# Function Breakdown & Codebase Review — `agent_mei_panel`

> Generated 2026-06-14. Per-file inventory of the bolt-on crate. file:line references are against the audited HEAD.

## 1. Crate overview

`agent_mei_panel` is the bolt-on that turns this Joule fork into an **energy-metered, federated, no-phone-home coding editor**. It adds a dock panel (`AgentMeiPanel`) that drives first-party login-based vendor agents (Claude Code / Gemini / Codex) over ACP — the vendor's own CLI owns its login and tokens; the panel never handles a key — and wraps every request in a five-tier **cascade** (L0 cache → L1 deterministic → L2 semantic retrieval → L3 on-device GGUF model → L4 remote agent) that closes at the cheapest tier that can, metering host energy and sealing JCR-1 signed receipts at each close. Three entry points: **`init(cx)`** (`agent_mei_panel.rs:84`) starts the control server, registers actions, attaches the on-device FIM provider to every file editor; the **`AgentMeiPanel`** view/struct (`:177`); and the **control protocol** (`control.rs`), a CDP-style JSON protocol whose methods land in **`control_dispatch`** (`:2261`).

## 2. Per-file breakdown

### `agent_mei_panel.rs` (5335 LOC) — panel, cascade, control dispatch

**Lifecycle & view:** `init` `:84`, `new` `:557`, `load` `:1080`, `Render::render` `:4208` (~500 lines: status, connect buttons, prompt, cascade/grant/methodology/session/hooks summaries, edit-review list, pending-edit Accept/Reject diff, agent step log), `impl Panel` `:4713`.

**Cascade tiers:** `submit_prompt` `:1600` (entry: resolve `@`-mentions, run cascade), `attempt_l1_deterministic` `:1834` (L1 exact substitution), `attempt_l2_then_l3` `:1673` (L2 embed+replay), `index_for_l2` `:1777`, `attempt_l3_then_l4` `:1883` (L3 model gen+apply), `send_to_l4` `:2462` (L4 ACP forward).

**Edit application & review:** `apply_multi_file_edit` `:2022`, `record_multi_edit` `:2100`, `stage_pending_edit` `:2178`, `apply_staged_now` `:2204`, `accept_pending_edit` `:2231`, `reject_pending_edit` `:2246`, `revert_edit` `:1002`, `record_review` `:986`, `line_diff` `:465`, `diff_stat` `:502`.

**Local-agent / index / prediction:** `run_local_agent` `:1370` (drives `local_agent::run_agent_loop` off-thread), `index_codebase` `:1181`, `predict_here` `:1269`.

**Sessions glue:** `ensure_session_mgr` `:2656`, `spawn_session` `:2699`, `delegate_session` `:2735`, `close_session` `:2777`, `verify_session` `:2799`, `merge_session` `:2839`, `set_active_session` `:2899`, `record_active_op` `:2883`, `active_session_worktree` `:2872`.

**Energy, receipts, ledger:** `host_energy` `:3196`, `energy_uj_now` `:3213`, `bracket_energy` `:2443`, `append_to_ledger` `:686`, `ensure_ledger_loaded` `:642`, `seal_op_receipt` `:738`, `ledger_receipt` `:751`, `verify_entry_seal` `:772`, `ensure_l2_loaded` `:790`, `append_l2_record` `:828`, `record_tier_edit` `:2542`, `record_l3_edit` `:2510`, `note_close` `:2602`, `authorize_tier` `:2611`, `life_spent_uj` `:2637`, `local_life_exhausted` `:2643`, `captured_op` `:3137`, `session_receipt` `:3107`.

**Control & attestation:** `control_dispatch` `:2261` (ping/state/submit/run_agent/accept/reject/open/save/buffer/revert/spawn_session/session_worktree/connect_agent), `control_state` `:2409`, `attest_unit` `:548`, `attest_in_sandbox` `:1025`, `attest_applied_edit` `:3039`.

**Agent connection:** `connect_agent` `:1096`, `do_connect` `:1155` (resolve `CustomAgentServer`, open ACP rooted in the active session worktree).

**L3 model (free fns):** `l3_engine` `:377`, `load_l3_model` `:3393`, `load_mellum_backend` `:3416`, `l3_generate` `:3540`, `l3_generate_fim` `:3560`, `l3_embed` `:3583`, `mellum_generate` `:3497`, `l3_sampling` `:3465`, `build_coding_op` `:3237`, `harness_prompt` `:3789`, `parse_edit` `:3830`, `parse_substitution` `:3273`, `resolve_at_mentions` `:3701`, `format_symbol_context` `:3619`, `format_codebase_context` `:4172`, `session_identity` `:3994`, `build_hook_registry` `:3983`.

### `control.rs` (732) — control protocol over Unix socket / TCP / MCP
`init_control_server` `:185`, `dispatch_foreground` `:276`, `serve_conn`/`process_line` `:340`/`:419` (token-aware), Unix/TCP accept loops, `list_peers` `:93` / `relay_command` `:138` / `register_self` `:61` (fleet), `run_client` `:473` / `run_client_tcp` `:506`, `mcp_tool_specs` `:533` / `handle_tool_call` / `run_mcp_bridge` `:673` (stdio MCP server). Types: `ControlCommand`, `ControlInstance` (gpui Global).

### `methodology.rs` (993) — spec-driven traceability
`MethodologyTracker` `:78`: `adopt`/`adopt_from_file` (verify-before-take signed spec), `cite_op`, `record_op`, `review`, `set_frame`/`check_op_in_frame` (fail-closed footprint gate), `coverage`, `ship_request`/`ship_summary`/`certify_release` (four-gate release cert), `amortization_line`. `SpecFile`, `RunSteering`+`RunCheckpoint`+`RunAmendment` (mid-run steering, monotonic only-narrowing budget).

### `sessions.rs` (855) — accountable worktree-isolated sessions
GPUI-free. `SessionManager` `:271`: `open`/`open_child` (attenuated delegation), `record_op`, `mark_verified`, `merge` (refuses unverified), `close`, `delegated_energy_uj`. `Session` (a `did:key` principal, worktree, branch, grant, status, chain): `verify_chain` `:249`. `SessionGrant::attenuate` `:101` (delegate only what you hold). `SealedEvent` (hash-chained, parent-signed).

### `local_agent.rs` (706) — on-device ReAct tool loop
`run_agent_loop` `:159` (prompt→generate→parse→gate→execute, fix-to-green verify before `finish`), `parse_tool_call`, `is_allowed_command` (allowlist), tools read/grep/list. `AgentStep`, `AgentTrace`.

### `codebase_index.rs` (433) — on-device repo-RAG
`CodebaseIndex::build` `:173` (incremental, reuses unchanged vectors), `search` `:69`, `find_symbol` `:101` (pure-text def ranking), `chunk_file`, `cosine`.

### `edit_blocks.rs` (356) — search/replace edit format
`parse_edit_blocks`, `apply_body`/`apply_edit`/`apply_patch` (exact → trailing-whitespace-tolerant → `SearchNotFound`, errors loudly naming the file). `EditBlock`/`Edit`/`Patch`/`ApplyError`.

### `hooks.rs` (284) — deny-capable lifecycle gates
`Hook` trait, `HookRegistry` (`with_reference_hooks`, `gate` deny-wins, `fire`). Reference gates `RefuseUnverifiedMerge` (PreMerge), `JouleCeiling` (PreTool budget). `LifecyclePoint`, `HookContext`, `Denied`.

### `mcp_client.rs` (230) — synchronous MCP stdio client
`McpClient::connect`/`list_tools`/`call_tool`, `parse_mcp_invocation`. Pure std + serde_json.

### `edit_prediction_local.rs` (216) — Cursor-Tab via on-device FIM
`LocalFimEditPredictionDelegate` (debounced off-thread infill, ghost-text), `CurrentCompletion::interpolate`.

### `cascade_gate.rs` (207) — JCP gate over L0–L4
`CascadeGate::from_env`/`authorize`/`l4_granted`/`grant`. Omit `l4` ⇒ remote agent structurally unreachable.

### `sandbox_bridge.rs` (202) — federate execution to `sandbox-mcp`
`attested_build` (S0–S7 attested build receipt, RATS EAT per step). `AttestedStep`/`AttestedBuild`/`UnitSpec`.

### `fim_local.rs` (182) — pure FIM engine
`FimFormat` (StarCoder/DeepseekCoder/CodeLlama), `fim_prompt`, `predict_infill`, `windows_around`, `clean_completion`.

### `tool_gate.rs` (136) — JCP gate over local-agent tools
`ToolGate::from_env`/`authorize` per tool call (read_file/grep/list_files/run/edit_file/mcp) against a grant + budget.

## 3. Key types

- **`AgentMeiPanel`** `:177` — central view. Field groups: connection (`session`, `prompt_editor`, `status`, `workspace`, `project`); energy (`energy_counter`, `energy_baseline`, `local_energy_uj`); cascade (`l0_cache`, `l2_index`, `l3_model`, `tier_closes:[u32;5]`, `codebase_index`); gating/accountability (`cascade_gate`, `hooks`, `methodology`, `session_key`, `session_mgr`, `active_session`); ledger (`ledger_ops`, `ledger_energy_uj`, `ledger_head`, `ledger_seq`, `ledger_intact`); review (`reviews`, `pending_edit`, `agent_steps`, `pending_context`, `last_intent`).
- **`L3Engine`** — `Runtime` (from-scratch GGUF) | `Mellum` (in-process safetensors). **`L3Backend`** — `Runtime(GgufModel,Vocab)` | `Mellum(Box<MellumModel>,BpeTokenizer,u32)`.
- **`StagedFile`** `{path, old, new, buffer}`, **`PendingEdit`** `{files, energy_before, single_path}`, **`LedgerEntry`** `{seq, prev, intent, energy_uj, op, seal}`.

## 4. Codebase review

**Architecture.** A clean spine: GPUI-free pure substrate modules + one GPUI orchestrator. Dependency-injection-by-closure (`run_agent_loop`, `CodebaseIndex::build`'s `embed`/`progress`, `predict_infill`'s `generate`) keeps heavy/model/IO parts out of the testable cores. The cascade is the central design; JCR-1 sealing + the hash-chained ledger are real with round-trip + tamper tests.

**The one debt: `agent_mei_panel.rs` at 5,335 LOC** — ~half the crate, 5× the next file, mixing seven concerns (render, cascade, L3 inference, ledger, energy, control dispatch, ~480 lines of inline tests). Recommended splits (all GPUI-free, move cleanly):
- **L3 model loading + generation** (`load_l3_model`/`l3_generate`/`mellum_generate`/`l3_sampling`/`harness_prompt`/`parse_edit`/`build_coding_op`, ~`:3237`–`:3600`) → `l3_model.rs`.
- **The persistent ledger** (`LedgerEntry`, `append_to_ledger`, `ensure_ledger_loaded`, `seal_op_receipt`, `verify_entry_seal`, ~`:329`–`:790`) → `ledger.rs` (a sibling of `sessions.rs` — both hash-chained sealed logs).

**Consistency notes:** two near-identical MCP stdio clients (`mcp_client::McpClient`, `sandbox_bridge::Mcp`); doc comments are unusually rich (occasionally essay-length). Adheres well to the repo's Rust guidelines (`let Some(..) else`, `?`, bounded indexing, `.detach()`/`.log_err()` on tasks) — except the load-bearing `let _ =` discards noted in [FINDINGS.md](FINDINGS.md).