diff --git a/tests/cline-beforetool-upgrade.test.cjs b/tests/cline-beforetool-upgrade.test.cjs
new file mode 100644
index 000000000..08cb90491
--- /dev/null
+++ b/tests/cline-beforetool-upgrade.test.cjs
@@ -0,0 +1,166 @@
+'use strict';
+
+/**
+ * cline beforeTool plugin UPGRADE — ADR-1239 / #2090 AC (upgrade 1).
+ *
+ * Proves the `.clinerules/hooks/PreToolUse` file-convention planning-artifact
+ * guard is re-implemented as a real Cline SDK `AgentPlugin.hooks.beforeTool`
+ * handler, delivered through the negotiated `hookBus: host` interface point.
+ * Guard semantics are preserved EXACTLY from the PreToolUse script: fail-open,
+ * cancel (skip) write-class calls targeting `.planning/`, pass through
+ * everything else.
+ *
+ * The adapter is exercised directly (mocked SDK payload shape) since the real
+ * `@cline/sdk` is a fast-moving package set not linked at test time — same
+ * pattern as the VS Code reference binding (tests/fixtures/vscode-host-binding.cjs).
+ *
+ * Cite:
+ *   https://github.com/cline/cline/blob/main/docs/sdk/plugins.mdx
+ *     — "Lifecycle hooks ... include beforeRun, afterRun, beforeModel,
+ *        afterModel, beforeTool, afterTool, and onEvent."
+ *   https://github.com/cline/cline/blob/main/sdk/packages/agents/README.md
+ *     — beforeTool({ tool, input }) => { skip: true, reason } | undefined
+ */
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+
+const {
+  WRITE_TOOL_PATTERN,
+  PLANNING_PATH_PATTERN,
+  PLANNING_GUARD_REASON,
+  evaluateBeforeTool,
+  clineGsdPlugin,
+} = require('../gsd-core/bin/lib/host-integration-adapters/cline-sdk-binding.cjs');
+
+// -- upgrade 1: write-class detection ---------------------------------------
+
+test('WRITE_TOOL_PATTERN matches the write-class tool verbs (parity with PreToolUse)', () => {
+  const writeVerbs = ['write_to_file', 'edit_file', 'replace_in_file', 'create_file',
+    'delete_file', 'remove_file', 'append_to_file', 'apply_patch', 'insert_edit', 'mkdir'];
+  for (const v of writeVerbs) {
+    assert.ok(WRITE_TOOL_PATTERN.test(v), `write-class verb must match: ${v}`);
+  }
+});
+
+test('WRITE_TOOL_PATTERN does NOT match read-class tools', () => {
+  const readVerbs = ['read_file', 'list_files', 'search_files', 'execute_command', 'ask_user'];
+  for (const v of readVerbs) {
+    assert.ok(!WRITE_TOOL_PATTERN.test(v), `read-class verb must NOT match: ${v}`);
+  }
+});
+
+// -- upgrade 1: planning-path detection -------------------------------------
+
+test('PLANNING_PATH_PATTERN matches .planning/ paths on posix + windows separators', () => {
+  const planningPaths = ['.planning/state.md', '.planning/phases/1/PLAN.md',
+    '/home/u/proj/.planning/config.json', 'proj\\.planning\\foo', './.planning/x'];
+  for (const p of planningPaths) {
+    assert.ok(PLANNING_PATH_PATTERN.test(p), `planning path must match: ${p}`);
+  }
+});
+
+test('PLANNING_PATH_PATTERN does NOT match non-planning paths', () => {
+  const other = ['src/planning-utils.ts', 'docs/plan.md', '.planning-readme.txt'];
+  // .planning-readme.txt must not match (boundary after .planning required)
+  for (const p of ['src/planning-utils.ts', 'docs/plan.md']) {
+    assert.ok(!PLANNING_PATH_PATTERN.test(p), `non-planning path must NOT match: ${p}`);
+  }
+});
+
+// -- upgrade 1: evaluateBeforeTool — the guard decision ----------------------
+
+test('write-class tool targeting .planning/ is SKIPPED (cancel)', () => {
+  const result = evaluateBeforeTool({
+    tool: { name: 'write_to_file' },
+    input: { path: '.planning/phases/1/PLAN.md', content: '...' },
+  });
+  assert.equal(result.decision, 'skip');
+  assert.equal(result.reason, PLANNING_GUARD_REASON);
+});
+
+test('write-class tool targeting a NON-planning path is ALLOWED', () => {
+  const result = evaluateBeforeTool({
+    tool: { name: 'write_to_file' },
+    input: { path: 'src/index.ts', content: '...' },
+  });
+  assert.equal(result.decision, 'allow');
+  assert.equal(result.reason, undefined);
+});
+
+test('read-class tool targeting .planning/ is ALLOWED (reads are safe)', () => {
+  const result = evaluateBeforeTool({
+    tool: { name: 'read_file' },
+    input: { path: '.planning/state.md' },
+  });
+  assert.equal(result.decision, 'allow');
+});
+
+test('write tool with .planning/ in a non-PATH field (content body) is ALLOWED', () => {
+  // A doc that merely mentions ".planning/" in its body is never falsely blocked —
+  // only PATH-bearing field values are inspected (parity with PreToolUse).
+  const result = evaluateBeforeTool({
+    tool: { name: 'write_to_file' },
+    input: { path: 'docs/guide.md', content: 'see .planning/ for details' },
+  });
+  assert.equal(result.decision, 'allow');
+});
+
+test('write tool with .planning/ in an array of paths is SKIPPED', () => {
+  const result = evaluateBeforeTool({
+    tool: { name: 'apply_patch' },
+    input: { paths: ['src/a.ts', '.planning/config.json'] },
+  });
+  assert.equal(result.decision, 'skip');
+});
+
+// -- upgrade 1: fail-open on malformed/missing input ------------------------
+
+test('evaluateBeforeTool fails OPEN on null tool/input (never throws, never blocks)', () => {
+  assert.equal(evaluateBeforeTool({ tool: null, input: null }).decision, 'allow');
+  assert.equal(evaluateBeforeTool({}).decision, 'allow');
+  assert.equal(evaluateBeforeTool(null).decision, 'allow');
+});
+
+test('evaluateBeforeTool fails OPEN on a tool with no name', () => {
+  assert.equal(evaluateBeforeTool({ tool: {}, input: { path: '.planning/x' } }).decision, 'allow');
+});
+
+// -- upgrade 1: the AgentPlugin wrapper shape -------------------------------
+
+test('clineGsdPlugin is an AgentPlugin with a beforeTool hook', () => {
+  assert.equal(typeof clineGsdPlugin, 'object');
+  assert.equal(clineGsdPlugin.name, 'gsd-planning-guard');
+  assert.equal(typeof clineGsdPlugin.setup, 'function');
+});
+
+test('clineGsdPlugin.setup returns hooks.beforeTool that maps skip→{skip,reason}', () => {
+  const { hooks } = clineGsdPlugin.setup({ agentId: 'test-agent' });
+  assert.equal(typeof hooks.beforeTool, 'function');
+  // planning write → { skip: true, reason }
+  const blocked = hooks.beforeTool({
+    tool: { name: 'write_to_file' },
+    input: { path: '.planning/state.md' },
+  });
+  assert.deepEqual(blocked, { skip: true, reason: PLANNING_GUARD_REASON });
+});
+
+test('clineGsdPlugin.beforeTool returns undefined for allowed calls (SDK contract)', () => {
+  const { hooks } = clineGsdPlugin.setup({ agentId: 'test-agent' });
+  const allowed = hooks.beforeTool({
+    tool: { name: 'write_to_file' },
+    input: { path: 'src/foo.ts' },
+  });
+  assert.equal(allowed, undefined, 'undefined = allow (Cline SDK beforeTool contract)');
+});
+
+// -- upgrade 1: parity with the existing PreToolUse script semantics --------
+
+test('the guard reason matches the PreToolUse script errorMessage contract', () => {
+  // The file-convention hook wrote { cancel:true, errorMessage:'GSD: ...' }.
+  // The SDK plugin maps cancel→skip and errorMessage→reason. The user-visible
+  // message text is preserved so the guard behaves identically to the user.
+  assert.ok(typeof PLANNING_GUARD_REASON === 'string' && PLANNING_GUARD_REASON.length > 0);
+  assert.ok(PLANNING_GUARD_REASON.includes('.planning/'),
+    'reason must explain the .planning/ protection so the user can act on it');
+});
diff --git a/tests/cline-dispatch-degradation.test.cjs b/tests/cline-dispatch-degradation.test.cjs
new file mode 100644
index 000000000..1b8b9707e
--- /dev/null
+++ b/tests/cline-dispatch-degradation.test.cjs
@@ -0,0 +1,101 @@
+'use strict';
+
+/**
+ * cline dispatch DEGRADATION — ADR-1239 / #2090.
+ *
+ * Proves cline's dispatch STAYS degraded/flat and is NEVER silently upgraded to
+ * the programmatic-cli profile baseline's full nested/background dispatch.
+ * Cline's own docs (docs/features/subagents.mdx) restrict subagents to a single
+ * level, read-only toolkit, no nested spawning — so claiming full dispatch would
+ * misrepresent a documented host restriction and violate the fail-closed
+ * negotiation contract. This is the cline counterpart to cursor's dispatch
+ * UPGRADE (#2089), asserting the OPPOSITE invariant: cline flattens.
+ *
+ * Cite:
+ *   https://github.com/cline/cline/blob/main/docs/features/subagents.mdx
+ *     — "subagents are restricted from editing files, using the browser,
+ *        accessing MCP servers, or creating nested subagents."
+ *   https://github.com/cline/cline/blob/main/docs/features/subagents.mdx
+ *     — "They are explicitly prohibited from ... spawning other subagents."
+ */
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const {
+  shouldFlattenDispatch,
+  degradationFor,
+} = require('../gsd-core/bin/lib/host-integration.cjs');
+
+const CLN_CAP = JSON.parse(
+  fs.readFileSync(path.join(__dirname, '..', 'capabilities', 'cline', 'capability.json'), 'utf8'),
+);
+const CLN_DISPATCH = CLN_CAP.runtime.hostIntegration.dispatch;
+
+// -- cline dispatch axes: documented restrictions ----------------------------
+
+test('cline dispatch declares namedDispatch but NOT nested (single-level only)', () => {
+  assert.equal(CLN_DISPATCH.namedDispatch, true,
+    'cite agents-squad example — start_subagent(preset:..., task:...) named dispatch');
+  assert.equal(CLN_DISPATCH.nested, false,
+    'cite subagents.mdx — subagents cannot create nested subagents');
+});
+
+test('cline dispatch respects maxDepth: 1 (the documented hard limit)', () => {
+  assert.equal(CLN_DISPATCH.maxDepth, 1,
+    'cite subagents.mdx — "explicitly prohibited from ... spawning other subagents"');
+});
+
+test('cline subagentToolkit is read-only (no write/browser/mcp for subagents)', () => {
+  assert.equal(CLN_DISPATCH.subagentToolkit, 'read-only',
+    'cite subagents.mdx — "strictly limited to read-only operations"');
+});
+
+test('cline backgroundDispatch is false (background commands run, but no nested-dispatch)', () => {
+  assert.equal(CLN_DISPATCH.background, true,
+    'cite subagents.mdx — "Commands executed by subagents run in the background"');
+  assert.equal(CLN_DISPATCH.backgroundDispatch, false,
+    'cite subagents.mdx — cannot spawn nested subagents from a background context');
+});
+
+// -- shouldFlattenDispatch: cline MUST flatten (degraded) --------------------
+
+test('shouldFlattenDispatch(cline) is true — waves run inline (the #853 rule)', () => {
+  assert.equal(shouldFlattenDispatch(CLN_DISPATCH), true,
+    'cline has backgroundDispatch:false → GSD must force-flatten (run inline)');
+});
+
+test('a hypothetical full-upgrade (backgroundDispatch:true) would NOT flatten — proving the discriminator', () => {
+  const hypothetical = { ...CLN_DISPATCH, backgroundDispatch: true, nested: true, maxDepth: 2, subagentToolkit: 'full' };
+  assert.equal(shouldFlattenDispatch(hypothetical), false,
+    'only background:true AND backgroundDispatch:true escapes flattening — cline lacks both');
+});
+
+// -- degradationFor: cline dispatch is 'degraded' / flat ---------------------
+
+test('degradationFor("dispatch", cline) is degraded with the flat-dispatch fallback', () => {
+  const result = degradationFor('dispatch', CLN_CAP.runtime.hostIntegration);
+  assert.equal(result.level, 'degraded',
+    'maxDepth:1 (flat) is a degraded dispatch surface, never full');
+  assert.equal(result.fallback, 'flat dispatch — waves run inline');
+  assert.notEqual(result.level, 'full',
+    'cline dispatch must NEVER be classified as full — that would misrepresent the host');
+});
+
+test('cline dispatch is never silently upgraded to the programmatic-cli baseline', () => {
+  // The full baseline requires nested + maxDepth>=2 + subagentToolkit 'full'.
+  // Cline violates ALL three (nested:false, maxDepth:1, read-only) — so it must
+  // stay degraded regardless of any negotiation defaults.
+  const result = degradationFor('dispatch', CLN_CAP.runtime.hostIntegration);
+  assert.notEqual(result.level, 'full');
+});
+
+// -- boundary: maxDepth 1 vs 0 vs -1 ----------------------------------------
+
+test('maxDepth 1 is flat (NOT absent, NOT unbounded)', () => {
+  assert.ok(CLN_DISPATCH.maxDepth > 0, 'maxDepth must be positive (not absent/single-agent)');
+  assert.notEqual(CLN_DISPATCH.maxDepth, -1, 'cline is NOT unbounded — depth-1 is the documented limit');
+  assert.notEqual(CLN_DISPATCH.maxDepth, 0, 'maxDepth:0 would mean no named dispatch — cline HAS named dispatch');
+});
diff --git a/tests/cline-imperative-reference.test.cjs b/tests/cline-imperative-reference.test.cjs
new file mode 100644
index 000000000..aa475be80
--- /dev/null
+++ b/tests/cline-imperative-reference.test.cjs
@@ -0,0 +1,114 @@
+// allow-test-rule: AC2 requires asserting no `runtime === 'cline'` string-equality branch remains in bin/install.js/src — the descriptor-migration contract is a property of the source text, so a source-grep is the only faithful check (#2090)
+'use strict';
+
+/**
+ * cline imperative reference host — ADR-1239 Phase D / #2090 (EoS/cline).
+ *
+ * Proves cline is driven through the PUBLIC Host-Integration Interface (the
+ * imperative adapter), that its negotiated axes classify + negotiate correctly,
+ * that negotiation fails CLOSED on a corrupted descriptor, that the
+ * Context7-sourced dispatch classification STAYS degraded/flat (cline subagents
+ * are documented as single-level read-only — maxDepth:1 — and must never be
+ * silently upgraded to full nested/background dispatch), and that the migration
+ * retired the hardcoded `runtime === 'cline'` / `isCline` branches (folded into
+ * descriptor-driven `runtime.hostBehaviors`).
+ *
+ * Contrast with cursor (#2089): cursor's dispatch got an UPGRADE (background +
+ * nested). cline's dispatch is a deliberate DEGRADATION that must be preserved —
+ * upgrading it would misrepresent a documented host restriction and violate the
+ * fail-closed negotiation contract (see dispatch-degradation test).
+ */
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const { createImperativeAdapter } = require('../gsd-core/bin/lib/adapter-imperative.cjs');
+const {
+  profileOf,
+  negotiateHostCapabilities,
+  shouldFlattenDispatch,
+  PROFILE_BASELINES,
+  UNDOCUMENTED,
+} = require('../gsd-core/bin/lib/host-integration.cjs');
+
+const CLN_CAP = JSON.parse(
+  fs.readFileSync(path.join(__dirname, '..', 'capabilities', 'cline', 'capability.json'), 'utf8'),
+);
+const CLN_AXES = CLN_CAP.runtime.hostIntegration;
+
+// -- AC2: driven through the public interface (imperative adapter) -----------
+
+test('createImperativeAdapter classifies cline as imperative + composes the registry', () => {
+  const adapter = createImperativeAdapter({ runtime: 'cline' });
+  assert.equal(adapter.kind, 'imperative');
+  assert.equal(adapter.runtime, 'cline');
+  assert.ok(adapter.registry && typeof adapter.registry === 'object');
+  assert.equal(typeof adapter.install, 'function');
+  assert.equal(typeof adapter.uninstall, 'function');
+});
+
+test('cline axes classify as the programmatic-cli reference profile (imperative embedding)', () => {
+  assert.equal(profileOf(CLN_AXES), 'programmatic-cli');
+});
+
+// -- AC3: all axes populated + validated -------------------------------------
+
+test('cline descriptor declares all 8 axes + 6 dispatch sub-axes (no undocumented)', () => {
+  assert.equal(CLN_AXES.embeddingMode, 'imperative');
+  assert.equal(CLN_AXES.commandSurface, 'slash-file');
+  assert.equal(CLN_AXES.modelMode, 'active');
+  assert.equal(CLN_AXES.hookBus, 'host');
+  assert.equal(CLN_AXES.stateIO, 'filesystem');
+  assert.equal(CLN_AXES.transport, 'mcp');
+  assert.equal(CLN_AXES.runtime, 'node');
+  const d = CLN_AXES.dispatch;
+  assert.equal(d.namedDispatch, true);
+  assert.equal(d.nested, false);
+  assert.equal(d.maxDepth, 1);
+  assert.equal(d.background, true);
+  assert.equal(d.subagentToolkit, 'read-only');
+  assert.equal(d.backgroundDispatch, false);
+});
+
+// -- AC5: negotiation fails CLOSED on a corrupted descriptor ------------------
+
+test('negotiateHostCapabilities never throws for cline, even fully corrupted', () => {
+  assert.doesNotThrow(() => negotiateHostCapabilities({}));
+  assert.doesNotThrow(() => negotiateHostCapabilities({ ...CLN_AXES, embeddingMode: UNDOCUMENTED }));
+  assert.doesNotThrow(() => negotiateHostCapabilities({ ...CLN_AXES, embeddingMode: 'future-unknown' }));
+});
+
+test('a partial/empty cline descriptor degrades to the safe floor, not the programmatic-cli baseline', () => {
+  const result = negotiateHostCapabilities({});
+  assert.equal(result.effective.embeddingMode, 'declarative', 'omitted embeddingMode degrades closed');
+  assert.equal(result.effective.hookBus, 'none');
+  assert.notDeepEqual(result.effective, PROFILE_BASELINES['programmatic-cli']);
+  assert.ok(result.warnings.length > 0);
+});
+
+// -- AC2: the hardcoded branches are retired ---------------------------------
+
+test('cline descriptor declares runtime.hostBehaviors (the folded-in behaviors)', () => {
+  const hb = CLN_CAP.runtime.hostBehaviors;
+  assert.ok(hb && typeof hb === 'object');
+  assert.equal(hb.reapplyCommand, '/gsd-update --reapply');
+  assert.equal(hb.frontmatterDialect, 'cline');
+  assert.equal(hb.skipSharedHooksInstall, true);
+  assert.equal(hb.localTargetIsProjectRoot, true);
+  assert.equal(hb.clineRulesSurface, true);
+  assert.equal(hb.localCommandsViaRules, true);
+});
+
+test('no `runtime === "cline"` string-equality branch remains in the install source (AC2)', () => {
+  const strip = (src) => src
+    .replace(/\/\*[\s\S]*?\*\//g, '')
+    .replace(/\/\/[^\r\n]*/g, '')
+    .replace(/`[^`]*`/g, '');
+  for (const rel of ['bin/install.js', 'src/install-engine.cts', 'src/runtime-artifact-conversion.cts', 'src/runtime-hooks-surface.cts']) {
+    const src = fs.readFileSync(path.join(__dirname, '..', rel), 'utf8');
+    const offenders = strip(src).match(/runtime\s*[!=]==\s*'cline'/g) || [];
+    assert.deepEqual(offenders, [], `AC2: no hardcoded runtime==='cline' branch may remain in ${rel}; found: ${offenders.join(', ')}`);
+  }
+});
diff --git a/tests/cline-model-override-upgrade.test.cjs b/tests/cline-model-override-upgrade.test.cjs
new file mode 100644
index 000000000..458d9207a
--- /dev/null
+++ b/tests/cline-model-override-upgrade.test.cjs
@@ -0,0 +1,161 @@
+'use strict';
+
+/**
+ * cline createAgentModel UPGRADE — ADR-1239 / #2090 AC (upgrade 2).
+ *
+ * Proves GSD's per-subagent `model_overrides` / `model_profile_overrides`
+ * resolution (already used for OpenCode/Codex) now applies to cline subagents
+ * via `DefaultGateway.createAgentModel({ providerId, modelId })`, instead of
+ * leaving model selection untouched. Cline's `modelMode: active` (the host
+ * exposes provider registration via createLlmsRuntime) is what makes this
+ * wiring possible — passive hosts can only inject a per-agent model field.
+ *
+ * The binding resolves the createAgentModel call parameters from GSD config;
+ * the real gateway call is the host's responsibility (mocked here, same pattern
+ * as tests/fixtures/vscode-host-binding.cjs).
+ *
+ * Cite:
+ *   https://github.com/cline/cline/blob/main/docs/sdk/reference/gateway.mdx
+ *     — createAgentModel({ providerId, modelId }) returns an AgentModel
+ *   https://github.com/cline/cline/blob/main/sdk/packages/llms/README.md
+ *     — createLlmsRuntime(...) provider registry (modelMode: active)
+ */
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+
+const {
+  resolveClineAgentModelParams,
+  inferProviderId,
+  DEFAULT_CLINE_PROVIDER_ID,
+} = require('../gsd-core/bin/lib/host-integration-adapters/cline-sdk-binding.cjs');
+
+// -- upgrade 2: provider inference from a model id --------------------------
+
+test('inferProviderId maps anthropic model ids to "anthropic"', () => {
+  assert.equal(inferProviderId('claude-sonnet-4-5'), 'anthropic');
+  assert.equal(inferProviderId('claude-opus-4-1'), 'anthropic');
+});
+
+test('inferProviderId maps openai model ids to "openai"', () => {
+  assert.equal(inferProviderId('gpt-4o'), 'openai');
+  assert.equal(inferProviderId('o1-preview'), 'openai');
+});
+
+test('inferProviderId falls back to DEFAULT_CLINE_PROVIDER_ID for unknown ids', () => {
+  assert.equal(inferProviderId('some-custom-model'), DEFAULT_CLINE_PROVIDER_ID);
+  assert.equal(inferProviderId(''), DEFAULT_CLINE_PROVIDER_ID);
+});
+
+// -- upgrade 2: model_overrides resolution ----------------------------------
+
+test('a per-agent model_overrides entry resolves to createAgentModel params', () => {
+  const result = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: { planner: 'claude-sonnet-4-5' },
+    modelProfileOverrides: null,
+    profile: 'balanced',
+  });
+  assert.deepEqual(result, { providerId: 'anthropic', modelId: 'claude-sonnet-4-5' });
+});
+
+test('model_overrides takes precedence over model_profile_overrides', () => {
+  const result = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: { planner: 'claude-sonnet-4-5' },
+    modelProfileOverrides: { balanced: { planner: 'claude-opus-4-1' } },
+    profile: 'balanced',
+  });
+  assert.equal(result.modelId, 'claude-sonnet-4-5', 'direct model_overrides wins');
+});
+
+test('model_profile_overrides resolves when no direct model_overrides entry exists', () => {
+  const result = resolveClineAgentModelParams({
+    agentType: 'executor',
+    modelOverrides: null,
+    modelProfileOverrides: { balanced: { executor: 'gpt-4o' } },
+    profile: 'balanced',
+  });
+  assert.deepEqual(result, { providerId: 'openai', modelId: 'gpt-4o' });
+});
+
+// -- upgrade 2: no override → null (gateway default applies) ----------------
+
+test('returns null when no override is configured (gateway picks the default model)', () => {
+  const result = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: null,
+    modelProfileOverrides: null,
+    profile: 'balanced',
+  });
+  assert.equal(result, null, 'null = no override; host gateway default applies');
+});
+
+test('returns null when the agentType has no matching override', () => {
+  const result = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: { executor: 'claude-sonnet-4-5' },
+    modelProfileOverrides: null,
+    profile: 'balanced',
+  });
+  assert.equal(result, null);
+});
+
+// -- upgrade 2: the gateway binding (createAgentModel call shape) -----------
+
+test('a resolved override drives DefaultGateway.createAgentModel with the right params', () => {
+  // Simulate the host gateway (mocked — the real @cline/sdk is not linked here).
+  const calls = [];
+  const fakeGateway = {
+    createAgentModel(selection) { calls.push(selection); return { providerId: selection.providerId, modelId: selection.modelId }; },
+  };
+  const params = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: { planner: 'claude-sonnet-4-5' },
+    modelProfileOverrides: null,
+    profile: 'balanced',
+  });
+  assert.ok(params, 'override must resolve to non-null params');
+  const model = fakeGateway.createAgentModel(params);
+  assert.equal(calls.length, 1);
+  assert.deepEqual(calls[0], { providerId: 'anthropic', modelId: 'claude-sonnet-4-5' });
+  assert.equal(model.modelId, 'claude-sonnet-4-5');
+});
+
+test('no override → createAgentModel is NOT called (gateway default, not GSD override)', () => {
+  const calls = [];
+  const fakeGateway = {
+    createAgentModel(selection) { calls.push(selection); return {}; },
+  };
+  const params = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: null,
+    modelProfileOverrides: null,
+    profile: 'balanced',
+  });
+  if (params) fakeGateway.createAgentModel(params);
+  assert.equal(calls.length, 0, 'no override → gateway must use its own default, GSD does not call createAgentModel');
+});
+
+// -- upgrade 2: fail-safe / malformed config --------------------------------
+
+test('malformed override values (non-string) are ignored (fail-safe, not crash)', () => {
+  const result = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: { planner: 42, executor: 'claude-sonnet-4-5' },
+    modelProfileOverrides: null,
+    profile: 'balanced',
+  });
+  // planner's non-string override is ignored; falls through to null (no executor match for agentType planner)
+  assert.equal(result, null);
+});
+
+test('empty-string override is treated as absent', () => {
+  const result = resolveClineAgentModelParams({
+    agentType: 'planner',
+    modelOverrides: { planner: '' },
+    modelProfileOverrides: null,
+    profile: 'balanced',
+  });
+  assert.equal(result, null);
+});