dsh-patch-edit-plus

Patch-style file editing for DeepSeek Harness (DSH): one model-facing apply_patch tool that accepts git/unified diff (default) and Codex apply_patch syntax (opt-in), applies every change all-or-nothing, and stays completely out of DSH's way.

DSH version compatibility

DSH version	Status	Notes
0.1.2-rc.1	✅ supported	Tool authoring contract (defineTool DSL, presentation intents) is byte-identical across 0.1.2–0.1.5; one code path serves both.
0.1.3-alpha.x	✅ supported	Same as above.
0.1.5-rc.2	✅ statically verified	npm run typecheck:0.1.5 typechecks src/ against the real 0.1.5-rc.2 peer packages. No readByteRange usage, no 0.1.5-only PTC identifiers.

Settings registration uses the dual-API fallback (settings.installSection on 0.1.2+, settings.register on older hosts).

Why patch at all? (tool routing guide)

The tool description explicitly routes the model:

• Single small change in one already-read file → prefer the native edit tool (a patch costs more tokens than a literal edit).
• Small change inside a LARGE file → apply_patch (no need to echo the whole file).
• Batched changes across MANY files → apply_patch (one call, verified atomically).
• New file with substantial content / delete / rename → apply_patch.

Installation

dsh plugin --profile web add <path-to-dsh-patch-edit-plus>
dsh web --dump-config   # verify the plugin row appears
# restart DSH

Usage

Unified diff (default, enabled)

--- a/src/app.ts
+++ b/src/app.ts
@@ -10,4 +10,4 @@ export function main() {
   init()
-  start(oldPort)
+  start(newPort)
   await shutdown()
 }

Codex apply_patch syntax (opt-in)

*** Begin Patch
*** Update File: src/app.ts
@@
   init()
-  start(oldPort)
+  start(newPort)
*** Add File: docs/notes.md
+# Notes
*** Delete File: tmp/junk.txt
*** Move to: src/app.ts   (via `*** Move to:` after *** Update File:)
*** End Patch

Enable with allowCodexPatch: true. When a Codex patch arrives while disabled, the tool returns an actionable hint (how to enable or how to retry in unified diff) instead of a generic parse error — Codex syntax is a strong prior for GPT-family models and a silent failure traps them in retry loops.

Operations

Operation	Unified diff	Codex	Execution path
Add	new file mode + /dev/null	*** Add File:	ctx.fs.writeText (official intent dance)
Update (multi-hunk)	@@ hunks	@@ hunks	ctx.fs.writeText
Delete	deleted file mode + /dev/null	*** Delete File:	ctx.shell (sandbox-aware, env-passed path)
Move / rename	rename from/to	*** Move to:	ctx.shell

Guarantees

• All-or-nothing: the whole patch is verified against current file content first (context location, workspace containment, symlink policy, duplicate paths); any failure aborts with zero bytes written.
• Read-before-write gate respected: every write replicates the official write tool's intent dance — fs/write-intent waterfall → guarded writeText → fs/observed emit. A bare writeText would silently bypass the gate because DSH providers never dispatch fs/* events themselves.
• Precise failure diagnostics: on hunk mismatch the error carries file + hunk index, search origin line, expected-line preview (whitespace made visible), the file's actual excerpt, and a targeted hint.
• Newline fidelity: CRLF files are written back as CRLF; no-trailing-newline tails are preserved unless the patch changes the tail.
• Pure addition: the plugin registers exactly one tool, never calls tools.restrict(), never overrides a native tool, registers no global services, and removes everything on unload. Name conflicts with other apply_patch providers (bainianlaoyao/dsh-codex-mode, shuind/dsh-codex-harness, …) are resolved by rename avoidance (apply_patch_1, …_2, …) so DSH never fails to start.

Configuration

Option	Default	Description
toolName	apply_patch	Model-facing tool name.
conflictPolicy	rename	rename / skip / fail when the tool name is taken.
renameSuffix	_1	Suffix used by rename avoidance.
allowUnifiedDiff	true	Accept git/unified diffs.
allowCodexPatch	false	Accept Codex apply_patch syntax.
deleteBackend	shell	shell or none (Delete/Move return a structured error).
shellDialect	auto	auto (pwsh on win32) / posix / pwsh.
deleteCommand / moveCommand	built-in	Custom command templates. Paths still arrive only via env (DSH_PATCH_TARGET / DSH_PATCH_SOURCE); never interpolate them into the command string.
dryRunByDefault	false	Treat calls as dry runs unless dryRun: false.
followSymlinks	false	Allow patch paths to traverse symlinks.
maxFiles	50	Max file sections per patch.
maxPatchBytes	524288	Max patch text size in bytes.
maxDiffBytes	16384	Max per-file diff kept in the result metadata (larger diffs are emptied and marked truncated).

Limitations (disclosed)

• Delete/Move run through ctx.shell. The sandbox strength is whatever the loaded shell executor enforces (bash-sandbox fences; bash-local does not) — the same risk posture as the native bash tool. Every request carries a sandboxPolicy and reports sandbox facts so "policy denied" is distinguishable from "command failed".
• Every write and every Delete/Move carries the session-scoped policy. apply_patch resolves ctx.sandboxPolicy.resolve({ session }) per call — the session's mode override plus its cwd as the workspace root — exactly like the native write/edit tools, and resolves plan paths against that same root. Without it the enforcing filesystem falls back to the deployment root, which makes in-workspace writes fail as workspace-write denials even in a danger-full-access session. A workspace-write denial surfaces as a PatchError whose message carries the backend text (the structured [sandbox: …] marker and the same-turn escalation fields are not implemented; use the native write/edit tools when you need to escalate).
• Add does not create parent directories. This matches the native write tool (ctx.fs has no mkdir); the error names the missing directory.
• No fuzzy/offset matching: hunk location is exact → trimEnd → trim, deliberately (fuzzy matching is unsafe for destructive ops; it is on the roadmap).
• Binary patches are rejected with a clear error.

Development

npm install
npm run typecheck        # against 0.1.2-rc.1 peers (devDependencies)
npm run typecheck:0.1.5  # against 0.1.5-rc.2 peers (static dual-version proof)
npm test                 # vitest, 90 tests
npm run lint
npm run build            # lib/
npm run verify:source    # static safety assertions (intent dance, no node:fs, …)
npm run smoke            # load-level smoke against a stub host

Manual verification on a live DSH (dsh plugin --profile web add → restart → call the tool in a session) is intentionally left to the operator.

License

MIT