diff --git a/docs/DOGFOOD.md b/docs/DOGFOOD.md
index ff9e1b4..caa3faa 100644
--- a/docs/DOGFOOD.md
+++ b/docs/DOGFOOD.md
@@ -107,3 +107,7 @@ and [Claude Code MCP scopes](https://code.claude.com/docs/en/mcp#local-scope).
 This signed snapshot remains a separate tool from the newer
 [local repository navigation bridge](LOCAL-NAVIGATION.md). The bridge does not
 enlarge the signed v1 format or automatically sign repository source.
+
+The [first paired diagnostic trial](PAIRED-TRIAL.md) now records the scanner
+truncation diagnosis, actual fixture checks and worker usage including repairs.
+It is a host-assisted context-selection experiment, not end-to-end billing proof.
diff --git a/docs/LOCAL-NAVIGATION.md b/docs/LOCAL-NAVIGATION.md
index ecbe06a..b212331 100644
--- a/docs/LOCAL-NAVIGATION.md
+++ b/docs/LOCAL-NAVIGATION.md
@@ -124,8 +124,9 @@ After reopening, inspect `/mcp`, then ask:
 Refresh after source edits. The two clients have independent ephemeral indexes;
 refreshing one does not refresh the other. No inference is needed to build or
 query the index. The agent interpreting its results may still incur inference
-costs. Real accepted-task savings require the paired trial in
-[DOGFOOD.md](DOGFOOD.md), which has not been run.
+costs. The [first paired diagnostic trial](PAIRED-TRIAL.md) used fewer worker
+tokens with selected excerpts, including repairs, but host selection/review
+costs were not measured. End-to-end inference-bill savings remain unproven.
 
 Configuration reference: [official Codex MCP documentation](https://learn.chatgpt.com/docs/extend/mcp?surface=cli).
 
diff --git a/docs/PAIRED-TRIAL.md b/docs/PAIRED-TRIAL.md
new file mode 100644
index 0000000..9360e45
--- /dev/null
+++ b/docs/PAIRED-TRIAL.md
@@ -0,0 +1,102 @@
+# First paired diagnostic trial — 21 September 2026
+
+This is a narrow, host-assisted context-selection experiment, not measured
+end-to-end savings or a billing result. Both arms needed reviewer correction.
+
+## Protocol
+
+Source revision: `3c2723e8e61ae8810a6e843de4b33b39e5074e4f`, subsequently
+squash-merged as `ab8026b1a14be0472f0fe74581676124f5353950` in
+[PR #9](https://github.com/forgesworn/context/pull/9). The two trees were verified
+identical. Initial requests used the original revision; repair prompts retained
+those exact source packets after the merge.
+
+Task: diagnose whether `filesSkipped=0` and
+`max(0, filesScanned + symbolsFound - records.length)` establish complete
+repository coverage. Distinguish discovery, depth, record and read limits;
+predict two fixture outcomes; recommend an honest bounded reporting change and
+two regressions without changing signed v1. No implementation was requested.
+
+Both arms used `deepseek-v4.1-flash:cloud`, `think=false`, a 16,384-token output
+allowance, the same question and separate stateless requests through the M4
+Ollama endpoint. Baseline ran first. No arm received the other arm's answer.
+
+- Baseline: complete `source-scan.ts`, `source-scan.test.ts` and
+  `scripts/dogfood.mjs`, with line numbers (46,584-byte initial packet).
+- Assisted: after actual `repository_search(filesSkipped)` located the relevant
+  code, the host selected scanner lines 1–30, 85–132, 175–220 and 260–268;
+  test lines 90–116 and 130–152; harness lines 70–85. Same question and original
+  line numbers (14,452-byte initial packet).
+
+Acceptance criteria were written before inference. Both first answers got the
+central coverage problem and fixture counts right but made material accounting
+or API-recommendation errors. Each received one focused repair, including the
+same reviewer corrections, its own prior answer and its original source packet.
+The repairs therefore benefited from host-supplied ground truth, not autonomous
+self-correction. The revised core diagnoses were accepted; their prose was not
+accepted verbatim as an implementation specification.
+
+## Worker usage, including repairs
+
+| Arm | Initial tokens | Repair tokens | Total input | Total output | Total |
+| --- | ---: | ---: | ---: | ---: | ---: |
+| Full files | 16,164 | 20,015 | 29,335 | 6,844 | 36,179 |
+| Selected excerpts | 6,589 | 9,083 | 10,847 | 4,825 | 15,672 |
+
+The assisted arm used **56.7% fewer provider-reported worker tokens**, including
+its repair. Four dispatched requests consumed 51,851 reported tokens in total.
+All returned HTTP 200 and terminal `stop`; no transport retries or 402 occurred.
+Helper-reported request durations sum to 34.480 seconds for baseline and 26.341
+seconds for assisted. These are not total task completion times.
+
+The helper summary records two partial first drafts and two accepted corrected
+diagnoses. Model and thinking settings did not change between arms.
+
+## Verified diagnosis
+
+An executable fixture used three small root TypeScript files, each exporting
+one named function. The built scanner returned:
+
+| Case | maxFiles | maxRecords | Files scanned | Files skipped | Symbols | Records | Candidate omissions |
+| --- | ---: | ---: | ---: | ---: | ---: | ---: | ---: |
+| A | 1 | 128 | 1 | 0 | 1 | 2 | 0 |
+| B | 64 | 1 | 3 | 0 | 3 | 1 | 5 |
+
+The formula is exact for omitted **constructed candidate records**: parsed file
+candidates plus filtered/deduplicated symbol candidates minus retained records.
+It does not count files outside discovery/depth limits. `filesSkipped` only
+counts particular observed exclusions; even `lstat` failures currently bypass
+that counter. Directory entries may have been enumerated without their files
+being inspected, so "never enumerated" is not universally accurate wording.
+
+Next implementation: preserve `filesSkipped: number`, all quotas and signed v1;
+add explicit discovery-cap/depth-limit indicators and scoped coverage wording.
+Reaching a cap means uncertainty, not proof that more eligible files exist.
+Do not walk unvisited subtrees merely to invent an exact uncovered-file count.
+Candidate-omission reporting should remain clearly separate from coverage.
+This reporting change is **not implemented by this trial**.
+
+## Limits and local evidence
+
+- One pair, one diagnostic task, baseline-first order; no statistical claim.
+- Comparison is against supplying three full relevant files, not an optimised
+  `rg` workflow or an autonomous agent using competing navigation tools.
+- Excerpt selection and review used Codex. Its token usage, initial review time,
+  packet preparation time, cache hits and monetary cost are unknown (`null`),
+  not zero. End-to-end cost reduction remains unmeasured.
+- Instrumented final-review wall intervals were 14.279 seconds (baseline) and
+  19.596 seconds (assisted); these include orchestration and exclude initial
+  review and preparation. They are not total human/agent review time.
+- No actual Claude-session inference was spent for acceptance; its connection
+  check is still separate from interactive tool use.
+
+Local prompt, answer, protocol, fixture and helper receipts are under
+`/private/tmp/z1p-paired-trial.DRWL5j/`; this temporary evidence is not a durable
+public archive. Prompt SHA-256 values in the receipts:
+
+| Request | Prompt SHA-256 |
+| --- | --- |
+| Baseline | `099ca389f09c12e52ad0740defdd41dc7b4f3df70c3ea80bb8cab0268fc4b271` |
+| Assisted | `a33b047ec371a1fcbb072195c9518fcad9f7bd88587eeffa54d09aedb7edebc2` |
+| Baseline repair | `dc7b80b74e8ff90d10247b3b1fca104c8ca1f04351df0af83f4e31f414983c09` |
+| Assisted repair | `b678c3c9ef967ce6487a2a771181076a505963b7c6e564dcfda9c1ce549b22a3` |