Treat expression-backed engine.model as omitted when empty (#46777)

Author: Copilot

.github/workflows/daily-cache-strategy-analyzer.lock.yml

@@ -53,6 +53,7 @@ const { emitMissingToolPermissionIssue, hasExpectedSafeOutputs, hasNoopInSafeOut
 const { countPermissionDeniedIssues, hasNumerousPermissionDeniedIssues, extractDeniedCommands, buildMissingToolPermissionIssuePayload } = require("./permission_denied_helpers.cjs");
 const { detectNonRetryableHarnessGuard, buildSoftTimeoutGuard, emitSoftTimeoutSignal, isAuthenticationFailedError } = require("./harness_retry_guard.cjs");
 const { MODEL_NOT_SUPPORTED_PATTERN: INVALID_MODEL_ERROR_PATTERN } = require("./detect_agent_errors.cjs");
+const { applyModelFallback } = require("./model_fallback.cjs");
 
 // Pattern to detect Anthropic API overload errors (HTTP 529).
 // Matches "overloaded_error" from the Anthropic error type field, and the
@@ -318,6 +319,7 @@ function stripContinueArgs(args) {
  */
 async function buildClaudeChildEnv() {
   const childEnv = { ...process.env };
+  applyModelFallback(childEnv, "ANTHROPIC_MODEL", log);
   const provider = normalizeReflectProviderName(process.env.GH_AW_LLM_PROVIDER, "anthropic");
   try {
     const raw = fs.readFileSync(AWF_REFLECT_OUTPUT_PATH, "utf8");
@@ -611,6 +613,7 @@ if (typeof module !== "undefined" && module.exports) {
     hasExpectedSafeOutputs,
     resolveRetryConfig,
     resolveStartupRetryLimit,
+    applyModelFallback,
   };
 }
 

.github/workflows/daily-caveman-optimizer.lock.yml

@@ -54,6 +54,7 @@ const { countPermissionDeniedIssues, hasNumerousPermissionDeniedIssues, extractD
 const { detectNonRetryableHarnessGuard, buildSoftTimeoutGuard, emitSoftTimeoutSignal, isAuthenticationFailedError } = require("./harness_retry_guard.cjs");
 const { MODEL_NOT_SUPPORTED_PATTERN: INVALID_MODEL_ERROR_PATTERN } = require("./detect_agent_errors.cjs");
 const { resolveRetryConfig } = require("./harness_retry_config.cjs");
+const { applyModelFallback, injectModelFlagAfterExec } = require("./model_fallback.cjs");
 
 // Pattern to detect OpenAI rate-limit errors.
 // Matches the JSON error type field ("rate_limit_exceeded"), the HTTP status code
@@ -221,6 +222,16 @@ function injectJsonFlag(args) {
   return ["exec", "--json", ...args.slice(1)];
 }
 
+function getCodexModelEnvVar(env = process.env) {
+  if ("GH_AW_MODEL_DETECTION_CODEX" in env) {
+    return "GH_AW_MODEL_DETECTION_CODEX";
+  }
+  if ("GH_AW_MODEL_AGENT_CODEX" in env) {
+    return "GH_AW_MODEL_AGENT_CODEX";
+  }
+  return "";
+}
+
 /**
  * Build child process environment for Codex execution.
  * Preserve API keys captured at harness startup, even if the parent environment
@@ -425,6 +436,10 @@ async function main() {
     process.exit(1);
   }
 
+  const codexModelEnvVar = getCodexModelEnvVar(process.env);
+  const resolvedModel = codexModelEnvVar ? applyModelFallback(process.env, codexModelEnvVar, log) : "";
+  resolvedArgs = injectModelFlagAfterExec(resolvedArgs, resolvedModel);
+
   // Safe arg list for logging: when --prompt-file was present, the last element of
   // resolvedArgs is the resolved prompt content. Replace it with a placeholder so that
   // task instructions are never written to stderr or captured in agent logs.
@@ -641,6 +656,9 @@ if (typeof module !== "undefined" && module.exports) {
     hasNoopInSafeOutputs,
     hasExpectedSafeOutputs,
     resolveRetryConfig,
+    applyModelFallback,
+    injectModelFlagAfterExec,
+    getCodexModelEnvVar,
   };
 }
 

.github/workflows/daily-doc-healer.lock.yml

@@ -65,6 +65,7 @@ const { runSafeOutputsCLI, buildMissingToolAlternatives, emitMissingToolPermissi
 const { countPermissionDeniedIssues, hasNumerousPermissionDeniedIssues, extractDeniedCommands, buildMissingToolPermissionIssuePayload } = require("./permission_denied_helpers.cjs");
 const { detectNonRetryableHarnessGuard, buildSoftTimeoutGuard, emitSoftTimeoutSignal, isAuthenticationFailedError: isCommonAuthenticationFailedError } = require("./harness_retry_guard.cjs");
 const { isCAPIQuotaExceededError } = require("./detect_agent_errors.cjs");
+const { applyModelFallback } = require("./model_fallback.cjs");
 const { loadModelsJson } = require("./model_costs.cjs");
 const { resolveConfiguredCopilotModel } = require("./resolve_model_alias.cjs");
 
@@ -950,6 +951,7 @@ async function main() {
     }
   }
 
+  applyModelFallback(process.env, "COPILOT_MODEL", log);
   applyCopilotModelAliasResolution({ awfReflectData, logger: log });
   applyCopilotWireAPI({ modelsJson: loadModelsJson(), logger: log });
 
@@ -1456,6 +1458,7 @@ if (typeof module !== "undefined" && module.exports) {
     parseCopilotSDKServerArgsFromEnv,
     isCAPIQuotaExceededError,
     hasTerminalSafeOutput,
+    applyModelFallback,
     applyCopilotModelAliasResolution,
     applyCopilotWireAPI,
     loadAwfConfigData,

.github/workflows/test-quality-sentinel.lock.yml

@@ -30,6 +30,7 @@ const fs = require("fs");
 const { runWithCopilotSDK, extractPromptFromArgs } = require("./copilot_sdk_session.cjs");
 const { parsePermissionConfigFromServerArgs } = require("./copilot_sdk_permissions.cjs");
 const { parseMultiProviderJson } = require("./copilot_sdk_multi_provider.cjs");
+const { applyModelFallback } = require("./model_fallback.cjs");
 
 // Re-export the session and permission helpers so that existing callers that
 // require("./copilot_sdk_driver.cjs") (e.g. copilot_harness.cjs) continue to work.
@@ -103,7 +104,7 @@ async function main() {
   const providers = multiProviderConfig.providers;
   /** @type {import("@github/copilot-sdk").ProviderModelConfig[]} */
   const sdkModels = multiProviderConfig.models;
-  let model = process.env.COPILOT_MODEL || multiProviderConfig.model || undefined;
+  let model = applyModelFallback(process.env, "COPILOT_MODEL", log) || multiProviderConfig.model || undefined;
   log(`multi-provider mode: ${providers.length} providers, ${sdkModels.length} models, model=${model ?? "(env)"}`);
   for (const p of providers) {
     log(`  provider: name=${p.name} type=${p.type} baseUrl=${p.baseUrl}${p.wireApi ? ` wireApi=${p.wireApi}` : ""}`);

actions/setup/js/claude_harness.cjs

@@ -36,6 +36,7 @@ const fs = require("fs");
 const path = require("path");
 const os = require("os");
 const { buildCopilotSDKPermissionHandler, getEnvPositiveIntOrDefault, parseMaxToolDenialsLimit, MAX_TOOL_DENIALS_DEFAULT } = require("./copilot_sdk_permissions.cjs");
+const { resolveModelWithFallback } = require("./model_fallback.cjs");
 const { extractShellCommandFromToolData } = require("./tool_call_details.cjs");
 
 // Default timeout for a single sendAndWait call: 10 minutes.
@@ -254,7 +255,7 @@ async function runWithCopilotSDK({ sdkUri, prompt, logger, attempt = 0, model, c
     // Build session config using the multi-provider surface.
     /** @type {import("@github/copilot-sdk").SessionConfig} */
     const sessionConfig = {
-      model: model || process.env.COPILOT_MODEL || undefined,
+      model: model || resolveModelWithFallback(process.env, "COPILOT_MODEL") || undefined,
       providers,
       models: providerModels,
       onPermissionRequest,

actions/setup/js/codex_harness.cjs

@@ -0,0 +1,48 @@
+"use strict";
+
+const MODEL_FALLBACK_ENV_VAR = "GH_AW_MODEL_FALLBACK";
+
+function readTrimmedEnv(env, name) {
+  return typeof env?.[name] === "string" ? env[name].trim() : "";
+}
+
+function resolveModelWithFallback(env, primaryEnvVar) {
+  return readTrimmedEnv(env, primaryEnvVar) || readTrimmedEnv(env, MODEL_FALLBACK_ENV_VAR);
+}
+
+/**
+ * @param {NodeJS.ProcessEnv} env
+ * @param {string} primaryEnvVar
+ * @param {(message: string) => void} [logger]
+ * @returns {string}
+ */
+function applyModelFallback(env, primaryEnvVar, logger = () => {}) {
+  const primary = readTrimmedEnv(env, primaryEnvVar);
+  if (primary) {
+    return primary;
+  }
+  const fallback = readTrimmedEnv(env, MODEL_FALLBACK_ENV_VAR);
+  if (fallback) {
+    env[primaryEnvVar] = fallback;
+    logger(`applied ${MODEL_FALLBACK_ENV_VAR} to ${primaryEnvVar}`);
+  }
+  return fallback;
+}
+
+function injectModelFlagAfterExec(args, model) {
+  if (!model || args.includes("--model")) {
+    return args;
+  }
+  const execIndex = args.indexOf("exec");
+  if (execIndex === -1) {
+    return [...args, "--model", model];
+  }
+  return [...args.slice(0, execIndex + 1), "--model", model, ...args.slice(execIndex + 1)];
+}
+
+module.exports = {
+  MODEL_FALLBACK_ENV_VAR,
+  resolveModelWithFallback,
+  applyModelFallback,
+  injectModelFlagAfterExec,
+};