33 lines
6.9 KiB
Markdown
33 lines
6.9 KiB
Markdown
# Agent Note: dsh-hook-protocol — the shared Claude Code / Codex hook wire-protocol core
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Status: implemented
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English | [中文](2026-06-30-hook-protocol-lib.zh.md)
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## Problem
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The hooks subsystem ships two bridge plugins: one that runs a user's existing Claude Code (CC) hooks, one for Codex hooks. Studying the reference implementations (`~/repos/refs/claude-code`, `~/repos/refs/codex`) surfaced a decisive fact: **Codex deliberately reimplements a SUBSET of the CC hook protocol.** Its engine reads the same `hooks.json`, uses the same matcher-group shape, the same exit-code/structured-stdout output contract, and the same command-hook execution model — Codex's source even names the engine after Claude's and comments where it "intentionally diverges." So the two bridges would otherwise duplicate the bulk of the protocol.
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This Agent Note introduces `@deepseek-ai/dsh-hook-protocol`, a **library** (not a plugin — it registers and injects nothing) holding the genuinely-identical primitives both bridges build on. The split between shared and per-dialect is the design's center of gravity.
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## Decision
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A new `packages/hooks/` group with `hook-protocol` as a pure library. It owns four primitive families and the `hook/*` session events; each bridge plugin (`dsh-hooks-claude`, `dsh-hooks-codex`) owns what genuinely differs.
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**Shared (here):**
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- **Matcher** — `compileMatchers(patterns, mode)`, `matcherDiagnostic(pattern, mode)`, and `matchesMatcher(pattern, query, mode)`. Pure `[A-Za-z0-9_|]+` patterns use the shared exact-match fast path (pipe = alternatives); the ONE remaining dialect axis is collapsed to `mode`: other Claude patterns use JavaScript `RegExp`, while other Codex patterns use Rust `regex`, including Rust-only syntax such as `(?i)`. Match-all on absent/`''`/`'*'`. Each bridge ignores unsupported events before group parsing, discards matcher fields on supported events without matcher subjects, collects the remaining runnable groups, and compiles their finite set of unique patterns ONCE. It reads validation diagnostics from that config registry: rejection disposes the registry before whole-config failure, while admission returns the SAME registry for hook-point matching and plugin-teardown disposal after detached runs drain. Codex valid instances and invalid diagnostics additionally use a versioned interner on the synchronous `rregex` CJS module, so one-shot calls and hook-protocol/Cordis reloads reuse them without putting state on `globalThis`. Because that dependency's WASM allocator does not shrink after `free()`, the interner deliberately retains at most `MAX_INTERNED_CODEX_REGEX_PATTERNS` (128) distinct non-literal patterns per process. At capacity, a new distinct pattern is rejected before native construction with a stable capacity/pattern/event diagnostic; known patterns remain usable and process restart resets the budget. The hard bound covers adversarial unique-pattern reloads without an unbounded cache, while direct library calls remain contained and never throw into the loop.
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- **Execution** — `runHook(bash, hook, options)`. Runs a command hook through the `ctx.bash` seam rather than a bespoke `spawn`: the executor already provides the scrubbed-but-overridable env, process-group kills, and timeout the protocol needs, and `dsh-bash`'s `stdin`/`env` fields (added for exactly this) are the trusted-plugin surface an in-process bridge is allowed to use. It serializes the bridge-built payload to stdin (trailing newline iff CC), honors the hook's `timeoutSec` (else `DEFAULT_HOOK_TIMEOUT_MS`, the 10-minute reference default both dialects share), and never throws (an executor rejection becomes a non-blocking-error `HookOutput`).
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- **Decode** — `parseHookOutput(exit, stdout, stderr)`, the exit-code + structured-stdout codec, producing a dialect-neutral `HookOutput`. Exit `0` → lenient JSON parse of stdout; exit `2` → blocking error with `stderr` as the reason (surfaced as `decision: 'block'` so no caller needs a separate exit-code branch); other → non-blocking error. Parses the CC structured-stdout fields that have a consumer on some path (`continue`/`stopReason`/`decision`/`hookSpecificOutput.{permissionDecision,additionalContext,updatedInput}`/`systemMessage`); the bridge honors only the subset meaningful for its dialect. Fields with no consumer on any path are not parsed at all (CC's `suppressOutput` — hook stdout never enters a transcript here, so there is nothing to suppress; see [the tighten-hook-protocol-contract Agent Note](../simplification/2026-07-04-tighten-hook-protocol-contract.md)).
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- **Merge** — `mergeHookOutputs(outputs)`, folding multiple matched hooks into one most-restrictive `MergedHookOutcome`: permission precedence **deny > ask > allow**, halt sticky on the first `continue:false`, block reasons joined `\n\n`, context/system-messages accumulated in order.
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- **`hook/*` session events** — `hook/invoked` / `hook/result`, declaration-merged into `SessionEventMap` (log-only, like `compact/*` — NOT `SurfaceEventType`s), with `appendHookInvoked`/`appendHookResult` helpers so the invoked/result pairing and owner-defined execution relation stay consistent across bridges. `appendHookResult` also owns the durable record's semantics — the decision string (the hook's parsed decision, else `'stop'` on `continue:false`, else `'pass'`) and the 500-character `stderrSummary` truncation derive from the `HookOutput` here, not per-bridge.
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**Per-dialect (the bridge plugins):** building each event's stdin payload (CC's base+per-event field sets vs Codex's snake_case with `turn_id`/`model` extras), the dialect's env + `${CLAUDE_PLUGIN_ROOT}` substitution (CC) vs none (Codex), and mapping the neutral `HookOutput`/`MergedHookOutcome` onto the harness's seam-specific typed Decisions (`PreToolDecision`, `PromptDecision`, `ContinuationDecision`, `PostToolDecision`).
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## Alternatives considered
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**One parameterized engine.** Rejected because payload construction and decision mapping genuinely differ by dialect. Matchers, codecs, execution, merge rules, and events remain shared; each bridge keeps its payload and mapping explicit so its wire behavior is readable in place.
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## Consequences
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Each bridge parses config atomically, builds its dialect payload, invokes the shared runner and merge logic, maps the decision, and appends `hook/*`. Protocol tests cover every matcher mode and diagnostic, exit-code and codec field, runner plumbing, merge precedence, and audit helper at per-file 100%; bridge tests exercise the library's load path and pin the exact warning. Keyless ACP snapshots boot both bridges through the real Loader/app path with a valid blocking group before an invalid matcher, then prove the request reaches the replay model and persists no `hook/*` rows, so partial registration cannot hide behind a hand-mounted context. `updatedInput` is parsed but only logged and warned until the [input-rewrite proposal](../../proposed/feature/2026-06-30-pre-tool-input-rewrite.md) lands.
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