release: v0.1.6

Since v0.1.5:
- fix(messages): Claude models no longer 400 with 'Invalid signature in
  thinking block' — thinking is replayed only for the active tool loop
  and only when genuinely signed (cross-backend/cross-model histories
  are stripped)
- fix(codex): ChatGPT Codex no longer 400s with 'System messages are
  not allowed' — system prompts ride the instructions field and
  encrypted reasoning is requested for stateless replay
- docs: AGENTS.md records both wire contracts

.github/workflows/warm-cache.yml

@@ -0,0 +1,85 @@
+name: Warm build cache
+
+# Release builds run on TAG refs, and GitHub Actions cache isolation only
+# lets a run restore caches created on its OWN ref or the DEFAULT branch.
+# No workflow ran on `main`, so every release compiled the whole workspace
+# cold on all five targets (~50 min wall clock, gated by Windows). This
+# workflow builds the same `release-dist` profile on `main` so tag builds
+# restore a warm default-branch cache.
+#
+# Triggers: dependency-affecting pushes to main (each release's version-bump
+# commit warms the cache for the NEXT release), a weekly refresh so the
+# cache never hits GitHub's 7-day unused-eviction, and manual dispatch.
+#
+# The setup steps mirror release.yml's build job (toolchain, target,
+# dotslash/protoc, rust-cache key) — keep them in lockstep, or the cache
+# key won't match and releases go back to cold builds.
+
+on:
+  push:
+    branches: ["main"]
+    paths:
+      - "Cargo.lock"
+      - "Cargo.toml"
+      - "rust-toolchain.toml"
+      - ".github/workflows/warm-cache.yml"
+  schedule:
+    - cron: "17 5 * * 1"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+env:
+  CARGO_TERM_COLOR: always
+
+concurrency:
+  group: warm-cache
+  cancel-in-progress: true
+
+jobs:
+  warm:
+    name: warm (${{ matrix.target }})
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - target: aarch64-apple-darwin
+            os: macos-14
+          - target: x86_64-apple-darwin
+            os: macos-14
+          - target: x86_64-unknown-linux-gnu
+            os: ubuntu-24.04
+          - target: aarch64-unknown-linux-gnu
+            os: ubuntu-24.04-arm
+          - target: x86_64-pc-windows-msvc
+            os: windows-2022
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install toolchain (rust-toolchain.toml)
+        run: rustup show
+
+      - name: Add build target
+        run: rustup target add ${{ matrix.target }}
+
+      - name: Install dotslash (protoc launcher)
+        run: cargo install dotslash --locked
+
+      - name: Install protoc (Windows PATH fallback)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.3/protoc-29.3-win64.zip"
+          Invoke-WebRequest -Uri $url -OutFile protoc.zip
+          Expand-Archive protoc.zip -DestinationPath "$env:USERPROFILE\protoc"
+          Add-Content $env:GITHUB_PATH "$env:USERPROFILE\protoc\bin"
+
+      # Same key as release.yml so tag builds restore this cache verbatim.
+      - uses: Swatinem/rust-cache@v2
+        with:
+          key: ${{ matrix.target }}
+
+      - name: Build kigi (release-dist)
+        run: cargo build --profile release-dist -p kigi-bin --locked --target ${{ matrix.target }}

AGENTS.md

@@ -32,9 +32,19 @@ import) or any `KIMI_*` env var.
 - **Observability is local**: `kigi-log` (unified session log, `--debug`
   firehose, subsystem file logs, opt-in instrumentation) writes under
   `~/.kigi` only. Its zero-network property is a contract.
+- **Atomic file replace goes through `util::fs::replace_file`** (tmp+rename
+  commit step; async callers wrap in `spawn_blocking`). Never inline a bare
+  `fs::rename` replace: Windows `MoveFileExW(REPLACE_EXISTING)` fails with a
+  sharing violation while AV/indexer/cloud-sync holds the destination open —
+  the "persists on macOS, silently doesn't on Windows" class (a /model
+  switch that never stuck). Plain rename stays correct only for true moves
+  whose destination doesn't pre-exist (worktree-pool markers, corrupt-file
+  backups). Write failures must at least `warn!` — never `let _ =`.
 - The root `Cargo.toml` is hand-maintained (upstream's generator is not in
   this repo). Members sorted; versions inherited from
-  `workspace.package.version` (0.1.0).
+  `workspace.package.version` — the single source of truth for the release
+  version (`kigi_version::VERSION` derives from it; the release workflow
+  gates the `v*` tag against it).
 
 ## Layout
 
@@ -79,8 +89,9 @@ node as one ordinary goal — the agentic loop lives INSIDE the node; the
 edges stay deterministic Rust. The harness appends a terminal
 `gn-final` verification node depending on every planner node.
 
-- Feature flag `KIGI_GRAPH=1` (default off); availability additionally
-  requires the goal harness (`BuiltinGate::Graph`).
+- Enabled by default (`KIGI_GRAPH=0` is the off-switch; the G0 gray
+  release is over); availability additionally requires the goal harness
+  (`BuiltinGate::Graph`).
 - Key modules (kigi-shell): `session/graph_tracker.rs` (pure state
   machine; reuses `GoalStatus`/`GoalPhase`/`GoalPauseReason`),
   `session/graph_plan.rs` (planner-JSON contract + validation + fnv id
@@ -209,7 +220,14 @@ edges stay deterministic Rust. The harness appends a terminal
       system prefix — gated on `SamplerConfig.anthropic_oauth` (claude-pro-max
       only), so API-key `anthropic`/`minimax` Messages requests stay
       byte-identical. Its `/v1/models` listing rides the same Bearer +
-      oauth-beta headers.
+      oauth-beta headers. THINKING REPLAY (`prune_replayed_thinking`,
+      all Messages requests): Anthropic validates every replayed
+      `thinking` block (signature model-bound, non-empty required), so
+      only the final assistant message's signed thinking is replayed and
+      only while its tool loop is open (request ends on the tool
+      results); everything else — unsigned cross-backend history, `tco_*`
+      Responses blobs, stale-model blocks — is stripped, or the request
+      400s "Invalid `signature` in `thinking` block".
     - `openai-codex` (ChatGPT Plus/Pro, `scope_key oauth/openai-codex`, port
       1455 `/auth/callback`, FORM body, authorize+token host `auth.openai.com`,
       client `app_EMoam…`, scope `openid profile email offline_access`, the 3
@@ -226,9 +244,15 @@ edges stay deterministic Rust. The harness appends a terminal
       `PlatformId::sends_codex_responses_headers()`): headers
       `chatgpt-account-id` (per-request from the JWT), `originator codex_cli_rs`,
       `OpenAI-Beta responses=experimental`, a codex `User-Agent`; `store:false`
-      is the shared Responses default. API-key `openai` Responses requests carry
-      NONE of this (byte-identical). `reasoning.effort` carries the thinking
-      level (incl. the codex-only `ultra`). NO websocket, NO base_instructions.
+      is the shared Responses default. BODY adaptation
+      (`adapt_body_for_codex_backend`, same gate): the backend 400s
+      `role:system` input ("System messages are not allowed") — system items
+      are hoisted into the top-level `instructions` field — and stateless
+      reasoning replay requires `include:["reasoning.encrypted_content"]`.
+      API-key `openai` Responses requests carry NONE of this
+      (byte-identical, pinned by a control wire test). `reasoning.effort`
+      carries the thinking level (incl. the codex-only `ultra`). NO
+      websocket, NO base_instructions.
       CATALOG is HARDCODED (`PlatformId::hardcoded_catalog` →
       `openai_codex_wire_models`, mapped through the SAME
       `platform_wire_model_to_entry` output): exactly the 4 `visibility=list` &&

Cargo.lock

@@ -5442,7 +5442,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-acp-lib"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "async-trait",
@@ -5456,7 +5456,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-agent"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "chrono",
  "dirs 6.0.0",
@@ -5486,7 +5486,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-agent-lifecycle"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "async-trait",
  "tokio",
@@ -5495,7 +5495,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-auth"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "async-trait",
  "http 1.4.2",
@@ -5508,7 +5508,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-bin"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "clap",
@@ -5543,7 +5543,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-chat-state"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "indexmap",
  "kigi-compaction",
@@ -5560,7 +5560,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-codebase-graph"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "ahash",
  "clap",
@@ -5596,7 +5596,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-compaction"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -5609,7 +5609,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-config"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "base64",
  "blake3",
@@ -5632,7 +5632,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-config-types"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "indexmap",
@@ -5646,7 +5646,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-crash-handler"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "backtrace",
  "libc",
@@ -5657,7 +5657,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-env"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "tracing",
  "url",
@@ -5665,7 +5665,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-fast-worktree"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "bytes",
@@ -5697,7 +5697,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-file-utils"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "aws-config",
@@ -5721,7 +5721,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-fsnotify"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "criterion",
  "dunce",
@@ -5742,7 +5742,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-gix-status"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "gix",
  "kigi-test-utils",
@@ -5752,7 +5752,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-hooks"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "fastrand",
  "kigi-config",
@@ -5771,7 +5771,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-hooks-plugins-types"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "serde",
  "serde_json",
@@ -5779,7 +5779,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-http"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "kigi-auth",
  "kigi-log",
@@ -5794,7 +5794,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-hunk-tracker"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "chrono",
  "dunce",
@@ -5815,14 +5815,14 @@ dependencies = [
 
 [[package]]
 name = "kigi-interjection-core"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "kigi-log"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "chrono",
@@ -5840,7 +5840,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-markdown"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anstyle",
  "anstyle-lossy",
@@ -5864,14 +5864,14 @@ dependencies = [
 
 [[package]]
 name = "kigi-markdown-core"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "pulldown-cmark",
 ]
 
 [[package]]
 name = "kigi-mcp"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "async-trait",
@@ -5908,7 +5908,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-memory"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "arc-swap",
@@ -5942,7 +5942,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-mermaid"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "fontdb",
  "image",
@@ -5960,7 +5960,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-models"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "kigi-env",
  "serde",
@@ -5970,7 +5970,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-pager-minimal"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "chrono",
  "crossterm",
@@ -5987,7 +5987,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-pager-pty-harness"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "alacritty_terminal",
  "anyhow",
@@ -6012,7 +6012,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-pager-render"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "anstyle",
@@ -6064,7 +6064,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-paths"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "camino",
  "serde",
@@ -6074,7 +6074,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-prompt-queue"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "serde",
  "serde_json",
@@ -6082,7 +6082,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-proto-build"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "pbjson-build",
@@ -6093,7 +6093,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-ratatui-inline"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "ansi-width",
  "anstyle-parse 0.2.7",
@@ -6110,7 +6110,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-ratatui-textarea"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "arboard",
  "chrono",
@@ -6131,7 +6131,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-sampler"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "async-openai",
  "async-stream",
@@ -6154,7 +6154,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-sampling-types"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "assert_matches",
  "async-openai",
@@ -6171,7 +6171,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-sandbox"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "chrono",
@@ -6192,7 +6192,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-secrets"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "regex",
  "serde_json",
@@ -6230,7 +6230,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-shell"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "anyhow",
@@ -6367,7 +6367,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-shell-base"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "chrono",
@@ -6392,7 +6392,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-sqlite-journal"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "libc",
  "rusqlite",
@@ -6403,7 +6403,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-subagent-resolution"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "kigi-sampling-types",
  "kigi-tool-types",
@@ -6418,7 +6418,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-system-power"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "windows-sys 0.59.0",
  "zbus",
@@ -6426,7 +6426,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-test-support"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "anyhow",
@@ -6448,7 +6448,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-test-utils"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "runfiles",
  "tracing",
@@ -6457,11 +6457,11 @@ dependencies = [
 
 [[package]]
 name = "kigi-token-estimation"
-version = "0.1.4"
+version = "0.1.6"
 
 [[package]]
 name = "kigi-tool-protocol"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "kigi-tool-types",
  "serde",
@@ -6472,7 +6472,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-tool-runtime"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -6490,7 +6490,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-tool-types"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "minijinja",
  "schemars 1.2.1",
@@ -6500,7 +6500,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-tools"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "arc-swap",
@@ -6577,7 +6577,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-tools-api"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "kigi-proto-build",
  "kigi-tool-protocol",
@@ -6590,11 +6590,11 @@ dependencies = [
 
 [[package]]
 name = "kigi-tracing-macros"
-version = "0.1.4"
+version = "0.1.6"
 
 [[package]]
 name = "kigi-tty-utils"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "libc",
  "nix 0.30.1",
@@ -6604,7 +6604,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-tui"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "ansi-to-tui",
@@ -6691,7 +6691,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-update"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "dunce",
@@ -6720,14 +6720,14 @@ dependencies = [
 
 [[package]]
 name = "kigi-version"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "semver",
 ]
 
 [[package]]
 name = "kigi-workspace"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "agent-client-protocol",
  "anyhow",
@@ -6806,7 +6806,7 @@ dependencies = [
 
 [[package]]
 name = "kigi-workspace-types"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "base64",
  "chrono",
@@ -8840,7 +8840,7 @@ dependencies = [
 
 [[package]]
 name = "ptyctl"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "alacritty_terminal",
  "anyhow",
@@ -8858,7 +8858,7 @@ dependencies = [
 
 [[package]]
 name = "ptyctl-cli"
-version = "0.1.4"
+version = "0.1.6"
 dependencies = [
  "anyhow",
  "axum",

Cargo.toml

@@ -76,7 +76,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.1.4"
+version = "0.1.6"
 edition = "2024"
 license = "Apache-2.0"
 

crates/codegen/kigi-sampler/src/client.rs

@@ -1183,6 +1183,9 @@ impl SamplingClient {
         // old raw_output machinery.
         kigi_sampling_types::patch_reasoning_text_types(&mut request_body);
         kigi_sampling_types::patch_reasoning_effort(&mut request_body, request.reasoning_effort);
+        if self.defaults.openai_codex {
+            kigi_sampling_types::adapt_body_for_codex_backend(&mut request_body);
+        }
         let http_request = self.post(self.endpoint("responses")).json(&request_body);
 
         let response = http_request.send().await.map_err(|e| {
@@ -1321,6 +1324,9 @@ impl SamplingClient {
         }
         kigi_sampling_types::patch_reasoning_text_types(&mut request_body);
         kigi_sampling_types::patch_reasoning_effort(&mut request_body, request.reasoning_effort);
+        if self.defaults.openai_codex {
+            kigi_sampling_types::adapt_body_for_codex_backend(&mut request_body);
+        }
         // Fresh per attempt so signals never leak across retries; `None`
         // (check disabled) sends no header and does no peek work per event.
         let doom_loop = self

crates/codegen/kigi-sampling-types/src/conversation.rs

@@ -3201,6 +3201,8 @@ pub fn build_messages_request(req: &ConversationRequest) -> crate::messages::Mes
     flush_assistant(&mut pending_assistant, &mut messages);
     flush_tool_results(&mut pending_tool_results, &mut messages);
 
+    prune_replayed_thinking(&mut messages);
+
     // Attach cache_control: {type: "ephemeral"} to last system block
     if let Some(last) = system_blocks.last_mut() {
         last.cache_control = Some(CacheControl {
@@ -3290,6 +3292,74 @@ pub fn build_messages_request(req: &ConversationRequest) -> crate::messages::Mes
     }
 }
 
+/// Strip replayed `thinking` blocks the Anthropic Messages API would
+/// reject — keep exactly the one it requires.
+///
+/// Anthropic validates EVERY `thinking` block in the request: the
+/// signature is bound to the emitting model and must be non-empty, so
+/// history from another backend (`encrypted_content: None` replays as
+/// `signature: ""`), a Responses-API `tco_*` blob (signature bytes with no
+/// text), or a block signed by a DIFFERENT model after a mid-session
+/// `/model` switch 400s the whole request with
+/// "messages.N.content.0: Invalid `signature` in `thinking` block".
+///
+/// The API only NEEDS thinking for the ACTIVE tool-use continuation: the
+/// final assistant message whose tool_use results follow must carry its
+/// signed thinking back verbatim. Prior turns' thinking is ignored even
+/// when valid (Pi/Claude Code replay exactly this way). So: keep the
+/// final assistant message's thinking when the loop is open and the block
+/// is genuinely signed (non-empty text AND signature — an open loop can
+/// never span a model switch, so that signature is always the current
+/// model's); strip every other thinking block. An assistant message left
+/// EMPTY by the strip (a thinking-only aborted turn) is removed — the API
+/// rejects empty content arrays.
+fn prune_replayed_thinking(messages: &mut Vec<crate::messages::Message>) {
+    use crate::messages::{ContentBlock, MessageContent, MessageRole};
+    let last_assistant = messages
+        .iter()
+        .rposition(|m| matches!(m.role, MessageRole::Assistant));
+    let active_tool_loop = last_assistant.is_some_and(|i| {
+        let has_tool_use = matches!(
+            &messages[i].content,
+            MessageContent::Blocks(blocks)
+                if blocks.iter().any(|b| matches!(b, ContentBlock::ToolUse { .. }))
+        );
+        // The loop is OPEN only while the request ends on the tool results:
+        // a later plain user turn closes it (the results answered, the model
+        // replied — its thinking is history the API ignores or rejects).
+        let continuation = &messages[i + 1..];
+        let ends_on_results = !continuation.is_empty()
+            && continuation.iter().all(|m| {
+                matches!(
+                    &m.content,
+                    MessageContent::Blocks(blocks)
+                        if blocks.iter().any(|b| matches!(b, ContentBlock::ToolResult { .. }))
+                )
+            });
+        has_tool_use && ends_on_results
+    });
+    let mut index = 0;
+    messages.retain_mut(|m| {
+        let i = index;
+        index += 1;
+        if !matches!(m.role, MessageRole::Assistant) {
+            return true;
+        }
+        let MessageContent::Blocks(blocks) = &mut m.content else {
+            return true;
+        };
+        let keep_thinking = active_tool_loop && Some(i) == last_assistant;
+        blocks.retain(|b| match b {
+            ContentBlock::Thinking {
+                thinking,
+                signature,
+            } => keep_thinking && !thinking.is_empty() && !signature.is_empty(),
+            _ => true,
+        });
+        !blocks.is_empty()
+    });
+}
+
 /// Convert a MessagesResponse to a single Assistant `ConversationItem`.
 ///
 /// Note: Anthropic `Thinking` blocks are dropped here because this `From`
@@ -5332,6 +5402,160 @@ mod tests {
     /// messages while setting top-level `thinking: null` — the Messages API
     /// rejects this with a 400.  Verify that stripped reasoning produces a
     /// valid request with no thinking blocks in messages.
+    /// Collect `(message_index, thinking, signature)` for every thinking
+    /// block in a built Messages request.
+    fn thinking_blocks(json: &serde_json::Value) -> Vec<(usize, String, String)> {
+        let mut out = Vec::new();
+        for (i, m) in json["messages"].as_array().unwrap().iter().enumerate() {
+            if let Some(content) = m.get("content").and_then(|c| c.as_array()) {
+                for b in content {
+                    if b.get("type").and_then(|t| t.as_str()) == Some("thinking") {
+                        out.push((
+                            i,
+                            b["thinking"].as_str().unwrap_or_default().to_string(),
+                            b["signature"].as_str().unwrap_or_default().to_string(),
+                        ));
+                    }
+                }
+            }
+        }
+        out
+    }
+
+    fn reasoning(text: &str, encrypted: Option<&str>) -> ConversationItem {
+        ConversationItem::Reasoning(rs::ReasoningItem {
+            id: String::new(),
+            summary: if text.is_empty() {
+                vec![]
+            } else {
+                vec![rs::SummaryPart::SummaryText(rs::SummaryTextContent {
+                    text: text.to_string(),
+                })]
+            },
+            content: None,
+            encrypted_content: encrypted.map(str::to_owned),
+            status: None,
+        })
+    }
+
+    fn assistant_text(text: &str) -> ConversationItem {
+        ConversationItem::Assistant(AssistantItem {
+            content: text.into(),
+            tool_calls: vec![],
+            model_id: None,
+            model_fingerprint: None,
+            reasoning_effort: None,
+        })
+    }
+
+    /// Anthropic validates EVERY replayed `thinking` block: an unsigned one
+    /// (history synthesized by another backend replays as `signature: ""`),
+    /// a Responses `tco_*` blob (signature with no text), or a block signed
+    /// by a different model after a mid-session `/model` switch 400s the
+    /// whole request — "messages.N.content.0: Invalid `signature` in
+    /// `thinking` block". The API only NEEDS thinking for the active
+    /// tool-use continuation, so outside one the builder must replay NO
+    /// thinking blocks at all.
+    #[test]
+    fn messages_request_strips_thinking_outside_active_tool_loop() {
+        let req = ConversationRequest::from_items(vec![
+            ConversationItem::system("sys"),
+            ConversationItem::user("q1"),
+            // Cross-backend history: unsigned reasoning (the Windows repro —
+            // session started on another model, then switched to Claude).
+            reasoning("some thinking", None),
+            assistant_text("a1"),
+            ConversationItem::user("q2"),
+            // Responses-API blob: signature-shaped bytes, no text.
+            reasoning("", Some("tco_blob")),
+            assistant_text("a2"),
+            ConversationItem::user("q3"),
+            // Genuinely signed — but its tool loop (none) is closed, so the
+            // API ignores it when valid and 400s it after a model switch.
+            reasoning("signed thinking", Some("sig-real")),
+            assistant_text("a3"),
+            ConversationItem::user("q4"),
+        ]);
+        let json = serde_json::to_value(build_messages_request(&req)).unwrap();
+        assert_eq!(
+            thinking_blocks(&json),
+            vec![],
+            "no thinking block may be replayed outside an active tool loop:\n{json:#}"
+        );
+    }
+
+    /// The active tool-use continuation is the one place Anthropic REQUIRES
+    /// the signed thinking block back: the final assistant message issued
+    /// tool_use and its results follow. Exactly that block is kept; a
+    /// prior turn's signed thinking is still stripped.
+    #[test]
+    fn messages_request_keeps_signed_thinking_for_active_tool_loop() {
+        let req = ConversationRequest::from_items(vec![
+            ConversationItem::user("q0"),
+            reasoning("old turn", Some("sig-old")),
+            assistant_text("a0"),
+            ConversationItem::user("q1"),
+            reasoning("current turn", Some("sig-current")),
+            ConversationItem::Assistant(AssistantItem {
+                content: "".into(),
+                tool_calls: vec![ToolCall {
+                    id: std::sync::Arc::from("tc1"),
+                    name: "read_file".to_string(),
+                    arguments: std::sync::Arc::from("{}"),
+                }],
+                model_id: None,
+                model_fingerprint: None,
+                reasoning_effort: None,
+            }),
+            ConversationItem::tool_result("tc1", "file contents"),
+        ]);
+        let json = serde_json::to_value(build_messages_request(&req)).unwrap();
+        let blocks = thinking_blocks(&json);
+        assert_eq!(
+            blocks.len(),
+            1,
+            "exactly the active loop's thinking survives:\n{json:#}"
+        );
+        let (msg_idx, thinking, signature) = &blocks[0];
+        assert_eq!(thinking, "current turn");
+        assert_eq!(signature, "sig-current");
+        // It sits at content.0 of the final assistant message.
+        let msg = &json["messages"].as_array().unwrap()[*msg_idx];
+        assert_eq!(msg["role"], "assistant");
+        assert_eq!(msg["content"][0]["type"], "thinking");
+        assert!(
+            msg["content"]
+                .as_array()
+                .unwrap()
+                .iter()
+                .any(|b| b["type"] == "tool_use"),
+            "the kept thinking belongs to the tool_use turn"
+        );
+    }
+
+    /// A thinking-only assistant turn (aborted before any text/tool output)
+    /// must not survive as an EMPTY assistant message after the strip —
+    /// Anthropic rejects empty content arrays.
+    #[test]
+    fn messages_request_drops_assistant_message_emptied_by_thinking_strip() {
+        let req = ConversationRequest::from_items(vec![
+            ConversationItem::user("q"),
+            reasoning("aborted turn thinking", Some("sig")),
+            assistant_text(""),
+            ConversationItem::user("follow-up"),
+        ]);
+        let json = serde_json::to_value(build_messages_request(&req)).unwrap();
+        for m in json["messages"].as_array().unwrap() {
+            if let Some(content) = m.get("content").and_then(|c| c.as_array()) {
+                assert!(
+                    !content.is_empty(),
+                    "no message may ship an empty content array:\n{json:#}"
+                );
+            }
+        }
+        assert_eq!(thinking_blocks(&json), vec![]);
+    }
+
     #[test]
     fn test_btw_stripped_reasoning_produces_no_thinking_blocks() {
         // Simulate a conversation where the model responded with thinking.

crates/codegen/kigi-sampling-types/src/types.rs

@@ -1041,6 +1041,71 @@ pub fn patch_reasoning_effort(body: &mut Value, effort: Option<ReasoningEffort>)
     }
 }
 
+/// Adapt a serialized Responses request body to the ChatGPT/Codex backend
+/// contract (`chatgpt.com/backend-api/codex/responses`) — ported from the
+/// same reference as the identity headers (official Codex CLI + Pi's
+/// `api/openai-codex-responses.ts`):
+///
+/// 1. The backend rejects `role: system` input items outright
+///    (400 `{"detail":"System messages are not allowed"}`); its system
+///    channel is the top-level `instructions` field. Hoist every system
+///    input message there (order preserved, blank-line joined, appended to
+///    any existing instructions) and remove them from `input`.
+/// 2. `store` is always `false` on this backend, so reasoning continuity
+///    is stateless: `include: ["reasoning.encrypted_content"]` is required
+///    for the response to carry replayable encrypted reasoning.
+///
+/// openai-codex-GATED at the call sites — API-key `openai` Responses
+/// bodies stay byte-identical.
+pub fn adapt_body_for_codex_backend(body: &mut Value) {
+    // 1. Hoist system messages into `instructions`.
+    let mut hoisted: Vec<String> = Vec::new();
+    if let Some(input) = body.get_mut("input").and_then(|v| v.as_array_mut()) {
+        input.retain(|item| {
+            let is_system = item.get("role").and_then(|r| r.as_str()) == Some("system");
+            if is_system {
+                match item.get("content") {
+                    Some(Value::String(s)) => hoisted.push(s.clone()),
+                    Some(Value::Array(parts)) => {
+                        for p in parts {
+                            if let Some(t) = p.get("text").and_then(|t| t.as_str()) {
+                                hoisted.push(t.to_string());
+                            }
+                        }
+                    }
+                    _ => {}
+                }
+            }
+            !is_system
+        });
+    }
+    if !hoisted.is_empty() {
+        let mut instructions = body
+            .get("instructions")
+            .and_then(|v| v.as_str())
+            .map(str::to_owned)
+            .unwrap_or_default();
+        for part in hoisted {
+            if !instructions.is_empty() {
+                instructions.push_str("\n\n");
+            }
+            instructions.push_str(&part);
+        }
+        body["instructions"] = Value::String(instructions);
+    }
+
+    // 2. Request replayable encrypted reasoning.
+    let include = body
+        .as_object_mut()
+        .map(|obj| obj.entry("include").or_insert_with(|| Value::Array(vec![])));
+    if let Some(Value::Array(entries)) = include {
+        let key = Value::String("reasoning.encrypted_content".to_string());
+        if !entries.contains(&key) {
+            entries.push(key);
+        }
+    }
+}
+
 /// Neutralize a `reasoning.effort` echo the typed `rs` enum cannot parse
 /// (`max`): remove it so response deserialization succeeds. The turn's
 /// canonical effort lives in the session sampling config regardless; only
@@ -1551,6 +1616,66 @@ mod tests {
     use super::*;
     use serde_json::json;
 
+    /// The Codex backend rejects `role: system` input outright
+    /// (400 `{"detail":"System messages are not allowed"}`) — its system
+    /// channel is the top-level `instructions` field, and stateless
+    /// (`store: false`) reasoning replay needs
+    /// `include: ["reasoning.encrypted_content"]`. The adapter must hoist
+    /// every system item (string or parts content, order preserved),
+    /// append to existing instructions, and leave the rest of the input
+    /// untouched.
+    #[test]
+    fn codex_adapter_hoists_system_messages_and_requests_encrypted_reasoning() {
+        let mut body = json!({
+            "model": "gpt-5.2-codex",
+            "instructions": "base",
+            "input": [
+                {"type": "message", "role": "system", "content": "sys head"},
+                {"type": "message", "role": "user", "content": "hello"},
+                {"type": "message", "role": "system", "content": [
+                    {"type": "input_text", "text": "memory reminder"}
+                ]},
+                {"type": "message", "role": "assistant", "content": "hi"}
+            ]
+        });
+        adapt_body_for_codex_backend(&mut body);
+
+        let input = body["input"].as_array().unwrap();
+        assert_eq!(input.len(), 2, "system items removed from input: {body:#}");
+        assert!(
+            input.iter().all(|i| i["role"] != "system"),
+            "no system role may remain: {body:#}"
+        );
+        assert_eq!(
+            body["instructions"], "base\n\nsys head\n\nmemory reminder",
+            "system content hoisted into instructions, order preserved"
+        );
+        assert_eq!(
+            body["include"],
+            json!(["reasoning.encrypted_content"]),
+            "stateless reasoning replay requires the include"
+        );
+
+        // Idempotent: a second pass changes nothing.
+        let before = body.clone();
+        adapt_body_for_codex_backend(&mut body);
+        assert_eq!(body, before);
+    }
+
+    /// No system items and no prior instructions: input untouched, no
+    /// empty-string instructions invented, include still requested.
+    #[test]
+    fn codex_adapter_without_system_messages_only_adds_include() {
+        let mut body = json!({
+            "model": "gpt-5.2-codex",
+            "input": [{"type": "message", "role": "user", "content": "q"}]
+        });
+        adapt_body_for_codex_backend(&mut body);
+        assert!(body.get("instructions").is_none(), "{body:#}");
+        assert_eq!(body["input"].as_array().unwrap().len(), 1);
+        assert_eq!(body["include"], json!(["reasoning.encrypted_content"]));
+    }
+
     /// String content (the only shape non-Mistral providers send) stays the
     /// answer verbatim with no thinking — byte-identical to the pre-change
     /// deserialization.

crates/codegen/kigi-shell-base/src/util/fs.rs

@@ -0,0 +1,87 @@
+//! Filesystem primitives shared across the shell.
+
+use std::io;
+use std::path::Path;
+
+/// Replace `dest` with `tmp` — the commit step of every tmp+rename atomic
+/// write in the product. This is the ONE place that knows how to make that
+/// commit stick on Windows; call sites must never inline a bare
+/// `fs::rename` replace again.
+///
+/// Unix `rename(2)` replaces atomically and needs no help. Windows
+/// `MoveFileExW(REPLACE_EXISTING)` fails with a sharing violation while
+/// ANOTHER process (antivirus scanner, search indexer, cloud sync) holds
+/// `dest` open — the classic "persists on macOS, silently doesn't on
+/// Windows" failure (a model switch that never sticks, a stale models
+/// cache). On Windows a failed rename therefore deletes the destination
+/// first (the pattern `auth/storage.rs` shipped first) and retries with two
+/// short back-offs for scanners that hold the file for a few milliseconds.
+///
+/// On final failure the tmp file is removed (no litter) and the error is
+/// returned — callers decide severity, but MUST at least log it (errors
+/// never pass silently).
+pub fn replace_file(tmp: &Path, dest: &Path) -> io::Result<()> {
+    let result = replace_file_inner(tmp, dest);
+    if result.is_err() {
+        let _ = std::fs::remove_file(tmp);
+    }
+    result
+}
+
+#[cfg(not(windows))]
+fn replace_file_inner(tmp: &Path, dest: &Path) -> io::Result<()> {
+    std::fs::rename(tmp, dest)
+}
+
+#[cfg(windows)]
+fn replace_file_inner(tmp: &Path, dest: &Path) -> io::Result<()> {
+    let mut last = match std::fs::rename(tmp, dest) {
+        Ok(()) => return Ok(()),
+        Err(e) => e,
+    };
+    for backoff_ms in [0u64, 10, 50] {
+        if backoff_ms > 0 {
+            std::thread::sleep(std::time::Duration::from_millis(backoff_ms));
+        }
+        // Delete-first: marks an open-with-delete-sharing file for deletion
+        // and clears the way for a plain rename; harmless when absent.
+        let _ = std::fs::remove_file(dest);
+        match std::fs::rename(tmp, dest) {
+            Ok(()) => return Ok(()),
+            Err(e) => last = e,
+        }
+    }
+    Err(last)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// The common contract on every platform: replace over an existing
+    /// destination, create a missing one, and error (cleaning the tmp)
+    /// when the tmp itself is missing.
+    #[test]
+    fn replace_file_commits_and_cleans_up() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let dest = dir.path().join("target.json");
+        let tmp = dir.path().join("target.json.tmp");
+
+        // Create-missing.
+        std::fs::write(&tmp, b"v1").unwrap();
+        replace_file(&tmp, &dest).expect("create");
+        assert_eq!(std::fs::read(&dest).unwrap(), b"v1");
+        assert!(!tmp.exists(), "tmp must be consumed");
+
+        // Replace-existing.
+        std::fs::write(&tmp, b"v2").unwrap();
+        replace_file(&tmp, &dest).expect("replace");
+        assert_eq!(std::fs::read(&dest).unwrap(), b"v2");
+        assert!(!tmp.exists());
+
+        // Missing tmp → error, dest untouched.
+        let err = replace_file(&tmp, &dest).expect_err("missing tmp must fail");
+        assert_eq!(err.kind(), io::ErrorKind::NotFound);
+        assert_eq!(std::fs::read(&dest).unwrap(), b"v2");
+    }
+}

crates/codegen/kigi-shell-base/src/util/mod.rs

@@ -1,4 +1,5 @@
 pub mod event_id;
+pub mod fs;
 pub mod kigi_home;
 pub mod secure_file;
 pub mod tips;

crates/codegen/kigi-shell/build.rs

@@ -109,21 +109,43 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         t = asset_triple
     );
 
+    // Transient CDN hiccups (502/503/timeouts) are retried with backoff: a
+    // single flaky response must not kill a ~50-minute release build (it
+    // did — the v0.1.5 tag build failed on one 502). Genuine failures
+    // (404, offline) still error out with the offline-build hint.
     let bytes: Vec<u8> = {
-        let resp = reqwest::blocking::get(&url).map_err(|e| {
-            format!(
-                "Failed to download ripgrep: {}\nSet KIGI_SHELL_BUNDLE_RG_PATH to a local rg for offline builds.",
-                e
-            )
-        })?;
-        if !resp.status().is_success() {
-            return Err(format!(
-                "HTTP {} downloading ripgrep. Set KIGI_SHELL_BUNDLE_RG_PATH for offline builds.",
-                resp.status()
-            )
-            .into());
+        let mut last_err = String::new();
+        let mut bytes = None;
+        for (attempt, backoff_secs) in [0u64, 2, 8].into_iter().enumerate() {
+            if backoff_secs > 0 {
+                std::thread::sleep(std::time::Duration::from_secs(backoff_secs));
             }
-        resp.bytes()?.to_vec()
+            match reqwest::blocking::get(&url) {
+                Ok(resp) if resp.status().is_success() => match resp.bytes() {
+                    Ok(b) => {
+                        bytes = Some(b.to_vec());
+                        break;
+                    }
+                    Err(e) => last_err = format!("reading ripgrep body: {e}"),
+                },
+                Ok(resp) => {
+                    let status = resp.status();
+                    last_err = format!("HTTP {status} downloading ripgrep");
+                    // Only server-side/transient statuses are worth retrying.
+                    if !(status.is_server_error() || status.as_u16() == 429) {
+                        break;
+                    }
+                }
+                Err(e) => last_err = format!("Failed to download ripgrep: {e}"),
+            }
+            println!(
+                "cargo:warning=ripgrep download attempt {} failed: {last_err}",
+                attempt + 1
+            );
+        }
+        bytes.ok_or_else(|| {
+            format!("{last_err}. Set KIGI_SHELL_BUNDLE_RG_PATH for offline builds.")
+        })?
     };
 
     let gz = flate2::read::GzDecoder::new(&bytes[..]);

crates/codegen/kigi-shell/src/active_sessions.rs

@@ -170,9 +170,7 @@ fn write_data_file_atomic(
     let json = serde_json::to_string_pretty(sessions)
         .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
     fs::write(tmp_path, json.as_bytes())?;
-    fs::rename(tmp_path, data_path).inspect_err(|_| {
-        let _ = fs::remove_file(tmp_path);
-    })
+    crate::util::fs::replace_file(tmp_path, data_path)
 }
 
 fn is_pid_alive(pid: u32) -> bool {

crates/codegen/kigi-shell/src/agent/config.rs

@@ -1881,12 +1881,17 @@ impl Config {
             .default(true)
             .resolve()
     }
-    /// Graph mode (`/graph`) master switch. Default OFF — gray-released via
-    /// `KIGI_GRAPH=1` only (plan.md G0 gate). Graph mode additionally
-    /// requires the goal harness (nodes execute as goals), enforced at
-    /// availability time, not here.
+    /// Graph mode (`/graph`) master switch. Default ON in the binary: the
+    /// README ships graph engineering enabled for every install, but the
+    /// old `default(false)` delegated enablement to installer env plumbing
+    /// (`install.sh` shell-rc export vs `install.ps1` registry write) — and
+    /// Windows terminals don't pick up freshly-written registry env, so
+    /// `/graph` went "missing on Windows". The product default lives HERE,
+    /// not in installers. `KIGI_GRAPH=0` is the off-switch. Graph mode
+    /// additionally requires the goal harness (nodes execute as goals),
+    /// enforced at availability time, not here.
     pub(crate) fn resolve_graph(&self) -> Resolved<bool> {
-        BoolFlag::env("KIGI_GRAPH").default(false).resolve()
+        BoolFlag::env("KIGI_GRAPH").default(true).resolve()
     }
     /// Max graph nodes running concurrently (`KIGI_GRAPH_CONCURRENCY`).
     /// 1 = serial (G0-identical); clamped to [1, 8] — the coordinator has
@@ -4337,6 +4342,24 @@ mod tests {
     /// Catalog key of the bundled fallback default (`default_models.json`):
     /// `{platform_id}/{model_id}` for `crate::models::default_model()`.
     const BUNDLED_DEFAULT_KEY: &str = "kimi-code/kimi-for-coding";
+
+    /// `/graph` ships ON by default: the G0 gray release (`KIGI_GRAPH=1`
+    /// only) made the command exist solely on machines with the dev env
+    /// var — which read as "missing on Windows". A fresh install with no
+    /// env must resolve `true`; `KIGI_GRAPH=0` stays the off-switch.
+    #[test]
+    #[serial]
+    fn graph_defaults_on_and_env_zero_disables() {
+        let cfg = Config::default();
+        {
+            let _unset = EnvGuard::unset("KIGI_GRAPH");
+            assert!(cfg.resolve_graph().value, "fresh install must offer /graph");
+        }
+        {
+            let _off = EnvGuard::set("KIGI_GRAPH", "0");
+            assert!(!cfg.resolve_graph().value, "KIGI_GRAPH=0 must disable");
+        }
+    }
     #[test]
     fn main_cli_tools_override_preserves_profile_injection_policy() {
         let overrides = CliAgentOverrides {

crates/codegen/kigi-shell/src/agent/models.rs

@@ -1637,16 +1637,31 @@ impl ModelsCacheManager {
         }
     }
 
-    /// Sync; see `load_fresh` note.
+    /// Unique tmp suffix (PID + nanos) so concurrent writers never share an
+    /// inode (mirrors `util::config::persist`).
+    fn tmp_path(&self) -> std::path::PathBuf {
+        let nanos = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .map(|d| d.as_nanos())
+            .unwrap_or(0);
+        self.path
+            .with_extension(format!("json.tmp.{}.{}", std::process::id(), nanos))
+    }
+
+    /// Sync; see `load_fresh` note. Best-effort, but NEVER silent: a failed
+    /// cache write leaves a stale catalog on disk, which on Windows (sharing
+    /// violations) previously diverged picker behavior with zero trace.
     fn atomic_write(&self, cache: &ModelsCache) {
         if let Some(parent) = self.path.parent() {
             let _ = std::fs::create_dir_all(parent);
         }
-        let tmp = self.path.with_extension("json.tmp");
-        if let Ok(json) = serde_json::to_vec_pretty(cache)
-            && std::fs::write(&tmp, &json).is_ok()
-        {
-            let _ = std::fs::rename(&tmp, &self.path);
+        let tmp = self.tmp_path();
+        let result = serde_json::to_vec_pretty(cache)
+            .map_err(std::io::Error::other)
+            .and_then(|json| std::fs::write(&tmp, &json))
+            .and_then(|()| crate::util::fs::replace_file(&tmp, &self.path));
+        if let Err(e) = result {
+            tracing::warn!(error = %e, path = %self.path.display(), "models cache write failed");
         }
     }
 
@@ -1654,12 +1669,25 @@ impl ModelsCacheManager {
         if let Some(parent) = self.path.parent() {
             let _ = tokio::fs::create_dir_all(parent).await;
         }
-        let tmp = self.path.with_extension("json.tmp");
-        let Ok(json) = serde_json::to_vec_pretty(cache) else {
+        let tmp = self.tmp_path();
+        let json = match serde_json::to_vec_pretty(cache) {
+            Ok(json) => json,
+            Err(e) => {
+                tracing::warn!(error = %e, "models cache serialize failed");
                 return;
+            }
         };
-        if tokio::fs::write(&tmp, &json).await.is_ok() {
-            let _ = tokio::fs::rename(&tmp, &self.path).await;
+        let result = match tokio::fs::write(&tmp, &json).await {
+            Ok(()) => {
+                let dest = self.path.clone();
+                tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &dest))
+                    .await
+                    .unwrap_or_else(|e| Err(std::io::Error::other(e)))
+            }
+            Err(e) => Err(e),
+        };
+        if let Err(e) = result {
+            tracing::warn!(error = %e, path = %self.path.display(), "models cache write failed");
         }
     }
 }

crates/codegen/kigi-shell/src/auth/storage.rs

@@ -430,17 +430,12 @@ fn write_store_to(path: &Path, auth_store: &AuthStore) -> std::io::Result<()> {
     Ok(())
 }
 
-/// Atomic write: tmp + rename. Unix `rename(2)` replaces atomically;
-/// Windows `rename` requires removing the target first.
+/// Atomic write: tmp + Windows-safe replace (see `util::fs::replace_file`,
+/// which this site's inline delete-first pattern graduated into).
 fn write_auth_json_atomic(auth_file: &Path, auth_store: &AuthStore) -> std::io::Result<()> {
     let tmp = auth_file.with_extension(format!("json.{}.tmp", std::process::id()));
     write_store_to(&tmp, auth_store)?;
-    #[cfg(windows)]
-    {
-        let _ = std::fs::remove_file(auth_file);
-    }
-    std::fs::rename(&tmp, auth_file)?;
-    Ok(())
+    crate::util::fs::replace_file(&tmp, auth_file)
 }
 
 /// Non-atomic fallback: truncate and rewrite `auth.json` in place.

crates/codegen/kigi-shell/src/claude_import.rs

@@ -670,10 +670,7 @@ fn write_import_marker(config_path: &Path) -> anyhow::Result<()> {
         let _ = std::fs::remove_file(&tmp);
         return Err(e.into());
     }
-    if let Err(e) = std::fs::rename(&tmp, config_path) {
-        let _ = std::fs::remove_file(&tmp);
-        return Err(e.into());
-    }
+    crate::util::fs::replace_file(&tmp, config_path)?;
     Ok(())
 }
 
@@ -854,7 +851,7 @@ fn apply_items_to_config(config_path: &Path, items: &[ImportableItem]) -> anyhow
             std::fs::create_dir_all(parent)?;
         }
         std::fs::write(&tmp, &toml_str)?;
-        std::fs::rename(&tmp, config_path)?;
+        crate::util::fs::replace_file(&tmp, config_path)?;
         info!(
             path = %config_path.display(),
             count,
@@ -1204,7 +1201,7 @@ fn apply_hooks_to_dir(hooks_dir: &Path, items: &[ImportableItem]) -> anyhow::Res
         let json_str = serde_json::to_string_pretty(&root)?;
         let tmp = target.with_extension("json.tmp");
         std::fs::write(&tmp, &json_str)?;
-        std::fs::rename(&tmp, &target)?;
+        crate::util::fs::replace_file(&tmp, &target)?;
         info!(
             path = %target.display(),
             count,

crates/codegen/kigi-shell/src/claude_import_state.rs

@@ -90,7 +90,7 @@ pub fn save_import_state(state: &ImportState) -> std::io::Result<()> {
     // `claude_import_state.json.tmp` (the last extension is replaced).
     let tmp = path.with_extension("json.tmp");
     std::fs::write(&tmp, &json)?;
-    std::fs::rename(&tmp, &path)?;
+    crate::util::fs::replace_file(&tmp, &path)?;
     Ok(())
 }
 

crates/codegen/kigi-shell/src/kimi_import.rs

@@ -528,10 +528,7 @@ pub fn apply_at(plan: &KimiImportPlan, kigi_home: &Path) -> anyhow::Result<KimiA
             let _ = std::fs::remove_file(&tmp);
             return Err(e.into());
         }
-        if let Err(e) = std::fs::rename(&tmp, &config_path) {
-            let _ = std::fs::remove_file(&tmp);
-            return Err(e.into());
-        }
+        crate::util::fs::replace_file(&tmp, &config_path)?;
         info!(
             path = %config_path.display(),
             added = applied.total_added(),

crates/codegen/kigi-shell/src/session/acp_session.rs

@@ -1147,7 +1147,7 @@ fn persist_chat_history_jsonl_sync(session_info: &SessionInfo, conversation: &[C
             buf.push(b'\n');
         }
         std::fs::File::create(&tmp_path)?.write_all(&buf)?;
-        std::fs::rename(&tmp_path, &final_path)?;
+        crate::util::fs::replace_file(&tmp_path, &final_path)?;
         Ok(())
     })();
     if let Err(e) = result {

crates/codegen/kigi-shell/src/session/goal_classifier.rs

@@ -594,10 +594,10 @@ async fn write_patch_file_atomic(path: &Path, body: &str) -> std::io::Result<()>
         .unwrap_or("goal-classifier.patch");
     let tmp = dir.join(format!(".{file_name}.{}.tmp", uuid::Uuid::now_v7()));
     tokio::fs::write(&tmp, body).await?;
-    if let Err(err) = tokio::fs::rename(&tmp, path).await {
-        let _ = tokio::fs::remove_file(&tmp).await;
-        return Err(err);
-    }
+    let dest = path.to_path_buf();
+    tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &dest))
+        .await
+        .map_err(std::io::Error::other)??;
     Ok(())
 }
 

crates/codegen/kigi-shell/src/session/goal_tracker.rs

@@ -895,7 +895,8 @@ impl GoalTracker {
         };
         let dest = goal_dir.join(name);
         let _ = std::fs::create_dir_all(&goal_dir);
-        if std::fs::rename(&src, &dest).is_ok() || copy_no_follow(&src, &dest).is_ok() {
+        if crate::util::fs::replace_file(&src, &dest).is_ok() || copy_no_follow(&src, &dest).is_ok()
+        {
             append_skeptic_reports(&scratch_root, &dest);
             o.last_classifier_details_path = Some(dest.to_string_lossy().into_owned());
         }

crates/codegen/kigi-shell/src/session/graph_project.rs

@@ -120,7 +120,7 @@ pub fn project(dir: &Path, state: &GraphOrchestration) -> std::io::Result<()> {
         f.write_all(&buf)?;
         f.sync_all()?;
     }
-    std::fs::rename(&tmp, &target)
+    crate::util::fs::replace_file(&tmp, &target)
 }
 
 /// Load the projected graph, `Ok(None)` when absent. Malformed content

crates/codegen/kigi-shell/src/session/prompt_history.rs

@@ -98,7 +98,7 @@ pub fn truncate_if_needed(cwd: &str) -> io::Result<()> {
         }
     }
 
-    std::fs::rename(temp_path, path)?;
+    crate::util::fs::replace_file(&temp_path, &path)?;
     Ok(())
 }
 

crates/codegen/kigi-shell/src/session/storage/jsonl/mod.rs

@@ -13,6 +13,16 @@ use std::fs::OpenOptions;
 use std::io::{self, Read};
 use std::path::{Path, PathBuf};
 use tokio::io::AsyncWriteExt;
+
+/// Commit `tmp` over `target` with the shared Windows-safe replace
+/// (`util::fs::replace_file`): a bare async rename silently lost session
+/// state — including the switched model — on Windows whenever AV/indexer
+/// held the destination open.
+async fn replace_file_async(tmp: PathBuf, target: PathBuf) -> io::Result<()> {
+    tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &target))
+        .await
+        .unwrap_or_else(|e| Err(io::Error::other(e)))
+}
 /// How the adapter resolves the session directory on disk.
 ///
 /// - `FromRoot` (default): computes `{root}/sessions/{urlencoded(cwd)}/{session_id}/`
@@ -289,7 +299,7 @@ impl JsonlStorageAdapter {
         }
         let tmp = path.with_extension("jsonl.tmp");
         tokio::fs::write(&tmp, &content).await?;
-        tokio::fs::rename(&tmp, &path).await
+        replace_file_async(tmp, path).await
     }
     fn read_jsonl<T: serde::de::DeserializeOwned>(&self, path: PathBuf) -> io::Result<Vec<T>> {
         if !path.exists() {
@@ -378,7 +388,7 @@ impl JsonlStorageAdapter {
             .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
         let tmp = summary_path.with_extension("json.tmp");
         std::fs::write(&tmp, &bytes)?;
-        std::fs::rename(&tmp, &summary_path)
+        crate::util::fs::replace_file(&tmp, &summary_path)
     }
     fn read_summary_sync(&self, info: &Info) -> io::Result<Summary> {
         let path = self.summary_file(info);
@@ -1057,7 +1067,7 @@ impl StorageAdapter for JsonlStorageAdapter {
         let target = self.plan_mode_state_file(info);
         let tmp = target.with_extension("json.tmp");
         tokio::fs::write(&tmp, json).await?;
-        tokio::fs::rename(&tmp, &target).await
+        replace_file_async(tmp, target).await
     }
     async fn write_signals(
         &self,
@@ -1069,7 +1079,7 @@ impl StorageAdapter for JsonlStorageAdapter {
         let target = self.signals_file(info);
         let tmp = target.with_extension("json.tmp");
         tokio::fs::write(&tmp, signals_json).await?;
-        tokio::fs::rename(&tmp, &target).await
+        replace_file_async(tmp, target).await
     }
     async fn write_announcement_state(
         &self,
@@ -1081,7 +1091,7 @@ impl StorageAdapter for JsonlStorageAdapter {
         let target = self.announcement_state_file(info);
         let tmp = target.with_extension("json.tmp");
         tokio::fs::write(&tmp, json).await?;
-        tokio::fs::rename(&tmp, &target).await
+        replace_file_async(tmp, target).await
     }
     async fn write_goal_mode_state(
         &self,
@@ -1096,7 +1106,7 @@ impl StorageAdapter for JsonlStorageAdapter {
         }
         let tmp = target.with_extension("json.tmp");
         tokio::fs::write(&tmp, json).await?;
-        tokio::fs::rename(&tmp, &target).await
+        replace_file_async(tmp, target).await
     }
     async fn write_graph_mode_state(
         &self,
@@ -1119,7 +1129,7 @@ impl StorageAdapter for JsonlStorageAdapter {
         }
         let tmp = target.with_extension("json.tmp");
         tokio::fs::write(&tmp, json).await?;
-        tokio::fs::rename(&tmp, &target).await
+        replace_file_async(tmp, target).await
     }
     async fn load_session(&self, info: &Info) -> io::Result<PersistedData> {
         let summary = self.read_summary_sync(info)?;

crates/codegen/kigi-shell/src/session/storage/summary_write.rs

@@ -230,7 +230,10 @@ fn write_summary_atomic(summary_path: &Path, summary: &Summary) -> io::Result<()
         .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
     let tmp = summary_path.with_extension("json.tmp");
     std::fs::write(&tmp, &bytes)?;
-    std::fs::rename(&tmp, summary_path)
+    // Windows-safe replace: this is the write that persists a session's
+    // CURRENT MODEL — a bare rename made a switched model silently revert
+    // on resume whenever AV/indexer held summary.json open on Windows.
+    crate::util::fs::replace_file(&tmp, summary_path)
 }
 
 #[cfg(test)]

crates/codegen/kigi-shell/src/util/config/campaigns.rs

@@ -114,9 +114,7 @@ fn dismiss_campaign_ids_at(
     let nonce = DISMISS_TMP_NONCE.fetch_add(1, Ordering::Relaxed);
     let tmp = path.with_extension(format!("json.{}.{}.tmp", std::process::id(), nonce));
     std::fs::write(&tmp, &json)?;
-    std::fs::rename(&tmp, &path).inspect_err(|_| {
-        let _ = std::fs::remove_file(&tmp);
-    })
+    crate::util::fs::replace_file(&tmp, &path)
 }
 
 /// `KIGI_CAMPAIGNS_OVERRIDE` JSON array replaces all sources (`[]` = none; beats

crates/codegen/kigi-shell/src/util/config/mcp.rs

@@ -367,7 +367,9 @@ pub async fn save_mcp_disabled_tools(server_name: &str, disabled_tools: &[String
         let _ = tokio::fs::create_dir_all(parent).await;
     }
     tokio::fs::write(&tmp, &toml_str).await?;
-    tokio::fs::rename(&tmp, &path).await?;
+    tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &path))
+        .await
+        .map_err(std::io::Error::other)??;
     Ok(())
 }
 
@@ -419,7 +421,9 @@ pub async fn save_mcp_server_enabled(server_name: &str, enabled: bool) -> Result
         let _ = tokio::fs::create_dir_all(parent).await;
     }
     tokio::fs::write(&tmp, &toml_str).await?;
-    tokio::fs::rename(&tmp, &path).await?;
+    tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &path))
+        .await
+        .map_err(std::io::Error::other)??;
     Ok(())
 }
 
@@ -476,7 +480,10 @@ pub async fn save_mcp_server_config_at(
         let _ = tokio::fs::create_dir_all(parent).await;
     }
     tokio::fs::write(&tmp, &toml_str).await?;
-    tokio::fs::rename(&tmp, &path).await?;
+    let dest = path.to_path_buf();
+    tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &dest))
+        .await
+        .map_err(std::io::Error::other)??;
     Ok(())
 }
 
@@ -553,7 +560,12 @@ pub async fn delete_mcp_server_config_at(
         let _ = tokio::fs::create_dir_all(parent).await;
     }
     tokio::fs::write(&tmp, &toml_str).await?;
-    tokio::fs::rename(&tmp, &path).await?;
+    {
+        let dest = path.to_path_buf();
+        tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &dest))
+            .await
+            .map_err(std::io::Error::other)??;
+    }
 
     // Clean up OAuth credentials for the deleted server.
     if let Ok(mut cred_store) = kigi_mcp::credentials::McpCredentialStore::load_default() {

crates/codegen/kigi-shell/src/util/config/persist.rs

@@ -88,7 +88,12 @@ pub async fn save_config(config: &Config) -> Result<()> {
     }
     let _ = prior_mode;
 
-    tokio::fs::rename(&tmp, &path).await?;
+    // Windows-safe replace (delete-first + retry on sharing violations) —
+    // a bare rename made `/model` persistence silently fail on Windows
+    // whenever AV/indexer/cloud-sync held config.toml open.
+    tokio::task::spawn_blocking(move || crate::util::fs::replace_file(&tmp, &path))
+        .await
+        .map_err(|e| anyhow::anyhow!("config replace task: {e}"))??;
     Ok(())
 }
 
@@ -138,11 +143,8 @@ pub(crate) fn atomic_write_string(path: &std::path::Path, content: &str) -> std:
     }
     let _ = prior_mode;
 
-    if let Err(e) = std::fs::rename(&tmp, path) {
-        let _ = std::fs::remove_file(&tmp);
-        return Err(e);
-    }
-    Ok(())
+    // Windows-safe replace; cleans up the tmp file on failure itself.
+    crate::util::fs::replace_file(&tmp, path)
 }
 
 /// Merge `[toolset.ask_user_question]` into the root table. `[toolset]` is

crates/codegen/kigi-shell/tests/test_sampling_client.rs

@@ -535,13 +535,20 @@ async fn responses_upgrade_roundtrips_reconstructed_reasoning_as_typed_input() {
 /// Upgrade path, Anthropic Messages API: a legacy session whose assistant
 /// carries inline `reasoning: {text, encrypted, id}` (text = thinking,
 /// encrypted = signature) must, on load, reconstruct a sibling Reasoning
-/// item that emits a Anthropic Messages `thinking` content block (with `thinking`
-/// + `signature`) on the outgoing `/v1/messages` request.
+/// item — and when that turn is the ACTIVE tool-use continuation, its
+/// `thinking` block (text + signature) must reach the outgoing
+/// `/v1/messages` request verbatim.
+///
+/// Outside an active tool loop the block must be STRIPPED: Anthropic
+/// validates every replayed signature (model-bound), so replaying stale
+/// thinking is exactly what 400'd with "Invalid `signature` in `thinking`
+/// block" after cross-model histories (see `prune_replayed_thinking`).
 #[tokio::test]
-async fn messages_upgrade_emits_reconstructed_reasoning_as_thinking_block() {
-    // 1. Seed a legacy Anthropic Messages-origin chat_history.jsonl. Anthropic Messages
-    //    thinking blocks never carried an id (stream/messages.rs sets
-    //    id=""), and the signature lives in `encrypted`.
+async fn messages_upgrade_replays_reconstructed_thinking_only_in_active_tool_loop() {
+    // 1. Seed a legacy Anthropic Messages-origin chat_history.jsonl whose
+    //    assistant turn issued a tool call (thinking blocks never carried an
+    //    id — stream/messages.rs sets id="" — and the signature lives in
+    //    `encrypted`). The pending tool_result makes this the active loop.
     let dir = tempfile::tempdir().unwrap();
     std::fs::write(
         dir.path().join("chat_history.jsonl"),
@@ -550,7 +557,9 @@ async fn messages_upgrade_emits_reconstructed_reasoning_as_thinking_block() {
             "\n",
             r#"{"type":"user","content":[{"type":"text","text":"q1"}]}"#,
             "\n",
-            r#"{"type":"assistant","content":"a1","reasoning":{"text":"legacy anthropic thinking","encrypted":"SIGNATURE_abc","id":""},"model_id":"kigi-4.5"}"#,
+            r#"{"type":"assistant","content":"a1","reasoning":{"text":"legacy anthropic thinking","encrypted":"SIGNATURE_abc","id":""},"model_id":"kigi-4.5","tool_calls":[{"id":"tc1","name":"read_file","arguments":"{}"}]}"#,
+            "\n",
+            r#"{"type":"tool_result","tool_call_id":"tc1","content":"file contents"}"#,
             "\n",
         ),
     )
@@ -558,7 +567,7 @@ async fn messages_upgrade_emits_reconstructed_reasoning_as_thinking_block() {
 
     // 2. Load + upgrade.
     let adapter = JsonlStorageAdapter::with_root(dir.path().to_path_buf());
-    let mut items = adapter.load_chat_history_from_dir(dir.path()).unwrap();
+    let items = adapter.load_chat_history_from_dir(dir.path()).unwrap();
     assert!(
         items
             .iter()
@@ -566,20 +575,18 @@ async fn messages_upgrade_emits_reconstructed_reasoning_as_thinking_block() {
         "legacy inline reasoning must be reconstructed as a sibling on load, got {items:?}"
     );
 
-    // 3. Continue and send over the Messages API, capturing the body.
-    items.push(ConversationItem::user("q2"));
-
+    // 3. Send the tool-loop continuation over the Messages API.
     let server = MockInferenceServer::start().await.unwrap();
     server.set_response("ok");
     let client = create_test_client(&server.url(), ApiBackend::Messages);
 
     let _ = client
-        .conversation_collect(ConversationRequest::from_items(items))
+        .conversation_collect(ConversationRequest::from_items(items.clone()))
         .await
         .unwrap();
 
-    // 4. The reconstructed reasoning must emit a Anthropic Messages `thinking`
-    //    content block carrying the thinking text + signature.
+    // 4. The active loop's reconstructed reasoning must emit an Anthropic
+    //    `thinking` content block carrying the thinking text + signature.
     let body = server.request_bodies().pop().unwrap();
     let messages = body.get("messages").unwrap().as_array().unwrap();
     let thinking_block = messages
@@ -593,7 +600,7 @@ async fn messages_upgrade_emits_reconstructed_reasoning_as_thinking_block() {
         })
         .find(|b| b.get("type").and_then(Value::as_str) == Some("thinking"))
         .unwrap_or_else(|| {
-            panic!("reconstructed reasoning must emit an Anthropic thinking block; messages: {messages:#?}")
+            panic!("active-loop reasoning must emit an Anthropic thinking block; messages: {messages:#?}")
         });
     assert_eq!(
         thinking_block.get("thinking").and_then(Value::as_str),
@@ -605,6 +612,25 @@ async fn messages_upgrade_emits_reconstructed_reasoning_as_thinking_block() {
         Some("SIGNATURE_abc"),
         "signature (encrypted) preserved — required to reuse the thought server-side"
     );
+
+    // 5. A follow-up user turn CLOSES the loop: the same history plus a new
+    //    user message must replay NO thinking block at all.
+    let mut closed = items;
+    closed.push(ConversationItem::user("q2"));
+    let _ = client
+        .conversation_collect(ConversationRequest::from_items(closed))
+        .await
+        .unwrap();
+    let body = server.request_bodies().pop().unwrap();
+    let any_thinking = body["messages"].as_array().unwrap().iter().any(|m| {
+        m.get("content")
+            .and_then(Value::as_array)
+            .is_some_and(|c| c.iter().any(|b| b["type"] == "thinking"))
+    });
+    assert!(
+        !any_thinking,
+        "stale thinking must be stripped outside the active tool loop; body: {body:#?}"
+    );
 }
 
 // ============================================================================
@@ -1443,3 +1469,79 @@ async fn test_chat_completions_backend_hits_chat_endpoint_not_responses() {
         "Should NOT have called /v1/responses"
     );
 }
+
+/// ChatGPT/Codex backend body contract (`openai_codex = true`): the
+/// `/codex/responses` endpoint rejects `role: system` input outright
+/// (400 {"detail":"System messages are not allowed"}) — system content
+/// must ride the top-level `instructions` field, and stateless reasoning
+/// replay needs `include: ["reasoning.encrypted_content"]`. Ported from
+/// the official Codex CLI + Pi's api/openai-codex-responses.ts, like the
+/// identity headers.
+#[tokio::test]
+async fn codex_responses_body_hoists_system_into_instructions() {
+    let server = MockInferenceServer::start().await.unwrap();
+    server.set_response("ok");
+    let mut config = common::test_sampler_config(&server.url(), ApiBackend::Responses, &[]);
+    config.openai_codex = true;
+    let client = Client::new(config).unwrap();
+
+    let _ = client
+        .conversation_collect(ConversationRequest::from_items(vec![
+            ConversationItem::system("You are Kigi."),
+            ConversationItem::user("test"),
+        ]))
+        .await
+        .unwrap();
+
+    let body = server.request_bodies().pop().unwrap();
+    let input = body["input"].as_array().unwrap();
+    assert!(
+        input
+            .iter()
+            .all(|i| i.get("role").and_then(Value::as_str) != Some("system")),
+        "codex backend must never receive system-role input: {body:#?}"
+    );
+    assert_eq!(
+        body["instructions"].as_str(),
+        Some("You are Kigi."),
+        "system prompt must ride the instructions field: {body:#?}"
+    );
+    assert_eq!(
+        body["include"],
+        serde_json::json!(["reasoning.encrypted_content"]),
+        "stateless reasoning replay requires the include: {body:#?}"
+    );
+}
+
+/// Control: the API-key `openai` Responses path (`openai_codex = false`)
+/// stays byte-compatible — system-role input preserved, no codex fields.
+#[tokio::test]
+async fn plain_responses_body_keeps_system_role_input() {
+    let server = MockInferenceServer::start().await.unwrap();
+    server.set_response("ok");
+    let client = create_test_client(&server.url(), ApiBackend::Responses);
+
+    let _ = client
+        .conversation_collect(ConversationRequest::from_items(vec![
+            ConversationItem::system("You are Kigi."),
+            ConversationItem::user("test"),
+        ]))
+        .await
+        .unwrap();
+
+    let body = server.request_bodies().pop().unwrap();
+    assert!(
+        body["input"]
+            .as_array()
+            .unwrap()
+            .iter()
+            .any(|i| i.get("role").and_then(Value::as_str) == Some("system")),
+        "api-key openai keeps system-role input: {body:#?}"
+    );
+    assert!(
+        body.get("instructions")
+            .map(|v| v.is_null())
+            .unwrap_or(true),
+        "no instructions hoist outside codex: {body:#?}"
+    );
+}

crates/codegen/kigi-tui/src/app/dispatch/settings/ui.rs

@@ -3,7 +3,7 @@
 use super::setters::{
     pr13_effective_default, set_ask_user_question_timeout_enabled_inner, set_auto_dark_theme_inner,
     set_auto_light_theme_inner, set_auto_update_inner, set_collapsed_edit_blocks_inner,
-    set_compact_mode, set_compact_mode_inner, set_contextual_hint_inner, set_default_model_inner,
+    set_compact_mode, set_compact_mode_inner, set_contextual_hint_inner,
     set_default_selected_permission_inner, set_display_refresh_auto_cadence_inner,
     set_fork_secondary_model_inner, set_group_tool_verbs_inner, set_hunk_tracker_mode_inner,
     set_invert_scroll_inner, set_keep_text_selection_inner, set_max_thoughts_width_inner,
@@ -844,7 +844,7 @@ pub(in crate::app::dispatch) fn apply_setting_rollback(
     rollback_value: &crate::settings::SettingValue,
 ) -> Vec<Effect> {
     use crate::settings::SettingValue;
-    let mut companion_effects: Vec<Effect> = Vec::new();
+    let companion_effects: Vec<Effect> = Vec::new();
     match (key, rollback_value) {
         ("compact_mode", SettingValue::Bool(b)) => set_compact_mode_inner(app, *b),
         ("show_timestamps", SettingValue::Bool(b)) => set_timestamps_inner(app, *b),
@@ -934,65 +934,24 @@ pub(in crate::app::dispatch) fn apply_setting_rollback(
             // other rollback arms must not clobber it from the global canonical.
             sync_active_auto_flag(app);
         }
-        // default_model: best-effort rollback. If the prior model no
-        // longer resolves, leave optimistic value + log.
-        ("default_model", SettingValue::String(s)) => {
-            if s.is_empty() {
+        // default_model: deliberately NO revert. The session switch already
+        // succeeded independently (its own failure path reports via
+        // `handle_switch_model_complete`); this arm fires when only the
+        // DISK write of the next-launch default failed — which must not
+        // undo a working switch. Same policy as `PersistPreferredModel`
+        // ("still active for this session"). Regression: reverting here
+        // (plus a reverse SwitchModel) made every picker selection appear
+        // to not take on Windows, where AV/indexer file locks routinely
+        // fail config.toml persists.
+        ("default_model", SettingValue::String(prior)) => {
             tracing::warn!(
                 target: "settings",
                 key = "default_model",
-                    "rollback to empty string requested but no \
-                     'clear current model' API exists — leaving live \
-                     state at optimistic value (next session reload \
-                     will resolve via shell default-resolution chain)",
+                prior = %prior,
+                "default-model persist failed; keeping the live session's \
+                 model (the switch succeeded) — only the next-launch \
+                 default is unsaved",
             );
-            } else {
-                // Resolve the prior model ID back to a ModelId
-                // and call the typed inner. If resolution fails
-                // (catalog changed mid-flight), log + leave
-                // optimistic.
-                let (resolved, session_id) = if let ActiveView::Agent(aid) = app.active_view
-                    && let Some(agent) = app.agents.get(&aid)
-                {
-                    (
-                        agent.session.models.resolve_by_name_or_id(s),
-                        agent.session.session_id.clone(),
-                    )
-                } else {
-                    (None, None)
-                };
-                match resolved {
-                    Some(id) => {
-                        let _ = set_default_model_inner(app, &id);
-                        // Emit reverse SwitchModel so the ACP session
-                        // matches the rolled-back pager mirror.
-                        if let ActiveView::Agent(aid) = app.active_view
-                            && let Some(sid) = session_id
-                        {
-                            if let Some(agent) = app.agents.get_mut(&aid) {
-                                agent.session.model_switch_pending = true;
-                            }
-                            companion_effects.push(Effect::SwitchModel {
-                                agent_id: aid,
-                                session_id: sid,
-                                model_id: id,
-                                effort: None,
-                                prev_model_id: None,
-                            });
-                        }
-                    }
-                    None => {
-                        tracing::warn!(
-                            target: "settings",
-                            key = "default_model",
-                            value = %s,
-                            "rollback model id no longer resolves in catalog — \
-                             in-memory state stays at optimistic value; ACP session \
-                             may diverge from pager mirror until next setter dispatch",
-                        );
-                    }
-                }
-            }
         }
         // max_thoughts_width: direct inner call.
         ("max_thoughts_width", SettingValue::Int(i)) => set_max_thoughts_width_inner(app, *i),

crates/codegen/kigi-tui/src/app/dispatch/tests/task_result.rs

@@ -1592,6 +1592,78 @@ fn rollback_reverts_thread_local_cache_too() {
     .unwrap();
 }
 
+/// A default_model persist failure must NOT revert the live session's
+/// model. The switch already succeeded in the session (its own failure
+/// path reports separately); a DISK write failure only means the default
+/// won't stick for the next launch — same policy as PersistPreferredModel
+/// ("still active for this session"). Regression: the rollback arm
+/// re-showed the ORIGINAL model and issued a reverse SwitchModel, which
+/// on Windows (persist failures from AV/indexer file locks) made every
+/// picker selection appear to not take.
+#[test]
+fn default_model_persist_failure_keeps_live_model() {
+    use crate::settings::SettingValue;
+    let mut app = test_app_with_agent();
+    let id = AgentId(0);
+    for (mid, name) in [("old-model", "Old Model"), ("new-model", "New Model")] {
+        let model_id = acp::ModelId::new(std::sync::Arc::from(mid));
+        let info = acp::ModelInfo::new(model_id.clone(), name.to_string());
+        app.agents
+            .get_mut(&id)
+            .unwrap()
+            .session
+            .models
+            .available
+            .insert(model_id.clone(), info.clone());
+        app.models.available.insert(model_id, info);
+    }
+    // User picked the new model; optimistic update applied.
+    let _ = dispatch(
+        Action::SetDefaultModel(acp::ModelId::new(std::sync::Arc::from("new-model"))),
+        &mut app,
+    );
+    assert_eq!(
+        app.agents[&id]
+            .session
+            .models
+            .current
+            .as_ref()
+            .map(|m| m.0.as_ref()),
+        Some("new-model"),
+    );
+
+    // Disk persist fails (the Windows sharing-violation shape).
+    let effects = dispatch(
+        Action::TaskComplete(TaskResult::SettingPersistFailed {
+            key: "default_model",
+            rollback_value: SettingValue::String("Old Model".into()),
+            error: "Access is denied. (os error 5)".into(),
+        }),
+        &mut app,
+    );
+
+    assert_eq!(
+        app.agents[&id]
+            .session
+            .models
+            .current
+            .as_ref()
+            .map(|m| m.0.as_ref()),
+        Some("new-model"),
+        "a persist failure must not revert the live session's model"
+    );
+    assert!(
+        !effects
+            .iter()
+            .any(|e| matches!(e, Effect::SwitchModel { .. })),
+        "no reverse SwitchModel may be issued for a disk-persist failure"
+    );
+    assert!(
+        read_toast(&app).contains("Could not save"),
+        "the save failure must still be surfaced"
+    );
+}
+
 /// `set_yolo_mode_inner` is the backstop: even a (stale) rollback
 /// value of "always-approve" must not re-enable yolo under the pin.
 #[test]

install.ps1

@@ -149,15 +149,13 @@ try {
         Write-Host "Run 'kigi' to get started."
     }
 
-    # Graph engineering ships enabled by default. Respect an explicit
-    # user choice: only set the variable when it is not already defined
-    # (so a persisted opt-out of "0" survives reinstalls).
-    $Graph = [Environment]::GetEnvironmentVariable("KIGI_GRAPH", "User")
-    if ($null -eq $Graph -or $Graph -eq "") {
-        [Environment]::SetEnvironmentVariable("KIGI_GRAPH", "1", "User")
-        Write-Host "Enabled graph engineering (KIGI_GRAPH=1)."
-        Write-Host "Disable: [Environment]::SetEnvironmentVariable('KIGI_GRAPH','0','User')"
-    }
+    # Graph engineering is enabled by default IN THE BINARY (resolve_graph
+    # defaults true) — no environment plumbing needed. The installer used
+    # to persist KIGI_GRAPH=1 into the User registry env, but running
+    # terminals (and new tabs of an open Windows Terminal) never pick up
+    # freshly-written registry variables, which made /graph "missing on
+    # Windows" while the shell-rc path worked on macOS/Linux. Opt out any
+    # time with: [Environment]::SetEnvironmentVariable('KIGI_GRAPH','0','User')
 } finally {
     Remove-Item -Path $TmpDir -Recurse -Force -ErrorAction SilentlyContinue
 }

install.sh

@@ -209,7 +209,6 @@ case "${SHELL:-}" in
     */zsh)
         RC_FILE="${ZDOTDIR:-$HOME}/.zshrc"
         PATH_LINE="export PATH=\"$BIN_DIR:\$PATH\""
-        GRAPH_LINE="export KIGI_GRAPH=1"
         ;;
     */bash)
         # macOS login shells read ~/.bash_profile; Linux reads ~/.bashrc.
@@ -219,7 +218,6 @@ case "${SHELL:-}" in
             RC_FILE="$HOME/.bashrc"
         fi
         PATH_LINE="export PATH=\"$BIN_DIR:\$PATH\""
-        GRAPH_LINE="export KIGI_GRAPH=1"
         ;;
     */fish)
         # fish_add_path in config.fish is fish's own idempotent way
@@ -228,12 +226,10 @@ case "${SHELL:-}" in
         mkdir -p "$FISH_CONF_DIR"
         RC_FILE="$FISH_CONF_DIR/config.fish"
         PATH_LINE="fish_add_path $BIN_DIR"
-        GRAPH_LINE="set -gx KIGI_GRAPH 1"
         ;;
     *)
         RC_FILE="$HOME/.profile"
         PATH_LINE="export PATH=\"$BIN_DIR:\$PATH\""
-        GRAPH_LINE="export KIGI_GRAPH=1"
         ;;
 esac
 
@@ -247,8 +243,8 @@ case ":$PATH:" in
         ;;
 esac
 
-# Graph engineering ships enabled by default. The KIGI_GRAPH guard makes
-# this idempotent AND respects an explicit user opt-out (an existing
-# `export KIGI_GRAPH=0` line is left untouched). Disable any time with:
+# Graph engineering is enabled by default IN THE BINARY (resolve_graph
+# defaults true) — the installer no longer writes KIGI_GRAPH=1 into shell
+# rc files (per-shell env plumbing was fragile and diverged per platform).
+# Disable any time with:
 #   echo 'export KIGI_GRAPH=0' >> <your shell rc>
-persist_line "$RC_FILE" "$GRAPH_LINE" "KIGI_GRAPH" "graph engineering (KIGI_GRAPH=1)"