diff --git a/base-action/action.yml b/base-action/action.yml
index 9c4aa08..7ec09ec 100644
--- a/base-action/action.yml
+++ b/base-action/action.yml
@@ -190,7 +190,7 @@ runs:
         PATH_TO_CLAUDE_CODE_EXECUTABLE: ${{ inputs.path_to_claude_code_executable }}
       run: |
         if [ -z "$PATH_TO_CLAUDE_CODE_EXECUTABLE" ]; then
-          CLAUDE_CODE_VERSION="2.1.203"
+          CLAUDE_CODE_VERSION="2.1.220"
           echo "Installing Claude Code v${CLAUDE_CODE_VERSION}..."
           for attempt in 1 2 3; do
             echo "Installation attempt $attempt..."
diff --git a/base-action/bun.lock b/base-action/bun.lock
index f7c79c7..61f58c2 100644
--- a/base-action/bun.lock
+++ b/base-action/bun.lock
@@ -5,7 +5,7 @@
       "name": "@step-security/claude-code-base-action",
       "dependencies": {
         "@actions/core": "^2.0.3",
-        "@anthropic-ai/claude-agent-sdk": "0.3.203",
+        "@anthropic-ai/claude-agent-sdk": "^0.3.220",
         "axios": "^1.16.1",
         "shell-quote": "^1.8.4",
       },
@@ -27,23 +27,23 @@
 
     "@actions/io": ["@actions/io@2.0.0", "", {}, "sha512-Jv33IN09XLO+0HS79aaODsvIRyduiF7NY/F6LYeK5oeUmrsz7aFdRphQjFoESF4jS7lMauDOttKALcpapVDIAg=="],
 
-    "@anthropic-ai/claude-agent-sdk": ["@anthropic-ai/claude-agent-sdk@0.3.203", "", { "optionalDependencies": { "@anthropic-ai/claude-agent-sdk-darwin-arm64": "0.3.203", "@anthropic-ai/claude-agent-sdk-darwin-x64": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-arm64": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-x64": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-x64-musl": "0.3.203", "@anthropic-ai/claude-agent-sdk-win32-arm64": "0.3.203", "@anthropic-ai/claude-agent-sdk-win32-x64": "0.3.203" }, "peerDependencies": { "@anthropic-ai/sdk": ">=0.93.0", "@modelcontextprotocol/sdk": "^1.29.0", "zod": "^4.0.0" } }, "sha512-K/GMQlB3IpLtvqjI+/9Xcu//4wDRSxO2JimHMOM3zxHBKJA0EIb6U+4Ea0RSrxe+SHwFHT23XATL6U/9JggxXw=="],
+    "@anthropic-ai/claude-agent-sdk": ["@anthropic-ai/claude-agent-sdk@0.3.220", "", { "optionalDependencies": { "@anthropic-ai/claude-agent-sdk-darwin-arm64": "0.3.220", "@anthropic-ai/claude-agent-sdk-darwin-x64": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-arm64": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-x64": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-x64-musl": "0.3.220", "@anthropic-ai/claude-agent-sdk-win32-arm64": "0.3.220", "@anthropic-ai/claude-agent-sdk-win32-x64": "0.3.220" }, "peerDependencies": { "@anthropic-ai/sdk": ">=0.93.0", "@modelcontextprotocol/sdk": "^1.29.0", "zod": "^4.0.0" } }, "sha512-glc7SdwPkOkLw8oxwLo9PKTdLJGqW/PIR4urWXFoRtX9YllwozsEVc5Tc1+EvLSkfrsxPJqQWqOgpjUOQXf1oA=="],
 
-    "@anthropic-ai/claude-agent-sdk-darwin-arm64": ["@anthropic-ai/claude-agent-sdk-darwin-arm64@0.3.203", "", { "os": "darwin", "cpu": "arm64" }, "sha512-9uG6wp3reCtiWXA1H7NWZV5HFO6WgmedcpRCMpw0iyborLdw3MEZonJVlfRh93eQEVpflfnTOARTqtt7NzgHqg=="],
+    "@anthropic-ai/claude-agent-sdk-darwin-arm64": ["@anthropic-ai/claude-agent-sdk-darwin-arm64@0.3.220", "", { "os": "darwin", "cpu": "arm64" }, "sha512-7VxlbEosK7DODiOnsjoVd0DSJzbnaPrM2jelMHI0y8zx1UnLS3WC6EFUXbvy74F2sXqEznh2tzn7EKWInaRN6Q=="],
 
-    "@anthropic-ai/claude-agent-sdk-darwin-x64": ["@anthropic-ai/claude-agent-sdk-darwin-x64@0.3.203", "", { "os": "darwin", "cpu": "x64" }, "sha512-iP2cg+VovTYeU9f/l32Cq4cESNrgBvjZn/NipyhQ7RD468vBUjn22ii9cnGF7g9TepNrY3/IdkCPmwSea9besA=="],
+    "@anthropic-ai/claude-agent-sdk-darwin-x64": ["@anthropic-ai/claude-agent-sdk-darwin-x64@0.3.220", "", { "os": "darwin", "cpu": "x64" }, "sha512-X9RwDsSmbF6ultKZroaip+DL8WRgC64gHbrAwrRlAFSPNZV7zmJyP2ur8rW7KrxqmtuehdMMkw8+SAC/6hD2PA=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-arm64": ["@anthropic-ai/claude-agent-sdk-linux-arm64@0.3.203", "", { "os": "linux", "cpu": "arm64" }, "sha512-p8wTbvWbQUscQBSefTdjwGbeVE6lYoEmMMdoNSOI8uR8jBr5YXoSwnSjBwmGDjz15WI4AIIdiWwyrf6sqrvqPA=="],
+    "@anthropic-ai/claude-agent-sdk-linux-arm64": ["@anthropic-ai/claude-agent-sdk-linux-arm64@0.3.220", "", { "os": "linux", "cpu": "arm64" }, "sha512-WkROPwWskqhKR9XgnmseHQ6rLi9zM9qt57IWoToIjL/eXOqDWipp7JXZ1L5ud+LrA42dunHPZfBwD/vXZ+A7LA=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": ["@anthropic-ai/claude-agent-sdk-linux-arm64-musl@0.3.203", "", { "os": "linux", "cpu": "arm64" }, "sha512-uQNRpgHKuavsEyvY3SnDRZuCxf1z2pjGI4Q73Q0GuIEapwXrY2UM0ucAj0b7KtS6hpu//CGhnBra2kKOXsDQAw=="],
+    "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": ["@anthropic-ai/claude-agent-sdk-linux-arm64-musl@0.3.220", "", { "os": "linux", "cpu": "arm64" }, "sha512-OHoZOZ8Cf2TBr6oXIXPwyvUxj9jrq2w8E4poA8dMpacXszcPSPiCQCMuuOh4aWJzfeJE1+TtWxhKMVb2csXyZQ=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-x64": ["@anthropic-ai/claude-agent-sdk-linux-x64@0.3.203", "", { "os": "linux", "cpu": "x64" }, "sha512-YTW0+njIC61fZP3Qa9uzH9fOlEmApHG6SSxwyNxAQ8U3XX+yviL5/MyqLsauuUTVbyI9K7IqYOaE6xcDVDXIGg=="],
+    "@anthropic-ai/claude-agent-sdk-linux-x64": ["@anthropic-ai/claude-agent-sdk-linux-x64@0.3.220", "", { "os": "linux", "cpu": "x64" }, "sha512-tkTJFnpR9VifvWX2fmkCAPkT6+8Wk/gVu8B5jsVekKZPiZoWRHmMXO30BnZn+f0TZhgYP+82PSX3S8crH1kn+w=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-x64-musl": ["@anthropic-ai/claude-agent-sdk-linux-x64-musl@0.3.203", "", { "os": "linux", "cpu": "x64" }, "sha512-Hw2NNW8crM7ENR8peWZ+hG3ehUl9IYPzNxyqc1VM+odznB6squaki2xQeCcIatHbQImeW+DzrUFIDJLLz4pltg=="],
+    "@anthropic-ai/claude-agent-sdk-linux-x64-musl": ["@anthropic-ai/claude-agent-sdk-linux-x64-musl@0.3.220", "", { "os": "linux", "cpu": "x64" }, "sha512-K+FWj+LcGhC1Z7wqeWoLxm1iemcba5xKpLLFVwYm4V6HyMx3ruYd/2r2TiQtjT+JWeNFWIys0ScHiItR6vWAiA=="],
 
-    "@anthropic-ai/claude-agent-sdk-win32-arm64": ["@anthropic-ai/claude-agent-sdk-win32-arm64@0.3.203", "", { "os": "win32", "cpu": "arm64" }, "sha512-EF2BPCSElFS9y76b/4TVU7RDw9xCr8DtxSUXAxYhcGsreo1gmJbMVdZ9tvLIvG6Ufquas4nrGmWh1ePLP2ol+g=="],
+    "@anthropic-ai/claude-agent-sdk-win32-arm64": ["@anthropic-ai/claude-agent-sdk-win32-arm64@0.3.220", "", { "os": "win32", "cpu": "arm64" }, "sha512-rIwgq0UwQExWl6KrHUyC4w5KwpL9l6nd95aUTx6RitexaAuEw//xtfTVLnuE4hDDQZFkzEwpdKc3nxDWoGcUbA=="],
 
-    "@anthropic-ai/claude-agent-sdk-win32-x64": ["@anthropic-ai/claude-agent-sdk-win32-x64@0.3.203", "", { "os": "win32", "cpu": "x64" }, "sha512-sYf4UokyYhYO6Nke99o+gtgCakoaohB+Q/71i+4hEq0FYqVf31WoJ6lUTTTUPeEGVp6Ju6BblzmAX2MpvlWwCw=="],
+    "@anthropic-ai/claude-agent-sdk-win32-x64": ["@anthropic-ai/claude-agent-sdk-win32-x64@0.3.220", "", { "os": "win32", "cpu": "x64" }, "sha512-MuOuXhbr66HlGaWXD2f3w0k2PsvmnbkwcUZ0dAe2poFLdl72GC2dapwwOBefxm9QmoNqk9+jmv/dSKGOVWyvLw=="],
 
     "@anthropic-ai/sdk": ["@anthropic-ai/sdk@0.104.1", "", { "dependencies": { "json-schema-to-ts": "^3.1.1", "standardwebhooks": "^1.0.0" }, "peerDependencies": { "zod": "^3.25.0 || ^4.0.0" }, "optionalPeers": ["zod"], "bin": { "anthropic-ai-sdk": "bin/cli" } }, "sha512-gGACa/+IaiXzRRmF96aOhamoBgapKRBiFWbmmTFP8aMkpaEcuStF+Q61bjo4vPxBM7gqWJNZqsngslRdnLHv0Q=="],
 
diff --git a/base-action/package.json b/base-action/package.json
index 8211230..91ddeb6 100644
--- a/base-action/package.json
+++ b/base-action/package.json
@@ -11,7 +11,7 @@
   },
   "dependencies": {
     "@actions/core": "^2.0.3",
-    "@anthropic-ai/claude-agent-sdk": "0.3.203",
+    "@anthropic-ai/claude-agent-sdk": "^0.3.220",
     "axios": "^1.16.1",
     "shell-quote": "^1.8.4"
   },
diff --git a/base-action/src/index.ts b/base-action/src/index.ts
index 163d3b5..cb9af5c 100644
--- a/base-action/src/index.ts
+++ b/base-action/src/index.ts
@@ -125,7 +125,8 @@ async function run() {
     core.setOutput("conclusion", "failure");
     process.exit(1);
   } finally {
-    // Stop refreshing the workload identity token file so the process can exit
+    // Stop refreshing the workload identity token file (so the process can
+    // exit) and delete the token material so it doesn't outlive this step
     workloadIdentity?.stop();
   }
 }
diff --git a/base-action/src/parse-sdk-options.ts b/base-action/src/parse-sdk-options.ts
index e109509..a2c58d5 100644
--- a/base-action/src/parse-sdk-options.ts
+++ b/base-action/src/parse-sdk-options.ts
@@ -201,6 +201,9 @@ export function parseSdkOptions(options: ClaudeOptions): ParsedSdkOptions {
   // Detect if --json-schema is present (for hasJsonSchema flag)
   const hasJsonSchema = "json-schema" in extraArgs;
 
+  const modelFromClaudeArgs = extraArgs["model"] || undefined;
+  delete extraArgs["model"];
+
   const additionalDirectories = extraArgs["add-dir"]
     ? extraArgs["add-dir"]
         .split(ACCUMULATE_DELIMITER)
@@ -304,7 +307,7 @@ export function parseSdkOptions(options: ClaudeOptions): ParsedSdkOptions {
   // Build SDK options - use merged tools from both direct options and claudeArgs
   const sdkOptions: SdkOptions = {
     // Direct options from ClaudeOptions inputs
-    model: options.model,
+    model: options.model || modelFromClaudeArgs,
     maxTurns: options.maxTurns ? parseInt(options.maxTurns, 10) : undefined,
     allowedTools:
       mergedAllowedTools.length > 0 ? mergedAllowedTools : undefined,
diff --git a/base-action/src/run-claude-sdk.ts b/base-action/src/run-claude-sdk.ts
index 67d2da1..f83edf5 100644
--- a/base-action/src/run-claude-sdk.ts
+++ b/base-action/src/run-claude-sdk.ts
@@ -208,7 +208,10 @@ export async function runClaudeWithSdk(
     throw new Error("No result message received from Claude");
   }
 
-  const isSuccess = resultMessage.subtype === "success";
+  // subtype "success" with is_error:true means the run errored without producing
+  // a real result — treat it as failure so CI does not show a misleading green check.
+  const isSuccess =
+    resultMessage.subtype === "success" && !resultMessage.is_error;
   result.conclusion = isSuccess ? "success" : "failure";
 
   // Handle structured output
@@ -234,14 +237,21 @@ export async function runClaudeWithSdk(
   }
 
   if (!isSuccess) {
+    if (resultMessage.subtype === "success" && resultMessage.is_error) {
+      core.error(
+        "Claude result reported subtype success with is_error:true (run did not complete successfully)",
+      );
+    }
     if ("errors" in resultMessage && resultMessage.errors) {
       core.error(`Execution failed: ${resultMessage.errors.join(", ")}`);
     }
     throw new Error(
       `Claude execution failed: ${
-        "errors" in resultMessage && resultMessage.errors
-          ? resultMessage.errors.join(", ")
-          : "unknown error"
+        resultMessage.subtype === "success" && resultMessage.is_error
+          ? "result is_error:true"
+          : "errors" in resultMessage && resultMessage.errors
+            ? resultMessage.errors.join(", ")
+            : "unknown error"
       }`,
     );
   }
diff --git a/base-action/src/workload-identity.ts b/base-action/src/workload-identity.ts
index 91266f3..79ebaf5 100644
--- a/base-action/src/workload-identity.ts
+++ b/base-action/src/workload-identity.ts
@@ -15,7 +15,8 @@
  */
 
 import * as core from "@actions/core";
-import { mkdirSync, writeFileSync } from "fs";
+import { createHash } from "crypto";
+import { mkdirSync, rmSync, writeFileSync } from "fs";
 import { join } from "path";
 import { retryWithBackoff } from "./retry";
 
@@ -50,6 +51,63 @@ async function fetchIdentityToken(audience: string) {
   return retryWithBackoff(() => core.getIDToken(audience));
 }
 
+/**
+ * Writes a profile config that switches federation resolution to the
+ * file-backed path. Resolving federation through a profile (rather than bare
+ * env vars) enables the SDK's on-disk credentials cache, so the several
+ * `claude` processes the action spawns (plugin installs, main query) share
+ * one exchanged access token instead of each re-exchanging the single-use
+ * GitHub OIDC token, which fails with 401 (`jti_reused`).
+ *
+ * The profile is intentionally minimal: the SDK gap-fills the federation
+ * fields (rule, organization, identity-token file, service account, base URL)
+ * from the ANTHROPIC_* env vars the action already exports, so the file only
+ * needs to exist to turn the cache on.
+ *
+ * The config dir name embeds a fingerprint of the federation inputs. The
+ * SDK's cache reuses a token on `expires_at` alone, with no record of the
+ * config that minted it, and the token's scope is bound at mint time — so a
+ * later action step in the same job (RUNNER_TEMP is per-job) with different
+ * federation inputs must land in a different dir or it would silently reuse
+ * the first step's token.
+ *
+ * Sharing the cache is only safe while the action spawns its `claude`
+ * subprocesses sequentially: the SDK cache is not cross-process serialized,
+ * and concurrent cache misses would each re-exchange the same single-use
+ * identity token. Parallelizing the plugin installs would reintroduce the
+ * `jti_reused` failures.
+ */
+function writeFederationProfile(baseDir: string): string {
+  // Every input that changes which credential the exchange mints must be in
+  // here; service_account_id and scope are sent in the exchange request body.
+  const fingerprint = createHash("sha256")
+    .update(
+      JSON.stringify([
+        process.env.ANTHROPIC_FEDERATION_RULE_ID?.trim() ?? "",
+        process.env.ANTHROPIC_ORGANIZATION_ID?.trim() ?? "",
+        process.env.ANTHROPIC_SERVICE_ACCOUNT_ID?.trim() ?? "",
+        process.env.ANTHROPIC_WORKSPACE_ID?.trim() ?? "",
+        process.env.ANTHROPIC_BASE_URL?.trim() ?? "",
+        process.env.ANTHROPIC_SCOPE?.trim() ?? "",
+      ]),
+    )
+    .digest("hex")
+    .slice(0, 16);
+  const configDir = join(baseDir, `config-${fingerprint}`);
+
+  mkdirSync(join(configDir, "configs"), { recursive: true, mode: 0o700 });
+  writeFileSync(
+    join(configDir, "configs", "default.json"),
+    JSON.stringify(
+      { version: "1.0", authentication: { type: "oidc_federation" } },
+      null,
+      2,
+    ),
+    { mode: 0o600 },
+  );
+  return configDir;
+}
+
 /**
  * Fetches a GitHub Actions OIDC token, writes it to a file in RUNNER_TEMP,
  * exports ANTHROPIC_IDENTITY_TOKEN_FILE, and starts a background refresh so
@@ -57,7 +115,8 @@ async function fetchIdentityToken(audience: string) {
  *
  * Returns undefined when federation is not configured or is shadowed by a
  * higher-precedence credential. Callers must invoke stop() when execution
- * finishes.
+ * finishes; it also deletes the identity token and any cached exchanged
+ * credential.
  */
 export async function setupWorkloadIdentity(): Promise<
   WorkloadIdentityHandle | undefined
@@ -101,6 +160,17 @@ export async function setupWorkloadIdentity(): Promise<
   }
 
   process.env.ANTHROPIC_IDENTITY_TOKEN_FILE = tokenFile;
+  if (
+    process.env.ANTHROPIC_CONFIG_DIR?.trim() ||
+    process.env.ANTHROPIC_PROFILE?.trim()
+  ) {
+    core.warning(
+      "ANTHROPIC_CONFIG_DIR or ANTHROPIC_PROFILE is already set, so the action will not write its own federation profile. Credential caching across the spawned Claude processes follows the existing profile configuration.",
+    );
+  } else {
+    process.env.ANTHROPIC_CONFIG_DIR = writeFederationProfile(tokenDir);
+    process.env.ANTHROPIC_PROFILE = "default";
+  }
   console.log(
     `Workload identity federation configured (rule: ${process.env.ANTHROPIC_FEDERATION_RULE_ID}, identity token file: ${tokenFile})`,
   );
@@ -115,6 +185,12 @@ export async function setupWorkloadIdentity(): Promise<
 
   return {
     tokenFile,
-    stop: () => clearInterval(refreshInterval),
+    stop: () => {
+      clearInterval(refreshInterval);
+      // RUNNER_TEMP is per-job, not per-step: remove the identity token, the
+      // profile, and the cached exchanged credential so they don't outlive
+      // this step.
+      rmSync(tokenDir, { recursive: true, force: true });
+    },
   };
 }
diff --git a/base-action/test/parse-sdk-options.test.ts b/base-action/test/parse-sdk-options.test.ts
index 924d7fb..813bafd 100644
--- a/base-action/test/parse-sdk-options.test.ts
+++ b/base-action/test/parse-sdk-options.test.ts
@@ -106,7 +106,8 @@ describe("parseSdkOptions", () => {
       const result = parseSdkOptions(options);
 
       expect(result.sdkOptions.extraArgs?.["allowedTools"]).toBeUndefined();
-      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-3-5-sonnet");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+      expect(result.sdkOptions.model).toBe("claude-3-5-sonnet");
     });
 
     test("should handle hyphenated --allowed-tools flag", () => {
@@ -366,7 +367,8 @@ describe("parseSdkOptions", () => {
       );
       expect(mcpConfig.mcpServers).toHaveProperty("server1");
       expect(mcpConfig.mcpServers).toHaveProperty("server2");
-      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-3-5-sonnet");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+      expect(result.sdkOptions.model).toBe("claude-3-5-sonnet");
     });
 
     test("should handle real-world scenario: action config + user config", () => {
@@ -436,7 +438,8 @@ describe("parseSdkOptions", () => {
       const result = parseSdkOptions(options);
 
       expect(result.sdkOptions.additionalDirectories).toEqual(["/path/to/dir"]);
-      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-3-5-sonnet");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+      expect(result.sdkOptions.model).toBe("claude-3-5-sonnet");
       expect(result.sdkOptions.extraArgs?.["add-dir"]).toBeUndefined();
     });
   });
@@ -464,7 +467,8 @@ describe("parseSdkOptions", () => {
 
       const result = parseSdkOptions(options);
 
-      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-haiku");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+      expect(result.sdkOptions.model).toBe("claude-haiku");
       expect(result.sdkOptions.allowedTools).toEqual(["Edit"]);
     });
 
@@ -475,7 +479,8 @@ describe("parseSdkOptions", () => {
 
       const result = parseSdkOptions(options);
 
-      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-haiku");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+      expect(result.sdkOptions.model).toBe("claude-haiku");
     });
 
     test("should not strip inline # that appears inside a quoted value", () => {
@@ -485,11 +490,37 @@ describe("parseSdkOptions", () => {
 
       const result = parseSdkOptions(options);
 
-      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-haiku");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+      expect(result.sdkOptions.model).toBe("claude-haiku");
       expect(result.sdkOptions.extraArgs?.["prompt"]).toBe("use color #ff0000");
     });
   });
 
+  describe("model handling", () => {
+    test("should map --model from claudeArgs to sdkOptions.model", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: "--model claude-haiku-4-5-20251001",
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.model).toBe("claude-haiku-4-5-20251001");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+    });
+
+    test("should prefer direct model option over --model from claudeArgs", () => {
+      const options: ClaudeOptions = {
+        model: "claude-sonnet-4-6",
+        claudeArgs: "--model claude-haiku-4-5-20251001",
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.model).toBe("claude-sonnet-4-6");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBeUndefined();
+    });
+  });
+
   describe("environment variables passthrough", () => {
     test("should include OTEL environment variables in sdkOptions.env", () => {
       // Set up test environment variables
diff --git a/base-action/test/run-claude-sdk.test.ts b/base-action/test/run-claude-sdk.test.ts
index 877e884..cb50318 100644
--- a/base-action/test/run-claude-sdk.test.ts
+++ b/base-action/test/run-claude-sdk.test.ts
@@ -63,4 +63,69 @@ describe("runClaudeWithSdk", () => {
       consoleLogSpy.mockRestore();
     }
   });
+
+  test("fails when result subtype is success but is_error is true", async () => {
+    const consoleErrorSpy = spyOn(console, "error").mockImplementation(
+      () => {},
+    );
+    const consoleLogSpy = spyOn(console, "log").mockImplementation(() => {});
+    const coreErrorSpy = spyOn(
+      await import("@actions/core"),
+      "error",
+    ).mockImplementation(() => {});
+
+    tempDir = await mkdtemp(join(tmpdir(), "claude-sdk-"));
+    process.env.RUNNER_TEMP = tempDir;
+
+    const promptPath = join(tempDir, "prompt.txt");
+    await writeFile(promptPath, "test prompt");
+
+    const initMessage = {
+      type: "system",
+      subtype: "init",
+      session_id: "session-123",
+      model: "claude-sonnet-5",
+    };
+
+    const errorResultMessage = {
+      type: "result",
+      subtype: "success",
+      is_error: true,
+      duration_ms: 434,
+      num_turns: 1,
+      total_cost_usd: 0,
+      permission_denials: [],
+    };
+
+    mock.module("@anthropic-ai/claude-agent-sdk", () => ({
+      query: async function* () {
+        yield initMessage;
+        yield errorResultMessage;
+      },
+    }));
+
+    try {
+      const { runClaudeWithSdk } = await import("../src/run-claude-sdk");
+
+      await expect(
+        runClaudeWithSdk(promptPath, {
+          sdkOptions: {},
+          showFullOutput: false,
+          hasJsonSchema: false,
+        }),
+      ).rejects.toThrow("result is_error:true");
+
+      const executionFile = join(tempDir, "claude-execution-output.json");
+      await expect(readFile(executionFile, "utf-8")).resolves.toBe(
+        JSON.stringify([initMessage, errorResultMessage], null, 2),
+      );
+      expect(coreErrorSpy).toHaveBeenCalledWith(
+        "Claude result reported subtype success with is_error:true (run did not complete successfully)",
+      );
+    } finally {
+      consoleErrorSpy.mockRestore();
+      consoleLogSpy.mockRestore();
+      coreErrorSpy.mockRestore();
+    }
+  });
 });
diff --git a/base-action/test/workload-identity.test.ts b/base-action/test/workload-identity.test.ts
index e95f4e0..53a39af 100644
--- a/base-action/test/workload-identity.test.ts
+++ b/base-action/test/workload-identity.test.ts
@@ -27,6 +27,12 @@ describe("workload identity federation", () => {
     delete process.env.ANTHROPIC_ORGANIZATION_ID;
     delete process.env.ANTHROPIC_OIDC_AUDIENCE;
     delete process.env.ANTHROPIC_IDENTITY_TOKEN_FILE;
+    delete process.env.ANTHROPIC_SERVICE_ACCOUNT_ID;
+    delete process.env.ANTHROPIC_WORKSPACE_ID;
+    delete process.env.ANTHROPIC_BASE_URL;
+    delete process.env.ANTHROPIC_SCOPE;
+    delete process.env.ANTHROPIC_CONFIG_DIR;
+    delete process.env.ANTHROPIC_PROFILE;
 
     getIDTokenSpy = spyOn(core, "getIDToken").mockResolvedValue(
       "test-identity-token",
@@ -123,5 +129,99 @@ describe("workload identity federation", () => {
         handle?.stop();
       }
     });
+
+    test("writes a minimal federation profile and selects it", async () => {
+      process.env.ANTHROPIC_FEDERATION_RULE_ID = "fdrl_test";
+      process.env.ANTHROPIC_ORGANIZATION_ID =
+        "00000000-0000-0000-0000-000000000000";
+      process.env.ANTHROPIC_SERVICE_ACCOUNT_ID = "svac_test";
+      process.env.ANTHROPIC_WORKSPACE_ID = "wrkspc_test";
+
+      const handle = await setupWorkloadIdentity();
+      try {
+        const configDir = process.env.ANTHROPIC_CONFIG_DIR;
+        expect(configDir).toBeDefined();
+        expect(
+          configDir!.startsWith(
+            join(tempDir, "claude-workload-identity", "config-"),
+          ),
+        ).toBe(true);
+        expect(process.env.ANTHROPIC_PROFILE).toBe("default");
+
+        const profilePath = join(configDir!, "configs", "default.json");
+        expect(statSync(profilePath).mode & 0o777).toBe(0o600);
+        // Minimal on purpose: the SDK gap-fills the federation fields from
+        // the ANTHROPIC_* env vars the action exports.
+        expect(JSON.parse(readFileSync(profilePath, "utf-8"))).toEqual({
+          version: "1.0",
+          authentication: { type: "oidc_federation" },
+        });
+      } finally {
+        handle?.stop();
+      }
+    });
+
+    test("derives the config dir from the federation inputs", async () => {
+      process.env.ANTHROPIC_FEDERATION_RULE_ID = "fdrl_test";
+      process.env.ANTHROPIC_ORGANIZATION_ID =
+        "00000000-0000-0000-0000-000000000000";
+      process.env.ANTHROPIC_WORKSPACE_ID = "wrkspc_a";
+
+      (await setupWorkloadIdentity())?.stop();
+      const firstConfigDir = process.env.ANTHROPIC_CONFIG_DIR;
+      expect(firstConfigDir).toBeDefined();
+
+      // A later step in the same job with a different workspace must not
+      // share the first step's credentials cache.
+      delete process.env.ANTHROPIC_CONFIG_DIR;
+      delete process.env.ANTHROPIC_PROFILE;
+      process.env.ANTHROPIC_WORKSPACE_ID = "wrkspc_b";
+
+      (await setupWorkloadIdentity())?.stop();
+      const secondConfigDir = process.env.ANTHROPIC_CONFIG_DIR;
+      expect(secondConfigDir).toBeDefined();
+      expect(secondConfigDir).not.toBe(firstConfigDir);
+
+      // Same inputs land in the same dir, so an unchanged config can still
+      // reuse a cached token.
+      delete process.env.ANTHROPIC_CONFIG_DIR;
+      delete process.env.ANTHROPIC_PROFILE;
+
+      (await setupWorkloadIdentity())?.stop();
+      expect(process.env.ANTHROPIC_CONFIG_DIR).toBe(secondConfigDir!);
+    });
+
+    test("does not overwrite an operator-set ANTHROPIC_PROFILE", async () => {
+      process.env.ANTHROPIC_FEDERATION_RULE_ID = "fdrl_test";
+      process.env.ANTHROPIC_ORGANIZATION_ID =
+        "00000000-0000-0000-0000-000000000000";
+      process.env.ANTHROPIC_PROFILE = "operator";
+
+      const handle = await setupWorkloadIdentity();
+      try {
+        // The action must warn and leave the operator's profile untouched.
+        expect(warningSpy).toHaveBeenCalledWith(
+          expect.stringContaining("ANTHROPIC_CONFIG_DIR or ANTHROPIC_PROFILE"),
+        );
+        expect(process.env.ANTHROPIC_PROFILE).toBe("operator");
+        expect(process.env.ANTHROPIC_CONFIG_DIR).toBeUndefined();
+      } finally {
+        handle?.stop();
+      }
+    });
+
+    test("stop() removes the token dir so credentials don't outlive the step", async () => {
+      process.env.ANTHROPIC_FEDERATION_RULE_ID = "fdrl_test";
+      process.env.ANTHROPIC_ORGANIZATION_ID =
+        "00000000-0000-0000-0000-000000000000";
+
+      const handle = await setupWorkloadIdentity();
+      const tokenFile = handle!.tokenFile;
+      const tokenDir = join(tempDir, "claude-workload-identity");
+
+      expect(existsSync(tokenFile)).toBe(true);
+      handle!.stop();
+      expect(existsSync(tokenDir)).toBe(false);
+    });
   });
 });
diff --git a/bun.lock b/bun.lock
index 884d84b..eac4d32 100644
--- a/bun.lock
+++ b/bun.lock
@@ -6,7 +6,7 @@
       "dependencies": {
         "@actions/core": "^2.0.3",
         "@actions/github": "^8.0.1",
-        "@anthropic-ai/claude-agent-sdk": "0.3.203",
+        "@anthropic-ai/claude-agent-sdk": "^0.3.220",
         "@modelcontextprotocol/sdk": "^1.29.0",
         "@octokit/graphql": "^8.2.2",
         "@octokit/rest": "^21.1.1",
@@ -37,23 +37,23 @@
 
     "@actions/io": ["@actions/io@2.0.0", "", {}, "sha512-Jv33IN09XLO+0HS79aaODsvIRyduiF7NY/F6LYeK5oeUmrsz7aFdRphQjFoESF4jS7lMauDOttKALcpapVDIAg=="],
 
-    "@anthropic-ai/claude-agent-sdk": ["@anthropic-ai/claude-agent-sdk@0.3.203", "", { "optionalDependencies": { "@anthropic-ai/claude-agent-sdk-darwin-arm64": "0.3.203", "@anthropic-ai/claude-agent-sdk-darwin-x64": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-arm64": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-x64": "0.3.203", "@anthropic-ai/claude-agent-sdk-linux-x64-musl": "0.3.203", "@anthropic-ai/claude-agent-sdk-win32-arm64": "0.3.203", "@anthropic-ai/claude-agent-sdk-win32-x64": "0.3.203" }, "peerDependencies": { "@anthropic-ai/sdk": ">=0.93.0", "@modelcontextprotocol/sdk": "^1.29.0", "zod": "^4.0.0" } }, "sha512-K/GMQlB3IpLtvqjI+/9Xcu//4wDRSxO2JimHMOM3zxHBKJA0EIb6U+4Ea0RSrxe+SHwFHT23XATL6U/9JggxXw=="],
+    "@anthropic-ai/claude-agent-sdk": ["@anthropic-ai/claude-agent-sdk@0.3.220", "", { "optionalDependencies": { "@anthropic-ai/claude-agent-sdk-darwin-arm64": "0.3.220", "@anthropic-ai/claude-agent-sdk-darwin-x64": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-arm64": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-x64": "0.3.220", "@anthropic-ai/claude-agent-sdk-linux-x64-musl": "0.3.220", "@anthropic-ai/claude-agent-sdk-win32-arm64": "0.3.220", "@anthropic-ai/claude-agent-sdk-win32-x64": "0.3.220" }, "peerDependencies": { "@anthropic-ai/sdk": ">=0.93.0", "@modelcontextprotocol/sdk": "^1.29.0", "zod": "^4.0.0" } }, "sha512-glc7SdwPkOkLw8oxwLo9PKTdLJGqW/PIR4urWXFoRtX9YllwozsEVc5Tc1+EvLSkfrsxPJqQWqOgpjUOQXf1oA=="],
 
-    "@anthropic-ai/claude-agent-sdk-darwin-arm64": ["@anthropic-ai/claude-agent-sdk-darwin-arm64@0.3.203", "", { "os": "darwin", "cpu": "arm64" }, "sha512-9uG6wp3reCtiWXA1H7NWZV5HFO6WgmedcpRCMpw0iyborLdw3MEZonJVlfRh93eQEVpflfnTOARTqtt7NzgHqg=="],
+    "@anthropic-ai/claude-agent-sdk-darwin-arm64": ["@anthropic-ai/claude-agent-sdk-darwin-arm64@0.3.220", "", { "os": "darwin", "cpu": "arm64" }, "sha512-7VxlbEosK7DODiOnsjoVd0DSJzbnaPrM2jelMHI0y8zx1UnLS3WC6EFUXbvy74F2sXqEznh2tzn7EKWInaRN6Q=="],
 
-    "@anthropic-ai/claude-agent-sdk-darwin-x64": ["@anthropic-ai/claude-agent-sdk-darwin-x64@0.3.203", "", { "os": "darwin", "cpu": "x64" }, "sha512-iP2cg+VovTYeU9f/l32Cq4cESNrgBvjZn/NipyhQ7RD468vBUjn22ii9cnGF7g9TepNrY3/IdkCPmwSea9besA=="],
+    "@anthropic-ai/claude-agent-sdk-darwin-x64": ["@anthropic-ai/claude-agent-sdk-darwin-x64@0.3.220", "", { "os": "darwin", "cpu": "x64" }, "sha512-X9RwDsSmbF6ultKZroaip+DL8WRgC64gHbrAwrRlAFSPNZV7zmJyP2ur8rW7KrxqmtuehdMMkw8+SAC/6hD2PA=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-arm64": ["@anthropic-ai/claude-agent-sdk-linux-arm64@0.3.203", "", { "os": "linux", "cpu": "arm64" }, "sha512-p8wTbvWbQUscQBSefTdjwGbeVE6lYoEmMMdoNSOI8uR8jBr5YXoSwnSjBwmGDjz15WI4AIIdiWwyrf6sqrvqPA=="],
+    "@anthropic-ai/claude-agent-sdk-linux-arm64": ["@anthropic-ai/claude-agent-sdk-linux-arm64@0.3.220", "", { "os": "linux", "cpu": "arm64" }, "sha512-WkROPwWskqhKR9XgnmseHQ6rLi9zM9qt57IWoToIjL/eXOqDWipp7JXZ1L5ud+LrA42dunHPZfBwD/vXZ+A7LA=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": ["@anthropic-ai/claude-agent-sdk-linux-arm64-musl@0.3.203", "", { "os": "linux", "cpu": "arm64" }, "sha512-uQNRpgHKuavsEyvY3SnDRZuCxf1z2pjGI4Q73Q0GuIEapwXrY2UM0ucAj0b7KtS6hpu//CGhnBra2kKOXsDQAw=="],
+    "@anthropic-ai/claude-agent-sdk-linux-arm64-musl": ["@anthropic-ai/claude-agent-sdk-linux-arm64-musl@0.3.220", "", { "os": "linux", "cpu": "arm64" }, "sha512-OHoZOZ8Cf2TBr6oXIXPwyvUxj9jrq2w8E4poA8dMpacXszcPSPiCQCMuuOh4aWJzfeJE1+TtWxhKMVb2csXyZQ=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-x64": ["@anthropic-ai/claude-agent-sdk-linux-x64@0.3.203", "", { "os": "linux", "cpu": "x64" }, "sha512-YTW0+njIC61fZP3Qa9uzH9fOlEmApHG6SSxwyNxAQ8U3XX+yviL5/MyqLsauuUTVbyI9K7IqYOaE6xcDVDXIGg=="],
+    "@anthropic-ai/claude-agent-sdk-linux-x64": ["@anthropic-ai/claude-agent-sdk-linux-x64@0.3.220", "", { "os": "linux", "cpu": "x64" }, "sha512-tkTJFnpR9VifvWX2fmkCAPkT6+8Wk/gVu8B5jsVekKZPiZoWRHmMXO30BnZn+f0TZhgYP+82PSX3S8crH1kn+w=="],
 
-    "@anthropic-ai/claude-agent-sdk-linux-x64-musl": ["@anthropic-ai/claude-agent-sdk-linux-x64-musl@0.3.203", "", { "os": "linux", "cpu": "x64" }, "sha512-Hw2NNW8crM7ENR8peWZ+hG3ehUl9IYPzNxyqc1VM+odznB6squaki2xQeCcIatHbQImeW+DzrUFIDJLLz4pltg=="],
+    "@anthropic-ai/claude-agent-sdk-linux-x64-musl": ["@anthropic-ai/claude-agent-sdk-linux-x64-musl@0.3.220", "", { "os": "linux", "cpu": "x64" }, "sha512-K+FWj+LcGhC1Z7wqeWoLxm1iemcba5xKpLLFVwYm4V6HyMx3ruYd/2r2TiQtjT+JWeNFWIys0ScHiItR6vWAiA=="],
 
-    "@anthropic-ai/claude-agent-sdk-win32-arm64": ["@anthropic-ai/claude-agent-sdk-win32-arm64@0.3.203", "", { "os": "win32", "cpu": "arm64" }, "sha512-EF2BPCSElFS9y76b/4TVU7RDw9xCr8DtxSUXAxYhcGsreo1gmJbMVdZ9tvLIvG6Ufquas4nrGmWh1ePLP2ol+g=="],
+    "@anthropic-ai/claude-agent-sdk-win32-arm64": ["@anthropic-ai/claude-agent-sdk-win32-arm64@0.3.220", "", { "os": "win32", "cpu": "arm64" }, "sha512-rIwgq0UwQExWl6KrHUyC4w5KwpL9l6nd95aUTx6RitexaAuEw//xtfTVLnuE4hDDQZFkzEwpdKc3nxDWoGcUbA=="],
 
-    "@anthropic-ai/claude-agent-sdk-win32-x64": ["@anthropic-ai/claude-agent-sdk-win32-x64@0.3.203", "", { "os": "win32", "cpu": "x64" }, "sha512-sYf4UokyYhYO6Nke99o+gtgCakoaohB+Q/71i+4hEq0FYqVf31WoJ6lUTTTUPeEGVp6Ju6BblzmAX2MpvlWwCw=="],
+    "@anthropic-ai/claude-agent-sdk-win32-x64": ["@anthropic-ai/claude-agent-sdk-win32-x64@0.3.220", "", { "os": "win32", "cpu": "x64" }, "sha512-MuOuXhbr66HlGaWXD2f3w0k2PsvmnbkwcUZ0dAe2poFLdl72GC2dapwwOBefxm9QmoNqk9+jmv/dSKGOVWyvLw=="],
 
     "@anthropic-ai/sdk": ["@anthropic-ai/sdk@0.104.1", "", { "dependencies": { "json-schema-to-ts": "^3.1.1", "standardwebhooks": "^1.0.0" }, "peerDependencies": { "zod": "^3.25.0 || ^4.0.0" }, "optionalPeers": ["zod"], "bin": { "anthropic-ai-sdk": "bin/cli" } }, "sha512-gGACa/+IaiXzRRmF96aOhamoBgapKRBiFWbmmTFP8aMkpaEcuStF+Q61bjo4vPxBM7gqWJNZqsngslRdnLHv0Q=="],
 
diff --git a/docs/configuration.md b/docs/configuration.md
index 017c82c..f4c311f 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -337,17 +337,17 @@ For a complete list of available settings and their descriptions, see the [Claud
 
 Many individual input parameters have been consolidated into `claude_args` or `settings`. Here's how to migrate:
 
-| Old Input             | New Approach                                             |
-| --------------------- | -------------------------------------------------------- |
-| `allowed_tools`       | Use `claude_args: "--allowedTools Tool1,Tool2"`          |
-| `disallowed_tools`    | Use `claude_args: "--disallowedTools Tool1,Tool2"`       |
-| `max_turns`           | Use `claude_args: "--max-turns 10"`                      |
-| `model`               | Use `claude_args: "--model claude-4-0-sonnet-20250805"`  |
-| `claude_env`          | Use `settings` with `"env"` object                       |
-| `custom_instructions` | Use `claude_args: "--system-prompt 'Your instructions'"` |
-| `mcp_config`          | Use `claude_args: "--mcp-config '{...}'"`                |
-| `direct_prompt`       | Use `prompt` input instead                               |
-| `override_prompt`     | Use `prompt` with GitHub context variables               |
+| Old Input             | New Approach                                                    |
+| --------------------- | --------------------------------------------------------------- |
+| `allowed_tools`       | Use `claude_args: "--allowedTools Tool1,Tool2"`                 |
+| `disallowed_tools`    | Use `claude_args: "--disallowedTools Tool1,Tool2"`              |
+| `max_turns`           | Use `claude_args: "--max-turns 10"`                             |
+| `model`               | Use `claude_args: "--model claude-4-0-sonnet-20250805"`         |
+| `claude_env`          | Use `settings` with `"env"` object                              |
+| `custom_instructions` | Use `claude_args: "--append-system-prompt 'Your instructions'"` |
+| `mcp_config`          | Use `claude_args: "--mcp-config '{...}'"`                       |
+| `direct_prompt`       | Use `prompt` input instead                                      |
+| `override_prompt`     | Use `prompt` with GitHub context variables                      |
 
 ## Custom Executables for Specialized Environments
 
diff --git a/docs/custom-automations.md b/docs/custom-automations.md
index 2123917..36def4e 100644
--- a/docs/custom-automations.md
+++ b/docs/custom-automations.md
@@ -26,7 +26,7 @@ This action supports the following GitHub events ([learn more GitHub event trigg
 
 ## Automated Documentation Updates
 
-Automatically update documentation when specific files change (see [`examples/claude-pr-path-specific.yml`](../examples/claude-pr-path-specific.yml)):
+Automatically update documentation when specific files change (see [`examples/pr-review-filtered-paths.yml`](../examples/pr-review-filtered-paths.yml)):
 
 ```yaml
 on:
@@ -47,7 +47,7 @@ When API files are modified, the action automatically detects that a `prompt` is
 
 ## Author-Specific Code Reviews
 
-Automatically review PRs from specific authors or external contributors (see [`examples/claude-review-from-author.yml`](../examples/claude-review-from-author.yml)):
+Automatically review PRs from specific authors or external contributors (see [`examples/pr-review-filtered-authors.yml`](../examples/pr-review-filtered-authors.yml)):
 
 ```yaml
 on:
diff --git a/docs/faq.md b/docs/faq.md
index 8ddac9e..0175c67 100644
--- a/docs/faq.md
+++ b/docs/faq.md
@@ -153,7 +153,7 @@ prompt: "Review this PR for security vulnerabilities"
 **These inputs are deprecated in v1.0:**
 
 - **`direct_prompt`** → Use `prompt` instead
-- **`custom_instructions`** → Use `claude_args` with `--system-prompt`
+- **`custom_instructions`** → Use `claude_args` with `--append-system-prompt` (appends to the default system prompt, matching v0 behavior; `--system-prompt` replaces it entirely)
 
 Migration examples:
 
@@ -165,7 +165,7 @@ custom_instructions: "Focus on security"
 # New (v1.0)
 prompt: "Review this PR"
 claude_args: |
-  --system-prompt "Focus on security"
+  --append-system-prompt "Focus on security"
 ```
 
 ### Why doesn't Claude execute my bash commands?
diff --git a/docs/migration-guide.md b/docs/migration-guide.md
index 362ab64..1d91c75 100644
--- a/docs/migration-guide.md
+++ b/docs/migration-guide.md
@@ -14,19 +14,19 @@ This guide helps you migrate from Claude Code Action v0.x to v1.0. The new versi
 
 The following inputs have been deprecated and replaced:
 
-| Deprecated Input      | Replacement                          | Notes                                         |
-| --------------------- | ------------------------------------ | --------------------------------------------- |
-| `mode`                | Auto-detected                        | Action automatically chooses based on context |
-| `direct_prompt`       | `prompt`                             | Direct drop-in replacement                    |
-| `override_prompt`     | `prompt`                             | Use GitHub context variables instead          |
-| `custom_instructions` | `claude_args: --system-prompt`       | Move to CLI arguments                         |
-| `max_turns`           | `claude_args: --max-turns`           | Use CLI format                                |
-| `model`               | `claude_args: --model`               | Specify via CLI                               |
-| `allowed_tools`       | `claude_args: --allowedTools`        | Use CLI format                                |
-| `disallowed_tools`    | `claude_args: --disallowedTools`     | Use CLI format                                |
-| `claude_env`          | `settings` with env object           | Use settings JSON                             |
-| `mcp_config`          | `claude_args: --mcp-config`          | Pass MCP config via CLI arguments             |
-| `timeout_minutes`     | Use GitHub Actions `timeout-minutes` | Configure at job level instead of input level |
+| Deprecated Input      | Replacement                           | Notes                                                                               |
+| --------------------- | ------------------------------------- | ----------------------------------------------------------------------------------- |
+| `mode`                | Auto-detected                         | Action automatically chooses based on context                                       |
+| `direct_prompt`       | `prompt`                              | Direct drop-in replacement                                                          |
+| `override_prompt`     | `prompt`                              | Use GitHub context variables instead                                                |
+| `custom_instructions` | `claude_args: --append-system-prompt` | Appends to the default prompt (v0 behavior); `--system-prompt` replaces it entirely |
+| `max_turns`           | `claude_args: --max-turns`            | Use CLI format                                                                      |
+| `model`               | `claude_args: --model`                | Specify via CLI                                                                     |
+| `allowed_tools`       | `claude_args: --allowedTools`         | Use CLI format                                                                      |
+| `disallowed_tools`    | `claude_args: --disallowedTools`      | Use CLI format                                                                      |
+| `claude_env`          | `settings` with env object            | Use settings JSON                                                                   |
+| `mcp_config`          | `claude_args: --mcp-config`           | Pass MCP config via CLI arguments                                                   |
+| `timeout_minutes`     | Use GitHub Actions `timeout-minutes`  | Configure at job level instead of input level                                       |
 
 ## Migration Examples
 
@@ -52,7 +52,7 @@ The following inputs have been deprecated and replaced:
     anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
     claude_args: |
       --max-turns 10
-      --system-prompt "Follow our coding standards"
+      --append-system-prompt "Follow our coding standards"
       --allowedTools Edit,Read,Write
 ```
 
@@ -255,14 +255,15 @@ claude_args: |
 
 ### Common claude_args Options
 
-| Option              | Description              | Example                                |
-| ------------------- | ------------------------ | -------------------------------------- |
-| `--max-turns`       | Limit conversation turns | `--max-turns 10`                       |
-| `--model`           | Specify Claude model     | `--model claude-4-0-sonnet-20250805`   |
-| `--allowedTools`    | Enable specific tools    | `--allowedTools Edit,Read,Write`       |
-| `--disallowedTools` | Disable specific tools   | `--disallowedTools WebSearch`          |
-| `--system-prompt`   | Add system instructions  | `--system-prompt "Focus on security"`  |
-| `--mcp-config`      | Add MCP server config    | `--mcp-config '{"mcpServers": {...}}'` |
+| Option                   | Description                                                               | Example                                                |
+| ------------------------ | ------------------------------------------------------------------------- | ------------------------------------------------------ |
+| `--max-turns`            | Limit conversation turns                                                  | `--max-turns 10`                                       |
+| `--model`                | Specify Claude model                                                      | `--model claude-4-0-sonnet-20250805`                   |
+| `--allowedTools`         | Enable specific tools                                                     | `--allowedTools Edit,Read,Write`                       |
+| `--disallowedTools`      | Disable specific tools                                                    | `--disallowedTools WebSearch`                          |
+| `--system-prompt`        | Replace the entire default system prompt                                  | `--system-prompt "Focus on security"`                  |
+| `--append-system-prompt` | Append to the default system prompt (keeps Claude Code's built-in prompt) | `--append-system-prompt "Follow our coding standards"` |
+| `--mcp-config`           | Add MCP server config                                                     | `--mcp-config '{"mcpServers": {...}}'`                 |
 
 ## Provider-Specific Updates
 
@@ -330,7 +331,7 @@ You can also pass MCP configuration from a file:
 - [ ] Remove `mode` input (auto-detected now)
 - [ ] Replace `direct_prompt` with `prompt`
 - [ ] Replace `override_prompt` with `prompt` using GitHub context
-- [ ] Move `custom_instructions` to `claude_args` with `--system-prompt`
+- [ ] Move `custom_instructions` to `claude_args` with `--append-system-prompt`
 - [ ] Convert `max_turns` to `claude_args` with `--max-turns`
 - [ ] Convert `model` to `claude_args` with `--model`
 - [ ] Convert `allowed_tools` to `claude_args` with `--allowedTools`
diff --git a/docs/usage.md b/docs/usage.md
index 3982338..ce01cbd 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -99,7 +99,7 @@ These inputs are deprecated and will be removed in a future version:
 | `mode`                | **DEPRECATED**: Mode is now automatically detected based on workflow context                 | Remove this input; the action auto-detects the correct mode    |
 | `direct_prompt`       | **DEPRECATED**: Use `prompt` instead                                                         | Replace with `prompt`                                          |
 | `override_prompt`     | **DEPRECATED**: Use `prompt` with template variables or `claude_args` with `--system-prompt` | Use `prompt` for templates or `claude_args` for system prompts |
-| `custom_instructions` | **DEPRECATED**: Use `claude_args` with `--system-prompt` or include in `prompt`              | Move instructions to `prompt` or use `claude_args`             |
+| `custom_instructions` | **DEPRECATED**: Use `claude_args` with `--append-system-prompt` or include in `prompt`       | Move instructions to `prompt` or use `claude_args`             |
 | `max_turns`           | **DEPRECATED**: Use `claude_args` with `--max-turns` instead                                 | Use `claude_args: "--max-turns 5"`                             |
 | `model`               | **DEPRECATED**: Use `claude_args` with `--model` instead                                     | Use `claude_args: "--model claude-4-0-sonnet-20250805"`        |
 | `fallback_model`      | **DEPRECATED**: Use `claude_args` with fallback configuration                                | Configure fallback in `claude_args` or `settings`              |
@@ -139,7 +139,7 @@ For a comprehensive guide on migrating from v0.x to v1.0, including step-by-step
     anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
     claude_args: |
       --max-turns 10
-      --system-prompt "Focus on security"
+      --append-system-prompt "Focus on security"
 ```
 
 #### Automation Workflows
diff --git a/package.json b/package.json
index 7bf9645..5272f79 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,7 @@
   "dependencies": {
     "@actions/core": "^2.0.3",
     "@actions/github": "^8.0.1",
-    "@anthropic-ai/claude-agent-sdk": "0.3.203",
+    "@anthropic-ai/claude-agent-sdk": "^0.3.220",
     "@modelcontextprotocol/sdk": "^1.29.0",
     "@octokit/graphql": "^8.2.2",
     "@octokit/rest": "^21.1.1",
diff --git a/src/entrypoints/format-turns.ts b/src/entrypoints/format-turns.ts
index 3241745..c18ab49 100755
--- a/src/entrypoints/format-turns.ts
+++ b/src/entrypoints/format-turns.ts
@@ -268,7 +268,8 @@ export function groupTurnsNaturally(data: Turn[]): GroupedContent[] {
           type: "system_init",
           tools_count: tools.length,
         });
-      } else {
+      } else if (subtype !== "thinking_tokens") {
+        // Skip thinking_tokens - internal progress events not meant for summary
         groupedContent.push({
           type: "system_other",
           data: turn,
diff --git a/src/entrypoints/run.ts b/src/entrypoints/run.ts
index c200607..42c4e0b 100644
--- a/src/entrypoints/run.ts
+++ b/src/entrypoints/run.ts
@@ -76,7 +76,7 @@ async function installClaudeCode(): Promise<string> {
     return customExecutable;
   }
 
-  const claudeCodeVersion = "2.1.203";
+  const claudeCodeVersion = "2.1.220";
   console.log(`Installing Claude Code v${claudeCodeVersion}...`);
 
   for (let attempt = 1; attempt <= 3; attempt++) {
@@ -366,7 +366,8 @@ async function run() {
   } finally {
     // Phase 4: Cleanup (always runs)
 
-    // Stop refreshing the workload identity token file
+    // Stop refreshing the workload identity token file and delete the token
+    // material so it doesn't outlive this step
     workloadIdentity?.stop();
 
     // Update tracking comment
diff --git a/src/github/data/fetcher.ts b/src/github/data/fetcher.ts
index 4d12388..cea2ea2 100644
--- a/src/github/data/fetcher.ts
+++ b/src/github/data/fetcher.ts
@@ -204,11 +204,9 @@ export function isBodySafeToUse(
  * @param excludeActors - Comma-separated actors to exclude
  * @returns Filtered array of comments
  */
-export function filterCommentsByActor<T extends { author: { login: string } }>(
-  comments: T[],
-  includeActors: string = "",
-  excludeActors: string = "",
-): T[] {
+export function filterCommentsByActor<
+  T extends { author: { login: string } | null },
+>(comments: T[], includeActors: string = "", excludeActors: string = ""): T[] {
   const includeParsed = parseActorFilter(includeActors);
   const excludeParsed = parseActorFilter(excludeActors);
 
@@ -219,7 +217,9 @@ export function filterCommentsByActor<T extends { author: { login: string } }>(
 
   return comments.filter((comment) =>
     shouldIncludeCommentByActor(
-      comment.author.login,
+      // author is null for comments from deleted ("ghost") accounts; treat them
+      // as the "ghost" login so filtering never dereferences null and crashes.
+      comment.author?.login ?? "ghost",
       includeParsed,
       excludeParsed,
     ),
diff --git a/src/github/data/formatter.ts b/src/github/data/formatter.ts
index 398cc74..95d5603 100644
--- a/src/github/data/formatter.ts
+++ b/src/github/data/formatter.ts
@@ -21,7 +21,7 @@ export function formatContext(
     const prData = contextData as GitHubPullRequest;
     const sanitizedTitle = sanitizeContent(prData.title);
     return `PR Title: ${sanitizedTitle}
-PR Author: ${prData.author.login}
+PR Author: ${prData.author?.login ?? "ghost"}
 PR Branch: ${prData.headRefName} -> ${prData.baseRefName}
 PR State: ${prData.state}
 PR Labels: ${formatLabels(prData.labels.nodes)}
@@ -33,7 +33,7 @@ Changed Files: ${prData.files.nodes.length} files`;
     const issueData = contextData as GitHubIssue;
     const sanitizedTitle = sanitizeContent(issueData.title);
     return `Issue Title: ${sanitizedTitle}
-Issue Author: ${issueData.author.login}
+Issue Author: ${issueData.author?.login ?? "ghost"}
 Issue State: ${issueData.state}
 Issue Labels: ${formatLabels(issueData.labels.nodes)}`;
   }
@@ -71,7 +71,7 @@ export function formatComments(
 
       body = sanitizeContent(body);
 
-      return `[${comment.author.login} at ${comment.createdAt}]: ${body}`;
+      return `[${comment.author?.login ?? "ghost"} at ${comment.createdAt}]: ${body}`;
     })
     .join("\n\n");
 }
@@ -85,7 +85,7 @@ export function formatReviewComments(
   }
 
   const formattedReviews = reviewData.nodes.map((review) => {
-    let reviewOutput = `[Review by ${review.author.login} at ${review.submittedAt}]: ${review.state}`;
+    let reviewOutput = `[Review by ${review.author?.login ?? "ghost"} at ${review.submittedAt}]: ${review.state}`;
 
     if (review.body && review.body.trim()) {
       let body = review.body;
diff --git a/src/github/operations/branch.ts b/src/github/operations/branch.ts
index 253f763..e095280 100644
--- a/src/github/operations/branch.ts
+++ b/src/github/operations/branch.ts
@@ -27,7 +27,7 @@ function extractFirstLabel(githubData: FetchDataResult): string | undefined {
  * This prevents command injection by ensuring only safe characters are used.
  *
  * Valid branch names:
- * - Start with alphanumeric character or @ (not dash, to prevent option injection)
+ * - Start with alphanumeric character, underscore, or @ (not dash, to prevent option injection)
  * - Contain only alphanumeric, forward slash, hyphen, underscore, period, hash (#), plus (+), comma (,), or at sign (@)
  * - Do not start or end with a period
  * - Do not end with a slash
@@ -68,12 +68,15 @@ export function validateBranchName(branchName: string): void {
   // @ is valid per git-check-ref-format anywhere in a ref name, including the first character
   //   (e.g. ticket conventions like "TICKET-123@add-feature" or prefixes like "@hotfix/...");
   //   the bare name "@" (HEAD shorthand) and the "@{" sequence (reflog syntax) are rejected below.
+  // _ is valid per git-check-ref-format anywhere in a ref name, including the first character;
+  //   leading underscores are a common convention for release/internal branches (e.g.
+  //   "_release/v1.2.3"), which previously failed validation as a PR's base branch.
   // All git calls use execFileSync (not shell interpolation), so none of these characters carry injection risk.
-  const validPattern = /^[a-zA-Z0-9@][a-zA-Z0-9/_.#+,@-]*$/;
+  const validPattern = /^[a-zA-Z0-9@_][a-zA-Z0-9/_.#+,@-]*$/;
 
   if (!validPattern.test(branchName)) {
     throw new Error(
-      `Invalid branch name: "${branchName}". Branch names must start with an alphanumeric character or '@' and contain only alphanumeric characters, forward slashes, hyphens, underscores, periods, hashes (#), plus signs (+), commas (,), or at signs (@).`,
+      `Invalid branch name: "${branchName}". Branch names must start with an alphanumeric character, underscore, or '@' and contain only alphanumeric characters, forward slashes, hyphens, underscores, periods, hashes (#), plus signs (+), commas (,), or at signs (@).`,
     );
   }
 
diff --git a/src/github/types.ts b/src/github/types.ts
index 6ed41e3..feeb7d7 100644
--- a/src/github/types.ts
+++ b/src/github/types.ts
@@ -1,4 +1,8 @@
 // Types for GitHub GraphQL query responses
+
+// GitHub's GraphQL `author`/`actor` fields resolve to null when the underlying
+// account has been deleted (the "ghost" user). Any field typed as
+// `GitHubAuthor | null` can therefore be null at runtime and must be guarded.
 export type GitHubAuthor = {
   login: string;
   name?: string;
@@ -8,7 +12,7 @@ export type GitHubComment = {
   id: string;
   databaseId: string;
   body: string;
-  author: GitHubAuthor;
+  author: GitHubAuthor | null;
   createdAt: string;
   updatedAt?: string;
   lastEditedAt?: string;
@@ -39,7 +43,7 @@ export type GitHubFile = {
 export type GitHubReview = {
   id: string;
   databaseId: string;
-  author: GitHubAuthor;
+  author: GitHubAuthor | null;
   body: string;
   state: string;
   submittedAt: string;
@@ -53,7 +57,7 @@ export type GitHubReview = {
 export type GitHubPullRequest = {
   title: string;
   body: string;
-  author: GitHubAuthor;
+  author: GitHubAuthor | null;
   baseRefName: string;
   headRefName: string;
   headRefOid: string;
@@ -95,7 +99,7 @@ export type GitHubPullRequest = {
 export type GitHubIssue = {
   title: string;
   body: string;
-  author: GitHubAuthor;
+  author: GitHubAuthor | null;
   createdAt: string;
   updatedAt?: string;
   lastEditedAt?: string;
diff --git a/src/github/utils/sanitizer.ts b/src/github/utils/sanitizer.ts
index 0cb8408..47f60ab 100644
--- a/src/github/utils/sanitizer.ts
+++ b/src/github/utils/sanitizer.ts
@@ -10,7 +10,13 @@ export function stripInvisibleCharacters(content: string): string {
 }
 
 export function stripMarkdownImageAltText(content: string): string {
-  return content.replace(/!\[[^\]]*\]\(/g, "![](");
+  // Inline images: ![alt](url) -> ![](url)
+  content = content.replace(/!\[[^\]]*\]\(/g, "![](");
+  // Reference-style images: ![alt][ref] -> ![][ref] (keep the label, drop the
+  // alt text, which is otherwise a hidden-instruction channel just like the
+  // inline form above).
+  content = content.replace(/!\[[^\]]*\](\[[^\]]*\])/g, "![]$1");
+  return content;
 }
 
 export function stripMarkdownLinkTitles(content: string): string {
@@ -83,6 +89,12 @@ export function redactGitHubTokens(content: string): string {
     "[REDACTED_GITHUB_TOKEN]",
   );
 
+  // GitHub user-to-server tokens: ghu_XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX (40 chars)
+  content = content.replace(
+    /\bghu_[A-Za-z0-9]{36}\b/g,
+    "[REDACTED_GITHUB_TOKEN]",
+  );
+
   // GitHub installation tokens: ghs_XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX (40 chars)
   content = content.replace(
     /\bghs_[A-Za-z0-9]{36}\b/g,
diff --git a/src/utils/branch-template.ts b/src/utils/branch-template.ts
index 0056dd6..fecfacd 100644
--- a/src/utils/branch-template.ts
+++ b/src/utils/branch-template.ts
@@ -28,6 +28,20 @@ function extractDescription(
     .replace(/^-|-$/g, ""); // Remove leading/trailing hyphens
 }
 
+/**
+ * Sanitizes a label into a git-safe branch segment. Labels are free-form and
+ * often scoped (e.g. "area:permissions"), so characters that are invalid in a
+ * branch name (":", "/", spaces, ...) are replaced with a hyphen rather than
+ * dropped, keeping the label readable. Returns "" if nothing usable remains.
+ */
+function sanitizeLabel(label: string): string {
+  return label
+    .toLowerCase()
+    .replace(/[^a-z0-9-]+/g, "-") // Replace runs of invalid chars with a hyphen
+    .replace(/-+/g, "-") // Collapse multiple hyphens
+    .replace(/^-|-$/g, ""); // Remove leading/trailing hyphens
+}
+
 export interface BranchTemplateVariables {
   prefix: string;
   entityType: string;
@@ -78,7 +92,7 @@ export function generateBranchName(
     entityNumber,
     timestamp: `${now.getFullYear()}${String(now.getMonth() + 1).padStart(2, "0")}${String(now.getDate()).padStart(2, "0")}-${String(now.getHours()).padStart(2, "0")}${String(now.getMinutes()).padStart(2, "0")}`,
     sha: sha?.substring(0, 8), // First 8 characters of SHA
-    label: label || entityType, // Fall back to entityType if no label
+    label: (label && sanitizeLabel(label)) || entityType, // Sanitize; fall back to entityType if empty/no label
     description: title ? extractDescription(title) : undefined,
   };
 
diff --git a/test/branch-template.test.ts b/test/branch-template.test.ts
index 62ab6c1..418eaae 100644
--- a/test/branch-template.test.ts
+++ b/test/branch-template.test.ts
@@ -5,6 +5,7 @@ import {
   applyBranchTemplate,
   generateBranchName,
 } from "../src/utils/branch-template";
+import { validateBranchName } from "../src/github/operations/branch";
 
 describe("branch template utilities", () => {
   describe("applyBranchTemplate", () => {
@@ -144,6 +145,53 @@ describe("branch template utilities", () => {
       expect(result).toBe("dev/enhancement-issue_789");
     });
 
+    it("should sanitize scoped labels that contain invalid git characters", () => {
+      const template = "{{prefix}}{{label}}/{{entityNumber}}";
+      const result = generateBranchName(
+        template,
+        "claude/",
+        "issue",
+        123,
+        undefined,
+        "area:permissions",
+      );
+
+      expect(result).toBe("claude/area-permissions/123");
+      // Regression: an unsanitized ":" here previously failed validateBranchName
+      // and crashed the run via process.exit(1).
+      expect(() => validateBranchName(result)).not.toThrow();
+    });
+
+    it("should replace spaces in labels with hyphens", () => {
+      const template = "{{prefix}}{{label}}-{{entityNumber}}";
+      const result = generateBranchName(
+        template,
+        "fix/",
+        "issue",
+        456,
+        undefined,
+        "needs review",
+      );
+
+      expect(result).toBe("fix/needs-review-456");
+      expect(() => validateBranchName(result)).not.toThrow();
+    });
+
+    it("should fall back to entityType when a label sanitizes to empty", () => {
+      const template = "{{prefix}}{{label}}-{{entityNumber}}";
+      const result = generateBranchName(
+        template,
+        "fix/",
+        "pr",
+        789,
+        undefined,
+        "🎉",
+      );
+
+      expect(result).toBe("fix/pr-789");
+      expect(() => validateBranchName(result)).not.toThrow();
+    });
+
     it("should use description in template when provided", () => {
       const template = "{{prefix}}{{description}}/{{entityNumber}}";
       const result = generateBranchName(
diff --git a/test/comments-common.test.ts b/test/comments-common.test.ts
new file mode 100644
index 0000000..b37dec9
--- /dev/null
+++ b/test/comments-common.test.ts
@@ -0,0 +1,74 @@
+import { describe, test, expect } from "bun:test";
+import {
+  SPINNER_HTML,
+  createJobRunLink,
+  createBranchLink,
+  createCommentBody,
+} from "../src/github/operations/comments/common";
+import { GITHUB_SERVER_URL } from "../src/github/api/config";
+
+describe("comments/common", () => {
+  describe("createJobRunLink", () => {
+    test("builds a markdown link to the workflow run", () => {
+      const result = createJobRunLink("anthropics", "claude-code-action", "42");
+      expect(result).toBe(
+        `[View job run](${GITHUB_SERVER_URL}/anthropics/claude-code-action/actions/runs/42)`,
+      );
+    });
+
+    test("honors GITHUB_SERVER_URL (GHES) rather than hardcoding github.com", () => {
+      // The link is built from the configured server URL, so it must point at
+      // whatever GITHUB_SERVER_URL resolves to (github.com by default, a GHES
+      // host in enterprise setups).
+      expect(createJobRunLink("o", "r", "1")).toContain(GITHUB_SERVER_URL);
+    });
+  });
+
+  describe("createBranchLink", () => {
+    test("builds a leading-newline markdown link to the branch tree", () => {
+      const result = createBranchLink(
+        "anthropics",
+        "claude-code-action",
+        "feature/x",
+      );
+      expect(result).toBe(
+        `\n[View branch](${GITHUB_SERVER_URL}/anthropics/claude-code-action/tree/feature/x)`,
+      );
+    });
+
+    test("prefixes the link with a newline so it renders on its own line", () => {
+      expect(createBranchLink("o", "r", "main").startsWith("\n")).toBe(true);
+    });
+  });
+
+  describe("createCommentBody", () => {
+    test("includes the spinner, the working message, and the job run link", () => {
+      const jobRunLink = createJobRunLink("o", "r", "7");
+      const body = createCommentBody(jobRunLink);
+
+      expect(body).toContain(SPINNER_HTML);
+      expect(body).toContain("Claude Code is working…");
+      expect(body).toContain(jobRunLink);
+    });
+
+    test("omits the branch link when none is provided (defaults to empty)", () => {
+      const body = createCommentBody(createJobRunLink("o", "r", "7"));
+      expect(body).not.toContain("View branch");
+      // No trailing branch content: body ends with the job run link.
+      expect(body.endsWith(")")).toBe(true);
+    });
+
+    test("appends the branch link when provided", () => {
+      const jobRunLink = createJobRunLink("o", "r", "7");
+      const branchLink = createBranchLink("o", "r", "feature/x");
+      const body = createCommentBody(jobRunLink, branchLink);
+
+      expect(body).toContain(jobRunLink);
+      expect(body).toContain(branchLink);
+      // The branch link (with its leading newline) comes after the job run link.
+      expect(body.indexOf(branchLink)).toBeGreaterThan(
+        body.indexOf(jobRunLink),
+      );
+    });
+  });
+});
diff --git a/test/create-prompt.test.ts b/test/create-prompt.test.ts
index 44e510c..046a78f 100644
--- a/test/create-prompt.test.ts
+++ b/test/create-prompt.test.ts
@@ -6,8 +6,10 @@ import {
   getEventTypeAndContext,
   buildAllowedToolsString,
   buildDisallowedToolsString,
+  prepareContext,
 } from "../src/create-prompt";
 import type { PreparedContext } from "../src/create-prompt";
+import { createMockContext } from "./mockContext";
 
 beforeAll(() => {
   process.env.GITHUB_ACTION_PATH = "/test/action/path";
@@ -1270,3 +1272,83 @@ describe("buildDisallowedToolsString", () => {
     expect(result).toBe("BadTool1,BadTool2");
   });
 });
+
+describe("prepareContext validation errors", () => {
+  const commentId = "12345";
+
+  test("throws on an unsupported event type", () => {
+    const context = createMockContext({
+      eventName: "deployment_status" as any,
+    });
+
+    expect(() => prepareContext(context, commentId)).toThrow(
+      "Unsupported event type: deployment_status",
+    );
+  });
+
+  test("pull_request event requires a PR number (isPR must be true)", () => {
+    const context = createMockContext({
+      eventName: "pull_request",
+      eventAction: "opened",
+      isPR: false,
+    });
+
+    expect(() => prepareContext(context, commentId)).toThrow(
+      "PR_NUMBER is required for pull_request event",
+    );
+  });
+
+  test("pull_request_review event requires a PR number", () => {
+    const context = createMockContext({
+      eventName: "pull_request_review",
+      isPR: false,
+      payload: {
+        review: { body: "please fix", user: { login: "user1" } },
+      } as any,
+    });
+
+    expect(() => prepareContext(context, commentId)).toThrow(
+      "PR_NUMBER is required for pull_request_review event",
+    );
+  });
+
+  test("issues event requires an event action", () => {
+    const context = createMockContext({
+      eventName: "issues",
+      eventAction: "",
+      isPR: false,
+      payload: { issue: { user: { login: "user1" } } } as any,
+    });
+
+    expect(() => prepareContext(context, commentId)).toThrow(
+      "GITHUB_EVENT_ACTION is required for issues event",
+    );
+  });
+
+  test("issues event rejects an unsupported action", () => {
+    const context = createMockContext({
+      eventName: "issues",
+      eventAction: "deleted",
+      isPR: false,
+      payload: { issue: { user: { login: "user1" } } } as any,
+    });
+
+    expect(() =>
+      prepareContext(context, commentId, "main", "claude/issue-1"),
+    ).toThrow("Unsupported issue action: deleted");
+  });
+
+  test("issue_comment on an issue requires a claude branch", () => {
+    const context = createMockContext({
+      eventName: "issue_comment",
+      isPR: false,
+      payload: {
+        comment: { id: 999, body: "@claude help", user: { login: "user1" } },
+      } as any,
+    });
+
+    expect(() => prepareContext(context, commentId)).toThrow(
+      "CLAUDE_BRANCH is required for issue_comment event",
+    );
+  });
+});
diff --git a/test/data-fetcher.test.ts b/test/data-fetcher.test.ts
index f92fc14..c054039 100644
--- a/test/data-fetcher.test.ts
+++ b/test/data-fetcher.test.ts
@@ -1499,4 +1499,42 @@ describe("filterCommentsByActor", () => {
     const filtered = filterCommentsByActor(comments, "user1", "");
     expect(filtered).toHaveLength(0);
   });
+
+  test("does not crash on comments from deleted (null-author) accounts", () => {
+    // GitHub's GraphQL returns author: null for comments whose account was
+    // deleted. With an exclude filter set (the exact `*[bot]` config we
+    // recommend), the null author must not throw when dereferenced.
+    const comments = [
+      { author: { login: "user1" }, body: "comment1" },
+      { author: null, body: "from a deleted account" },
+      { author: { login: "bot[bot]" }, body: "comment3" },
+    ];
+
+    const { filterCommentsByActor } = require("../src/github/data/fetcher");
+    const filtered = filterCommentsByActor(comments, "", "*[bot]");
+    // ghost comment is retained (it matches no exclude pattern); the bot is dropped.
+    expect(filtered).toHaveLength(2);
+    expect(filtered.map((c: any) => c.body)).toEqual([
+      "comment1",
+      "from a deleted account",
+    ]);
+  });
+
+  test("treats null author as the 'ghost' login for include/exclude", () => {
+    const comments = [
+      { author: null, body: "from a deleted account" },
+      { author: { login: "user1" }, body: "comment2" },
+    ];
+
+    const { filterCommentsByActor } = require("../src/github/data/fetcher");
+    // Excluding "ghost" removes the deleted-account comment.
+    expect(filterCommentsByActor(comments, "", "ghost")).toHaveLength(1);
+    expect(filterCommentsByActor(comments, "", "ghost")[0].body).toBe(
+      "comment2",
+    );
+    // Including only "ghost" keeps just the deleted-account comment.
+    const onlyGhost = filterCommentsByActor(comments, "ghost", "");
+    expect(onlyGhost).toHaveLength(1);
+    expect(onlyGhost[0].body).toBe("from a deleted account");
+  });
 });
diff --git a/test/data-formatter.test.ts b/test/data-formatter.test.ts
index 5f7aad3..f72539d 100644
--- a/test/data-formatter.test.ts
+++ b/test/data-formatter.test.ts
@@ -159,6 +159,21 @@ Issue State: OPEN
 Issue Labels: architecture, agent-sdk, drift:functional`,
     );
   });
+
+  test("renders a deleted (null-author) issue author as 'ghost'", () => {
+    const issueData: GitHubIssue = {
+      title: "Test Issue",
+      body: "Issue body",
+      author: null,
+      createdAt: "2023-01-01T00:00:00Z",
+      state: "OPEN",
+      labels: { nodes: [] },
+      comments: { nodes: [] },
+    };
+
+    const result = formatContext(issueData, false);
+    expect(result).toContain("Issue Author: ghost");
+  });
 });
 
 describe("formatBody", () => {
@@ -257,6 +272,24 @@ describe("formatComments", () => {
     expect(result).toBe("");
   });
 
+  test("renders deleted (null-author) comments as 'ghost'", () => {
+    // GitHub returns author: null for comments from deleted accounts.
+    const comments: GitHubComment[] = [
+      {
+        id: "1",
+        databaseId: "100001",
+        body: "From a deleted account",
+        author: null,
+        createdAt: "2023-01-01T00:00:00Z",
+      },
+    ];
+
+    const result = formatComments(comments);
+    expect(result).toBe(
+      "[ghost at 2023-01-01T00:00:00Z]: From a deleted account",
+    );
+  });
+
   test("replaces image URLs in comments", () => {
     const comments: GitHubComment[] = [
       {
@@ -528,6 +561,29 @@ describe("formatReviewComments", () => {
     );
   });
 
+  test("renders deleted (null-author) reviews as 'ghost'", () => {
+    const reviewData = {
+      nodes: [
+        {
+          id: "review1",
+          databaseId: "300099",
+          author: null,
+          body: "Left before deleting the account",
+          state: "COMMENTED",
+          submittedAt: "2023-01-01T00:00:00Z",
+          comments: {
+            nodes: [],
+          },
+        },
+      ],
+    };
+
+    const result = formatReviewComments(reviewData);
+    expect(result).toBe(
+      `[Review by ghost at 2023-01-01T00:00:00Z]: COMMENTED\nLeft before deleting the account`,
+    );
+  });
+
   test("returns empty string for null reviewData", () => {
     const result = formatReviewComments(null);
     expect(result).toBe("");
diff --git a/test/format-turns.test.ts b/test/format-turns.test.ts
index e6ac058..7b59bbe 100644
--- a/test/format-turns.test.ts
+++ b/test/format-turns.test.ts
@@ -484,4 +484,34 @@ describe("system_other handling", () => {
     ]);
     expect(markdown).toContain("## ⚙️ System Message");
   });
+
+  test("filters out thinking_tokens system messages", () => {
+    const data: Turn[] = [
+      { type: "system", subtype: "init", tools: [{ name: "tool1" }] },
+      { type: "system", subtype: "thinking_tokens" },
+      { type: "system", subtype: "thinking_tokens" },
+      { type: "system", subtype: "other_subtype" },
+    ];
+
+    const grouped = groupTurnsNaturally(data);
+
+    // Should have init and other_subtype, but not thinking_tokens
+    expect(grouped).toHaveLength(2);
+    expect(grouped[0]?.type).toBe("system_init");
+    expect(grouped[1]?.type).toBe("system_other");
+    expect(grouped[1]?.data?.subtype).toBe("other_subtype");
+  });
+
+  test("thinking_tokens does not appear in formatted output", () => {
+    const data: Turn[] = [
+      { type: "system", subtype: "init", tools: [] },
+      { type: "system", subtype: "thinking_tokens" },
+      { type: "system", subtype: "thinking_tokens" },
+    ];
+
+    const result = formatTurnsFromData(data);
+
+    expect(result).not.toContain("thinking_tokens");
+    expect(result).toContain("## 🚀 System Initialization");
+  });
 });
diff --git a/test/sanitizer.test.ts b/test/sanitizer.test.ts
index e69a399..2cb7e30 100644
--- a/test/sanitizer.test.ts
+++ b/test/sanitizer.test.ts
@@ -59,6 +59,22 @@ describe("stripMarkdownImageAltText", () => {
   it("should handle empty alt text", () => {
     expect(stripMarkdownImageAltText("![](image.png)")).toBe("![](image.png)");
   });
+
+  it("should remove alt text from reference-style images", () => {
+    expect(stripMarkdownImageAltText("![example alt text][img1]")).toBe(
+      "![][img1]",
+    );
+    expect(
+      stripMarkdownImageAltText("Text ![description][ref] more text"),
+    ).toBe("Text ![][ref] more text");
+  });
+
+  it("should preserve the reference label of a reference-style image", () => {
+    // the [ref] label must survive so the image definition still resolves;
+    // only the alt text (the injection channel) is removed
+    expect(stripMarkdownImageAltText("![alt][my-ref]")).toBe("![][my-ref]");
+    expect(stripMarkdownImageAltText("![][keep]")).toBe("![][keep]");
+  });
 });
 
 describe("stripMarkdownLinkTitles", () => {
@@ -276,6 +292,16 @@ describe("redactGitHubTokens", () => {
     );
   });
 
+  it("should redact user-to-server tokens (ghu_)", () => {
+    const token = "ghu_16C7e42F292c6912E7710c838347Ae178B4a";
+    expect(redactGitHubTokens(`User token: ${token}`)).toBe(
+      "User token: [REDACTED_GITHUB_TOKEN]",
+    );
+    expect(
+      redactGitHubTokens(`In a URL: x-access-token:${token}@github.com`),
+    ).toBe("In a URL: x-access-token:[REDACTED_GITHUB_TOKEN]@github.com");
+  });
+
   it("should redact installation tokens (ghs_)", () => {
     const token = "ghs_xz7yzju2SZjGPa0dUNMAx0SH4xDOCS31LXQW";
     expect(redactGitHubTokens(`Install token: ${token}`)).toBe(
diff --git a/test/validate-branch-name.test.ts b/test/validate-branch-name.test.ts
index fe03ce4..6ee26a0 100644
--- a/test/validate-branch-name.test.ts
+++ b/test/validate-branch-name.test.ts
@@ -74,6 +74,16 @@ describe("validateBranchName", () => {
       expect(() => validateBranchName("@hotfix/login-timeout")).not.toThrow();
       expect(() => validateBranchName("agent/task@abc123")).not.toThrow();
     });
+
+    it("should accept branch names starting with underscore (git-valid, common for release branches)", () => {
+      // Leading underscores are valid per git check-ref-format and a common
+      // convention for release/internal branches. Rejecting them broke the
+      // action on any open PR whose base branch was e.g. "_release/v1.2.3",
+      // since setupBranch validates the PR's baseRefName after checkout.
+      expect(() => validateBranchName("_release/v1.2.3")).not.toThrow();
+      expect(() => validateBranchName("_internal")).not.toThrow();
+      expect(() => validateBranchName("_wip/feature-x")).not.toThrow();
+    });
   });
 
   describe("command injection attempts", () => {