[tumberger]

Registers a devin agent adapter so kontext hook --agent devin can translate
the Devin runtime's plugin hook payloads. Policy evaluation is untouched — the
adapter decodes the incoming event and encodes the decision in the form that
runtime reads from stdout. Same shape as the existing Codex adapter.

What's here

• internal/hookruntime/devin.go — decode/encode
• internal/agent/devin/ — registration, plus the blank import in main.go
• hook.ErrSkipEvent — a skip contract honored by both hook runners

Decisions worth reviewing

prompt_id is dropped for now. It's a useful per-turn correlator, but it has
no home on hook.Event, and folding it into ToolInput would be wrong:
ToolInput becomes the Cedar evaluation context, so a synthetic attribute there
would be policy-visible and would change the parameters hash recorded on every
decision. A first-class field is a follow-up.

Only pre-tool-use carries a decision. Every other event is observation and
emits no directive. Anything other than an explicit allow blocks, so an
unrecognized decision value fails closed.

An updated tool input is refused, not applied. That runtime replaces
tool_input wholesale rather than merging, so emitting a partial rewrite would
silently drop every field the policy didn't restate, and the post-tool-use hook
would then observe only the rewritten input — leaving the original absent from
the ledger. Nothing populates UpdatedInput today, so this is a guard against a
future change rather than active logic. Input rewriting is worth supporting
properly later, with the pre-rewrite input as the authoritative ledger entry.

hook.ErrSkipEvent is new, and touches shared runners. Some agent runtimes
read a non-zero hook exit as "block the tool call", so reporting an unhandled
lifecycle event as a decode failure would stall the agent on a legitimate
signal. Both runners now exit successfully and emit nothing for a skipped event.
Unknown event names skip for the same reason; malformed input still fails, since
that indicates a bug or a contract change rather than an event we chose not to
handle. The change is additive — it only triggers on that specific sentinel, so
existing adapters are unaffected.

Follow-ups, deliberately not in this PR

Both change behavior for existing agents and deserve their own review:

1. No recover() on the hook path. An unrecovered panic exits 2, which some
   runtimes read as "block" — so a nil-map bug becomes an opaque stall rather
   than a visible failure. Worth fixing for every adapter, not just this one.
2. Runner selection. kontext hook uses the managed-observe lifecycle but
   exits 2 on any decode failure; --mode gets the runner that always writes a
   decision and exits 0, but bypasses the lifecycle and dials the Guard socket
   with no autostart. Neither branch is quite right for a hook that must never
   stall the agent.

Testing

New tests cover field mapping, prompt_id exclusion from the Cedar context,
large-integer precision, skip vs. failure classification, the block/allow encode
forms, observation events never emitting a directive, rewrite refusal, and
fail-closed behavior on an unknown decision.

go build ./..., go vet, and gofmt are clean. Full go test ./... passes
except two pre-existing load-sensitive timing tests in internal/guard/judge
(llama_server_test.go), which also fail on main under full-suite load and
pass in isolation.

[tumberger]

• feat(agent): add a Devin hook adapter #430 👈 (View in Graphite)
• main

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[greptile-apps]

Greptile Summary

Adds a Devin hook adapter and a shared sentinel for silently skipping non-actionable lifecycle events.

• Registers devin in the agent registry and CLI binary.
• Translates Devin pre-tool-use and lifecycle payloads into shared hook events while preserving numeric precision.
• Encodes policy denials using Devin’s blocking response and refuses unsupported input rewrites.
• Updates both hook runners to exit successfully without output when an adapter returns ErrSkipEvent.
• Adds coverage for registration, payload mapping, decision encoding, malformed input, and skip behavior.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete blocking or independently actionable non-blocking issues identified.

The Devin adapter follows the existing registry and hook-runner boundaries, limits directives to pre-tool-use events, fails closed on non-allow decisions, and keeps deliberate event skips distinct from malformed input.

Important Files Changed

Filename	Overview
internal/hookruntime/devin.go	Implements Devin payload decoding, supported-event filtering, input normalization, fail-closed decision encoding, and rewrite refusal without an identified defect.
internal/agent/devin/devin.go	Registers the Devin adapter and correctly delegates the shared agent interface to the new codec.
internal/hookruntime/runner.go	Treats the new wrapped skip sentinel as successful no-output completion while preserving existing behavior for ordinary decode errors.
internal/guard/hookruntime/runtime.go	Adds equivalent skip handling to the mode-aware runner without changing policy evaluation or malformed-input behavior.
internal/hook/domain.go	Introduces a dedicated, wrappable sentinel distinguishing deliberately unsupported events from malformed payloads.
cmd/kontext/main.go	Blank-imports the Devin package so its adapter is available through --agent devin.

Sequence Diagram

sequenceDiagram
    participant Devin as Devin runtime
    participant CLI as kontext hook
    participant Adapter as Devin adapter
    participant Policy as Policy runtime
    Devin->>CLI: Hook payload on stdin
    CLI->>Adapter: DecodeDevinEvent
    alt Unsupported lifecycle event
        Adapter-->>CLI: ErrSkipEvent
        CLI-->>Devin: Exit 0 with no output
    else Supported event
        Adapter-->>CLI: hook.Event
        CLI->>Policy: Evaluate or ingest event
        Policy-->>CLI: hook.Result
        CLI->>Adapter: EncodeDevinResult
        alt PreToolUse denied
            Adapter-->>Devin: "decision=block and reason"
        else Allowed or observation event
            Adapter-->>Devin: Empty directive object
        end
    end

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_{Reviews (1): Last reviewed commit: "feat(agent): add a Devin hook adapter" | Re-trigger Greptile}