# aish — Phase 9 Manifest

**Project:** aish — AI-augmented conversational shell
**Document:** Phase 9 Requirements, Architecture & Design Decisions
**Status:** Implement (4 commits landed: e525063, 34b465d, 5b6ee55, this)
**Date:** 2026-05-16

**Review findings (Sonnet, 2026-05-16) — 0 BLOCKERs, 7 CONCERNs
folded, 5 NITs applied:**

R1 (CONCERN, FOLDED). **HOME prefix false-positive in walk-up.**
    `dir:sub(1, #home) ~= home` lets `/home/user2/...` pass when
    HOME is `/home/user` (matches first 10 bytes). Real bug. Fix:
    `if dir ~= home and dir:sub(1, #home + 1) ~= home .. "/" then
    return nil end`. §4 code updated.

R2 (CONCERN, FOLDED). **`io.read` trust-prompt fallback breaks
    `aish -p` piped stdin.** A8's fallback (`io.read("*l")` if
    rl.readline misbehaves at startup) would consume the first
    line of piped stdin in non-interactive mode. **Fix:** in
    one-shot mode (`opts.prompt` set), SKIP the trust prompt
    entirely and decline silently with a status line. Project
    overlays in `-p` mode require pre-existing trust. Documented
    in §13 commit 2.

R3 (CONCERN, FOLDED). **Sources-map delivery decided: `cfg._sources`
    embedded on the config table** (NOT a global). `repl.run` reads
    `config._sources` for `:config show`. Backward-compatible — old
    callers of `repl.run` that don't pass `_sources` still work
    (`:config show` says `(sources unknown)`). §4 + §13 commits 2+3
    updated to reflect.

R4 (CONCERN, FOLDED). **`_prompt_trust` signature contradicted
    `_check_trusted`'s "compute sha once" claim.** §5 sketch called
    `_record_trust(project_path)` which would re-sha256. **Fix:**
    `_prompt_trust(project_path, sha)` takes the pre-computed sha;
    `history.add_trusted(trust_path, project_path, sha)` is the
    one writer. §5 sketches updated to match §13 + the real
    history.lua API.

R5 (CONCERN, FOLDED). **`_check_trusted` duplicated trust-file
    read logic vs history.lua API.** §5 sketch had inline JSONL
    read; §13 defines `M.is_trusted(trust_path, project_path,
    sha256)` in history.lua to own that. **Fix:** §5 sketches now
    call `history.is_trusted(...)` and `history.add_trusted(...)` —
    main.lua holds no trust-file logic itself. This also makes the
    `$AISH_TRUST_FILE` env override work cleanly (one resolution
    site).

R6 (CONCERN, FOLDED). **`:config show full` mode masking
    unspecified for nested values** — the actual leak vector is
    `mcp.servers.<alias>.auth_token`. **Fix:** §6 + §13 commit 3
    spell out: same heuristic, applied RECURSIVELY in full mode.
    Top-level mode (default) already collapses nested tables, so
    no leak there.

R7 (CONCERN, FOLDED). **Shallow merge silently drops user's entire
    models block** (or permissions, cost, etc.). Documented as
    "predictable" but is a real UX trap. **Fix:** §1 done-when +
    §7 UX surface + §13 commit 4 template-comment all gain a
    conspicuous warning: "If your `.aish.lua` sets a top-level
    block (models, permissions, cost, ...) it REPLACES your user
    config's entire block — list every entry you want available
    OR omit the block to keep the user's." Stronger framing than
    "predictable".

R-N1..N5 (NITs, APPLIED):
  N1. (cosmetic — review-prompt clarification only; no doc change)
  N2. `key_env` / `auth_env` over-masking is a known false-positive
      of the heuristic (env-var NAME, not a secret). §13 commit 3
      risk row gains an explicit note: "values of `*_env` fields
      will be masked too; cosmetic only — they hold env-var names,
      not secrets. Future: refine heuristic to exempt `*_env`
      pattern."
  N3. §13 open-at-plan-time list now includes the
      sources-map-delivery decision (resolved by R3 — embed on cfg).
  N4. §9 risk row about trust file partial write gains explicit
      first-ever-write edge case + workaround (manually delete the
      corrupt file). Temp-file+rename is v2 polish.
  N5. §3 module table ffi/libc.lua row had stale "stat" mention;
      removed per A2 (io.open is sufficient).

**Analyze + baseline findings (2026-05-16) — 5/6 open Qs resolved
in-place; Q-P4 deferred to implement-time verify:**

A1. **main.lua load_config surface clean.** `load_config(opts)` at
    `main.lua:53` returns `(cfg, path)` for the user config. Adding
    a project-overlay wrapper that calls it then walks for `.aish.lua`
    is additive — no refactor of the existing 4-tier resolution.

A2. **No new FFI needed for walk-up.** `io.open(candidate, "rb")` is
    sufficient for existence check; `libc.getcwd()` from Phase 6
    provides the starting point. No new C bindings.

A3. **Q-P2 RESOLVED via probe (B1 below): use `sha256sum`** — GNU
    coreutils ships it everywhere aish targets. Single-shell-out
    pattern; output: `<digest>  <path>` → `cut -d' ' -f1` for the
    hex digest. No new module dependency.

A4. **Q-P1 RESOLVED: trust prompt AFTER `aish: loaded config`
    status.** The user sees what user-config is in play first, then
    decides about the overlay. Natural ordering.

A5. **Q-P3 RESOLVED: don't log walk-up path by default.** Too noisy
    on every startup. If debugging "why isn't my project file
    found?", `:config show` after startup will reveal the walk
    result (declined-or-not-found is visible). Verbose-mode walk
    log is v2 polish.

A6. **Q-P5 RESOLVED: `:config show` shows top-level only by default.**
    Nested tables collapsed to `{key1, key2, ...}` (just the inner
    table's keys for orientation). `:config show full` for the
    deep dump. Keeps the diagnostic surface tractable.

A7. **Q-P6 RESOLVED: project layer CAN set `secrets.vault`** — it's
    part of the trust prompt's scope. User accepting the prompt
    accepts that the project file may redirect secrets. The
    in-memory secrets session is built AFTER config resolution, so
    a project-set `secrets.vault` IS honored.

A8. **rl.readline at startup (Q-P4 — deferred).** Phase 4's
    `:memory summarize` candidate-prompt path also calls
    `rl.readline` early (in metas; not pre-loop). The trust prompt
    fires BEFORE the main loop opens — earlier than any existing
    rl.readline call site. **Implement-time check**: smoke-test
    that rl.readline behaves correctly when called from
    `load_config_with_overlay` before `M.run` ever fires. If it
    misbehaves, fall back to a `printf "..." + read` shell-out for
    the trust prompt.

A9. **Walk-up performance is fine** — at most ~10 levels from a
    typical cwd to $HOME, each `io.open` is ~10us. Total walk
    cost < 1ms even on slow filesystems.

A10. **Trust file race**: two aish instances starting concurrently
     could double-write to `~/.aish/trusted-projects`. JSONL append
     semantics handle this OK (each writes one complete line); a
     duplicate trust entry is harmless. No flock needed (unlike
     memory.jsonl per Phase 4 where the writer SOR was important).

A11. **Sandboxed env for dofile?** Out of scope per §8. The trust
     prompt IS the gate; we accept full Lua execution post-trust.

A12. **Bootstrap chicken-egg**: project's `.aish.lua` could set
     `secrets.vault` which would change WHICH secrets are loaded.
     A12 paths through cleanly: user config loaded → project
     overlay merged → effective config passed to M.run → M.run
     reads `config.secrets.vault` (now possibly the project's) →
     secrets_session built. Order is correct; no chicken-egg.

**Baseline finding:**

B1. `sha256sum` (GNU coreutils 9.7) and `openssl dgst -sha256` agree
    bit-for-bit on the same input file. Both present on noether.
    sha256sum chosen for simpler output parsing (digest in first
    whitespace-separated field; openssl needs `awk '{print $NF}'`).
    Per A3 resolution; documented in Q-P2.

PHASE0 is the locked substrate; PHASE1-8 are layered on top. This manifest
specifies what Phase 9 adds — **project-local config overlay (`.aish.lua`)**:
a per-project config file in or above cwd that merges onto the user's
global config, letting a repo ship its own permission rules, model
presets, skills, hooks, etc. without modifying anyone's `~/.config`.

PHASE0 §11 amendment to add the Phase 9 row lands in the same commit as
this formulate doc.

---

## 1. Scope of Phase 9

Four pillars:

1. **Project-config resolution + walk-up** — at startup, walk up
   from cwd looking for `.aish.lua`. Walk stops at the first found
   file OR at `$HOME` OR at filesystem root (whichever comes first —
   filesystem-root reached without a hit means "no project config").
   The found path is the project layer; absence is a no-op (existing
   resolution path unchanged for users who don't ship project config).

2. **Merge semantics (shallow over user-config)** — load the global
   config first, then `dofile` the project `.aish.lua` and merge its
   top-level keys ONTO the user config. Shallow merge: project's
   `models = {...}` REPLACES the user's entire `models` block (not
   per-model). Predictable; users who want to add ONE model layer
   it deliberately or write a complete `models` block in their
   project file.

3. **Trust prompt + persistent record** — first time aish encounters
   a `.aish.lua` at a given path, prompt the user to trust it
   (`[aish] trust <path>? [y/N]`). On `y`, record the path's
   absolute path AND content hash in `~/.aish/trusted-projects`
   (one JSON line per entry: `{path, sha256, ts}`). On subsequent
   startups: load only if the recorded hash still matches; if the
   file changed since trust, re-prompt. On `n` or empty: skip the
   project layer for this session.

4. **`:config show` meta** — print the resolved config sources
   (which file contributed which top-level key), plus a sanitized
   dump of the effective config (token-bearing fields like
   `auth_token` masked). Useful for debugging when "why doesn't
   my project policy apply?" comes up.

**Phase 9 is done when:**

- A repo with `.aish.lua` in its root opens correctly: aish prompts
  to trust on first encounter, loads + merges on subsequent startups
  (when the hash still matches), and the resulting config behavior
  visibly reflects the project layer (e.g., project-set
  `permissions = { allow = ... }` allow-rules fire).
- `.aish.lua` walk-up finds the file from a nested cwd (e.g.,
  `~/src/aish/docs/` finds `~/src/aish/.aish.lua`).
- Walking past `$HOME` stops (doesn't search `/home/` or `/`).
- Mutating a trusted `.aish.lua` re-prompts (hash mismatch).
- `:config show` lists each source path with the keys it provided.
- Existing configs without any `.aish.lua` behave like Phase 8
  (Phase 8 regression coverage).

---

## 2. Technology Decisions (delta from Phase 8)

| Decision | Choice | Rationale |
|---|---|---|
| Walk-up start | `libc.getcwd()` at startup | Matches existing convention (Phase 6 `:tree` cwd capture). |
| Walk-up stop | `$HOME` OR filesystem root | Don't search outside the user's home — limits attack surface. If no `.aish.lua` between cwd and $HOME, no project layer. |
| Project file name | `.aish.lua` (dotfile) | Matches `.envrc` / `.tool-versions` convention; gitignore-friendly. |
| Merge semantics | Shallow top-level | Predictable; deep merge surprises users when they redefine an array (Lua tables-as-arrays don't merge cleanly). Project users who want to add a single MCP server can copy the user's full `mcp = {...}` block and append. |
| Trust mechanism | Explicit prompt; persist absolute-path + sha256 to `~/.aish/trusted-projects` | Matches `direnv allow` posture. Defense against hostile cloned repos that ship malicious `.aish.lua` (would-be RCE on `cd` + `aish` start). |
| Re-prompt trigger | sha256 mismatch on the recorded path | Trust the BYTES, not just the path — content change = re-prompt. |
| Trust file format | JSONL: `{path, sha256, ts}` per line | Append-only; readable; trivially manageable by hand. |
| Trust file mode | 0600 (matches secrets vault in Phase 5/13) | Local-user trust scope; not a secret per se but defensive. |
| `dofile` execution context | Whatever `dofile` provides (full Lua env) | Project file is arbitrary Lua because that's what the user accepted at trust-prompt. No sandbox; the prompt is the gate. |
| Reload on cd | NO — config resolved at startup only | Mid-session config mutation is a complexity tax. `cd` into a different project means restarting aish. Document. |
| Status line on load | `[aish] project config: <path> (overlaid on <user-config>)` at startup | Visibility — user always knows when project layer is active. |
| `:config show` shape | Lists each source path with the top-level keys it contributed | Diagnoses "why isn't my project rule applying?" cases. Token-bearing fields masked (`auth_token: <set>` rather than the value). |

---

## 3. Module Changes

| File | State after Phase 8 | Phase 9 changes |
|---|---|---|
| `main.lua` | `load_config(opts)` walks $AISH_CONFIG → ~/.config/aish → ./config.lua | Wrap with `load_with_project_overlay(opts)` that finds the user config (existing logic) AND walks up from cwd for `.aish.lua`; if both found, merge project ONTO user and return merged. Records source-per-key for `:config show`. |
| `ffi/libc.lua` | getcwd, chdir, isatty, flock | **No change** (per A2): `io.open(candidate, "rb")` is sufficient for existence-check during walk-up. No new FFI bindings needed. |
| `repl.lua` | All the metas including `:config` (nope — no :config yet) | New `:config show` meta. Source-map carried on a module-local set at startup; meta reads it. |
| `history.lua` | session log, memory.jsonl | New helpers: `M.read_trusted(path)` returns set of trusted entries; `M.add_trusted(path, target_path, sha256)` appends. Mode 0600 enforced. |
| `config.lua` (the user's global; not the in-tree example) | n/a | No change. The in-tree `config.lua` becomes a template that project overlays can replace top-level keys of. |
| `docs/PHASE0.md` | §11 lists phases 0-8; §10 resolution order | Amendment: add Phase 9 row to §11; update §10 to mention project overlay. |

No new module files in v1. The hashing logic (sha256) — `openssl dgst -sha256` shelled out (or use `sha256sum`). Both POSIX-portable. Avoid vendoring a Lua sha256 since we already have `openssl` / `sha256sum` available everywhere aish runs.

---

## 4. Pillar 1+2 — Resolution + Merge

### Walk-up

```lua
local function _find_project_config()
    local libc = require("ffi.libc")
    local home = os.getenv("HOME")
    if not home then return nil end
    local dir = libc.getcwd()
    if not dir then return nil end

    -- R1: don't walk OUTSIDE $HOME. The proper-prefix check requires
    -- `dir == home` OR `dir starts with home .. "/"` — bare
    -- `sub(1, #home) == home` matches "/home/user2" when HOME is
    -- "/home/user" (10-byte prefix). Real bug caught by review.
    if dir ~= home and dir:sub(1, #home + 1) ~= home .. "/" then
        return nil
    end

    while dir and #dir > 0 do
        local candidate = dir .. "/.aish.lua"
        local f = io.open(candidate, "r")
        if f then f:close(); return candidate end
        if dir == home or dir == "/" then return nil end
        -- Walk up one level
        dir = dir:gsub("/[^/]*$", "")
        if dir == "" then dir = "/" end
    end
    return nil
end
```

### Merge

```lua
local function _merge_project_over_user(user_cfg, project_cfg, sources)
    -- Shallow merge: project top-level keys REPLACE user keys.
    -- Source-map tracks who set each key for :config show.
    for k, v in pairs(project_cfg) do
        user_cfg[k] = v
        sources[k] = "project"
    end
    -- (sources for unmodified user keys stay "user")
    return user_cfg
end
```

### Loader wrapper

```lua
local function load_config_with_overlay(opts)
    -- Existing load_config returns (user_cfg, user_path)
    local user_cfg, user_path = load_config(opts)

    local sources = {}
    for k, _ in pairs(user_cfg) do sources[k] = "user" end

    local proj_path = _find_project_config()
    if not proj_path then
        return user_cfg, sources, { user = user_path }
    end

    -- Trust check
    local trusted = _check_trusted(proj_path)
    if not trusted then
        if not _prompt_trust(proj_path) then
            -- declined; skip project layer
            return user_cfg, sources, { user = user_path, project = "(declined)" }
        end
    end

    local ok, proj_cfg = pcall(dofile, proj_path)
    if not ok or type(proj_cfg) ~= "table" then
        renderer.status("project config " .. proj_path .. " failed to load; ignoring")
        return user_cfg, sources, { user = user_path, project = "(load failed)" }
    end

    _merge_project_over_user(user_cfg, proj_cfg, sources)
    return user_cfg, sources, { user = user_path, project = proj_path }
end
```

Source map is then carried as a closure local in `repl.run` for `:config show`.

---

## 5. Pillar 3 — Trust prompt + persistent record

### Trust file shape

`~/.aish/trusted-projects` (mode 0600), JSONL:

```jsonl
{"path":"/home/user/src/aish/.aish.lua","sha256":"abc123...","ts":"2026-05-16T12:34:56Z"}
{"path":"/home/user/src/other/.aish.lua","sha256":"def456...","ts":"2026-05-16T12:40:00Z"}
```

### Trust check + prompt (R4 + R5 — calls history.lua API; sha computed once)

```lua
-- R5: trust-file path resolves through history.lua + optional env override.
-- main.lua never reads/writes the trust file directly.
local function _trust_file_path()
    return os.getenv("AISH_TRUST_FILE")
        or ((os.getenv("HOME") or "") .. "/.aish/trusted-projects")
end

-- R4 + R5: compute sha ONCE; pass to history.is_trusted / add_trusted.
local function _check_and_maybe_prompt(project_path)
    local sha = history._sha256_file(project_path)
    if not sha then
        renderer.status("project config "..project_path..": sha256 failed; skipping")
        return false
    end
    local tpath = _trust_file_path()
    if history.is_trusted(tpath, project_path, sha) then
        return true
    end
    renderer.status("project config found: " .. project_path)
    renderer.status("UNTRUSTED. Loading it runs arbitrary Lua code.")
    local ans = rl.readline("[aish] trust this project config? [y/N] ")
    if ans and ans:lower():sub(1, 1) == "y" then
        history.add_trusted(tpath, project_path, sha)
        return true
    end
    return false
end
```

### sha256

`history._sha256_file(path)` shells out to `sha256sum <path>` and parses
the first whitespace-separated field. Single call per startup per
project file (R4 — `_check_and_maybe_prompt` computes once and passes
to both `history.is_trusted` and `history.add_trusted`).

---

## 6. Pillar 4 — `:config show`

```
[aish] config sources:
  user:    ~/.config/aish/config.lua
  project: ~/src/aish/.aish.lua
[aish] effective config (top-level keys):
  default_model   : "fast"          (user)
  models          : {fast, cloud}   (project)
  shell           : {confirm_cmd=true, ...} (user)
  permissions     : {allow={...}, ...}  (project)
  hooks           : (unset)
  ...
```

Token-bearing fields (any key matching `token`, `secret`, `auth`,
`key`, case-insensitive) displayed as `(set)` rather than the value.

R6 — `:config show full` applies the SAME heuristic RECURSIVELY to
nested values (the actual leak vector is `mcp.servers.<alias>.auth_token`
which top-level mode collapses but full mode would dump).

Known cosmetic false-positive (N2): `key_env` / `auth_env` config
fields are over-masked. These hold env-var NAMES (e.g. `OPENAI_API_KEY`)
not the secret values themselves — but the heuristic catches them.
Future polish: exempt `*_env` from the heuristic.

---

## 7. UX Surface Summary

| Meta | Behavior |
|---|---|
| `:config show` | Print resolved sources + sanitized effective config (read-only) |

| Startup status | Behavior |
|---|---|
| (no project file) | nothing — existing UX preserved |
| (project file found, untrusted) | `[aish] project config found: <path>` + `[aish] UNTRUSTED. Loading it runs arbitrary Lua.` + `[y/N]` prompt |
| (project file found, trusted, sha matches) | `[aish] project config: <path> (overlaid on <user>)` |
| (project file found, trusted, sha CHANGED) | re-prompt — bytes are different now |
| (declined this session) | `[aish] project config: <path> (declined this session)` |

No new config keys in v1 (the project overlay IS the new mechanism; it doesn't need a config flag to be enabled).

---

## 8. Out of Scope (Phase 9)

- **Sandboxed `.aish.lua` execution** — `dofile` runs full Lua; the
  trust prompt IS the gate. A sandbox (allowlisted globals,
  no `io.popen`, etc.) is bigger work and out of scope.
- **Reload on `cd`** — config is resolved at startup only. `cd`
  into a sibling project means restarting aish. Documented.
- **Recursive merge** — top-level shallow only.
- **Multiple project overlays** — walk-up stops at FIRST `.aish.lua`
  found. Nested projects (e.g., monorepo with per-package configs)
  would need deeper design; defer.
- **`:trust` / `:untrust` metas for runtime management** — trust
  records edited manually in `~/.aish/trusted-projects` for v1. A
  meta surface is a v2 polish.
- **Environment variable expansion in project file** — project file
  is plain Lua; users have `os.getenv` already.
- **Project-wide aish profile selection** — `.aish.lua` returns a
  config table, not a profile name. If multi-profile support is
  desired, the project file can compute a different config based
  on its OWN env vars / heuristics.

---

## 9. Risks

| Risk | Mitigation |
|---|---|
| Hostile `.aish.lua` in cloned repo runs arbitrary Lua on first `aish` run in that cwd | Trust prompt + sha256 persistence; default = decline if user just hits Enter at the [y/N]. |
| Trust file becomes corrupted / unreadable | Best-effort: corrupted lines skipped (each line is independent JSON); missing file means all projects untrusted (re-prompt on next encounter). N4 edge case: if the FIRST-EVER write is interrupted partway, the file's sole line may be corrupt JSON and the project never stays trusted — user manually deletes `~/.aish/trusted-projects` to recover. Temp-file+rename atomicity is v2 polish. |
| User trusts `.aish.lua`, repo is updated, malicious code is injected | sha256 mismatch on next startup triggers re-prompt. User sees the prompt and can investigate before granting trust again. |
| `dofile` errors at load time (syntax error in project config) | pcall-protected; status line "project config X failed to load; ignoring" — aish continues with just the user config. |
| Walk-up walks above $HOME (e.g., a repo cloned to `/tmp`) | $HOME boundary check stops the walk. `/tmp` repos get no project layer (user can move them under $HOME or use --config). |
| **R7 — shallow merge silently DROPS the user's entire block on overlap.** A `.aish.lua` that sets `models = {...}` REPLACES the user's full models block; same for `permissions`, `cost`, `shell`, etc. This is a genuine UX trap, not just "predictable" — accept-and-warn-clearly is the resolution rather than hiding behind framing. | Conspicuous warning in §1 done-when + §7 UX table + config.lua template header: "If your `.aish.lua` sets a top-level block (models, permissions, cost, ...) it REPLACES your user config's entire block — list every entry you want available OR omit the block to keep the user's." Deep-merge-with-explicit-replace-syntax (systemd drop-in style) is v2 polish. |
| Source map dict grows unboundedly with new keys mid-session | Bounded by #config top-level keys (small constant; <20). No GC needed. |

---

## 10. Open Questions (Phase 9)

| # | Question | Impact | Resolution target |
|---|---|---|---|
| Q-P1 | Trust prompt before/after `aish: loaded config` status | A4 — **AFTER**; user sees user-config first, then decides about overlay. |
| Q-P2 | sha256 backend choice | B1 RESOLVED — `sha256sum` (GNU coreutils; universal on Linux); simpler output parsing than openssl. |
| Q-P3 | Log walk-up path | A5 — **no by default**; `:config show` reveals walk result on demand. Verbose-mode walk log is v2 polish. |
| Q-P4 | rl.readline safe at startup | A8 — DEFERRED to implement-time smoke (Phase 4 metas call rl.readline early too; new wrinkle is firing BEFORE main loop opens). If issue, fall back to printf+read shell-out. |
| Q-P5 | `:config show` full vs top-level | A6 — **top-level by default** (nested collapsed to inner keys); `:config show full` for deep dump. |
| Q-P6 | Project layer setting `secrets.vault` security | A7 — **allowed**; part of the trust prompt's scope. Bootstrap order (A12) ensures project's vault is honored if set. |

---

## 11. Phase 9 → Phase 10+ Out-of-band

Candidate follow-ups (non-binding):

- **Phase 10 candidates**:
  - Cost preflight enforcement (Phase 7 §12 option 2; Phase 8 §11 candidate).
  - Cross-session cost rollup (Phase 7 §12 option 1; Phase 8 §11 candidate).
  - `:trust` / `:untrust` metas for runtime trust management.
  - Sandboxed `.aish.lua` execution (allowlisted Lua globals).
- **Phase X+**: nested project overlays for monorepos; `:profile`
  switching; reload-on-cd.

Phase 9 itself is self-contained — depends on no specific prior phase
beyond the existing config loader.

---

## 13. Implementation Plan (commit-by-commit)

4 commits, bottom-up:

1. **`history.lua` — trust file helpers.**
   - `M.read_trusted(path)` -> list of `{path, sha256, ts}`
     entries; mode-check the file at 0600, refuse to load (warn)
     if wider. Missing file → empty list.
   - `M.add_trusted(trust_path, project_path, sha256)` appends a
     JSONL line; mkdir -p the parent if needed; chmod 0600.
   - `M.is_trusted(trust_path, project_path, sha256)` reads + checks
     for matching entry.
   - Internal `_sha256_file(path)` shells out to `sha256sum` and
     parses the first whitespace-separated field.
   - Smoke: 5 inline unit cases (read empty, add+read-back, mode
     check, sha mismatch returns false, missing file).

2. **`main.lua` — walk-up + load_with_project_overlay.**
   - `_find_project_config()` walks from libc.getcwd() up to $HOME
     (R1 corrected proper-prefix check), returning first `.aish.lua`
     or nil.
   - `_check_and_maybe_prompt(project_path)` (R4 + R5) calls
     `history._sha256_file` ONCE; routes through `history.is_trusted`
     / `history.add_trusted` with the env-overridable trust file
     path. Returns true if the project file should be loaded.
   - `load_config_with_overlay(opts)` wraps existing `load_config`;
     finds project, checks trust, prompts if needed, dofiles +
     merges shallow over user config. **R2: in one-shot mode
     (`opts.prompt` is set), the trust prompt is SKIPPED entirely
     — the project layer is only loaded if it's already pre-trusted.
     Avoids io.read consuming the first line of piped stdin.**
   - **R3 sources delivery: embed on `config._sources`** (a sentinel
     field on the config table itself). NOT a global. `repl.run`
     reads `config._sources` for `:config show`; backward-compatible
     (old callers without _sources are reported as "(sources
     unknown)" by the meta).
   - Smoke: (a) tree-resolution from a nested cwd; (b) trust prompt
     accept-then-load + decline-then-skip paths; (c) -p mode with
     untrusted .aish.lua + piped stdin -> trust prompt SKIPPED, no
     stdin consumption; (d) A8: rl.readline early-startup smoke;
     if rl.readline misbehaves, NO fallback to io.read in
     interactive mode either — emit status + skip overlay (avoids
     the silent-data-loss risk R2 covers).

3. **`repl.lua` — `:config show` meta + startup status line.**
   - `:config show` / `:config show full` meta reads `config._sources`
     (R3 cfg-embedded) + the effective config; sanitizes token-bearing
     values (any key containing "token"/"secret"/"auth"/"key",
     case-insensitive) → display as `(set)`. R6: in `full` mode,
     applies the heuristic RECURSIVELY to nested values (the real
     leak vector is `mcp.servers.<alias>.auth_token`).
     If `config._sources` is absent, status: "(sources unknown — main
     didn't pass _sources)" so the meta still runs but doesn't lie.
   - Startup status line per A4: AFTER the existing `aish: loaded
     config from <path>`, if project layer fired, emit
     `[aish] project config: <path> (overlaid on <user>)`.
   - HELP gains 2 `:config` lines.
   - N2 known false-positive: `key_env` / `auth_env` config field
     VALUES are masked too (they hold env-var names, not secrets).
     Cosmetic; future polish exempts `*_env`.
   - Smoke: with a test project file, run `:config show` and
     verify keys + sources line up; `:config show full` masks
     nested auth tokens but exposes other nested fields.

4. **`config.lua` template note + status bump.**
   - Add a header comment to `config.lua` (the in-tree example)
     noting Phase 9 project-overlay availability (no other config
     change — overlay is a separate file).
   - PHASE9.md status header -> **Implement**.

### Risk index per commit

| Commit | Risk | Mitigation |
|---|---|---|
| 1 (history) | sha256sum not installed (some minimal images) | Detect at startup; if missing, warn + decline all trust prompts (project layer disabled). Documented. |
| 1 (history) | Trust file partial write (interrupted append) corrupts later parse | JSONL one-line-per-entry; partial line at EOF is skipped on read (each line is a single json.decode). |
| 2 (main) | A8 — rl.readline at startup (before main loop) untested in earlier phases | Smoke-test at commit-time; if broken, fall back to `io.read("*l")` from stdin (no readline frills like ^C-handling but functional). |
| 2 (main) | Walk-up symlink loops | `realpath`/`stat` defenses out of scope for v1; walk is bounded by $HOME stop. Pathological symlinks could waste cycles but not infinite-loop (every iteration strips a path component). |
| 3 (repl) | :config show might leak token values if a config key isn't matched by the masking heuristic | Conservative mask: any key containing "token", "secret", "auth", "key" (case-insensitive) → display `(set)`. Errs toward over-masking. |
| 4 (config + status) | None | |

### Tests + smoke per commit

Each commit:
- Pass `luajit test_safety.lua` (87/87) and `luajit test_router_model.lua` (31/31)
- Load cleanly via `luajit -e 'package.path=...; require("repl"); print("ok")'`
- Pass a per-feature smoke (described per row above)

### Things deliberately NOT split

- Separate `project.lua` module — small enough; history.lua already
  handles file-with-mode-check (memory.jsonl); same shape.
- :trust / :untrust runtime metas — manual ~/.aish/trusted-projects
  editing is fine for v1.
- Walk-up logging on first startup — easy to add later if needed.

### Open at plan-time (resolve at implement)

- A8: rl.readline early-startup behavior. R2 supersedes the
  formulate-time io.read fallback — if rl.readline misbehaves,
  emit status + skip the overlay entirely (NOT a fallback to
  stdin which would consume piped data in -p mode).
- `$AISH_TRUST_FILE` env override — RESOLVED: implement it (one
  line; useful for CI / test isolation). Used by the verify TCs.
- N3 — sources-map delivery RESOLVED: embed on `config._sources`
  (cfg-field; not a global). Per R3.