8870da4313
Round-1 Codex review findings on the bridges: - Stop force-continue (both bridges): a blocking Stop hook with EMPTY stderr yielded decision 'deny' + reason undefined, and the `&& reason !== undefined` guard let the turn STOP — the opposite of a blocking Stop hook. Force-continue on any deny; fall back to a generic steering line when there is no reason. - Codex payload tool_name: hardcoded "Bash" disagreed with the exec.name matcher subject, so a real Codex `matcher:"Bash"` never fired against the harness's lowercase `bash` tool. Use exec.name in both payload builders (matches the matcher subject and the sibling CC bridge). Doc/RFC updated. - Codex plain-stdout context: SessionStart/UserPromptSubmit are documented to treat a clean hook's PLAIN (non-JSON) stdout as additionalContext, but nothing folded it. runPoint now folds plain stdout into context for those two events, gated on the codec's JSON gate so structured stdout is never dumped as prose. - continue:false is deferred, not honored: the seams have no hard-halt primitive yet. TODO(hook-continue-false) at both bridges + an RFC deferred note; the two tests now assert the LOG records the halt request AND that the run is NOT actually halted (no longer misleading). - README concurrency wording: hooks run SERIALLY (deliberate — adjacent invoked/result log pairs, order-independent fold), not concurrently. Fixed the CC README claim + an RFC note. Regression guards proven red on the unfixed code, then reverted. The mismatched- hookEventName discard (also flagged) is fixed in dsh-hook-protocol and merged down.
57 lines
7.7 KiB
Markdown
57 lines
7.7 KiB
Markdown
# RFC: dsh-hooks-claude + dsh-hooks-codex — the Claude Code / Codex hook bridges
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Status: implemented (accepted 2026-06-30)
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<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
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## Context
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The harness's extension surface is its typed interception seams ([the interception-seams RFC](2026-06-30-interception-seams.md)): a "native hook" is just an ordinary cordis plugin subscribing to `agent/session-start`, `agent/prompt-submit`, `tools/pre-execute`, `tools/post-execute`, `agent/turn-continuation`, `subagent/start`, `subagent/end`. But users arrive with **existing** Claude Code (CC) and Codex hook configs — a `hooks.json` (or a settings file's `hooks` key) full of shell-command hooks — and want those to run unmodified. This RFC introduces the two **bridge plugins** that translate that external shell-hook protocol onto the typed seams, built on the shared wire-protocol library ([the hook-protocol-lib RFC](2026-06-30-hook-protocol-lib.md)).
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The framing that shapes the whole design: **a bridge is a faithfulness adapter, not a power tool.** Anything a bridge does (block a tool, inject context, force continuation, observe a subagent) a native cordis plugin does more powerfully — typed returns, full `ctx`, no serialization boundary. The bridge's only reason to exist is to run an UNMODIFIED external CC/Codex hook with byte-faithful semantics. That keeps each bridge thin: parse the config, pick a matcher mode, build the per-event payload, call `runHook` + `mergeHookOutputs` from the shared lib, map the neutral outcome onto a seam Decision.
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## Decision
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Two independent plugins in the `packages/hooks/` group, each a function/namespace plugin (`name`/`inject`/`Config`/`apply`, NO default export — see [postmortem 0001](../../../postmortem/0001-acp-default-export-drops-inject.md)) injecting only `bash`:
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- **`dsh-hooks-claude`** — the CC dialect. Seven hook points: `SessionStart`, `UserPromptSubmit`, `PreToolUse`, `PostToolUse`, `Stop`, `SubagentStart`, `SubagentStop`. Owns CC's per-event stdin payloads (a base of `session_id`/`cwd`/`hook_event_name` plus per-event fields), CC's env + `${CLAUDE_PLUGIN_ROOT}`/`${CLAUDE_PROJECT_DIR}` substitution, and the literal-or-regex matcher mode. A CC hook's stdin carries a **trailing newline**.
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- **`dsh-hooks-codex`** — the Codex dialect: a deliberate SUBSET. Five hook points (`PreToolUse`, `PostToolUse`, `SessionStart`, `UserPromptSubmit`, `Stop` — no subagent/notification/compaction), an always-regex matcher, snake_case payloads with `turn_id`/`model`/`permission_mode` extras written WITHOUT a trailing newline, no env and no `${…}` substitution, and a block-only decision model (a Codex hook can never pre-approve, so `allow`/`ask` are not honored). A tool call's payload carries the real `tool_name` (the value the matcher tests, so a config's tool matcher fires) in Codex's `tool_input: { command }` shape.
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### Outcome → Decision mapping
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Each bridge maps the neutral `MergedHookOutcome` from the shared lib onto the seam's typed Decision:
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| Seam | CC | Codex |
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|---|---|---|
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| `agent/session-start` (emit) | additionalContext → `agent.inject()` | plain-stdout output → additionalContext → `agent.inject()` |
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| `agent/prompt-submit` | `deny`→`block`; context→`allow` | `block`→`block`; context→`allow` |
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| `tools/pre-execute` | `deny`→`deny`; `ask`→`ask` | `block`→`deny` (no allow/ask) |
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| `tools/post-execute` | `deny`→`block`+feedback; context→`accept` | same |
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| `agent/turn-continuation` | blocking Stop → `continue` (reason = next-step steering) | same |
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| `subagent/start` (emit) | additionalContext → inject into the live child | — (not a Codex event) |
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| `subagent/end` (emit) | observe-only | — |
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### Context source is always the plugin (the mislabel guard)
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`agent.inject()` defaults a missing `MessageSource` to `{ kind: 'user' }` — which would record plugin-injected context as if the user had typed it. So every bridge `inject()` and every `HookContext` passes an explicit `{ kind: 'plugin', plugin: 'hooks-claude' | 'hooks-codex' }` source. A test asserts the resulting `context/message.source` is the plugin, never `user`.
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### Containment
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The config is parsed ONCE at load; a read/parse failure logs and registers nothing rather than crashing boot (a typo'd path must not take the agent down). Only `type: 'command'` hooks run — a `prompt`/`agent`/HTTP hook (CC) or an `async: true` / non-command hook (Codex) is parsed-and-skipped with a warning. The emit-listener paths (`session-start`, `subagent/start`) run detached, with their `inject` contained in a `.catch` that logs (a throwing inject must not break session boot or the loop).
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## Deferred (faithful-but-degraded)
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- **Tool-input rewrite.** A CC/Codex `updatedInput` is logged + warned, not honored — input rewrite is a deferred consistency-design problem ([the pre-tool-input-rewrite RFC](../../proposed/feature/2026-06-30-pre-tool-input-rewrite.md)), because the pre-execution args are read by `tool/call` audit + `assistant/message` history + ACP/tool-bash presentation, so an honest rewrite is a design unit, not a field.
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- **Stop loop-guard** (`TODO(stop-loop-guard)`). CC/Codex break an infinite force-continue with `stop_hook_active` (true once a Stop hook fired this run) plus a max-consecutive cap; both are deferred. Today `stop_hook_active` is always `false`, so a Stop hook that unconditionally blocks would force-continue every step — a hook author must self-limit until the guard lands.
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- **Permission `ask`** degrades to `deny` at the `tools/pre-execute` seam (`FIXME(permissions)` in the interception-seams RFC) — there is no interactive permission prompt yet.
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- **Hook `continue:false` (hard halt).** A hook can ask to halt the whole run (CC/Codex `continue:false`); the shared merge folds it into `MergedHookOutcome.stop`/`stopReason`, but no bridge acts on it (`TODO(hook-continue-false)`) — the interception seams have no "hard-halt the agent" primitive yet (a Decision blocks/steers a single point, not the run). Deferred with the loop-guard work; the halt request is recorded in the `hook/result` log, and the hook keeps its per-point effect (decision/context) meanwhile.
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- **Config discovery.** The path is explicit in `cordis.yml`; the full multi-layer CC/Codex precedence walk and the trust/hash model are not reimplemented (`TODO`).
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### Multiple hooks on one point run serially, not concurrently
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The reference engines run a point's matched hooks concurrently and fold the results. These bridges run them **serially** (`await` per hook inside the match loop) and fold with the same most-restrictive merge. Serial is deliberate: it keeps each hook's `hook/invoked`/`hook/result` pair adjacent and in a deterministic order in the session log, and the fold is order-independent for the decision (`deny > ask > allow`) so the outcome matches. The cost is latency (hook *N* waits for hook *N−1*) and that per-hook timeouts are not overlapped — acceptable for the hook counts real configs use; revisit if a config ever fans out enough for the wall-clock to matter.
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## Consequences
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The bridges are thin and readable standalone: the correctness-critical halves (matcher semantics, exit-code contract, merge precedence) live in the shared `dsh-hook-protocol`, so each bridge is just config-parse + payload-build + outcome-map. Each is covered at per-file 100% — config-parse branches as unit tests, and the seam mappings end-to-end through the REAL loop + REAL `dsh-bash-local` + REAL shell scripts from a temp `hooks.json` (a scripted mock MODEL is the only stand-in), plus a real-Loader export-shape guard so a stray default export can't silently drop `inject`. Because the seams already carry typed Decisions, a future native plugin needs none of this bridge machinery — it returns a Decision directly.
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