = createLoggerMock();
+
+    axios.getHandler = async () => ({
+        data: {
+            value: [
+                {
+                    _internal: "ignore",
+                    pinswg_appeal: "appeal-123"
+                }
+            ]
+        }
+    });
+
+    const caseService = loadServiceModule("caseDirectService.js", {
+        axios,
+        BASE_URL: "",
+        consoleLogger: logger.consoleLogger
+    });
+
+    const result = await caseService.getAppealID("REF-1", "pinswg_cases", "id");
+
+    assert.strictEqual(result, "appeal-123");
+    assert.strictEqual(
+        axios.calls[0].url,
+        "/api/endpoint/getappealid_api?updateFormCollection=pinswg_cases&primaryAttribute=id&caseReference=REF-1"
+    );
+});
+
+test("case/getAppealPDFDocument logs and returns error.response on failure", async () => {
+    const axios = createAxiosMock();
+    const logger = createLoggerMock();
+    const error = createAxiosError(404, "Not Found");
+
+    axios.getHandler = async () => Promise.reject(error);
+
+    const caseService = loadServiceModule("caseDirectService.js", {
+        axios,
+        BASE_URL: "http://example.local",
+        consoleLogger: logger.consoleLogger
+    });
+
+    const result = await caseService.getAppealPDFDocument("inc-123");
+
+    assert.strictEqual(result, error.response);
+    assert.strictEqual(logger.calls.length, 1);
+});
+
+const run = async () => {
+    let passed = 0;
+
+    for (const currentTest of tests) {
+        await currentTest.fn();
+        passed += 1;
+    }
+
+    console.log(
+        `Phase 22 case-service tests passed (${passed}/${tests.length}).`
+    );
+};
+
+module.exports = run;
+
+if (require.main === module) {
+    run().catch((error) => {
+        console.error(error);
+        process.exit(1);
+    });
+}
diff --git a/tests/phase22/index.test.cjs b/tests/phase22/index.test.cjs
index 976bf9ee..bacc8e98 100644
--- a/tests/phase22/index.test.cjs
+++ b/tests/phase22/index.test.cjs
@@ -1,11 +1,13 @@
 const runCoreTokenTests = require("./core-token-behaviour.test.cjs");
 const runClientUtilsTests = require("./client-utils-behaviour.test.cjs");
 const runFileClientTests = require("./file-client-behaviour.test.cjs");
+const runCaseServiceTests = require("./case-service-behaviour.test.cjs");
 
 const run = async () => {
     await runCoreTokenTests();
     await runClientUtilsTests();
     await runFileClientTests();
+    await runCaseServiceTests();
     console.log("Phase 22 combined suite passed.");
 };