diff --git a/.github/workflows/smoke-copilot-sub-agents.lock.yml b/.github/workflows/smoke-copilot-sub-agents.lock.yml
index a38a0f252e0..5faa07a089b 100644
--- a/.github/workflows/smoke-copilot-sub-agents.lock.yml
+++ b/.github/workflows/smoke-copilot-sub-agents.lock.yml
@@ -1,4 +1,4 @@
-# gh-aw-metadata: {"schema_version":"v4","frontmatter_hash":"904043e6f7d1d1121005edda7e346e977d286e134537e7bd802a9966571ef72d","body_hash":"0daed06ad9ab37f712e54a71683b2f3c690ab0cce61735ab8ecf312216a2f4ec","strict":true,"agent_id":"copilot","agent_model":"gpt-5.3-codex","engine_versions":{"copilot":"1.0.90","copilot-sdk":"1.0.16"}}
+# gh-aw-metadata: {"schema_version":"v4","frontmatter_hash":"ff0cbc82b1f5518390c58553431e35b62580466e05b3edcbfac040f2ba86ebdb","body_hash":"0daed06ad9ab37f712e54a71683b2f3c690ab0cce61735ab8ecf312216a2f4ec","strict":true,"agent_id":"copilot","agent_model":"gpt-5.3-codex","engine_versions":{"copilot":"1.0.90","copilot-sdk":"1.0.16"}}
 # gh-aw-manifest: {"version":1,"secrets":["GH_AW_DEFAULT_OTLP_ENDPOINT","GH_AW_DEFAULT_OTLP_HEADERS","GH_AW_GITHUB_MCP_SERVER_TOKEN","GH_AW_GITHUB_TOKEN","GITHUB_TOKEN"],"actions":[{"repo":"actions/checkout","sha":"3d3c42e5aac5ba805825da76410c181273ba90b1","version":"v7.0.1"},{"repo":"actions/download-artifact","sha":"9000827ccba6bdab643e8b6fd33ac0654aef8333","version":"v8.0.2"},{"repo":"actions/github-script","sha":"3a2844b7e9c422d3c10d287c895573f7108da1b3","version":"v9.0.0"},{"repo":"actions/setup-node","sha":"949feb2413d6458794dcd2491c4babbbce0c15c1","version":"v7.1.0"},{"repo":"actions/upload-artifact","sha":"cf430e030ddbb5b0abf93d22962f4752f3646cd9","version":"v7.0.2"}],"containers":[{"image":"ghcr.io/github/gh-aw-firewall/agent:0.28.50","digest":"sha256:91fe4af8373c723d4d2e0706a0c35d310c2eeadaea5e0738c725b3861042f620","pinned_image":"ghcr.io/github/gh-aw-firewall/agent:0.28.50@sha256:91fe4af8373c723d4d2e0706a0c35d310c2eeadaea5e0738c725b3861042f620"},{"image":"ghcr.io/github/gh-aw-firewall/api-proxy:0.28.50","digest":"sha256:11f12bcd3dde377ba822df7c670d6b937e9e0cebc46218946d4edc972d7fd965","pinned_image":"ghcr.io/github/gh-aw-firewall/api-proxy:0.28.50@sha256:11f12bcd3dde377ba822df7c670d6b937e9e0cebc46218946d4edc972d7fd965"},{"image":"ghcr.io/github/gh-aw-firewall/squid:0.28.50","digest":"sha256:cc9b6b979edf4aafbb3811c2bdc4891039d5346473afa88e304aa692167004f9","pinned_image":"ghcr.io/github/gh-aw-firewall/squid:0.28.50@sha256:cc9b6b979edf4aafbb3811c2bdc4891039d5346473afa88e304aa692167004f9"},{"image":"ghcr.io/github/gh-aw-mcpg:v0.4.30","digest":"sha256:ab5a436a1490438db473e4e3d4c973cb1d75e3cb233fb08b73d31b42d7d18fba","pinned_image":"ghcr.io/github/gh-aw-mcpg:v0.4.30@sha256:ab5a436a1490438db473e4e3d4c973cb1d75e3cb233fb08b73d31b42d7d18fba"},{"image":"ghcr.io/github/gh-aw-node","digest":"sha256:11c2c544876cdbaffefe0f7f1283b74838c209654b4934a78e23ed11f750490f","pinned_image":"ghcr.io/github/gh-aw-node@sha256:11c2c544876cdbaffefe0f7f1283b74838c209654b4934a78e23ed11f750490f"},{"image":"ghcr.io/github/github-mcp-server:v1.12.2","digest":"sha256:508a0857ec762b1ab1cece29193345b501fab1dd9d1228a7b617062954cecac6","pinned_image":"ghcr.io/github/github-mcp-server:v1.12.2@sha256:508a0857ec762b1ab1cece29193345b501fab1dd9d1228a7b617062954cecac6"}],"mcp_servers":[{"name":"github","tools":["get_commit","get_file_contents","get_latest_release","get_me","get_pull_request","get_pull_request_comments","get_pull_request_diff","get_pull_request_files","get_pull_request_review_comments","get_pull_request_reviews","get_pull_request_status","get_release_by_tag","get_tag","issue_read","list_branches","list_commits","list_issue_types","list_issues","list_pull_requests","list_releases","list_starred_repositories","list_tags","pull_request_read","search_code","search_issues","search_pull_requests","search_repositories"]},{"name":"safeoutputs","tools":["create_issue","missing_data","missing_tool","noop","report_incomplete"]}],"threat_detection":{"mode":"enabled"}}
 # This file was automatically generated by gh-aw. DO NOT EDIT. To debug this workflow, load the skill at https://github.com/github/gh-aw/blob/main/debug.md
 #
@@ -159,7 +159,7 @@ jobs:
           GH_AW_EXPERIMENT_SPEC: '{"sub_agent_strategy":{"variants":["inline_strict","delegated_sequential","single_agent_control"],"description":"Measure whether inline sub-agent orchestration is the best reliability/cost tradeoff for a model-identity smoke test.","hypothesis":"H0: no change in pass_rate between inline_strict and delegated_sequential. H1: delegated_sequential improves pass_rate by \u003e= 0.15 absolute versus inline_strict. Note: single_agent_control is a synthetic negative baseline (always FAIL by design) excluded from H1 comparisons.","metric":"pass_rate","secondary_metrics":["run_duration_seconds","output_validity_rate"],"guardrail_metrics":[{"name":"empty_output_rate","direction":"min","threshold":"0.01"},{"name":"false_pass_rate","direction":"min","threshold":"0.05"}],"min_samples":30,"weight":[34,33,33],"issue":47551,"start_date":"2026-07-23","end_date":"2026-10-23"}}'
           GH_AW_EXPERIMENT_STATE_FILE: /tmp/gh-aw/experiments/state.jsonl
           GH_AW_EXPERIMENT_STATE_DIR: /tmp/gh-aw/experiments
-          GH_AW_HARNESS_VERSION: 904043e6f7d1d1121005edda7e346e977d286e134537e7bd802a9966571ef72d:0daed06ad9ab37f712e54a71683b2f3c690ab0cce61735ab8ecf312216a2f4ec
+          GH_AW_HARNESS_VERSION: ff0cbc82b1f5518390c58553431e35b62580466e05b3edcbfac040f2ba86ebdb:0daed06ad9ab37f712e54a71683b2f3c690ab0cce61735ab8ecf312216a2f4ec
         with:
           script: |
             const path = require('path');
@@ -1167,6 +1167,15 @@ jobs:
           if [ ! -f /tmp/gh-aw/agent_output.json ]; then
             echo '{"items":[]}' > /tmp/gh-aw/agent_output.json
           fi
+      - env:
+          SMOKE_EXECUTION: ${{ steps.agentic_execution.outcome }}
+          SMOKE_VARIANT: ${{ needs.activation.outputs.sub_agent_strategy }}
+        if: always()
+        name: Assert sub-agent model and wire API evidence
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: "const assert = require(\"node:assert/strict\");\nconst fs = require(\"node:fs\");\nconst path = require(\"node:path\");\nconst root = \"/tmp/gh-aw\";\nconst { writeUnifiedSession } = require(path.join(process.env.RUNNER_TEMP, \"gh-aw/actions/unified_session.cjs\"));\nwriteUnifiedSession({ rootDir: root, engine: \"copilot\" });\nconst readJsonl = file => fs.readFileSync(file, \"utf8\")\n  .split(\"\\n\").filter(line => line.trim()).map(line => JSON.parse(line));\nconst events = readJsonl(path.join(root, \"usage/aw_session.jsonl\"));\nconst started = events.filter(event => event.type === \"subagent.started\");\nif (process.env.SMOKE_VARIANT === \"single_agent_control\") {\n  assert.equal(started.length, 0, \"Control variant must not invoke sub-agents\");\n  return;\n}\nassert.equal(process.env.SMOKE_EXECUTION, \"success\", \"Copilot SDK execution failed\");\nconst proxyPaths = [\n  \"sandbox/firewall/logs/api-proxy-logs/token-usage.jsonl\",\n  \"sandbox/firewall/audit/api-proxy-logs/token-usage.jsonl\",\n  \"sandbox/firewall-audit-logs/api-proxy-logs/token-usage.jsonl\",\n];\nconst proxyFile = proxyPaths.map(file => path.join(root, file)).find(file => fs.existsSync(file));\nassert.ok(proxyFile, \"Missing api-proxy token usage evidence\");\nconst requests = readJsonl(proxyFile);\nconst expected = [\n  [\"haiku-whoami\", \"claude-haiku-4.5\", \"/chat/completions\"],\n  [\"mini-whoami\", \"gpt-5-mini\", \"/responses\"],\n  [\"nano-whoami\", \"gpt-5-nano\", \"/responses\"],\n];\nconst servedModel = model => String(model || \"\")\n  .replace(/^copilot(?:-(?:responses|completions))?(?:-\\d+)?\\//, \"\")\n  .replace(/-[0-9]{4}(?:-[0-9]{2}-[0-9]{2}|[0-9]{4})$/, \"\")\n  .replace(/^(claude-.+)-([0-9]+)-([0-9]+)$/, \"$1-$2.$3\");\nfor (const [agentName, model, endpoint] of expected) {\n  const invocations = started.filter(event => event.data.agentName === agentName);\n  assert.equal(invocations.length, 1, `${agentName} must actually run exactly once`);\n  const invocation = invocations[0];\n  const invocationId = invocation.data.invocationId || invocation.agentId;\n  assert.ok(invocationId, `${agentName} is missing an invocation ID`);\n  const activity = events.filter(event => event.data?.invocationId === invocationId || event.agentId === invocationId);\n  assert.ok(activity.some(event => event.type === \"subagent.completed\"), `${agentName} did not complete`);\n  assert.ok(!activity.some(event => event.type === \"subagent.failed\"), `${agentName} failed`);\n  const models = activity.flatMap(event => [\n    event.data.model, event.data.selectedModel, event.data.resolvedModel, event.data.firstDispatchedModel,\n  ]).filter(Boolean);\n  assert.ok(models.length > 0, `${agentName} has no recorded model`);\n  assert.ok(models.every(value => servedModel(value) === model), `${agentName} changed or fell back from ${model}`);\n  assert.ok(requests.some(request =>\n    servedModel(request.model) === model &&\n    (request.path || request.endpoint) === endpoint &&\n    Number(request.status) === 200 &&\n    request.purpose !== \"routing_classification\"),\n    `${agentName} has no successful ${model} request on ${endpoint}`);\n}"
+
       # Small dedicated copy of the agent output so safe-output processing
       # survives a failed or timed-out upload of the larger agent artifact
       - name: Upload agent output fallback artifact
diff --git a/.github/workflows/smoke-copilot-sub-agents.md b/.github/workflows/smoke-copilot-sub-agents.md
index 0b4dae0cdad..a70c52a6753 100644
--- a/.github/workflows/smoke-copilot-sub-agents.md
+++ b/.github/workflows/smoke-copilot-sub-agents.md
@@ -54,6 +54,68 @@ evals:
 sandbox:
   agent:
     id: awf
+post-steps:
+  - name: Assert sub-agent model and wire API evidence
+    if: always()
+    uses: actions/github-script@v9.0.0
+    env:
+      SMOKE_VARIANT: ${{ needs.activation.outputs.sub_agent_strategy }}
+      SMOKE_EXECUTION: ${{ steps.agentic_execution.outcome }}
+    with:
+      script: |
+        const assert = require("node:assert/strict");
+        const fs = require("node:fs");
+        const path = require("node:path");
+        const root = "/tmp/gh-aw";
+        const { writeUnifiedSession } = require(path.join(process.env.RUNNER_TEMP, "gh-aw/actions/unified_session.cjs"));
+        writeUnifiedSession({ rootDir: root, engine: "copilot" });
+        const readJsonl = file => fs.readFileSync(file, "utf8")
+          .split("\n").filter(line => line.trim()).map(line => JSON.parse(line));
+        const events = readJsonl(path.join(root, "usage/aw_session.jsonl"));
+        const started = events.filter(event => event.type === "subagent.started");
+        if (process.env.SMOKE_VARIANT === "single_agent_control") {
+          assert.equal(started.length, 0, "Control variant must not invoke sub-agents");
+          return;
+        }
+        assert.equal(process.env.SMOKE_EXECUTION, "success", "Copilot SDK execution failed");
+        const proxyPaths = [
+          "sandbox/firewall/logs/api-proxy-logs/token-usage.jsonl",
+          "sandbox/firewall/audit/api-proxy-logs/token-usage.jsonl",
+          "sandbox/firewall-audit-logs/api-proxy-logs/token-usage.jsonl",
+        ];
+        const proxyFile = proxyPaths.map(file => path.join(root, file)).find(file => fs.existsSync(file));
+        assert.ok(proxyFile, "Missing api-proxy token usage evidence");
+        const requests = readJsonl(proxyFile);
+        const expected = [
+          ["haiku-whoami", "claude-haiku-4.5", "/chat/completions"],
+          ["mini-whoami", "gpt-5-mini", "/responses"],
+          ["nano-whoami", "gpt-5-nano", "/responses"],
+        ];
+        const servedModel = model => String(model || "")
+          .replace(/^copilot(?:-(?:responses|completions))?(?:-\d+)?\//, "")
+          .replace(/-[0-9]{4}(?:-[0-9]{2}-[0-9]{2}|[0-9]{4})$/, "")
+          .replace(/^(claude-.+)-([0-9]+)-([0-9]+)$/, "$1-$2.$3");
+        for (const [agentName, model, endpoint] of expected) {
+          const invocations = started.filter(event => event.data.agentName === agentName);
+          assert.equal(invocations.length, 1, `${agentName} must actually run exactly once`);
+          const invocation = invocations[0];
+          const invocationId = invocation.data.invocationId || invocation.agentId;
+          assert.ok(invocationId, `${agentName} is missing an invocation ID`);
+          const activity = events.filter(event => event.data?.invocationId === invocationId || event.agentId === invocationId);
+          assert.ok(activity.some(event => event.type === "subagent.completed"), `${agentName} did not complete`);
+          assert.ok(!activity.some(event => event.type === "subagent.failed"), `${agentName} failed`);
+          const models = activity.flatMap(event => [
+            event.data.model, event.data.selectedModel, event.data.resolvedModel, event.data.firstDispatchedModel,
+          ]).filter(Boolean);
+          assert.ok(models.length > 0, `${agentName} has no recorded model`);
+          assert.ok(models.every(value => servedModel(value) === model), `${agentName} changed or fell back from ${model}`);
+          assert.ok(requests.some(request =>
+            servedModel(request.model) === model &&
+            (request.path || request.endpoint) === endpoint &&
+            Number(request.status) === 200 &&
+            request.purpose !== "routing_classification"),
+            `${agentName} has no successful ${model} request on ${endpoint}`);
+        }
 ---
 
 # Smoke Test: Copilot SDK Inline Sub-Agents
diff --git a/actions/setup/js/awf_reflect.cjs b/actions/setup/js/awf_reflect.cjs
index b9c677ad73a..b06aae1efdc 100644
--- a/actions/setup/js/awf_reflect.cjs
+++ b/actions/setup/js/awf_reflect.cjs
@@ -24,6 +24,7 @@ const tls = require("tls");
 const { withRetry, sleep } = require("./error_recovery.cjs");
 const { getErrorMessage } = require("./error_helpers.cjs");
 const { AWF_REFLECT_OUTPUT_PATH } = require("./awf_reflect_paths.cjs");
+const { qualifyModelForMultiProvider, isCopilotProviderName } = require("./copilot_sdk_multi_provider.cjs");
 
 function parseReflectTimeoutMs(value) {
   const rawValue = String(value || "").trim();
@@ -919,15 +920,13 @@ function resolveOpenAICompatibleEndpointFromReflect(options) {
  * Returns `null` when no configured endpoints are present or the data is
  * unavailable.
  *
- * Each endpoint becomes a `NamedProviderConfig` (using the endpoint's `provider`
- * field as the stable name) and every model advertised by that endpoint becomes a
- * `ProviderModelConfig` tuple `{ id, provider }` referencing it.  Callers can
- * derive provider-qualified selection ids as `"<providerName>/<modelId>"` if needed.
+ * Copilot endpoints become separate responses and completions providers. Other
+ * endpoints retain a single provider. Models reference their inferred wire API.
  *
  * The primary model is the first model that matches `options.model` (if set),
  * otherwise the first model across all providers.
- * A valid `options.wireApi` overrides inference for the primary provider only,
- * except for Anthropic providers, which do not use an OpenAI wire API.
+ * A valid `options.wireApi` routes only the configured Copilot model; it never
+ * changes the wire API used by the other models. The primary model is qualified.
  *
  * @param {{
  *   model?: string,
@@ -970,6 +969,11 @@ function resolveMultiProviderFromReflect(options) {
   // provider label (e.g. two "copilot" entries at different ports).
   /** @type {Map<string, number>} */
   const providerNameCount = new Map();
+  const configuredWireApi = String(options?.wireApi || "")
+    .toLowerCase()
+    .trim();
+  let configuredModelMapped = false;
+  let mappedConfiguredModel = "";
 
   for (const endpoint of endpoints) {
     const baseUrl = endpointBaseUrl(endpoint);
@@ -985,18 +989,62 @@ function resolveMultiProviderFromReflect(options) {
     }
 
     // Ensure unique provider names by appending a suffix when the same name appears twice.
-    const existing = providerNameCount.get(rawProviderName) ?? 0;
-    providerNameCount.set(rawProviderName, existing + 1);
-    const providerName = existing === 0 ? rawProviderName : `${rawProviderName}-${existing}`;
+    const isCopilot = isCopilotProviderName(rawProviderName);
+    const stableProviderName = isCopilot ? "copilot" : rawProviderName;
+    const existing = providerNameCount.get(stableProviderName) ?? 0;
+    providerNameCount.set(stableProviderName, existing + 1);
+    const suffix = existing === 0 ? "" : `-${existing}`;
+    const providerName = `${stableProviderName}${suffix}`;
 
     const endpointModels = Array.isArray(endpoint.models) ? endpoint.models.filter(m => typeof m === "string" && m.trim().length > 0) : [];
 
-    // Infer provider type and wire API using the configured model if available,
-    // otherwise fall back to the first model.
-    // For multi-model providers (e.g. Copilot), different models may have different wire APIs,
-    // so we prefer the configured model to ensure the correct wireApi is selected.
+    if (isCopilot) {
+      /** @type {Array<"responses" | "completions">} */
+      const wireApis = ["responses", "completions"];
+      for (const wireApi of wireApis) {
+        providers.push({ name: `copilot-${wireApi}${suffix}`, type: "openai", baseUrl, wireApi });
+      }
+      // Routing metadata uses model_id (not id); HTTP paths exclude ws:/responses.
+      const routingModels = Array.isArray(endpoint.routing_models) ? endpoint.routing_models : Array.isArray(rd.routing_models) ? rd.routing_models : [];
+      for (const modelId of endpointModels) {
+        const catalogEntry = getCatalogModelEntry(options?.modelsJson ?? null, modelId, "github-copilot");
+        let wireApi = inferWireApiForModel("openai", modelId, catalogEntry);
+        const metadata = routingModels.find(model => model?.model_id === modelId);
+        const supported = metadata?.supported_endpoints;
+        if (Array.isArray(supported)) {
+          const responses = supported.includes("/responses");
+          const completions = supported.includes("/chat/completions");
+          if (!responses && !completions) {
+            logger(`sdk-mode(multi): skipping Copilot model="${modelId}" with no supported SDK wire API`);
+            continue;
+          }
+          if (responses !== completions) wireApi = responses ? "responses" : "completions";
+        }
+        const matchesConfigured = configuredModel === modelId || configuredModel === `copilot/${modelId}` || ["responses", "completions"].some(api => configuredModel === `copilot-${api}${suffix}/${modelId}`);
+        if (!configuredModelMapped && matchesConfigured) {
+          configuredModelMapped = true;
+          const qualifiedWireApi = wireApis.find(api => configuredModel === `copilot-${api}${suffix}/${modelId}`);
+          if (qualifiedWireApi && (!Array.isArray(supported) || supported.includes(qualifiedWireApi === "responses" ? "/responses" : "/chat/completions"))) {
+            wireApi = qualifiedWireApi;
+          }
+          if (configuredWireApi === "responses" || configuredWireApi === "completions") {
+            const requestedEndpoint = configuredWireApi === "responses" ? "/responses" : "/chat/completions";
+            if (Array.isArray(supported) && !supported.includes(requestedEndpoint)) {
+              throw new Error(`Model endpoint mismatch: model "${modelId}" with COPILOT_PROVIDER_WIRE_API=${configuredWireApi} requires ${requestedEndpoint}; supported endpoints: ${supported.join(", ")}`);
+            }
+            wireApi = configuredWireApi;
+          }
+          mappedConfiguredModel = `copilot-${wireApi}${suffix}/${modelId}`;
+        }
+        models.push({ id: modelId, provider: `copilot-${wireApi}${suffix}` });
+      }
+      logger(`sdk-mode(multi): split provider="${providerName}" into responses/completions modelCount=${endpointModels.length} baseUrl="${baseUrl}"`);
+      continue;
+    }
+
+    // Other endpoints retain their provider-wide inference.
     const firstModel = endpointModels.length > 0 ? endpointModels[0] : "";
-    const modelForInference = configuredModel && endpointModels.includes(configuredModel) ? configuredModel : firstModel;
+    const modelForInference = endpointModels.find(modelId => configuredModel === modelId || configuredModel === `${providerName}/${modelId}`) || firstModel;
     const catalogProviderName = rawProviderName.toLowerCase() === "copilot" ? "github-copilot" : rawProviderName;
     const catalogEntry = modelForInference ? getCatalogModelEntry(options?.modelsJson ?? null, modelForInference, catalogProviderName) : null;
     const providerType = inferProviderTypeForModel(rawProviderName, modelForInference, catalogEntry);
@@ -1026,13 +1074,9 @@ function resolveMultiProviderFromReflect(options) {
 
   // Determine the primary model: prefer the configured model if it appears in the model list;
   // otherwise fall back to the first model across all providers.
-  let primaryModel = "";
-  if (configuredModel) {
-    const match = models.find(m => m.id === configuredModel);
-    if (match) primaryModel = match.id;
-  }
+  let primaryModel = qualifyModelForMultiProvider(configuredModel, { providers, models }) || mappedConfiguredModel;
   if (!primaryModel && models.length > 0) {
-    primaryModel = models[0].id;
+    primaryModel = `${models[0].provider}/${models[0].id}`;
   }
 
   if (!primaryModel) {
@@ -1040,12 +1084,12 @@ function resolveMultiProviderFromReflect(options) {
     return null;
   }
 
-  const primaryProviderName = models.find(m => m.id === primaryModel)?.provider;
+  const primaryProviderName = models.find(m => `${m.provider}/${m.id}` === primaryModel)?.provider;
   const primaryProvider = providers.find(p => p.name === primaryProviderName);
   const wireApi = String(options?.wireApi || "")
     .toLowerCase()
     .trim();
-  if (primaryProvider && primaryProvider.type !== "anthropic" && (wireApi === "responses" || wireApi === "completions")) {
+  if (primaryProvider && !primaryProvider.name.startsWith("copilot-") && primaryProvider.type !== "anthropic" && (wireApi === "responses" || wireApi === "completions")) {
     primaryProvider.wireApi = wireApi;
     logger(`sdk-mode(multi): primary provider="${primaryProvider.name}" wireApi="${wireApi}" selected from configured wire API`);
   }
diff --git a/actions/setup/js/awf_reflect.test.cjs b/actions/setup/js/awf_reflect.test.cjs
index 4ee05e6c2e8..42fee967ec7 100644
--- a/actions/setup/js/awf_reflect.test.cjs
+++ b/actions/setup/js/awf_reflect.test.cjs
@@ -959,6 +959,73 @@ describe("awf_reflect.cjs", () => {
   });
 
   describe("resolveMultiProviderFromReflect", () => {
+    const splitEndpoint = {
+      provider: "copilot",
+      configured: true,
+      port: 10002,
+      models: ["claude-haiku-4.5", "gpt-5.6-luna", "gpt-5-mini", "gpt-4o", "unsupported"],
+      routing_models: [
+        { model_id: "claude-haiku-4.5", supported_endpoints: ["/chat/completions", "/v1/messages"] },
+        { model_id: "gpt-5.6-luna", supported_endpoints: ["/responses", "ws:/responses"] },
+        { model_id: "gpt-5-mini", supported_endpoints: ["/chat/completions", "/responses", "ws:/responses"] },
+        { model_id: "gpt-4o", supported_endpoints: ["/chat/completions", "/responses"] },
+        { model_id: "unsupported", supported_endpoints: ["/v1/messages"] },
+      ],
+    };
+
+    it("splits Copilot models using HTTP endpoint support and per-model inference", () => {
+      const result = resolveMultiProviderFromReflect({ reflectData: { endpoints: [splitEndpoint] }, model: "gpt-5.6-luna" });
+      expect(result.providers).toEqual([
+        { name: "copilot-responses", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "responses" },
+        { name: "copilot-completions", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "completions" },
+      ]);
+      expect(result.models).toEqual([
+        { id: "claude-haiku-4.5", provider: "copilot-completions" },
+        { id: "gpt-5.6-luna", provider: "copilot-responses" },
+        { id: "gpt-5-mini", provider: "copilot-responses" },
+        { id: "gpt-4o", provider: "copilot-completions" },
+      ]);
+      expect(result.model).toBe("copilot-responses/gpt-5.6-luna");
+    });
+
+    it.each(["gpt-5.6-luna", "copilot/gpt-5.6-luna", "copilot-responses/gpt-5.6-luna"])("rejects an unsupported endpoint override for %s", model => {
+      expect(() => resolveMultiProviderFromReflect({ reflectData: { endpoints: [splitEndpoint] }, model, wireApi: "completions" })).toThrow(
+        'Model endpoint mismatch: model "gpt-5.6-luna" with COPILOT_PROVIDER_WIRE_API=completions requires /chat/completions; supported endpoints: /responses, ws:/responses'
+      );
+    });
+
+    it("routes a compatible override only for the selected model, not its siblings", () => {
+      const model = "gpt-5-mini";
+      const result = resolveMultiProviderFromReflect({ reflectData: { endpoints: [splitEndpoint] }, model, wireApi: "completions" });
+      expect(result.model).toBe("copilot-completions/gpt-5-mini");
+      expect(result.models.find(entry => entry.id === "gpt-5.6-luna").provider).toBe("copilot-responses");
+      expect(result.models.find(entry => entry.id === "claude-haiku-4.5").provider).toBe("copilot-completions");
+      expect(result.providers[0].wireApi).toBe("responses");
+    });
+
+    it("uses top-level routing model metadata when an endpoint does not have it", () => {
+      const result = resolveMultiProviderFromReflect({
+        reflectData: {
+          endpoints: [{ provider: "github", configured: true, port: 10002, models: ["gpt-5.6-luna"] }],
+          routing_models: [{ model_id: "gpt-5.6-luna", supported_endpoints: ["/chat/completions"] }],
+        },
+      });
+      expect(result.model).toBe("copilot-completions/gpt-5.6-luna");
+    });
+
+    it("preserves a qualified API preference for a both-supported model instead of selecting the first model", () => {
+      const reflectData = { endpoints: [splitEndpoint] };
+      expect(resolveMultiProviderFromReflect({ reflectData, model: "copilot-responses/gpt-4o" }).model).toBe("copilot-responses/gpt-4o");
+      expect(resolveMultiProviderFromReflect({ reflectData, model: "copilot-completions/gpt-5-mini" }).model).toBe("copilot-completions/gpt-5-mini");
+      expect(resolveMultiProviderFromReflect({ reflectData, model: "copilot-responses/gpt-4o", wireApi: "completions" }).model).toBe("copilot-completions/gpt-4o");
+    });
+
+    it("qualifies a fallback and preserves valid endpoint-qualified selections", () => {
+      const reflectData = { endpoints: [splitEndpoint, { ...splitEndpoint, port: 10003 }] };
+      expect(resolveMultiProviderFromReflect({ reflectData, model: "unknown" }).model).toBe("copilot-completions/claude-haiku-4.5");
+      expect(resolveMultiProviderFromReflect({ reflectData, model: "copilot-responses-1/gpt-5-mini" }).model).toBe("copilot-responses-1/gpt-5-mini");
+    });
+
     it("returns null when reflectData is null", () => {
       const logs = [];
       const result = resolveMultiProviderFromReflect({ reflectData: null, logger: msg => logs.push(msg) });
@@ -971,8 +1038,8 @@ describe("awf_reflect.cjs", () => {
         reflectData: { endpoints: [{ provider: "copilot", port: 10002, configured: true, models: ["gpt-5.4"] }] },
       });
       expect(result).not.toBeNull();
-      expect(result.providers).toHaveLength(1);
-      expect(result.model).toBe("gpt-5.4");
+      expect(result.providers).toHaveLength(2);
+      expect(result.model).toBe("copilot-responses/gpt-5.4");
     });
 
     it("rewrites provider baseUrl to the host bridge in sbx HOSTALIASES mode", () => {
@@ -1033,7 +1100,7 @@ describe("awf_reflect.cjs", () => {
         ],
       };
       const result = resolveMultiProviderFromReflect({ reflectData });
-      expect(result.model).toBe("gpt-5.4");
+      expect(result.model).toBe("openai/gpt-5.4");
     });
 
     it("prefers the configured model when it appears in model list", () => {
@@ -1044,7 +1111,7 @@ describe("awf_reflect.cjs", () => {
         ],
       };
       const result = resolveMultiProviderFromReflect({ reflectData, model: "claude-sonnet-4.6" });
-      expect(result.model).toBe("claude-sonnet-4.6");
+      expect(result.model).toBe("anthropic/claude-sonnet-4.6");
     });
 
     it("falls back to first model when configured model is not found in list", () => {
@@ -1055,7 +1122,7 @@ describe("awf_reflect.cjs", () => {
         ],
       };
       const result = resolveMultiProviderFromReflect({ reflectData, model: "nonexistent-model" });
-      expect(result.model).toBe("gpt-5.4");
+      expect(result.model).toBe("openai/gpt-5.4");
     });
 
     it("derives provider baseUrl from models_url origin when available", () => {
@@ -1083,9 +1150,9 @@ describe("awf_reflect.cjs", () => {
         },
       };
       const result = resolveMultiProviderFromReflect({ reflectData, modelsJson });
-      expect(result.providers[0]).toMatchObject({ name: "copilot", type: "openai", wireApi: "responses" });
-      expect(result.providers[1]).toMatchObject({ name: "anthropic", type: "anthropic" });
-      expect(result.providers[1]).not.toHaveProperty("wireApi");
+      expect(result.providers[0]).toMatchObject({ name: "copilot-responses", type: "openai", wireApi: "responses" });
+      expect(result.providers[2]).toMatchObject({ name: "anthropic", type: "anthropic" });
+      expect(result.providers[2]).not.toHaveProperty("wireApi");
     });
 
     it("infers wireApi from the base catalog model for a Copilot utility variant", () => {
@@ -1102,7 +1169,7 @@ describe("awf_reflect.cjs", () => {
         reflectData,
         modelsJson,
       });
-      expect(result.providers[0]).toMatchObject({ name: "copilot", type: "openai", wireApi: "responses" });
+      expect(result.providers[0]).toMatchObject({ name: "copilot-responses", type: "openai", wireApi: "responses" });
     });
 
     it.each([null, { providers: { "github-copilot": { models: { "gpt-6-luna": { wire_api: "completions" } } } } }])("honors an explicit Responses API for gpt-6-luna with a missing or stale catalog", modelsJson => {
@@ -1112,8 +1179,8 @@ describe("awf_reflect.cjs", () => {
         reflectData: { endpoints: [{ provider: "copilot", port: 10002, configured: true, models: ["gpt-6-luna"] }] },
         modelsJson,
       });
-      expect(result.model).toBe("gpt-6-luna");
-      expect(result.providers[0]).toMatchObject({ name: "copilot", type: "openai", wireApi: "responses" });
+      expect(result.model).toBe("copilot-responses/gpt-6-luna");
+      expect(result.providers[0]).toMatchObject({ name: "copilot-responses", type: "openai", wireApi: "responses" });
     });
 
     it("applies the wire API override only to the selected provider", () => {
@@ -1127,8 +1194,8 @@ describe("awf_reflect.cjs", () => {
           ],
         },
       });
-      expect(result.providers[0].wireApi).toBe("completions");
-      expect(result.providers[1]).toMatchObject({ name: "copilot-1", wireApi: "responses" });
+      expect(result.models[0].provider).toBe("copilot-completions");
+      expect(result.models[1].provider).toBe("copilot-responses-1");
     });
 
     it("honors an explicit Completions API over catalog inference", () => {
@@ -1138,7 +1205,7 @@ describe("awf_reflect.cjs", () => {
         reflectData: { endpoints: [{ provider: "copilot", port: 10002, configured: true, models: ["gpt-6-luna"] }] },
         modelsJson: { providers: { "github-copilot": { models: { "gpt-6-luna": { wire_api: "responses" } } } } },
       });
-      expect(result.providers[0].wireApi).toBe("completions");
+      expect(result.model).toBe("copilot-completions/gpt-6-luna");
     });
 
     it.each(["Responses", " responses "])("normalizes explicit wire API overrides (%s)", wireApi => {
@@ -1150,14 +1217,13 @@ describe("awf_reflect.cjs", () => {
       expect(result.providers[0].wireApi).toBe("responses");
     });
 
-    it("applies an explicit wire API override to the fallback primary model", () => {
+    it("does not apply an unmatched model's wire API override to the fallback primary model", () => {
       const result = resolveMultiProviderFromReflect({
         model: "nonexistent-model",
         wireApi: "responses",
-        reflectData: { endpoints: [{ provider: "copilot", port: 10002, configured: true, models: ["gpt-6-luna"] }] },
+        reflectData: { endpoints: [{ provider: "copilot", port: 10002, configured: true, models: ["gpt-4o"] }] },
       });
-      expect(result.model).toBe("gpt-6-luna");
-      expect(result.providers[0].wireApi).toBe("responses");
+      expect(result.model).toBe("copilot-completions/gpt-4o");
     });
 
     it("infers the fallback primary model wire API instead of inheriting an automatic GPT default", () => {
@@ -1166,7 +1232,7 @@ describe("awf_reflect.cjs", () => {
         reflectData: { endpoints: [{ provider: "openai", port: 10002, configured: true, models: ["gpt-4.1"] }] },
         modelsJson: { providers: { openai: { models: { "gpt-4.1": { wire_api: "completions" } } } } },
       });
-      expect(result.model).toBe("gpt-4.1");
+      expect(result.model).toBe("openai/gpt-4.1");
       expect(result.providers[0].wireApi).toBe("completions");
     });
 
@@ -1197,10 +1263,9 @@ describe("awf_reflect.cjs", () => {
         ],
       };
       const result = resolveMultiProviderFromReflect({ reflectData });
-      expect(result.providers[0].name).toBe("copilot");
-      expect(result.providers[1].name).toBe("copilot-1");
-      expect(result.models[0]).toEqual({ id: "gpt-5.4", provider: "copilot" });
-      expect(result.models[1]).toEqual({ id: "gpt-5.5", provider: "copilot-1" });
+      expect(result.providers.map(provider => provider.name)).toEqual(["copilot-responses", "copilot-completions", "copilot-responses-1", "copilot-completions-1"]);
+      expect(result.models[0]).toEqual({ id: "gpt-5.4", provider: "copilot-responses" });
+      expect(result.models[1]).toEqual({ id: "gpt-5.5", provider: "copilot-responses-1" });
     });
 
     it("skips endpoints with no resolvable baseUrl", () => {
diff --git a/actions/setup/js/copilot_dynamic_workflow.test.cjs b/actions/setup/js/copilot_dynamic_workflow.test.cjs
index cf247d0ac80..bb4da9dd113 100644
--- a/actions/setup/js/copilot_dynamic_workflow.test.cjs
+++ b/actions/setup/js/copilot_dynamic_workflow.test.cjs
@@ -216,7 +216,7 @@ describe("Copilot dynamic workflow sessions", () => {
       .split("\n")
       .map(JSON.parse);
     expect(events.filter(event => event.type.startsWith("workflow.run_"))).toEqual(lifecycle.filter(event => event.type.startsWith("workflow.run_")));
-    expect(events.find(event => event.type === "subagent.started")).toEqual(lifecycle[3]);
+    expect(events.find(event => event.type === "subagent.started")).toEqual({ ...lifecycle[3], data: { ...lifecycle[3].data, agentDisplayName: lifecycle[3].data.agentName } });
     expect(events.find(event => event.type === "assistant.message")).toEqual(lifecycle[5]);
     expect(events.filter(event => event.type === "assistant.message_delta")).toEqual([delta]);
     expect(setTimeoutSpy.mock.calls.filter(([, timeout]) => timeout === 1234)).toHaveLength(0);
diff --git a/actions/setup/js/copilot_harness.cjs b/actions/setup/js/copilot_harness.cjs
index 6d9fab6727f..c3a541002cd 100644
--- a/actions/setup/js/copilot_harness.cjs
+++ b/actions/setup/js/copilot_harness.cjs
@@ -91,6 +91,7 @@ const { detectNonRetryableHarnessGuard, buildSoftTimeoutGuard, emitSoftTimeoutSi
 const { isCrashSignalExitCode, crashSignalNameForExitCode } = require("./harness_crash_signals.cjs");
 const { isCAPIQuotaExceededError, isCAPIServerError } = require("./detect_agent_errors.cjs");
 const { applyModelFallback } = require("./model_fallback.cjs");
+const { parseMultiProviderJson, qualifyModelForMultiProvider } = require("./copilot_sdk_multi_provider.cjs");
 const { isRoutingReasoningEffort } = require("./copilot_routing_effort.cjs");
 const { resolveAWFModelRoutingSelection, isModelAvailableInReflectData, getAWFModelRoutingPolicy, getAWFModelRoutingFailureCode } = require("./awf_model_routing.cjs");
 const { recordAWFModelRoutingOutcome } = require("./awf_model_routing.cjs");
@@ -928,11 +929,16 @@ function buildCopilotSDKChildEnv({ sdkEnv, copilotSDKMode, copilotConnectionToke
   if (!copilotSDKMode) {
     return sdkEnv;
   }
+  const multiProvider = parseMultiProviderJson(multiProviderJson);
+  const qualifiedModel = qualifyModelForMultiProvider(resolvedModel || multiProvider?.model, multiProvider);
+  if (multiProvider && !qualifiedModel) {
+    throw new Error(`Copilot SDK model '${resolvedModel || multiProvider.model}' is not available in the configured BYOK provider catalog`);
+  }
   return {
     ...sdkEnv,
     COPILOT_CONNECTION_TOKEN: copilotConnectionToken,
     ...(multiProviderJson ? { GH_AW_COPILOT_SDK_MULTI_PROVIDER_JSON: multiProviderJson } : {}),
-    COPILOT_MODEL: resolvedModel,
+    COPILOT_MODEL: qualifiedModel || resolvedModel,
     ...(routingEffort ? { COPILOT_REASONING_EFFORT: routingEffort } : {}),
     // Native Copilot CLI BYOK env vars — consumed by the headless sidecar for all sessions.
     COPILOT_PROVIDER_BASE_URL: providerBaseUrl,
@@ -1267,7 +1273,7 @@ async function main() {
   let multiProviderJson = "";
   let primaryProviderName = "";
   if (copilotSDKMode) {
-    const configuredModel = process.env.COPILOT_MODEL || "";
+    const configuredModel = modelRoutingSelection?.wire_model || process.env.COPILOT_MODEL || "";
     const modelsJson = loadModelsJson();
 
     const multiProvider = resolveMultiProviderFromReflect({ model: configuredModel, wireApi: process.env.COPILOT_PROVIDER_WIRE_API, reflectData: awfReflectData, modelsJson, logger: log });
@@ -1278,25 +1284,13 @@ async function main() {
     resolvedModel = multiProvider.model;
     // Set the primary provider's details as COPILOT_PROVIDER_* env vars for the headless sidecar
     // (which still reads those to configure its own sub-agent sessions).
-    primaryProviderName = multiProvider.models.find(m => m.id === resolvedModel)?.provider ?? multiProvider.providers[0]?.name ?? "";
+    primaryProviderName = multiProvider.models.find(m => `${m.provider}/${m.id}` === resolvedModel)?.provider ?? multiProvider.providers[0]?.name ?? "";
     const primaryProvider = multiProvider.providers.find(p => p.name === primaryProviderName) ?? multiProvider.providers[0];
-    if (modelRoutingSelection) {
-      providerWireApi = modelRoutingSelection.endpoint === "/responses" ? "responses" : "completions";
-      if (primaryProvider) primaryProvider.wireApi = providerWireApi;
-    }
     providerBaseUrl = primaryProvider?.baseUrl ?? "";
     providerType = primaryProvider?.type ?? "openai";
     providerWireApi = providerWireApi || primaryProvider?.wireApi || "";
     multiProviderJson = JSON.stringify({ model: multiProvider.model, providers: multiProvider.providers, models: multiProvider.models });
 
-    // For BYOK copilot providers, prefix the model with "copilot/" so subagents treat it as BYOK.
-    // The headless sidecar reads COPILOT_MODEL to configure sub-agent sessions spawned via the task tool,
-    // and the "copilot/" prefix signals to use the custom provider config from COPILOT_PROVIDER_* env vars.
-    const isCopilotProvider = primaryProviderName && (primaryProviderName.toLowerCase().includes("copilot") || primaryProviderName.toLowerCase().includes("github-copilot"));
-    if (!modelRoutingSelection && isCopilotProvider && resolvedModel && !resolvedModel.includes("/")) {
-      resolvedModel = `copilot/${resolvedModel}`;
-    }
-
     log(`copilot-sdk driver mode: multi-provider config resolved (${multiProvider.providers.length} providers, ${multiProvider.models.length} models, model=${resolvedModel})`);
     logCopilotInferenceConfiguration({
       copilotSDKMode,
@@ -1402,6 +1396,7 @@ async function main() {
         lastExitCode = 1;
       } else {
         let driverServerArgs = parseCopilotSDKServerArgsFromEnv(process.env.GH_AW_COPILOT_SDK_SERVER_ARGS, { logger: log });
+        if (driverServerArgs.length === 0) driverServerArgs = buildCopilotSDKServerArgs(childEnv ?? process.env);
         if (process.env.GITHUB_WORKSPACE) {
           driverServerArgs = [...driverServerArgs, "--add-dir", process.env.GITHUB_WORKSPACE];
           log(`copilot-sdk driver mode: appended workspace --add-dir ${process.env.GITHUB_WORKSPACE}`);
diff --git a/actions/setup/js/copilot_harness.test.cjs b/actions/setup/js/copilot_harness.test.cjs
index 08e23fbfc8e..9ad462c9ab7 100644
--- a/actions/setup/js/copilot_harness.test.cjs
+++ b/actions/setup/js/copilot_harness.test.cjs
@@ -387,6 +387,53 @@ describe("copilot_harness.cjs", () => {
   });
 
   describe("buildCopilotSDKChildEnv", () => {
+    it("rejects an unknown model instead of passing it bare with a valid BYOK catalog", () => {
+      expect(() =>
+        buildCopilotSDKChildEnv({
+          sdkEnv: {},
+          copilotSDKMode: true,
+          copilotConnectionToken: "",
+          providerBaseUrl: "http://api-proxy:10002",
+          providerType: "openai",
+          providerWireApi: "responses",
+          resolvedModel: "unknown",
+          multiProviderJson: JSON.stringify({
+            model: "copilot-responses/gpt-5.6-luna",
+            providers: [{ name: "copilot-responses", type: "openai", baseUrl: "http://api-proxy:10002" }],
+            models: [{ id: "gpt-5.6-luna", provider: "copilot-responses" }],
+          }),
+        })
+      ).toThrow("not available in the configured BYOK provider catalog");
+    });
+
+    it.each(["gpt-5.6-luna", "copilot/gpt-5.6-luna", "copilot-responses/gpt-5.6-luna"])("passes a qualified routed model (%s) with isolated model routes", resolvedModel => {
+      const config = {
+        model: "copilot-responses/gpt-5.6-luna",
+        providers: [
+          { name: "copilot-responses", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "responses" },
+          { name: "copilot-completions", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "completions" },
+        ],
+        models: [
+          { id: "gpt-5.6-luna", provider: "copilot-responses" },
+          { id: "claude-haiku-4.5", provider: "copilot-completions" },
+        ],
+      };
+      const env = buildCopilotSDKChildEnv({
+        sdkEnv: {},
+        copilotSDKMode: true,
+        copilotConnectionToken: "",
+        providerBaseUrl: "http://api-proxy:10002",
+        providerType: "openai",
+        providerWireApi: "responses",
+        resolvedModel,
+        routingEffort: "high",
+        multiProviderJson: JSON.stringify(config),
+      });
+      expect(env.COPILOT_MODEL).toBe("copilot-responses/gpt-5.6-luna");
+      expect(env.COPILOT_REASONING_EFFORT).toBe("high");
+      expect(JSON.parse(env.GH_AW_COPILOT_SDK_MULTI_PROVIDER_JSON)).toEqual(config);
+    });
+
     it("includes native sidecar provider vars and multiProviderJson when wireApi is configured", () => {
       const multiProviderJson = JSON.stringify({ model: "gpt-5.4", providers: [{ name: "copilot", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "completions" }], models: [{ id: "gpt-5.4", provider: "copilot" }] });
       const env = buildCopilotSDKChildEnv({
@@ -405,7 +452,7 @@ describe("copilot_harness.cjs", () => {
         COPILOT_SDK_URI: "http://127.0.0.1:4000",
         COPILOT_CONNECTION_TOKEN: "token-123",
         GH_AW_COPILOT_SDK_MULTI_PROVIDER_JSON: multiProviderJson,
-        COPILOT_MODEL: "gpt-5.4",
+        COPILOT_MODEL: "copilot/gpt-5.4",
         COPILOT_REASONING_EFFORT: "high",
         COPILOT_PROVIDER_BASE_URL: "http://api-proxy:10002",
         COPILOT_PROVIDER_TYPE: "openai",
@@ -1234,6 +1281,23 @@ describe("copilot_harness.cjs", () => {
       expect(spawnImpl).toHaveBeenCalledWith("copilot", engineGeneratedArgs, expect.objectContaining({ stdio: ["ignore", "pipe", "pipe"] }));
     });
 
+    it.each(["not-json", '{"port":3002}'])("retains headless defaults and workspace access for invalid SDK args %s", async value => {
+      const child = new EventEmitter();
+      child.stdout = new PassThrough();
+      child.stderr = new PassThrough();
+      child.exitCode = null;
+      child.signalCode = null;
+      const spawnImpl = vi.fn(() => child);
+      const logger = vi.fn();
+      const env = { COPILOT_SDK_URI: "http://127.0.0.1:3002" };
+      let args = parseCopilotSDKServerArgsFromEnv(value, { logger });
+      if (args.length === 0) args = buildCopilotSDKServerArgs(env);
+      args = [...args, "--add-dir", "/w"];
+      await startCopilotSDKServer({ command: "copilot", env, serverArgs: args, logger, spawnImpl, waitForReady: async () => {} });
+      expect(spawnImpl).toHaveBeenCalledWith("copilot", ["--headless", "--no-auto-update", "--port", "3002", "--add-dir", "/w"], expect.anything());
+      expect(logger.mock.calls.flat().join("\n")).toMatch(/GH_AW_COPILOT_SDK_SERVER_ARGS/);
+    });
+
     it("uses only base headless args when extraArgs is empty or omitted", async () => {
       const child = new EventEmitter();
       child.stdout = new PassThrough();
diff --git a/actions/setup/js/copilot_sdk_driver.cjs b/actions/setup/js/copilot_sdk_driver.cjs
index 879050d6ea4..cf786458185 100644
--- a/actions/setup/js/copilot_sdk_driver.cjs
+++ b/actions/setup/js/copilot_sdk_driver.cjs
@@ -27,10 +27,10 @@
 "use strict";
 
 const fs = require("fs");
-const { runWithCopilotSDK, extractPromptFromArgs } = require("./copilot_sdk_session.cjs");
+const { runWithCopilotSDK, extractPromptFromArgs, isCopilotSDKBareMode, resolveCopilotSDKWorkingDirectory } = require("./copilot_sdk_session.cjs");
 const { parsePermissionConfigFromServerArgs } = require("./copilot_sdk_permissions.cjs");
 const { parseCopilotSDKToolConfig } = require("./copilot_sdk_tool_config.cjs");
-const { parseMultiProviderJson } = require("./copilot_sdk_multi_provider.cjs");
+const { parseMultiProviderJson, qualifyModelForMultiProvider } = require("./copilot_sdk_multi_provider.cjs");
 const { applyModelFallback } = require("./model_fallback.cjs");
 const { resolveRoutingReasoningEffort } = require("./copilot_routing_effort.cjs");
 const { getErrorMessage } = require("./error_helpers.cjs");
@@ -109,6 +109,9 @@ async function main() {
   const sdkModels = multiProviderConfig.models;
   const routingEnabled = process.env.GH_AW_MODEL_ROUTING === "1";
   let model = (routingEnabled ? process.env.COPILOT_MODEL : applyModelFallback(process.env, "COPILOT_MODEL", log)) || multiProviderConfig.model || undefined;
+  const qualifiedModel = qualifyModelForMultiProvider(model, multiProviderConfig);
+  if (!qualifiedModel) throw new Error(`Cannot qualify session model "${model || "(none)"}" against the configured provider models`);
+  model = qualifiedModel;
   const reasoningEffort = resolveRoutingReasoningEffort(process.env);
   log(`multi-provider mode: ${providers.length} providers, ${sdkModels.length} models, model=${model ?? "(env)"}`);
   for (const p of providers) {
@@ -135,6 +138,8 @@ async function main() {
     models: sdkModels,
     permissionConfig,
     toolConfig,
+    workingDirectory: resolveCopilotSDKWorkingDirectory(),
+    bare: isCopilotSDKBareMode(process.env.GH_AW_COPILOT_SDK_SERVER_ARGS, log),
   });
 
   process.exit(result.exitCode);
diff --git a/actions/setup/js/copilot_sdk_driver.test.cjs b/actions/setup/js/copilot_sdk_driver.test.cjs
index e53ead6bd85..eb5430310da 100644
--- a/actions/setup/js/copilot_sdk_driver.test.cjs
+++ b/actions/setup/js/copilot_sdk_driver.test.cjs
@@ -1,7 +1,6 @@
 import { describe, it, expect, vi, beforeAll, afterAll } from "vitest";
 import { createRequire } from "module";
 import * as fs from "fs";
-import * as os from "os";
 import * as path from "path";
 
 const require = createRequire(import.meta.url);
@@ -10,18 +9,129 @@ const { runWithCopilotSDK, parsePermissionConfigFromServerArgs } = require("./co
 describe("copilot_sdk_driver.cjs", () => {
   let testSessionStateDir;
   let prevSessionStateDir;
+  let agentDirectorySpy;
   beforeAll(() => {
     prevSessionStateDir = process.env.GH_AW_SESSION_STATE_BASE_DIR;
-    testSessionStateDir = fs.mkdtempSync(path.join(os.tmpdir(), "gh-aw-test-session-state-"));
+    testSessionStateDir = fs.mkdtempSync(path.join(process.cwd(), ".gh-aw-test-session-state-"));
     process.env.GH_AW_SESSION_STATE_BASE_DIR = testSessionStateDir;
+    const runtimeFs = require("fs");
+    const readdirSync = runtimeFs.readdirSync;
+    agentDirectorySpy = vi.spyOn(runtimeFs, "readdirSync").mockImplementation((directory, options) => {
+      // Never inspect the developer checkout's agents when exercising the SDK.
+      if (!String(directory).startsWith(testSessionStateDir) && String(directory).endsWith("/.github/agents")) return [];
+      return readdirSync(directory, options);
+    });
   });
   afterAll(() => {
     if (prevSessionStateDir === undefined) delete process.env.GH_AW_SESSION_STATE_BASE_DIR;
     else process.env.GH_AW_SESSION_STATE_BASE_DIR = prevSessionStateDir;
     if (testSessionStateDir) fs.rmSync(testSessionStateDir, { recursive: true, force: true });
+    agentDirectorySpy.mockRestore();
   });
 
   describe("runWithCopilotSDK", () => {
+    it.each([
+      ["gpt-5.4", "claude-sonnet-4.6", "copilot-responses", "copilot-completions"],
+      ["claude-sonnet-4.6", "gpt-5.4", "copilot-completions", "copilot-responses"],
+    ])("qualifies %s session and cross-provider %s custom agents at runtime", async (sessionModel, agentModel, sessionProvider, agentProvider) => {
+      const workspace = path.join(testSessionStateDir, `${sessionProvider}-workspace`);
+      const workflow = path.join(testSessionStateDir, `${sessionProvider}-workflow`);
+      fs.mkdirSync(path.join(workspace, ".github/agents"), { recursive: true });
+      fs.mkdirSync(path.join(workflow, ".github/agents"), { recursive: true });
+      fs.writeFileSync(
+        path.join(workspace, ".github/agents/researcher.agent.md"),
+        `---\nname: researcher\ndescription: >-\n  Research across\n  providers\ntools:\n  - read\n  - grep\nmodel: copilot/${agentModel}\n---\nResearch carefully.\n`
+      );
+      fs.writeFileSync(path.join(workflow, ".github/agents/workflow.agent.md"), "---\nname: workflow-agent\nmodel: medium\ntools: read, grep\n---\nWorkflow prompt.");
+      for (const alias of ["small", "large"]) fs.writeFileSync(path.join(workflow, `.github/agents/${alias}.agent.md`), `---\nmodel: ${alias}\n---\nAlias prompt.`);
+      fs.writeFileSync(path.join(workflow, ".github/agents/unknown.agent.md"), "---\nname: unknown-agent\nmodel: unavailable-model\n---\nKeep this agent.");
+      const createSession = vi.fn().mockResolvedValue({
+        sessionId: `${sessionProvider}-agent-session`,
+        on: () => {},
+        sendAndWait: vi.fn().mockResolvedValue({ data: { content: "done" } }),
+        disconnect: vi.fn().mockResolvedValue(undefined),
+      });
+      const constructor = vi.fn();
+      class FakeCopilotClient {
+        constructor(options) {
+          constructor(options);
+        }
+        start = vi.fn().mockResolvedValue(undefined);
+        createSession = createSession;
+        stop = vi.fn().mockResolvedValue(undefined);
+      }
+      const logger = vi.fn();
+      const result = await runWithCopilotSDK({
+        sdkUri: "http://127.0.0.1:3002",
+        prompt: "test prompt",
+        model: `copilot/${sessionModel}`,
+        models: [
+          { id: sessionModel, provider: sessionProvider },
+          { id: agentModel, provider: agentProvider },
+        ],
+        providers: [
+          { name: "copilot-responses", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "responses" },
+          { name: "copilot-completions", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "completions" },
+        ],
+        workingDirectory: workspace,
+        agentsBaseDir: workflow,
+        bare: true,
+        logger,
+        sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: vi.fn(() => ({})) }, approveAll: () => "allow" },
+      });
+      expect(result.exitCode).toBe(0);
+      expect(constructor).toHaveBeenCalledWith(expect.objectContaining({ workingDirectory: workspace }));
+      expect(createSession).toHaveBeenCalledWith(
+        expect.objectContaining({
+          model: `${sessionProvider}/${sessionModel}`,
+          workingDirectory: workspace,
+          skipCustomInstructions: true,
+          customAgents: expect.arrayContaining([
+            { name: "researcher", displayName: "researcher", description: "Research across providers", tools: ["read", "grep"], prompt: "Research carefully.", model: `${agentProvider}/${agentModel}` },
+            { name: "workflow-agent", displayName: "workflow-agent", tools: ["read", "grep"], prompt: "Workflow prompt.", model: `${sessionProvider}/${sessionModel}` },
+            { name: "unknown-agent", displayName: "unknown-agent", prompt: "Keep this agent.", model: `${sessionProvider}/${sessionModel}` },
+            { name: "small", displayName: "small", prompt: "Alias prompt.", model: `${sessionProvider}/${sessionModel}` },
+            { name: "large", displayName: "large", prompt: "Alias prompt.", model: `${sessionProvider}/${sessionModel}` },
+          ]),
+        })
+      );
+      expect(logger).toHaveBeenCalledWith(expect.stringMatching(/warning:.*unknown-agent.*unavailable-model.*session model/i));
+      const captured = fs
+        .readFileSync(path.join(testSessionStateDir, `${sessionProvider}-agent-session/events.jsonl`), "utf8")
+        .trim()
+        .split("\n")
+        .map(JSON.parse);
+      expect(captured.filter(event => event.type === "subagent.model_unavailable")).toEqual([
+        expect.objectContaining({ data: { agentName: "unknown-agent", declaredModel: "unavailable-model", model: `${sessionProvider}/${sessionModel}` } }),
+      ]);
+    });
+
+    it("captures ephemeral selection and final model results including BYOK and subagent context", async () => {
+      const event = { type: "model.call_final_result", ephemeral: true, timestamp: "2026-10-10T00:00:00Z", data: { isByok: true, model: "anthropic/claude-sonnet-4.6", agentId: "researcher", parentToolCallId: "delegate-1" } };
+      const selected = { type: "subagent.selected", ephemeral: true, timestamp: event.timestamp, data: { agentName: "researcher", model: "anthropic/claude-sonnet-4.6", resolvedModel: "anthropic/claude-sonnet-4.6" } };
+      let onEvent = () => {};
+      class FakeCopilotClient {
+        start = vi.fn().mockResolvedValue(undefined);
+        stop = vi.fn().mockResolvedValue(undefined);
+        createSession = vi.fn().mockResolvedValue({
+          sessionId: "final-model-result",
+          on: handler => {
+            onEvent = handler;
+          },
+          sendAndWait: async () => {
+            onEvent(selected);
+            onEvent(event);
+            return { data: { content: "done" } };
+          },
+          disconnect: vi.fn().mockResolvedValue(undefined),
+        });
+      }
+      await runWithCopilotSDK({ sdkUri: "http://127.0.0.1:3002", prompt: "test", logger: () => {}, sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: vi.fn(() => ({})) }, approveAll: () => "allow" } });
+      const events = fs.readFileSync(path.join(testSessionStateDir, "final-model-result/events.jsonl"), "utf8").trim().split("\n").map(JSON.parse);
+      expect(events).toContainEqual(event);
+      expect(events).toContainEqual(selected);
+    });
+
     it("disconnects session and stops client on success", async () => {
       const disconnect = vi.fn().mockResolvedValue(undefined);
       const stop = vi.fn().mockResolvedValue(undefined);
@@ -990,7 +1100,7 @@ describe("copilot_sdk_driver.cjs", () => {
         sdkUri: "http://127.0.0.1:3002",
         prompt: "test prompt",
         logger: () => {},
-        model: "gpt-5.4",
+        model: "copilot/gpt-5.4",
         providers,
         models,
         sdkModule: {
@@ -1003,7 +1113,7 @@ describe("copilot_sdk_driver.cjs", () => {
       expect(result.exitCode).toBe(0);
       expect(createSession).toHaveBeenCalledWith(
         expect.objectContaining({
-          model: "gpt-5.4",
+          model: "copilot/gpt-5.4",
           providers,
           models,
         })
diff --git a/actions/setup/js/copilot_sdk_multi_provider.cjs b/actions/setup/js/copilot_sdk_multi_provider.cjs
index f5eda347657..b6d0974ec75 100644
--- a/actions/setup/js/copilot_sdk_multi_provider.cjs
+++ b/actions/setup/js/copilot_sdk_multi_provider.cjs
@@ -58,8 +58,38 @@ function parseMultiProviderJson(value) {
   }
 }
 
+/**
+ * Resolve a catalog model to its BYOK selection id without guessing unknown models.
+ *
+ * @param {string | undefined} model
+ * @param {{ providers: Array<{name: string}>, models: Array<{id: string, provider: string}> } | null | undefined} config
+ * @returns {string | null}
+ */
+function qualifyModelForMultiProvider(model, config) {
+  const value = typeof model === "string" ? model.trim() : "";
+  if (!value || !config) return null;
+  const models = config.models.filter(entry => config.providers.some(provider => provider.name === entry.provider));
+  const qualified = models.find(entry => `${entry.provider}/${entry.id}` === value);
+  if (qualified) return value;
+  const legacy = value.startsWith("copilot/");
+  const id = legacy ? value.slice("copilot/".length) : value;
+  const matches = models.filter(entry => entry.id === id && (!legacy || isCopilotProviderName(entry.provider)));
+  if (new Set(matches.map(entry => entry.provider)).size > 1) {
+    throw new Error(`Ambiguous model "${value}"; specify an explicit <provider>/<model>: ${matches.map(entry => `${entry.provider}/${entry.id}`).join(", ")}`);
+  }
+  const match = matches[0];
+  return match ? `${match.provider}/${match.id}` : null;
+}
+
+/** @param {string} name @returns {boolean} */
+function isCopilotProviderName(name) {
+  return /^(?:copilot(?:-(?:responses|completions))?|github-copilot|github)(?:-\d+)?$/i.test(name);
+}
+
 module.exports = {
   isValidProviderConfig,
   isValidModelConfig,
   parseMultiProviderJson,
+  qualifyModelForMultiProvider,
+  isCopilotProviderName,
 };
diff --git a/actions/setup/js/copilot_sdk_multi_provider.test.cjs b/actions/setup/js/copilot_sdk_multi_provider.test.cjs
new file mode 100644
index 00000000000..b05f4b98d79
--- /dev/null
+++ b/actions/setup/js/copilot_sdk_multi_provider.test.cjs
@@ -0,0 +1,56 @@
+const { qualifyModelForMultiProvider, parseMultiProviderJson } = require("./copilot_sdk_multi_provider.cjs");
+
+describe("qualifyModelForMultiProvider", () => {
+  const config = {
+    providers: [{ name: "copilot-responses" }, { name: "copilot-completions-1" }, { name: "openai" }],
+    models: [
+      { id: "gpt-5.6-luna", provider: "copilot-responses" },
+      { id: "claude-haiku-4.5", provider: "copilot-completions-1" },
+      { id: "org/model", provider: "openai" },
+      { id: "orphan", provider: "missing" },
+    ],
+  };
+
+  it.each([
+    ["gpt-5.6-luna", "copilot-responses/gpt-5.6-luna"],
+    ["copilot/gpt-5.6-luna", "copilot-responses/gpt-5.6-luna"],
+    ["claude-haiku-4.5", "copilot-completions-1/claude-haiku-4.5"],
+    ["copilot/claude-haiku-4.5", "copilot-completions-1/claude-haiku-4.5"],
+    ["copilot-completions-1/claude-haiku-4.5", "copilot-completions-1/claude-haiku-4.5"],
+    ["org/model", "openai/org/model"],
+    ["openai/org/model", "openai/org/model"],
+  ])("qualifies %s", (model, expected) => {
+    expect(qualifyModelForMultiProvider(model, config)).toBe(expected);
+  });
+
+  it.each(["small", "medium", "large", "", "unknown", "orphan", "other/gpt-5.6-luna", "copilot/org/model", undefined])("does not guess %s", model => {
+    expect(qualifyModelForMultiProvider(model, config)).toBeNull();
+  });
+
+  it("returns null without a catalog", () => {
+    expect(qualifyModelForMultiProvider("gpt-5.6-luna", null)).toBeNull();
+  });
+
+  it.each(["shared", "copilot/shared"])("rejects ambiguous model %s and accepts explicit qualification", model => {
+    const ambiguous = {
+      providers: [{ name: "copilot-responses" }, { name: "copilot-completions" }],
+      models: [
+        { id: "shared", provider: "copilot-responses" },
+        { id: "shared", provider: "copilot-completions" },
+      ],
+    };
+    expect(() => qualifyModelForMultiProvider(model, ambiguous)).toThrow(/Ambiguous model.*explicit <provider>\/<model>/);
+    expect(qualifyModelForMultiProvider("copilot-completions/shared", ambiguous)).toBe("copilot-completions/shared");
+  });
+
+  it("uses the same per-model mapping after JSON handoff", () => {
+    const parsed = parseMultiProviderJson(
+      JSON.stringify({
+        model: "copilot-completions/claude-haiku-4.5",
+        providers: [{ name: "copilot-completions", type: "openai", baseUrl: "http://api-proxy:10002", wireApi: "completions" }],
+        models: [{ id: "claude-haiku-4.5", provider: "copilot-completions" }],
+      })
+    );
+    expect(qualifyModelForMultiProvider("claude-haiku-4.5", parsed)).toBe(parsed.model);
+  });
+});
diff --git a/actions/setup/js/copilot_sdk_session.cjs b/actions/setup/js/copilot_sdk_session.cjs
index 39bac3e8ce8..c609a51b9fb 100644
--- a/actions/setup/js/copilot_sdk_session.cjs
+++ b/actions/setup/js/copilot_sdk_session.cjs
@@ -35,8 +35,10 @@ const { buildCopilotSDKToolCallBudget } = require("./copilot_sdk_tool_budget.cjs
 const { resolveModelWithFallback } = require("./model_fallback.cjs");
 const { COPILOT_WORKFLOW_EVENT_TYPES } = require("./copilot_workflow_events.cjs");
 const { copilotSessionContext } = require("./copilot_session.cjs");
+const { loadCopilotSDKCustomAgents } = require("./extract_inline_sub_agents.cjs");
+const { qualifyModelForMultiProvider, parseMultiProviderJson } = require("./copilot_sdk_multi_provider.cjs");
 
-const CAPTURED_EPHEMERAL_EVENTS = new Set([...COPILOT_WORKFLOW_EVENT_TYPES, "assistant.usage", "assistant.message_delta", "assistant.reasoning_delta", "model.call_failure"]);
+const CAPTURED_EPHEMERAL_EVENTS = new Set([...COPILOT_WORKFLOW_EVENT_TYPES, "assistant.usage", "assistant.message_delta", "assistant.reasoning_delta", "model.call_failure", "model.call_final_result"]);
 
 // Default timeout for a single sendAndWait call: 10 minutes.
 // This is intentionally generous — the headless Copilot CLI has its own internal
@@ -88,6 +90,23 @@ function extractPromptFromArgs(args) {
   return null;
 }
 
+/** @param {string | undefined} serverArgs @param {(message: string) => void} [logger] @returns {boolean} */
+function isCopilotSDKBareMode(serverArgs, logger = message => process.stderr.write(`[copilot-sdk] ${message}\n`)) {
+  try {
+    const args = JSON.parse(serverArgs || "[]");
+    if (!Array.isArray(args) || args.some(arg => typeof arg !== "string")) throw new Error("expected a string array");
+    return args.includes("--no-custom-instructions");
+  } catch (error) {
+    logger(`warning: Invalid GH_AW_COPILOT_SDK_SERVER_ARGS: ${getErrorMessage(error)}; using sidecar default args`);
+    return false;
+  }
+}
+
+/** @returns {string} */
+function resolveCopilotSDKWorkingDirectory() {
+  return path.resolve(process.env.GITHUB_WORKSPACE || process.cwd(), process.env.GH_AW_ENGINE_CWD || ".");
+}
+
 /**
  * Run a Copilot agentic session using the @github/copilot-sdk.
  *
@@ -126,6 +145,9 @@ function extractPromptFromArgs(args) {
  *     defineTool?: typeof import("@github/copilot-sdk").defineTool,
  *   },
  *   sessionStateBaseDir?: string,
+ *   workingDirectory?: string,
+ *   agentsBaseDir?: string,
+ *   bare?: boolean,
  * }} options
  * @returns {Promise<{exitCode: number, output: string, hasOutput: boolean, durationMs: number}>}
  */
@@ -146,6 +168,9 @@ async function runWithCopilotSDK({
   coreLogger,
   sdkModule,
   sessionStateBaseDir,
+  workingDirectory = resolveCopilotSDKWorkingDirectory(),
+  agentsBaseDir = path.join(os.tmpdir(), "gh-aw"),
+  bare = isCopilotSDKBareMode(process.env.GH_AW_COPILOT_SDK_SERVER_ARGS, logger),
 }) {
   // Lazy-require to avoid loading the SDK when it is not needed.
   // The SDK is large and has side-effects on import (worker threads, etc.).
@@ -192,7 +217,7 @@ async function runWithCopilotSDK({
   });
   const client = new CopilotClient({
     connection,
-    workingDirectory: process.env.GITHUB_WORKSPACE || process.cwd(),
+    workingDirectory,
     logLevel,
   });
   /** @type {any} */
@@ -321,7 +346,7 @@ async function runWithCopilotSDK({
       coreLogger,
       logger: log,
       onDenied: requestSummary => recordToolDenial(`permission denied: ${requestSummary}`),
-      workspaceRoot: process.env.GITHUB_WORKSPACE,
+      workspaceRoot: workingDirectory,
     });
     const toolCallBudget = buildCopilotSDKToolCallBudget(toolConfig?.maxToolCalls, event => {
       writeDriverEvent(event.exhausted ? "guard.tool_call_budget_exceeded" : "guard.tool_call_budget_debit", event);
@@ -330,12 +355,34 @@ async function runWithCopilotSDK({
     // Build session config using the multi-provider surface.
     /** @type {any} */
     const sdkReasoningEffort = reasoningEffort;
+    const reflectedConfig = parseMultiProviderJson(process.env.GH_AW_COPILOT_SDK_MULTI_PROVIDER_JSON);
+    providers ??= reflectedConfig?.providers;
+    providerModels ??= reflectedConfig?.models;
+    const envModel = process.env.GH_AW_MODEL_ROUTING === "1" ? process.env.COPILOT_MODEL : resolveModelWithFallback(process.env, "COPILOT_MODEL");
+    const requestedModel = model || envModel || reflectedConfig?.model || undefined;
+    const providerConfig = providers && providerModels ? { providers, models: providerModels } : null;
+    const sessionModel = providerConfig ? qualifyModelForMultiProvider(requestedModel, providerConfig) : requestedModel;
+    if (providerConfig && !sessionModel) throw new Error(`Cannot qualify session model "${requestedModel || "(none)"}" against the configured provider models`);
+    const unavailableModels = [];
+    const customAgents = loadCopilotSDKCustomAgents(workingDirectory, agentsBaseDir, log).map(agent => {
+      const requested = agent.model;
+      const alias = !requested || ["small", "medium", "large"].includes(requested.toLowerCase());
+      const qualified = alias ? sessionModel : providerConfig ? qualifyModelForMultiProvider(requested, providerConfig) : requested;
+      if (!alias && !qualified) {
+        log(`warning: custom agent "${agent.name}" model "${requested}" is not in the configured provider models; using session model "${sessionModel || "(none)"}"`);
+        unavailableModels.push({ agentName: agent.name, declaredModel: requested, model: sessionModel || undefined });
+      }
+      return { ...agent, model: qualified || sessionModel || undefined };
+    });
     /** @type {import("@github/copilot-sdk").SessionConfig} */
     const sessionConfig = {
-      model: model || resolveModelWithFallback(process.env, "COPILOT_MODEL") || undefined,
+      model: sessionModel || undefined,
       ...(sdkReasoningEffort ? { reasoningEffort: sdkReasoningEffort } : {}),
       providers,
       models: providerModels,
+      workingDirectory,
+      skipCustomInstructions: bare,
+      customAgents,
       onPermissionRequest,
       ...(toolCallBudget ? { hooks: { onPreToolUse: toolCallBudget.onPreToolUse } } : {}),
       ...buildCopilotSDKSessionToolConfig(toolConfig, sdk, webFetchOptions),
@@ -349,6 +396,7 @@ async function runWithCopilotSDK({
     fs.mkdirSync(sessionDir, { recursive: true });
     const eventsPath = path.join(sessionDir, "events.jsonl");
     eventsStream = fs.createWriteStream(eventsPath, { flags: "a" });
+    for (const unavailable of unavailableModels) writeDriverEvent("subagent.model_unavailable", unavailable);
     // Snapshot to a non-null local for closure-safe writes (JSDoc nullability narrowing).
     const stream = eventsStream;
     const assistantEvents = [];
@@ -373,6 +421,10 @@ async function runWithCopilotSDK({
     session.on(event => {
       if (event.ephemeral && !CAPTURED_EPHEMERAL_EVENTS.has(event.type)) return;
       const data = { ...event.data };
+      if (event.type.startsWith("subagent.") && data.agentName && data.agentDisplayName) data.agentDisplayName = data.agentName;
+      if (data.agentMetrics) {
+        data.agentMetrics = Object.fromEntries(Object.entries(data.agentMetrics).map(([id, metric]) => [id, metric.agentName ? { ...metric, agentDisplayName: metric.agentName } : metric]));
+      }
       const context = copilotSessionContext(event);
       const scope = JSON.stringify([context.agentId, context.parentToolUseId]);
       const toolKey = JSON.stringify([scope, data.toolCallId]);
@@ -594,4 +646,4 @@ async function runWithCopilotSDK({
   }
 }
 
-module.exports = { SDK_SEND_TIMEOUT_MS_DEFAULT, SDK_POST_COMPLETION_IDLE_MS_DEFAULT, SDK_IDLE_TIMEOUT_PATTERN, extractPromptFromArgs, runWithCopilotSDK };
+module.exports = { SDK_SEND_TIMEOUT_MS_DEFAULT, SDK_POST_COMPLETION_IDLE_MS_DEFAULT, SDK_IDLE_TIMEOUT_PATTERN, extractPromptFromArgs, runWithCopilotSDK, isCopilotSDKBareMode, resolveCopilotSDKWorkingDirectory };
diff --git a/actions/setup/js/copilot_sdk_session.test.cjs b/actions/setup/js/copilot_sdk_session.test.cjs
new file mode 100644
index 00000000000..56b658b1b79
--- /dev/null
+++ b/actions/setup/js/copilot_sdk_session.test.cjs
@@ -0,0 +1,226 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { createRequire } from "module";
+import * as fs from "fs";
+import * as path from "path";
+import os from "node:os";
+
+const require = createRequire(import.meta.url);
+const { runWithCopilotSDK, resolveCopilotSDKWorkingDirectory } = require("./copilot_sdk_session.cjs");
+const models = [
+  { id: "gpt-5.4", provider: "openai" },
+  { id: "claude-sonnet-4.6", provider: "anthropic" },
+];
+const providers = [
+  { name: "openai", type: "openai", baseUrl: "http://api-proxy:10002" },
+  { name: "anthropic", type: "anthropic", baseUrl: "http://api-proxy:10002" },
+];
+
+describe("copilot_sdk_session runtime configuration", () => {
+  let base;
+  beforeEach(() => {
+    base = fs.mkdtempSync(path.join(os.tmpdir(), "sdk-session-test-"));
+    vi.stubEnv("GH_AW_SESSION_STATE_BASE_DIR", base);
+    vi.stubEnv("GH_AW_ENGINE_CWD", base);
+    vi.stubEnv("COPILOT_MODEL", "");
+    vi.stubEnv("GH_AW_MODEL_FALLBACK", "");
+    vi.stubEnv("GH_AW_MODEL_ROUTING", "");
+    vi.stubEnv("GH_AW_COPILOT_SDK_SERVER_ARGS", "[]");
+    vi.stubEnv("GH_AW_COPILOT_SDK_MULTI_PROVIDER_JSON", JSON.stringify({ model: "claude-sonnet-4.6", models, providers }));
+  });
+  afterEach(() => {
+    vi.unstubAllEnvs();
+    fs.rmSync(base, { recursive: true, force: true });
+    vi.restoreAllMocks();
+  });
+
+  it("resolves engine.cwd against the workspace rather than the driver process directory", async () => {
+    vi.stubEnv("GITHUB_WORKSPACE", "/w");
+    vi.stubEnv("GH_AW_ENGINE_CWD", "packages/app");
+    const cwd = vi.spyOn(process, "cwd").mockReturnValue("/w/packages/app");
+    expect(resolveCopilotSDKWorkingDirectory()).toBe("/w/packages/app");
+    cwd.mockRestore();
+
+    const app = path.join(base, "packages/app");
+    fs.mkdirSync(path.join(app, ".github/agents"), { recursive: true });
+    fs.writeFileSync(path.join(app, ".github/agents/local.agent.md"), "---\nmodel: small\n---\nApp agent.");
+    vi.stubEnv("GITHUB_WORKSPACE", base);
+    vi.spyOn(process, "cwd").mockReturnValue(app);
+    const createSession = vi.fn().mockResolvedValue({
+      sessionId: "relative-cwd",
+      on: () => {},
+      sendAndWait: async () => ({ data: { content: "done" } }),
+      disconnect: async () => {},
+    });
+    class FakeCopilotClient {
+      start = async () => {};
+      stop = async () => {};
+      createSession = createSession;
+    }
+    const result = await runWithCopilotSDK({
+      sdkUri: "http://127.0.0.1:3002",
+      prompt: "test",
+      logger: () => {},
+      agentsBaseDir: base,
+      sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: () => ({}) }, approveAll: () => "allow" },
+    });
+    expect(result.exitCode).toBe(0);
+    expect(createSession).toHaveBeenCalledWith(
+      expect.objectContaining({
+        workingDirectory: app,
+        customAgents: [{ name: "local", displayName: "local", prompt: "App agent.", model: "anthropic/claude-sonnet-4.6" }],
+      })
+    );
+  });
+
+  it.each(["{bad json", '{"args":["--no-custom-instructions"]}'])("warns and starts a session for invalid server args %s", serverArgs => {
+    vi.stubEnv("GH_AW_COPILOT_SDK_SERVER_ARGS", serverArgs);
+    const createSession = vi.fn().mockResolvedValue({
+      sessionId: "invalid-args",
+      on: () => {},
+      sendAndWait: async () => ({ data: { content: "done" } }),
+      disconnect: async () => {},
+    });
+    class FakeCopilotClient {
+      start = async () => {};
+      stop = async () => {};
+      createSession = createSession;
+    }
+    const logger = vi.fn();
+    return runWithCopilotSDK({
+      sdkUri: "http://127.0.0.1:3002",
+      prompt: "test",
+      logger,
+      agentsBaseDir: base,
+      sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: () => ({}) }, approveAll: () => "allow" },
+    }).then(result => {
+      expect(result.exitCode).toBe(0);
+      expect(createSession).toHaveBeenCalledWith(expect.objectContaining({ skipCustomInstructions: false }));
+      expect(logger).toHaveBeenCalledWith(expect.stringMatching(/warning: Invalid GH_AW_COPILOT_SDK_SERVER_ARGS.*using sidecar default args/));
+    });
+  });
+
+  it("preserves explicit agent models without a BYOK catalog or misleading warnings", async () => {
+    vi.stubEnv("GH_AW_COPILOT_SDK_MULTI_PROVIDER_JSON", "");
+    fs.mkdirSync(path.join(base, ".github/agents"), { recursive: true });
+    fs.writeFileSync(path.join(base, ".github/agents/researcher.agent.md"), "---\nmodel: claude-sonnet-4.6\n---\nResearch carefully.");
+    const createSession = vi.fn().mockResolvedValue({
+      sessionId: "no-catalog",
+      on: () => {},
+      sendAndWait: async () => ({ data: { content: "done" } }),
+      disconnect: async () => {},
+    });
+    class FakeCopilotClient {
+      start = async () => {};
+      stop = async () => {};
+      createSession = createSession;
+    }
+    const logger = vi.fn();
+    const result = await runWithCopilotSDK({
+      sdkUri: "http://127.0.0.1:3002",
+      prompt: "test",
+      model: "gpt-5.4",
+      logger,
+      agentsBaseDir: base,
+      sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: () => ({}) }, approveAll: () => "allow" },
+    });
+    expect(result.exitCode).toBe(0);
+    expect(createSession).toHaveBeenCalledWith(expect.objectContaining({ model: "gpt-5.4", customAgents: [{ name: "researcher", displayName: "researcher", prompt: "Research carefully.", model: "claude-sonnet-4.6" }] }));
+    expect(logger.mock.calls.flat().some(message => message.includes("warning: custom agent"))).toBe(false);
+  });
+
+  it("fails an unknown session model explicitly rather than warning and continuing", async () => {
+    const createSession = vi.fn();
+    class FakeCopilotClient {
+      start = async () => {};
+      stop = async () => {};
+      createSession = createSession;
+    }
+    const logger = vi.fn();
+    const result = await runWithCopilotSDK({
+      sdkUri: "http://127.0.0.1:3002",
+      prompt: "test",
+      model: "unavailable-session-model",
+      logger,
+      agentsBaseDir: base,
+      sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: () => ({}) }, approveAll: () => "allow" },
+    });
+    expect(result.exitCode).toBe(1);
+    expect(result.output).toMatch(/Cannot qualify session model "unavailable-session-model"/);
+    expect(logger).toHaveBeenCalledWith(expect.stringMatching(/error: Cannot qualify session model/));
+    expect(createSession).not.toHaveBeenCalled();
+  });
+
+  it("attributes SDK lifecycle and metrics to declared names instead of task display names", async () => {
+    let handler;
+    const events = [
+      { type: "subagent.started", data: { invocationId: "child", agentName: "file-summarizer", agentDisplayName: "readme-summarizer" } },
+      { type: "subagent.completed", data: { invocationId: "child", agentName: "file-summarizer", agentDisplayName: "summarize-readme" } },
+      { type: "session.shutdown", data: { agentMetrics: { child: { agentName: "file-summarizer", agentDisplayName: "readme-summarizer" }, main: { totalNanoAiu: 1 } } } },
+    ];
+    class FakeCopilotClient {
+      start = async () => {};
+      stop = async () => {};
+      createSession = async () => ({
+        sessionId: "declared-names",
+        on: callback => {
+          handler = callback;
+        },
+        sendAndWait: async () => {
+          events.forEach(event => handler(event));
+          return { data: { content: "done" } };
+        },
+        disconnect: async () => {},
+      });
+    }
+    const result = await runWithCopilotSDK({
+      sdkUri: "http://127.0.0.1:3002",
+      prompt: "test",
+      logger: () => {},
+      agentsBaseDir: base,
+      sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: () => ({}) }, approveAll: () => "allow" },
+    });
+    expect(result.exitCode).toBe(0);
+    const captured = fs
+      .readFileSync(path.join(base, "declared-names/events.jsonl"), "utf8")
+      .trim()
+      .split("\n")
+      .map(line => JSON.parse(line));
+    expect(captured[0].data.agentDisplayName).toBe("file-summarizer");
+    expect(captured[1].data.agentDisplayName).toBe("file-summarizer");
+    expect(captured[2].data.agentMetrics.child.agentDisplayName).toBe("file-summarizer");
+    expect(captured[2].data.agentMetrics.main).toEqual({ totalNanoAiu: 1 });
+    expect(events[0].data.agentDisplayName).toBe("readme-summarizer");
+    expect(events[2].data.agentMetrics.child.agentDisplayName).toBe("readme-summarizer");
+  });
+
+  it.each(["routing", "environment", "fallback", "reflect"])("qualifies the %s model before createSession", async source => {
+    const expected = source === "reflect" ? "anthropic/claude-sonnet-4.6" : "openai/gpt-5.4";
+    if (source === "routing" || source === "environment") vi.stubEnv("COPILOT_MODEL", "gpt-5.4");
+    if (source === "routing") {
+      vi.stubEnv("GH_AW_MODEL_ROUTING", "1");
+      vi.stubEnv("GH_AW_MODEL_FALLBACK", "claude-sonnet-4.6");
+    }
+    if (source === "fallback") vi.stubEnv("GH_AW_MODEL_FALLBACK", "gpt-5.4");
+    vi.stubEnv("GH_AW_COPILOT_SDK_SERVER_ARGS", '["--no-custom-instructions"]');
+    const createSession = vi.fn().mockResolvedValue({
+      sessionId: source,
+      on: () => {},
+      sendAndWait: async () => ({ data: { content: "done" } }),
+      disconnect: async () => {},
+    });
+    class FakeCopilotClient {
+      start = async () => {};
+      stop = async () => {};
+      createSession = createSession;
+    }
+    const result = await runWithCopilotSDK({
+      sdkUri: "http://127.0.0.1:3002",
+      prompt: "test",
+      logger: () => {},
+      agentsBaseDir: base,
+      sdkModule: { CopilotClient: FakeCopilotClient, RuntimeConnection: { forUri: () => ({}) }, approveAll: () => "allow" },
+    });
+    expect(result.exitCode).toBe(0);
+    expect(createSession).toHaveBeenCalledWith(expect.objectContaining({ model: expected, providers, models, workingDirectory: base, skipCustomInstructions: true, customAgents: [] }));
+  });
+});
diff --git a/actions/setup/js/copilot_workflow_events.cjs b/actions/setup/js/copilot_workflow_events.cjs
index 65659f645c4..f0ff173c2f9 100644
--- a/actions/setup/js/copilot_workflow_events.cjs
+++ b/actions/setup/js/copilot_workflow_events.cjs
@@ -27,6 +27,17 @@ const COPILOT_WORKFLOW_EVENT_FIELDS = {
     spawnDepth: ["spawnDepth", "spawn_depth"],
   },
   "subagent.configured": { invocationId: ["invocationId"], model: ["model"], contextTier: ["contextTier"], reasoningEffort: ["reasoningEffort"], multiTurn: ["multiTurn"] },
+  "subagent.selected": {
+    invocationId: ["invocationId"],
+    toolCallId: ["toolCallId"],
+    agentName: ["agentName"],
+    agentDisplayName: ["agentDisplayName"],
+    tools: ["tools"],
+    model: ["model"],
+    selectedModel: ["selectedModel"],
+    resolvedModel: ["resolvedModel"],
+    modelSelectionSource: ["modelSelectionSource"],
+  },
   "subagent.request": {
     invocationId: ["invocationId"],
     agentName: ["agentName"],
diff --git a/actions/setup/js/copilot_workflow_events.test.cjs b/actions/setup/js/copilot_workflow_events.test.cjs
new file mode 100644
index 00000000000..dad76f72f02
--- /dev/null
+++ b/actions/setup/js/copilot_workflow_events.test.cjs
@@ -0,0 +1,37 @@
+import { describe, expect, it } from "vitest";
+import { createRequire } from "node:module";
+
+const require = createRequire(import.meta.url);
+const { COPILOT_WORKFLOW_EVENT_TYPES } = require("./copilot_workflow_events.cjs");
+const { normalizeCopilotSession } = require("./copilot_session.cjs");
+const { normalizeUnifiedSessionEvent } = require("./unified_session_payload.cjs");
+
+describe("Copilot subagent selection evidence", () => {
+  it("captures selected events and preserves model evidence through unified projection", () => {
+    const event = {
+      type: "subagent.selected",
+      ephemeral: true,
+      agentId: "child",
+      timestamp: "2026-10-10T00:00:00Z",
+      data: {
+        agentName: "researcher",
+        agentDisplayName: "Researcher",
+        tools: ["read", "grep"],
+        invocationId: "invoke-1",
+        toolCallId: "delegate-1",
+        parentToolCallId: "delegate-1",
+        model: "copilot/claude-sonnet-4.6",
+        selectedModel: "anthropic/claude-sonnet-4.6",
+        resolvedModel: "anthropic/claude-sonnet-4.6",
+        modelSelectionSource: "custom-agent",
+      },
+    };
+    expect(COPILOT_WORKFLOW_EVENT_TYPES.has(event.type)).toBe(true);
+    const normalized = normalizeCopilotSession([event]).find(entry => entry.type === event.type);
+    expect(normalizeUnifiedSessionEvent(normalized)).toMatchObject({
+      type: event.type,
+      agentId: "child",
+      data: event.data,
+    });
+  });
+});
diff --git a/actions/setup/js/extract_inline_sub_agents.cjs b/actions/setup/js/extract_inline_sub_agents.cjs
index 31ac7aa6b17..226269cecc8 100644
--- a/actions/setup/js/extract_inline_sub_agents.cjs
+++ b/actions/setup/js/extract_inline_sub_agents.cjs
@@ -330,4 +330,62 @@ function writeInlineSubAgents(content, workspaceDir, agentsBaseDir, engineId) {
   return mainContent;
 }
 
-module.exports = { extractInlineSubAgents, writeInlineSubAgents, getEngineSubAgentTarget, preserveSubAgentFrontmatter, closeUnterminatedSubAgentMarkers };
+/**
+ * Read repository and workflow-written Copilot agents when the SDK session starts.
+ * Workflow definitions override repository definitions with the same name.
+ *
+ * @param {string} workspaceDir
+ * @param {string} agentsBaseDir
+ * @param {(message: string) => void} logger
+ * @returns {import("@github/copilot-sdk").CustomAgentConfig[]}
+ */
+function loadCopilotSDKCustomAgents(workspaceDir, agentsBaseDir, logger) {
+  const { extractFrontmatterAndBody } = require("./frontmatter_hash_pure.cjs");
+  const { parseDocument } = require("./work_queue_yaml.cjs");
+  const target = inlineArtifactTarget("SUB_AGENT", getEngineSubAgentTarget("copilot"));
+  const directories = new Set([path.join(workspaceDir, ".github/agents"), path.join(agentsBaseDir, target.dir)]);
+  const agents = new Map();
+  for (const directory of directories) {
+    let entries;
+    try {
+      entries = fs.readdirSync(directory, { withFileTypes: true });
+    } catch (error) {
+      if (!(error instanceof Error && "code" in error && error.code === "ENOENT")) logger(`warning: cannot read custom agents in ${directory}: ${String(error)}`);
+      continue;
+    }
+    for (const entry of entries.sort((a, b) => a.name.localeCompare(b.name))) {
+      if (!entry.isFile() || !entry.name.endsWith(".agent.md")) continue;
+      const agentPath = path.join(directory, entry.name);
+      try {
+        const { frontmatterText, markdown } = extractFrontmatterAndBody(fs.readFileSync(agentPath, "utf8"));
+        /** @type {any} */
+        const document = parseDocument(frontmatterText);
+        if (!document) throw new Error("cannot parse agent frontmatter");
+        if (document.errors.length) throw new Error(document.errors.map(error => error.message).join("; "));
+        const frontmatter = document.toJS() || {};
+        if (typeof frontmatter !== "object" || Array.isArray(frontmatter)) throw new Error("agent frontmatter must be a mapping");
+        const name = typeof frontmatter.name === "string" && frontmatter.name.trim() ? frontmatter.name.trim() : entry.name.slice(0, -".agent.md".length);
+        let tools = frontmatter.tools;
+        if (typeof tools === "string")
+          tools = tools
+            .split(",")
+            .map(tool => tool.trim())
+            .filter(Boolean);
+        if (tools !== undefined && tools !== null && (!Array.isArray(tools) || !tools.every(tool => typeof tool === "string"))) throw new Error("agent tools must be a list of names or a comma-separated string");
+        agents.set(name, {
+          name,
+          displayName: name,
+          prompt: markdown.trim(),
+          ...(typeof frontmatter.description === "string" ? { description: frontmatter.description } : {}),
+          ...(typeof frontmatter.model === "string" ? { model: frontmatter.model.trim() } : {}),
+          ...(tools !== undefined ? { tools } : {}),
+        });
+      } catch (error) {
+        logger(`warning: cannot load custom agent ${agentPath}: ${String(error)}`);
+      }
+    }
+  }
+  return [...agents.values()];
+}
+
+module.exports = { extractInlineSubAgents, writeInlineSubAgents, getEngineSubAgentTarget, preserveSubAgentFrontmatter, closeUnterminatedSubAgentMarkers, loadCopilotSDKCustomAgents };
diff --git a/actions/setup/js/extract_inline_sub_agents.test.cjs b/actions/setup/js/extract_inline_sub_agents.test.cjs
index 588b9e58536..da252ae39ee 100644
--- a/actions/setup/js/extract_inline_sub_agents.test.cjs
+++ b/actions/setup/js/extract_inline_sub_agents.test.cjs
@@ -4,7 +4,6 @@
 import { describe, it, expect, beforeEach, afterEach } from "vitest";
 const fs = require("fs");
 const path = require("path");
-const os = require("os");
 
 // Provide a minimal core mock so the module loads correctly.
 global.core = {
@@ -14,11 +13,36 @@ global.core = {
   setFailed: () => {},
 };
 
-const { extractInlineSubAgents, writeInlineSubAgents, preserveSubAgentFrontmatter, closeUnterminatedSubAgentMarkers } = require("./extract_inline_sub_agents.cjs");
+const { extractInlineSubAgents, writeInlineSubAgents, preserveSubAgentFrontmatter, closeUnterminatedSubAgentMarkers, loadCopilotSDKCustomAgents } = require("./extract_inline_sub_agents.cjs");
 
 // Helper: returns a ## agent: `name` start marker line.
 const agentMarker = name => `## agent: \`${name}\``;
 
+describe("loadCopilotSDKCustomAgents", () => {
+  it("loads runtime files, preserving YAML descriptions and workflow precedence", () => {
+    const base = fs.mkdtempSync(path.join(process.cwd(), ".sdk-agents-test-"));
+    try {
+      const workspace = path.join(base, "workspace");
+      const workflow = path.join(base, "workflow");
+      fs.mkdirSync(path.join(workspace, ".github/agents"), { recursive: true });
+      fs.mkdirSync(path.join(workflow, ".github/agents"), { recursive: true });
+      fs.writeFileSync(path.join(workspace, ".github/agents/helper.agent.md"), "---\nname: helper\n---\nRepository version.");
+      fs.writeFileSync(path.join(workflow, ".github/agents/helper.agent.md"), "---\nname: helper\ndescription: |\n  First line\n  Second line\ntools: []\nmodel: small\n---\nWorkflow version.");
+      fs.writeFileSync(path.join(workspace, ".github/agents/plain.agent.md"), "Prompt without frontmatter.");
+      fs.writeFileSync(path.join(workspace, ".github/agents/ignored.md"), "Ignored file.");
+      fs.writeFileSync(path.join(workspace, ".github/agents/broken.agent.md"), "---\ntools: {invalid: true}\n---\nInvalid tools.");
+      const warnings = [];
+      expect(loadCopilotSDKCustomAgents(workspace, workflow, message => warnings.push(message))).toEqual([
+        { name: "helper", displayName: "helper", description: "First line\nSecond line\n", tools: [], model: "small", prompt: "Workflow version." },
+        { name: "plain", displayName: "plain", prompt: "Prompt without frontmatter." },
+      ]);
+      expect(warnings).toEqual([expect.stringContaining("agent tools must be a list")]);
+    } finally {
+      fs.rmSync(base, { recursive: true, force: true });
+    }
+  });
+});
+
 // ─────────────────────────────────────────────────────────────────────────────
 // extractInlineSubAgents — unit tests
 // ─────────────────────────────────────────────────────────────────────────────
@@ -230,7 +254,7 @@ describe("writeInlineSubAgents", () => {
   let tmpDir;
 
   beforeEach(() => {
-    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "inline-agents-test-"));
+    tmpDir = fs.mkdtempSync(path.join(process.cwd(), ".inline-agents-test-"));
   });
 
   afterEach(() => {
diff --git a/actions/setup/js/smoke_copilot_sub_agents.test.cjs b/actions/setup/js/smoke_copilot_sub_agents.test.cjs
new file mode 100644
index 00000000000..18f9bd8e485
--- /dev/null
+++ b/actions/setup/js/smoke_copilot_sub_agents.test.cjs
@@ -0,0 +1,87 @@
+import fs from "node:fs";
+import { createRequire } from "node:module";
+import { describe, test, expect } from "vitest";
+
+const require = createRequire(import.meta.url);
+const workflow = fs.readFileSync(new URL("../../../.github/workflows/smoke-copilot-sub-agents.md", import.meta.url), "utf8");
+const script = workflow
+  .split("      script: |\n")[1]
+  .split("\n---")[0]
+  .replace(/^        /gm, "");
+const AsyncFunction = Object.getPrototypeOf(async function () {}).constructor;
+
+function evidence() {
+  const agents = [
+    ["haiku-whoami", "copilot-completions/claude-haiku-4.5", "/chat/completions"],
+    ["mini-whoami", "copilot-responses/gpt-5-mini", "/responses"],
+    ["nano-whoami", "copilot-responses/gpt-5-nano", "/responses"],
+  ];
+  return {
+    events: agents.flatMap(([agentName, model]) => [
+      { type: "subagent.started", data: { agentName, model, invocationId: agentName } },
+      { type: "subagent.completed", data: { model, invocationId: agentName } },
+    ]),
+    requests: agents.map(([, model, endpoint]) => ({ model: model.split("/")[1], path: endpoint, status: 200 })),
+  };
+}
+
+async function assertEvidence({ events, requests }, variant = "inline_strict") {
+  const mockRequire = name => {
+    if (name.endsWith("unified_session.cjs")) return { writeUnifiedSession() {} };
+    if (name === "node:fs") {
+      return {
+        existsSync: () => true,
+        readFileSync: file => (file.endsWith("aw_session.jsonl") ? events : requests).map(record => JSON.stringify(record)).join("\n"),
+      };
+    }
+    return require(name);
+  };
+  await new AsyncFunction("require", "process", script)(mockRequire, {
+    env: { RUNNER_TEMP: "/tmp", SMOKE_VARIANT: variant, SMOKE_EXECUTION: "success" },
+  });
+}
+
+describe("Copilot sub-agent smoke evidence", () => {
+  test("accepts completed delegation with qualified models and matching proxy requests", async () => {
+    await expect(assertEvidence(evidence())).resolves.toBeUndefined();
+  });
+
+  test("accepts the served dated Claude model identity", async () => {
+    const data = evidence();
+    data.events[1].data.model = "copilot-completions/claude-haiku-4-5-20251001";
+    await expect(assertEvidence(data)).resolves.toBeUndefined();
+  });
+
+  test("rejects success without delegation", async () => {
+    await expect(assertEvidence({ events: [], requests: evidence().requests })).rejects.toThrow("must actually run");
+  });
+
+  test("rejects a sub-agent that falls back to the main model", async () => {
+    const data = evidence();
+    data.events[1].data.model = "copilot-responses/gpt-5.3-codex";
+    await expect(assertEvidence(data)).rejects.toThrow("changed or fell back");
+  });
+
+  test("rejects selection of a different model", async () => {
+    const data = evidence();
+    data.events.push({ type: "subagent.selected", data: { invocationId: "haiku-whoami", selectedModel: "copilot-responses/gpt-5-mini" } });
+    await expect(assertEvidence(data)).rejects.toThrow("changed or fell back");
+  });
+
+  test("rejects requests using the wrong wire API", async () => {
+    const data = evidence();
+    data.requests[0].path = "/responses";
+    await expect(assertEvidence(data)).rejects.toThrow("no successful");
+  });
+
+  test("rejects failed invocations even with successful model requests", async () => {
+    const data = evidence();
+    data.events.push({ type: "subagent.failed", data: { invocationId: "haiku-whoami" } });
+    await expect(assertEvidence(data)).rejects.toThrow("failed");
+  });
+
+  test("requires no delegation in the negative control", async () => {
+    await expect(assertEvidence({ events: [], requests: [] }, "single_agent_control")).resolves.toBeUndefined();
+    await expect(assertEvidence(evidence(), "single_agent_control")).rejects.toThrow("must not invoke");
+  });
+});
diff --git a/actions/setup/js/unified_session_payload.cjs b/actions/setup/js/unified_session_payload.cjs
index 2621d04e55c..225beed8bb7 100644
--- a/actions/setup/js/unified_session_payload.cjs
+++ b/actions/setup/js/unified_session_payload.cjs
@@ -23,6 +23,7 @@ const SCOPED_AGENT_TYPES = new Set([
   "tool.execution_complete",
   "usage.report",
   "session.result",
+  "model.call_final_result",
 ]);
 
 /** @type {Fields} */
diff --git a/actions/setup/js/unified_session_payload.test.cjs b/actions/setup/js/unified_session_payload.test.cjs
index 15cb37a93d9..059b5ba4aec 100644
--- a/actions/setup/js/unified_session_payload.test.cjs
+++ b/actions/setup/js/unified_session_payload.test.cjs
@@ -14,6 +14,32 @@ import { dynamicWorkflow } from "./fixtures/claude_dynamic_workflow.cjs";
 import { DYNAMIC_WORKFLOW_EVENT_TYPES } from "./dynamic_workflow_session.cjs";
 
 describe("essential unified session payloads", () => {
+  it.each([true, false])("retains final model result and BYOK=%s through persisted unified projection", isByok => {
+    const source = {
+      type: "model.call_final_result",
+      ephemeral: true,
+      agentId: "researcher",
+      parentToolCallId: "delegate-1",
+      data: {
+        model: "anthropic/claude-sonnet-4.6",
+        isByok,
+        result: { status: "success", usage: { inputTokens: 0, outputTokens: 42 }, stopReason: "end_turn" },
+        extensionEvidence: { retained: true },
+      },
+    };
+    const original = structuredClone(source);
+    const projected = normalizeUnifiedSessionEvent(source);
+    expect(projected.data).toEqual({ ...source.data, agentId: "researcher", parentToolCallId: "delegate-1" });
+    const [unified] = mergeSessionSources([{ component: "agent", phase: "agent", path: "sdk.jsonl", events: normalizeCopilotSession([source]) }]);
+    const persisted = JSON.parse(JSON.stringify(unified));
+    expect(persisted.data).toMatchObject(source.data);
+    expect(persisted.data.parentToolCallId).toBe("delegate-1");
+    expect(normalizeUnifiedSessionEvent(persisted).data).toEqual(persisted.data);
+    const validate = createSessionValidator("unified").event;
+    expect(validate(persisted), JSON.stringify(validate.errors)).toBe(true);
+    expect(source).toEqual(original);
+  });
+
   it.each([401, 503, 0, null])("retains observed session-error status codes through projection and schema validation (%s)", statusCode => {
     const source = { type: "session.error", data: { errorType: "provider", message: "Observed failure.", statusCode, opaque: "PRIVATE_ERROR_CONTEXT" } };
     const original = structuredClone(source);
diff --git a/docs/adr/67509-split-copilot-sdk-providers-by-wire-api.md b/docs/adr/67509-split-copilot-sdk-providers-by-wire-api.md
new file mode 100644
index 00000000000..cf6f7b8376d
--- /dev/null
+++ b/docs/adr/67509-split-copilot-sdk-providers-by-wire-api.md
@@ -0,0 +1,102 @@
+# ADR-67509: Split Copilot SDK Providers by Wire API and Qualify Every Routed Model
+
+**Date**: 2026-10-10
+**Status**: Proposed
+**Deciders**: gh-aw maintainers
+
+---
+
+### Context
+
+The Copilot coding agent opened PR #67509 for issue #67507.
+
+The Copilot SDK engine configured a single provider per Copilot endpoint and passed bare model names
+(for example `gpt-5.6-luna`) to routed SDK sessions. Two problems followed. First, bare model names
+bypassed BYOK inference routing under organization billing, so spend attribution and proxy routing
+were wrong. Second, one provider carries one wire API, but Copilot exposes both the Responses API
+(`/responses`) and Chat Completions (`/chat/completions`) and different model families support
+different ones — so a GPT main agent and a Claude sub-agent could not coexist in the same session.
+Separately, declared sub-agents (inline and repository agent files) were parsed but never handed to
+the SDK, so delegation silently ran on the main agent's model. Smoke coverage asserted on model-name
+replies, which a model can hallucinate, so none of this was reliably caught.
+
+### Decision
+
+We will split each Copilot endpoint into two sibling SDK providers, `copilot-responses` and
+`copilot-completions`, derived from `/reflect` endpoint capabilities, and route each model to the
+provider matching its wire API (`inferWireApiForModel`, with explicit `wire_api`/`wireApi` from the
+model catalog winning over the GPT-5+ `responses` heuristic). Every model identifier that reaches the
+SDK — routed, fallback, reflected, and sub-agent — is qualified as `<provider>/<model>` so BYOK
+inference is used; explicitly configured API selections are preserved when supported.
+Each Copilot model's provider must match its `/reflect` `supported_endpoints`. An incompatible
+`COPILOT_PROVIDER_WIRE_API` override fails at startup before the sidecar starts with
+`Model endpoint mismatch: …`, naming the model, override, and supported endpoints.
+Declared agents are loaded as SDK `customAgents` carrying name, description, prompt, and tools, with
+concrete models qualified and aliases inheriting the session model. Unknown concrete agent models
+inherit without failing the run, but emit `subagent.model_unavailable` with the declared agent name,
+declared model, and inherited model; audit surfaces this as a warning finding. Aliases inherit quietly.
+Non-Copilot endpoints and CLI mode are deliberately left unchanged. Observability captures
+`subagent.selected` and `model.call_final_result` including BYOK status, and `pkg/cli` normalizes
+qualified identities (`copilot-(responses|completions)` stripped) so audit spend attribution still
+groups by real model. Smoke tests now require evidence of completed delegation on the expected model
+and proxy endpoint instead of model-name replies.
+
+### Alternatives Considered
+
+#### Alternative 1: Keep one provider per endpoint and pick a single wire API
+
+Continue with a provider-wide wire API, choosing `responses` or `completions` per run. This is the
+smallest change and keeps the provider list short. Rejected because it structurally prevents
+cross-family sessions: a Claude sub-agent delegated from a GPT main agent needs a different wire API
+in the same session, which is the primary defect this PR fixes.
+
+#### Alternative 2: Qualify models only at the top-level session, not for sub-agents and fallbacks
+
+Qualify the main session model and leave sub-agent, fallback, and reflected models bare, relying on
+server-side defaults. Tempting because it touches far fewer call sites. Rejected because the bare
+paths are exactly where BYOK routing was being bypassed; partial qualification would leave spend
+attribution wrong for delegated work and make failures intermittent and hard to diagnose.
+
+#### Alternative 3: Resolve wire API dynamically per request instead of per provider
+
+Let the driver choose the HTTP path at call time rather than modelling two providers. Rejected
+because the SDK's provider abstraction owns `wireApi`; per-request override would fork the SDK's
+transport handling and lose the SDK-native `customAgents` routing we rely on.
+
+### Consequences
+
+#### Positive
+
+- Cross-family sessions work: a GPT main agent on `/responses` can delegate to a Claude sub-agent on
+  `/chat/completions` within one session.
+- Routed, fallback, reflected, and sub-agent calls all use BYOK inference, so org-billed runs route
+  through the intended proxy and attribute spend correctly.
+- Declared inline and repository sub-agents are actually honored by the SDK, with their prompts and
+  tool sets intact.
+- Smoke and audit assertions are grounded in delegation/proxy evidence rather than model self-reports,
+  which a model can fake.
+
+#### Negative
+
+- The provider list roughly doubles for every Copilot endpoint, making reflected configuration and
+  debug output noisier and harder to read.
+- Wire-API inference adds a heuristic (`GPT-5+ → responses`) that will need maintenance as new model
+  families ship; a wrong inference produces a routing failure rather than a graceful degradation.
+- Qualified identifiers (`copilot-responses/gpt-5.6-luna`) leak into logs, session records, and
+  fixtures, requiring normalization in `pkg/cli` and in any downstream consumer that matched on bare
+  model names.
+- Behaviour now diverges between SDK mode and CLI mode, which stays on the old path — two code paths
+  to reason about until CLI mode is migrated.
+
+#### Neutral
+
+- Non-Copilot endpoints (including Anthropic-typed providers, where `wireApi` is ignored) are
+  unaffected by this change.
+- Unknown sub-agent models inherit the session model without failing the run; structured events and
+  audit findings make this compatibility fallback visible.
+- `docs/src/content/docs/reference/engines.md` documents the new provider naming, so the qualified
+  form is now part of the user-facing contract.
+
+---
+
+*Proposed for review by the gh-aw maintainers.*
diff --git a/docs/src/content/docs/reference/engines.md b/docs/src/content/docs/reference/engines.md
index cf424a24ea9..7fea6510c85 100644
--- a/docs/src/content/docs/reference/engines.md
+++ b/docs/src/content/docs/reference/engines.md
@@ -561,6 +561,16 @@ Enable `engine.copilot-sdk: true` to run Copilot in SDK mode.
 In this mode, the harness starts a local sidecar and runs the
 SDK driver process instead of the default CLI-only flow.
 
+The built-in SDK driver loads inline sub-agents and repository
+`.github/agents/*.agent.md` files as custom agents. It qualifies session and
+sub-agent models against the AWF model catalog. Copilot models use separate
+Responses and Chat Completions providers according to their supported endpoints,
+so GPT and Claude agents can use different wire APIs in the same session.
+The aliases `small`, `medium`, and `large` inherit the session model; an unknown
+sub-agent model logs a warning and inherits it. Sub-agent activity and final model
+results, including BYOK status, are retained in `usage/aw_session.jsonl`.
+This behavior applies to SDK mode, not the default CLI mode.
+
 Use top-level `max-tool-denials` to stop SDK inference when
 tool requests are repeatedly denied. The default is `5`.
 This field is only supported when `engine.id: copilot` and
diff --git a/pkg/cli/audit_finding_codes.go b/pkg/cli/audit_finding_codes.go
index 0af796fadcd..00e620b17c9 100644
--- a/pkg/cli/audit_finding_codes.go
+++ b/pkg/cli/audit_finding_codes.go
@@ -15,6 +15,7 @@ const (
 	AuditFindingBlockedNetworkRequests   AuditFindingCode = "blocked_network_requests"
 	AuditFindingWorkflowSucceeded        AuditFindingCode = "workflow_succeeded"
 	AuditFindingSubagentModelNotObserved AuditFindingCode = "subagent_model_not_observed"
+	AuditFindingSubagentModelUnavailable AuditFindingCode = "subagent_model_unavailable"
 	AuditFindingSubagentFailed           AuditFindingCode = "subagent_failed"
 	AuditFindingDetectionJobFailed       AuditFindingCode = "threat_detection_job_failed"
 	AuditFindingThreatDetected           AuditFindingCode = "threat_detected"
diff --git a/pkg/cli/audit_report_analysis.go b/pkg/cli/audit_report_analysis.go
index 4b8c8bdaea9..e8043bc5a70 100644
--- a/pkg/cli/audit_report_analysis.go
+++ b/pkg/cli/audit_report_analysis.go
@@ -35,6 +35,7 @@ func generateFindings(processedRun ProcessedRun, metrics MetricsData, errors []V
 	findings = append(findings, generateToolingFindings(processedRun)...)
 	findings = append(findings, generateFirewallFindings(processedRun)...)
 	findings = append(findings, generateSubagentModelFindings(processedRun.TokenUsage)...)
+	findings = append(findings, generateSubagentModelUnavailableFindings(processedRun.Run.LogsPath)...)
 	findings = append(findings, generateSuccessFindings(processedRun.Run, metrics, errors)...)
 	return findings
 }
diff --git a/pkg/cli/audit_subagent_model.go b/pkg/cli/audit_subagent_model.go
new file mode 100644
index 00000000000..e6a8eb3cc6e
--- /dev/null
+++ b/pkg/cli/audit_subagent_model.go
@@ -0,0 +1,31 @@
+package cli
+
+import "fmt"
+
+func generateSubagentModelUnavailableFindings(runDir string) []AuditFinding {
+	attribution, _, err := readSessionModelRouting(runDir)
+	if err != nil {
+		auditReportLog.Printf("failed to read sub-agent model availability: %v", err)
+		return nil
+	}
+	if attribution == nil {
+		return nil
+	}
+	var findings []AuditFinding
+	seen := make(map[sessionSubagentModelUnavailable]struct{})
+	for _, model := range attribution.UnavailableSubagentModels {
+		if _, duplicate := seen[model]; duplicate {
+			continue
+		}
+		seen[model] = struct{}{}
+		findings = append(findings, AuditFinding{
+			Code:        AuditFindingSubagentModelUnavailable,
+			Category:    "tooling",
+			Severity:    "medium",
+			Title:       "Sub-agent Model Unavailable",
+			Description: fmt.Sprintf("Sub-agent %s declared model %s was unavailable; used inherited session model %s", model.AgentName, model.DeclaredModel, model.Model),
+			Impact:      "The sub-agent used the session model instead of its declared model. This fallback is a warning, not a delegation failure.",
+		})
+	}
+	return findings
+}
diff --git a/pkg/cli/audit_subagent_model_test.go b/pkg/cli/audit_subagent_model_test.go
new file mode 100644
index 00000000000..2788f2afd2a
--- /dev/null
+++ b/pkg/cli/audit_subagent_model_test.go
@@ -0,0 +1,78 @@
+package cli
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAuditSubagentModelUnavailable(t *testing.T) {
+	runDir := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(runDir, "usage"), 0755))
+	event := `{"type":"subagent.model_unavailable","data":{"agentName":"research","declaredModel":"claude-haiku-4.5","model":"anthropic/claude-opus-4.8"},"provenance":{"component":"agent","phase":"agent"}}`
+	content := subagentSessionHeader + event + "\n" + event + "\n"
+	require.NoError(t, os.WriteFile(filepath.Join(runDir, "usage", "aw_session.jsonl"), []byte(content), 0600))
+
+	attribution, found, err := readSessionModelRouting(runDir)
+	require.NoError(t, err)
+	assert.False(t, found, "availability warnings do not imply workflow.info was found")
+	require.Len(t, attribution.UnavailableSubagentModels, 2)
+	assert.Nil(t, attribution.modelRouting())
+
+	run := ProcessedRun{Run: WorkflowRun{Conclusion: "success", LogsPath: runDir}}
+	findings := generateFindings(run, MetricsData{}, nil)
+	require.Len(t, findings, 2, "one deduplicated warning and the existing success finding")
+	warning := findings[0]
+	assert.Equal(t, AuditFindingSubagentModelUnavailable, warning.Code)
+	assert.Equal(t, "tooling", warning.Category)
+	assert.Equal(t, "medium", string(warning.Severity))
+	assert.Contains(t, warning.Description, "research")
+	assert.Contains(t, warning.Description, "claude-haiku-4.5")
+	assert.Contains(t, warning.Description, "anthropic/claude-opus-4.8")
+	assert.Equal(t, AuditFindingWorkflowSucceeded, findings[1].Code)
+	assert.Empty(t, generateSubagentModelFindings(run.TokenUsage))
+
+	requests, actuals, _, err := parseSessionSubagentModels(strings.NewReader(content), true)
+	require.NoError(t, err)
+	assert.Empty(t, requests, "availability warnings must not create invocations or failures")
+	assert.Empty(t, actuals, "fallback metadata is not observed model traffic")
+}
+
+func TestAuditSubagentModelUnavailableSources(t *testing.T) {
+	event := `{"type":"subagent.model_unavailable","data":{"agentName":"research","declaredModel":"haiku","model":"anthropic/opus"},"provenance":{"component":"agent","phase":"agent"}}`
+	for _, relative := range []string{"usage/aw_session.jsonl", "aw_session.jsonl"} {
+		t.Run(relative, func(t *testing.T) {
+			runDir := t.TempDir()
+			path := filepath.Join(runDir, filepath.FromSlash(relative))
+			require.NoError(t, os.MkdirAll(filepath.Dir(path), 0755))
+			require.NoError(t, os.WriteFile(path, []byte(event), 0600))
+			require.Len(t, generateSubagentModelUnavailableFindings(runDir), 1)
+			if relative == "usage/aw_session.jsonl" {
+				require.NoError(t, os.WriteFile(filepath.Join(runDir, "aw_session.jsonl"), []byte("invalid"), 0600))
+				require.Len(t, generateSubagentModelUnavailableFindings(runDir), 1, "usage artifact takes precedence")
+			}
+		})
+	}
+	assert.Empty(t, generateSubagentModelUnavailableFindings(""))
+	assert.Empty(t, generateSubagentModelUnavailableFindings(t.TempDir()))
+}
+
+func TestDecodeSubagentModelUnavailableIgnoresInvalidEvidence(t *testing.T) {
+	for _, event := range []string{
+		`{"type":"subagent.model_unavailable","data":{"agentName":"research","declaredModel":"haiku","model":"anthropic/opus"},"provenance":{"component":"detection","phase":"agent"}}`,
+		`{"type":"subagent.model_unavailable","data":{"agentName":"research","declaredModel":"haiku","model":"anthropic/opus"},"provenance":{"component":"agent","phase":"detection"}}`,
+		`{"type":"subagent.model_unavailable","data":{"agentName":"research","declaredModel":"haiku"},"provenance":{"component":"agent","phase":"agent"}}`,
+		`{"type":"subagent.model_unavailable","data":{"declaredModel":"haiku","model":"anthropic/opus"},"provenance":{"component":"agent","phase":"agent"}}`,
+		`{"type":"subagent.model_unavailable","data":{"agentName":"research","model":"anthropic/opus"},"provenance":{"component":"agent","phase":"agent"}}`,
+		`{"type":"subagent.model_unavailable","data":[],"provenance":{"component":"agent","phase":"agent"}}`,
+		`{"type":"subagent.model_unavailable","data":{"model":42},"provenance":{"component":"agent","phase":"agent"}}`,
+	} {
+		attribution := &sessionModelRoutingAttribution{}
+		require.NoError(t, decodeSessionModelRoutingEvent([]byte(event), 1, attribution))
+		assert.Empty(t, attribution.UnavailableSubagentModels)
+	}
+}
diff --git a/pkg/cli/model_identity.go b/pkg/cli/model_identity.go
index 3ab21da24c2..4749116b03b 100644
--- a/pkg/cli/model_identity.go
+++ b/pkg/cli/model_identity.go
@@ -13,6 +13,7 @@ import (
 var (
 	modelDateSuffix            = regexp.MustCompile(`-[0-9]{4}(?:-[0-9]{2}-[0-9]{2}|[0-9]{4})$`)
 	claudeModelVersionSpelling = regexp.MustCompile(`^(claude-.+)-([0-9]+)-([0-9]+)$`)
+	copilotSDKModelProvider    = regexp.MustCompile(`^copilot-(?:responses|completions)(?:-[0-9]+)?$`)
 )
 
 type modelIdentityResolver struct {
@@ -45,6 +46,7 @@ func newModelIdentityResolver(runDir string) *modelIdentityResolver {
 
 func normalizeModelIdentity(model string) string {
 	model, _, _ = strings.Cut(strings.ToLower(strings.TrimSpace(model)), "?")
+	model = modelNameWithoutProvider(model)
 	model = modelDateSuffix.ReplaceAllString(model, "")
 	return claudeModelVersionSpelling.ReplaceAllString(model, "$1-$2.$3")
 }
@@ -106,7 +108,7 @@ func modelPatternMatches(pattern, observed, provider string) bool {
 	observed, _, _ = strings.Cut(strings.ToLower(observed), "?")
 	originalObserved := observed
 	patternProvider, patternModel, patternQualified := strings.Cut(pattern, "/")
-	observedProvider, observedModel, observedQualified := strings.Cut(observed, "/")
+	observedProvider, _, observedQualified := strings.Cut(observed, "/")
 	if patternQualified {
 		if provider == "" && observedQualified {
 			provider = observedProvider
@@ -120,7 +122,7 @@ func modelPatternMatches(pattern, observed, provider string) bool {
 		if provider != "" && normalizeModelProvider(observedProvider) != normalizeModelProvider(provider) {
 			return modelPatternMatches(patternModel, originalObserved, "")
 		}
-		observed = observedModel
+		observed = modelNameWithoutProvider(originalObserved)
 	}
 	patterns := []string{pattern, normalizeModelIdentity(pattern)}
 	observedModels := []string{observed, normalizeModelIdentity(observed)}
@@ -135,6 +137,10 @@ func modelPatternMatches(pattern, observed, provider string) bool {
 }
 
 func normalizeModelProvider(provider string) string {
+	provider = strings.ToLower(strings.TrimSpace(provider))
+	if copilotSDKModelProvider.MatchString(provider) {
+		return "github-copilot"
+	}
 	switch provider {
 	case "github", "copilot", "github-copilot":
 		return "github-copilot"
@@ -148,8 +154,10 @@ func normalizeModelProvider(provider string) string {
 }
 
 func modelNameWithoutProvider(model string) string {
-	_, name, qualified := strings.Cut(model, "/")
+	provider, name, qualified := strings.Cut(model, "/")
 	if qualified {
+		// SDK metric keys can repeat the provider after the qualified model.
+		name = strings.TrimSuffix(name, ":"+provider)
 		return name
 	}
 	return model
diff --git a/pkg/cli/model_identity_test.go b/pkg/cli/model_identity_test.go
new file mode 100644
index 00000000000..dbec4e79ba9
--- /dev/null
+++ b/pkg/cli/model_identity_test.go
@@ -0,0 +1,90 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNormalizeSDKModelIdentity(t *testing.T) {
+	t.Parallel()
+	for _, test := range []struct {
+		model, want string
+	}{
+		{"copilot-responses/gpt-5.6-luna", "gpt-5.6-luna"},
+		{"copilot-responses/gpt-5.4-mini-2026-03-17:copilot-responses", "gpt-5.4-mini"},
+		{"copilot-completions/claude-haiku-4.5", "claude-haiku-4.5"},
+		{"copilot-completions/claude-haiku-4-5-20251001:copilot-completions", "claude-haiku-4.5"},
+		{" COPILOT-COMPLETIONS/CLAUDE-HAIKU-4-5-20251001?effort=low ", "claude-haiku-4.5"},
+		{"openai/gpt-5.4-mini", "gpt-5.4-mini"},
+		{"copilot-responses/gpt-5.4-mini:other", "gpt-5.4-mini:other"},
+		{"copilot-responses-1/gpt-5.4-mini:copilot-responses-1", "gpt-5.4-mini"},
+		{"copilot-completions-2/claude-haiku-4-5-20251001:copilot-completions-2", "claude-haiku-4.5"},
+	} {
+		t.Run(test.model, func(t *testing.T) {
+			require.Equal(t, test.want, normalizeModelIdentity(test.model))
+			require.Equal(t, test.want, newModelIdentityResolver("").resolve(test.model, "", nil))
+		})
+	}
+}
+
+func TestModelIdentityMatchesSDKProviders(t *testing.T) {
+	t.Parallel()
+	resolver := newModelIdentityResolver("")
+	for _, test := range []struct {
+		pattern, observed, provider string
+		want                        bool
+	}{
+		{"copilot/gpt-*", "copilot-responses/gpt-5.6-luna:copilot-responses", "github-copilot", true},
+		{"copilot/claude-haiku-4.5", "copilot-completions/claude-haiku-4-5-20251001:copilot-completions", "github-copilot", true},
+		{"claude-haiku-4.5", "copilot-completions/claude-haiku-4-5-20251001:copilot-completions", "", true},
+		{"copilot/claude-*", "copilot-completions/claude-haiku-4.5", "", true},
+		{"anthropic/claude-*", "copilot-completions/claude-haiku-4.5", "", false},
+		{"copilot/gpt-*", "copilot-completions/claude-haiku-4.5", "", false},
+		{"copilot/claude-*", "claude-haiku-4.5", "anthropic", false},
+		{"copilot/gpt-*", "copilot-responses-1/gpt-5.6-luna:copilot-responses-1", "github-copilot", true},
+		{"copilot/claude-*", "copilot-completions-2/claude-haiku-4.5:copilot-completions-2", "", true},
+		{"copilot/gpt-*", "copilot-arbitrary/gpt-5.6-luna", "", false},
+		{"copilot/gpt-*", "copilot-responses-extra/gpt-5.6-luna", "", false},
+		{"copilot/claude-*", "copilot-completions-1-extra/claude-haiku-4.5", "", false},
+	} {
+		t.Run(test.pattern+"_"+test.observed+"_"+test.provider, func(t *testing.T) {
+			require.Equal(t, test.want, resolver.matches(test.pattern, test.observed, test.provider))
+		})
+	}
+
+	require.Equal(t, "claude-haiku-4.5", resolver.resolve("haiku", "github-copilot", []string{
+		"copilot-completions/claude-haiku-4-5-20251001:copilot-completions",
+	}))
+}
+
+func TestNormalizeSDKModelProvider(t *testing.T) {
+	t.Parallel()
+	for _, provider := range []string{"copilot-responses", "copilot-completions", "copilot-responses-1", "copilot-completions-12", " COPILOT-RESPONSES-2 "} {
+		require.Equal(t, "github-copilot", normalizeModelProvider(provider))
+	}
+	for _, provider := range []string{"copilot-arbitrary", "copilot-responses-extra", "copilot-completions-1-extra", "copilot-responses-", "copilot-responses-1.2", "other-copilot-responses-1"} {
+		require.Equal(t, provider, normalizeModelProvider(provider))
+	}
+}
+
+func TestSDKQualifiedModelsMergeAttributionWithoutMixingFamilies(t *testing.T) {
+	t.Parallel()
+	resolver := newModelIdentityResolver("")
+	actuals := resolveSubagentActualModels([]SubagentModelActual{
+		{Model: "copilot-responses/gpt-5.4-mini:copilot-responses", Provider: "github-copilot", Requests: 2, TokenCoreMetrics: TokenCoreMetrics{InputTokens: 20}, AIC: 0.2},
+		{Model: "gpt-5.4-mini", Provider: "github-copilot", Requests: 1, TokenCoreMetrics: TokenCoreMetrics{InputTokens: 10}, AIC: 0.1},
+		{Model: "copilot-completions/claude-haiku-4-5-20251001:copilot-completions", Provider: "github-copilot", Requests: 1, TokenCoreMetrics: TokenCoreMetrics{InputTokens: 40}, AIC: 0.4},
+	}, resolver, "gpt-5.4-mini", "claude-haiku-4.5")
+	require.Len(t, actuals, 2)
+	require.Equal(t, "gpt-5.4-mini", actuals[0].ResolvedModel)
+	require.Equal(t, 3, actuals[0].Requests)
+	require.Equal(t, 30, actuals[0].InputTokens)
+	require.InDelta(t, 0.3, actuals[0].AIC, 0.000001)
+	require.NotContains(t, actuals[0].ServedModels, "claude-haiku-4.5")
+	require.Equal(t, "claude-haiku-4.5", actuals[1].ResolvedModel)
+	require.Equal(t, 1, actuals[1].Requests)
+	require.Equal(t, 40, actuals[1].InputTokens)
+	require.InDelta(t, 0.4, actuals[1].AIC, 0.000001)
+	require.NotContains(t, actuals[1].ServedModels, "gpt-5.4-mini")
+}
diff --git a/pkg/cli/model_routing_session.go b/pkg/cli/model_routing_session.go
index a5f3a496e04..db371eb60b9 100644
--- a/pkg/cli/model_routing_session.go
+++ b/pkg/cli/model_routing_session.go
@@ -64,8 +64,15 @@ type sessionModelRoutingEvent struct {
 }
 
 type sessionModelRoutingAttribution struct {
-	WorkflowInfo *sessionWorkflowInfo
-	Outcome      *sessionModelRoutingOutcome
+	WorkflowInfo              *sessionWorkflowInfo
+	Outcome                   *sessionModelRoutingOutcome
+	UnavailableSubagentModels []sessionSubagentModelUnavailable
+}
+
+type sessionSubagentModelUnavailable struct {
+	AgentName     string `json:"agentName"`
+	DeclaredModel string `json:"declaredModel"`
+	Model         string `json:"model"`
 }
 
 func readSessionModelRouting(runDir string) (*sessionModelRoutingAttribution, bool, error) {
@@ -140,6 +147,12 @@ func decodeSessionModelRoutingEvent(line []byte, lineNumber int, attribution *se
 			return fmt.Errorf("invalid model_routing.outcome on line %d: %w", lineNumber, err)
 		}
 		attribution.Outcome = &outcome
+	case event.Type == "subagent.model_unavailable" && event.Provenance.Component == "agent" && event.Provenance.Phase == "agent":
+		var unavailable sessionSubagentModelUnavailable
+		if json.Unmarshal(event.Data, &unavailable) == nil &&
+			unavailable.AgentName != "" && unavailable.DeclaredModel != "" && unavailable.Model != "" {
+			attribution.UnavailableSubagentModels = append(attribution.UnavailableSubagentModels, unavailable)
+		}
 	}
 	return nil
 }
diff --git a/pkg/cli/testdata/subagent_attribution/copilot-qualified-cross-family/aw_session.jsonl b/pkg/cli/testdata/subagent_attribution/copilot-qualified-cross-family/aw_session.jsonl
new file mode 100644
index 00000000000..ae512f004a5
--- /dev/null
+++ b/pkg/cli/testdata/subagent_attribution/copilot-qualified-cross-family/aw_session.jsonl
@@ -0,0 +1,9 @@
+{"type":"session.format","data":{"version":1},"provenance":{"component":"collector","phase":"conclusion","path":"usage/aw_session.jsonl","index":0}}
+{"type":"session.init","data":{"sourceEngine":"copilot","sessionId":"copilot-qualified-parent"},"timestamp":"2026-10-08T10:00:00Z","provenance":{"component":"agent","phase":"agent","path":"agent-session.jsonl","index":0}}
+{"type":"subagent.started","agentId":"child","data":{"invocationId":"child","agentName":"file-summarizer","agentDisplayName":"File-summarizer","model":"copilot-completions/claude-haiku-4.5","resolvedModel":"copilot-completions/claude-haiku-4-5-20251001"},"timestamp":"2026-10-08T10:00:01Z","provenance":{"component":"agent","phase":"agent","path":"agent-session.jsonl","index":1}}
+{"type":"subagent.configured","agentId":"child","data":{"invocationId":"child","model":"copilot-completions/claude-haiku-4.5"},"timestamp":"2026-10-08T10:00:02Z","provenance":{"component":"agent","phase":"agent","path":"agent-session.jsonl","index":2}}
+{"type":"subagent.completed","agentId":"child","data":{"invocationId":"child","agentName":"file-summarizer","outcome":"completed"},"timestamp":"2026-10-08T10:00:03Z","provenance":{"component":"agent","phase":"agent","path":"agent-session.jsonl","index":3}}
+{"type":"session.result","data":{"agentMetrics":{"main":{"totalNanoAiu":250000000,"modelMetrics":{"copilot-responses/gpt-5.6-luna:copilot-responses":{"requests":{"count":1},"usage":{"inputTokens":100,"outputTokens":10},"totalNanoAiu":250000000}}},"child":{"agentName":"file-summarizer","totalNanoAiu":750000000,"modelMetrics":{"copilot-completions/claude-haiku-4-5-20251001:copilot-completions":{"requests":{"count":2},"usage":{"inputTokens":200,"outputTokens":20,"cacheReadTokens":30,"cacheWriteTokens":40},"totalNanoAiu":750000000}}}}},"timestamp":"2026-10-08T10:00:04Z","provenance":{"component":"agent","phase":"agent","path":"agent-session.jsonl","index":4}}
+{"type":"firewall.token_usage","data":{"provider":"github-copilot","model":"claude-haiku-4.5","path":"/chat/completions","status":200,"requestId":"child-1","purpose":"subagent","inputTokens":100,"outputTokens":10,"aic":0.375},"timestamp":"2026-10-08T10:00:02Z","provenance":{"component":"firewall","phase":"agent","path":"token-usage.jsonl","index":0}}
+{"type":"firewall.token_usage","data":{"provider":"github-copilot","model":"claude-haiku-4.5","path":"/chat/completions","status":200,"requestId":"child-2","purpose":"subagent","inputTokens":100,"outputTokens":10,"aic":0.375},"timestamp":"2026-10-08T10:00:03Z","provenance":{"component":"firewall","phase":"agent","path":"token-usage.jsonl","index":1}}
+{"type":"firewall.token_usage","data":{"provider":"github-copilot","model":"gpt-5.6-luna","path":"/responses","status":200,"requestId":"main-1","inputTokens":100,"outputTokens":10,"aic":0.25},"timestamp":"2026-10-08T10:00:04Z","provenance":{"component":"firewall","phase":"agent","path":"token-usage.jsonl","index":2}}
diff --git a/pkg/cli/token_usage_subagent_session.go b/pkg/cli/token_usage_subagent_session.go
index 87533690a36..441e7e16d28 100644
--- a/pkg/cli/token_usage_subagent_session.go
+++ b/pkg/cli/token_usage_subagent_session.go
@@ -41,6 +41,7 @@ type sessionSubagentData struct {
 	RequestedModel   string                                `json:"requestedModel"`
 	ResolvedModel    string                                `json:"resolvedModel"`
 	Outcome          string                                `json:"outcome"`
+	Cancelled        bool                                  `json:"cancelled"`
 	ErrorCode        string                                `json:"errorCode"`
 	ErrorMessage     string                                `json:"errorMessage"`
 	ReasoningEffort  string                                `json:"reasoningEffort"`
@@ -906,6 +907,9 @@ func (models *subagentSessionModels) observeLifecycle(event sessionSubagentEvent
 }
 
 func observeLifecycleOutcome(row *SubagentModelRequest, agentUsage *AgentUsageBreakdown, event sessionSubagentEvent, data sessionSubagentData) {
+	if event.Type == "subagent.completed" && data.Cancelled && (row.CompletedCount > 0 || row.FailedCount > 0) {
+		return
+	}
 	if event.Type == "subagent.completed" {
 		row.CompletedCount++
 		row.IncompleteCount = max(0, row.IncompleteCount-1)
diff --git a/pkg/cli/token_usage_subagent_session_test.go b/pkg/cli/token_usage_subagent_session_test.go
index 027c58f8208..552add4cc13 100644
--- a/pkg/cli/token_usage_subagent_session_test.go
+++ b/pkg/cli/token_usage_subagent_session_test.go
@@ -100,6 +100,41 @@ func TestSubagentSessionStart(t *testing.T) {
 	}
 }
 
+func TestSessionSubagentSDKCancelledCompletion(t *testing.T) {
+	t.Parallel()
+	for _, terminal := range []string{"subagent.completed", "subagent.failed", ""} {
+		t.Run(terminal, func(t *testing.T) {
+			t.Parallel()
+			content := subagentSessionHeader +
+				subagentSessionRecord(`{"type":"subagent.started","data":{"invocationId":"child","agentName":"file-summarizer","model":"copilot-completions/claude-haiku-4.5"}}`)
+			if terminal != "" {
+				content += subagentSessionRecord(`{"type":"` + terminal + `","data":{"invocationId":"child","agentName":"file-summarizer"}}`)
+			}
+			content += subagentSessionRecord(`{"type":"subagent.completed","data":{"invocationId":"child","agentName":"file-summarizer","cancelled":true}}`)
+			requests, _, usage, found, err := parseSessionSubagentModelsDetailed(strings.NewReader(content), true)
+			require.NoError(t, err)
+			require.True(t, found)
+			require.Len(t, requests, 1)
+			require.Len(t, usage, 1)
+			assert.Equal(t, 1, requests[0].InvocationCount)
+			assert.Equal(t, 1, usage[0].InstanceCount)
+			assert.Zero(t, requests[0].IncompleteCount)
+			assert.Zero(t, usage[0].IncompleteCount)
+			if terminal == "subagent.failed" {
+				assert.Equal(t, 1, requests[0].FailedCount)
+				assert.Equal(t, 1, usage[0].FailedCount)
+				assert.Zero(t, requests[0].CompletedCount)
+				assert.Zero(t, usage[0].CompletedCount)
+			} else {
+				assert.Equal(t, 1, requests[0].CompletedCount)
+				assert.Equal(t, 1, usage[0].CompletedCount)
+				assert.Zero(t, requests[0].FailedCount)
+				assert.Zero(t, usage[0].FailedCount)
+			}
+		})
+	}
+}
+
 func TestSessionSubagentModels(t *testing.T) {
 	start := `{"type":"subagent.started","agentId":"research","data":{"agentName":"research","agentDisplayName":"routing-research","model":"opus","executionMode":"background"}}`
 	config := `{"type":"subagent.configured","agentId":"research","data":{"model":"sonnet","reasoningEffort":"low"}}`
@@ -475,6 +510,59 @@ func TestCopilotUnifiedFixtureRetainsFailedCrossFamilySubagent(t *testing.T) {
 	require.Zero(t, summary.AgentUsage[1].AIC)
 }
 
+func TestCopilotUnifiedFixtureAttributesQualifiedCrossFamilyModels(t *testing.T) {
+	t.Parallel()
+	fixture := filepath.Join("testdata", "subagent_attribution", "copilot-qualified-cross-family")
+	entries, err := readUnifiedTokenUsageEntries(fixture)
+	require.NoError(t, err)
+	require.Len(t, entries, 3)
+	require.Equal(t, "/chat/completions", entries[0].Path)
+	require.Equal(t, "/responses", entries[2].Path)
+	summary := &TokenUsageSummary{AICFound: true, TotalAIC: 1, ByModel: map[string]*ModelTokenUsage{
+		"claude-haiku-4.5": {Provider: "github-copilot", Requests: 2},
+		"gpt-5.6-luna":     {Provider: "github-copilot", Requests: 1},
+	}}
+	augmentSubagentModelAttribution(fixture, summary)
+
+	require.Empty(t, summary.Warnings)
+	require.Zero(t, summary.MismatchCount)
+	require.Len(t, summary.SubagentModelRequests, 1)
+	request := summary.SubagentModelRequests[0]
+	require.Equal(t, "File-summarizer", request.AgentName)
+	require.Equal(t, "copilot-completions/claude-haiku-4.5", request.RequestedModel)
+	require.Equal(t, "claude-haiku-4.5", request.ResolvedModel)
+	require.Equal(t, "claude-haiku-4.5", request.EffectiveModel)
+	require.Equal(t, 1, request.CompletedCount)
+	require.Zero(t, request.FailedCount)
+	require.Contains(t, request.ServedModels, "claude-haiku-4.5")
+	require.NotContains(t, request.ServedModels, "gpt-5.6-luna")
+	require.Empty(t, request.ReasonCode)
+
+	require.Len(t, summary.AgentUsage, 2)
+	main, child := summary.AgentUsage[0], summary.AgentUsage[1]
+	require.Equal(t, "main", main.AgentType)
+	require.Equal(t, 1, main.Requests)
+	require.InDelta(t, 0.25, main.AIC, 0.000001)
+	require.Equal(t, "gpt-5.6-luna", main.Models[0].ResolvedModel)
+	require.Contains(t, main.ServedModels, "gpt-5.6-luna")
+	require.NotContains(t, main.ServedModels, "claude-haiku-4.5")
+	require.Equal(t, "file-summarizer", child.AgentName)
+	require.Equal(t, "subagent", child.AgentType)
+	require.Equal(t, 2, child.Requests)
+	require.InDelta(t, 0.75, child.AIC, 0.000001)
+	require.Contains(t, child.ServedModels, "claude-haiku-4.5")
+	require.NotContains(t, child.ServedModels, "gpt-5.6-luna")
+	require.Len(t, child.Models, 1)
+	require.Equal(t, "claude-haiku-4.5", child.Models[0].ResolvedModel)
+	require.InDelta(t, 0.75, child.Models[0].AIC, 0.000001)
+	require.Len(t, summary.SubagentModelActuals, 1)
+	actual := summary.SubagentModelActuals[0]
+	require.Equal(t, "claude-haiku-4.5", actual.Model)
+	require.Equal(t, 2, actual.Requests)
+	require.Equal(t, TokenCoreMetrics{InputTokens: 200, OutputTokens: 20, CacheReadTokens: 30, CacheWriteTokens: 40}, actual.TokenCoreMetrics)
+	require.InDelta(t, 0.75, actual.AIC, 0.000001)
+}
+
 func TestCopilotAgentMetricsWithoutLifecycleRetainAttribution(t *testing.T) {
 	root := t.TempDir()
 	require.NoError(t, os.MkdirAll(filepath.Join(root, "usage"), 0o755))