# Reported issues for diffctx Pod holds 18 of 20 GitHub reports that passed its relevance review. This can include external user reports, maintainer-confirmed bugs, and concrete feature gaps. Treat them as evidence to inspect, not a count of distinct defects. Back to [diffctx](/mcp/diffctx). ## Most discussed ### Agents do not call diffctx_context unprompted, and get little when they do Observed 2026-09-23 while an agent (Claude Code) worked in this repo for a whole session with the diffctx MCP server installed: it never called `diffctx_context` until the owner asked why. Two calls made afterwards, on 1.17.0: - `cc89b04b..a320ccaf` (the session's real work: `.github/workflows/*.yml` + `uv.lock`) → **0 items**. The repo's own `.diffctx/ignore` withholds `*.yml`, `*.yaml` and `tests`, so CI/infra changes and test context are invisible here. - `373bbf3d..f047eeae` (55 changed… [Read the thread](https://github.com/nikolay-e/diffctx/issues/289) · 2026-09-23 · closed · 11 comments ### plugin: 1.18.0 `hook pretooluse/posttooluse` prints nothing where the CLI reports callers **Version:** diffctx 1.18.0 release binary (the plugin's `data/bin/diffctx-1.18.0`), macOS arm64, 2026-10-01. **Observed.** `diffctx hook pretooluse` and `diffctx hook posttooluse` print nothing, exit 0, write nothing to stderr, for every command tried — on a staged change whose impact is not empty. Same repository, same index, the CLI answers: ``` $ diffctx . --diff --mode impact -f md diffctx impact for HEAD: 1 changed file(s), 49 caller(s) outside the diff, 43 untested -… [Read the thread](https://github.com/nikolay-e/diffctx/issues/323) · 2026-09-30 · closed · 4 comments ### Unprompted use is 0/260: inject a ≤2k impact table at commit/merge/push via hook instead of asking the model to call **Summary.** A survey of 8 live agent sessions on 2026-09-29 (transcript-counted, ~260 code changes across a dozen repositories, diffctx 1.17.0 installed as plugin + CLI everywhere) found **0 unprompted calls** of `diffctx_context` or the plugin skills. Every one of the 7 calls that happened was forced by a QA checklist. Detailed tallies are on #289. This issue is the design conclusion, not more evidence. **Why the model does not decide to call it (converging causes):** 1. The tool is deferred… [Read the thread](https://github.com/nikolay-e/diffctx/issues/310) · 2026-09-29 · closed · 4 comments ### Self-diff impact-oracle mode (WIP patch -> callers/tests/blast radius) > **Status 2026-09-22:** the presentation half shipped in 1.12.x (worktree input, blast-radius summary, impact groups). What remains is gated: scoring preset (Q-class), `mode=impact` (#127), latency (#134), acceptance eval (#128). ## Context The unique wedge vs the query-seeded codegraph-MCP crowd: nobody answers questions about the patch the agent is writing *right now*. diffctx's native input is a diff; backward PPR / reverse edges already exist. Self-diff mode = agent calls diffctx on its… [Read the thread](https://github.com/nikolay-e/diffctx/issues/135) · 2026-07-25 · closed · 4 comments ### Plugin impact hook goes silent for the rest of a session after a plugin upgrade (binary version mismatch, exit 0) **Observed.** In one long Claude Code session (~65 commits, ~40 pushes, many of them multi-file), the plugin's PreToolUse/PostToolUse impact hook injected nothing, not once. Nothing told the agent the hook was inactive, so "no impact context" read as "nothing outside the diff". **Why.** `hooks/diffctx-impact.sh` resolves `bin="$data/bin/diffctx-$version"`, where `$version` comes from the plugin root the session loaded at start. The plugin was upgraded 1.17.0 → 1.18.0 mid-session (the installer… [Read the thread](https://github.com/nikolay-e/diffctx/issues/315) · 2026-09-29 · closed · 3 comments ### CLI default budget: unbounded dumps (145 KB) teach agents to skip the mandatory run **Version:** diffctx 1.17.0, CLI `diffctx . --diff ` with no `--budget`. **Observed.** Two sessions, counted from transcripts: - a 28-file range with no `--budget` produced 145 KB (~36k tokens). The agent read only the section headers. A real bug (a gate reading a missing findings file as a clean pass) was inside the unread part and was found by hand a day later. - the same class of range with `--budget 12000` produced 28 KB; the agent read all of it and caught a real off-by-cap bug in… [Read the thread](https://github.com/nikolay-e/diffctx/issues/307) · 2026-09-29 · open · 3 comments ### locate on a CI YAML change returns only same-file proximity; referenced templates and sibling configs are absent **Version:** diffctx 1.17.0 (MCP `diffctx_context`, `mode="locate"`) **Range:** one commit in a Kubernetes/Argo infra repo that changes a single CI event-sensor YAML. It adds a second event dependency with an inline Lua filter and gives all 11 triggers an explicit `conditions:`. **Observed:** all 142 returned items come from **the changed file itself**: 14 `changed` fragments plus 128 context fragments whose only reasons are `edge, proximity`. That is neighbouring blocks of the same YAML… [Read the thread](https://github.com/nikolay-e/diffctx/issues/301) · 2026-09-27 · open · 3 comments ### Files excluded by .diffctx/ignore still surface as context fragments ## Observed A path excluded via `.diffctx/ignore` is correctly dropped from `changed_files` and carries no `role: changed` — but the graph can still pull it back as a context fragment, content included. ``` repo/ .diffctx/ignore -> "excluded.py" keep.py (changed) excluded.py (changed, tracked) ``` `diffctx . --diff HEAD~1 --format yaml`: ```yaml changed_files: - keep.py # correct: excluded.py is absent fragments: - path: keep.py role: changed ... -… [Read the thread](https://github.com/nikolay-e/diffctx/issues/173) · 2026-07-26 · closed · 2 comments ## Most recent ### impact/locate misses direct callers and reports tests:0 despite existing tests referencing the changed class ## Summary On a Java Maven repo, `diffctx_context` (engine 1.18.2, build f5e2a42e) for diff `HEAD~1..HEAD` missed the direct call sites of the changed class entirely and reported `summary.tests = 0` even though test classes referencing the changed class exist in the repo. ## Environment - diffctx 1.18.2 via MCP (`uvx --from 'diffctx[mcp]' diffctx-mcp`) - Call: `diffctx_context(repo_path=..., diff_ref omitted, mode default)` — the repo had a clean tree, so HEAD was used; effective range was… [Read the thread](https://github.com/nikolay-e/diffctx/issues/335) · 2026-10-02 · open · external user · 0 comments ### `diffctx-mcp` lacks `--version`/`-v` despite exposing package version to MCP clients ## Summary `diffctx-mcp` rejects `--version` even though the main CLI supports version reporting and the MCP server already imports `diffctx.version.__version__` and injects it into the MCP server metadata. Observed on **diffctx 1.18.2**. ## Reproduction ```bash diffctx --version diffctx-mcp --version ``` Observed: ```text diffctx 1.18.2 usage: diffctx-mcp [-h] diffctx-mcp: error: unrecognized arguments: --version ``` The MCP server itself is installed and functional; only the executable… [Read the thread](https://github.com/nikolay-e/diffctx/issues/334) · 2026-10-02 · open · 0 comments ### Plain `diffctx` install exposes `diffctx-mcp` executable that crashes without MCP extras ## Summary Installing the base package creates both `diffctx` and `diffctx-mcp` console scripts, but the latter is not runnable unless the optional `mcp` extra was installed. The result is a published executable that fails immediately with a Python traceback. Observed on **diffctx 1.18.2** on macOS arm64. ## Reproduction ```bash uv tool install --force 'diffctx@latest' diffctx --version diffctx-mcp --help ``` Base CLI succeeds: ```text diffctx 1.18.2 ``` MCP entrypoint fails because its… [Read the thread](https://github.com/nikolay-e/diffctx/issues/333) · 2026-10-02 · open · 0 comments ### impact: an import-only fragment is listed as a caller and counted UNTESTED **Version:** diffctx 1.18.0, `diffctx . --diff 0d75e73a..ae7b4886 --mode impact -f md` on this repository (the 1.18.0 epoch: 53 changed files). **Observed.** Under `src/diffctx/mcp/server.py::diffctx_context` the impact lists ``` - called from src/diffctx/mcp/legacy.py:1-28 — UNTESTED ``` Lines 1-28 of that file are the module docstring and the import block; nothing there calls `diffctx_context`. The import edge from the language builder reaches the changed symbol, the fragment has no symbol… [Read the thread](https://github.com/nikolay-e/diffctx/issues/316) · 2026-09-29 · closed · 1 comment ### plugin: identical impact block injected five times in one commit sequence **Version:** diffctx 1.17.0, Claude Code plugin hooks, 2026-09-29. **Observed:** in one commit sequence on an unchanged working tree the plugin injected the same impact block five times, ~1.5k tokens each, byte-identical apart from the range label (`HEAD` vs `HEAD..`): - PostToolUse after `git status --short` - PostToolUse after `git diff --cached --numstat` - PostToolUse after `git add -A && git diff --cached --stat` - PreToolUse before `git commit` (failed on a formatter hook) -… [Read the thread](https://github.com/nikolay-e/diffctx/issues/314) · 2026-09-29 · closed · 1 comment ### Kotlin files are all 'unparsed': locate returns text excerpts only, confidence 0.09 **Observed** (diffctx 1.17.0, build bf723ad0, MCP `diffctx_context`, `mode=locate`, `budget_tokens=6000`) on a one-commit range in a Kotlin/Spring backend: 11 changed files, 10 of them `.kt`. - `coverage.unparsed_files` lists **all 10** Kotlin files; `confidence` is **0.09**. - Every changed Kotlin fragment comes back as `kind: excerpt` or `chunk` with `score: 0.0` — no function/class fragments, no symbol-level edges. - The context that would have explained the change was reachable only… [Read the thread](https://github.com/nikolay-e/diffctx/issues/303) · 2026-09-29 · open · 1 comment ### --diff drops a file the range deletes: no fragment, no deletion marker Observed with `diffctx . --diff 6ff54b5f..25f66008` on nikolay-e/yay-tsa (diffctx from `$PATH`, 2026-09-28). `git diff --name-only` lists 34 files; the context covers 33. The one missing is a file the range **deletes outright**: `apps/backend/infra-karaoke-worker/src/main/kotlin/dev/yaytsa/worker/karaoke/KaraokePriorityQueue.kt` (0 insertions, 70 deletions). There is no fragment for it and no line saying it was removed. A deletion is part of what a change does. Here the removed class held the… [Read the thread](https://github.com/nikolay-e/diffctx/issues/302) · 2026-09-28 · closed · 1 comment ### locate: serialized response is ~3x budget_tokens and overflows the MCP client on a one-file commit **Version:** diffctx 1.17.0 (MCP `diffctx_context`, Claude Code plugin) **Command:** `diffctx_context(repo_path=, diff_ref=^.., mode="locate")`, all other arguments at their defaults (`budget_tokens=8000`, `max_tokens=25000`). **Range:** one commit that changes a single 800-line YAML file: 14 changed lines (a new event dependency and a `conditions:` line on 11 triggers). **Observed:** the result has 142 items whose `tokens` add up to **7,879**, which is inside the… [Read the thread](https://github.com/nikolay-e/diffctx/issues/300) · 2026-09-27 · open · 1 comment ### diffctx_context returns a JSON string, so MCP clients get the locate document double-encoded in {"result": ...} `diffctx_context` is declared `-> str` and returns `json.dumps(doc)` (`mcp/server.py:142`). FastMCP wraps a string return as structured output `{"result": ""}`, so the client receives the locate document JSON-encoded inside a JSON string: ``` {"result":"{\"schema\":\"diffctx.locate.v1\",\"name\":\"...\",\"items\":[{\"path\":\"src/...\", ... ``` Every quote is escaped once more, so the payload costs more tokens than the document itself, and a model has to mentally decode it before it… [Read the thread](https://github.com/nikolay-e/diffctx/issues/292) · 2026-09-25 · closed · 0 comments ### MCP server breaks after an in-place upgrade: lazy imports hit the new package tree Observed 2026-09-26: `uv tool install --force "diffctx[mcp]@latest"` (1.16.0 → 1.17.0) while a Claude Code session held the MCP server (`diffctx mcp`) open. The next `diffctx_context` call failed with: ``` Error executing tool diffctx_context: No module named 'diffctx.tokens' ``` The running process kept the 1.16.0 modules it had already imported, but the tool body imports lazily (`from diffctx.tokens import count_tokens` in `mcp/server.py:81`, `from .fetch import fetch_result` at :254, `from… [Read the thread](https://github.com/nikolay-e/diffctx/issues/291) · 2026-09-25 · closed · 0 comments The remaining reports are on [the project's issue tracker](https://github.com/nikolay-e/diffctx/issues).