feat(eval): export Gym trajectories as ATIF

fern/versions/latest/pages/reference/cli-commands.mdx

@@ -49,6 +49,7 @@ gym env status                # show running servers
 gym eval prepare              # prepare benchmark data and dump it to disk
 gym eval run                  # collate data, start servers, and collect rollouts
 gym eval aggregate            # merge sharded rollout results
+gym eval export               # export supported Gym trajectories as ATIF
 gym eval health-check         # verify rollout artifact quality for an existing run
 gym eval profile              # compute a reward profile from rollouts
 gym eval reverify             # recompute rewards from existing rollouts without re-running inference
@@ -801,6 +802,35 @@ gym eval aggregate \
     --output results/rollouts.jsonl
 ```
 
+### `gym eval export`
+
+Export supported `ng_trajectory` attachments from a Gym rollouts JSONL file as ATIF v1.7. The command writes one ATIF
+trajectory per rollout plus a manifest that preserves Gym's task and rollout identity. It is a strict offline conversion:
+if Gym cannot represent a source trajectory completely in the supported ATIF subset, the export fails instead of silently
+omitting data. The destination directory must not already exist.
+
+This command does not parse ATOF and does not load NeMo Relay. Each ATIF trajectory takes its agent name from the source
+row's `agent_ref.name`; `--agent-version` records the version of that agent implementation.
+
+| Option | Description |
+| --- | --- |
+| `--format atif` | Output format. ATIF is the only format supported initially. |
+| `--rollouts PATH` | Gym rollouts JSONL containing `ng_trajectory` version `1.0` attachments. |
+| `--output-dir DIR` | New directory for the ATIF files and manifest. |
+| `--session-id ID` | Stable identifier for the source evaluation run. |
+| `--agent-version VERSION` | Version of the agent implementation that produced the rollouts. |
+
+```bash
+gym eval export \
+    --format atif \
+    --rollouts results/rollouts.jsonl \
+    --output-dir results/atif \
+    --session-id eval-2026-08-25 \
+    --agent-version 1.2.3
+```
+
+See the [trajectory capability matrix](/reference/trajectory-capabilities#atif-export) for the initial conversion boundary.
+
 ### `gym eval health-check`
 
 Verify rollout quality for an existing run directory. The command reads `<run-dir>/rollouts.jsonl` by default and writes

fern/versions/latest/pages/reference/trajectory-capabilities.mdx

@@ -35,6 +35,53 @@ under `ng_model_call_capture` and `ng_agent_observations`.
 See [Model-call capture](/model-server/model-call-capture) for payload retention and access-control requirements. Token
 fields are `prompt_tokens`, `completion_tokens`, `reasoning_tokens`, `total_tokens`, and `cached_tokens`.
 
+## ATIF export
+
+`gym eval export --format atif` converts the supported `ng_trajectory` version `1.0` subset into ATIF v1.7 without loading
+NeMo Relay. The initial converter accepts a completed root invocation with one initial system/user input phase, exactly one
+captured model call per turn, text-only output (including ordered multipart tool results), and unambiguous function-call and
+function-result relationships. Model calls may be joined by `model_call_id` or by a unique `(model_ref, response_id)`
+pair. It rejects later user/system turns and source records when their status, evidence gaps, content type, invocation
+structure, tool correlation, or provider completion evidence would require dropping or guessing information. This strict
+boundary means an accepted conversion is complete for the supported source profile; it does not claim that the original
+agent harness observed every action outside Gym.
+
+Responses message `phase` values such as `commentary` and `final_answer` are rejected because ATIF v1.7 has no equivalent
+field. Namespaced Responses function calls are also rejected because the standard ATIF tool-call fields cannot retain the
+separate namespace identity. A missing or null phase or namespace is accepted because it carries no additional source meaning.
+Provider-native hosted tools, shell and patch calls, tool search, compaction records, approvals, and additional-tool records
+remain outside the initial generic function-call profile and are rejected rather than flattened.
+
+The semantic profile maps ordered messages, reasoning, function calls and results, turn identity and resolution, tool timing,
+normalized model identity, and normalized token counts. Training token IDs, log probabilities, and routed-expert metadata are
+outside the initial profile and fail conversion rather than being copied into an extension. Captured provider request and
+response values are retained opaquely under step-level `extra.nemo_gym.model_call` metadata because ATIF's standard step
+fields do not carry those provider-specific payloads. The converter does not parse those raw payloads or use them to
+reconstruct the canonical trajectory; the producer-owned `response_metadata` and `token_stats` fields supply completion,
+model, and usage evidence. Per-step token fields are preserved when available. Final prompt, completion, and cached-token
+totals are emitted only when every model call provides the corresponding field, so unavailable values are never counted as
+zero. Each agent step retains the normalized model identity. The root agent model is populated only when
+every model-backed step uses the same known model; routed or fallback trajectories keep their model identities on the
+individual steps instead.
+
+The strict ATIF reverify path additionally requires complete prompt and completion counts when any supported usage is
+present because one Gym response cannot represent partial standard usage. A partial-metric export remains valid ATIF for
+other consumers, but Gym reverify rejects it instead of dropping the known counts or reporting a false complete aggregate.
+
+The ATIF `agent.name` comes from each rollout row's `agent_ref.name`. The initial batch exporter accepts one agent identity
+per input file because the caller supplies one corresponding agent implementation version. Conversion provenance is kept under the ATIF root's
+`extra.nemo_gym` namespace rather than overloading the agent identity fields:
+
+| Metadata | Value | Purpose |
+| --- | --- | --- |
+| Exporter | NeMo Gym and its package version | Identifies the implementation that created the ATIF file. |
+| Source | Gym rollout and `ng_trajectory` schema version | Records the format that was converted. |
+| Conversion status | `complete` | Confirms that the supported normalized `ng_trajectory` profile was mapped without omission; it does not attest to the contents of opaque provider payloads. |
+| Conversion warnings | Not emitted by strict v1 | Reserved for a future best-effort mode that can describe information it could not represent. |
+
+The initial strict converter does not emit partial files or conversion warnings. Unsupported or lossy inputs fail validation.
+A future best-effort mode would need an explicit `partial` status and structured warnings rather than reusing `complete`.
+
 ## Acceptance criteria
 
 | ID | Criterion |