fix: merge multiple --mcp-config flags and support --allowed-tools parsing (#748)

* fix: merge multiple --mcp-config flags instead of overwriting

When users provide their own --mcp-config in claude_args, the action's
built-in MCP servers (github_comment, github_ci, etc.) were being lost
because multiple --mcp-config flags were overwriting each other.

This fix:
- Adds mcp-config to ACCUMULATING_FLAGS to collect all values
- Changes delimiter to null character to avoid conflicts with JSON
- Adds mergeMcpConfigs() to combine mcpServers objects from multiple configs
- Merges inline JSON configs while preserving file path configs

Fixes #745

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Ashwin Bhat <ashwin-ant@users.noreply.github.com>

* fix: support hyphenated --allowed-tools flag and multiple values

The --allowed-tools flag was not being parsed correctly when:
1. Using the hyphenated form (--allowed-tools) instead of camelCase (--allowedTools)
2. Passing multiple space-separated values after a single flag
   (e.g., --allowed-tools "Tool1" "Tool2" "Tool3")

This fix:
- Adds hyphenated variants (allowed-tools, disallowed-tools) to ACCUMULATING_FLAGS
- Updates parsing to consume all consecutive non-flag values for accumulating flags
- Merges values from both camelCase and hyphenated variants

Fixes #746

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Ashwin Bhat <ashwin-ant@users.noreply.github.com>

.github/workflows/claude.yml

@@ -36,4 +36,4 @@ jobs:
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
           claude_args: |
             --allowedTools "Bash(bun install),Bash(bun test:*),Bash(bun run format),Bash(bun typecheck)"
-            --model "claude-opus-4-1-20250805"
+            --model "claude-opus-4-5"

.github/workflows/sync-base-action.yml

@@ -94,5 +94,5 @@ jobs:
           echo "✅ Successfully synced \`base-action\` directory to [anthropics/claude-code-base-action](https://github.com/anthropics/claude-code-base-action)" >> $GITHUB_STEP_SUMMARY
           echo "" >> $GITHUB_STEP_SUMMARY
           echo "- **Source commit**: [\`${GITHUB_SHA:0:7}\`](https://github.com/anthropics/claude-code-action/commit/${GITHUB_SHA})" >> $GITHUB_STEP_SUMMARY
-          echo "- **Triggered by**: ${{ github.event_name }}" >> $GITHUB_STEP_SUMMARY
+          echo "- **Triggered by**: $GITHUB_EVENT_NAME" >> $GITHUB_STEP_SUMMARY
-          echo "- **Actor**: @${{ github.actor }}" >> $GITHUB_STEP_SUMMARY
+          echo "- **Actor**: @$GITHUB_ACTOR" >> $GITHUB_STEP_SUMMARY

.github/workflows/test-base-action.yml

@@ -118,3 +118,61 @@ jobs:
             echo "❌ Execution log file not found"
             exit 1
           fi
+
+  test-agent-sdk:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+
+      - name: Test with Agent SDK
+        id: sdk-test
+        uses: ./base-action
+        env:
+          USE_AGENT_SDK: "true"
+        with:
+          prompt: ${{ github.event.inputs.test_prompt || 'List the files in the current directory starting with "package"' }}
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          allowed_tools: "LS,Read"
+
+      - name: Verify SDK output
+        run: |
+          OUTPUT_FILE="${{ steps.sdk-test.outputs.execution_file }}"
+          CONCLUSION="${{ steps.sdk-test.outputs.conclusion }}"
+
+          echo "Conclusion: $CONCLUSION"
+          echo "Output file: $OUTPUT_FILE"
+
+          if [ "$CONCLUSION" = "success" ]; then
+            echo "✅ Action completed successfully with Agent SDK"
+          else
+            echo "❌ Action failed with Agent SDK"
+            exit 1
+          fi
+
+          if [ -f "$OUTPUT_FILE" ]; then
+            if [ -s "$OUTPUT_FILE" ]; then
+              echo "✅ Execution log file created successfully with content"
+              echo "Validating JSON format:"
+              if jq . "$OUTPUT_FILE" > /dev/null 2>&1; then
+                echo "✅ Output is valid JSON"
+                # Verify SDK output contains total_cost_usd (SDK field name)
+                if jq -e '.[] | select(.type == "result") | .total_cost_usd' "$OUTPUT_FILE" > /dev/null 2>&1; then
+                  echo "✅ SDK output contains total_cost_usd field"
+                else
+                  echo "❌ SDK output missing total_cost_usd field"
+                  exit 1
+                fi
+                echo "Content preview:"
+                head -c 500 "$OUTPUT_FILE"
+              else
+                echo "❌ Output is not valid JSON"
+                exit 1
+              fi
+            else
+              echo "❌ Execution log file is empty"
+              exit 1
+            fi
+          else
+            echo "❌ Execution log file not found"
+            exit 1
+          fi

action.yml

@@ -127,6 +127,9 @@ outputs:
   structured_output:
     description: "JSON string containing all structured output fields when --json-schema is provided in claude_args. Use fromJSON() to parse: fromJSON(steps.id.outputs.structured_output).field_name"
     value: ${{ steps.claude-code.outputs.structured_output }}
+  session_id:
+    description: "The Claude Code session ID that can be used with --resume to continue this conversation"
+    value: ${{ steps.claude-code.outputs.session_id }}
 
 runs:
   using: "composite"
@@ -140,10 +143,12 @@ runs:
     - name: Setup Custom Bun Path
       if: inputs.path_to_bun_executable != ''
       shell: bash
+      env:
+        PATH_TO_BUN_EXECUTABLE: ${{ inputs.path_to_bun_executable }}
       run: |
-        echo "Using custom Bun executable: ${{ inputs.path_to_bun_executable }}"
+        echo "Using custom Bun executable: $PATH_TO_BUN_EXECUTABLE"
         # Add the directory containing the custom executable to PATH
-        BUN_DIR=$(dirname "${{ inputs.path_to_bun_executable }}")
+        BUN_DIR=$(dirname "$PATH_TO_BUN_EXECUTABLE")
         echo "$BUN_DIR" >> "$GITHUB_PATH"
 
     - name: Install Dependencies
@@ -182,6 +187,8 @@ runs:
     - name: Install Base Action Dependencies
       if: steps.prepare.outputs.contains_trigger == 'true'
       shell: bash
+      env:
+        PATH_TO_CLAUDE_CODE_EXECUTABLE: ${{ inputs.path_to_claude_code_executable }}
       run: |
         echo "Installing base-action dependencies..."
         cd ${GITHUB_ACTION_PATH}/base-action
@@ -190,8 +197,8 @@ runs:
         cd -
 
         # Install Claude Code if no custom executable is provided
-        if [ -z "${{ inputs.path_to_claude_code_executable }}" ]; then
+        if [ -z "$PATH_TO_CLAUDE_CODE_EXECUTABLE" ]; then
-          CLAUDE_CODE_VERSION="2.0.55"
+          CLAUDE_CODE_VERSION="2.0.70"
           echo "Installing Claude Code v${CLAUDE_CODE_VERSION}..."
           for attempt in 1 2 3; do
             echo "Installation attempt $attempt..."
@@ -210,9 +217,9 @@ runs:
           echo "Claude Code installed successfully"
           echo "$HOME/.local/bin" >> "$GITHUB_PATH"
         else
-          echo "Using custom Claude Code executable: ${{ inputs.path_to_claude_code_executable }}"
+          echo "Using custom Claude Code executable: $PATH_TO_CLAUDE_CODE_EXECUTABLE"
           # Add the directory containing the custom executable to PATH
-          CLAUDE_DIR=$(dirname "${{ inputs.path_to_claude_code_executable }}")
+          CLAUDE_DIR=$(dirname "$PATH_TO_CLAUDE_CODE_EXECUTABLE")
           echo "$CLAUDE_DIR" >> "$GITHUB_PATH"
         fi
 

base-action/action.yml

@@ -82,6 +82,9 @@ outputs:
   structured_output:
     description: "JSON string containing all structured output fields when --json-schema is provided in claude_args (use fromJSON() or jq to parse)"
     value: ${{ steps.run_claude.outputs.structured_output }}
+  session_id:
+    description: "The Claude Code session ID that can be used with --resume to continue this conversation"
+    value: ${{ steps.run_claude.outputs.session_id }}
 
 runs:
   using: "composite"
@@ -101,10 +104,12 @@ runs:
     - name: Setup Custom Bun Path
       if: inputs.path_to_bun_executable != ''
       shell: bash
+      env:
+        PATH_TO_BUN_EXECUTABLE: ${{ inputs.path_to_bun_executable }}
       run: |
-        echo "Using custom Bun executable: ${{ inputs.path_to_bun_executable }}"
+        echo "Using custom Bun executable: $PATH_TO_BUN_EXECUTABLE"
         # Add the directory containing the custom executable to PATH
-        BUN_DIR=$(dirname "${{ inputs.path_to_bun_executable }}")
+        BUN_DIR=$(dirname "$PATH_TO_BUN_EXECUTABLE")
         echo "$BUN_DIR" >> "$GITHUB_PATH"
 
     - name: Install Dependencies
@@ -115,9 +120,11 @@ runs:
 
     - name: Install Claude Code
       shell: bash
+      env:
+        PATH_TO_CLAUDE_CODE_EXECUTABLE: ${{ inputs.path_to_claude_code_executable }}
       run: |
-        if [ -z "${{ inputs.path_to_claude_code_executable }}" ]; then
+        if [ -z "$PATH_TO_CLAUDE_CODE_EXECUTABLE" ]; then
-          CLAUDE_CODE_VERSION="2.0.55"
+          CLAUDE_CODE_VERSION="2.0.70"
           echo "Installing Claude Code v${CLAUDE_CODE_VERSION}..."
           for attempt in 1 2 3; do
             echo "Installation attempt $attempt..."
@@ -135,9 +142,9 @@ runs:
           done
           echo "Claude Code installed successfully"
         else
-          echo "Using custom Claude Code executable: ${{ inputs.path_to_claude_code_executable }}"
+          echo "Using custom Claude Code executable: $PATH_TO_CLAUDE_CODE_EXECUTABLE"
           # Add the directory containing the custom executable to PATH
-          CLAUDE_DIR=$(dirname "${{ inputs.path_to_claude_code_executable }}")
+          CLAUDE_DIR=$(dirname "$PATH_TO_CLAUDE_CODE_EXECUTABLE")
           echo "$CLAUDE_DIR" >> "$GITHUB_PATH"
         fi
 

base-action/bun.lock

@@ -1,10 +1,12 @@
 {
   "lockfileVersion": 1,
+  "configVersion": 0,
   "workspaces": {
     "": {
       "name": "@anthropic-ai/claude-code-base-action",
       "dependencies": {
         "@actions/core": "^1.10.1",
+        "@anthropic-ai/claude-agent-sdk": "^0.1.70",
         "shell-quote": "^1.8.3",
       },
       "devDependencies": {
@@ -25,8 +27,40 @@
 
     "@actions/io": ["@actions/io@1.1.3", "", {}, "sha512-wi9JjgKLYS7U/z8PPbco+PvTb/nRWjeoFlJ1Qer83k/3C5PHQi28hiVdeE2kHXmIL99mQFawx8qt/JPjZilJ8Q=="],
 
+    "@anthropic-ai/claude-agent-sdk": ["@anthropic-ai/claude-agent-sdk@0.1.70", "", { "optionalDependencies": { "@img/sharp-darwin-arm64": "^0.33.5", "@img/sharp-darwin-x64": "^0.33.5", "@img/sharp-linux-arm": "^0.33.5", "@img/sharp-linux-arm64": "^0.33.5", "@img/sharp-linux-x64": "^0.33.5", "@img/sharp-linuxmusl-arm64": "^0.33.5", "@img/sharp-linuxmusl-x64": "^0.33.5", "@img/sharp-win32-x64": "^0.33.5" }, "peerDependencies": { "zod": "^3.24.1" } }, "sha512-4jpFPDX8asys6skO1r3Pzh0Fe9nbND2ASYTWuyFB5iN9bWEL6WScTFyGokjql3M2TkEp9ZGuB2YYpTCdaqT9Sw=="],
+
     "@fastify/busboy": ["@fastify/busboy@2.1.1", "", {}, "sha512-vBZP4NlzfOlerQTnba4aqZoMhE/a9HY7HRqoOPaETQcSQuWEIyZMHGfVu6w9wGtGK5fED5qRs2DteVCjOH60sA=="],
 
+    "@img/sharp-darwin-arm64": ["@img/sharp-darwin-arm64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-darwin-arm64": "1.0.4" }, "os": "darwin", "cpu": "arm64" }, "sha512-UT4p+iz/2H4twwAoLCqfA9UH5pI6DggwKEGuaPy7nCVQ8ZsiY5PIcrRvD1DzuY3qYL07NtIQcWnBSY/heikIFQ=="],
+
+    "@img/sharp-darwin-x64": ["@img/sharp-darwin-x64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-darwin-x64": "1.0.4" }, "os": "darwin", "cpu": "x64" }, "sha512-fyHac4jIc1ANYGRDxtiqelIbdWkIuQaI84Mv45KvGRRxSAa7o7d1ZKAOBaYbnepLC1WqxfpimdeWfvqqSGwR2Q=="],
+
+    "@img/sharp-libvips-darwin-arm64": ["@img/sharp-libvips-darwin-arm64@1.0.4", "", { "os": "darwin", "cpu": "arm64" }, "sha512-XblONe153h0O2zuFfTAbQYAX2JhYmDHeWikp1LM9Hul9gVPjFY427k6dFEcOL72O01QxQsWi761svJ/ev9xEDg=="],
+
+    "@img/sharp-libvips-darwin-x64": ["@img/sharp-libvips-darwin-x64@1.0.4", "", { "os": "darwin", "cpu": "x64" }, "sha512-xnGR8YuZYfJGmWPvmlunFaWJsb9T/AO2ykoP3Fz/0X5XV2aoYBPkX6xqCQvUTKKiLddarLaxpzNe+b1hjeWHAQ=="],
+
+    "@img/sharp-libvips-linux-arm": ["@img/sharp-libvips-linux-arm@1.0.5", "", { "os": "linux", "cpu": "arm" }, "sha512-gvcC4ACAOPRNATg/ov8/MnbxFDJqf/pDePbBnuBDcjsI8PssmjoKMAz4LtLaVi+OnSb5FK/yIOamqDwGmXW32g=="],
+
+    "@img/sharp-libvips-linux-arm64": ["@img/sharp-libvips-linux-arm64@1.0.4", "", { "os": "linux", "cpu": "arm64" }, "sha512-9B+taZ8DlyyqzZQnoeIvDVR/2F4EbMepXMc/NdVbkzsJbzkUjhXv/70GQJ7tdLA4YJgNP25zukcxpX2/SueNrA=="],
+
+    "@img/sharp-libvips-linux-x64": ["@img/sharp-libvips-linux-x64@1.0.4", "", { "os": "linux", "cpu": "x64" }, "sha512-MmWmQ3iPFZr0Iev+BAgVMb3ZyC4KeFc3jFxnNbEPas60e1cIfevbtuyf9nDGIzOaW9PdnDciJm+wFFaTlj5xYw=="],
+
+    "@img/sharp-libvips-linuxmusl-arm64": ["@img/sharp-libvips-linuxmusl-arm64@1.0.4", "", { "os": "linux", "cpu": "arm64" }, "sha512-9Ti+BbTYDcsbp4wfYib8Ctm1ilkugkA/uscUn6UXK1ldpC1JjiXbLfFZtRlBhjPZ5o1NCLiDbg8fhUPKStHoTA=="],
+
+    "@img/sharp-libvips-linuxmusl-x64": ["@img/sharp-libvips-linuxmusl-x64@1.0.4", "", { "os": "linux", "cpu": "x64" }, "sha512-viYN1KX9m+/hGkJtvYYp+CCLgnJXwiQB39damAO7WMdKWlIhmYTfHjwSbQeUK/20vY154mwezd9HflVFM1wVSw=="],
+
+    "@img/sharp-linux-arm": ["@img/sharp-linux-arm@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linux-arm": "1.0.5" }, "os": "linux", "cpu": "arm" }, "sha512-JTS1eldqZbJxjvKaAkxhZmBqPRGmxgu+qFKSInv8moZ2AmT5Yib3EQ1c6gp493HvrvV8QgdOXdyaIBrhvFhBMQ=="],
+
+    "@img/sharp-linux-arm64": ["@img/sharp-linux-arm64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linux-arm64": "1.0.4" }, "os": "linux", "cpu": "arm64" }, "sha512-JMVv+AMRyGOHtO1RFBiJy/MBsgz0x4AWrT6QoEVVTyh1E39TrCUpTRI7mx9VksGX4awWASxqCYLCV4wBZHAYxA=="],
+
+    "@img/sharp-linux-x64": ["@img/sharp-linux-x64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linux-x64": "1.0.4" }, "os": "linux", "cpu": "x64" }, "sha512-opC+Ok5pRNAzuvq1AG0ar+1owsu842/Ab+4qvU879ippJBHvyY5n2mxF1izXqkPYlGuP/M556uh53jRLJmzTWA=="],
+
+    "@img/sharp-linuxmusl-arm64": ["@img/sharp-linuxmusl-arm64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linuxmusl-arm64": "1.0.4" }, "os": "linux", "cpu": "arm64" }, "sha512-XrHMZwGQGvJg2V/oRSUfSAfjfPxO+4DkiRh6p2AFjLQztWUuY/o8Mq0eMQVIY7HJ1CDQUJlxGGZRw1a5bqmd1g=="],
+
+    "@img/sharp-linuxmusl-x64": ["@img/sharp-linuxmusl-x64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linuxmusl-x64": "1.0.4" }, "os": "linux", "cpu": "x64" }, "sha512-WT+d/cgqKkkKySYmqoZ8y3pxx7lx9vVejxW/W4DOFMYVSkErR+w7mf2u8m/y4+xHe7yY9DAXQMWQhpnMuFfScw=="],
+
+    "@img/sharp-win32-x64": ["@img/sharp-win32-x64@0.33.5", "", { "os": "win32", "cpu": "x64" }, "sha512-MpY/o8/8kj+EcnxwvrP4aTJSWw/aZ7JIGR4aBeZkZw5B7/Jn+tY9/VNwtcoGmdT7GfggGIU4kygOMSbYnOrAbg=="],
+
     "@types/bun": ["@types/bun@1.2.19", "", { "dependencies": { "bun-types": "1.2.19" } }, "sha512-d9ZCmrH3CJ2uYKXQIUuZ/pUnTqIvLDS0SK7pFmbx8ma+ziH/FRMoAq5bYpRG7y+w1gl+HgyNZbtqgMq4W4e2Lg=="],
 
     "@types/node": ["@types/node@20.19.9", "", { "dependencies": { "undici-types": "~6.21.0" } }, "sha512-cuVNgarYWZqxRJDQHEB58GEONhOK79QVR/qYx4S7kcUObQvUwvFnYxJuuHUKm2aieN9X3yZB4LZsuYNU1Qphsw=="],
@@ -50,5 +84,7 @@
     "undici": ["undici@5.29.0", "", { "dependencies": { "@fastify/busboy": "^2.0.0" } }, "sha512-raqeBD6NQK4SkWhQzeYKd1KmIG6dllBOTt55Rmkt4HtI9mwdWtJljnrXjAFUBLTSN67HWrOIZ3EPF4kjUw80Bg=="],
 
     "undici-types": ["undici-types@6.21.0", "", {}, "sha512-iwDZqg0QAGrg9Rav5H4n0M64c3mkR59cJ6wQp+7C4nI0gsmExaedaYLNO44eT4AtBBwjbTiGPMlt2Md0T9H9JQ=="],
+
+    "zod": ["zod@3.25.76", "", {}, "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ=="],
   }
 }

base-action/package.json

@@ -11,6 +11,7 @@
   },
   "dependencies": {
     "@actions/core": "^1.10.1",
+    "@anthropic-ai/claude-agent-sdk": "^0.1.70",
     "shell-quote": "^1.8.3"
   },
   "devDependencies": {

base-action/src/parse-sdk-options.ts

@@ -0,0 +1,261 @@
+import { parse as parseShellArgs } from "shell-quote";
+import type { ClaudeOptions } from "./run-claude";
+import type { Options as SdkOptions } from "@anthropic-ai/claude-agent-sdk";
+
+/**
+ * Result of parsing ClaudeOptions for SDK usage
+ */
+export type ParsedSdkOptions = {
+  sdkOptions: SdkOptions;
+  showFullOutput: boolean;
+  hasJsonSchema: boolean;
+};
+
+// Flags that should accumulate multiple values instead of overwriting
+// Include both camelCase and hyphenated variants for CLI compatibility
+const ACCUMULATING_FLAGS = new Set([
+  "allowedTools",
+  "allowed-tools",
+  "disallowedTools",
+  "disallowed-tools",
+  "mcp-config",
+]);
+
+// Delimiter used to join accumulated flag values
+const ACCUMULATE_DELIMITER = "\x00";
+
+type McpConfig = {
+  mcpServers?: Record<string, unknown>;
+};
+
+/**
+ * Merge multiple MCP config values into a single config.
+ * Each config can be a JSON string or a file path.
+ * For JSON strings, mcpServers objects are merged.
+ * For file paths, they are kept as-is (user's file takes precedence and is used last).
+ */
+function mergeMcpConfigs(configValues: string[]): string {
+  const merged: McpConfig = { mcpServers: {} };
+  let lastFilePath: string | null = null;
+
+  for (const config of configValues) {
+    const trimmed = config.trim();
+    if (!trimmed) continue;
+
+    // Check if it's a JSON string (starts with {) or a file path
+    if (trimmed.startsWith("{")) {
+      try {
+        const parsed = JSON.parse(trimmed) as McpConfig;
+        if (parsed.mcpServers) {
+          Object.assign(merged.mcpServers!, parsed.mcpServers);
+        }
+      } catch {
+        // If JSON parsing fails, treat as file path
+        lastFilePath = trimmed;
+      }
+    } else {
+      // It's a file path - store it to handle separately
+      lastFilePath = trimmed;
+    }
+  }
+
+  // If we have file paths, we need to keep the merged JSON and let the file
+  // be handled separately. Since we can only return one value, merge what we can.
+  // If there's a file path, we need a different approach - read the file at runtime.
+  // For now, if there's a file path, we'll stringify the merged config.
+  // The action prepends its config as JSON, so we can safely merge inline JSON configs.
+
+  // If no inline configs were found (all file paths), return the last file path
+  if (Object.keys(merged.mcpServers!).length === 0 && lastFilePath) {
+    return lastFilePath;
+  }
+
+  // Note: If user passes a file path, we cannot merge it at parse time since
+  // we don't have access to the file system here. The action's built-in MCP
+  // servers are always passed as inline JSON, so they will be merged.
+  // If user also passes inline JSON, it will be merged.
+  // If user passes a file path, they should ensure it includes all needed servers.
+
+  return JSON.stringify(merged);
+}
+
+/**
+ * Parse claudeArgs string into extraArgs record for SDK pass-through
+ * The SDK/CLI will handle --mcp-config, --json-schema, etc.
+ * For allowedTools and disallowedTools, multiple occurrences are accumulated (null-char joined).
+ * Accumulating flags also consume all consecutive non-flag values
+ * (e.g., --allowed-tools "Tool1" "Tool2" "Tool3" captures all three).
+ */
+function parseClaudeArgsToExtraArgs(
+  claudeArgs?: string,
+): Record<string, string | null> {
+  if (!claudeArgs?.trim()) return {};
+
+  const result: Record<string, string | null> = {};
+  const args = parseShellArgs(claudeArgs).filter(
+    (arg): arg is string => typeof arg === "string",
+  );
+
+  for (let i = 0; i < args.length; i++) {
+    const arg = args[i];
+    if (arg?.startsWith("--")) {
+      const flag = arg.slice(2);
+      const nextArg = args[i + 1];
+
+      // Check if next arg is a value (not another flag)
+      if (nextArg && !nextArg.startsWith("--")) {
+        // For accumulating flags, consume all consecutive non-flag values
+        // This handles: --allowed-tools "Tool1" "Tool2" "Tool3"
+        if (ACCUMULATING_FLAGS.has(flag)) {
+          const values: string[] = [];
+          while (i + 1 < args.length && !args[i + 1]?.startsWith("--")) {
+            i++;
+            values.push(args[i]!);
+          }
+          const joinedValues = values.join(ACCUMULATE_DELIMITER);
+          if (result[flag]) {
+            result[flag] =
+              `${result[flag]}${ACCUMULATE_DELIMITER}${joinedValues}`;
+          } else {
+            result[flag] = joinedValues;
+          }
+        } else {
+          result[flag] = nextArg;
+          i++; // Skip the value
+        }
+      } else {
+        result[flag] = null; // Boolean flag
+      }
+    }
+  }
+
+  return result;
+}
+
+/**
+ * Parse ClaudeOptions into SDK-compatible options
+ * Uses extraArgs for CLI pass-through instead of duplicating option parsing
+ */
+export function parseSdkOptions(options: ClaudeOptions): ParsedSdkOptions {
+  // Determine output verbosity
+  const isDebugMode = process.env.ACTIONS_STEP_DEBUG === "true";
+  const showFullOutput = options.showFullOutput === "true" || isDebugMode;
+
+  // Parse claudeArgs into extraArgs for CLI pass-through
+  const extraArgs = parseClaudeArgsToExtraArgs(options.claudeArgs);
+
+  // Detect if --json-schema is present (for hasJsonSchema flag)
+  const hasJsonSchema = "json-schema" in extraArgs;
+
+  // Extract and merge allowedTools from all sources:
+  // 1. From extraArgs (parsed from claudeArgs - contains tag mode's tools)
+  //    - Check both camelCase (--allowedTools) and hyphenated (--allowed-tools) variants
+  // 2. From options.allowedTools (direct input - may be undefined)
+  // This prevents duplicate flags being overwritten when claudeArgs contains --allowedTools
+  const allowedToolsValues = [
+    extraArgs["allowedTools"],
+    extraArgs["allowed-tools"],
+  ]
+    .filter(Boolean)
+    .join(ACCUMULATE_DELIMITER);
+  const extraArgsAllowedTools = allowedToolsValues
+    ? allowedToolsValues
+        .split(ACCUMULATE_DELIMITER)
+        .flatMap((v) => v.split(","))
+        .map((t) => t.trim())
+        .filter(Boolean)
+    : [];
+  const directAllowedTools = options.allowedTools
+    ? options.allowedTools.split(",").map((t) => t.trim())
+    : [];
+  const mergedAllowedTools = [
+    ...new Set([...extraArgsAllowedTools, ...directAllowedTools]),
+  ];
+  delete extraArgs["allowedTools"];
+  delete extraArgs["allowed-tools"];
+
+  // Same for disallowedTools - check both camelCase and hyphenated variants
+  const disallowedToolsValues = [
+    extraArgs["disallowedTools"],
+    extraArgs["disallowed-tools"],
+  ]
+    .filter(Boolean)
+    .join(ACCUMULATE_DELIMITER);
+  const extraArgsDisallowedTools = disallowedToolsValues
+    ? disallowedToolsValues
+        .split(ACCUMULATE_DELIMITER)
+        .flatMap((v) => v.split(","))
+        .map((t) => t.trim())
+        .filter(Boolean)
+    : [];
+  const directDisallowedTools = options.disallowedTools
+    ? options.disallowedTools.split(",").map((t) => t.trim())
+    : [];
+  const mergedDisallowedTools = [
+    ...new Set([...extraArgsDisallowedTools, ...directDisallowedTools]),
+  ];
+  delete extraArgs["disallowedTools"];
+  delete extraArgs["disallowed-tools"];
+
+  // Merge multiple --mcp-config values by combining their mcpServers objects
+  // The action prepends its config (github_comment, github_ci, etc.) as inline JSON,
+  // and users may provide their own config as inline JSON or file path
+  if (extraArgs["mcp-config"]) {
+    const mcpConfigValues = extraArgs["mcp-config"].split(ACCUMULATE_DELIMITER);
+    if (mcpConfigValues.length > 1) {
+      extraArgs["mcp-config"] = mergeMcpConfigs(mcpConfigValues);
+    }
+  }
+
+  // Build custom environment
+  const env: Record<string, string | undefined> = { ...process.env };
+  if (process.env.INPUT_ACTION_INPUTS_PRESENT) {
+    env.GITHUB_ACTION_INPUTS = process.env.INPUT_ACTION_INPUTS_PRESENT;
+  }
+
+  // Build system prompt option - default to claude_code preset
+  let systemPrompt: SdkOptions["systemPrompt"];
+  if (options.systemPrompt) {
+    systemPrompt = options.systemPrompt;
+  } else if (options.appendSystemPrompt) {
+    systemPrompt = {
+      type: "preset",
+      preset: "claude_code",
+      append: options.appendSystemPrompt,
+    };
+  } else {
+    // Default to claude_code preset when no custom prompt is specified
+    systemPrompt = {
+      type: "preset",
+      preset: "claude_code",
+    };
+  }
+
+  // Build SDK options - use merged tools from both direct options and claudeArgs
+  const sdkOptions: SdkOptions = {
+    // Direct options from ClaudeOptions inputs
+    model: options.model,
+    maxTurns: options.maxTurns ? parseInt(options.maxTurns, 10) : undefined,
+    allowedTools:
+      mergedAllowedTools.length > 0 ? mergedAllowedTools : undefined,
+    disallowedTools:
+      mergedDisallowedTools.length > 0 ? mergedDisallowedTools : undefined,
+    systemPrompt,
+    fallbackModel: options.fallbackModel,
+    pathToClaudeCodeExecutable: options.pathToClaudeCodeExecutable,
+
+    // Pass through claudeArgs as extraArgs - CLI handles --mcp-config, --json-schema, etc.
+    // Note: allowedTools and disallowedTools have been removed from extraArgs to prevent duplicates
+    extraArgs,
+    env,
+
+    // Load settings from all sources to pick up CLI-installed plugins, CLAUDE.md, etc.
+    settingSources: ["user", "project", "local"],
+  };
+
+  return {
+    sdkOptions,
+    showFullOutput,
+    hasJsonSchema,
+  };
+}

base-action/src/run-claude-sdk.ts

@@ -0,0 +1,151 @@
+import * as core from "@actions/core";
+import { readFile, writeFile } from "fs/promises";
+import { query } from "@anthropic-ai/claude-agent-sdk";
+import type {
+  SDKMessage,
+  SDKResultMessage,
+} from "@anthropic-ai/claude-agent-sdk";
+import type { ParsedSdkOptions } from "./parse-sdk-options";
+
+const EXECUTION_FILE = `${process.env.RUNNER_TEMP}/claude-execution-output.json`;
+
+/**
+ * Sanitizes SDK output to match CLI sanitization behavior
+ */
+function sanitizeSdkOutput(
+  message: SDKMessage,
+  showFullOutput: boolean,
+): string | null {
+  if (showFullOutput) {
+    return JSON.stringify(message, null, 2);
+  }
+
+  // System initialization - safe to show
+  if (message.type === "system" && message.subtype === "init") {
+    return JSON.stringify(
+      {
+        type: "system",
+        subtype: "init",
+        message: "Claude Code initialized",
+        model: "model" in message ? message.model : "unknown",
+      },
+      null,
+      2,
+    );
+  }
+
+  // Result messages - show sanitized summary
+  if (message.type === "result") {
+    const resultMsg = message as SDKResultMessage;
+    return JSON.stringify(
+      {
+        type: "result",
+        subtype: resultMsg.subtype,
+        is_error: resultMsg.is_error,
+        duration_ms: resultMsg.duration_ms,
+        num_turns: resultMsg.num_turns,
+        total_cost_usd: resultMsg.total_cost_usd,
+        permission_denials: resultMsg.permission_denials,
+      },
+      null,
+      2,
+    );
+  }
+
+  // Suppress other message types in non-full-output mode
+  return null;
+}
+
+/**
+ * Run Claude using the Agent SDK
+ */
+export async function runClaudeWithSdk(
+  promptPath: string,
+  { sdkOptions, showFullOutput, hasJsonSchema }: ParsedSdkOptions,
+): Promise<void> {
+  const prompt = await readFile(promptPath, "utf-8");
+
+  if (!showFullOutput) {
+    console.log(
+      "Running Claude Code via SDK (full output hidden for security)...",
+    );
+    console.log(
+      "Rerun in debug mode or enable `show_full_output: true` in your workflow file for full output.",
+    );
+  }
+
+  console.log(`Running Claude with prompt from file: ${promptPath}`);
+  // Log SDK options without env (which could contain sensitive data)
+  const { env, ...optionsToLog } = sdkOptions;
+  console.log("SDK options:", JSON.stringify(optionsToLog, null, 2));
+
+  const messages: SDKMessage[] = [];
+  let resultMessage: SDKResultMessage | undefined;
+
+  try {
+    for await (const message of query({ prompt, options: sdkOptions })) {
+      messages.push(message);
+
+      const sanitized = sanitizeSdkOutput(message, showFullOutput);
+      if (sanitized) {
+        console.log(sanitized);
+      }
+
+      if (message.type === "result") {
+        resultMessage = message as SDKResultMessage;
+      }
+    }
+  } catch (error) {
+    console.error("SDK execution error:", error);
+    core.setOutput("conclusion", "failure");
+    process.exit(1);
+  }
+
+  // Write execution file
+  try {
+    await writeFile(EXECUTION_FILE, JSON.stringify(messages, null, 2));
+    console.log(`Log saved to ${EXECUTION_FILE}`);
+    core.setOutput("execution_file", EXECUTION_FILE);
+  } catch (error) {
+    core.warning(`Failed to write execution file: ${error}`);
+  }
+
+  if (!resultMessage) {
+    core.setOutput("conclusion", "failure");
+    core.error("No result message received from Claude");
+    process.exit(1);
+  }
+
+  const isSuccess = resultMessage.subtype === "success";
+  core.setOutput("conclusion", isSuccess ? "success" : "failure");
+
+  // Handle structured output
+  if (hasJsonSchema) {
+    if (
+      isSuccess &&
+      "structured_output" in resultMessage &&
+      resultMessage.structured_output
+    ) {
+      const structuredOutputJson = JSON.stringify(
+        resultMessage.structured_output,
+      );
+      core.setOutput("structured_output", structuredOutputJson);
+      core.info(
+        `Set structured_output with ${Object.keys(resultMessage.structured_output as object).length} field(s)`,
+      );
+    } else {
+      core.setFailed(
+        `--json-schema was provided but Claude did not return structured_output. Result subtype: ${resultMessage.subtype}`,
+      );
+      core.setOutput("conclusion", "failure");
+      process.exit(1);
+    }
+  }
+
+  if (!isSuccess) {
+    if ("errors" in resultMessage && resultMessage.errors) {
+      core.error(`Execution failed: ${resultMessage.errors.join(", ")}`);
+    }
+    process.exit(1);
+  }
+}

base-action/src/run-claude.ts

@@ -5,6 +5,8 @@ import { unlink, writeFile, stat, readFile } from "fs/promises";
 import { createWriteStream } from "fs";
 import { spawn } from "child_process";
 import { parse as parseShellArgs } from "shell-quote";
+import { runClaudeWithSdk } from "./run-claude-sdk";
+import { parseSdkOptions } from "./parse-sdk-options";
 
 const execAsync = promisify(exec);
 
@@ -122,6 +124,36 @@ export function prepareRunConfig(
   };
 }
 
+/**
+ * Parses session_id from execution file and sets GitHub Action output
+ * Exported for testing
+ */
+export async function parseAndSetSessionId(
+  executionFile: string,
+): Promise<void> {
+  try {
+    const content = await readFile(executionFile, "utf-8");
+    const messages = JSON.parse(content) as {
+      type: string;
+      subtype?: string;
+      session_id?: string;
+    }[];
+
+    // Find the system.init message which contains session_id
+    const initMessage = messages.find(
+      (m) => m.type === "system" && m.subtype === "init",
+    );
+
+    if (initMessage?.session_id) {
+      core.setOutput("session_id", initMessage.session_id);
+      core.info(`Set session_id: ${initMessage.session_id}`);
+    }
+  } catch (error) {
+    // Don't fail the action if session_id extraction fails
+    core.warning(`Failed to extract session_id: ${error}`);
+  }
+}
+
 /**
  * Parses structured_output from execution file and sets GitHub Action outputs
  * Only runs if --json-schema was explicitly provided in claude_args
@@ -165,6 +197,17 @@ export async function parseAndSetStructuredOutputs(
 }
 
 export async function runClaude(promptPath: string, options: ClaudeOptions) {
+  // Feature flag: use SDK path by default, set USE_AGENT_SDK=false to use CLI
+  const useAgentSdk = process.env.USE_AGENT_SDK !== "false";
+  console.log(
+    `Using ${useAgentSdk ? "Agent SDK" : "CLI"} path (USE_AGENT_SDK=${process.env.USE_AGENT_SDK ?? "unset"})`,
+  );
+
+  if (useAgentSdk) {
+    const parsedOptions = parseSdkOptions(options);
+    return runClaudeWithSdk(promptPath, parsedOptions);
+  }
+
   const config = prepareRunConfig(promptPath, options);
 
   // Detect if --json-schema is present in claude args
@@ -355,6 +398,9 @@ export async function runClaude(promptPath: string, options: ClaudeOptions) {
 
     core.setOutput("execution_file", EXECUTION_FILE);
 
+    // Extract and set session_id
+    await parseAndSetSessionId(EXECUTION_FILE);
+
     // Parse and set structured outputs only if user provided --json-schema in claude_args
     if (hasJsonSchema) {
       try {

base-action/test/parse-sdk-options.test.ts

@@ -0,0 +1,315 @@
+#!/usr/bin/env bun
+
+import { describe, test, expect } from "bun:test";
+import { parseSdkOptions } from "../src/parse-sdk-options";
+import type { ClaudeOptions } from "../src/run-claude";
+
+describe("parseSdkOptions", () => {
+  describe("allowedTools merging", () => {
+    test("should extract allowedTools from claudeArgs", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--allowedTools "Edit,Read,Write"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual(["Edit", "Read", "Write"]);
+      expect(result.sdkOptions.extraArgs?.["allowedTools"]).toBeUndefined();
+    });
+
+    test("should extract allowedTools from claudeArgs with MCP tools", () => {
+      const options: ClaudeOptions = {
+        claudeArgs:
+          '--allowedTools "Edit,Read,mcp__github_comment__update_claude_comment"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual([
+        "Edit",
+        "Read",
+        "mcp__github_comment__update_claude_comment",
+      ]);
+    });
+
+    test("should accumulate multiple --allowedTools flags from claudeArgs", () => {
+      // This simulates tag mode adding its tools, then user adding their own
+      const options: ClaudeOptions = {
+        claudeArgs:
+          '--allowedTools "Edit,Read,mcp__github_comment__update_claude_comment" --model "claude-3" --allowedTools "Bash(npm install),mcp__github__get_issue"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual([
+        "Edit",
+        "Read",
+        "mcp__github_comment__update_claude_comment",
+        "Bash(npm install)",
+        "mcp__github__get_issue",
+      ]);
+    });
+
+    test("should merge allowedTools from both claudeArgs and direct options", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--allowedTools "Edit,Read"',
+        allowedTools: "Write,Glob",
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual([
+        "Edit",
+        "Read",
+        "Write",
+        "Glob",
+      ]);
+    });
+
+    test("should deduplicate allowedTools when merging", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--allowedTools "Edit,Read"',
+        allowedTools: "Edit,Write",
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual(["Edit", "Read", "Write"]);
+    });
+
+    test("should use only direct options when claudeArgs has no allowedTools", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--model "claude-3-5-sonnet"',
+        allowedTools: "Edit,Read",
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual(["Edit", "Read"]);
+    });
+
+    test("should return undefined allowedTools when neither source has it", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--model "claude-3-5-sonnet"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toBeUndefined();
+    });
+
+    test("should remove allowedTools from extraArgs after extraction", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--allowedTools "Edit,Read" --model "claude-3-5-sonnet"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.extraArgs?.["allowedTools"]).toBeUndefined();
+      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-3-5-sonnet");
+    });
+
+    test("should handle hyphenated --allowed-tools flag", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--allowed-tools "Edit,Read,Write"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual(["Edit", "Read", "Write"]);
+      expect(result.sdkOptions.extraArgs?.["allowed-tools"]).toBeUndefined();
+    });
+
+    test("should accumulate multiple --allowed-tools flags (hyphenated)", () => {
+      // This is the exact scenario from issue #746
+      const options: ClaudeOptions = {
+        claudeArgs:
+          '--allowed-tools "Bash(git log:*)" "Bash(git diff:*)" "Bash(git fetch:*)" "Bash(gh pr:*)"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.allowedTools).toEqual([
+        "Bash(git log:*)",
+        "Bash(git diff:*)",
+        "Bash(git fetch:*)",
+        "Bash(gh pr:*)",
+      ]);
+    });
+
+    test("should handle mixed camelCase and hyphenated allowedTools flags", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--allowedTools "Edit,Read" --allowed-tools "Write,Glob"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      // Both should be merged - note: order depends on which key is found first
+      expect(result.sdkOptions.allowedTools).toContain("Edit");
+      expect(result.sdkOptions.allowedTools).toContain("Read");
+      expect(result.sdkOptions.allowedTools).toContain("Write");
+      expect(result.sdkOptions.allowedTools).toContain("Glob");
+    });
+  });
+
+  describe("disallowedTools merging", () => {
+    test("should extract disallowedTools from claudeArgs", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--disallowedTools "Bash,Write"',
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.disallowedTools).toEqual(["Bash", "Write"]);
+      expect(result.sdkOptions.extraArgs?.["disallowedTools"]).toBeUndefined();
+    });
+
+    test("should merge disallowedTools from both sources", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: '--disallowedTools "Bash"',
+        disallowedTools: "Write",
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.disallowedTools).toEqual(["Bash", "Write"]);
+    });
+  });
+
+  describe("mcp-config merging", () => {
+    test("should pass through single mcp-config in extraArgs", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: `--mcp-config '{"mcpServers":{"server1":{"command":"cmd1"}}}'`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.extraArgs?.["mcp-config"]).toBe(
+        '{"mcpServers":{"server1":{"command":"cmd1"}}}',
+      );
+    });
+
+    test("should merge multiple mcp-config flags with inline JSON", () => {
+      // Simulates action prepending its config, then user providing their own
+      const options: ClaudeOptions = {
+        claudeArgs: `--mcp-config '{"mcpServers":{"github_comment":{"command":"node","args":["server.js"]}}}' --mcp-config '{"mcpServers":{"user_server":{"command":"custom","args":["run"]}}}'`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      const mcpConfig = JSON.parse(
+        result.sdkOptions.extraArgs?.["mcp-config"] as string,
+      );
+      expect(mcpConfig.mcpServers).toHaveProperty("github_comment");
+      expect(mcpConfig.mcpServers).toHaveProperty("user_server");
+      expect(mcpConfig.mcpServers.github_comment.command).toBe("node");
+      expect(mcpConfig.mcpServers.user_server.command).toBe("custom");
+    });
+
+    test("should merge three mcp-config flags", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: `--mcp-config '{"mcpServers":{"server1":{"command":"cmd1"}}}' --mcp-config '{"mcpServers":{"server2":{"command":"cmd2"}}}' --mcp-config '{"mcpServers":{"server3":{"command":"cmd3"}}}'`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      const mcpConfig = JSON.parse(
+        result.sdkOptions.extraArgs?.["mcp-config"] as string,
+      );
+      expect(mcpConfig.mcpServers).toHaveProperty("server1");
+      expect(mcpConfig.mcpServers).toHaveProperty("server2");
+      expect(mcpConfig.mcpServers).toHaveProperty("server3");
+    });
+
+    test("should handle mcp-config file path when no inline JSON exists", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: `--mcp-config /tmp/user-mcp-config.json`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.extraArgs?.["mcp-config"]).toBe(
+        "/tmp/user-mcp-config.json",
+      );
+    });
+
+    test("should merge inline JSON configs when file path is also present", () => {
+      // When action provides inline JSON and user provides a file path,
+      // the inline JSON configs should be merged (file paths cannot be merged at parse time)
+      const options: ClaudeOptions = {
+        claudeArgs: `--mcp-config '{"mcpServers":{"github_comment":{"command":"node"}}}' --mcp-config '{"mcpServers":{"github_ci":{"command":"node"}}}' --mcp-config /tmp/user-config.json`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      // The inline JSON configs should be merged
+      const mcpConfig = JSON.parse(
+        result.sdkOptions.extraArgs?.["mcp-config"] as string,
+      );
+      expect(mcpConfig.mcpServers).toHaveProperty("github_comment");
+      expect(mcpConfig.mcpServers).toHaveProperty("github_ci");
+    });
+
+    test("should handle mcp-config with other flags", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: `--mcp-config '{"mcpServers":{"server1":{}}}' --model claude-3-5-sonnet --mcp-config '{"mcpServers":{"server2":{}}}'`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      const mcpConfig = JSON.parse(
+        result.sdkOptions.extraArgs?.["mcp-config"] as string,
+      );
+      expect(mcpConfig.mcpServers).toHaveProperty("server1");
+      expect(mcpConfig.mcpServers).toHaveProperty("server2");
+      expect(result.sdkOptions.extraArgs?.["model"]).toBe("claude-3-5-sonnet");
+    });
+
+    test("should handle real-world scenario: action config + user config", () => {
+      // This is the exact scenario from the bug report
+      const actionConfig = JSON.stringify({
+        mcpServers: {
+          github_comment: {
+            command: "node",
+            args: ["github-comment-server.js"],
+          },
+          github_ci: { command: "node", args: ["github-ci-server.js"] },
+        },
+      });
+      const userConfig = JSON.stringify({
+        mcpServers: {
+          my_custom_server: { command: "python", args: ["server.py"] },
+        },
+      });
+
+      const options: ClaudeOptions = {
+        claudeArgs: `--mcp-config '${actionConfig}' --mcp-config '${userConfig}'`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      const mcpConfig = JSON.parse(
+        result.sdkOptions.extraArgs?.["mcp-config"] as string,
+      );
+      // All servers should be present
+      expect(mcpConfig.mcpServers).toHaveProperty("github_comment");
+      expect(mcpConfig.mcpServers).toHaveProperty("github_ci");
+      expect(mcpConfig.mcpServers).toHaveProperty("my_custom_server");
+    });
+  });
+
+  describe("other extraArgs passthrough", () => {
+    test("should pass through json-schema in extraArgs", () => {
+      const options: ClaudeOptions = {
+        claudeArgs: `--json-schema '{"type":"object"}'`,
+      };
+
+      const result = parseSdkOptions(options);
+
+      expect(result.sdkOptions.extraArgs?.["json-schema"]).toBe(
+        '{"type":"object"}',
+      );
+      expect(result.hasJsonSchema).toBe(true);
+    });
+  });
+});

base-action/test/structured-output.test.ts

@@ -4,7 +4,10 @@ import { describe, test, expect, afterEach, beforeEach, spyOn } from "bun:test";
 import { writeFile, unlink } from "fs/promises";
 import { tmpdir } from "os";
 import { join } from "path";
-import { parseAndSetStructuredOutputs } from "../src/run-claude";
+import {
+  parseAndSetStructuredOutputs,
+  parseAndSetSessionId,
+} from "../src/run-claude";
 import * as core from "@actions/core";
 
 // Mock execution file path
@@ -35,16 +38,19 @@ async function createMockExecutionFile(
 // Spy on core functions
 let setOutputSpy: any;
 let infoSpy: any;
+let warningSpy: any;
 
 beforeEach(() => {
   setOutputSpy = spyOn(core, "setOutput").mockImplementation(() => {});
   infoSpy = spyOn(core, "info").mockImplementation(() => {});
+  warningSpy = spyOn(core, "warning").mockImplementation(() => {});
 });
 
 describe("parseAndSetStructuredOutputs", () => {
   afterEach(async () => {
     setOutputSpy?.mockRestore();
     infoSpy?.mockRestore();
+    warningSpy?.mockRestore();
     try {
       await unlink(TEST_EXECUTION_FILE);
     } catch {
@@ -156,3 +162,66 @@ describe("parseAndSetStructuredOutputs", () => {
     );
   });
 });
+
+describe("parseAndSetSessionId", () => {
+  afterEach(async () => {
+    setOutputSpy?.mockRestore();
+    infoSpy?.mockRestore();
+    warningSpy?.mockRestore();
+    try {
+      await unlink(TEST_EXECUTION_FILE);
+    } catch {
+      // Ignore if file doesn't exist
+    }
+  });
+
+  test("should extract session_id from system.init message", async () => {
+    const messages = [
+      { type: "system", subtype: "init", session_id: "test-session-123" },
+      { type: "result", cost_usd: 0.01 },
+    ];
+    await writeFile(TEST_EXECUTION_FILE, JSON.stringify(messages));
+
+    await parseAndSetSessionId(TEST_EXECUTION_FILE);
+
+    expect(setOutputSpy).toHaveBeenCalledWith("session_id", "test-session-123");
+    expect(infoSpy).toHaveBeenCalledWith("Set session_id: test-session-123");
+  });
+
+  test("should handle missing session_id gracefully", async () => {
+    const messages = [
+      { type: "system", subtype: "init" },
+      { type: "result", cost_usd: 0.01 },
+    ];
+    await writeFile(TEST_EXECUTION_FILE, JSON.stringify(messages));
+
+    await parseAndSetSessionId(TEST_EXECUTION_FILE);
+
+    expect(setOutputSpy).not.toHaveBeenCalled();
+  });
+
+  test("should handle missing system.init message gracefully", async () => {
+    const messages = [{ type: "result", cost_usd: 0.01 }];
+    await writeFile(TEST_EXECUTION_FILE, JSON.stringify(messages));
+
+    await parseAndSetSessionId(TEST_EXECUTION_FILE);
+
+    expect(setOutputSpy).not.toHaveBeenCalled();
+  });
+
+  test("should handle malformed JSON gracefully with warning", async () => {
+    await writeFile(TEST_EXECUTION_FILE, "{ invalid json");
+
+    await parseAndSetSessionId(TEST_EXECUTION_FILE);
+
+    expect(setOutputSpy).not.toHaveBeenCalled();
+    expect(warningSpy).toHaveBeenCalled();
+  });
+
+  test("should handle non-existent file gracefully with warning", async () => {
+    await parseAndSetSessionId("/nonexistent/file.json");
+
+    expect(setOutputSpy).not.toHaveBeenCalled();
+    expect(warningSpy).toHaveBeenCalled();
+  });
+});

bun.lock

@@ -1,11 +1,13 @@
 {
   "lockfileVersion": 1,
+  "configVersion": 0,
   "workspaces": {
     "": {
       "name": "@anthropic-ai/claude-code-action",
       "dependencies": {
         "@actions/core": "^1.10.1",
         "@actions/github": "^6.0.1",
+        "@anthropic-ai/claude-agent-sdk": "^0.1.70",
         "@modelcontextprotocol/sdk": "^1.11.0",
         "@octokit/graphql": "^8.2.2",
         "@octokit/rest": "^21.1.1",
@@ -35,8 +37,40 @@
 
     "@actions/io": ["@actions/io@1.1.3", "", {}, "sha512-wi9JjgKLYS7U/z8PPbco+PvTb/nRWjeoFlJ1Qer83k/3C5PHQi28hiVdeE2kHXmIL99mQFawx8qt/JPjZilJ8Q=="],
 
+    "@anthropic-ai/claude-agent-sdk": ["@anthropic-ai/claude-agent-sdk@0.1.70", "", { "optionalDependencies": { "@img/sharp-darwin-arm64": "^0.33.5", "@img/sharp-darwin-x64": "^0.33.5", "@img/sharp-linux-arm": "^0.33.5", "@img/sharp-linux-arm64": "^0.33.5", "@img/sharp-linux-x64": "^0.33.5", "@img/sharp-linuxmusl-arm64": "^0.33.5", "@img/sharp-linuxmusl-x64": "^0.33.5", "@img/sharp-win32-x64": "^0.33.5" }, "peerDependencies": { "zod": "^3.24.1" } }, "sha512-4jpFPDX8asys6skO1r3Pzh0Fe9nbND2ASYTWuyFB5iN9bWEL6WScTFyGokjql3M2TkEp9ZGuB2YYpTCdaqT9Sw=="],
+
     "@fastify/busboy": ["@fastify/busboy@2.1.1", "", {}, "sha512-vBZP4NlzfOlerQTnba4aqZoMhE/a9HY7HRqoOPaETQcSQuWEIyZMHGfVu6w9wGtGK5fED5qRs2DteVCjOH60sA=="],
 
+    "@img/sharp-darwin-arm64": ["@img/sharp-darwin-arm64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-darwin-arm64": "1.0.4" }, "os": "darwin", "cpu": "arm64" }, "sha512-UT4p+iz/2H4twwAoLCqfA9UH5pI6DggwKEGuaPy7nCVQ8ZsiY5PIcrRvD1DzuY3qYL07NtIQcWnBSY/heikIFQ=="],
+
+    "@img/sharp-darwin-x64": ["@img/sharp-darwin-x64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-darwin-x64": "1.0.4" }, "os": "darwin", "cpu": "x64" }, "sha512-fyHac4jIc1ANYGRDxtiqelIbdWkIuQaI84Mv45KvGRRxSAa7o7d1ZKAOBaYbnepLC1WqxfpimdeWfvqqSGwR2Q=="],
+
+    "@img/sharp-libvips-darwin-arm64": ["@img/sharp-libvips-darwin-arm64@1.0.4", "", { "os": "darwin", "cpu": "arm64" }, "sha512-XblONe153h0O2zuFfTAbQYAX2JhYmDHeWikp1LM9Hul9gVPjFY427k6dFEcOL72O01QxQsWi761svJ/ev9xEDg=="],
+
+    "@img/sharp-libvips-darwin-x64": ["@img/sharp-libvips-darwin-x64@1.0.4", "", { "os": "darwin", "cpu": "x64" }, "sha512-xnGR8YuZYfJGmWPvmlunFaWJsb9T/AO2ykoP3Fz/0X5XV2aoYBPkX6xqCQvUTKKiLddarLaxpzNe+b1hjeWHAQ=="],
+
+    "@img/sharp-libvips-linux-arm": ["@img/sharp-libvips-linux-arm@1.0.5", "", { "os": "linux", "cpu": "arm" }, "sha512-gvcC4ACAOPRNATg/ov8/MnbxFDJqf/pDePbBnuBDcjsI8PssmjoKMAz4LtLaVi+OnSb5FK/yIOamqDwGmXW32g=="],
+
+    "@img/sharp-libvips-linux-arm64": ["@img/sharp-libvips-linux-arm64@1.0.4", "", { "os": "linux", "cpu": "arm64" }, "sha512-9B+taZ8DlyyqzZQnoeIvDVR/2F4EbMepXMc/NdVbkzsJbzkUjhXv/70GQJ7tdLA4YJgNP25zukcxpX2/SueNrA=="],
+
+    "@img/sharp-libvips-linux-x64": ["@img/sharp-libvips-linux-x64@1.0.4", "", { "os": "linux", "cpu": "x64" }, "sha512-MmWmQ3iPFZr0Iev+BAgVMb3ZyC4KeFc3jFxnNbEPas60e1cIfevbtuyf9nDGIzOaW9PdnDciJm+wFFaTlj5xYw=="],
+
+    "@img/sharp-libvips-linuxmusl-arm64": ["@img/sharp-libvips-linuxmusl-arm64@1.0.4", "", { "os": "linux", "cpu": "arm64" }, "sha512-9Ti+BbTYDcsbp4wfYib8Ctm1ilkugkA/uscUn6UXK1ldpC1JjiXbLfFZtRlBhjPZ5o1NCLiDbg8fhUPKStHoTA=="],
+
+    "@img/sharp-libvips-linuxmusl-x64": ["@img/sharp-libvips-linuxmusl-x64@1.0.4", "", { "os": "linux", "cpu": "x64" }, "sha512-viYN1KX9m+/hGkJtvYYp+CCLgnJXwiQB39damAO7WMdKWlIhmYTfHjwSbQeUK/20vY154mwezd9HflVFM1wVSw=="],
+
+    "@img/sharp-linux-arm": ["@img/sharp-linux-arm@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linux-arm": "1.0.5" }, "os": "linux", "cpu": "arm" }, "sha512-JTS1eldqZbJxjvKaAkxhZmBqPRGmxgu+qFKSInv8moZ2AmT5Yib3EQ1c6gp493HvrvV8QgdOXdyaIBrhvFhBMQ=="],
+
+    "@img/sharp-linux-arm64": ["@img/sharp-linux-arm64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linux-arm64": "1.0.4" }, "os": "linux", "cpu": "arm64" }, "sha512-JMVv+AMRyGOHtO1RFBiJy/MBsgz0x4AWrT6QoEVVTyh1E39TrCUpTRI7mx9VksGX4awWASxqCYLCV4wBZHAYxA=="],
+
+    "@img/sharp-linux-x64": ["@img/sharp-linux-x64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linux-x64": "1.0.4" }, "os": "linux", "cpu": "x64" }, "sha512-opC+Ok5pRNAzuvq1AG0ar+1owsu842/Ab+4qvU879ippJBHvyY5n2mxF1izXqkPYlGuP/M556uh53jRLJmzTWA=="],
+
+    "@img/sharp-linuxmusl-arm64": ["@img/sharp-linuxmusl-arm64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linuxmusl-arm64": "1.0.4" }, "os": "linux", "cpu": "arm64" }, "sha512-XrHMZwGQGvJg2V/oRSUfSAfjfPxO+4DkiRh6p2AFjLQztWUuY/o8Mq0eMQVIY7HJ1CDQUJlxGGZRw1a5bqmd1g=="],
+
+    "@img/sharp-linuxmusl-x64": ["@img/sharp-linuxmusl-x64@0.33.5", "", { "optionalDependencies": { "@img/sharp-libvips-linuxmusl-x64": "1.0.4" }, "os": "linux", "cpu": "x64" }, "sha512-WT+d/cgqKkkKySYmqoZ8y3pxx7lx9vVejxW/W4DOFMYVSkErR+w7mf2u8m/y4+xHe7yY9DAXQMWQhpnMuFfScw=="],
+
+    "@img/sharp-win32-x64": ["@img/sharp-win32-x64@0.33.5", "", { "os": "win32", "cpu": "x64" }, "sha512-MpY/o8/8kj+EcnxwvrP4aTJSWw/aZ7JIGR4aBeZkZw5B7/Jn+tY9/VNwtcoGmdT7GfggGIU4kygOMSbYnOrAbg=="],
+
     "@modelcontextprotocol/sdk": ["@modelcontextprotocol/sdk@1.16.0", "", { "dependencies": { "ajv": "^6.12.6", "content-type": "^1.0.5", "cors": "^2.8.5", "cross-spawn": "^7.0.5", "eventsource": "^3.0.2", "eventsource-parser": "^3.0.0", "express": "^5.0.1", "express-rate-limit": "^7.5.0", "pkce-challenge": "^5.0.0", "raw-body": "^3.0.0", "zod": "^3.23.8", "zod-to-json-schema": "^3.24.1" } }, "sha512-8ofX7gkZcLj9H9rSd50mCgm3SSF8C7XoclxJuLoV0Cz3rEQ1tv9MZRYYvJtm9n1BiEQQMzSmE/w2AEkNacLYfg=="],
 
     "@octokit/auth-token": ["@octokit/auth-token@4.0.0", "", {}, "sha512-tY/msAuJo6ARbK6SPIxZrPBms3xPbfwBrulZe0Wtr/DIY9lje2HeV1uoebShn6mx7SjCHif6EjMvoREj+gZ+SA=="],

package.json

@@ -12,6 +12,7 @@
   "dependencies": {
     "@actions/core": "^1.10.1",
     "@actions/github": "^6.0.1",
+    "@anthropic-ai/claude-agent-sdk": "^0.1.70",
     "@modelcontextprotocol/sdk": "^1.11.0",
     "@octokit/graphql": "^8.2.2",
     "@octokit/rest": "^21.1.1",

src/create-prompt/index.ts

@@ -192,11 +192,6 @@ export function prepareContext(
       if (!isPR) {
         throw new Error("IS_PR must be true for pull_request_review event");
       }
-      if (!commentBody) {
-        throw new Error(
-          "COMMENT_BODY is required for pull_request_review event",
-        );
-      }
       eventData = {
         eventName: "pull_request_review",
         isPR: true,
@@ -464,6 +459,123 @@ export function generatePrompt(
   return mode.generatePrompt(context, githubData, useCommitSigning);
 }
 
+/**
+ * Generates a simplified prompt for tag mode (opt-in via USE_SIMPLE_PROMPT env var)
+ * @internal
+ */
+function generateSimplePrompt(
+  context: PreparedContext,
+  githubData: FetchDataResult,
+  useCommitSigning: boolean = false,
+): string {
+  const {
+    contextData,
+    comments,
+    changedFilesWithSHA,
+    reviewData,
+    imageUrlMap,
+  } = githubData;
+  const { eventData } = context;
+
+  const { triggerContext } = getEventTypeAndContext(context);
+
+  const formattedContext = formatContext(contextData, eventData.isPR);
+  const formattedComments = formatComments(comments, imageUrlMap);
+  const formattedReviewComments = eventData.isPR
+    ? formatReviewComments(reviewData, imageUrlMap)
+    : "";
+  const formattedChangedFiles = eventData.isPR
+    ? formatChangedFilesWithSHA(changedFilesWithSHA)
+    : "";
+
+  const hasImages = imageUrlMap && imageUrlMap.size > 0;
+  const imagesInfo = hasImages
+    ? `\n\n<images_info>
+Images from comments have been saved to disk. Paths are in the formatted content above. Use Read tool to view them.
+</images_info>`
+    : "";
+
+  const formattedBody = contextData?.body
+    ? formatBody(contextData.body, imageUrlMap)
+    : "No description provided";
+
+  const entityType = eventData.isPR ? "pull request" : "issue";
+  const jobUrl = `${GITHUB_SERVER_URL}/${context.repository}/actions/runs/${process.env.GITHUB_RUN_ID}`;
+
+  let promptContent = `You were tagged on a GitHub ${entityType} via "${context.triggerPhrase}". Read the request and decide how to help.
+
+<context>
+${formattedContext}
+</context>
+
+<${eventData.isPR ? "pr" : "issue"}_body>
+${formattedBody}
+</${eventData.isPR ? "pr" : "issue"}_body>
+
+<comments>
+${formattedComments || "No comments"}
+</comments>
+${
+  eventData.isPR
+    ? `
+<review_comments>
+${formattedReviewComments || "No review comments"}
+</review_comments>
+
+<changed_files>
+${formattedChangedFiles || "No files changed"}
+</changed_files>`
+    : ""
+}${imagesInfo}
+
+<metadata>
+repository: ${context.repository}
+${eventData.isPR && eventData.prNumber ? `pr_number: ${eventData.prNumber}` : ""}
+${!eventData.isPR && eventData.issueNumber ? `issue_number: ${eventData.issueNumber}` : ""}
+trigger: ${triggerContext}
+triggered_by: ${context.triggerUsername ?? "Unknown"}
+claude_comment_id: ${context.claudeCommentId}
+</metadata>
+${
+  (eventData.eventName === "issue_comment" ||
+    eventData.eventName === "pull_request_review_comment" ||
+    eventData.eventName === "pull_request_review") &&
+  eventData.commentBody
+    ? `
+<trigger_comment>
+${sanitizeContent(eventData.commentBody)}
+</trigger_comment>`
+    : ""
+}
+
+Your request is in <trigger_comment> above${eventData.eventName === "issues" ? ` (or the ${entityType} body for assigned/labeled events)` : ""}.
+
+Decide what's being asked:
+1. **Question or code review** - Answer directly or provide feedback
+2. **Code change** - Implement the change, commit, and push
+
+Communication:
+- Your ONLY visible output is your GitHub comment - update it with progress and results
+- Use mcp__github_comment__update_claude_comment to update (only "body" param needed)
+- Use checklist format for tasks: - [ ] incomplete, - [x] complete
+- Use ### headers (not #)
+${getCommitInstructions(eventData, githubData, context, useCommitSigning)}
+${
+  eventData.claudeBranch
+    ? `
+When done with changes, provide a PR link:
+[Create a PR](${GITHUB_SERVER_URL}/${context.repository}/compare/${eventData.baseBranch}...${eventData.claudeBranch}?quick_pull=1&title=<url-encoded-title>&body=<url-encoded-body>)
+Use THREE dots (...) between branches. URL-encode all parameters.`
+    : ""
+}
+
+Always include at the bottom:
+- Job link: [View job run](${jobUrl})
+- Follow the repo's CLAUDE.md file for project-specific guidelines`;
+
+  return promptContent;
+}
+
 /**
  * Generates the default prompt for tag mode
  * @internal
@@ -473,6 +585,10 @@ export function generateDefaultPrompt(
   githubData: FetchDataResult,
   useCommitSigning: boolean = false,
 ): string {
+  // Use simplified prompt if opted in
+  if (process.env.USE_SIMPLE_PROMPT === "true") {
+    return generateSimplePrompt(context, githubData, useCommitSigning);
+  }
   const {
     contextData,
     comments,

src/create-prompt/types.ts

@@ -23,7 +23,7 @@ type PullRequestReviewEvent = {
   eventName: "pull_request_review";
   isPR: true;
   prNumber: string;
-  commentBody: string;
+  commentBody?: string; // May be absent for approvals without comments
   claudeBranch?: string;
   baseBranch?: string;
 };

src/entrypoints/update-comment-link.ts

@@ -152,7 +152,7 @@ async function run() {
 
     // Check if action failed and read output file for execution details
     let executionDetails: {
-      cost_usd?: number;
+      total_cost_usd?: number;
       duration_ms?: number;
       duration_api_ms?: number;
     } | null = null;
@@ -179,11 +179,11 @@ async function run() {
             const lastElement = outputData[outputData.length - 1];
             if (
               lastElement.type === "result" &&
-              "cost_usd" in lastElement &&
+              "total_cost_usd" in lastElement &&
               "duration_ms" in lastElement
             ) {
               executionDetails = {
-                cost_usd: lastElement.cost_usd,
+                total_cost_usd: lastElement.total_cost_usd,
                 duration_ms: lastElement.duration_ms,
                 duration_api_ms: lastElement.duration_api_ms,
               };

src/github/operations/branch.ts

@@ -6,13 +6,112 @@
  * - For Issues: Create a new branch
  */
 
-import { $ } from "bun";
+import { execFileSync } from "child_process";
 import * as core from "@actions/core";
 import type { ParsedGitHubContext } from "../context";
 import type { GitHubPullRequest } from "../types";
 import type { Octokits } from "../api/client";
 import type { FetchDataResult } from "../data/fetcher";
 
+/**
+ * Validates a git branch name against a strict whitelist pattern.
+ * This prevents command injection by ensuring only safe characters are used.
+ *
+ * Valid branch names:
+ * - Start with alphanumeric character (not dash, to prevent option injection)
+ * - Contain only alphanumeric, forward slash, hyphen, underscore, or period
+ * - Do not start or end with a period
+ * - Do not end with a slash
+ * - Do not contain '..' (path traversal)
+ * - Do not contain '//' (consecutive slashes)
+ * - Do not end with '.lock'
+ * - Do not contain '@{'
+ * - Do not contain control characters or special git characters (~^:?*[\])
+ */
+export function validateBranchName(branchName: string): void {
+  // Check for empty or whitespace-only names
+  if (!branchName || branchName.trim().length === 0) {
+    throw new Error("Branch name cannot be empty");
+  }
+
+  // Check for leading dash (prevents option injection like --help, -x)
+  if (branchName.startsWith("-")) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot start with a dash.`,
+    );
+  }
+
+  // Check for control characters and special git characters (~^:?*[\])
+  // eslint-disable-next-line no-control-regex
+  if (/[\x00-\x1F\x7F ~^:?*[\]\\]/.test(branchName)) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot contain control characters, spaces, or special git characters (~^:?*[\\]).`,
+    );
+  }
+
+  // Strict whitelist pattern: alphanumeric start, then alphanumeric/slash/hyphen/underscore/period
+  const validPattern = /^[a-zA-Z0-9][a-zA-Z0-9/_.-]*$/;
+
+  if (!validPattern.test(branchName)) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names must start with an alphanumeric character and contain only alphanumeric characters, forward slashes, hyphens, underscores, or periods.`,
+    );
+  }
+
+  // Check for leading/trailing periods
+  if (branchName.startsWith(".") || branchName.endsWith(".")) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot start or end with a period.`,
+    );
+  }
+
+  // Check for trailing slash
+  if (branchName.endsWith("/")) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot end with a slash.`,
+    );
+  }
+
+  // Check for consecutive slashes
+  if (branchName.includes("//")) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot contain consecutive slashes.`,
+    );
+  }
+
+  // Additional git-specific validations
+  if (branchName.includes("..")) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot contain '..'`,
+    );
+  }
+
+  if (branchName.endsWith(".lock")) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot end with '.lock'`,
+    );
+  }
+
+  if (branchName.includes("@{")) {
+    throw new Error(
+      `Invalid branch name: "${branchName}". Branch names cannot contain '@{'`,
+    );
+  }
+}
+
+/**
+ * Executes a git command safely using execFileSync to avoid shell interpolation.
+ *
+ * Security: execFileSync passes arguments directly to the git binary without
+ * invoking a shell, preventing command injection attacks where malicious input
+ * could be interpreted as shell commands (e.g., branch names containing `;`, `|`, `&&`).
+ *
+ * @param args - Git command arguments (e.g., ["checkout", "branch-name"])
+ */
+function execGit(args: string[]): void {
+  execFileSync("git", args, { stdio: "inherit" });
+}
+
 export type BranchInfo = {
   baseBranch: string;
   claudeBranch?: string;
@@ -53,14 +152,19 @@ export async function setupBranch(
         `PR #${entityNumber}: ${commitCount} commits, using fetch depth ${fetchDepth}`,
       );
 
+      // Validate branch names before use to prevent command injection
+      validateBranchName(branchName);
+
       // Execute git commands to checkout PR branch (dynamic depth based on PR size)
-      await $`git fetch origin --depth=${fetchDepth} ${branchName}`;
+      // Using execFileSync instead of shell template literals for security
-      await $`git checkout ${branchName} --`;
+      execGit(["fetch", "origin", `--depth=${fetchDepth}`, branchName]);
+      execGit(["checkout", branchName, "--"]);
 
       console.log(`Successfully checked out PR branch for PR #${entityNumber}`);
 
       // For open PRs, we need to get the base branch of the PR
       const baseBranch = prData.baseRefName;
+      validateBranchName(baseBranch);
 
       return {
         baseBranch,
@@ -118,8 +222,9 @@ export async function setupBranch(
 
       // Ensure we're on the source branch
       console.log(`Fetching and checking out source branch: ${sourceBranch}`);
-      await $`git fetch origin ${sourceBranch} --depth=1`;
+      validateBranchName(sourceBranch);
-      await $`git checkout ${sourceBranch}`;
+      execGit(["fetch", "origin", sourceBranch, "--depth=1"]);
+      execGit(["checkout", sourceBranch, "--"]);
 
       // Set outputs for GitHub Actions
       core.setOutput("CLAUDE_BRANCH", newBranch);
@@ -138,11 +243,13 @@ export async function setupBranch(
 
     // Fetch and checkout the source branch first to ensure we branch from the correct base
     console.log(`Fetching and checking out source branch: ${sourceBranch}`);
-    await $`git fetch origin ${sourceBranch} --depth=1`;
+    validateBranchName(sourceBranch);
-    await $`git checkout ${sourceBranch}`;
+    validateBranchName(newBranch);
+    execGit(["fetch", "origin", sourceBranch, "--depth=1"]);
+    execGit(["checkout", sourceBranch, "--"]);
 
     // Create and checkout the new branch from the source branch
-    await $`git checkout -b ${newBranch}`;
+    execGit(["checkout", "-b", newBranch]);
 
     console.log(
       `Successfully created and checked out local branch: ${newBranch}`,

src/github/operations/comment-logic.ts

@@ -1,7 +1,7 @@
 import { GITHUB_SERVER_URL } from "../api/config";
 
 export type ExecutionDetails = {
-  cost_usd?: number;
+  total_cost_usd?: number;
   duration_ms?: number;
   duration_api_ms?: number;
 };

test/comment-logic.test.ts

@@ -258,7 +258,7 @@ describe("updateCommentBody", () => {
       const input = {
         ...baseInput,
         executionDetails: {
-          cost_usd: 0.13382595,
+          total_cost_usd: 0.13382595,
           duration_ms: 31033,
           duration_api_ms: 31034,
         },
@@ -301,7 +301,7 @@ describe("updateCommentBody", () => {
       const input = {
         ...baseInput,
         executionDetails: {
-          cost_usd: 0.25,
+          total_cost_usd: 0.25,
         },
         triggerUsername: "testuser",
       };
@@ -322,7 +322,7 @@ describe("updateCommentBody", () => {
         branchName: "claude-branch-123",
         prLink: "\n[Create a PR](https://github.com/owner/repo/pr-url)",
         executionDetails: {
-          cost_usd: 0.01,
+          total_cost_usd: 0.01,
           duration_ms: 65000, // 1 minute 5 seconds
         },
         triggerUsername: "trigger-user",

test/fixtures/sample-turns.json

@@ -189,7 +189,7 @@
   },
   {
     "type": "result",
-    "cost_usd": 0.0347,
+    "total_cost_usd": 0.0347,
     "duration_ms": 18750,
     "result": "Successfully removed debug print statement from file and added review comment to document the change."
   }

test/mockContext.ts

@@ -401,6 +401,53 @@ export const mockPullRequestReviewContext: ParsedGitHubContext = {
   inputs: { ...defaultInputs, triggerPhrase: "@claude" },
 };
 
+export const mockPullRequestReviewWithoutCommentContext: ParsedGitHubContext = {
+  runId: "1234567890",
+  eventName: "pull_request_review",
+  eventAction: "dismissed",
+  repository: defaultRepository,
+  actor: "senior-developer",
+  payload: {
+    action: "submitted",
+    review: {
+      id: 11122233,
+      body: null, // Simulating approval without comment
+      user: {
+        login: "senior-developer",
+        id: 44444,
+        avatar_url: "https://avatars.githubusercontent.com/u/44444",
+        html_url: "https://github.com/senior-developer",
+      },
+      state: "approved",
+      html_url:
+        "https://github.com/test-owner/test-repo/pull/321#pullrequestreview-11122233",
+      submitted_at: "2024-01-15T15:30:00Z",
+    },
+    pull_request: {
+      number: 321,
+      title: "Refactor: Improve error handling in API layer",
+      body: "This PR improves error handling across all API endpoints",
+      user: {
+        login: "backend-developer",
+        id: 33333,
+        avatar_url: "https://avatars.githubusercontent.com/u/33333",
+        html_url: "https://github.com/backend-developer",
+      },
+    },
+    repository: {
+      name: "test-repo",
+      full_name: "test-owner/test-repo",
+      private: false,
+      owner: {
+        login: "test-owner",
+      },
+    },
+  } as PullRequestReviewEvent,
+  entityNumber: 321,
+  isPR: true,
+  inputs: { ...defaultInputs, triggerPhrase: "@claude" },
+};
+
 export const mockPullRequestReviewCommentContext: ParsedGitHubContext = {
   runId: "1234567890",
   eventName: "pull_request_review_comment",

test/prepare-context.test.ts

@@ -10,6 +10,7 @@ import {
   mockPullRequestCommentContext,
   mockPullRequestReviewContext,
   mockPullRequestReviewCommentContext,
+  mockPullRequestReviewWithoutCommentContext,
 } from "./mockContext";
 
 const BASE_ENV = {
@@ -126,6 +127,24 @@ describe("parseEnvVarsWithContext", () => {
     });
   });
 
+  describe("pull_request_review event without comment", () => {
+    test("should parse pull_request_review event correctly", () => {
+      process.env = BASE_ENV;
+      const result = prepareContext(
+        mockPullRequestReviewWithoutCommentContext,
+        "12345",
+      );
+
+      expect(result.eventData.eventName).toBe("pull_request_review");
+      expect(result.eventData.isPR).toBe(true);
+      expect(result.triggerUsername).toBe("senior-developer");
+      if (result.eventData.eventName === "pull_request_review") {
+        expect(result.eventData.prNumber).toBe("321");
+        expect(result.eventData.commentBody).toBe("");
+      }
+    });
+  });
+
   describe("pull_request_review_comment event", () => {
     test("should parse pull_request_review_comment event correctly", () => {
       process.env = BASE_ENV;

test/validate-branch-name.test.ts

@@ -0,0 +1,201 @@
+import { describe, expect, it } from "bun:test";
+import { validateBranchName } from "../src/github/operations/branch";
+
+describe("validateBranchName", () => {
+  describe("valid branch names", () => {
+    it("should accept simple alphanumeric names", () => {
+      expect(() => validateBranchName("main")).not.toThrow();
+      expect(() => validateBranchName("feature123")).not.toThrow();
+      expect(() => validateBranchName("Branch1")).not.toThrow();
+    });
+
+    it("should accept names with hyphens", () => {
+      expect(() => validateBranchName("feature-branch")).not.toThrow();
+      expect(() => validateBranchName("fix-bug-123")).not.toThrow();
+    });
+
+    it("should accept names with underscores", () => {
+      expect(() => validateBranchName("feature_branch")).not.toThrow();
+      expect(() => validateBranchName("fix_bug_123")).not.toThrow();
+    });
+
+    it("should accept names with forward slashes", () => {
+      expect(() => validateBranchName("feature/new-thing")).not.toThrow();
+      expect(() => validateBranchName("user/feature/branch")).not.toThrow();
+    });
+
+    it("should accept names with periods", () => {
+      expect(() => validateBranchName("v1.0.0")).not.toThrow();
+      expect(() => validateBranchName("release.1.2.3")).not.toThrow();
+    });
+
+    it("should accept typical branch name formats", () => {
+      expect(() =>
+        validateBranchName("claude/issue-123-20250101-1234"),
+      ).not.toThrow();
+      expect(() => validateBranchName("refs/heads/main")).not.toThrow();
+      expect(() => validateBranchName("bugfix/JIRA-1234")).not.toThrow();
+    });
+  });
+
+  describe("command injection attempts", () => {
+    it("should reject shell command substitution with $()", () => {
+      expect(() => validateBranchName("$(whoami)")).toThrow();
+      expect(() => validateBranchName("branch-$(rm -rf /)")).toThrow();
+      expect(() => validateBranchName("test$(cat /etc/passwd)")).toThrow();
+    });
+
+    it("should reject shell command substitution with backticks", () => {
+      expect(() => validateBranchName("`whoami`")).toThrow();
+      expect(() => validateBranchName("branch-`rm -rf /`")).toThrow();
+    });
+
+    it("should reject command chaining with semicolons", () => {
+      expect(() => validateBranchName("branch; rm -rf /")).toThrow();
+      expect(() => validateBranchName("test;whoami")).toThrow();
+    });
+
+    it("should reject command chaining with &&", () => {
+      expect(() => validateBranchName("branch && rm -rf /")).toThrow();
+      expect(() => validateBranchName("test&&whoami")).toThrow();
+    });
+
+    it("should reject command chaining with ||", () => {
+      expect(() => validateBranchName("branch || rm -rf /")).toThrow();
+      expect(() => validateBranchName("test||whoami")).toThrow();
+    });
+
+    it("should reject pipe characters", () => {
+      expect(() => validateBranchName("branch | cat")).toThrow();
+      expect(() => validateBranchName("test|grep password")).toThrow();
+    });
+
+    it("should reject redirection operators", () => {
+      expect(() => validateBranchName("branch > /etc/passwd")).toThrow();
+      expect(() => validateBranchName("branch < input")).toThrow();
+      expect(() => validateBranchName("branch >> file")).toThrow();
+    });
+  });
+
+  describe("option injection attempts", () => {
+    it("should reject branch names starting with dash", () => {
+      expect(() => validateBranchName("-x")).toThrow(
+        /cannot start with a dash/,
+      );
+      expect(() => validateBranchName("--help")).toThrow(
+        /cannot start with a dash/,
+      );
+      expect(() => validateBranchName("-")).toThrow(/cannot start with a dash/);
+      expect(() => validateBranchName("--version")).toThrow(
+        /cannot start with a dash/,
+      );
+      expect(() => validateBranchName("-rf")).toThrow(
+        /cannot start with a dash/,
+      );
+    });
+  });
+
+  describe("path traversal attempts", () => {
+    it("should reject double dot sequences", () => {
+      expect(() => validateBranchName("../../../etc")).toThrow();
+      expect(() => validateBranchName("branch/../secret")).toThrow(/'\.\.'$/);
+      expect(() => validateBranchName("a..b")).toThrow(/'\.\.'$/);
+    });
+  });
+
+  describe("git-specific invalid patterns", () => {
+    it("should reject @{ sequence", () => {
+      expect(() => validateBranchName("branch@{1}")).toThrow(/@{/);
+      expect(() => validateBranchName("HEAD@{yesterday}")).toThrow(/@{/);
+    });
+
+    it("should reject .lock suffix", () => {
+      expect(() => validateBranchName("branch.lock")).toThrow(/\.lock/);
+      expect(() => validateBranchName("feature.lock")).toThrow(/\.lock/);
+    });
+
+    it("should reject consecutive slashes", () => {
+      expect(() => validateBranchName("feature//branch")).toThrow(
+        /consecutive slashes/,
+      );
+      expect(() => validateBranchName("a//b//c")).toThrow(
+        /consecutive slashes/,
+      );
+    });
+
+    it("should reject trailing slashes", () => {
+      expect(() => validateBranchName("feature/")).toThrow(
+        /cannot end with a slash/,
+      );
+      expect(() => validateBranchName("branch/")).toThrow(
+        /cannot end with a slash/,
+      );
+    });
+
+    it("should reject leading periods", () => {
+      expect(() => validateBranchName(".hidden")).toThrow();
+    });
+
+    it("should reject trailing periods", () => {
+      expect(() => validateBranchName("branch.")).toThrow(
+        /cannot start or end with a period/,
+      );
+    });
+
+    it("should reject special git refspec characters", () => {
+      expect(() => validateBranchName("branch~1")).toThrow();
+      expect(() => validateBranchName("branch^2")).toThrow();
+      expect(() => validateBranchName("branch:ref")).toThrow();
+      expect(() => validateBranchName("branch?")).toThrow();
+      expect(() => validateBranchName("branch*")).toThrow();
+      expect(() => validateBranchName("branch[0]")).toThrow();
+      expect(() => validateBranchName("branch\\path")).toThrow();
+    });
+  });
+
+  describe("control characters and special characters", () => {
+    it("should reject null bytes", () => {
+      expect(() => validateBranchName("branch\x00name")).toThrow();
+    });
+
+    it("should reject other control characters", () => {
+      expect(() => validateBranchName("branch\x01name")).toThrow();
+      expect(() => validateBranchName("branch\x1Fname")).toThrow();
+      expect(() => validateBranchName("branch\x7Fname")).toThrow();
+    });
+
+    it("should reject spaces", () => {
+      expect(() => validateBranchName("branch name")).toThrow();
+      expect(() => validateBranchName("feature branch")).toThrow();
+    });
+
+    it("should reject newlines and tabs", () => {
+      expect(() => validateBranchName("branch\nname")).toThrow();
+      expect(() => validateBranchName("branch\tname")).toThrow();
+    });
+  });
+
+  describe("empty and whitespace", () => {
+    it("should reject empty strings", () => {
+      expect(() => validateBranchName("")).toThrow(/cannot be empty/);
+    });
+
+    it("should reject whitespace-only strings", () => {
+      expect(() => validateBranchName("   ")).toThrow();
+      expect(() => validateBranchName("\t\n")).toThrow();
+    });
+  });
+
+  describe("edge cases", () => {
+    it("should accept single alphanumeric character", () => {
+      expect(() => validateBranchName("a")).not.toThrow();
+      expect(() => validateBranchName("1")).not.toThrow();
+    });
+
+    it("should reject single special characters", () => {
+      expect(() => validateBranchName(".")).toThrow();
+      expect(() => validateBranchName("/")).toThrow();
+      expect(() => validateBranchName("-")).toThrow();
+    });
+  });
+});