yasyf · yasyf · Sep 2, 2026 · Sep 2, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -17,6 +17,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   the same 64 KiB pipe boundary.
 
 ### Changed
+- **Claude runs no longer inherit the host's user settings, and that is a default
+  change.** `claude -p` loads `user`, `project`, and `local` settings unless told
+  otherwise, which handed every spawned session the caller's hooks. On a machine
+  with a real hook stack those hooks dominate the call. A one-word prompt to
+  `claude-haiku-4-5` measured 63s with the host's hooks against 6s without, and
+  the session exited printing `SessionEnd hook … failed`. Non-isolated runs now
+  plan `--setting-sources project`; isolated runs keep the `--setting-sources ""`
+  they already passed. The new `ClaudeConfig.setting_sources` (Go
+  `SettingSources`) names the sources instead, on isolated runs too. Pass
+  `("user", "project", "local")` to restore what non-isolated runs did before, or
+  `()` to load none. `--settings` is no substitute, because settings merge: a
+  `{"hooks":{}}` payload leaves the inherited hooks in place.
 - **The Apple backend no longer needs the `apple` extra, `apple-fm-sdk`, or
   Xcode.** A prebuilt Swift sidecar ships inside the macOS platform wheel
   (`macosx_26_0_arm64`), so installing spawnllm on an Apple-Intelligence-capable

diff --git a/conformance/vectors/plan/claude-append-system-prompt.json b/conformance/vectors/plan/claude-append-system-prompt.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-disable-slash-commands.json b/conformance/vectors/plan/claude-disable-slash-commands.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-disallowed-tools.json b/conformance/vectors/plan/claude-disallowed-tools.json
@@ -25,6 +25,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-explicit-max-budget.json b/conformance/vectors/plan/claude-explicit-max-budget.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": "acceptEdits",
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-full-explicit-agent.json b/conformance/vectors/plan/claude-full-explicit-agent.json
@@ -34,6 +34,7 @@
         "mcp_config": "{\"mcpServers\":{}}",
         "output_format": null,
         "permission_mode": "bypassPermissions",
+        "setting_sources": null,
         "settings": "{\"model\":\"opus\"}",
         "strict_mcp": true,
         "system_prompt": "terse",

diff --git a/conformance/vectors/plan/claude-isolated-false.json b/conformance/vectors/plan/claude-isolated-false.json
@@ -30,6 +30,8 @@
       "--no-session-persistence",
       "--model",
       "haiku",
+      "--setting-sources",
+      "project",
       "--system-prompt",
       ""
     ],

diff --git a/conformance/vectors/plan/claude-max-turns.json b/conformance/vectors/plan/claude-max-turns.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-mcp-config.json b/conformance/vectors/plan/claude-mcp-config.json
@@ -22,6 +22,7 @@
         "mcp_config": "{\"mcpServers\":{}}",
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-output-format.json b/conformance/vectors/plan/claude-output-format.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": "stream-json",
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-permission-mode.json b/conformance/vectors/plan/claude-permission-mode.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": "bypassPermissions",
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-setting-sources-empty.json b/conformance/vectors/plan/claude-setting-sources-empty.json
@@ -0,0 +1,70 @@
+{
+  "name": "claude-setting-sources-empty",
+  "op": "plan",
+  "input": {
+    "provider": "claude",
+    "spec": {
+      "prompt": "hi",
+      "model": "haiku",
+      "agent": false,
+      "isolated": false,
+      "timeout": 180,
+      "max_attempts": 5,
+      "api_auth": false,
+      "schema": null,
+      "apple": null,
+      "claude": {
+        "append_system_prompt": null,
+        "disable_slash_commands": false,
+        "disallowed_tools": [],
+        "max_budget_usd": null,
+        "max_turns": null,
+        "mcp_config": null,
+        "output_format": null,
+        "permission_mode": null,
+        "setting_sources": [],
+        "settings": null,
+        "strict_mcp": false,
+        "system_prompt": null,
+        "tools": null,
+        "verbose": false
+      },
+      "codex": null,
+      "gemini": null,
+      "openai_endpoint": null
+    },
+    "host": {
+      "platform": "darwin"
+    }
+  },
+  "expected": {
+    "kind": "exec",
+    "argv": [
+      "claude",
+      "-p",
+      "--no-session-persistence",
+      "--model",
+      "haiku",
+      "--setting-sources",
+      "",
+      "--system-prompt",
+      ""
+    ],
+    "stdin": "hi",
+    "files": [
+      {
+        "id": "stdout",
+        "suffix": ".json",
+        "content": null
+      }
+    ],
+    "stdout_to_file": true,
+    "read_result_from": "stdout",
+    "env": {},
+    "env_unset": [
+      "ANTHROPIC_API_KEY",
+      "ANTHROPIC_AUTH_TOKEN"
+    ],
+    "needs_claude_isolation": false
+  }
+}
diff --git a/conformance/vectors/plan/claude-setting-sources-host.json b/conformance/vectors/plan/claude-setting-sources-host.json
@@ -0,0 +1,74 @@
+{
+  "name": "claude-setting-sources-host",
+  "op": "plan",
+  "input": {
+    "provider": "claude",
+    "spec": {
+      "prompt": "hi",
+      "model": "haiku",
+      "agent": false,
+      "isolated": false,
+      "timeout": 180,
+      "max_attempts": 5,
+      "api_auth": false,
+      "schema": null,
+      "apple": null,
+      "claude": {
+        "append_system_prompt": null,
+        "disable_slash_commands": false,
+        "disallowed_tools": [],
+        "max_budget_usd": null,
+        "max_turns": null,
+        "mcp_config": null,
+        "output_format": null,
+        "permission_mode": null,
+        "setting_sources": [
+          "user",
+          "project",
+          "local"
+        ],
+        "settings": null,
+        "strict_mcp": false,
+        "system_prompt": null,
+        "tools": null,
+        "verbose": false
+      },
+      "codex": null,
+      "gemini": null,
+      "openai_endpoint": null
+    },
+    "host": {
+      "platform": "darwin"
+    }
+  },
+  "expected": {
+    "kind": "exec",
+    "argv": [
+      "claude",
+      "-p",
+      "--no-session-persistence",
+      "--model",
+      "haiku",
+      "--setting-sources",
+      "user,project,local",
+      "--system-prompt",
+      ""
+    ],
+    "stdin": "hi",
+    "files": [
+      {
+        "id": "stdout",
+        "suffix": ".json",
+        "content": null
+      }
+    ],
+    "stdout_to_file": true,
+    "read_result_from": "stdout",
+    "env": {},
+    "env_unset": [
+      "ANTHROPIC_API_KEY",
+      "ANTHROPIC_AUTH_TOKEN"
+    ],
+    "needs_claude_isolation": false
+  }
+}
diff --git a/conformance/vectors/plan/claude-setting-sources-isolated.json b/conformance/vectors/plan/claude-setting-sources-isolated.json
@@ -0,0 +1,75 @@
+{
+  "name": "claude-setting-sources-isolated",
+  "op": "plan",
+  "input": {
+    "provider": "claude",
+    "spec": {
+      "prompt": "hi",
+      "model": "haiku",
+      "agent": false,
+      "isolated": true,
+      "timeout": 180,
+      "max_attempts": 5,
+      "api_auth": false,
+      "schema": null,
+      "apple": null,
+      "claude": {
+        "append_system_prompt": null,
+        "disable_slash_commands": false,
+        "disallowed_tools": [],
+        "max_budget_usd": null,
+        "max_turns": null,
+        "mcp_config": null,
+        "output_format": null,
+        "permission_mode": null,
+        "setting_sources": [
+          "project"
+        ],
+        "settings": null,
+        "strict_mcp": false,
+        "system_prompt": null,
+        "tools": null,
+        "verbose": false
+      },
+      "codex": null,
+      "gemini": null,
+      "openai_endpoint": null
+    },
+    "host": {
+      "platform": "darwin"
+    }
+  },
+  "expected": {
+    "kind": "exec",
+    "argv": [
+      "claude",
+      "-p",
+      "--no-session-persistence",
+      "--model",
+      "haiku",
+      "--setting-sources",
+      "project",
+      "--strict-mcp-config",
+      "--system-prompt",
+      ""
+    ],
+    "stdin": "hi",
+    "files": [
+      {
+        "id": "stdout",
+        "suffix": ".json",
+        "content": null
+      }
+    ],
+    "stdout_to_file": true,
+    "read_result_from": "stdout",
+    "env": {
+      "CLAUDE_CONFIG_DIR": "${isolated_config_dir}"
+    },
+    "env_unset": [
+      "ANTHROPIC_API_KEY",
+      "ANTHROPIC_AUTH_TOKEN"
+    ],
+    "needs_claude_isolation": true
+  }
+}
diff --git a/conformance/vectors/plan/claude-settings.json b/conformance/vectors/plan/claude-settings.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": "{\"model\":\"opus\"}",
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-strict-mcp.json b/conformance/vectors/plan/claude-strict-mcp.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": true,
         "system_prompt": null,
@@ -44,6 +45,8 @@
       "--no-session-persistence",
       "--model",
       "haiku",
+      "--setting-sources",
+      "project",
       "--strict-mcp-config"
     ],
     "stdin": "hi",

diff --git a/conformance/vectors/plan/claude-system-prompt.json b/conformance/vectors/plan/claude-system-prompt.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": "You are terse.",

diff --git a/conformance/vectors/plan/claude-tools-empty.json b/conformance/vectors/plan/claude-tools-empty.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-tools-list.json b/conformance/vectors/plan/claude-tools-list.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,

diff --git a/conformance/vectors/plan/claude-verbose.json b/conformance/vectors/plan/claude-verbose.json
@@ -22,6 +22,7 @@
         "mcp_config": null,
         "output_format": null,
         "permission_mode": null,
+        "setting_sources": null,
         "settings": null,
         "strict_mcp": false,
         "system_prompt": null,