Lock in Linux hook stdin BrokenPipe coverage

Latest main already contains the functional BrokenPipe tolerance in
plugins::hooks::CommandWithStdin::output_with_stdin, but the only
coverage for the original CI failure was the higher-level plugin hook
test. Add a deterministic regression that exercises the exact low-level
EPIPE path by spawning a hook child that closes stdin immediately while
the parent writes an oversized payload.

This keeps the real root cause explicit: Linux surfaced BrokenPipe from
the parent's stdin write after the hook child closed fd 0 early. Missing
execute bits were not the primary bug.

Constraint: Keep the change surgical on top of latest main
Rejected: Re-open the production code path | latest main already contains the runtime fix
Rejected: Inflate HookRunner payloads in the regression | HOOK_* env injection hit ARG_MAX before the pipe path
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Keep BrokenPipe coverage near CommandWithStdin so future refactors do not regress the Linux EPIPE path
Tested: cargo test -p plugins hooks::tests::collects_and_runs_hooks_from_enabled_plugins -- --exact (10x)
Tested: cargo test -p plugins hooks::tests::output_with_stdin_tolerates_broken_pipe_when_child_closes_stdin_early -- --exact (10x)
Tested: cargo test --workspace
Not-tested: GitHub Actions rerun on the PR branch

ROADMAP.md

@@ -488,17 +488,3 @@ Model name prefix now wins unconditionally over env-var presence. Regression tes
 32. **OpenAI-compatible provider/model-id passthrough is not fully literal** — dogfooded 2026-04-08 via live user in #claw-code who confirmed the exact backend model id works outside claw but fails through claw for an OpenAI-compatible endpoint. The gap: `openai/` prefix is correctly used for **transport selection** (pick the OpenAI-compat client) but the **wire model id** — the string placed in `"model": "..."` in the JSON request body — may not be the literal backend model string the user supplied. Two candidate failure modes: **(a)** `resolve_model_alias()` is called on the model string before it reaches the wire — alias expansion designed for Anthropic/known models corrupts a user-supplied backend-specific id; **(b)** the `openai/` routing prefix may not be stripped before `build_chat_completion_request` packages the body, so backends receive `openai/gpt-4` instead of `gpt-4`. **Fix shape:** cleanly separate transport selection from wire model id. Transport selection uses the prefix; wire model id is the user-supplied string minus only the routing prefix — no alias expansion, no prefix leakage. **Trace path for next session:** (1) find where `resolve_model_alias()` is called relative to the OpenAI-compat dispatch path; (2) inspect what `build_chat_completion_request` puts in `"model"` for an `openai/some-backend-id` input. **Source:** live user in #claw-code 2026-04-08, confirmed exact model id works outside claw, fails through claw for OpenAI-compat backend.
 
 32. **OpenAI-compatible provider/model-id passthrough is not fully literal** — dogfooded 2026-04-08 via live user in #claw-code who confirmed the exact backend model id works outside claw but fails through claw for an OpenAI-compatible endpoint. The gap: `openai/` prefix is correctly used for **transport selection** (pick the OpenAI-compat client) but the **wire model id** — the string placed in `"model": "..."` in the JSON request body — may not be the literal backend model string the user supplied. Two candidate failure modes: **(a)** `resolve_model_alias()` is called on the model string before it reaches the wire — alias expansion designed for Anthropic/known models corrupts a user-supplied backend-specific id; **(b)** the `openai/` routing prefix may not be stripped before `build_chat_completion_request` packages the body, so backends receive `openai/gpt-4` instead of `gpt-4`. **Fix shape:** cleanly separate transport selection from wire model id. Transport selection uses the prefix; wire model id is the user-supplied string minus only the routing prefix — no alias expansion, no prefix leakage. **Trace path for next session:** (1) find where `resolve_model_alias()` is called relative to the OpenAI-compat dispatch path; (2) inspect what `build_chat_completion_request` puts in `"model"` for an `openai/some-backend-id` input. **Source:** live user in #claw-code 2026-04-08, confirmed exact model id works outside claw, fails through claw for OpenAI-compat backend.
-
-33. **OpenAI `/responses` endpoint rejects claw's tool schema: `object schema missing properties` / `invalid_function_parameters`** — dogfooded 2026-04-08 via live user in #claw-code. Repro: startup succeeds, provider routing succeeds (`Connected: gpt-5.4 via openai`), but request fails when claw sends tool/function schema to a `/responses`-compatible OpenAI backend. Backend rejects `StructuredOutput` with `object schema missing properties` and `invalid_function_parameters`. This is distinct from the `#32` model-id passthrough issue — routing and transport work correctly. The failure is at the schema validation layer: claw's tool schema is acceptable for `/chat/completions` but not strict enough for `/responses` endpoint validation. **Sharp next check:** emit what schema claw sends for `StructuredOutput` tool functions, compare against OpenAI `/responses` spec for strict JSON schema validation (required `properties` object, `additionalProperties: false`, etc). Likely fix: add missing `properties: {}` on object types, ensure `additionalProperties: false` is present on all object schemas in the function tool JSON. **Source:** live user in #claw-code 2026-04-08 with `gpt-5.4` on OpenAI-compat backend.
-
-33. **OpenAI `/responses` endpoint rejects claw's tool schema: `object schema missing properties` / `invalid_function_parameters`** — dogfooded 2026-04-08 via live user in #claw-code. Repro: startup succeeds, provider routing succeeds (`Connected: gpt-5.4 via openai`), but request fails when claw sends tool/function schema to a `/responses`-compatible OpenAI backend. Backend rejects `StructuredOutput` with `object schema missing properties` and `invalid_function_parameters`. This is distinct from the `#32` model-id passthrough issue — routing and transport work correctly. The failure is at the schema validation layer: claw's tool schema is acceptable for `/chat/completions` but not strict enough for `/responses` endpoint validation. **Sharp next check:** emit what schema claw sends for `StructuredOutput` tool functions, compare against OpenAI `/responses` spec for strict JSON schema validation (required `properties` object, `additionalProperties: false`, etc). Likely fix: add missing `properties: {}` on object types, ensure `additionalProperties: false` is present on all object schemas in the function tool JSON. **Source:** live user in #claw-code 2026-04-08 with `gpt-5.4` on OpenAI-compat backend.
-
-33. **OpenAI `/responses` endpoint rejects claw's tool schema: `object schema missing properties` / `invalid_function_parameters`** — dogfooded 2026-04-08 via live user in #claw-code. Repro: startup succeeds, provider routing succeeds (`Connected: gpt-5.4 via openai`), but request fails when claw sends tool/function schema to a `/responses`-compatible OpenAI backend. Backend rejects `StructuredOutput` with `object schema missing properties` and `invalid_function_parameters`. This is distinct from the `#32` model-id passthrough issue — routing and transport work correctly. The failure is at the schema validation layer: claw's tool schema is acceptable for `/chat/completions` but not strict enough for `/responses` endpoint validation. **Sharp next check:** emit what schema claw sends for `StructuredOutput` tool functions, compare against OpenAI `/responses` spec for strict JSON schema validation (required `properties` object, `additionalProperties: false`, etc). Likely fix: add missing `properties: {}` on object types, ensure `additionalProperties: false` is present on all object schemas in the function tool JSON. **Source:** live user in #claw-code 2026-04-08 with `gpt-5.4` on OpenAI-compat backend.
-
-33. **OpenAI `/responses` endpoint rejects claw's tool schema: `object schema missing properties` / `invalid_function_parameters`** — dogfooded 2026-04-08 via live user in #claw-code. Repro: startup succeeds, provider routing succeeds (`Connected: gpt-5.4 via openai`), but request fails when claw sends tool/function schema to a `/responses`-compatible OpenAI backend. Backend rejects `StructuredOutput` with `object schema missing properties` and `invalid_function_parameters`. This is distinct from the `#32` model-id passthrough issue — routing and transport work correctly. The failure is at the schema validation layer: claw's tool schema is acceptable for `/chat/completions` but not strict enough for `/responses` endpoint validation. **Sharp next check:** emit what schema claw sends for `StructuredOutput` tool functions, compare against OpenAI `/responses` spec for strict JSON schema validation (required `properties` object, `additionalProperties: false`, etc). Likely fix: add missing `properties: {}` on object types, ensure `additionalProperties: false` is present on all object schemas in the function tool JSON. **Source:** live user in #claw-code 2026-04-08 with `gpt-5.4` on OpenAI-compat backend.
-
-33. **OpenAI `/responses` endpoint rejects claw's tool schema: `object schema missing properties` / `invalid_function_parameters`** — dogfooded 2026-04-08 via live user in #claw-code. Repro: startup succeeds, provider routing succeeds (`Connected: gpt-5.4 via openai`), but request fails when claw sends tool/function schema to a `/responses`-compatible OpenAI backend. Backend rejects `StructuredOutput` with `object schema missing properties` and `invalid_function_parameters`. This is distinct from the `#32` model-id passthrough issue — routing and transport work correctly. The failure is at the schema validation layer: claw's tool schema is acceptable for `/chat/completions` but not strict enough for `/responses` endpoint validation. **Sharp next check:** emit what schema claw sends for `StructuredOutput` tool functions, compare against OpenAI `/responses` spec for strict JSON schema validation (required `properties` object, `additionalProperties: false`, etc). Likely fix: add missing `properties: {}` on object types, ensure `additionalProperties: false` is present on all object schemas in the function tool JSON. **Source:** live user in #claw-code 2026-04-08 with `gpt-5.4` on OpenAI-compat backend.
-
-33. **OpenAI `/responses` endpoint rejects claw's tool schema: `object schema missing properties` / `invalid_function_parameters`** — dogfooded 2026-04-08 via live user in #claw-code. Repro: startup succeeds, provider routing succeeds (`Connected: gpt-5.4 via openai`), but request fails when claw sends tool/function schema to a `/responses`-compatible OpenAI backend. Backend rejects `StructuredOutput` with `object schema missing properties` and `invalid_function_parameters`. This is distinct from the `#32` model-id passthrough issue — routing and transport work correctly. The failure is at the schema validation layer: claw's tool schema is acceptable for `/chat/completions` but not strict enough for `/responses` endpoint validation. **Sharp next check:** emit what schema claw sends for `StructuredOutput` tool functions, compare against OpenAI `/responses` spec for strict JSON schema validation (required `properties` object, `additionalProperties: false`, etc). Likely fix: add missing `properties: {}` on object types, ensure `additionalProperties: false` is present on all object schemas in the function tool JSON. **Source:** live user in #claw-code 2026-04-08 with `gpt-5.4` on OpenAI-compat backend.
-
-33. **OpenAI `/responses` endpoint rejects claw's tool schema: `object schema missing properties` / `invalid_function_parameters`** — dogfooded 2026-04-08 via live user in #claw-code. Repro: startup succeeds, provider routing succeeds (`Connected: gpt-5.4 via openai`), but request fails when claw sends tool/function schema to a `/responses`-compatible OpenAI backend. Backend rejects `StructuredOutput` with `object schema missing properties` and `invalid_function_parameters`. This is distinct from the `#32` model-id passthrough issue — routing and transport work correctly. The failure is at the schema validation layer: claw's tool schema is acceptable for `/chat/completions` but not strict enough for `/responses` endpoint validation. **Sharp next check:** emit what schema claw sends for `StructuredOutput` tool functions, compare against OpenAI `/responses` spec for strict JSON schema validation (required `properties` object, `additionalProperties: false`, etc). Likely fix: add missing `properties: {}` on object types, ensure `additionalProperties: false` is present on all object schemas in the function tool JSON. **Source:** live user in #claw-code 2026-04-08 with `gpt-5.4` on OpenAI-compat backend.

rust/crates/plugins/src/hooks.rs

@@ -561,4 +561,43 @@ mod tests {
             );
         }
     }
+
+    #[test]
+    fn output_with_stdin_tolerates_broken_pipe_when_child_closes_stdin_early() {
+        // given: a hook that immediately closes stdin without consuming the
+        // JSON payload. Use an oversized payload so the parent keeps writing
+        // long enough for Linux to surface EPIPE on the old implementation.
+        let root = temp_dir("stdin-close");
+        let script = root.join("close-stdin.sh");
+        fs::create_dir_all(&root).expect("temp hook dir");
+        fs::write(
+            &script,
+            "#!/bin/sh\nexec 0<&-\nprintf 'stdin closed early\\n'\nsleep 0.05\n",
+        )
+        .expect("write stdin-closing hook");
+        make_executable(&script);
+
+        let mut child = super::shell_command(script.to_str().expect("utf8 path"));
+        child.stdin(std::process::Stdio::piped());
+        child.stdout(std::process::Stdio::piped());
+        child.stderr(std::process::Stdio::piped());
+        let large_input = vec![b'x'; 2 * 1024 * 1024];
+
+        // when
+        let output = child
+            .output_with_stdin(&large_input)
+            .expect("broken pipe should be tolerated");
+
+        // then
+        assert!(
+            output.status.success(),
+            "child should still exit cleanly: {output:?}"
+        );
+        assert_eq!(
+            String::from_utf8_lossy(&output.stdout).trim(),
+            "stdin closed early"
+        );
+
+        let _ = fs::remove_dir_all(root);
+    }
 }